Chapter 5 Geologic Assessment of Undiscovered Petroleum Resources in the Waltman Shale Total Petroleum System,
Wind River Basin Province, Wyoming Volume Title Page
By Steve Roberts, Laura N.R. Roberts, and Troy Cook
Chapter 5 of Petroleum Systems and Geologic Assessment of Oil and Gas in the Wind River Basin Province, Wyoming
Compiled by USGS Wind River Basin Province Assessment Team
U.S. Geological Survey Digital Data Series DDS–69–J
U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior DIRK KEMPTHORNE, Secretary U.S. Geological Survey Mark D. Myers, Director
U.S. Geological Survey, Reston, Virginia: 2007
For product and ordering information: World Wide Web: http://www.usgs.gov/pubprod Telephone: 1–888–ASK–USGS
For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment: World Wide Web: http://www.usgs.gov Telephone:1–888–ASK–USGS
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report.
Suggested citation: Roberts, Steve, Roberts, Laura N.R., and Cook, Troy, 2007, Geologic assessment of undiscovered petroleum resources in the Waltman Shale Total Petroleum System, Wind River Basin Province, Wyoming, in USGS Wind River Basin Province Assessment Team, Petroleum systems and geologic assessment of oil and gas in the Wind River Basin Province, Wyoming: U.S. Geological Survey Digital Data Series DDS–69–J, ch.5, 32 p.
ISBN 1-4113-2027-7 iii
Contents
Abstract… ……………………………………………………………………………………… 1 Introduction……………………………………………………………………………………… 2 Geologic Setting… ……………………………………………………………………………… 7 Source Rocks: Maturation and Petroleum Generation… ……………………………………… 14 Hydrocarbon Migration and Accumulation……………………………………………………… 18 Assessment Units… …………………………………………………………………………… 18 Upper Fort Union Sandstones Conventional Oil And Gas Au (50350301)…………………… 18 Waltman Fractured Shale Continuous Oil Au (50350361)…………………………………… 27 Assessment of Undiscovered Resources–Summary of Results… ……………………………… 27 Acknowledgments… …………………………………………………………………………… 28 References Cited………………………………………………………………………………… 28 Appendix A. Input data for the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit…………………………………………………………………………………… 31
Figures
1. Map showing location of the Waltman Shale Total Petroleum System in the Wind River Basin Province, Wyoming………………………………………………………………… 3 2. Generalized stratigraphic chart for the Wind River Basin Province, Wyoming… ………… 4 3. Generalized tectonic map of the Wind River Basin Province and adjoining areas, showing major structural features… ……………………………………………………………… 5 4. Map showing locations of oil and gas fields producing oil derived from source rocks in the Waltman Shale Member of the Fort Union Formation… ………………………………… 6 5. Map showing the extent of the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit in the Waltman Shale Total Petroleum System, Wind River Basin Province, Wyoming… …………………………………………………………………… 8 6. Map showing the extent of the Waltman Fractured Shale Continuous Oil Assessment Unit (hypothetical) in the Waltman Shale Total Petroleum System, Wind River Basin Province, Wyoming… ……………………………………………………………………………… 9 7. Structure contour map on the base of the Waltman Shale Member of the Fort Union Formation, Wind River Basin Province, Wyoming……………………………………… 10 8. Map showing estimated depth to the base of the Waltman Shale Member of the Fort Union Formation, Wind River Basin Province, Wyoming… ……………………………… 12 9. Subsurface interpretations of Fort Union Formation and Wind River Formation stratigraphy based on geophysical log traces from two drill holes in the northern part of the Wind River Basin Province, Wyoming… ………………………………………… 13 10. Modified van Krevelen diagrams showing mixed kerogen types for the Waltman Shale Member of the Fort Union Formation, Wind River Basin Province, Wyoming… ………… 14 11. Map showing estimated thermal maturity (Ro) values (in percent) at the base of the Waltman Shale Member of the Fort Union Formation, Wind River Basin Province, Wyoming… …… 15 iv
12. Schematic cross sections A–A’ and B–B’ showing Upper Cretaceous and Lower Tertiary stratigraphic units… …………………………………………………………… 16 13. Burial history reconstructions and estimated vitrinite reflectance (Ro) levels for Upper Cretaceous (part) and lower Tertiary stratigraphic units estimated from three well locations in the north-central part of the Wind River Basin Province, Wyoming………… 17 14. Timing of oil generation from source rocks at the base of the Waltman Shale Member of the Fort Union Formation in seven well locations in the Wind River Basin Province, Wyoming… ……………………………………………………………………………… 19 15. Map showing structure contours and estimated thermal maturity (Ro) values (in percent) at the base of the Waltman Shale Member of the Fort Union Formation, Wind River Basin Province, Wyoming… …………………………………………………………… 20 16. Map showing interpreted orientations of petroleum migration pathways from mature source rocks in the Waltman Shale Member of the Fort Union Formation, Waltman Shale Total Petroleum System, Wind River Basin Province, Wyoming… ……………… 22 17. Schematic diagram showing proposed scenarios for petroleum migration and accumulation near Madden anticline in the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit, Waltman Shale Total Petroleum System, Wind River Basin Province, Wyoming… …………………………………………………………… 23 18. Examples of clinoform morphologies in lacustrine depositional sequences… …………… 24 19. Map showing locations of clinoform morphologies expressed in seismic lines in the Wind River Basin Province, Wyoming…………………………………………………… 25 20. Events chart showing interpreted timing of elements and processes related to hydrocarbon (oil) generation and accumulation in the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit (50350301), Waltman Shale Total Petroleum System, Wind River Basin Province, Wyoming… ……………………………………… 26 21. Estimated ultimate recoveries calculated for wells producing oil sourced by the Waltman Shale Member in the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit, Waltman Shale Total Petroleum System, Wind River Basin Province, Wyoming… ……………………………………………………………………………… 26
Table
1. Waltman Shale Total Petroleum System assessment results……………………………… 27 Geologic Assessment of Undiscovered Petroleum Resources in the Waltman Shale Total Petroleum System, Wind River Basin Province, Wyoming
By Steve Roberts, Laura N.R. Roberts, and Troy Cook
Abstract
The Waltman Shale Total Petroleum System encompasses milligrams of hydrocarbon per gram of rock and numerous about 3,400 square miles in the Wind River Basin Province, samples had generative potentials exceeding 6.0 milligrams Wyoming, and includes accumulations of oil and associated of hydrocarbon per gram of rock. Waltman source rocks are gas that were generated and expelled from oil-prone, oil prone, and contain a mix of Type-II and Type-III kerogen, lacustrine shale source rocks in the Waltman Shale Member of indicating organic input from a mix of algal and terrestrial the Paleocene Fort Union Formation. Much of the petroleum plant matter, or a mix of algal and reworked or recycled migrated and accumulated in marginal lacustrine (deltaic) material. Thermal maturity at the base of the Waltman Shale and fluvial sandstone reservoirs in the Shotgun Member of Member ranges from a vitrinite reflectance value of less than the Fort Union, which overlies and intertongues with the 0.60 percent along the south basin margin to projected values Waltman Shale Member. Additional petroleum accumulations exceeding 1.10 percent in the deep basin west of Madden derived from Waltman source rocks are present in fluvial anticline. Burial history reconstructions for three wells in deposits in the Eocene Wind River Formation overlying the the northern part of the Wind River Basin indicate that the Shotgun Member, and also might be present within fan-delta Waltman Shale Member was well within the oil window (Ro deposits included in the Waltman Shale Member, and in equal to or greater than 0.65 percent) by the time of maximum fluvial sandstone reservoirs in the uppermost part of the lower burial about 15 million years ago; maximum burial depths member of the Fort Union Formation immediately underlying exceeded 10,000 feet. Onset of oil generation calculated for the Waltman. To date, cumulative production from 53 wells the base of the Waltman Shale member took place from about producing Waltman-sourced petroleum exceeds 2.8 million 49 million years ago to about 20 million years ago. Peak oil barrels of oil and 5.8 billion cubic feet of gas. Productive generation occurred from about 31 million years ago to 26 horizons range from about 1,770 feet to 5,800 feet in depth, million years ago in the deep basin west of Madden anticline. and average about 3,400 to 3,500 feet in depth. Two assessment units were defined in the Waltman Formations in the Waltman Shale Total Petroleum System Shale Total Petroleum System: the Upper Fort Union (Fort Union and Wind River Formations) reflect synorogenic Sandstones Conventional Oil and Gas Assessment Unit deposition closely related to Laramide structural development (50350301) and the Waltman Fractured Shale Continuous Oil of the Wind River Basin. In much of the basin, the Fort Union Assessment Unit (50350361). The conventional assessment Formation is divided into three members (ascending order): unit primarily relates to the potential for undiscovered the lower unnamed member, the Waltman Shale Member, and petroleum accumulations that are derived from source rocks the Shotgun Member. These members record the transition in the Waltman Shale Member and trapped within sandstone from deposition in dominantly fluvial, floodplain, and mire reservoirs in the Shotgun Member (Fort Union Formation) and environments in the early Paleocene (lower member) to a in the lower part of the overlying Wind River Formation. The depositional setting characterized by substantial lacustrine potential for Waltman-sourced oil accumulations in fan-delta development (Waltman Shale Member) and contemporaneous deposits within the Waltman Shale Member, and in fluvial fluvial, and marginal lacustrine (deltaic) deposition (Shotgun sandstone deposits in the uppermost part of the lower member Member) during the middle and late Paleocene. of the Fort Union also is considered in the assessment of this Waltman Shale Member source rocks have total organic assessment unit. Definition of the Waltman Fractured Shale carbon values ranging from 0.93 to 6.21 weight percent, Continuous Oil Assessment Unit is based on previous studies averaging about 2.71 weight percent. The hydrocarbon indicating a potential for hydrocarbon (oil) saturation and generative potential of the source rocks typically exceeds 2.5 entrapment within the Waltman Shale Member in areas near Assessment of Undiscovered Oil and Gas in the Wind River Basin Province, Wyoming
