Geo Morphology of Oil and Gas Fields in Sandstone Bodies

Developments in Petroleum Science, 4

GEOMORPHOLOGY OF OIL AND GAS FIELDS IN SANDSTONE BODIES

FURTHER TITLES IN THIS SERIES

1 A. GENE COLLINS GEOCHEMISTRY O F OILFIELD WATERS

2 W.H. FERTL ABNORMAL FORMATION PRESSURES

3 A.P. SZILAS PRODUCTION AND TRANSPORT O F OIL AND GAS

5 T.F. YEN and G.V. CHILINGARIAN OIL SHALE

Developments in Petroleum Science, 4

GEOMORPHOLOGY OF OIL AND GAS FIELDS IN SANDSTONE BODIES

C.E.B. CONYBEARE

Australian National University, Canberra (A. C. T. )

ELSEVIER SCIENTIFIC PUBLISHING COMPANY Amsterdam - Oxford - New York 1976

ELSEVIER SCIENTIFIC PUBLISHING COMPANY 335 Jan van Galenstraat P.O. Box 211, Amsterdam, The Netherlands

AMERICAN ELSEVIER PUBLISHING COMPANY, INC. 5 2 Vanderbilt Avenue New York, New York 10017

Library 01 C0ngrr.a Calaloging in Publication Data

Conyheare, C E B Geomorphology of o i l and gas f i e l d s i n sandstone

bodies.

(Developments i n petroleum science ; 4 ) Includes h ib l iographica l re ferences and indexes. 1. Geornorphology. 2. Rock t r a p s (Hydraulic

engineer ing) 3. Sandstone. 4. Petroleum-Geology. 5. Gas, Natural-Geology. I. T i t l e . 11. Ser ies . GB406. c63 553' .B 7537974 ISBN O-~!+I&-lJ.398-7

Copyright b 1976 by Elsevier Scientific Publishing Company, Amsterdam

AH rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher, Elsevier Scientific Publishing Company, Jan van Galenstraat 3 3 5 , Amsterdam

Printed in The Netherlands

ACKNOWLEDGEMENTS

The author wishes to acknowledge the assistance of Ms P.M. Carle, Ms E.A. Kilner, Mr L. Seeuwen and Mr G.R. Harper in the preparation of the typescript and illustrations. Acknowledgement is also due to the following organizations, institutions, and publishers from whose publications the quota- tions and many of the illustrations in this book have been drawn: Geological Society of America, American Association of Petroleum Geologists, Society of Economic Paleontologists and Mineralogists, Canadian Society of Petroleum Geologists, Canadian Institute of Mining and Metallurgy, Royal Geological and Mining Society of the Netherlands, Australian Petroleum Exploration Association, Four Corners Geological Society, Delaware Geological Society, Rocky Mountains Association of Geologists, Wyoming Geological Association, Houston Geological Society, Gulf Coast Association of Geological Societies, Dallas Geological Society, Tulsa Geological Society, Kansas Geological Society- United States Geological Survey, U.S. Bureau of Reclamation, U.S. Navy Hydrographic Office, Mississippi River Commission, Illinois Geological Survey, Indiana Geologcal Survey, Geologische Dienst der Nederlanden, U.S.S.R. Ministry of Oil Industries, University of Texas, Schlumberger Well Services, Nedra Press (U.S.S.R.), John Wiley and Sons, Prentice-H'dl, Princeton University Press, Chapman and Hall, Springer-Verlag, Gulf Publishing Company, Tracer Petroleum and Mining Publications, and Elsevier Scientific Publishing Company.

The author also wishes to acknowledge the facilities offered to him during visiting appointments a t the University of Calgary and the Colorado School of Mines.

PREFACE

This book is essentially about stratigraphic traps for oil and gas. Many of the examples discussed are geomorphologic features having inherent closures without any secondary structural element; others are primarily geomorphologic features modified by folding or faulting to produce local closures. The first category comprises traps that are purely stratigraphic, although the accumulation of hydrocarbons may have been assisted by regional or local tilting of the strata, or by deformation caused by compaction of the underlying sediments. The second category, which includes a much larger number of known examples, comprises structural-stratigraphic traps. Many of these traps have proved to be elusive, particularly those of the first category which commonly defy detection by seismic methods. In some cases, discovery has been ac- cidental, and further exploration to delineate the accumulation has been empirical.

geological characteristics of geomorphologic features that have controlled or influenced the accumulation of oil and gas in particular fields, with a view to using such examples as models in the search for new fields in sandstone bodies. Many of the examples presented have been so well documented that they stand as classic examples of stratigraphic fields in which oil and gas accumulations are controlled by geomorphologic features. Others have yet t o be defined unequivocally, but are included as additional references to assist in the interpretation of geophysical and sub-surface geological data.

The author is indebted to the many geologists who have written about the hydrocarbon accumulations and geological features described herein, without whose efforts it would not have been possible to compile this book.

The purport of this book is to briefly present examples illustrating the main

Canberra, A.C.T. C.E.B. CONYBEARE

CONTENTS

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . .

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 1 . River channels . . . . . . . . . . . . . . . . . . . . Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

E-log characteristics . . . . . . . . . . . . . . . . . . . . .

Ancient sand bodies . . . . . . . . . . . . . . . . . . . . . . Pulaski and Fayettville Channels. Tennessee . . . . . . . . . . . . . Bedford Channels. Ohio . . . . . . . . . . . . . . . . . . . Anvil Rock Channel. Illinois . . . . . . . . . . . . . . . . . . Carbondale Channel. Illinois . . . . . . . . . . . . . . . . . . Graham Channels. Texas . . . . . . . . . . . . . . . . . . . Bartlesville Channels. Kansas . . . . . . . . . . . . . . . . . . Shinarump Charinels. Utah . . . . . . . . . . . . . . . . . .

Oil and gas fields . . . . . . . . . . . . . . . . . . . . . . . . Red Earth Oil Field. Alberta . . . . . . . . . . . . . . . . . . Music Mountain Oil Pool. Pennsylvania . . . . . . . . . . . . . . Cabin Creek Gas Field. Ohio . . . . . . . . . . . . . . . . . . Gay-Spencer Richardson Trend. Virginia . . . . . . . . . . . . .

Tyler Oil Fields. Montana . . . . . . . . . . . . . . . . . . . Delaware Extension Oil Field. Oklahoma . . . . . . . . . . . . . . Bush City Oil Field. Kansas . . . . . . . . . . . . . . . . . . Red Fork Sandstone Production. Oklahoma . . . . . . . . . . . . . Moomba Gas Field. South Australia . . . . . . . . . . . . . . . Pickanjinnie Gas Field. Queensland . . . . . . . . . . . . . . . . Moonie Oil Field. Queensland . . . . . . . . . . . . . . . . . Athabasca Oil Sands. Alberta . . . . . . . . . . . . . . . . . . Bellshill Lake and Hughenden Oil Fields. Alberta . . . . . . . . . . . South Glenrock Oil Field. Wyoming . . . . . . . . . . . . . . .

Donkey Creek. Rozet. and O’Connor Oil Fields. Wyoming . . . . . . . . Coyote Creek and Miller Creek Oil Fields. Wyoming . . . . . . . . . . Reimers-Lane-Hart Trend. Nebraska . . . . . . . . . . . . . . . Cut Bank Oil Field. Montana . . . . . . . . . . . . . . . . . . Nahorkatiya Oil Field. Assam . . . . . . . . . . . . . . . . . Maikop Oil Field. U.S.S.R. . . . . . . . . . . . . . . . . . .

Chapter 2 . Distributary and delta-fringe sand . . . . . . . . . . . . . Introduction . . . . . . . . . . . . . . . . . . . . . . . .

Geomorphology . . . . . . . . . . . . . . . . . . . . . . E-log characteristics . . . . . . . . . . . . . . . . . . . . .

Ancient sand bodies . . . . . . . . . . . . . . . . . . . . . . Appalachian Delta. U.S.A. . . . . . . . . . . . . . . . . . .

Geomorphology . . . . . . . . . . . . . . . . . . . . . .

Compaction . . . . . . . . . . . . . . . . . . . . . . .

Jackpile Channel. New Mexico . . . . . . . . . . . . . . . . .

Bethel Sandstone Trend. Kentucky . . . . . . . . . . . . . . . . .

Recluse Oil Field. Wyoming . . . . . . . . . . . . . . . . .

Compaction . . . . . . . . . . . . . . . . . . . . . . .

V VI

1

13 13 13 17 23 26 27 28 31 33 36 36 37 39 40 41 43 45 47 48 50 52 54 56 60 62 64 66 69 73 76 79 80 82 84 88 90

93 93 93

103 106 107 108

VIII

Cisco Delta. Texas . . . . . . . . . . Volgograd Delta. U.S.S.R. . . . . . . . . Identification of delta distributary channel sands

Oil and gas fields . . . . . . . . . . . . Booch Sandstone Oil Fields. Oklahoma South Pine Hollow Gas Fields. Oklahoma . . Pokrovsk Oil Field. U.S.S.R. . . . . . . . East Tuskegee Oil Field. Oklahoma . . . . . Dale Consolidated Oil Field. Illinois Bellshill Lake Oil Field. Alberta . . . . . . Belly River Pool. Pembina Oil Field. Alberta . Asiefere and Eriemu Oil Fields. Nigeria Wilcox Oil and Gas Fields. Texas . . . . . Seeligson Oil Field. Texas . . . . . . . . Ostra Oil Field. Venezuela . . . . . . . Main Pass Block 35 Oil Field. Louisiana

. . .

. . . .

. . .

. . .

. . . . . . . . . . . 110

. . . . . . . . . . . 112

. . . . . . . . . . . 113

. . . . . . . . . . . 117

. . . . . . . . . . . 118

. . . . . . . . . . . 121

. . . . . . . . . . . 123

. . . . . . . . . . . 124

. . . . . . . . . . . 126

. . . . . . . . . . . 127

. . . . . . . . . . . 129

. . . . . . . . . . . 131

. . . . . . . . . . . 133

. . . . . . . . . . . 134

. . . . . . . . . . . 137

. . . . . . . . . . . 138

Chapter 3 . Barrier and other offshore bars . . Introduction . . . . . . . . . . . .

Geomorphology . . . . . . . . . . E-log characteristics . . . . . . . . . Compaction . . . . . . . . . . .

Ancient sand bodies . . . . . . . . . . Oil and gas fields . . . . . . . . . . .

Austin Gas Field. Michigan . . . . . .

Wakiti Trend. Oklahoma . . . . . . . Olympic Oil Field. Oklahoma . . . . . Matu-Catu Trend. Brazil . . . . . . . Bell Creek Oil Field. Montana . . . . . GasDraw Oil Field. Wyoming . . . . . Garrington and Crossfield Oil Fields. Alberta Bisti Oil Field. New Mexico . . . . . . Salt Creek-Teapot Dome Oil Field. Wyoming BigPiney Gas Field. Wyoming . . . . . Hardin Oil Field. Texas . . . . . . .

Shira Streak Oil Field. Pennsylvania

Sallyards Trend Oil Fields. Kansas

. . .

. . . .

. . . . . . . . . . . . 141

. . . . . . . . . . . . 141

. . . . . . . . . . . . 141

. . . . . . . . . . . . 147

. . . . . . . . . . . . 147

. . . . . . . . . . . . 151

. . . . . . . . . . . . 152

. . . . . . . . . . . . 153

. . . . . . . . . . . . 155

. . . . . . . . . . . . 158

. . . . . . . . . . . . 159

. . . . . . . . . . . . 161

. . . . . . . . . . . . 161

. . . . . . . . . . . . 164

. . . . . . . . . . . . 169

. . . . . . . . . . . . 169

. . . . . . . . . . . . 174 , . . . . . . . . . . . 176 . . . . . . . . . . . . 179 . . . . . . . . . . . . 181

Chapter 4 . Regressive marine shoreline sand . . . . . . . . . . . . . . 183 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 183

Geomorphology . . . . . . . . . . . . . . . . . . . . . . 183 E-log characteristics . . . . . . . . . . . . . . . . . . . . . 192

Ancient sand bodies . . . . . . . . . . . . . . . . . . . . . . 197 Oil and gas fields . . . . . . . . . . . . . . . . . . . . . . . 199

Wattenberg Gas Field, Colorado . . . . . . . . . . . . . . . . . 200 Burbank Oil Field. Oklahoma . . . . . . . . . . . . . . . . . 202 Viking Oil and Gas Fieids. Alberta and Saskatchewan . . . . . . . . . . 203 Sabre Oil Field. Colorado . . . . . . . . . . . . . . . . . . . 208

Chapter 5 . Transgressive marine shoreline deposits . . . . . . . . . . . . 211 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 211

Geomorphology . . . . . . . . . . . . . . . . . . . . . . 211

Compaction . . . . . . . . . . . . . . . . . . . . . . 195

IX

E-log characteristics . . . . . . . . . . . . . . . . . . . . . 213 Compaction . . . . . . . . . . . . . . . . . . . . . . . 214


Yardarino.- Dongara Gas Field, Western Australia . . . . . . . . . . . 219 Red Oak, Wilberton. and Kinta Gas Fields. Oklahoma . . . . . . . . . 220 Morrow Oil Fields. Oklahoma . . . . . . . . . . . . . . . . . 221 Milligan Oil Field. British Columbia . . . . . . . . . . . . . . . 224 Horseshoe Oil Field. New Mexico . . . . . . . . . . . . . . . . 227 Carbon Gas Field. Alberta . . . . . . . . . . . . . . . . . . . 231

Chapter 6 . Submarine valleys . . . . . . . . . . . . . . . . . . . 235 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 235

Geomorphology . . . . . . . . . . . . . . . . . . . . . . 235 E-log characteristics . . . . . . . . . . . . . . . . . . . . . 240 Compaction . . . . . . . . . . . . . . . . . . . . . . . 242

Ancient sand bodies . . . . . . . . . . . . . . . . . . . . . . 244 Y oakum Channel Texas . . . . . . . . . . . . . . . . . . . 247 Rosedale Channel . . . . . . . . . . . . . . . . . . . . . 249

Oil and gas fields . . . . . . . . . . . . . . . . . . . . . . . 251 Brentwood. Dutch Slough and Wets Thornton Oil and Gas Fields. California . . 252 Marlin Gas Field. Victoria . . . . . . . . . . . . . . . . . . . 255 Ventura Oil and Gas Field. California . . . . . . . . . . . . . . . 258

Chapter 7 . Tidal current sand bodies . . . . . . . . . . . . . . . . 261 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 261


Ancient sand bodies . . . . . . . . . . . . . . . . . . . . . . 267

Chapter 8 . Alluvial fans and sheets . . . . . . . . . . . . . . . . . 273 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 273



Chapter 9 . Eolian sand . . . . . . . . . . . . . . . . . . . . . 285 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 285



North Sea Gas Fields . . . . . . . . . . . . . . . . . . . . 292 Hassi R’Mel and Houd Berkaoui Gas and Oil Fields. Algeria . . . . . . . . 294

References . . . . . . . . . . . . . . . . . . . . . . . . . 297

Subject Index . . . . . . . . . . . . . . . . . . . . . . . . 333

This Page Intentionally Left Blank

1

INTRODUCTION

Accumulation of o i l and gas i n a sands tone body depends on s e v e r a l

f a c t o r s i nc lud ing t h e s t a t e of gene ra t ion and t i m e of mig ra t ion o f

hydrocarbons o r t h e i r p r e c u r s o r s , d i r e c t i o n a l v a r i a t i o n s i n p o r o s i t y

and p e r m e a b i l i t y , t h e e x i s t e n c e of s t r a t i g r a p h i c o r s t r u c t u r a l c l o s u r e

wi th a s u i t a b l e s e a l , and t h e geometry of t h e sands tone body. Many

ho le s have been d r i l l e d on t h e b a s i s o f geophys ica l i n t e q r e t a t i o n s t h a t

i n d i c a t e d s t r u c t u r a l c l o s u r e w i t h i n a p r o s p e c t i v e s e c t i o n , on ly t o f i n d

t h e s e c t i o n l ack ing i n s u i t a b l e s o u r c e beds f o r hydrocarbons, o r w i th

no impermeable s e a l above t h e p o t e n t i a l s ands tone r e s e r v o i r . The

sands tone i t s e l f may be l o c a l l y t i g h t . F u r t h e r , t h e s p a t i a l r e l a t i o n -

s h i p s of d e p o s i t i o n a l t r e n d s and geometry t o permeable zones w i t h i n t h e

sands tone body are commonly unknown. To compl ica te our unders tanding of

t h e s i t u a t i o n , t h e d e p o s i t i o n a l t r ends and geometry of t h e sands tone body

i t s e l f may n o t b e known. With t h e s e p o s s i b i l i t i e s i n mind, t h e fo l lowing

comments are o f f e r e d on t h e c l a s s i f i c a t i o n of sands tone bod ies .

A s h e e t o r b l a n k e t sands tone body may b e des igna ted as a mappable

s t r a t i g r a p h i c u n i t , such as a member o r fo rma t ion , and y e t l a c k c o n t i n u i t y

and homogeneity. A t one l o c a l i t y i t may c o n s i s t of a s i n g l e sands tone

u n i t , and a t ano the r i t may comprise two o r more sands tone beds t h a t have

i n d i v i d u a l d e p o s i t i o n a l t r e n d s , shapes , and p e t r o p h y s i c a l c h a r a c t e r i s t i c s .

A t a p a r t i c u l a r l o c a t i o n o i l o r gas may be encountered i n Sandstone "A",

where i t occurs below t h e up-dip edge , bu t no t i n ad jacen t Sandstone "B"

t h a t p inches o u t e l sewhere . This t ype of s i t u a t i o n i s common i n a l l u v i a l

po in t b a r and c h a n n e l - f i l l s ands , i n anastomosing d e l t a d i s t r i b u t a r y sands ,

and i n o f f - l apo ing marine s h o r e l i n e sands .

2

A c l a s s i f i c a t i o n of s a n d body s h a p e s is proposed by P e t t i j o h n ,

P o t t e r and S i e v e r (1972) a f t e r t h e c l a s s i f i c a t i o n of P o t t e r (1962, b ) .

They s a y t h a t t h e r e are a t least f o u r d i f f e r e n t b a s i c r e c u r r i n g s h a p e s

t o sand b o d i e s , i l l u s t r a t e d by F i g . 1-1, and make t h e f o l l o w i n g s t a t e m e n t

on p . 4 4 0 , "Equid imens iona l s a n d b o d i e s h a v e l e n g t h - w i d t h r a t i o s of

a p p r o x i m a t e l y 1:l and may c o v e r a few t o t h o u s a n d s of s q u a r e k i l o m e t e r s .

These h a v e b e e n c a l l e d s h e e t s and b l a n k e t s . E l o n g a t e s a n d b o d i e s , on

t h e o t h e r h a n d , a r e t h o s e w i t h l o n g d imens ion n o t a b l y e x c e e d i n g w i d t h

and a r e one of t h r e e t y p e s : pods , r i b b o n s and d e n d r o i d s ( P o t t e r , 1962,

F ig . 3 ) .

a r e much more e l o n g a t e w i t h length-width r a t i o s of t h r e e o r more and

p o s s i b l y as h i g h as 20 t o 1 o r more. Rich (1923, p. 103) used t h e term

s h o e s t r i n g f o r s u c h b o d i e s .

have b r a n c h e s , e i ther t r i b u t a r i e s o r d i s t r i b u t a r i e s . By l a t e r a l m i g r a t i o n ,

c o a l e s c e n t r i b b o n s and d e n d r o i d s may form belts, d e n d r i t i c b e l t s b e i n g t h e

more common. 'I

-have l e n g t h - w i d t h r a t i o s o f three o r less where r i b b o n s

Dendroids are commonly more s i n u o u s and

S h e e t s

E I o n g a t e

Fig . 1-1 C l a s s i f i c a t i o n of s a n d body s h a p e s . (Modif ied by P e t t i j o h n ,

P o t t e r and S i e v e r , 1972, a f t e r P o t t e r , 1962b) .

3

These des igna t ions are based on t h e geometry of t h e sandstone bodies

and do not have any i m p l i c i t connotat ion as t o

o r geomorphology. Also, they can be misconstrued and misappl ied, w i th

p a r t i c u l a r r e fe rence t o some so-cal led shee t o r b l anke t sandstones.

Nevertheless , they s e r v e a u s e f u l purpose i n q u a l i f y i n g and t o some ex ten t

quan t i fy ing t h e shapes of sandstone bodies .

d e p o s i t i o n a l environment

Sheet- l ike s t r a t i g r a p h i c u n i t s , c o n s i s t i n g e s s e n t i a l l y of sandstone,

may have o r i g i n a t e d as t r a n s g r e s s i v e o r r e g r e s s i v e s h o r e l i n e sands, as

e o l i a n sands , as widespread sand beds w i t h i n coa le sc ing a l l u v i a l f a n s , a s

braided and l a t e r a l l y mig ra t ing e s t u a r i n e d e p o s i t s , a s r i v e r sediments on

a broad p l a i n , o r as l a y e r s of sand swept ou t on abyssa l p l a i n s of t he ocean.

Apart from t h e s i m i l a r i t y of t h e i r g ros s dimensions, t h e s e u n i t s are

markedly d i f f e r e n t i n t h e i r i n t e r n a l s t r u c t u r e and s t r a t i g r a p h i c

r e l a t i o n s h i p s . A l l are diachronous t o some degree , a l though a l a y e r

of sand swept r a p i d l y on t o an abyssa l p l a i n w i l l r e p r e s e n t s o s h o r t

a per iod of t i m e t h a t i t can be regarded a s a s t r a t i g r a p h i c marker bed.

I n t e r n a l l y , a s h e e t - l i k e s t r a t i g r a p h i c u n i t may c o n s i s t of s e v e r a l

d i s t i n c t sandstone bodies t h a t may be l o c a l l y connected o r e n t i r e l y

sepa ra t ed by impermeable s h a l e l a y e r s .

nea r ly equidimensional o r e longa te i n shape.

e longa te s h o r e l i n e sands may have a wide a r e a l d i s t r i b u t i o n wi th in a

comparatively t h i n s t r a t i g r a p h i c i n t e r v a l , and consequently form a sheet-

- l i k e u n i t i n g r o s s dimensions.

o r i e n t a t i o n s of t hese e longa te sandstone bodies are p a r a l l e l t o t h e

o r i g i n a l c o a s t l i n e ; b u t t h e i n t e r v a l may a l s o i n c l u d e o t h e r e longa te

sandstone bod ies , o r i e n t e d approximately normal t o t h e c o a s t l i n e , t h a t

were formed as d i s t r i b u t a r y sands f i l l i n g channels cut i n t o t h e s h o r e l i n e

sands. In many cases t h e d i s t r i b u t a r y sands cannot r e a d i l y be d i s t ingu i shed

from the s h o r e l i n e sands wi th which they are a s s o c i a t e d , although v a r i a t i o n s

These s e p a r a t e bod ie s may be

A sequence of offlapping,

Within such an i n t e r v a l t h e p re fe r r ed

4

,,, Q ,x

ENVIRONM E NTS

LONGlTUDlNAl

TRANSVERSE

ALLUVIAL

( F L U V I A L )

E O L I A N

Figs. 1-2, 1-3 and 1-4

ALLUVIAL FANS

(APEX, MIDDLE 8 BASE OF F A N )

BRA I DED STREAMS

MEANDERING STREAMS

(ALLUVIAL VALLEY)

DUNES

STREAM FLOWS

VlSCOUS FLOWS

MEANDER B E L T S

F LOODBASINS

COASTAL DUNES

DESERT DUNES

OTHER DUNES

CHANNELS

SHEET F LOODS

“ S I E V E DEPOSITS” 4 I DEBRIS FLOWS 4

M U D FLOWS

CHANNELS (VARYING SIZES)

CHANNELS

NATURAL LEVEES

POlNT BARS

1 STREAMS, LAKES 8 SWAMPS

1

T Y P E S :

TRANSVERSE

S E l F ( LONGlTUDlN AL )

BARCHAN PARABOLIC

DOME-SHAPED

C l a s s i f i c a t i o n of depos i t iona l environments of sand bodies

and t h e i r r e l a t e d geomorphologic fea tures .

1972, and Bernard and Le Blanc, 1965).

( A f t e r Le Blanc,

5

DEPOSIT ION A L MODELS

O R A l D t D C H A N N t L S I W A I H t l l A N D A O A N D O N f D C M A N N f L 5

A L L U V I A L F A N U f N ,

M E A N D E R I N G STREAM

COASTAL DUNES

6

- ?: 1 L L

E N V IRO N M E N T S

I N N E R

2

a Z 0 c- Z

- v,

a pi I-

~~

DELTAIC

UPPER DELTAll

P L A I N

LOWER DELTAIC

P L A I N

F RlNGE

DISTAL

M E A N D E R BELTS

F LOODB A S INS

DlSTR IBUTARY C H A N N E L S

INTER- DISTRIBUTARY

AREAS

CHANNELS

NATURAL LEVEES

POINT BARS

ST REAMS, LAKES

& SWAMPS

C H A N N EL5

NATURAL LEVEE!

MARSH, LAKES,

TIDAL CHANNEL: & TIDAL FLATS

R I V E R - M O U T H BARS

BEACHES & BEACH RIDGES

TIDAL FLATS

F i g . 1-3. For c a p t i o n see p.4 .

7

DEPOSI TlON A L MODELS

B I RDFOOT - LOB ATE DELTA

MARINE C U R R E N l S

ESTUARINE DE1:A

ESTUARINE DELTA

8

COASTA L I N T E R -

D E L T A I C

S H A L L O W

M A R I N E

DEEP

M A R I N E

E N V l RON M E N T S

COASTAL P L A I N

‘ S U B A E R I A L )

S U B A Q U E O U S

SHELF

( N E R I T I C )

C A N Y O N S

F A N S (DELTAS)

SLOPE 8 ABYSSAL

TRENCHES & TROUGHS

BARRIER I S L A N D S

CHENIER P L A I N S

T I D A L

L A G O O N S

T I D A L C H A N N E L S

S M A L L ESTUAR I E S

INNER

M I D D L E

OUTER

BACK BAR, BARRIER, B E A C H ,

BARRIER FACE, SPITS & F L A T S ,

WASHOVER F A N

B E A C H & R IDGES

T IDAL FLATS

T I D A L FLATS

T I D A L DELTAS

S H O A L S 8 R E E F S

S H O A L S 8 B A N K S

F i g . 1-4. For c a p t i o n see p . 4 .

9

DEPOSITION A L MODELS

B A R R I E R IS . COMPLEX

C H E N I E R P L A I N

SHALLOW

MARINE

D E E P

MARINE

10

in grain gradation, which may be reflected in the geophysical log character-

istics, and in sedimentary structures and fossil content may be diagnostic.

Discrete sandstone bodies may be the products of erosion, such as

elongate strike-valley sands deposited along cuestas, or pod-shaped sand-

stone bodies formed as erosional outliers. Other elongate sandstone bodies,

particularly those that are sinuous or branching, some of which are referred

to as shoestring sands, owe their configuration entirely to depositional

control. Some have been variously interpreted as off-shore bars, barrier

islands, or channel sands depending on the criteria available or current

trend of geological thought.

Le Blanc (1972), after Bernard and Le Blanc (1965), set up a

classification (Figs. 1-2, 1-3 and 1-4) based on depositional environments

and geomorphology. Other classifications have been presented by Laporte

(1968), Selley (1970), Kukal (1971), and Crosby (1972). Le Blanc's

classification depends in part on the geometry of large sedimentary

accumulations such as deltas, barrier island complexes, and submarine fans,

but not on the geometry of individual sandstone bodies. Nevertheless,

where the geometry of a sedimentary accumulation is known, the probable

geometry and depositional trends of sandstone bodies contained within that

accumulation can be inferred. It is important to set up, as early as

possible during the course of exploration, a conceptual model of the

depositional relationships, bearing in mind that the model may be ephemeral

and is certain to be subject to modification. Such a model will serve as

a working basis with which to test the viability o f various interpretations

as new data come to hand.

The usefulness of such a model has been pointed out by Le Blanc

(1972, p. 135) who states, 'The realm of clastic sedimentation can be

divided into several conceptual models, each of which is characterized

by certain depositional environments, sedimentary processes, sequences,

11

and patterns.'

interpretation of geomorphic and environmental origins of oil and gas

fields in sandstone bodies.

This type of approach is of particular value in the

Porosity and permeability trends in sandstone bodies are commonly

influenced or controlled by depositional trends which in turn reflect geo-

morphic influences.

folding or faulting, the stratigraphic factors may be of minor importance to

the distribution of oil and gas.

trap, the sedimentologic and geomorphic factors, considered with reference

to other factors such as regional tilting of the strata and hydro-

dynamics of formation fluids, are additional keys to future exploration

for similar accumulations of hydrocarbons.

Where closure in a sandstone body is effected by

But in the case of a purely stratigraphic


13

Chapter 1

R I V E R CHANNELS

I n t r o d u c t i o n

Geomorphology

Channel d e p o s i t s , c o n s i s t i n g of sand , s i l t and c l a y , f i l l t h e

v a l l e y s c u t by a r i v e r system. The e r o s i o n a l s u r f a c e d i s s e c t e d by such

va l l eys may subsequent ly become an unconformity i n t h e s t r a t i g r a p h i c

sequence. The channel d e p o s i t s , which i n c l u d e sed iments f i l l i n g

subs id i a ry channels w i t h i n t h e main channel , can have a ve ry cons ide rab le

a e r i a l e x t e n t , as shown by Fig . 1-5, and i n t h e case of a l a r g e r i v e r

may range i n t h i c k n e s s t o more than 50 m. Within such d e p o s i t s t h e r e

may be numerous p o t e n t i a l t r a p s f o r o i l and gas i n s e p a r a t e sands tone

bodies .

The term channel sand impl i e s a c u t - a n d - f i l l o r i g i n . Channels,

which may have been c u t i n t o o l d e r s t ra ta exposed as an e r o s i o n a l s u r f a c e ,

or i n t o penecontemporaneous sed iments of t h e same r i v e r system, such as

flood p l a i n d e p o s i t s , may subsequent ly b e f i l l e d wi th sand.

l ag between c u t t i n g and f i l l i n g , w i t h i n t h e same r i v e r cour se o r branch ,

may be n e g l i g i b l e and t h e two p rocesses can b e cons idered a s contemporaneous

The t i m e

Channel sands are depos i t ed w i t h i n an a l l u v i a l v a l l e y , o r on t h e

upper p a r t of a d e l t a p l a i n .

d e l t a p l a i n , t h e r i v e r d i s t r i b u t a r i e s form channe l - l i ke sand bodies by a

process of d e p o s i t i o n w i t h i n t h e i r own cour ses , each d i s t r i b u t a r y flowing

out t o sea w i t h i n t h e conf ines of i t s own l evee . D i s t r i b u t a r y sands ,

commonly r e f e r r e d t o as ' s h o e s t r i n g sands' can be d i s t i n g u i s h e d from channel

sands by s e v e r a l c r i t e r i a which w i l l b e d i scussed i n t h e fo l lowing pages.

F a r t h e r down a r i v e r system, on t h e lower

14

Fig. 1-5 A l l u v i a l v a l l e y and d e l t a p l a i n of t h e M i s s i s s i p p i River .

The a l l u v i a l v a l l e y i s u n d e r l a i n by r i v e r d e p o s i t s commonly

150-200 f e e t (46-61m) t h i c k . (Redrawn from F i s k , 1947).

I n d i v i d u a l sand b o d i e s , f i l l i n g e r o s i o n a l f e a t u r e s c u t by a r i v e r ,

may b e e l o n g a t e o r a r c u a t e depending on t h e course of t h e r i v e r . A s t he

r i v e r cour se undergoes minor changes, t h e s e sand bod ies may be e n t i r e l y

o r p a r t l y re-worked, o r may coa le sce wi th younger sand bod ies t o form a

15

Fig. 1-6 General ized d i s t r i b u t i o n of meander b e l t s of a l a r g e r i v e r

'A' such a s t h e M i s s i s s i p p i , and a s m a l l r i v e r ' B ' .

f a i r l y s t r a i g h t o r meandering b e l t up t o s e v e r a l m i l e s wide (Fig. 1-6).

Such b e l t s have been t r aced i n the subsurface f o r more than 50 km (Figs

1-34, 1-36, 1-44, 1-50, 1-51). Major changes i n a r i v e r course r e s u l t i n

both l a t e r a l s h i f t s of t h e o ld meander b e l t and i n t h e development of new

b e l t s . These may even tua l ly coalesce t o form an anastomosing system of

channel sands wi th in a broad v a l l e y . I n t h e case of a l a r g e r i v e r such

a s the Miss i s s ipp i (Fig. 1 - 5 ) , such a v a l l e y can be up t o 150 km i n width

and 1,000km i n length.

16

It w i l l b e noted t h a t a d i s t i n c t i o n has been made between sand bodies

formed by t h e f i l l i n g of an e r o s i o n a l channel and those formed by a d e l t a

d i s t r i b u t a r y t h a t b u i l d s r a t h e r t han c u t s i t s course . Both sand bod ies

may have s u p e r f i c i a l resemblances in t h a t bo th are narrow, l i n e a r , and

d e p o s i t e d by a r i v e r . On c l o s e r examinat ion , t h e assemblage of g ra in - s i ze

d i s t r i b u t i o n , g r a i n g r a d a t i o n , sed imentary s t r u c t u r e s , and p a l e o n t o l o g i c a l

a s s o c i a t i o n s a f f o r d cr i ter ia which d i s t i n g u i s h t h e i r o r i g i n s . These

f a c t o r s , which have been d e a l t w i t h i n g r e a t d e t a i l i n t h e l i t e r a t u r e ,

w i l l be d i scussed la ter . But i t i s recognized t h a t e r o s i o n a l channels

are a l s o formed and f i l l e d w i t h sand i n s h o r e l i n e environments. The

i n - f i l l i n g sand bod ies are n o t p o i n t b a r d e p o s i t s , a l though they may show

c e r t a i n s imi la r i t i es such as g r a i n g r a d a t i o n and p l a n a r cross-bedding.

The l a t t e r sed imentary f e a t u r e i s common i n e s t u a r i e s where t h e development

of c u t - a n d - f i l l d e p o s i t s of sand is s t r o n g l y in f luenced by t i d a l movements.

Channel s ands , (sensu s t r i c t o ) , are depos i t ed as a l l u v i a l sed iments

i n a r ive r -cu t channel . A s such , they c o n s i s t l a r g e l y o f p o i n t b a r

d e p o s i t s . P o i n t b a r s develop a long t h e i n n e r curve of a main l o o p o r

meander of a r i v e r . A s t h e r i v e r c u t s i n t o t h e bank along t h e o u t e r

edge of i t s cu rve , t h e p o i n t b a r grows by a c c r e t i o n (F ig . 1-7) . The

b a s a l p a r t of t h e p o i n t b a r , c o n s i s t i n g of t h e c o a r s e s t f r a c t i o n s of

t h e load such as coa r se sand , g r i t , and g r a v e l , is depos i t ed ad jacen t

t o the undercut bank i n t h e deepes t p a r t o f t h e r i v e r where t h e c u r r e n t

i s s t r o n g e s t . On t h e more g e n t l y s lop ing i n n e r bank of t h e r i v e r , where

s p i l l - o v e r b a r s and l a r g e r i p p l e s of medium t o f i n e sand a r e formed, t h e

cross-bedded middle p o r t i o n of t h e p o i n t b a r i s depos i t ed . The upper

p o r t i o n of t h e p o i n t b a r i s normally above r i v e r l e v e l and i s formed

dur ing t i m e s of f l ood when heavy loads of f i n e sand , s i l t and mud a r e

depos i t ed i n sha l lower water where t h e v e l o c i t y i s lower than i n t h e na in

channel . The uppermost beds a r e e s s e n t i a l l y h o r i z o n t a l b u t a l s o show

17

SP

0 FEE1

0 500 !50

FEET 0 100 m

Fig . 1-7 Diagramat ic s e c t i o n through a r i v e r p o i n t b a r d e p o s i t t o

i l l u s t r a t e t h e g r a d a t i o n from coa r se sand , g r i t , and g r a v e l

(1) a t t h e b a s e , through cross-bedded sands (2) t o h o r i z o n t a l

and r i p p l e d beds of f i n e sand and s i l t ( 3 ) . The s u r f a c e of t h e

r i v e r i s shown dur ing a low water s t a g e .

a t y p i c a l E-log s e l f - p o t e n f i a l cu rve t o t h e g r a i n g r a d a t i o n

is a l s o shown. The arrow p o i n t s t o t h e d i r e c t i o n of growth

of t h e p o i n t b a r .

The r e l a t i o n s h i p of

small-scale cross-bedding, commonly of t h e c l imbing v a r i e t y i l l u s t r a t e d

by Conybeare and Crook (1968, p l a t e 17) , formed by s m a l l r i p p l e s .

E-log C h a r a c t e r i s t i c s

A s a r i v e r moves back and f o r t h a c r o s s i t s meander b e l t i t c u t s

i n t o o l d e r p o i n t b a r d e p o s i t s and r e d i s t r i b u t e s t h e sed iments . The new

channel may n o t c u t down t o t h e base of t h e o ld . Consequently, w i t h i n

a t h i c k a l l u v i a l s e c t i o n , t h e sequence shown i n F ig . 1-7 could b e

r epea ted i n whole o r i n p a r t s e v e r a l times, bu t always i n t h a t o rde r .

This sequence of g r a i n g r a d a t i o n , from c o a r s e r below t o f i n e r above, is

c h a r a c t e r i s t i c of a l l u v i a l d e p o s i t s and is commonly r e f l e c t e d i n t h e

s e l f - p o t e n t i a l E-log curve as a be l l - shape , o r i n t h e case of s e v e r a l

superimposed b u t incomplete sequences , a s a block-shape. These shapes ,

c h a r a c t e r i s t i c of cu t - and- f i l l sands tone channel d e p o s i t s , commonly show

a marked d e f l e c t i o n a t t h e base of t h e sands tone u n i t , i n d i c a t i n g an

18

abrup t e r o s i o n a l c o n t a c t . With upward dec reas ing g r a i n s i z e t h e

d e f l e c t i o n of t h e s e l f - p o t e n t i a l curve a l s o dec reases t o form a b e l l -

shape . I n t h e case of s ands tone bod ies of uniform g r a i n s i z e , such as

those depos i t ed by d e l t a d i s t r i b u t a r i e s and those t h a t have been formed

as p o i n t b a r complexes by success ive t r u n c a t i o n and d e p o s i t i o n , t h e

shape of t h e s e l f - p o t e n t i a l curve is c y l i n d r i c a l o r blocky. A l l u v i a l

s ands tone bod ies f i l l i n g channels are commonly of t h e l a t t e r type as

shown i n F ig . 1-8.

C D

Fig . 1-8 Diagrammatic E-log s e c t i o n showing an e r o s i o n a l channel f i l l e d

wi th a l l u v i a l s ands tone , o v e r l a i n by a l t e r n a t i n g beds of

s ands tone and mudstone. Note t h e b locky c h a r a c t e r i s t i c of

of t h e s e l f - p o t e n t i a l curve of t h e v a l l e y - f i l l sands tone .

(Af t e r P i r s o n , 1970, cour t e sy of Schlumberger Well Se rv ices ) .

The s e l f - p o t e n t i a l curve g ives an i n d i c a t i o n of pe rmeab i l i t y which

a p a r t from t h e e f f e c t s of cementa t ion caused by t h e i n t r o d u c t i o n of

c a l c i t e , e t c . and d i a g e n e s i s , is commonly r e l a t e d t o t h e c l a y con ten t

of t h e m a t r i x i n t h e o r i g i n a l sand . In g e n e r a l t h e coa r se r t h e sand t h e

lower t h e c l a y con ten t and h i g h e r t h e Pe rmeab i l i t y . Secondary cement-

a t i o n of t h e m a t r i x and s e v e r e compaction of t h e sands tone w i l l a l s o

a f f e c t t h e pe rmeab i l i t y and t h e degree of d e f l e c t i o n of t h e s e l f - p o t e n t i a l

19

curve. Consequently, t h e shape of t h e s e l f - p o t e n t i a l cu rve , a s an

i n d i c a t o r of g r a i n - s i z e g r a d a t i o n , must b e used w i t h cau t ion .

An example of t h e r e l a t i o n s h i p commonly o b t a i n i n g between g ra in - s i ze

g rada t ion and t h e shape of t h e s e l f - p o t e n t i a l curve is shown i n F ig . 1-9

which c o n t r a s t s t h e c h a r a c t e r i s t i c s of sands tones of mar ine and a l l u v i a l

o r i g i n s . Lower Cre t ac ious v a l l e y - f i l l sands (VF) of t h e Denver Bas in ,

o v e r l a i n by t h e Huntsman Formation and u n d e r l a i n by t h e "52" Sandstone

and S k u l l Creek Formation, have bo th b locky and be l l - shaped s e l f - p o t e n t i a l

POROSITY MEDIAN GRAIN

.I.. ... , . . . . . . . . . _ _ . 'I: :;)V F1 ;:. . . . . ; . . .

. __ . . . 4 : :;: AJ.F:i

E - L O G S OF

, .05SIZE mm.

c

a

5

A

B

CRETACEOUS MARINE (A) AND RIVER (6) SANDS, NEBRASKA

Fig. 1-9 E-log c h a r a c t e r i s t i c s r e l a t e d t o g r a i n s i z e and p o r o s i t y i n

t h e Lower Cre taceous "52" and v a l l e y - f i l l (VF) sands tones ,

Denver Basin, Nebraska. (Redrawn from H a r m s , 1966).

20

curves which r e f l e c t r e spec t ive ly a uniform g r a i n s i z e and a g rada t ion

from coa r se r below t o f i n e r above.

s i z e t h e r e a l s o appears t o be l i t t l e v a r i a t i o n i n pe rmeab i l i t y , al though

p o r o s i t y inc reases toward t h e base of t he sandstone body.

showing an inc rease of g r a i n s i z e toward t h e base of t h e u n i t both permeab-

i l i t y and po ros i ty i n c r e a s e , a s i nd ica t ed by t h e s e l f - p o t e n t i a l curve. I n

c o n t r a s t t h e “52” sandstone, which o r i g i n a t e d a s a r eg res s ive marine

s h o r e l i n e sand, shows a decrease of p o r o s i t y , permeabi l i ty and g r a i n s i z e

toward t h e base of t h e sandstone body.

In t h e example showing a uniform g r a i n

In t h e example

I n t h i s example t h e main o i l and gas product ion comes from t h e

v a l l e y - f i l l sandstone u n i t s , but some is a l s o obtained from t h e marine

s h o r e l i n e sandstones.

wide and 15 m t h i c k , t r ends north-south and has been t r aced f o r 40 km.

Seven f i e l d s have been loca ted along t h i s t rend where t h e axes of north-

-west-plunging a n t i c l i n e s c ros s t h e t rend of t h e anc ien t va l l ey .

The main v a l l e y - f i l l u n i t , which i s above 450 km

Fig. 1-10 S e l f - p o t e n t i a l curves of e l e c t r i c l o g s , and general ized

s e c t i o n s of p o i n t b a r and channel f i l l d e p o s i t s , showing

bel l -shape and cylinder-shape c h a r a c t e r i s t i c s of t h e log

and t h e i r r e l a t i o n s h i p t o a l l u v i a l and d e l t a i c po in t b a r

and c h a n n e l - f i l l depos i t s . Arrow i n d i c a t e s d i r e c t i o n of

growth of p o i n t b a r . A - Upper Cretaceous Tuscaloosa

Sandstone, Wisner F i e l d , Louisiana. B - Oligocene 19B

Sandstone, Seel igson F i e l d , Texas. C - Lower Cretaceous

Blairmore Sandstone, Carbon F i e l d , A lbe r t a . D - Upper

Cretaceous Tuscaloosa “4” Sandstone, L i t t l e Creek F i e l d ,

Miss i s s ipp i .

F i e l d , Louisiana.

Club F i e l d , Louis iana.

E - Miocene “MI’ Sandstone, West Lake Ver re t

F - Miocene ” S ” Sandstone, De l t a Duck

21

RIVER DEPOSITS ALLUVIAL A N D DELTA DISTRIBUTARY

c W Lu

SP LL

0 -+

100 POINT BAR DEPOSll

ro

C H A N N E L F I L L DEPOSIT

22

Other examples of t h e c h a r a c t e r i s t i c s of E-log s e l f - p o t e n t i a l

curves of r i v e r p o i n t b a r and channel d e p o s i t s a r e shown i n Fig. 1-10.

The upper t h r e e examples are as fol lows:

Sandstone, Wisner F i e l d , Louis iana; B - Oligocene 19B Sandstone, Seel igson

F i e l d , Texas; and C - Lower Cretaceous Blairmore Sandstone, Carbon F i e l d ,

A lbe r t a . A l l show t h e t y p i c a l bel l -shape c h a r a c t e r i s t i c of a l l u v i a l

sandstone grading from c o a r s e r a t t h e base t o f i n e r a t t h e top. These

sandstones are i n t e r p r e t e d as having o r i g i n a l l y been p o i n t b a r d e p o s i t s .

The lower t h r e e examples have a blocky o r c y l i n d r i c a l shape c h a r a c t e r i s t i c

of sand bod ies of uniform g r a i n s i z e , o r of a sequence of success ive ly

t runca ted graded beds. They inc lude t h e fol lowing: D - Upper Cretaceous

Tuscaloosa "Q" Sandstone, L i t t l e Creek F i e l d , M i s s i s s i p p i ; E - Miocene "M"

Sandstone, West Lake Verret F i e l d , Louis iana; and F - Miocene "S" Sandstone,

Delta Duck Club F i e l d , Louis iana. These examples a r e considered t o have

been d e l t a d i s t r i b u t a r y sands . The paleogeographic d i s t i n c t i o n made between

t h e upper and lower examples is somewhat a r b i t r a r y .

sand i n t h e middle t o upper reaches of a r i v e r system shows d i s t i n c t g r a i n

g r a d a t i o n of t h e p o i n t b a r t ype , whereas sand i n t h e lower r eaches ,

p a r t i c u l a r l y i n d e l t a d i s t r i b u t a r i e s , shows much less g rada t ion and

comonly has a f a i r l y uniform g r a i n s i z e .

A - Upper Cretaceous Tuscaloosa

I n g e n e r a l , a l l u v i a l

K r a f t , Sheridan and Maisano (1971, p. 671-672) show another example

of bel l -shaped s e l f - p o t e n t i a l curves .

channel sands i n t h e Lower Cretaceous Potomac Group i n Delaware (Fig. 1-11).

They s ta te , " S p o l j a r i c (1967) p re sen ted a d e t a i l e d a n a l y s i s of Potomac

channel sands (Fig. 12) . A sand i s o l i t h contour map of one of t h e

meandering Potomac sand u n i t s r e v e a l s t h a t t h i s Lower Cretaceous nonmarine

sequence might w e l l i nco rpora t e cond i t ions s u i t a b l e f o r petroleum entrap-

ment, p a r t i c u l a r l y in t hose areas where t h e Potomac Group sands and t h e i r

equ iva len t s are more deeply bu r i ed i n t h e Baltimore Canyon trough. I n

These are of meandering r i v e r

23

SP R

F i g . 1-11 E-log of s e c t i o n through stream c h a n n e l s a n d s t o n e s ( s t i p p l e d )

and f l o o d p l a i n d e p o s i t s of s i l t s t o n e and mudstone, i n t h e

Lower C r e t a c e o u s Potomac Group of Delaware.

shaped E-log c h a r a c t e r of t h e c h a n n e l s a n d s t o n e s .

from K r a f t , S h e r i d a n and Maisano, 1971, a f t e r S p o l j a r i c , 1967).

Note t h e b e l l -

(Redrawn

s i t u a t i o n s such as b r a i d e d stream and f l o o d p l a i n areas where t h e Potomac

s a n d s compr ise up t o 50 p e r c e n t of che t o t a l sequence , i t i s u n l i k e l y t h a t

s e p a r a t e d i s t i n c t t r a p s would h a v e formed. Hosrever, where l a t e r a l f a c i e s

changes o c c u r i n Arundel t y p e p a l u d a l o r backswamp l i t h o l o g i e s , and sands

c o n s t i t u t e a p p r o x i m a t e l y 20 p e r c e n t of t h e t o t a l s e c t i o n , a d i s t i n c t

s e p a r a t i o n of sand b o d i e s is more l i k e l y , w i t h updip en t rapment p o s s i b i l i t i e s

i n meandering c h a n n e l sands".

Compaction

Some of t h e problems i n v o l v i n g d i f f e r e n t i a l compaction and i n t e r -

p r e t a t i o n of t h e g e n e s i s of s a n d s t o n e b o d i e s are i l l u s t r a t e d i n F i g s .

24

PEPOSITION I

Fig. 1-12 Diagrammatic sections showing A , erosional channel in

compacted shale and overlying uncompacted clay;

fill sand and flanking clay undergoing compaction;

compacted clay and warped sand body overlain by sediments

draped by differential compaction. (After Pirson, 1970,

courtesy of World Oil).

B, channel-

and C,

1-12 and 1-13. These problems have been pointed out by Rittenhouse (1961),

Oswaldt and Sens (19631, P i r s o n (19701, and Pettijohn, Potter and Siever

(1972). Interpretation of the original geometry of a sandstone body, in

particular whether it formed a bar-shaped mound or filled an erosional

channel, depends on its relationship to the enclosing beds. If some thin

bed or zone within a bed can be chosen as a time-stratigraphic marker, then

certain assumptions can be made regarding differential compaction of the

25

Before Compaction

Surface of Sediment - - ~ a

~- - ~ ~ ~ ~ _. ~ ~ -. . ~ ~ ~ ~ SIDERITE::

-++-&FIXED SUBSTRATUM-~+L+&&

After Compaction

a

Fig. 1-13 Cross-sections showing distortion of a sand body (lower)

resulting from compaction of a channel sand (above).

(Modified by Pettijohn, Potter and Siever, 1972, after

Dupuy, Oswaldt and Sens, 1963) .

sandstone body and its enclosing strata.

then interpretation is likely to be equivocal. In all cases, the use of a

marker implies certain assumptions as to its configuration at the time of

deposition. Commonly, it is assumed that a marker was a fairly flat surface,

possibly with minor undulations but with very little warping or tilting.

These tacit assumptions can in some cases be misleading. In particular, it

is obvious that the choice of a marker either above or below a linear

sandstone body can lead to quite different interpretations. In the former

case it may be concluded that the sandstone body was originally a channel-

If such a marker is not available,

26

- f i l l d e p o s i t , whereas i n t h e l a t t e r case t h e sands tone body may r e p r e s e n t

a sand "build-up' ' such as a b a r o r b a r r i e r i s l a n d ,

e i t h e r i n t e r p r e t a t i o n , i n a s s o c i a t i o n wi th t h e i n f e r r e d pa leogeographic t r e n d s ,

w i l l have a b e a r i n g on t h e d i r e c t i o n i n which a sands tone t r e n d i s ex t r a -

po la t ed .

The i m p l i c a t i o n of

Ancient Sand Bodies

F l u v i a t i l e sed iments a r e known w i t h i n a l l sequences from t h e

Precambrian System t o t h e Quaternary System. But o i l and gas accumul-

a t i o n s i n f l u v i a t i l e sed iments are known on ly i n Devonian and younger rocks .

Some of t h e known examples of a n c i e n t f l u v i a t i l e sed iments have been

demonstrated t o b e channel sands . The c r i t e r i a f o r such r e c o g n i t i o n a r e

mainly geometry of t h e sands tone body, sequences o f g r a i n g r a d a t i o n , and

sed imentary s t r u c t u r e s as i n d i c a t e d by d r i l l - h o l e and ou tc rop d a t a . The

p resence of c e r t a i n s h e l l s , commonly f resh-water gas t ropods and b i v a l v e s ,

and of abundant carbonized wood fragments i s probably i n d i c a t i v e of a

non-marine o r i g i n , a l though bo th can be t r a n s p o r t e d t o an e s t u a r i n e o r

c o a s t a l sand environment. P l a n t m a t t e r is a l s o known t o be f a i r l y abundant

i n some deep-water d e p o s i t s such as t h e f a n formed by t u r b i d i t y c u r r e n t s

sweeping down t h e submarine canyon of t h e Congo R ive r (Shepard, 1965).

Composition and s o r t i n g a r e n o t d e f i n i t i v e of d e p o s i t i o n a l environ-

ment, a l though i n g e n e r a l , poor ly s o r t e d sands tones t h a t are k a o l i n i t i c

and q u a r t z o s e , bu t w i th a f a i r l y l a r g e percentage of l i t h i c f ragments ,

a r e l i k e l y t o b e of f l u v i a t i l e o r i g i n , formed e i t h e r a s channel sands i n

a r i v e r system o r a s b ra ided stream d e p o s i t s on an a l l u v i a l f an . F l u v i a t i l e

s ands depos i t ed by d e l t a d i s t r i b u t a r i e s a r e a l s o qua r t zose , b u t g e n e r a l l y

f ine -g ra ined , w e l l s o r t e d , and n o t r e a d i l y d i s t i n g u i s h e d by l i t h o l o g y from

marine s h o r e l i n e sands .

The o l d e s t known f l u v i a t i l e d e p o s i t s , i nc lud ing t h e Torr idonian

27

Formation of S c o t l a n d , are P r o t e r o z o i c . The o l d e s t known f l u v i a t i l e

d e p o s i t s of t h e Cambrian System are molasse s e d i m e n t s of t h e w e s t e r n

S i b e r i a n P l a t f o r m .

d e l i n e a t e d f o r d i s t a n c e s of s e v e r a l m i l e s a r e t h e O r d o v i c i a n P u l a s k i and

F a y e t t v i l l e Channels of Tennessee.

The o l d e s t known c h a n n e l sand d e p o s i t s t h a t have been

P u l a s k i and F a y e t t v i l l e Channels , Tennessee

The Upper O r d o v i c i a n (Richmondian) Pulaslci Channel and F a y e t t v i l l e

7,

0-1 10 MILES

ORDOVICIAN PULASKI CHANNEL

TENNESSEE

Fig. 1-14 Map and s e c t i o n s of t h e O r d o v i c i a n P u l a s k i and F a y e t t e v i l l e

r i v e r c h a n n e l s i n Giles and L i n c o l n c o u n t i e s , Tennessee.

(Redrawn from Wilson, 1948).

Channel (F ig . 1-14) i n Tennessee are l o c a l l y exposed by ou tc rops . The

P u l a s k i Channel, en t renched i n Lower Ordovic ian (Trentonian) l imes tone , i s

up t o 40 m deep , h a s a wid th i n t h e range 300-750 m, and has been t r a c e d

i n l e n g t h f o r more than 50 km. The b a s a l p a r t of t h i s channel i s f i l l e d

wi th q u a r t z o s e , conglomera t ic g r i t s t o n e and abundant rubb le of l imes tone

cobbles and bou lde r s . Above t h e b a s a l s e c t i o n , bu t w i t h i n t h e lower p a r t

of t h e channe l , t h e f i l l c o n s i s t s of coa r se sands tone con ta in ing a f a i r l y

h igh pe rcen tage of well-rounded q u a r t z g r a i n s . Some outcrops of sands tone

a r e up t o 10 m t h i c k and show cross-bedding i n d i c a t i n g a g e n e r a l c u r r e n t

d i r e c t i o n from s o u t h e a s t t o nor thwes t . The sands tone u n i t is o v e r l a i n

by g rey i sh green s h a l e which f i l l s t h e v a l l e y and i s i n t u r n o v e r l a i n by

sands tone and l imes tone .

I t i s of i n t e r e s t t o n o t e t h a t t h e d i r e c t i o n of t r a n s p o r t of t h e

s a n d , a s i n d i c a t e d by c ross -beddinp ,appears t o be a t v a r i a n c e wi th t h e

i n t e r p r e t a t i o n of r e g i o n a l Richmondian geography, accord ing t o Wilson

0 9 4 8 , p. 7 4 3 ) who s t a t e s , "These d i r e c t i o n s are upstream w i t h r e f e r e n c e

t o t h e d i r e c t i o n t h e e rod ing stream flowed; landward w i t h r e f e r e n c e t o

t h e invading sea".

a t t r i b u t e s t h e d i r e c t i o n of c u r r e n t bedding t o t h e e f f e c t of t i d a l bo res .

The s h a l e s f i l l i n g t h e upper p a r t of t h e channel a r e a l s o cons idered t o have

been depos i t ed i n an e s t u a r i n e environment t o t h e nor thwes t of an encroaching

sea.

H e r e f e r s t o t h e s e sands as e s t u a r i n e and presumably

Bedford Channels, Ohio

The Bedford Channels (F ig . 1-15), which l i e w i t h i n r ed s h a l e s of t h e

Miss i s s ipp ian Bedford Formation i n Ohio, a r e f i l l e d wi th q u a r t z o s e sands tone

and form a s inuous p a t t e r n t h a t has been t r a c e d f o r 100 km i n a nor th-south

d i r e c t i o n . The p a t t e r n shows a marked s i m i l a r i t y t o p a t t e r n s of meander

loops of t h e M i s s i s s i p p i R ive r , and i s i n t e r p r e t e d as a d ra inage system

29

CHANNEL S A N D S

A- MISSISSIPPI RIVER

6-MISSISSIPPIAN BEDFORD

F O R M A T I O N , OHIO

M I L E S

Fig. 1-15 A - Channels of t h e M i s s i s s i p p i R ive r n e a r Natchez,

M i s s i s s i p p i . Drainage from n o r t h t o sou th . (Redrawn

from F i s k , 1 9 4 4 ) .

B - Channel sands w i t h i n t h e M i s s i s s i p p i a n Bedford Formation

i n n o r t h e r n Ohio. Drainage from n o r t h t o s o u t h . Same

s c a l e a s ( A ) . (Redrawn from Pepper , D e W i t t , and

Demarest, 1 9 5 4 ) .

wi th in t h e Bedford De l t a .

channels c o n s t i t u t e s t h e b a s a l u n i t of t h e ove r ly ing Miss i s s ipp ian Berea

Sandstone. Th i s b a s a l u n i t of sands tone ocdupies channels c u t i n t o t h e

Bedford Formation and a l s o l o c a l l y i n t o t h e under ly ing Cleveland Member

of t h e Upper Devonian Ohio Shale .

A s l i g h t l y younger system of sands tone - f i l l ed

Nany o f t h e s e channels communly have a

30

width i n t h e range 300-600 m , and depths of up t o 60 m. O i l and gas

p roduc t ion has been ob ta ined from t h e s e younger channels (F ig . 1-28),

i nc lud ing t h e Cabin Creek Channel. I n t h e Cabin Creek F i e l d (F ig . 1-27)

gas is ob ta ined from f r i a b l e qua r t zose sands tone o v e r l a i n by a cap rock of

s i l i c i f i e d q u a r t z i t i c sands tone . Pepper, D e W i t t and Demarest (1954) are

of t h e op in ion t h a t s i l i c i f i c a t i o n of t h e qua r t zose sands tone r e s u l t e d

from downward cementa t ion of t h e s a n d - f i l l e d channel .

COAL N 0 . 7

A

L 200 B 0 1

O-' - K M MILE

PENNSYLVANIAN CHANNEL SAND,

ILLINOIS

0

lOOln

F ig . 1-16 A - Cross-sec t ion of Anvil Rock Sandstone, a Pennsylvanian

channel sand , i n t h e I l l i n o i s Basin. Coal seam Yo. 7

is t aken as a datum. (Redrawn from P o t t e r , 1963).

B - R e i n t e r p r e t a t i o n of (A) t o show p o s s i b l e concordance of

e l e v a t i o n of remnants of r i v e r v a l l e y terraces.

31

Anvil Rock Channel, I l l i n o i s

The Pennsylvanian Anvil Rock Sandstone of t h e I l l i n o i s Basin f i l l s

channels formed by streams which meandered down a paleoslope and cu t i n t o

d e l t a i c shee t - l i ke sands (Hopkins, 1958; P o t t e r and Simon, 1961). The

s e c t i o n i l l u s t r a t e d by Fig. 1-16 shows one channel t o have a width of more

than 5 km and a th i ckness of n e a r l y 60 m.

A s mentioned e a r l i e r , i n t h e s e c t i o n on compaction of channel sands,

t he choice of a datum may i n i t s e l f have i m p l i c i t assumptions a s t o the

genesis and o r i g i n a l geometry of a sandstone body. I n cons t ruc t ing the

shape of a l i n e a r sandstone body t h a t may have o r i g i n a t e d a s a channe l - f i l l

sand, a datum can be taken below, a t t h e base , a t t h e top, o r above t h e

sandstone body. I f t he sandstone body was, i n f a c t , deposi ted a s a channel

sand, then a datum taken on some s t r a t i g r a p h i c marker below t h e body may not

be meaningful, a s t h e marker would commonly be deformed by compaction

occurr ing during t h e growth of t h e ove r ly ing sand body.

sand body d i r e c t l y overlying an unconformity, a marker beldw t h e sand body

may have been t i l t e d o r otherwise deformed p r i o r t o t h e depos i t i on of t h e

sand. S i m i l a r l y , i f t h e sand body was o r i g i n a l l y a channel sand, a datum

taken a t t h e base of t h e body o r channel would obviously r e s u l t i n an

erroneous r econs t ruc t ion . A datum taken a t t h e top of t h e sand body w i l l

g ive a reasonable r econs t ruc t ion of t he c ros s - sec t iona l shape of t h e

channel sand a t t h e time i t was i n i t i a l l y bu r i ed , provided the su r face was

nea r ly f l a t .

s t r a t i g r a p h i c marker above, bu t c l o s e t o t h e upper s u r f a c e of t h e sand body

w i l l r e s u l t i n t h e b e s t r econs t ruc t ion and may f a c i l i t a t e t h e i n t e r p r e t a t i o n

of s t r u c t u r a l l y high p a r t s of t he sandstone u n i t formed a s e r o s i o n a l

remnants of r i v e r v a l l e y t e r r a c e s , and buried a s sand h i l l s . Provided they

have c l o s u r e , t hese "highs" can form r e s e r v o i r s f o r o i l and gas such a s the

B e l l s h i l l Lake, Hughenden, and Al l i ance f i e l d s i n t h e Lower Cretaceous

E l l e r s l i e Sandstone of Alberta (Figs. 1-41, 1-42, 1-43).

In t h e case of a

But t h i s may seldom be t h e case. A datum taken on some

32

SCALE

0- 6 MILES

Fig. 1-17 Map showing t h e conf igu ra t ion of a channel sand wi th in t h e

No . 5 coa l seam of t h e Pennsylvanian Carbondale Formation i n

sou theas t e rn I l l i n o i s . Medium coa l is more than 5 f e e t

(1.5m) t h i c k . (Wanless, 1970, a f t e r T r e s c o t t , 1964, and

V a i l , 1965).

33

Carbondale Channel, I l l i n o i s

The Carbondale Channel of sou theas t e rn I l l i n o i s is an i n t e r e s t i n g

example of an anc ien t meandering stream t h a t flowed through a f l a t t e r r a i n

of marsh and swamp. Within t h e Pennsylvanian Carbondale Formation t h e No. 5

coal zone con ta ins a sandstone body t h a t o r i g i n a t e d as a c h a n n e l - f i l l sand.

Reconstructed i n cons ide rab le d e t a i l (Fig. 1-17) from subsu r face d a t a , t he

channel appears t o have been p a r t of t h e drainage system of a f l a t , marshy

land t h a t probably formed p a r t of a d e l t a complex.

shown t o be approximately 2 km i n wid th , can be t r a c e d f o r 100 km. With

r e fe rence t o t h i s channel Wanless (1970, p. 288) says "Because t h e sandstone

does n o t extend s t r a t i g r a p h i c a l l y h ighe r than t h e c o a l , i t does n o t seem

l i k e l y t h a t t h e c o a l w a s depos i t ed and s w s e q u e n t l y c u t ou t by e ros ion ,

b u t i n s t e a d t h e r i v e r w a s d i scha rg ing through the winding channel while

t he c o a l w a s forming i n t h e ad jacen t swamp". It i s of i n t e r e s t t o no te

t h a t t h e t h i c k e r c o a l seams are loca ted i n a 10 - 15 km-wide b e l t along

which

which vege ta t ion accumulated more r a p i d l y than on t h e ad jacen t uplands.

The channel , which i s

t h e channel meanders, sugges t ing t h a t t h i s b e l t formed a v a l l e y i n

Fig. 1-18 i l l u s t r a t e s ano the r example of a Pennsylvanian channel

sandstone i n t h e I l l i n o i s Basin. This sandstone body ranges up t o 25 m

t h i c k and has been t r a c e d alongameandering course f o r more than 30 km.

The p a t t e r n of t h e isopach map i s t y p i c a l of p a t t e r n s r e s u l t i n g from t h e

superimposi t ion of anastomosing t r i b u t a r i e s d ra in ing i n t o t h e main

channel , and probably i n d i c a t e s a d ra inage p a t t e r n on a f a i r l y f l a t

t e r r a i n .

Another example of a channel c u t i n t o a coal-bearing s e c t i o n

(Fig. 1-19) is given by Wier (1953). This channel , f i l l e d wi th cross-

-bedded sandstone, is w i t h i n t h e Pennsylvanian Petersburgh Formation of

t h e I l l i n o i s Basin.

a width i n excess of 2 km, has been t r a c e d f o r s e v e r a l k i lome te r s i n an

The channel , which has a th i ckness of up t o 20 m and

34

0 0

w 1-20

0 21-80

0 2 L 6 8km

0 I 2 3 L 5miles

I I I I I I I I

F i g . 1-18 I s o p a c h map of a P e n n s y l v a n i a n s a n d s t o n e i n t h e I l l i n o i s

B a s i n , showing t h i c k n e s s i n f e e t of a meandering body.

(Modified by P e t t i j o h n , P o t t e r and S i e v e r , 1972, a f t e r

P o t t e r , 1963).

e a s t - w e s t d i r e c t i o n . The a t t i t u d e of t h e c ross -bedding i n d i c a t e s t h a t

t h e c u r r e n t f lowed t o t h e w e s t . The c h a n n e l i s b e l i e v e d t o have been

formed by a d e l t a d i s t r i b u t a r y t h a t f lowed through a low-lying c o a s t a l

marsh. The c h a n n e l is o v e r l a i n by s i l t s t o n e a n d , of p a r t i c u l a r i n t e r e s t ,

by l e n t i c u l a r beds of l i m e s t o n e . T h i s s t r a t i g r a p h i c s u c c e s s i o n s u g g e s t s

t h a t t h e d e p o s i t i o n a l environment may have been s imilar t o t h a t s e e n today

i n p a r t s of F l o r i d a , as d e s c r i b e d by Spackman, S c h o l l , and T a f t (1964).

35

V

F E E T

K M

M I L E

SANDSTONE CHANNEL IN COAL SEAM,

P E N N SYLVAN I A N PETE RSBU RG H FOR M A TI 0 N, I NDI A N A

0

25 m

Fig. 1-19 Cross-bedded sandstone channel formed i n a washout, i n

Coal V , Pennsylvanian Petersburgh Formation, I l l i n o i s

Basin, P ike County, Indiana. (Redrawn from Wier, 1953).

u 1 K M M I L L S

300 i too8

CROSS-SECTION OF CHANNEL SANDSTONES,

P E N N SYLVAN IAN G R A H A M FO R M AT I 0 N,

BRAZOS BASIN, TEXAS

Fig. 1-20 S t r a t i g r a p h i c r e l a t i o n s h i p s of. unconformable channel

sandstones w i t h i n t h e Pennsylvanian Graham Formation,

Cisco Group, Brazos Basin, Texas. (Redrawn from Lee, 1938).

36

Graham Channels, Texas

Sandstone-f i l led channels w i t h i n . t h e Graham Formation of t h e Upper

Pennsylvanian Cisco Group i n t h e Brazos Basin, Texas, have been descr ibed

i n d e t a i l by Lee (1938). The r e l a t i o n s h i p s of i n d i v i d u a l , superimposed

channels is i l l u s t r a t e d i n Fig. 1-20 which shows ove r ly ing channels

c u t t i n g i n t o those below. Ind iv idua l channels have widths of up t o 15 km

and depths up t o 60 m. The sandstones f i l l i n g these channels a r e quartzose,

we l l - so r t ed , cross-bedded, and l o c a l l y con ta in abundant fragments of

carbonized p l a n t remains.

The channels , thought t o have been cu t by a system of anastomosing

d i s t r i b u t a r i e s , l i e w i t h i n beds of l imestone and s h a l e deposi ted i n

n e r i t i c t o p a r a l i c environments t h a t probably bordered an ex tens ive and

subsiding c o a s t a l p l a i n .

B a r t l e s v i l l e Channels, Kansas

Linear sandstone bodies w i t h i n t h e Lower Pennsylvanian Cherokee

Shale of Kansas and Oklahoma have been va r ious ly i n t e r p r e t e d . Rees

(1972, p. 176) s a y s , "Many workers have s t u d i e d t h e " shoes t r ing sands"

of sou theas t e rn Kansas and no r theas t e rn Oklahoma. They have been

descr ibed a s off-shore b a r s , b a r r i e r - i s l a n d b a r s , beach r i d g e s , channel

s ands , dune sands, and point-bar sands. The wide diversence of opinion

stems l a r g e l y from d i f f e r e n t i n t e r p r e t a t i o n s placed on the bed geometry."

Fig. 1-21 i l l u s t r a t e s t h e t r ends of two such o i l -bea r ing sandstone

bodies i n t h e Chanute F i e l d of Kansas. Reconstruct ion of t h e o r i g i n a l

geometry, by D i l l a r d , Oak, and B a s s (1941), shows them as o f f shore ba r s

w i t h f l a t bases ; although i t was noted by these au tho r s t h a t t h e cross-

-bedded sandstone bodies o v e r l i e a coa l seam. Previous s t u d i e s by Lewis

(1929) and l a t e r work by Rees (1972) supported t h e view t h a t t he Bart les-

v i l l e "shoestr ing sands" a r e f l u v i a t i l e i n o r i g i n and t h a t they were

37

Fig. 1-21 Isometric diagram showing interpreted configuration of a

shoestring sand body in the Lower Pennsylvanian Bartlesville

Sandstone, Chanute Field, Kansas. The grid is k mile

(0.4km) square and the contour interval is 10 feet (3m).

(After Dillard, Oak, and Bass, 1941).

deposited by distributaries. These long, narrow sandstone bodies are

commonly less than 30 m thick.

Shinarump Channels, Utah

The Upper Triassic Shinarump Formation (Fig. 1-22) of Utah, Colorado,

Arizona, and New Mexico comprises fluviatile sandstones and conglomeratic

gritstones filling channels eroded in the underlying Lower Triassic

Moenkopi Formation. These channels, which form sinuous courses at the

base and within the lowermost part of the Upper Triassic Chinle Formation,

38

-.. . , . > , ' . C H I N L E

MOENROPI o F E E T r0

L ' o o I,,,. 1 0 1

MILE KM

SANDSTONE CHANNELS I N TRIASSIC BEDS,

FOUR CORNERS AREA, U.S.A.

Fig. 1-22 Diagrammatic c r o s s s e c t i o n showing sandstone channels a t

t h e base of and w i t h i n t h e Triassic Chinle Formation. The

b a s a l channels , named t h e Shinarump Formation, c u t i n t o t h e

Ea r ly T r i a s s i c Moenkopi Formation. These f o r n a t i o n s crop

o u t i n t h e Four Corners area (Utah, Colorado, Arizona and

New Mexico) where t h e Shinarump con ta ins uranium-vanadium

mine ra l i za t ion . Contour i n t e r v a l i n f e e t (1' = 0.305m).

