An interpretive study of multi-component seismic data overa Cardium oil reservoir in the Carrot Creek field of WestCentral Alberta

Brad D. Nazar and Don. C. Lawton

INTRODUCTION

The use of multi-component seismic data is presently believed, by many, to be thenext logical step in the evolution of seismic exploration. The purpose of this study is toundertake the analysis and interpretation of a set of multi-component seismic data obtainedover the Carrot Creek oilfield of West Central Alberta. One of the unique features of thisdata set are the presence of converted shear-wave amplitude anomalies corresponding to theposition of producing sandstone and conglomerate bodies of the Cardium Formation. Theobjective of this study is to obtain an understanding of the origins of these anonlalies, andto draw conclusions about the usefulness of multi-component seismic data in identifyingCardium and other, similar clastic plays.

GEOLOGICAL SETTING

The Carrot Creek field of West Central Alberta is located within townships 51-53ranges 11-14 west of the 5th meridian, just N.W. of the giant Pembina oilfield (Figure 1).Initially discovered in 1963, it produces from several sandstone and conglomerate bodiesof the Cardium Formation, which is of Turonian age. Present estimates of reserves for thefield are placed at approximately 7 million barrels of initially recoverable oil and a further 2million barrels of oil recoverable through waterflood (Bergman and Walker, 1987).

In the subsurface the Cardium Formation extends over a large portion of WesternAlberta (Figure 1). It shows a west to east thinning from about 100m in the foothills to lessthan 30m in the plains (Bergman and Walker, 1987).

The Cardium Formation of the Carrot Creek field occurs at a depth of 1560m. It isunderlain by the dark shales of the Blackstone Formation and overlain by the shales of theWapiabi Formation (Williams and Burk, 1964). Krause and Nelson (1984) recognize twolithostratigraphic units within the Cardium Formation itself, namely the Pembina RiverMember and the Cardium Zone Member (Figure 2). Although this stratigraphy is based onlithologies recorded in the Pembina field, they are consistent with the the lithology found inthe Carrot Creek field.

The Pembina River Member corresponds to a coarsening- upward sequence ofsediments. This member is variably thick throughout the Carrot Creek field and may reacha maximum thickness of 30m. The sediment grades from silty mudstone at the base of themember through sandstone and into conglomerate (Krause and Nelson, 1984), as shown inFigure 3. These sandstone and conglomerate units act as the reservoir rocks for the field.The conglomerate is found in bodies possessing an asymmetric lensoid shape quite similarto those of modern shelf sand ridges. This conglomerate is found in thicknesses of up to20m. The orientation of these oil producing conglomerate bodies show a northwest-southeast trend (Figure 4).

iii

The top of the Pembina River Member is marked by an abrupt change fromconglomerates to the mudstones of the overlying Cardium Zone Member. The CardiumZone Member possesses a maximum thickness of 10m throughout the Carrot Creek fieldand is capped by a chert pebble and nodular siderite layer.

Generally the Cardium Formation is best known as an oil reservoir with productionfrom fine-grained sandstone, interpreted as having been deposited in a shallow marineenvironment. The transport mechanisms and depositional environments of theseconglomerate bodies are however more difficult to explain. Many geologists are stillpuzzled by the seeming contradiction of having coarse conglomerates contained whollywithin what is believed to have been offshore muds. Presently it is believed that theconglomerates in this field were deposited in a series of shelf ridges during a time of lowsea-level and transported by a combination of storm induced geostrophic currents, andwave action (Joiner, 1989).

DATA BASE

The CREWES Project has obtained five seismic lines within the Carrot Creek field(Figure 4). Two of these lines (CC-SW-01 and CC-SW-02) consist of three-componentseismic data with the remaining three lines (CR851, CR852 and CR853) consisting ofconventional vertical-component data only.

Figure 4 also shows that considerable well control is available in the Carrot Creekfield. Over 300 wells are present, of which greater than 100 have been cored. Samplesfrom well 6-12-53-13W5 have undergone analysis to obtain the elastic properties of theconglomerate and sandstone units of the Cardium Formation. These results can be seen inAppendix A.

PROPOSED WORK

Presently the processing of the vertical and radial components of lines CC-SW-01and CC-SW-02 has been undertaken using Western Geophysical's seismic processingsoftware. The results can be seen in Figures 5 and 6. The processing of the transversecomponent has yet to be undertaken, but visual inspection of the shot records show thatlittle if any coherent signal is present.

The three vertical-component lines (CR851, CR852 and CR853) also have yet to beprocessed but upon inspection of the shot records (Figure 7) significant signal can be seenand therefore the final processed sections should be of quite high quality.