Madden anticline. This assessment unit is hypothetical and of the basin gas-prone source rocks (coal and carbonaceous was not quantitatively assessed. shale) in the lower unnamed member of the Fort Union and Mean estimates of the total undiscovered petroleum deeper formations reached peak gas generation well before resources in the Upper Fort Union Sandstones Conventional onset of oil generation from the Waltman Shale Member Oil and Gas AU are 12 million barrels of oil, 24 billion cubic (Roberts and others, Chapter 6, this CD-ROM). Potential feet of gas, and 1.4 million barrels of natural gas liquids. overpressure induced by gas generation, migration, and accumulation in strata sealed below the thick Waltman also might have impeded any significant downward migration of Waltman-sourced oil into underlying, overpressured units. Introduction For these reasons, potential reservoirs for Waltman-sourced oil accumulations in the lower part of the Fort Union are most The Waltman Shale Total Petroleum System (TPS) in likely to be in close proximity (a few hundred feet or less?) to the Wind River Basin, Wyoming (fig. 1), includes strata in the the base of the Waltman Shale Member. Fort Union Formation (Paleocene) and in the lower part of The upper limit of the TPS also is problematic as Wind River Formation (Eocene) (fig. 2). The Waltman Shale there is no identifiable, regionally pervasive seal that would TPS is an oil-prone system, based on the concept that oil and inhibit the upward migration of hydrocarbons derived from associated gas was generated and expelled from thick, organic- the Waltman. Interbedded shale or mudstone in fluvial rich lacustrine shale beds in the Waltman Shale Member of strata of the Fort Union (Shotgun Member) and Wind River the Fort Union Formation. Much of the petroleum migrated Formations overlying the Waltman might form seals locally, and accumulated in marginal lacustrine (deltaic) and fluvial but the stratigraphic position of such seals could vary greatly sandstone reservoirs in the Shotgun Member of the Fort throughout the basin. Additionally, potential faults or fractures Union, which overlies and intertongues with the Waltman in units overlying major structures in the basin (for example, Shale Member (fig. 1). Additional petroleum accumulations Madden anticline; fig. 3) could allow for upward migration derived from Waltman source rocks are in fluvial deposits in of petroleum into shallow horizons well above the Waltman the Wind River Formation overlying the Shotgun Member, Shale Member. However, current oil production is mainly and also might be present within fan-delta deposits in the from reservoirs within 1,000 to 1,500 feet (ft) above the top Waltman Shale Member, and in fluvial sandstone reservoirs in of the Waltman and most production and tests for oil typically the uppermost part of the lower unnamed member of the Fort target sandstone units bounded by lacustrine shale in the Union Formation immediately underlying the Waltman Shale uppermost part of the Waltman, or target the lowermost, Member. In areas of the basin where individual members of coarsening upward sandstone successions in the Shotgun the Fort Union are not present or recognized, a potential for Member immediately overlying the shale. Because of the hydrocarbon accumulation might exist in fluvial deposits in the oil production and exploration trends to date, the authors undifferentiated Fort Union Formation. However, undiscovered restrict the top of the TPS to the lower part of the Wind River petroleum accumulations in Fort Union strata in areas where Formation, arbitrarily suggesting a horizon within about 1,500 the Waltman Shale Member is absent or only represented by ft of the top of the Waltman Shale Member. However, upward thin shale intervals (for example, Johnson, Chapter 10, this migration of petroleum from the Waltman could exceed this CD-ROM) are assessed as part of the Cretaceous–Tertiary designated limit in some areas. Lower Composite TPS (Johnson and others, Chapter 4, this Several fields in the Wind River Basin are producing oil CD–ROM) because of the possibility of mixing hydrocarbons sourced by the Waltman Shale Member (fig. 4), although Katz (especially gas) that have migrated from deeper source rocks and Liro (1993) suggested that oil produced from Shotgun with hydrocarbons sourced by the Waltman. Member reservoirs in Fuller Reservoir field is not solely The TPS encompasses about 3,400 square miles (mi2) derived from the Waltman. Based on data from the Wyoming and the boundary is generally defined by the outcrop limits Oil and Gas Conservation Commission (2005), most of the of the Fort Union Formation, or the inferred limits where historic production has taken place in the Fuller Reservoir overlapped by the Wind River Formation (fig. 1). Adjacent to field where cumulative production from 33 wells has totaled the Owl Creek Mountains and Casper arch on the north and more than 2.3 million barrels of oil (MMBO) and 4.4 billion east margins of the basin, respectively, the TPS extends to the cubic feet (BCF) of gas; cumulative production from 8 wells estimated subthrust limits of the Waltman Shale Member. in Haybarn field is more than 330,000 barrels of oil and about The stratigraphic top and base of the petroleum system 1.4 BCF of gas, and in the greater Madden area (Madden, is difficult to pinpoint because both horizons essentially Lost Cabin, and Lysite fields) 11 wells have produced some represent the uppermost and lowermost limits for migration 183,000 barrels of oil and 0.36 BCF of gas. One well in the of hydrocarbons derived from the Waltman. Downward Carvner Field produced about 5,600 barrels of oil and 5 migration of Waltman-sourced oil into lower Fort Union million cubic feet (MMCF) of gas (Wyoming Oil and Gas rocks might be inhibited by the counteractive effects of Conservation Commission, 2005). buoyancy or capillary pressure if underlying rocks are tight Two assessment units (AUs) were defined in the Waltman (having low permeability). Additionally, throughout most Shale TPS: the Upper Fort Union Sandstones Conventional 110° 109° 108° 107° Undiscovered PetroleumResources—Waltman ShaleTotal Petroleum System—WindRiverBasinProvince,Wyoming
789 Absaroka Bighorn Powder Mountains Basin River 120 Basin Bighorn Kaycee Thermopolis Mountains Dubois Owl Creek Mountains Shotgun Butte 26 W ind 25 Victor 1–14 River River Boysen Bighorn 1–5 Casper arch Reservoir Type Section Powder Ocean Waltman Shale River W Bull Lake 20 Member ind River Mountains Lake
Green 43° Riverton
Casper Pinedale 789
135 189 Lander
River
Platte 351 Granite Mountains
220 Sweetwater North Hoback 28 River Basin 287 487 191 Pathfinder Reservoir
EXPLANATION MT 0 15 30 Miles Wind River Basin Wind River Basin Province boundary Province Wind River Indian Reservation boundary ID WY Waltman Shale Total Petroleum System Fort Union Formation outcrops
Figure 1. Location of the Waltman Shale Total Petroleum System (blue shade) in the Wind River Basin Province, Wyoming; red dots represent the locations of the Bighorn
1–5 and Victor 1–14 oil and gas exploration wells. Fort Union Formation outcrops from Green and Drouillard (1994) after Love and Christiansen (1985). Assessment of Undiscovered Oil and Gas in the Wind River Basin Province, Wyoming
System Series Western Wind River Basin Southern and central Eastern Wind River Basin Wind River Basin
Wind River Wind River Wind River Formation Formation Formation (part) R R R EOCENE (part)
Y Waltman Shale R R Shotgun Shotgun Shotgun Total Petroleum Member Member Member System R S S Waltman Shale R TIAR Member Waltman Shale Waltman Shale R S R Member Member R R R ALEOCENE lower unnamed lower unnamed lower unnamed TER P Fort Union Formation Fort Union Formation member member Fort Union Formation member Lance Lance Lance Formation Formation Formation Meeteetse Formation Meeteetse Meeteetse and Formation Formation Lewis Shale undivided Teapot Sandstone Member Teapot Sandstone Teapot Sandstone Member Member
Unnamed middle member Parkman Sandstone Member Wallace Creek Tongue of Cody Shale
lower part Mesaverde Formation Fales Sandstone Member UPPER
lower part Mesaverde Formation Upper unnamed sandy member
Mesaverde Formation Cody Shale ? Cody Shale Upper sandy Upper sandy member member Cody Shale Lower shaly member Lower shaly member
ACEOUS Lower shaly member Frontier Formation Frontier Formation Frontier Formation
CRET Mowry Shale
Muddy Sandstone
Thermopolis Shale
LOWER Cloverly Formation
Jurassic rocks JURASSIC/ Jurassic and Triassic rocks undifferentiated TRIASSIC Triassic rocks (part)
PERMIAN Phosphoria/Park City/ Goose Egg Formation PENNSYLVANIAN (part) Tensleep Sandstone
Erosion or nondeposition
Western Wind R, reservoir rocks River Basin Southern and Central Wind S, source rocks River Basin Eastern Wind River Basin
Figure 2. Generalized stratigraphic chart for the Wind River Basin Province, Wyoming, showing units in the Waltman Shale Total Petro- leum System, and intervals of petroleum reservoir and source rocks. Ages of stratigraphic units older than Cretaceous Cloverly Formation were estimated using Love and others (1993). The ages at system and series boundaries were adjusted to the 1999 Geologic Time Scale (Palmer and Geissman, 1999) and ages of Cretaceous and younger stratigraphic units are from Finn (Chap. 9, pl. 1, this CD-ROM). 110° 109° 108° 107° Undiscovered PetroleumResources—Waltman ShaleTotal Petroleum System—WindRiverBasinProvince,Wyoming
Bighorn Powder Absaroka Basin River Mountains Basin
Thermopolis Kaycee 3 Dubois 4 Owl Creek Mountains Bighorn 6 Mountains 1 5 MS 10 2 S LD 7
P MR MA PB Casper arch W WD ind River Mountains
SC 43° Riverton DB RD RM Mu RH Casper L Pinedale CC WPS Lander Da BSD DD Hoback Basin SM 8 Granite Mountains 9
EXPLANATION MT 0 15 30 Miles RH Fold axis Wind River Basin Province boundary Wind River Basin Province Waltman Shale Total Petroleum System ID WY Thrust fault–sawteeth on overriding plate Precambrian rocks
Inferred fault
Figure 3. Generalized tectonic map of the Wind River Basin Province and adjoining areas, showing major structural features. All structures from Love and Christiansen (1985) are shown in black; dashed where inferred in subsurface; faults shown in blue are interpreted from unpublished seismic studies of M. A. Kirschbaum (USGS, written commun.). Numbered faults: 1, White Rock thrust; 2, Wind Ridge and Coulee Mesa thrust system; 3, Black Mountain thrust; 4, Red Creek thrust (Blackstone, 1990); 5, Rolff Lake fault; 6, Circle Ridge/Maverick Springs thrust; 7, Shotgun Butte thrust; 8, Clear Creek fault; 9, Emigrant Trail fault; and 10, South Owl Creek Mountains fault. Anticlines: BSD, Big Sand Draw; CC,
Conant Creek; Da, Dallas; DB, Dutton Basin; DD, Derby Dome L, Lander; LD, Little Dome; MS, Maverick Springs; Mu, Muskrat; MR, Muddy Ridge; P, Pavillion; PB, Pilot Butte; RD, Riverton Dome/Beaver Creek; RH, Rattlesnake Hills; RM, Rogers Mountain; S, Sheldon; SC, Sage Creek; SM, Sheep Mountain; WD, Winkleman Dome; WPS, West Poison Spider; and MA, Madden anticline.