(Redrawn from Stokes, 1961).

are commonly less than 30 m deep.

have been p o i n t b a r s , s p i l l - o v e r b a r s and a s s o c i a t e d sand bodies deposi ted

by a meandering r i v e r t h a t developed an ex tens ive system i n t h e Four Corners

region.

i n t h e s e sandstones.

p a r t s of t h e s e sandstones are mined l o c a l l y f o r uranium-vanadium mine ra l s

depos i t ed by s o l u t i o n s moving along the more permeable courses of t he

channels .

The channel saQdstones are thought t o

Carbonized p l a n t remains and cross-bedding are common f e a t u r e s

Of p a r t i c u l a r i n t e r e s t i s t h e fa.ct t h a t t h e lower

39

J a c k p i l e Channel, New Mexico

The J a c k p i l e Sandstone (F ig . 1-23), which l i es w i t h i n the uppermost

p a r t of t h e Upper J u r a s s i c Morrison Formation i n New Mexico, f i l l s a

no r theas t - t r end ing channel t h a t is up t o 20 km wide , 60 m deep , and more

than 50 km long. The n o r t h e a s t e r n ex tens ion of t h i s channel s p l i t s i n t o

t h r e e s e p a r a t e channels c u t by d i s t r i b u t a r i e s which flowed t o t h e n o r t h e a s t .

The J a c k p i l e , which a l s o f i l l s t h e s e s u b s i d i a r y channels , v a r i e s i n comp-

o s i t i o n from ca lc i te -cemented f e l d s p a t h i c sands tone a t t h e base t o kao-

l i n i t i c , qua r t zose sands tone a t t h e top . This v a r i a t i o n i s thought by

Fig. 1-23 Genera l ized i s o m e t r i c b lock diagram showing t h e conf igu ra t ion

of t h e a l l u v i a l J a c k p i l e Sandstone, t h e uppermost member

of t h e Upper J u r a s s i c Morrison Formation, New Mexico.

(Af t e r Schlee and Moench, 1961).

40

MILLI- GRAIN SIZE

I 1 I 0 8 I;O(M E T E R s 0.2 0.4 06

n LL 0

Q m

W

I ( 2 READINGS) & 150 W ( F E E T )

m

n

Fig. 1-24 V e r t i c a l g r a d a t i o n i n g r a i n - s i z e w i t h i n t h e a l l u v i a l Upper

J u r a s s i c J a c k p i l e Sands tone , New Mexico. (Af te r Schlee

and Moench, 1961).

Schlee and Moench (1961) t o b e t h e r e s u l t of weather ing p r i o r t o t h e

d e p o s i t i o n of t h e ove r ly ing Lower Cre taceous Dakota sed iments . These

channel sands tones are modera te ly w e l l s o r t e d , cross-bedded, f i n e t o

med im-gra ined , and show an o v e r a l l f i n i n g from bottom t o top (F ig . 1-24)

The J a c k p i l e is an impor tan t h o s t rock f o r uranium mine ra l s mined i n t h e

Laguna a r e a , w e s t of Albuquerque, New Mexico.

O i l and Gas F i e l d s

F l u v i a t i l e sands tones have been recorded i n a l l Systems from

P r o t e r o z o i c t o Quaternary i n c l u s i v e , bu t o i l and gas accumulations a r e

n o t known i n f l u v i a t i l e sands tones o l d e r t han t h e Devonian.

twenty-eight examples g iven i n t h i s book are as fo l lows:

H i s s i s s i p p i a n - 3 , Pennsylvanian -5, Permian -1, T r i a s s i c -1, J u r a s s i c -1,

Cretaceous - 1 2 , and T e r t i a r y - 3 . Although i t would appear from t h i s l i m i t e d

sampling t h a t t h e Cre taceous occupies a s p e c i a l p l a c e favour ing t h e

accumulation of hydrocarbons i n r i v e r sed iments , i t must be poin ted out

The a<es of

Devonian -2,

41

t h a t t h e examples g iven are from t h e A l b e r t a , Powder B ive r , and Denver

bas ins where t h e Mesozoic has been e x t e n s i v e l y d r i l l e d . There is no

b a s i s f o r assuming, on a world-wide b a s i s , t h a t f l u v i a t i l e d e p o s i t s w e r e

more abundant i n one Pe r iod than i n ano the r .

Red Earth O i l F i e l d , A l b e r t a

In the Red Ea r th F i e l d (F ig . 1-25) of no r the rn A l b e r t a o i l i s

produced from t h e b a s a l Pa leozo ic G r a n i t e Wash which l i es on t h e eroded

Precambrian s u r f a c e . The age of t h e Gran i t e Wash has n o t been determined;

bu t i t i s o v e r l a i n by a n h y d r i t i c and d o l o m i t i c ca rbona te s o f t h e Middle

Devonian Muskeg Formation, and is probably Ea r ly Devonian. The Gran i t e

Wash i s mainly a f i n e t o ve ry c o a r s e , poor ly s o r t e d qua r t zose and f e l d s -

p a t h i c sands tone , of sub-rounded t o angu la r g r a i n s , b u t c o n t a i n s t h i n

beds of g reen i sh s h a l e having a waxy appearance. Lying on t h e basement

topography i t t h i n s over t h e "highs" and th i ckens t o 30 m o f more i n t h e

"lows". Maximum t h i c k n e s s of t h e n e t porous sands tone is 29 m , and t h e

average t h i c k n e s s of t h e n e t producing sands tone i s 5m. Pe rmeab i l i t y i s

good, be ing i n t h e range 120-120 m i l l i d a r c y s v e r t i c a l l y , and 300-450

m i l l i d a r c y s h o r i z o n t a l l y . P o r o s i t y averages 14%.

The o i l recovered has a g r a v i t y of 38OA.P.I., a p a r a f f i n base , and

a su lphur con ten t of 0.3%. The e s t ima ted amount of o i l i n p l ace w i t h i n

two separa te pools is 110 m i l l i o n b a r r e l s of which only 22 m i l l i o n b a r r e l s

(3.5 m i l l i o n cub ic met res ) a r e l i k e l y t o b e recovered

f i e l d ' s n a t u r a l wa te r d r i v e .

by means of t h e

The t e r m ' g r a n i t e wash' imp l i e s a sandy sediment , probably of qua r t -

zose and f e l d s p a t h i c composi t ion , de r ived and t r a n s p o r t e d from g r a n i t i c

and g n e i s s i c t e r r a i n . Flawn (1965, p. 885) s a y s , " I f i t i s n o t a t r anspor t ed

sediment and i t i s no t "washed'', t h e terms weathered g r a n i t e o r a l t e r e d

g r a n i t e o r decomposed g r a n i t e are more accu ra t e" . F i l l i n g topographic

42

A -

RGE. 8 W. 5 MER

I - 3000'

- 3300'

12 17

_ _ _ - 0 - 2986

PRECAMBRIAN

0 I

MILE

O U ' KM

STRUCTURAL MAP AND SECTION,

RED EARTH FIELD, ALBERTA

Fig . 1-25 S t r u c t u r a l map showing c o n f i g u r a t i o n of t he Precambrian

s u r f a c e under t h e Red Ea r th Fi.eld, A lbe r t a .

f e e t sub-sea l e v e l . S t r u c t u r a l s e c t i o n A-A' shows t h e o i l -

bea r ing Middle Devonian Gran i t e Wash draped ove r a Precambrian

topographic ' h igh ' . The o i l -wa te r c o n t a c t is a t -2986 f e e t

(-911 m) sub-sea l e v e l .

m i l t n n i Q c I c 1 3 n ~ i a s l n t n V i o ~ c \

Contour i n t e r v a l s i n

(Redrawn and r e i n t e r p r e t e d from

43

depres s ions , t h e poor ly s o r t e d Gran i t e Wash i n t h e Red Ea r th F i e l d w a s ev i -

den t ly no t moved very f a r from i ts a r e a of o r i g i n and was appa ren t ly

t r anspor t ed by sur face-water which r an o f f t h e s l o p e s and formed a

dra inage system a long v a l l e y s eroded i n t h e Precambrian basement. A s

t h e v a l l e y s f i l l e d wi th g r a n i t i c d e b r i s , t h e basement h i l l s were even tua l ly

bu r i ed by wedges of Gran i t e Wash swept o u t on a f a i r l y f l a t outwash-plain.

On t h i s s u r f a c e t h e encroaching Muskeg Sea developed a carbonate bank

f r inged by c o a s t a l sabkhas i n which gyps i f e rous d e p o s i t s were formed.

The Gran i t e Wash o r i g i n a l l y cons i s t ed of a l l u v i a l sands and minor

muds, much of which were probably f l u v i a t i l e . L i t t l e is known of t h e

paleogeomorphology of t h i s u n i t , and i t can only b e surmised t h a t

channels may e x i s t which could c o n t a i n accumula t ions of o i l i n s t r u c t u r a l -

- s t r a t i g r a p h i c s i t u a t i o n s r e s u l t i n g from compaction over basement topography,

r eg iona l t i l t i n g of t h e s t ra ta , and wa te r d r i v e .

Music Mountain O i l Pool , Pennsylvania

The Music Mountain O i l Pool (F ig . 1-26) i n McLean County, Pennsylvania

i s i n t h e Upper Devonian S l i v e r v i l l e Sandstone of t h e Canadaway Group.

This sands tone i s q u a r t z o s e , medium t o coarse-gra ined , i n p a r t conglomera t ic ,

and c o n s i s t s of sub-angular t o angul-ar g r a i n s . P o r o s i t y averages 13%, and

pe rmeab i l i t y ranges up t o s e v e r a l hundred m i l l i d a r c y s . Angular c l ays tone

fragments, resembling f ragments of sun-dried c l a y , are con ta ined w i t h i n

t h e sands tone .

In t h e producing a r e a t h e S l i v e r v i l l e Sandstone forms a channel - l ike

body which t r ends nor theas t - southwes t on t h e f l a n k o f an a n t i c l i n e .

sands tone body, which has been t r a c e d f o r more than 6 km, i s 250-300m wide

and up t o 25 m t h i c k .

c o n s i s t s of i n t e rbedded grey s h a l e and f i n e t o coa r se brownish sands tones .

F e t t k e (1941) cons idered t h e group t o be mar ine , and i n t e r p r e t e d t h e

This

The Canadaway Group, of which i t forms a p a r t ,

44

GEOMETRY OF SLIVERVILLE SANDSTONE,

P E N N S Y LVAN I A

F i g . 1-26. I sopach map of S l i v e r v i l l e Sands tone i n t h e Upper Devonian

Canadaway Group, Music Mountain O i l P o o l , McLean County,

Pennsylvania . Contour i n t e r v a l i n f e e t ( 1 ' = 0.305 m).

(Redrawn from F e t t k e , 1941).

45

S l i v e r v i l l e Sandstone as an o f f s h o r e b a r . The n a t u r e of t h e sand ( i n p a r t

coarse-grained and pebbly , c o n s i s t i n g of sub-angular t o angu la r g r a i n s ,

and con ta in ing angular ch ips of c l a y s t o n e resembling f ragments of d r i e d

mud) i n d i c a t e s a f l u v i a t i l e r a t h e r than a wave-washed environment, and

sugges t s t h a t t h e S l i v e r v i l l e sand body w a s p robably a d e l t a - d i s t r i b u t a r y

sand.

The Music Mountain O i l P o o l y i e l d s both o i l and g a s , t h e o i l having

a p a r a f f i n b a s e and a waxy con ten t . It i s of i n t e r e s t t o n o t e , i n t h i s

r e s p e c t , t h a t Hedberg (1968) concluded t h a t waxy o i l s w e r e c h a r a c t e r i s t i c a l l y

der ived from sands tone-sha le sequences of non-marine o r p a r a l i c o r i g i n .

The f i e l d has a gas d r i v e , and du r ing i t s e a r l y h i s t o r y i n i t i a l producing

rates of up t o 500 b a r r e l s of o i l and 15 m i l l i o n cubic f e e t of gas pe r day

were recorded .

Cabin Creek G a s F i e l d , Ohio

Product ion of gas and some l i g h t ( 4 7 O A.P.I.) o i l i n t h e Cabin

Creek Gas F i e l d , Ohio (Fig. 1-27) has been obta ined from t h e Ea r ly Mississ-

i p i a n Berea Sandstone. I n t h e f i e l d area t h e Berea occupies a b road ,

s inuous channel c u t i n t o t h e Miss i s s ipp ian Bedford Formation. This channel

i s 5-6 km wide , up t o 15 m deep, and has been t r a c e d i n t h e sub-sur face

f o r more than 15 km. It appears t o b e p a r t of a d ra inage system t h a t

t rended nor th-south f o r more than 80 km.

I n t h e lower p a r t of t h e channel t h e Berea Sandstone is l i g h t

grey , qua r t zose , and coa r se t o g r i t t y w i t h well-rounded pebbles . The

sand g r a i n s are angu la r . I n t h e upper p a r t of t h e channel t h e sands tone

is f i n e r g r a i n e d , h a r d , and well-cemented by q u a r t z . This q u a r t z i t i c

s ands tone , which has a p o r o s i t y of only 4% compared wi th an average

p o r o s i t y of 16% i n t h e lower sands tone , forms a cap rock f o r t h e gas

conta ined i n t h e sands tone below.

46

B A

A ,- L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . .

, . : . . ' --------- :i-_. F E E T 10,000

0 2000 0 1

METRES

ISOPACH A N D S E C T I O N S O F MlSSlSSlPlAN

BEREA SAND, C A B I N CREEK GAS FIELD, OHIO

Fig. 1-27. Isopach map of part of the Mississippian.Berea Sand in the

Cabin Creek gas field, Ohio, showing thickness in feet of the

sandstone body.

quartz sandstone (stippled) and the basal poorly-cemented,

gas-bearing quartz gritstone (solid). (Redrawn from Pepper,

De Witt and Demarest, 1954).

Sections AB and AC show tightly-cemented

47

Gay-Spencer-Richardson Trend, V i r g i n i a

O i l and gas p roduc t ion has been ob ta ined from t h e Ea r ly Miss i s s ipp ian

Berea Sandstone i n t h e Gay-Spencer-Richardson f i e l d s (Fig. 1-28) of wes te rn

Virg in ia .

t rending channel f i l l e d wi th Berea Sandstone. The channel is up t o 5 km

wide and 40 km long i n t h e f i e l d a r e a , and ex tends a f u r t h e r 55 km t o t h e

no r theas t . The sands tone , which i s s i m i l a r i n composition and t e x t u r e t o

the Berea i n t h e Cabin Creek Gas F i e l d of Ohio, is u n d e r l a i n by grey , s i l t y

s h a l e and o v e r l a i n by brown s h a l e con ta in ing abundant carbonized p l a n t

ma t t e r . The c o n t a c t between t h e ove r ly ing s h a l e and t h e Berea is marked

by an abundance of p y r i t e .

These f i e l d s merge w i t h one ano the r a long a nor theas t - southwes t

DISTRIBUTION OF OIL AND GAS PRODUCTION

IN B E R E A SANDSTONE, WEST VIRGINIA

Fig . 1-28. D i s t r i b u t i o n of o i l and gas p roduc t ion i n t h e Ea r ly

M i s s i s s i p p i a n Berea Sandstone, Jackson , Roane, and Calhoun

Count ies , West V i r g i n i a . (Redrawn from d i s t r i b u t i o n of o i l

and gas w e l l s p l o t t e d by Heck, 1941).

48

G a s has been produced a long t h e e n t i r e Gay-Spencer-Richardson t r e n d

which is i n t e r s e c t e d by nor th-south t r end ing f o l d s t r u c t u r e s . Of p a r t i c u l a r

i n t e r e s t is t h e f a c t t h a t t h e Berea i n t h i s l o c a l i t y i s no t water -bear ing ,

and consequent ly t h e o i l accumula t ions are w i t h i n s y n c l i n e s . Although t h e

sands tone is d r y , t h e e a r l y producing w e l l s showed t h a t p r e s s u r e w i t h i n

t h e sands tone w a s c o n s i s t e n t w i th h y d r o s t a t i c p r e s s u r e f o r t h e depth of

measurement. The o i l was f i r s t ob ta ined by gas d r i v e and some e a r l y w e l l s

had i n i t i a l p roduc t ion rates of up t o 750 b a r r e l s of o i l and 10 m i l l i o n

c u b i c f e e t of gas p e r day.

Bethe l Sandstone Trend, Kentucky

Seve ra l o i l and gas f i e l d s i n wes tern Kentucky, i n c l u d i n g t h e

Midland, S t . Cha r l e s , Barns ley , Luzerne, Sharon School, and Elk Creek,

have produced from t h e Upper Miss i s s ipp ian Bethe l Sandstone. The

Bethe l f i l l s a channel (F ig . 1-29) c u t i n t o t h e Middle M i s s i s s i p p i a n

(Meramecian) l imes tones and s h a l e s , and is o v e r l a i n by Upper Miss i s s ipp ian

(Ches t e r i an ) l imes tones . The channel , which i s 3 km wide, has been t r a c e d

i n t h e subsu r face f o r a d i s t a n c e of more than 160 km southwes t from where

i t c rops o u t . Toward t h e southwes tern l i m i t s t o which i t h a s been t r a c e d

t h e channel branches and c o n t a i n s s e v e r a l o i l and gas accumula t ions i n

s t r u c t u r a l - s t r a t i g r a p h i c t r a p s , i nc lud ing Midland Gas F i e l d . S i m i l a r

types of t r a p s con ta in ing o i l a r e found i n s a n d s t o n e - f i l l e d d i s t r i b u t a r y

channels c u t t i n g l imes tone and s h a l y beds i n a d e l t a i c sequence of t h e

Upper Pennsylvanian t o Lower Permian Cisco Group i n n o r t h - c e n t r a l l e x a s

(Galloway and Brown, 1973). Many of t h e s e a r e commercial o i l f i e l d s .

The Bethe l Sandstone i n t h e Midland f i e l d has a g ross th i ckness of

up t o 75 m and a maximum producing s e c t i o n of 55 m. The mean pe rmeab i l i t y

i s 117 m i l l i d a r c y s and t h e mean p o r o s i t y is 13%. The Midland f i e l d is

es t ima ted t o have o r i g i n a l l y conta ined 163,000 m i l l i o n cub ic f e e t (4,560

m i l l i o n cub ic me t re s ) of r ecove rab le gas averaging 98% methane, and s e v e r a l

49

LIMESTONE SHALE Figure 4 A Pic Bethel erosion channel

LIMESTONE SHALE SANDSTONE CALCAREOUS SANDSTONE AND/ORSHALE

Figure 4 8 Chonnel o t te r Bethel deporitmn ond bockfil l

LIMESTONE SHALE SANDSTONE

Fig. 1-29. Schematic block diagrams showing the stratigraphic relation-

ships of the channel-forming Upper Mississippian Bethel

Sandstone to the overlying Upper Mississippian (Chesterian)

and underlying Middle Mississippian (Xeramecian) sediments,

Kentucky. (After Reynolds and Vincent, 1972).

50

t e n s of m i l l i o n s of b a r r e l s of heavy ( 2 4 0 A . P . I . ) o i l . The volume of gas-

-producing sands tone is es t ima ted t o be 542,000 a c r e - f e e t .

Tyler O i l Fields,Mont*

O i l is produced from t h r e e sands tone members i n t h e lower u n i t of

t h e Lower Pennsylvanian Tyler Formation of c e n t r a l Montana. These sand-

s t o n e members f i l l channels w i t h i n a broad , meandering v a l l e y (F ig . 1-30)

M O N T A N A

. A R E A O F

.A.. ' \I

W Y O M I N G

LOWER TYLER DISTRIBUTION

Fig . 1-30. D i s t r i b u t i o n of channel sands tone members i n t h e lower u n i t

of t h e Lower Pennsylvanian Ty le r Formation, Montana. (After

Kranz le r , 1966).

51

t rending f o r more than 500 km eas tward a c r o s s c e n t r a l Xontana i n t o North

Dakota. This v a l l e y c u t s i n t o l imes tone and s h a l e members of t h e :+ississ-

ipp ian Heath Formation (F ig . 1-31). The lower two sands tone members l i e

on the e r o s i o n a l s u r f a c e ; t h e upper sands tone member, c a l l e d t h e Stensvad

Sand, occupies a s t r a t i g r a p h i c a l l y h i g h e r p o s i t i o n w i t h i n t h e v a l l e y - f i l l

sediments of t h e Lower Ty le r .

The pos t -Miss i ss ippian v a l l e y , i n which t h e Lower Ty le r sediments

N E KEG COULEE IVANHOE STENSVAD s w

A v DATUM 0 TOP OF 0 TYLER 0 4 A'

1 UPPER I TYLER I I

S C A L E S I H F E E T

PAL EOS JRUC TURAL GROSS SECTION KEG COULEE- MANHOE -SJENSVAD

Fig. 1-31. Sec t ion of e r o s i o n a l v a l l e y i n M i s s i s s i p p i a n Heath Formation,

through t h e Keg Coulee, Ivanhoe and Stensvad f i e l d s , showing

s t r a t i g r a p h i c r e l a t i o n s h i p s o f o i l -bea r ing sands tone members

w i t h i n t h e lower u n i t of t h e Lower Pennsylvanian Ty le r

Formation, Montana. (Af t e r Kranz le r , 1966).

52

l i e , has a depth of up t o 100 m and a wid th of up t o 15 km. It is f i l l e d

mainly wi th s i l t s and grey s h a l e s ( con ta in ing abundant carbonaceous p l a n t

remains) depos i t ed a s f lood p l a i n and backswamp muds. The sands tone

members, which are f ine -g ra ined a t t h e top , g rad ing downward t o g r i t and

conglomerate a t t h e b a s e , a r e 10-45 m t h i c k .

Qil has been t rapped w i t h i n t h e s e sands tone members a t c e r t a i n

l o c a l i t i e s where l o c a l f o l d i n g of t h e s t r a t a has formed s t r u c t u r a l c l o s u r e s ,

and appa ren t ly where t h e sands tone i s i n c o n t a c t w i th t h e Heath Limestone

which may be t h e source-rock. Loca l v a r i a t i o n s o f pe rmeab i l i t y and

l e n t i c u l a r i t y of t h e sands tone members, s t r u c t u r a l c o n t r o l , and proximi ty

t o l imes tone beds (through which t h e o i l h a s mig ra t ed , and i n which i t may

a l s o have been gene ra t ed ) are k e y . f a c t o r s c o n t r o l l i n g t h e o i l accumula t ions .

E ight f i e l d s producing from t h e s e sands tone members of t h e Lower

Ty le r c o n t a i n e s t ima ted t o t a l cumula t ive r e s e r v e s of 70 m i l l i o n b a r r e l s

(11 m i l l i o n cub ic me t re s ) of r ecove rab le o i l .

Delaware Extens ion O i l F i e l d , Oklahoma

O i l p roduct ion i n t h e Delaware Extens ion F i e l d , Oklahoma, (F ig . 1-32)

is ob ta ined from t h e B a r t l e s v i l l e Sandstone i n t h e middle p a r t of t h e Lower

t o Middle Pennsylvanian Cherokee Formation, a s h a l y sequence. I n t h e f i e l d

a r e a t h e B a r t l e s v i l l e forms a l i n e a r s ands tone body 600 - 1800 m wide, and

up t o 20 m t h i c k . I t has been t r aced f o r more than 10 km and i s i n t e r p r e t e d

by L e w i s (1929) as a channel d e p o s i t having a no r thwes te r ly provenance.

D i l l a r d , Oak and Bass (1941), on t h e o t h e r hand, i n t e r p r e t e d t h e B a r t l e s v i l l e

Sandstone o f t h e Chanute O i l F i e l d , Kansas, as an o f f s h o r e b a r . They no ted ,

however, t h a t t h e B a r t l e s v i l l e was n o t only cross-bedded, b u t was immed-

i a t e l y unde r l a in by a c o a l seam. I n a p a r a l i c environment e i t h e r i n t e r -

p r e t a t i o n could b e c o r r e c t , a l though a cross-bedded sands tone ove r ly ing

c o a l is probably of f l u v i a t i l e o r i g i n . L e w i s (1929, p. 364) s t a t e s ,

53

PENNSYLVANIAN BARTLESVILLE SANDSTONE

DELAWARE EXTENTION OIL FIELD

Fig. 1-32. Map showing t h e d i s t r i b u t i o n and subsu r face s t r u c t u r e of t h e

o i l -bea r ing , lower Pennsylvanian B a r t l e s v i l l e sands tone ,

Delaware Extens ion F i e l d , Nowata County, Oklahoma. The

sands tone is i n t e r p r e t e d as a channel sand depos i t ed by a

r i v e r f lowing i n a s o u t h e a s t e r l y d i r e c t i o n i n d i c a t e d by t h e

arrow. (Redrawn from L e w i s , 1929).

“Conditions of t h e sand i n t h e Delaware Extens ion pool i n d i c a t e a cond i t ion

s i m i l a r t o t h e northwest-southwest shoes t r ing-sand pools of e a s t e r n Kansas”

The c o r r e c t n e s s of t h i s i n t e r p r e t a t i o n i s f u r t h e r suppor ted by t h e e r r a t i c

d i s t r i b u t i o n of t h e sands tone , t y p i c a l of r i v e r d e p o s i t s , which was noted

by Lewis (p. 3 6 4 ) who s a y s , “In s e v e r a l p l a c e s , w e l l s w i th t h i c k sand and

r i c h product ion o f f s e t l o c a t i o n s i n which no sand w a s found”.

The Delaware Extens ion F i e l d y i e l d s o i l from a compara t ive ly sha l low

depth. A t t h e e a s t e r n end of t h e f i e l d t h e top of t h e producing B a r t l e s v i l l e

Sandstone is 30 m below sea l e v e l and 240 m below t h e s u r f a c e , and a t t h e

wes tern end t h e sands tone is 335 m below t h e s u r f a c e . I n i t i a l p roduct ion

from some wells was a t rates exceeding 1,000 b a r r e l s a day, t h e b e s t

54

p roduc t ion be ing ob ta ined from f r i a b l e sands tone l e n s e s o r s t r i n g e r s a long

t h e t r e n d of t h e main sands tone body.

p roduc t ion , o r no p roduc t ion was i n some cases found i n we l l sad jacen t t o

those w i t h good p roduc t ion from t h e f r i a b l e sands tone l e n s e s . The

exp lana t ion probably l i es i n t h e i n t e r p r e t a t i o n t h a t t h e p roduc t ive

l e n s e s and s t r i n g e r s were depos i t ed a s l o c a l s t r eam channel f i l l i n g s of

permeable sand , whereas t h e l a t e r a l l y ad jacen t beds were r i v e r f lood

p l a i n d e p o s i t s of r e l a t i v e l y impermeable s i l t s . The B a r t l e s v i l l e Sand-

s t o n e i n t h e area of t h e Delaware Extens ion F i e l d is a westward

ex tens ion of o i l -bea r ing sands tones t h a t a r e thought t o have been marine

o f f s h o r e sands .

A s noted by Lewis (1929), poor

Bush C i ty O i l F i e l d , Kansas

S t r a t i g r a p h i c a l l y h ighe r than t h e B a r t l e s v i l l e Sandstone, w i t h i n

t h e uppermost s h a l y s e c t i o n of t h e Lower t o Middle Pennsylvanian Cherokee

Formation, a s inuous sands tone body known as t h e S q u i r r e l sands tone is

t h e o i l p roducer i n t h e Bush C i ty F i e l d , Kansas (F ig . 1-33). This

sands tone body, which i s i n t e r p r e t e d as a c h a n n e l - f i l l s and , has a

t h i ckness of up t o 15 m , a wid th of up t o 300 m , and h a s been found t o

be o i l -bea r ing f o r 24 km a long i t s course . The c h a n n e l - - f i l l sed iment ,

which shows a f i n i n g upward i n mean g r a i n s i z e , c o n s i s t s of 5-6 m of

f ine -g ra ined , micaceous, o i l -bea r ing sands tone o v e r l a i n by up t o 10 m of

a l t e r n a t i n g beds of sandy s h a l e and s h a l y sands tone con ta in ing s t r i n g e r s

of carbonaceous matter.

The producing sands tone , composed of sub-angular g r a i n s , has a

p o r o s i t y of 17-22% and a pe rmeab i l i t y of up t o 60 m i l l i d a r c y s . I n i t i a l

o i l p roduc t ion from i n d i v i d u a l w e l l s has ranged up t o 800 b a r r e l s a day,

bu t averaged 60 b a r r e l s a day. The o i l , i n i t i a l l y produced by gas-dr ive ,

has a g r a v i t y of 35O A . P . I . Although t h e most p roduc t ive wells have

some s t r u c t u r a l c o n t r o l , t h e f i e l d i s e s s e n t i a l l y s t r a t i g r a p h i c , be ing

55

B

D

0 500 1000 Feet 1,

PENNSYLVANIAN BUSH CITY OIL FIELD, KANSAS

Fig. 1-33. Map and s e c t i o n s of t h e Bush C i ty o i l f i e l d , Anderson

County, Kansas. The o i l -bea r ing sands tone forms a s i n u o u s

body, and is thought t o b e an a l l u v i a l channel f i l l i n g .

(Redrawn from Char l e s , 1941).

t e rmina ted up-dip by an i n c r e a s e i n t h e c l a y and s i l t con ten t of t h e

sands tone , w i th consequent decrease i n p o r o s i t y . The b e s t w e l l s a r e

s i t u a t e d a t t h e j u n c t i o n s of t h e sands tone body and t h e crests o f low

a n t i c l i n e s having c l o s u r e s of 3-12 m. Regional d i p t o t h e southwest i s

approximately 4m/km, and t h e depth t o t h e producing sands tone is commonly

i n t h e range 200-300 m. It i s of i n t e r e s t t o n o t e t h a t t h e g r a v i t y of

56

t h e o i l a t t h e down-dip end of t h e f i e l d i n c r e a s e s a b r u p t l y t o 14O A . P . I . ,

and t h a t beyond t h e down-dip l i m i t t h e sands tone con ta ins n e i t h e r o i l

n o r water. Secondary recovery mechods by means of gas d r i v e have inc reased

t h e p o t e n t i a l of producing w e l l s , bu t u l t i m a t e recovery of o i l from t h e

f i e l d w i l l p robably n o t exceed 6 m i l l i o n b a r r e l s ( l e s s than 1 m i l l i o n

cub ic met res ) of o i l .

Red Fork Sandstone P roduc t ion , Oklahoma

Seve ra l f i e l d s from t h e Middle i n n o r t h e r n and n o r t h e a s t e r n

Oklahoma produce o i l and gas from t h e Middle Pennsylvanian (Desmoinesian)

Red Fork Sandstone. These f i e l d s i n c l u d e t h e South Ceres Poo l , Wakita

Trend, Cheyenne Valley F i e l d , and Shoes t r ing F i e l d .

The Red Fork Sandstone is approximate ly t h e same age as t h e

B a r t l e s v i l l e Sandstone i n t h e Cherokee Formation. I t comprises l i n e a r

sands tone bodies ranging i n th i ckness t o 20 m , i n wid th t o 3 km, and i n

l e n g t h t o 50 km. The sands tone is q u a r t z o s e , g e n e r a l l y f i n e t o very

f ine -g ra ined b u t l o c a l l y shorrinz sone degree of coarseninq toward t h e

base .

Ea r ly w r i t e r s , i nc lud ing Wright (1941), regarded t h e Red Fork

Sandstone as having been a s h o r e l i n e sand formed w i t h i n t h e Cherokee Sea.

Later wr i te rs , i nc lud ing Withrow (1968) and Lyons and Dobrin (1972),

recognized t h a t t h e Red Fork inc luded sands tone bod ies Eormed as r i v e r

channel s ands , such a s t h e producing sands of t h e South Ceres P o o l ,

Cheyence Va l l ey , and Shoes t r ing f i e l d s . The Wakita Trend (Fig. 3-14)

is desc r ibed by Withrow (1968) as an off -shore b a r and is inc luded under

t h a t ca tegory i n t h i s book.

The South Ceres P o o l (F ig . 1-34) i s a remarkable horseshoe-shaped

channel up t o 2 km wide , t h a t c o n t a i n s o i l and gas throughout a l eng th

of 40 km. The sands tone , which i s commonly up t o 10 m t h i c k , has an

57

- 1

' i

Fig. 1-34. Isopach map of the Middle Pennsylvanian Red Fork Sandstone,

South Ceres Pool, Oklahoma, showing the sandstone distrib-

ution within a narrow channel. Contour interval is 20 feet

(6.1 m). (After Lyons and Dobrin, 1972).

SOUTH CERES POOL AREA Noblm Co., Oklohomo

/SOfACH

c. 1. - 20' Rl.tyoni 7f

58

a v e r a g e p o r o s i t y of 20% and a n a v e r a g e p e r m e a b i l i t y of 100 m i l l i d a r c y s .

Of p a r t i c u l a r i n t e r e s t i s t h e f a c t t h a t t h e down-dip l imb of t h e w e s t

y i e l d s 4 2 O A.P.I . o i l , and t h e up-dip l imb y i e l d s m a i n l y g a s . Depths

t o t h e p r o d u c i n g s a n d s t o n e a r e i n t h e r a n g e 1,300 .- 1,350 m . The

N

A A '

0 F E E T

I 0

50 m

F i g . 1-35. I s o p a c h and s e c t i o n of t h e P e n n s y l v a n i a n Red Fork Sands tone

i n t h e Cheyenne V a l l e y o i l f i e l d , Major County, Oklahoma,

showing a r iver s a n d f i l l i n g a c h a n n e l on t h e e r o d e d s u r f a c e

of t h e M i s s i s s i p p i a n . (Redrawn from Withrow, 1968).

59

producing mechanism i s water d r i v e . I n d i v i d u a l o i l w e l l s , each d ra in ing

approximately 15 a c r e s , may u l t i m a t e l y y i e l d 75,000 b a r r e l s accord ing t o

Lyons and Dobrin (1972). Maximum product ion from t h e f i e l d i s n o t l i k e l y

t o be much i n excess of 10 m i l l i o n b a r r e l s (1 .6 m i l l i o n cub ic me t re s ) .

The Cheyenne Val ley F i e l d (Fig. 1-35) is l o c a t e d w i t h i n a l i n e a r

sandstone body of t h e Red Fork Sandstone t h a t t r e n d s g e n e r a l l y eas t -wes t ,

s t r a t i g r a p h i c a l l y h i g h e r and normal t o t h e south- t rending wes te rn

ex tens ion (Oakdale F i e l d ) of t h e Wakita Trend of s h o r e l i n e sands . It i s

p e r t i n e n t t o n o t e t h a t Withrow (1968) i n t e r p r e t e d t h e upper p a r t of t h e

producing Red Fork Sandstone i n t h e Oakdale F i e l d a s an of f - shore b a r ,

and t h e lower p a r t a s a r i v e r channel sand.

The Cheyenne Val ley F i e l d i s s i t u a t e d where t h e l i n e a r t r end of t h e

Red Fork Sandstone bends l o c a l l y t o t h e s o u t h , i n which d i r e c t i o n t h e

s t r a t a d i p 10 m p e r k i lome t re . Average depth t o t h e producing sands tone

is 2,G75 m , and t h e average t h i c k n e s s exceeds 10 m . The f i e l d i s

e s t ima ted t o c o n t a i n 6.5 m i l l i o n b a r r e l s (1 m i l l i o n cub ic met res ) of

recoverable o i l .

The Shoes t r ing O i l F i e l d (Fig. 1-36) i n n o r t h e a s t e r n Oklahoma y i e l d s

o i l from a l i n e a r , no r the r ly - t r end ing sands tone body of t h e Red Forks

Sandstone. This sands tone body was cons idered by Wright (1941) t o b e a

s h o r e l i n e sand , bu t i t s conf igu ra t ion sugges t s t h a t i t w a s a r i v e r channel

sand. The producing sands tone i s g e n e r a l l y f i n e g ra ined , i n p a r t s i l t y ,

vary ing from poorly-cemented t o well-cemented by ca l c i t e , and c o n s i s t s of

sub-angular g r a i n s mainly of q u a r t z and cherc .

sands tone body i s g e n e r a l l y more permeable and less s i l t y . Product ion of

40' A.P.I. o i l i s ob ta ined by pumping, a s s i s t e d by a weak gas and wa te r

d r i v e . Average y i e l d s amounted t o only 10-15 b a r r e l s a day from each w e l l

d r a in in? 15 a c r e s .

The lower p a r t of t h e

60

DISTRIBUTION OF OIL PRODUCTION IN

RED FORK SANDSTONE, OKLAHOMA

F i g . 1-36. Map showing d i s t r i b u t i o n of o i l p r o d u c t i o n i n t h e Pennsyl -

v a n i a n Red Fork S a n d s t o n e , Red Fork S h o e s t r i n g O i l F i e l d ,

Pawnee Creek and T u l s a C o u n t i e s , Oklahoma. (Drawn from

d i s t r i b u t i o n o f p r o d u c i n g w e l l s p l o t t e d by W r i g h t , 1941) .

MoombaGas F i e l d , South A u s t r a l i a

Gas and c o n d e n s a t e p r o d u c t i o n i n t h e Moomba F i e l d (F ig . 1-37) o f t h e

Cooper B a s i n , South A u s t r a l i a i s o b t a i n e d f rom s a n d s t o n e b e d s w i t h i n t h e

Middle t o Upper Permian (Kungurian) Toolachee Format ion which is d e s i g n a t e d

as t h e u p p e r u n i t of t h e G i d g e a l p a Group. P r o d u c t i o n i s a l s o o b t a i n e d from

o t h e r s a n d s t o n e s i n the G i d g e a l p a . The c o n t r o l f o r g a s a c c u m u l a t i o n i s

.-- - - 6000

- 8000- ’ I UPPER PERMIAN

) YMOOMBA

- OLDER PALEOZOIC

~ 10000 -

MILES

‘ I K M

0 s w K M

p IF 0,o

MILES K M

Fig . 1-37. S t r u c t u r a l map of t h e Gidgealpa and Noomba gas-condensate

f i e l d s , South A u s t r a l i a . Sec t ion A-B shows t h e Upper

Permian g r o s s sands tone i n t e r v a l draped over e r o s i o n a l

f e a t u r e s u n d e r l a i n by o l d e r Pa leozo ic rocks . (Redrawn

from Greer, 1965, and Mar t in , 1967).

e s s e n t i a l l y s t r u c t u r a l , t h e Upper Permian and ovei-lying Mesozoic beds

having been fo lded over f a u l t e d basement b locks . Local v a r i a t i o n s i n

pe rmeab i l i t y , depending on d e p o s i t i o n a l t r e n d s w i t h i n t h e sands tones , a r e

a l s o impor tan t f a c t o r s .

The Toolachee d i r e c t l y o v e r l i e s a major unconformity t h a t t r u n c a t e s

o l d e r Permian beds , and consequent ly has a wider d i s t r i b u t i o n than t h e

under ly ing sands tones of t h e Gidgealpa. Greer (1965) cons idered t h e

Gidgealpa sands tones were e v i d e n t l y depos i t ed i n a h igh energy environment.

The f l u v i a t i l e n a t u r e of t hese sands tones was recognized by Martin (1967)

and Kapel (1972) who cons idered t h e Toolachee Formation t o be r i v e r ,

l a c u s t r i n e , and swamp d e p o s i t s .

The Toolachee sands tone i s g rey , medium t o coarse-gra ined , conglom-

e r a t i c , q u a r t z o s e , and cross-bedded. Rock f ragments , i nc lud ing v o l c a n i c s ,

62

a r e common, and t h e m a t r i x c o n s i s t s l a r g e l y of k a o l i n and i l l i t e . I n t e r -

bedded wi th t h e sands tone are t h i n ' b e d s of dark g r e y , micaceous, carbonac-

eous s h a l e , and c o a l . The Toolachee h a s a t h i c k n e s s of 20-40 m and t h e n e t

producing sands tone is up t o 26 m t h i c k .

pe rmeab i l i t y i s good.

P o r o s i t y is 10-20% and t h e

The approximate dep th of t h e producing zone i n t h e Moomba F i e l d is

A t t h i s depth t h e p r e s s u r e is approximate ly 3,000 p . s . i . , 2,135 m.

i n d i c a t i n g normal h y d r o s t a t i c p r e s s u r e f o r a s e c t i o n s a t u r a t e d wi th wa te r

i n t h e upper s a l i n i t y range (55,000 p.p.m.) f o r sea water. I n i t i a l l y ,

w e l l s flowed gas a t rates of up t o 15 m i l l i o n cubic f e e t a day through a

h a l f i nch choke. The g a s , c o n s i s t i n g of 77% methane wi th an unusual ly

h igh con ten t (20%) of carbon d iox ide , y i e l d s up t o 50 b a r r e l s of condensa te

p e r m i l l i o n cub ic f e e t . Proven r e s e r v e s of r ecove rab le gas from t h e Moomba

and a d j a c e n t Gidgea lpa , T i r r awar ra , and Moorari f i e l d s amount to 2,000,000

m i l l i o n ( 2 t r i l l i o n ) cub ic f e e t (56,000 m i l l i o n cub ic me t re s ) .

P i c k a n j i n n i e G a s F i e l d , Queensland

Gas and condensa te p roduc t ion i n t h e P i c k a n j i n n i e F i e l d (F ig . 1-38)

of t h e S u r a t Bas in , Queensland is ob ta ined from t h e Upper T r i a s s i c Show-

grounds Sandstone and Moolyember Sandstone, and a l s o from t h e Lower J u r a s s i c

P r e c i p i c e Sandstone. More than h a l f of t h e p roduc t ion comes from t h e

Showgrounds which i s desc r ibed by Gray (1969) as l i g h t g r e y , medium t o very

coarse-gra ined , poor ly s o r t e d and composed mainly o f sub-angular g r a i n s

of q u a r t z . P o r o s i t y averages 16% and h o r i z o n t a l pe rmeab i l i t y is i n t h e

range of 200 - 2,000 m i l l i d a r c y s .

t h i c k n e s s 6 m i n t h e P i c k a j i n n i e F i e l d , t h i ckens t o 15 m a long t h e

e a s t e r n f l a n k of t h e Roma S h e l f , accord ing t o Swindon (1968).

The sands tone , which has a maximum

The e l e c t r i c l o g c h a r a c t e r i s t i c s of t h e Showgrounds Sandstone and

P r e c i p i c e Sandstone i n d i c a t e t h a t t h e lower p a r t s of t h e sands tone bod ies

63

2 O- 0 KM 2

P l C K A N J l N N l E NO. 1

S P R

100 J m

- 0

- 2 0 0 '

- M I L E S

P I C K A N J I N N I E G A S FIELD, QUEENSLAND

Fig. 1-38. P i c k a n j i n n i e gas f i e l d n e a r Roma, Su ra t Bas in , Queensland,

showing a s t r u c t u r a l - s t r a t i g r a p h i c t r a p formed by t h e

pinch-out edge of t h e gas-bear ing Upper T r i a s s i c Showgrounds

Sandstone (1) where i t c r o s s e s a nose i n d i c a t e d by s t r u c t u r e

contours of a marker w i t h i n t h e Upper T r i a s s i c Moolayember

Sandstone ( 2 ) . The Moolayember i s o v e r l a i n by t h e gas-bearing

Lower J u r a s s i c P r e c i p i c e Sandstone (3 ) . (Redrawn from

Swindon, 1968).

a r e more permeable and probably coa r se r . This accords wi th t h e i n t e r -

p r e t a t i o n t h a t bo th t h e Showgrounds and P r e c i p i c e are of f l u v i a t i l e o r i g i n .

The i n t e r v e n i n g Moolayember i s cons idered t o be l a c u s t r i n e . Lying uncon-

formably on t h e Lower T r i a s s i c Rewan Formation, t h e Showgrounds forms a

sou theas t - t r end ing d ra inage p a t t e r n . Entrapment of gas has r e s u l t e d from

t h e co inc idence of a pinch-out edge of t h e sands tone c r o s s i n g a s t r u c t u r a l

64

nose draped over a b u r i e d h i l l on t h e eroded s u r f a c e of t h e igneous-meta-

morphic basement. The f i e l d i s consequent ly l i m i t e d t o t h e east by a

s t r a t i g r a p h i c pe rmeab i l i t y b a r r i e r , and i n o t h e r d i r e c t i o n s by s t r u c t u r a l

c l o s u r e .

The P i c k a n j i n n i e F i e l d c o n t a i n s proven p roduc ib le r e s e r v e s of gas

amounting t o more than 25,000 m i l l i o n cubic f e e t , of which approximately

15,000 m i l l i o n a r e w i t h i n t h e Showgrounds. The g a s , which c o n s i s t s of

96% methane, w a s i n i t i a l l y con ta ined a t a p r e s s u r e of about 1,900 p . s . i .

a t an approximate dep th of 1,500 m. The f i e l d has a s t r o n g water d r i v e ,

t h e water having a s a l i n i t y of less than 5,000 p.7.m. which p l a c e s i t i n

t h e compara t ive ly f r e s h t o b rack i sh water range.

Moonie O i l F i e l d , Queensland

The Moonie F i e l d (F ig . 1-39) is s i t u a t e d on t h e s o u t h e a s t e r n f l a n k

of t h e S u r a t Bas in , Queensland, and produces 4 5 O A.P.I. o i l from t h e Lower

J u r a s s i c P r e c i p i c e Sandstone. I n t h e f i e l d area, t h e P r e c i p i c e comprises

a lower sands tone u n i t t h a t l i e s unconformably on Permian and T r i a s s i c

rocks , and an upper sands tone u n i t s epa ra t ed from t h e lower by a s i l t y

s e c t i o n . A t Xoonie t h e P r e c i p i c e has a g r o s s th i ckness of approximate ly

75 m , and i s o v e r l a i n by s i l t s t o n e and mudstone of t h e Lower J u r a s s i c

Evergreen Formation.

Both t h e upper and lower sands tone u n i t s of t h e P r e c i p i c e a r e o i l -

-bear ing . The upper u n i t is l i g h t g r e y , f i n e t o medium-grained, poor ly

s o r t e d , qua r t zose t o l i t h i c , and has a w h i t e , k a o l i n i t i c m a t r i x . The

lower u n i t is l i g h t g r e y , medium t o very coarse-gra ined , i n p a r t cong-

l o m e r a t i c , poor ly s o r t e d , qua r t zose t o l i t h i c , and poorly-cemented t o

f r i a b l e . P o r o s i t y is i n t h e range 13-25%. Pe rmeab i l i t y of t h e upper

sands tone u n i t averages 300 m i l l i d a r c y s , and t h a t of t h e lower u n i t ranges

from s e v e r a l hundred t o 2,000 m i l l i d a r c y s . I n t h e Moonie F i e l d these

65

I

c

3

0 E L

o

66

sands tone u n i t s a r e sepa ra t ed by 100 f e e t o f l i g h t grey s h a l e and s i l t s t o n e

con ta in ing t h i n sands tone l a y e r s and coa ly laminae. This i n t e r v e n i n g u n i t

is cons idered t o have been deposited a s r i v e r f lood p l a i n and l a c u s t r i n e

sed iments . Both sands tone u n i t s are cross-bedded and of f l u v i a t i l e o r i g i n .

I n g e n e r a l , they e x h i b i t g r a i n g r a d a t i o n from c o a r s e r below t o f i n e r above,

a c h a r a c t e r i s t i c commonly found i n r i v e r sand d e p o s i t s . This f e a t u r e i s

r e f l e c t e d i n t h e blocky t o be l l - shaped s e l f - p o t e n t i a l curves o f t h e E-logs

shown i n F ig . 1-39.

O i l accumulation i n t h e Moonie F i e l d has r e s u l t e d from a s t r u c t u r a l -

s t r a t i g r a p h i c s i t u a t i o n where permeable zones w i t h i n the P r e c i p i c e Sandstone

o v e r l i e a basement ' h igh ' of b lock f a u l t e d and t runca ted Permian and

T r i a s s i c beds . The s t r u c t u r e w i t h i n t h e P r e c i p i c e i s a no r theas t - t r end ing

c losed dome, s i x m i l e s l ong and two mi l e s wide. The volume of o i l i n t h e

r e s e r v o i r i s e s t ima ted t o be about 125 m i l l i o n b a r r e l s (19 .9 m i l l i o n

c u b i c m e t r e s ) , b u t u l t i m a t e recovery w i l l p robably n o t exceed 35 m i l l i o n

b a r r e l s (5 .6 m i l l i o n cub ic me t re s ) . The o i l i s unde r l a in by f a i r l y f r e s h

wa te r (approximately 2,500 p .p .m.) , i n d i c a t i n g a hydrodynamic cond i t ion .

Product ion problems have a r i s e n as t h e r e s u l t of i nvas ion of t h e o i l -bea r ing

zone by wa te r .

Athabasca O i l Sands, A lbe r t a

The Athabasca O i l Sands (F ig . 1-40) c o n s i s t of t a r r y o i l - s a t u r a t e d

sands of t h e Lower Cre taceous McMurray Formation i n no r the rn Albe r t a .

These uncemented t o poorly-cemented sands , which o v e r l i e Devonian lime-

s t o n e s , have a very g e n t l e r e g i o n a l d i p t o t h e wes t and consequent ly crop

o u t , o r a r e c l o s e t o t h e s u r f a c e , over a wide a r e a . I n p l a c e s t h e sands

can b e mined i n open c u t s , a method c u r r e n t l y be ing employed; e l sewhere t h e

overburden is too t h i c k and o i l p roduct ion w i l l depend on sub-sur face

methods such as f i r e - f l o o d i n g o r steam i n j e c t i o n and t h e use of s o l v e n t s .

0'

100'

200'

3 0 0 '

L E G E N D X - B u r r o w s . . . . .I-] M I c r o - c r 0 s 1 - 1 o m no e . H I g h - a n g I e c ros I - s t r J t I f I c a t I on b- Tor Sands . . -

l i g . 1-40. Genera l ized s e c t i o n through t h e Athabasca a i l Sands of t h e

Lower Cre taceous McT4urray Formation, A l b e r t a , showing t h e

o i l - s a t u r a t e d b a s a l r i v e r sands and g r i t s , and ove r ly ing

f l u v i a l beds of t h e YuYurray Delta. (Af t e r Ca r r igy , 1971).

0'

100'

200'

300'

68

The o i l -bea r ing sands are qua r t zose and of f l u v i a t i l e and l a c u s t r i n e

o r i g i n . The lowermost sands have a th i ckness of 10-13 m. These c o n s i s t

of r i v e r d e p o s i t s , are coa r se t o very coa r se , and commonly have l e n s e s

of coa r se g r i t s t o n e and f i n e conglomerate composed of poorly-rounded

pebbles . Cross-bedding of t h e type found i n p o i n t b a r s is very common.

These sands a r e o v e r l a i n by a s e c t i o n , 30-45 m t h i c k , of sands and s i l ts

con ta in ing v a r i a b l e amounts of t a r r y o i l .

by t h e o r i g i n a l p o r o s i t y and pe rmeab i l i t y of t h e sands , t h e h ighe r v a l u e s

i n o i l con ten t be ing found i n t h e c l e a n , we l l - so r t ed f l u v i a t i l e sands .

Maximum o i l con ten t amounts t o 18-20% by weight of t h e s a t u r a t e d sand .

O i l s a t u r a t i o n i s c o n t r o l l e d

The Neocomian HcMurray Formation i s o v e r l a i n by marine beds of t h e

Lower Cre taceous (Albian) Clearwater Formation, t h e b a s a l u n i t of which i s

t h e Wabiskaw Member. This u n i t i s r e f e r r e d t o i n F ig . 1-40 a s a b a r r i e r

b a r s and , which i t may b e i n p a r t . C e r t a i n l y i t i s a t r a n s g r e s s i v e marine

sand .

t h e s e c t i o n , has a th i ckness of 50-100 m.

a r i v e r system t h a t d ra ined an a r e a of t h e Precambrian Sh ie ld t o t h e e a s t ,

and flowed nor thwes te r ly t o t h e Clearwater Sea. Subsequent t r a n s g r e s s i o n

of t h e sea r e s u l t e d i n b u r i a l of PlcXurray sed iments by t h e Clearwater

sands and muds.

The McMurray, which has a h ighe r sand conten t i n t h e lower p a r t of

The format ion w a s depos i t ed by

Regional d i p of t h e McMurray Formation, amounting t o less than 2m/km,

may have p e r n i t t e d t h e up-dip mig ra t ion of o i l t o i t s p r e s e n t l o c a t i o n , and

c o n s t i t u t e s t h e only b a s i s f o r a s t r u c t u r a l element t o t h i s v a s t accumulation

of o i l . The r e s e r v o i r , and t h e mechanisms c o n t r o l l i n g t h e l o c a l concent-

r a t i o n s of o i l are e n t i r e l y s t r a t i g r a p h i c . Xuch has been w r i t t e n by many

writers (Convbeare, 1966) about t h e p o s s i b l e o r i g i n s of t h e o i l , and t h i s

problem has n o t been exp la ined t o t h e s a t i s f a c t i o n of a l l . The ques t ion

may b e of academic i n t e r e s t o n l y , bu t t h e problems concerning product ion

from l e n t i c u l a r beds of v a r i a b l e pe rmeab i l i t y and o i l s a t u r a t i o n a r e of

69

consequence t o t h e f u t u r e a p p l i c a t i o n of sub-sur face p roduc t ion methods.

These problems may b e so lved as d r i l l i n g proceeds and subsu r face d e t a i l s

a r e eva lua ted and i n t e r p r e t e d t o show t h e r e l a t i o n s h i p s of pe rmeab i l i t y

t r ends t o d e p o s i t i o n a l t r ends w i t h i n t h e p a t t e r n of t h e b a s a l IlcMurray

dra inage system.

In t h e a r e a n o r t h of F o r t Mclurray t h e Athabasca O i l Sands a r e

es t imated t o con ta in more than 300,000 m i l l i o n b a r r e l s (57,700 m i l l i o n

cubic met res )of o i l . S i m i l a r accumula t ions i n o t h e r areas of no r the rn

Alber ta con ta in a d d i t i o n a l p o t e n t i a l r e s e r v e s .

r e se rves of o i l i n p l a c e probably amount t o 500,000 - 600,000 m i l l i o n

b a r r e l s , b u t how much of t h i s o i l can u l t i m a t e l y be produced as a v i a b l e

economic o p e r a t i o n is open t o ques t ion . The economic l i m i t may prove t o

be less than 200,000 m i l l i o n b a r r e l s (31,800 m i l l i o n cub ic me t re s ) .

The t o t a l p o t e n t i a l

The o i l which occupies up t o 90 pe rcen t of pore space i n t h e water-

-wet q u a r t z s and , can be s e p a r a t e d by t r ea tmen t w i th steam and h o t water .

It has a g r a v i t y of 10 degrees A . P . I . , a riaphthene base , and a r e l a t i v e l y

high con ten t of s u l p h u r , n i t r o g e n and t r a c e elements.

B e l l s h i l l Lake and Hughenden O i l F i e l d s , A lbe r t a

O i l p roduct ion i n t h e B e l l s h i l l Lake and Hughenden f i e l d s of east-

c e n t r a l .4lberta is ob ta ined from s t r a t i g r a p h i c t r a p s i n t h e Lower Cretaceous

(2eocomian) E l l e r s l i e Sandstone. This sands tone was depos i t ed as a r i v e r

sand i n a broad v a l l e y (F ig . 1-41) c u t i n t o the r e g i o n a l l y t i l t e d Devonian

carbonates and s h a l e s . The v a l l e y , which i s 15-65 km wide and more than

150 km long , t e rmina te s i n t h e a r e a of t h e El lers l ie d e l t a and t r ends

eastward t o a d ra inage source on t h e Precambrian S h i e l d . Heavy mine ra l

conten t of t h e E l l e r s l i e Sandstone i n d i c a t e s t h a t t h e sands were de r ived

from g r a n i t i c Precambrian rocks.

O i l accumula t ions i n t h e E l le rs l ie Sandstone are conta ined wi th in

EDMONTON 70

SANDSTONE, ALBER

RHINE DELTA, NETHERLAN

0 20KM

IDS

- 20 Miles O-

Fig . 1-41. Upper-Map showing t h e d i s t r i b u t i o n of t h e Lower Cre taceous

El le rs l ie Sandstone ( s t i p p l e d ) f i l l i n g a broad v a l l e y i n

Devonian ca rbona te s and s h a l e s (ha t chured ) , e a s t - c e n t r a l

A lbe r t a . Loca t ions of t h e B e l l s h i l l Lake F i e l d (1) and

Hughenden F i e l d (2) a r e shown. The c o n f i g u r a t i o n and s c a l e

of t h e areas of a l l u v i a l and d e l t a i c sed iments are remarkably

s imi la r t o those of t h e Rhine and Waal Rivers shown below.

Lower-Map showing t h e d i s t r i b u t i o n of f l u v i a l sands and si l ts

d e p o s i t e d i n t h e lower r eaches of t h e Rhine and Waal R ive r s ,

t h e Nether lands . These sed iments f i l l a broad v a l l e y i n

P l e i s t o c e n e d e p o s i t s (ha tchured) . (Redrawn from Geol-

o g i c a l Map of t h e Nether lands , compiled by Geologische

D i e n s t , 1951).

71

topographic e l e v a t i o n s ( i . e . b u r i e d sands tone h i l l s ) t h a t have s t r u c t u r a l

c losu re .

only because of t h e i r geometry b u t because they are f l anked by s h a l e s and

a t h i n l imes tone bed con ta in ing forams and os t r acods . Subsequent work

(Conybeare, 1964, 1972, and Mar t in , 1966) i n d i c a t e d t h a t t h e e l e v a t i o n s

are s t r u c t u r a l l y h igh p o r t i o n s of eroded r i v e r t e r r a c e s (F ig . 1-42) and

t h a t t h e r i v e r v a l l e y w a s subsequent ly inundated by an e s t u a r y t h a t produced

These e l e v a t i o n s were o r i g i n a l l y r e f e r r e d t o as sand b a r s , n o t

SOUTH 7-36-39-13-4 ALLIANCE FIELD BELLSHILL LAKE FIELD

WAEAMUN

___--- NISKU

_-

IRETON

Fig . 1-42.

NORTH 13 -28-42-12-4

0

100 m

S t r u c t u r a l s e c t i o n t r e n d i n g nor th-south a c r o s s t h e B e l l s h i l l

Lake and A l l i a n c e F i e l d s of e a s t - c e n t r a l A l b e r t a , showing

t h e o i l and gas-bearing Lower Cre taceous E l l e r s l i e Sandstone

ove r ly ing the eroded s u r f a c e of t h e Devonian Wabamun and

Nisku ca rbona te s .

McLennan 6-32, a w e l l i n t h e B e l l s h i l l Lake F i e l d . The

o i l -wa te r c o n t a c t is shown a t -715 f e e t (-218 m) below a

sea l e v e l datum. (E-log redrawn from Rudolph, 1960).

The i n s e t shown t h e E-log of R i c h f i e l d ,

1 2

a brackish-water , c o a s t a l marsh environment i n which muddy sediments w e r e

depos i t ed t o form a r e l a t i v e l y impermeable seal over t h e E l l e r s l i e sands .

The geometry and s i z e o f t h i s Neocomian r i v e r v a l l e y is s t r i k i n g l y similar

t o t h a t of t h e p r e s e n t v a l l e y of t h e Rhine River i n t h e Nether lands (F ig .

1-41).

The E l l e r s l i e Sands tone , which ranges i n th i ckness t o 75 m i s commonly

medium t o coa r se -g ra ined , f a i r l y well s o r t e d , and qua r t zose . Cross-bedding,

of t h e p l a n a r type found i n r i v e r p o i n t b a r d e p o s i t s , i s common. Gra in

g r a d a t i o n , from c o a r s e r below t o f i n e r above i n r e p e a t e d , t r u n c a t e d

sequences w i t h i n t h e E l le rs l ie Sandstone i n t e r v a l is a l s o ev iden t .

P o r o s i t y and pe rmeab i l i t y are g e n e r a l l y good, a l though l o c a l l y a f f e c t e d

by c a l c i t e cementa t ion . Rudolph (1959) s ta tes t h a t i n t h e B e l l s h i l l Lake

F i e l d t h e average p o r o s i t y exceeds 26%, and t h e average pe rmeab i l i t y i s

630 m i l l i d a r c y s . Loca l ly , t h e pe rmeab i l i t y ranges up t o 7,000 m i l l i d a r c y s .

I n t h e B e l l s h i l l Lake F i e l d t h e o i l column has a maximum th i ckness

of 16 m and an average th i ckness of 10 m. Flow r a t e s from i n d i v i d u a l w e l l s

were i n i t i a l l y i n t h e range 100-200 b a r r e l s of o i l per day , bu t product ion

rates were subsequent ly c u t back t o 25 b a r r e l s p e r day. The o i l has a

g r a v i t y of 28O A . P . I . Es t imated o i l i n p l a c e amounts t o 180 m i l l i o n

b a r r e l s , bu t wa te r d r i v e problems have caused d i f f i c u l t i e s i n p roduc t ion

and t h e u l t i m a t e y i e l d w i l l probably b e less than 35 m i l l i o n b a r r e l s

(5 .5 m i l l i o n cub ic me t re s ) .

The Hughenden Z i e l d (F ig . 1-43) con ta ins 15 m i l l i o n b a r r e l s of o i l ,

b u t accord ing t o Suey (1960) only 1.5 m i l l i o n b a r r e l s w i l l u l t i m a t e l y b e

recovered . The maximun th i ckness of t h e o i l - b e a r i n g sands tone i s 11 m , and

t h e average th i ckness is 7 m. Allowable product ion of t h e heavy o i l , which

has an average g r a v i t y of 1 7 O A . P . I . , was i n i t i a l l y a t t h e r a t e of 30

b a r r e l s p e r day.

73

R.8 R.7 W.4 M

A

Miles 0 5 K M -

B 0

CRETACEOUS E L L ERSL I E SANDSTONE

HUGHENDEN OIL FIELD. ALBERTA

Fig. 1-43. Map and s t r u c t u r a l s e c t i o n of t h e Hughenden F i e l d , east-

c e n t r a l A l b e r t a , showing t h e d i s t r i b u t i o n ( s t i p p l e d ) of t h e

Lower C r e t a c e o u s Ellerslie Sands tone occupying a U-shaped

loop i n a r i v e r v a l l e y w i t h i n t h e e roded c a r b o n a t e s and

s h a l e s of t h e Devonian Nisku and I r e t o n Format ions .

Regional d i p t o t h e s o u t h w e s t i s i n d i c a t e d by t h e arrow.

The f i e l d area l i e s w i t h i n Township 4 0 , Range 7 , West of t h e

4 t h Mer id ian , as shown i n A, and o c c u p i e s a s t r u c t u r a l l y

h i g h p a r t . (Redrawn from M a r t i n , 1 9 6 6 ) .

South Glenrock O i l F i e l d , Wyoming

I n t h e South Glenrock F i e l d (F ig . 1-44) s i t u a t e d on t h e s o u t h w e s t e r n

f l a n k of t h e Powder R i v e r B a s i n , Wyoming, p a r t of t h e o i l p r o d u c t i o n comes

74

SOUTH GLENROGK OIL FIELD c5=3 Oullinc T w o B u r i e d Slreom Chonnel i

ISOPACH LOWER MUDDY SHOWING TWO BURIED STREAM CHANNELS

Iwpach Contour 1nt.rvd - 10'

Sl ruc lur i Conlour Interval - 500'

Fig . 1-44. I sopach map of Lower Cre taceous Muddy Sands tone , South Glenrock

F i e l d , Wyoming, showing a meandering b e l t comprising two

channels . Contour i n t e r v a l i s 10 f e e t ( 3 m). (Af t e r Curry

and Curry , 1972) .

from channel sands tones a t t h e b a s e of t h e Lower Cretaceous Muddy Formation.

These channe l s , which a r e c u t i n t o t h e eroded s u r f a c e of t h e marine Lower

Cretaceous S k u l l Creek Formation, form a b e l t up t o 3 kn wide and more than

2 km long .

75

The sands tone bod ies f i l l i n g t h e s e channels are up t o 20 m t h i c k

and c o n s i s t mainly of f a i r l y well-rounded, we l l - so r t ed g r a i n s of q u a r t z

and c h e r t i n a m a t r i x of s i l t and c l a y . Carbonized p l a n t remains are

commonly abundant.

above, p o r o s i t y averages 14%, and pe rmeab i l i t y averages 82 m i l l i d a r c y s .

Gra in g r a d a t i o n v a r i e s from c o a r s e r below t o f i n e r

The o i l , produced from depths i n t h e range 1,700 - 1,800 m , ha s a

g r a v i t y of 370 A.P.I .

imated r ecove rab le r e s e r v e s of o i l amounted t o 50 m i l l i o n b a r r e l s .

estimate w a s based on recovery from t h r e e producing ho r i zons i n c l u d i n g ,

from o l d e r t o younger, d i s t r i b u t a r y and s h o r e l i n e sands of t h e Dakota

Following d i scove ry of t h e f i e l d i n 1950 t h e est-

This

O U 2 O L - 2

MILES KM

MEANDERING CHANNEL OF

SANDSTONE, MUDDY FORMATION

SOUTH GLENROCK FIELD

WYOMING

Fig . 1-45. Map of South Glenrock o i l f i e l d on t h e southwes tern f l a n k

of t h e Powder River Bas in , e a s t - c e n t r a l Wyoming.

s t i p p l e d area ahows t h e d i s t r i b u t i o n of a c l e a n , permeable

sands tone i n t h e lower p a r t of t h e Lower Cretaceous Muddy

Formation. The arrow i n d i c a t e s d i r e c t i o n of sediment t r a n s -

p o r t a t i o n . (Redrawn from Curry and Curry , 1954).

The

76

Formation, b a s a l r i v e r sands of t h e Muddy Formation, and younger Muddy

s h o r e l i n e sands . L a t e r estimates of Curry and Curry (1972) i n d i c a t e t h a t

t h e u l t i m a t e r ecove ry , by means of water f l o o d , may b e 75 m i l l i o n b a r r e l s

(12 m i l l i o n cub ic m e t r e s ) . The f i e l d has r e s u l t e d from a combination of

s t r a t i g r a p h i c and s t r u c t u r a l f a c t o r s , t h e o i l accumulation be ing s i t u a t e d

i n a t r a p where t h e channel is i n t e r s e c t e d by t h e a x i s of a s t r u c t u r a l f o l d

o r nose (F ig . 1-45).

It i s of p a r t i c u l a r i n t e r e s t t o n o t e t h a t t h e o i l -wa te r con tac t i n

t h e producing Dakota sands tone , a long t h e sou th s i d e of t h e f i e l d , has

225 m of tilt downdip t o t h e east a long t h e c r e s t of t h e s t r u c t u r a l nose.

This i n d i c a t e s a hydrodynamic c o n d i t i o n wi th a ve ry marked po ten t iome t r i c

g r a d i e n t .

Recluse O i l F i e l d , Wyoming

The Recluse F i e l d (Figs.l-46 and 1-47) i s s i t u a t e d on t h e n o r t h e a s t e r n

O i l i s ob ta ined from t h e Recluse f l a n k of t h e Powder River Bas in , Wyoming.

Sandstone a t t h e base of t h e Lower Cre taceous Muddy Formation a t a depth

of approximate ly 2,300 m. Th i s s ands tone , which a l s o y i e l d s oil i n t h e

nearby East Sandbar, H i l i g h t , and K i t t y f i e l d s , i s i n t e r p r e t e d by Woncik

(1972) a s a mar ine s h o r e l i n e sand , p o s s i b l y a b a r r i e r i s l a n d . On t h e o t h e r

hand , .Forgotson and S t a r k (1972) i n t e r p r e t t h e sands tone body as a channel-

- f i l l sand . In f a c t , t h e sands tone body comprises two u n i t s , each wi th a

d i f f e r e n t o i l -wa te r c o n t a c t i n t h e Recluse F i e l d . The body t r e n d s nor thwes t

f o r more than 24 k m and i s up t o 5 km wide.

dimensions of roughly 12 km by 3 km.

The o i l f i e l d i t s e l f has

The sands tone , which has a maximum th i ckness of 15 m and an average

o i l -bea r ing s e c t i o n of 8 m , i s q u a r t z o s e , has an average p o r o s i t y of 19%

and an average pe rmeab i l i t y of 300 m i l l i d a r c y s . Rese rvo i r p r e s s u r e i s

approximate ly 2,150 p . s . i . , which i s compara t ive ly low f o r t h a t p a r t i c u l a r

depth .

77

T 57 N

T 56 N

Fig. 1-46. I sopach map of Lower Cretaceous Muddy Sands tone , Recluse

F i e l d , Wyoming. Contour i n t e r v a l i s 10 f e e t (3 m). (Af te r

Woncik, 1972).

The o i l , which is produced a t an a l lowab le r a t e of 300 b a r r e l s per

day , has a g r a v i t y of 42O A.P.I. Cumulative p roduc t ion t o 1973 was 1 7

m i l l i o n b a r r e l s . T o t a l o i l i n p l a c e i s e s t ima ted t o b e 150 m i l l i o n

b a r r e l s , of which 20-40% (5-10 m i l l i o n cub ic met res ) may u l t i m a t e l y b e

78

1 58

N

1

57 N

1 56 N

LOWtR MUDDY l Y P f LOG . M O W R Y

1 I 7500'

ISOLITH LWR. MUDDY SS.

(SHOWING LOWER MUDDY PRODUCllON)

0 0 - 3 0 '

I> 3 0 '

0 < 80 ' T O T A L M U D D Y T H I C K N f S S

Fig . 1-47. I s o l i t h of t h e Upper Recluse Sandstone and Recluse Sandstone

which c o n s t i t u t e t h e lower p a r t of t h e Muddy Formation,

showing a l i n e a r p a t t e r n where t h e Recluse F i e l d i s more than

30 f e e t (9 m) t h i c k . (Af t e r S tone , 1972).

recovered economica l ly , depending on t h e r e s e r v o i r response t o p re s su re

maintenance. The recovery mechanism i s gas-so lu t ion d r i v e , t h e down-dip

p o r t i o n s of t h e sands tone body be ing only p a r t l y s a t u r a t e d wi th water.

The f i e l d is pure ly s t r a t i g r a p h i c , t h e o i l be ing t rapped by up-dip

pe rmeab i l i t y b a r r i e r s caused by p inching ou t of t h e sands tone . The only

s t r u c t u r a l element is a r e g i o n a l southwes t d i p , a l though Stone (1972)

s a y s t h a t i n some Lower Muddy o i l f i e l d s entrapment is provided by a

combination of s ands tone pinch-out and s t r u c t u r a l nos ing where a s t r u c t u r e

i n t e r s e c t s t h e t r e n d of a d i s t r i b u t a r y channel (Fig. 1-38).

79

Donkey Creek, Rozet , and O'Connor O i l F i e l d s , Wyoming

On t h e e a s t e r n f l a n k of t h e Powder R ive r Bas in , Wyoming, s e v e r a l

f i e l d s produce o i l from t h e Lower Cre taceous Newcastle Sandstone (Fig. 1-48) .

Stapp (1967) r eco rds t h a t t h e Newcastle, which has an average th i ckness of

9 m was depos i t ed i n a d e n d r i t i c r i v e r system t h a t d ra ined northward.

