Geologic Assessment of Undiscovered Oil and Gas

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Chapter 5 Geologic Assessment of Undiscovered Oil and Gas Resources in the Mowry Composite Total Petroleum System, Southwestern Wyoming Province, Volume Title Page Wyoming, Colorado, and Utah

By Mark A. Kirschbaum and Laura N.R. Roberts

Chapter 5 of Petroleum Systems and Geologic Assessment of Oil and Gas in the Southwestern Wyoming Province, Wyoming, Colorado, and Utah By USGS Southwestern Wyoming Province Assessment Team

U.S. Geological Survey Digital Data Series DDS–69–D

U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Gale A. Norton, Secretary U.S. Geological Survey Charles G. Groat, Director

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ISBN= 0-607-99027-9 Contents

Abstract ……………………………………………………………………………………… 1 Introduction …………………………………………………………………………………… 1 Acknowledgments …………………………………………………………………………… 2 Geologic History of Mowry Composite Total Petroleum System ……………………………… 2 Total Petroleum System ……………………………………………………………………… 2 Source Rock ………………………………………………………………………………… 2 Maturation …………………………………………………………………………………… 6 Migration Summary …………………………………………………………………………… 6 Reservoir Rocks ……………………………………………………………………………… 9 Dakota and Muddy Sandstones and Equivalents ……………………………………… 11 Frontier Formation ……………………………………………………………………… 11 Traps/Seals …………………………………………………………………………………… 12 Resource Assessment ………………………………………………………………………… 12 Mowry Conventional Oil and Gas Assessment Unit (AU 50370201) ……………………… 12 Mowry Composite Continuous Gas Assessment Unit (AU 50370261) …………………… 14 Characteristics of the Assessment Unit ...... 14 Potential Additions to Reserves in the Next 30 Years ...... 14 Assessment Results ………………………………………………………………………… 17 References …………………………………………………………………………………… 17 Appendix A. Data Form for Conventional Assessment Units ………………………………… 20 Appendix B. Input Data for the Mowry Continuous Gas Assessment Unit …………………… 22

Figures

1. Index map of the Mowry Composite Total Petroleum System (TPS) ……………………… 3 2. Diagrammatic columnar sections of the Mowry Composite Total Petroleum System …… 4 3. Map showing boundaries of two assessment units and selected gas fields ……………… 5 4. Map showing depth to top of the Frontier and thermal maturity values ………………… 7 5 A. Petroleum system events chart ………………………………………………………… 8 5 B. Timing of petroleum generation ………………………………………………………… 8 5 C. Burial-history plot ……………………………………………………………………… 9 6. Stratigraphic cross section of the Mowry Composite TPS ………………………………… 10 7. Plot showing size of grown oil accumulations (fields) versus the discovery year ………… 13 8. Plot showing size of grown gas accumulations (fields) versus the discovery year ……… 13 9. Graphic representation of producing and dry holes ……………………………………… 15 10. Graph showing truncated estimated ultimate recovery (EUR) thirds ……………………… 15 11. Graph showing truncated estimated ultimate recovery (EUR) distribution ……………… 16

III Table

1. Summary of assessment results for the Mowry Composite Total Petroleum System ……… 16

IV Geologic Assessment of Undiscovered Oil and Gas Resources in the Mowry Composite Total Petroleum System, Southwestern Wyoming Province, Wyoming, Colorado, and Utah

By Mark A. Kirschbaum and Laura N.R. Roberts

Abstract Oil and Gas AU totaled 6.6 million barrels of oil (MMBO), 0.2 trillion cubic feet of gas (TCFG), and 5.5 million barrels of natural gas liquids (MMBNGL). Mean resource estimates The Mowry Composite Total Petroleum System (TPS) for the Mowry Continuous Gas AU are 8.5 TCFG and 171 encompasses the entire Southwestern Wyoming Province, MMBNGL. Total undiscovered gas resources for the continu- which includes most of southwestern Wyoming and parts of ous and conventional AUs having potential for production over northwestern Colorado and northeastern Utah. The TPS is a the next 30 years are estimated at a mean of about 8.8 TCFG composite system because it contains petroleum generated with a range from 6.8 to 10.9 TCFG. from multiple source rocks including marine shale units of the Mowry and Thermopolis Shales and their equivalents and possibly contributions from marine shale of the Allen Hollow Shale Member of the Frontier Formation, and from coaly and Introduction lacustrine facies in continental units of the Bear River, Fron- tier, and Dakota Formations. Petroleum was generated during The purpose of this study is to assess the potential for at least two separate tectonic events leading to (1) generation undiscovered oil and gas resources in the Mowry Composite and migration of oil and gas at about 80–100 million years Total Petroleum System (TPS) in the Southwestern Wyoming ago eastward out of a foredeep basin now preserved in the Province. The TPS approach to resource assessment requires Idaho-Wyoming-Utah thrust belt, which forms the western defining an area of active source rock and all known and border of the province; and (2) Cretaceous through present- undiscovered reservoirs and also requires an understanding day generation (80 million years ago to present) of petroleum of petroleum generation, trap formation, and seals, which are from source rocks buried during Laramide basin development factors needed for oil and gas accumulations to exist (Magoon within the province. Oil and gas migrated into fluvial, tidal, and Dow, 1994). The Mowry is a composite system because deltaic, and shoreface sandstone reservoirs of the Bear River there are multiple source rocks present within about a 1,000-ft and Frontier, Cloverly, Dakota Sandstone Formations, and stratigraphic interval, and the relative contribution of petro- Muddy Sandstone Member of the Thermopolis Shale. The leum from individual sources cannot be distinguished on the hydrocarbons were trapped in structural, stratigraphic, and basis of data presently available. The name Mowry is applied basin-centered accumulations. Seals include thick, continuous to the TPS because it is by far the most important contribu- marine shale and in some cases terrestrial to estuarine mud- tor to the petroleum system (Burtner and Warner, 1984). Two stone units, diagenetic seals, and capillary pressure seals. AUs were defined during this study, one conventional and one A conventional oil and gas assessment unit and a continu- continuous. ous gas assessment unit (AU) were defined for the Mowry The petroleum system approach used in this assessment Composite TPS. The Mowry Conventional Oil and Gas AU is somewhat different from a play approach used for con- covers the entire province and includes mainly intrabasinal and ventional accumulations in previous assessments (Law and basin margin structures and stratigraphic traps and also includes others, 1989; Law, 1996), although the methodology is similar traps located stratigraphically below the basin-centered accu- in both studies. Conventional accumulations of the Mowry mulation of the Mowry Continuous Gas AU. The continuous TPS units were previously included in seven different plays gas AU underlies an area of about 11.5 million acres where (Law, 1996, Plays 3701–3707). These seven plays contained the approximate limit of gas saturation is defined by (1) areas hydrocarbons from multiple source rocks, whereas the current of overpressure, (2) bottom hole temperature greater than 200 approach combines all accumulations from Mowry composite degrees, (3) vitrinite reflectance greater than 0.8 percent, (4) source rocks together into one AU. The Mowry TPS continu- low-permeability sandstones, and (5) no reported gas/water ous assessment unit can be compared very closely with the contacts in the reservoirs. Cloverly-Frontier Play of the last assessment (Law 1996, Play Mean resource estimates for the Mowry Conventional 3740). In addition to the TPS approach, our current method- 1 2 Petroleum Systems and Geologic Assessment of Oil and Gas in the Southwestern Wyoming Province, Wyoming, Colorado, and Utah ology employs a “sweet spot” analysis to refine the in-place with a thick succession of volcaniclastic sediments to at least volumetric calculations and play-scale technologically recov- an elevation surface about 4,000 ft above present-day topogra- erable calculations used in previous assessments (Law and phy (Mears, 1993). The total basin fill (Cretaceous to Eocene) others, 1989; Law, 1996). buried the Mowry Composite TPS source rocks to a depth and thermal regime that allowed petroleum generation within the province resulting in continuous accumulations of oil and gas in the basin centers and parts of the Moxa arch and conven- Acknowledgments tional accumulations where stratigraphic pinch-outs and structural traps were present at the margins of these subbasins—for Valuable advice was provided by Ron Charpentier, Bob example, the Rock Springs uplift. Erosion and dissection of Crovelli, Troy Cook, Tim Klett, Rich Pollastro, and Chris the basins to present-day topography took place from the late Schenk. Significant geologic input to this work was made Miocene to present (Mears, 1993). available by Troy Cook, Tom Finn, Tim Klett, and Phil Nelson. Troy Cook provided estimated ultimate recoveries shown in figures 10 and 11. Discussions with Bob Basse, Wayne Camp, Ed Coalson, Ron Johnson, Ben Law, Jeff May, Total Petroleum System Ira Pasternack, Steve Roberts, John Robinson, Lee Shan- non, Keith Shanley, and Chuck Spencer greatly increased The total petroleum system (TPS) approach defines a our understanding of the petroleum system. The report was mappable pod of active source rock, all known and undiscov- improved by reviews and edits from Mary Kidd, Phil Nelson, ered reservoirs, and the processes and mechanisms required Doug Nichols, Kathy Varnes, and Ira Pasternack. Wayne Hus- for oil and gas accumulations to exist (Magoon and Dow, band and Chris Anderson are gratefully acknowledged for 1994). The Mowry Composite TPS is present within all of graphic design and GIS management, respectively. the Southwestern Wyoming Province (fig. 1) and extends westward to the approximate footwall cutoffs of strata against the Hogsback and Prospect thrusts (see cross sections by Lamerson, 1982). The Mowry Composite TPS is considered a Geologic History of Mowry Composite composite system because there are multiple source rocks that Total Petroleum System could have generated petroleum mainly from Type-II and III organic matter in marine shales of the Mowry and Thermopo- lis Shales and their equivalents, and from Type-III, with minor The Southwestern Wyoming Province is an area bounded contributions of Type-I organic matter from terrestrial facies of by major thrust faults or related structures and includes the the Bear River and Frontier Formations and Dakota Sandstone Green River, Great Divide, Hoback, Sand Wash, and Washakie (Burtner and Warner, 1984; Burtner and others, 1994) (fig. 2). Basins (fig.1). The province also contains the Rock Springs Reservoirs are sandstones in the Frontier Formation, Bear uplift and four major intrabasinal anticlines: the Cherokee River Formation, Dakota Sandstone and equivalents, and the ridge, Moxa arch, Pinedale anticline, and Wamsutter arch Muddy Sandstone Member of the Thermopolis Shale (fig. (fig. 1). Sediments of the Mowry Composite TPS were depos- 2). Traps are stratigraphic, structural, and basin centered, and ited on the western edge of the Cretaceous Western Interior seals are diagenetic, capillary, or lithologic, including marine, seaway in a foreland basin during Albian through Turonian estuarine, and terrestrial shale. There are AUs that extend over time with a fold and thrust belt to the west active between much of the Southwestern Wyoming Province: one is a basin- Jurassic and latest Paleocene time (Jordan, 1981; Wiltschko centered (continuous) accumulation (AU 261) and the other is and Dorr, 1983). Marine and terrestrial source rocks were conventional (AU 201). buried within the foredeep and overridden by the eastward- breaking thrusts between approximately 100 and 80 million years ago (Ma) (Burtner and others, 1994) at which time petroleum was generated. Oil and gas migrated through car- Source Rock rier beds, such as the Oyster Ridge Sandstone Member of the Frontier Formation, and were trapped in stratigraphic pinch- Cretaceous shales are thought to be the source of much outs or contemporaneous intrabasinal structures, such as the of the petroleum found in reservoirs of the Dakota Sandstone Moxa arch. By the Late Cretaceous and continuing into the and Frontier Formation (Warner, 1982; Burtner and Warner, Eocene, compressional tectonics created major basin-bound- 1984). Oil produced from the Dakota in the Bridger Lake ing structures of the Uinta and Wind River Mountains and field (fig. 3) has saturated hydrocarbon distributions similar lesser magnitude structures such as the Sparks Ranch thrust to oils derived from other Cretaceous source rocks in Rocky and Rawlins uplift (fig. 1). Subbasins and arches were created Mountain basins (Law and Clayton, 1987). In the Tip Top concurrently with these uplifts, which subdivide the province field on the northern Moxa arch (fig. 3), liquids produced from today. These basins were filled during Eocene to Miocene time the Frontier are thought to have a Cretaceous source based Undiscovered Oil and Gas Resources of the Mowry Composite Total Petroleum System, Southwestern Wyoming Province 3