110° 109° 108° 107° Assessment ofUndiscoveredOilandGasintheWindRiverBasinProvince,Wyoming
Bighorn Powder Absaroka Basin River Mountains Basin
Thermopolis Kaycee Owl Creek Mountains Dubois Bighorn Mountains
Lysite Madden
Lost Carvner Cabin Casper arch W ind River Mountains Fuller Haybarn Riverton Reservoir 43° Castle Signor Gardens Ridge Casper Pinedale Lander
Hoback Basin Granite Mountains
0 15 30 Miles EXPLANATION MT Haybarn Wind River Basin Province boundary Wind River Basin Field producing oil sourced Province Castle from the Waltman Shale Member Waltman Shale Total Petroleum System ID WY Gardens Oil-stained outcrops–oil sourced Fort Union Formation outcrops from the Waltman Shale Member
Figure 4. Locations of oil and gas fields producing oil derived from source rocks in the Waltman Shale Member of the Fort Union Formation, Wind River Basin Province, Wyo- ming. Identification of Waltman-sourced accumulations in fields shown is based on Ray (1982), Robertson (1984), Katz and Liro (1993), Palacas and others (1994), and Lillis and Palacas (U.S. Geological Survey, unpub. data, 2006). Fort Union Formation outcrops from Green and Drouillard (1994) after Love and Christiansen (1985). Undiscovered Petroleum Resources—Waltman Shale Total Petroleum System—Wind River Basin Province, Wyoming
Oil and Gas AU (fig. 5) and the Waltman Fractured Shale floodplain, and mire environments in the early Paleocene (lower Continuous Oil AU (fig. 6). Although some potential for unnamed member) to a depositional setting characterized by microbial (biogenic) gas generation from the Waltman is significant lacustrine development (Waltman Shale Member) evidenced by gas production in one well within the basin and contemporaneous fluvial, and marginal lacustrine (deltaic) (Johnson and Rice, 1993), no assessment of these resources deposition (Shotgun Member) during the middle and late was completed for this study. Paleocene (for example, Phillips, 1983; Liro and Pardus, 1990; The conventional assessment unit primarily addresses Flores and others, 1994; Nichols, 1994; Osborn, 2001). Keefer the potential for undiscovered petroleum accumulations that (1961; 1965) previously recognized the Waltman member are derived from source rocks in the Waltman Shale Member, as deposits of an extensive body of water that developed in and trapped primarily within sandstone or conglomeratic the basin during late Paleocene time, and suggested that this reservoirs in the Shotgun Member, and the lower part of the water body might represent an arm or embayment of the overlying Wind River Formation. Potential Waltman-sourced marine Cannonball Sea. However, based on the studies and accumulations also may exist in areally restricted reservoirs interpretations in Liro and Pardus (1990), Katz and Liro (1993), within basin margin fan-delta systems within the Waltman Flores and others (1994), and Liro (1993), the Waltman Shale Shale Member, and in sandstone reservoirs in the uppermost Member represents lacustrine deposits in this study. part of the lower unnamed member of the Fort Union The three members of the Fort Union Formation are Formation. not present or recognized everywhere in the basin. In areas The Waltman Fractured Shale Continuous Oil AU is where the Waltman Shale Member is absent (for example, based on concepts in Jorjorian and others (1989) and Katz Shotgun Butte; fig. 1), the Shotgun Member directly overlies and Liro (1993) describing the potential for hydrocarbon (oil) the lower unnamed member (fig. 2). The Shotgun Member in saturation and entrapment within the Waltman Shale Member outcrops along the south and southeast basin margins cannot in areas near Madden anticline. This AU is hypothetical and be distinguished from the lower unnamed member and the was not quantitatively assessed. entire Paleocene section is included in the undifferentiated Fort Union Formation (Keefer, 1965). At most outcrop locations the contact between the Fort Union and underlying Lance Formation is unconformable; however, this contact is Geologic Setting likely conformable in the major basin trough areas (Keefer, 1965). Prior to deposition of the Wind River Formation, The Wind River Basin developed as Laramide erosion removed significant portions of the underlying Fort deformation reshaped the Rocky Mountain foreland. Uplift Union Formation. At Shotgun Butte in the northern part of the of the Wind River, Granite, and Owl Creek Mountains (fig. basin (fig. 1), about 1,100 ft of the lower unnamed member 3) surrounding the basin began in the Late Cretaceous, and of the Fort Union is exposed. There, the lower unnamed rapid basin subsidence in the latest Cretaceous (Maastrichtian) member consists mainly of conglomerate and sandstone is evidenced by thickening of the Lance Formation in areas with subordinate gray shale and brown carbonaceous shale adjacent to the Owl Creek Mountains (Keefer, 1970; Johnson (Keefer, 1997). The member thickens eastward to more than and others, 1996a). Structural development of the basin 4,500 ft in the deep basin trough in the west-central part of the and uplifts continued during deposition of the Fort Union basin (Johnson and others, 1996a), and through most of the Formation in the Paleocene, with interpreted rise of the Casper central basin area, the member is characterized by sandstone arch along the eastern basin margin in late early (?) through (locally arkosic or containing chert clasts), siltstone, shale, late Paleocene time (for example, Gries, 1983; Flemings carbonaceous shale, and coal (Keefer and Johnson, 1997). and Nelson, 1991; Flores and others, 1994). Subtle folds in Coal is widespread in the upper part of the lower unnamed the Waltman Shale Member of the Fort Union (fig. 7) and member and cumulative coal thickness exceeds 100 ft in significant folding and uplift of the member on the Madden some areas. Adjacent to the Owl Creek Mountains and anticline resulted from post-Waltman deformation in the latest Casper arch in the north and northeast basin-margin areas, Paleocene (?) through early Eocene (for example, Dunleavy subsurface studies show that the lower unnamed member and Gilbertson, 1986). Subsidence and uplift ended by the is predominantly fine grained and consists mainly of sandy close of early Eocene time (Keefer, 1970), during the latter mudstone and thin (< 10 ft thick) ‘muddy’ sandstone (Johnson stages of Wind River deposition. and others, 1996a). Formations in the Waltman Shale TPS (Fort Union and The Waltman Shale Member, which overlies the lower Wind River Formations; fig. 2) reflect synorogenic deposition unnamed member, is named for exposures of shale near the closely related to Laramide structural development of the east basin margin (fig. 1). At the type locality, the Waltman Wind River Basin. The Fort Union Formation in much of the is about 645 ft thick and characterized by chocolate-brown basin is divided into three members (ascending order): the and gray silty and shaly claystone interbedded with a few thin lower unnamed member, the Waltman Shale Member, and resistant sandstone beds; disseminated mica is abundant within the Shotgun Member (fig. 2) (Keefer, 1961). These members the claystone. Cuttings and core samples of the Waltman record the transition from deposition in dominantly fluvial, recovered in oil and gas exploration wells are characteristically 110° 109° 108° 107° Assessment ofUndiscoveredOilandGasintheWindRiverBasinProvince,Wyoming
Bighorn Powder Absaroka Basin River Mountains Basin
Thermopolis Kaycee Owl Creek Mountains Dubois Bighorn Mountains
Lysite Madden
Lost Cabin Carvner Casper arch W ind River Mountains Fuller Reservoir Riverton Haybarn 43° Castle Gardens Signor Ridge Casper Pinedale Lander
Hoback Basin Granite Mountains
0 15 30 Miles EXPLANATION MT Haybarn Wind River Basin Province boundary Wind River Basin Field producing oil sourced Province Castle from the Waltman Shale Member Waltman Shale TPS boundary ID WY Gardens Oil-stained outcrops–oil sourced Upper Fort Union Sandstones Conventional from the Waltman Shale Member Oil and Gas Assessment Unit Fort Union Formation outcrops
Figure 5. The extent of the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit in the Waltman Shale Total Petroleum System, Wind River Basin Province, Wyoming. Identification of Waltman-sourced accumulations in fields shown is based on Ray (1982), Robertson (1984), Katz and Liro (1993), Palacas and others (1994), and Lillis and Palacas (U.S. Geological Survey, unpub. data, 2006). Fort Union Formation outcrops from Green and Drouillard (1994) after Love and Christiansen (1985). Undiscovered Petroleum Resources—Waltman Shale Total Petroleum System—Wind River Basin Province, Wyoming River Basin Casper Powder Kaycee AU
° Casper arch Assessment Unit 107 Common boundary with Upper Fort Union Sandstones Conventional Oil and Gas Bighorn Mountains 0 otal Petroleum System boundary T
0.60 altman Shale Member TION
Granite Mountains 0.73 altman Shale altman Fractured Shale Continuous Oil EXPLANA W W Fort Union Formation outcrops Wind River Basin Province boundary Thermal maturity (R in percent) at the base of the W Basin ° Bighorn 0.73
108 0.60 1.10 AU Thermopolis Owl Creek Mountains 30 Miles Riverton Lander 15 Common boundaries with Upper Fort Union Sandstones Conventional Oil and Gas ° 109 in percent) modified from Johnson and others (1996b). Fort Union Formation outcrops from Green and Drouillard (1994) after in percent) modified from Johnson and others (1996b). Fort Union Formation o 0