This r i v e r sys tem w a s developed penecontemporaneously wi th t h a t which

depos i t ed t h e b a s a l sands of t h e Muddy Formation i n t h e South Glenrock

F i e l d (F ig . 1-44) t o t h e s o u t h , as evidenced by t h e f a c t t h a t t h e channels

of t h i s system are a l s o c u t i n t o t h e e roded s u r f a c e of t h e marine Lower

Cretaceous S k u l l Creek Formation, as i s t h e s i t u a t i o n i n t h e South Glenrock

F i e l d . The s t r a t i g r a p h i c sequence on t h e e a s t e r n f l a n k of t h e b a s i n i s

s i m i l a r t o t h a t of t h e South Glenrock F i e l d area on t h e sou the rn f l ank .

Reservoi rs i n Lower Cretaceous beds have been formed n o t on ly i n t h e

- lo cr 0

1 MILES

Fig. 1-48. D e n d r i t i c d i s t r i b u t i o n of t h e Lower Cre taceous Newcastle

Sandstone i n p a r t of t h e Powder River Bas in , Wyoming. Areas

where o i l i s produced from t h e Newcastle a r e shown i n b lack .

Arrows i n d i c a t e northward d i r e c t i o n s of sediment t r a n s p o r t

i n t h e Newcastle r i v e r system. (Redrawn from Stapp , 1967).

80

Newcastle b u t a l s o i n t h e under ly ing marginal-marine ( d i s t r i b u t a r y and

s h o r e l i n e sands ) F a l l R ive r Sandstone and i n t h e ove r ly ing t r a n s g r e s s i v e

marine Dynneson Sandstone.

conf ined w i t h i n more permeable zones of sands tone beds where they a r e

bounded by up-dip edges , and consequent ly are pure ly s t r a t i g r a p h i c t r a p s .

Stapp (1967, p . 2055) concludes , “ O i l accumulation i s p r e s e n t i n t h e

up-dip edges of t h e o f f s h o r e , b lanket - type sands tone of t h e Dynneson,

t h e channel sands tone of t h e Newcastle, and t h e complex marginal-marine

sands tone of t h e F a l l River . P rospec t ing f o r such s t r a t i g r a p h i c t r a p s

r e q u i r e s an unders tanding of t h e pa l eodepos i t i ona l environments of t h e

rocks” .

O i l accumula t ions i n t h e Newcastle a r e

Coyote Creek and Miller Creek O i l F i e l d s , Wyoming

The Coyote Creek F i e l d and Miller Creek F i e l d (F ig . 1-49) are a l s o

s i t u a t e d on t h e e a s t e r n f l a n k of t h e Powder River Basin, Wyoming, approx-

ima te ly 15 km s o u t h e a s t and n o r t h e a s t r e s p e c t i v e l y from t h e Rozet F i e ld .

The producing zone i s t h e Lower Cre taceous F a l l S i v e r Sandstone which l i e s

approximate ly 60 m below t h e Newcastle Sandstone. Stapp (1967) says t h a t

t h e F a l l River comprises t h r e e s e p a r a t e sands tone bod ies which l o c a l l y

merge, as i n p a r t s of t h e Coyote Creek F i e l d , t o form a s i n g l e porous

u n i t approximate ly 25 m t h i c k . Elsewhere, t h e F a l l River ranges i n

t h i c k n e s s up t o 50 m . Stapp d e s c r i b e s t h e s e sands tone bod ies as having

been depos i t ed i n a marginal-marine environment, t h e lower two bodies

be ing s h o r e l i n e sands depos i t ed by a r e g r e s s i n g s e a .

i n t e r p r e t e d a s t h e b a s a l u n i t of a marine t r a n s g r e s s i v e sequence r e f e r r e d

t o as t h e S k u l l Creek Formation. Berg (1968), on tho o t h e r hand, states

t h a t t h e F a l l River Sandstone bod ies were, i n p a r t a t l e a s t , depos i t ed as

d e l t a d i s t r i b u t a r y p o i n t b a r s f l anked 3y muddy sediments w i t h i n t h e same

channel . H e s a y s , p . 2116, “Because t h e F a l l River is l a r g e l y of marine

and d e l t a i c o r i g i n , t h e r e s e r v o i r s ands tone was be l i eved t o have been

The upper sand is

81

N

A

/ CHANNEL FILL / / OIL-WATER CONTAC

/ /

ISOPACH OF POROUS SANDSTONE I N

POINT BARS OF FALL RIVER

SANDSTONE, WYOMING

Fig . 1-49. Isopach of n e t porous sands tone i n t h e o i l -producing Lower

Cre taceous F a l l R ive r Sands tone , Coyote Creek F i e l d (A)

and Miller Creek F i e l d ( B ) , Crook and Weston Count ies ,

Wyoming, showing o i l accumulation i n r i v e r p o i n t b a r s .

(Redrawn from Berg, 1968, and Truchot , 1963).

depos i t ed i n a l i t t o r a l environment, perhaps as a series of b a r r i e r - b a r

sands f l anked by l agoona l c l a y s .

been proposed f o r t h e s e sands tone beds at t h e West Moorcroft f i e l d

(Met t l e r , 1966) and a t Coyote Creek f i e l d (Bolyard and McGregor, 1966,

p . 2236)." Bolyard and McGregor i n t e r p r e t e d t h e F a l l River Sandstone

bodies as po in t - -bar channel d e p o s i t s a s s o c i a t e d wi th a d e l t a f r o n t .

They s a y , p. 2238, "The l i t h o l o g y , cross-bedding, c l a y g a l l s , and o t h e r

Recen t ly , however, a f l u v i a l o r i g i n has

82

f e a t u r e s a r e ve ry s imi la r t o those of t h i c k , mass ive , c h a n n e l - f i l l i n g

sands tone beds observed i n outcrop . I t i s d i f f i c u l t t o r e c o n s t r u c t a

p a t t e r n of convincing f a c i e s r e l a t i o n s t h a t would b e c o n s i s t e n t w i th

e i t h e r t h e o f f shore -ba r , b a r r i e r - i s l a n d , o r beach-deposit i n t e r p r e t a t i o n s " .

I n t h e Coyote and Miller Creek f i e l d s t h e F a l l River Sandstone is

l i g h t g rey t o w h i t i s h , q u a r t z o s e , f i n e t o medium-grained, and w e l l s o r t e d .

Carbonized p l a n t m a t t e r i s p r e s e n t throughout t h e i n t e r v a l . The n e t pay

comprises 10-15 m having a p o r o s i t y of 15-18% and a pe rmeab i l i t y t h a t

averages 200 m i l l i d a r c y s b u t ranges up t o 1,000 m i l l i d a r c y s . Both f i e l d s

are i n t e r p r e t e d by Berg (1968) as p o i n t b a r segments of a r i v e r meander

b e l t t h a t t r e n d s i n a nor th-south d i r e c t i o n f o r more than 50 km. This

t r e n d c o n t a i n s several o t h e r o i l f i e l d s of s i m i l a r o r i g i n .

The Coyote Creek and Mil ler Creek f i e l d s have e s t ima ted p roduc ib le

r e s e r v e s of 20 m i l l i o n b a r r e l s (3.2 m i l l i o n cub ic metres) of 41' A.P . I . o i l

and 5 m i l l i o n b a r r e l s of 33' A.P.I. o i l r e s p e c t i v e l y .

are a l s o e s t ima ted t o be i n t h e range 150-250 b a r r e l s pe r acre- foot . The

recovery mechanism i s an a c t i v e water d r i v e i n t h e Coyote Creek F i e l d and

a combined water and gas - so lu t ion d r i v e i n t h e Miller Creek F i e l d . The

. a r eas of t h e Coyote Creek and Miller Creek f i e l d s are approximate ly 2,000

and 1,000 acres r e s p e c t i v e l y .

U l t i m a t e r e c o v e r i e s

Reimers-Lane-Hart Trend, Nebraska

I n t h e Denver Basin of wes te rn Nebraska t h e R e i m e r s , Faro , Dal ton ,

Lane, Deep Creek and H a r t O i l f i e l d s form a nor th-south t r e n d (Fig. 1-50)

w i t h i n a Lower Cre taceous l i n e a r sands tone body. This body f i l l s a channel

c u t i n t o t h e "J" Member which is o v e r l a i n by t h e Lower Cretaceous Huntsman

Shale and u n d e r l a i n by t h e Lower Cre taceous S k u l l Creek Formation, bo th of

which are marine. The channel is a l s o l o c a l l y c u t i n t o t h e S k u l l Creek.

It h a s an average wid th of 450 m, a depth of 15-20 m, and a l eng th of more

than 30 Icm.

T 16

83

011 FIkt-DS IN CRETACEOUS RIVER DEPOSITS, NEBRASKA

A A'

F i g . 1-50. Map and s e c t i o n showing o i l a c c u m u l a t i o n s i n r iver d e p o s i t s

f i l l i n g a v a l l e y i n t h e Lower C r e t a c e o u s "J" s a n d s t o n e ,

Denver B a s i n , Nebraska . Arrow i n d i c a t e s t h e d i r e c t i o n of

r e g i o n a l d i p . (Redrawn from Harms, 1966).

84

The c h a n n e l - f i l l s ands tone i s predominantly l i g h t g rey , qua r t zose ,

f i n e t o medium-grained, and cross-bedded. Clays tone c h i p s , probably

de r ived from t h e e r o s i o n of d r i e d and cracked mud on t h e r i v e r banks ,

a r e f a i r l y common w i t h i n t h e sands tone .

s ands tone and da rk grey s i l t s t o n e show slump s t r u c t u r e s s imi la r t o those

formed i n t h e s i l t y , upper l a y e r s of p o i n t b a r d e p o s i t s .

are a l s o common, a s a r e carbonized p l a n t remains. I n g e n e r a l , t h e

sands tone body appears t o have been depos i t ed by a r i v e r , p o s s i b l y a

d i s t r i b u t a r y f lowing on a c o a s t a l p l a i n .

Some t h i n beds of l aye red

Scour s t r u c t u r e s

O i l has accumulated i n more permeable p a r t s o f t h e sands tone body

where i t i s g e n t l y fo lded by northwest-plunging a n t i c l i n e s t h a t c r o s s t h e

t r e n d of t h e channel . I n t h e s e producing s e c t i o n s t h e sands tone commonly

has p o r o s i t y and pe rmeab i l i t y i n t h e ranges 15-25% and 100 - 1,000 m i l l i -

darcys r e s p e c t i v e l y .

s t o n e body are h o r i z o n t a l b u t a t v a r i o u s e l e v a t i o n s .

format ion wa te r v a r i e s from 90,000 t o 110,000 ppm accord ing t o Harms (1966)

I n d i v i d u a l wells have an average p roduc t ion r a t e of 25,000 b a r r e l s of o i l

pe r y e a r , and t h e e s t ima ted cumula t ive product ion t h a t w i l l u l t i m a t e l y be

ob ta ined from a l l f i e l d s a long t h e t r e n d i s less than 10 m i l l i o n b a r r e l s

(1.6 m i l l i o n cubic me t re s ) .

The o i l -wa te r c o n t a c t s i n a l l f i e l d s a long t h e sand-

S a l i n i t y of t h e

Cut Bank O i l F i e l d , Montana

I n nor thwes tern Montana o i l p roduc t ion i n t h e Cut Bank F i e l d ,

s i t u a t e d on t h e w e s t f l a n k of t h e Sweetgrass Arch, i s ob ta ined from t h e

Lower Cre taceous Cut Bank Sandstone. This s ands tone , which f i l l s channels

c u t i n t o s h a l e s and s i l t y marine beds of t h e Upper J u r a s s i c Swif t Formation

and Rierdon Formation, is t h e b a s a l member of t h e Kootenai Formation and

i s o v e r l a i n by s e v e r a l hundred f e e t of non-marine, v a r i c o l o r e d mudstones

and s i l t y s ands tones . The channels form a meandering p a t t e r n t h a t t r ends

85

R 6 R 5 R 4 W

O- 5 KM

0 5 Miles

B B' YELLOW OWL I HARWOOD I

RIERDON

Fig. 1-51. D i s t r i b u t i o n of t h e Lower Cre taceous Cut Bank Sandstone where

i t i s more than 50 f e e t (15 m) t h i c k i n t h e Cut Bank o i l

f i e l d a r e a , Montana. I n s e t shows t h e l o c a t i o n . The arrow

i n d i c a t e s d i r e c t i o n of flow. (Redrawn f rom She l ton , 1967).

86

nor th-south . Drainage w a s t o t h e n o r t h and i n d i v i d u a l channels b i f u r c a t e

i n t h a t d i r e c t i o n . The l i m i t s of t h e Cut Bank Sandstone are broadly

de f ined by a d e p o s i t i o n a l edge f l a n k i n g t h e up-dip boundary of t h e o i l

f i e l d and by ou tc rops 50 km westward. Northward, t h e p a t t e r n of channels

ex tends f o r more than 80 km i n t o Albe r t a . The Cut Bank d ra inage system,

comprising a number of s e p a r a t e channe l s , w a s formed on a broad and f a i r l y

f l a t c o a s t a l p l a i n . The p a t t e r n of channels w i t h i n t h e Cut Bank F i e l d

(F ig . 1-51) can b e de f ined by a n i sopach map of t h e Cut Bank Sandstone

showing t h i c k n e s s s s exceeding 15 m (She l ton , 1967). These meandering

channels commonly have a wid th of 450-1,200 m and a th i ckness o f up t o 25 m .

Where t h e Cut Bank Sandstone c rops o u t , 50 km southwest of t h e f i e l d , i t

h a s a t h i c k n e s s of up t o 70 m .

The sands tone is composed mainly of g r a i n s of q u a r t z and dark grey

c h e r t .

g r a i n s i z e g r a d a t i o n i s w e l l de f ined w i t h i n sequences of l a y e r s , ranging

from coa r se below t o f i n e above. Loca l ly , t h e coarse-gra ined l a y e r s are

conglomera t ic , t h e maximum pebble s i z e be ing 15 mm.

common f e a t u r e ; o t h e r sed imentary s t r u c t u r e s i n c l u d e burrows (?> , c lays tone

ch ips (probably fragments of d r i e d mud), and deformat ion probably caused bv

slumping of t h e unconsol ida ted sediment i n a h y d r o p l a s t i c s ta te (Conybeare

and Crook, 1968). A s h a l e bed , l o c a l l y p re sen t w i t h i n t h e upper p a r t o f t h e

Cut Bank Sands tone , con ta ins f resh-water o s t r acods and

Within i n d i v i d u a l l a y e r s t h e g r a i n s are f a i r l y w e l l s o r t e d , bu t

Cross-bedding i s a

gas t ropods . P o r o s i t y of t h e sands tones is i n t h e ranges 12-19%, pe rmeab i l i t y

ranges up t o 300 m i l l i d a r c y s and averages 100 m i l l i d a r c y s . The b e s t va lues

f o r p o r o s i t y and pe rmeab i l i t y are found i n t h e medium-grained sands tone ,

whereas poore r v a l u e s are found i n bo th t h e f ine -g ra ined and conglomera t ic

s ands tones .

O i l p roduc t ion (F ig . 1-52) i s more p r o l i f i c i n t h e t h i c k e r p a r t s of

t h e sands tone bod ies w i t h i n t h e channe l s , b u t is n o t p r e c i s e l y confined

0 5

0 KM I

M I L E S

I/

I N I T I A L DAILY P R O D U C T I O N IN BARRELS,

CUT B A N K S A N D S T O N E S , M O N T A N A

Fig . 1-52. I n i t i a l d a i l y p r o d u c t i o n ( f i r s t 10 day average) of o i l w e l l s

p roducing from t h e Cut Bank Sands tone . L o c a l l y , t h e i n i t i a l

P r o d u c t i o n exceeded 100 b a r r e l s a day. (Redrawn from B l i x t , 1941).

t o t h e s e l o c a t i o n s . Rates of p r o d u c t i o n depends on v a r i a t i o n s of p o r o s i t y

and p e r m e a b i l i t y w i t h i n t h e f i e l d area where t h e o i l and g a s i s t r a p p e d

a g a i n s t t h e up-dip edge of t h e Cut Bank Sands tone . The main producing zone ,

compr is ing a p p r o x i m a t e l y 5 m of n e t s a n d s t o n e , i s i n t h e lower p a r t o f t h e

Cut Bank a t a d e p t h of a p p r o x i m a t e l y 900 m .

A .P . I . P r o d u c t i o n is a s s i s t e d by g a s s o l u t i o n and a gas-cap d r i v e .

I n i t i a l d a i l y p r o d u c t i o n p e r w e l l d u r i n g t h e f i r s t 10 day p e r i o d averaged

56 b a r r e l s .

The o i l h a s a g r a v i t y of 3 8 O

F a i r l y f r e s h w a t e r , h a v i n g a s a l i n i t y of a p p r o x i m a t e l y 10,000 ppm,

u n d e r l i e s t h e o i l , i n d i c a t i n g movement of s u r f a c e water i n t o t h e Cut Bank

88

Sandstone.

of t i l t i n g of t h e o i l -wa te r c o n t a c t .

y i e l d more than 30 m i l l i o n b a r r e l s (4 .8 m i l l i o n cub ic me t re s ) of o i l and

80,000 m i l l i o n cub ic f e e t (2,200 m i l l i o n cub ic me t re s ) of gas .

This hydrodynamic s i t u a t i o n may have caused some s l i g h t degree

The Cut Bank F i e l d may u l t i m a t e l y

Nahorkatiya O i l F i e l d , A s s a m

O i l p roduc t ion i n t h e Nahorkatiya F i e l d of A s s a m is ob ta ined from

sands tones w i t h i n a 300 m i n t e r v a l i n t h e upper p a r t of t h e Oligocene Barail

Series. These sands tones o r i g i n a t e d as r i v e r channel sands (F ig . 1-53)

depos i t ed on a f a i r l y f l a t f l o o d p l a i n of s i l t and c l a y i n t h e upper reaches

of a d e l t a . I n d i v i d u a l channe l s , which range i n th i ckness t o 30 m and i n

wid th t o more than 450 m , are in te rbedded wi th t h i n beds of c o a l and

l i g n i t e formed i n backswamp areas of a r i v e r f l o o d p l a i n . More than 50

0 I i- -~ . ~ ~ ~~ _1

Km

E-LOG SECTION OF CHANNEL SANDS NAHORKATIYA FIELD ASSAM

Fig . 1-53. E-log s e c t i o n showing o i l -bea r ing r i v e r channel sands i n the

Oligocene B a r a i l Series, Nahorkatiya F i e l d , A s s a m . (Redrawn

from Azad, Bhat tacharyya , D a t t a , and S tevens , 1971).

89

r o

E-LOG OF CHANNEL SANDS,

NAHORKATIYA FIELD, ASSAM.

Fig. 1-54. E-log of a composite channel sand i n t h e Oligocene Barail

S e r i e s , Nahorkatiya O i l f i e l d , A s s a m . Three s e p a r a t e channels

are superimposed, each grading upward from coa r se sand t o s i l t .

Note t h e c h a r a c t e r i s t i c be l l - shape of t h e l o g of each channel.

(Redrawn from Azad, Bhat tacharyya , Datta, and Stevens , 1971).

s e p a r a t e channels have been recognized i n t h e Nahorkatiya F i e l d .

l o c a t i o n s , two o r more channels are superimposed (F ig . 1-54) t o form

sands tone u n i t s more than 50 m t h i c k . The e l e c t r i c l og c h a r a c t e r of many

of t h e s e channel sands shows t h e t y p i c a l be l l - shape i n d i c a t i n g g r a i n grad-

a t i o n from c o a r s e r below t o f i n e r above.

A t some

O i l accumulation is c o n t r o l l e d by a combination of s t r a t i g r a p h i c

and s t r u c t u r a l f a c t o r s . Reg iona l ly , t h e Barail S e r i e s d i p s away from a

basement r i d g e . This s t r u c t u r a l element has probably been impor tan t i n

c o n t r o l l i n g t h e d i r e c t i o n of mig ra t ion and e x t e n t of t h e area unde r l a in

by accumulations of o i l . L o c a l l y , t h e o i l has accumulated i n t r a p s con-

t r o l l e d by f a u l t i n g and p inch ing o u t of t h e channel sands . The o i l ,

which i s waxy and has a g r a v i t y of 3 3 O A.P.I. i n a l l t h e s e p a r a t e r e s e r v o i r s ,

90

i s thought t o have o r i g i n a t e d i n marine s h a l e s and l imes tones o f t h e under-

l y i n g Eocene sequence.

Maikop O i l F i e l d , U.S.S.R.

The Maikop F i e l d (F ig . 1-55) i n t h e Black Sea rea, U . S . S . R . , produces

o i l from meandering T e r t i a r y channel sands . These s h o e s t r i n g sand bod ies

meander a t v a r i o u s levels w i t h i n a c l a y - f i l l e d v a l l e y c u t i n t o Cre taceous

marly l imes tone . The main producing sand body, which i s s t r a t i g r a p h i c a l l y

t h e h i g h e s t , i s 150-300 m wide and more than 8 km long . It i s g e n e r a l l y

conf ined t o t h e v a l l e y , bu t i n p l a c e s meanders ou t of t h e v a l l e y on t o t h e

sur rounding f lood p l a i n . The sands , which a r e encountered a t ve ry sha l low

SANDS --

TERTIARY RIVER CHANNEL MAIKOP OIL FIELD

U.S.S. R.

Fig . 1-55. Map and s e c t i o n s of bu r i ed stream-channel sands i n a clay-

f i l l e d T e r t i a r y v a l l e y , Maikop o i l f i e l d , Black Sea a r e a ,

U.S.S.R. (Redrawn from Prokopov and Maksimov, 1937).

91

depths of a few hundred metres, have good porosity and permeability. They

are commonly medium to coarse-grained, but locally include grit and gravel.

Entrapment of oil has resulted from a combination of stratigraphic

and structural factors by which closure results from the coincidence of

meander belts and a monocline dipping northward from the Caucasus Mountains.

Initial rates of production from some wells have ranged up to 7,000 barrels

of oil per day, and the amount of oil that can ultimately be recovered from

the field is estimated to exceed 15 million barrels ( 2 . 4 million cubic

metres).


93

Chapter 2

DISTRIBUTARY AND DELTA-FRINGE SAND

Introduction

Geomorphology

Patterns of deltas are ephemeral. They change continuously in

response to, (a) shifts in the courses of distributaries, (b) to fluct-

uations in the load of sediments transported to the delta and seashore,

(c) to variations in rates of compaction causing uneven subsidence in

different parts of the delta, (d) to the effects of storms and tidal

changes and, (e) to the bathymetry of the continental shelf on which the

delta is building outward.

foot delta of the present-day Mississippi River has been formed as a result

of the shallowness of the continental shelf and the comparative slight

variations in tidal levels. By contrast, the Niger River cuspate-arcuate

delta (Fig. 1 - 3 ) , currently building outward on a very narrow continental

shelf subject to large tidal variations with strong current and wave action,

has smooth, curved shoreline of delta-fringe sands.

The dendritic pattern of the classic birds-

Viewed in three dimensions, an ever-changing delta pattern is only

the surface or geographic expression of a prograding lobe of sediment, of

irregular outline and variable thickness, that is building seaward in

response to fluctuations in the rate of sedimentation.

ically changes course and discharges its load of sediment in other parts of

the delta, it successively builds a sequence of lobes. These lobes not only

prograde seaward, but merge laterally to fbrm piles of sediment which them-

selves may merge with piles from adjacent rivers to constitute the paralic

facies of a sedimentary basin.

A s a river period-

From a paleogeomorphic point of view, the

94

d e n d r i t i c and anastomosing p a t t e r n of d i s t r i b u t a r i e s i n t h e Miss i s s ipp i

River d e l t a complex (Fig. 2-1) i s t h r e e dimensional.

downward i n t o Recent and T e r t i a r y s e c t i o n s underlying t h e present-day

d e l t a , s u b s t a n t i a t i n g t h e view t h a t depos i t i ona l p a t t e r n s and sedimentol-

o g i c a l processes observed today i n t h e Miss i s s ipp i Del ta a r e r e p e t i t i o n s

of those marking t h e geo log ica l h i s t o r y of t h e underlying T e r t i a r y .

The p a t t e r n extends

Of p a r t i c u l a r i n t e r e s t i n t h e f i e l d of petroleum exp lo ra t ion a r e t h e

three-dimensional p a t t e r n s of modern d i s t r i b u t a r y and de l t a - f r inge sand

bod ies , t h e geometry of t hese bod ies , and t h e i r i n t e r n a l f e a t u r e s such a s

sedimentary s t r u c t u r e s , g r a i n g rada t ion , and l i t h o l o g i c v a r i a t i o n s . The

s p a t i a l a s s o c i a t i o n s of t h e s e bodies with ad jacen t beds, and t h e n a t u r e

of t hese beds, a r e e s s e n t i a l t o t h e i n t e r p r e t a t i o n of t h e o r i g i n s of t h e

sandstone bodies .

KM M I L E S /

D I ST R I BUTA RY C H A N N E LS, M I S S I SS I PP I D E LTA

Fig. 2-1. P a t t e r n of a c t i v e and abandoned d i s t r i b u t a r y channels of

The Miss i s s ipp i d e l t a . (Redrawn from Kolb and van Lopik,

1966).

95

I n t h e lower reaches of a d e l t a bo rde r ing t h e s h o r e , where t h e s u r f a c e

of t he subs id ing landmass has a n e l e v a t i o n of less than one metre above sea

l e v e l , t h e main d i s t r i b u t a r i e s f low through areas of marsh. The channels ,

bounded by l e v e e s , are commonly h ighe r t han t h e sur rounding marshlands

which r e c e i v e s mud and s i l t du r ing t i m e s of f l o o d when t h e d i s t r i b u t a r i e s

overflow t h e i r banks. Sands are conf ined t o channels i n which they are

t r anspor t ed t o t h e d i s t r i b u t a r y mouths where they are depos i t ed and subseq-

uen t ly swept by ocean c u r r e n t s t o form d i s t r i b u t a r y mouth b a r s (F ig . 2-2) .

A s t h e d i s t r i b u t a r y con t inues t o grow seaward i t cont inuous ly over - r ides

t h e sand b a r s a t i t s mouth t o form a prograding , l i n e a r sand body r e f e r r e d

t o by F i s k (1961) as a ba r - f inge r . The upper and c e n t r a l p a r t o f such a

sand body, be ing conf ined t o t h e channel , i s f l u v i a l and may show i n t e r n a l

f e a t u r e s c h a r a c t e r i s t i c of t h i s o r i g i n . The lower and l a t e r a l l y more

ex tens ive p a r t of t h e sand body may show i n t e r n a l f e a t u r e s , such as g r a i n

g rada t ion from c o a r s e r above t o f i n e r below (Fig. Z-ZC), c h a r a c t e r i s t i c

of a s h o r e l i n e sand. Th i s appa ren t anomaly i n t h e d e p o s i t i o n a l environment

of t h e sands tone body p e r t a i n s on ly t o t h a t p a r t of t h e d i s t r i b u t a r y sand

body t h a t has been b u i l t o u t i n t o t h e sea. The r e m i n d e r of t h e body, which

i n many examples probably r e p r e s e n t s t h e longe r p o r t i o n of t h e d i s t r i b u t a r y ,

is e n t i r e l y of f l u v i a l o r i g i n . These r e l a t i o n s h i p s i l l u s t r a t e some of t h e

d i f f i c u l t i e s encountered i n recogniz ing t h e o r i g i n of a sands tone body i n

t h e subsur f ace .

The p r o g r a d a t i o n a l sequence o f d e l t a d i s t r i b u t a r i e s , c h a r a c t e r i z e d

by g r a i n g r a d a t i o n from c o a r s e r above t o f i n e r below, i s seen n o t on ly i n

ba r - f inge r sands b u i l d i n g o u t t o sea on a sha l low sea f l o o r , bu t a l s o i n

t h e seaward ex tens ion of c o a s t a l sand bod ies such as b a r r i e r b a r s . Upstream,

t h e ba r - f inge r s merge i n t o sand bod ies depos i t ed i n d i s t r i b u t a r y channels

where t h e f l u v i a l sequence i s c h a r a c t e r i z e d by g r a i n g r a d a t i o n from coa r se r

below t o f i n e r above, provided t h a t t h e sand i s n o t uniform i n g r a i n s i z e .

96

\

A

PRODELTA

PRODE LTA 9 c 9 I-

GEOMETRY AND GRAIN GRADATION OF

FINGER SAND

BA. R

F i g . 2-2. A - P l a n v iew of a b a r - f i n g e r s a n d body formed a t t h e mouth

of Southwest P a s s , a main d i s t r i b u t a r y i n t h e b i r d f o o t

d e l t a of t h e M i s s i s s i p p i R i v e r , showing t h e d i s t r i b u t i o n

of s a n d s i n t h e d i s t r i b u t a r y mouth b a r , and of s a n d s and

s i l ts i n t h e d i s t a l b a r o v e r - r i d i n g t h e p r o d e l t a s i l t s

and c l a y s . (Redrawn from Coleman and G a g l i a n o , 1965).

97

Another p o s s i b l e f a c t o r i n t h e development of ba r - f inge r s h a s been

poin ted o u t by Moore (1970). H e s ays t h a t t h e l i n e a r bod ie s of f ine-gra ined

sand i n t h e M i s s i s s i p p i River d i s t r i b u t a r i e s , termed ba r - f inge r s , are formed

no t only by t h e seaward growth of prograding d is t r ibu tary-mouth b a r s , bu t

a l s o by t h e i n t r u s i o n of a s a l t wa te r wedges i n t o t h e d i s t r i b u t a r y channel

dur ing pe r iods of less than maximum d i scha rge . A wedge causes r educ t ion i n

t h e bottom-carrying power of t h e d i s t r i b u t a r y and r e s u l t s i n d e p o s i t i o n of

a sand s i l l (Fig. 2-3) t h a t mig ra t e s w i th t h e ebb and f low of t h e wedge a long

t h e lower course of t h e d i s t r i b u t a r y .

The geometry of ba r - f inge r sand bod ies has been desc r ibed by F i sk

(1961) and Gould (1970). Each ba r - f inge r is a prograding , l i n e a r body

formed by a c c r e t i o n of d i s t r ibu tary-mouth sand b a r s (F ig . 2 - 4 ) . A t any

p o i n t i n t i m e , t h e sand b a r forms a n a r c u a t e body of sand t h a t has a w id th ,

normal t o t h e cour se of t h e d i s t r i b u t a r y , of 5-8 km. Deposited i n sha l low

B - Cross-sec t ion of a ba r - f inge r sand a t t h e mouth of a

d e l t a d i s t r i b u t a r y , showing t h e channel f l anked by

l e v e e s and u n d e r l a i n by sands depos i t ed as a d i s t r i b u t a r y

mouth b a r , and by satid and s i l t depos i t ed as a d i s t a l

b a r o v e r r i d i n g p r o d e l t a s i l ts and c l a y s . No scale.

(Redrawn from F i s k , 1961).

C - E-log c h a r a c t e r i s t i c s of a p rograda t iona l sequence from

coarser -gra ined above t o f ine r -g ra ined below, such as

t h e sequence shown i n t h e b a r f i n g e r sand body i l l u s t r a t e d

by A and B. (Redrawn from F i s h e r , 1969 and F i s h e r e t aZ . ,

1969).

98 S E C T I O N A L O N G DELTA DlSTRtBUTARY

R I V E R L E V E L - 0 , I _____ ~ ' 1 SEA LEVEL ~~~~~~

+-.- F R E S H WATER

I ' IOG'

50 " 0 25 0 25 L - ~ _ _ _ 4 L-

M I I EL K M

Fig . 2-3. Diagrammatic s e c t i o n a long t h e channel of a d e l t a d i s t r i b u t a r y ,

showing t h e r e l a t i o n s h i p s of a sand s i l l and wedge of sa l t

water w i t h i n t h e f resh-water channel. (Redrawn from Moore,

1970).

A /

LJ M I L E S

A

0- 2 K M

A' 0 FEET

400 0 10

0 10 M I L E S

K M

BAR - FINGER SAND, MISSISSIPPI DELTA.

Fig . 2-4. P l an and s e c t i o n a l views i l l u s t r a t i n g p rograda t ion du r ing

t h e y e a r s 1764 t o 1959, of t h e ba r - f inge r sand body forming

Southwest Pass, M i s s i s s i p p i River. Sec t ion A-A' shows t h e

t r a c e s of t i m e p l anes w i t h i n t h e ba r - f inge r sand body (1)

which o v e r l i e s d e l t a - f r o n t s i l t s ( 2 ) and p r o d e l t a c l a y s ( 3 ) .

(Redrawn from Gould, 1970, a f t e r F i s k , 1961).

99

water a t t h e mouth of a d i s t r i b u t a r y , t h e sand g rades seaward t o s i l t and

c l ay . Prograding seaward, t h e ba r - f inge r grows as a d iachronous sand body,

time-planes (o r t h e i r t r a c e s seen i n s e c t i o n s having a n en echeZon and

d iagonal arrangement w i t h i n t h e sand body.

up t o 75 m t h i c k and 30 km long . Lateral and v e r t i c a l growth o f t h e d e l t a

complex r e s u l t s i n t h e ever-changing p a t t e r n of ba r - f inge r sand bod ies

Bar- f inger sand bodies can b e

HIGH TIDE

-22

0 1 2 I I

Km

MOUTH OF PO RIVER AT PlLA

Fig . 2-5. Arcuate sand b a r s ( s t i p p l e d ) formed a t t h e mouth of t h e Po

River a t P i l a , and a s e c t i o n through s t a t i o n s 3 t o 2 2 showing

t h e conf igu ra t ion of t h e wave-built b a r s and under ly ing wedge

of sand . (Redrawn from Melson, 1970).

100

Fig . 2-6. S tages i n development of a b i r d f o o t d e l t a and d e p o s i t i o n of

a d e l t a i c sequence , showing growing p a t t e r n of b i f u r c a t i n g

d i s t r i b u t a r i e s , and s t r a t i g r a p h i c sequence through a s e c t i o n

a t v a r i o u s s t a g e s . (Af t e r L e Blanc, 1972, and F i s k , 1961).

101

0 20 40 b0

80

F i g . 2-6. (Continued).

102

0 10 40 b0 80

0 20 40 bO

80

Fig. 2-6. (Continued)

103

b u i l d i n g up through t h e s e c t i o n t o form a complex of anastomosing s h o e s t r i n g -

-sand bod ies s e p a r a t e d by l e n t i c u l a r l a y e r s of s i l t and c l a y .

Another modern example of d i s t r ibu tary-mouth sand b a r s has been

desc r ibed by Nelson (1970). This i s t h e complex o f sand b a r s a t t h e mouth

of t h e Po R ive r at P i l a , I t a l y (F ig . 2-5). These b a r s form a r c u a t e i s l a n d s

on t h e seaward pe r iphe ry of a prograding wedge of sand which is up t o 15 m

t h i c k and 3 km wide.

L e Blanc (1972), based on s t u d i e s of t h e M i s s i s s i p p i d e l t a ba r - f inge r

sands , ( F i s k , 1961) i l l u s t r a t e d t h e growth of a d e l t a complex i n F ig . 2 - 6 .

These diagrams show t h e s t a g e s of development of a b i r d f o o t d e l t a i n a

d e l t a complex comprising b i f u r c a t i n g d i s t r i b u t a r i e s s e p a r a t e d by swamp.

lobes of t h e d e l t a prograde and s h i f t l a t e r a l l y , t h e sand bod ies depos i t ed i n

o l d e r d i s t r i b u t a r y channels are b u r i e d t o form a system of anastomosing

shoes t r ing-sands i n t h e subsu r face .

A s

L e Blanc (1972) f u r t h e r p o i n t s o u t (F ig . 2-7) t h a t such lobes coa le sce ,

by la teral s h i f t i n g r e s u l t i n g from changes i n t h e cour ses o f i t h e d i s t r i b -

u t a r i e s , t o form a d e l t a p l a i n t h a t may have a wid th exceeding 160 km. I n

t h e subsu r face a b u r i e d d e l t a p l a i n is u n d e r l a i n by a s t r a t i g r a p h i c complex

of s i l t s and c l a y s in t e rbedded wi th sand bod ies formed as d i s t r i b u t a r y

channel s ands , ba r - f inge r s ands , beach b a r s , and b a r r i e r i s l a n d s . I n g e n e r a l ,

d e p o s i t i o n a l t r e n d s of t h e channels and ba r - f inge r s are approximate ly normal

t o those of t h e s h o r e l i n e b a r s and b a r r i e r i s l a n d s .


The c o a s t a l f r i n g e of each d e l t a l o b e i n c l u d e s ba r - f inge r sands which

prograde seaward.

s i l t and c l a y , t h e r e s u l t i n g g r a i n g r a d a t i o n be ing r e f l e c t e d i n a serrate,

funnel-shaped s e l f - p o t e n t i a l curve on t h e E-log. Th i s shape i n d i c a t e s ,

(a) a g r a d a t i o n a l c o n t a c t , sand l e n s e s be ing in te rbedded w i t h l a y e r s of

P rograda t ion r e s u l t s i n t h e sand ove r - r id ing p r o d e l t a

104

Ili i

F i g . 2-7. S t a g e s i n development of a d e l t a - p l a i n complex and s t ra t i -

g r a p h i c sequence r e s u l t i n g from t h e c o a l e s c e n c e of s e p a r a t e

d e l t a l o b e s . ( A f t e r Le Blanc , 1972) .

105

STACE I

106

s i l t and c l a y and, (b) a g e n e r a l t h i cken ing upward of t h e sand l a y e r s ,

commonly w i t h an i n c r e a s e i n g r a i n s i z e . In t h e lower p a r t of t h e bar -

- f i n g e r sequence, i n t e rbedded l a y e r s o f sand , s i l t , and c l a y are depos i t ed

as t h e r e s u l t of f l u c t u a t i o n s i n t h e r i v e r f lood c y c l e s . During f lood

s t a g e s sand is depos i t ed seaward from t h e d i s t r i b u t a r y mouth, whereas

du r ing low-water s t a g e s t h e sediment depos i t ed c o n s i s t s mainly of s i l t o r

c l a y . A s t h e d i s t r i b u t a r y advances, and t h e b a r - f i n g e r progrades seaward,

t h e sediment depos i t ed a t any l o c a t i o n w i t h i n t h e lower reaches of a

d i s t r i b u t a r y channel becomes i n c r e a s i n g l y sandy. The r e s u l t is t h a t a

s e c t i o n through a d i s t r i b u t a r y channel n e a r i ts mouth shows an o v e r a l l

upward i n c r e a s e i n g r a i n s i z e .

D i s t r i b u t a r y channel sand bod ies may ove r - r ide o r c u t through d e l t a -

--marine f r i n g e sands , and l o c a l l y can be d i s t i n g u i s h e d from t h e l a t t e r by

t h e i r be l l - shaped o r c y l i n d r i c a l s e l f - p o t e n t i a l curves .

r eaches of a d i s t r i b u t a r y channel t h e curve tends t o b e be l l - shaped ,

i n d i c a t i n g g r a i n g r a d a t i o n from f i n e r above t o c o a r s e r below.

lower r eaches , subs idence of t h e d i s t r i b u t a r y channel sand body, and f a i r l y

uniform rates of flow and sed imen ta t ion , can r e s u l t i n a t h i c k sand body

of uniform g r a i n s i z e . Th i s t ype of sand body is c h a r a c t e r i z e d by a

c y l i n d r i c a l s e l f - p o t e n t i a l curve . A s e r r a t e d curve i n d i c a t e s i n t e r b e d s of

In t h e upper

I n t h e

s i l t and c l a y depos i t ed du r ing p e r i o d i c dec reases i n t h e v e l o c i t y of t h e

d i s t r i b u t a r y .

- Compaction

Prograding ba r - f inge r sand bod ies are over-ridden by d i s t r i b u t a r y

channels as t h e sho re - l ine retreats. These channe l s , which commonly are

only one t h i r d t o one f i f t h as wide as t h e seaward-trending ba r - f inge r sand

b o d i e s , converge landward t o form l a r g e r channels . The ba r - f inge r sand

bod ies , merge l a t e r a l l y a t the s u r f a c e .

and s i l ts , may cause them t o merge o r l o c a l l y come i n t o c o n t a c t i n t h e

Compaction of t h e sur rounding muds

107

subsur face . In consequence, where viewed i n t h r e e dimensions, t h e s e bar -

- f inge r sand bodies may have an en eckeZon arrangement i n s e c t i o n s bo th

normal and p a r a l l e l t o t h e g e n e r a l d e p o s i t i o n a l t r e n d . Th i s arrangement

f a c i l i t a t e s t h e movement o f f l u i d s through t h e sand bod ies du r ing compaction.

The movement is g e n e r a l l y l a t e ra l and upward i n t h e s t r a t a , a long more

permeable zones t h a t t r e n d up t h e d e p o s i t i o n a l s l o p e toward t h e margin of

t he sed imentary p i l e . It may b e i n f e r r e d t h a t f l u i d s expe l l ed from

compacting muds w i l l move i n t o b a r - f i n g e r sand bod ies and mig ra t e upward

a long t h e b u r i e d d i s t r i b u t a r y channel sand bod ies . In f a c t , t h e movement

of format ion f l u i d s through t h e sand bod ies may b e i n h i b i t e d by penecontemp-

oraneous slumping of l a r g e b locks of sed iment , forming f a u l t s which r e s t r i c t

t h e movement of f l u i d s and r e s u l t i n above-normal f l u i d p r e s s u r e s i n

i s o l a t e d bod ies of sand ,

Loca l warping of d i s t r i b u t a r y channel and ba r - f inge r sand bod ies ,

caused by compaction o r t e c t o n i c deformat ion , may r e s u l t i n numerous c losu res

which can become m u l t i p l e s t r a t i g r a p h i c o r s t r a t i g r a p h i c - s t r u c t u r a l t r a p s

f o r o i l and gas . Many such m u l t i p l e pay-zones are known i n T e r t i a r y beds

of t h e Gulf Coast area of t h e Uni ted S t a t e s (Hartman, 1972). Other examples

a r e found i n o i l f i e l d s i n t h e Booch Sandstone of t h e Pennsylvanian NcAlester

Formation (Busch, 1971).

Ancient Sand Bodies

Ancient examples of d e l t a d i s t r i b u t a r y and d e l t a - f r i n g e sand bodies

occur i n many p a r t s of t h e world and are known from bo th ou tc rop and

subsu r face d a t a . Most examples a r e w i t h i n F l i s s i s s ipp ian , Pennsylvanian ,

Cre taceous , and T e r t i a r y sequences. S e l l e y (1970) d e s c r i b e s some of t h e

f e a t u r e s of t h e s e sands tone bod ies known from outcrops of Carboni ferous

rocks i n n o r t h e r n England. Se l l ey p o i n t s o u t (p. 77) t h a t , "In sea rch ing

f o r a n c i e n t d e l t a s , t h e r e f o r e , w e must look f o r t h i c k c l a s t i c sequences

108

showing r epea ted c y c l e s of upward-coarsening g r a i n s i z e . Each cyc le should

beg in , a t t h e base , w i th a marine s h a l e which passes up through s i l ts i n t o

c o a r s e r f resh-water channel sands a t t h e top . I n p l a n t h e channels should

show a r a d i a t i n g s h o e s t r i n g p a t t e r n and b e c u t i n t o f r e shwa te r s h a l e s and

c o a l s . " Coal seams a r e a l s o commonly p r e s e n t j u s t above t h e d i s t r i b u t a r y

channel sand bod ies (F ig . 2-22) .

Appalachian Delta, U.S.A.

I n t h e n o r t h e r n Appalachian r eg ion , Middle Pennsylvanian sands tone

bod ies were depos i t ed as d i s t r i b u t a r y channe l s , b a r - f i n g e r s , and o t h e r

d e l t a - f r i n g e sands . P rograda t ion , l a t e r a l s h i f t i n g and coa lescence of

d e l t a l obes a r e i l l u s t r a t e d by Fern (1970) i n F i g s . 2-8 ( a ) and (b ) . The

a s s o c i a t i o n of ca rbona te and non-barbonate rocks shown i s n o t t y p i c a l of

modern d e l t a s b u t i s c h a r a c t e r i s t i c of Pennsylvanian d e l t a s i n t h e Appal-

ach ians o f t h e e a s t e r n U.S.A., and a l s o i n no r th -cen t r a l Texas (Galloway

and Brown, 1973).

These schemat ic diagrams show t h e development of o l d e r and younger

d e l t a l obes formed i n response t o major s h i f t i n g of t h e main r i v e r channel

and i t s d i s t r i b u t a r i e s . Subsidence of abandoned d e l t a l o b e s , r e s u l t i n g

from nea r - su r face compaction of muds and s i l t s , causes t r a n s g r e s s i o n of t h e

sea and t h e development of a drowned c o a s t a l topography. Loca l winnowing

of t h e sed iments , p a r t i c u l a r l y du r ing pe r iods when p a r t s of t h e c o a s t

remain r e l a t i v e l y s t a t i c , forms s h o r e l i n e sands such as beaches and b a r s

which t r a n s g r e s s over t h e s i n k i n g landmass. I n such a s i t u a t i o n , mar ine

d e l t a - f r i n g e sand bod ies o v e r l i e non-marine d e l t a - f r i n g e channel s ands .

Subsequent s h i f t s of t h e r i v e r system may r e s u l t i n new d e l t a l obes b u i l d i n g

o u t over p a r t s of o l d e r l o b e s .

o r t h r e e t i m e s . Fu r the r r e p e t i t i o n s are u n l i k e l y because p rograda t ion

r e s u l t s i n t h e o r i g i n a l d e p o s i t i o n a l s i t e be ing bu r i ed deeper and removed

f a r t h e r i n l a n d .

I n t h i s way, t h e c y c l e may be repea ted two

109

MARGINAL PLAIN DELTA PLAIN

A* A

Limey clay Sand Silt and Clay Clay with roots Peat and marl

Vertical exoggeration ontheorder of 1000 X

ABANDONED WEDGE ACTIVELY PROGRADING DELTA WEDGE I

B 0

Limey clay and marl

Sand =Silt and Clay R C l a y with roots Peat

Vertical exaggeration on the order of I000 X .

F i g . 2-8

( a ) and (b)

Schemat ic d iagram showing r e c o n s t r u c t e d and g e n e r a l i z e d p l a n

and s e c t i o n a l views A-A1 and B-B1 of a Middle P e n n s y l v a l i a n

p r o g r a d i n g d e l t a i n the n o r t h e r n Appalachian r e g i o n .

Ferm, 1970) .

( A f t e r

110

Cisco Delta, Texas

Within t h e Upper PennsylvaniAn t o Lower Permian Cisco Group of north-

- c e n t r a l Texas, anastomosing s h o e s t r i n g sands form a c ros s - sec t iona l p a t t e r n

shown i n Figs . 2-9 and 2-10. These sandstone bod ies , which o r i g i n a t e d a s

c h a n n e l - f i l l sands i n t h e Cisco De l t a , form contemporaneous sets, each s e t

occu r r ing a t a d i f f e r e n t s t r a t i g r a p h i c horizon. Ind iv idua l sandstone bodies

tend t o o f f s e t one another i n ad jacen t ho r i zons , a r e l a t i o n s h i p t h a t has

been noted a l s o i n Oligocene c h a n n e l - f i l l sands of t h e Seel igson F i e l d ,

Texas (Nanz, 1954). This arrangement i s probably t h e r e s u l t of contemp-

oraneous depos i t i on of sands w i t h i n t h e channels confined by t h e topograph-

i c a l l y h ighe r l e v e e s , and compaction of t h e s i l t s and c l ay deposi ted i n t h e

topographical ly low backswamps between t h e d i s t r i b u t a r i e s .

channels , which subsequently form ad jacen t and s t r a t i g r a p h i c a l l y higher

Younger

t. 500

VERTICAL A R R A N G E M E N T OF SANDSTONE CHANNELS,

P E N N S Y L V A N I A N C l S C O GROUP, T E X A S

Fig. 2-9. Cross s e c t i o n , normal t o t h e paleoslope, of s ands tone - f i l l ed

channels i n t h e Upper Pensylvanian Cisco Group, c e n t r a l Texas.

(Redrawn from Brown, 1969).

111

QUARTZOSE S A N D TRENDS IN PENNSYLVANIAN

LIMESTONE SECTION, TEXAS

Fig . 2-10. T o t a l sand i s o l i t h exceeding a th i ckness of 40 f e e t , showing

t r e n d s of qua r t zose sands w i t h i n t h e Upper Pennsylvanian -

Lower Permian Cisco Group ( C r y s t a l F a l l s and Saddle Creek

l imes tone s e c t i o n ) i n c e n t r a l Texas. (Redrawn from

Galloway, 1969).

s e t s , t end t o fo l low t h e topographic dep res s ions between t h e o l d e r

channels .

The Cisco Delta has been desc r ibed i n cons ide rab le d e t a i l by Galloway

and Brown (1973). They s a y , p. 1187, "The Cisco f l u v i a l - d e l t a i c system

is updip from a s s o c i a t e d s h e l f edges and c o n s i s t s o f s ands tone and mud-

s t o n e in t e rbedded wi th subord ina te amounts of l imes tone and c o a l . Fac ie s

composition of t h e system is s i m i l a r t o , and i t s areal e x t e n t co inc iden t

w i th , t h e Cisco Group as de f ined a t t h e ou tc rop .

and d e l t a i c systems are c l o s e l y a s s o c i a t e d wi th t h i s system and cannot be

Components of bo th f l u v i a l

112

a r e a l l y seg rega ted a t t h e system level. Fac ies of t h e d e l t a system inc lude

d i s t r ibu ta ry -mou th b a r s ands tone , delta-margin sands tone , d e l t a - p l a i n mud

and s i l t s t o n e , and p r o d e l t a and i n t e r d i s t r i b u t a r y mudstone. F l u v i a l f a c i e s

i n c l u d e channel s ands tone , c r evasse s p l a y sands tone and s i l t s t o n e , overbank

mudstone, and l a c u s t r i n e depos i t s " . They s a y f u r t h e r , p . 1189, "The Cisco

f l u v i a l d e l t a i c system ex tends 50-70 m i westward from t h e ou tc rop b e l t i n t o

t h e subsu r face , where i t g rades i n t o l imes tone f a c i e s of t h e S y l v e s t e r

she l f -edge bank system".

Seve ra l s t r u c t u r a l - s t r a t i g r a p h i c t r a p s f o r o i l have been found i n

c h a n n e l - f i l l sands tone bod ies of t h e Cisco Group, i n c l u d i n g t h e Mor r i s ,

Buie-Blaco, Cook Ranch and Bluff Creek f i e l d s .

Volgograd Delta, U.S.S.R.

P a r t of a Lower Carboni ferous system of d e l t a d i s t r i b u t a r i e s , s i t u a t e d

n o r t h of Volgograd ( S t a l i n g r a d ) U.S.S.R., i s i l l u s t r a t e d i n F ig . 2-11. The

p a t t e r n shown i s t h e g r o s s d i s t r i b u t i o n of d i s t r i b u t a r y c h a n n e l - f i l l sands

O L 50KM

0 50 VOLGOGRAD

I

MILES

Fig . 2-11. Lower Carboni ferous p a l e o d e l t a , nea r Volgograd ( S t a l i n g r a d ) ,

U.S.S.R. (Redrawn from Xarkovsk i i , 1967).

113

wi th in a p a r t i c u l a r s t r a i t g r a p h i c i n t e r v a l . It consequent ly r e p r e s e n t s

t he supe r impos i t i on of success ive d i s t r i b u t a r y sys tems t h a t grew south-

ward wi th in t h e t i m e span r ep resen ted by t h e s t r a t i g r a p h i c i n t e r v a l .

I n d i v i d u a l l y , t h e s e c h a n n e l - f i l l s ands have a wid th of 3-8 km and

c o l l e c t i v e l y they have been t r a c e d f o r 163 km. Smal le r sands tone bod ies

a r e commonly 10-20 m t h i c k , bu t range up t o 45 m. The p a t t e r n o f d i s t -

r i b u t a r i e s is s i m i l a r t o t h a t of t h e M i s s i s s i p p i a n Bedford Formation

(Fig. 1-15) i n Ohio, and o f t h e Pennsylvanian Booch Sandstone i n (Fig. 2-15)

i n Oklahoma.

I d e n t i f i c a t i o n of Delta D i s t r i b u t a r y Channel Sands

Previous examples i l l u s t r a t i n g t h e branching and anastomosing geo-

g raph ic p a t t e r n o f s h o e s t r i n g sands , and t h e s t r a t i g r a p h i c r e l a t i o n s h i p s

of i n d i v i d u a l sands tone bod ies , c l e a r l y i n d i c a t e t h a t t h e s h q e s t r i n g

sands o r i g i n a t e d a s d e l t a d i s t r i b u t a r y c h a n n e l - f i l l sands . Where on ly

one sands tone body i s known, i t s p o s s i b l e d e p o s i t i o n a l environment and

pa leogeographic s e t t i n g may be d i f f i c u l t t o de te rmine . In such cases ,

d i f f e r e n c e s of op in ion may a r i s e as t o t h e o r i g i n o f t h e sands tone body

and i t s s i g n i f i c a n c e t o t h e s t r a t i g r a p h i c h i s t o r y of t h e r eg ion ,

A case i n p o i n t is i l l u s t r a t e d i n F ig . 2-12, an i sopach map showing

t h r e e p a r a l l e l t r e n d s i n t h e Upper Miss i s s ipp ian P a l e s t i n e Sandstone of

I l l i n o i s . The P a l e s t i n e Sandstone, which ranges i n th i ckness t o 30 m ,

i s an upper u n i t of t h e Ches te r S e r i e s wnich i n c l u d e s t h i r t e e n major

sands tone u n i t s ( s ee F ig . 2-20) c o n s t i t u t i n g 25% of t h e s e c t i o n i n t h e

I l l i n o i s Basin. A g e n e r a l c h a r a c t e r i s t i c of a l l t h e s e sands tone u n i t s is

t h a t they have sha rp e r o s i o n a l c o n t a c t s w i th t h e under ly ing beds , a

f e a t u r e r e f l e c t e d i n t h e blocky t o be l l - shaped s e l f - p o t e n t i a l curve of

t h e i r E-logs. Locall j- , t h e s e sands tone u n i t s are unde r l a in by e r o s i o n a l

channels up t o 15 m i n depth . The sands tones are f i n e t o ve ry f ine -g ra ined ,

114

0 10 0- 10 - MILES KM

Fig . 2-12. Isopach map showing t r e n d s i n t h e Upper Miss i s s ipp ian

P a l e s t i n e Sandstone, I l l i n o i s . Arrow i n d i c a t e s mean

d i r e c t i o n of c ross -bedding , i n d i c a t i n g southward t r a n s p o r t

of sand. (Redrawn from P o t t e r e t al., 1958, F ig . 13 ) .

and are composed a lmost e n t i r e l y of moderately well-rounded q u a r t z g r a i n s ,

w i th g e n e r a l l y less than 1% f e l d s p a r . Cross bedding i s p a r t i c u l a r l y w e l l

developed i n t h e t h i c k e r p a r t s of t h e sands tone u n i t s which a l s o con ta in

r i p p l e marks and p l a n t remains.

P o t t e r , e t al. (1958) say t h a t a l though marine f o s s i l s a r e n o t common

w i t h i n t h e b a s i n , t hey have been found i n some p a r t s of t h e b a s i n i n nea r ly

every sands tone u n i t of t h e Ches te r . Could they have been re-worked from

penecontemporaneous ad jacen t marine beds? Some sands tone u n i t s con ta in

ca l ca reous zones t h a t l o c a l l y grade i n t o sandy l imes tone . On t h e o t h e r

hand, P o t t e r , e t aZ. (1958, p . 1016) say t h a t , '*Thin c o a l beds a r e assoc-

i a t e d wi th t h e Ches t e r sands tones a t e i g h t hor izons" .

The o r i g i n of t h e s e l i n e a r sands tone u n i t s i s p rob lema t i ca l . O f f

(1963) w a s of t h e op in ion t h a t they may have been t i d a l c u r r e n t r i d g e s .

A l t e r n a t i v e l y , they may have been depos i t ed i n d i s t r i b u t a r i e s on a d e l t a

115

cha rac t e r i zed by a r e l a t i v e s c a r c i t y of non-carbonate mud and by t h e

formation of ca l ca reous beds . This sed imento logic and l i t h o l i g i c assoc-

i a t i o n i s n o t common today , b u t is t y p i c a l of Pennsylvanian d e l t a s i n

t h e Appalachian reg ion .

Many of t h e Ches t e r s ands tone bod ies form good r e s e r v o i r s f o r o i l .

With r e f e r e n c e t o t h e l a t e ra l v a r i a t i o n of sands i n t h e Upper Miss i s s ipp ian

of southern I l l i n o i s , Levorsen (1967, p. 289) s t a t e s , "These Miss i s s ipp ian

rocks a r e c h a r a c t e r i z e d by sand pa tches , l e n s e s , b a r s , channels , and

f a c i e s changes, and i n a d d i t i o n they are t r u n c a t e d toward t h e n o r t h by

over lapping Pennsylvanian fo rma t ions , which con ta in l e n t i c u l a r sands . A

g r e a t many o i l poo l s are found i n t h e s e Miss i s s ipp ian and Pensylvanian

sands ; most of them are a s s o c i a t e d wi th f o l d i n g , b u t many are l i m i t e d on

one o r more s i d e s by t h e edges of pe rmeab i l i t y" . The l a t e r a l v a r i a t i o n s

of t h e s e sands tone bod ies have been po in ted o u t by Swann and Ather ton

(1948).

One of t h e many Pennsylvanian c h a n n e l - f i l l sands tones of t h e

I l l i n o i s Basin i s shown i n F ig . 2-13. This sands tone u n i t has a t h i ckness

of 5-25 m, a wid th of 3-8 km, and t r e n d s i n a meandering cour se t o t h e

s o u t h e a s t , t h e d i r e c t i o n of flow of t h e a n c i e n t r i v e r system. The sand-

s t o n e l ies ad jacen t t o and s t r a t i g r a p h i c a l l y between t h e Summun and

Harr i sburg c o a l seams, a r e l a t i o n s h i p t h a t sugges t s a marshy environment.

The meandering p a t t e r n of t h e sands tone body, and a l s o i t s a s s o c i a t i o n

wi th c o a l s e a m s , p o i n t s t o i t s o r i g i n i n t h e channel system of a r i v e r

flowing through a low-lying t e r r a i n t h a t w a s p robably t h e c o a s t a l p l a i n

of a d e l t a .

An i n t e r e s t i n g example of d i s t r i b u t a r y channel s ands , mapped i n

outcrop as d i s c r e t e sands tone bod ies , bu t shown by e x t r a p o l a t i o n t o b e

p a r t s of a branching d i s t r i b u t a r y sys tem, is shown i n Fig. 2-14.

These sands tone bod ies are w i t h i n t h e n e a r l y f l a t - l y i n g Upper Cretaceous

116

MEANDERING PENNSYLVANIAN SANDSTONE

CHANNEL, I LLlNOlS

Fig. 2-13. Meandering Pennsylvanian sandstone channel between the

Summun and Harr isburg c o a l seams i n e a s t - c e n t r a l I l l i n o i s .

The sandstone body o u t l i n e d ranges i n th i ckness from 20

t o 80 f e e t (6-24 m). D i rec t ion of sediment t r a n s p o r t i s

t o t h e south-east . (Redrawn from P o t t e r , 1962).

Bearpaw Shale of c e n t r a l Montana.

p a t t e r n of Bearpaw d i s t r i b u t a r i e s resembles t h a t of t h e Lower Carbon-

i f e r o u s Volgograd d e l t a i n t h e U.S .S .R. , and a l s o t h e d e l t a i c Pennsylvanian

Booch Sandstone of Oklahoma. These Bearpaw s h o e s t r i n g sands have a

th i ckness of up t o 20 m, and a width of up t o 2km. I n d i v i d u a l l y , they

have been t r a c e d i n outcrop f o r s e v e r a l k i lome t re s . They c o n s i s t of

l i g h t g rey , f i n e t o coarse-grained, cross-bedded l i t h i c sandstones

con ta in ing c l ays tone (mud) b a l l s and abundant carbonized p l a n t remains.

Overlain and unde r l a in by s i l t s t o n e s and s h a l e s , they are considered t o

Although on a much smaller s c a l e , t he

117

R 21 E R 2 2 E

0 M I L E S 5 1 I

Fig . 2-14. D i s t r i b u t i o n of s h o e s t r i n g sands tone bod ies formed a s

channels i n t h e n e a r l y f l a t - l y i n g Upper Cretaceous Bearpaw

Sha le , c e n t r a l Montana. (Af t e r Wulf, 1964) .

be d i s t r i b u t a r i e s formed on p a r t of a Bearpaw delta-complex t h a t

prograded eas tward .

The area shown i n F ig . 2-14 o v e r l i e s t h e Lake Basin o i l and gas

f i e l d , a s t r u c t u r a l dome. I n t h e subsu r face , t h e p a t t e r n of Bearpaw

s h o e s t r i n g sands now cropping o u t could form p o t e n t i a l s t r u c t u r a l -

- s t r a t i g r a p h i c t r a p s f o r hydrocarbons.

O i l and Gas F i e l d s . - The fo l lowing examples of o i l and gas f i e l d s i n d i s t r i b u t a r y and

d e l t a - f r i n g e sand bod ies range i n age from Late Pa leozo ic t o Middle

Cenozoic. Of t h e s e , f o u r are Pennys lvanian , two are M i s s i s s i p p i a n ,

118

t h r e e a r e Cre taceous , and f o u r are T e r t i a r y . E igh t examples a r e i n

t h e U . S . A . , two i n Canada, and one each i n Venezuela, N i g e r i a , and

t h e U.S.S.E. This d i s t r i b u t i o n is n o t p re sen ted as be ing r e p r e s e n t a t i v e

of t h e world o r of Xorth America, as i t i s obvious ly b i a sed by a ve ry

l i m i t e d sampling.

Booch Sandstone O i l F i e l d s , Oklahoma

The Ea r ly Pennsylvanian Booch Sandstone of t h e 14cAlester Formation

i n Oklahoma (Fig . 2-15) forms a branching sys tem of d i s t r i b u t a r y shoe-

- s t r i n g sands t h a t cover an a r e a a t least 112 km wide. Flowing t o t h e

s o u t h , t h i s d i s t r i b u t a r y sys tem comprised a c e n t r a l main channel , i n

which sand bod ies more than 60 m t h i c k w e r e d e p o s i t e d , and a l s o secondary

channels which commonly conta ined sand bod ies less than 30 m t h i c k .

F ig . 2-15 shows t h e g e n e r a l i z e d p a t t e r n formed by t h e composite d i s t r i b -

u t i o n of t h e s e sand bod ies . In t h e n o r t h e a s t e r n p a r t of t h e a r e a , t h e

upper sands tone member of t h e Booch Sandstone i s t h e predominant u n i t ,

whereas i n t h e southwes tern p a r t t h e Booch Sandstone i s r ep resen ted by

members lower i n t h e sequence. Busch (1971) s a y s t h a t t h e Booch d i s t -

r i b u t a r i e s were formed on a l a r g e delta-complex t h a t covered an area of

approximate ly 5120 s q . km w i t h i n t h e Arkoma Basin. It i s i n t e r e s t i n g

t o n o t e t h a t t h e present-day conf igu ra t ion of composite channels w i t h i n

t h e d e l t a of t h e Rio Grande R ive r , Texas, is comparable i n s i z e and

shape t o t h a t of t h e Booch Sandstone (F ig . 2-15). The Booch Sandstone

i s commonly very f ine-gra ined and l i t h i c , w i th a f a i r l y h igh (ave. 15%)

con ten t of c l a y . Pe rmeab i l i t y improves where, l o c a l l y , t h e sands tone i s

medium t o coarse-gra ined .

There a r e numerous o i l f i e l d s producing from t h e Booch Sandstone,

most of which are n o t i n t h e t h i c k e r main channel bu t i n t h e t h i n n e r

d i s t r i b u t a r i e s . Many of t h e s e a r e pu re ly s t r a t i g r a p h i c t r a p s , t he

119

OIL FIELDS IN PENNSYLVANIAN BOOCH SANDSTONE OKLAHOM

RIO GRANDE DELTA, TEXAS

Fig . 2-15. Upper - Map showing composite d i s t r i b u t i o n of t h e Booch

Sandstone member i n t h e Pennsylvanian McAlester

Formation, Seminole d i s t r i c t , Oklahoma.

f i e l d s , where p roduc t ion is obta ined from t h e Booch,

are shown i n b l ack . (Redrawn from Dicky and Rohn,

1958, a f t e r Br;sch, 1953; Busch, 1971).

Numerous o i l

Lower - Map showing present-day d i s t r i b u t a r y channels on t h e

d e l t a of t h e Rio Grande R ive r , Texas. This d e l t a

h a s grown a c r o s s t h e lagoon where i t s ex tens ion i s

c u r r e n t l y l i m i t e d by wave and c u r r e n t a c t i o n t h a t

forms t h e b a r r i e r i s l a n d . Con t inua l ly changing cour se ,

t h e d i s t r i b u t a r y channels b u i l d up a complex p a t t e r n

of s inuous s h o e s t r i n g sands . Same s c a l e as above.

120

14

4

4

0 23

.

26

121

o i l be ing conf ined by pe rmeab i l i t y b a r r i e r s where t h e sands tone p inches

out and is f l anked by s h a l e s and s i l t s t o n e s which o r i g i n a t e d as sediments

depos i ted i n a backswamp environment between t h e d i s t r i b u t a r i e s . Others

have a s t r u c t u r a l i n f l u e n c e where westward-plunging noses i n t e r s e c t more

permeable sands tone zones w i t h i n t h e d i s t r i b u t a r y t r ends .

The Hawkins O i l F i e l d , l o c a t e d a t t h e southwes tern ex t r emi ty of t h e

Booch d e l t a ( see i n s e t i n F ig . 2-15), produces from thP Booch Sandstone

shown i n Fig. 2-16. This f i g u r e i s an i sopach map of a member comprising

d i s t r i b u t a r y sand bod ies s i t u a t e d i n t h e middle of t h e Booch s t r a t i g r a p h i c

i n t e r v a l . 'This o i l -bea r ing sands tone member w a s depos i t ed i n a main nor th-

-south t r end ing d i s t r i b u t a r y channel t h a t branched t o t h e south-eas t and

south-west. The maximum th i ckness of sands tone i n t h e main channel is

-1itrapment of o i l has r e s u l t e d from the co inc idence of t h e s e 10 m.

s h o e s t r i n g sands and a s t r u c t u r a l "high" t h a t has r e s u l t e d from compaction.

Busch (1971) shows t h a t r a t e s of p roduc t ion co inc ide wi th t r e n d s of maximum

sands tone t h i c k n e s s , t h e o i l y i e l d be ing g r e a t e r where t h e sands tone i s

t h i c k e r .

South P ine Hollow Gas F i e l d , Oklahoma

In t h e South P ine Hollow Gas F i e l d (F ig . 2-17) of Oklahoma t h e

producing u n i t i s t h e Ea r ly Pennsylvanian Lower Har t shorne Sandstone.

This s ands tone , which is t h e b a s a l u n i t of t h e Desmoinesian S tage , i s

Fig . 2-16. I sopach map of t h e o i l -bea r ing middle member of t h e Booch

Sandstone i n t h e Pennsylvanian McAlester Formation, Oklahoma.

The a r e a shown covers t h e Hawkins O i l F i e l d . Sca le of g r i d

i n squa re m i l e s (1 m i l e = 1 . 6 km).

5 f e e t (1.5 m). (Af t e r Busch, 1971).

Contours show i n t e r v a l s of

122

ISOPACH OF N E T SANDSTONE, LOWER

HARTSHORNE SANDSTONE, OKLAHOMA

Fig . 2-17. Isopach of n e t s ands tone , Pennsylvanian Lower Har t shorne

Sands tone , South P ine Hollow Gas F i e l d , P i t t s b u r g County,

Oklahoma. This l i n e a r s ands tone body is i n t e r p r e t e d as

f i l l i n g a d i s t r i b u t a r y channel .

1968).

(Redrawn from McDaniel,

unde r l a in by t h e Atokan Formation and o v e r l i a n by t h e HcAles te r Formation

which i n c l u d e s t h e Booch Sandstone.

The Har tshorne Sandstone is a l i n e a r sands tone body which i s i n t e r -

p r e t e d as having been a d e l t a d i s t r i b u t a r y sand.

has been t r a c e d f o r more than 25 km. It has a f a i r l y cons t an t wid th

of about 2-3 km, and a g ross th i ckness which ranges i n excess of 60 m.

The n e t sands tone th i ckness is approximately h a l f t h e g r o s s th i ckness a t

any p a r t i c u l a r l o c a t i o n , and has a maximum of 40 m.

p o r o s i t y i n c r e a s e toward t h e t h i c k e r p a r t s of t h e sands tone body.

This sands tone body

Pe rmeab i l i t y and

O f p a r t i c u l a r i n t e r e s t i s t h e f a c t t h a t t h e sands tone body l i e s

i n a s t r u c t u r a l l y low f e a t u r e , and t h a t t h e gas accumulation i s

c o n t r o l l e d e n t i r e l y by s t r a t i g r a p h i c parameters i n c l u d i n g v a r i a t i o n s i n

123

p o r o s i t y , pe rmeab i l i t y , and n e t sands tone th i ckness . Recoverable

r e se rves i n t h e South P ine Hollow G a s F i e l d are es t ima ted t o be i n

excess of 100,000 m i l l i o n cubic f e e t (2,800 m i l l i o n cub ic me t re s ) .

Pokrovsk O i l F i e l d , U . S . S . R .

I n t h e Pokrovsk F i e l d (F ig . 2-18) of sou th -cen t r a l U . S . S . R . , o i l

i s produced from a s inuous sands tone body enc losed w i t h i n a c l ays tone

bed o v e r l a i n and u n d e r l a i n by Carboni ferous l imes tone . The sands tone

body, which has been t r a c e d by d r i l l i n g f o r n e a r l y 15 krn a long i t s

l e n g t h , has a wid th of up t o 2 kn and a maxirr.um th i ckness of 10 m.

CARBONIFEROUS POKROVSK OIL FIELD, U S S R

Fig. 2-18. Map and s e c t i o n s of t h e Pokrovsk o i l f i e l d i n t h e Russian

P la t fo rm, U.S.S.R. The o i l -bea r ing sands tone , cons idered t o

have been depos i t ed by a r i v e r f lowing i n t h e d i r e c t i o n

i n d i c a t e d by t h e a r row, forms a s inuous body w i t h i n a c lay-

s t o n e bed t h a t l i e s between l a y e r s of Lower Carboni ferous

l imes tone . (Redrawn from Markovskii , 1965).

124

The sands tone i s cons idered t o have been a c h a n n e l - f i l l sand

depos i t ed by a d i s t r i b u t a r y f lowing over a f l a t c o a s t a l p l a i n du r ing

a pe r iod of l i m i t e d emergence of t h e l and preceded and fo l lowed by

t h e development of carbonate s h o a l s . The sands tone i s q u a r t z o s e , f i n e

t o medium-grained, and w e l l s o r t e d . The mean p o r o s i t y i s 20% and t h e

p e r m e a b i l i t y , which i s g e n e r a l l y good, i n c r e a s e s i n t h e c e n t r a l p a r t s

of t h e body where t h e sands tone is t h i c k e r and c o a r s e r . The p a t t e r n of

h o l e s sugges t s t h a t o i l accumulation i n t h e f i e l d is c o n t r o l l e d e s sen t -

i a l l y by s t r a t i g r a p h i c f e a t u r e s r e l a t e d t o t h e d i s t r i b u t i o n of t h e

sands tone body, and t h a t e x p l o r a t i o n proceeded on a h i t -or -miss b a s i s .

