UINTAH AND OURAY RESERVATION Currently, the Ute Tribe, Ute Allottees, and the Ute Distri-

Introduction bution Corporation in joint management hold 102,000 acres under lease, and more than 490 wells in production. The Utah Oil, Gas,

The Uintah and Ouray Indian Reservation is located in the Uinta Ba- and Mining Board conduct conservation spacing in cooperation

sin, in northeast Utah (FIGURES UO-1 and UO-2). The terrain is High with the Ute Tribe. Spacing rules for the Altamont-Bluebell field

Mountain desert in the central part of the basin, which is surrounded are set at a multi-well level allowing two wells per section, while

by mountain ranges on the edge of the basin. Elevation varies from undesignated field spacing is 40 acres for oil and 640 acres for gas.

approximately 5,600 feet to over 11,000 feet above sea level. The Some variations or exceptions exist by special ruling and order

area's main transportation conduit is U.S. Highway 40, which leads (Anderson, 1995).

east to Salt Lake City, Utah, and west to Denver, Colorado. The ba­sin covers approximately 11,500 square miles, and Ute Indian Tribe jurisdiction comprises just over 4 million acres of this area, reaching from the Utah-Colorado border west to the Wasatch Mountain range.

Mineral Ownership

The Uintah and Ouray Indian Reservation is a checkerboard owner­ship reservation containing Ute Indian Tribe, Ute Indian Allotted, Ute Indian Tribe and Ute Distribution Corporation Jointly Managed Indian Trust minerals, along with fee (privately owned) and federal minerals. Indian properties cover approximately 1.2 million surface-owned acres, and 400,000 mineral-owned acres within the 4 million-acre jurisdictional boundary. Ute Indian Allottees, the Ute Indian Tribe, and the Ute Distribution Corporation own both surface and mineral properties in joint management.

112O 111O 110O 109OO 108O 107O

WA

SAT

CH

R

AN

GE

UINTA MOUNTAINS

WYOMING

UINTA BASIN

BO

OK

UTA

H

CO

LOR

AD

O

WA

SA

TCH

P

LATE

AU

CLIFFS

DO

UG

LAS

CR

EE

KA

RC

H

SAN

RAFA

EL

SWEL

L

UNCOMPAHGRE

UPLIFT

PIC

EA

NC

E C

RE

EK

BA

SIN

41O

40O

0 50Miles

0 80Kilometers

Figure UO-2. Index map showing the Uintah and Ouray Indian Reservation in yellow (modified after Anonymous, 1995).

0 5 10 20 30

Scale, miles

N

L E G E N D

Oil Field

Gas Field

Reservation Boundary

COUNTY

CARBON

DUCHESNE COUNTY

COUNTY

Price

CARBON COUNTY COUNTY

MERY

PETERS POINT

COUNTY

UTAH

WASATCH

NUTTER CANYON

CHOKECHERRY CANYON

INDIAN RIDGE

FLAT ROCK

UINTAH COUNTY

COUNTYGRAND

MOON RIDGE

SEGUNDO CANYON

GR

EE

N

UINTAH

DUCHESNE

BLUE BENCH

FLAT MESA

WEST PLEASANT VALLEY

RIVER

PARIETTE BENCH

CASTLE PEAK

REFUGE

RANDLETT GYPSUM

HILLS

Fort Duchesne

Duchesne

MONUMENT BUTTE

WEST GUSHER

EAST GUSHER

Vernal

BITTER CREEK

SOUTH OURAY

UTE TRAIL

CHAPITA WELLS

Ouray

WONSITS VALLEY

BRENNER BOTTOM

HORSE SHOE BEND

BLUEBELL

ROOSEVELT

COTTONWOOD WASH

STARR FLATS

ALTAMONT TREND

CEDAR RIM

CEDAR STARVATION

ALTAMONT

DAGGET

UINTAH

DUCHESNE

COUNTY

COUNTYCOUNTY

COUNTY

COUNTY

SUM

MIT

WASATCH

RED WASH

Figure UO-1. Location of Uinta Basin and surrounding structural and physiographic features.Yellow area shows approximate boundary of Uintah and Ouray Indian Reservation (modified after Cashion, 1992).

UINTAH AND OURAY INDIAN RESERVATION Overview UTAH

39O

1

Uintah and Ouray Reservation Petroleum Exploration and Development

The Uinta Basin is a rich source of many energy-producing minerals. The greatest portion of the energy resources is hydrocarbons in the form of coal, oil, gas, oil shale, and bituminous sandstone and lime­stone.

Resources contained within the Uintah and Ouray Reservation include conventional and unconventional hydrocarbon deposits of oil and gas, oil shale, and tar sands in major quantity; coal, uranium, sil­ver, copper, gold, gypsum, and phosphate are also present in minor to mid-economic quantities.

Cretaceous and older rocks contain many productive oil and gas zones. However, the major portion of the energy production from the Uinta Basin is from Tertiary rocks, and the distribution of the hydro­carbons and minerals is directly related to their depositional environ­ment.

Uinta Basin production of oil and gas began in the late 1940's, with major development commencing in the late 1960's and expand­ing in the late 1970's and early 1980's. Over 300 million barrels of oil (MMBO) have been produced from the Greater Altamont-Blue-bell field alone. Conventional oil and gas deposits have been exten­sively explored and developed. The Green River and Wasatch For­mations contain the bulk of the producing zones, with depth to these zones ranging from 6,000 to 18,000 feet. This has resulted in the de­velopment of the Greater Altamont-Bluebell oil field, and numerous undesignated smaller fields (FIGURES UO-2, UO-6).

The oil produced is high in paraffin content (pour point = 120 de­grees F), making it an excellent gasoline refining feedstock. It is ex­tremely rich with associated natural gas, with values falling between 900 and 1700 British thermal units (Btu). Only one natural gas field has been developed, and it is located east and south of the Green and White Rivers. It is bordered by the Natural Buttes Gas Field Unit, which covers 76,000 acres.

Total Ute Indian oil production approximates 1,250 barrels per day, a level that has held for the last 10 years. New well development and workover activity has been sufficient to offset the normal decline of the many oil and gas fields within the basin and the reservation area (Anderson, 1995).

Geology of the Uinta Basin

The Uinta Basin is a major sedimentary basin in the western-central Rocky Mountain province. It is bounded by the Uinta Mountain Up­lift on the north and by the Wasatch Mountain Uplift and the eastern faulted margin of the Wasatch Plateau on the west. On the southwest and south, the San Rafael Swell and the Uncompahgre Uplift border the basin (FIGURES UO-2 and UO-3). The southern basin edge is gen­erally considered to be the Book and Roan Cliffs, escarpments of Up­per Cretaceous and Lower Tertiary formations which dip northwest,

north, and northeast into the basin. The northwest-southeast trending salt folds of the northern Paradox Basin plunge beneath the Book Cliffs in the southernmost part of the basin, and the two downwarps merge imperceptibly in this area. On the east, the Uinta Basin is sep­arated from the Piceance Basin of northwest Colorado by the Doug­las Creek Arch, which parallels the Utah-Colorado border (FIGURE

UO-3). The basin is quite asymmetric. Beds on the north flank dip 10 to

35 degrees south, whereas beds on the south flank dip only 4 to 6 de­grees north (Chidsey, 1993). The north flank is highly complex, with

major faulting, steep to overturned beds, and multiple unconformi­ties that allow youngest Eocene rocks to lie unconformably on top of Precambrian rocks. The basin axis is close to the mountain flank and moves northward with depth.

The Uinta Basin formed in Late Cretaceous and Paleocene time when, in response to rapid uplift and formation of the Uinta Moun­tains, the dominant north-south tectonic and sedimentation patterns of Cretaceous time shifted to west-east. The Uintas impose a domi­nant west-east trend through most of the basin; however, structures in the southeast portion have a strong northwest grain, reflecting the older buried Uncompahgre and Paradox trends.

Figure UO-3. Location and structural element map of the Uinta and Piceance Basin Provinces (modified after Gautier et al., 1995).

0

0

25

KILOMETERS

SAN

RA

FAEL

SWEL

L Green River

38o

40o

UT WY CO

AXIAL

UPLIFT Rangely

Springs

Grand Junction

CLIFFSBOOK

UINTA

BASIN

BOOK CLIFFS

PICEANCE CREEK

GUNNISON UPLIFT

WHITE RIVER

UPLIFT

UNCOMPAHGRE UPLIFT

SAWATC

H R

AN

GE

DO

UG

LA

SC

RE

EK

AR

CH

Craig

UPPER

ABSENT BY

UINTA MTNS. UPLIFT

Price

o110 o

108 o106

UT CO

EXPLANATION

Upper Cretaceous rocks present

Thrust fault

25 50

50 MILES

SANDWASH BASIN

Vernal

Glenwood

BASIN EAGLE BASIN

CRETACEOUS

EROSION

PROVINCE BOUNDARY

Upper Cretaceous rocks absent

UINTAH AND OURAY INDIAN RESERVATION Geology UTAH

2

The Uinta Basin is filled with 30,000 to 32,000 feet of sediment in its northern and deepest portion (Figs. UO-4 and UO-5). Although the majority of the rocks exposed on the reservation are of Tertiary age, some pre-Tertiary age rocks are exposed on the northern and northwestern boundaries. Percentages of basin strata are subdivided as follows:

Tertiary (Eocene - Paleocene) ­ 55% Upper Cretaceous - 25% Triassic - Lower Cretaceous ­ 10% Paleozoic - 10%

GEOLOGIC TIME

GROUP AND FORMATION

CHARACTER OF BEDS THICKNESS (ft.)

EAST WEST

Quaternary Alluvium Alluvium, gravel surfaces, talus deposits, and other windblown deposits

Pleistocene Glacial Deposits Glacial drift, alluvium, and terrace deposits 0-70 0-70

Ter t

iary

Miocene Bishop Conglomerate Conglomerate, boulders 1 to 6 feet in diameter, sand and gravel

0-500 0-500

Oligocene Duchesne River Formation Varicolored shale, sandstone, and conglomerate 1370 1500

Eocene Uinta Formation Shale with sandstone interbeds 700-1650 1800-5400

Green River Formation Green to white shale, sandstone, oil shale in middle of formation

1800-2400 0-5000

Wasatch Formation Varicolored sandstone, shale, limestone 0-5000

Paleocene deposits absent due to unconformity

Cretaceous Currant Creek Formation Conglomerate, sandstone, and varicolored shale 0-4800

North Horn Formation Varicolored shale with sandstone interbeds 0-400 0-200

Upper Cretaceous

Mesaverde Group Upper section - Brackish-water sandstone, sandy shale, carbonaceous shale, and coal

0-3000 1000-2200

Lower section - Marine sandstone 0-500 300-1000

Mancos Shale (including Frontier Sandstone Member)

Black marine shale, thick massive sandstone, shaly sandstone

5000-6000 800-3500

Dakota Sandstone Cross-bedded tan sandstone 30-50 30-50

Jurassic Morrison Formation Varicolored shale with sandstone interbeds 780-800 780-800

Triassic Chinle Formation Shale with minor sandstone and conglomerate 230 300-380

Moenkopi Formation Shale, sandstone, siltstone, and limestone 2300 800

Permian Park City Formation Argillaceous, sandy limestone 80-500 80-500

Pennsylvanian Weber Sandstone Massive sandstone 1000-1500 1000-1500

Morgan Formation Varicolored shale and limestone with sandstone 300-800 300-800

Mississippian

Upp

er

Manning Canyon Shale Humbug Formation Great Blue Formation Interbedded shale, limestone, and sandstone 0-900 0-900 Molas Formation Doughnut Formation

Redwall Formation

Low

er

Leadville Formation Deseret Formation

Massive dolomite and limestone 0-1100 0-1100

Madison Formation

Devonian Sandstone, shale, carbonate 1000 2000

No identifiable Silurian or Ordovician deposits

Cambrian Tintic Quartzite or Lodore Formation

Sandstone, shale, and carbonate 0-2000 0-2000

Precambrian Uinta Mountain Group Quartzite with shale and conglomerate 12,000-20,000

Uncompahgre Suite Schist, gneiss, and granite

JUR

AS

SIC

TR

IAS

SIC

PE

RM

.P

EN

N.

p C

SIL.