ind River Mountains Province Absaroka Mountains W , vitrinite reflectance. Wind River Basin o Dubois WY MT ° 10 ID Pinedale 1 The extent of the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit in the Waltman Shale Total Petroleum System, Wind River Basin Province, Shale Total The extent of the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit in Waltman The extent of the Waltman Fractured Shale Continuous Oil Assessment Unit (hypothetical) in the Waltman Shale Total Petroleum System, Wind River Basin Province, Shale Total Fractured Shale Continuous Oil Assessment Unit (hypothetical) in the Waltman The extent of the Waltman
.
. 6 ° 43 Figure accumulations in fields shown is based on Ray (1982), Robertson (1984), Katz and Liro (1993), Palacas others (1994), Lillis Identification of Waltman-sourced Wyoming. unpub. data, 2006). Fort Union Formation outcrops from Green and Drouillard (1994) after Love Christiansen (1985). and Palacas (U.S. Geological Survey, Figure Thermal maturity (isoreflectance) lines (R Wyoming. Love and Christiansen (1985). R 10 Assessment of Undiscovered Oil and Gas in the Wind River Basin Province, Wyoming River Basin Casper Powder Kaycee
° Casper arch otal Petroleum System boundary 107 T Assessment Unit , Madden anticline altman Shale Bighorn Mountains W Upper Fort Union Sandstones Conventional Oil and Gas Fort Union Formation outcrops MA Wind River Basin Province boundary TION 0 0 Granite Mountains MA
EXPLANA
4,000 2,000 sawteeth on – Basin ° Bighorn Axis 0 108
Basin Thrust fault overriding plate Normal fault Fold axis 0
-6,000 -4,000 -2,000 Thermopolis Riverton
Owl Creek Mountains 30 Miles 2,000 4,000 Lander 15 ° 109 0 Absaroka Mountains
ind River Mountains Province W Wind River Basin Dubois WY MT ° Basin Hoback 10 ID Pinedale 1 Structure contour map on the base of the Waltman Shale Member of the Fort Union Formation, Wind River Basin Province, Wyoming. Structure contours modified Shale Member of the Fort Union Formation, Wind River Basin Province, Wyoming. Structure contour map on the base of Waltman
. 7 ° 43 Figure from Johnson and others (1996a) based on new interpretations of (2005). Contour interval is 500 feet; contour values in elevation relative to mean sea after Love and Christiansen (1985). level. Fort Union Formation outcrops from Green and Drouillard (1994) Undiscovered Petroleum Resources—Waltman Shale Total Petroleum System—Wind River Basin Province, Wyoming 11 dark brown to black and uniformly silty and micaceous placement of the contact separating the two members is (Keefer, 1961; 1965). The thickness of the Waltman problematic and can result in the inclusion of lacustrine exceeds 3,800 ft in structurally deep areas near the basin shale tongues within the Shotgun Member, or alternatively, axis (Keefer, 1997), and depth to the base of the member marginal lacustrine or deltaic sandstone in the Waltman Shale is more than 10,000 ft near the basin axis in areas west of Member. Additionally, rapid lateral facies variations also can Madden anticline (fig. 8). The contact between the Waltman complicate the differentiation of the individual members. For Shale Member and underlying lower unnamed member in example, in the Bighorn 1–5 well near the northern basin outcrops is transitional and is generally defined by a zone of margin (fig. 1), geophysical logs indicate that about 2,000 ft interbedded sandstone, black micaceous shale, carbonaceous of shale immediately overlies the lower unnamed member shale, and coal (Keefer, 1961). In electric logs, the Waltman of the Fort Union; the contact separating the Shotgun and is characterized by low self-potential and resistivity curves Waltman Shale Members is logically placed at the top of relative to underlying and overlying units (Keefer, 1965); the thick shale interval (fig. 9). However, in the Victor 1–14 in sonic logs, there is a distinct decrease in velocity within well, which is only a few miles north of the Bighorn 1–5 the shale (fig. 9). The contact between the Waltman Shale well (fig. 1), strata equivalent to the Waltman Shale Member Member and the lower unnamed member is considered to be include only about 1,000 ft of shale overlain by more that conformable (Keefer, 1965) although seismic studies in areas 1,500 ft of coarser lithologies (sandstone or conglomerate?) near the Carvner and Fuller Reservoir fields (fig. 4) indicate interpreted, in part, to represent deposits of a fan-delta that an unconformity may separate the Waltman Shale system (for comparison, see Hollis, 2001) that developed Member from the underlying lower unnamed member (Ray, contemporaneously with offshore lacustrine environments 1982). The Waltman covers an area exceeding 1,000 mi2 and nearby. A strictly lithologic definition might place the contact is interpreted to have also been deposited in areas overridden at the top of the shale interval in the Victor 1–14 well; by the Casper arch thrust to the east (Keefer, 1965). Recent whereas, an alternative approach might include fan-delta subsurface studies (Johnson and others, 2005; Johnson, deposits (in part) as a facies variant within the Waltman Shale Chapter 10, this CD-ROM) indicate that Waltman deposition Member. In this study, the latter approach is preferred and also may have extended farther westward than previously the fan-delta system (at least in part) is included within the interpreted (for comparison, see Johnson and others, 1996a); Waltman Shale Member (fig. 9). However, circumstances structure contours and depths at the base of the Waltman such as this might be limited to only a few areas near the Shale Member shown in figures 7 and 8 are based on the basin margins; throughout most of the basin, identification of newly interpreted extent. the contact between the Shotgun Member and the Waltman The Shotgun Member, which overlies and intertongues Shale Member follows criteria set forth by Keefer (1961; with the Waltman Shale Member, was named for a succession 1965). of soft claystone, siltstone, shale, carbonaceous shale, Lower Eocene alluvial strata overlie the Fort Union and sandstone exposed at Shotgun Butte (fig. 1). At that Formation and are present in outcrops throughout much of locality, the Shotgun Member is about 2,830 ft thick; near the Wind River Basin. In this study, the name Wind River the north margin of the basin, the member is more than Formation is applied to all lower Eocene rocks, including the 2,200 ft thick (Keefer, 1961; 1965). The Shotgun Member Indian Meadows Formation and the Lost Cabin and Lysite was deposited in fluvial and shoreline areas landward of Members of the Wind River Formation (Keefer, 1965). The open-water lacustrine environments that expanded during Wind River nomenclature is applied because in subsurface the late Paleocene; Waltman deposits reflect offshore (well-log) data, there are no viable criteria for distinguishing deposition contemporaneous with onshore Shotgun Member the individual members within the Wind River Formation or deposition (Keefer, 1961). The contact between the Shotgun for differentiating the Indian Meadows Formation from the and Waltman Shale Members is transitional and typically Wind River (Keefer, 1965). characterized by alternating thin beds of black shale and The Wind River Formation unconformably overlies the fine-grained sandstone, carbonaceous shale, and coal (Keefer, Fort Union Formation at most outcrop localities, although 1965). The contact in the subsurface is typically placed at the the contact may be conformable in central basin areas. The base of the lowermost, coarsening-upward succession above maximum thickness of the Wind River may exceed 9,000 ft the main shale mass, as expressed in gamma-ray (GR) and in the north-central and southeastern parts of the basin. The spontaneous potential (SP) logs (for comparison, see Keefer, formation in the basin center is characterized by varicolored 1965; Keefer and Johnson, 1997). These successions are red, gray, and gray-green claystone interbedded with white or indicative of shale or siltstone changing upward to sandstone, gray fine- to medium-grained sandstone (Keefer, 1965). The reflecting a facies shift from offshore lacustrine environments varicolored aspect of the Wind River Formation can, in some to nearshore, shoreface, or deltaic environments. However, places, provide a basis for distinguishing Wind River strata in certain areas of the basin, units overlying the lowermost from underlying Fort Union rocks, which tend to be drab coarsening upward succession consist of alternating and darker in color. However, in many cases, differentiation lacustrine and shoreface deposits resulting from oscillations of these formations based on well-log data is difficult. The in lake level and relative shoreline position. In these areas, Wind River Formation includes a wide range of lithologies 1 Assessment of Undiscovered Oil and Gas in the Wind River Basin Province, Wyoming River Basin Casper Powder Kaycee ° Casper arch otal Petroleum System boundary T Assessment Unit 107
5,000 , Madden anticline altman Shale W Upper Fort Union Sandstones Conventional Oil and Gas Fort Union Formation outcrops MA Wind River Basin Province boundary Bighorn Mountains
8,000
TION 7,000
5,000 EXPLANA 6,000
Granite Mountains 7,000 MA sawteeth on