Eas t Tuskegee O i l F i e l d , Oklahoma

The Misener Sandstone i s one of t h e main producing members i n t h e

Eas t Tuskegee F i e l d of Oklahoma, y i e l d i n g o i l having a g r a v i t y of 39O

A . P . I . This sands tone unconformably o v e r l i e s t h e Ordovic ian and i s

conformably o v e r l a i n by t h e Ea r ly H i s s i s s i p p i a n Chattanooga Shale which i s

a very widespread , d iachronous u n i t . The uppermost p a r t of t h e Misener

Sandstone i s composed mainly of angu la r t o rounded g r a i n s of q u a r t z , and

c o n t a i n s conodonts and phospha t i c g a s t r d i t h s (Borden and Bran t , 1941).

The lower p a r t is coarse-gra ined , commonly g r i t t y , and qua r t zose wi th

abundant g r a i n s of c h e r t .

The o r i g i n of t h e Hisener Sandstone has been t h e s u g j e c t of cont-

rove r sy . White (1928) was of t h e op in ion t h a t t h e sands tone was e o l i a n ,

whereas Borden and Brant (1941) concluded t h a t t h e sands tone was depos i ted

nea r s h o r e i n a marine environment. The s t r a t i g r a p h i c p o s i t i o n of t h e

sands tone , l y i n g d i r e c t l y on an unconformity, and t h e coa r se n a t u r e of

t h e lower s e c t i o n sugges t a f l u v i a l o r i g i n f o r t h e lowermost p a r t . When

t h e Misener was depos i t ed t h e l and must have been very f l a t and nea r

s e a l e v e l t o a l low e x t e n s i v e t r a n s g r e s s i o n of t h e s e a i n Chattanooga

125

t i m e . It i s no t s u r p r i s i n g t h e n , t h a t t h e upper p a r t of t h e Misener

should c o n t a i n a marine fauna . The p a t t e r n of d i s t r i b u t i o n and th i ck -

ness of t h e Misener , as shown i n F ig . 2-19, nay r ep resen t a composite

p i c t u r e of a d i s t r i b u t a r y sand body t h a t has been re-worked i n t h e upper

p a r t by a t r a n s g r e s s i n g s e a , p o s s i b l y i n an e s t u a r i n e environment.

GEOMETRY OF MISENER SANDSTONE, EAST

TUSKEGEE OIL FIELD, OKLAHOMA

Fig. 2-19. I sopach map of Miss i s s ipp ian Misener Sandstone, E a s t Tuskegee

O i l Fi .eld, Creek County, Oklahoma. (Redrawn from Borden and

Bran t , 1941) .

126

Dale Consol ida ted O i l F i e l d , I l l i n o i s

In t h e Dale Consol ida ted F i e l d of I l l i n o i s , o i l p roduc t ion i s

ob ta ined from t h e Upper Miss i s s ipp ian Hardinsburg Sandstone, one of

s e v e r a l hydrocarbon-bearing sands tone u n i t s i n t h e Ches t e r S e r i e s ( see

F ig . 2-12). F ig . 2-20 i l l u s t r a t e s t h e sha rp e r o s i o n a l c o n t a c t of t h e

Hardinsburg Sandstone wi th t h e under ly ing beds , and t h e upward decrease

of mean g r a i n s i z e i n t h e upper p a r t of t h e Hardinsburg. These cha rac t -

e r i s t i c s a r e t y p i a a l of sands tone u n i t s i n t h e Ches t e r and are i n d i c a t i v e

of t h e i r o r i g i n a s c h a n n e l - f i l l sands . The use of a c l o s e l y under ly ing

l imes tone marker as a datum r e s t o r e s t h e o r i g i n a l c o n f i g u r a t i o n of t h e

channel and s u g g e s t s t h a t when t h e channel w a s i n i t i a l l y f i l l e d wi th

c o a r s e r s and , c h a r a c t e r i z e d by t h e b locky s e l f - p o t e n t i a l E-log cu rve ,

t h e l imes tone marker and o t h e r beds under ly ing t h e e r o s i o n a l channel had

a low r e g i o n a l d ip .

1 0 MILE L I

0 KM 1

Fig . 2-20. S t r a t i g r a p h i c s e c t i o n of channel f i l l e d wi th Upper Miss i s s ipp ian

Hardinsburg Sandstone, Dale Consol ida ted o i l f i e l d , Hamilton

County, I l l i n o i s . Datum i s a l imes tone bed. (Redrawn from

P o t t e r e t aZ., 1958).

127

The Hardinsburg Sandstone and o t h e r s ands tone u n i t s of t h e Ches te r

a r e cons idered by P o t t e r e t aZ.

- e x i s t i n g sed iments , as they are q u a r t z a r e n i t e s composed almost e n t i r e l y

of moderately well-rounded g r a i n s . I n d i c a t i v e of t h e i r o r i g i n as

c h a n n e l - f i l l s ands , t h e s e sands tone u n i t s commonly show f l u v i a l - t y p e

cross-bedding. Also i n d i c a t i v e of t h e i r d e p o s i t i o n a l environment i s

t h e i r s t r a t i g r a p h i c r e l a t i o n s h i p wi th t h i n c o a l seams, which sugges t

t h a t t h e channels meandered ove r a marshy d e l t a i c p l a i n .

(1958) t o have been de r ived from pre-

B e l l s h i l l Lake O i l F i e l d , A lbe r t a

The B e l l s h i l l Lake F i e l d of e a s t - c e n t r a l A l b e r t a produces o i l from

the E l l e r s l i e Sands tone , t h e b a s a l u n i t of t h e Lower Cre taceous B la i r -

more Group. The E l l e r s l i e , which f i l l s a broad ,eas t -wes t t r end ing v a l l e y

(F igs . 1-41, 1-42) on t h e eroded s u r f a c e of t h e Devonian ca rbona te s , is

composed of qua r t zose sands tone de r ived from Precambrian rocks . F luv ia l -

type cross-bedding i s a common f e a t u r e , i n d i c a t i n g t h a t t h e El lers l ie was

depos i t ed by a r i v e r . Pa leogeographic r e c o n s t r u c t i o n (Conybeare, 1972)

sugges t s t h a t t h i s r i v e r flowed eas tward from t h e Precambrian Sh ie ld t o

a Lower Cre taceous sea t r a n s g r e s s i n g southward. T ransg res s ion subsequent ly

r e s u l t e d i n drowning t h e E l le rs l ie r i v e r sys tem, t h e sands of which are

o v e r l a i n by e s t u a r i n e , c o a s t a l marsh, and b r a c k i s h t o f resh-water

l a c u s t r i n e sed iments .

F ig . 2-21 i l l u s t r a t e s a p o r t i o n of a sha l low stream channel t h a t

meandered on a c o a s t a l p l a i n ove r ly ing t h e E l l e r s l i e r i v e r sand a t

B e l l s h i l l Lake O i l F i e l d . In t h i s c a s e , hydrocarbon accumulation i n

t h e meandering sand body i s n o t s i g n i f i c a n t w i th r e spec t t o p roduc t ion

from t h e E l l e r s l i e , b u t where such an a r c u a t e body is t h i c k e r and convex

up-dip, i t may form an e x c e l l e n t s t r a t i g r a p h i c t r a p . A s i m i l a r example

(Fig. 1-43) i s i l l u s t r a t e d by Mar t in (1966) who s t a t e s t h a t i n t h e

1 2 8

0

E l

u 0 KM I ! I

MILE

- IOOFEET

ISOPACH M A P OF MANNVILLE SANDSTONE 'A, BELLSHILL LAKE FIELD, ALBERTA.

F i g . 2-21. Upper - I sopach map of a t h i n s a n d s t o n e 'A' i n t h e lower p a r t

of the B l a i n o r e Group, B e l l s h i l l Lake F i e l d , A l b e r t a .

T h i s s a n d s t o n e w a s d e p o s i t e d as a stream meander on a

c o a s t a l p l a i n .

Lower - E l e c t r i c l o g showing t h e r e l a t i o n s h i p of s a n d s t o n e 'A'

t o t h e o i l - p r o d u c i n g b a s a l q u a r t z s a n d s t o n e (B) of t h e

E l le rs l ie Format ion i n t h e B e l l s h i l l Lake F i e l d .

Hughenden F i e l d , which a l s o produces from t h e E l l e r s l i e , o i l is t r a p p e d

w i t h i n t h e E l l e r s l i e a g a i n s t a c l a y - f i l l e d meander t h a t i n t e r s e c t s t h e

r e g i o n a l s t r i k e . Both examples r e q u i r e a c l o s u r e formed by t h e co in-

c i d e n c e of a meander l o o p and r e g i o n a l d i p : b u t i n F i q . 2 2 1 %he t r a p IS

129

a s a n d - f i l l e d loop , whereas i n M a r t i n ' s example t h e t r a p i s w i t h i n a

s a n d - f i l l e d loop of t h e E l l e r s l i e where i t is l o c a l l y s e a l e d by a younger

c l a y - f i l l e d loop .

Conybeare (1972), Swindon (1968), Berg (1968) and Truchot (1963).

Other examples of a s i m i l a r n a t u r e a r e i l l u s t r a t e d by

The Ellerslie Sandstone is cross-bedded, qua r t zose , f i n e t o coarse-

-gra ined and up t o 75 m t h i c k . It h a s v a r i a b l e p o r o s i t y and pe rmeab i l i t y ,

i n p a r t determined by l o c a l cementa t ion w i t h c a l c i t e and c l a y mine ra l s .

In t h e B e l l s h i l l Lake F i e l d t h e p o r o s i t y and pe rmeab i l i t y a r e commonly i n

t h e range 25-28% and 1,000-1,500 m i l l i d a r c y s r e s p e c t i v e l y , t h e l a t t e r

ranging up t o 6,000 b u t averaging 600 m i l l i d a r c y s . Product ion problems

d e r i v e mainly from an e f f e c t i v e water d r i v e t h a t invades t h e o i l -bea r ing

zone. The o i l has a g r a v i t y of 280 A . P . I . and a gas con ten t of approx-

imate ly 150 cub ic f e e t p e r b a r r e l of oil. (approximately 20 cub ic metres

of gas pe r cub ic metre of o i l ) . The e s t ima ted o i l i n p l a c e i s approx-

imate ly 180 m i l l i o n b a r r e l s (28.6 m i l l i o n cubic m e t r e s ) , b u t water d r i v e

problems p rec lude t h e p roduc t ion of ve ry l i t t l e more than 36 m i l l i o n

b a r r e l s (5 .7 m i l l i o n cub ic m e t r e s ) .

B e l l y River P o o l , Pembina O i l F i e l d , A lbe r t a

I n t h e Pembina F i e l d of wes t - cen t r a l A l b e r t a , t h e main o i l p roduct ion

comes from t h e Upper Cre taceous Cardium Sands tone , approximate ly 300 m

below t h e b a s a l sands tone number of t h e Upper Cretaceous Be l ly River

Formation. Add i t iona l p roduc t ion i s ob ta ined from t h e Be l ly River P o o l

which y i e l d s o i l from t h i s b a s a l sands tone member.

sequence of marine s h a l e s of t h e Upper Cretaceous Lea Park Formation, t h e

b a s a l member of t h e Be l ly River i s found throughout a wide a r e a . It is

diachxonous and c o n s i s t s of two o r more g e n e t i c u n i t s . One of t h e s e u n i t s

i s a marine s h o r e l i n e sand , another i s a sand t h a t f i l l s channels c u t

i n t o t h e marine sand by d i s t r i b u t a r i e s of t h e eas tward prograding Bel ly

Overlying a t h i c k

130

CRETACEOUS BELLY RIVER SANDSTONE, PEMSINA

OIL FIELD, ALBERTA

BUCK CREEK 14-30 A1

Fig . 2-22. Map and s t r a t i g r a p h i c s e c t i o n A - A 1 showing d e p o s i t i o n a l

t r e n d s of t h e b a s a l sands tones of t h e Upper Cretaceous Bel ly

River Formation, Pembina F i e l d , A lbe r t a .

d i s t r i b u t a r y sands ( s t i p p l e d ) c u t t i n g a c r o s s a mar ine s h o r e l i n e

sand (ha tchured ) . The s t i p p l e d and ha tchured a r e a s a l s o

i n d i c a t e where t h e sands tones are more than 30 f e e t t h i c k .

The arrow shows t h e approximate d i r e c t i o n of r e g i o n a l d ip .

The s e c t i o n shows coa r se t o medium sand (1) f i l l i n g t h e lower

p a r t of a channel o v e r l a i n by f i n e sand ( 2 ) .

is i n t u r n o v e r l a i n by s i l t s and a c o a l seam.

1944, 1972).

The map shows r i v e r

This f i n e sand

(Af te r Conybeare,

131

River d e l t a . The marine sand is g e n e r a l l y f ine -g ra ined , w i t h poor

po ros i ty and pe rmeab i l i t y , whereas t h e channel sands are c o a r s e r and

more permeable. The Bel ly River P o o l i s conta ined w i t h i n one of t h e s e

channels (F ig . 2-22).

The producing sands tone i s l i t h i c , c o n s i s t i n g of g r a i n s of q u a r t z ,

q u a r t z i t e , c h e r t , f e l d s p a r , a r g i l l i t e , and v o l c a n i c rocks de r ived from

a wes tern sou rce . The sands tone grades from coa r se t o medium a t t h e

base t o f i n e a t t h e top .

t he sands tone . Within t h e channel , which i s about 2 km i n wid th , t h e

maximum t h i c k n e s s of s ands tone i s 20 m . The maximum t h i c k n e s s of t h e

o i l -bea r ing zone is 10 m. P o r o s i t y averages 18% and pe rmeab i l i t y is f a i r

bu t v a r i a b l e . The poo l is pure ly s t r a t i g r a p h i c , o i l be ing con ta ined

w i t h i n t h e t h i c k e r and c o a r s e r p a r t s of t h e sands tone where i t i s t r apped

by pe rmeab i l i t y b a r r i e r s on t h e f l a n k s of t h e channel .

Mudstone, c o n t a i n i n g a t h i n c o a l seam, o v e r l i e s

The Be l ly River Pool i s e s t ima ted t o c o n t a i n more than 30 m i l l i o n

(4 .8 m i l l i o n cub ic me t re s ) of 36O A . P . I . o i l , bu t r ecove rab le r e s e r v e s

a r e e s t ima ted a t only 2 m i l l i o n b a r r e l s (0 .2 m i l l i o n cub ic me t re s ) .

Gas s o l u t i o n d r i v e i s t h e main producing mechanism, t h e i n i t i a l gas con ten t

of t h e o i l amounting t o 350 cub ic f e e t per b a r r e l of o i l (approximately 50

cubic metres of gas pe r cub ic metre of o i l ) .

a r e 25-30 b a r r e l s a day pe r well.

Allowable p roduc t ion rates

Af ie se re and Eriemu O i l F i e l d s , N ige r i a

The o i l -producing sands tones i n t h e A f i e s e r e and Eriemu O i l F i e l d s

(Fig. 2-23) of t h e Niger Delta, N i g e r i a , o r i g i n a t e d a s a L a t e Cretaceous

t o Pa leocene complex of b a r r i e r b a r and d e l t a d i s t r i b u t a r y sands.

t h i s p a r a l i c environment, t h e complex of sand bod ies developed i n a

c y c l i c a l sequence of o f f - l app ing sed imentary beds , g rad ing upward from

marine c l a y s t o f luv iomar ine , i n t e r l a m i n a t e d s i l t s and sands o v e r l a i n

I n

132

Fig . 2-23. S t r u c t u r a l s e c t i o n ac ross t h e A f i e s e r e and Eriemu o i l f i e l d s

i n t h e Niger Delta, N ige r i a , showing s e p a r a t e r e s e r v o i r s i n

a b a m i e r b a r and channel f i l l complex of Late Cretaceous

and Paleocene sands tones . (Af t e r Weber, 1 9 7 1 ) .

by b a r r i e r b a r and d i s t r i b u t a r y c h a n n e l - f i l l sands .

i n t h i c k n e s s from 15 t o 100 metres, is te rmina ted by a marine t r a n s g r e s s i o n

which e roded p a r t of t h e o f f - l a p sequence , l e a v i n g a t h i n l a y e r of f o s s i l -

i f e r o u s and g l a u c o n i t i c coa r se sand.

l o c a l , i n response t o l a t e r a l s h i f t s i n t h e main r i v e r course which

would have p e r i o d i c a l l y swung back and f o r t h a c r o s s t h e d e l t a f r o n t ,

b u i l d i n g an o f f - l ap sequence

Each c y c l e , ranging

These t r a n s g r e s s i o n s a r e probably

wherever i t en te red t h e sea.

133

I n d i v i d u a l b a r r i e r b a r s i n t h e A f i e s e r e and Eriumu f i e l d s

have a l e n g t h of up t o 20 km, a wid th of s e v e r a l k i l o m e t e r s , a th i ckness

of up t o 1 2 m . They c o n s i s t g e n e r a l l y of f ine -g ra ined , va r i ab ly - so r t ed

sand. A s shown i n F ig . 2-23, t h e s e b a r s a r e c u t by channels f i l l e d wi th

sand which i s somewhat c o a r s e r . Separa ted by i n t e r v a l s of mudstone,

laminated sandy s i l t , and l i g n i t e , t h e s e b a r r i e r b a r and channel sand

bodies form s e v e r a l i n d i v i d u a l t r a p s f o r o i l . The accumula t ions are

e s s e n t i a l l y s t r a t i g r a p h i c , bu t l o c a l i z e d by g e n t l y , e longa ted domes

termed ' r o l l ove r ' s t r u c t u r e s (Weber, 1971). These s t r u c c u r e s a r e

a s s o c i a t e d wi th growth f a u l t s be l i eved t o have been caused by g r a v i t -

a t i o n a l s l i d i n g and r o t a t i o n of unconsol ida ted b locks of sed iment , du r ing

t h e pe r iod of format ion of t h e d e l t a .

Wilcox O i l and Gas F i e l d s , Texas

In t h e Texas Gulf Coast a r e a of t h e U . S . A . , s e v e r a l o i l and gas

f i e l d s are oroducing from m u l t i p l e pay zones i n t h e lower p a r t o f t h e

Early Eocene Wilcox Group. The Lower Wilcox, comprising up t o 1,500 m of

s ands tone , s i l t s t o n e , and carbonaceous mudstone, was depos i t ed as a

d e l t a i c complex (F ig . 2-24), t h e shape and dimensions of which a r e s imi la r

t o t h e present-day M i s s i s s i p p i d e l t a . She l ton (1973), s t a t e s t h a t t h i s

complex, known as t h e Rockdale d e l t a sys tem, c o n s t i t u t e s 80% vo lumet r i ca l ly

of t h e known d e p o s i t s of t h e Lower Wilcox. The Rockdale system is

c h a r a c t e r i z e d by sou the r ly - t r end ing l o b e s ( F i s h e r and McGowan, 1969)

c o n s i s t i n g mainly o f sands tone . T o t a l n e t sands tone th i ckness w i t h i n

t h e Rockdale ranges from 750 m t o less than 30 m at t h e sou the rn pinch-out

(seaward) edge.

The Wilcox sands tones are qua r t zose and g e n e r a l l y f i n e t o medium-

-gra ined . They have an average p o r o s i t y and pe rmeab i l i t y of 20% and 100

m i l l i d a r c y s r e s p e c t i v e l y . Smal l - sca le cross-bedding is common, and

carbonized p l a n t f ragments are l o c a l l y abundant.

134

0 100 w

M I L E S 100

O w KM

EARLY E O C E N E D E P O S I T I O N A L S Y S T E M

Fig . 2 - 2 4 . Genera l ized d i s t r i b u t i o n o f t h e Lower Wilcox Group (Ear ly

Eocene) d e p o s i t i o n a l system, Texas. (Redrawn from F i she r

and McGowen, 1969) .

I n t e r f i n g e r i n g of p ro -de l t a muds w i t h b a r r i e r - b a r s ands , d i s t r i b u t a r y

c h a n n e l - f i l l s ands , and l i t t o r a l sands has provided numerous s e p a r a t e

r e s e r v o i r s s i m i l a r t o those of t h e Af i e se re and Eriemu f i e l d s of N ige r i a

(F ig . 2-23) . F i s h e r and McGowan (1969) s ta te t h a t l a r g e r f i e l d s i n t h i s

ca tegory i n c l u d e F a l l C i t y , Sher idan , Columbus, Lake Creek, New U l m , and

Quicksand Creek. Most f i e l d s i n t h e Lower Wilcox are e s s e n t i a l l y s t ra t i -

g raph ic , bu t l o c a l growth f a u l t s and d i a p i r i c s t r u c t u r e s , a s s o c i a t e d wi th

t h i c k e r p a r t s of t h e d e l t a l o b e s , co inc ide wi th s t r a t i g r a p h i c t r e n d s t o

form t r a p s .

See l ig son O i l F i e l d , Texas

One of t h e main o i l -bea r ing zones i n t h e See l ig son F i e l d of Texas

is t h e Oligocene Zone 19-b Sandstone. S i t u a t e d i n t h e Frio-Vicksburg

135

trelid of o i l f i e l d s , Zone 19-b forms an i r r e g u l a r , e a s t e r l y - t r e n d i n g

b e l t of sands tone t h a t has been t r a c e d a long i t s l e n g t h f o r 11 km, and

i s known t o have a wid th of 3-8 km. The geometry of t h i s sands tone

b e l t , which t r ends i n a d i r e c t i o n approximately normal t o t h e r eg iona l

d e p o s i t i o n a l s t r i k e of ad jacen t marine sands tone beds i n t h e Oligocene

sequence, sugges t s t h a t i t w a s formed by a branching r i v e r system on a

d e l t a p l a i n . In t h e See l ig son F i e l d a r e a t h r e e s u b s i d i a r y channels , 1,000-

2,000 m wide , b ranch from t h e main channel which h a s a wid th of 2,000-

2,000 m. An i sopach nap of Zone 19-b (F ig . 2-25 shows t h e main body of

t h e c h a n n e l - f i l l sands tone t o have a maximum th i ckness of more than 20 m ;

t he s u b s i d i a r y channels have a th i ckness i n t h e range 6-12 m.

The sands tone is predominantly l i t h i c . I t con ta ins fragments of

rock and f e l d s p a r , b u t i nc ludes up t o 50% q u a r t z , and 5-20% i n t e r s t i t i a l

s i l t and c l a y . Commonly we l l - so r t ed , and f i n e t o medium-grained, t h e

sands tone bod ies i n Zone 19-b show d i s t i n c t g r a i n g r a d a t i o n from c o a r s e r

below t o f i n e r above, a f e a t u r e c h a r a c t e r i s t i c of r i v e r d e p o s i t s . Sed i -

mentary s t r u c t u r e s commonly p r e s e n t i nc lude medium-scale cross-bedding

and c l ays tone fragments probably de r ived from t h e e r o s i o n of mud-cracked

c l ay a long t h e r i v e r banks. Var iab le p o r o s i t y and pe rmeab i l i t y sugges t

t h a t t h e o r i g i n a l composition of t h e sands tone v a r i e d from c lean sand t o

s i l t y and muddy sand. Local cementation by c a l c i t e and i l l i t e has a l s o

decreased p o r o s i t y and pe rmeab i l i t y .

O i l entrapment i n Zone 19-h has r e s u l t e d from t h e co inc idence of

permeable zones w i t h i n t h e d i s t r i b u t a r y channels and t h r e e g e n t l e domal

s t r u c t u r e s on t h e downthrow s i d e of a major normal f a u l t . Although t h e

Zone 19-b Sandstone h a s been a major c o n t r i b u t o r t o o i l p roduc t ion ,

s e v e r a l o t h e r zones i n the See l ig son F i e l d a r e p roduc t ive . She l ton

(1973, p. 30) s a y s , at See l igson F i e l d more than 40 sands , a l l of

vh ich a r e i r r e g u l a r l y developed, have combined wi th t h e s t r u c t u r a l

136

OLIGOCENE 196

S AN DS TONE

a' SEELIGSON OIL

I Mile 0-1 KM OU

Fig . 2-25. Isopach map and f ence diagram of t h e Oligocene 19B sands tone ,

See l ig son F i e l d , Gulf Coast a r e a , Texas. This sands tone body

is i n t e r p r e t e d a s a branching r i v e r d e p o s i t . (Redrawn from

Nanz, 1954).

137

p a t t e r n t o account f o r more than 140 i n d i v i d u a l r e s e r v o i r s . These sand

u n i t s are p r e s e n t i n a 1,500-foot s e c t i o n of Oligocene (or Hiocene)

F r io s t r a t a , which are cons idered non-marine i n o r ig in" .

Ostra O i l F i e l d , Venezuela

In t h e Ostra F i e l d , Venezuela (F ig . 2-26), o i l i s produced from

l e n t i c u l a r sands tone beds of t h e Oligocene Of ic ina Formation. These

sands tone beds are n o t only markedly l e n t i c u l a r , b u t a l s o r e l a t i v e l y

t h i n , commonly having a th i ckness of n o t more than 12 m , b u t l o c a l l y

ranging up t o 60 m. They o v e r l i e non-marine beds of t h e Oligocene

Mercure Formation and are cons idered t o be d e l t a d i s t r i b u t a r y channel l -

- f i l l sands and f r i n g i n g s h o r e l i n e sand d e p o s i t s . Young (1971, p . 250)

s a y s , "The sands tones a r e p a r t of a c y c l i c s e r i e s of s i l t s t o n e s , l i g n i t e s ,

s ands tones , s h a l e s and c l ays tone depos i t ed i n d e l t a i c and p a r a l i c environ-

ments through r ep rea t ed a l t e r n a t i o n of lagoonal-swamp, brackish-water and

shallow-wa te r marine cond i t ions ' I .

The sands tone l e n s e s a r e sepa ra t ed by s h a l e beds t h a t form an e f f e c t -

DATUM

krn L50m

CHANNEL SANDS, OSTRA FIELD, VENEZUELA.

Fig . 2-26. Sec t ion through o i l -bea r ing channel sands of t h e Oligocene

O f i c i n a Formation, Ostra F i e l d , Venezuela.

Young, 1971).

(Redrawn from

138

i v e seal f o r o i l . Although warped by compaction, t h e r e is only s l i g h t

f o l d i n g of t h e sands tone l e n s e s , and t h e o i l accumulations are i n s t r u c t u r a l -

- s t r a t i g r a p h i c t r a p s c o n t r o l l e d by f a u l t s and pinch-out edges of t h e

sands tone bod ies . The d e p o s i t i o n a l o r i g i n s and s t r u c t u r a l - s t r a t i g r a p h i c

s i t u a t i o n s of t h e o i l -bea r ing sands tone bod ies a r e s imi la r t o those found

i n t h e Eocene beds of t h e X g e r d e l t a , N i g e r i a , and i n t h e Oligocene beds

of t h e Frio-Vicksburg t r e n d i n t h e Gulf Coast a r e a of t h e U . S . A .

:.lain Pass Block 35 O i l F i e l d , Lou i s i ana

O i l p roduc t ion i n t h e Main Pass Block 35 F i e l d (F ig . 2-27) of t h e

? I i s s i s s i p p i d e l t a , Lou i s i ana , comes from t h e Miocene "GZ" Sandstone vh ich

was depos i t ed a s a c h a n n e l - f i l l sand i n a d e l t a d i s t r i b u t a r y .

sands tone is q u a r t z o s e , bu t up t o 20% of i ts volume c o n s i s t s of f ragments

This

/

ttt I

CHANNEL SAND, BLOCK 35 FIELD

LOUISIANA

Fig . 2-27. Isopach map showing n e t f e e t (1 ' = 0.305 m) of sands tone i n t h e

Miocene "G2" channel s ands tone , and t h e w e l l s producing from

t h i s s ands tone , Maln Pass Block 35 F i e l d , M i s s i s s i p p i d e l t a ,

Louis iana . (Redrawn from Nartman, 1972) .

139

of rock and f e l d s p a r . It i s g e n e r a l l y c l e a n , w e l l s o r t e d , and f ine-gra ined .

Average p o r o s i t y and pe rmeab i l i t y a r e 34% and 3,000 m i l l i d a r c y s i n t h e

t h i c k e r and c o a r s e r p a r t s of t h e sands tone body, b u t dec rease t o 26% and

75 m i l l i d a r c y s i n t h e t h i n n e r p a r t s , f l a n k i n g n a t u r a l l evee and backs lope

d e p o s i t s , of very f ine-gra ined sands tone and s i l t s t o n e . The main channel-

- f i l l sand body, which has a wid th of 600-900 m and a maximum th i ckness of

more than 25 m , ha s been t r a c e d by d r i l l i n g f o r more than 5 km i n the

f i e l d a rea .

Entrapment of o i l w i t h i n t h e "G2" Sandstone r e s u l t s from a combination

of s t r a t i g r a p h i c and s t r u c t u r a l f a c t o r s ;

sands tone body c r o s s e s a f a u l t e d dome. Hartman (1972) says t h a t t h e "G2"

Sandstone, which i s t h e l a r g e s t s i n g l e r e s e r v o i r i n t h e Main Pass Block 35

F i e l d , is a c l a s s i c example of o i l p roduc t ion from a s t r eam channel.

U l t i m a t e p roduct ion from t h e Block 35 F i e l d , i n which o i l i s ob ta ined from

23 i n d i v i d u a l Miocene sands tone bod ies , is e s t ima ted t o be 100 m i l l i o n

b a r r e l s (15.9 m i l l i o n cubic m e t r e s ) , of which more than 12 m i l l i o n b a r r e l s

(1.9 m i l l i o n cub ic me t re s ) w i l l come from tile "G2" Sandstone. Product ion

i s a s s i s t e d by a s t r o n g wa te r d r i v e .

o i l be ing t rapped where t h e l i n e a r


141

Chapter 3

BARRIEA A;W OTHER OFFSHORE BARS

I n t r o d u c t i o n ___-

Geomorphology

B a r r i e r and o t h e r o f f s h o r e b a r s are l i n e a r sands tone bodies which

commonly have a th i ckness i n t h e range 5-15 m. Barrier b a r s a r e exposed

above sea l e v e l a s b a r r i e r i s l a n d s t h a t commonly form a cha in t r end ing f o r

many miles along t h e main c o a s t l i n e , s e p a r a t i n g l a soons and c o a s t a l bays

from t h e open s e a (F igs 3-1, 3--2). These i s l a n d s a r e commonly a m i l e o r

more wide and s e v e r a l m i l e s long . Other o f f s h o r e b a r s may develop w i t h i n

t h e o u t e r p a r t of a bay where t h e seaward edge of a sha l low-wa te r shoa l

s lopes downward i n t o deeper w a t e r , o r o f f a headland t o form a s p i t .

The seaward c o a s t of a b a r r i e r i s l a n d forms a nea r ly s t r a i g h t

t o g e n t l y curved f l a t beach washed by waves and c u r r e n t s t h a t winnow t h e

sand and t r a n s p o r t i t both seaward and along t h e c o a s t . The l azoona l

coas t of a b a r r i e r i s l a n d i s i r r e g u l a r , w i th numerous sma l l embayments

and c o a s t a l f l a t s of s i l t y sand and marsh. Other i s l a n d s t h a t rise from

o f f s h o r e b a r s w i t h i n a bay , o r t h a t forni s p i t s , commonly show t h e same

s h o r e l i n e c h a r a c t e r i s t i c s .

The a r e a exposed as i s l a n d s r e p r e s e n t s l e s s than h a l f t h e a r e a of

most sand b o d i e s , t h e seaward and landward o u t l i n e s of which are equa l ly

i r r e g u l a r as i n d i c a t e d by i sopach maps of bo th r ecen t (F ig . 3-5) and

anc ien t (F igs . 3-10, 3-14, 3-15, 3-18) b a r r i e r b a r s . Continuously s h i f t i n g ,

although no t n e c e s s a r i l y a t a cons t an t r a t e , t h e s e i s l a n d s t end t o mig ra t e

p a r a l l e l t o t h e main c o a s t l i n e , i n t h e d i r e c t i o n of t h e long-shore c u r r e n t

(Fig. 3-3).

t he sand be ing t r a n s p o r t e d along t h e o u t e r coas t and depos i t ed on t h e

The u p c u r r e n t end of each i s l a n d i s consequent ly e roded ,

142

0-20

0

I PADRE ISLAND, A BARRIER

GULF OF MEXICO

I S L A N D,

Fig . 3-1. Padre I s l a n d , a b a r r i e r i s l a n d of f t h e c o a s t of Texas, Gulf of

Mexico. Laguna Nadre l i e s between t h e b a r r i e r i s l a n d and t h e

mainland. (Redrawn from Rusnak, 1960).

L.

M I L F S

OFFSHORE BARS, LONG ISLAND, NEW YORK

Fig . 3-2. Offshore b a r s , Long I s l a n d , New York, showing t h e i r d i s t r i b -

u t i o n and geograph ica l r e l a t i o n s h i p s . Arrows show t h e long-

sho re c u r r e n t d i r e c t i o n s . (Lledrawn from Bass, 1934).

143

W T

MAINLAND E

1959 SHORELI

1890 SHORELINE

0 4 K M - MIGRATION OF TlMBALlER ISLAND,

GULF OF MEXICO.

Fig . 3-3. Shoreward and westward mig ra t ion of Timbal ie r I s l a n d ,

Lou i s i ana , du r ing t h e y e a r s 1890-1959, i n response t o nor th-

w e s t e r l y movement of c o a s t a l c u r r e n t s . '(Redrawn from Otvos,

1970) .

seaward ex tens ion of' beaches and a t t h e down-current end of t h e i s l a n d

where i t may form a s p i t . Wave a c t i o n moves t h e sand up t h e d e p o s i t i o n a l

s l o p e t o t h e beaches , except du r ing pe r iods of e x c e p t i o n a l l y h igh t i d e s

and heavy s torms when beaches a r e e roded and massive q u a n t i t i e s of sand

a r e t r a n s p o r t e d a long t h e c o a s t . Some sand i s swept i n l a n d over t h e

i s l a n d du r ing s torms , and some i s moved in l and a s sand dunes.

Unequal rates of e r o s i o n and d e p o s i t i o n , and v a r i a t i o n s i n t h e

rates of flow i n t i d a l channels between ad jacen t i s l a n d s , r e s u l t s i n

merging o r f u r t h e r s e p a r a t i o n of t h e i s l a n d s , a l though t h e scb-sea

d i s t r i b u t i o n of sand may form a s i n g l e sand body. I n some c a s e s , an

i s l a n d may s h i f t back t o a l o c a t i o n i t p rev ious ly occupied , so t h a t

a h o l e d r i l l e d through i t w i l l show two sand u n i t s s e p a r a t e d by s i l t -

s t o n e o r s h a l e . These sand u n i t s a r e commonly no t completely s e p a r a t e d ,

bu t merge l a t e r a l l y a c r o s s o r a long s t r i k e when viewed i n t h r e e

dimensions (F igs . 3-5, 3-1 8, 3-23).

144

A t y p i c a l c ros s s e c t i o n of a s imple b a r r i e r b a r is shown i n

Fig. 3 - 4 ) . The s u r f a c e exposed above s e a l e v e l , forming a b a r r i e r

i s l a n d , h a s an i r r e g u l a r topography formed by sand dunes. The seaward

s l o p e is a smooth, g e n t l y undu la t ing t ime-plane on which t h e sand

grade s i z e ranges from c o a r s e r on t n e beach , where t h e energy l e v e l

caused by waves and c u r r e n t s i s h i g h e r , t o f i n e r in deepe r wa te r where

t h e f i n e sand grades i n t o s i l t and c l a y . Sub-para l le l t o t h e seaward

s l o p e , o l d e r t ime-planes l i e w i t h i n t h e sand body. The t r a c e s of

such t ime-plane wi th t h e p l ane of a s e c t i o n c u t a c r o s s a b a r r i e r b a r

a r e shown by t h e d o t t e d l i n e s i n F ig . 3-4. Although no t u s u a l l y

v i s i b l e , and commonly d i f f i c u l t t o d e t e c t by geophys ica l methods i n

a f a i r l y homogeneous sand body, i t is p o s s i b l e f o r p a r t of t h e a r e a

of a t ime-plane t o be a u s e f u l t i m e - s t r a t i g r a p h i c marker , p a r t i c u l a r l y

where i t can be d i s t i n g u i s h e d by some sedimento logic c h a r a c t e r i s t i c o r

f o s s i l con ten t . The co inc idence of any t ime-plane and i t s contemporary

d e p o s i t i o n a l s l o p e c l e a r l y i n d i c a t e s t h e manner i n which t r a n s p o r t e d

sand a c c r e t e s t o t h e o f f s h o r e ex tens ion of beaches t o form a sequence of

seaward-prograding l a y e r s . A s a consequence of t h e g r a d a t i o n of s e d i n e n t

on t h e d e p o s i t i o n a l s l o p e , from cour se r sand on t h e beach t o f i n e r sand

CROSS SECTION OF BARRIER ISLAND

Fig . 3 - 4 . Cross s e c t i o n of a t y p i c a l b a r r i e r i s l a n d o f f t h e coas t

t h e Gulf of Mexico. (Redrawn from Bernard et a l . , 1962

of

145

s i l t , and mud i n p rogres s ive ly deeper w a t e r , sand s i z e g r a d a t i o n w i t h i n

the sand body dec reases f r o top t o bottom, t h e r e v e r s e r e l a t i o n s h i p t o

c h a n n e l - f i l l r i v e r s ands .

Sands of b a r r i e r b a r s and o t h e r o f f s h o r e b a r s have a t e r r i g e n o u s

o r i g i n , having been t r a n s p o r t e d a long d i s t r i b u t a r i e s t o b a r - f i n g e r r

sand bodies then swept a long t h e c o a s t by c u r r e n t s and wave a c t i o n .

A t Grand Isle, Louis iana (F ig . 3 - 5 ) t h e sand i s f ine -g ra ined , l o c a l l y

s i l t y , and has a composition of approximate ly 80% q u a r t z and 20% f e l d s p a r .

Loca l ly , l e n t i c u l a r l a y e r s of g r i t o r pebbly sand may be p r e s e n t w i t h i n a

\ 1 ISOLITH OF SAND A

t 1 2 3

0 0- SEA LEVEL SAND A

S A N ~ ~

so'--

Fig . 3 - 5 . Eas te rn end of Grand I s l e , Lou i s i ana , showing c o n f i g u r a t i o n

of t h e i s l a n d , la teral e x t e n t of t h e upper Sand A ( i s o l i t h

contours i n f e e t ) , and a c ros s - sec t ion of t h e b a r r i e r i s l a n d

complex. (Redrawn from Cona t se r , 1971).

146

b a r r i e r b a r , having formed where some topographic f e a t u r e a long a beach

causes t h e sand t o be winnowed more v igo rous ly . Cross-bedding is a l s o

an i n t e r n a l f e a t u r e , b u t i n most ca ses i s of t h e low-angle type ( l e s s

than 10') i n c o n t r a s t t o t h e h i g h e r ang le of f l u y i a t i l e cross-bedding.

I n b a r r i e r and o t h e r b a r s t h e cross-bedding commonly r e f l e c t s changes

i n t h e d e p o s i t i o n a l s l o p e of an undu la t ing beach , bu t may a l s o r e s u l t

from c u r r e n t a c t i o n caused by t i d a l movements through channels between

b a r s . I n such channe l s , a high-angle type of cross-bedding, s i m i l a r t o

t h a t observed i n r i v e r p o i n t b a r s , may be developed. I n f a c t , t h e

r e l a t i o n s h i p s of cross-bedding t o t h e geometry of a b a r r i e r b a r t h a t i s

prograding i n t o a mig ra t ing t i d a l channel are no t f u l l y understood.

Gra in o r i e n t a t i o n w i t h i n t h e i n t e r t i d a l beach u n i t i s cha rac t e r -

i s t i c a l l y more-or-less normal t o t h e c o a s t l i n e , t h e long axes of t h e

sand g r a i n s be ing a l igned p a r a l l e l t o t h e predominant d i r e c t i o n of swash

movement caused by waves and t i d e s moving up and down t h e mean beach s l o p e .

This f a c i e s of a modern beach i s probably seldom preserved i n t h e

g e o l o g i c a l r eco rd , a l though an except ion i s noted by She l ton (1970, p . 1105)

who s a y s , "Grain o r i e n t a t i o n is normal t o t h e sands tone t r e n d of t h e lover -

most u n i t of t h e Eagle Sandstone a t B i l l i n g s , Montana. Gra in imbr i ca t ion

i n t h a t b a r r i e r - b a r sands tone sugges t s t h a t oncoming s u r f was t h e most

impor tan t d e p o s i t i n g c u r r e n t du r ing l o c a l westward accre t ion ' . .

p a r t of t h e sand body formed i n deepe r wa te r , where t h e predominant

c u r r e n t d i r e c t i o n i s a long t h e c o a s t , g r a i n o r i e n t a t i o n tends t o be p a r a l l e l

t o t h e c o a s t and consequent ly t o t h e d i r e c t i o n of t r e n d of t h e sand body.

This deeper-water f a c i e s , depos i t ed s e v e r a l hundred met res seaward fro.1 t h e

beach , i s commonly p rese rved i n t h e g e o l o g i c a l record . An im?or tan t

c o r o l l a r y is t h a t t h e r e l a t i o n s h i p between g r a i n o r i e n t a t i o n and geometry of a

marine sands tone body can be an impor tan t key t o e x p l o r a t i o n , f o r sands tone

t r e n d s , a l though i t must b e use5 i i t h sone r e s e r v a t i o n .

Within t h a t

147


Within a prograding b a r r i e r b a r o r o t h e r o f f s h o r e b a r , t h e g r a i n

g rada t ion from c o a r s e r above t o f i n e r below is r e f l e c t e d i n t h e c h a r a c t e r

of t he E-log s e l f - p o t e n t i a l curve which t ends t o b e funnel-shaped. A s previous-

l y d i scussed , t h i s shape i s t h e r e v e r s e of t h a t r i v e r sands i n which t h e

g r a i n g rada t ion i s from c o a r s e r below t o f i n e r above. The s e l f - p o t e n t i a l

cha rac t e r is i n d i r e c t l y r e l a t e d t o t h e sand g r a i n s i z e , bu t d i r e c t l y r e l a t e d

t o the p e t r o p h y s i c a l p r o p e r t i e s of t h e m a t r i x i n t h e sand. In sands t h a t

have no t been e x t e n s i v e l y a l t e r e d by d i a g e n e s i s and cementa t ion , t h e r e is a

r e l a t i o n s h i p between g r a i n s i z e and s i l t y c l a y c o n t e n t , t h e c o a r s e r sand

being c l e a n e r t han t h e f i n e r s and , and consequent ly more permeable.

Typica l b a r r i e r b a r E-log c h a r a c t e r i s t i c s , as seen i n a marine

t r a n s g r e s s i v e sequence, are i l l u s t r a t e d by P i r s o n (1970), and by Corlybeare

and Je s sop (1972) i n F ig . 3-6. The €unnel-shaped s e l f - p o t e n t i a l curve

of t h e Eocene sands is w e l l marked. The lower sands of t h e Miocene b a r r i e r

b a r complex show t h e same c h a r a c t e r i s t i c s , bu t t h e upper sands tend t o b e

blocky, p o s s i b l y r e f l e c t i n g a f a i r l y uniform g r a i n s i z e and l i t t l e v a r i a t i o n

i n t h e s i l t y c l a y con ten t . A 1.ower Cre taceous complex of s t acked sands tone

bod ies , showing a s imilar r e l a t i o n s h i p of E-log c h a r a c t e r i s t i c s t o t h e

Miocene b a r s , i s a l s o i n t e r p r e t e d a s a sequence of o f f - l app ing marine sands ,

probably formed a s b a r r i e r b a r s . These sands tone bodies a r e qua r t zose and

have good p o r o s i t y and pe rmeab i l i t y . A t t h e l o c a t i o n shown they are

sepa ra t ed by s i l t y mudstone, b u t i t is probable t h a t a t o t h e r l o c a t i o n s they

merge i n v a r i o u s ways, a s shown i n F ig . 3-5 .

Compact i o n

Compaction of t h e muddy sediments f l ank ing and i n t e r f i n g e r i n g wi th 'a

b a r r i e r b a r complex may cause d i f f i c u l t i e s i n r e c o n s t r u c t i n g t h e

pa leogeonorphic r e l a t i o n s h i p s of t h e v a r i o u s sand bod ies w i t h i n t h e

148

M A G O B U IS N o 1 S P R

___

I L O W E R

C R E T A C E O U S

( U N I T 2 )

I

1

Fig . 3-6.

4 0 0 0

4 500

B ' R E F L E C T O R

M I O C E N E B A R R I E R B A R

S A N D S , T E X A S

s P I 1 R ] E O C E N E B A R R I E R B A R

S A N O S , T E X A S R E L A T I V E

G R A I N S I Z E

0 0

- 0 ... .

E - L O G C H A R A C T E R O F B A R R I E R B A R S A N D S

E-logs of T e r t i a r y b a r r i e r b a r s i n Texas, and a Lower

Cre taceous sands tone i n Papua, showing t h e s i m i l a r i t y of

c o n f i g u r a t i o n and t h e r e l a t i o n s h i p of t h e s e l f - p o t a n t i a l

c h a r a c t e r i s t i c s t o g r a i n g rada t ion .

J e s sop , 1972).

(Af t e r Conybeare and

complex.

complex of marine s h o r e l i n e sands (F ig . 3-6 ) p e n e t r a t e d by Magobu I s l a n d No.

1 Well i n Papua.

f a c e of t h e Lower Cre taceous (B r e f l e c t o r ) and t h e top of t h e sand body

complex (B ' r e f l e c t o r ) i s shown i n F i g . 3-8. This map i n d i c a t e s a l i n e a r ,

no r theas t - t r end ing sands tone u n i t a t t h e Magobu l o c a t i o n , and sugges t s

t h e p o s s i b i l i t y of a t h i c k e r sand development a long a p a r a l l e l t r end

t o t h e nor thwes t (F ig . 3-7). But what is n o t known is t h e s t r a t i g r a p h i c

F igs . 3-7 and 3-8 i l l u s t r a t e an example i n a Lower Cretaceous

An i so t ime map of t h e i n t e r v a l between t h e e r o s i o n a l su r -

Y M A G O B U IS N o 1

s w Y '

N E

149

M I L E S 0 5 10

D I AG R A M M A T 1C S T R U C T U R A L S E CTlON D R A P I N G OF B' S E I S M I C REFLECTOR O V E R BARRIER BARS

F i g . 3-7. Diagrammatic s t r u c t u r a l s e c t i o n Y-Y' showing t h e i n f e r r e d

r e l a t i o n s h i p o f t h e B ' s e i s m i c r e f l e c t o r t o t h e upper

c o n f i g u r a t i o n of a Lower C r e t a c e o u s s a n d s t o n e (Unit 2) i n

t h e F l y River Area, Papua. ( A f t e r Conybeare and J e s s o p , 1 9 7 2 ) .

r e l a t i o n s h i p of t h e s a n d body o r b o d i e s i n t h e n o r t h w e s t t r e n d t o t h o s e

a t Magobu. C o n s e q u e n t l y , any pa leogeomorphic i n t e r p r e t a t i o n i s q u e s t i o n a b l e .

F ig . 3-7 i s b a s e d on two i n f e r e n c e s : f i r s t l y , t h a t t h e e r o s i o n a l s u r f a c e

of t h e Upper C r e t a c e o u s , which i s o v e r l a i n by sha l low-water m a r i n e l i m e -

s t o n e , is f a i r l y f l a t and g e n t l y d i p p i n g ; and s e c o n d l y , t h a t e s s e n t i a l l y

t h e same complex of s a n d s t o n e b o d i e s a t Magohu is p r e s e n t i n t h e n o r t h w e s t

t r e n d . An a l t e r n a t i v e i n t e r p r e t a t i o n c o u l d show t h e s t r u c t u r a l r e l a t i o n -

s h i p between t h e B and B ' r e f l e c t o r s t o b e a s i n d i c a t e d , h u t w i t h o n l y t h e

uppermost Magobu s a n d body p r e s e n t i n t h e n o r t h w e s t t r e n d . Another i n t e r -

p r e t a t i o n c o u l d show t h e B ' r e f l e c t o r t o f o l l o w a n e r o s i o n a l d e p r e s s i o n

150

ISOTIME MAP SEISMIC INTERVAL B-8'

C O N T O U R I N T E R V h L 5 0 M S

Fig. 3-8. Isotime map of the interval between the seismic reflectors

B and B', showing the line of section Y-Y' (Fig. 3-7) and

the topography of sandstone Unit 2. (After Conybeare and

Jessop, 1972) .

over the northwest'trend, with only the lowermost sand body present. Other

interpretations showing faulting, or inferring mis-correlations in plotting

the B' reflector, may be valid.

Parallel trends of sandstone bodies, formed as off-lapping barrier

bar and other sand body complexes, can contain excellent traps for oil and

gas, particularly where they are intersected by anticlines, domes, and

faults. Such traps are essentially stratigraphic and geomorphic, with

structural modifications. Their discovery may, in some cases, hinge largely

on interpretation of the compactional effects within and flanking a known

or inferred bar complex.

151

Apcient Sand Bodies ~ ~~ ~~~~~

Numerous examples of a n c i e n t b a r r i e r b a r s and o t h e r b a r s are

known, many of which a r e recorded i n t h e l i t e r a t u r e , and some of which

a r e desc r ibed i n t h e fol lowing s e c t i o n on o i l and gas f i e l s . Only a

s m a l l percentage of known examples a r e so w e l l exposed i n outcrops t h a t

they can be seen as a cont inous s e c t i o n measuring s e v e r a l k i lome t re s

ac ross t h e t r end of t h e b a r . One such example i s t h e lower u n i t of t h e

Upper Cretaceous Eagle Sandstone (Fig. 3-9) t h a t crops ou t as rim-rock

i n t h e e sca rpen t a t B i l l i n g s , Montana, and has been descr ibed by Shel ton

(1965).

The lower u n i t of t h e Eagle i s a wel l -sor ted, l i t h i c and

g l aucon i t i c marine sandstone t h a t shows an upward g rada t ion i n g r a i n s i z e

from very f i n e t o f i n e . The u n i t t r ends north-northwest, has a known

l eng th of 65 km, a width of 30-50 km, and a maximum th i ckness of 30 m.

In t h e upper p a r t of t h e u n i t low-angle ( l e s s than loo) cross-bedding

is a common f e a t u r e .

con t inua l changes i n t h e d e p o s i t i o n a l s l o p e s of a sand body, probably

This cross-bedding could have been formed by

TOP LOWER SANDSTONE UNIT

CLAY STONE, SILTSTO N E I KM

40m i[' I LL 40 O-

MILE

I; UPPER CRETACEOUS EAGLE SANDSTONE, MONTANA

Fig. 3-9. Sec t ion of t h e Upper Cretaceous Eagle Sandstone t h a t forms

(Redrawn rim-rock i n t h e escarpment a t B i l l i n g s , Montana.

from She l ton , 1965).

i n a p a r t of t h e body depos i t ed i n water too deep f o r i t t o be exposed

a t l o w t i d e , and which is consequent ly preserved i n t h e g e o l o g i c a l

r eco rd . I n t h e lower p a r t of t h e s e c t i o n b i o t u r b a t i o n is a common

f e a t u r e .

I n F ig . 3-9 t h e i n t e r s e c t i o n s of bedding p l anes wi th t h e

f a c e of t h e ou tc rop are shown as broken l i n e s . They have t h e same

r e l a t i o n s h i p t o t h e gemorphology of t h e b a r r i e r b a r as is shown i n

F ig . 3-4, and i n d i c a t e p rograda t ion i n a d i r e c t i o n toward t h e coas t -

l i n e , a s i n f e r r e d from pa leogeographic r e c o n s t r u c t i o n . Th i s geographic

r e l a t i o n s h i p sugges t s t h a t t h e b a r r i e r b a r w a s s i t u a t e d on a sha l low

c o n t i n e n t a l s h e l f , more than 80 km from t h e sho re toward which i t was

b u i l d i n g . I n such a geographic s i t u a t i o n t h e b a r , which e x t e r n a l l y

and i n t e r n a l l y has t h e f e a t u r e s of a barrier b a r , may i n f a c t no t have

formed a b a r r i e r .


O i l and gas f i e l d s i n b a r r i e r and o t h e r o f f s h o r e b a r s are

w e l l r ep resen ted i n t h e l i t e r a t u r e where they have o f t e n been recorded

s i n c e t h e e a r l y 1 9 2 0 ' s . I n f a c t , many of t h e ear l ier recorded sand

bod ies , r e f e r r e d t o as b a r s , have subsequent ly been found t o be d i s t r i -

bu ta ry channel sands . Lacking t h e c r i t e r i a t o adequte ly i n t e r p r e t t h e

o r i g i n of c e r t a i n hydrocarbon-bearing, l e n t i c u l a r and l i n e a r sands tone

bod ies , g e o l o g i s t s commonly r e f e r r e d t o then as b a r s . In some c a s e s t h e

term ba r w a s p robably used on ly t o d e s c r i b e t h e morphology o f t h e sand-

s t o n e body, w i th no i m p l i c a t i o n as t o i t s o r i g i n . In o t h e r c a s e s t h e

conno ta t ion of o r i g i n a s a b a r r i e r o r o t h e r o f f s h o r e b a r was i m p l i c i t .

Not u n t i l t h e 1 9 6 0 ' s were g e o l o g i s t s , i n g e n e r a l , d e s c r i b i n g such

sands tone bod ies i n more p r e c i s e geomorphologic t e r m s . Even s o , geolo-

g i s t s w e r e n o t always i n accord as t o t h e i n t e r p r e t a t i o n of t h e d a t a ,

153

and even in the early 1970's these differences were apparent.

example, with reference to the Recluse Field in Wyoming, where production

is obtained from the Recluse Sandstone at the base of the Lower Creta-

ceous Muddy Formation, Woncik (1972) interpreted the producing sandstone

as a marine shoreline sand that may have formed a barrier island, whereas

Forgotson and Stark (1972) interpreted the sandstone body as a channel-

fill sand.

For

Interpretations of the genesis and geomorphology of a sand-

stone body can be critical in cases where further exploration and

acquisition of petroleum leases depends upon, or is influenced by the

possible or probably trends of a prospective sandstone body.

Eighteen examples of oil and gas accumulations in barrier

bars and other offshore bars are given in the following pages. With the

exception of one example in Brazil, they are all in North America. They

range in age from Devonian to Tertiary, but do not include examples from

the Triassic or Jurassic. More than half are from the Cretaceous. A s

with the examples given of oil and gas accumulations in river distributary

and other channel-fill sand bodies, the number o f examples of accumulations

in bars is too small for their age and geographic distributions to be

significant. The distributions given relate in large measure to be

gecgaphic density of drilling.

accumulations in Eocene to Miocene bsrs trending parallel to the coast

in the Gulf Coast region of the U.S.A. and Mexico, and it does appear that

in North America the majority of examples are Cretaceous to Tertiary.

Many more cases could be cited of

Shira Streak Oil Field, Pennsylvania

The Shira Streak Oil Field (Fig. 3-10) of Pennnsylvania

produces from the Shira Sandstone in the upper part of the Third Sandstone

interval of the Upper Devonian Venango Group. The Shira, which is over-

lain and underlain by dark grey shales, is quartzose, meduim to coarse

154

2 O I

M I L E S

GEOMETRY OF SHlRA SANDSTONE,

P E N N S Y LVA N I A

Fig. 3-10. Isopach map of Shira Sandstone in the Upper Devonian Venango

Group, Shira Streak Oil Field, Pennsylvania. Contours in

feet (1 ' = 0.305 m). (Redrawn from Sherrill, Dickey, and

Matteson, 1941) .

grained, with local lenses of grit containing pebbles of quartz up to an

inch in diameter. Ranging up to 5m in thickness, the sandstone forms a

thin lenticular body more than 2Okm in length and up to 5km in width.

Sherrill, Dickey, and Matteson (1941) state that at the time

of deposition of the Shira Sandstone a continental environment was

situated to the southeast, and a marine environment to the northwest.

They suggest that the sandstone was possibly formed as an offshore bar.

If s o , it must have been in very shallow water, possibly in part exposed

155

as a beach subject to scouring and winnowing action by waves and currents

The coarseness of the sand, and the presence of pebbles, suggests that

if it had been an offshore bar, it would also have been near shore.

The Shira Streak Field, which yields oil having a gravity of

45' A.P.I., is essentially a stratigraphic trap. Other accumulations

within the Shira, yielding mainly gas, are located further up-dip where

a low, southeast-plunging fold crosses the trend of the sandstone body.

The Third Sandstone interval (Fig. 3-11) comprises two main

sandstone bodies, the upper one being the Shira. Several oil and gas

accumulations are known within the Third Sandstone. Initially, some

wells flowed oil at rates up to 3,000 barrels a day from the more

permeable zones within the pebbly, coarse sandstone zones, and early

production from many well approached 100 barrels a day.

gas at rates of 3-4 million cubic feet a day are also recorded. Most of

these accumulations have long since ceased to be of any economic signif-

icance. Sherrill, Dickey, and Matteson (1941, p. 509) state, "The

productive sands of this district lie at shallow depths - generally less than 1,000 feet. The pools discussed were discovered during the period

extending from 1859 to about 1900. They were found through random

drilling, prospecting near oil seeps, or through following trends. Many

of them have been partly or entirely abandoned one or more times and then

reclaimed through drilling between old locations, de-watering, air or gas

drive, or other methods".

Flows of wet

Austin Gas Field, Michigan

The Austin Field, Michigan (Fig. 3-12), produces gas from

the Michigan Stray Sand of the Mississippian Michigan Formation. The

Michigan Stray rests unconformably on the eroded surface of older

Mississippian rocks and occurs intermittently, as discrete sandstone

bodies, over a distance of 50-65 km. Ball, Weaver, and Crider (1941)

156

O d

0 KM 5 u

M I L E S

GEOMETRY OF THIRD SANDSTONE,

PE N N S Y L V A N I A

Fig . 3-11. Isopach map of Thi rd Sandstone i n t e r v a l , Upper Devonian

Venango Group, Pennsylvania. Contour i n t e r v a l i n f e e t

(1' = 0.305 m). (Redrawn from S h e r r i l l , Dickey, and

I l a t t e son , 1941).

i n t e r p e t t h e s e sands tone bodies a s o f f s h o r e b a r s , and show them t o be

b u i l t up on e r o s i o n a l r i d g e s t h a t more-or-less o v e r l i e and follow

a pre-Miss i ss ippian a n t i c l i n a l t r end . They show f u r t h e r a remarkable

co inc idence between t h e s t r u c t u r a l c o n f i g u r a t i o n and t h e t h i c k n e s s

of t h e sands tone body i n t h e Aus t in F i e l d , t h e body be ing t h i c k e s t

where i t i s h i g h e s t . In view of t h e f a c t t h a t no datum i s i n d i c a t e d on

157

L- M I L E A

GEOMETRY OF MICHIGAN STRAY SAND, AUSTIN

FIELD, MICHIGAN

Fig . 3-12. Isopach map of t h e Michigan S t r ay Sand i n t h e Miss i s s ipp ian

Michigan Formation, Aus t in Gas F i e l d , Michigan. Contour

i n t e r v a l i n f e e t (1 ' - 0.305 m). (Redrawn from Bal l , Weaver,

and C r i d e r , 1941).

t he s t r u c t u r e contour map, t h e i r i n t e r p r e t a t i o n of t h e o r i g i n a l shape

of t h e sand body i s s u s p e c t . These d i s c r e t e sand bodies were depos i t ed

on an unconformity, and o v e r l a i n by do lomi t i c and gyps i f e rous muds t h a t

probably i n d i c a t e l i t t o r a l and e v a p o r i t i c c o n d i t i o n s f l u c t u a t i n g from

very sha l low water t o c o a s t a l mud f l a t s .

t hese sand bod ies may have accumulated i n e r o s i o n a l dep res s ions , r a t h e r

than as sand b a r s buil-up from t h e s e a f l o o r . Such an a l t e r n a t i v e i n t e r -

p r e t a t i o n can be d e r i v e d , u s ing t h e same sub-sur face d a t a , a s d i scussed

i n an ear l ier s e c t i o n on compaction of sands tone bod ies (F igs . 1-12, 1-13),

Deposited by a t r a n s g r e s s i v e s e a ,

The sands tone body comprising t h e Aus t in F i e l d i s approxi-

mately 8 km i n l e n g t h and up t o 2 km i n wid th . The sands tone has a

maximum th i ckness of 10-12 m and is s a i d by B a l l , Weaver, and Cr ide r

158

(1941) to be more permeable where it is thicker.

one of several gas fields within the Michigan Stray Sand which originally

contained an estimated 150,000 million cubic feet (4,203 million cubic

metres) of gas.

The Austin Field is

Sallyards Trend Oil Fields, Kansas

In Butler and Greenwood Counties, Kansas, a number of oil fields

form a northeast-trending chain known as the Sallyards Trend (Fig. 3-13).

A shorter chain of oil fields, the Teeter Trend, lies nearly parallel to

the Sallyards along the border between Chase and Greenwood Counties.

Three other trends, from south to north respectively, known as the Haver-

Fig. 3-13. Geographical distribution of oil fields in shoestring sand-

stone trends within the lower part of the Pennsylvanian

Cherokee Formation, Kansas. Small squares are townships of

36 square miles (92 sq. km). (After Hilpman, 1958).

159

h i l l , Quincy, and Lamont Trends, c u t more-or-less a t r i g h t ang le , and a t

d i f f e r e n t ho r i zons , a c r o s s t h e S a l l y a r d s Trend. A l l of t h e o i l f i e l d s

a long t h e s e t r e n d s are i n s h o e s t r i n g sands tone bod ies w i t h i n t h e lower

p a r t o f t h e Lower t o Middle Pennsylvanian Cherokee Formation.

These sands tone bod ies form e l o n g a t e l e n s e s 15-30 m t h i c k , up t o

10 km long , and commonly more than 2 km wide. Arranged i n a l i n e a r

p a t t e r n l i k e a s t r i n g of beads , they form t r e n d s up t o 100 km long , and

a r e i n t e r p r e t e d by Bass (1936) and Hilpman (1958) as o f f s h o r e b a r s . The

sands tone bod ies a r e comple te ly surrounded by s h a l e c o n t a i n i n g a f a i r l y

h igh o r g a n i c con ten t . In t h e upper p a r t of t h e Cherokee Formation t h i s

o rgan ic - r i ch s h a l e c o n t a i n s c o a l beds and o i l -bea r ing s h o e s t r i n g sand-

s t o n e bod ies , i nc lud ing t h e Bush C i t y O i l F i e l d (Fig. 1-33), which are

i n t e r p r e t e d as d i $ t r i b u t a r y c h a n n e l - f i l l sands .

The sands tones i n t h e S a l l y a r d s and a s s o c i a t e d t r e n d s are

q u a r t z o s e , poor ly cemented, and f ine -g ra ined . They have f a i r t o good

pe rmeab i l i t y . Cumulative p roduc t ion t o 1970 amounted t o 250 m i l l i o n

b a r r e l s (39.8 m i l l i o n cub ic me t re s ) .

Wakita Trend, Oklahoma

The Wakita Trend of t h e Anadarko Bas in , Oklahoma h a s s e v e r a l

s e p a r a t e o i l and gas accumula t ions i n t h e Pennsylvanian Red Fork Sandstone

(F ig . 3-14).

forming an a r c u a t e t r e n d , i n t e r p r e t e d as a seuqence of p a r a l l e l o f f s h o r e

b a r s , i n t e r s e c t e d by two main s inuous t r e n d s i n t e r p r e t e d as younger

d i s t r i b u t a r y c h a n n e l - f i l l sands . The Wakita Trend, which has a l eng th

of more than 50 km, and a width of 2-3 km, w a s formed dur ing a l a t e

phase of t h e o f f s h o r e b a r depos i t i on . The t r e n d , c o n s i s t i n g o f t h r e e

b a r s t h a t are wider a t t h e base than a t t h e t o p , is te rmina ted f a i r l y

a b r u p t l y on bo th s i d e s by t h i n n i n g o f t h e sands tone bod ies and i n t e r -

The Red Fork comprises a complex o f s ands tone bod ies

160

ISOPACH OF WAKITA TREND,

RED FORK SANDSTONE,

O K L A H O M A .

Fig. 3-14. Isopach of the Wakita trend, Pennsylvanian Red Fork Sandstone,

Grant and Alfalfa Counties, Oklahoma, showing east-west

trending composite offshore bars. (Redrawn from Withrow, 1968).

fingering with shale. The sandstone bodies comprising the Wakita Trend

have a maximum composite thickness of 15 m and consist of fine to very

fine-grained quartzose sandstone that is generally micaceous and locally

argillaceous.

and permeability which average 15% and 2 millidarcys respectively.

Cementation by calcite and silica has reduced porosity

161

During the first decade of production, since discovery of the

Wakita Trend in 1953, not much more than 500,000 barrels of oil were

produced, mainly from the western half of the trend. Gas is also

produced, mainly from the eastern half of the trend. Producible reserves

have been estimated to be in excess of 65,000 million cubic feet (1,800

million cubic metres). Withrow (1968) points out that although the Wakita

Trend has yielded the poorest reservoirs, other Red Fork reservoirs in

the Anadarko Basin are much more profitable; and that additional

accumulations may be found on the basis of interpretations of the dep-

ositional environments and trends of the Red Fork Sandstone.

Olympic Oil Field, Oklahoma_

Production in the Olympic Oil Field, Oklahoma, is obtained from

the Pennsylvanian Olympic Sandstone (Fig. 3-15) which is developed as a

linear trend more than 10 km in length and up to 2 km in width. The

Olympic is a composite unit, up to 20 m thick, comprising two or more

overlapping sandstone bodies that are interpreted as marine ‘offshore

bars. The sandstone is quartzose, well-sorted and fine-grained. Thin

layers of sandy shale, and carbonaceous fragments are locally present.

Average porosity and permeability are 20% and 35 millidarcys respectively.

The Olympic dips to the northwest and is locally folded into

gentle noses.

some structural control. Production of greenish-black, 3 4 O A.P.I. oil

is obtained from a shallow depth of about 550 m. Recovery to date has

amounted to more than 12 million barrels (19 million cubic metres).

Entrapment of oil is essentially stratigraphic, but with

Mata-Catu Trend, Brazil

In the Salvador area of the Reconcavo Basin, Brazil (Fig. 3-16),

oil is produced from several reservoirs in the “A” Sandstone of the Lower

Cretaceous Itaparica Formation. This sandstone unit forms two narrow

162

1 J

GEOMETRY OF PRODUCING SANDSTONE,

OLYMPIC OIL FIELD, OKLAHOMA

Fig . 3-15. I sopach map of t h e Pennsylvanian Olympic Sandstone, Olympic

O i l F i e l d , Okfuskee County, Oklahoma. (Redrawn from D i l l a r d ,

1 9 4 1 ) .

p a r a l l e l t r ends and a b raode r , less wel l -def ined t r e n d s u b - p a r a l l e l t o

t h e o t h e r two. The longes t t r e n d , t h e Mata-Catu, has a l e n g t h of 40 km

and a wid th of 3-5 km. The sands tone bod ies comprising t h i s t r end have

a maximum composite t h i c k n e s s of 45 m.

The "A" u n i t is a wh i t e t o l i g h t g rey , predominantly qua r t zose ,

ve ry f i n e t o ve ry coarse-gra ined sands tone t h a t l o c a l l y c o n t a i n s g r i t - s i z e

g r a i n s and s m a l l pebbles . Other c o n s t i t u e n t s i nc lude g r a i n s of b l ack

163

\ \

0 20

KILOMETERS -

OIL FIELDS IN CRETACEOUS

'?I" SANDSTONE, BRAZIL

Fig. 3-16. D i s t r i b u t i o n of o i l f i e l d s i n l i n e a r t r ends of t h e Lower

Cre taceous "A" Sandstone, Sa lvador area, B r a z i l . Arrow

i n d i c a t e s i n f e r r e d d i r e c t i o n of sand t r a n s p o r t . (Redrawn

from Bauer, 1967).

c h e r t , f e l d s p a r , f l a k e s of mica, and heavy mine ra l s . The sands tone m a t r i x

c o n s i s t s of c l a y mine ra l s and carbonaceous ma t t e r . Grain g r a d a t i o n , where

i t has been no ted , is from f i n e r below t o c o a r s e r above, a common

r e l a t i o n s h i p i n prograding sand b a r s . This sands tone u n i t i s commonly

thick-bedded and mass ive , w i th s i l t y and carbonaceous l amina t ions . Minor

f e a t u r e s i n c l u d e low-angle cross-bedding, w i th scour and slump s t r u c t u r e s .

The sands tone bod ies comprising t h i s u n i t , which o v e r l i e s s h a l e s con ta in ing

f resh-water o s t r a c o d s , a r e cons idered by Bauer (1967) t o b e bar-shaped

l e n s e s of sand depos i t ed by c u r r e n t s and shaped by wave a c t i o n . He was

164

of t h e o p i n i o n t h a t t h e s e sand l e n s e s formed on s h e l v e s a n d s h o a l s i n sha l low

w a t e r , b u t a t some d i s t a n c e from s h o r e , i n a l a c u s t r i n e envi ronment .

The o i l r e s e r v o i r s have good p o r o s i t y , i n t h e ' range 12-20%, and

e x c e l l e n t p e r m e a b i l i t y , commonly 200-1,300 m i l l i d a r c y s b u t r a n g i n g up t o

4,000 m i l l i d a r c y s i n some medium-grained and w e l l s o r t e d s a n d s t o n e s . O i l ,

h a v i n g a g r a v i t y of 40°A.P.I., h a s accumula ted i n s t r u c t u r a l l y h i g h p a r t s

( a c c e n t u a t e d by compaction) of t h e s a n d s t o n e b o d i e s where t h e y o v e r l i e

u p - t h r u s t b l o c k s o f basement r o c k s . It is t h o u g h t by Bauer (1967) t h a t

basement s t r u c t u r e is r e f l e c t e d i n t h e p a l e o t o p o g r a p h y , and t h a t t h e sand

b a r s were developed on t h e h i g h e r areas. On t h e b a s i s of t h i s i n t e r p r e t -

a t i o n , h e s u g g e s t s t h a t t h e s e a r c h f o r new f i e l d s w i l l b e a s s i s t e d by a n

u n d e r s t a n d i n g o f t h e p a l e o s t r u c t u r a l and r e l a t e d paleogeomorphic f e a t u r e s

w i t h i n t h e Reconcavo Bas in .

B e l l Creek O i l F i e l d , Montana

The g e o g r a p h i c and paleogeomorphic r e l a t i o n s h i p of t h e B e l l Creek

and R e c l u s e o i l f i e l d s , Powder R i v e r B a s i n , Montana and Wyoming, are

shown i n F i g . 3-17, a f t e r t h e i n t e r p r e t a t i o n o f Forgotson and S t a r k (1972). ,

T h i s i n t e r p r e t a t i o n d i f f e r s from t h a t of Woncik (1972) who c o n s i d e r e d t h e

p r o d u c i n g s a n d s t o n e of t h e R e c l u s e O i l F i e l d (F ig . 1-46) t o b e a mar ine

s h o r e l i n e s a n d , p o s s i b l y a b a r r i e r i s l a n d . The producing zone i n b o t h

f i e l d s is t h e Lower C r e t a c e o u s Muddy Sands tone . The i n t e r p r e t a t i o n p l a c e d

on t h e i r paleogeomorphic r e l a t i o n s h i p , by Forgotson and S t a r k , i s t h a t t h e

o i l - b e a r i n g s a n d s t o n e body i n t h e B e l l ' C r e e k f i e l d (F ig . 3-18) i s a b a r r i e r

b a r complex. T h i s complex is l o c a t e d n e a r t h e i n t e r s e c t i o n of n o r t h e a s t -

- t r e n d i n g l i t t o r a l mar ine b a r s and a s o u t h e a s t - t r e n d i n g d e l t a sys tem.