107 111° 110° 109° 108° ° Jackson EXPLANATION 191 T 40 N Teton 287 TPS boundary Pod of active source rock

t s u

u Immature source rock r h

h t t

c y

e Outcrop of Mowry Composite TPS units b W

p r

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o d Fremont D r Producing wells from TPS units 43 Hoback ° T 35 N P R iv e r � Wells used in cross section A-A' fig. 6 Basin M o u Anticlines n P R115W R 110 W ta in Synclines r e in e d s v

i a R 105 W R le Sublette a n t n i e c e li T 30 N r n G e LaBarge 287 platform R 90 W R 110 W R 105 W R 100 W R 85 W

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G T 25 N � r � T 25 N e T 25 N � a t 191

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H a r W T 20 N � T 20 N amsu e tter T 20 N v i R Rock Springs � 80 arc n � h Carbon e

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S M in s Evanston 80 a B T 15 N T 15 N T 15 N

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R 90 W R 85 W 41° R115W R 110 W R 105 W R 100 W R 95 W Cherokee ridge Sp ark s R San th an d ru ch Daggett st W n Summit T 1 N T 10 N ash Basi T 10 N Uinta Mountains

Craig Y er am iv pa R Routt Vernal Moffat 40 T 5 N r 40 Rive

n 40 e ° e r T 1 S G Rio Blanco

miles

0 10 20

Glenwood Springs R 83 W 70 UTAH COLORADO Garfield Eagle

Figure 1. Mowry Composite Total Petroleum System (TPS) showing the pod of active source rock, producing wells, the line of cross section A–A’, and major structural elements. 4 Petroleum Systems and Geologic Assessment of Oil and Gas in the Southwestern Wyoming Province, Wyoming, Colorado, and Utah i m r s u a l u s i g t s o i u l d i u i t l i b s u t e n i n d a o l r t a r r i o i h d o t e a o c d p i t p a u w b j c h i a a n a l s m i r s e u y s s s a a r g g a q h e e a r H r t t r r s e s s i i s s a e l l e c a a a u u c c r p p r l l r o w i e o o o e c c e n n i s c r r c y y c a o t t e d o c c o t o s s g r n i h o o n n e a a a t g i h n n i o v l c g g n l p o o p n l n o o o a i i a i u o e o e e r r c c c P S P C N S D A C N N l o e u e C T C A r ) o 7 h 8 s ) 0 1 2 3 8 9 0 1 2 3 4 5 6 7 8 9 9 f s 3 1 0 0 0 0 8 8 9 9 9 9 9 9 9 9 9 9 f e ( 9 1 1 1 1 v 9 O s r r 1 u ( l e l c h a h l t c F e o i v v d e o l n d a a a e r q S a b e H O r e t o a r h S S ) r d r s b b 6 N e f b 8 M e f p g k M 9 e n M p e a a s o n 1 a o ) e e / n t t e ( c r G e s h G o r e i n i g d c a n r C e e o t c n l r n t y p t i l a l a a a a ( e u l s t d h b m a S f i a n d o S o e d b d m a h l m e y y n s F r n i o u o r r a W d ) a l w g S o i i t d o h e C S o o p s l d p r u m M S a l s y o a h F r d a E a e r M e y m r n R S r p c — e d B ) y e a o ( w c - s l h o 2 h o r r t o T i n h 6 n 3 C n e i d e . / a S l s 9 a l i h e t g 0 e c u v M t t l 1 k i t e a f w a ( e e e c i v t o + i y s e e n e a l r r h r h e t w u l 6 e e . C w e R S C . P D . r h P . l I 6 l S e c e i 9 h * e M E S S c a r e f S S l t b ) l N e f e 6 M r i ) B l s e 8 4 o u h m d 9 p c 8 n i h r k F 1 e a u 9 ) u e ( c S t m e r o e i n 1 r i r l s x F ( e n r a o e i — C a g a e t t p s l m e ( e r c h b s i l n n l v e e a g i o b o h d S o ) h e h r r r h l n o t S n S t n S a I o p F r . y s r h C o a i P r r l a e S S t G b B o S d d s p . i p x w l ) n n M r k ( o a g o a a 5 a a l o k c p t v m B e s n r 6 o r r a / s e i o e u o s t r 9 u e e d m h x M u i t r r i t C k e 1 h h n T u R t e l m a d t t ( n k a h i a i p e l r a l e e y r T a l m o l n n e h i i h D c w w i e p . d . F C t e H e e s . . P t N I I r r i n n e e a n o o S H M M C m r e S S h h m ) i t N e t S 4 4 m l A n / ) t 8 o d d F a r r r r 9 e r a h 3 F a 1 i e p n l ( S i ( l t i o ) s t n 5 3 y r / 7 / H s o r 4 2 e h e 8 r e 1 d l B B n h ) c 9 a t w B F o t r n h t 1 t o r o s ( S n a a e a d s l d s s i r n S i a l a p r M n a s e v o s ) ( i e s i x n a p a k t u e 9 r h o t k t o r q c t n e e 9 n e m i o e i o e o t r o 9 u r r e h r n k M t 1 s h d C o F e a ( e e r T t l n S i l c F s d h a r w e D t p d n h e s u r a r r n S 2 c e i o e f S a y t S M R S S ) s r s 6 a S S S S S ) n s b u h E ) 8 g u n 4 ) t n o t S M i a 9 t r c ) 8 5 t c o e t e a i 1 n l w c 0 9 i 9 r l r l ( p i a t e o e u 6 1 ( 9 e l v r . c l ( l a m n I i d 9 s 1 a b b h o f a a r u ( i s o 1 o t . S r r H m t ( b b u n C s N M h r e n s p r b d n g r n i r S h M e e o ) o o u ) l a t w a t c l S r h i 3 n F k b C o . r o t l A r l l h 8 e e N b o a i l b r t d d 9 e p l o o s p i e r H n n M s d 1 e ( g C o n ( a a e d v n H C i A g i t o n a ) i r r r o i d d i r y s k t i n e e e 6 r a l R n e o s s c R i a l h h h g i 7 i d a a r l m t t t s r u D r c l o g 9 a m i e h n e e e o n i 3 t r e o f d g a e 3 . 1 i s l o . . l o n C l 0 d Diagrammatic columnar sections of the Mowry Composite Total Petroleum System for three locations within the Southwestern Wyoming Province and ( f o y y w w w e 0 a r n w i o r e M o p e e e + . O r e o s d g + p o r r r i i B . e C 6 e w G t . W 6 . I e e ' e . . S e y 6 n 3 M C 9 9 o R R M M M M * * r m W F F Figure 2. one for the Wyoming thrust belt located west of the province. Generalized depositional environments, significantpotential fossils, significant source rocks are shown. oil and gas producing The units, columns show stratigraphic and names from outcrops. Subsurface equivalent names are shownbenches for within the Moxa arch area; the second B1–B5 Frontier. are [Abbreviations: Sh, shale; member; Mbr, Al, Albian; Ce, Cenomanian; Turonian; Tu, Co, Coniacian] Undiscovered Oil and Gas Resources of the Mowry Composite Total Petroleum System, Southwestern Wyoming Province 5

111° 110° 109° 108° 107° Jackson Teton191 T40N Assessment Unit 261 287 (Continuous) Assessment Unit 201 (Conventional) Diagonal rule shows Fremont 43° T35N overlap of AUs TPS boundary

Lincoln R Sublette R105W

n e e T30N r G

Tip Top Chimney Butte 287 R90W Birch Creek Unit Happy Springs La Figure 4 Canyon R85W Bison Basin Barge Bird Canyon Green Lost Soldier River Bend SteadCanyon T25N Fontenelle Swan T25N Lincoln Road 191 Blue Forest 42 Emigrant Nitchie Gulch ° Springs Mesa Shute Creek Storm Shelter Pine Canyon Cow Sweetwater Hollow Rawlins WhiskeyButte Seven Mile Gulch Crooked Canyon Deadman Wash T20N T20N Wilson Ranch Fabian Ditch 80 Bruff Rock Springs Carbon Green River Baxter Uinta Church Buttes Basin Evanston 80 South T15N Butcher Knife Springs 191 Henry Flaming Gorge Reservoir Lucky Ditch South Henry WY R85W 41° R110W R105W R100W R95W R90W Bridger Lake Clay Basin CO