UINTA BASIN PICEANCE BASIN AXIAL UPLIFTDOUGLAS CREEK ARCH

Browns Park Fm.

UTAH COLORADO

Duchesne River Fm. Uinta Fm. Green River Formation

Colton Fm. Wasatch

Fort Union FormationsFlagstaff Limestone

North Horn Formation

Wasatch Fm.

Lance Formation Lewis Shale

Mesaverde Gp.Price River Fm.

Sego Sandstone

Castlegate Sandstone Blackhawk Fm.

Mancos "B"

Mancos Shale

Ferron Sandstone Tununk Shale

Emery Sandstone

Frontier Formation

Mowry Shale

Dakota Sandstone

Entrada Sandstone

Navajo Sandstone

Cedar Mountain Formation

Morrison Formation

Stump Formation

Preuss Formation

Ankareh Fm.

Twin Creek–Carmel Formation

Curtis Formation

Chinle Formation Gartra Member Shinarump Conglomerate

Thaynes Limestone

Woodside Shale Moenkopi Formation State

Bridge Fm.Cutler Formation

Upper Weber SandstoneUpper Weber Sandstone

Lower Weber Sandstone Lower Weber Sandstone

Park City Fm. (Phosphoria)

Morgan Formation

Round Valley Limestone

Morgan Formation Minturn

Formation

MaroonFormation

Belden Shale Manning Canyon Shale

Humbug Fm. — Doughnut Sh.

Deseret Limestone

Madison Formation Madison Formation

Pinyon Peak Fm.

Leadville Limestone

Chaffee Fm.

Manitou Fm.

Dotsero Fm.

Sawatch Sandstone

Precambrian

Ophir Shale

Lodore Sandstone

Significant oil production

Significant gas production

Source rocksS

S

S

S

S

S

S S

S

S

S ?

S

S S

S

S

S

S

S

Currant C

reek

Conglom

erate

TE

RT

IAR

YC

RE

TAC

EO

US

MIS

S.

DE

V.C

AM

B.

ORD.

Figure UO-5. Diagram showing general correlation of rock units from the Uinta Basin, Utah, to the Axial Uplift, Colorado, and significant producing and source horizons (modified after Spencer and Wilson, 1988)

Figure UO-4. General stratigraphic column of the Uinta Basin (modified after Anonymous, 1995).

UINTAH AND OURAY INDIAN RESERVATION Geology Overview 3 UTAH

�During Eocene time (38-50 million years ago) lar ge amounts of sediment from adjacent higher areas were deposited in lacustrine and fluvial environments in the basin. These sediments, assigned to the Wasatch, Green River, and Uinta Formations, are perhaps more than 15,000 feet thick in the center of the basin, and contain important mineral resources (FIGURE UO-6). �Much of the area no w occupied by the Uinta Basin was covered by a large lake during Eocene time. Lacustrine marlstone, oil shale, limestone, siltstone, and sandstone of the Green River Formation were deposited in the lake. During the lake's expansionary periods, fluvial sediments were deposited which are now beneath and periph eral to the lacustrine sediments. These fluvial deposits form the shale, sandstone, and conglomerate of the Wasatch Formation. As the lake receded, fluvial sediments were deposited on its periphery, and eventually covered the entire area formerly occupied by the lake. These deposits comprise the Uinta Formation (Anderson,1995).�

Uinta Formation The Late Eocene Uinta Formation consists of fluvial deposits that overlie the Green River Formation from the last phase of Lake Uinta. Later, the lake filled up with volcaniclastic material, followed by abundant bedded evaporites. Depths to the top of the formation range from 2,566 feet to 3,678 feet, with the average being 3,554 feet. �Most of the production is from the Lo wer Uinta, which is a tran sitional unit between the Green River Formation and the fluvial Up per Uinta. The Lower Uinta is 350 to 450 feet thick in the Horse shoe Bend field, a reservoir that has produced over 15 BCF of non-associated gas and 5,000 barrels of condensate. This is the only res ervoir that has produced at least 5 BCFG from the Uinta Formation, although minor production exists elsewhere in the basin (FIGURES

UO-6 and UO-7). �The primary dri ve mechanism is gas expansion and gravity, and

0

0

1

1

2 3

2 3mi

4km

Horseshoe Bend

1600

D

U

1400

1800

2000

2200

R21E R22E

T 6 S

T 7 S

6 1 6

31 31

6

31 36 31

Producing gas well

Abandoned gas well

Field boundary

Federal no. 3

N

UINTA

COLORADO

0

0

10

10 20 30 40 20 30mi

50km

FERC

designated area

House 3

Buttes 2,3

2 2

Horseshoe Bend

1

2

Butte 2

Bluebell 2,3

Cedar Rim 2,3

2,3 Altamont

CO

LOR

AD

O

Duchesne

MOUNTAINS

WYOMING UTAH

UINT A

B ASIN

UTAH

Tight formation

Rock Natural

Powder Springs Walker

Hollow

Wonsits Valley

Vernal

Monument

Maximum extent of Uinta Basin plays

Rangeley

the trap is an updip stratigraphic pinch-out. The average monthly gas production has been increasing since 1981 due to development drilling and new wells that were drilled in the ear ly to mid-1980s. �The Uinta F ormation is rarely a primary drilling target, but it is a shal low, low cost target with potential for new discoveries (Morgan, 1993a).

�Green River Formation � The Eocene-Paleocene Green River Formation is 2,000 to over 8,000 feet thick. It accumulated in and around ancestral Lake Flagstaff and Lake Uinta, along with the alluvial-fluvial deposits of the Wasatch Formation.

Figure UO-7. Structure contour map of the Horseshoe Bend area. Datum is the top of Unit A,The Green River Formation was de average porosity of Green River reservoirs ranges from 5 to 20 per

posited as thick, regionally extensive cent, and the permeability ranges from 0.1 to 42 millidarcies (mD). Uinta Formation with a contour interval of 200 ft. stratigraphic sequences in marginal �The source rocks for oil and associated g as found in the Green Only wells that have produced from the Uinta

Formation are shown (modified after Morgan,and open lacustrine environments. River Formation are interbedded organic-rich carbonate mudstones 1993a).Depths to the top of the formation range from 2,315 to 7,456 feet, and

located at depths of 8,500 to 12,500 feet in the north-central part of the basin. Hydrocarbons, which were generated in deep overpres

most wells produce from zones 3­ sured zones, migrated laterally along fracture systems to shallow 4,000 feet below the top. reservoirs located on the south and east flanks of the basin. �The majority of the producing �There are more than 60 kno wn reservoirs producing from the zones are channel sandstones about 10 Green River Formation, 9 of which have each produced more than 5 to 30 feet thick, but some reservoirs BCFG (FIGURE UO-6). The Roosevelt reservoir was the first to pro produce from carbonate grainstones duce gas from this formation in 1949. Monthly production peaked in

Figure UO-6. The Uinta Basin with the maximum extent of play areas based on production and hy 10 to 20 feet in thickness (FIGURE UO- the mid-1970s, and decreased to a low in 1982. It has been increasdrocarbon shows. Reservoirs are labeled: 1, Uinta Formation; 2, Green River Formation; and 3, Wa 8). The porosity and permeability of ing since then due to in-fill drilling programs in several reservoirs satch Formation. Note outline for Federal Energy Regulatory Commission (FERC) tight formation these zones can be either reduced or enhanced by diagenetic effects. The

designated area (Wasatch/Mesaverde) in the east part of the basin. Hachured line indicates approx imate limits of Tertiary units in the Uinta Basin (modified after Chidsey, 1993a).

(Chidsey, 1993b). �

UINTAH AND OURAY INDIAN RESERVATION Producing Formations UTAH

4

N

Figure UO-8.

Net sandstone isopachs (solid lines with contour in­

Alluvial-fluvial

Alluvial-fluvial

N 0

0

10 20mi

10 20 30km

Carbon Co. Emery Co.

Uintah Co. Grand Co.

Duc

hesn

e C

o.

Gre

en

Rive

r

Approximate base of T

Colton Formation

Colton Formation

Colton Formation

Was

atch

Form

atio

n

Green River Formation Uta

h C

olor

ado

Figure UO-9. Note

4926'-6975'

IPF 1900 MCFGPD 3 BWPD

Green River Formation .

Natural Buttes Field Coastal Oil Gas Corp.

CIG 62D-36-9-22

'

4400

4600

4800

5000

5200

5400

5600

5800

6000

6200

6400

Figure UO-10.

T 9 S

R17E

+1000

+1200

+1400

+1600

+1800

Duc

hesn

e C

o.U

inta

h C

o.

+8000

0

0 1km

1mi

20

20

10

10

20

30

20

20 10

Depths to the top of the formation range from 3,147 to 10,754 feet (FIGURE UO-9).

Most of the production comes from lenticular fluvial-alluvial

sandstones are usually isolated and encased in siltstones, mudstones, and shales (Figure UO-10). Porosity and permeability are generally reduced by diagenesis, so production is enhanced near or along ma­

north-central part of the basin. Source rocks for the non-associated

least 5 BCFG (Figure UO-6).

The total monthly gas production in­creased between 1973 and 1982, and

Structure contour map with isopach of single sandstone bed, Monument Butte reservoir, Duchesne and Uinta Counties, Utah. Structure con­tours (dashed lines with contour interval of 200 ft.) are based on a datum ap­proximately 150 ft. below the middle marker of the Green River Formation and show no structural closure.terval of 10 ft.) are based on one of many individual productive sandstone units encased by shale or mudstone. Isopach geometry indicates deposition of sand­stone by meandering streams. The trap is created by updip pinch-out of chan­nel sandstone to south along regional strike (modified after Chidsey, 1993b).

Marginal lacustrine

Open lacustrine

Vernal

Was

atch

Co.

Price

ertiary rocks

Major depositional facies and distribution of formations at the Paleocene-Eocene boundary.widespread Wasatch-Colton deposition in the Uinta Basin (modified after Chidsey, 1993).

Mesaverde Group

Perf.

(gross)

Was

atch

For

mat

ion

T.D. 7000' Completed: 4-26-81

S.P Res.

nw sw sec. 36 T9S R22E Uintah County, Utah

K.B. 4949

Typical SP-resistivity log of the Natural Buttes Wasatch reservoir, Uintah County, Utah (modified after Chidsey, 1993c).

Wasatch Formation

The Eocene-Paleocene Wasatch Formation is up to 3,000 feet thick. It accumulated in and around ancestral Lake Flagstaff and Lake Uin­ta in an intertonguing relationship with the Green River Formation. It was deposited as thick, regionally extensive stratigraphic sequen­ces primarily in an alluvial-fluvial environment peripheral to the an­cestral lakes.

channel and alluvial overbank sandstone deposits. The productive

jor fault and fracture zones. The average porosity ranges from 5 to 20 percent, and the permeability is 0.1 mD or lower.

The source rocks for oil and associated gas found in the Wasatch Formation are organic-rich carbonate mudstones of the Green River Formation, and are located at a depth of 8,500 to 12,500 feet in the

gas are organic-rich siltstones and mudstones, carbonate shales, and coals of the Mesaverde Group, located at depths of 6,000 feet or greater.

There are more than 60 known res­ervoirs, 5 of which have produced at

The first reservoir to produce from the Wasatch Formation was Peters Point in 1953.

has been fairly constant since then (Chidsey, 1993c).

UINTAH AND OURAY INDIAN RESERVATION Producing Formations UTAH

5

30

25

20

15

10 9

8

7

6

5

4

3

2

1

25th to 75th PERCENTILES

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.5 2.0 2.5 3.0

PO

RO

SIT

Y, I

N P

ER

CE

NT

10th percentile

VITRINITE REFECTANCE, IN PERCENT

Type curve

90th percentile

Mesaverde Group Figure UO-11. Plot of core-plug porosity vs. reflectance for 25th

Gas from Mesaverde Group reservoirs is found in both structural and 75th porosity percentiles (joined by vertical lines) of nonmarine sandstone intervals of the Mesaverde Group, Uinta and Piceance

and stratigraphic traps. Some reservoirs, like those in Natural Buttes Field, are part of larger, basin-centered gas traps where the gas collects downdip from more permeable water-filled reservoirs. Average depth to the top of productive reservoirs ranges from 1300 to >8500 feet.