– 7,000
Basin 4,000 ° Bighorn 108 Thrust fault overriding plate Normal fault 5,000
8,000
9,000
10,000
7,000 Thermopolis
1,000
1 Riverton
Owl Creek Mountains
6,000 30 Miles
2,000
3,000 Lander 15 ° 109 0 Absaroka Mountains
ind River Mountains Province W Wind River Basin Dubois WY MT ° Basin Hoback 10 ID Pinedale 1 Estimated depth to the base of the Waltman Shale Member of the Fort Union Formation, Wind River Basin Province, Wyoming. Depth contours (in feet) based on Shale Member of the Fort Union Formation, Wind River Basin Province, Wyoming. Estimated depth to the base of Waltman
. 8 ° 43 Figure Shale Member (Johnson and others, 2005). Contour interval is 1,000 feet. Fort Union Formation outcrops from Green revised structural interpretations for the base of Waltman and Drouillard (1994) after Love Christiansen (1985). Figure . Estimated depth to the base of the Waltman Shale Member of the Fort Union Formation, Wind River Basin Province, Wyoming. Depth contours (in feet) based on revised structural interpretations for the base of the Waltman Shale Member (Johnson and others, 2005). Contour interval is 1,000 feet. Fort Union Formation outcrops from Green and Drouillard (1994) after Love and Christiansen (1985).
South North Undiscovered PetroleumResources—Waltman ShaleTotal Petroleum System—WindRiverBasinProvince,Wyoming
Bighorn 1-5 MDU Victor 1-14 API 49013213620000 API 49013089000000 KB: 5,508 feet KB: 5,741 feet TD: 24,900 feet TD: 21,012 feet
G.R. Res. Sonic G.R. Res. Sonic
Decreasing Decreasing Velocity Decreasing Decreasing Velocity Decreasing Decreasing
2 1 (part) (part)
3 2 ind River Formation ind River Formation W W ? ? ? 4 ? Shotgun 3 ? Shotgun Member Member Fan delta ? 5 deposits (?) 4 Waltman Waltman Shale Shale Shale 6 Member Member 5 Shale Shale
7 6 Datum lower lower unnamed 8 unnamed Fort Union Formation (part) member 7 member Fort Union Formation (part) (part)
Depth in Depth in thousands of feet thousands of feet
Figure 9. Subsurface interpretations of Fort Union Formation and Wind River Formation stratigraphy based on geophysical log traces from two drill holes in the northern part of the Wind River Basin Province, Wyoming; drill-hole locations are shown in figure 2. Datum is the top of the lower unnamed member of the Fort Union Formation. Contact (position 1 queried) between the Wind River and Fort Union Formations (red-dashed line) is unconformable. G.R., gamma ray; Res., Resistivity; MDU, Madden Deep Unit. 1 Assessment of Undiscovered Oil and Gas in the Wind River Basin Province, Wyoming representing a variety of depositional settings, including alluvial Thermal maturity at the base of the Waltman Shale fans, fluvial and floodplain environments, and lake systems that Member ranges from a vitrinite reflectance R( o) value of less developed during a time of intense folding and uplift during the than 0.60 percent along the south basin margin to projected latter stages of the Laramide orogeny (Keefer, 1965). values exceeding 1.10 percent in the deep basin west of the Lysite field (Johnson and others, 1996b) (fig. 11). Maturity values of 1.10 percent or greater are extrapolated from Ro measurements at stratigraphic horizons near the base of the Source Rocks: Maturation and Shotgun Member in the Dome Shoshone-Arapahoe 6-1 and Petroleum Generation Boysen Tribal 1-24 drill holes just west of the Upper Fort Union Sandstones Conventional Oil and Gas AU boundary (Nuccio and others, 1996) (fig. 11). These horizons are As described previously, source rocks in the Waltman stratigraphically equivalent to the base of the Waltman Shale Shale TPS are the thick lacustrine shales and siltstones within Member, and the level of thermal maturity at these horizons the Waltman Shale Member. Katz and Liro (1993) completed is interpreted to continue eastward into the deep basin area of a detailed study of Waltman source-rock characteristics, the AU where thick shale is present. Nuccio and Finn (1994) based on 226 samples of drill cuttings from 13 wells in the suggested that Ro values at the base of the Waltman might basin. Their analyses show that the total organic carbon not exceed 0.80 percent, even in deeper basin areas, although (TOC) ranges from 0.93–6.21 weight percent, averaging 2.71 Johnson and others (1996b) indicate that higher thermal weight percent. For comparison, Hunt (1996) suggested that maturity levels have been attained (fig. 12). productive oil source rocks require a minimum TOC of 1.5 Burial history reconstructions (methodology discussed weight percent. Hydrocarbon generative potentials in 204 in Roberts and others, Chapter 6, this CD–ROM) for three samples exceeded 2.5 milligrams of hydrocarbon per gram wells in the northern part of the Wind River Basin (fig. 13) of rock (mg HC/g rock) and 132 samples had generative indicate that the Waltman Shale Member was well within the potentials exceeding 6.0 mg HC/g rock. The Waltman is oil window by the time of maximum burial about 15 million considered an oil-prone source rock, and includes a mix of years ago (Ma), assuming an onset of oil generation at an Ro Type-II and Type-III kerogen (fig. 10), indicating organic input of 0.65 percent; maximum burial depths exceeded 10,000 ft from a mix of algal and terrestrial plant matter, or a mix of at each of the three locations prior to uplift and cooling. The algal and reworked or recycled material (Katz and Liro, 1993). timing of oil generation calculated for the base of the Waltman
1000 Type I
800
Type II 600
May be oxidized or reworked organic material Hydrogen Index 400
200
Type III
50 100 150 200 250 300 350 Oxygen Index Figure 10. Modified van Krevelen diagrams based on whole rock Rock–Eval pyrolysis for drill cuttings samples from 13 oil and gas exploration wells (Katz and Liro, 1993) showing mixed kerogen types for the Waltman Shale Member of the Fort Union Formation, Wind River Basin Province, Wyoming. 110° 109° 108° 107° Undiscovered PetroleumResources—Waltman ShaleTotal Petroleum System—WindRiverBasinProvince,Wyoming
Bighorn Powder Absaroka Basin River Mountains Basin
Thermopolis Kaycee Owl Creek Mountains Dubois Bighorn Mountains
0.73 1 2 Lysite Madden Only thin tongue(s) of Waltman Shale present in this area 1.10 Lost Cabin Carvner Casper arch W ind River Mountains Fuller Reservoir 0.73 0.60 Riverton Haybarn 43° Castle Gardens Signor Ridge Casper Pinedale Lander
Hoback Basin Granite Mountains
0 15 30 Miles EXPLANATION MT Thermal maturity (R 0 in percent) Wind River Basin Province boundary 0.60 isolines at the base of the Waltman Wind River Basin Shale Member or equivalent strata Waltman Shale Total Petroleum System boundary Province ID WY Haybarn Field producing oil sourced Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit Castle from the Waltman Shale Member Gardens Fort Union Formation outcrops Oil-stained outcrops–oil sourced from the Waltman Shale Member Drill hole
Figure 11. Estimated thermal maturity (Ro) values (in percent) at the base of the Waltman Shale Member of the Fort Union Formation, Wind River Basin Province, Wyoming. In drill holes (1) Dome Shoshone-Arapahoe 6-1 and (2) Boysen Tribal 1-24, Ro values were estimated from strata in the Shotgun Member the Fort Union that are considered to be equivalent to the base of the Waltman Shale Member. Modified from Johnson and others (1996b). Fort Union Formation outcrops from Green and Drouillard (1994) after Love and 1 Christiansen (1985). 1 Assessment of Undiscovered Oil and Gas in the Wind River Basin Province, Wyoming
A A' Owl Creek Mountains South North Madden Anticline
Wind River and Indian Meadows Waltman Shale Tertiary (?) and Formations (undifferentiated) Member Shotgun Member older rocks
Ro 0.73% Fort Union 0 R 1.10% Formation 200 F o Meeteetse Formation Mesaverde Formation Lance Formation lower unnamed member
0 300 F
Fault Fault Lower Cretaceous Cody Shale and older rocks Frontier Formation Mowry Shale
B B' Casper Arch Madden West Anticline East
Wind River and Indian Meadows Waltman Shale Formations (undifferentiated) Fort Union Member Tertiary (?) Formation and older rocks Shotgun Member Ro 0.73% 0 R 1.10% lower unnamed member 200 F o Frontier Formation Mesaverde Formation Lance Formation
Meeteetse Formation 0 300 F
Cody Shale
Fault
Lower Cretaceous and older rocks Mowry Shale
A' Waltman Shale B TPS B'
Wind River Basin A Province
Figure 12. Schematic cross sections A–A’ and B–B’ showing Upper Cretaceous and Lower Tertiary stratigraphic units, the estimated position of the 0.73 percent and 1.10 percent vitrinite reflectance (Ro) levels, and the estimated positions of the 200˚ F and 300˚ F present- day isotherms in the Wind River Basin Province, Wyoming. Cross section locations are approximate. Modified from Johnson and others (1996b). Undiscovered Petroleum Resources—Waltman Shale Total Petroleum System—Wind River Basin Province, Wyoming 1
Bonneville 23-1 Maximum Age in millions of years burial 60 40 20 Uplift and cooling 0
MESOZOIC CENOZOIC CRETACEOUS PALEOGENE NEOGENE & QUATERNARY 0 Post-lower Eocene rocks
Wind River Formation 5,000 Fort Union Shotgun Member
Fort Union 10,000 –Waltman Shale Member Fort Union
Burial Depth in feet –lower unnamed member
15,000 Lance Formation
Adams OAB 1-17 Maximum Age in millions of years burial 60 40 20 Uplift and cooling 0
MESOZOIC CENOZOIC CRETACEOUS PALEOGENE NEOGENE & QUATERNARY 0 Post-lower Eocene rocks