Summit T1N Daggett T10N

Ya er mp iv a R Craig Routt Vernal Moffat 40

r 40 Rive

n 40 e ° e r Rio Blanco G

miles

0 10 20

Glenwood Springs R83W Garfield 70 UT Eagle

Figure 3. Map of the Mowry Composite TPS showing boundaries of the two assessment units and selected gas fields that produce from units of the TPS. Note that the Mowry Conventional Oil and Gas AU covers the entire TPS. The Mowry Continuous Gas AU overlaps the conventional AU. Colored lettering corresponds to respective field. 6 Petroleum Systems and Geologic Assessment of Oil and Gas in the Southwestern Wyoming Province, Wyoming, Colorado, and Utah

on pristane/phytane ratios (Edman and Cook, 1992, p. 19). cent Ro have been recorded from the Bear River Formation in Hydrocarbons have not been directly typed back to the Mowry, the northern thrust belt (Wallem and others, 1981). but the Mowry/Aspen is the Cretaceous shale with the highest The Mowry has sufficient TOC and level of maturity to content of total organic matter (Burtner and Warner, 1984) and have provided an early Late Cretaceous (100–80 Ma) pulse of is thought to be the dominant contributor of petroleum (Burt- petroleum generation prior to the development of the Hogs- ner and Warner, 1984; Law and Clayton, 1987). Other possible back and Prospect thrusts (figs. 5A and B). The Mowry was source rocks in the Mowry Composite Total Petroleum System buried in a rapidly subsiding foreland basin due to tectonic are marine shales of the Allen Hollow and Thermopolis Shales loading associated with the more westward Meade-Crawford and Bear River Formation and coals and carbonaceous shale in thrusts (Burtner and others, 1994). Presumably, coals and car- the Frontier and Bear River Formations and Dakota Sandstone. bonaceous shale in the Frontier, and perhaps the Bear River Type-II and III organic matter and minor amounts of Type-I Formation and Dakota Sandstone, also generated petroleum organic matter are present in these strata (Burtner and others, early in the development of this petroleum system. Another 1994, p. 1620). Total organic carbon (TOC) extracted from 19 period of generation may have taken place between 70 and samples of the Mowry Shale in the Green River Basin ranges 60 Ma following burial of the foredeep deposits beneath the between 1.2 and 2.5 percent, anomalously low according to Absaroka thrust (see Warner, 1982; Reisser and Blanke, 1989; Burtner and Warner (1984) who believe the anomaly is due to Burtner and others, 1994). the expulsion of carbon dioxide and hydrocarbons from the One-dimensional modeling of burial history and thermal source rock. maturity was performed for seven well locations within the In the province, the Mowry consists of laminated and province east of the Wyoming thrusts, to determine thermal bioturbated organic-rich mudrock (Byers and Larson, 1979). maturity and timing of petroleum generation (figs. 5B and High resistivity values indicated on geophysical logs measured C) (Roberts and others, Chapter 3, this CD–ROM). The start throughout the Mowry generally correspond to siliceous shales of oil generation for the Mowry Shale, a mix of Type-II and while low resistivity values (and high gamma values) can be Type-III kerogen, occurred as early as 70 Ma in the deep- related to bentonites (Nixon, 1973). The shale is siliceous est part of the province (Adobe Town location, fig. 5B). Oil due to the presence of abundant radiolarians that favored the generation started at about 46 Ma on the Moxa arch (Bruff 2 cool waters of the restricted boreal Mowry sea (Davis, 1970). location, fig. 5B), which is consistent with the work of Dutton The silica was originally provided from volcanic sources and Hamlin (1992) who thought these source rocks passed near the Idaho batholith (Davis, 1970). This high-resistivity, through the oil window at about 45 Ma at the earliest on the organic-rich siliceous shale was deposited on an anoxic sea Moxa arch. Oil generation ended at all locations by about floor (Byers and Larson, 1979; Burtner and Warner, 1984). 43 Ma except on the Moxa arch. In the deepest parts of the The anoxic condition of the Mowry sea not only preserved province at the Adobe Town, Eagles Nest, and Wagon Wheel the radiolarian tests but preserved organic matter as well. The locations (fig. 5B), the generation of gas from the cracking laminated mudrock grades upward and landward (westward) of oil began at about 56 Ma, within about 6 m.y. of the end into bioturbated mudstone and sandstone, indicating more of oil generation. Gas generation from oil cracking ended at oxic conditions, shallower water, and proximity to the clastic these deep locations by 41 Ma. Gas-prone source rocks of the source area (Burtner and Warner, 1984). Mowry (those containing predominantly Type-III kerogen), Coals and carbonaceous shales in the Frontier, Dakota, which were modeled only for those locations west of the Rock and Bear River most likely contributed gas following burial Springs uplift (fig. 5B), began generating gas at about 78 Ma. and maturation. Thicker coals in the Frontier, which are pres- Gas generation from the Mowry has reached a peak at all loca- ently restricted to the western thrust belt, attained maturity tions but has ended only at Wagon Wheel. as early as the Late Cretaceous (Valenti, 1987). Coals of the Reisser and Blanke (1989) suggest a higher convective Frontier reach a maximum reported thickness of 24 ft and heat flow on the highest parts of the Moxa arch (for example are present in as many as nine separate seams (Weaver and Church Buttes/Bruff fields, fig. 3) and further suggest that M’Gonigle, 1987). thermal alteration of the oil accounts for observed variation in gas to oil ratios. They think liquid hydrocarbons are more likely to be found in the chilled thermal margins along the Uinta Mountains or in stratigraphic traps off the east flank of Maturation the Moxa arch, for example Swan field (Reisser and Blanke, 1989, their fig. 16). The source rocks of the Mowry Composite TPS are mature over much of the province except where vitrinite reflectance values (Ro) are less than 0.6 percent at the basin margins and within the interior of the basin at the Rock Migration Summary Springs uplift (fig. 4). Mature source rocks are also present in parts of the upper plates of the western Wyoming thrusts Migration of petroleum from source rocks of the Mowry (Burtner and others, 1994), and maturities as high as 2.01 per- Composite Total Petroleum System may have been two-phase Undiscovered Oil and Gas Resources of the Mowry Composite Total Petroleum System, Southwestern Wyoming Province 7

107 111° 110° 109° 108° °

T 40 N Outcrop of Mowry Composite TPS units Vitrinite reflectance (source rocks and reservoirs) (percent Ro) >1.3 10 Depth to top of Frontier Formation (in thousands of feet) 0.8 - 1.3

43 ° T 35 N 24 TPS boundary 0.6 - 0.8 20 <0.6 R115W R 110 W 16 R 105 W 10 T 30 N 8 R 90 W R 110 W R 105 W R 100 W R 85 W 10 6 16

T 25 N T 25 N T 25 N 10 20 24 42° 16 10 6

T 20 N t T 20 N T 20 N f

p 16 u

S 10 6

R T 15 N 16 T 151N 0 T 15 N 10 6 24 WY 10 R 90 W R 85 W 41° R115W R 110 W 6 R 100 W 20 R 95 W UT 16 CO 16 16

T 1 N T 10 N T 10 N 16

6 T 5 N 6

40° T 1 S

miles

0 10 20

R 83 W

Figure 4. Extent of the Mowry Composite Total Petroleum System. Contours show depth to top of the Frontier Formation in thousands of feet using a 2,000-foot contour interval. Ranges of thermal maturity values (in percent Ro) at the top of the Frontier are indicated by colors. 8 Petroleum Systems and Geologic Assessment of Oil and Gas in the Southwestern Wyoming Province, Wyoming, Colorado, and Utah

250 200 150 100 75 70 60 50 40 30 20 10 0 Geologic MESOZOIC CENOZOIC time scale TR JURASSIC CRETACEOUS TERTIARY QUAT. (Ma) Petroleum E. M. L. E. M. L. E. L. PALEO. EOCENE OLIG. MIOCENE PP system events marine shale/minor coal Source rock eroded Overburden rock thrust Type II belt basin (see fig. 5B for details) thrust Generation Type III belt basin thrust belt basin Migration structural Moxa arch early RSU late RSU stratigraphic basin centered Trap formation Dakota/Cloverly Ss peak gas Muddy Ss Frontier Fm Reservoir rock lithologic diagenetic capillary? Seal foreland intermontane Basin type

BB Southwestern Wyoming Province boundary

 Wagon Wheel 

s Federal 31-1 g Eagles Nest n

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S  Bruff 2 p k u

o Currant Creek R  Wagon Wheel  Adobe Town WY CO UT Bear 1  Burial history Federal 31-1 locations

Mowry Shale Bruff 2 Timing of petroleum generation for Type-II source rock Timing of Timing of oil generation oil cracking to gas Currant Creek Start of oil Start of gas Peak oil Peak gas Eagles Nest End of oil End of gas Minor generation Minor generation may continue may continue Adobe Town Timing of gas generation Timing of gas generation for Type-III source rock Start of gas Peak gas Bear 1 End of gas Minor generation may continue

100 90 80 70 60 50 40 30 20 10 0 Geologic Time (Ma)

Figures 5A, B. A, Petroleum system events chart for the Mowry Continuous and Conventional Assessment Units [Abbreviations: E, Early; M, Middle; L, Late; TR, Triassic; Paleo., Paleocene; Olig., Oligocene; PP, Pliocene/Pleistocene; RSU, Rock Springs uplift; Ss, Sandstone]. B, Timing of petroleum generation for Type-II and Type-III source rocks of the Mowry Shale in the Southwest Wyoming Province (from Roberts and others, Chapter 3, this CD–ROM). [Abbreviations: P, Permian; Tr, Triassic; J, Jurassic; K, Cretaceous; Pg, Paleogene; Ng, Neogene] Undiscovered Oil and Gas Resources of the Mowry Composite Total Petroleum System, Southwestern Wyoming Province 9

C Age (Ma)

Eocene rocks

5,000

T Fort Union E E F Mesaverde N I , H T

P percent R range Hilliard

E o 10,000 D Frontier L

A 0.50 - 0.60 I Mowry R Dakota U

B 0.60 - 0.80

Triassic and 0.80 - 1.10 Jurassic rocks 15,000 1.10 - 1.35 Phosphoria Weber 1.35 - 2.00