Creek Basins. Mesaverde data are compared with type curve and to 10th and 90th porosity percentiles representing sandstones in general. Note that the porosity does not decrease within the win­dow of hydrocarbon generation (Ro of 0.070-1.8%) (modified after Nuccio et al., 1992).

The terminology of the Mesaverde Group is complex, due to fa­cies changes that occurred as the Cretaceous Interior Sea trans­gressed and regressed along its western margin in the Piceance-Uin-ta Basin area. The Mesaverde consists of three dominant reservoir facies: lenticular, fluvial sandstones of the Williams Fork Forma­tion, coals that occur in the basal portion of the Williams Fork For­mation, and extensive shoreline-marine sandstones of the Iles For­mation.

The fluvial sandstones of the Williams Fork Formation are ap­proximately 4000 feet thick in the eastern part of the Piceance Ba­sin, thinning to <2000 feet on the Douglas Creek Arch and 2200­

Figures UO-12A and 12B. Map showing the region (pink area) between Ro2900 feet in Natural Buttes Field in the Uinta Basin. These sand-0.70 and 1.8%, where porosity of sandstones at the base of the Mesaverde

stones are lithic arkoses and feldspathic arenites containing authi- Group does not decrease as a function of increasing Ro. This region defines genic quartz and carbonate cement. They have low porosities, rang- the area of optimum gas recovery for A, Upper Mesaverde; B, Lower Mesa­ing from 7-12%, and low matrix permeabilities (<0.1 mD) due to verde (modified after Nuccio et al., 1992).

the abundance of authigenic clays. The shoreline-marine sandstones of the lower Mesaverde Iles o o o o o o o o o o o o o o o o o o111 00' 110 45' 110 30' 110 15' 110 00' 109 45' 109 30' 109 15' 109 00' 111 00' 110 45' 110 30' 110 15' 110 00' 109 45' 109 30' 109 15' 109 00'

A

Duchesne

Altamont Jensen

Gre

en R

iver

MILES0

0

10 20 30

10 20 C

OL

OR

AD

O

2.00

1.10

0.75

0.60

0.50

Price

Vernal

30 KILOMETERS

UT

AH

B

Duchesne

Altamont Jensen

Gre

en R

iver

MILES0

0

10 20 30

10 20

1.50

1.10

0.75

0.65

CO

LO

RA

DO

Price

Vernal

30 KILOMETERS

UT

AH

Formation were deposited during transgressive and regressive cycles along northeast-southwest trending shorelines. These sandstones merge with fluvial facies to the northwest and the Mancos Shale to the southeast. The most productive members are the Cozzette, Cor­coran, and Castlegate Sandstones.

The Castlegate Sandstone is a clean, fine-grained, subarkose to sublitharenite, with low porosity and permeability due to pore-filling authigenic clays. It was deposited along ancient shorelines or as offshore bars. In the southeastern part of the Uinta Basin, 50-70 feet thick Castlegate sandstones produce from structural traps at depths of 8000 feet. Permeabilities range from 0.5-0.9 mD. All fields that produce from the Castlegate involve some type of structural closure, and several close against faults. Production rates are enhanced by the associated tectonic fractures.

Source rocks for gas produced from the fluvial sandstones at

o40 30' o40 30'

oo 40 15'40 15'

oo 40 00'40 00'

o

Natural Buttes Field are coals and carbonaceous shales. The source 39 45'

for the shoreline-marine sandstones is probably the Mancos Shale. Porosities of the Mesaverde Group sandstones remain unusually sta­ble over a large vitrinite reflectance interval (FIGURES UO-11 and UO-

o39 45'

o

12), implying that sparsely explored deep central basins may hold 39 30'

some promise (Tremain, 1993).

o39 30'

o39 15'

UINTAH AND OURAY INDIAN RESERVATION

o39 15'

Producing Formations UTAH

6

Mancos Shale

As of December 1990, almost 359.5 BCF of natural gas have been produced from Upper Cretaceous Mancos Shale reservoirs (FIGURE

UO-13). Most of the production comes from the silty, tight gas sand­stone reservoirs of the Mancos B (also called the Emery Sandstone) in the middle of the Mancos Shale. Gas is also produced from the Mancos A/Morapos Sandstone, a conventional, clean sandstone found in the upper transition zone between the Mancos Shale and the overlying Mesaverde Group (FIGURE UO-14).

The Douglas Creek North Field has produced >5 BCFG from the Upper Mancos/Morapos Sandstone (figure 13). In this area, the Up­per Mancos consists of up to 34 feet of mud to coarse-grained, well-sorted sandstone with 20% porosity and 100 mD permeability. It was deposited as shelf sands in a marginal-marine setting, and is probably time-equivalent to the Castlegate Sandstone.

The Mancos B consists of 500 to >1000 feet of finely interbed­ded and discontinuous claystone, siltstone, and very fine- to fine-grained sandstone, with an average net pay interval of 30-250 feet. It is characterized by low porosities and permeabilities, with porosities ranging from 10-11% on the Douglas Creek Arch, to <2% on the flanks. Permeabilities are <0.1 mD on the average. Mancos B sedi­ments were deposited on a northerly prograding submarine slope or foreslope, approximately 100 miles to the east of the time-equivalent Emery shoreline in Utah (Noe, 1993a).

Utah Colorado

Gas fields <5BCF >5BCF

FERC tight sand areas

Approximate line of section

Mancos Marine Sandstone play

Grand Junction

0

0

10 20 30mi

50km40302010

Rangeley Douglas Cr. N.

Philadelphia Cr.

Cathedral

Douglas Cr. W.

Dragon Trail

Lower Horse Draw

UIN

TA

BA

SIN

UNCOMPAHGRE UPLIFT

PARADOX BASIN Mesa

Delta

DO

UG

LA

S C

RE

EK

AR

CH

CO

LO

RA

DO

UTA

H

PICEANCE BASIN

C

A

B

C'

A'B

'

Douglas Cr.

3000

0

0 20,000

6,000

40,000 ft

12,000 m

Vertical exaggeration 50:1

Douglas Creek fault

Datum 3000 ft above sea level

00

100

500

200 750

300 1000

m ft

Argo Unit 2-20

sec 20, T5S, R102W

Cities Service USA 1

sec 7, T4S, R102W

Nat. Assoc. Pet Govt. 1

sec 6 T3S, R102W Superior

Unit 3 sec 1 T3S, R102W

Texas Douglas Cr. 1

sec 9 T2S,R101W

Phillips Unit B-1

sec 18, T1S, R101W

G. E. Kadane Moran 1

sec 2, T1N, R101W

Mesaverde Group

Anchor Tongue

Mancos A

Mancos B(Emery)

Mancos B

(Morapos)

L. SegoU. Sego

Mancos A

U. Sego

L. Sego

Buck Tongue

(Morapos)

Silt Marker

S.P. R

S.P. RS.P. R

S.P. RS.P. RS.P. RSP RS.P. R

Man

cos

Sha

le

5000

40

00

3000

5000

40

00

1000

2000

1000

2000

1000

2000

1000

2000

1000

2000

S N

Figure UO-14. South to north structural cross section along the Douglas Creek Arch of the Mancos B interval and other sandstones in the transitional zone between the Mancos Shale and Mesaverde Group (modified after Noe, 1993a).

Figure UO-13. Gas fields of the Upper Cretaceous Mancos Shale (modified after Noe, 1993a)

UINTAH AND OURAY INDIAN RESERVATION Producing Formations UTAH

7

UINTAH AND OURAY INDIAN RESERVATIONUTAH

TYPE LOGS a n A r r o y o F i e l d

D A K O TA S I LT

D A K O TA

S A N D S T O N E

C E D A R M O U N TA I N

F O R M AT I O N

M O R R I S O NF O R M AT I O N

E N T R A D AS A N D S T O N E

B u c k h o r nM e m b e r

B r u s h y B a s i nM e m b e r

S a l t W a s hM e m b e r

48

00

50

00

52

00

54

00

Figure UO-15. Type log from the San Arroyo Field (modified after Hill and Bereskin, 1993).

Figure UO-16. Three dimensional model of Dakota Sandstone depositional environments at Hell's Hole Field (modified after Moretti et al., 1992).

ALLUVIAL

VALLEY

COASTAL

PLAIN

FORSHORE

SHOREFACE

M I L E S

FE

ET

00

25

50

1 2 3

Distributary Channel

Braided Stream

Coastal Plain with Marshes

Cross Bedding

Beach Ridges

Foreshore Sand

Shoreface Slope and Sand

Highlands

Marine Shale

Figure UO-17. Structure contour map of the top of the Entrada Sandstone, San Arroyo/Westwater area, Grand County, Utah. The area that is productive from the Entrada Sandstone is colored in pink. The Bar X Field has produced less than 5 BCF of gas from the Entrada Sandstone. Contour interval is 500 feet (modified after Morgan, 1993b).

R 24 E R 25 E R 26 E

T16S

T17S

R 23 E

1000

500

250020001500

1000

500

0

-500

500

500

0-500

DU

D DU U

DU D

U DU

0

0

1

1

2

2

3

3

4

4 5 6

mi

km

Westwater

San Arroyo

Bar X

Producing Formations 8

Dakota Sandstone, Cedar Mountain Formation,Morrison Formation

The Dakota Sandstone, Cedar Mountain Formation, and Morrison Formation are similar in lithologic succession. Each contains a bas-al, continuous, conglomeratic sandstone or conglomerate, like the Salt Wash Member of the Morrison Formation, the Buckhorn Con-glomerate of the Cedar Mountain Formation, and the lower part of the Dakota Sandstone. This is overlain by interbedded shales and lenticular sandstones, like the Brushy Basin Member of the Morrison and the upper units of the Cedar Mountain and Dakota (Figure UO-15). The basal conglomeratic units are braided stream deposits, while the upper units of the Morrison and Cedar Mountain Forma-tions are thought to be floodplain and meandering stream deposits. The Upper Dakota was deposited in a complex coastal setting con-

sisting of coastal plain, fluvial, swamp, marsh, tidal flat, delta, beach, and nearshore marine environments (Fig. UO-16).

The Morrison Formation is approximately 350-450 feet thick, the Cedar Mountain Formation is approximately 0-150 feet thick, and the Dakota Sandstone is approximately 40-250 feet thick (Noe, 1993b).

Entrada Sandstone

In northeastern Utah, the Entrada Sandstone consists of dune and in-terdune eolian deposits associated with the northerly retreat of a Ju-rassic sea. The sandstones are gray to orange, fine- to medium-grained, well-sorted and cross-bedded.

Gas and some oil are produced from traps formed by anticlinal closures on Laramide structures. Three Entrada reservoirs have pro-duced >44 BCF gas; most of this production comes from San Arroyo Field (FIGURE UO-17). Average depth to the top of the reservoir var-ies from 5250 feet at San Arroyo to 6700 feet at Wilson Creek Field in Colorado. Average net pay thickness in the Uinta Basin is 118 feet at Westwater Field. Average porosity ranges from 16% at San Ar-

royo to 24% at Westwater.Source rocks for San Arroyo and

Westwater Fields may have been or-ganic-rich marine deposits of the Per-mian Phosphoria and Pennsylvanian Paradox Formations (Morgan, 1993b).

UINTAH AND OURAY INDIAN RESERVATIONUTAH

Figure UO-18. Location map of Rangely Field and other major and minor Weber Sandstone reservoirs (modified after Hemborg, 1993).