The s a n d s t o n e body i n t h e R e c l u s e f i e l d i s i n t e r p r e t e d a s p a r t of a

d i s t r i b u t a r y c h a n n e l - f i l l sand w i t h i n t h e d e l t a sys tem.

The Muddy Sands tone i n t h e B e l l Creek O i l F i e l d i s a composi te

165

IN MILES ,

Fig. 3-17. Residual isopach values i n f e e t (1' = 305 m) of t h e Lower

Cretaceous Muddy Sandstone, Powder River Basin, Montana and

Wyoming.

polynomial va lues of r eg iona l s u r f a c e , shown by t h i n

con tour s , from isopach va lues . (After Forgotson and S ta rk ,

1972).

Residual va lues obtained by removal of 3d-degree

bar complex formed by merging, l i n e a r sandstone l e n s e s , t h e Muddy has a

cumulative maximum th i ckness of 10 m , and an average thickness of 6 m.

Four u n i t s have been descr ibed: (a) an upper, massive u n i t of f ine-grained

sandstone, (b) an underlying, s l i g h t l y coa r se r and s t rong ly laminated

sandstone, showing small-scale c ros s bedding, (c) a massive, very f ine -

-gpained, s l i g h t l y laminated sandstone with minor b io tu rba t ion , and (d)

a t h i n b a s a l u n i t of i n t e r l amina ted s h a l e and s i l t s t o n e with ex tens ive

166

MUDDY SANDSTONE, BELL CREEK FIELD, MONTANA.

Fig. 3-18. Isopach showing gross thickness in feet (1' = 0.305 m) of

Lower Cretaceous Muddy Sandstone, Bell Creek Field, Montana.

Lines of sections a-a' and b-b' are approximate. Sections

show lenticularity of oil-producing sandstone bodies.

(Redrawn from McGregor and Biggs, 1968, and Berg and Davis,

1968).

bioturbation. The sandstone is quartzose (ave. 86% quartz), well sorted,

and fine to very-fine-grained. The average grain size increases with

increasing quartz content. Porosity and permeability are exceptionally

good, ranging up to 30% and 3,500 millidarcys respectively.

167

5 0;03m.m

.I

A

4 670'

4 680'

BELL CREEK FIELD, MONTANA.

0

l m

C

0 '

lo'

2 0'

30'

,\

_1

B

GALVESTON ISLAND, TEXAS

Fig. 3-19. A - core from t h e o i l -producing Lower Cre taceous Wuddy

Sandstone i n Well No. 6-14, B e l l Creek F i e l d , Montana.

B - c o r e No. R 3963 from Recent sediments on Galves ton

I s l a n d , Texas, a t y p i c a l b a r r i e r i s l a n d . (Redrawn from

Davies , E t h r i d g e , and Berg, 1971).

Davies , E th r idge , and Berg (1971) made a comparison of t e x t u r e s

and s t r u c t u r e s i n co res (Fig. 3-19) from t h e Muddy Sandstone i n t h e B e l l

Creek O i l F i e l d and from Galveston I s l a n d , Texas, a t y p i c a l b a r r i e r i s l a n d .

The l e n g t h s of t h e Muddy and Galveston co res are approximate ly 6 m and 9 m

168

r e s p e c t i v e l y . The Galves ton I s l a n d co re shows an uppermost u n i t of e o l i a n

sand , w i th o c c a s i o n a l p l a n t r o o t s , ove r ly ing a u n i t of sand c o n t a i n i n g

i n t e r v a l s showing low-angle cross-bedding o f t h e type found w i t h i n beach

d e p o s i t s . Th i s t ype of cross-bedding r e f l e c t s v a r i a t i o n s i n d e p o s i t i o n a l

s l o p e s of t h e beach. The cross-bedded u n i t o v e r l i e s a homogeneous t o

f a i n t l y lamina ted u n i t o f sand depos i t ed as t h e seaward ex tens ion of an

i n t e r t i d a l beach. The lowermost u n i t i s of e x t e n s i v e l y b i o t u r b a t e d c layey

s i l t in t e rbedded wi th ve ry f ine -g ra ined sand . Gra in s i z e dec reases from

a f i n e sand i n t h e uppermost u n i t t o a very f i n e sand i n t h e lowermost

u n i t . This g r a d a t i o n i s t y p i c a l of b a r r i e r i s l a n d and o t h e r o f f - l app ing

s h o r e l i n e sand d e p o s i t s .

The B e l l Creek F i e l d co re shows t h e same sequence i n l i t h o l o g y ,

The uppermost u n i t i s o f ve ry f ine -g ra ined wi th minor v a r i a t i o n s .

homogeneous sand c o n t a i n i n g t r a c e s o f p l a n t r o o t s t r u c t u r e s . The i n t e r -

t i d a l beach u n i t con ta ins some organism burrows; and t h e o u t e r beach

s u r f a c e u n i t c o n t a i n s some rounded i n c l u s i o n of c l a y s t o n e , poss ib ly formed

from mudcrack fragments washed t o sea from a beach. The lowermost u n i t

c o n s i s t s e n t i r e l y of e x t e n s i v e l y b i o t u r b a t e d c l ays tone and s i l t s t o n e

laminae showing some very f i n e c ross - lamina t ions . Grain s i z e is w i t h i n

t h e f i n e sand r ange , 0 .25 - 0.12 nun, w i t h t h e excep t ion of t h e lowermost

u n i t which i s o f s i l t , 0.06 - 0.03 mm.

The B e l l Creek F i e l d was d i scove red i n 1967. It i s a s t r a t i g r a p h i c

t r a p i n which t h e f o u r s e p a r a t e accumula t ions of o i l have d i f f e r e n t o i l -

-water c o n t a c t s . The o i l , pumped from a depth o f about 1,400 m , i s su lphur-

- f r e e and has a g r a v i t y of 34O A.P.I.

t h e f i e l d y i e lded 65,000 b a r r e l s a day from w e l l s having an average d a i l y

p roduc t ion of 500 b a r r e l s . Cumulative p roduc t ion t o 1973 amounted t o 45

m i l l i o n b a r r e l s (7 .2 m i l l i o n cub ic me t re s ) . It is es t ima ted (McGregor

and Biggs, 1968) t h a t t h e r e s e r v e s o f p roduc ib le o i l amount t o 200 m i l l i o n

b a r r e l s (31.8 m i l l i o n cub ic me t re s ) .

During t h e pe r iod of peak product ion

169

Gas D r a w O i l F i e l d , Wyoming

The G a s D r a w O i l F i e l d (Fig. 3-20) i n t h e Powder River Bas in , Wyoming,

produces o i l from t h e 'Gas D r a w Sandstone i n t h e Lower Cre taceous Muddy

Formation. The Gas D r a w o v e r l i e s t h e o i l -producing sands tone i n t h e

B e l l Creek F i e l d (50 km n o r t h e a s t ) , and forms a composite l i n e a r sands tone

body more than 40 km long , 2-3 km wide, and up t o 10 m t h i c k . The main

o i l accumulation o f t h e f i e l d ex tends a long t h e c e n t r a l p a r t of t h i s

trer.d f o r a d i s t a n c e o f 20 km.

The Gas D r a w , c o n s i s t i n g of very f i n e t o f ine -g ra ined qua r t zose

sands tone , i s thought by Stone (1972) t o have o r i g i n a t e d a s a sequence of

o f f s h o r e b a r s and beaches a long t h e same s h o r e l i n e t r e n d as t h e B e l l

Creek Sandstone i n t h e upper p a r t of t h e Muddy Formation. I n t h i s

con tex t i t i s i n t e r e s t i n g t o n o t e t h e funnel-shaped c h a r a c t e r of t h e

E-log of b o t h t h e G a s D r a w and B e l l Creek sands tones (Fig. 3-21). A s i n

t h e B e l l Creek F i e l d , t h e producing sands tone of t h e Gas Draw F i e l d has

e x c e l l e n t r e s e r v o i r c h a r a c t e r i s t i c s i nc lud ing good p o r o s i t y and pe rmeab i l i t y .

The B e l l Creek, U t e , and K i t t y f i e l d s a l s o o b t a i n p a r t of t h e i r p roduct ion

from t h e Gas D r a w Sandstone.

Garr ington and C r o s s f i e l d O i l F i e l d s , A lbe r t a

The Garr ington and C r o s s f i e l d f i e l d s i n Albe r t a (Fig. 3-22) produce

o i l from t h e Upper Cre taceous Cardium Sands tsne . In t h i s area t h e Cardium

i s de f ined by two p a r a l l e l , ribbon-shaped sands tone t r e n d s about 15 km

a p a r t . The younger t r e n d , l y i n g f a r t h e r t o t h e n o r t h e a s t , i s t h e producing

sands tone of t h e Garr ington F i e l d .

d i r e c t i o n f o r more than 100 km. The C r o s s f i e l d t r e n d ex tends f o r more than

115 km. Both of t h e s e sands tone t r e n d s a r e 2-5 km wide and range i n

th i ckness up t o 6 m. They w e r e formed as o f f s h o r e b a r s , p o s s i b l y as

b a r r i e r b a r s , du r ing a pe r iod of marine r e g r e s s i o n i n t h e e a r l y L a t e

It has been t r a c e d i n a nor thwes t

+--

TYPE LOG

-.- '5 + GAS DRAW SANDSTONE

h d 1 7200' MUDDY

51

T

N 5 0

SANDSTONE ISOLIT GAS DRAW ZONE

C.I. 10'

-7 -60' TOTAL MUDDY

a MUDDY SANDSTONES UNDIFFERENTIATED UPPER

y @ ! I i ' l l l lr! . i __ .I__ A

? s p ) E T T E

Fig. 3-20. I s o l i t h of the Lower Cretaceous Gas Draw Sandstone showing a

l i n e a r p a t t e r n where the thickness ranges i n excess of 30

f e e t (9 m ) . Contour i n t e r v a l i s 10 f e e t (3 m). (After Stone,

1972).

'H

171

TYPE MUDDY LOG

I 1

S P R I N G E N R C H .

U P P E R R E C L U S E

O A K O T A S I L T

O A K O T A

7400'

Fig. 3-21. Type E-log from t h e G a s D r a w o i l f i e l d , Powder River Basin,

Wyoming. (Af t e r S tone , 1972).

Cretaceous. Subsequent ly , t hey were b u r i e d by da rk s i l t s and muds of

t h e Colorado Group when t h e s e a aga in t r ansg res sed westward.

The Cardium Sandstone i s l i t h i c , be ing composed o f g r a i n s of

c h e r t , q u a r t z , q u a r t z i t e , s i l i c i f i e d a r g i l l i t e , and o t h e r rock fragments.

In g e n e r a l , t h e sands tone is f ine -g ra ined , t h e g r a i n s be ing angu la r t o

sub-rounded.

g r i t t y t o pebbly , t h e l a r g e r g r a i n s and pebbles be ing w e l l rounded and

c o n s i s t i n g of l i g h t grey and b l ack c h e r t y rock . The cement i n t h e ma t r ix

i s l a r g e l y s i d e r i t e , i l l i t e and c h l o r i t e . Diagenes is and compaction have

r educed .po ros i ty and pe rmeab i l i t y which have mean va lues of approximate ly

10% and 35 m i l l i d a r c i e s r e s p e c t i v e l y .

In t h e upper p a r t of t h e s e c t i o n t h e sands tone i s l o c a l l y

172

ISOPACH MAP CARDIUM BARRIER

N w

CAL(

1 OJO KM

0- 10 MILES

Fig . 3-22. I sopach map of b a r r i e r b a r s of t h e Upper Cre taceous

Cardium Formation, Garr ington (A) and C r o s s f i e l d (B)

o i l f i e l d s , A lbe r t a . Isopach i n t e r v a l is 10 f e e t ( 3 m).

(Redrawn from Berven, 1966).

The o i l accumula t ions a r e i n pu re ly s t r a t i g r a p h i c t r a p s c o n t r o l l e d

by t h e up-dip l i m i t e s of pinch-out edges on t h e f l a n k s of t h e sands tone

b o d i e s , and by t h e d i s t r i b u t i o n of zones of v a r i a b l e p o r o s i t y and per-

m e a b i l i t y a long t h e t r e n d s . Regional d i p of t h e s t r a t a i s about 10 m/km

t o t h e west-southwest. The n e t producing sands tone i n bo th f i e l d s has a

range of on ly 1-2 m , and f r a c t u r i n g of t h e o i l -bea r ing zone is necessary .

The i n i t i a l r e s e r v o i r d r i v e was by s o l u t i o n g a s , bu t secondary recovery

methods invo lve t h e use of wa te r f lood ing .

In t h e Garr ington F i e l d t h e r e are two producing sands tone u n i t s ,

each having an average th i ckness of about 3m. The upper sands tone body

173

is ribbon-shaped and has s i m i l a r dimensions t o t h e sands tone body i n t h e

C r o s s f i e l d F i e l d . The lower body has t h e same t r e n d , bu t i s much more

i r r e g u l a r i n shape , ranging i n wid th up t o 10 km. Most w e l l s produce

from e i t h e r one sands tone o r t h e o t h e r , b u t some produce from both where

the u n i t s ove r l ap . The pa ra f f in -base o i l has a g r a v i t y of 370 A . P . I . and

i s su lphur - f r ee , O r i g i n a l o i l i n p l a c e i n both sands tone bod ies amounted

to 190 m i l l i o n b a r r e l s (20.2 m i l l i o n cub ic m e t r e s ) , of which i t i s

es t ima ted ( T y r e l l , 1966) t h a t 40 m i l l i o n (6 .4 m i l l i o n cubic metres) can

u l t i m a t e l y b e recovered . J a v e r i (1966) estimates t h a t t h e C r o s s f i e l d

had an o r i g i n a l o i l con ten t of 160 m i l l i o n b a r r e l s ( 2 5 . 4 m i l l i o n cubic

met res ) of which 16 m i l l i o n ( 2 . 5 m i l l i o n cub ic met res ) may be recovered ,

The d a i l y p roduc t ion rate pe r w e l l i s t h e range 20-40 b a r r e l s .

Fig. 3-23. Facies map of B i s t i o i l f i e l d , San Juan Bas in , New

Mexico, showing b a r r i e r b a r complex comprising t h e Marye,

Carson, and Huerfano o i l -bea r ing sand b a r s of t h e Upper

Cretaceous Gal lup Formation. (Af t e r Sab ins , 1963).

174

t 1

T26, I t-

ISOPACH MAP OF

L__I

o c , Feet 1

I ' &Om

E-LOG CHARACTERISTICS OF BlSTl FIELD SANDS

Pig . 3-24. Isopach map of a producing b a r r i e r b a r , B i s t i o i l f i e l d ,

San Juan Bas in , New Mexico. Contour i n v e r v a l i n f e e t (1' =

0.305 m).

shape c h a r a c t e r i s t i c of b a r r i e r - b a r sands .

Sab ins , 1963).

The spon taneous -po ten t i a l curves show a funnel -

(Redrawn from

B i s t i O i l F i e l d , New Mexico

The B i s t i O i l F i e l d i n New Mexico (F igs . 3-23 and 3-24 ) has

been desc r ibed by Sabins (1963) who s t a t e s t h a t p roduct ion is ob ta ined

from t h r e e ove r l app ing sands tone bod ies des igna ted t h e Marye, Carson, and

Huerfano members of t h e Upper Cre taceous Gal lup Formation. These l i n e a r

sands tone bod ies a r e i n t e r p r e t e d by Sabins as sand b a r s t h a t formed a

b a r r i e r - b a r complex. H e recognized t h a t t h e l i n e a r i t y of t h e s e sands tone

bod ies co inc ides w i t h t h e topography o f t h e upper s u r f a c e of t h e under-

l y i n g Gallup Sandstone, b u t t h a t t h e bod ies are n o t n e c e s s a r i l y b e t t e r

developed i n t h e topographic dep res s ions , some t h i c k e r p a r t s of t h e

175

bodies ove r ly ing escarpments . Sabins states, p. 224, "In summary, t h e

d e p o s i t i o n a l topography of t h e upper s u r f a c e of t h e Main Gal lup Sand

resembles longshore b a r and t rough topography wi th some seaward-facing

d e p o s i t i o n a l escarpments . Th i s topography w a s formed dur ing t h e f i n a l

d e p o s i t i o n of Main Gallup Sand and w a s t h e s u r f a c e upon which t h e B i s t i

ba r complex was depos i ted" . Sabins i n t e r p r e t s t h e Main Gal lup Sandstone

under ly ing t h e Marye, Carson, and t h e Huerfano sands tone bod ies as a re-

g r e s s i v e marine shee t -sand on t h e s u r f a c e of which sand b a r s and a s s o c i a t e d

f a c i e s (F ig . 3-23) were developed.

McCubbin (1969) on t h e o t h e r hand, i n t e r p r e t s t h e upper s u r f a c e of

t h e Main Gal lup Sandstone a s an e r o s i o n a l s u r f a c e on which l i n e a r sands tone

bod ies w e r e depos i t ed i n marine s t r j k e v a l l e y s f l a n k i n g c u e s t a s du r ing

t h e t r a n s g r e s s i o n of t h e Niobrara sea.

s p e c i f i c a l l y d e a l w i th t h e B i s t i F i e l d , b u t w i th t h e nearby Horseshoe,

Many Rocks, Mesa, South Waterflow, Cha Cha, and Totah f i e l d s which are

producing from t h e same s t r a t i g r a p h i c ho r i zon . McCubbin s ta tes , p. 2116,

"Most p rev ious s t u d i e s of t h e s e o i l f i e l d s l e d t o t h e i n t e r p r e t a t i o n t h a t

t h e r e s e r v o i r sands tone bod ies were depos i t ed as "o f f shore ba r s " o r

"marine ba r s " contemporaneously wi th t h e beach and nearshore-marine

sands tones of t h e Gal lup , and t h a t t h e i r l o c a t i o n and t r e n d are r e l a t e d

t o t h e maximum e x t e n t of t h e Gal lup r e g r e s s i o n @bight and Budd, 1959;

Sab ins , 1963; Tomkins, 1957). P e n t t i l a (1964) recognized t h a t t h e

sands tone beds i n t h e nor thwes tern p a r t of t h e b a s i n o v e r l i e an uncon-

fo rmi ty which s e p a r a t e s them from t h e o l d e r Gallup Sandstone, and t h a t

t h e d i s t r i b u t i o n of t h e sands tone bod ies i s r e l a t e d t o e r o s i o n a l l o w s

on t h e unconformity".

t o t h e B i s t i F i e l d , t hen t h e Marye, Carson, and Huerfano sands tone bodies

a r e b a s a l members of t h e Upper Cre taceous Niobrara Formation, and as

s t r i k e - v a l l e y sands f l a n k i n g c u e s t a s should be a s s igned t o Chapter 5 on

McCubbin's s t u d y d i d n o t

I f McCubbin's i n t e r p r e t a t i o n can b e a p p l i e d a l s o

176

t r a n s g r e s s i v e marine s h o r e l i n e sand bod ies . They are p laced i n t h i s

c h a p t e r , because:

( a ) t h e q u e s t i o n of t h e i r o r i g i n does n o t y e t seem t o

have been s a t i s f a c t o r i l y r e s o l v e d ,

t hey were a p p a r e n t l y formed i n a nea r shore marine

environment, and

(b)

(c) t h e i r funnel-shaped E-log c h a r a c t e r (F ig . 3-24)

s u g g e s t s that they w e r e sand b a r s

The producing sands tones of t h e B i s t i f i e l d form a l i n e a r t r e n d

more than 55 km long , 3-5 km wide and up t o 20 m t h i c k . The sands tones

are qua r t zose , g l a u c o n i t i c , and c o n s i s t of f i n e t o medium, sub-rounded

g r a i n s . Gra in g r a d a t i o n is from f i n e r below t o c o a r s e r above, a

r e l a t i o n s h i p t h a t i s c h a r a c t e r i s t i c of b a r r i e r b a r s . The funnel-shaped

E-logs (Fig. 3-24) r e f l e c t t h i s g r a d a t i o n . P o r o s i t y is i n t h e range

10-20% b u t i s commonly 12-55%. Pe rmeab i l i t y i n t h e c o a r s e r sands tones

ranges up t o 400 m i l l i d a r c y s , b u t t h e average sands tones a r e w i t h i n t h e

range 50-175 m i l l i d a r c y s .

The B i s t i F i e l d i s a s t r a t i g r a p h i c t r a p , t h e r e be ing no s t r u c t u r a l

i n f l u e n c e by noses o r c l o s u r e s e i t h e r above o r below t h e producing sand-

s t o n e u n i t s i n t h e f i e l d . Well completions normally r e q u i r e f r a c t u r i n g

of t h e sands tone t o y i e l d an average product ion of more than 900 b a r r e l s

pe r w e l l pe r month.

s o l u t i o n d r i v e . I t is es t ima ted t h a t u l t i m a t e recovery from t h e f i e l d

w i l l amount t o 50 m i l l i o n b a r r e l s (8 m i l l i o n cubic me t re s ) .

The primary producing mechanism i s by means of gas

S a l t Creek - Teapot Dome O i l F i e l d , Wyoming

The S a l t Creek F i e l d (Fig. 3-25) and t h e ad jacen t Teapot Dome t o

t h e sou th are p r o l i f i c o i l f i e l d s producing mainly from t h e Second Sand-

s t o n e member of t h e Upper Cre taceous F r o n t i e r Formation. The Second

177

? ;o

O U KM 10

M I L E S

C A S P E R @

OIL FIELDS IN OFFSHORE BAR, FRONTIER

FORMATION, WYOMING

Fig. 3-25. Salt Creek oil field within a structural nose along the

trend of the Second Sandstone, an offshore bar in the Upper

Cretaceous Frontier Formation. (Redrawn from Barlow and

Haun, 1966) .

Sandstone lies about 60 m stratigraphically below the First Sandstone, at

depths of 400-900 m.

The Second Sandstone is interpreted by Barlow and H a m (1966) as

a marine offshore bar fringing a deltaic lobe that prograded eastward.

The sandstone body trends north-northwest for more than 100 km. It

178

ave rages about 15 km i n wid th , and i s up t o 30 m t h i c k .

c o i n c i d e s w i t h t h e a x i s of an undu la t ing a n t i c l i n e a long which s e p a r a t e

c l o s u r e s , such as t h e Teapot Dome, have developed. The sands tone i s

q u a r t z o s e , w e l l s o r t e d , ve ry f i n e t o medium-grained and l o c a l l y c ros s -

-bedded. It has an average p o r o s i t y of 20%. Glaucon i t e is a common

c o n s t i t u e n t , and i n p l a c e s t h e sands tone c o n t a i n s carbonaceous f ragments .

The g r a i n s , which are sub-rounded t o sub-angular , show a g r a d a t i o n i n

s i z e from f i n e r below t o c o a r s e r above. Th i s g r a d a t i o n i s r e f l e c t e d i n

t h e funnel-shaped E-log c h a r a c t e r of t h e Second Sandstone. L o c a l l y , t h e

sands tone body c o n t a i n s l e n s e s of pebb les , and w i t h i n t h e uppermost p a r t

t h e r e i s a widespread pebble bed. A s imilar pebble bed , which r e p r e s e n t s

a p e r i o d of s c o u r i n g of t h e o f f s h o r e b a r s , is p r e s e n t a t t h e t o p of t h e

o i l -p roduc ing Cardium Sandstone (F ig . 3-22) of A lbe r t a .

The t r e n d

Bech (1929) shows d i f f e r e n t o i l -wa te r c o n t a c t s w i t h i n t h e S a l t

Creek - Teapot Dome s t r u c t u r e .

r a t h e r t han t i l t i n g of t h e o i l -wa te r s u r f a c e . The s a l i n i t y range of t h e

w a t e z i n t h e Second Sandstone is 8,000-15,000 p.p.m., w e l l below the

average sea water range o f 30,000 p.p.m., which s u g g e s t s t h a t t h e r e h a s

been some d i l u t i o n of t h e connate water w i t h me teo r i c w a t e r , and t h a t

consequent ly t h e r e may be some movement of wa te r w i t h i n t h e sands tone

body. Lack of e a r l y p r e s s u r e d a t a , however, p rec ludes t h e p o s s i b i l i t y

o f making a s a t i s f a c t o r y hydrodynamic a n a l y s i s .

These a r e p o s s i b l y t h e r e s u l t of f a u l t i n g ,

Barlow and Haun (1966, p. 2195) summarize t h e f i e l d as fo l lows ,

" S a l t Creek f i e l d commonly h a s been s e l e c t e d as an o u t s t a n d i n g example of

an a n t i c l i n a l accumula t ion . It h a s been c i t e d a s an example of d i f f e r -

e n t i a l en t rapment by Gussow (1954) and as an example of f i e l d s w i t h

t i l t e d o i l -wa te r c o n t a c t s by Levorsen (1954, p. 295)*. The writers have

a t t empted t o show t h a t t h e major accumula t ion , i n t h e second F r o n t i e r

Footnote : p. 151 of t h e 2nd E d i t i o n (1967)

179

sands tone , i s w i t h i n a sand b a r t h a t w a s depos i t ed a t t h e seaward margin

of a l o b a t e concen t r a t ion of c o a r s e , t e r r i g e n o u s c l a s t i c s (a d e l t a ? ) ,

which were de r ived from a l and a r e a on t h e w e s t and nor thwes t . The b a r

w a s sub jec t ed t o s t r o n g wave and c u r r e n t a c t i o n which produced r e l a t i v e l y

high p o r o s i t y through s o r t i n g p rocesses . The b a r became a s t r a t i g r a p h i c

t r a p du r ing t h e e a r l y s t a g e s of sediment compaction and accumulated

petroleum de r ived from t h e sur rounding source beds i n t h e F r o n t i e r . During

Laramide f o l d i n g , t h e o i l migra ted t o approximate ly i t s p r e s e n t s t r u c t u r a l

p o s i t i o n . Subsequent hydrodynamic g r a d i e n t s may have modified s l i g h t l y

t h e s t r u c t u r a l p o s i t i o n of t h e o i l " .

The S a l t Creek - Teapot Dome F i e l d has y i e lded up ' to 1966, a t o t a l

of 420 m i l l i o n b a r r e l s (66.8 m i l l i o n cub ic met res ) of o i l having a g r a v i t y

range of 33O-380 A . P . I . I n i t i a l l y , p roduc t ion was p a r t l y a s s i s t e d by

gas-so lu t ion d r i v e , and the average d a i l y product ion from e a r l y w e l l s

d r i l l e d du r ing t h e pe r iod 1917-1921 was 670 b a r r e l s p e r w e l l .

Big Piney Gas F i e l d , Wyoming

The Big Piney F i e l d of t h e Green River Bas in , Wyoming, produces gas

from l e n t i c u l a r sands tone u n i t s i n t h e Paleocene Almy Formation. One of

these u n i t s , t h e "La" Sandstone member (Fig. 3-26) is a major producer .

This sands tone u n i t comprises two s e p a r a t e sands tone bod ies wi th a s l i g h t

en echelon alignment i n p l an view. Both bod ies t r e n d s n o r t h , a r e l i n e a r ,

l e n t i c u l a r , and ranges i n t h i c k n e s s up t o 40 m. They p inch ou t f a i r l y

a b r u p t l y t o t h e w e s t and become s i l t y t o t h e east . These sands tone bodies

are i n t e r p r e t e d as o f f s h o r e b a r s .

i n t e r p r e t e d a s e s t u a r i n e o r d e l t a i c i n o r i g i n .

Other a s s o c i a t e d sands tone bod ies are

The Big Piney f i e l d w a s d i scovered i n 1938. One of t h e e a r l y w e l l s

blew i n wh i l e be ing cored a t a depth of about 300 m. Gas flowed a t t h e

180

0 KM 6

M I L E S I

GEOMETRY OF "La" GAS SAND, B I G

PI N E Y FIELD, WYOMING

Fig . 3-26. Isopach map of t h e "La" Sandstone i n t h e Paleocene Almy

Formation, Big Piney Gas F i e l d , Green River Basin, Wyoming.

Contour i n t e r v a l i n f e e t (1' = 0.305 m). (Redrawn from

Krueger, 1968).

r a t e of 70 m i l l i o n cubic f e e t a day f o r 10 days be fo re being brought under

c o n t r o l .

t h i c k . Within t h e f i e l d , 20 s e p a r a t e and l e n t i c u l a r sandstone bodies

within t h e Almy Formation, of which t h e "La" member is one, con ta in gas

and minor q u a n t i t i e s of o i l .

s t r a t i g r a p h i c , t h e gas and o i l being confined by po ros i ty and permeabi l i ty

The producing sandstone a t t h i s l o c a t i o n is approximately 30 m

These hydrocarbon accumulations a r e e s s e n t i a l l y

181

b a r r i e r s on t h e f l a n k s of t h e sands tone bod ies . Within t h e producing zones

t h e p o r o s i t y is commonly 26-28% and t h e p e r m e a b i l i t y 50-200 m i l l i d a r c y s .

The gas , which i s s u l p h u r - f r e e , c o n t a i n s 89-99% methane, up t o 6%

e thane , and 3% propane. Cumulative p roduc t ion t o 1966, from Almy Formation

sands tone bod ies i n t h e P iney and a d j a c e n t L a Barge f i e l d s , amounted t o

650,000 m i l l i o n c u b i c f e e t (18,200 m i l l i o n cub ic me t re s ) .

Hardin O i l F i e l d , Texas

The Hardin O i l F i e l d , Texas, h a s n i n e producing sands tone u n i t s

w i t h i n t h e Upper Eocene Yegua Formation. One of t h e s e , i n t h e Eponides

FEET

I d

KM

L50 FEET

Fig . 3-27. I sopach and s e c t i o n C-D of t h e Davis Sands tone , Upper Eocene

Yegua Format ion , Hardin o i l f i e l d , Texas. I sopach i n t e r v a l

i n f e e t (1' = 0.305 m). (Redrawn from Casey and C a n t r e l l , 1941).

182

yeguaens i s zone o f t h e Tegua, is t h e Davis Sandstone (F ig . 3-27) which

y i e l d s g a s , d i s t i l l a t e , and o i l . The Davis is a l i n e a r and l e n t i c u l a r body

having a l e n g t h of 3 . 3 km, a wid th i n t h e range 150-350 m , and a maximum

t h i c k n e s s of 15 m. In g e n e r a l , i t forms a massive sands tone body and

shows no s t r a t i f i c a t i o n excep t i n t h e s h a l y zones , a long t h e f l a n k s of

t h e body, where i t e x h i b i t s some cross-bedding. The sands tone i s medium-

-grained and c o n s i s t s of approximate ly 98% qua r t z . The g r a i n s are

sub-angular t o angu la r . Carbonized p l a n t f ragments are common. The

sands tone body i s i n t e r p r e t e d as a marine o f f s h o r e b a r depos i t ed i n a

r e g r e s s i n g sea. The E-log c h a r a c t e r s of the Yegua sands tone u n i t s are

d i s t i n c t l y funnel-shaped, which sugges t s t h a t t h e u n i t s o r i g i n a t e d as

sand b a r s . The E-log c h a r a c t e r of t h e Davis Sandstone i s l e s s w e l l

d e f i n e d , p o s s i b l y because i t is f a i r l y uniform i n g r a i n s i z e .

The sands tone h a s e x c e l l e n t p e t r o p h y s i c a l p r o p e r t i e s , t h e average

p o r o s i t y and pe rmeab i l i t y be ing 27% and 2,200 m i l l i d a r c y s r e s p e c t i v e l y .

The presence o f b r a c k i s h water, having a s a l i n i t y of 12,000 p a r t s p e r

m i l l i o n , sugges t s some degree of d i l u t i o n of t h e connate water by

me teo r i c water. Consequently, t h e r e is a p o s s i b i l i t y t h a t a hydrodynamic

c o n d i t i o n e x i s t s i n , t h e f i e l d . The Davis Sandstone, encountered a t a

dep th of about 2,285 m below t h e s u r f a c e , y i e l d s gas , 550 A.P . I . d i s t i l l a t e ,

and 3 7 O A.P.I. o i l .

183

Chapter 4

REGRESSIVE MARINE SHORELINE SAND


Geomorphology

Regress ive marine s h o r e l i n e sand bod ies c o n s i s t of s t r a t i f o r m and

l e n t i c u l a r bod ie s of sand depos i t ed as beaches o r of f - shore sands dur ing

a pe r iod of r e g r e s s i o n of t h e sea.

a long t h e c o a s t . They commonly e x h i b i t a p a r a l l e l arrangement i n p l an

view and an en echeZon arrangement i n s e c t i o n a l view.

no t always e v i d e n t w i thou t v e r t i c a l exagge ra t ion of t h e s e c t i o n , p a r t i c u l a r l y

where i n t e r n a l s t r a t i g r a p h i c markers cannot c l e a r l y be de f ined . A sand-

s tone u n i t t h a t appears t o have a s h e e t - l i k e d i s t r i b u t i o n , and which has

been r e f e r r e d t o as a ' b l a n k e t s a n d ' , may i n f a c t comprise a sequence of

s e p a r a t e , o f f - l app ing sands tone bod ies t h a t c o n s t i t u t e a diachronous u n i t .

Other s ands tone bod ies , such as beach r i d g e s , may b e c l e a r l y sepa ra t ed by

s h a l e o r s i l t s t o n e . Inc luded i n t h e ca t egory of s h o r e l i n e sand bod ies

depos i t ed by a r e g r e s s i n g s e a are some d e l t a - f r o n t sand bodies such a s

bar - f inger s ands , and a l so some i n t e r - d e l t a i c sand bod ies such a s b a r r i e r

i s l a n d sands and o t h e r o f f s h o r e b a r s . i k l t a - f r o n t sand bod ies a r e n o t

d e a l t w i th i n t h i s chap te r because they are e s s e n t i a l l y t h e prograding

seaward ex tens ions of d e l t a d i s t r i b u t a r y sand bod ies (F igs . 2-2 and 2-4)

t h a t t r e n d , i n g e n e r a l , normal t o t h e c o a s t l i n e . Some b a r r i e r and o t h e r

o f f s h o r e b a r s could p rope r ly be inc luded i n t h i s chap te r , b u t because they

can a l s o form i n marine t r a n s g r e s s i v e s i t u a t i o n s (F ig . 3-9) they a r e

inc luded i n a separate chap te r .

These sand bod ies a r e l i n e a r and t r end

The l a t t e r view i s

Regress ive and t r a n s g r e s s i v e s i t u a t i o n s can a r i s e where t h e

184

landmass ad jacen t t o t h e sea i s f l a t and low.

n a t u r e of t h e t e r r a i n , low-re l ie f topography may be developed t o a l a r g e

e x t e n t by e r o s i o n a l p rocesses . Very f l a t c o a s t a l areas a d j o i n i n g t h e

low- re l i e f topography a r e formed e s s e n t i a l l y by prograding d e p o s i t i o n a l

p rocesses . Vast a r e a s o f c o a s t a l f l a t - l a n d s can , subsequent t o t h e i r

format ion by sed iments a c c r e t i n g t o t h e c o a s t du r ing a pe r iod of marine

r e g r e s s i o n , b e subsequent ly inundated and p a r t l y re-worked du r ing a

pe r iod of marine t r a n s g r e s s i o n .

Depending on t h e geo log ica l

P rograda t ion , and t h e consequent seaward ex tens ion of f l a t c o a s t a l

p l a i n s , can be r a p i d in s i t u a t i o n s where t h e d e l t a s of l a r g e r i v e r systems

are growing o u t on a sha l low c o n t i n e n t a l p la t form. I n t h i s s i t u a t i o n ,

beach r i d g e s , b a r r i e r b a r s , and o t h e r o f f s h o r e sand bod ies can b e seen a s

topographic f e a t u r e s , commonly a s vege ta t ion-covered , low-lying sandy

r i d g e s , f o r many k i lome te r s i n l a n d . Subsequent drowning of t h e c o a s t a l

topography, du r ing a pe r iod of marine t r a n s g r e s s i o n , may bury t h e s e

f e a t u r e s i n mud and p rese rve them i n t h e g e o l o g i c a l r eco rd . 4 l though

world-wide rises of sea l e v e l are known t o co inc ide wi th pe r iods du r ing

which t h e i c e caps w e r e me l t ing , and may also r e f l e c t major t e c t o n i c

movements, t r a n s g r e s s i o n s do n o t n e c e s s a r i l y imply an a b s o l u t e r ise of

sea l e v e l . Loca l marine t r a n s g r e s s i o n s commonly occur i n a r e a s of l a r g e

d e l t a s where p rograda t ion i s no longe r t a k i n g p l a c e because t h e r i v e r

sys tem has changed i t s course and is n o t supply ing sediment t o t h a t p a r t

of t h e c o a s t . In t h i s s i t u a t i o n t h e c o a s t l i n e ceases t o mig ra t e seaward

by t h e a c c r e t i o n of sed iment , bu t t h e d e l t a sediments benea th t h e c o a s t a l

p l a i n con t inue t o compact. A s much of t h e swampy s u r f a c e of t h e d e l t a is

less than one meter above sea l e v e l , t h e s u r f a c e s i n k s benea th t h e sea .

Drowning of t h e s e f l a t c o a s t a l p l a i n s can t a k e p l a c e over a pe r iod of a

few y e a r s , a l though t h e advance of t h e sea may n o t b e a t a cons t an t rate.

During p e r i o d s of slow advance, cond i t ions approximating a s t i l h s t a n d may

185

be reached du r ing which s h o r e l i n e bod ies of s i l t y sand may be formed by

winnowing o f t h e sed iments by waves and c u r r e n t s .

Cont inua l p rograda t ion of a d e l t a f r o n t , compaction of sedimentary

l a y e r s , l o c a l re-working o f s u r f i c i a l sed iments , and widespread d e p o s i t i o n

of muds du r ing t r a n s i t o r y pe r iods of marine t r a n s g r e s s i o n are p rocesses

t h a t de te rmine t h e s t r a t i g r a p h i c n a t u r e and e x t e r n a l geometry of sands tone

bodies . p i l e of

sediments t h a t w i l l e v e n t u a l l y c o n s t i t u t e p a r t of a sed imentary b a s i n .

Depos i t i ona l f e a t u r e s observed i n modern sed iments are formed by sed i -

mentary p rocesses t h a t were o p e r a t i v e i n t h e p a s t . Although t h e th ree -

-dimensional c o n f i g u r a t i o n of a delta-complex changes con t inuous ly , t h e

d i s t r i b u t i o n o f sed imentary f a c i e s and geomorphic f e a t u r e s seen on t h e

s u r f a c e of a modern d e l t a can be matched by t h e d i s t r i b u t i o n of l i t h o -

f a c i e s and sands tone bod ies w i t h i n p a r t i c u l a r s t r a t i g r a p h i c i n t e r v a l s i n

the subsu r face benea th t h e d e l t a . Recent h i s t o r y of sed imenta t ion i s thus

seen t o be a r e c a p i t u l a t i o n of t h e p a s t .

These bod ies and t h e i r e n c l o s i n g beds form a s i n k i n g

The geography of modern d e l t a s is c o n t r o l l e d o r i n f luenced by many

f a c t o r s , i nc lud ing t h e n a t u r e and mass of sediment d i scha rged , p a t t e r n of

sediment d i s t r i b u t i o n by d i s t r i b u t a r i e s , bathymetry of t h e c o n t i n e n t a l

s h e l f on which t h e d e l t a i s b u i l d i n g o u t , and t h e s t r e n g t h of wave and

c u r r e n t a c t i o n . Three examples are shown by F igs . 4-1, 4-2 , and 4 - 3 .

The Irrawaddy River of Burma (Fig. 4-1) is prograding r a p i d l y on

t o a broad , sha l low c o n t i n e n t a l s h e l f under ly ing t h e Andaman Sea. The

e n t i r e d e l t a covers an area of n e a r l y 50,000 sq . km. In t h e sou the rn

p a r t of t h e d e l t a t h e annual sediment d i scha rge i s s t a t e d by F i she r e t al.

(1969) t o be about 300 m i l l i o n tons of mud, s i l t , and f ine-gra ined sand.

Along t h e c o a s t , a c c r e t i o n a r y sand b a r s have been formed by t h e winnowing

a c t i o n o f waves and c u r r e n t s on t h e s i l t y sands .

r a t e s va ry ing from one l o c a t i o n t o ano the r depending on s h i f t s of t h e

Cont inua l growth, a t

186

D I S T R I B U T A R I E S A N D SAND BARS,

I R R A W A D D Y DELTA

Fig . 4-1. P a t t e r n of main d i s t r i b u t a r i e s , t i d a l channe l s , and

a c c r e t i o n a r y sand b a r s i n t h e sou the rn p a r t of t h e Holocene

d e l t a of t h e Irrawaddy R ive r , Burma. (Redrawn from F i s h e r

e t aZ. 1969).

d i s t r i b u t a r i e s and changes i n t h e i r volume of d i scha rge , h a s r e s u l t e d i n

t h e abandonment of o l d e r a c c r e t i o n a r y b a r s .

i n l m d where they form l i n e a r t r e n d s o u t l i n i n g t h e p re -ex i s t ing s h o r e l i n e s .

Later pe r iods of r e g i o n a l o r l o c a l marine t r a n s g r e s s i o n s may bury t h e s e

i n l a n d sand bod ies wi th mud, t hus p re se rv ing them i n t h e g e o l o g i c a l record .

Subsequent growth of t h e sed imentary p i l e r e s u l t s i n t h e b u r i a l of sand

bod ies t o dep ths of hundreds o r thousands of metres where hydrocarbon

g e n e r a t i o n , f l u i d movements, and penecontemporaneous deformation by

compaction, slumping, and growth s t r u c t u r e s combine t o concen t r a t e o i l

and gas w i t h i n some of t h e sand o r sands tone u n i t s .

These g r a d u a l l y r e t r e a t f a r t h e r

Regions where t h e d e p o s i t i o n a l environments are of t h i s n a t u r e ,

187

and where they have been similar i n t h e g e o l o g i c a l p a s t , are a t t r a c t i v e

a reas i n which t o exp lo re f o r o i l and gas. Such r eg ions a r e l i k e l y t o

have a r e l a t i v e l y h igh o r g a n i c con ten t n o t on ly i n t h e present-day muds

but a l s o i n t h e subsu r face mudstones o r s h a l e s . Depos i t i ona l environments

t h a t have n o t been t e c t o n i c a l l y d i s t u b e d o r s u b j e c t e d t o ex tens ive

pe r iods of e r o s i o n a r e less l i k e l y t o have l o s t an apprec i ab le volume of

hydrocarbons. Furthermore, t h e broad and sha l low c o n t i n e n t a l she lves on

which such d e l t a i c systems grow are amenable t o d r i l l i n g .

In c o n t r a s t t o t h e d e l t a of t h e Irrawaddy River , t h e Nile d e l t a

(F ig . 4-2 ) i n t h e United Arab Republ ic has marked d i f f e r e n c e s i n geometry,

and probably a l s o i n i n t e r n a l s t r u c t u r e . These d i f f e r e n c e s are t h e r e s u l t

F ig . 4-2 . P a t t e r n of t h e main d i s t r i b u t a r i e s and c o a s t a l sands t h a t

form b a r r i e r - s t r a n d p l a i n s i n t h e Holocene d e l t a of t h e N i l e

R ive r , United Arab Republ ic . (Redrawn from F i s h e r e t al.,

1969).

188

of s e v e r a l f a c t o r s r e l a t e d t o rates of sediment d i scha rge , c l i m a t e , and

t h e bathymetry of t h e Medi te r ranean Sea east of Alexandr ia .

d i s t r i b u t a r i e s of t h e N i l e R ive r , shows i n F ig . 4-2 are t h e wes te rn Rose t t a

branch and t h e e a s t e r n D a n i e t t a branch. The t o t a l annual d i scha rge of

sediment from t h e s e d i s t r i b u t a r i e s is s t a t e d by F i she r e t aZ. (1969) t o

be approximate ly 60 m i l l i o n t o n s , o r one f i f t h of t h e d i scha rge from t h e

Irrawaddy River . However, much of t h e f ine -g ra ined sediment c a r r i e d by

t h e N i l e R iver du r ing pe r iods of f l o o d never r eaches t h e s e a , bu t i s

depos i t ed on t h e f l o o d p l a i n when t h e r i v e r l e v e l f a l l s .

of d i scha rge i n t o t h e sea is r e f l e c t e d n o t on ly i n s i z e , t h e Nile d e l t a

cover ing 15,000 s q . km. which i s less than one t h i r d t h e area of t h e

Irrawaddy d e l t a , b u t a l s o i n t h e g r e a t e r development of o f f s h o r e b a r s . In

p a r t i c u l a r , b a r r i e r b a r s have formed a c r o s s l a r g e lagoons , a lmost completely

c u t t i n g them o f f and consequent ly r a i s i n g t h e s a l i n i t y s o t h a t t hey a r e

surrounded by c o a s t a l s a l t marsh and e v a p o r i t e mud f l a t s . Fa r the r i n l a n d

t h e d e l t a forms an e x t e n s i v e f lood p l a i n .

The two main

The lower r a t e

E x t e r n a l l y , t h e N i l e d e l t a c o n t r a s t s markedly n o t on ly wi th t h e

Irrawaddy d e l t a , b u t a l s o wi th t h e c l a s s i c M i s s i s s i p p i d e l t a . In t h e

M i s s i s s i p p i d e l t a t h e predominant sands tone bod ies are d i s t r i b u t a r y and

ba r - f inge r s ands ; b a r r i e r b a r s are on ly developed away from t h e d e l t a

f r o n t where sands are t r a n s p o r t e d a long t h e c o a s t by c u r r e n t s . In t h e

Irrawaddy d e l t a t h e r a p i d r a t e of sediment d i scha rge l a r g e l y p rec ludes any

s i g n i f i c a n t development of b a r r i e r b a r s ; whereas i n t h e N i l e d e l t a they

a r e a major f e a t u r e . I n t e r n a l l y , t h e M i s s i s s i p p i d e l t a shows sedimentary

f a c i e s and geomorphologic f e a t u r e s s i m i l a r t o t hose p r e s e n t i n t h e

s u r f a c e . The same r e l a t i o n s h i p probably o b t a i n s i n t h e Irrawaddy d e l t a ,

and may a l s o o b t a i n i n t h e N i l e d e l t a . I f s o , bu r i ed b a r r i e r b a r s and

o t h e r o f f s h o r e sand bod ies should prove t o be p r o s p e c t i v e t a r g e t s f o r

pe t ro leum e x p l o r a t i o n .

189

0 25

KM

DISTRIBUTARIES A N D BARRIER BARS, PO

DELTA

Fig . 4-3. P a t t e r n of d i s t r i b u t a r i e s and b a r r i e r b a r s i n t h e Holocene

d e l t a of t h e Po River , Gulf of Venice, I t a l y . (Redrawn

from F i s h e r e t a Z . , 1969) .

The Po River (F ig . 4-3) of n o r t h e r n I t a l y i s r a p i d l y b u i l d i n g a

d e l t a i n t o t h e A d r i a t i c Sea ,

500 squa re k i lome te r s .

i t has a comparable rate of sediment d i scha rge i n t o t h e sea, s t a t e d by

F i she r e t aZ. (1969) t o be 70 m i l l i o n tons pe r yea r . Most of t h i s

sediment l oad i s c a r r i e d by t h e two main d i s t r i b u t a r i e s , t h e Po d i Goro

t o t h e s o u t h , and t h e Po d e l l e T o l l e t o t h e n o r t h . Loca l ly , t h i s l oad

of sediment i s s u f f i c i e n t t o b u i l d t h e c o a s t l i n e seaward a t rates of up

t o 60 m per yea r . During t h e P l e i s t o c e n e and Holocene t h i s r a u i d rate

of p rograda t ion has been main ta ined , and sand bod ies formed as r e g r e s s i v e

marine s h o r e l i n e sands are now b u r i e d a t dep ths of up t o 450 m. I n t h e

subsu r face t h e s e bod ies form l e n s e s , some of which a r e s t r a t i g r a p h i c t r a p s

from which low p r e s s u r e gas product ion i s obta ined . Between t h e main and

s u b s i d i a r y d i s t r i b u t a r i e s a r e bays and marshy c o a s t a l p l a i n s . Shore l ine

The area of t h i s d e l t a i s approximate ly

Although very much smaller than t h e N i l e d e l t a ,

190

sands , o f f s h o r e sands , and b a r r i e r b a r s have formed a long t h e c o a s t .

Where t h e seaward mig ra t ion of a d e l t a s h o r e l i n e c o a s t is f a i r l y

r a p i d , t h e sediment depos i t ed i s commonly s i l t and mud wi th some f i n e sand.

The ra te of s ed imen ta t ion is r e l a t e d t o t h e proximi ty of t h e s h o r e l i n e t o

t h e mouth of t h e r i v e r d i s t r i b u t a r y d i scha rg ing sediment i n t o t h e sea, and

a l s o t o t h e mass of sediment d i scharged . The l a t t e r f a c t o r depends on t h e

sediment l o a d c a r r i e d by t h e d i s t r i b u t a r y t o i t s mouth, and obvious ly is

r e l a t e d t o seasona l v a r i a t i o n s c o n t r o l l i n g pe r iods of f lood o r low water .

The former f a c t o r depends on changes i n t h e course of t h e r i v e r d i s t r i b u t a r y

i t s e l f . I n t i m e s o f f l ood a d i s t r i b u t a r y may b u r s t through i t s l e v e e s and

abandon i t s o l d channel . Such a change of cour se may a lmost comple te ly

c u t o f f t h e sou rce of sediment supply t o a p a r t i c u l a r p a r t of t h e c o a s t .

Subsequent ly , a d i s t r i b u t a r y may aga in change course t o debouch i t s load

nea r t h e mouth of i t s o l d e r , abandoned channel . This c y c l i c , a l though

commonly i r r e g u l a r , v a r i a t i o n i n t h e r a t e of s ed imen ta t ion a long a s h o r e l i n e

may r e s u l t i n t h e a l t e r n a t e development of mud f l a t s and beach r i d g e s of

sand t o form a prograding sequence of chen ie r s .

During pe r iods when t h e rate of sed imenta t ion i s h igh , t h e sediment

a c c r e t i n g t o t h e coas t i s predominantly f ine -g ra ined , r e s u l t i n g i n t h e

r a p i d seaward growth o f c o a s t a l mud f l a t s . During pe r iods when t h e rate

of sed imenta t ion i s ve ry much lower , t h e sediment a long t h e s h o r e l i n e i s

winnowed by wave and c u r r e n t a c t i o n . The mud is swept away and t h e

r e s i d u a l sand con ten t remains t o form a beach. With t ime, wind a c t i o n

may c a r r y some of t h e beach sand landward t o b u i l d dunes t h a t form a

b a r r i e r between t h e sea and t h e now land-locked c o a s t a l mud f l a t s and

chen ie r s . The development of a beach r i d g e depends on t h e p e r i o d i c i t y of

sed imentary a c c r e t i o n t o t h e c o a s t . Sooner o r la ter t h e r a t e of sed imenta t ion

i n c r e a s e s beyond t h e c a p a c i t y of winnowing a c t i o n t o s o r t o u t and concen t r a t e

t h e sand , so t h a t mud a c c r e t e s on t h e seaward s i d e of t h e sandy beach which

191

S I L T A N D

2 000

500 rn 0

CROSS S E C T I O N OF CHENIER ON P E C A N ISLAND,

LOUISIANA

Fig . 4-4. Cross s e c t i o n of a chen ie r on Pecan I s l a n d , Gulf Coast of

Lou i s i ana , showing d r i l l h o l e l o c a t i o n s . (Redrawn from

Gould and Morgan, 1962) .

i n t u r n becomes land-locked as a low, sandy r i d g e l y i n g between mud f l a t s .

These r i d g e s , o r c h e n i e r s (F ig . 4 - 4 ) , are named a f t e r t h e French woru

c h h e , meaning oak , because trees c a l l e d sc rub oaks comnonly grow on t h e s e

r i d g e s i n Louis iana .

Cheniers have a p a r a l l e l , g e n t l y a r c u a t e alignment r e f l e c t i n g t h e

migra tory h i s t o r y of t h e s h o r e l i n e . I n d i v i d u a l l y they can be t r a c e d f o r

s e v e r a l k i l o m e t r e s . The s u r f i c i a l wid th of an i n d i v i d u a l chen ie r may be

less than 300 m , b u t i t s subsu r face wid th may be up t o 1,500 m. Thickness

commonly ranges up t o 5 m. Viewed i n t h r e e dimensions, wi thout v e r t i c a l

exagge ra t ion , c h e n i e r s a r e ribbon-shaped. I n t e r n a l l y , t hey c o n s i s t of

f i ne -g ra ined , s h e l l y sand wi th a v a r i a b l e con ten t of s i l t and mud. In

t h e s u b s u r f a c e , a n c i e n t c h e n i e r s are i l l u s i v e s t r a t i g r a p h i c t a r g e t s f o r

pe t ro leum e x p l o r a t i o n , and because of t h e i r t h i n n e s s a r e n o t e s p e c i a l l y

a t t r a c t i v e . Neve r the l e s s , where found t o c o n t a i n economically v i a b l e

accumulations o f o i l o r gas i E should be kep t i n mind t h a t o t h e r p a r a l l e l -

10

F E E T

D

192

- t r end ing c h e n i e r s probably e x i s t nearby , and t h a t some of t h e s e may form

hydrocarbon r e s e r v o i r s .


Regress ive marine s h o r e l i n e sand bod ies , b a r r i e r b a r s , and o t h e r

o f f s h o r e b a r s t h a t are prograding seaward, o r landward (F ig . 3-9) i n

p a r t i c u l a r s i t u a t i o n s , t end t o have an i n t e r n a l g r a i n g rada t ion from f i n e r

below t o c o a r s e r above. Th i s g r a d a t i o n , which i s d i scussed i n t h e i n t r o -

duc t ion t o Chapter 3 on b a r r i e r and o t h e r o f f s h o r e b a r s , i s r e f l e c t e d i n

t h e funnel-shaped c h a r a c t e r of t h e E-log s e l f - p o t e n t i a l curve . The

s i m i l a r i t y of t h i s c h a r a c t e r i n l i n e a r sands tone bod ies of d i f f e r e n t a g e s ,

and from wide ly s e p a r a t e d l o c a l i t i e s , is i l l u s t r a t e d i n F ig . 4-5. The

sands tone u n i t des igna ted ' A ' c o n s t i t u t e s an o f f - l app ing sequence of

sands tone bod ies i n t h e Lower Cre taceous Viking Formation of t h e Joarcam

O i l F i e l d , A lbe r t a . The Viking forms a sequence of p a r a l l e l and a r c u a t e

t r e n d s , each o f which is a complex of s e p a r a t e bu t l o c a l l y connected

sands tone bod ies depos i t ed a s s h o r e l i n e sands .

du r ing a pe r iod of i n c o n s t a n t marine r eg res s ion . Sandstone ' B ' i s a u n i t

w i t h i n t h e lower p a r t of t h e Upper Cre taceous Be l ly River Formation i n t h e

Pembina O i l F i e l d , A lbe r t a .

of t h e fo rma t ion , a l s o form a sequence of s h o r e l i n e , o f f - l app ing sands tone

bod ies (Fig. 4-7 ) depos i t ed du r ing a r e g r e s s i v e phase of t h e sea. The

sands tone u n i t s i n t h e i n t e r v a l des igna ted ' C ' are s t acked , o f f - l app ing

sands tone bod ies formed as b a r s i n a r e g r e s s i v e sequence of t he Oligocene

F r i o Formation i n Texas.

These t r e n d s were formed

This s ands tone body, and o t h e r s a t t h e base

The Viking Formation (F ig , 4 - 6 ) is an i n t e r e s t i n g example of

r e g r e s s i v e marine s h o r e l i n e sand bod ies t h a t show a t y p i c a l funnel-shaped

s e l f - p o t e n t i a l curve . In c e n t r a l A lbe r t a t h e Viking comprises a sequence

of s u b - p a r a l l e l , l i n e a r sands tone bodies t h a t have a r e g i o n a l a r c u a t e t r end

193

SHORELINE DEPOSITS

BARRIER BARS A N D REGRESSIVE SANDS

c y1 tu

SP I BEACH

SEA LEVEL ' L

00 REGRESSIVE SHORELINE DEPOSIT

0

50 m

F ig . 4-5. S e l f - p o t e n t i a l curves of e lectr ic l o g s , and a gene ra l i zed

s e c t i o n of a r e g r e s s i v e s h o r e l i n e sand d e p o s i t , showing

funnel-shape c h a r a c t e r i s t i c of t h e l o g and i t s r e l a t i o n s h i p

t o of f - lapping c o a s t a l sands such as b a r r i e r b a r s . A -

Lower Cre taceous Viking Sands tone , Joarcam F i e l d , A lbe r t a .

B - Upper Cre taceous Be l ly River Sands tone , Pembina F i e l d ,

A lbe r t a . C - Oligocene F r i o Sandstone, Texas.

t o t h e nor thwes t . This t r e n d t a k e s a broad sweep a c r o s s t h e whole of

sou the rn and c e n t r a l A l b e r t a , and ex tends a l s o i n t o sou the rn Saskatchewan.

Each sands tone body i n t h e sequence t ends t o have an of f - lapping r e l a t i o n -

194

- t zoo

-+loo z c 0

- 0 M S L 2 2 W

I J

Fig . 4-6. E l e c t r i c - l o g s t r u c t u r a l s e c t i o n showing funnel-shaped

c h a r a c t e r i s t i c of t h e s e l f - p o t e n t i a l curve of o i l and

gas-bear ing Lower Cre taceous Viking Formation nea r Edmonton,

A lbe r t a . (Af t e r T i x i e r and For sy the , 1951).

s h i p and r e p r e s e n t s a s h o r e l i n e sand formed dur ing a t i m e o f eastward

r e g r e s s i o n of t h e s e a .

Re fe r r ing t o t h e l i t h o l o g y and g r a i n g r a d a t i o n of sands tone bodies

i n t h e Viking Formation, Game11 (1955, p . 65) s a y s , "These sands are

o f t e n concen t r a t ed i n t o beds averaging 25 f e e t i n t h i c k n e s s , though beds

over 100 f e e t a r e found nea r Edmonton. The sands are subgraywackes, be ing

made up of wh i t e q u a r t z and rounded b l a c k c h e r t g r a i n s secondar i ly cemented

w i t h s i l i c a . G laucon i t e , wh i t e c h e r t , k a o l i n and i r o n s t o n e conc re t ions a r e

195

found i n t h e sands i n va ry ing amounts. Regional ly t h e sands a r e f i n e s t

a t t h e n o r t h e a s t p inchout edge of t h e member and become s l i g h t l y c o a r s e r

a t t h e southwes t , c l o s e r t o t h e source . Loca l ly , however, cons ide rab le

v a r i a t i o n i n g r a i n s i z e may occur i n a s i n g l e bed. The r e g r e s s i v e type

of sand bed , w i t h upward dec reas ing amounts of s h a l e and s i l t t o a sands tone

followed above by a t h i n b l a c k c h e r t conglomerate, is common. The Viking

s h a l e s are u s u a l l y s i l t y o r sandy and c o n t a i n carbonaceous m a t e r i a l and

f i s h remains". The upward-fining o f t h e Viking sands tone r e f e r r e d t o by

Gammell i s c l e a r l y i n d i c a t e d by t h e funnel-shaped c h a r a c t e r of t h e s e l f -

- p o t e n t i a l curve shown i n F ig . 4-6. The same E-log c h a r a c t e r i s t i c s are

e x h i b i t e d by t h e o f f - l app ing b a s a l sands tone u n i t s of t h e Upper Cretaceous

Bel ly River Formation i n t h e Pembina O i l F i e l d , A l b e r t a (Fig. 4 - 7 ) .

Compaction

Where sandy sediment is a c c r e t i n g con t inuous ly a t a cons t an t rate,

and where t h e c u r r e n t and wave a c t i o n does n o t va ry apprec i ab ly , t h e u n i t

depos i t ed has a homogeneous t e x t u r e and composition. A marked i n c r e a s e i n

t h e l o a d of s i l t and mud, o r a dec rease i n c u r r e n t and wave a c t i o n , w i l l

cause t h e seaward f l a n k of t h e sand body t o grade i n t o , o r a b r u p t l y

t e rmina te a g a i n s t , a l a y e r of s i l t y mud. R e p e t i t i o n of t h e s e d e p o s i t i o n a l

even t s w i l l produce a sequence of of f - lapping sand bod ies s e p a r a t e d by

l a y e r s of s i l t y mud. P r i o r t o compaction and l i t h i f i c a t i o n , t h e boundar ies

of each sand body a r e c l e a r l y de f ined . Following compaction, t h i n l a y e r s

of s i l t y mud s e p a r a t i n g t h e sand bod ies may become squeezed i n t o sha le -

-breaks t h a t a r e n o t de f ined by E-logs. A sands tone u n i t may then super-

f i c i a l l y appear t o be one cont inuous sands tone body, whereas i n f a c t i t

w a s depos i t ed a s a r e g r e s s i v e s t r a t i g r a p h i c zone comprising s e v e r a l o f f -

- lapping bod ies of sand. Thicker l a y e r s of s i l t y mud w i l l compact i n t o

s h a l y beds t h a t may e f f e c t i v e l y s e a l o f f t h e subsequent movement of hydro-

carbons w i t h i n t h e sands tone body. Recogni t ion of t h e i n t e r n a l s t r u c t u r e

196

P ? h

,BELLY RIVER,? OIL PRODUCTION 7

m * 0

M A R K E R I I I I I

r' ilea

BOOD i

OFFLAPPI NG COASTAL SANDS, UPPER CRETACEOUS BELLY RIVER FM, PEMBINA FIELD, ALBERTA

Fig . 4-7. S t r a t i g r a p h i c s e c t i o n s through e a s t e r n and s o u t h e a s t e r n

p a r t s of Pembina F i e l d , A l b e r t a , showing o f f l a p p i n g marine

c o a s t a l sands (1, 2 , 3 , and 4 ) t r end ing north-south a t t h e

base of t h e Upper Cre taceous Bel ly River Formation which

o v e r l i e s marine s h a l e s of t h e Lea Park Formation. These

sands are c u t by c h a n n e l - f i l l sands (5) depos i t ed by d i s t r i b -

u t a r i e s t r end ing east-west a t t h e f r o n t of a d e l t a prograding

from west t o east . Note t h e funnel-shaped s e l f - p o t e n t i a l

s u r v e of t h e E-log, t y p i c a l of c o a s t a l sands such as b a r r i e r

b a r s .

197

of such a sands tone u n i t s is e s s e n t i a l t o pa leogeographic and paleogeomorphic

r e c o n s t r u c t i o n s app l i ed t o t h e s e a r c h f o r o i l and gas i n sands tone bodies .

Ancient Sand Bodies

Regress ive marine s h o r e l i n e sand bod ies t h a t have an of f - lapping

r e l a t i o n s h i p , commonly wi th ang le s of less than one degree (Shel ton , 1965),

a r e developed as widespread s h e e t s of sand t h a t u l t i m a t e l y form t h i n ,

diachronous u n i t s of sands tone . These u n i t s c o n s t i t u t e e x c e l l e n t s t ra t i -

g raph ic marker beds , as they o v e r l i e s h a l y marine sequenees , and where

exposed as a n e a r l y h o r i z o n t a l l a y e r t hey resist e r o s i o n to form the

rim-rock i n canyons and mesas. Examples inc lude t h e Upper Cre taceous

Eagle Sandstone (Fig. 3-9) t h a t forms a rim-rock i n t h e escarpment a t

B i l l i n g s , Montana, and the lower sands tone beds of t h e Upper Cretaceous

Mesaverde Formation i n New Mexico. In t h e subsu r face , examples comprising

o f f - l app ing bod ies can b e seen i n t h e Lower Cre taceous Viking Formation

(Fig. 4-11) i n Saskatchewan, and i n t h e b a s a l sands tone u n i t of t h e Upper

Cre taceous Be l ly R ive r Formation (Fig. 4-7) i n A lbe r t a .

The b a s a l u n i t of t h e Be l ly River Formation i s a s h e e t - l i k e sand-

s t o n e t h a t comprises a sequence of o f f - l app ing marine s h o r e l i n e sand

bod ies l o c a l l y c u t by d i s t r i b u t a r y channels f i l l e d wi th c o a r s e r sand of

t h e Buck Creek Member (Fig. 73) . This widespread sands tone u n i t is

o v e r l a i n by Be l ly River s h a l e s , s i l t s t o n e s , and c o a l seams depos i t ed i n

a d e l t a i c environment; and is u n d e r l a i n by s e v e r a l hundred f e e t of marine

s h a l e s of t h e Upper Cre taceous L e a Park Formation on which t h e b a s a l

Be l ly River sands t r a n s g r e s s e d du r ing a r e g r e s s i v e phase of t h e sea .

In t h e Pembina O i l T i e l d r eg ion , where some o i l p roduct ion i s

ob ta ined from t h e Buck Creek Member, t h e b a s a l sands tone u n i t has a f a i r l y

uniform th i ckness o f 35-45 m. S u p e r f i c i a l l y , t h i s u n i t resembles a

homogeneous s h e e t of f ine-gra ined sands tone , bu t d e t a i l e d E-log c o r r e l -

198

a t i o n s (Fig. 4-7) show t h e i n t e r n a l s t r u c t u r e t o c o n s i s t of s e p a r a t e

sands tone bod ies o f f - l app ing t o t h e east , and ctit i n t o by d i s t r i b u t a r y

channels f i l l e d w i t h medium t o coarse-gra ined sand. Th i s sequence w a s

depos i t ed du r ing an eas tward r e g r e s s i o n of t h e sea i n response t o

p rograda t ion of a l a r g e d e l t a .

A t t h e c l o s e of Lea Park t i m e t h e Pembina r eg ion l a y under a

sha l low sea. Marine r e g r e s s i o n cont inued i n t o B e l l y R ive r t i m e , beg inning

w i t h t h e d e p o s i t i o n of b a s a l marine s h o r e l i n e sands . As t h e sea withdrew,

t h e marine s h o r e l i n e sands migra ted eas tward , forming an of f - lapping

sequence of s e p a r a t e sand bod ies . These w e r e followed and o v e r l a i n by a

d e l t a c o n s i s t i n g of d e p o s i t s formed i n bays , l agoons , e s t u a r i e s , c o a s t a l

marshes and r i v e r d i s t r i b u t a r i e s . These d e p o s i t s now form beds of

s ands tone , s i l t s t o n e , s h a l e and c o a l ove r ly ing t h e b a s a l sands tone u n i t

of r e g r e s s i v e s h o r e l i n e sands . The r e g r e s s i v e n a t u r e of t h i s sands tone

SEA LEVEL 7 7 -

S W A M P

M A R I N E S E D I M E N T S

OFFLAPPING MARINE SHORELINE

SANDS

Fig . 4-8. Diagram i l l u s t r a t i n g a c c r e t i o n of o f f l a p p i n g mar ine s h o r e l i n e

sands , such as t h e r e g r e s s i v e lower member of t h e Mesaverde

Sandstones (Upper Cre taceous) i n New Mexico. (Redrawn from

Hollenshead and P r i t c h a r d , 1961).

199

u n i t is r e f l e c t e d i n i t s g r a i n s i z e d i s t r i b u t i o n which t ends t o range from

f i n e above t o ve ry f i n e below, a g r a d a t i o n r e f l e c t e d i n t h e funnel-shaped

s e l f - p o t e n t i a l curve of t h e E-log (Fig. 4 - 7 ) .

The s p a t i a l r e l a t i o n s h i p s of such o f f - l app ing sands tone bodies

i s i l l u s t r a t e d wi th cons ide rab le v e r t i c a l exagge ra t ion i n F ig . 4-8, wi th

r e fe rence t o t h e i n t e r n a l s t r a t i g r a p h i c r e l a t i o n s h i p s of sands tone bod ies

i n t h e Mesaverde Formation.

r i s i n g o f f - l app ing sands tone bod ies formed as beaches , b a r s , and o t h e r

of f - shore sands , i s t h a t it w i l l , a l though widespread , have some degree

of l i n e a r i t y .

A g e n e r a l f e a t u r e of a sands tone u n i t comp-

O i l and G a s F i e l d s

S i g n i f i c a n t accumula t ions of o i l and gas a r e known w i t h i n r e g r e s s i v e

marine s h o r e l i n e sand bod ies . I n c o n t r a s t t o t r a n s g r e s s i v e marine s h o r e l i n e

F ig . 4-9. Schematic diagram i l l u s t r a t i n g types of sand bod ies formed

dur ing r e g r e s s i o n and subsequent t r a n s g r e s s i o n of a s ea .

g e n e r a l e v a l u a t i o n of pe t ro leum entrapment p o t e n t i a l is

i n d i c a t e d . (Af t e r MacKenzie, 1972, F i g . 5 ) .

A

200

s a n d s MacKenzie (1972) c o n t e n d s t h a t r e g r e s s i v e sand b o d i e s a r e less

a t t r a c t i v e a s e x p l o r a t i o n t a r g e t s . He s a y s , p. 57 , "During p e r i o d s of

o v e r a l l r e g r e s s i o n , s h o r e l i n e s a n d b o d i e s , i f p r e s e n t , may b e r e p l a c e d

updip by d e l t a i c d e p o s i t s (F ig . 4-9 t h i s t e x t ) . These d e l t a i c d e p o s i t s ,

b e c a u s e of t h e i r many a s s o c i a t e d t y p e s of sands - p a r t i c u l a r l y d i s t r i b u t a r y

c h a n n e l s a n d s - p r o b a b l y would b e r e l a t i v e l y poor b a r r i e r s t o up d i p

m i g r a t i o n .

In c o n t r a s t , d u r i n g p e r i o d s of o v e r a l l t r a n s g r e s s i o n , t h e s h o r e l i n e

s a n d b o d i e s would be r e p l a c e d updip by sand-poor l a g o o n a l muds which , when

compacted, would b e r e l a t i v e l y good b a r r i e r s t o updip m i g r a t i o n of o i l .

Fur thermore , t h e s a n d s would b e o v e r l a i n by mar ine s h a l e s , which s h o u l d b e

e f f e c t i v e b a r r i e r s " .

The c o r r e c t n e s s of t h i s c o n t e n t i o n i s open t o q u e s t i o n , as some

mar ine r e g r e s s i v e s a n d s t o n e b o d i e s are t h e r e s e r v o i r s f o r many o i l and

g a s f i e l d s . I m p o r t a n t examples i n c l u d e t h e Wattenberg Gas F i e l d producing

from t h e Lower C r e t a c e o u s "J" Sands tone of t h e Deaver Bas in i n Colorado , ,

and s e v e r a l f i e l d s p r o d u c i n g from t h e Lower C r e t a c e o u s Vik ing Formation

i n A l b e r t a and Saskatchewan.