20,000

Figure 5C. C, Burial-history plot for the Bruff 2 well on the Moxa arch showing calculated ranges of vitrinite reflectance values in percent Ro (from Roberts and others, Chapter 3, this CD–ROM). [Abbreviations: P, Permian; Tr, Triassic; J, Jurassic; K, Cretaceous; Pg, Paleogene; Ng, Neogene]

and migrated into the Frontier about 43 Ma. Burial-history or perhaps continuous and consisted of lateral, vertical, and plots conducted during this study (Roberts and others, Chapter localized migration. Early lateral migration of petroleum gen- 3, this CD–ROM) also show similar patterns of thermal history erated between 100 and 80 Ma in what is now the overthrust for the Moxa arch (fig. 5C). Burial-history plots do not show belt took place before most of the major intrabasinal structures the oil cracking to gas on the Moxa, and API gravities from all had formed in the province. The continuous Oyster Ridge fields range between 33 and 60 degrees (light oil to conden- Sandstone (2d bench of second Frontier, fig. 6) could have sate) (Cardinal and Stewart, 1979; Miller and others, 1992). acted as a carrier bed and allowed the migration of gas east- Burtner and Warner (1984) show distinct Type-III, gas-prone ward into the basin, perhaps even into stratigraphic traps east source rock in many areas of the Greater Green River Basin. of the Rock Springs uplift. Migration of oil and gas into fluvial Light oil and condensate now reservoired in the Frontier may reservoirs of the Dakota is interpreted at about 70 Ma follow- have been expelled from any Type-II kerogen present in the ing emplacement of the Absaroka thrust (Reisser and Blanke, Mowry on the Moxa arch or the thrust belt during an earlier 1989). Vertical migration took place from about 55 Ma until period of migration. present after most of the large Laramide structures, like the Rock Springs uplift were already developed. Migration of gas in sufficient volumes to displace interstitial water in areas such as the marginally mature La Barge platform is indicated from Reservoir Rocks the low water yields, variable gas/water contacts, low permeability, and overpressured reservoirs (Webel, 1979; Edman and Reservoirs in the province can be divided into two groups Cook, 1992). In-place generation, localized migration, and of rocks separated by the Mowry Shale: the lower group is trapping took place within the basin centers. almost entirely Early Cretaceous and consists of the Dakota Dutton and Hamlin (1992) showed that most of the and Muddy Sandstones and equivalents; the upper group is Mowry had not passed through the gas window on the Moxa Late Cretaceous and consists of the Frontier Formation (figs. arch and thought that gas was generated from the deep basin 2 and 6). 10 Petroleum Systems and Geologic Assessment of Oil and Gas in the Southwestern Wyoming Province, Wyoming, Colorado, and Utah . W 3 r ) 0 e y t 1 k x . R s ' a R u 2 B 0 t , 6 H . 5 A 3 o ( 5 s 0 N , c , n 6 o 4 a 9 o ? 1 m t B h D e t . ) f A t G K i T a T r l r h , a 5 t a p 5 p 2 ( - 2 M u u 6 e . l c a o h e s s S S g r e n t i x r . a B W p C 4 r S 2 e 0 - e w 1 h 4 , t k o . l 1 k n c c l i R 2 3 n 0 e c B i o i h o a c , r t 3 a i r a o r . K t a t d f l 7 e p n w e l u , N e e 7 o a x r d R s 3 d m c t 1 h / o G e i 9 e , e h S y n 3 s 1 D F , c s a u W e y . a T 6 r f n e M e T S l e w o , r t m . b ) F o s o e o a ? 4 t ( d s h M n M . 1 a t s n l y o . l n e t n l i a e c e s e h r l a a t r S r t d e a c m e o i n n s v n . s o t i o i l t c l o a n u s a t n c s s o q e t d l n r i n i e e y i y t . a F e l n a t a e t s h ? m t u d n s n W s e m l n n r n r a i o ; f a t o a e o p n 1 4 s e i c r l l n e i m i d 0 r a r a r y m e i v n t 1 o h a a m o v s a f n r s . s a d u n u l e M m i t o f e l y R l e l r . 4 e l o e t B S l s r a r , P C c n 3 a o e . o K a n t e r a . o d 3 h t n o N , s s n c s u s i i 6 t r l e f e i t 5 u f i r c d o 0 s 1 m l P o s e n n o o o f i 7 o 2 4 5 f D r a , o p h i ; c d s . o s p e T 6 e r e d D t e T l r i d k t e e n a , p . . s c a c y y w : h D o i u l l 6 o l l G o r s Y s p a l t o 3 a a t n i d l e s c c o . s o u e R d u z o o o c l l i w l d o m t r / p a e e e e o t e e e e s c h n n c n d c h a r o o a t e a t f t e e n f ; n s s i e . k n o e t e r i C r d r d l b r n a o r n o n a W a o h a a h a h m 5 C c s S s M s s 0 3 1 1 1 . 0 l t i R B i 0 , n G O K 5 . , U s 9 N 8 i e s 7 1 v 0 n e 6 a , 2 o D n t D i . 6 s T r T D d e , n r b 7 a e f m .

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O 8 7 e 2 2 G G . W 6 0 s 0 3 e 1 - c . 1 r C 0 . R u g B ) 7 d , o n . e i K 9 e s , g h N F e 7 N 6 7 s n 6 1 1 R 3 2 1 u a m r 7 i O 2 b y , I D , . R g 6 y p T r T l i T l G , e e h e 0 u n A s l K 3 n E B , . N w c B o e A t K s ; , l L n e o v P i e t e l c m X e a d s E n n ( r u e . n l o o t r o o W i a ) t h r G s 8 a l e , l n a i 0 c n p L n r s 1 o i o 1 r o n i O D G . L t s i a 3 d e R a t C B 1 n K a , d . ( . K 4 e m c , a N B y r y B 4 W l 6 t g o 2 e e 0 3 1 0 y p r r l 9 6 5 e 4 1 1 F 5 1 2 1 d e p , e e 1 D e H . r f n n S 6 v u T T 1 G a v e E e . , i i S 0 t S 1 f L 4 l l R 0 e l n 1 o R i e , 0 a r a . o . , u r r W c e 6 n N m e F e F u S s t d f n e 1 n n 5 i e o o . i e c a a t F T 7 r . t p e a , u n o W v 1 G r M T u e . 7 l t o c 0 r E 1 e e M t S . A C s n 1 5 R L u 4 , e . H G 0 s , i N r n 7 7 p a 3 5 1 r c 7 2 i , e r D . t 7 6 6 e T T 1 n 1 , E m 0 A 3 G . c e s . W 8 0 r 1 e t . n 5 1 R L u 2 R , y . H G 9 a , N n 0 6 5 6 w 1 1 a 0 5 1 a c r 9 2 i , r a D . 6 G e T F T , m 7 A 1 . c e s . ) W n 0 w o 1 r 1 9 B . - R 5 R B 4 7 m , 4 K 1 . o , l T 8 N 1 1 0 a ( 1 1 r 8 1 5 s e 6 , 2 c d D i . 6 t G e T T e F , g r 9 e . c n r )

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c o D e D , r M e N i 5 o C l h h ? l 9 m h 4 L r t 6 S s e c 0 e 2 D , a n r h . T 9 e R T G t T a , l n 2 a o r a 2 F 7 8 9 u . x t c a e o G N s M . W . c 2 n 1 9 I - 1 2 s . R 1 e 5 R B c 7 d , r K . 8 a u , 7 8 Stratigraphic cross section of the Mowry Composite TPS units from the overthrust belt, across the Moxa arch, to the Rock Springs uplift. A more detailed version 9 N t e o 8 t 4 s 6 s S ? 9 e D , G 2 t e . T 6 R s T e , G w 9 W O A ) . h ? E c t ( t e e r n s n e r o l t o e a i s t v i d n t u n N o s r q r a i f F s e Figure 6. of this cross section is shown in Kirschbaum and Roberts, Chapter 15, this CD–ROM. Line of section shown in figuresandstones Datum 1. is the in the first Frontier. significant flooding surface above Undiscovered Oil and Gas Resources of the Mowry Composite Total Petroleum System, Southwestern Wyoming Province 11

Dakota and Muddy Sandstones and Equivalents northernmost conventional accumulation in the Dakota/Muddy/ Bear River interval. Along the arch, the mode of deposition The Dakota Sandstone consists of two informal members, changes from primarily fluvial in the south to primarily shore- lower and upper (Ryer and others, 1987), in the southern part face in the north (Ryer and others, 1987). It is possible that both of the Moxa arch and interfingers, in part, with the Thermopo- types of accumulation exist here, with conventional reservoirs lis Shale to the north. The lower member of the Dakota is associated with the fluvial facies and continuous reservoirs about 100–210 ft thick on the Moxa arch, intertongues with present within the shoreface facies. the Thermopolis Shale and changes nomenclature into the lower part of the Bear River Formation to the west and into the Cloverly Formation to the northeast (fig. 2) (Ryer and others, Frontier Formation 1987). The upper member of the Dakota is as thick as 275 ft in the northern part of the Moxa arch (Ryer and others, 1987) On outcrop just west of the Province boundary, the Fron- and can be correlated with the upper part of the Bear River tier Formation consists of five members (fig. 2): in ascending Formation to the west and with the Muddy Sandstone to the order, the Chalk Creek, Coalville, Allen Hollow, Oyster Ridge, northeast (fig. 2). and Dry Hollow Members (Hale, 1960; M’Gonigle and others, Reservoirs in the Dakota and Muddy Sandstones and 1995). These members are exposed on the hanging walls of equivalent strata in the Bear River Formation consist of fluvial, imbricate thrusts in western Wyoming and northern Utah estuarine, and nearshore marine sandstones. The fluvial sys- (fig. 1). In the subsurface, the Frontier is informally divided tems were sourced from the south, fed a generally east-west into the first through fourth Frontier. The second Frontier is oriented shoreline, and prograded over much of the province further divided into benches 1–5 (fig. 2, Moxa arch column). before being transgressed by the Thermopolis Shale (Ryer and The first and second Frontier sandstones are the main reser- others, 1987). Subsequent progradation and incision during voirs (fig. 2). Total thickness of the formation on the hanging deposition of the Muddy Sandstone also extended northward, wall is over 1,000 ft, and these units thin into the province to encompassing a large part of the province before being trans- about 250 ft thick in the footwall of the Hogsback thrust. The gressed by Mowry Shale. The Muddy consists of coarsen- rapid thinning of the members is partly due to shortening of ing-upward and fining-upward successions deposited over the the section because of thrusting and subsequent erosion of Thermopolis Shale. To the west on the Moxa arch, the Muddy strata of intermediate thickness from the hanging wall and consists of silty beds but grades into coarsening-upward suc- partly due to thinning associated with decreasing accommoda- cessions of the Bear River Formation just west of the province tion space within the foreland basin. On the Moxa arch and boundary. The coarsening-upward successions are replaced Rock Springs uplift, remnants of the Chalk Creek Member are in the northeastern part of the province by fining-upward suc- interpreted on well logs (fig. 6) and in core. The Oyster Ridge cessions, which have been interpreted as valley-fill deposits is easily traced from outcrop, where the unit is dated by the (Dolson and others, 1991). presence of Collignoniceras woollgari, into the subsurface Dakota reservoirs on the south part of the Moxa arch to the western flank of the Rock Springs uplift and then back are conventional oil accumulations. Reservoirs produce from to outcrop near Flaming Gorge where the unit contains the depths as great as about 17,700 ft (IHS Energy Group, 2001). ammonite Prionocyclus hyatti. The Dry Hollow Member can The reservoirs have distinct gas or oil/water contacts and have also be interpreted in the subsurface and traced as far as the higher permeabilities than the Dakota or Bear River in the Rock Springs uplift. northern Moxa arch. Dakota/Muddy sandstone porosity has On the northeast margin of the province, the Frontier is a range of 8–23 percent and permeability of 0.06–750 mil- about 600–1,000 ft thick and is divided into three members: lidarcies (mD) (Cardinal and Stewart, 1979; Miller and others, in ascending order, the Belle Fourche, the Emigrant Gap 1992). Sandstones are dominantly sublitharenites, but minor (formerly called the unnamed member), and the Wall Creek quartz arenites, subarkoses, and litharenites are also present (Merewether, 1983; Mieras, 1993). A correlation diagram (Muller and Coalson, 1989, their fig. 5). Fields in the Moxa/ (fig. 2) shows the age control and interpretations of the physi- La Barge area produce much less water than southern Moxa cal correlation of the units within the Southwestern Wyoming arch fields. Some of these Dakota reservoirs have low perme- Province. The Belle Fourche Member approximately corre- abilities, such as at Seven Mile Gulch field (fig. 3) where the lates to the Chalk Creek Member, the Emigrant Gap Member permeability is as low as 0.06 mD and are thought to be part of to the Oyster Ridge Member, and the Dry Hollow Member, in regional accumulations (Morton, 1992a). The northernmost part, to the Wall Creek Member. Others have made this corre- reported gas/water contact is in Church Buttes field (fig. 3) lation as well (for example, Merewether and Cobban, 1986). (Curry, 1992); farther north in the Whiskey Butte and Seven The main reservoirs in the Frontier are shoreface/deltaic, Mile Gulch fields the gas column is reported to be part of a estuarine, and fluvial sandstones at depths down to about regional accumulation (Morton, 1992a and b). The fields in 19,950 ft (IHS Energy Group, 2001). Sandstones are mainly between (primarily Fabian Ditch and Bruff) show some evi- sublitharenites and litharenites with relatively minor amounts dence to support a conventional rather than continuous type of of feldspathic litharenites and lithic arkoses (Dutton and accumulation. In this study, Bruff field is considered to be the others, 1992, their fig. 33). Fluvial facies are more lithic-rich 12 Petroleum Systems and Geologic Assessment of Oil and Gas in the Southwestern Wyoming Province, Wyoming, Colorado, and Utah