0 150 30 10

Fluvial

Dune

Dune

Extra

Extra

Dune

FluvialDuneExtra

Dune

Extra

Extra

Dune

Dune

Dune

FluvialExtra

Fluvial

Extra

Fluvial

Extra

Extra

Fluvial

Fluvial

Fluvial

Dune

Extra

Fluvial

Flu

vial

Ext

raD

un

eD

un

e C

om

ple

x E

xtra

Du

ne

Ext

raD

un

eD

un

eD

un

e

Sedimentarystructure

Density porosity(%)

Gamma ray(API units)

Horizontallamination

Cross-lamination

Convolutelamination Burrows Root casts

Depth(ft)

5600

5700

5800

5900

6000

6100

6200

6300

- 5800

- 5820

- 5840

- 5860

- 5880

- 5900

Depth(ft)

Extra=Extradune

Figure UO-19. Wireline log and core description of the No. 139Y UPRR, Rangely Field. Core shows one cycle of Weber deposition (modified after Hemborg, 1993)

Weber Sandstone

The Weber Sandstone is a fine-grained, subarkosic to quartz arenite of eolian origin deposited during Desmoinesian, Missourian, and Wolfcampian time. In Rangely Field, productive eolian sands were deposited in dune, interdune, and extradune environments (FIGURE

UO-19). These sandstones are either cross-laminated or massively-bedded, the cross-laminated lithofacies being the major producer with an average porosity of 12%. Permeability along laminae averages 2 mD, while permeability across laminae averages 0.4 mD.

Cumulative production from the Weber Sandstone as of 1990 is

724.7 BCF of associated gas and 772 MMBO. The Rangely Weber reservoir contributed 98.9% of the total gas production (FIGURE UO-

18). Average depth to the top of the Weber is 6500 feet, and the trap-ping mechanism in all Weber reservoirs is anticlinal closure (Hem-borg, 1993).

N

GREEN RIVER BASIN

WYOMINGUTAH

WYOMING

UTA

H

COLORADO

CO

LO

RA

DO

UINTABASIN

PICEANCEBASIN

White Riveruplift

SAND WASHBASIN

Uncompahgreuplift

RIO BLANCO

GARFIELDMESA

Thornburg

MOFFAT ROUTT

DUCHESNE UINTAH

UTAH COLO

WASATCH

Weber Sandstone play

Precambrian outcrop

Major oil and gas fields without Weber production

<5BCF Weber associated gas fields

>5BCF Weber associated gas fields

Altamont - Bluebell WonsitsValley

Ashley Valley

Vernal

Uinta Basin boundary fault Split Mtnanticlines

Red Wash

Dou

glas

Cre

ek A

rch

Yampa fault

Skull Cr. anticline

Willow Creek faultRangely

WinterValley

ElkSprings

DanforthHills

Maudlin Gulch

Moffat

Craig

Grand hogback

Glenwood Springs

North Flank fault

Henry's Fork fault

Uinta fault

Wolf Creek fault

111o 110o 109o 108o

41o

40o

0

0

10 20 30 40 50

10 40 60 80

mi

km

Producing Formations 9

Play Summary The United States Geological Survey identifies several petroleum plays in the Uinta-Piceance Basin Province and classifies them as Conventional and Unconventional (Gautier et al., 1995). The discussions that follow are limited to those with direct significance for future petroleum development in the Uintah and Ouray Indian Reservation (TABLE 1).

Play Types Conventional Plays- Discrete deposits, usually bounded by a downdip water contact, from which oil, gas or NGL can be ex-

tracted using traditional development practices, including production at the surface from a well as a consequence of natural

pressure within the subsurface reservoir, artificial lifting of oil from the reservoir to the surface where applicable, and the main-

tenance of reservoir pressure by means of water or gas injection.

Unconventional Plays- A broad class of hydrocarbon deposits of a type (such as gas in tight sandstones, gas shales, and

coal-bed gas) that historically has not been produced using traditional development practices. Such accumulations include

most continuous-type deposits.

Reservation: Uintah and Ouray Total Production in Geologic Province: Uinta-Piceance Basin Province as of 1996 Uinta-Piceance Basin Undiscovered resources and numbers of fields are

Province Area: 40,000 sq. miles (25.6 million acres) Oil:Reservation Area: 6250 sq. miles (4 million acres) Gas:

NGL:

486,712 MBO for Province-wide plays. No attempt has been made 1,992,627 MMCFG to estimate number of undiscovered fields within the 40,262 MBNGL Uintah and Ouray Indian Reservation.

Undiscovered Accumulations > 1 MMBOE Play Probability Drilling depths Pay Thickness Porosity/PermeabilityPlay Type USGS Description of Play Oil or Gas Known Accumulations Field Size and Number (chance of success) (min., mean, max.)Designation

Field Size (median, mean)Uinta Tertiary Oil and Gas Gas (15 BCFG, 18.9 BCFG)Play Fluvial and lacustrine sandstones Gas

Gas (917,288 MMCFG) Oil (2 MMBO, 2.8 MMBO) (500, 3000, 6000)ft Variable 10-15%/v, low to 1000 md 2002 in the Wasatch and Green River Both

Oil (485,592 MBO) No. of Undiscovered Fields (min., median, max., mean) 1 Oil

1 Formations. Gas (2, 6, 15, 7.1) (1000, 5000, 14000)ftOil (4, 13, 30, 14.7)

Upper Cretaceous Field Size (median, mean)

Conventional Play Shallow sandstones of the Mostly Gas Gas (129,540 MMCFG) Gas (12 BCFG, 15.2 BCFG) Gas up to 80 feet 8-18%/<0.1md

2 2003 Mesaverde Group. No. of Undiscovered Fields (min., median, max., mean) 1 (500, 3500, 6000)ft

Gas (10, 23, 50, 25.9)

Cretaceous Dakotato Jurassic Play

Fluvial Dakota Sandstone,

3 discontinuous fluvial Morrison 90% Gas2004 Sandstone, blanket eolian 10% Oil

Field Size (median, mean)Gas (10 BCFG, 13.1 BCFG)Oil (1 MMBOE, 1.5 MMBOE)

Gas Dakota - 25 feet 10-25%/Gas (579,169 MMCFG)

No. of Undiscovered Fields (min., median, max., mean) 1 (500, 3500, 6000)ft Buckhorn - 26 feet Unknown PermeabilityOil

Entrada Sandstone. Gas (3, 15, 25, 14.6) (1000, 4000, 6500)ft Morrison - 11 feet

Oil (1, 2, 4, 2.2)

Permian-Pennsylvanian Field Size (median, mean)Very high risk Oil (9 MMBO, 25.0 MMBO) Oil 11-14%/ sandstones and carbonates. Mostly Oil Oil EUR (980.5 MMBO) No. of Undiscovered Fields (min., median, max., mean) 1 275 feet

Sandstones and 2005 Permian-PennsylvanianCarbonates Play

Gas EUR (>706 BCFG) Oil (1, 4, 15, 5.7) (6000, 10000, 12000)ft Unknown Permeability

4 Basin Margin Field Size (median, mean)

Subthrusts Play 2014 reservoirs range from Both N/A

Oil (2 MMBO, 5.3 MMBO) Oil Gas (15 BCFG, 25.0 BCFG) (5000, 12000, 18000)ft Unknown No. of Undiscovered Fields (min., median, max., mean) Gas

Closures beneath thrusts,

(hypothetical) Paleozoic to Tertiary in age. 0.18

Oil (1, 2, 7, .05) (5000, 14000, 25000)ft5 Gas (1, 3, 10, .07)

Cretaceous Self-Sourced Fractured Shales Play Upper Mancos fractured shale.

1 Oil/Gas 10->50 feet 10-20%/0.01-100md(hypothetical, continuous) 2009 Best fracturing occurs in brittle Both Oil EUR(14 MMBO) Per well EUR estimates vary (500, 2800, 6000)ft

6 siltstones, carbonates, and calcareous shales.

Tight Gas Uinta Tertiary East Play

Medium- to fine-grained fluvial2015 sandstones interbedded with

(3000, 6400, 10500)ft

7 (continuous) mudstones, siltstones, shales, Gas N/A N/A 1 Gas up to 80 feet <5-9%/<0.1md

and some coal of the Wasatch Fm.

Tight Gas Uinta Medium- to fine-grained fluvial

GasTertiary West Play sandstones interbedded with up to 80 feet 4-8%/<0.01md(hypothetical, continuous) 2016 mudstones, siltstones, shales, Gas N/A N/A 1 (4500, 7500, 11000)ft

8 and some coal of the Wasatch Fm.

9

Basin Flank UintaMesaverde Play Based on widespread occurrence Gas

(hypothetical, continuous) 2018 of tight, gas-saturated continental Gas N/A N/A 1 (8000, 9500, 15000)ft 4->12%/<0.1mdand marginal marine sandstone.

Deep Synclinal UintaMesaverde Play Based on expected occurrence of Gas 3-8%

10 (hypothetical, continuous) 2020 gas-saturated tight Mesaverde Gas N/A N/A 1 (15000, 20000, 25000)ft

N/A Unknown permeability

Sandstone at depths >15,000 feet.

Table 1. Play summary chart. Conventional play type Unconventional/Hypothetical play type

UINTAH AND OURAY INDIAN RESERVATION Play Summary Table 10 UTAH

UINTAH AND OURAY INDIAN RESERVATIONUTAH

Summary of Play Types

The United States Geological Survey has identified many petroleum plays in the Uinta-Piceance Basin Province, classifying them as Con-ventional and Unconventional. The discussions that follow are limit-ed to those plays with direct significance for future petroleum devel-opment on the Uintah and Ouray Indian Reservation. Most of the following is extracted from USGS CD-ROMs DDS-30 and 35 (Gaut-ier et al., 1995). Table 1 is a summary of applicable USGS plays of the Uinta-Piceance Basin Province pertaining to the Uintah and Our-ay Reservation.

Conventional PlaysDefinition - Discrete deposits, usually bounded by a downdip water contact, from which oil, gas, or NGL can be extracted using tradi-tional development practices, including production at the surface from a well as a consequence of natural pressure within the subsur-face reservoir, artificial lifting of oil from the reservoir to the surface where applicable, and the maintenance of reservoir pressure by means of water or gas injection.

PLAY 1 - UINTA TERTIARY OIL AND GAS PLAYThe Uinta Tertiary Oil and Gas Play is based on oil and gas accumu-lations primarily in stratigraphic traps in fluvial and lacustrine sand-stones in the Wasatch and Green River Formations. The play area is limited updip by the presence of brackish and fresh water in rocks near the outcrop.

Reservoirs: Reservoir sandstones of the Wa-satch and Green River Formations are Paleo-cene and Eocene in age and are predominant-ly litharenites and feldspathic litharenites over most of the basin. Some lacustrine limestones produce in the deeper part of the basin. Po-rosities range from <10 percent in the deep Altamont-Bluebell field area to >15 percent at shallower depths (<4,000 feet).

Source rocks: The source rocks for much of the non-associated Wasatch gas in the basin are the underlying Cretaceous Mesaverde gas-prone coals, shales, and mudstones, but some may have a Tertiary origin. In the northern part of the basin, oil is the predominant hy-drocarbon. This oil comes from lipid-rich la-custrine shales and marlstones in the Green River Formation. A complex mixing of oil and gas from different sources has resulted in more gas fields at shallower depths and pre-dominantly oil in deeper reservoirs. This is the opposite of what occurs in many other ba-sins.

Timing and migration: The Mesaverde Group began generating gas in the Early Terti-ary, and the Green River Formation began generating oil and gas in the Middle Tertiary to the present. The deep (>10,000 feet) Terti-ary oil fields are highly overpressured as a re-sult of present-day hydrocarbon generation.Traps: The traps are mostly stratigraphic, but some structural-stratigraphic traps occur, such as the Red Wash Field area (EUR 175 MMBO, 373 BCFG). The largest producing area is the greater Altamont-Bluebell area, which has an estimated ultimate recovery of

260 MMBO and 378 BCFG; however, the field is being actively downspaced from 640 acres per well to 320 acres per well. This ad-ditional drilling should significantly increase recovery.