Wattenberg Gas F i e l d , Colorado

The Wat tenberg G a s F i e l d c o v e r s an o v e r a l l area of a p p r o x i m a t e l y

2 ,500 s q u a r e k i l o m e t r e s . The f i e l d , which i s s i t u a t e d on t h e axis of t h e

Denver B a s i n , i s c o n s i d e r e d t o i n c l u d e s e v e r a l s t r a t i g r a p h i c t r a p s , t h e

g a s b e i n g c o n t a i n e d i n a b l a n k e t s a n d s t o n e u n i t , t h e Lower C r e t a c e o u s "3"

S a n d s t o n e , compr is ing r e g r e s s i v e mar ine s a n d s t o n e b o d i e s d e p o s i t e d i n t h e

f r o n t o f a n o r t h w e s t e r l y p r o g r a d i n g d e l t a . Entrapment of g a s i s c o n t r o l l e d

by d e c r e a s i n g p e r m e a b i l i t y a l o n g t h e edges o f t h e s a n d s t o n e b o d i e s .

Encountered w i t h i n t h e d e p t h r a n g e 2,200-2,600 m , t h e a v e r a g e n e t t h i c k n e s s

of t h e gas-bear ing s a n d s t o n e , o r pay , i s 8 m. Average p o r o s i t y i s 9.5%.

201

PRODUCTION EXCEEDING 500 BARRELS

BURBANK FIELD, OKLAHOMA

Fig . 4-10. D i s t r i b u t i o n of i n i t i a l d a i l y o i l p roduc t ion exeeeding 500

b a r r e l s p e r day p e r w e l l , Burbank and South Burbank f i e l d s ,

Osage and Kay Coun t i e s , Oklahoma, F i g u r e shows s p a t i a l

r e l a t i o n s h i p of p roduc t ion t o t h i c k e r p a r t s of curved,

l i n e a r bodies of Pennsylvanian sands tone depos i t ed as

s h o r e l i n e sands . Note en eche lon t r ends east of t h e main

c u r v i l i n e a r b e l t . (Redrawn from Bass , 1941).

202

Pe rmeab i l i t y , ave rag ing less than one m i l l i d a r c y , i s ex t remely low, and

gas f lows on ly a f t e r t h e sands tone has been f r a c t u r e d . A f t e r comple t ion ,

t h e average w e l l y i e l d s gas and 64O A . P . I . condensa te a t rates of 300-600

thousand cub ic f e e t and 10-20 b a r r e l s p e r day. Ul t imate gas product ion i s

e s t ima ted t o b e 1.3 t r i l l i o n (thousand b i l l i o n ) cub ic f e e t (36,400 m i l l i o n

cub ic met res ) over a 40 year p e r i o d , each w e l l on a 320-acre spac ing

producing 2 b i l l i o n cub ic f e e t .

Burbank O i l F i e l d , Oklahoma

Product ion i n t h e Burbank O i l F i e l d o f Oklahoma (Fig. 4-10) i s

ob ta ined from a number of Pennsylvanian sands tone bod ies t h a t form f o u r

p a r a l l e l and a r c u a t e t r e n d s , t h e c e n t r a l and n o r t h e r n t r e n d s showing an

en echeZon arrangement. These t r e n d s c o n s t i t u t e a b e l t , t h e t h i c k e r and

more p roduc t ive p a r t o f which has a wid th of 5 km and a l eng th of 25 km.

The sands tone bod ies range i n th i ckness up t o 30 m and c o n s i s t of w e l l -

- so r t ed g r a i n s which show a g rada t ion from f i n e i n t h e t h i c k e r p a r t s t o

ve ry f i n e n e a r the edges of t h e bod ies .

consequent ly conform t o t h e d e p o s i t i o n a l t r e n d s and a r e h i g h e r where t h e

sands tone i s t h i c k e r a long t h e axis of each body. I n t e r p r e t a t i o n of t h e

d e p o s i t i o n a l environment o f t h e s e sands tone bodies sugges t s (Bass, 1941)

t h a t t hey were depos i t ed as a sequence of o f f - l app ing beaches and b a r s

a long s h o r e l i n e t r e n d s t h a t migra ted t o t h e n o r t h e a s t .

t h e s e t r e n d s a l s o sugges t s t h a t they were developed as a p e r i p h e r a l

margin of s h o r e l i n e sands f l a n k i n g t h e prograding edge of a d e l t a l obe .

P o r o s i t y and pe rmeab i l i t y t r e n d s

The cu rva tu re of

I n i t i a l d a i l y p roduc t ion from some w e l l s exceeded 2,000 b a r r e l s

of o i l a day. Fig. 4-10 shows l i n e a r t r e n d s where t h e i n i t i a l d a i l y

p roduc t ion p e r w e l l exceeded 500 b a r r e l s a day.

i n c l u d i n g p a r t o f t h e South Burbank f i e l d , have y i e lded more than 40

m i l l i o n b a r r e l s (6 .4 m i l l i o n cub ic me t re s ) .

These p roduc t ion t r e n d s ,

203

Viking O i l and Gas F i e l d s , A l b e r t a and Saskatchewan

I n A l b e r t a and Saskatchewan, s e v e r a l f i e l d s produce o i l and gas

from t h e Lower Cre taceous Viking Formation. I n A l b e r t a , t h e main o i l f i e l d s

are t h e Joarcam, J o f f r e , Hamilton Lake, and Gilby-Bentley; t h e main gas

f i e l d s a r e t h e Vik ing-Kinse l la , P rovos t , B e a v e r h i l l Lake, Bindloss , Fa i ry-

d e l l , S e d a l i a , Cessford , and For t Saskatchewan. The main o i l and gas

f i r l d s i n Saskatchewan are t h e Mi l ton , Hoos ier , Smiley-Dewar, Whi tes ide ,

Colv i l le -Smi ley , Eureka, Beauf i e ld , Dodsland, and Avon H i l l . A l l of

t hese accumula t ions occur i n up-dip s e c t i o n s of l i n e a r and l e n t i c u l a r

sands tone bod ies , p a r t i c u l a r l y where s t r a t i g r a p h i c t r a p s have been

modified by c l o s u r e s r e s u l t i n g from d rap ing over h i l l s on t h e eroded

s u r f a c e of t h e Pa leozo ic , o r from d rap ing over s e c t i o n s f l anked by c o l l a p s e

f e a t u r e s r e s u l t i n g from t h e s o l u t i o n of s a l t l a y e r s w i t h i n t h e Pa leozoic .

The Viking Formation i s a d iachronous s t r a t i g r a p h i c u n i t , comprising

beds of sands tone and s h a l e , t h a t forms an a r c u a t e b e l t t r end ing nor th-

-wes ter ly a c r o s s sou the rn Saskatchewan and sou th -cen t r a l A lbe r t a . These

l i n e a r sands tone beds a r e markedly l e n t i c u l a r , l o c a l l y sepa ra t ed by s h a l e

l a y e r s , and s t r a t i g r a p h i c a l l y a r ranged as an o f f - l app ing sequence.

Deposited as s h o r e l i n e and near-shore sands i n a r e g r e s s i n g sea, they

formed beaches and o f f - sho re b a r s . The l i t h o l o g y and E-log cha rac t e r -

i s t i c s of t h e Viking sands tones are desc r ibed i n an e a r l i e r s e c t i o n of

t h i s chap te r . These sands tones a r e unde r l a in by marine s h a l e s of t h e

J o l i Fou Formation, which is the lowes t u n i t of t h e Lower Cre taceous

Colorado Group, and a r e o v e r l a i n by s h a l e s and s i l t s t o n e s of t h e same

group. In Saskatchewan, a minor d i sconfo rmi ty a t t h e base of t h e Viking

Formation i n d i c a t e s t h a t l o c a l l y t h e r e w a s wi thdrawal of t h e J o l i Fou sea

p r i o r t o d e p o s i t i o n of t h e Viking sands .

t h e Mannville Group ( s e e Carbon Gas F i e l d s , F ig . 5 - 9 ) , c o n s i s t s of dark

g rey , f i s s i l e , non-ca lcareous , b e n t o n i t i c s h a l e s wi th some lamina t ions

The J o l i Fou, which o v e r l i e s

204

SECTION ACROSS TREND OF V I K I N G FM., SASKATCHEWAN. "7

z

- E

0 M I L E S 3 - 0 K m 5

Fig . 4-11. La te ro log s e c t i o n E-El of t h e Lower Cre taceous Viking Formation

showing o f f - l app ing r e l a t i o n s h i p of sands tone members N , M ,

L 1 , Lu, and K through Eureka and Avon H i l l o i l and gas f i e l d s ,

Saskatchewan. Arrow i n d i c a t e s d i r e c t i o n of retreat of t h e

Colorado Sea . (Redrawn from Evans, 1970).

of s i l t s t o n e and ve ry f ine-gra ined sands tone .

a d i s t a n c e of 300 km, from 6 m nea r Calgary t o 30 m n e a r Edmonton, and

a l s o t h i c k e n s eas tward t o 45 m i n wes t - cen t r a l Saskatchewan. The fauna

i n t h e J o l i Fou c o n s i s t s mainly o f b i v a l v e s and arenaceous forams, sugg-

e s t i n g a shallow-water, near-shore mar ine environment.

It th i ckens nor thward , over

The o f f - l app ing r e l a t i o n s h i p of Viking sands tone bod ies is

i l l u s t r a t e d i n F ig . 4-11 which i s a s e c t i o n a c r o s s t h e Viking Formation

t r e n d i n t h e v i c i n i t y of t h e Eureka and Avon H i l l s f i e l d s i n Saskatchewan.

This t r e n d s t r i k e s west-southwest t o n e a r t h e Alberta-Saskatchewan boundary

where i t j o i n s t h e main Viking t r e n d i n a wide no r thwes te r ly - t r end ing arc.

The main p roduc t ion comes from t h e 'M' sands tone member shown i n F igs .

4-11 and 4-12. This member forms a l e n t i c u l a r r ibbon of sands tone , 10-20

km wide and up t o 8 m t h i c k , t h a t fo l lows a remarkably s t r a i g h t w e s t -

-southwest t r end f o r w e l l over 100 km. The 'M' member i s sepa ra t ed from

t h e under ly ing 'N' member (F ig . 4-11) by a b e n t o n i t e l a y e r which probably

o r i g i n a t e d as a f a l l of vo lcan ic a sh . Gra in g r a d a t i o n w i t h i n t h e 'M'

205

M I L E S 0

0 Km 10 I--r++A

ISOPACH M A P ' M I M E M B E R VIKING FM, SASKATCHEWAN

Fig . 4-12. Isopach map of 'M' member, Lower Cretaceous Viking format ion ,

i n a r e a of Hoos ier , Smiley-Dewar, Colv i l le -Smi ley , Eureka,

Beauf i e ld , and Dodsland o i l and gas f i e l d s , Saskatchewan.

(Redrawn from Evans, 1970).

l a y e r i s from f i n e r below t o c o a r s e r above. P o r o s i t y i n c r e a s e s i n t h e

t h i c k e r p a r t s o f t h e sands tone body, and p a r t i c u l a r l y improves i n t h e

c h e r t pebble zones.

d e p o s i t s on beaches , where c u r r e n t and wave a c t i o n has more v igo rous ly

winnowed t h e sed iments .

These pebble zones were probably formed a s l a g

O i l and gas accumula t ions w i t h i n the numerous sands tone bodies

of t h e Viking Formation are i n t h e more porous and permeable up-dip

s e c t i o n s .

t he t h i n n e r and l e s s permeable p a r t s up-dip may be o i l -bea r ing . F ig . 4 - 1 3

is an i sopach map of t h e net--producing sands tone of t h e Viking Formation

Thicker p a r t s of asands tone body may b e water -bear ing , whereas

206

N

Fig . 4-13. Isopach map of n e t producing sands tone body i n Lower Cret-

aceous Viking Formation, F o r t Saskatchewan gas f i e l d no r th -eas t

of Edmonton, A lbe r t a . Contour i n t e r v a l i n f e e t (1' = 0.305 m).

@drawn from White and Qrr , 1968).

i n t h e For t Saskatchewan Gas F i e l d . F ig . 4-14 i s a sand-percentage map

o f t h e Viking Formation i n t h e same a r e a , showing s t r u c t u r e contours

( f e e t below s e a l e v e l ) i n t h e gas f i e l d . The gas accumulation is n o t , i n

t h i s example, r e l a t e d t o t h e r a t i o of sands tone t o s h a l e w i t h i n t h e

fo rma t ion , bu t t o t h e up-dip p o s i t i o n of an i n d i v i d u a l sands tone body.

The n e t producing zone of t h i s sands tone body ranges i n th i ckness up t o

15 m , and has an average p o r o s i t y of 22%. Down-dip t h e Viking sands tones

a r e s a t u r a t e d wi th wa te r .

A s of e a r l y 1966, t he For t Saskatchewan Gas F i e l d a lone had y i e lded

MILES

207

n KM 6

Fig . 4-14. Sand-percentage map of Lower Cretaceous Viking'Formation,

F o r t Saskatchewan gas f i e l d , A l b e r t a , showing f i e l d area

( s t i p p l e d ) and Viking s t r u c t u r e contours (broken l i n e s ) i n

f e e t (1 ' = 0.305 m) sub-sea l e v e l . (Redrawn from White and

O r r , 1968).

more than 87 b i l l i o n (thousand m i l l i o n ) cub ic f e e t of gas from es t ima ted

r ecove rab le r e s e r v e s of 205 b i l l i o n (5,740 m i l l i o n cubic me t re s ) .

Es t ima tes of t o t a l gas i n i t i a l l y i n p l a c e i n t h e Viking sands tones of

A l b e r t a are p laced a t about 4 . 3 t r i l l i o n (thousand b i l l i o n ) cub ic f e e t ,

of which r ecove rab le r e s e r v e s are e s t ima ted t o be i n excess of 3 t r i l l i o n

(84,000 m i l l i o n cubic m e t r e s ) , which i s about 7% of t h e t o t a l r ecove rab le

gas r e s e r v e s i n A l b e r t a , a s of 1970. The e s t ima ted t o t a l o i l i n i t i a l l y

i n p l a c e i n t h e Viking sands tones of A l b e r t a is more than 320 m i l l i o n

b a r r e l s , of which 110 m i l l i o n (17.5 m i l l i o n cubic m e t r e s ) , r e p r e s e n t i n g

less than 1.5% of t h e i n i t i a l t c t a l r ecove rab le o i l r e s e r v e s i n A l b e r t a ,

may u l t i m a t e l y b e produced.

208

Sabre O i l F i e l d , Colorado

Product ion i n t h e Sabre O i l F i e l d (Fig. 4-15), s i t u a t e d on t h e

westward-dipping e a s t e r n f l a n k of t h e Denver Bas in , Colorado, i s ob ta ined

from a sands tone body w i t h i n t h e Upper Cre taceous "D" Sandstone u n i t . The

I, 11 D Sandstone is o v e r l a i n and u n d e r l a i n by marine sed iments of t h e Upper

Cre taceous Graneros Shale and Huntsman Shale r e s p e c t i v e l y . The Huntsman

o v e r l i e s t h e o f f - sho re marine "J" Sandstone which i s t h e producing sands tone

of t h e Wattenberg O i l F i e l d , Colorado, ncnt ioned ear l ier i n t h i s chap te r .

I n Nebraska, t h e "J" Sandstone on t h e e a s t e r n f l a n k of t h e Denver Basin is

c u t by r i v e r channels f i l l e d wi th sands which l o c a l l y form s t r u c t u r a l -

- s t r a t i g r a p h i c t r a p s f o r o i l (Fig. 1-50). The o i l - b e a r i n g sands tone body

of the Sabre F i e l d i s a l i n e a r , nor thward- t rending l e n s t h a t has a th i ckness

of up t o 15 m , a wid th o f approximate ly 2 km, and a l e n g t h of more than 15

km. This body, r e f e r r e d t o as t h e Sabre Bar, shows v a r i a t i o n s i n th i ckness

W E

0 1,800'

SECTION ACROSS SABER BAR

F ig . 4-15. Sec t ion a c r o s s Upper Cre taceous "D" Sandstone where it forms

an o i l -bea r ing b a r r i e r b a r known a s Saber F i e l d , Logan and

Weld Count ies , Colorado.

c o r r e l a t i o n of pe rmeab i l i t y i n f i v e wells shown.

from G r i f f i t h , 1966).

I n t e r n a l s t r u c t u r e i s sugges ted from

(Redrawn

209

along s t r i k e , so t h a t t h e geometry of t h e body i s t h a t of a connected s t r i n g

of pod-shaped, l e n t i c u l a r sandstone beds. The sandstone is micaceous and

very f ine-grained. Po ros i ty and permeabi l i ty a r e v a r i a b l e , t h e l a t t e r

ranging up t o 500 mi l l i da rcys . Reconstruct ion of t h e probable o r i g i n a l

shape of t h e Sabre sandstone body (Fig. 4-15) shows it t o be bar-shaped.

This i n t e r p r e t a t i o n is s u b s t a n t i a t e d by c o r r e l a t i o n of w e l l s ac ross the

body, which i n d i c a t e s t h a t t h e pe rmeab i l i t y inc reases upward, a cha rac t e r -

i s t i c a s soc ia t ed with b a r r i e r b a r s and o t h e r off-shore b a r s i n which t h e

g r a i n g rada t ion is from f i n e r below t o coa r se r above.

b

Wells in t h e Sabre F ie ld r e q u i r e hydrau l i c f r a c t u r i n g t reatment

i n o r d e r t o rpoduce o i l a t r a t e s o f 10-60 b a r r e l s p e r day, accompanied

by small flows of gas. Gas-oil and oi l -water con tac t s w i th in t h e sand-

s tone body appear t o be h o r i z o n t a l .


21 1

Chapter 5

TRANSGRESSIVE MARINE SHORELINE SAND

In t roduc t ion

Geomorphology

Transgressive marine s h o r e l i n e sand bodies a r e formed i n an inne r

n e r i t i c t o l i t t o r a l environment where t h e sea l e v e l i s r i s i n g r e l a t i v e t o

the land. The sand bod ies , which commonly coa le sce t o form discont inuous

s h e e t s of sand, grow landward over a d e l t a p l a i n o r an e r o s i o n a l su r f ace .

Depressions on t h e land s u r f a c e , such a s s t r i k e v a l l e y s f l ank ing cues t a s ,

are f i l l e d with sand.

sand may l eave only remnants w i th in these depressions. Where t h e remnants

a r e wi th in anc ien t s t r i k e v a l l e y s , t h e sand bodies form l i n e a r l e n s e s

p a r a l l e l t o t he s t r i k e of t h e underlying beds. These remnant, sand bodies

commonly tend t o be p a r a l l e l t o t h e s h o r e l i n e t r end of t h e sea i n which

they were deposi ted.

a c o a s t a l p l a i n o r f l a t e r o s i o n a l s u r f a c e , t h e i n d i v i d u a l sand bodies ,

formed a s beach r i d g e s , a l s o t r end along t h e coas t . Recognition of t h e

o r i g i n of sand bod ies , and t h e na tu re of t h e i r l i n e a r i t y , is e s s e n t i a l

t o r econs t ruc t ion of t h e paleogeographic and paleogeomorphic s i t u a t i o n s

t h a t may have a bea r ing on exp lo ra t ion f o r o i l and gas.

Se l l ey (1970, p. l l l ) , "Obviously a considerable understanding not only

of sedimentology but a l s o of geomorphology i s needed t o p r e d i c t t h e

l o c a t i o n of hydrocarbon r e s e r v o i r s i n t h e b a s a l sands of t r a n s g r e s s i v e

c l a s t i c sho re l ines" .

Subsequent e ros ion of a t r a n s g r e s s i v e shee t of

Where a shee t - l i ke complex of sand bodies t r ansg res ses

A s s t a t e d by

A d i s t i n c t i o n is drawn between sand bodies t r ansg res s ing over a

d e l t a p l a i n o r e r o s i o n a l su r f ace and sand bod ies , s i t u a t e d on a cont in-

212

ental shelf many miles from land, that are prograding toward the coast.

An example of the latter type is the Upper Cretaceous Eagle Sandstone of

Montana (Fig. 3-9). This sandstone unit exhibits all the characteristics

of a barrier bar complex, but was apparently growing toward a coast

situated more than 50 miles away (Shelton, 1965). A further distinction

must be drawn where transgressing marine sands over-ride alluvial sands.

There are examples where alluvial sand bodies have been mistaken for

marine sand bars, because of their shape. A case in point is the Lower

Cretaceous Ellerslie Sandstone in the Bellshill Lake Oil Field, Alberta

(Figs. 39 and 4 0 ) .

originally thought to be a sand bar flanked by marine to brackish-water

silty muds and limey beds containing forams and ostracods. Conybeare

(1964, 1972) and Martin (1966) showed the sandstone body to be a remnant

of an eroded alluvial terrace situated in a broad valley that was inundated

by brackish-water as the sea advanced southward. Other examples, where

interpretations of depositional environment must proceed with caution, are

cited by Selley (1970, p. 110) and Levorsen (1967, p. 336-337). Selley

cites Levorsen's references to the Lower Cretaceous Cutbank Sandstone of

Montana, and the basal sandstone of the Pliocene Quirequire Formation,

Venezuela, as examples of transgressive sand units. Both units are of

non-marine origin, the Cutbank filling channels of an ancient drainage

system (Fig. 1-51).

The producing sandstone body in this field was

Transgressive sheet-like units of marine sand are comparatively

Where transgression takes place over a delta the thin and widespread.

sands overlie coastal-marsh peat, bay muds, and distributary sands.

Where transgression is over an unconformity the sands overlie eroded

rocks, soils, and alluvial or lacustrine sediments. Transgressive sand

units are formed from the re-working of pre-existing sediments and soils,

from the erosion of sandstone headlands cropping out along beaches, and

213

from the accretion of sand carried from river mouths by longshore currents.

The last factor is probably of minor importance in a transgressive

situation in which the sediment load carried to the sea is probably

much lighter than in the regressive phase. The lower rate of sedi-

mentation in transgressive units results in a greater degree of

winnowing of the sediment, comparative thinness of the unit, and in

some situations is also reflected in a relatively high quartz content

of the sands.

E-log Characteristics

Transgressive, sheet-like units of sand are built up by the

gradual encroachment of a beach upon a land surface.

facilitated where the land surface is low-lying with respect to sea

level, such as on delta plains and other coastal lowlands. The

encroaching sand body includes a beach exposed at low tide and a

broad, sub-sea extension of the beach. Landward, in the zone of

strongest wave action, the beach sand is a mixture of coarser grain

sizes. Seaward, in deeper and quieter water, finer-grained sand is

deposited. In still deeper water, the sand grades into silts and muds

which, with continuing transgression of the beach, progressively buries

the sand unit. The physical principle involved in the differential

deposition of sand grains on a transgressive beach is the same as that

previously described with reference to the development of a prograding

barrier bar, except that in the former case, the depositional front is

migrating landward, and in the latter seaward.

Encroachment is

Grain gradation within a transgressive sandstone unit is from

finer above to coarser below. The same gradation is found in river

sand deposits such as channel-fill and point bar sand bodies. For this

reason, caution is necessary in the interpretation of some basal

214

sandstone units, and may in part explain why a sandstone such as the

Lower Cretaceous Cutbank Sandstone of Montana should have been referred

to as a transgressive unit (Selley, 1970, p. 110). Grain gradation is

not always evident, but where present is commonly reflected in the bell-

-shaped self-potential curve of the E-log. These characteristics of

transgressive sands are illustrated by Pirson (1970) in diagrams combining

self-potential curves and dipmeter plots. They are also shown by Pate

(1959) in E-log sections of the stratigraphic interval including the

transgressive Pennsylvanian Tonkawa Sandstone of the Anadarko Basin,

Oklahoma. Pirson further shows theoretical self-potential curves of the

regressive Point Lookout Formation and transgressive Cliff House Formation

of the Upper Cretaceous Mesaverde Group in the San Juan Basin of New

Mexico. These formations merge laterally, passing upward from a regressive

to a transgressive phase. Pirson states that the rapidity of transgression

can be gauged by the accentuation of the bell-shaped self-potential curve.

The accentuation is indirectly a measure of the degree of grain gradation

effected by winnowing which will be greater under more vigorous energy

conditions such as those existing along the shoreline of a rapidly

advancing sea.

Compaction

Transgressive marine shoreline sand bodies are comparatively thin

and widespread. They are deposited on the land surface of a coastal plain

which may be an erosional surface or the depositional surface of a delta.

Where the transgressive sand unit is lying on eroded rocks, compaction of

the overlying beds will have little or no effect on its geometry. The

important factor controlling the original geometry is the configuration of

the surface on which the sands are deposited. Subsequent erosion of the

overlying beds and of the sandstone unit itself will modify its geometry,

leaving isolated sandstone bodies such as wedges, strike valley lenses,

215

and sandstone patches in the older topographic depressions. Where

erosion of the underlying beds occurs, remnants of the sheet-like trans-

gressive sandstone unit may be left as cap rock on buttes and mesas.

Cessation of uplift and erosion, subsequent transgression of the sea, and

burial of the individual residual sandstone bodies by fine-grained

estuarine and marine sediments may result in the formation, by compaction

of the overlying sediments, of a number of potential reservoirs for oil

and gas.

Where the transgressing sand unit is lying on poorly consolidated

to unconsolidated sediments, such as clays and silts underlying the

surface of a delta coastal-plain, compaction of these underlying beds

may have a marked effect on the subsequent geometry of the unit. Gentle

variations in the dip of the sheet-like sand unit may reflect differences

of sand-mud ratio in various parts of the underlying pile of sediments

undergoing compaction. More accentuated variatic IS in dip may reflect

local draping of underlying clays over a deeper body of sand Fuch as a

barrier bar. Other factors influencing variations in the post-depositional

dip of a transgressive sand unit are compaction of the underlying pile of

sediments over basement topographic features, and penecontemporaneous

faults caused by mass slumping within the underlying section. The latter

may result in local deformation of the transgressive sand unit to form

monoclinal structures.

Ancient Sand Bodies

A classic exmaple of a transgressing sand is the Ordovician St.

Peter Sandstone of Minnesota. This friable sandstone is composed entirely

of well-rounded grains of quartz having a fairly uniform size. The

rounded quartz grains are pitted, a feature that has been regarded as

indicative of an eolian origin. The sandstone, as a unit, is remarkably

sheet-like; it has an average thickness of 23 m but ranges up to 90 m,

and covers an area of approximately 575,000 sq. km according to Dapples

(1955). The St. Peter is associated with shelf carbonates and was regarded

by Dapples as a continuous series of coalescent shoreline sands migrating

over a stable shelf. The Devonian Oriskany Sandstone of West Virginia,

a quartz arenite cemented by quartz to form an orthoquartzite, is also

considered to be a transgressive sandstone unit. These examples are

probably exceptional in that they are composed entirely of quartz grains,

although in general it can be said that transgressive sands are commonly

quartzose. Regressive sands are commonly lithic, but can also be quartzose,

as is the case with some present-day beach sands in the Gulf of Mexico.

The composition of river sands is a mixture of quartz and lithic grains,

with the former commonly predominant.

The origin of sands composed entirely of quartz grains is by no

means certain.

stones, from sand dunes, or from pre-existing sands. It is probable that

the sand grains in all such quartz sands have been re-cycled several times.

Arguments bearing on this problem are discussed by Pettijohn, Potter, and

Siever (1972, p. 224-225).

They may have formed from the erosion of quartzose sand-

Another classic example of a transgressive marine sandstone is the

Lower Cambrian Tapeats Sandstone exposed in the Grand Canyon of Arizona.

The Tapeats overlies Precambrain rocks, and is overlain by marine shales

of the Middle Cambrian Bright Angel Formation. Referring to the great

unconformity on which the Tapeats rests, McKee (1969, p . 79) says, "Its

record is plainly seen from many vantage points on the canyon rims, but

it is perhaps even more impressive where observed from closer sites along

the Colorado.

surface for a distance of miles; it bevels the upturned ends of schists

and other metamorphic rocks of early Precambrian time and is covered by

flat-lying strata of the Cambrian. Elsewhere it is seen as cross sections

In places this unconformity is a remarkably flat, even

21 7

of rugged h i l l s o r r i d g e s , some hundreds of f e e t h igh , of l a te Precambrian

q u a r t z i t e s and o t h e r r e s i s t a n t rocks , surrounded by and b u r i e d benea th

sed iments depos i t ed i n t h e Cambrian sea".

by t h i s unconformity is c i t e d by McKee, a f t e r estimates by Sharp ( 1 9 4 0 ) , t o

be 100 m i l l i o n yea r s .

The g r e a t span of t i m e r ep resen ted

The Tapea ts Sandstone i s desc r ibed by McKee (1969, p. 80) as fo l lows .

"The Tapea ts Sandstone is a massive, c l i f f - fo rming u n i t w i th a

th i ckness ranging from 100 t o 300 f e e t th roughout t h e canyon area. In

most p l a c e s i t i s choco la t e brown, bu t i n some p l a c e s i t is g rey o r cream-

-coloured and i n o t h e r s , a deep r e d brown. The sand i s coa r se t o medium

g ra ined ; coa r se p a r t i c l e s are dominant except i n p a r t s of t h e upper h a l f ,

where medium-size g r a i n s are more common. Bedding is conspicuous because

of c o n t r a s t s i n degree of cementa t ion t h a t cause l a y e r s t o weather i n t o

a l t e r n a t i n g r e s i s t a n t l edges and sha l low recesses. F l a t , even beds up t o

a few inches t h i c k a r e common, bu t by f a r t h e more abundant s t r u c t u r a l

f e a t u r e s is crossbedding w i t h i n l a y e r s ranging i n t h i c k n e s s from 4 t o 2

f e e t . Most c r o s s - s t r a t a are t a b u l a r p l a n a r o r wedge p l a n a r bu t l o c a l l y

some are of t rough type . Asymmetrical r i p p l e marks, t r i l o b i t e t ra i l s , and

p rob lema t i ca l worm bor ings are wide ly d i s t r i b u t e d and numerous a t some

l o c a l i t i e s . In many p l a c e s t h e Tapea ts grades upward i n t o t h e Br ight

Angel through a zone i n which coa r se sands tone beds a l t e r n a t e wi th green

s h a l y muds tones".


Transg res s ive marine s h o r e l i n e sand bod ies are known t o c o n t a i n

o i l and g a s , a l though more examples areknown i n r e g r e s s i v e sands .

MacKenzie (1970) has advanced t h e i d e a t h a t t h e percentage of good t r a p s

i n t r a n s g r e s s i v e sands tones should be h ighe r than i n r e g r e s s i v e sands tones ,

because t h e former are o v e r l a i n by less permeable marine s h a l e s , whereas

218

the latter are overlain by delta sands and silts which on compaction

would form a less effective seal. Argued on this basis MacKenzie has a

point, although it can be said that on the basis of statistics, the number

of known oil and gas reservoirs in regressive sandstone bodies considerably

exceeds the number known in transgressive bodies. A factor that probably

has considerable relevance to the hydrocarbon potential of transgressive

and regressive sedimentary sequences is the relative amounts of organic

matter incorporated with the sediments. In regressive sequences the

river systems drain large areas and carry organic matter as colloids and

macerated plant fragments. This organic matter is carried to the sea

where the macerated plant remains are deposited and the colloids are

precipitated by intermingling of fresh and salt water.

sediments deposited in brackish-water bays and coastal swamp environments

are rich in organic matter, both plant and animal.

on the other hand, are commonly deposited over flat coastal areas that

border on lowlands from which little sediment or organic matter is being

Also, the delta

Transgressive sequences,

derived. The transgressive nature of the coastline itself, subject to

active erosion by wave action, is not conducive to the growth of coastal

swamps, nor to the many forms of organisms that thrive in more protected

environments. Furthermore, high energy environments are not conducive to

the retention of organic matter in muds.

A third consideration is the nature of the surface over which the

sand unit is transgressing. Where the surface is erosional and underlain

by consolidated material and bedrock, the source of oil or gas that

subsequently becomes entrapped in the transgressive sand unit is probably

within the overlying marine sediments. But where the surface is a delta

plain underlain by unconsolidated, organic-rich muds and silts, the

source may be either the underlying deltaic sequence of the overlying

marine sediments.

21 9

It is of interest to note that the first significant flow of oil

in Australia, although not the first discovery, was obtained in 1953 from

a Lower Cretaceous transgressive unit in Western Australia, the Birdrong

Sandstone.

oil at rates of up to 600 barrels per day, but later proved to be non-

-commercial. The accumulation within the Birdrong, a sheet-like sandstone

unit unconformably overlying Jurassic and older rocks, is located in a

structure formed by draping of the sandstone over an elongate buried hill.

The Birdrong, a clean quartzose sandstone, is glauconitic in its upper

part. It has good porosity and permeability and is the main fresh-water

artesian aquifer in the Carnarvon Basin.

The well, Rough Range No. 1, initially flowed 30' A.P.I. waxy

Yardarino-Dongara Gas Field, Western Australia

In the Yardarino-Dongara Field of Western Australia gas and oil are

produced from the basal Yardarino Sandstone of the Lower Triassic Kockatea

Formation. This sandstone, which lies unconformably on Precambrian and

Permian beds, is a transgressive marine unit.

quartzose, very fine to coarse-grained sandstone with conglomeratic layers.

In the field area the sandstone is about 55 m thick and is overlain by

marine shales. Porosity ranges up to 25% but averages about 17%; permeability

ranges up to several thousand millidarcys, but is comonly in the range

100-700 millidarcys .

It consists 0) light grey,

The field is essentially a structural-stratigraphic trap, the

Yardarino Sandstone showing marked thinning over a basement erosional

high. Production consists mainly of gas containing approximately 97%

methane, with a condensate content of up to 15 barrels per million cubic

feet of gas, and minor quantities of 35' A.P.I. waxy oil. Producible

gas reserves are estimated (Cope, 1972) to be in the order of 500,000

million cubic feet (14,000 million cubic metres) containing a minimum

220

of 500,000 b a r r e l s (79,500 cub ic met res ) of condensa te . Formation water

unde r ly ing t h e g a s and o i l is b r a c k i s h t o s a l t y .

Red Oak, Wi lber ton , and Kin ta Gas F i e l d s , Oklahoma

Gas product ion i n t h e Red Oak, Wi lber ton , and Kin ta f i e l d s of t h e

McAl is te r Bas in , Oklahoma, is ob ta ined from sands tones a t t h e b a s e , and

i n t h e lower s e c t i o n of t h e Lower Pennsylvanian Atoka Formation. The

b a s a l s ands tones , termed t h e F o s t e r Sand, c o n s i s t o f fou r s e p a r a t e b e l t s

t r e n d i n g t o t h e s o u t h e a s t (F ig . 5-1). These l i e unconformably, i n

e r o s i o n a l d e p r e s s i o n s , on l imes tones and s h a l e s of t h e Pennsylvanian

Wapanucka Formation. The Fos t e r Sand, which has a t h i c k n e s s of up t o 9 m ,

is composed predominantly of well-rounded, f i n e t o medium q u a r t z g r a i n s .

N

0 20

K M

DLSTRIBUTARY A N D S H O R E L I N E S A N D

T R E N D S , P E N N S Y L V A N I A N A T O K A F M ,

O K L A H O M A

F i g . 5-1. Fos te r Sand t r ends 1 , 2 , 3 and 4 , formed as d i s t r i b u t a r i e s

f i l l i n g e r o s i o n a l d e p r e s s i o n s , o v e r l a i n by no r theas t - t r end ing

s h o r e l i n e Sp i ro Sand ranging i n th i ckness t o 100 f e e t (30 m).

The F o s t e r i s t h e lowes t number of t h e Lower Pennsylvanian

Atoka Formation, Mdl i s t e r Bas in , e a s t e r n Oklahoma. (Redrawn

from Lumsden, P i t tman and Buchanan, 1 9 7 1 ) .

221

It i s commonly cross-bedded and c o n t a i n s s h a l e c l a s t s and f ragments of

f o s s i l wood. The o r i g i n of t h i s b a s a l sands tone u n i t is e v i d e n t l y

a l l u v i a l , t h e sands having been depos i t ed i n a system of p a r a l l e l r i v e r

d i s t r i b u t a r i e s t h a t t rended s o u t h e a s t a c r o s s a c o a s t a l p l a i n t h a t w a s a t

l e a s t 60 km i n wid th . Some gas p roduc t ion , i n c l u d i n g t h a t of t h e Kin ta

F i e l d , i s ob ta ined from t h e F o s t e r Sand.

The F o s t e r Sand is o v e r l a i n by t h e S p i r o Sand, a t r a n s g r e s s i v e

marine u n i t up t o 30 m t h i c k . The Sp i ro forms an e l o n g a t e sands tone u n i t

t h a t t r e n d s southwes t , normal t o t h e F o s t e r t r e n d , f o r more than 100km.

The Sp i ro Sand is a l s o q u a r t z o s e , p robably having been i n l a r g e p a r t

de r ived from t h e F o s t e r Sand. I t i s moderately w e l l s o r t e d , and ve ry

f i n e t o f ine -g ra ined . A s a whole, t h e Spi ro is r e f e r r e d t o as a b l anke t

s ands tone b u t c o n s i s t s of mass ive , l e n t i c u l a r beds , depos i t ed as s h o r e l i n e

sand b o d i e s , i n t e rbedded wi th t h i n l a y e r s of s i l t y sands tone and s h a l e .

Low-angle cross-bedding and b i o t u r b a t i o n have been desc r ibed , t h e former

probably r e s u l t i n g from v a r i a t i o n s i n d e p o s i t i o n a l s l o p e s of ,the seaward

ex tens ions of beaches .

The Sp i ro Sand, which t r ansg res sed t o t h e no r thwes t , is n o t uniformly

developed, some l o c a l i t i e s a long i t s t r end be ing t h i c k e r and more permeable.

Dry gas accumula t ions , which are l a r g e l y r e l a t e d t o s t r a t i g r a p h i c c o n t r o l ,

i nc lude t h e Red Oak and Wilburton F i e l d s .

Morrow O i l F i e l d s , Oklahoma

O i l p roduc t ion from s e v e r a l f i e l d s i n t h e Anadarko Basin of

Oklahoma is ob ta ined from t h e Cherokee Sandstone, t h e b a s a l u n i t of t h e

Lower Pennsylvanian Morrow Formation. The Cherokee, which l i e s unconfor-

mablg on M i s s i s s i p p i a n beds of l imes tone and s h a l e (F ig . 5-Z), is a

marine t r a n s g r e s s i v e u n i t t h a t forms a co r ruga ted s h e e t of sands tone

comprising p a r a l l e l t r e n d s a long which t h e sands tone is t h i c k e r .

222

-. LS. DATUM

200

SEA LEVEL

MILE

North L

SANDSTONE CHARACTERISTICS I LENGTY MANY MILES

2 WIDTH, ONE -HALF TO ONE MILE

3 BICONVEX

4 ABRUPT SEAWARD PINCHOUT

5 TRANSITIONAL LANDWARD PINCHOUT

(I TWO OR MORE SAND BODIES ARE SUBPARALLEL

7 TRENDS CONTROLLED BY W S T - M I S S . STRUCT,

NOT PRESENT STRUCTURAL GRAIN

Fig . 5-2 E-log s e c t i o n (a ) and gene ra l i zed b lock diagram (b) showing

a , b . r e l a t i o n s h i p of o i l -bea r ing Pennsylvanian Cherokee Sandstone,

developed as s t r i k e - v a l l e y sands , t o c u e s t a s formed on eroded

s u r f a c e of t h e Miss i s s ipp ian i n Anadarko Bas in , Oklahoma.

(Af t e r Busch, 1959).

223

Depending on whether the top or bottom of the sandstone unit is taken as

a datum, these thick trends appear respectively as topographic depressions

or as ridges. The interpretation placed on them by Busch (1959) is that

they are bar-shaped sand bodies deposited in erosional depressions at the

base of cuestas formed by unequal erosion of outcropping layers of

limestone and shale.

Busch (1959, p. 2832) says, "Strike valley sands derive their name from

the fact that they are deposited in the low areas between cuestas at the

As such, they can be defined as strike valley sands.

rig. 3 - 3 . isopacn map or incervai LaDove (+) or below ( - ) J between a

datum and the top of a sandstone unit in the Pennsylvanian

Morrow Formation, northwestern Oklahoma. Figure shows

known (black) and inferred (hatchured) oil fields developed

where sand ridges are intersected by northwest-plunging folds.

(After Busch , 1959).

224

time the land surface is inundated by a transgressive sea. Such cuestas

may be either erosional escarpments or fault-scarps.''

These thick, linear sandstone bodies are lenticular in section,

ranging in width up to 3 km,in thickness to 1 5 m, and in length to 65 km.

They terminate fairly abruptly along the thicker edge where they merge

into a shale facies, the landward edge pinching out on the flank of each

cuesta. These parallel sandstone lenses are intersected by northwest-

-plunging folds which form structural closures within the sandstone at

some of the intersections. Within these closures oil has accumulated to

form two parallel strings of separate pools (Fig. 5 - 3 ) .

Milligan Oil Field, British Columbia

In the Milligan Oil Field of northeastern British Columbia,

production is obtained from the Upper Triassic Halfway Sandstone. The

Halfway unconformably overlies silty dolomite beds of the Doig Tormation,

and is overlain conformably by silty dolomite beds of the Charlie Lake

Formation (Fig. 5-6). It has a linear northwest trend and is lenticular

in section (Figs 5-4 , 5 - 5 ) . In the field area this trend, which bifurcates

into two parallel but connected sub-trends, is known to have alength of

more than 80 km.

overall width of the main trend ranging up to 10 km.

Each sub-trend has a width of approximately 3-5 km, the

In the Milligan Field the gross thickness of the Halfway ranges

up to 15 m. The sandstone is quartzose and fine to very fine-grained,

except at the base which is commonly gritty. The grains are sub-angular

to sub-rounded. Porosity ranges up to 28%, but averages 2 2 % , and

permeability is in the range 400-600 millidarcys (Clark, 1 9 6 1 ) . The

E-log (Fig. 5-6) of the Halfway is characterized by a blocky, slightly

bell-shaped self-potential curve. Both top and bottom boundaries are

225

F i g . 5-4. I s o p a c h map o f t h e o i l - b e a r i n g Upper T r i a s s i c H d f w a y Sands tone ,

B r i t i s h Columbia. S t r u c t u r e c o n t o u r s show t h e c o n f i g u r a t i o n of

t h e b a s e of t h e s a n d s t o n e . (Redrawn from M o t h e r s i l l , 1968) .

loo,..

0 MILES

o - - - 4 K M

MILLIGAN FIELD

L I.

NORTH 4

I

4 1

B C

F i g . 5-5. S t r a t i g r a p h i c s e c t i o n t h r o u g h t h e X i l l i g a n F i e l d , B r i t i s h

Columbia, showing i n f e r r e d c o n f i g u r a t i o n of t h e o i l - b e a r i n g

Upper T r i a s s i c Halfway Sands tone a t t h e t i m e of d e p o s i t i o n .

(Redrawn from C l a r k , 1961) .

226

UNION- H B d - 5 4 - G

1 1 CHARLIE LAKE FM

E -LOG, MlLLlGAN FIELD

Fig. 5-6. Typ ica l E-log of t h e Upper T r i a s s i c Halfway Sandstone

i n t e r v a l i n Union - H.B. d-54-G, Y i l l i g a n F i e l d , B r i t i s h

Columbia, showing t h e blocky c h a r a c t e r i s t i c of t h e s e l f -

p o t e n t i a l cu rve , and t h e o i l -wa te r con tac t . (Redrawn from

C l a r k , 1961).

sha rp . The b locky c h a r a c t e r r e f l e c t s t h e e x c e l l e n t s o r t i n g of f i n e - t o

ve ry - f ine q u a r t z g r a i n s , and t h e s l i g h t d e f l e c t i o n a t t h e base r e f l e c t s

a t h i c k g r i t t y l a y e r .

beds commonly d ipping a t ang le s of less than 20° ( M o t h e r s i l l , 1968).

The ampl i tudes of t h e cross-beds range from less than an inch t o s e v e r a l

i n c h e s , p l a c i n g them i n t h e sma l l t o medium s i z e ca t egory (Conybeare and

Crook, 1968) of r i p p l e s formed by c u r r e n t s . In t h e sou the rn p a r t of t h e

Halfway Sandstone t r e n d , i n t h e v i c i n i t y of t h e Pee jay and Curran t o i l

f i e l d s , t h e upper p a r t of t h e Balfway, which is t h e o i l -bea r ing s e c t i o n

i n t h e s e f i e l d s , c o n t a i n s t h i n beds of coquina c o n s i s t i n g mainly of

b i v a l v e s h e l l s .

Cross-bedding i s a n o t a b l e f e a t u r e , t h e f o r e s e t

In t h e Mi l l i gan F i e l d area t h e Doig Formation, which unconformably

u n d e r l i e s t h e Halfway Sandstone, d i p s southwest a t 7 m/km, whereas t h e

221

Halfway d i p s southwest a t about 5 m/km. Th i s r e l a t i o n s h i p sugges t s t h a t a t

t h e t i m e of d e p o s i t i o n of t h e Halfway, t h e Doig beds must have had a

sou thwes te r ly d i p of about 2 m/km.

o u t a long t h e f o o t h i l l s of n o r t h e a s t e r n B r i t i s h Columbia and th i ckens

southwestward i n t h e subsu r face . Although t h e Halfway w a s depos i t ed as

an i r r e g u l a r s h e e t of s and , du r ing a pe r iod of marine t r a n s g r e s s i o n t o

t h e n o r t h e a s t , i t s l i n e a r t r e n d s , cur ren t -bedding c h a r a c t e r i s t i c s , and

c o a r s e r b a s a l l a y e r raises problems concern ing t h e r e l a t i o n s h i p s of t h e

sand body geometry t o i t s pa leogeographic s e t t i n g . I n p a r t i c u l a r , i t is

p e r t i n a n t t o know whether , i n t h e ' 4 i l l i gan F i e l d area, t h e sands tone t r ends

r e p r e s e n t d e p o s i t i o n as s h o r e l i n e sand b a r s o r a s d i s t r i b u t a r i e s . The use

of s e v e r a l datums i n t h e c o n s t r u c t i o n of s t r a t i g r a p h i c s e c t i o n s d e p i c t i n g

t h e d e p o s i t i o n a l r e l a t i o n s h i p s o f t h e Halfway sugges t d i f f e r e n t poss i -

b i l i t i e s . Probably t h e most r easonab le i n t e r p r e t a t i o n (C la rk , 1961),

u s ing a datum j u s t above t h e Halfway, shows t h e sand bod ies f i l l i n g

dep res s ions , i n t e r p r e t e d as s t r i k e - v a l l e y s , i n t h e under ly ing Doig

Formation. Pa ra l l e l sub- t rends of t h e Halfway i n t h e Mi l l i gan F i e l d

area are thought t o have r e s u l t e d from concen t r a t ion of sand i n s e p a r a t e

s t r i k e - v a l l e y s between c u e s t a s a long t h e coas t . Subsequent s t r u c t u r a l

deformat ion of t h e s e t r e n d s has formed s e v e r a l t r a p s f o r o i l , i nc lud ing

t h e M i l l i g a n F i e l d .

The lower p a r t of t h e Halfway crops

Horseshoe O i l F i e l d , New M e x i

The Horseshoe F i e l d of t h e San Juan Bas in , New Mexico, y i e l d s o i l

from t h e b a s a l sands tone u n i t of t h e Upper Cretaceous Niobrara Formation.

This s ands tone l i e s unconformably on g e n t l y fo lded beds of sandy s h a l e , and

l imes tone which c o n s t i t u t e p a r t of t h e Upper Cre taceous Gallup and C a r l i l e

Formations. D i s t r i b u t i o n of t h e sands tone shows a marked p a r a l l e l i s m of

l e n t i c u l a r t r e n d s , r e s u l t i n g from concen t r a t ion of t h e o r i g i n a l sand i n

s t r i k e v a l l e y s f l a n k i n g c u e s t a s formed by d i f f e r e n t i a l e r o s i o n of s h a l y

and sandy beds benea th t h e unconformity (F igs . 5-7 and 5-8).

228

KM 0 F E E T 0 1

1

M I L E

C R O S S - S E C T I O N S OF B A S A L NIOBRARA SANDSTONE

H O R S E S H O E FIELD, N E W MEXICO

Fig. 5-7. S t r a t i g r a p h i c c ros s - sec t ions of t h e Upper Cretaceous b a s a l

Niobrara Sandstone i n t h e Horseshoe o i l f i e l d , San Juan Basin,

New Mexico.

eroded s u r f a c e of t h e Gal lup Formation and C a r l i l e Formation

The sand bod ies w e r e formed along cues t a s on t h e

during cransgression of the Niobrara sea. (&dram from

P e n t t i l a , 1964).

Work by P e n t t i l a (1964) and McCubbin (1969) e s t a b l i s h e d t h e

d e p o s i t i o n a l and s t r a t i g r a p h i c r e l a t i o n s h i p s of t he b a s a l Niobrara Sand-

s tone which they b e l i e v e t o have been depos i t ed as a s h o r e l i n e sand by a

t r a n s g r e s s i v e sea.

f a c t t h a t t h e unconformity which underl ies the Niobrara and b e v e l s t h e Gallup,

w a s p rev ious ly no t recognized.

w a s thought t o be equ iva len t t o t h e b a s a l Gallup Sandstone.

t h a t i n d i v i d u a l sandstone bodies are l o c a l i z e d on t h e seaward s i d e of

c u e s t a s , t h e s t e e p e r s lopes of which faced seaward.

t h e s e cues t a s formed r i d g e s which temporar i ly impeded t r a n s g r e s s i o n ,

r e s u l t i n g i n a s t a t i o n a r y s h o r e l i n e , w i th t h e consequent depos i t i on of

a t h i c k e r body of sand.

The importance of t h i s i n t e r p r e t a t i o n l ies i n t h e

Consequently, t h e b a s a l Niobrara Sandstone

McCubbin says

A s t h e sea advanced,

229

Fig. 5-8. Generalized diagram showing the stratigraphic relationship

of the Upper Cretaceous basal Niobrara Sandstone to cuestas

and strike-valleys formed on the eroded surface of the Upper

Cretaceous Carlile Formation during transgression of the

Niobrara sea. (Modified by MacKenzie, 1972, after McCubbin,

1969).

The basal Niobrara Sandstone in the Horseshoe Field area comprises

three units which lie in different stratigraphic positions resulting from

deposition against separate ridges at various times during the overall

period of marine transgression. The oldest unit is the lower reservoir

in the Horseshoe Field.

distance of more than 40 km.

trend has a width of 6 km, and a thickness of up to 15 m. It divides

to the northwest into two separate oil-bearing trends, the Many Rocks and

Mesa, each of which has a width of about 2 km.

This sandstone body strikes southeast for a

The main sandstone body in the Horseshoe

230

The Niobrara is t e x t u r a l l y v a r i a b l e , grading from f i n e t o coarse-

-grained. Average p o r o s i t y and pe rmeab i l i t y a r e 15% and 175 mi l l i da rcys

r e s p e c t i v e l y . Thin s t r i n g e r s of coa r se , pebbly sandstone a r e common i n

s e c t i o n s where t h e sandstone is gene ra l ly f ine-grained. In t e rbeds of

dark s h a l e a r e a l s o p resen t . McCubbin (1969, p. 2122) s t a t e s , "The most

no tab le compositional f e a t u r e s o f t h e sandstone a r e t h e b r i g h t green

g l aucon i t e g r a i n s , which compose a s much a s 10 percent of t h e rock, and

t h e very common and widespread phosphat ic nodules and pebbles".

sandstone a l s o con ta ins Inoceramus, Os t r ea , shark t e e t h and bone fragments

In t h e s h a l y beds, b i o t u r b a t i o n is a common f e a t u r e .

The

The sandstone is commonly cross-bedded, i nd iv idua l s e t s ranging

i n th i ckness from a few cen t ime t re s i n t h e subsurface t o more than a

metre i n outcrops. The d i p s of t hese cross-beds exceed 20°, i n d i c a t i n g

t h e i r d e r i v a t i o n as current-bedded sands. The depos i t i ona l environment

is ind ica t ed t o have been one of f a i r l y high energy on beaches, probably

a s soc ia t ed wi th t i d a l channels c u t t i n g through sand b a r s a+ re-working

sands i n l o c a l i n l e t s .

In t h e Horseshoe F ie ld t h e o l d e s t sandstone member of t h e Niobrara

forms a long, narrow body t h a t t r ends sou theas t f o r up t o 60 km toward

t h e Cha Cha F i e l d which a l s o produces o i l from t h e Niobrara.

of o i l and gas has r e s u l t e d from s t r a t i g r a p h i c f a c t o r s modified l o c a l l y

by s t r u c t u r e . A t most l o c a t i o n s , pinch-out of t h e sandstone body is

s o l e l y r e spons ib l e ; i n o t h e r s t h e accumulation of gas , i n p a r t i c u l a r , has

r e s u l t e d from t h e i n t e r s e c t i o n of t h e sandstone body t r end with no r theas t -

-plunging fo lds . In t h e Horseshoe-Mesa F i e l d s t h e gas -o i l column exceeds

990 m (McCubbin, 1969). The est imated u l t ima te recovery of o i l from t h e

Horseshoe-Mesa and Many Rocks f i e l d s i s i n excess of 46 m i l l i o n b a r r e l s

( 7 . 3 m i l l i o n cubic metres) . An a d d i t i o n a l e s t ima te of 13 m i l l i o n from t h e

Cha Cha F i e l d suggests t h a t t he lower u n i t a lone of t h e Niobrara Sandstone

Entrapment

231

w i l l u l t i m a t e l y y i e l d more than 60 m i l l i o n b a r r e l s (9 .5 m i l l i o n cub ic

met res ) of o i l .

Carbon Gas F i e l d , A lbe r t a

The Carbon Gas F i e l d of A l b e r t a (F ig . 5-9) produces from t h e

Carbon Sandstone of t h e Lower Cre taceous Mannville Group. This sands tone

i s t h e approximate s t r a t i g r a p h i c equ iva len t of t h e widespread Glaucon i t e

Sands tone , a marine t r a n s g r e s s i v e sands tone u n i t w i t h i n t h e Mannville

Group. In o t h e r a r e a s of A l b e r t a , t h e s t r a t i g r a p h i c zone equ iva len t t o

t h e Glauconi te sands tone i n c l u d e s sands tone members known by o t h e r names.

The marine Home Sand of Turner Val ley i n southwes tern A l b e r t a , t h e

Wabiskaw member of n o r t h - c e n t r a l A l b e r t a , t h e g l a u c o n i t e sands tone a t

t h e base of t h e Clearwater Formation i n n o r t h e a s t e r n A l b e r t a , and t h e

Bluesky Sandstone of t h e Peace River a r e a i n wes t - cen t r a l A lbe r t a a r e

a l l cons ide red by Workman (1958) t o be s t r a t i g r a p h i c e q u i v a l e n t s of t h e

Glauconi te Sandstone.

20

'0

GEOMETRY OF C A R B O N GAS 0 5

5 S A N D , ALBERTA

~ KM

0,- . ~~ 2

M I L E S

Fig . 5-9. Isopach map of n e t porous sands tone i n t h e producing sand-

s t o n e of t h e Ear ly Cre taceous Mannville Group, Carbon G a s

F i e l d , Alber ta . Contour i n t e r v a l i n f e e t (1 ' = 0.305 m).

(Redrawn from Workman, 1968).

232

The Glauconite Sandstone i s a p e r s i s t e n t s t r a t i g r a p h i c uni t over

much of c e n t r a l Alberta. It over l ies the Ostracod Member (a t h i n

a rg i l laceous limestone containing a brackish water fauna) and cons is t s

of one o r more glauconi t ic sandstone bodies. Over a wide area the comp-

o s i t i o n and tex ture of the Glauconite Sandstone shows considerable var ia t ion .

It is e s s e n t i a l l y a fine-grained quartzose sandstone containing var iab le

amounts of l i t h i c cons t i tuents . East of the F i f th Meridian and south of

Edmonton the Glauconite Sandstone is commonly not glauconi t ic . Glaister

(1959, p. 623) s t a t e s , "The member is predominantly marine i n the Edmonton

area but becomes more non-marine toward the south and gradually loses i t s

l i t h o l o g i c ident i ty" .

commonly i n the order 6-9 m but ranges up t o more than 30 m , changes

markedly over a dis tance of a few kilometres. This i s p a r t i c u l a r l y

not iceable i n the area lying e a s t of t h e F i f t h Meridian where the sands

are commonly a l l u v i a l . In t h e Carbon and Ghost Pine gas f i e l d s f o r

example, the producing sandstones a r e non-glauconitic and vary i n thickness

The thickness of the Glauconite member, which i s

within the range 6-25 m. East of the F i f t h Meridian, the a l l u v i a l sand-

s tones t h a t a r e the approximate s t r a t i g r a p h i c equivalent of the Gl.auconite

Sandstone t rend northwest, west, and southwest. The t rends were formed by

a r i v e r system draining lowlands ly ing t o the e a s t . West of the F i f t h

Meridian the Glauconite Sandstone is general ly glauconi t ic and contains

a higher percentage of l i t h i c fragments. In t h i s region, the sandstone

bodies f r inge a marine shorel ine trending approximately north-northwest.

I n the area of the Carbon Gas F ie ld , the Carbon Sandstone,

encountered a t a depth of 1,460 m, cons is t s of severa l l e n t i c u l a r

sandstone bodies separated by shaly layers . These sandstone bodies,

which t h i n and become less porous, t o the e a s t , form a northwesterly-

-trending b e l t up t o 5 km i n width and 25 km i n length. The Carbon

Sandstone l ies approximately 15 m above t h e Ostracod member, and 15-23 m

feet below a coal seam. It ranges in thickness from 6 to 25 m, the maximum

net-porous sandstone being in the range 12-15 m. The basal sandstone body

is thicker and coarser than the upper bodies, a relationship indicated by

the bell-shaped self-potential curve of E-logs of the producing zone in

the Carbon field. The sandstone is generally quartzose, fine to medium-

-grained, fairly well sorted,and predominantly of sub-angular grains.

Porosity is in the range 15-25%, averaging 21%. Permeability ranges up to

3,000 millidarcys but averages only 80 millicarcys.

The Carbon Sandstone has been placed in the category of trans-

gressive sands because it was deposited during a period of widespread

inundation of alluvial-deltaic sediments by the Early Clearwater sea

transgressing to the south. The beds adjacent to the Carbon Sandstone,

both above and below, contain arenaceous forams, suggesting an inner

neritic environment such as a salt-water bay of tidal estuary. Smooth-

-shelled ostracods within an underlying stratigraphic unit comprising two

or more thin, discontinuous layers of argillaceous limestone, indicate

local brackish-water conditions. Overlying coal seams must have been

formed by the accumulation of vegetation in coastal marshes. The

paleogeomorphic origin of the Carbon Sandstone is not known, but it may

have been formed from bodies of sand, filling a tidal channel on a coastal

plain.

Regional dip of the strata in the Carbon Gas Field area is

westerly; and within the field, a stratigraphic marker at the top of the

Carbon Sandstone interval indicates a local monoclinal structure.

Entrapment of gas may in part be controlled by this structure, although

the field is considered to be essentially a stratigraphic trap.

gas in place is estimated to be 155 billion (thousand million) cubic feet,

of which 130 billion (3,640 million cubic metres) will ultimately be

recovered.

Initial


235

Chaptei 6

SUBMARINE VALLEYS


Geomorphology

The e x i s t e n c e of pr fsen t -day submarine v a l l e y s on c o n t i n e n t a l

s h e l v e s and s l o p e s h a s been known f o r many y e a r s .

t h e advent o f marine seismic surveys t h a t a n c i e n t v a l l e y s , commonly

bu r i ed by T e r t i a r y t o Quaternary sed iments , could be demonstrated.

Present-day v a l l e y s t r e n d seaward from t h e landmass, some appa ren t ly

forming d e n d r i t i c p a t t e r n s , b u t o t h e r s fo l lowing b road ly s inuous o r

a r c u a t e cour ses . Although some submarine v a l l e y s are known t o b i f u r c a t e

But i t was n o t u n t i l

SUNDA SHELF VALLEYS

Fig . 6-1. I n f e r r e d d e n d r i t i c p a t t e r n of submarine v a l l e y s on t h e

Sunda Shel f o f f t h e coas t of Indones ia . (Redrawn from

Kuenen. 1950).

236

a t t h e i r landward e x t r e m i t i e s , t h e development of d e n d r i t i c p a t t e r n s i s

open t o ques t ion . An example i s t h e Sunda Shel f of Indones ia (Fig. 6-1).

During t h e P l e i s t o c e n e much of t h e Sunda Shel f w a s a landmass, and t h e

i n f e r r e d d e n d r i t i c system of submarine v a l l e y s , as i n t e r p r e t e d by

Molengraaff (1922), i s thought t o have o r i g i n a t e d as a f l u v i a l s t r eam

system. Molengraaff gave t h e name Sunda River t o t h e main v a l l e y i n t h e

n o r t h e r n d e n d r i t i c system. H i s i n t e r p r e t a t i o n was endorsed by Kuenen

(1950) who r e f e r r e d t o t h e s e submarine v a l l e y s a s drowned r i v e r channels

deepened by t i d a l s cour . Shepard and D i l l (1966), however, d i d n o t accep t

t h i s exp lana t ion wi thou t r e s e r v a t i o n and po in ted o u t t h a t i n t e r p r e t a t i o n s

based on t h e p o s s i b l e e x i s t e n c e of a d e n d r i t i c p a t t e r n a r e somewhat

s p e c u l a t i v e .

Some submarine v a l l e y s and canyons ex tend t o t h e upper p a r t s of a

c o n t i n e n t a l s h e l f , o t h e r s a r e conf ined t o t h e r eg ion of t h e c o n t i n e n t a l

s lope . Many l a r g e r i v e r s t e rmina te a t t h e upper r eaches of submarine

v a l l e y s which may, i n p a r t , owe t h e i r genes i s t o t h e r i v e r ' s development

du r ing some ear l ier pe r iod when sea l e v e l w a s lower and much of t h e

c o n t i n e n t a l s h e l f w a s exposed a s a c o a s t a l p l a i n .

v a l l e y s have no appa ren t r e l a t i o n s h i p t o any p r e s e n t o r p rev ious r i v e r

sys tem, and t h e i r genes i s i s n o t understood. They may have been formed

by submarine c u r r e n t s sweeping down t h e c o n t i n e n t a l s l o p e . Such c u r r e n t s

could have r e s u l t e d from t i d a l a c t i o n in f luenced by C o r i o l i s fo rce .

Submarine canyons, having formed by whatever mechanisms, a r e t h e p re sen t -

-day cour ses f o r s t r o n g c u r r e n t s which a r e p e r i o d i c a l l y augmented by

t u r b i d i t y c u r r e n t s f lowing down t h e lower r eaches . Hypotheses concern ing

t h e o r i g i n s of submarine v a l l e y s and canyons are d i scussed by Kuenen

(1950, 1953) , and a r e e x t e n s i v e l y d e a l t w i th by Shepard and D i l l (1966).

Other submarine

Scho l l and Hopkins (1968, p . 266) , i n d e s c r i b i n g t h e g i g a n t i c

submarine canyons of t h e Bering Sea , s ay t h a t a l though t h e i r l o c a t i o n ,

231

t r e n d , and gene ra l shape a r e s t r u c t u r a l l y determined, e ros ion of t h e

canyons was e f f e c t e d by s l i d i n g masses of sediment which began t h e i r

movements i n t h e Late T e r t i a r y , a ided by t h e s l u i c i n g of f l u v i a l sediment

from a l a r g e r i v e r .

Canyon, t h e world 's l onges t known submarine s lope v a l l e y , and Zhemchug

Canyon, poss ib ly t h e wor ld ' s l a r g e s t , i n c i s e the no r theas t e rn c o n t i n e n t a l

margin of t h e Bering Sea.

t h i s margin and a l s o is very l a r g e i n comparison t o most submarine canyons.

Bering Canyon i s n e a r l y 400 km i n l eng th and has a volume of about 4300 km3.

Zhemchug Canyon has a volume of n e a r l y 8500 km3, and i s 15 t o 20 t imes

l a r g e r than t h e most " large" submarine canyons ( f o r example, Monterey

Canyon).

unusual headward b i f u r c a t i o n t h a t has con t r ibu ted t o t h e formation of

deep, e longated, outer-shelf basins".

They desc r ibe these canyons a s fo l lows , "Bering

A t h i r d v a l l e y , P r i b i l o f Canyon, also c u t s

Zhemchug and P r i b i l o f Canyons a r e f u r t h e r d i s t ingu i shed by an

Of p a r t i c u l a r i n t e r e s t t o petroleum geo log i s t s i s t h e presence of

coa r se , well-washed, ripple-marked sand wi th in submarine val$eys (Heezen

and H o l l i s t e r , 1 9 7 1 ; Shepard and Marshal l , 1 9 7 3 ) . These sands a r e worked

by c u r r e n t s t h a t flow w i t h i n t h e v a l l e y s . In t h e case of canyons o f f t h e

coas t of C a l i f o r n i a , Shepard and Marshall (1973) record c u r r e n t s of less

than 50 cm/sec t h a t a l t e r n a t e l y flow up and down t h e canyons during

pe r iods ranging from 20 minutes t o 12 hours. The n e t movement of t h e sand

i s down t h e canyons. Shepard and Marshall s t a t e , p . 257 , "We a r e not ye t

i n a p b s i t i o n t o a s s ign d e f i n i t e causes t o t h e canyon-floor c u r r e n t s . It

i s obvious t h a t a t most deeper water s t a t i o n s t h e t i d e s have an important

i n f luence . However, t he much s h o r t e r cyc le s , with a peak around 4 hours

(Marshall, i n prep.) a r e not r e l a t e d t o t h e t i d e s . These s h o r t e r cyc le s

can b e s t be explained by i n t e r n a l waves".

The n a t u r e and s t r a t i g r a p h i c sequence of sediments f i l l i n g a

submarine v a l l e y o r canyon w i l l depend on s e v e r a l f a c t o r s r e l a t e d t o the

composition of sou rce mater ia l and t h e dynamics of t h e environment.

Inc luded i n t h e s e f a c t o r s , which o b t a i n i n vary ing degrees a t d i f f e r e n t

p o i n t s a l ang t h e cour se of a submarine v a l l e y , are t h e r e l a t i v e volumes

of sediment of v a r i o u s s i z e grades be ing t r a n s p o r t e d , t h e rates of

s ed imen ta t ion , t h e c u r r e n t v e l o c i t i e s , and t h e rates a t which sea l e v e l

may r ise o r f a l l . These f a c t o r s a r e i n t e r - r e l a t e d du r ing pe r iods of normal

sed imen ta t ion . I n t e r u p t i o n s by t u r b i d i t y c u r r e n t s i n t roduce o t h e r f a c t o r s

c h a r a c t e r i s t i c of t h a t p a r t i c u l a r hydrodynamic s ta te . The normal sediment-

a r y and s t r a t i g r a p h i c sequence depos i t ed i n a submarine v a l l e y du r ing a

pe r iod of r i s i n g sea l e v e l i s desc r ibed by Normark and P i p e r (1969) and

i l l u s t r a t e d by Fig . 6-2. Th i s sequence of sed iments is based on t h e

assumption t h a t , i n g e n e r a l , c u r r e n t s f lowing a long t h e bottom o f a

submarine v a l l e y tend t o wane wi th i n c r e a s i n g dep th , and u l t i m a t e l y

d i s p e r s e on t h e submarine f a n a t t h e base of a v a l l e y . The r e s u l t o f

such a f low p a t t e r n is t o d e p o s i t c o a r s e r sediment up-current and f i n e r

sediment down-current, a l a t e r a l g rada t ion of sediment t h a t forms a wedge

of sand p inching o u t a t some p o i n t down t h e v a l l e y . The o v e r a l l v e r t i c a l

sequence i s a l s o graded and i s , i n e f f e c t , a t r a n s g r e s s i n g sequence of

sediment i n which t h e c o a r s e r g rades , such a s sand , a r e depos i t ed i n t h e

upper reaches of a v d l e y and a r e subsequent ly bu r i ed by f i n e r sediments

as t h e s e a l e v e l rises. The r e s u l t i n g wedge of b a s a l sand may u l t i m a t e l y

by comple te ly bu r i ed by muds.

T h e p o s s i b l e a p p l i c a t i o n of t h i s concept t o petroleum e x p l o r a t i o n

i s ev iden t . Where such wedges of sand a r e depos i t ed , t h e i r i n i t i a l d i p

i s commonly inc reased by r e g i o n a l t i l t i n g a long t h e f l a n k of t h e sed i -

mentary b a s i n . I n such a s i t u a t i o n , t h e ove r ly ing marine muds could be

source beds f o r hydrocarbons, o r t h e i r p r e c u r s o r s , which would then mig ra t e

i n t o t h e wedge of sand du r ing subsequent compaction of t h e s e c t i o n .

T e r t i a r y submarine v a l l e y s o f f t h e Gippsland coas t of A u s t r a l i a , f o r

239

1 2 3 4 5 S L

SECTIONAL V I E W S OF SUBMARINE

CUT-AN D-F I L L CH A N N ELS

Fig . 6-2. A - Cross - sec t iona l views showing development of a submarine

c u t - a n d - f i l l channel du r ing a pe r iod of r i s i n g sea l e v e l .

(Redrawn from Normark and P i p e r , 1969).

B - Long i tud ina l s e c t i o n i n t e r p r e t e d from c ross - sec t ions

above.

example, should be cons idered as p o s s i b l e t a r g e t s f o r o i l and gas accum-

u l a t i o n s . C e r t a i n of t hese v a l l e y s appear t o b e l a r g e l y f i l l e d wi th

Oligocene mudstone, b u t t h e bottoms of t h e s e v a l l e y s have n o t been t e s t e d

a t v a r i o u s l o c a t i o n s by d r i l l i n g . It is p o s s i b l e , and p a r t i c u l a r l y s o as

t h e a r e a i s a p r o l i f i c pe t ro leum p rov ince , t h a t i f wedges of sands tone a r e

l o c a l l y p r e s e n t a t t h e base of t h e s e T e r t i a r y submarine v a l l e y s , they may

prove t o be t raps f o r o i l and gas a t t h e i r up-dip, wedge-out e x t r e m i t i e s .

240


Sand bod ies i n submarine v a l l e y s and canyons are l i n e a r , bu t commonly

b i f u r c a t e on a submarine f a n at t h e mouth of t h e canyon. Some bod ies

are formed dur ing long per iods of normal sed imen ta t ion , o t h e r s are

depos i t ed d u r i n g s h o r t pe r iods by t u r b i d i t y c u r r e n t s .

sand may be w e l l s o r t e d and c l e a n , i n t h e l a t t e r i t is poor ly s o r t e d and

e x h i b i t s graded bedding from c o a r s e r below t o f i n e r above.

bod ie s depos i t ed d u r i n g p e r i o d s of normal se idmen ta t ion may a l s o b e

graded. Loca l ly , and probably r a r e l y , they may have grading from f i n e r

below t o c o a r s e r above. This t ype of g rad ing i s normally c h a r a c t e r i s t i c

of b a r r i e r b a r s and o t h e r r e g r e s s i v e s h o r e l i n e sand bod ies .

v a l l e y sands t h e p o s s i b l e e x i s t e n c e of t h i s i n v e r s e g r a d a t i o n may be

exp la ined by a s i t u a t i o n i n which t h e sand i s be ing depos i t ed by a c u r r e n t

thad l o c a l l y f lows down t h e v a l l e y wi th dec reas ing v e l o c i t y .

may r e s u l t from v a r i a t i o n s i n t h e topography of t h e v a l l e y , such as a

downstream i n c r e a s e i n wid th .

by f i n e r sands f a r t h e r down t h e v a l l e y . Addi t ion of more sand , c a r r i e d

from the upper r eaches of t h e submarine v a l l e y , r e s u l t s i n f u r t h e r a c c r e t i o n

t o t h e sand body which progrades down t h e v a l l e y .

i n t h e development of g r a i n g r a d a t i o n from c o a r s e r up-current t o f i n e r

down-current on t h e d e p o s i t i o n a l s u r f a c e of t h e sand body. A s a c c r e t i o n

con t inues , g rada t ion is a l s o developed w i t h i n t h e v e r t i c a l sequence of t h e

sand body, i n t h e same way as i n s h o r e l i n e r e g r e s s i v e sands , from f i n e r

below t o c o a r s e r above.