(Winn and Smithwick, 1980). Within the province, sandstone the Frontier (Stands, 1999). Early clay cementation in upper porosity has a range of 2.4–28 percent and permeability has a Dakota fluvial channels sealed the reservoirs in the lower range of 0.0008–500 mD (Cardinal and Stewart, 1979; Miller Dakota during early migration of petroleum (Muller and Coal- and others, 1992). In the Moxa arch area, tidal, fluvial, and son, 1989). These diagenetic seals were sufficient to preserve shoreface sandstones have similar porosity ranging from an the integrity of the reservoirs during subsequent structural average of 9.3 to 11 percent (Winn and others, 1984; Stone- movement of the Moxa arch when the reservoirs might have cipher and Diedrich, 1993). Porosity is as much as about 17 been breached, allowing remigration of the petroleum (Reisser percent and permeability is as much as 50 mD, with most and Blanke, 1989). Diagenetic seals can also act as localized measurements less than 2 mD for tidal and fluvial sandstones permeability barriers (for example, at Tip Top field, Edman on the Moxa arch (Stonecipher and Diedrich, 1993). The flu- and Cook, 1992). Capillary pressure seals associated with the vial and tidally influenced sandstones tend to be better quality development of basin-centered accumulations usually are cre- reservoirs than shoreface sandstones because of early quartz ated at the time of peak gas generation (Law and Dickinson, cementation in the shoreface sandstones and dissolution of late 1985). calcite cements in fluvial/tidal sandstones (Winn and others, 1984). Lower shoreface sandstones have the lowest quality because of compaction and clay cementation (Dutton and others, 1992; Stonecipher and others, 1984). Frontier reser- Resource Assessment voirs produce from 123 named fields in the province, and the fields that rank highest in terms of number of producing wells The Mowry Composite Total Petroleum System consists (more than 100 wells) are Bruff, Church Buttes, Fontenelle, of two assessment units (AU): AU 50370201 is conventional Green River Bend, Lincoln Road, Tip Top, and Whiskey and covers all of the Southwestern Wyoming Province, and Buttes (IHS Energy Group, 2001). AU 50370261 is continuous and covers about 11,500,000 acres of the province (fig. 3).

Traps/Seals Mowry Conventional Oil and Gas Assessment Unit (AU 50370201) Production from conventional accumulations of the Mowry Composite TPS is from anticlines, fault-bounded clo- This assessment unit, which covers the entire area of the sures, stratigraphic traps, or combinations of the three TPS, contains conventional structural and stratigraphic traps at (Cardinal and Stewart, 1979; Miller and others, 1992). The or near normal hydrostatic reservoir pressures. The reservoirs most important structure influencing conventional accumula- generally have permeabilities greater than 1 mD and have oil/ tion is the Rock Springs uplift, which had minor expression water or gas/water contacts. during the latest Cretaceous and earliest Paleocene (Kirsch- Historically, 11 conventional oil fields and 29 conven- baum and Nelson, 1988) and major expression by latest tional gas fields have been found in the province (NRG Asso- Eocene and possibly Oligocene time. The Moxa arch also ciates, 2001) above the minimum accumulation size consid- shows evidence of recurrent movement and initially may have ered in this study of 0.5 million barrels of oil (MMBO) or 0.3 provided structures for conventional accumulations, some of billion cubic feet of gas (BCFG). Oil accumulations range in which were later modified or partially modified into continu- size from about 0.65 to 40 MMBO (fig. 7) and gas accumula- ous accumulations. Production from continuous (unconven- tions range in size from about 3 to 900 BCFG (fig. 8). No con- tional) accumulations is concentrated on the Moxa arch, pre- ventional accumulations above the minimum size cutoff have sumably associated with intense fracturing and minor faulting been discovered since the mid-1980s. on the structure (see Dutton and others, 1992; Anderson and The areas that have potential for additions to reserves Dietz, 2003) although depositional environment and diagenetic in the next 30 years are estimated to contain relatively small history are also important controls on reservoir quality (for fields located mainly in compartments having local structural example see Stonecipher and others, 1984; Stonecipher and closure or in small stratigraphic traps within the Rock Springs Diedrich, 1993). uplift, such as Deadman Wash field (fig. 3). Reservoir tar- Major seals are provided by marine shale units of the gets are fluvial sandstones in the Frontier, Dakota, or Muddy Thermopolis, Mowry/Aspen, and Hilliard Shales (figs. 2 and sandstones, shoreface sandstones in the Frontier, and possibly 5A). Locally, seals are provided by mudrock deposited in lowstand deltaic sandstones of the Frontier east of the Rock coastal- or alluvial-plain settings. Diagenetic permeability Springs uplift. Based on plots of size relative to discovery time barriers can act as seals or traps in some fields (Muller and (figs. 7 and 8), we estimate a median number of 3 undiscov- Coalson, 1989; Reisser and Blanke, 1989). Diagenetic traps ered oil accumulations and 14 undiscovered gas accumulations are described for Dakota reservoirs on the southern Moxa that have the potential to be discovered in the next 30 years arch (Reisser and Blanke, 1989), and some workers think with a median size of 1.5 MMBO and a median of 12 BCFG, these traps also control production on the Moxa arch within respectively (Appendix A). Undiscovered Oil and Gas Resources of the Mowry Composite Total Petroleum System, Southwestern Wyoming Province 13

Mowry Conventional Oil and Gas, Assessment Unit 50370201

100 E Z I S ) N L I O I

O 10 T S A L L E U R M R U A C B C N A -

O 1 L I I L O L I N M ( W O R G

0 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 ACCUMULATION-DISCOVERY YEAR

Figure 7. Plot showing size of grown oil accumulations (fields) relative to the discovery year for the Mowry Conventional Oil and Gas Assessment Unit 50370201. Data from NRG Associates (2001).

Mowry Conventional Oil and Gas, Assessment Unit 50370201

1,000 E Z I ) S S N A O I G T T

A 100 E L E U F M C I U B C U C C A - N S A O I G L 10 L N I B W ( O R G

1 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 ACCUMULATION-DISCOVERY YEAR

Figure 8. Plot showing size of grown gas accumulations (fields) relative to the discovery year for the Mowry Conventional Oil and Gas Assessment Unit 50370201. Data from NRG Associates (2001). 14 Petroleum Systems and Geologic Assessment of Oil and Gas in the Southwestern Wyoming Province, Wyoming, Colorado, and Utah