Exploration status and resource potential: The conventional gas part of this play is fairly well explored, but a maximum of 15 conven-tional fields greater than 6 BCFG may be found, according to U.S.G.S. estimates (Table 1). Because of the very large volume of oil generated deep in the basin, a maximum of 30 oil fields greater than 1 MMBO may remain to be found.

Analog Example: Greater Altamont - BluebellFigures: UO-20 and UO-21

Location: T 1 N - 4 S, R 2 E - 7 W, on ReservationProducing formations: Wasatch and Green River FormationsOther significant shows: Mesaverde Sandstone, gas;

Uintah Formation, gas and oilLithology: Fluvial sandstone, lacustrine sandstones,

limestones, dolomitesType of drive: Solution gasNet pay thickness: Multiple zones with variable thicknessPorosity: 2-20%, average >10%Permeability: Variable in individual pay sections, ranges

from very low up to 1,000 mD inunconsolidated sands

Estimated primary 316 MMBO, 360.5 BCFG, 330.2 MMBWrecovery:Other major analog fields: Greater Natural Buttes

Monument ButtesRed WashWalker HollowWonsits Valley

GreenRiver

outcrop

NorthHorn

outcrop

Coltonoutcrop

Wasatchoutcrop

GreenRiver

outcrop

Uinta and DuchesneRiver outcrop

A

A'

Price

Duchesne

Vernal

Uinta uplift

WYOMING

UTAH

UTA

H

CO

LOR

AD

O

8000'

9000'

7000

'

6000

'

5000

'

4000

'

3000

'

39o

40o

41o

109

o

110

o

111

oN

30

50

0

0

10

10

20

20 30 40

mi

km

Figure UO-20. Combined thickness of the Green River, Wasatch/Colton, and North Horn Formations with outcrop areas indicated. Contour interval is 1000 feet. Cross section A-A' is shown in Figure UO-21 (modified after Chidsey, 1993a).

Figure UO-21. Generalized southwest to northeast cross section of Tertiary rocks in the Uinta Basin showing major facies, intertonguing relationships, and stratigraphic names. Area of fluid-pressure gradients >0.5 psi/ft indicated in red. Line of section is shown in Figure UO-11 (modified after Chidsey, 1993a).

CONVENTIONAL PLAY TYPE: Uinta Tertiary Oil and Gas Play 11

6000 2000

3000 1000

00

4 8 12 16 20 mi

5 10 15 20 km

ft m

Paleozoic-Mesozoic rock

Duchesne River Fm.

Uinta Fm.

Colton Fm.

Wasatch F

m.

North Horn Fm. (part)

Colton Fm.

Green River Fm.

9000

6000

3000

SL

-3000

-6000

-9000

Altamont - Bluebell fields

North Horn Fm. (part) & Mesaverde Group

ASW

A'NE

Area of fluid-pressuregradients >0.5 psi/ft

UPPER CRETACEOUS CONVENTIONAL PLAY

This is primarily a gas play in sandstones of the Mesaverde Group at shallow depths in both the Piceance and Uinta Basins; however, dis­covered fields are mostly in the Piceance Basin. Fields are localized by structure, but stratigraphic traps have also been found. The play is limited downdip where the reservoirs become unconventional (tight) and is limited updip by fresh-water flushing. The Mesaverde part of this play has some areal overlap with tight Mesaverde reser­voirs. The tight rocks are generally beneath and/or downdip of con­ventional Mesaverde reservoirs.

Reservoirs: The reservoir rocks are Cretaceous Mesaverde Group sandstones deposited in marginal-marine, fluvio-deltaic, and fluvial environments. Some very fine-grained sandstone and siltstone reser­voirs were deposited in a shallow-marine shelf environment seaward of, and in part beneath, the Mesaverde Group. These reservoirs in­clude the Mancos Shale "B" and equivalents, but much of the Man-cos "B" fields are tight and developed by drilling, although there is some potential for field growth.

Source Rocks: The Mesaverde Group source beds are organic shales (including some coals) interbedded with sandstones.

Timing and Migration: Time of generation is Late Tertiary to pres­ent. Traps: Traps are predominantly structural-stratigraphic and strati­graphic. Accumulations are found at depths of <1,000 feet to 6,000 feet, with a median depth of 3,500 feet.

Exploration Status: The conventional part of the play is well ex­plored in the Piceance Basin and only moderately explored in the Uinta Basin. Because of the large volume of gas generated by Me­saverde source beds, the U.S.G.S. estimates that a minimum of 10 and a maximum of 50 conventional fields may be discovered (Table 1).

Analog Field Greater Natural Buttes Figures: UO-22 to UO - 25

Location: T 8-10 S, R 19-23 E (SLB&M), T 36 S, R 25-26 E (SLPM), Uinta County, Utah, on Reservation

Producing formations: Green River Formation, Wasatch Formation Mesaverde Group

Other significant shows: None Lithology: Fluvial and lacustrine sandstones,

limestones, dolomites Type of drive: Pressure depletion Net pay thickness: Individual sands may be up to 80 feet in

thickness Porosity: 8-18%, average 12% (logs) Permeability: Generally less than 0.1 mD Estimated ultimate recovery: 0.5 BCFG Other major analog fields: Devil's Playground

Red Wash Wonsits Valley

0

0

6mi

10km NOutline of gas field

Outline of oil field

Line of cross section

Fault (E-W) dashed where uncertain

Gilsonite vein (NW-SE) dashed where uncertain

T

S11

T

S10

T

S9

R18E

R21E R22E R23E

White

River

Gre

en

River

A

A'

Figure UO-22. Map of the Greater Natural Buttes Gas Field (modified after Osmond, 1992).

A A'31 MILES

GREEN RIVER FM.

WASATCH FM.

2000 FT.

MESAVERDE GROUP

2500 FT.

CASTLEGATE SANDSTONE

MANCOS SHALE

NORTH HORN FM.

Figure UO-23. Diagrammatic west-east cross section showing stratigraphy of the Greater Natural Buttes Field and position of Wasatch producing sandstones that overlie the Mesaverde. Line of section is shown in Figure UO­14 (modified after Osmond, 1992).

Figure UO-25. Stratigraphic column for Greater Natural Buttes (GNB) Field, showing formations which produce oil and gas in GNB and nearby fields (modified after Osmond, 1992).

Gray-Green Shale and Fluvial SandstoneUINTA

FM.

0-1700

Gilsonite Veins

GREEN

RIVER

FM.

3800'

MAHOGANY OIL SHALE BED

'H' MARKER

Lacustrine and Marginal Lacustrine Gray-Green Shale,

Marlstone and Sandstone

DOUGLAS CREEK MEMBER

PRODUCTION

Horseshoe Bend 12 Miles N of GNB

WASATCH

FM.

2000'

White River, 5 Miles North of GNB OIL with ASSOCIATED GAS

Red Wash/Wonsits to N and NE Monument Butte and Other Fields to W

GAS Greater Natural Buttes, SE Red Wash/Powder Springs 9 Miles NE of GNB

Greater Natural Buttes Peters Point, 20 Miles SW of GNB

Red Shale and Fluvial Sandstone

NORTH HORN - FLAGSTAFF Varicolored Shales, Fluvial Sandstone, Lacustrine Limestone and Coal 'OHIO CRK CGL' - BEDS AT DARL CYN' Sandstone with Dark Chert Pebbles

West

Farrer FM. Tight Sands and Siltstones, Gray Shale and Coal

NELSEN FM. - 700FT. COAL BEARING

IMMATURE FOR GAS

MATURE

East

MESAVERDE

GROUP

2200' - 2900'

MANCOS SHALE - 5000' (Marine)

Dakota Sandstone (Fluvial)

Upper Level for Gas Generation Cuts Down, Stratigraphically, Eastward Across GNB from 1000' Above Mesaverde to below the Base of Mesaverde; Based on Coal Rank High Volitile A Bituminous R 0.85%

(Nuccio and Johnson 1986)

+-

o

Greater Natural Buttes

Book Cliffs 30 Miles S of GNB

PAL

EO

­C

EN

EC

RE

TA

CE

OU

S

EO

CE

NE

SURFA

CE

Figure UO-24. Structural contour map of Natural Buttes Field. Bold line depicts approximate Reservation boundary (modified after Hill and Bereskin, 1993).

+1000

+500

+500

+1000

- 500

+1000

- 500

_0+

_0+

Field Outline

Uintah Special Meridian

Salt Lake Meridian

R 20 E R 22 E R 23 ER 21 E

T 8 S

T 9 S

T 1 0 S

T 1 1 S

Datum: Top Wasatch Formation Contour Interval: 500 feet

UINTAH AND OURAY INDIAN RESERVATION CONVENTIONAL PLAY TYPE: Upper Cretaceous Conventional Play 12 UTAH

CRETACEOUS DAKOTA TO JURASSIC PLAY

This is primarily a conventional reservoir play, but tight reservoirs are mixed with the conventional rocks. The discovered fields are mostly structurally controlled. Based on known fields, it appears to be predominantly a gas play (90 percent gas, 10 percent oil). The Cretaceous Dakota Group (including the Cedar Mountain Formation) and the Jurassic rocks were combined into one play by the U.S.G.S. because many fields produce from rocks of both ages and any struc­ture drilled has the potential for accumulations in both. The Wilson Creek Field is the southeasternmost structure along a series of pro­ducing structures that includes the Maudlin Gulch Field. The down-dip limits of the play are where the rocks become tight and reservoirs are unconventional (>6,000 feet).

Reservoirs: The Cretaceous Dakota reservoirs vary from lenticular to continuous, and are predominantly fluvial in the play area. The Jurassic reservoirs range from discontinuous fluvial sandstones of the Morrison Formation to blanket eolian sandstones of the Entrada Sandstone. Porosities range from <11 percent to about 25 percent.

Source rocks: Source rock data for this play are lacking in the pub­lic record, but some dark shales, mudstones, and thin coals are pres­ent in the Dakota Group. The overlying marine Cretaceous Mowry

R 22 E R 23 E R 24 E

from the Dakota Group (including the Cedar Mountain Formation) and the Jurassic Entrada Sandstone (FIG­

URES 27 and 28). Many of the fields have significant amounts of nitrogen and CO2 (as much as 25 percent). T

Exploration status and resource 15

potential: The play is maturely de- S

veloped for large fields, but subtle structures and stratigraphic traps

T may contain as many as 25 signifi- 15.5 cant accumulations (TABLE 1). S

- 990

26 25

- 753

30

- 710

29

- 342

28

35

-1570 - 100

­

- 600 - 400

36

- 617

31

- 523

32 33

0

800 ­- 1200- 1400

- 1600

- 828

UINTAH CO

31 32 33 34 CARBON, CO 35

- 1121

3 FENCE

- 351

CANYON

6 5 4

- 13

3

91

2

SP IEL

TYPE LOG F i e l d

M O R R I S O N

B u c k h o r n M e m b e r

B r u s h y B a s i n M e m b e r

FENCE CANYON FIELD Uintah and Carbon Counties, Utah

T E X A C O 3 F E N C E C A N Y O N

S a n A r r o y o

D A K O TA S I L T

S A N D S T O N E

C E D A R M O U N TA I N

F O R M AT I O N

F O R M A T I O N

48

00

D A K O TA

50

00

5

20

0

54

00

OO

OO

OO

O

OO

OO

O

78

00 MANCOS

SHALE

MARKER

CGL.

MORRISON FM.

79

00

8

00

0

81

00

8

20

0

PERFS: 7978-8016 Ft.

DATUM

DA KOTA SILT

DAKOTA SS

CEDAR MTN. FM.

BUCKHORN

8079-8106 Ft.T IPF: 877 MCFGPD COMPLETED: 9-29-61 16

S G E O L O G Y B Y J O H N O S M O N D

S a l t W a s h M e m b e r

0 2000' 4000' 1 M I L ESTRUCTURE MAP DATUM: TOP OF DA KOTA SILT

and Mancos Shales are both known source beds (mostly oil prone). Figure UO-26. Structure map and typical electric log from Fence Canyon Field (modified after Hill and Bereskin, 1993).