Fort Union Wind River Formation 5,000 Shotgun Member Fort Union –Waltman Shale Member 10,000 Fort Union –lower unnamed member Burial Depth in feet
15,000 Lance Formation
Bighorn 1-5 Maximum Age in millions of years burial 60 40 20 Uplift and cooling 0
MESOZOIC CENOZOIC CRETACEOUS PALEOGENE NEOGENE & QUATERNARY 0 Post-lower Eocene rocks Fort Union Shotgun Member Wind River Formation 5,000 Fort Union –Waltman Shale Member Fort Union 10,000 –lower unnamed member
Burial Depth in feet Lance Formation.
15,000
Explanation MT Wind River Basin 0.50–0.60% R Province 0 ID WY
0.60–0.80% R 0 (Onset oil generation ~ 0.65% R 0 ) Bonneville 23-1 0.80–1.10% R0 Bighorn 1-5 1.10–1.35% R0 Adams OAB 1-17
1.35–2.00% R0
Figure 13. Burial history reconstructions and estimated vitrinite reflectance (Ro) levels for Upper Cretaceous (part) and lower Tertiary stratigraphic units estimated from three well locations in the north-central part of the Wind River Basin Province, Wyoming. Onset of oil generation from Type-II source rocks in the Waltman Shale Member of the Fort Union Formation is interpreted to be at an Ro level of about 0.65 percent (Roberts and others, Chap. 6, this CD-ROM). Vertical dashed line at 15 million years ago represents beginning of major uplift, erosion, and subsequent cooling. 1 Assessment of Undiscovered Oil and Gas in the Wind River Basin Province, Wyoming at seven well locations is shown in figure 14. Start (onset) and core sample. Average pay thickness is about 13 ft and the oil peak oil generation reflect transformation ratios of 0.01 and column is from 0–25 ft in height (Evans, 1989). Oil produced 0.50, respectively (Roberts and others, Chapter 6, this CD- in Haybarn Field has a high paraffin content, an API gravity of ROM). This timing is based on hydrous-pyrolysis (HP) kinetic 43.7˚, a pour point near 80˚ F, and an average sulfur content of parameters derived from a Type-II, oil-prone source rock about 0.22 percent; associated gas is liquid-rich with a heating which, in the authors opinion, best represents the Waltman value of 1,365 BTUs and the gas to oil ratio is about 1,200 Shale Member. Source-rock oil-generation kinetic parameters (Robertson, 1984). from hydrous-pyrolysis experiments, combined with burial In Fuller Reservoir field, traps are a combination of and thermal history, determine the timing of the generation structural and stratigraphic; the field is located on a broad of expelled oil where expulsion is considered a consequence structural nose where lithofacies variations in lacustrine, of generation (Lewan, 1997). Timing of oil generation in marginal lacustrine (deltaic), and fluvial deposits enhance the Dome Shoshone-Arapahoe 6-1 and Boysen Tribal 1-24 trapping potential (Ray, 1982; Specht, 1989). Sandstone and wells (fig. 11) is calculated for stratigraphic horizons in the conglomerate reservoirs are present within the Fort Union basal part of the Shotgun Member that are equivalent to the (Shotgun Member) and Wind River Formations. Sandstone Waltman base. Given that Ro values at these stratigraphic units are generally from 6 to 15 ft thick, with an average pay horizons approach 1.10 percent, HP kinetics applied with from 4 to 6 ft; porosities range from 18 to 30 percent (Ray, burial history in this area indicate that onset of oil generation 1982; Specht, 1989). As in Haybarn field, the produced oil has probably occurred about 49–46 Ma, and peak oil generation a paraffin base, and the API gravity is about 45˚ with a pour might have been achieved about 31–26 Ma. At the remaining point as high as 75˚ F (Specht, 1989). five locations, onset of oil generation from the Waltman In fields producing Waltman-sourced oil on Madden ranged from about 39 to 20 Ma and peak generation was not anticline (fig. 4), production also is from the Wind River and achieved at any of these locations. Fort Union Formations (Shotgun Member) (Wyoming Oil and Gas Conservation Commission, 2005). Traps are primarily stratigraphic, resulting from pinchout of discontinuous sandstones into surrounding shale; main producing intervals Hydrocarbon Migration and are interpreted to be deposits of an alluvial fan system that Accumulation emanated from the Owl Creek Mountains (Osborn, 2001). Sandstone reservoirs in the Shotgun Member are typically fine grained, with average pay of 35 ft, log porosities ranging from Oil generated by the Waltman Shale Member migrated 10 to 15 percent (average 13 percent), and permeability (in laterally (up structural dip) and vertically, charging reservoirs core) ranging from 6 to 44 md (average 19 md); produced oil in several fields within the Wind River Basin. Most of the has an API gravity of 36˚ (Brown and Shannon, 1989). fields are in or near areas where the Waltman is thermally mature for oil generation (Ro of 0.65 percent or greater; fig. 15), indicating that significant migration distances were not necessary for known accumulations. However, oil-stained Assessment Units outcrops sourced by the Waltman Shale Member in Fort Union Formation outcrops at Castle Gardens and Signor Two assessment units were defined for the Waltman Ridge (Palacas and others, 1994; Keighin and Flores, 1994) Shale TPS: (1) the Upper Fort Union Sandstones Conventional (fig. 15) indicate migration distances at least on the order of Oil and Gas AU (fig. 5), and (2) the Waltman Fractured Shale 10–15 miles (mi), and may indicate distances exceeding 20 mi Continuous Oil AU (fig. 6), which was not quantitatively (Palacas and others, 1994). Fields producing Waltman-sourced assessed. oil on Madden anticline (Madden, Lost Cabin, and Lysite; fig. 11) might have been charged, at least in part, by vertical migration of oil from mature source rocks at depth, and it is Upper Fort Union Sandstones Conventional Oil likely that faults and fractures associated with the Madden and Gas AU (50350301) structure are conduits for hydrocarbon migration in this area. Traps in known oil accumulations in the Waltman Shale This AU (fig. 5) includes about 1,176,000 acres, and TPS are typically classified as stratigraphic or a combination represents the area where the Waltman Shale Member of stratigraphic and structural. In Haybarn field (fig. 4), provides an effective seal preventing the migration of updip pinchout of deltaic sands (Shotgun Member) in hydrocarbons from deeper sources below the shale into lacustrine shale is considered the primary trapping mechanism reservoirs interbedded with or overlying the shale; thus all (Robertson, 1984). The reservoirs are primarily fine- to petroleum production within the assessment unit is attributed medium-grained arkosic sandstone (noncalcareous) with to a Waltman source. To date, cumulative production from porosities ranging from 18 to 26 percent (average 20 percent), 53 wells within the AU exceeds 2.8 MMBO and 5.8 BCF and permeability of about 7 millidarcies (md), based on one of gas. Productive horizons in wells range from about 1,770 Maximum burial Undiscovered PetroleumResources—Waltman ShaleTotal Petroleum System—WindRiverBasinProvince,Wyoming Present-day transformation Age,million years ago (Ma) Uplift and cooling ratio (in percent) MT 50 40 30 20 15 10 0 Wind River Basin Province 2 ID WY Bighorn 1-5 Dome Shoshone–Arapahoe 6-1
Dome Moneta 1-29 Bonneville 23-1 9 Bighorn 1-5 Boysen Tribal 1-24 Adams OAB 1-17 Adams OAB 1-17 Mobil F33-14-G 18 Dome Moneta 1-29
Mobil F33-14-G 5
Bonneville 23-1 EXPLANATION 12 Timing of oil generation: Waltman Shale Member
Start of oil generation *Dome Shoshone–Arapahoe 6-1 96 Peak oil generation Minor oil generation *Boysen Tribal 1-24 * indicates wells where Waltman Shale Member source rock is not present; timing of oil generation 94 calculated for equivalent stratigraphic horizon at the base of the Shotgun Member 50 40 30 20 15 10 0
Figure 14. Timing of oil generation from source rocks at the base of the Waltman Shale Member of the Fort Union Formation in seven well locations in the Wind River Basin Province, Wyoming. Timing is based on hydrous-pyrolysis (HP) kinetic parameters derived from a Type-II, oil-prone source rock. Vertical dashed line at 15 million years ago represents beginning of major uplift, erosion, and subsequent cooling. The models indicate that oil generation is continuing; however, the rate of these reactions is significantly reduced with negligible generation during the last 15 million years. Start (onset) and peak oil generation reflect transformation ratios of 0.01 and 0.50, respectively (Roberts and 1 others, Chap. 6, this CD-ROM). 0 Assessment of Undiscovered Oil and Gas in the Wind River Basin Province, Wyoming - River Basin Powder oil sourced – ° Casper arch otal Petroleum System boundary T 107 Assessment Unit altman Shale Member altman Shale Bighorn Mountains Oil-stained outcrops from the W W Upper Fort Union Sandstones Conventional Oil and Gas Fort Union Formation outcrops Wind River Basin Province boundary
0.73 TION 0.60 Castle Gardens 0 Castle Gardens Granite Mountains
EXPLANA 4,000
0 2,000 0.73 MA Signor Ridge sawteeth on – Basin ° Bighorn 108 Thrust fault overriding plate Normal fault Thermal maturity (R ) (values in percent) Oil field -4,000
-6,000 -2,000 1.10 0.60
2,000 0 4,000 30 Miles Owl Creek Mountains ) values (in percent) at the base of the Waltman Shale Member of the Fort Union Formation, Wind River Basin ) values (in percent) at the base of Waltman o 15 ° 109 0 Absaroka Mountains