In t h e former, t h e

The sand

In submarine

Th i s dec rease

The c o a r s e r sand is d e p o s i t e d f i T s t , followed

This growth i s r e f l e c t e d

The o v e r a l l s e c t i o n of sediment i n a submarine v a l l e y or f a n a t t h e

base of a canyon, is a composite sequence of sand-bodies formed under

d i f f e r i n g hydrodynamic c o n d i t i o n s , i n t e rbedded wi th muds and si l ts . There

i s no o r d e r l y o r p r e d i c t a b l e sequence. In g e n e r a l , t h e graded bed , which

i s t h e g e n e t i c u n i t i n t u r b i d i t y c u r r e n t d e p o s i t s , i s too t h i n and poor ly

241

S U B M A R I N E C A N Y O N DEPOSITS

F A N S A N D TURBlDlTES

c

SP :

A

J

100

c

SP :

Fig. 6-3. Self-potential curves of electric logs of a submarine canyon

fan (A) and turbidity current deposits (B,C, and D).

Generalized section (E) shows self-potential curves of

graded sandstone beds deposited by turbidity currents in a

submarine canyon.

A - Upper Miocene Stevens Sandstone, Rosedale Field,

California. This unit is oil-bearing and overlies the

Rosedale Sandstone which fills a channel (Fig. 6-7). B and

C - Upper Pliocene Pic0 Sandstone, Saticoy Field, California.

D - Lower Pliocene Repetto Sandstone, Ventura Field, California.

242

s e p a r a t e d from o t h e r graded beds t o be d e t e c t e d as such on t h e E-log.

sequence of graded beds , on t h e o t h e r hand, shows on t h e s e l f - p o t e n t i a l

curve as a s e r r a t e d o r f a i r l y smooth c y l i n d e r (F ig . 6 - 3 , B , C , and D) w i th

ab rup t upper and lower c o n t a c t s r e p r e s e n t i n g boundar ies between t h e

sequence and muds depos i t ed d u r i n g pe r iods of normal sed imenta t ion . The

s e r r a t i o n s r e p r e s e n t i n d i v i d u a l graded beds , b u t do n o t r e f l e c t t h e g r a i n

g rada t ion . Such a sequence may be up t o 100 f e e t o r more t h i c k .

A

In Fig . 6 - 3 , sequences B and C are s e c t i o n s of t h e Upper P l iocene

P ic0 Sandstone i n t h e Sa t i coy o i l f i e l d , C a l i f o r n i a , and sequence D is a

s e c t i o n of t h e Lower P l iocene Repet to Sandstone i n t h e Ventura o i l f i e l d ,

C a l i f o r n i a .

i n t h e Rosedale F i e l d (F ig . 6-7 ) , , C a l i f o r n i a . A l l of t h e s e sequences a r e

o i l -bea r ing .

Some are i n t e r p r e t e d as t u r b i d i t y c u r r e n t d e p o s i t s , some are s h a l e beds

depos i t ed as muds du r ing pe r iods of normal sed imen ta t ion , and o t h e r s may

be sands tone bodies formed by s t r o n g c u r r e n t s , bu t no t necessa r iSy by

t u r b i d i t y c u r r e n t s .

Sequence A i s a s e c t i o n of t h e Upper Miocene Stevens Sandstone

Sequence A shows a s e c t i o n composed of s e v e r a l sub-sequences.

Compaction

The e f f e c t s of compaction on a sed imentary sequence depos i t ed i n a

submarine v a l l e y depends on t h e vo lumet r i c and s p a t i a l r e l a t i o n s h i p s of

beds of mud and sand , and a l s o on t h e geometry and p e t r o p h y s i c a l cha rac t -

e r i s t i c s of i n d i v i d u a l sand bod ies . These sand bod ies are l i n e a r , and

commonly forked where they s p i l l over t h e s u r f a c e of a submarine f an . Some

are composed of c l ean sand; o t h e r s , depos i t ed by t u r b i d i t y c u r r e n t s , a r e com-

posed of poor ly s o r t e d , d i r t y sand.

imposed graded beds . Both types of sand bod ies may b e o v e r l a i n o r under-

l a i n by beds of f ine-gra ined sed iments o r by each o t h e r ; and t h e whole

sequence may a t t a i n a th i ckness of s e v e r a l thousand f e e t .

The l a t t e r commonly c o n s i s t s of super -

243

Within a submar ine v a l l e y t h e e f f e c t s of compaction on t h e geometry

of a s a n d s t o n e body a t t h e b a s e of t h e v a l l e y is minimal , b e c a u s e t h e

v a l l e y c u t s i n t o c o n s o l i d a t e d s e d i m e n t s and rock . Wi th in t h e upper p a r t

o f a v a l l e y - f i l l s e c t i o n sand b o d i e s o v e r l y i n g t h e f l a n k s of t h e v a l l e y

w i l l b e t i l t e d . Wi th in a submarine f a n , where t h e s a n d s are d e p o s i t e d

n e a r t h e mouth of a submarine canyon and t h e muds are d e p o s i t e d n e a r t h e

f r i n g e s of t h e f l a n k , t h e e f f e c t of compaction is t o a c c e n t u a t e t h e wedge

s h a p e o f t h e sandy s e c t i o n . I n d i v i d u a l sand b o d i e s w i t h i n t h i s s e c t i o n

are b r o a d l y l e n t i c u l a r .

Of pr imary concern t o p e t r o l e u m g e o l o g i s t s i s t h e e f f e c t o f

compaction on t h e p e t r o p h y s i c a l c h a r a c t e r i s t i c s of sand b o d i e s d e p o s i t e d

by t u r b i d i t y c u r r e n t s . P o o r l y s o r t e d , l i t h i c , and s i l t y , t h e s e s a n d s do

n o t resist compaction as w e l l as q u a r t z o s e s a n d s . With i n c r e a s i n g d e p t h

of b u r i a l , and by t e c t o n i c d e f o r m a t i o n , b o t h s t a t i c and dynamic p r e s s u r e s

c a u s e s h a t t e r i n g of s a n d g r a i n s , accompanied by d i a g e n e t i c a l t e r a t i o n s

which p r o g r e s s i v e l y d e c r e a s e t h e p o r o s i t y and p e r m e a b i l i t y . &This f e a t u r e

w i l l b e d e a l t w i t h s p e c i f i c a l l y i n l a t e r pages d e s c r i b i n g t h e Ventura O i l

F i e l d where compaction h a s been e f f e c t e d n o t o n l y by d e p t h of b u r i a l b u t

a d d i t i o n a l l y by f o l d i n g and t h r u s t - f a u l t i n g .

In t h e a b s e n c e of l a r g e s t r u c t u r e s , t u r b i d i t y c u r r e n t sand b o d i e s

are n o t at tractive t a r g e t s f o r e x p l o r a t i o n . E x p l o r a t i o n f o r such s a n d

b o d i e s is d i f f i c u l t b e c a u s e of l a c k of w e l l - d e f i n e d l i t h o l o g i c sequences

s u i t a b l e t o t h e conta inment of s t r a t i g r a p h i c t r a p s . Fur thermore , where t h e

o i l - b e a r i n g zone i s d e e p , e x p l o i t a t i o n of t h e r e s e r v o i r may b e h i n d e r e d by

r e c o v e r y problems i n v o l v i n g e x c e p t i o n a l l y low p e r m e a b i l i t y . Apar t from

d e p t h and p e r m e a b i l i t y , t h e volume and geometry of t h e hydrocarbon-bear ing

s a n d s t o n e body may p r e c l u d e economica l ly v i a b l e p r o d u c t i o n .

244

Ancient Sand Bodies

Submarine v a l l e y sediments and t h e i r a s soc ia t ed submarine f a n

sediments a r e deposi ted i n v a l l e y s s i t u a t e d on t h e o u t e r f r i n g e s of

c o n t i n e n t a l she lves , i n canyons c u t t i n g i n t o c o n t i n e n t a l s l o p e s , and a s

f ans spreading down t h e lower c o n t i n e n t a l s lopes t o t h e abyssa l p l a ins .

They a r e commonly included i n t h e f l y s c h f a c i e s cha rac t e r i zed by t h i c k

sequences of sediment deposi ted i n a deep-sea environment i n a t e c t o n i c a l l y

a c t i v e , r a p i d l y subsiding sedimentary bas in . The f l y s c h f a c i e s probably

con ta ins t h e ma jo r i ty of sandy sequences deposi ted by t u r b i d i t y c u r r e n t s ,

including t h e o i l -bea r ing sandstone beds of t h e Ventura a n t i c l i n e , a g i a n t

o i l f i e l d i n Ca l i fo rn ia . Most submarine v a l l e y sediments a r e deposi ted i n

r e l a t i v e l y deep water but some, including bodies of we l l s o r t e d , c l ean sand

a r e deposi ted i n t h e upper reaches of submarine v a l l e y s i n r e l a t i v e l y

shallow water . The l a t t e r can be r e f e r r e d t o an o u t e r n e r i t i c kac ie s

cha rac t e r i zed by w e l l - s t r a t i f i e d sediments deposi ted i n a r e l a t i v e l y

s t a b l e t o g e n t l y warping sedimentary bas in . This category of o u t e r n e r i t i c

d e p o s i t i o n a l environments probably inc ludes t h e sedimentological condi t ions

t h a t obtained du r ing t h e per iod of formation and i n f i l l i n g of t h e Oligocene

submarine v a l l e y s t h a t i n f luence t h e entrapment of gas i n t h e Marlin f i e l d

of t h e Gippsland Basin, V i c t o r i a .

Large submarine f ans a t t h e mouths of major submarine v a l l e y s comprise

a complex of e r o s i o n a l and d e p o s i t i o n a l f e a t u r e s , including minor canyons

and v a l l e y s , v a l l e y - f i l l d e p o s i t s , l e v e e s , and shee t s of sediments. The

whole complex forms a prograding wedge t h a t t h i n s away from the mouth of

t h e major submarine va l l ey . The Bengal Fan complex (Figs. 6-4 and 6-5)

Fig. 6-4. Bathymetric c h a r t of Bengal Fan based on soundings. Contours,

ranging from 200 meters t o 5,000 mete r s , have v a r i a b l e i n t e r -

v a l s . (After Curray and Moore, 1971).

245

246

2s' 23" 15" 10" 10"

F i g . 6-5. Hypo the t i ca l l o n g i t u d i n a l s e c t i o n , from n o r t h t o sou th , of

t h e Bengal Pan complex. (Af t e r Curray and Moore, 1971).

l y i n g between t h e Andaman I s l a n d s and t h e e a s t c o a s t of I n d i a i s an out -

s t a n d i n g example. Th i s complex has a l e n g t h of 3,000 km, a wid th of 1,000 km,

and a t h i c k n e s s ranging up t o 12 km. The sed iments i n t h i s g i g a n t i c

accumulation have been de r ived from t h e d e l t a of t h e Ganges-Brahyaputra

River sys tem i n Bangladesh. Curray and Moore (1971) s ta te t h a t t h e f a n

has been formed by t u r b i d i t y c u r r e n t s sweeping sed iments from t h e d e l t a

a long a main submarine canyon, and d i s p e r s i n g them i n t o a b ra ided network

of f a n v a l l e y s . On t h e b a s i s of seismic r e f l e c t i o n p r o f i l e s t h e Bengal

Fan is d iv ided i n t o t h r e e s t r a t i g r a p h i c u n i t s d e p o s i t e d du r ing t h e Miocene,

P l iocene , and Quaternary r e s p e c t i v e l y . These u n i t s , which are sepa ra t ed

by prominent d i s c o n f o r m i t i e s , are b e l i e v e d t o have formed dur ing pe r iods

of i nc reased u p l i f t of t h e Himalayan o rogen ic b e l t . The qua te rna ry sed i -

ments are l a r g e l y undeformed, whereas t h e o l d e r sed iments a r e fo lded and

f a u l t e d , p robably by g r a v i t y s l i d i n g of unconsol ida ted sed iments benea th

t h e c o n t i n e n t a l s lope .

The s u r f a c e of t h e Bengal Fan shows f e a t u r e s s i m i l a r t o those of

some r i v e r systems. Curray and Moore (1971, p. 566) s a y , "Details of

247

s h a l l o w sub-bottom s t r u c t u r e show a g r e a t v a r i e t y of c h a n n e l t y p e s . In

some p a r t s of t h e f a n s u r f a c e , c h a n n e l s are p a r t l y o r c o m p l e t e l y f i l l e d .

Elsewhere t h e c h a n n e l s a p p e a r t o b e b r a i d e d o r are i n c i s e d f o r o v e r 100 m

i n t o s e d i m e n t a r y f i l l w i t h i n f o r m e r l y much d e e p e r v a l l e y s . The most

s i g n i f i c a n t f e a t u r e b r o u g h t o u t by t h e s e r e c o r d s i s t h e u n m i s t a k a b l e

e v i d e n c e f o r pronounced m i g r a t i o n of t h e c h a n n e l s by c u t - a n d - f i l l p r o c e s s e s

a n a l a g o u s t o t h o s e of s u b a e r i a l streams. The t u r b i d i t y c u r r e n t c h a n n e l s ,

i n f a c t , show a l l of t h e d e p o s i t i o n a l and e r o s i o n a l c a p a b i l i t i e s of sub-

ae r i a l streams f o r a d j u s t i n g t o v a r i a b l e b a s e l e v e l s , stream l o a d s , and

d i s c h a r g e volumes".

f e a t u r e s s u g g e s t t h a t submarine f a n s p r o b a b l y c o n t a i n numerous p o t e n t i a l

s t r a t i g r a p h i c t r a p s of t h e t y p e s found i n a l l u v i a l sequences formed by

r i v e r sys tems. Abandoned submar ine c h a n n e l s , c u t t i n g f l a t - l y i n g to

g e n t l y - d i p p i n g b e d s , are f i l l e d w i t h sed iment which may s u b s e q u e n t l y form

a b a r r i e r t o t h e movement of o i l o r g a s w i t h i n t h e a d j a c e n t i n c i s e d b e d s .

Curray and Moore (1971, F i g . 3c) i n c l u d e one seismic p r o f i l e t h a t shows

These similari t ies of d e p o s i t i o n a l and e r o s i o n a l

abandoned, s e d i m e n t - f i l l e d c h a n n e l s 60 m deep , and 2 km wide. These are

r e m i n i s c e n t of t h e M a r l i n Channel , b e l i e v e d t o b e of submarine o r i g i n ,

f l a n k i n g t h e up-dip s i d e of t h e M a r l i n F i e l d ( F i g . 6-11) i n V i c t o r i a .

The M a r l i n Channel , however, is more t h a n 300 m deep.

Viewed i n t h r e e d imens ions , t h e Bengal Fan complex compr ises a

s e d i m e n t a r y b a s i n i n which t h e lower and p o s s i b l e t h i c k e s t u n i t rests on

basement r o c k s and is of unknown o r i g i n , whereas t h e upper u n i t s are

p r i m a r i l y t u r b i d i t e s .

Yoakum Channel, Texas

The Yoakum Channel (Fig. 6-6) i n Lavaca County, Texas , w a s formed

as a submarine v a l l e y d u r i n g t h e E a r l y Eocene and l a t e r f i l l e d main ly w i t h

f i n e - g r a i n e d muddy s e d i m e n t , now s h a l e , of t h e Eocene Wilcox Group. T h i s

248

15 I

- M I L E S

0'5 K M

I S O P A C H M A P OF E O C E N E

S U B M A R I N E C A N Y O N , T E X A S .

Fig. 6-6. Isopach map and s e c t i o n of t h e Yoakum Channel, Lavaca

County, Texas. This channel w a s a submarine canyon and is

f i l l e d wi th s h a l e of t h e Eocene Wilcox Group. (Redrawn from

Halbouty, 1969 a f t e r Hoyt, 1959).

s h a l e s e c t i o n , which i s l o c a l l y up t o 750 m t h i c k , is o v e r l a i n by massive

sandstone beds of t he same group. The channel , which has a f a i r l y uniform

width of 10-15 km and a l eng th of more than 100 km, w a s t h e s i t e f o r a

h o l e d r i l l e d t o a depth of 5,490 m t o tes t the hydrocarbon-bearing p o t e n t i a l

of a p o s s i b l e sandstone s e c t i o n a t t h e base. Halbouty (1969, p. 27)

comments on t h i s e x p l o r a t i o n ven tu re as fol lows.

t h e i d e a t h a t the Yoakum s h a l e channel (Hoyt, 1959) i n western Lavaca

County, Texas, o r i g i n a l l y had been f i l l e d wi th lower and middle Wilcox

sandstone and s h a l e s imi la r t o t h e sediments on t h e channel f l a n k s . It

w a s thought t h a t t h e o r i g i n a l f i l l , w i th an e s t ima ted volume of 75 cu m i

"The p lay w a s based on

249

o r 250,000 a c r e - f t , was e roded from t h e channel and r e d e p o s i t e d downdip

from t h e Lavaca County area.

covered w i t h t y p i c a l upper Wilcox s a n d s t o n e d e p o s i t s " . Halbouty a l s o

s a y s , "The d r i l l i n g v e n t u r e , which w a s an a t t e m p t t o l e a r n more about

t h e s a n d s t o n e - d i s t r i b u t i o n p a t t e r n of t h e downdip Wilcox a t t h e mouth of t h e

Yoakum c h a n n e l , w a s n o t s u c c e s s f u l b e c a u s e e x p e c t e d s a n d s t o n e b e d s w e r e n o t

p r e s e n t b e n e a t h t h a t p a r t i c u l a r d r i l l s i te" .

p o s s i b i l i t y t h a t t h e s e d i m e n t s e roded from t h e Yoakum Channel may have

b e e n r e - d e p o s i t e d f a r t h e r downdip from t h e mouth of t h e c h a n n e l t h a n t h e

s i t e of t h e u n s u c c e s s f u l w i l d c a t t e s t .

The c h a n n e l t h e n w a s f i l l e d w i t h s h a l e and

Halbouty ment ions t h e

The c o n c e p t o f hydrocarbon en t rapment w i t h i n t h e up-dip p a r t o f a

s a n d s t o n e wedge w i t h i n a submarine c h a n n e l is a t t r a c t i v e , p a r t i c u l a r l y

where t h e c h a n n e l i s s i t u a t e d w i t h i n an o i l o r gas-bear ing p r o v i n c e . But

f i n d i n g t h e l o c a t i o n of such a s a n d s t o n e wedge may u l t i m a t e l y depend on

t e c h n o l o g i c a l developments i n g e o p h y s i c a l methods.

Rosedale Channel., C a l i f o r n i a

The Rosedale Channel i n C a l i f o r n i a (F ig . 6-7) i s f i l l e d w i t h t h e

Late Miocene Rosedale Sands tone , a c o a r s e t o f i n e - g r a i n e d , f e l d s p a t h i c t o

l i t h i c s a n d s t o n e which l o c a l l y shows graded bedding . The Rosedale Channel

r a n g e s from less t h a n 2 km t o n e a r l y 3 km i n w i d t h , h a s b e e n t r a c e d f o r

more t h a n 10 km, and is a t least 360 m deep. M i c r o f o s s i l s i n t h e Rosedale

Sands tone s u g g e s t t h a t d e p o s i t i o n o c c u r r e d a t water d e p t h s of more t h a n

300 m. M a r t i n (1963, p . 4 5 4 ) s a y s , "From t h e i n v e s t i g a t i o n s of t h e char -

a c t e r i s t i c s of t h e Rosedale Channel and t h e Rosedale Sands tone such as t h e

s e d i m e n t s , m i c r o f a u n a l a g e s , d e p t h o f water, and d i s p l a c e d f a u n a s , t h e

e v i d e n c e s t r o n g l y s u g g e s t s t h a t e r o s i o n and f i l l i n g o c c u r r e d e n t i r e l y w i t h i n

t h e mar ine environment". H e s a y s f u r t h e r , p. 4 5 5 , " T u r b i d i t y c u r r e n t s o r

g r a v i t y f lows of sed iment are c o n s i d e r e d t o have a f f e c t e d t h e downcut t ing ;

250

ISOPACH A N D S E C T I O N OF ROSEDALE

C H A N N E L S A N D S T O N E

Fig. 6-7. Isopach and s e c t i o n of Late Miocene Rosedale Sandstone

f i l l i n g a submarine channe l , Great V a l l e y , nea r Bake r s f i e ld ,

C a l i f o r n i a . (Redrawn from Mar t in , 1963).

however, i t seems l i k e l y t h a t t h e lower F r u i t v a l e Shale i n t o which t h e

canyon c u t probably w a s n o t i ndura t ed t o any g r e a t degree du r ing t h i s

t i m e and because of t h e l a c k of much i n d u r a t i o n , e r o s i o n probably w a s

f a c i l i t a t e d " .

O i l o r gas have n o t been d i scove red w i t h i n t h e Rosedale Sandstone,

a l though t h e ove r ly ing Lower Massive Uni t of t h e S tevens Sandstone (Fig.

6-3), which i s t h e producing zone i n t h e Rosedale O i l F i e l d , may be a

f a c i e s of beds t h a t can be t r a c e d down-channel t o t h e Rosedale Sandstone.

Mar t in ho lds o u t some hope f o r t h e Rosedale and s a y s , p. 4 5 5 , " L i t t l e o r

no pe t ro leum h a s been d i scove red i n t h e sed iments of t h e Rosedale Channel,

bu t t h i s does n o t p rec lude t h e p o s s i b i l i t y t h a t f u t u r e d i s c o v e r i e s may be

251

made. F i l l e d and b u r i e d submarine canyons should have an e x c e l l e n t

p o t e n t i a l f o r any exp lo ra to ry e f f o r t s a l though from t h e n a t u r e of t h e

sands tone b o d i e s , l o c a t i o n and r e c o g n i t i o n may b e d i f f i c u l t " .

O i l and G a s F i e l d s

Sediments i n a n c i e n t submarine v a l l e y s have n o t o f t e n been

s t r a t i g r a p h i c t a r g e t s f o r o i l and gas e x p l o r a t i o n , a l though such f e a t u r e s

are p r e s e n t on a l l c o n t i n e n t a l margins and appear t o have been s o i n t h e

p a s t . The d i f f i c u l t i e s t h a t arise i n s e a r c h i n g f o r a s t r a t i g r a p h i c t r a p

i n a b u r i e d submarine v a l l e y have h i t h e r t o prec luded much en thus iasm f o r

such an e x p l o r a t i o n programme. With few excep t ions , such as t h e pre-

v i o u s l y mentioned e x p l o r a t o r y h o l e d r i l l e d i n t o t h e Yoakum Channel i n

Texas, e x p l o r a t i o n i n submarine v a l l e y and f a n d e p o s i t s has been r e s t r i c t e d

t o areas such as t h e Ventura O i l F i e l d of C a l i f o r n i a , where f o l d i n g of t h e

beds a f f o r d s s t r u c t u r a l c l o s u r e . And y e t , as po in ted o u t by Hedberg (1970,

p . 3 ) , "For t h e pe t ro leum g e o l o g i s t , it is s i g n i f i c a n t t h a t through t h e

ages t h e c o n t i n e n t a l margin has been t h e g r e a t mixing bowl i'n which has

been brewed most o f t h e w o r l d ' s pe t ro leum and from which most of i t s

pe t ro leum p roduc t ion t o d a t e h a s been der ived" .

d e p o s i t i o n a l environment and pe t ro leum p o t e n t i a l of submarine f a n s on a

c o n t i n e n t a l rise, Emery e t al. (1970, p . 103) say , "The l a r g e mass

movements t h a t remove t h i c k sequences o f sed iments from t h e c o n t i n e n t a l

s l o p e b r i n g them t o t h e upper p a r t of t h e c o n t i n e n t a l r ise. Because

t h e s e d i s p l a c e d sed iments are f i n e g r a i n e d , when depos i t ed en masse they

can r e t a i n most of t h e i r o rgan ic matter o u t of r each of t h e ove r ly ing

oxygen-rich water. Continuous se i smic r e f l e c t i o n p r o f i l e s and co res

sugges t t h a t sandy t u r b i d i t e s a l s o are p resen t th roughout most of t h e

c o n t i n e n t a l r i se , and some of them are in te rbedded w i t h t h e d i sp laced

s i l t s and c l a y s from t h e c o n t i n e n t a l s lope . Under such c o n d i t i o n s , w e

might expec t t h e d i s p l a c e d s i l t s and c l a y s t o s e r v e as o i l sou rce beds and

Commenting on t h e

252

t h e sandy t u r b i d i t e s t o be r e s e r v o i r beds. The sesimic d a t a a l s o r e v e a l

t h e presence of many s t r a t i g r a p h i c and s t r u c t u r a l t r aps" .

F i e l d , one of the wor ld ' s l a r g e f i e l d s , is an impor tan t example. Other

o i l and gas accumula t ions i n submarine v a l l e y and f a n d e p o s i t s may i n t h e

f u t u r e b e found f a r o u t t o sea under ly ing t h e upper s l o p e s of a cont in-

e n t a l r ise. A s po in ted o u t by Beck and Lehner (1974), t e c h n o l o g i c a l

advances i n deep-sea d r i l l i n g a r e b r i n g i n g t h e s e g e o l o g i c a l l y a t t r a c t i v e

r eg ions w i t h i n t h e realm of e x p l o r a t i o n f e a s i b i l i t y .

i n t h e s e o f f - sho re r eg ions w i l l u l t i m a t e l y prove t o be economically

f e a s i b l e is a q u e s t i o n f o r t h e f u t u r e .

The Ventura O i l

Whether e x p l o r a t i o n

Brentwood, Dutch Slough and West Thornton O i l and G a s F i e l d s , C a l i f o r n i a

The Brentwood, Dutch Slough, and West Thornton f i e l d s i n t h e

Scaramento Va l l ey , C a l i f o r n i a , y i e l d o i l and gas from massive sands tone

beds o f t h e Paleocene Mar t inez Formation. These beds are t runca ted by t h e

Meganos Channel (Fig. 6-8) which i s f i l l e d mainly wi th Paleocene s i l t y

s h a l e which forms a cap rock f o r o i l and gas accumula t ions w i t h i n t h e

sands tone beds . Entrapment of b o t h o i l and gas r e s u l t s from a s t r u c t u r a l -

- s t r a t i g r a p h i c s i t u a t i o n (F ig . 6-9), t h e hydrocarbon-bearing beds having

been fo lded and t i l t e d , then t r u n c a t e d by t h e Meganos Channel which w a s

f i l l e d wi th impermeable sed iments .

Dickas and Payne (1967) say t h a t 95% of t h e sediments f i l l i n g t h e

Meganos Channel are s h a l e s , l o c a l l y g l a u c o n i t i c , t h a t g rade i n t o s i l t y

beds i n t h e lower p a r t of t h e s e c t i o n . Some t h i n b a s a l sands tone beds

are p r e s e n t i n t h e n o r t h e r n and upper p a r t o f t h e channel , bu t t hese have

proved t o b e unproduct ive .

have been depos i t ed i n a submarine v a l l e y i n water dep ths ranging from

n e r i t i c t o upper b a t h y a l . The Meganos Channel, which h a s a l eng th of

more than 80 km and a wid th of 3-10 km, is f i l l e d wi th up t o 600 m of

sediment. These dimensions a r e comparable t o those o f t h e Congo River

These v a l l e y - f i l l sed iments are be l i eved t o

253

ISOPACH OF MEGANOS CHANNEL. CALIFORNIA

F i g . 6-8. I sopach of t h e P a l e o c e n e Meganos Channel, Sacramento V a l l e y ,

C a l i f o r n i a . T h i s c h a n n e l e r o d e s Pa leocene s a n d s t o n e beds and

i s f i l l e d main ly w i t h s h a l e and s i l t s t o n e deposii ted as mud i n

water d e p t h s r a n g i n g from n e r i t i c t o upper b a t h y a l . (Redrawn

from Dickas and Payne, 1967).

submar ine canyon which a c c o r d i n g t o Heezen e t a l . (1964) h a s a l e n g t h

o f 320 km, a w i d t h of up t o 8 k m , and a d e p t h of up t o 900 m below t h e

canyon r i m . Shepard and Emery (1973 a ) f u r t h e r d e s c r i b e t h e Congo River

canyon as V-shaped and r a n g i n g i n d e p t h up t o 1,400 m from t h e r i m t o t h e

b a s e .

Although t h e Brentwood, Dutch Slough, and West Thornton f i e l d s

are no t producing from s e d i m e n t s w i t h i n t h e submarine v a l l e y , t h e i r

l o c a t i o n s depend on t h e j u x t a p o s i t i o n of f o l d e d and upturned hydrocarbon-

- b e a r i n g s a n d s t o n e s w i t h impermeable s h a l y b e d s i n t h e Meganos Channel.

254

- O I O F E E T

L! B D A T U M I ' I

I -

-

M A R l I N € Z FM

I 1, KM

1 3 0 0 0

STRUCTURAL SECTIONS ACROSS MEGANOS

C H A N N E L , CALIFORNIA

Fig . 6-9. S t r u c t u r a l s e c t i o n s A-A' and €3-B' a c r o s s t h e Paleocene hleganos

Channel, Sacramento Va l l ey , C a l i f o r n i a , showing o i l and gas

accumulations i n Paleocene beds of t h e Martinez Formation,

Brentwood f i e l d . (Redrawn from Dickas and Payne, 1967).

255

S t r a t i g r a p h i c and s t r u c t u r a l c o n t r o l i s s i m i l a r t o t h a t of t h e Mar l in

F i e l d (F ig . 6-11) i n the Gippsland Bas in , V i c t o r i a . The Brentwood and

Dutch Slough, cons idered t o b e major f i e l d s , a r e l o c a t e d i n t h e south-

-western p a r t of t h e channel shown i n F ig . 6-8, whereas t h e West Thornton

f i e l d l i e s i n t h e n o r t h e r n p a r t . Ul t imate p roduc ib le r e s e r v e s of gas i n

t h e Dutch Slough f i e l d a r e e s t ima ted t o amount t o more than 300,000 m i l l i o n

cub ic f e e t (8,400 m i l l i o n cub ic metres).

Mar l in Gas F i e l d , V i c t o r i a

I n t h e Mar l in F i e l d (F igs . 6-10 and 6-11) o f t h e Gippsland Basin,

V i c t o r i a , gas and some l i g h t o i l are produced from f i v e sands tone u n i t s

w i t h i n t h e Paleocene t o Eocene Lat robe Group. These u n i t s are t i l t e d ,

t r u n c a t e d by an e r o s i o n a l s u r f a c e , and f l anked on t h e east by a submarine

channel f i l l e d wi th mudstones of t h e Oligocene t o Miocene Lakes Entrance

Formation. The mudstones provide an e f f e c t i v e s e a l . The gas-bear ing

sands tones l i e w i t h i n a s e c t i o n approximate ly 180 m t h i c k .

sands tone beds have a th i ckness of up t o 30 m , and t h e cumulative net-pay

th i ckness f o r a l l f i v e u n i t s exceeds 100 m. The sands tones a r e l i g h t grey ,

f r i a b l e , qua r t zose t o l i t h i c , g e n e r a l l y f ine -g ra ined , micaceous, and

l o c a l l y s i l t y wi th carbonaceous f l a k e s . P o r o s i t y and pe rmeab i l i t y have

ranges of 15-30% and up t o 1,000 m i l l i d a r c y s r e s p e c t i v e l y . The f i v e

sands tone u n i t s a r e sepa ra t ed by carbonaceous mudstones inc lud ing beds of

c o a l .

I n d i v i d u a l i

These gas-bear ing sands tones were depos i t ed i n a p a r a l i c t o

a l l u v i a l environment, b u t d e t a i l e d informat ion concerning t h e i r paleo-

geomorphic o r i g i n s have n o t been publ i shed . G r i f f i t h and Hodgson (1971)

are of t h e op in ion t h a t they a r e b ra ided s t r eam d e p o s i t s . The Lat robe

Group comprises a wedge of sed iments , t h i ckccn ing t o many thousands of

f e e t o f f s h o r e , t h a t formed a s a d e l t a i c complex. Coal beds i n t h e Mar l in

F i e l d a r e a , 50 km o f f s h o r e , are i n d i v i d u a l l y up t o 6 m t h i c k , bu t onshore

256

MARLIN GAS AND OIL FIELD GIPPSLAND BASIN, VICTORIA

Fig . 6-10. S t r u c t u r e map showing sub-sea l e v e l c o n f i g u r a t i o n of t h e

e r o s i o n a l s u r f a c e of t h e Lat robe Group, Mar l in Gas F i e l d ,

V i c t o r i a . S e c t i o n A-A' ex tends t o t h e upper l e v e l of t h e

Mar l in Channel, a submarine v a l l e y . Contour i n t e r v a l i s 100

f e e t (30 m ) . (Af t e r G r i f f i t h and Hodgson, 1971, modified

by Beddoes, 1973).

25 7

MARLIN GAS A N D OIL FIELD STUCTURE CROSS-SECTION A-A'

A

SCALE

I L D M L T R L S

1 c n*,

Vertical Exaggeration 10 1

Fig . 6-11. S t r u c t u r e s e c t i o n A-A' a c r o s s t h e Mar l in Gas F i e l d , V i c t o r i a ,

showing a f a u l t bounding t h e wes te rn f l a n k of t h e Mar l in

Channel shown i n F ig . 6-10. (Af t e r G r i f f i t h and Hodgson, 1971,

modi f ied by Beddoes, 1973)

they range up t o 90 m t h i c k . In t h e o f f s h o r e a r e a s s t r a t i g r a p h i c zonat ion

w i t h i n t h e Lat robe Group depends on t h e assemblage of p o l l e n s and spores .

During t h e l a t e h i s t o r y of t h e Lat robe Group a marine t r a n s g r e s s i o n , which

began i n t h e Late Eocene, r e s u l t e d i n t h e d e p o s i t i o n e l sewhere of up t o

300 m of marine mudstone and up t o 30 m of g l a u c o n i t i c , ve ry f ine-gra ined

sands tone .

w e r e depos i t ed du r ing t h e i n i t i a l s t a g e s of a r e g i o n a l marine t r ansg res s ion

t h a t l a t e r l a i d down t h e Lakes Gnt racce Group.

These beds a r e inc luded i n t h e Lat robe Group, a l though they

The f i e l d , which has a s t r o n g wa te r d r i v e , i s a s t r u c t u r a l -

s t r a t i g r a p h i c t r a p . A southwest-plunging f o l d w a s eroded du r ing t h e Late

258

Eocene t o form a c losed e r o s i o n a l f e a t a e (a dome-shaped h i l l ) f l anked on

t h e east by a v a l l e y ( subsequent ly a submarine channe l ) .

c l o s u r e is approximate ly 275 m. The e s t ima ted u l t i m a t e p roduc ib le r e s e r v e s

of gas amount t o 3,500,000 m i l l i o n cub ic f e e t (98,000 m i l l i o n cub ic met res )

c o n t a i n i n g 175 m i l l i o n b a r r e l s ( 2 7 . 8 m i l l i o n cub ic met res ) of condensa te .

E s t i m a t e s of u l t i m a t e recovery of t h e l i g h t o i l have n o t been publ i shed .

Of p a r t i c u l a r i n t e r e s t i s t h e f a c t t h a t t h e f i l l i n g o f t h e Mar l in submarine

channel w i th muds h a s been a prime f a c t o r i n forming an up-dip seal f o r gas

in t h e t i l t e d and eroded sands tone beds of t h e Lat robe Group. The s t r u c t -

t u r a l - s t r a t i g r a p h i c s i t u a t i o n i s similar t o t h a t of t h e Brentwood F i e l d

(F ig . 6-9) i n C a l i f o r n i a .

Maximum v e r t i c a l

Ventura O i l and Gas F i e l d , C a l i f d r n i a .

Product ion i n t h e Ventura O i l F i e l d of t h e Ventura Basin,

C a l i f o r n i a , is ob ta ined from t h e Upper P l iocene P ic0 Sandstone and t h e

Lower P l iocene Repet to Sandstone. Both u n i t s form a cont inuous sequence,

more than 3,000 m t h i c k , of o i l -beaz ing sands tones , sandy s i l t d t o n e s and

o rgan ic - r i ch s i l t y c l ays tones . The sequence comprises t u r b i d i t y c u r r e n t

d e p o s i t s and normal deep-sea sed iments t h a t formed a submarine f a n i n a

t e c t o n i c a l l y a c t i v e b a s i n (Natland and Kuenen, 1951). Coincidence of t h e

a r e a of optimum sand d e p o s i t i o n and t h e a r e a of growth of t h e Ventura

a n t i c l i n e has r e s u l t e d i n a t h i c k o i l -bea r ing s e c t i o n . Th i s s e c t i o n has

been d iv ided i n t o s e v e r a l o i l -producing zones a t depths ranging from 300

t o 2 ,700 m . The upper most zone y i e l d s gas and condensa te (56' A .P . I . ) ,

t h e upper zones y i e l d l i g h t o i l ( 4 2 O A.P . I . ) , and t h e lower zones y i e l d

h e a v i e r o i l (300 A.P . I . ) . These accumula t ions , which occur i n a number

of i n d i v i d u a l t r a p s i n s e p a r a t e f a u l t b locks w i t h i n a r e v e r s e and t h r u s t -

f a u l t e d a n t i c l i n e , have d i f f e r e n t r e s e r v o i r p r e s s u r e s and o i l cha rac t e r -

i s t i c s (Levorsen, 1967). Other accumula t ions having a similar d e p o s i t i o n a l

and s t r u c t u r a l genes i s a r e p r e s e n t i n the Lower P l iocene of t h e Los Angeles

259

Basin , and i n t h e Upper Miocene o f t h e San Joaquin Bas in , bo th i n C a l i f -

o r n i a .

Within t h e 2,700 metres of o i l - b e a r i n g s e c t i o n i n t h e Ventura

F i e l d , pe rmeab i l i t y of t h e sands tones d e c r e a s e s p r o g r e s s i v e l y wi th dep th

from a range of 60-250 m i l l i d a r c y s i n t h e upper zone t o less t h a t 5 m i l l i -

d a rcys i n t h e lower. The o i l - b e a r i n g sands tones i n t h e lowermost zone

commonly have a pe rmeab i l i t y of on ly one m i l l i d a r c y , sugges t ing t h a t t h e

p e r m e a b i l i t y of t h i s u n i t has been reduced by a f a c t o r of s e v e r a l hundred

times s i n c e i t was depos i t ed . This d r a s t i c r e d u c t i o n h a s r e s u l t e d d i r e c t l y

from t h e s h a t t e r i n g and compaction of g r a i n s by a combination of s t a t i c

and dynamic p r e s s u r e s caused by depth of b u r i a l and t h e s t r e s s e s t h a t

produced f o l d i n g and f a u l t i n g , and i n d i r e c t l y by t h e p lugging of pore

space r e s u l t i n g from d i a g e n e t i c a l t e r a t i o n s . There is no ev idence (Natland

and Kuenen, 1951) t h a t s ed imen to log ica l d i f f e r e n c e s i n t h e upper and lower

p a r t s o f t h e s e c t i o n account i n any way f o r t h e v a r i a t i o n s i n pe rmeab i l i t y .

The Ventura F i e l d area was t h e s i t e of d e p o s i t i o n by t u r b i d i t y c u r r e n t s

du r ing most of t h e P l iocene , and t h i s f a c i e s c h a r a c t e r i z e s t h e e n t i r e

o i l - b e a r i n g s e c t i o n .

Hertel (1929) e s t ima ted t h a t u l t i m a t e recovery from t h e Ventura

F i e l d would amount t o more than 250 m i l l i o n b a r r e l s of o i l and 600,000

m i l l i o n cubic f e e t of gas . S ince then: a d d i t i o n a l producing zones w i t h i n

t h e f i e l d have been d iscovered . Halbouty (1978) states t h a t a t t h e

beginning of 1967 t h e cumula t ive p roduc t ion p l u s t h e e s t ima ted r ecove rab le

r e s e r v e s of o i l i n t h e Ventura f i e l d amounted t o approximate ly 818 m i l l i o n

b a r r e l s (130 m i l l i o n cubic m e t r e s ) . He a l s o states t h a t a t t h e beginning

of 1966 t h e cumula t ive product ion of gas was 1,847,000 m i l l i o n cubic f e e t

(52,000 m i l l i o n cub ic me t re s ) . It i s of i n t e r e s t t o n o t e t h a t more r e c e n t

estimates of u l t i m a t e p roduc t ion i n t h i s f i e l d , d i scovered i n 1916, have proved

t o be about t h r e e t i m e s g r e a t e r t han t h e e a r l i e r estimates.


261

Chapter 7

TIDAL CURRENT SAND BODIES


Geomorphology

T i d a l c u r r e n t r i d g e s of sand and s i l t are known i n many p a r t s of

t h e world. They are developed as ribbon-shaped sand bod ies a l igned

p a r a l l e l t o t h e t i d a l c u r r e n t d i r e c t i o n . These sand bod ies are commonly

found a t dep ths w i t h i n t h e range 10-100 m , on p a r t s of t h e c o n t i n e n t a l

s h e l f s u b j e c t t o s t r o n g t i d a l c u r r e n t s f lowing a t v e l o c i t i e s of up t o

5 km/hr. Of those d e s c r i b e d , examples i n t h e North Sea ( P e t t i j o h n ,

P o t t e r , and S i e v e r , 1972; B l a t t , Middle ton , and Murray, 1972; Houbolt , 1968;

and S t r i d e , 1963) , i n t h e Gulf of Korea (Off, 1963), and i n Taiwan S t r a i t

(Boggs, 1974) are mentioned h e r e . The dimensions of t h e s e r i d g e s are

remarkably similar. I n t h e North Sea (F igs . 7-1 and 7-2) t hey have a

t h i c k n e s s o f up t o 50 m, a l e n g t h of up t o 70 km bu t commonly less than

50 km, and a wid th of 3-5 km. I n t h e Gulf of Korea (Fig. 7-3) t hey have

a t h i c k n e s s o f 10-35 m, a l e n g t h of 10-60 km, and a wid th of 2-3 km. In

Taiwan S t r a i t they are 5-30 m t h i c k , and up t o 3.5 km wide. Swif t and

HcMullen (1968) a l s o d e s c r i b e t i d a l sand bqd ies i n t h e Bay of Fundy, Nova

S c o t i a . These bod ies a r e up t o 30 m t h i c k and 30 km long .

In t h e North Sea t i d a l r i d g e s were e x t e n s i v e l y s t u d i e d by Houbolt

(1968).

a c r o s s t h e i r s t r i k e , are l a r g e c u r r e n t r i p p l e s r e f e r r e d t o as t i d a l sand

waves. Although ve ry l i t t l e i s known about t h e i n t e r n a l s t r u c t u r e of t i d a l

c u r r e n t r i d g e s , the movement of sand waves a c r o s s t h e i r s u r f a c e s is r e f l e c t e d

i n t e r n a l l y as cross-bedding. The n a t u r e of t h i s cross-bedding is n o t w e l l

known, b u t i s i n d i c a t e d by spa rke r surveys t o be p l a n a r and sweeping.

On t h e s u r f a c e of t h e s e asymmetrical r i d g e s , and t r e n d i n g ob l ique ly

262

Gentle back slope with megoripples

Steep slope with

F i g . 7-1. O u t l i n e s and g e n e r a l i z e d c r o s s - s e c t i o n of s a n d r i d g e s i n t h e

s o u t h e r n b i g h t of t h e North Sea .

P o t t e r and S i e v e r , 1972, a f t e r Houbol t , 1968).

(Redrawn by P e t t i j o h n ,

These Nor th Sea sand r i d g e s , formed on t h e f l a t s e a f l o o r of an open s h e l f ,

a p p e a r t o have f l a t b a s e s and convex t o p s . T h i s i n t e r p r e t a t i o n i s i n d i c a t e d

by s p a r k e r s u r v e y s which o u t l i n e t h e geometry of t h e r i d g e s , and i s f u r t h e r

s u g g e s t e d by t h e f a c t t h a t t h e sand b o d i e s m i g r a t e a c r o s s t h e sea f l o o r

l i k e g i a n t r i p p l e s .

-day r i v e r b u t from t h e sea f l o o r i t s e l f , i s e x t r e m e l y w e l l s o r t e d and f i n e -

-gra ined .

The sand which is n o t d i r e c t l y d e r i v e d from any p r e s e n t -

Cor ing does n o t show any g r a i n g r a d a t i o n w i t h i n t h e r i d g e s .

263

Well Bank sea level ____ -

~ --<k-l

Smith Knoll seo level

Vorfolk , , , ,L , , , YL L u i A ' " ' ' , . L A

35' 40' 45' 50' 55' 2" 5' 10' 15' 20' 25' 30' 35'

35'

30 '

25'

20 '

15'

10'

5'

53"

55'

50'

45'

F ig . 7-2. Isopach map of sand r i d g e s formed by t i d a l c u r r e n t s i n t h e

sou the rn b i g h t of t h e North Sea.

Middleton, and Murray, 1972, a f t e r Houbolt , 1968).

(Modified by B l a t t ,

264

TIDAL CURRENT D I R E C T I O N -.I

Q

TI DAL CURRENT RIDGES

THE GULF OF KOREA

20 MILES

Fig . 7-3. T i d a l c u r r e n t r i d g e s of sand i n t h e Gulf of Korea. T i d a l

c u r r e n t d i r e c t i o n s i n d i c a t e d by a r rows . (Af t e r O f f , 1963,

redrawn from U.S. Navy Hydrographic O f f i c e c h a r t s . )

265

Measurements of grain orientation indicate a preferred direction at 45' to

the strike of the sand ridges, a result that is not surprising in view of

the oblique movement of current ripples across the leading edges of the

sand ridges. The non-parallelism of average grain orientation to the trend

of the sand ridges suggests that measurements of mean grain orientation in

sandstones should be applied to the interpretation of sandstone body trends

with some reservation.

Off (1963) describes tidal current ridges (Fig. 7-3) in the Gulf of

Korea.

where in places the water depths, at distances up to 65 km from shore, do

not exceed 40 m. The ridges form an arcuate pattern trending parallel to

the direction of flow of the tidal currents. Of particular interest is an

example showing the alignment of ridges both parallel and normal to the

coast line. Other examples illustrated by Off show the alignment of tidal

current ridges in straits and estuaries to be essentially parallel to the

coast. These geomorphologic relationships w i l l have some bearing on the

interpretation of ancient sand bodies such as off-shore bars and barrier

islands which also lie parallel to the coastline. Off (1963, p. 327)

describes the tidal current ridges in the Gulf of Korea as follows, "Here,

the ridges are spaced with an average of 3 miles between crests and rise

an average of 65 feet from their base. They are oriented approximately

parallel with the west coast of Korea and perpendicular to the north end

of the Yellow Sea".

These ridges have developed on a flat and shallow continental shelf

With reference to sand ridges in Taiwan Strait, Boggs (1974, p. 253)

says, "The rather widespread development of large, asymmetrical sand waves

in Taiwan Strait suggests active transport of bottom sediment. The pattern

of sediment transport, although not yet accurately determined, appears to

be complex; transport in a seaward direction, transport in a landward

direction, and longshore transport are all indicated in various parts of

266

t h e s t ra i t . The sand waves are developed i n areas o f sandy bottom sed i -

ments t h a t Niino and Emery (1961) cons idered t o be r e l i c t P l e i s t o c e n e

sed iments ; i t appears q u i t e l i k e l y , however, t h a t t h e sediment has been

e x t e n s i v e l y reworked s i n c e P l e i s t o c e n e t i m e by bottom c u r r e n t s t h a t may

have markedly a l t e r e d o r i g i n a l sed imentary s t r u c t u r e s and mine ra l concent-

r a t i o n s , as w e l l as l o c a l topography of t h e sea f loo r" .


In t h e North Sea t h e sand i n t i d a l c u r r e n t r i d g e s i s commonly f i n e -

-gra ined and ex t remely w e l l s o r t e d , having been de r ived from o l d e r beds

d e p o s i t e d i n t h e sea o r on a s u r f a c e subsequent ly inundated by t h e sea.

Some r i d g e s c o n s i s t of muddy sand o r muddy s i l t . Sand r i d g e s , be ing

composed of re-worked sediment of f a i r l y uniform g r a i n s i z e , have a homo-

geneous t e x t u r e and show no s i g n i f i c a n t g r a i n g rada t ion . A s shown by

Houbolt (1968) some r i d g e s i n t e r n a l l y r e f l e c t shock waves from a s p a r k e r ,

i n d i c a t i n g cross-bedding o r i n c l i n e d bedding having minor v a r i a t i o n s of

t e x t u r e and composi t ion , whereas o t h e r r i d g e s g ive no r e f l e c t i o n s and

appear t o be i n t e r n a l l y homogeneous. In e i t h e r case i t can bi: expected

that t h e E-log s e l f - p o t e n t i a l curve of an a n c i e n t t i d a l c u r r e n t sand body

w i l l show n e i t h e r a tendency t o b e be l l - shaped nor funnel-shaped, bu t

e x h i b i t a b locky c h a r a c t e r i s t i c s i m i l a r t o t h a t of some d i s t r i b u t a r y channel

sand bod ies .

Compaction

A t some s t a g e i n t h e geo log ica l h i s t o r y o f t i d a l c u r r e n t sand r i d g e s ,

p rovided they remain below s e a l e v e l , t hey are b u r i e d i n a sed imentary p i l e .

Thus p re se rved i n t h e g e o l o g i c a l r eco rd , they are sub jec t ed by i n c r e a s i n g

dep th of b u r i a l t o t h e e f f e c t s of compaction.

ence of t h e sands tone body, and i n d rap ing of t h e ove r ly ing f i n e r sediments.

Subsidence may be minimal, depending on t h e degree of compaction and th ick-

These w i l l r e s u l t i n subs id-

267

n e s s of t h e under ly ing s e c t i o n of sed iments . In t h e case of t h e North Sea

t i d a l c u r r e n t sand r i d g e s , t h e s e c t i o n o f sediment r e s t i n g on conso l ida t ed

rock is compara t ive ly t h i n . The f l a t s ea - f loo r between t h e sand r i d g e s is

covered wi th a g r a v e l l y l a g d e p o s i t , composed of c h e r t pebbles and s k e l e t a l

f ragments , whi& m r l i e s a bed of s t i f f b lu ish-grey c l a y . S i m i l a r l y , where

t i d a l c u r r e n t sand r i d g e s are formed i n a marine t r a n s g r e s s i v e s i t u a t i o n ,

t h e compactional e f f e c t s r e s u l t i n g from subs idence of t h e sand body w i l l

n o t g r e a t l y a l t e r t h e o r i g i n a l shape of t h e body. Consequently, i t s topo-

g raph ic c o n f i g u r a t i o n w i l l be p re se rved , a l though somewhat modi f ied , i n t h e

s t ra ta i n which i t is b u r i e d . I n t e r p r e t a t i o n of t h e o r i g i n a l geometry of

such sands tone bod ies can b e s t b e done by means of s e c t i o n s and maps drawn

w i t h a datum benea th t h e body.

Ancient Sand Bodies

Many examples have been c i t e d of sands tone bod ies depos i t ed as sand

b a r s on sha l low marine s h e l v e s s u b j e c t t o t h e a c t i o n of waves and ocean

c u r r e n t s .

and s i l t , and some accumulated on a carbonate s h e l f . Others appear t o

t r a n s g r e s s b o t h ca rbona te and non-carbonate environments. S e l l e y (1967)

d e s c r i b e s a Miocene s e c t i o n i n Libya where f l u v i a l and p a r a l i c sands

depos i t ed i n a d e l t a i c environment can be t r a c e d i n t o l imes tone beds

depos i t ed on a sha l low marine ca rbona te s h e l f . Desc r ip t ions o f sands tone

bod ies are commonly incomple te , and t h e i n t e r p r e t a t i o n s p laced on t h e i r

o r i g i n s may be equ ivoca l . P e t t i j o h n , P o t t e r and S ieve r (1972, p. 493)

s a y , " In t h e absence of p l e n t i f u l , good d e s c r i p t i o n s of a n c i e n t marine

s h e l f sand b o d i e s , w e have a t tempted t o summarize and s y n t h e s i z e t h e i r

p r o p e r t i e s from few and s c a t t e r e d d a t a (Table 11-6). Much remains t o b e

learned" .

a n c i e n t marine s h e l f sands as fo l lows .

Some of t h e s e a n c i e n t sands w e r e swept on t o a se& f l o o r of c l a y

They f u r t h e r d e s c r i b e some o f t h e g e n e r a l c h a r a c t e r i s t i c s of

"The sand o f many a n c i e n t marine s h e l v e s t ends t o be m i n e r a l o g i c a l l y

mature , e s p e c i a l l y on c r a t o n s , presumably because i t h a s passed through t h e

s h o r e l i n e complex. Thus a r g i l l a c e o u s rock f ragments and u n s t a b l e mine ra l s

g e n e r a l l y are n o t ve ry abundant. G laucon i t e , d e t r i t a l ca rbona te s k e l e t a l

d e b r i s , marine f o s s i l s , and co l lophane are commonly p r e s e n t . A r e l i c t

fauna and anomalously coa r se g r a i n s are common i n t h e upper few f e e t of

some s h e l f sands . Grave l o r conglomerate may b e de r ived l o c a l l y . Cementing

a g e n t s are mostly chemica l , b u t may inc lude a p p r e c i a b l e d e t r i t a l material

proximal t o c l a y o r s h a l e t r a n s i t i o n s . S o r t i n g g e n e r a l l y is good t o e x c e l l e n t ,

and t h e r e i s perhaps a tendency f o r be t te r - than-average rounding. The

v a r i a b i l i t y of t e x t u r a l parameters between samples i s g e n e r a l l y very l o w " .

T i d a l c u r r e n t sand bod ies probably have f o s s i l c o u n t e r p a r t s , b u t

none have been proven. The E l a t e r i t e Bar i n t h e Lower Permian White R i m

Sandstone o f Utah (Baars and Seagar , 1970) h a s morphological s i m i l a r i t i e s .

So do some of t h e a r c u a t e sand bod ies of t h e Lower Cre taceous Viking

Formation i n A l b e r t a and Saskatchewan (Evans, 1970), a l though o t b e r Viking

sand bod ies are i n t e r p r e t e d as s h o r e l i n e and near -shore sands depos i t ed as

beaches and of f -shore b a r s . Off (1963) has sugges ted t h a t t i d a l c u r r e n t s

were e f f e c t i v e i n t h e d e p o s i t i o n of t h e Upper Miss i s s ipp ian P a l e s t i n e

Sands tone , which l i e s s t r a t i g r a p h i c a l l y above t h e channel-forming Bethe l

Sandstone (Fig. 1-29), and a l s o i n t h e d e p o s i t i o n of t h e Upper Cretaceous

Cardium Sandstone o f A lbe r t a . With r e f e r e n c e t o t h e P a l e s t i n e Sandstone

h e s a y s , p . 335, " In a r e c e n t s tudy o f t h e Ches te r sands of t h e I l l i n o i s

Basin ( P o t t e r e t az., 1958) , a t t e n t i o n w a s c a l l e d t o t h e alignment of

sand bod ies p a r a l l e l w i th t h e c u r r e n t d i r e c t i o n s i n d i c a t e d by cross-bedding,

and pe rpend icu la r t o r e g i o n a l s t r i k e . The r e l a t i v e p o s i t i o n s of some of

t h e s e sand bod ies ( a s shown by P o t t e r ' s F igure 13 f o r example) and t h e i r

unique d imens iona l s c a l e , bo th as t o i n d i v i d u a l t h i ckness and d i s t a n c e of

s e p a r a t i o n , combined wi th t h e presence of cross-bedding and sugges t ion of

269

a marine environment, s t r o n g l y suggest t h a t they are t i d a l c u r r e n t r i dges” .

The P a l e s t i n e is i n t e r p r e t e d by P o t t e r et aZ. (1958) as a channel sand-

s tone . The Cardium (Fig. 3-22) sand bodies are considered by Berven (1966)

and o t h e r s t o be o f f - sho re b a r s .

The E la t e r i t e Bar (Fig. 7-4 ) is composed of f ine -g ra ined , w e l l

s o r t e d , qua r t zose sandstone t h a t is f a i r l y uniformly s a t u r a t e d with heavy

a s p h a l t i c o i l t h a t seeps ou t as bitumen from t h i s exhumed s t r a t i g r a p h i c t r a p .

The sandstone body, which t r e n d s i n a s l i g h t arc, is up t o 60 m t h i c k , 2-3

km wide, and 16 km long. I n t e r n a l l y , t h e sandstone e x h i b i t s l a rge - sca l e

sets of sweeping c r o s s - s t r a t i f i c a t i o n t h a t d i p 20-25 degrees sou theas t

and have long t a n g e n t i a l b a s a l con tac t s .

The o r i g i n of t h e Ela te r i te Bar is n o t e n t i r e l y c l e a r . Several

i n v e s t i g a t o r s have agreed t h a t a l though t h e White R i m e Sandstone w a s i n

p a r t depos i t ed i n shal low w a t e r , i t w a s mainly e o l i a n . The ch ie f proponent

S E A W A R D

W L A G O O N A L

E

Fig. 7-4 . General ized c ros s - sec t ion of E la te r i te Bar i n t h e Lower

Permian White R i m Sandstone, sou theas t e rn Utah. (After

Baars and Seager , 1970).

270

of t h i s i n t e r p r e t a t i o n is Baker ( 1 9 4 6 ) . Baars and Seager (1970) have

r e f u t e d t h i s i n t e r p r e t a t i o n f o r t h e E la te r i te Bar which t h e y d e s c r i b e as a

d e f i n i t e and r e g u l a r sand bui ld-up conformably o v e r l y i n g t h e Organ Rock

S h a l e . They s a y , p . 716, "It i s p r o b a b l e t h a t t h e White R i m Sands tone i s

o f shallow-marine o r i g i n . The b e s t e v i d e n c e is t h e g e o m e t r i c and geo-

g r a p h i c c o n f i g u r a t i o n o f i t s c o n t a i n e d s a n d b a r s , t h e n a t u r e of t h e c r o s s -

- s t r a t i f i c a t i o n and r i p p l e marks , t h e r e g i o n a l r e l a t i o n s of t h e f o r m a t i o n ,

t h e p r e s e n c e of a p r o b l e m a t i c a l g a , and t h e absence of t r a c k s " .

Elateri te Bar i s conformably o v e r l a i n by Lower Permian s h a l y b e d s which i n

t u r n are unconformably o v e r l a i n by t h e T r i a s s i c Moenkopi Formation. No

e v i d e n c e h a s b e e n advanced t o s u g g e s t t h a t t h e E la t e r i t e Bar may b e ( o t h e r

t h a n t h e uppermost p a r t which h a s been re-worked) a n e r o s i o n a l f e a t u r e

formed by c u r r e n t s c o u r i n g . I n f a c t , Baars and Seager o f f e r e v i d e n c e t o

s u g g e s t t h a t t h i s i s n o t t h e case. With r e f e r e n c e t o t h e c o n f i g u r a t i o n of

t h e E la te r i te Bar t h e y s a y , p . 714, "The topography is of s e d i m e n t a r y

r a t h e r t h a n e r o s i o n a l o r i g i n , as shown by t h e g r a d u a l change of wavelength

of the r i p p l e s a l o n g c o n t i n u o u s bedding p l a n e s from 2 i n . a t t h e t o p t o

6 i n . a t t h e margin i n r e s p o n s e t o deepening of t h e water o v e r t h e edge of

t h e bar. From t h i s e v i d e n c e , i t i s a p p a r e n t t h a t t h e E l a t e r i t e Bar was

b u i l t where water d e p t h s r e a c h e d a t l e a s t 50 f t a l o n g i t s seaward margin".

F u r t h e r i n v e s t i g a t i o n s may c l a r i f y t h e s e d i f f e r e n c e s of i n t e r p r e t a t i o n and

d e t e r m i n e t h e o r i g i n of t h e E la te r i te Bar. E x t e r n a l l y and i n t e r n a l l y t h i s

s a n d s t o n e body h a s s imi la r i t i es o f d imens ions and a p p a r e n t d e p o s i t i o n a l

envi ronment t o t h o s e of t h e North Sea sand r i d g e s d e s c r i b e d by Houbolt

(1968) .

The

The p o t e n t i a l o f t i d a l c u r r e n t sand r i d g e s as r e s e r v o i r s f o r o i l

and g a s h a s been p o i n t e d o u t by Houbolt (1968, p . 2 6 4 ) w i t h r e f e r e n c e t o

mar ine t r a n s g r e s s i v e s i t u a t i o n s where l a r g e , t h i c k and e l o n g a t e d sand

b o d i e s c a n b e formed. He s a y s , "These sand b o d i e s w i l l c o n s i s t of c l e a n ,

271

wel l - so r t ed sand , w i thou t a v e r t i c a l g rada t ion i n g r a i n s i z e and w i l l be

o v e r l a i n by c layey marine sed iments i f t h e t r a n s g r e s s i o n con t inues .

Hence they w i l l form e x c e l l e n t r e s e r v o i r s f o r o i l " . To i l l u s t r a t e h i s

p o i n t h e c i t e s t h e Well Bank, one of t h e l a r g e t i d a l c u r r e n t r i d g e s i n

t h e North Sea. Assuming t h a t t h i s sand body has a p o r o s i t y of 30%, t h e

pore space be ing comple te ly f i l l e d wi th o i l , and t h a t 20% of t h e o i l can

b e r ecove red , he estimates t h a t t h e body could y i e l d 950 m i l l i o n b a r r e l s

(151 m i l l i o n cub ic meters ) of o i l . This i s a t h e o r e t i c a l c o n s i d e r a t i o n bu t

i l l u s t r a t e s t h e p o s s i b l e p o t e n t i a l of sands tone bod ies having s imilar

dimensions and good poros i ty -pe rmeab i l i t y c h a r a c t e r i s t i c s .


273

Chapter 8

ALLUVIAL FANS AND SHEETS


Geomorphology

A l l u v i a l f a n s and s h e e t s are composed of g r a v e l , s and , and s i l t

de r ived as d e t r i t u s from t h e r a p i d e r o s i o n o f an u p l i f t e d c r u s t a l b e l t o r

b lock that i s commonly bounded by an a c t i v e f a u l t . The s u r f a c e expres s ion

of coa le sc ing f a n s and s h e e t s , f ed by v a l l e y s d i s s e c t i n g t h e u p l i f t e d

b lock (F ig . 8-1), is seen as a pediment o r a l l u v i a l p l a i n . In t h e sub-

s u r f a c e f a n s commonly merge t o form a wedge of sediment s e v e r a l thousand

f e e t t h i c k , whereas s h e e t s are ve ry much t h i n n e r and more widespread.

Where such f a n s are formed i n a semi-deser t environment, p a r t i c u l a r l y where

b lock f a u l t i n g movements of t h e e a r t h ' s c r u s t have formed a b a s i n and range

topography, g r e a t t h i c k n e s s e s of accumulated f a n s , commonly exceeding

3,000 m, b u t i n p l a c e s up t o 8,000 m (Crowel l , 1954) are known t o e x i s t .

B u l l (1972, p. 63) d e f i n e s a l l u v i a l f a n d e p o s i t s as fo l lows , "Fans c o n s i s t

of wa te r - l a id sed iments , debr i s - f low d e p o s i t s , o r bo th . Water-laid

sed iments occur as channel , s h e e t f l o o d , o r s e i v e d e p o s i t s . Entrenched

stream channels commonly are b a c k f i l l e d wi th g r a v e l t h a t may be imbr i ca t ed ,

mass ive , o r t h i c k bedded. Braided s h e e t s of f i ne r -g ra ined sed iments

depos i t ed downslope from t h e channel may be cross-bedded, massive, lamin-

a t e d , o r t h i c k bedded. Se ive d e p o s i t s a r e over lapping lobes of permeable

g rave l " . Leopold, Wolman, and Mil ler (1964) d e s c r i b e an a l l u v i a l f an

f l a n k i n g t h e Sandia Mountains, New Mexico. They say t h a t w i t h i n h a l f a

m i l e of t h e mountain f r o n t , which i s bonnded by a normal f a u l t , w e l l s

p e n e t r a t e d 10-30 m of sand and g r a v e l ove r ly ing g r a n i t e , whereas w e l l s

274

Fig . 8-1. Sketch of c o a l e s c i n g a l l u v i a l f a n s , showing o r i g i n a l

d e p o s i t i o n a l s l o p e s ( S e c t i o n s A-A' and B-B ' ) . ( A f t e r Le

Blanc , 1 9 7 2 ) .

215

d r i l l e d on ly a s h o r t d i s t a n c e f a r t h e r from t h e mountains p e n e t r a t e d more

than 100 m of sand and g r a v e l , i n d i c a t i n g a r a p i d th i ckenn ing of t h e

a l l u v i a l wedge. F a r t h e r from t h e sou rce , bo th f a n and s h e e t g r a v e l s and

sands become t r a n s i t i o n a l w i t h r i v e r and l a k e sands , s i l t s , and muds (F ig .

8-2), o r w i th marine sed iments where t h e pediment s l o p e s down t o t h e sea .

The middle t o lower s l o p e s of a l l u v i a l f a n s and s h e e t s are commonly

remarkable f o r t h e i r b ra ided s t r zam d e p o s i t s which c h a r a c t e r i z e d ra inage

p a t t e r n s h e a v i l y l aden wi th sediment. S e l l e y (1970, p . 24) s a y s , "Many

present -day b ra ided r i v e r s are found on piedmont f a n s a t t h e edge of

mountains where t h e r e are l a r g e amounts of sediment and d i scha rge is o f t e n ,

b u t n o t a lways , s easona l . Examples have been desc r ibed from t h e h o t

d e s e r t s of t h e mid w e s t of U . S . A . and from t h e p e r i g l a c i a l mountains of

FEET

0 5

0 5

- MILES -

K M

Fig . 8-2. Sec t ion of an a l l u v i a l f a n (1) grading i n t o r i v e r d e p o s i t s

(2) and ove r ly ing P l e i s t o c e n e l a k e c l a y s ( 3 ) i n a v a l l e y

f l a n k i n g t h e Sierra Nevada mountains of C a l i f o r n i a .

from B u l l , 1972 a f t e r Magleby and Kle in , 1965).

(Redrawn

276

t h e Yukon i n Canada (e.g. Bl issenbach, 1954, and Williams and Rust, 1969).

I n these regions e ros ion i s r a p i d , d i scha rge is sporadic and h igh , and

t h e r e i s l i t t l e vege ta t ion t o h inde r runoff . Because of t h e s e f a c t o r s

r i v e r s a r e gene ra l ly overloaded with sediment. A channel is no sooner

c u t than i t chokes i n i t s own d e t r i t u s . This i s dumped a s ba r s i n t h e

c e n t r e of t he channel around which two new channels a r e d ive r t ed . Repeated

b a r formation and channel branching gene ra t e s a network of braided channels

over t h e whole d e p o s i t i o n a l a r e a . Thus t h e alluvium of braided r i v e r s i s

t y p i c a l l y composed of sand and g rave l channel depos i t s t o t h e exclusion of

f ine-grained overbank s i l ts and c l ays .

and f l u c t u a t i n g discharge t h e r e i s gene ra l ly an absence of l a t e r a l l y

ex tens ive c y c l i c sequences s i m i l a r t o those produced by meandering channels.

Fining-upward g r a v e l , sand, s i l t sequences have been recorded however and

a r e a t t r i b u t e d t o waning cu r ren t v e l o c i t i e s a s a channel is gradual ly

i n f i l l e d ( W i l l i a m and Rust , 1969)".

Due t o repeated channel switching

The term fan r e f e r s t o t h e topographic shape of an accumulakion of

sediment discharged on t h e g e n t l e s lope of a pediment (commonly 2-3 degrees)

from a narrow v a l l e y c u t t i n g i n t o an adjacent range of h i l l s o r mountains.

The d i s t a l p o r t i o n s of f ans merge down t h e s lope t o form s h e e t s of sediment

which a r e gene ra l ly f i n e r grained than those deposi ted c l o s e r t o t h e

mountains. Fans a r e b u i l t up by an accumulation of l a y e r s of sediment

deposi ted l a r g e l y a s s easona l outwash during r a iny per iods. The depos i t

consequently progrades i n t o t h e v a l l e y , which may be a broad topographic

f e a t u r e .

i t having been deposi ted along t h e f l ank of a va l l ey . It is a l s o wedge-

-shaped t o l e n t i c u l a r (Bu l l , 1972) . Var i a t ions i n t h e r a t e s of seasonal

run-off , and t e c t o n i c in f luences such a s f a u l t movements of t h e v a l l e y

f l o o r o r f l a n k s w i l l i n f luence t h e development of t he a l l u v i a l wedge.

Ind iv idua l l a y e r s , which grade from coa r se r t o f i n e r away from the mountains,

The subsurface conf igu ra t ion of a fan depos i t is somewhat l i n e a r ,

271

and which may a l s o show g r a i n gradat ion from coa r se r below t o f i n e r above,

w i l l no t have any r e g u l a r sequence with r e spec t t o one another . Layers of

coa r se g rave l may o v e r l i e l a y e r s of sand and g r i t , and the l a y e r s them-

s e l v e s may thicken and t h i n t o such an e x t e n t t h a t they a r e ind i s t ingu i shab le

as s t r a t i g r a p h i c u n i t s . Whether o r not such l a y e r s can be t r aced l a t e r a l l y

depends l a r g e l y on t h e l i n e of s e c t i o n taken, and on t h e geometry of t h e

a l l u v i a l fan body. A s pointed out by Bull (1972), i n d i v i d u a l beds may be

t r aced f o r long d i s t a n c e s a long r a d i a l s e c t i o n s , bu t along cross-fan

s e c t i o n s t h e beds appear t o be l e n t i c u l a r and a r e commonly cu t by channels.

These channels a r e most common nea r t h e apex of t h e a l l u v i a l fan body,

whereas i n t h e d i s t a l p a r t s , away from t h e source of t h e sediment, t h e

l a y e r s a r e more shee t - l i ke . The t o t a l s e c t i o n of sediment i n an a l l u v i a l

f an body may appear i n the subsurface, and poss ib ly a l s o i n outcrop, a s a

s i n g l e u n i t comprising poorly s o r t e d , unsequent ia l l a y e r s and l enses of

g r a v e l , sand, and s i l t .