Timing and migration: The hydrocarbons were probably generated in Late Cretaceous to Early Tertiary time, and some may have mi­grated into younger Tertiary structures.

Traps: The known traps are predominantly structural, and some have stratigraphically modified the accumulation. Many of the fields are situated on surface anticlines; they tend to be large and were dis-

Figure UO-28. Type log from the San Arroyo Field (modified after Hill

covered relatively early in the exploration cycle. San Arroyo-East

SAN FIELD R 2 5 E R 2 6 E

T

S 1 6

U N I T

CO

LO

RA

DO

1 2 0 0

1 3 0 0

1 4 0 0

1 5 0 0

1 6 0 0

1 7 0 0

1 8 0 0

1 9 0 0

2 0 0 0

1 7 0 0

S A N A R R OYO

A N T I C L I N E

B A R - X

A N T I C L I N E

ARROYO

S A N A R R O Y O

UT

AH

DATUM: TOP OF DAKOTA SILT CONTOUR INTERVAL: 100 FT.

and Bereskin, 1993). Canyon (EUR 174 BCFG) was discovered in 1955 and produces

Figure 26

Location:

Cretaceous Mancos Shale

Lithology:

10-16%

10 BCFG

Other major analog fields:

Analog Example: Fence Canyon

T 15-16 S, R 22-23 E, (SLB&M), Uinta and Grand Counties, Utah, on Reservation

Producing formations: Dakota Sandstone, Buckhorn Conglomerate, Morrison Formation

Other significant shows:

Sandstone, white, fine-medium grained, conglomeratic

Type of drive: Gas expansion

Net pay thickness: Dakota - 25 ft., Buckhorn - 26 ft., Morrison - 11ft.

Porosity:

Permeability: Unknown

Estimated ultimate recovery:

Evacuation Creek, Hell's Hole, Park Mountain, San Arroyo

Analog Example:Figures: UO-27, UO-28

Location:

None Lithology:

Member), shale with occasional sandstone beds

10-20%

NA

Not calculated

San Arroyo

T 16 S, R 25-26 E, (SLPM), Grand County, Utah, just east of Reservation

Producing formations: Dakota Sandstone

Other producing zones: Castlegate Sandstone, Cedar Mountain and Buckhorn Conglomerate Members of the Cedar Mountain Formation, Brushy Basin and Salt Wash Members of the Morrison Formation, Entrada Sandstone

Other significant shows: Interbedded sandstone and shale (Dakota), variegated mudstone with sandstone lenses (Cedar Mountain), sandstone to conglomerate (Buckhorn

(Morrison), sandstone (Entrada)

Type of drive: Gas expansion

Net pay thickness: 13-80 feet, variable

Porosity:

Permeability:

Estimated primary recovery:

E N T R A D A

S A N D S T O N E

Figure UO-27. Structural contour map of San Arroyo Field (modified after Hill and Bereskin, 1993).

UINTAH AND OURAY INDIAN RESERVATION CONVENTIONAL PLAY TYPE: Cretaceous Dakota to Jurassic Play 13 UTAH

UINTAH AND OURAY INDIAN RESERVATIONUTAH

Analog Field: Greater Hell's HoleFigures: UO-29 to UO-31

Location: T 10 S, R 25 E, (SLB&M), Uinta County, Utah; T 1-2 S, R 104 W, Rio Blanco County, Colorado,east of Reservation

Producing formations: Dakota GroupOther significant shows: Mesaverde shales and coals, Mancos Shale (B),

Weber Sandstone (Maroon), LeadvilleLithology: SandstoneType of drive: Gas depletionNet pay thickness: 25 ft. average, max 57 ft., min 5.5 ft.Porosity: 14-18%Permeability: 0.1-10 mDEstimated ultimate recovery: 26.2 BCFG, 65,000 BC

COMPOSITE TYPE LOGHELL'S HOLE FIELD

D a k o t a S i l t

U p p e r D a k o t a A

U p p e r D a k o t a B

M i d d l e D a k o t a C

L o w e r D a k o t a D

M o r r i s o n

M a r i n e S h a l e

S h o r e f a c e t o F o r e s h o r eM a r i n e S a n d s

S h o r e f a c e M a r i n e S a n d s

C o a s t a l P l a i n ,F l u v i a l C h a n n e l ,

O v e r b a n k

B r a i d e d A l l u v i a lC h a n n e l s

C o n t i n e n t a lM u d , S i l t , a n d S a n d

T D

70

00

69

00

68

00

67

00

66

00

0 100 200 30 20 10 0 -10

Figure UO-29. Composite type log for the Dakota section at Hell's Hole, Rio Blanco County, CO, and Uintah County, UT (modified after Moretti et al., 1992).

ALLUVIAL

VALLEY

COASTAL

PLAIN

FORESHORE

SHOREFACE

M I L E S

FE

ET

0

0

25

50

1 2 3

Distributary Channel

Braided Stream

Coastal Plain with Marshes

Cross Bedding

Beach Ridges

Foreshore Sand

Shoreface Slope and Sand

Highlands

Marine Shale

Figure UO-30. Three dimensional model of Dakota Sandstone depositional environments at Hell's Hole Field. (modified after Moretti et al., 1992).

UINTAMOUNTAINS

DAGGET

MOFFAT

UINTAH

DUCHESNE

RIO BLANCO

GARFIELD

MESAGRAND

CARBON

WYOMING

UTAH COLORADO0 10 20 50mi.

UTA

HC

OL

OR

AD

O

RangelyField

AXIAL ARCH

DOUGLAS

CREE

KA

RC

H

Hell's HoleArea

UINTA

BASIN

PICEANCE

BASIN

ALTAMONT

NATURAL BUTTES

N. DOUGLAS

RED WASH

PICEANCE CR.

SAND WASHBASIN

111O

110O

109O

108O

107O

107O

41O

40O

39O Figure UO-31. Map showing the Hell's Hole area (modified after Moretti et al., 1992).

CONVENTIONAL PLAY TYPE: Cretaceous Dakota to Jurassic Play 14

UINTAH AND OURAY INDIAN RESERVATIONUTAH

Analog Example: RangelyFigures: UO-18, 19, 32, 33

Location: Rio Blanco County, Colorado, east of ReservationProducing formations: Weber SandstoneOther significant shows: NoneLithology: SandstoneType of drive: CombinationNet pay thickness: 275 feetPorosity: 15%Permeability: 25 mDEstimated ultimate recovery: 904 MMBOOther major analog fields: Ashley Valley, Thornburg

Figure UO-32. Map showing the Early Wolfcampian paleogeography of the Uinta-Piceance Basin Region during maximum transgression (modified after Johnson et al., 1992).

Highland area of low to moderate relief

Alluvial fan, alluvial plain, delta plain

Eolian dune field

Sabkha, playa, restricted shallow-marine setting

Shallow- or nearshore-marinesand-rich environment

Offshore-marine sand-rich environment

Carbonate shelf, platform, or reef

ELEPHANTCANYON

FORMATION

CUTLERFORMATION

WEBERSANDSTONE

WEBERSANDSTONE

MAROONFORMATION MAROON

FORMATION

FRONT RANGEUPLIFT

SAWATCHUPLIFT

UNCOMPAHGRE

UPLIFT

OQUIRRHGROUP

FRYINGPANMEMBER

UTA

H

CO

LO

RA

DO

Vernal

fault zone

Grand Junction

Glenwood Springs

fault

zone

Gore

Green RiverSalina

Salt Lake City

Uncompahgre fault zone

Garmesa

Price

PAKOONDOLOMITE

Craig

loessite

112o 111o 110o 109o 108o 107o

41o

40o

39o

Highland area of high to moderate relief30 mi50 km

00 100 km

60 mi

PLAY TYPE 4

PERMIAN-PENNSYLVANIAN SANDSTONES AND CARBONATES PLAY

This is primarily a play for structural and stratigraphic traps in Per-mian and Pennsylvanian sandstones and carbonates. The objective reservoirs were deposited in predominantly marine and eolian envi-ronments. Some redbeds occur, but are not part of the prospective facies.

The eastern part of the play is bounded by the expected limit of porous sandstone. The southern boundary is limited by expected presence of structural and stratigraphic traps in the Uinta Basin; the northern limit is based on the expected limit of conventional reser-voirs. This play is thought by the U.S.G.S to be very high risk.

Reservoirs: The Permian-Pennsylvanian reservoirs are both sand-stone and carbonate. The sandstones have good reservoir quality at shallow depths (<8,000 feet). The carbonates are expected to be po-rous at least as deep as 12,000 feet. The shallow sandstones (Weber Sandstone) have about 11-14 percent porosity in the only two dis-covered fields in the play.

Source rocks: The source rocks for the discovered oil fields are not known, but the Park City (Phosphoria) Formation was probably the source, requiring long-range migration. Some local Pennsylvanian marine shales may also be a source.

Timing and migration: The hydrocarbons must have migrated pri-or to Tertiary tectonism, so generation was probably during the Up-per Cretaceous.

Exploration status and resource potential: Only two fields have been found in the province, both of which are related to anticlinal closures, and both of which produce oil. The play is for oil with as-sociated gas, but it is possible that some gas fields of less than mini-mum size (6 BCFG) may also be found. Several Pennsylvanian sandstone and carbonate reservoirs produce on closures just outside the province in the Maudlin Gulch Field area (Danforth Hills Anti-cline).

The two producing fields in the play are Ashley Valley Field in Utah (EUR 25.5 MMBO) and Rangely Field in Colorado (EUR 955 MMBO, 706 BCFG). Ashley Valley produces from about 4,000 feet and Rangely from 5,500 to more than 6,000 feet. The play depths for undiscovered accumulations range from 6,000 to 12,000 feet. The play below 8,000 feet is relatively unexplored by drilling, but is

CONVENTIONAL PLAY TYPE: Permian-Pennsylvanian Sandstones and Carbonates Play 15

?

?

Maroon FmSs

Fm

Ss

Morgan Fm

Ss

Mor

gan

Fm

Maroon Fm

Belden Sh M

intu

mF

m

Ss

Mar

oon

Fm

Round

Ls

Schoolhouse

Leonardian

Virgilian

Desmoinesian

Atokan

SeriesSystemEra Eastern Uinta Basin Piceance Basin

PE

RM

IAN

Weber

Park City Fm Park City

Weber Web

erW

eber

Mor

rison

Fm

Valley

Tongue

Wolfcampian

Missourian

Morrowan

PE

NN

SY

LVA

NIA

N

PAL

EO

ZO

IC

PLAY TYPE 5 BASIN MARGIN SUBTHRUSTS PLAY (HYPOTHETICAL)

This play is primarily for closures beneath high- to low-angle thrusts. Figure UO-3 shows some of the flanking thrusts present along the northern to eastern part of the province. The play is hypothetical, and both oil and gas should be present. The only nearby analog is the Tepee Flats Field in the eastern Wind River Basin-Casper Arch area. Here, thick, unfractured Cretaceous marine shale provides a seal for an oil and gas accumulation in the Upper Cretaceous Frontier Formation.

Reservoirs: The reservoirs for this play range in age from Paleozoic to Tertiary. Reservoir quality may be poor, especially for prospects deeper than 12,000 feet. The Mississippian carbonates are expected to be porous in most parts of the play.

Source rocks: The source rocks are within the subthrust section. Possible source

rocks containing more than 1 percent total organic carbon (TOC) are found in the Lower Tertiary, Upper Cretaceous, and Pennsylvanian Belden Shale (FIGURE UO-33). The Jurassic Curtis Formation may be a local source bed.

Timing and migration: The timing is uncertain, but most of the thrusting took place during the Laramide Orogeny.

Traps: Traps are most likely structural and structural-stratigraphic (FIGURES UO-34

and UO-35). Play depths should range from 5,000 feet to as much as 25,000 feet.

Exploration status and resource potential: The play is almost unexplored by drilling and only moderately explored by seismic mapping. Based on the abundant fields near the thrusts in the Uinta Basin, a median field size of 2 MMBO and 15 BCF of non-associated gas, and a maximum field size of approximately 50 MMBO and 150 BCFG are estimated for this play.