ind River Mountains Province W Wind River Basin WY MT ° Basin Hoback 10 ID 1 Structure contours and estimated thermal maturity (R
° . 5 43 Figure 1 Structure contours modified from Johnson and others (1996a) based on new interpretations of (2005); structure contour interval is Province, Wyoming. maturity contours modified from Johnson and others (1996b). MA, Madden anticline. Fort Union Forma 500 ft and contour values in elevation relative to mean sea level. Thermal (1985). tion outcrops from Green and Drouillard (1994) after Love Christiansen Undiscovered Petroleum Resources—Waltman Shale Total Petroleum System—Wind River Basin Province, Wyoming 1 ft to 5,800 ft, and average about 3,400 to 3,500 ft in depth hydrocarbons might be present in zones of depositional onlap (Wyoming Oil and Gas Conservation Commission, 2005). or erosional truncation within the progradational successions. Input data used in the assessment of undiscovered A comparison of clinoform morphology in the Shotgun resources within the AU are shown in appendix A. Geologic Member with chronostratigraphic models for hydrocarbon information that factored into estimates of the numbers and accumulation in the Sirikit oil field in Thailand (fig. 18) also sizes of undiscovered accumulations included the location might provide some insight into the potential for petroleum and distribution of mature source rocks, the potential for accumulation. In the Sirikit oil field, more than 100 MMBO pathways of migration (updip and vertical migration) from have been produced from reservoirs within the fluvial and mature source rocks into porous sandstone reservoirs, the lacustrine Lan Krabu Formation (Ainsworth and others, 1999). location of structures (folds or faulted areas) that might The best reservoirs are within deposits of fluvio-lacustrine entrap hydrocarbons, and trapping potential related to facies mouth-bar complexes that lie up-depositional dip from variations in vertically and laterally juxtaposed fluvial, lacustrine shale. Down-depositional dip, reservoir quality marginal lacustrine, and lacustrine strata. decreases with the increase in thin-bedded heterolithic strata in Based on structural trends at the base of the Waltman transitional zones adjacent to lacustrine shale (Ainsworth and Shale Member (fig. 7) there seems to be a strong potential for others, 1999). Although described fluvio-lacustrine sequences numerous migration pathways throughout the AU that could in the Sirikit oil field are much smaller in scale than clinoform facilitate the movement of petroleum from the deep basin morphologies in the Shotgun Member (fig. 18), the proven into reservoirs adjacent to and updip from mature Waltman productivity of these depositional sequences in Sirikit might source rocks (fig. 16). This updip migration was probably the be an indication of the potential for petroleum accumulation primary means for charging the more productive fields (Fuller in similar depositional sequences recognized in seismic in Reservoir and Haybarn fields). In fields on Madden anticline the Shotgun Member (figs. 18 and 19). In addition, future (Lost Cabin, Lysite, and Madden fields) vertical fractures or exploration might target higher (updip) positions on the foreset faults may have provided conduits for petroleum migration slopes in anticipation of better quality reservoirs. from mature source rocks underlying productive reservoirs; Figure 20 summarizes the geologic units and timing high angle normal faults have been documented in seismic of major geologic events related to petroleum generation, data near producing areas (for example, Osborn, 2001). migration, and accumulation in the Upper Fort Union A diagram depicting petroleum migration and Sandstones Conventional Oil and Gas AU. The range in accumulation scenarios in the area of Madden anticline is estimates for the number of undiscovered accumulations shown in figure 17. Potential reservoirs might be present in (1) within the AU (appendix A) is based in large part on the marginal lacustrine (shoreface) sandstone units that prograded considerations discussed previously (for example, potential northward and eastward into lacustrine shale, (2) fluvial for undiscovered accumulations in progradational successions sandstones overlying the shoreface sandstones, (3) sandstones and clinoform features) as well as the fact that the AU is or conglomerates within a fan-delta system emanating from largely untested. The minimum and mode estimates are the Owl Creek uplift north of Madden, and (4) sandstones somewhat conservative (1 and 3 undiscovered accumulations, deposited within braided fluvial and braidplain environments respectively) and based primarily on the limited discoveries to in the Shotgun Member overlying the Waltman Shale date, but tempered somewhat at the mode with consideration Member along the axis of the Madden structure (Osborn, for the largely untested nature of the AU. The maximum 2001). Traps might form due to updip pinchout of shoreface estimate of 15 undiscovered accumulations was influenced and fan-delta sandstone bodies into impermeable lacustrine by the strong potential for migration pathways from mature shale, pinchout of discontinuous fluvial sandstone bodies in source rocks in the central basin areas (fig. 16), and the fine-grained floodplain deposits, and fault juxtaposition of presence of abundant progradational successions (clinoform porous sandstones with impermeable lacustrine or floodplain morphologies) that have similar characteristics to the highly (braidplain) shale. productive Sirikit oil field in Thailand (fig. 18) and are widely An additional potential for petroleum accumulation may distributed throughout much of the basin (fig. 19). exist within progradational successions that can be identified The sizes (grown) of the undiscovered accumulations by the presence of clinoform morphologies (foresets or (appendix A) also reflects a high degree of uncertainty, in large downlap surfaces; fig. 18) in seismic lines throughout much part because there are not enough fields in the AU exceeding of the basin (fig. 19). In previous seismic studies of the Fort the USGS minimum (500,000 barrels of oil) to calculate a Union Formation, Ray (1982) and Liro and Pardus (1990) field size (grown) distribution based on past production. Only identified numerous clinoform packages within the Shotgun the Fuller Reservoir field has exceeded the USGS minimum Member and concluded that well-developed or continuous size. Estimated ultimate recoveries (EURs) calculated for reflectors within clinoforms represented the progradation of oil wells in the AU (fig. 21) indicate that the median oil a delta. Ray (1982) also recognized low relief clinoforms production ranges from 20,000 barrels of oil per well (Madden in the transition zone from shoreface deposits to lacustrine and Haybarn fields) to a high of 70,000 barrels of oil per well shale and interpreted these as accretionary profiles on the (Fuller Reservoir field). Future discoveries might require a shoreline of the lake; Ray indicated that potential traps for 10 to 20 well field in order to produce 500,000 barrels, based Assessment of Undiscovered Oil and Gas in the Wind River Basin Province, Wyoming River Basin Powder 0 otal Petroleum System boundary T altman Shale Member and thermal Assessment Unit boundary ° Casper arch 107 altman Shale W Estimated limit of altman Shale altman Shale Member W Upper Fort Union Sandstones Conventional Oil and Gas Area of thick W maturity conducive to petroleum generation Fort Union Formation outcrops Wind River Basin Province boundary Thermal maturity (R ) at the base of W Bighorn Mountains TION Madden anticline area: vertical migration from mature source rocks at depth into sandstone in the Shotgun Member and overlying units
0.60%
0.60% EXPLANA
MA
M
Granite Mountains Castle Gardens 0.73% L sawteeth on – altman Shale Member Basin ° Bighorn H
0.73% Signor Ridge 108 FR altman Shale Member
HR Thrust fault overriding plate Oil-stained sandstone in Fort Union Formation outcrops Field producing oil generated from the W Potential updip migration direction based on structure at the base of W
C 1.10% C Castle Gardens
Owl Creek Mountains altman in this area
0.60% altman Shale present Only thin tongue(s) of W 30 Miles Shale present in this area Only thin tongue(s) of W ° 15 109 0
ind River Mountains Province Absaroka Mountains W Wind River Basin WY MT ° 10 ID 1 Interpreted orientations of petroleum migration pathways from mature source rocks in the Waltman Shale Member of the Fort Union Formation, Waltman Shale Total Shale Total Shale Member of the Fort Union Formation, Waltman Interpreted orientations of petroleum migration pathways from mature source rocks in the Waltman
. 6 ° 43 Figure 1 field; M, Madden field (including Lost Cabin field); FR, Fuller MA, Madden anticline. Oil fields: C, Carvner field; L, Lysite Petroleum System, Wind River Basin Province, Wyoming. outcrops from Green and Drouillard (1994) after Love Christiansen (1985). Reservoir field; and H, Haybarn field. AU, assessment unit. Fort Union Formation Undiscovered PetroleumResources—Waltman ShaleTotal Petroleum System—WindRiverBasinProvince,Wyoming South North
Juxtaposed sandstone and Discontinuous fluvial sandstones shale (lacustrine or floodplain) encased in fine-grained floodplain across faults (floodplain or braidplain) deposit
? ?