Mowry Composite Continuous Gas Assessment second third, with a median EUR of 1.3 BCF, reflects success Unit (AU 50370261) related to solving the technological and geological problems of the early third, while the late third, with a median value of This assessment unit is defined as that part of the petro- 0.5 BCF suggests that the best wells may have already been leum system where the following conditions favorable for con- drilled or that interference exists in drainage areas among tinuous gas accumulations are met in wells (Spencer, 1987): wells (Ira Pasternack, Colorado School and Mines, written 1. Overpressure exists. commun., 2004). Better technology and more subtle strategies may be needed to increase median EURs in the future. 2. The bottom hole temperature is greater than 200 degrees. Potential Additions to Reserves in the Next 3. The vitrinite reflectance is greater than 0.8 percent. 30 Years 4. Permeabilities are low. The estimated size of the assessment unit is 11,500,000 5. No gas/water contacts have been reported. acres (fig. 3). Drainage area per cell of untested cells with potential for additions to reserves is estimated to be distrib- These conditions are generally reached at depths of 8,000 uted within a range of 40 and 300 acres, with a median of 120 to 12,000 ft in the province because of the interrelationship of acres, and is based on current and anticipated well- heat flow, source rock maturity, and overpressuring due to gas spacing information for the assessment unit area. The area of generation in low-permeability rocks (see Law, 1984, his figs. the assessment unit that is already tested can be calculated by 10, 12; Spencer, 1987, his fig. 5). The 10,000-ft depth contour applying the median cell size of 120 acres to 3,193 tested cells at the top of the petroleum system approximates where the drilled in the unit and equals about 4 percent. The untested favorable conditions overlap for the Mowry Composite Total area, about 96 percent of the 11.5 million acres, interpreted to Petroleum System. The AU boundary is drawn to follow this have potential is based on the concept that these low perme- contour except along where the AU boundary is defined by the ability sandstones require enhanced natural fracturing or better footwall cutoff of the Hogsback-Prospect thrust, essentially than normal porosity in order to have completions above the the same boundary as the province and the TPS. The assess- minimum EUR. ment unit includes a transition zone where reservoirs can A median value of about 9 percent of the untested assess- be either gas charged or water saturated. Input data for this ment unit area is thought to have potential for additions to assessment unit are provided in Appendix B. reserves in the next 30 years (Appendix B). The EUR distribution used for the untested area is based on historical values but is truncated to exclude wells below the 0.02 BCF minimum Characteristics of the Assessment Unit (fig. 11). The median estimated EUR of 0.7 BCF is based on the actual median value shown on the truncated EUR distribu- Exploration of the province began in the early 1900’s tion (fig. 11), and the maximum EUR is estimated at 15 BCF (IHS Energy Group, 2001); since then, 3,193 wells are inter- based on the best historical well shown in the late third split preted to have tested the Mowry Composite TPS units for (fig. 10). petroleum. Of these wells, 2,527 are listed as producers and Potential for adding to reserves in the next 30 years could 666 are interpreted to be dry holes for the TPS (fig. 9). Esti- come from: mated ultimate recoveries (EUR) were calculated for about 1. Infill drilling around existing production; 550 of these producing wells completed between 1954 and 2. Recompletions in the Frontier from producing holes in 2000, and about 4 percent of these wells were determined to the Dakota or Morrison Formation; be below our minimum EUR of 0.02 BCFG. The 4 percent is extrapolated to all producing wells to give a value of 101 pro- 3. Hypothetical accumulations in the Frontier, including: ducing wells below the minimum EUR (fig. 9). Production data used in this study included about 550 (a) Fractured areas around the flanks of the Rock wells completed between 1954 and 2000 (fig. 10). An EUR Springs Uplift, distribution, truncated to include only wells producing above (b) Top-truncated lowstand deltas in the Frontier east of our minimum (0.02 BCF), was used to help predict the poten- the Rock Springs uplift, and tial recoveries for future addition to reserves (figs. 10 and 11). For details of the methods used to calculate EURs see Cook (c) Possibly deeper targets in relatively thick reservoir (Chapter 23, this CD–ROM). The early third of the data had a units in the Frontier in the northeastern Great median EUR of 0.5 BCF, the median being 50 percent of that Divide Basin. sample. This EUR probably reflects limiting factors related to the technology of the day and the early geologic concepts Infill drilling is expected to have a better success ratio that existed in the beginning stages of development. The than the historical ratio of 76 percent (fig. 9), stepout drilling Undiscovered Oil and Gas Resources of the Mowry Composite Total Petroleum System, Southwestern Wyoming Province 15

Tested cells AU50370261 Success ratio = 76% (2,426/3,193)

2,426 wells 101 wells 71 wells 294 wells 301 wells

Produce 666 wells above the Produces Produces, but TD in the TPS TD below the TPS, but TD from the below minimum (dry) TPS in, or below, TPS EUR (dry) reservoirs the TPS

Younger rocks

Mowry Composite TPS units

Morrison

Older rocks

Producers Counted as dry holes

Figure 9. Graphic representation of producing and dry holes as determined for the Mowry Continuous Gas Assessment Unit 50370261. Producing wells plus dry holes equal tested cells (see Appendix B). Colors show general depositional environments (see fig. 2). Red dots denote perforated zone. Note: there are 101 wells that produced below our minimum cutoff (0.02 billion cubic feet of gas) and were not included in our final count of producers. [Abbreviations: EUR, estimated ultimate recovery; TPS, Total Petroleum System; TD, total depth] EURs by Thirds 100,000 Early average 1954–1985 Middle average 1986–1993 N = 550 Late average 1994–2000 10,000

1,000 F C M M

100

1 0 10 20 30 40 50 60 70 80 90 100 PERCENTAGE OF SAMPLE

Figure 10. Truncated estimated ultimate recovery (EUR) thirds for wells producing from the Mowry Continuous Gas Assessment Unit. The curves are truncated to remove wells less than our minimum cutoff (< 0.02 billion cubic feet of gas). EURs were calculated from a sampling of 550 wells from IHS Energy Group (2001) completed between 1954 and 2000. Data provided by Troy Cook, U.S. Geological Survey. “Thirds” refers to the division into three parts, over time, of the wells drilled in a given area. In this usage, the wells are divided by time according to their completion date. [Abbreviations: MMCF, million cubic feet.] 16 Petroleum Systems and Geologic Assessment of Oil and Gas in the Southwestern Wyoming Province, Wyoming, Colorado, and Utah

Well EUR Distributions

100,000

N = 550 10,000 Average value

1,000 ) F C M M ( R

U 100 E

1 0 10 20 30 40 50 60 70 80 90 100

PERCENTAGE OF SAMPLE

Figure 11. Truncated estimated ultimate recovery (EUR) distribution for wells in the Mowry Continuous Gas Assessment Unit completed between 1954 and 2000.

Table 1. Summary of assessment results for the Mowry Composite Total Petroleum System. [MMBO, million barrels of oil. BCFG, billion cubic feet of gas. MMBNGL, million barrels of natural gas liquids. Results shown are fully risked estimates. For gas fields, all liquids are included under the NGL (natural gas liquids) category. F95 denotes a 95-percent chance of at least the amount tabulated. Other fractiles are defined similarly. Fractiles are additive under the assumption of perfect positive correlation. Shading indicates not applicable]

Total undiscovered resources Total Petroleum Systems Field (TPS) Type Oil (MMBO) Gas (BCFG) NGL (MMBNGL) and Assessment Units (AU) F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean Mowry Composite TPS Mowry Conventional Oil Oil 1.70 5.70 14.80 6.60 2.70 9.40 25.90 11.20 0.30 1.30 3.70 1.60 and Gas AU Gas 85.80 196.30 301.40 195.10 1.60 3.80 6.70 3.90 Total conventional 1.70 5.70 14.80 6.60 88.50 205.70 327.30 206.30 1.90 5.10 10.40 5.50 resources

Oil 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mowry Continuous Gas AU Gas 6,745.90 8,461.90 10,614.40 8,542.80 110.90 165.80 247.90 170.90 Total continuous 0.00 0.00 0.00 0.00 6,745.90 8,461.90 10,614.40 8,542.80 110.90 165.80 247.90 170.90 resources Undiscovered Oil and Gas Resources of the Mowry Composite Total Petroleum System, Southwestern Wyoming Province 17 is expected to have a similar success ratio (76 percent), and in Davis. J.C., 1970, Petrology of Cretaceous Mowry Shale of undrilled areas, the ratio is expected to be less than the histori- Wyoming: American Association of Petroleum Geologists cal success ratio. Bulletin, v. 54, p. 487–502. Dolson, John, Muller, Dave, Evetts, M.J., and Stein, J.A., 1991, Regional paleotopographic trends and production, Assessment Results Muddy Sandstone (Lower Cretaceous), central and northern Rocky Mountains: American Association of Petroleum Geologists Bulletin v. 75, p. 409–435. The Mowry Conventional Oil and Gas Assessment Unit is estimated to contain a mean of 6.60 million barrels of oil, Dutton, S.P., and Hamlin, H.S., 1992, Interaction of burial 11.20 billion cubic feet of associated gas, and 1.60 million history and diagenesis of the Upper Cretaceous Frontier barrels of associated natural gas liquids (table 1). Gas ﬁelds Formation, Moxa arch, Green River Basin, Wyoming, in within the assessment unit are estimated at the mean to be Mullen, C.E., ed., Rediscover the Rockies: Wyoming Geo- 195.10 billion cubic feet of gas and 3.90 million barrels of logical Association Guidebook, Forty-Third Field Confer- natural gas liquids (table 1). ence, p. 37–50. The Mowry Continuous Gas Assessment Unit has a mean estimate of 8,542.80 billion cubic feet of gas and 170.9 million Dutton, S.P., Hamlin, H.S., and Laubach, S.E., 1992, Geologic barrels of natural gas liquids (table 1). controls on reservoir properties of low-permeability sandstone, Frontier Formation, Moxa arch, southwest Wyoming: Gas Research Institute, GRI–92/012, 199 p. References Edman, J.D., and Cook, Lance, 1992, Tip Top field—U.S.A. Wyoming-Utah-Idaho overthrust belt, Wyoming, in Beau- mont, E.A., and Foster, N.H., compilers, Structural traps Anderson, Greg, and Dietz, Carl, 2003, Depositional, diage- VII: American Association of Petroleum Geologists Spe- netic, and structural controls on natural gas production from cial Publication, p. 1–27. the Frontier Formation Moxa arch, Wyoming: Outcrop, Newsletter of the Rocky Mountain Association of Geolo- Eicher, D.L., 1962, Biostratigraphy of the Thermopolis, gists Abstract, v. 52, no. 10, p. 4. Muddy, and Shell Creek Formations, in Enyert, R.L., and Curry, W.H., eds., Symposium on Early Cretaceous rocks of Burtner, R.L., Nigrini, A., and Donelick, R.A., 1994, Thermo- Wyoming and adjacent areas: Wyoming Geological Asso- chronology of Lower Cretaceous source rocks in the Idaho- ciation Seventeenth Annual Field Conference Guidebook, Wyoming thrust belt: American Association of Petroleum p. 72–93. Geologists Bulletin, v. 78, p. 1613–1636. Hale, L.A., 1960, Frontier Formation—Coalville, Utah and Burtner, R.L., and Warner, M.A., 1984, Hydrocarbon genera- nearby areas of Wyoming and Colorado, in Overthrust Belt tion in Lower Cretaceous Mowry and Skull Creek Shales of southwest Wyoming: Wyoming Geological Association of the Northern Rocky Mountain area, in Woodward, Jane, Fifteenth Annual Field Conference Guidebook, p. 137–146. Meissner, F.F., and Clayton, J.L., eds., Hydrocarbon source rocks of the Greater Rocky Mountain Region: Rocky Moun- Hansen, W.R., 1965, Geology of the Flaming Gorge area, tain Association of Geologists, p. 449–467. Utah-Colorado-Wyoming: U.S. Geological Survey Profes- sional Paper 490, 196 p. Byers, C.W., and Larson, D.W., 1979, Paleoenvironments of Mowry Shale (Lower Cretaceous), western and central Haq, B.U., Hardenbol, J., and Vail, P.R., 1987, Chronology of Wyoming: American Association of Petroleum Geologists fluctuating sea levels since the Triassic: Science, v. 235, Bulletin, v. 63, p. 354–375. p. 1156–1167. Cardinal, D.F., and Stewart, W.W., 1979, Wyoming Oil and IHS Energy Group, 2001, [includes data current as of Decem- Gas Fields Symposium, Greater Green River Basin: Wyo- ber, 2000] PI/Dwights Plus U.S. Production and Well Data: ming Geological Association, 428 p. Englewood, Colo., database available from IHS Energy Group, 15 Inverness Way East, D205, Englewood, CO Curry, W.H. III, 1992, Church Buttes, in Miller, T.S., Crockett, 80112, U.S.A. F.J., and Hollis, S.H., eds., Wyoming Oil and Gas Fields Symposium, Greater Green River Basin and Overthrust Jordan, T.E., 1981, Thrust loads and foreland basin evolution, Belt: Wyoming Geological Association Symposium Cretaceous, western United States: American Association of p. 100–102. Petroleum Geologists Bulletin, v. 65, p. 2506–2520. 18 Petroleum Systems and Geologic Assessment of Oil and Gas in the Southwestern Wyoming Province, Wyoming, Colorado, and Utah