Figure UO-33. Nomenclature and correlation for the Weber Sandstone in the East Uinta and Piceance Basins. Unconformities indicated by white patches (modified after Hemborg, 1993).

N

32 35

R 7 E

T 3 N

A A'

T 2 N

Nugget completion

5

8 contact

(-3415')

-3800 -3600

-3400-3200

-3000 -2800

-2600

-2400

-2800-3000-3200-3400-3600-3800

-3000

-320

0-3

400

-3800-3600

Oil-Water contact (-3415')

Dry Hole

Twin Creek completion

Twin Creek and Nugget completion

11

Oil-Water

4-10S 3-2 UPRR

3-3 UPRR 2-1 Bingham

2-5 Bingham,

Frontier Fm (Kf)

Aspen Sh (Ka)

Kelvin Fm (Kk)

Stump/Preuss Ss (Jsp)

Twin Creek Ls (Jtc)

Nugget Ss (Jn)

Ankareh Fm (TR a)

Thaynes Ls (TR t)

R w)

Bear Rive

r Fm

(Kbr

) Ka

Absaroka

thrust Hilliard Sh (Kh)

0

0 1km

1 mi

Oil

Jsp

Jsp

Jsp

Kk

Kk Kk

Kk

KeKe

Te

Te

Tw-TfWasatchFowkes?

+8000'

+6000'

+4000'

+2000'

-2000'

-4000'

-6000'

-8000'

-10000'

A'A WEST EAST

B

Pineview Field Evanston Fm (Te)

Wasatch Fm (Tw) 1 Pineview

1 Newton Sheep

3-9 UPRR 2-1 A

Evanston Fm (Ke)

Woodside Sh (T

Frontier Fm (Kf)

Water

Sea level

Figure UO-34. Typical geometry of a shallow east-trending structure, Pineview Nugget Reservoir, Summit County, Utah (not on reservation). Gas is trapped in an asymmetrical thrusted anticline in the hanging wall of the Absaroka Thrust system. Structure contour map of the top of the Nugget Sandstone (modified after Hjellming, 1993). Figure UO-35. Cross section through the reservoir. Line of section shown in Figure UO-34 (modified after Hjellming, 1993).

UINTAH AND OURAY INDIAN RESERVATION CONVENTIONAL PLAY: Basin Margin Subthrusts Play (Hypothetical) 16 UTAH

DEFINITION: Unconventional Plays Unconventional Play- A broad class of hydrocarbon deposits of a type (such as gas in "tight" sandstones, gas shales, and coal-bed gas) that historically has not been produced using traditional development practices. Such accumulations include most continuous-type depos­its.

Cretaceous Self-Sourced Fractured Shales Play (Hypothetical)

Oil is produced from fractured Upper Cretaceous Mancos Shale and its equivalents. The best fracturing occurs in brittle siltstones, carbo­nates, and calcareous shales.

The play outline is based by the U.S.G.S. on the known occur­rence of production and the tectonic features associated with known and suspected potential. In the play, the best open fractures occur at the maximum flexure on anticlines or monoclines. Fractures also produce well where shear zones or faults occur. The play boundary is fairly easy to define except in the area between Rangely and the Axial Uplift, where proprietary seismic data indicate the presence of several subsurface thrusts, including thrusts associated with the White River Field structure.

Reservoirs: The reservoirs are open fractures in brittle siltstones, carbonates, and calcareous and siliceous shales. The producing inter­vals vary from 10 feet to more than 50 feet thick. The fracturing is highly variable, and one well in the play has produced over 1 MMBO.

Source rocks: The enclosing marine shales are the source rocks. The richness varies from about one percent to more than four percent TOC, based on unpublished information.

Timing and migration: The oil was probably generated in the Late Tertiary during maximum burial.

Traps: The traps are formed by the enclosing unfractured, more plastic shale, which contains less silt and carbonate than the brittle facies. The largest accumulation in the play is found in Rangely Field (EUR 14 MMBO). The highest concentration of oil wells pro­ducing from the Mancos Shale at Rangely is along the south flank of the structure at the point of maximum flexure.

Exploration Status and Resource Potential: The play is moderate­ly well explored by vertical wells but nearly unexplored by slant- and horizontal-hole drilling. The U.S.G.S. assumed a low success ratio for the overall play area. Although this play is classified as a contin-uous-type play (e.g., tight gas), production should be localized by in­dividual fractured structures and fracture trends.

EUR estimates per well are extremely variable and, although the play is treated as a continuous-type occurrence, the U.S.G.S also simulat­ed individual undiscovered fields or "sweet spots" within it to assist in assessment. On this basis, the success ratio in well-mapped struc­

tural flexures is considered quite high, perhaps more than 50 percent; also, there is high potential for finding many areas of small produc­tion, and perhaps as many as 10 larger fields (Table 1).

Analog Example: Greater Douglas Creek FIGURES UO-13, UO-14

Location: Rio Blanco County, Colorado west of Reservation

Producing formations: Mancos, Mancos (B) Shale Other significant shows: Morapos Formation Lithology: Sandstone Type of drive: Pressure depletion and water drive Net pay thickness: 30-250 feet Porosity: 2-20% Permeability: 0.01-100 mD

TIGHT GAS UINTA TERTIARY EAST PLAY

This play is based on well-established gas production from the Ute-land Butte, Chapita, and Buck Canyon zones of the Tertiary Wasatch Formation. Updip to the south and east, the play limit is based on an increase in reservoir quality and a change to mostly conventional res­ervoirs that have gas-water contacts, which are included in the Uinta Tertiary Oil and Gas Play. Downdip to the north, the play boundary is defined as the point where it becomes predominantly an oil play and is included in Play Type 1. The western limit is along the Green River drainage, where the play becomes higher risk and has been as­sessed separately by the U.S.G.S. as Tight Gas Uinta Tertiary West Play (Play Type 8). The overall Wasatch tight gas plays (7 and 8) are based on vitrinite reflectance (Ro) levels in the underlying Creta­ceous Mesaverde Group. Rice and others (1992) and Fouch and oth­ers (1992) showed that Wasatch gas has migrated upward from the Mesaverde Group and that the play occurs between the basal Mesa-verde Ro limits at 1.1-1.5 percent.

Reservoirs: Reservoir rocks are generally medium- to fine-grained feldspathic litharenites and litharenites deposited primarily in fluvial environments. They are interbedded with mudstones, siltstones, shales, and some coal. Porosity ranges from less than 5 percent to more than 9 percent. The reservoirs range in depth from about 3,000 feet to about 10,500 feet, having a median depth of 6,400 feet.

Source rocks: The predominant source of the gas is in the underly­ing Mesaverde Group (Fouch and others, 1992; Nuccio and others, 1992; Rice and others, 1992).

112 o 111o 110o 109o 108o

41o

40o

39o

38o

Contact

core samples:

CIRCLE

CLIFFS

UPLIFT

SAN RAFA

EL

SWELL

SE

VIE

R

WA

SAT

CH

P

LAT

EA

U

BO

OK

CO

LO

RA

DO

UPLIFT

UNCOMPAHGRE

CLIFFS

CREEK

PICEANCE

BASIN

NB SC

BELT

UINTA UPLIFT BASIN

Riv

er

Gre

en

30 mi 50 km

0 0 100 km

60 mi

EXPLANATION

Fault

Thrust fault

Gas well that provided

NB, Natural Buttes field SC, Southman Canyon field

Tertiary volcanic and intrusive rocks

Tertiary sedimentary rocks

Precambrian sedimentary rocks

Precambrian metamorphic rocks

Precambrian intrusive rocks

HENRY MOUNTAINS

UTA

H

WYOMING

OR

OG

EN

IC

SAND WASH

UINTA BASIN

Figure UO-36. Generalized geologic map of the Uinta Basin Province showing location of cored wells (modified after Pitman et al., 1986)

UNITAH AND OURAY INDIAN RESERVATION UNCONVENTIONAL PLAY TYPE: Cretaceous Self-Sourced Fractured Shales Play (Hypothetical) 17 UTAH

Play 8: TIGHT GAS UINTA TERTIARY WEST PLAY Play 9: BASIN FLANK UINTA MESAVERDE PLAY (HYPOTHETICAL) (HYPOTHETICAL)

This play is the western extension of Tight Gas Uinta Tertiary East Play (Play Type 7) and is separated from Play 7 along the Green Riv­er drainage. Although the river is a surface feature, it more or less coincides with a westward decrease in drilling activity and reservoir quality. It is higher risk than Play 7 and, on this basis, it was decided by the U.S.G.S to use separate assessment parameters.

Reservoirs: This play draws on the same reservoirs as Play 7, yet porosities are somewhat lower here, ranging from less than 4 percent to about 8 percent in reservoir sandstones. The play depths range from about 4,500 feet to 11,000 feet, with a median depth of 7,500 feet.

Source rocks: The underlying Mesaverde Group is the gas source. The play limits approximately coincide with maturation levels of Ro 1.1-1.5 percent in gas-prone source beds in the basal part of the Me­saverde Group.

Timing and migration: Gas generation began in the Late Tertiary and may be continuing presently in the Mesaverde in the deeper parts of the basin; however, it is possible that vertical gas migration from the Mesaverde may not be as effective as it is in Play 7.

Traps: Traps are both stratigraphic and diagenetic.

Exploration status: There is considerably less drilling activity in this play relative to Play 7. The play is only sparsely to moderately explored by drilling.

1890

1910

1930

1950

1970

1990

A B

Cor

ed

l

Cor

ed

l

1 10 100 1 10 100

Carbonate

1280

1300

1320

1340

1360

1380

OHM-M /M2

DE

PT

H

IN

ME

TE

RS

inte

rva

inte

rva

marker

RESISTIVITY,

Tusc

her

form

atio

n

Was

atch

form

atio

n (u

pper

par

t)

This play is based on the widespread occurrence of tight, gas-saturated continental and marginal marine sandstone. The south, east, and west limits of the play are based on thermal maturation levels in the basal part of the Mesaverde Group. The reservoirs grade updip into more conventional Mesaverde reservoirs having gas-water contacts (see Up­per Cretaceous Conventional Play Type 2). Mesaverde burial depths greater than 15,000 feet designate the downdip (north) play boundary (Fouch and others, 1994).

Reservoirs: The reservoirs are fine- to medium-grained litharenites to feldspathic litharenites, becoming coarser to the west. Most reservoir permeabilities are <0.1 md. Porosities range from <4 percent to >12 percent, averaging about 8 percent (FIGURES UO-11 and UO-12) (Nuccio and others, 1992). Play depth varies from 8,000 feet to 15,000 feet, having a median of 9,500 feet.

Source rocks: Source rocks are gas-prone, thermally mature coals, carbonaceous shales, and mudstones of the Mesaverde Group (FIG­

URES UO-11 and UO-12).

Timing and migration: Gas generation began in the Tertiary and may be continuing to the present in the deeper parts of the play. The basal Mesaverde has a thermal maturity greater than Ro 1.1 percent.

Traps: Traps are both stratigraphic and diagenetic.

Exploration status: The play is essentially unexplored due to depth, economics, poor reservoir quality, and the fact that it is mostly overlain by oil- and gas-producing rocks of the Tertiary Green River Formation.

Figure UO-37. Electric log profile of cored wells (modified after Pitman et al., 1986).

UINTAH AND OURAY INDIAN RESERVATION Unconventional Play 8: Tight Gas Uinta Tertiary East and West Plays 18 UTAH

DEEP SYNCLINAL UINTA MESAVERDE PLAY (HYPOTHETICAL)

This play is based on the expected occurrence of gas-saturated, tight Mesaverde sandstones at depths greater than 15,000 feet. The limits of the play are based on depth and reservoir quality. This play bor­ders Play 9 and involves the same suite of rocks.

Reservoirs: Reservoir rocks are sandstones interbedded with mud­stones, siltstones, shales, and some coals. Porosity is generally lower than in Play 9, and although there is almost no drilling, the U.S.G.S. expects porosity to be <8 percent to about 3 percent, having a median of 5-6 percent (Table 1). Reservoir depths are >15,000 feet, as deep as 25,000 ft, and have a median of 20,000 feet (FIGURES UO-42 through

UO-44).