A l l u v i a l f a n d e p o s i t s c o n s i s t l a r g e l y of poorly s o r t e d c l a s t i c s

deposi ted by drainage systems t h a t commonly form braided s t reams, bu t

which may a l s o discharge t h e i r sediment loads during i n t e r m i t t e n t per iods

of s h e e t run-off. Consequently, t hese sediments accumulate r ap id ly t o

form t h i c k s e c t i o n s of superimposed l a y e r s and l e n s e s , each of which may

have no g r a i n g rada t ion o r may show some degree of gradat ion from coa r se r

below t o f i n e r above. Where p r e s e n t , i n an ind iv idua l l a y e r o r l e n s , g ra in

g rada t ion may be r e f l e c t e d i n the cha rac t e r of t h e s e l f - p o t e n t i a l curve,

i nd ica t ed by a poorly def ined bell-shape.

o r i n t e r c a l a t e d with po r t ions of t h e s e l f - p o t e n t i a l curve t h a t show no

meaningful c h a r a c t e r , t h e ove r -a l l con f igu ra t ion of t h e E-log may i n d i c a t e

merely a t h i c k s e c t i o n of poorly def ined l a y e r s . In t h i s r e s p e c t , where

t h e s e c t i o n i s s e v e r a l hundred f e e t t h i c k , t h e r e may be s i m i l a r i t i e s

Superimposed one on t h e o t h e r ,

278

between t h e E-logs of a l l u v i a l fan and t u r b i d i t y cu r ren t depos i t s . In

gene ra l , t h e E-log s e l f - p o t e n t i a l of an a l l u v i a l f an depos i t tends t o be

blocky and s e r r a t e d .

Compaction

Wedges of c l a s t i c sediments accumulating along a s ink ing trough

unde r l a in by a graben complex, o r p i l i n g up along t h e f l ank of an upthrust-

i n g range of mountains, a r e r e l a t i v e l y uncompactible and s o r e t a i n t o a

l a r g e degree t h e i r o r i g i n a l shape a f t e r b u r i a l . E s s e n t i a l l y , a l l u v i a l f an

d e p o s i t s a r e f l a t on t h e top and markedly bu t i r r e g u l a r l y concave a t the

base. The d e p o s i t s a r e always f lanked on one s i d e by o l d e r rock which is

probably i n l a r g e p a r t t h e source m a t e r i a l f o r t h e depos i t , and may a l s o

be unde r l a in by a l l u v i a l and l a c u s t r i n e sediments. In some a reas where the

u p l i f t e d b e l t of mountains i s f lanked by a marine c o a s t l i n e , o r where the

b e l t f l anks a v a l l e y invaded by t h e s e a , t h e a l l u v i a l fan depos i t may

o v e r l i e and merge l a t e r a l l y i n t o marine carbonate o r non-carbonate

sediments.

i s deposi ted, subsequent compaction w i l l modify t h e shape of t h e f an which

neve r the l e s s r e t a i n i t s c h a r a c t e r i s t i c of being r egu la r a t t h e top and

i r r e g u l a r a t t h e base. The choice of a datum f o r cons t ruc t ing a c ros s

s e c t i o n consequently l i e s i n t h e sequence of beds immediately overlying

t h e a l l u v i a l f an depos i t .

Depending on t h e n a t u r e of t h e base on which an h l l u v i a l f an

The o r i g i n a l po ros i ty and permeabi l i ty of a l l u v i a l f an sediments i s

e x c e l l e n t , and s u r f a c e water permeates downward so r a p i d l y t h a t only t h e

lowermost beds a r e water-bearing.

f l ank ing the Sandia Mountains, New Mexico, Leopold, Wolman, and Mi l l e r

(1964) s t a t e t h a t i n bores d r i l l e d nea r t h e base of t h e mountain range

water i s usua l ly obtained from t h e t h i n edge of t h e a l l u v i a l f an depos i t ,

c o n s i s t i n g of g rave l l y i n g on t h e rock of which t h e range is composed.

With r e fe rence t o a l l u v i a l f a n depos i t s

In

279

bores d r i l l e d s l i g h t l y f a r t h e r from t h e r ange , where s e v e r a l hundred f e e t

of a l l u v i a l f a n sand and g r a v e l w e r e p e n e t r a t e d , t h e sed iments a r e dry .

Compaction, w i th i n c r e a s i n g p r e s s u r e and tempera ture , dec reases t h e

p e r m e a b i l i t y of t h e l i t h i c clastics which are much more r e a d i l y a l t e r e d

than qua r t zose sands . A l t e r a t i o n s are e f f e c t e d by mechanica l ly f r a c t u r i n g

t h e g r a i n s , p a r t i c u l a r l y those of rock f ragments , f e l d s p a r s , and t h e f e r r o -

magnesian mine ra l s , by d i a g e n e t i c a l t e r a t i o n of t h e mine ra l c o n s t i t u e n t s

t o form c l a y mine ra l s which p a r t i a l l y p l u g t h e pore space, and by cement-

a t i o n of t h e g r a i n s wi th c a l c i t e , i r o n oxide and o t h e r c o n s t i t u e n t s

depos i t ed by c i r c u l a t i n g wa te r . The e f f e c t on water movements w i t h i n

deeply b u r i e d a l l u v i a l f a n d e p o s i t s i s t o dec rease t h e v e r t i c a l pe rmeab i l i t y

and t o deve lop t r e n d s of r e l a t i v e l y g r e a t e r pe rmeab i l i t y a long d e p o s i t i o n a l

and l a t e r a l l y d i r e c t i o n a l f e a t u r e s such as channels .

k c i e n t Sand Bodies

Examples of a n c i e n t a l l u v i a l f a n d e p o s i t s are n o t common, b u t some

have been desc r ibed i n t h e l i t e r a t u r e . Other d e p o s i t s , which probably are

a l l u v i a l f a n s , have been desc r ibed bu t n o t s p e c i f i c a l l y de f ined , as t o t h e i r

o r i g i n . S e l l e y (1970, p. 3 0 ) , based on S e l l e y (1965), d e s c r i b e s Precambrian

a l l u v i a l f a n d e p o s i t s i n nor thwes t Scot land as fo l lows . "The coa r se g r a i n

s i z e , a n g u l a r i t y , poor s o r t i n g , and pe t rography of t h e b a s a l f a c i e s d e p o s i t s

c l e a r l y show t h a t t hey were de r ived l o c a l l y from t h e Lewisian gne i s s . Thei r

geometry and t h e r a d i a t i n g d e p o s i t i o n a l d i p s l e a v e s l i t t l e doubt t h a t t hey

are a n c i e n t piedmont f a n s . Depos i t ion w a s p robably due t o ava lanches , mud-

f lows , and s h e e t f l o o d s such as occur on s t e e p s l o p e s n e a r t h e a p i c e s o f

Recent f a n s f e .g . Blackwelder, 1928)". Seve ra l samples, which may i n p a r t

b e of a l l u v i a l f an o r i g i n , are mentioned by S e l l e y (1970). Some of t h e s e

a r e sequences , many hundreds of metres t h i c k , which show a la teral t r ans -

i t i o n from b ra ided s t r eam d e p o s i t s n e a r t h e i r source t o f l u v i a l sediments

d e p o s i t e d i n a meandering stream sys tem, o r t o l a c u s t r i n e sed iments .

O the r s c o n s t i t u t e widespread b u t compara t ive ly t h i n (more than 100 m)

s h e e t s o f conglomera t ic s ands tone . These examples, i n v a r i o u s p a r t s of

t h e wor ld , range i n age from t h e Precambrian t o t h e Cenozoic.

Of p a r t i c u l a r i n t e r e s t , because l o c a l l y they form r e s e r v o i r s f o r

pe t ro leum, are L a t e Pa leozo ic t o Mesozoic a l l u v i a l f a n and s h e e t d e p o s i t s

i n North A f r i c a . These have c o l l e c t i v e l y been r e f e r r e d t o as t h e Nubia

Sandsfone. Cons ide rab le confus ion exists i n t h e l i t e r a t u r e on t h e Nubia

Sands tone (Pomeyrol, 1968). The term, used a t v a r i o u s l o c a l i t i e s i n

North A f r i c a , i n c l u d e s beds r ang ing from Carboni ferous t o Ea r ly Cre taceous .

Beds r e f e r r e d t o as Nubia Sands tone (sensu stricto) are predominant ly of

terrestrial and f resh-water o r i g i n , a l though some s t r a t i g r a p h i c sequences

which have been l o o s e l y r e f e r r e d t o as Nubia i n c l u d e beds w i t h mar ine

f o s s i l s . McKee (1963) s t u d i e d t h e sequence and types of sed imentary

s t r u c t u r e s w i t h i n beds r e f e r r e d t o as Nubia and concluded t h a t t hey were

d e p o s i t e d i n f l u v i a t i l e , l a c u s t r i n e , e s t u a r i n e and l agoona l environments

on a b road c o n t i n e n t a l p l a i n t h a t w a s c o n t i n u a l l y b u t i r r e g u l a r l y sub-

s i d i n g .

Saharan and Arabian Precambrian S h i e l d s . They have an e x t e n s i v e d i s t r i b -

u t i o n and are no ted f o r c ross -bedding of t h e type found i n b r a i d e d stream

d e p o s i t s . S e l l e y (1970) advanced t h e i n t e r p r e t a t i o n , a f t e r views expres sed

by S tokes (1950) and W i l l i a m s (1969) w i t h r e s p e c t t o beds i n o t h e r p a r t s of

t h e wor ld , t h c t t h e s e d e p o s i t s were l a i d down as piedmont f a n s formed of

d e t r i t u s d e r i v e d from t h e e r o s i o n of r e t r e a t i n g s c a r p s of o l d e r beds of

s ands tone and conglomerate.

Such beds o f terrestrial o r i g i n occur around t h e margins of t h e

In t h e S i r t e Bas in , L ibya , v a s t q u a n t i t i e s of t e r r i g e n o u s c l a s t i c s

were d e r i v e d from t h e e r o s i o n of a Precambrian mass i f t o t h e sou th . These

c l a s t i c s are mentioned by Conant and Goudarzi (1967, p. 721) who s a y ,

"Widespread ove r s o u t h e r n Libya is a t h i c k sequence of c o n t i n e n t a l beds

281

THIRD RETREATING SCARP

ISHRIN ALLUVIAL FAN

G\

UM SAHM FMN. ( marine shelf sand )

DlSl ALLUVIAL FAN

f - r ,

t + + + t t + t ,

SECOND RETREATING SCARP

SALE8 ALLUVIAL FAN

\r,

,'1 0 - . 0 ' . . .

I ' . ' . ' . ~ I

. . . . . . , . . . , , , . . . . . . . t t + + + + L . . + t t + + + + + + ~ + + + + + + + + + + + + + + + +

FIRST RETREATING SCARP

PRECAMBRIAN

F ig . 8-3. Cambro-Ordovician s e c t i o n i n Jordan showing o r i g i n as

on-lapping a l l u v i a l fans r e s u l t i n g f r o m repeated u p l i f t and

pedimentat ion. ( A f t e r S e l l e y , 1970).

282

long known a s t h e Nubian Sandstone, which is a l s o p r e s e n t i n much of

n o r t h e a s t e r n A f r i c a and t h e Arabian Pen insu la , though l o c a l l y known by

d i f f e r e n t names". S e l l e y (1970) d e s c r i b e s Cambro-Ordovician conglomera t ic

s ands tone beds i n Jordan (Fig. 8-3) which, he s a y s , are s imilar i n l i t h o -

logy and sequence of sed imentary s t r u c t u r e s t o terrestr ia l beds of t h e

Nubia Sandstone i n Egypt. The beds i n Jo rdan , comprising a t h i c k n e s s of

700 m of c o a r s e , cross-bedded a l l u v i a l s ands tones , a r e be l i eved t o have been

l a i d down by b ra ided streams f lowing over a coa le sc ing complex of broad ,

imbr i ca t ed a l l u v i a l f a n s t h a t formed a piedmont p l a i n . This sequence of

beds rests on t h e Precambrian igneous basement and is o v e r l a i n by sands tone

depos i t ed as marine s h o r e l i n e sands .


Lower Cre taceous sands tones i n t h e S i r t e Bas in , Libya, r e f e r r e d t o

by Conant and Goudarzi (1967) as Nubian Sandstone, and a l i t h o l o g i c a l l y

s i m i l a r sequence of non-marine Carboni ferous sands tones i n t h e Gul'f of

Suez r eg ion of t h e United Arab Republ ic , a l s o r e f e r r e d t o as Nuhian by

Weeks (1952) c o n t a i n o i l i n s t r u c t u r a l - s t r a t i g r a p h i c t r a p s . S e l l e y (1970,

p . 47) r e f e r s t o t h e s e o i l accumula t ions i n t h e S i r t e Basin as fo l lows ,

"Here Lower Cre taceous a l l u v i a l f a n s are banked a g a i n s t an i r r e g u l a r (?

f a u l t e d ) basement topography. They were bu r i ed by marine s h a l e s of t he

Cenomanian t r a n s g r e s s i o n . Where s t r u c t u r a l l y h igh r e l a t i v e t o t h e s h a l e s ,

t h e s e f a n d e p o s i t s , s t i l l l a r g e l y uncemented, con ta in some i n t e r e s t i n g o i l

f i e l d s " .

a l l u v i a l f a n d e p o s i t s w a s penecontemporaneous wi th subs idence and b lock

f a u l t i n g . Conant and Goudarzi (19673 s t a t e t h a t o i l accumulations i n t h e s e

Lower Cre taceous beds are a t depths i n t h e range 2,700-4,300 m. I n t h e Gulf

of Suez r eg ion t h e o i l accumula t ions are i n Carboni ferous sands tone where

t h e up-dip edges of t h e sands tone form f a u l t s c a r p s o v e r l a i n by Miocene

I n t h e e a s t e r n embayment of t h e S i r t e Basin d e p o s i t i o n of t h e s e

283

marine mudstone. I t i s of interest t o n o t e t h a t in bo th t h e S i r t e Bas in

and t h e Gulf of Suez r e g i o n , where i n t h e former a r e a t h e accumulations may

b e e s s e n t i a l l y s t r a t i g r a p h i c - s t r u c t u r a l and i n t h e l a t te r are c e r t a i n l y

s t r u c t u r a l , t h e r e s e r v o i r beds o f a l l u v i a l f an d e p o s i t s are o v e r l a i n by

marine s h a l e s o r mudstone.

f an d e p o s i t s are o v e r l a i n by marine t r a n s g r e s s i v e sed iments , t r a p s f o r

pe t ro leum can occur w i t h i n them, depending l a r g e l y on t h e presence of

s t r u c t u r a l c l o s u r e . This type of s t r a t i g r a p h i c - d e p o s i t i o n a l s i t u a t i o n may

arise where an u p t h r u s t b lock of t h e e a r t h ' s c r u s t forms a b e l t of mountains

a d j a c e n t and p a r a l l e l t o a marine c o a s t l i n e , o r where a v a l l e y , f l anked by

a l l u v i a l f ans de r ived from ad jacen t mountains, and unde r l a in by an a c t i v e l y

s i n k i n g graben complex, i s f looded by a t r a n s g r e s s i n g sea. Where t h e

a l l u v i a l f a n d e p o s i t s are o v e r l a i n by marine mudstones, which may be

c a l c a r e o u s , t h e pe t ro leum genera ted i n t h e marine beds and t r apped i n t h e

a l l u v i a l f a n d e p o s i t s may c o n s i s t of bo th o i l and p e t r o l i f e r o u s gas. But

where t h e ove r ly ing beds are no tab ly carbonaceous, having formed i n a

The g e n e r a l i t y can b e s t a t e d t h a t where a l l u v i a l

c o a s t a l swamp t o r i v e r backswamp environment, t h e hydrocarbons genera ted

are more l i k e l y t o predominantly c o n s i s t of n a t u r a l gas.

I n Libya, ve ry cons ide rab le p roduc t ion of o i l is ob ta ined from

Cre taceous sands tones which g e n e r a l l y are r e f e r r e d t o as Nubian. Lador

(1971) g ives f i g u r e s f o r t h e cumula t ive product ion of o i l , t o 1971, from

a number of f i e l d s , a l l o f which have been brought on stream s i n c e the

e a r l y 1960's.

t h e Cre taceous . The Z e l t e n F i e l d h a s a cumula t ive product ion of approximately

1,000 m i l l i o n b a r r e l s (159 m i l l i o n cub ic met res ) from Cretaceous and Paleocene

beds ; t h e S a r i r F i e l d h a s a cumula t ive product ion of approximate ly 380

m i l l i o n b a r r e l s (60 m i l l i o n cub ic metres) from Upper Cre taceous beds ; and

t h e Waha F i e l d has a cumulative p roduc t ion of approximate ly 300 m i l l i o n

b a r r e l s ( 4 8 m i l l i o n cub ic met res ) from Cretaceous and Eocene beds . A l l of

These f i e l d s are producing e i t h e r e x c l u s i v e l y o r mainly from

284

t h e o t h e r f i e l d s producing from t h e Cre taceous have a cumula t ive product ion

of 320 m i l l i o n b a r r e l s (51 m i l l i o n cub ic me t re s ) . These f i e l d s inc lude t h e

Dor, Ko t l a , Magid, Mansour, L-65, J e b e l , Lehib, Ora, Bahi, B e 1 Hedan, and

Samah. The t o t a l cumula t ive p roduc t ion of a l l t h e s e f i e l d s , t o 1971, amounts

t o approximate ly 2,000 m i l l i o n b a r r e l s (218 m i l l i o n cub ic met res ) of l i g h t

g r a v i t y o i l . A new d i scove ry mentioned by Lador (1971), which i s s i t u a t e d

some 16 km southwes t of t h e Ze l t en F i e l d , y i e lded a flow of 4 9 O A . P . I . o i l ,

a t rates up t o 1,000 b a r r e l s pe r day, from a sands tone a t a depth of about

3,350 m. Lador r e f e r s t o t h i s sands tone as Nubian.

285

Chapter 9

EOLIAN SAND


Geomorphology

E o l i a n s a n d s accumula te on a l a n d s u r f a c e t h a t may be p r e s e r v e d as

a n unconformi ty o r a d i s c o n f o r m i t y i n t h e s t r a t i g r a p h i c r e c o r d . Discon-

t i n u i t y may b e profound as i n t h e case of a widespread d e s e r t , o r of v e r y

minor s i g n i f i c a n c e a s i n t h e c a s e of sand dunes formed i n r i v e r p o i n t

b a r s o r mar ine and l a c u s t r i n e s h o r e l i n e d e p o s i t s .

dunes are forming , t h e sand is i n i t i a l l y d e r i v e d from areas of d e f l a t i o n ,

n o t e d f o r t h e i r l a g d e p o s i t s of s a n d - b l a s t e d p e b b l e s o r f r o n t h e wind-swept

b e a c h e s o f a c o a s t a l envi ronment .

c o n t i n u a l s h i f t i n g of t h e s a n d dunes themselves .

I n d e s e r t s where sand

Sand i s s e c o n d a r i l y d e r i v e d from t h e

Sand dunes e x h i b i t a v a r i e t y of s h a p e s which have been v a r i o u s l y

c l a s s i f i e d ( P e t t i j o h n , P o t t e r , and S i e v e r , 1972) w i t h r e f e r e n c e t o p h y s i c a l

p a r a m e t e r s , s u c h as volume of sand s u p p l y and v e l o c i t y of wind, which have

de te rmined o r i n f l u e n c e d t h e i r morphology. But a l l such dunes are charac-

t e r i z e d by l a r g e a m p l i t u d e , h i g h a n g l e (> 3 0 " ) , sweeping cross -beds (Fig. 9-1)

These f e a t u r e s have been d e s c r i b e d by McKee (1966).

S e t s of c r o s s - b e d s , p i l e d one on t h e o t h e r , a r e known t o form

a c c u m u l a t i o n s s e v e r a l hundred feet t h i c k . The b a s e of such an accumula t ion

may b e a s h e e t of h o r i z o n t a l l y bedded, c o a r s e r - g r a i n e d , p o o r l y s o r t e d ,

pebbly sand over - r idden by a moving f r o n t of dunes.

formed by d e f l a t i o n of t h e d e s e r t s u r f a c e and c a n cover v a s t areas. The

sand removed i s b o r n e by t h e wind and d e p o s i t e d on dunes which may i n t u r n

m i g r a t e o v e r some o t h e r area of t h e sand s h e e t . Reineck and Singh (1973,

Such sand s h e e t s are

286

-LO

.30

- 20

10

0

Detail of asymmetrical trough, Side trench S E NW

feet 5 -

Mmn trench

fl-

0 5 10 IS 20 Ice1

Main trench, Norlh wall SW NE feet

I isa feet ILO 130 120 110 IOO 90 80 70 60 50 LO 30 20 10 0

- Hoiindlng iurfoce Selected c r o ~ 5 - 5 i i o i u n i 28" Apparent dip

F i g . 9-1. I n t e r n a l s t r u c t u r e o f a s a n d dune a t White Sands N a t i o n a l

Monument, New Mexico, showing a SW-NE s e c t i o n i n t h e I

d i r e c t i o n of s a n d t r a n s p o r t , and a SE-NW t r a n s v e r s e s e c t i o n .

( A f t e r McKee, 1966).

p . 196) d e s c r i b e such s h e e t s i n p r e s e n t day d e s e r t s a s f o l l o w s , "Sand

s h e e t s a r e u s u a l l y v e r y l a r g e areas o f d e s e r t c o u n t r y , more o r less f l a t

i n n a t u r e . S l i g h t u n d u l a t i o n s o r s m a l l dune- l ike f e a t u r e s may b e p r e s e n t .

The s u r f a c e r a r e l y shows such f e a t u r e s as wind sand r i p p l e s o r wind

g r a n u l e r i p p l e s . However, d u r i n g s t o r m s s a n d s t r i p s commonly develop

( c f . Bagnold, 1954). The s u r f a c e of sand s h e e t s is s p r i n k l e d w i t h c o a r s e r

s e d i m e n t s - p e b b l e s .

bedded sand l a y e r s s e p a r a t e d by s i n g l e l a y e r s of p e b b l e s . Such e v e n l y

l a m i n a t e d sand ( h o r i z o n t a l l y bedded sand) i s a l s o a common t y p e of

I n t e r n a l l y a sand s h e e t is made up of h o r i z o n t a l l y

281

bedding i n in t e rdune areas" .

s h e e t s known which a r e devoid of any k ind of pebbles . Such sand s h e e t s

are made up of we l l - so r t ed a e o l i a n sand wi th well-developed h o r i z o n t a l l y

lamina ted sand. A combination of r a p i d sed imen ta t ion , h igh wind v e l o c i t i e s ,

and f a i r l y uniform g r a i n s i z e of t h e sand cause d e p o s i t i o n of s h e e t sand

wi th an abundant ly developed evenly lamina ted sand bedding ( c f . Bagnold,

1954; Glennie , 1970) ."

And f u r t h e r , "There a r e v a s t a r e a s of sand

Reineck and Singh (1974, p . 212) a f t e r Glennie (1970) l i s t t h e

fo l lowing c r i t e r i a as c h a r a c t e r i s t i c of wind-deposited sands .

1.

2 .

3 .

4 .

5.

6 .

7 .

8.

Bedding can be h o r i z o n t a l b u t u s u a l l y e x h i b i t s l a r g e - s c a l e c ross -

-bedding, showing f a i r l y cons t an t o r i e n t a t i o n .

I n d i v i d u a l laminae are w e l l s o r t e d , e s p e c i a l l y i n t h e f i n e r g r a i n

s i z e s ; sha rp g r a i n s i z e d i f f e r e n c e s between lamlnae a r e common.

Gra in s i z e s commonly ranges from s i l t t o coa r se sand. Maximum s i z e

f o r g ranu le s and s m a l l pebbles t r a n s p o r t e d by wind is i n t h e o rde r

of 1 cm, b u t p a r t i c l e s exceeding 5 mm i n d iameter are , rare .

The l a r g e r sand g r a i n s 0.5 - 1.0 mm) t end t o be w e l l rounded.

Clay d rapes are rare.

Sands a r e f r e e of c l ay .

Uncemented q u a r t z g r a i n s e x h i b i t a f r o s t e d s u r f a c e .

Mica is commonly absen t .


Sand dunes t h a t have been preserved i n a sequence of marine o r

l a c u s t r i n e s h o r e l i n e sands , o r i n r i v e r p o i n t b a r d e p o s i t s , commonly

appear t o b e l a c k i n g i n s t r a t i f i c a t i o n .

t h a t t h e dune d e p o s i t i s i n f a c t cross-bedded, b u t t h a t i t s equid imens iona l

g r a i n s i z e tends t o mask t h e laminae. I n o t h e r dunes, ad jacen t laminae may

be r e a d i l y apparent where they e x h i b i t a marked degree o f v a r i a t i o n i n

Close examination may i n d i c a t e

g r a i n s i z e . But w i t h i n t h e dune as a whole t h e r e is commonly l i t t l e

v a r i a t i o n i n mean g r a i n s i z e from top t o bottom. A l s o , t h e r e is l i t t l e

i n t e r g r a n u l a r material, t h e sands be ing c l e a n and ve ry w e l l s o r t e d .

Winnowing by t h e wind, r epea ted c o n t i n u a l l y , r e s u l t s i n t h e s e g r e g a t i o n of

sands i n t o accumulations of Yrarious b u t c o n s i s t e n t ranges i n g r a i n s i z e .

Subsequent c y c l e s of winnowing, caused by a change of c l i m a t e o r wind

p a t t e r n , may r e s u l t i n t he development of younger ove r - r id ing dunes composed

of sand wi th a d i f f e r e n t mean g r a i n s i z e . Consequently, an accumulation of

sand dunes , t h a t may be more than 100 m t h i c k , w i l l have a c o n s i s t e n t mean

g r a i n s i z e w i t h i n each i n d i v i d u a l dune, bu t may show v a r i a t i o n s , between

dunes. The s e l f - p o t e n t i a l curve r e f l e c t i n g a sequence of supzrimposed

dunes w i l l b e c h a r a c t e r i z e d by i t s c y l i n d r i c a l shape , b u t t h e curve may

show e i t h e r a f a i r l y cons t an t ampl i tude , o r superimposed segments ( r ep res -

e n t i n g superimposed dunes) of d i f f e r e n t ampl i tudes .

Compact i o n

With t h e excep t ion of s m a l l ;and dunes i n r i v e r p o i n t b a r s and

s h o r e l i n e sand b o d i e s , e o l i a n sands are depos i t ed i n d e s e r t environments

on a l a n d s u r f a c e . Th i s l and s u r f a c e may b e an unconformity, o r i t may

c l o s e l y r e p r e s e n t an h i a t u s w i t h i n an a l l u v i a l f a n o r s h e e t hundreds of

f e e t t h i c k . It may a l s o r e p r e s e n t an h i a t u s i n a p a r a l i c t o i n n e r n e r i t i c

environment where a ca rbona te s h e l f o r t i d a l f l a t is exposed by a r e g r e s s i n g

sea t o form an e x t e n s i v e c o a s t a l p l a i n t h a t subsequent ly is encroached upon

by s h e e t s and dunes of sand.

bod ie s such a s d i s c r e t e bu t composite dunes, and on sand s h e e t s o r sand

beds composed of merging dunes w i l l depend on t h e s t r a t i g r a p h i c r e l a t i o n s h i p s

t h a t o b t a i n . Where a sand dune, s imple o r complex, l i e s on an unconformity,

o r on a t h i c k s e c t i o n composed e s s e n t i a l l y of a l l u v i a l f a n sands , i t w i l l

r e t a i n t o a l a r g e degree i ts o r i g i n a l shape , which i s mainly p l a n a r a t t h e

base and convex a t t h e top .

The e f f e c t s of compaction on i n d i v i d u a l sand

But where a dune o v e r l i e s compactible sed iments ,

such as c o a s t a l d e p o s i t s of mud, i t s o r i g i n a l p l a n a r base may be deformed

s o t h a t t h e sand body becomes hi-convex. In t h i s con tex t i t might be

d i f f i c u l t t o d i s t i n g u i s h such a dune, subsequen t ly bu r i ed by marine sed i -

ments, from a t i d a l c u r r e n t sand body (Fig. 7 - 4 ) .

D i s c r e t e e o l i a n sand bod ies of t h i s t ype are t h e excep t ion , and most

wind-deposited sands form beds l y i n g on f a i r l y f l a t s u r f a c e s which have

been b e v e l l e d p r i o r t o o r penecontemporaneously w i t h t h e d e p o s i t i o n of t h e

o v e r l y i n g bed. Compaction of such a bed i s compara t ive ly uniform and does

n o t p r e s e n t problems of morphology d i f f e r e n t from those encountered i n t h e

compaction of sands tone beds of o t h e r o r i g i n s .

With r e f e r e n c e t o t h e e f f e c t s of compaction on t h e p o r o s i t y and

pe rmeab i l i t y of e o l i a n sands , t h e o r i g i n a l d i f f e r e n c e s i n composition

between wind depos i t ed and wa te r - l a in sands are s i g n i f i c a n t . Eo l i an sands

are commonly, b u t n o t always, q u a r t z sands . They are of f a i r l y uniform

g r a i n s i z e , and do n o t have an apprec i ab le o r i g i n a l con ten t of s i l t o r c l a y

depos i t ed as d u s t w i th t h e sand. Exceptions are found i n tHe d e l t a of t h e

Rio Grande R ive r , Texas, where dunes of ex t remely f i n e sand and s i l t a r e

r e f e r r e d t o as ' c l a y dunes ' . D iagene t i c a l t e r a t i o n s r e s u l t i n g from

compaction a f t e r b u r i a l a r e minimal i n most e o l i a n sands , a l though meteor ic

waters moving through a bed of sand may cause some s o l u t i o n and re -prec ip-

i t a t i o n (R i t t enhouse , 1971) r e s u l t i n g i n p i t t i n g of t h e g r a i n s and i n t h e

development of i n t e r g r a n u l a r growths of q u a r t z t h a t dec rease p o r o s i t y and

pe rmeab i l i t y .

space , and compaction has less e f f e c t on them than i t does on sands of

o t h e r o r i g i n s .

i l i t y i s f a i r l y uniform throughout t h e body, a cond i t ion t h a t o b t a i n s i n

some marine sands , but; r a r e l y i n f l u v i a l sands .

I n g e n e r a l , e o l i a n sands r e t a i n much of t h e i r o r i g i n a l pore

In many e o l i a n sands tone bod ies t h e p o r o s i t y and permeab-

290

Ancient Sand Bodies

Among t h e many a n c i e n t e o l i a n sand d e p o s i t s , some c l a s t i c examples

are found i n t h e J u r a s s i c Navajo Sandstone (S tokes , 1961) of t h e Colorado

P l a t e a u , t h e J u r a s s i c Ent rada Formation (Tanner, 1965) of New Mexico, t h e

T r i a s s i c BotucatCl Formation (de Almeida, 1953) of t h e Sdo Paulo area, B r a z i l ,

t h e Permian Coconino Sandstone (McKee, 1969) of t h e Grand Canyon, and t h e

Pennsylvanian t o Permian Caspar Formation (Conybeare and Crook, 1968) of

Wyoming. These sands tone beds e x h i b i t t h e l a r g e - s c a l e , sweeping cross-beds

c h a r a c t e r i s t i c o f sand dunes. F o s s i l sand s h e e t s , on t h e o t h e r hand, do no t

have t h e marked d i a g n o s t i c f e a t u r e s of e o l i a n dunes , and consequent ly have

n o t been r e a d i l y recognized .

Beds of a n c i e n t e o l i a n sands commonly range i n th i ckness t o more than

100 m.

s ands tone (Lessen t ine , 1965) , r anges up t o 300 m. It is of i n t e r e s t t o n o t e

t h a t present-day accumula t ions of sand dunes i n t h e Sahara are known t o

l o c a l l y a t t a i n a t h i ckness o f 200-3C0 m. The Ent rada , which i s b v e r l a i n by

beds of a n h y d r i t i c l imes tone , has an upper sands tone member t h a t is p a r t l y

o f e o l i a n o r i g i n . This sands tone i s desc r ibed by Pe te r son e t aZ. (1965) as

mass ive , orjlnge to grey , f r i a b l e , f i n e t o medium-grained, and ranging i n

t h i c k n e s s up t o 150 f e e t . They r ega rd t h e Ent rada Sandstone a s a porous

and permeable b l anke t sands tone t h a t forms e s s e n t i a l l y one hydro log ic u n i t .

The Coconino Sands tone , which i n cross-bedded ou tc rops resembles t h e Navajo,

is desc r ibed by McKee (1969) a s a we l l - so r t ed q u a r t z sand t h a t forms a

wedge, r ang ing i n th i ckness t o more than 150 m , a c r o s s no r the rn Arizona.

McKee (1969, p. 88) d e s c r i b e s t h e Coconino a s fo l lows:

The Navajo, which i s a h i g h l y porous medium t o f ine -g ra ined q u a r t z

"The most d i s t i n c t i v e s t r u c t u r e i n t h e Coconino i s t h e l a r g e - s c a l e ,

wedge p l a n a r c r o s s - s t r a t i f i c a t i o n t h a t i s prominent ly d i sp layed i n t h e wh i t e

c l i f f f a c e s of t h i s sands tone throughout t h e r eg ion (McKee, 1933). The

291

i n c l i n e d laminae , having d i p s of as much as 34 degrees , have g e n t l y curv ing

s u r f a c e s t h a t i n p l a c e s are 60-70 f e e t long . The b e v e l l e d upper edges of

i n d i v i d u a l sets a r e formed by low ang le e r o s i o n s u r f a c e s t h a t c o n s t i t u t e

t h e bases of h ighe r sets of c r o s s - s t r a t a . Other s t r u c t u r e s t y p i c a l of t h e

Coconino are long , p a r a l l e l r i p p l e marks, w i th rounded crests and o r i e n t e d

w i t h axes p a r a l l e l t o t h e d i p s lopes" .

The above d e s c r i p t i o n i s t y p i c a l of many ou tc rops of a n c i e n t e o l i a n

sands which form massive and magn i f i cen t ly s c u l p t u r e d geo log ica l monuments

i n some of t h e n a t i o n a l pa rks of t h e U.S.A. , and i n o t h e r p a r t s of t h e world.

The Botucatfi Formation, which ex tends southward from B r a z i l i n t o Uruguay

and Argen t ina , is of p a r t i c u l a r i n t e r e s t because i t may b e , accord ing t o

Sanford and Lange (1960), t h e l a r g e s t cont inuous e o l i a n d e p o s i t i n t h e

wor ld , cover ing an a r e a of more than 1,300,000 sq . km. Th i s format ion ,

which commonly ranges i n th i ckness up t o 200 m b u t is more than 300 m t h i c k

i n t h e SQo Paulo area, c o n s i s t s of f i n e t o medium-grained qua r t zose sands tone .

The sand g r a i n s are w e l l rounded, have p i t t e d s u r f a c e s , and ?re covered wi th

a r ed f e r rug inous pigment.

c h a r a c t e r i s t i c e o l i a n cross-bedding s imi la r t o t h a t of t h e Coconino

desc r ibed above.

o v e r l a i n by Upper T r i a s s i c vo lcan ic s .

A s t r i k i n g f e a t u r e o f t h e ou tc rops i s t h e

The Botucatci l i e s on an unconformity and is unconformably

The Botucatci h a s good p o r o s i t y and pe rmeab i l i t y , and i n favourable

s t r a t i g r a p h i c and s t r u c t u r a l cond i t ions could be a p o t e n t i a l l y a t t r a c t i v e

r e s e r v o i r bed f o r o i l o r gas . Sanford and Lange (1960, p. 1344) say , "In

t h e s t a t e of Sgo Paulo are l a r g e a r e a s i n which t h e s e sands tones are impreg-

na t ed wi th r e s i d u a l a s p h a l t de r ived from o i l s eep ing up through f a u l t s " .


R e f e r r i n g t o t h e economic s i g n i f i c a n c e of e o l i a n d e p o s i t s , S e l l e y

(1970, p. 63) s a y s , "Eol ian sands tones are p o t e n t i a l l y of h igh p o r o s i t y and

292

pe rmeab i l i t y because they are t y p i c a l l y well-rounded, we l l - so r t ed , and

gene ra l ly only l i g h t l y cemented.

good due t o absence of s h a l e in t e rbeds . Because of these f e a t u r e s e o l i a n

sandstones can be important a q u i f e r s and hydrocarbon r e sd rvo i r s " . Se l l ey

i s of t he opinion t h a t i n gene ra l e o l i a n d e p o s i t s can be r a t e d as poor

p rospec t s because they commonly occur w i t h i n c o n t i n e n t a l b a s i n s , although

t h e s e may o v e r l i e , o r be o v e r l a i n by a sequence of marine t o p a r a l i c s t ra ta

t h a t i n c l u d e s source beds f o r o i l o r gas . The Lower Permian Rotl iegendes

red-beds of northwest Europe and t h e North Sea con ta in examples of gas-

-bear ing e o l i a n sandstones ove r ly ing source beds.

Regional pe rmeab i l i t y i s l i k e l y t o be

North Sea Gas F i e l d s

Major gas f i e l d s producing from t h e Rotl iegendes i n t h e North Sea

i n c l u d e Groningen on t h e n o r t h coas t of t h e Nether lands, and I n d e f a t i g a b l e ,

Leman, and West Sole i n B r i t i s h waters o f f t he coas t of E a s t Anglia and

L inco lnsh i r e . The Rotl iegendes, which inc ludes e o l i a n and o t h e r d e s e r t

environment sands tones , l i e s unconformably on Carboniferous c o a l nieasures.

Glennie (1972) shows t h a t t h e d i s t r i b u t i o n of t h e Rotl iegendes i s confined

t o northwest Europe and t h e southern p a r t of t h e North Sea where i t extends

t o t h e east coas t of England. From south to no r th t h e f a c i e s grade from

those formed i n a f l u v i a t i l e environment cha rac t e r i zed by wadis, t o d e s e r t

sand dunes formed on a c o a s t a l p l a i n , and f a r t h e s t no r th t o s h a l y sediments

and e v a p o r i t e s on a t i d a l p l a i n s i m i l a r t o t h e p re sen t day sabkha environment

of t he Pe r s i an Gulf. With r e f e r e n c e t o t h e th i ckness and l i t h o l o g i c

v a r i a t i o n s of t h e s e beds, Kent (1967, p . 739) remarked, "It i s no t p o s s i b l e

a t t h e p r e s e n t t i m e t o comment on t h e r e g i o n a l v a r i a t i o n of t h e Lower

Permian Rotl iegendes. The c r i t i c a l p o i n t is t h a t i t inc ludes the main

o b j e c t i v e of t he North Sea gas sea rch : a b a s a l sandstone u n i t w i th a

th i ckness i n some p laces measured i n hundreds of f e e t . This sandstone

con ta ins i n the discovery f i e l d s a t Slochteren and probably elsewhere an

293

important

and permeabi l i ty" .

t h e n o r t h coas t of t h e Nether lands. Some f i v e y e a r s l a t e r , with r e fe rence

t o s e c t i o n s i n the southwestern and sou th -cen t r a l p a r t s of t h e Rotl iegendes

b a s i n , Glennie (1972, p. 1055) was a l s o r e t i c e n t about quan t i fy ing th i ckness

o r gene ra l l i t h o l o g y and s t a t e d , "Total t h i ckness and r e l a t i v e p ropor t ions

of each f a c i e s change from p lace t o p l a c e , hence no scale can be given. One

o r more of t hese sedimentary f a c i e s may be absen t i n any p a r t i c u l a r area".

p ropor t ion of almost uncemented dune sandstone of high p o r o s i t y

The S loch te ren w e l l s are s i t u a t e d n e a r Groningen on

In g e n e r a l , t h e Rotl iegendes comprises a lower u n i t of conglomeratic

sandstone interbedded wi th cross-bedded sands tone , and an upper u n i t of

we l l - so r t ed , p l a n a r cross-bedded sandstone which i s o v e r l a i n by beds of

dolomite and evapor i t e s . The lower u n i t i s i n t e r p r e t e d by Glennie (1972)

as comprising dune and f l u v i a t i l e sands formed i n a mixed e o l i a n and wadi

environment.

These gas-bearing sandstones form a f a c i e s which is d i s t r i b u t e d from

Groningen west t o England, covering an a r e a approximately 1,OOd km long and

up t o 300 km wide. The Rotl iegendes b a s i n , as a whole, a l s o t r ends east-

- w e s t and i s up t o 2,000 km long and 500 km wide.

The upper u n i t he i n t e r p r e t s as an accumulation of sand dunes.

The geo log ica l h i s t o r y of t h e s e gas-bearing sands and a s s o c i a t e d

beds has been o u t l i n e d by Glennie (1972). U p l i f t and l e v e l l i n g of t h e

Carboniferous c o a l measures was accompanied by the in l and r eg res s ion of an

escarpment i n c i s e d by wadis and f lanked by a l l u v i a l fans .

formed a s h e e t of dunes over a p l a i n extending t o t h e sabkhas which f r inged t h e

c o a s t l i n e of a l a r g e in l and body of s a l t water.

t h i s d e s e r t sea over the c o a s t a l p l a i n r e s u l t e d i n reworking of t h e uppermost

p a r t of t h e dune sands , and subsequent ly i n depos i t i on of t h e Kupferschiefer ,

t h e cupr i f e rous s h a l e s t h a t are t h e b a s a l u n i t of t h e Zechstein evapor i t e s .

Wind-blown sands

Subsequent t r ansg res s ion of

With r e fe rence t o t h e l i t h o l o g y of t h e gas-bearing dune sands

Glennie (1972, p. 1058) s a y s , "The g r a i n s i z e of t hese sands ranges from

294

very f i n e t o medium and, l o c a l l y , p a r t i c u l a r l y n e a r t h e base of an i n t r a -

fo rma t iona l sequence , may be coa r se . The f i n e r g r a i n s are subangular and

t h e c o a r s e r ones subrounded o r , r a r e l y , rounded. F ros t ed g r a i n s a r e common.

No a r g i l l a c e o u s material i s p r e s e n t a p a r t from a u t h i g e n i c c l a y . The

sands tones g e n e r a l l y are cemented wi th hemat i t e and a u t h i g e n i c c l a y , bu t

l o c a l l y dolomi te and a n h y d r i t e are impor tan t as cements, t o g e t h e r w i th

minor a u t h i g e n i c q u a r t z . Depending on t h e amount of cement p r e s e n t , t h e

sands tone may b e ha rd o r q u i t e f r i a b l e .

t h e s e sands tones form t h e main r e s e r v o i r rock f o r t h e Rot l iegendes gas".

Where primary p o r o s i t y is p rese rved ,

According t o Glennie (1972) t h e probable p roduc ib le r e s e r v e s of gas

from known major f i e l d s w i t h i n t h e Rot l iegendes amount t o about 2,500

b i l l i o n (thousand m i l l i o n ) cub ic meters. Th i s i s t h e e q u i v a l e n t of 85

t r i l l i o n ( m i l l i o n m i l l i o n ) cub ic f e e t . Th i s amount i n c l u d e s 1,800 b i l l i o n

cub ic meters i n t h e Groningen f i e l d and 700 b i l l i o n cub ic meters i n o f f -

-shore North Sea F i e l d s ( I n d e f a t i g a b l e , Leman, and West So le ) . Add i t iona l

r ecove rab le r e s e r v e s o f about 250 b i l l i o n cub ic meters (8.5 t r i l l i o n cub ic

f e e t ) are e s t ima ted t o b e conta ined i n smaller f i e l d s y i e l d i n g gas from the

Rot l iegendes i n t h e Nether lands and West Germany.

Hassi R ' M e l and Houd Berkaoui G a s and O i l F i e l d s , A lge r i a

The Hassi R ' M e l Gas F i e l d and t h e Houd Berkaoui O i l F i e l d s a r e

s i t u a t e d 600 km and 800 km r e s p e c t i v e l y s o u t h e a s t of Oran, A lge r i a .

of t h e s e f i e l d s are producing from g e n t l y e longa te domes w i t h i n Lower

Triassic sands tones which unconformably o v e r l i e an undu la t ing s u r f a c e of

Pa leozo ic ( i n par t Cambro-Ordovician) rocks . The dome s t r u c t u r e s appear

t o r e s u l t from d rap ing of t h e Lower Triassic sands tones over b u r i e d h i l l s

of Pa leozo ic rock . These sands tones , which have n o t been named, are

desc r ibed by A l i (1973). They cover an area o f a t least 150,000 sq km i n

no r thwes te rn A l g e r i a , and range i n th i ckness up t o 200 m depending on t h e

topography of t h e unde r ly ing Pa leozo ic . I n t h e no r th -cen t r a l area of t h e

Alge r i an Sahara t h e Lower T r i a s s i c l i es d i r e c t l y on t h e Precambrian.

Both

295

The Lower T r i a s s i c has been divided by A l i (1973) i n t o fou r u n i t s a s

fol lows: a b a s a l S e r i e s I n f e r i o r comprising 70 m of s h a l e , andes i t e and

sandstone; a lower u n i t "C" c o n s i s t i n g of 50 m of sandstone; a middle u n i t

con ta in ing 40 m of sha le and sandstone; and an upper u n i t "A" of I 1 II B

quartzose sandstone having a thickness i n the range 10-30 m.

conformably o v e r l a i n by s h a l e and evapor i t e s .

t h e main r e s e r v o i r i s Unit"A", whereas i n t h e Houd Berkaoui F ie ld

product ion i s obtained l a r g e l y from sandstone beds i n t h e S e r i e s I n f e r i o r .

A l i (1973) desc r ibes Unit "A" a s f i n e t o medium-grained, cons i s t ing of

sub-rounded g r a i n s , p a r t l y cemented with anhydri te . The sandstone is

f a i r l y w e l l s o r t e d and has f a i r t o good p o r o s i t y ranging up t o 16%.

Sandstone beds i n the S e r i e s I n f e r i o r a r e f i n e t o coarse-grained. I n

gene ra l , t h e Lower T r i a s s i c sandstones a r e qua r t zose , c o n s i s t i n g of

sub-rounded t o sub-angular g ra ins . Po ros i ty i s commonly i n t h e range

12-15% but ranges up t o 20%. Permeabi l i ty averages 500 mi l l i da rcys and

ranges up t o 1,300 mi l l i da rcys .

Unit "A" is

In t h e Hassi R ' M e l F i e l d ,

A l i (1973) s t a t e s t h a t gas r e se rves i n Hassi R'Mel F ie ld a r e

es t imated t o be 70 t r i l l i o n cub ic f e e t (1,960 b i l l i o n cubic metres) .

No e s t ima tes of product ion c a p a b i l i t i e s a r e given f o r Houd Berkaoui

F i e l d which contains 13 m of n e t sand.

No f o s s i l s have been found i n the Lower T r i a s s i c sandstones i n

the northwestern p a r t of t h e Algerian Sahara. The sandstones l i e

unconformably on a gen t ly undulat ing e r o s i o n a l su r f ace of Paleozoic and

Precambrian rocks and a r e conformably o v e r l a i n by a Middle t o Upper

T r i a s s i c e v a p o r i t i c sequence. These s t r a t i g r a p h i c r e l a t i o n s h i p s a r e

s i m i l a r t o those of t h e Rotliegendes i n the North Sea a rea and suggest

t h a t t h e Lower T r i a s s i c gas and oi l -bear ing sandstones of Algeria a r e

l a r g e l y non-marine and probably, i n p a r t a t l e a s t , of e o l i a n o r i g i n .


297

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333

SUBJECT INDEX

abnormal p r e s s u r e , 107

A f i e s e r e F i e l d , N i g e r i a , 131

A l b e r t a , 41 , 66 , 127, 203, 231

Albuquerque, 40

A l g e r i a , 294

A l l i a n c e F i e l d , A l b e r t a , 31

a l l u v i a l f a n , 273 - 276

Almy Formation, 179

Anadarko Bas in , 159, 214, 221

Andaman Sea , 185 - I s l a n d s , 246

a n h y d r i t e , 41 , 294

Anvi l Rock Sands tone , 30

Appalachian D e l t a , 108

Arabian Pen insu la , 282

Argen t ina , 291

Ar izona , 37 , 216

Arkoma Bas in , 118

a s p h a l t , 291

a s p h a l t i c o i l , 269

A s s a m , 88

Athabasca O i l Sands, 66

Atoka Format ion , 122, 220

Aus t in F i e l d , Michigan, 155

Avon H i l l F i e l d , Saskatchewan, 203

Bahi F i e l d , L ibya , 284

Bal t imore Canyon, 22

Bangladesh, 246

B a r a i l S e r i e s , 88

b a r - f i n g e r s a n d , 95 , 183

Barns l ey F i e l d , Kentucky, 48

b a r r i e r b a r , 95 , 131, 133, 141, 145,

148, 151, 174, 184, 189, 208

- i s l a n d , 26, 103, 119, 141,

144, 167, 183

B a r t l e s v i l l e Channel, 36 - Sands tone , 52

basement topography, 43

Bay of Fundy, 261

beach r i d g e , 183, 211

Beaspaw Sha le , 116

Beauf i e ld F i e l d , Saskatchewan, 203, 205

B e a v e r h i l l Lake F i e l d , A l b e r t a , 203

Bedford Formation, 23, 45

B e 1 Hedan F i e l d , L ibya , 284

B e l l Creek F i e l d , Wyoming, 164, 169

B e l l s h i l l Lake F i e l d , A l b e r t a , 31,

69 , 127, 212

Be l ly R ive r Formation, 129, 192, 196

- Poo l , A l b e r t a , 129, 131

Bengal Fan, 244

b e n t o n i t e , 203

Beria Sands tone , 29, 45

Ber ing Canyon, 237

Be the l Sands tone , 48, 268

Big P iney F i e l d , Wyoming, 179

B ind loss F i e l d , A l b e r t a , 203

b i o t u r b a t i o n , 165, 168, 230

b i r d f o o t d e l t a , 100 - 103

Bi rdrong Sands tone , 219

B i s t i F i e l d , New Mexico, 173

bitumen, 69 , 269

b i v a l v e s 26, 204, 226

Black Sea , 90

Bla i rmore Sands tone , 20 - Group, 128

b l a n k e t s and , 183

334

Bluesky Sandstone, 231

Bluf f Creek F i e l d , Texas, 1 1 2

Booch Sandstone, 107, 113, 116, 118

Botuca t tu Formation, 290

b r a i d e d streams, 274, 279, 280

B r a z i l , 161, 290

Brazos Basin, 35

Brentwood F i e l d , C a l i f o r n i a , 252

Br ight Angel Formation, 216

B r i t i s h Columbia, 224

Buck Creek Member, 197

Buie-Blaco F i e l d , Texas, 112

Burbank F i e l d , Oklahoma, 201

b u r i e d h i l l s , 7 1

Burma, 185

Bush C i t y F i e l d , Kansas, 54

Cabin Creek F i e l d , Ohio, 30, 45

c a l c i t e , 39, 59, 72, 129, 160, 279

C a l i f o r n i a , 241, 249, 252, 258, 275

Cambrian System, 27

Canadaway Group, 43

Carbon F i e l d , A l b e r t a , 20, 231 - Sandstone, 231, 233

ca rbona te rocks , 108

Carbondale Formation, 32 - Channel, 33

Carboni ferous P e r i o d , 107, 112

Carbonized p l a n t remains , 26, 36, 47,

52 , 75, 82, 116, 133, 182

Cardium Sandstone, 169, 178, 268

Carnarvon Bas in , 219

Carlile Formation, 227

Caspar Formation, 290

Caucasus Mountains, 91

Cessford F i e l d , A l b e r t a , 203

Cha Cha F i e l d , New Mexico, 175, 230

c h a n n e l - f i l l , 21, 81, 110

channel s and , 13, 25, 29

Chanute F i e l d , Kansas, 36, 52

C h a r l i e Lake Formation, 229

Chattanooga Sha le , 124

c h e n i e r , 190

Cherokee Formation, 52 , 158, 221

Ches te r S e r i e s , 113, 126

Cheyenne Val ley F i e l d , Oklahoma,

56, 59

Chin le Formation, 37

C h l o r i t e , 1 7 1

Cisco Group, 35, 48, 110

c l a s s i f i c a t i o n , 1 - sand body shapes , 2

- d e p o s i t i o n a l intrironments,

4 - 10

Clearwater Formation, 68 , 231

Cleveland Member, 29

C l i f f House Formation, 214

c o a l seam, 32, 52 , 66, 88 , 111, 130,

159, 198, 233, 255

c o a s t a l marsh, 34, 72, 233 - p l a i n , 184

Coconino Sandstone, 290

c o l l o i d s , 218

Colorado, 37, 2 0 0 , 208, 290 - Group, 171, 203

Columbus F i e l d , Texas, 134

C o l v i l l e - Smiley F i e l d , Saskatchewan,

203, 205 compaction, 1 2 1 , 185 - r i v e r d e p o s i t s , 23 - 25

d e l t a - f r i n g e sand , 106

b a r r i e r b a r , 147

r e g r e s s i v e marine sand , 195

t r a n s g r e s s i v e marine sand , 214

-

- -

- submarine v a l l e y sand , 242

- t i d a l c u r r e n t s and , 266

- a l l u v i a l f a n , 278

- e o l i a n sand , 288

335

Congo Rive r , 26 , 252

conodonts , 129

c o n t i n e n t a l s h e l f , 93

Cook Ranch F i e l d , Texas, 112

Cooper Bas in , 60

Coyote Creek F i e l d , Wyoming, 80

Cre t aceous , 40

C r o s s f i e l d F i e l d , A l b e r t a , 169, 172

C r y s t a l F a l l s Formation, 111

c u e s t a , 10, 211, 222, 228

Cur ran t F i e l d , B r i t i s h Columbia, 226

Cut Bank F i e l d , Montana, 84 - Sands tone , 8 7 , 212

Dale Consol ida ted F i e l d , I l l i n o i s , 126

datum, 25 , 31, 71, 126, 223, 225, 227,

267, 278

Davis Sands tone , 181

Delaware, 22 - Extens ion F i e l d , Oklahoma, 52

d e l t a d i s t r i b u t a r y , 97 , 113, 131

- l o b e , 104, 108

- f r i n g e sand , 93 , 117

Delta Duck Club F i e l d , Lou i s i ana , 20

Denver Bas in , 19 , 41, 82, 200, 208

d e p o s i t i o n a l t r e n d , 11

Devonian, 26 , 40, 66 , 70

d iachronous u n i t , 3 , 99 , 183, 197

d i a p i r i c s t r u c t u r e , 134

D i s i Formation, 281

d i s t r i b u t a r y , 13, 93 , 119 - mouth b a r , 95 , 97

Dodsland F i e l d , Saskatchewan, 203, 205

Doig Formation, 224

do lomi te , 41, 157, 294

Donkey Creek F i e l d , Wyoming, 79

Dor F i e l d , L ibya , 284

Dutch Slough F i e l d , C a l i f o r n i a , 252

Dynneson Sands tone , 80

Eagle Sands tone , 146, 151, 197, 212

East Angl ia , 292

East Tuskegee F i e l d , Oklahoma, 124

East Sandbar F i e l d , Wyoming, 76

Edmonton, 70

Ela te r i te Bar, 268 - 270

Elk Creek F i e l d , 48

E l l e r s l i e Sands tone , 31, 69, 127, 212

E-log c h a r a c t e r i s t i c s ,

- p o i n t b a r , 1 7 - d e l t a - f r i n g e sand , 103

- b a r r i e r b a r , 147

- r e g r e s s i v e marine sand , 192

- t r a n s g r e s s i v e marine sand , 213

- submarine v a l l e y sand , 240

- c i d a l c u r r e n t s and , 266

- a l l u v i a l f a n , 277

- e o l i a n sand , 287

En t rada Formation, 290

entrapment p o t e n t i a l , 199

e o l i a n sand , 168, 215 , ,285 , 287

Eriemu F i e l d , N i g e r i a , 131

e s t u a r y , 26, 28, 71

Eureka F i e l d , Saskatchewan, 203, 205

Evergreen Formation, 64

F a i r y d e l l F i e l d , A l b e r t a , 203

F a l l C i t y F i e l d , Texas, 134

F a l l R ive r Sands tone , 80

f a u l t i n g , 89

F a y e t t v i l l e Channel, 27

f e l d s p a r , 139, 145, 278

f i r e - f l o o d i n g , 66

F l o r i d a , 34

F ly R ive r , Papua, 149

f l y s c h f a c i e s , 244

forams, 7 1 , 204, 212, 233

format ion f l u i d s , 107

F o r t Saskatchewan F i e l d , 203, 206

336

F o s t e r Sandstone, 220

Four Corners , 38

F r i o Sandstone, 193

Frio-Vicksburg Trend, Texas, 134

F r o n t i e r Formation, 176

F r u i t v a l e Sha le , 250

Gal lup Formation, 173, 227

Galves ton I s l a n d , 167

Ganges - Brahmaputra River system, 2

Garr ington F i e l d , A l b e r t a , 169, 172

gas d r i v e , 45, 48, 54

gas - so lu t ion d r i v e , 78, 172, 176

Gas Draw F i e l d , Wyoming, 169

g a s t r o l i t h s , 124

gas t ropods , 26, 86

146

Gay - Spencer - Richardson Trend,

V i r g i n i a , 47

geometry of sands tone b o d i e s , 3, 94

Ghost P ine F i e l d , A l b e r t a , 232

Gidgealpa F i e l d , South A u s t r a l i a , 62 - Group, 60

Gilby - Bent ley F i e l d , A lbe r t a , 203

Gipplsand Bas in , 238, 244, 255

g l a u c o n i t e , 132, 151, 176, 194, 230,

252, 257, 268

Glauconi te s ands tone , 231

graben , 278, 283

Graham Formation, 35

g r a i n g r a d a t i o n , 10, 16, 19, 40, 72,

75, 86, 89, 93, 106, 148, 151, 176,

213.

- o r i e n t a t i o n , 146, 265

- i m b r i c a t i o n , 146

Grand Canyon, 2 16, 290

Grand I s l e , 145

Graneros Sha le , 208

Gran i t e Wash, 41

Green River Bas in , 179

Groningen F i e l d , Nether lands , 292

growth s t r u c t u r e s , 107, 133, 186

Gulf Coas t , 107

Gulf of Korea, 261, 264

Gulf of Mexico, 142 - 144, 216 Gulf of Suez, 282

Gulf of Venice, 189

gypsum, 43, 157

Hague, The, 70

Halfway Sandstone,224

Hamilton Lake F i e l d , A l b e r t a , 203

Hardin F i e l d , Texas, 181

Hardinsburg Ser i s, 124

Hartshorne Sandstone, 121

H a s s i R ' M e l F i e l d , A lge r i a , 294

Hawkins F i e l d , Oklahoma, 121

Heath Formation, 51

H i l i g h t F i e l d , Wyoming, 76

Home Sand, 231

Hoosier F i e l d , Saskatchewan, 203, 205

Horseshoe F i e l d , New Mexico, 227

Houd Berkaoui F i e l d , A lge r i a , 294

Hughenden F i e l d , A l b e r t a , 31, 69, 128

Huntsman Sha le , 19, 82, 208

hydrodynamic c o n d i t i o n , 11, 66, 88, 182

h y d r o s t a t i c p r e s s u r e , 48, 62

I l l i n o i s , 32, 113, 126 - Basin , 30, 33, 115, 268

i l l i t e , 62, 171

I n d e f a t i g a b l e F i e l d , North Sea, 292

I n d i a , 246

Ind iana , 35

Indones i a , 235

I r e t o n Formation, 73

Irrawaddy River , 185, 188

I s h r i n Formation, 281

i s o l i t h map, 22, 145, 170

337

i so t ime map, 150

I t a l y , 189

I t a p a r i c a Formation, 161

Ivanhoe F i e l d , Montana, 51

J a c k p i l e Sandstone, 39

J e b e l F i e l d , Libya, 284

Joarcam F i e l d , A lbe r t a , 192, 203

J o f f r e F i e l d , A l b e r t a , 203

J o l i Fou Formation, 203

Jo rdan , 2 8 1 7 1 1, J Sands tone , 19, 200

J u r a s s i c , 40

Kansas, 36, 54 , 158

k a o l i n , 26, 39, 62, 194

Keg Coulee F i e l d , Montana, 51

Kin ta F i e l d , Oklahoma, 220

K i t t y F i e l d , Wyoming, 76, 169

Kockatea Formation, 219

Kootenai Formation, 84

Ko t l a F i e l d , Libya, 284

Kupfe r sch ie fe r Sha le , 293

Laguna Madre, 142

Lake Basin F i e l d , Montana, 117

Lake Creek F i e l d , Texas, 134

Lakes Ent rance Formation, 255

Laramide orogeny, 179

Lat robe Group, 255, 257

Lea Park Formation, 129

Lehib F i e l d , Libya, 284

Leman F i e l d , North Sea, 292

l e v e e , 95 , 190

l i b y a , 267, 280, 283

l i g n i t e , 88, 133

l imes tone , 34, 52 , 66, 71, 90, 111,

123, 223, 233, 267

L i n c o l n s h i r e , 292

L i t t l e Creek F i e l d , M i s s i s s i p p i , 20

Long I s l a n d , 142

Los Angeles Bas in , 258

Louis iana , 143, 191

Luzerne F i e l d , Kentucky, 48

Magid F i e l d , Libya, 284

Maikop F i e l d , U.S.S.R. , 90

Main P a s s Block 35 F i e l d , Louis iana , 138

Mannville Group, 203, 231

Mansour F i e l d , L ibya , 284

Many Rocks F i e l d , New Mexico, 175, 229

marine f o s s i l s , 114

marker bed, 144, 197

Mar l in F i e l d , V i c t o r i a , 244, 247, 255

Mar t inez Formation, 252

Mata - Catu Trend, B r a z i l , 161

McAlester Bas in , 220 - Formation, 107, 118, 122

McMurray Formation, 66 meander b e l t , 15 Medi te r ranean Sea , 188

Meganos Channel , 252

Mercure Formation, 137

Mesa F i e l d , New Mexico, 175, 229

Mesaverde Sandstone, 197, 214

Michigan Formation, 155, 157

Midland F i e l d , Kentucky, 48

Miller Creek F i e l d , Wyoming, 80

Mi l l i gan F i e l d , 224

Milton F i e l d , Saskatchewan, 203

Minnesota, 215

Misener Sandstone, 124

M i s s i s s i p p i , 29 - River , 14, 93 , 96

- Delta , 188

Miss i s s ipp ian , 40

Moenkopi Formation, 37, 270

monocline, 91 , 215

338

Montana, 50, 8 4 , 116 , 146 , 151, 197 O'Connor Field, Wyoming, 79 Moolayember Sandstone, 62 Moomba Field, South Australia, 6 0 Moonie Field, Queensland, 64 Moorari Field, South Australia, 62 Morris Field, Texas, 112 Morrison Formation, 39

Morrow Field, Oklahoma, 221 - Formation, 2 2 3

Muddy Formation, 7 4 , 76 , 153, 164 , 169 Music Mountain Oil Pool, Pennsylvania,

4 3 Muskeg Formation, 4 1

Nahorkatiya Field, Assam, 88

Navajo Sandstone, 290 Nebraska, 19 Neocomian, 6 8 , 72 Netherlands, The, 70

net sandstone, 1 2 3 Newcastle Sandstone, 79

New Mexico, 3 7 , 39, 173 , 197 , 227 ,

278 , 286 , 290 New Ulm Field, Texas, 134 New York, 142 Nicobar Fan, 245 Niger Delta, 131, 138

- River, 9 3 Nigeria, 131

Nile Delta, 187 Niobrara Formation, 227, 230 Nisku Formation 7 1

North Dakota, 51

North Africa, 280 North Sea, 261, 263 , 271 , 292 Nova Scotia, 2 6 1 Nubia Sandstone, 280

Oakdale Field, Oklahoma, 59

offshore bar, 141, 154 , 160 , 169 , 175 , 177 , 183

Oficina Formation 137

Ohio Shale, 29 oil, accumulation in synclines, 4 8

- production, 2 0 1 Oklahoma, 36, 5 2 , 118, 124 , 1 5 9 , 220 Olympic Field, Oklahoma, 161

Ora Field, Libya, 284 Ordovician, 27

Organ Rock Shale, 270 Oriskany Sandstone, 216

Ostra Field, Venezuela, 137 ostracods, 71, 8 6 , 163 , 212 , 233 Ostracod Member, 232 outwash-plain, 4 3

Padre Island, 142

paleoslope, 31

Palestine Sandstone, 113, 268 Papua, 148 i

Pecan Island, 191 Peejay Field, British Columbia, 226

Pembina Field, Alberta, 129, 1 9 2 , 196 Pennsylvania, 40 permeability, 11, 18, 121 , 123 , 129 , 139 Permian, 40 Petersburg Formation, 33, 35

Pickanjinnie Field, Queensland, 62 Pic0 Sandstone, 241, 258 Pleistocene, 70 Po River, 9 9 , 103 , 189 point bar, 1 7 , 21 , 38, 72 , 80 Point Lookout Formation, 214 Pokrovsk Field, U.S.S.R., 123 porosity, 11, 1 9 , 123 , 129,139 potentiometric gradient, 76 Potomac Group, 22

339

Powder R ive r Bas in , 41, 73, 76, 79,

164, 169

Precambrian System, 26, 42 - S h i e l d , 68 , 127, 280

P r e c i p i c e Sands tone , 62

P r i b i l o f Canyon, 237

p r o d e l t a , 96 , 103

p rograda t ion , 98, 185 p r o t e r o z o i c , 40

P rovos t F i e l d , A l b e r t a , 203

P u l a s k i Channel, 27

p y r i t e , 47

q u a r t z s and , 289

Quaternary System, 26, 40

Queensland, 62

Quicksand Creek F i e l d , Texas, 134

Qu i requ i r e Formation, 212

Recluse F i e l d , Oklahoma, 76, 153 , 164

Red E a r t h F i e l d , A l b e r t a , 4 1

Red Oak F i e l d , Oklahoma, 220

Red Fork Sands tone , 56 , 159

r e g r e s s i v e marine Sand, 183 , 198

R e i m e r s - Lane - Har t Trend,

Nebraska, 82

Repe t to Sands tone , 241, 258

Rewan Formation, 63

Rhine R i v e r , 70, 72

Rierdon Formation, 84

Rio Grande R ive r , 118, 289

r i v e r channe l s , 13

- d e p o s i t s , 21

- terraces, 71

Roma S h e l f , 62

Rosedale F i e l d , C a l i f o r n i a , 241 - Sands tone , 249

Ro t l i egendes red-beds, 292

Rozet F i e l d , Wyoming, 79

Russ ian P la t fo rm, 123

Sabkha, 292

Sabre F i e l d , C a l i f o r n i a , 208

Saddle Creek Formation, 111

Sahara , 290

Sa leb Formation, 281

s a l i n i t y , 62, 64, 66, 84, 87, 182, 220

S a l l y a r d s Trend F i e l d s , Kansas, 158

S a l t Creek F i e l d , Wyoming, 176

Samah F i e l d , L ibya , 284

Sandia Mountains, 273, 278

sand dunes , 143, 216

- s h e e t , 285 - 287, 290

- s i l l , 98

- percen tage map, 207

San Joaquin Bas in , 259

San Juan Bas in , 173, 214, 227

S a r i r F i e l d , L ibya , 283

Saskatchewan, 19 7, 200, 203

S a t i c o y F i e l d , C a l i f o r n i a , 241

Sco t l and , 279

S e d a l i a F i e l d , A l b e r t a , 203

sed imentary s t r u c t u r e s , 10, 16, 86, 94

See l ig son F i e l d , Texas, 20 , 110 , 134

s e i s m i c r e f l e c t o r , 149

s e l f - p o t e n t i a l cu rve , 18, 22

Series I n f e r i o r , 295

Sharon School F i e l d , Kentucky, 48

Sher idan F i e l d , Texas, 134

Shinarump Formation, 37 S h i r a S t r e a k F i e l d , Pennsylvania , 153

S h o e s t r i n g F i e l d , Oklahoma, 56 , 59

s h o e s t r i n g sands , 13, 36, 103, 110, 113, 116, 119, 158

Showgrounds Sands tone , 62

S i b e r i a n P la t fo rm, 27

s i d e r i t e , 171

S i e r r a Nevada Mountains, 275

340

silica, 3 0 , 160, 194

Sirte Basin, 280

Skull Creek Formation, 1 9 , 7 4 , 7 9 , 82

Sliverville Sandstone, 43

Slochteren Field, Netherlands, 292

Smiley - Dewar Field, Saskatchewan, 7-03, 205

South Australia, 60

South Ceres Pool, Oklahoma, 56

South Glenrock Field, Wyoming, 7 3 , 79

South Pine Hollow Field, Oklahoma, 121

South Waterflow Field, New Mexico, 175

Southwest Pass, 9 6 , 98

spill-over bar, 38

Spiro Sandstone, 220

steam injection, 66

Stensvad Field, Montana, 5 1

Stevens Sandstone, 241, 250

St. Peter Sandstone, 215

St. Charles Field, Kentucky, 48

strike-valley, 1 0 , 211, 222, 229

submarine valley, 235, 2 4 8 , 250, 256

- fan, 244, 258

sulphur, 69

Sunda Shelf, 235

Surat Basin, 63

Sweetgrass Arch, 84

Swift Formation, 84

Taiwan Strait, 261, 265

Tapeats Sandstone, 216

tarry oil, 68

Teapot Dome, Wyoming, 176

tectonic deformation, 107

Tennessee, 27

Tertiary, 40

Texas, 3 5 , ' 1 0 8 , 110, 134, 181, 193

- Gulf Coast, 133

tidal channels, 186, 230

- current ridges, 114, 261 - 265, 269

Timbalier Island, 143

time-stratigraphic marker, 24

Tirrawarra Field, South Australia, 62

Tonkawa Sandstone, 214

Toolachee Formation, 60

Torridonian Formation, 26

Totah Field, New Mexico, 175

trace elements, 69

transgressive marine sand, 211, 233

Triassic, 40

trilobite, 217

turbidity current, 240, 242, 244, 249, 258

Tuscaloosa Sandstone, 20

Tyler Field, Montana, 50

Um Sahm Formation, 281

United Arab Republic, 1 8 7 , 282

uranium, 3 8 , 40

Uruguay, 291

U.S.S .R. , 112, 116, 123'

Utah, 3 7 , 268

Ute Field, Wyoming, 169

vanadium, 38

Venango Group, 153

Venezuela, 137, 212

Ventura Field, California, 241, 243,

2 5 1 , 258

- Basin, 258

Victoria, 244, 247, 255

Viking - Kinsella Field, Alberta, 203

- Formation, 192

Volgograd Delta, 112, 116

Waal River, 60

Wabamun Formation, 7 1

341

Wabiskaw Member, 68, 231

wadi, 292

Wakita Trend, Oklahoma, 56, 159

Wapanucka Formation, 220

water d r i v e , 41 , 59, 64 , 7 2 , 129, 139

Wattenberg F i e l d , Colorado, 200

waxy o i l , 45, 89. 219

West A u s t r a l i a , 219

West Germany, 294

West Lake Verret F i e l d , Lou i s i ana , 20

West Moorcroft F i e l d , Wyoming, 81

West Sole F i e l d , North Sea, 292

West Thornton F i e l d , C a l i f o r n i a , 252

White Sands Na t iona l Monument, 286

White R i m Sands tone , 268

Whi tes ide F i e l d , Saskatchewan, 203

Wilber ton F i e l d , Oklahoma, 220

Wilcox F i e l d , Texas 133

- Group, 247

Wisner F i e l d , Lou i s i ana , 20

Wyoming, 73, 76, 176, 179, 290

Yardar ino - Dongara F i e l d , West A u s t r a l i a ,

2 19

Yegua Formation, 181

Yoakum Channel, 247

Yukon, 276

Zechs t e in e v a a o r i t e s , 293 Z e l t e n F i e l d , Libya, 283

Zhemchug Canyon, 237


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Geo Morphology of Oil and Gas Fields in Sandstone Bodies