Kirschbaum, M.A., and Nelson, S.N., 1988, Geologic history Merewether, E.A., 1983, The Frontier Formation and mid-Cre- and palynologic dating of Paleocene deposits, western Rock taceous orogeny in the foreland of southwestern Wyoming: Springs uplift, Sweetwater County, Wyoming: Contributions The Mountain Geologist, v. 20, p. 121–138. to Geology, Laramie, University of Wyoming, v. 26, no. 1, p. 21–28. Merewether, E.A., Blackmon, P.D., and Webb, J.C., 1984, The Mid-Cretaceous Frontier Formation near the Moxa arch, Lamerson, P.R., 1982, The Fossil Basin and its relationship to southwestern Wyoming: U.S. Geological Survey Profes- the Absaroka thrust system, Wyoming and Utah, in Powers, sional Paper 1290, 29 p. R.B., ed., Geologic studies of the Cordilleran Thrust Belt: Rocky Mountain Association of Geologists, v. 1, Merewether, E.A., and Cobban, 1986, Biostratigraphic units p. 279–340. and tectonism in the Mid-Cretaceous foreland of Wyo- ming, Colorado, and adjoining areas, in Peterson, J.A., ed., Law, B.E., 1984, Relationship of source-rock, thermal matu- Paleotectonics and sedimentations in the Rocky Mountain rity, and overpressuring to gas generation and occurrence in Region, United States: American Association of Petroleum low-permeability Upper Cretaceous and lower Tertiary rock, Geologists Bulletin, v. 41, p. 443–468. Greater Green River basin, Wyoming, Colorado, and Utah, in Woodward, Jane, Meissner, F.F., and Clayton, J.L., eds., M’Gonigle, J.W., Dalrymple, G.B., Holmes, C.W., 1995, 40 39 Hydrocarbon source rocks of the Greater Rocky Mountain Single-crystal Ar/ Ar ages for rocks in the lower part Region: Rocky Mountain Association of Geologists, of the Frontier Formation (Upper Cretaceous), southwest p. 469–490. Wyoming: The Mountain Geologist v. 32, p. 47–53. Law, B.E., 1996, Southwestern Wyoming Province (037), in Mieras, B.D., 1993, Sequence stratigraphy and depositional Gautier, D.L., Dolton, G.L., Takashashi, K.I., and Varnes, controls, mid-Cretaceous Frontier Formation, south-central K.L., eds., 1995 National assessment of United States oil Wyoming: Boulder, University of Colorado Ph.D. disserta- and gas resources—Results, methodology, and supporting tion, 397 p. data: U.S. Geological Survey Digital Data Series DDS–30, Miller, T.S., Crockett, F.J., and Hollis, S.H., 1992, Wyoming release 2, 67 p. oil and gas fields symposium, Greater Green River Basin Law, B.E., and Clayton, J.L., 1987, A burial, thermal, and and Overthrust Belt: Wyoming Geological Association hydrocarbon source rock evaluation of Lower Cretaceous Symposium, 372 p. rocks in the southern Moxa arch area, Utah and Wyoming, Morton, 1992a, Seven Mile Gulch, in Miller, T.S., Crockett, in Miller, W.R., ed., The Thrust Belt revisited: Wyoming F.J., and Hollis, S.H., eds., Wyoming Oil and Gas Fields Geological Association Thirty-Eighth Field Conference Symposium, Greater Green River Basin and Overthrust Belt Guidebook, Abstract, p. 357. Wyoming: Geological Association, p. 275–277. Law, B.E., and Dickinson, W.W., 1985, Conceptual model for Morton, 1992b, Whiskey Butte, in Miller, T.S., Crockett, F.J., origin of abnormally pressured gas accumulations in low- and Hollis, S.H., eds., Wyoming Oil and Gas Fields Sym- permeability reservoirs: American Association of Petroleum posium, Greater Green River Basin and Overthrust Belt: Geologists v. 69, p. 1295–1304. Wyoming Geological Association, p. 342–344.

Law, B.E., Spencer, C.W., Charpentier, R.R., Crovelli, R.A., Muller, M.M., and Coalson, E.B., 1989, Diagenetic and petro- Mast, R.F., Dolton, G.L., and Wandrey, C.J., 1989, Esti- physical variations of the Dakota Sandstone, Henry Field, mates of gas resources in overpressured low-permeability Green River Basin, Wyoming, in Coalson, E.B., Kaplan, Cretaceous and Tertiary sandstone reservoirs, Greater Green S.S., Keighin, C.W., Oglesby, C.A., and Robinson, J.W., River Basin, Wyoming, Colorado, and Utah, in Eisert, J.L., eds., Petrogenesis and petrophysics of selected sandstone ed., Gas resources of Wyoming: Wyoming Geological reservoirs of the Rocky Mountain Region: Rocky Mountain Association Fortieth Field Conference Guidebook, Association of Geologists, p. 149–158. p. 39–61. Nixon, R.P., 1973, Oil source beds in Cretaceous Mowry Shale Magoon, L.B., and Dow, W.G., 1994, The petroleum sys- of northwestern interior United States: American Associa- tem, in Magoon, L.B., and Dow, W.G., ed., The Petroleum tion of Petroleum Geologists Bulletin, v. 57, p.136–161. System—From source to trap: American Association of Petroleum Geologists Memoir 60, p. 3–24. NRG Associates, 2001, [includes data current as of 1999], The significant oil and gas fields of the United States: Colorado Mears, Brainerd, Jr., 1993, Geomorphic history of Wyoming Springs, Colorado, NRG Associates, Inc.; database avail- and high-level erosion surfaces, in Snoke, A.W., Steidt- able from NRG Associates, Inc.; P.O. Box 1655, Colorado mann, J.R., and Roberts, S.M., eds., Geology of Wyoming: Springs, CO 80901, U.S.A. Geological Survey of Wyoming Memoir no. 5, p. 608–626. Undiscovered Oil and Gas Resources of the Mowry Composite Total Petroleum System, Southwestern Wyoming Province 19

Obradovich, J.D., 1993, A Cretaceous time scale, in Caldwell, Valenti, G.L., 1987, Review of the hydrocarbon potential of W.G.E., and Kauffman, E.G., Evolution of the Western Inte- the Crawford Thrust Plate Wyoming-Idaho-Utah Thrust rior Basin: Geological Association of Canada Special Paper Belt, in Miller, W.R., ed., The Thrust Belt revisited: Wyo- 39, p. 379–396. ming Geological Association Thirty-Eighth Field Confer- ence Guidebook, v. 38, p. 257–266. Reeside, J.B., Jr., and Cobban, W.A., 1960, Studies of the Mowry Shale (Cretaceous) and contemporary formations Wallem, D.B., Surdam, R.C., and Steidtmann, J.R., 1981, in the United States and Canada: U.S. Geological Survey Source rock analysis of the lower Cretaceous Bear River Professional Paper 355, 126 p. Formation, western Wyoming overthrust belt, in Reid, S.G., and Miller, D.D., eds., Energy resources of Wyoming: Reisser, K.D., and Blanke, S.J., 1989, Paleostructural control Wyoming Geological Association Thirty-Second Annual of Dakota hydrocarbon accumulations on the southern Field Conference Guidebook, p. 41–64. Moxa arch, southwest Wyoming and northeast Utah, in Coalson, E.B., Kaplan, S.S, Keighin, C.W., Oglesby, C.A., Warner, M.A., 1982, Source and time of generation of hydro- and Robinson, J.W., eds., Petrogenesis and petrophysics carbons in the fossil basin, western Wyoming thrust belt, of selected sandstone reservoirs of the Rocky Mountain in Powers, R.B., ed., Geologic studies of the Cordilleran Region: Rocky Mountain Association of Geologists, Thrust Belt: Rocky Mountain Association of Geologists, p. 135–148. p. 805–815. Ryer, T.A., 1976, Cretaceous stratigraphy of the Coalville and Weaver, J.N., and M’Gonigle, J.W., 1987, Location of coal and Rockport areas, Utah: Utah Geology, v. 3, p. 71–83. carbonaceous shale beds exposed in the eastern part of the Kemmerer 15-minute quadrangle, Lincoln County, Wyo- Ryer, T.A., McClurg, J.J., and Muller, M.M., 1987, Dakota– ming: U.S. Geological Survey Coal Investigations Series Bear River paleoenvironments, depositional history and Map I–110, 1 plate. shoreline trends— Implications for foreland basin paleotectonics, southwestern Green River Basin and southern Webel, Suzanne,1979, Tip Top in Cardinal, D.F., and Stew- Wyoming overthrust belt, in Miller, W.R., ed., The Thrust art, W.W., eds., Wyoming Oil and Gas Fields Symposium, Belt revisited: Wyoming Geological Association Annual Greater Green River Basin: Wyoming Geological Associa- Field Conference Guidebook, v. 38, p. 179–206. tion, p. 388–389. Spencer, C.W., 1987, Hydrocarbon generation as a mechanism Wiltschko, D.V., and Dorr, Jr., J.A., 1983, Timing of deforma- for overpressuring in Rocky Mountain region: American tion in overthrust belt and foreland of Idaho, Wyoming, and Association of Petroleum Geologists Bulletin, v. 71, no. 4, Utah: American Association of Petroleum Geologists Bul- p. 368–388. letin, v. 67, p. 1304–1322. Stands, R.E., 1999, Depositional sequence analysis of the Winn, R.D., Jr., and Smithwick, M.E., 1980, Lower Frontier Upper Cretaceous Frontier Formation, Darby thrust—Moxa Formation, southwestern Wyoming—Depositional controls arch area, southwestern Wyoming: Golden, Colorado on sandstone compositions and on diagenesis, in Stratigra- School of Mines, Ph.D. dissertation, 619 p. phy of Wyoming: Wyoming Geological Association 31st Annual Field Conference Guidebook, p. 137–153. Stonecipher, S.A., and Diedrich, R.P., 1993, Petrographic differentiation of fluvial and tidally influenced estua- Winn, R.D., Jr., Stonecipher, S.A., and Bishop, M.G., 1984, rine channels in second Frontier sandstones, Moxa arch Sorting and wave abrasion—Controls on composition and area, Wyoming, in Strock, Betty, and Andrew, Sam, eds., diagenesis in lower Frontier sandstones, southwestern Wyoming geology— Past, present and future: Wyoming Wyoming: American Association of Petroleum Geologists Geological Association Jubilee Anniversary Field Confer- Bulletin, v. 68, p. 268–284. ence Guidebook, p. 181–200. Stonecipher, S.A., Winn, R.D., Jr., and Bishop, M.G., 1984, Diagenesis of the Frontier Formation, Moxa arch—A function of sandstone geometry, texture and composition, and fluid flux, in McDonald, D.A., and Surdam, R.C., eds., Clastic diagenesis: American Association of Petroleum Geologists Memoir 37, p. 289–316. 20 Petroleum Systems and Geologic Assessment of Oil and Gas in the Southwestern Wyoming Province, Wyoming, Colorado, and Utah