Source rocks: Gas-prone organic material interbedded with sandstone has generated large volumes of gas.

Timing and migration: Gas generation commenced in the Tertiary, and may be continuing at the present time. The thermal maturity of the Mesaverde is in excess of Ro 1.5 percent, and the deeper rocks exhibit >Ro 2.0 percent.

Traps: Traps are both stratigraphic and diagenetic.

Exploration status: The play is not well explored, due to the fact that primary interest in the area is in the overlying Tertiary reservoirs.

PRICE

WA

SA

TC

H

PLA

TEA

U

SAN

RA

FAEL

UPL

IFT

Price

BOOK CLIFFS

B

Utah Lake

Green River

0

0

25 50

4020 Miles

BOOK

CLIFFS

BOOK CLIFFS

Colora

do Rive

r

CO

LO

RA

DO

Grand

UNCOMPAHGRE

UPLIFT

Natural Buttes field

PICEANCE CREEK

PCreekD

ougl

as C

reek

A

rch

Gre

en

Riv

er

Island field

field

B'

A

A'

Greater Altamont-Bluebell field

WA

SATCH

MTN

S

Lak

eM

tns

Salt Lake City

field

Oil field

Gas field

Rifle Springs

WH

ITE

RIV

ER

UPLIFT

ELKMOUNTAINS

Uinta and Piceance Creek Basins

111o 110o 109o 108o

40o

39o

CANYON

Kilometers

Sunny-side Tar Sand

UINTA

BASIN

UTA

H

Junction

BASIN

arachute

Pariette Bench

Roosevelt

Duchesne

UINTA MOUNTAINS

Vernal

Greater Red Wash

Glenwood

Rangely

Approximate outline of

Green River Fm.

Green River Fm.

Alluvial and minor lake

Upper Cretaceous Nonmarine

Neslen Fm.

Marine

Sego Sandstone

Mancos Shale

Mancos Shale

Castlegate SS and

Littoral and shelf

0.50% Rm

0.75% Rm

1.10% Rm

2.0% Rm

Eocene

16 mi 0

650 ft

A

Altamont-Bluebell Bench Island

A'

1 2 3 4 5 6 7 8

Tertiary

Open Lake; Type I

Marginal Lacustrine Mixed Lake and Fluvial Type I, II, and III Colton and Wasatch Fms. Alluvial; Type III

Tertiary and U. Cretaceous North Horn Fm.

Type I, II, and III

Tuscher and Farrer Fms. Braided and meandering fluvial; Type III

Coastal Plain; Type III

Shore, nearshore

Open marine; Type II and III

Buck Tongue of

Blackhawk Fm.; Type III;

Mes

aver

de G

roup

Paleocene

Gas Well

Oil Well

Dry Hole

Oil producing zone

Gas producing zone

Pariette

Figure UO-38. Index map of the Uinta and Piceance Creek Basins area showing location of cross-sections A-A' (Figure UO-43) and B-B' (Figure UO-44) (modified after Nuccio et al., 1992).

Figure UO-40. Cross section B-B', which ex- B tends from outcrops on the southwest flank of the Uinta Basin through the Altamont-Bluebell Field. Producing intervals for some of the basin's fields are projected into the line of section. See Figure UO-42 for line of section (modified after Nuccio et al., 1992).

6000 2000

3000 1000

0 0

4 8 12 16 20 mi

5 10 15 20 km

ft m

Uinta Fm.

Colton Fm.

Wasatch F

m.

North Horn Fm. (part)

Colton Fm.

9000

6000

3000

SL

-3000

-6000

-9000

Altamont - Bluebell fields (A-B)

North Horn Fm. (part) & Mesaverde Group

B'

BW

AB

GAS

OIL & GAS

Island

Horseshoe Bend Tertiary

Cretaceous

Paleozoic-Mesozoic rock

Duchesne River Fm.

Green River Fm.

Redwash Field (RW)

Sunnyside Tar Sand

Natural Buttes Pariette Bench

Duchesne, Monument

Figure UO-39. Cross section A-A' through the Uinta Basin, Utah, showing types of kerogen found at various stratigraphic intervals, levels of thermal maturity (Rm lines), and associated hydrocarbon producing zones. See Figure UO­42 for line of section (modified after Nuccio et al., 1992).

UINTAH AND OURAY INDIAN RESERVATION UNCONVENTIONAL PLAY: Deep Synclinal Uinta Mesaverde Play (Hypothetical) 19 UTAH

REFERENCES

Anderson, R. C., 1995, ed., The Oil and Gas Opportunity on Indian Lands: Exploration Policies and Procedures, Bureau of Indian Affairs.

Anonymous, 1995, Uintah and Ouray Reservation, in Anderson, Rob­ert C., ed., The Oil and Gas Opportunity on Indian Lands: Explo­ration Policies and Procedures, 1995 Edition, Bureau of Indian Affairs, p.93-106.

Cashion, W.B., 1992, Oil-Shale resources of the Uintah and Ouray In­dian Reservation, Uinta Basin, Utah, in Fouch, T.D., Nuccio, V.F., and Chidsey, T.C., Jr., ed., Hydrocarbon and Mineral Resources of the Uinta Basin, Utah and Colorado: Utah Geological Associ­ation Guidebook 20, Salt Lake City, Utah U.S.A., Utah Geologi­cal Association.

Chidsey, Thomas C. Jr., 1993a, Uinta Basin [UN] Plays-Overview, in Hjellming, Carol A., ed., Atlas of Major Rocky Mountain Gas Reservoirs: New Mexico Bureau of Mines and Mineral Resour­ces, Socorro, New Mexico, p. 83.

Chidsey, Thomas C. Jr., 1993b, Green River Formation, in Hjellming, Carol A., ed., Atlas of Major Rocky Mountain Gas Reservoirs: New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico, p. 85-86.

Chidsey, Thomas C. Jr., 1993c, Wasatch Formation, in Hjellming, Carol A., ed., Atlas of Major Rocky Mountain Gas Reservoirs: New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico, p. 87.

Fouch, Thomas D., Nuccio, Vito F., Osmond, John C., Macmillan, Logan, Cashion, William B., and Wandrey, Craig J., 1992, Oil and gas in uppermost Cretaceous and Tertiary rock, Uinta Basin, Utah, in Fouch, T.D., Nuccio, V.F., and Chidsey, T.D. Jr.ed., Hy­drocarbon and Mineral Resources of the Uinta Basin, Utah and Colorado: U.S. Geological Association Guidebook 20, Salt Lake City, Utah U.S.A.

Fouch, T.D., Schmoker, J.W., Boone, L.E., Wandrey, C.J., Crovelli, R.A., and Butler, W.C., 1994, Nonassociated gas resources in low-permeability sandstone reservoirs, lower Tertiary Wasatch Formation, and Upper Cretaceous Mesaverde Group, Uinta Ba­sin, Utah: U.S. Geological Survey Open-File Report (in press).

Gautier, Donald L., Dolton, Gordon L., Takahashi, Kenneth I., and Varnes, Katherine L., eds., 1995 National Assessment of United States Oil and Gas resources- Results, Methodology, and Sup­porting Data: U.S. Geological Survey Digital Data Series DDS­30 1995.

Hemborg, H. Thomas, 1993, Weber Sandstone, in Hjellming, Carol A., ed., Atlas of Major Rocky Mountain Gas Reservoirs: New Mexi­

co Bureau of Mines and Mineral Resources, Socorro, New Mex­ico, p. 104.

Hill, Bradley G., and Bereskin, S. Robert, eds., 1993, Oil and Gas Fields of Utah: Utah Geological Association Publication 22, Salt Lake City, Utah, U.S.A.

Hjellming, Carol A., ed., 1993, Atlas of Major Rocky Mountain Gas Reservoirs: New Mexico Bureau of Mines and Mineral Resour­ces, Socorro, New Mexico.

Johnson, Samuel Y., Chan, Marjorie A., and Konopka, Edith A.,1992, Pennsylvanian and Early Permian Paleogeography of the Uinta-Piceance Basin Region, Northwestern Colorado and Northeast­ern Utah: U.S. Geological Survey Bulletin 1787-CC.

Moretti, George, Jr., Lipinski, Paul, Gustafson and Slaughter, Arville, 1992, Dakota Sandstone deposition and trap door structure of Hells Hole Field , eastern Uinta basin, Utah and Colorado, in Fouch, T.D., Nuccio, V.F., and Chidsey, T.C., Jr., eds., Hydrocar­bon and Mineral Resources of the Uinta Basin, Utah and Colorado: Utah Geological Association Guidebook 20, Salt Lake City, Utah U.S.A.

Morgan, Craig D., 1993a, Uinta Formation, in Hjellming, Carol A., ed., Atlas of Major Rocky Mountain Gas Reservoirs: New Mex­ico Bureau of Mines and Mineral Resources, Socorro, New Mexico, p. 84.

Morgan, Craig D., 1993b, Entrada Sandstone, in Hjellming, Carol A., ed., Atlas of Major Rocky Mountain Gas Reservoirs: New Mex­ico Bureau of Mines and Mineral Resources, Socorro, New Mexico, p. 104.

Noe, David C., 1993a, Mancos Marine Sandstones, in Hjellming, Carol A., ed., Atlas of Major Rocky Mountain Gas Reservoirs: New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico, p. 99-100.

Noe, David C., 1993b, Dakota Sandstone, Cedar Mountain Forma­tion, and Morrison Formation, in Hjellming, Carol A., ed., Atlas of Major Rocky Mountain Gas Reservoirs: New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico, p. 101­102.

Nuccio, V.F., J.W. Schmoker, and T.D. Fouch, 1992, Thermal maturi­ty, porosity, and lithofacies relationships applied to gas genera­tion and production in Cretaceous and Tertiary low permeability (tight) sandstones, Uinta Basin, Utah, in Fouch, T.D., Nuccio, V.F., and Chidsey,T.C., Jr., eds., Hydrocarbon and mineral re­sources of the Uinta Basin, Utah and Colorado: Utah Geologi­cal Association Field Symposium, 1992, Guidebook 20, p. 77­93.

Osmond, John C., 1992, Greater Natural Buttes gas field, Uintah

County, Utah, in Fouch, T.D., Nuccio, V.F., and Chidsey, T.C., Jr., eds., Hydrocarbon and Mineral Resources of the Uinta Ba­sin, Utah and Colorado: Utah Geological Association Guide­book 20, Salt Lake City, Utah U.S.A.

Pitman, J.K., Anders, D.E., Fouch, T.D., and Nichols, D.J., 1986, Hydrocarbon Potential of Nonmarine Upper Cretaceous and Lower Tertiary Rocks, Eastern Uinta Basin, Utah, in Spencer, Charles W., and Mast, Richard F., eds., Geology of Tight Gas Reservoirs, AAPG Studies in Geology #24.

Rice, D.D., Fouch, T.D., and Johnson, R.C., 1992, Influence of source rock type, thermal maturity and migration on composi­tion and distribution of natural gases, Uinta Basin, Utah, in Fouch, T.D., Nuccio, V.F., and Chidsey, T.C., Jr., eds., Hydrocar­bon and mineral resources of the Uinta Basin, Utah and Colora­do: Utah Geological Association Field Symposium, 1992, Guidebook 20, p. 95-109.

Spencer, Charles W., and Wilson, Robert J., 1988, Petroleum Geology and Principal Exploration Plays in the Uinta-Piceance-Eagle Ba­sins Province, Utah and Colorado: U.S. Geological Survey Open-File Report 88-450-G.

Tremain, Carol M., 1993, Mesaverde Group, in Hjellming, Carol A., ed., Atlas of Major Rocky Mountain Gas Reservoirs: New Mex­ico Bureau of Mines and Mineral Resources, Socorro, New Mexico, p. 97-98.

UINTAH AND OURAY INDIAN RESERVATION References 20 UTAH