Figures 5 and 6 show that amplitude anomalies can be seen along the Cardiumreflector. These correspond well to the producing pools shown in Figure 4. Although thisincrease in amplitude is visible in both the vertical and radial components, it is moreprominent on the radial section (Figure 8). During this study it is hoped that the origin ofthis anomaly can be determined and in doing so determine if other Cardium and similarclastic plays can be identified in this way. This will be accomplished through detailedlogging of cores, and seismic modelling using Sierra, Landmark and GMA modelingsoftware. Constraints on Vp/Vs over the zone of interest will be provided frompetrophysical measurements on core samples. Some initial work has shown that Vp/Vs forthe conglomerate is about 1.75 at reservoir conditions (see Appendix A).

112

14 1 13 I 12 I II I I0 t 9

55 ALBERTA

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52

%study area

500 KM IO

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Figure 1: Location map of Carrot Creek field (Bergman andWalker, 1987)

113

PLAINS FOOTHILLS

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Figure 2: Stratigraphic age and correlation chart for CarrotCreek field (Krause and Nelson, 1984)

114

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Figure 3: Lithologies of the Cardium Zone and Pembina RiverMembers (Krause etal, 1987)

115

R12W5R13W5

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-

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Figure 4: Well and seismic line locations in the Carrot Creekfield, producing conglomerate bodies outlined(Joiner, 1989)

1 km

Cardi 1.0

0

O

,.2.0

1.0

2

Cardium ,_,C_

2.0 gJ.

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b)

Figure 5: Final stack section for a) the vertical (P-P) componentdata and b) the radial (P-SV) component data of line

CC-SW-01 117

a)

lkm

................................................................................................................................................. !.......... 7"'7"'"': •0 .0

Cardium

.2.0

-- 3.0

.4.0

b)

Figure 6: Final stack section for a) the vertical (P-P) componentdata and b) the radial (P-SV) component d;m_ of line

CC-SW-02

118

1.0 Cardium

0¢D

kO

[-2.0

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Figure 7: Sample shot records for the conventional vertical (P-P)component data from line CR851

2_ mIll Ii IIIIi

0.8

1.2

a)

2_ mIlilllllll

1.4

0o 1.6_," _ Cardium

b... 1.8

2.0

b)

Figure 8: Amplitude anomalies on a) the vertical (P-P) and b) theradial (P-SV) components of line CC-SW-02

120

ACKNOWLEDGEMENTS

I would like to thank Boyd Exploration and Polyseis Research for the donation ofthe multi-component data. In addition, thank Suncor Resources for the donation of thevertical-component data.

REFERENCES

Bergman, K.M. and Walker, F.G., 1987, The importance of sea-level fluctuations in the formation of linearconglomerate bodies: Carrot Creek Member of the Cardium Formation, Cretaceous WesternInterior Seaway, Alberta, Canada: Journal of Sedimentary Petrology, 57, 651-665.

Harrison,M., 1989, Three-component seismic data processing: Carrot Creek Alberta: in this volume.Joiner, S., 1989, Sedimentology and ichnology of the Cardium Carrot Creek field, West Central Alberta,

Course work: Geology 701, University of Calgary.Krause, F.F., Collins, H.N., Nelson, D.A., Machemer, S.D. and French, P.R., 1987, Multiscale anatomy

of a reservoir: geological characterization of the Pembina-Cardium pool, West Central Alberta,Canada: The American Association of Petroleum Geologists Bulletin, 71, 1233-1260.

Krause, F.F. and Nelson, D.A., 1984, Storm event sedimentation: lithofacies formation in the CardiumFormation, Pembina area, West Central Alberta, Canada: in Stoth, D.F. and Glass, D.J. eds., The

Mesozoic of Middle North America, C.S.P.G. Memoir 9,485-511.Slatt, M.R., Robinson, J.C., Lighty, K.A. and Moore, G.F., 1987, Seismic reflection character analysis of

stratigraphic traps in Cretaceous Cardium Formation, Alberta, Canada: The American Associationof Petroleum Geologists Bulletin, 71,298-307.

Swagor, N.S., Oliver, T.A. and Johnson, B.A., 1976, Carrot Creek field, Central Alberta: in Lerand, M.M.ed., Sedimentology of selected clastic oil and gas reservoirs in Alberta: Canadian Society ofPetroleum Geologists, 4th Core Conference, pp125.

Wang, Z., 1989, Carrot Creek core analysis: Core Laboratories, Calgary.Williams, G.D. and Burk, C.F. Jr., 1964, Upper Cretaceous: in McCrosson, R.G. and Gallister, R.P. eds.,

Geological His_ry of Western Canada, A.S.P.G., Calgary, Alberta, 169-189.

APPENDIX A

Following are the results of the core analysis carded out upon the samples from thewell 6-12-53-13W5 as obtained by Wang (1989). These results include; P and S-wavevelocities, Vs/Vp ratios, shear moduli, bulk moduli and Young's moduli for variousconfining pressures under gas and oil-saturated conditions.