Appendix A. Input data for the Mowry Conventional Oil and Gas Assessment Unit (AU 50370201). Seventh Approximation Data Form for Conventional Assessment Units (NOGA, version 5, 06-30-01). Complete form including allocations is shown in Klett and Le (Chapter 28, this CD–ROM). SEVENTH APPROXIMATION DATA FORM FOR CONVENTIONAL ASSESSMENT UNITS (NOGA, Version 5, 6-30-01)

IDENTIFICATION INFORMATION Assessment Geologist:…….. M.A. Kirschbaum Date: 8/21/2002 Region:……………………….. North America Number: 5 Province:……………………… Southwestern Wyoming Number: 5037 Total Petroleum System:…… Mowry Composite Number: 503702 Assessment Unit:…………… Mowry Conventional Oil and Gas Number: 50370201 Based on Data as of:………. NRG 2001 (data current through 1999), IHS Energy Group 2001, WGA Guidebooks Notes from Assessor………. NRG Reservoir Lower 48 growth function

CHARACTERISTICS OF ASSESSMENT UNIT

Oil (<20,000 cfg/bo overall) or Gas (>20,000 cfg/bo overall):… Gas

What is the minimum accumulation size?………. 0.5 mmboe grown (the smallest accumulation that has potential to be added to reserves in the next 30 years)

No. of discovered accumulations exceeding minimum size:………… Oil: 11 Gas: 29 Established (>13 accums.) X Frontier (1-13 accums.) Hypothetical (no accums.)

Median size (grown) of discovered oil accumulation (mmbo): 1st 3rd 8 2nd 3rd 0.85 3rd 3rd Median size (grown) of discovered gas accumulations (bcfg): 1st 3rd 37.2 2nd 3rd 9.5 3rd 3rd 30.6

Assessment-Unit Probabilities: Attribute Probability of occurrence (0-1.0) 1. CHARGE: Adequate petroleum charge for an undiscovered accum. > minimum size……………… 1.0 2. ROCKS: Adequate reservoirs, traps, and seals for an undiscovered accum. > minimum size…… 1.0 3. TIMING OF GEOLOGIC EVENTS: Favorable timing for an undiscovered accum. > minimum size 1.0

Assessment-Unit GEOLOGIC Probability (Product of 1, 2, and 3):……...…….....…. 1.0

4. ACCESSIBILITY: Adequate location to allow exploration for an undiscovered accumulation > minimum size……………………………………………………..………………..……..………… 1.0

UNDISCOVERED ACCUMULATIONS No. of Undiscovered Accumulations: How many undiscovered accums. exist that are > min. size?: (uncertainty of fixed but unknown values)

Oil Accumulations:…………………min. no. (>0) 1 median no. 3 max no. 7 Gas Accumulations:……………….min. no. (>0) 3 median no. 14 max no. 22

Sizes of Undiscovered Accumulations: What are the sizes (grown) of the above accums?: (variations in the sizes of undiscovered accumulations)

Oil in Oil Accumulations (mmbo):…...…min. size 0.5 median size 1.5 max. size 20 Gas in Gas Accumulations (bcfg):…..…min. size 3 median size 12 max. size 80 Undiscovered Oil and Gas Resources of the Mowry Composite Total Petroleum System, Southwestern Wyoming Province 21

Appendix A. Input data for the Mowry Conventional Oil and Gas Assessment Unit (AU 50370201). Seventh Approximation Data Form for Conventional Assessment Units (NOGA, version 5, 06-30-01). Complete form including allocations is shown in Klett and Le (Chapter 28, this CD–ROM).—Continued Assessment Unit (name, no.) Mowry Conventional Oil and Gas, Assessment Unit 50370201

AVERAGE RATIOS FOR UNDISCOVERED ACCUMS., TO ASSESS COPRODUCTS (uncertainty of fixed but unknown values) Oil Accumulations: minimum median maximum Gas/oil ratio (cfg/bo)………………………...……… 842 1,684 2,526 NGL/gas ratio (bngl/mmcfg)…………………....…. 70 140 210

Gas Accumulations: minimum median maximum Liquids/gas ratio (bliq/mmcfg)….…………..…….. 10 20 30 Oil/gas ratio (bo/mmcfg)………………………….…

SELECTED ANCILLARY DATA FOR UNDISCOVERED ACCUMULATIONS (variations in the properties of undiscovered accumulations) Oil Accumulations: minimum median maximum API gravity (degrees)…………………….…………. 17.5 38 47 Sulfur content of oil (%)………………………...….. 0.1 0.2 0.5 Drilling Depth (m) ……………...…………….…….. 3,650 4,250 4,875 Depth (m) of water (if applicable)……………...…..

Gas Accumulations: minimum median maximum Inert gas content (%)……………………….....…… 0.1 1 20 CO2 content (%)……………………………….....… 0.2 0.6 3.2 Hydrogen-sulfide content (%)………………...……. 0 0 0 Drilling Depth (m)…………………………………… 650 2,500 5,800 Depth (m) of water (if applicable)…………………. 22 Petroleum Systems and Geologic Assessment of Oil and Gas in the Southwestern Wyoming Province, Wyoming, Colorado, and Utah

Appendix B. Input data for the Mowry Continuous Gas Assessment Unit (AU 50370261). FORSPAN assessment model for continuous accumulations- Basic Input data form (Version 4, 10-05-00). Complete form including allocations is shown in Klett and Le (Chapter 28, this CD–ROM).

FORSPAN ASSESSMENT MODEL FOR CONTINUOUS ACCUMULATIONS--BASIC INPUT DATA FORM (NOGA, Version 7, 6-30-00)

IDENTIFICATION INFORMATION Assessment Geologist:… M.A. Kirschbaum Date: 8/20/2002 Region:…………………… North America Number: 5 Province:…………………. Southwestern Wyoming Number: 5037 Total Petroleum System:. Mowry Composite Number: 503702 Assessment Unit:………. Mowry Continuous Gas Number: 50370261 Based on Data as of:…… IHS Energy Group 2001 (data current through 2000) Notes from Assessor…..

CHARACTERISTICS OF ASSESSMENT UNIT

Assessment-Unit type: Oil (<20,000 cfg/bo) or Gas (>20,000 cfg/bo) Gas What is the minimum total recovery per cell?… 0.02 (mmbo for oil A.U.; bcfg for gas A.U.) Number of tested cells:.………… 3193 Number of tested cells with total recovery per cell > minimum: ……... 2426 Established (>24 cells > min.) X Frontier (1-24 cells) Hypothetical (no cells) Median total recovery per cell (for cells > min.): (mmbo for oil A.U.; bcfg for gas A.U.) 1st 3rd discovered 0.5 2nd 3rd 1.3 3rd 3rd 0.5

Assessment-Unit Probabilities: Attribute Probability of occurrence (0-1.0) 1. CHARGE: Adequate petroleum charge for an untested cell with total recovery > minimum …… 1.0 2. ROCKS: Adequate reservoirs, traps, seals for an untested cell with total recovery > minimum. 1.0 3. TIMING: Favorable geologic timing for an untested cell with total recovery > minimum……….. 1.0

Assessment-Unit GEOLOGIC Probability (Product of 1, 2, and 3):………...... ……. 1.0

4. ACCESS: Adequate location for necessary petroleum-related activities for an untested cell with total recovery > minimum ……………………………………………………………… 1.0

NO. OF UNTESTED CELLS WITH POTENTIAL FOR ADDITIONS TO RESERVES IN THE NEXT 30 YEARS

1. Total assessment-unit area (acres): (uncertainty of a fixed value) minimum 11,229,000 median 11,458,000 maximum 12,010,000

2. Area per cell of untested cells having potential for additions to reserves in next 30 years (acres): (values are inherently variable) calculated mean 130 minimum 40 median 120 maximum 300

3. Percentage of total assessment-unit area that is untested (%): (uncertainty of a fixed value) minimum 92 median 96 maximum 99

4. Percentage of untested assessment-unit area that has potential for additions to reserves in next 30 years (%): ( a necessary criterion is that total recovery per cell > minimum) (uncertainty of a fixed value) minimum 6 median 9 maximum 12 Undiscovered Oil and Gas Resources of the Mowry Composite Total Petroleum System, Southwestern Wyoming Province 23

Assessment Unit (name, no.) Mowry Continuous Gas, Assessment Unit 50370261

TOTAL RECOVERY PER CELL

Total recovery per cell for untested cells having potential for additions to reserves in next 30 years: (values are inherently variable) (mmbo for oil A.U.; bcfg for gas A.U.) minimum 0.02 median 0.7 maximum 15

AVERAGE COPRODUCT RATIOS FOR UNTESTED CELLS, TO ASSESS COPRODUCTS (uncertainty of fixed but unknown values) Oil assessment unit: minimum median maximum Gas/oil ratio (cfg/bo)………………………...……. NGL/gas ratio (bngl/mmcfg)………………….….

Gas assessment unit: Liquids/gas ratio (bliq/mmcfg)….…………..…… 10 20 30

SELECTED ANCILLARY DATA FOR UNTESTED CELLS (values are inherently variable) Oil assessment unit: minimum median maximum API gravity of oil (degrees)…………….…………. Sulfur content of oil (%)………………………...… Drilling depth (m) ……………...…………….…… Depth (m) of water (if applicable)……………….

Gas assessment unit: Inert-gas content (%)……………………….....….. 0.10 0.75 11.00 CO2 content (%)………………………………..….. 0.10 1.00 12.00 Hydrogen-sulfide content (%)……………...……. 0.00 0.00 0.00 Drilling depth (m)…………………………………. 2,100 3,600 5,200 Depth (m) of water (if applicable)……………….

Success ratios: calculated mean minimum median maximum Future success ratio (%)..... 76 61 76 91

Historic success ratio, tested cells (%). 76

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