121

University of Calgary Oct. 21,1989Carrot Creek Sample 6-12-53-13w5

Velocity TestPorosi_=5.8% Perm. = 0.85 md Grain Densi_=2.73 _em 3

length = 10.695cmT = 60°C

gas-saturated pore pres.= 0

Confining Pressure P-Wave S-Wave P-Wave S-wave Vp/Vs Poisson's(psi) (MPa) Time Time Vel. Vel. Ratio Ratio

(m/s)1600 ll.0 33.85 63.15 4580 2605 1.758 0.2612600 17.9 32.5 60.45 4861 2789 1.743 0.255

3600 24.8 32.2 58.9 4929 2906 1.696 0.233

4600 31.7 32 58.45 4974 2942 1.691 0.231

5600 38.6 31.85 58.25 5009 2959 1.693 0.232

Shear Bulk Young'sModulus Modulus Modulus

(GPa) (GPa) (GPa)

17.5 30.7 44.0

20.0 34.1 50.2

21.7 33.5 53.6

22.3 34.0 54.8

22.5 34.5 55.5

oil-saturated pore pres.= 1425 psi (9.83 MPa)

Confining Pressure P-Wave S-Wave P-Wave S-wave Vp/Vs Poisson' s(psi) (MPa) Time Time Vel. Vel. Ratio Ratio

(m/s)3025 20.9 31.8 60.4 5021 2792 1.798 0.276

4025 27.8 31.45 59.05 5105 2894 i. 764 0. 2635025 34.7 31.25 58.65 5154 2926 i. 761 0. 262

6025 41.6 31.1 58.3 5192 2954 1.757 0.261

7025 48.4 31 58 5217 2979 1.751 0.258

Shear Bulk Young 'sModulus Modulus Modulus

(SPa) (GPa) (GPa)

20.1 38.1 51.2

21.5 38.3 54.4

22.0 39.0 55.6

22.4 39.4 56.6

22.8 39.6 57.4

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Compressional Waves, Gas-Saturated1,718- ,m

":_'&'°:_t, i

";""';"'"'"""-":""""''"-qr'-_-'ed- 11.oMea I .,,,-It-,...,.,--"-_""'-':"x ..j/r. ¢_./ ._. _,,.... tL

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--,'_,; .,,.,._.-_-,,.. ,..--'_,. l :, / ",. ,, ;. _ ,-,, . Oj"UI _ #--_11'.0 II.. Td " _.wJ _ I '. _ /

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\.,:j '-"

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2,165E-05 ,9009369 5,215E-05 _--4ii

Travel Time (sec) _}

1 °1,822 ShearWaves, Gas-Saturated

/ ,----_--._--_-----' -------__-_z--_.--- ,._/ _.,/

._ Pd = ll.OMPa y.:.\

__.-_'_..__.j _'._I/'v'_,__. / r\x.# _-z ; /,_.

Pd = 17.9 _ _,h .f,,-L O

6833

Pd= 31.7 t.,:/ , _,I ._ i _ r\ I t?

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Travel Time (sec)

Compressiona! Waves, Off-Saturated I,"_".','.",-,',,,,'_.._ ,_ II_, / '; ,._ ; t 1.0.O"#"%' '"-'-,',_.i;,,,. ,f _ / 'f 'i ) _ i"_ / i, ,.."_

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..o,_,....,, ..., I// /", I',,' ""_'--""*"*-"L _" I r_f., -, / _ -,,

"-"' ,---:-,.,_.,..,,,Ill ',;i't ..,,v ,'\,,.,,

Pd "--24.8 _ 't '1'It " t /Ak /_ I"_ i " _ /",,751 "_,,[t.,f L/ v i / l,.P'--I .,', W ',, o,

Pd : 31.7 "',,,.lJ "i t t,p,.j 't ("<,,,".-,,/ " "\/",..,.:_.:.,. .-!1i".t,.," _d" ,;\. t I

• -'" '"--_"--,,,,--,i" !1 I r _ _ _'_ ! \ ,,_

/

I // I i I-"% / ,t ^ . c r \

Pd --38.6 V ltj t/l "w_ Ij/\J"x,,j '_ _.l"\

-,5117

,. , i , i , i , _ _ii1,965F1t5 3,665E-I!5 5,365E-15 _t

2,574 ShearWaves, Oil-Saturated

Pd = ll.OMPa ;" "" ""_,:\ m0

_" _,_.,,,,,-.._._--...._..--.,_.,, ,,"\I'},_•"- ---- -.,.._ , .._- % :'-.._---.._i ,_ ,_'_ I _ , i I_. Ill

¢ Pd = 17.9 J \L,' k

= 9651 ....... - . . _ 1.

, Pd----24.8 v v • \J '_ k j'/ k i

Pd=31.-7"" ""_ v \fw ,_,,,'_I, . . .,-_:",\.I,

.-. i.:lI-, 643't _""_

Trave| Time (sec) _i__