Petroleum migration upward through faults and fractures Fan-delta Updip pinchout of fan-delta complex sandstones interbedded with lacustrine shale Base of Waltman Shale Member Updip pinchout of shoreface and R0 = 0.73% Petroleum migration updip marginal lacustrine sandstones through progradational in lacustrine shale sandstone successions Madden anticline
Updip pinchout of fluvial sandstones in floodplain shale and siltstone
EXPLANATION
Fluvial/floodplain deposits Unconformity (queried) Fluvial, marginal lacustrine braided fluvial, braidplain, and fan-delta deposits Petroleum migration pathway Lacustrine shale Fault (offset indicated by arrow) Sandstone or conglomerate Fracture Potential petroleum reservoir
Figure 17. Schematic diagram showing proposed scenarios for petroleum migration and accumulation near Madden anticline in the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit, Waltman Shale Total Petroleum System, Wind River Basin Province, Wyoming. Diagram is not to scale. Ro, thermal maturity based on vitrinite reflectance. Assessment of Undiscovered Oil and Gas in the Wind River Basin Province, Wyoming
A Seismic line 304 Bucy State 21-16 West Section 16, T.37N., R.93W. East G.L. 5,144 feet
0.60
Wind River Formation 0.80 (part)
1.00 WInd River Formation
1.20 UC ? Shotgun Member
1.40 Waltman Shale Member 1.60 (part) Operator: top lower member 1.80 lower unnamed member Fort Union Formation Fort Union Formation
~ 6 mi
Wind River Basin Province
Line 304
Waltman Shale TPS Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit
B Sirikit Oil Field, Phitsanulok Basin, Thailand
Drill Drill hole hole ~ 0.25–0.40 mi Flooding shale (datum)
~ 30–65 feet
EXPLANATION Mouth-bar sandstone–good reservoir Heterolithic strata–moderate reservoir Lacustrine shale
Figure 18. Examples of clinoform morphologies in lacustrine depositional sequences. A, seismic line 304 within the Fort Union Forma- tion (Shotgun and Waltman Shale Members) in the Wind River Basin Province, Wyoming. B, Sirikit oil field, Phitsanulok Basin, Thailand. Interpretations (in part) shown in seismic line 304 are based on Ray (1982); stratigraphic position of the unconformity (UC) separating the Fort Union and Wind River Formations (red dashed line) is questionable; Sirikit oil field example is modified from Ainsworth and others (1999). G.L., ground level; TPS, total petroleum system. Undiscovered Petroleum Resources—Waltman Shale Total Petroleum System—Wind River Basin Province, Wyoming - River Basin Powder otal Petroleum System boundary T altman Shale Member and thermal
° Casper arch Assessment Unit boundary 107 altman Shale W Estimated limit of altman Shale W Area of thick W maturity conducive to petroleum generation Fort Union Formation outcrops Clinoform set Upper Fort Union Sandstones Conventional Oil and Gas Bighorn Mountains delta TION Prograding fan
MA M Granite Mountains EXPLANA Prograding fluvial and deltaic systems Castle Gardens L 0 Signor Ridge Basin ° Bighorn H Line 304 sawteeth on
0.60% – altman Shale Member 108 FR
HR C altman Shale Member Thrust fault overriding plate Oil-stained sandstone in Fort Union Formation outcrops Field producing oil generated from the W Thermal maturity (R ) at the base of W Wind River Basin Province boundary fluvial and Prograding C deltaic systems
0.60%
Owl Creek Mountains Castle Gardens 30 Miles ° 109 15 0
ind River Mountains Province Absaroka Mountains W Wind River Basin WY MT ° 10 ID 1 Locations of clinoform morphologies expressed in seismic lines in the Wind River Basin Province, Wyoming. Bold arrows indicate generalized directions of progra the Wind River Basin Province, Wyoming. Locations of clinoform morphologies expressed in seismic lines °
. 9 43 Figure 1 in the case of fan-delta system, arrow orientation is based on correlations geophysical logs dation based on apparent dip orientations of foresets in seismic lines or, field; C, Carvner FR, Fuller Reservoir and H, Haybarn field. field (including Lost Cabin field; L, Lysite from oil and gas wells. MA, Madden anticline. Oil fields: M, Assessment of Undiscovered Oil and Gas in the Wind River Basin Province, Wyoming
250 200 150 100 75 70 60 50 40 30 20 10 0 Geologic MESOZOIC CENOZOIC Time Scale TR JURASSIC CRETACEOUS TERTIARY QUAT. Petroleum E.M. L. E. M. L. E. L. PALEO. EOCENE OLIG. MIOCENE P1 P2 Fort Union Formation (part) and Wind River Formation ROCK UNIT Waltman Shale Member (Fort Union Formation) SOURCE ROCK Fort Union Formation (part): fluvial, fan-delta, and marginal lacustrine (deltaic) sandstone; Wind River Formation (part): fluvial sandstone RESERVOIR ROCK Floodplain shale/mudstone interbeds Fort Union and Wind River Formations Lacustrine shale (Waltman Shale Member) SEAL ROCK Fort Union (part) and Wind River Formations OVERBURDEN ROCK Structural and stratigraphic traps TRAP FORMATION Onset oil at base of Waltman Uplift and cooling; little or no petroleum TION TION TION between 49 and 20 Ma generation GENERA MIGRA ACCUMULA Central basin Deep basin areas Madden west of Madden anticline anticline 20 Ma 49 Ma COMMENTS Peak oil generation in deep basin (31–26 Ma)
Figure 20. Events chart showing interpreted timing of elements and processes related to hydrocarbon (oil) generation and accumula- tion in the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit (50350301), Waltman Shale Total Petroleum System, Wind River Basin Province, Wyoming. Onset of oil generation and timing of peak oil generation are from Roberts and others (Chap. 6, this CD–ROM). Peak generation refers to maximum rate of oil generation (transformation ratio 0.50). TR., Triassic; E., Early; M., Middle; L., Late; Paleo., Paleocene; Olig., Oligocene; P1, Pliocene; P2, Pleistocene; Quat., Quaternary. Events chart format modified from Magoon and Dow (1994).
ALL WELLS–ALL FIELDS FULLER RESERVOIR FIELD MEDIAN=50,000 BARRELS MEDIAN=70,000 BARRELS (N=42) (N=28)
1,000 1,000
100 100
10 10 (THOUSANDBARRELS) (THOUSANDBARRELS)
ESTIMATEDULTIMATE RECOVERY 1 ESTIMATEDULTIMATE RECOVERY 1 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 PERCENTAGE OF SAMPLE PERCENTAGE OF SAMPLE
HAYBARN FIELD MADDEN FIELD MEDIAN=20,000 BARRELS MEDIAN=20,000 BARRELS (N=8) (N=6) 1,000 100
100
10
10 (THOUSANDBARRELS) (THOUSANDBARRELS) ESTIMATEDULTIMATE RECOVERY ESTIMATEDULTIMATE RECOVERY 1 1 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 PERCENTAGE OF SAMPLE PERCENTAGE OF SAMPLE Figure 21. Estimated ultimate recoveries calculated for wells producing oil sourced by the Waltman Shale Member in the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit, Waltman Shale Total Petroleum System, Wind River Basin Province, Wyoming. Madden field includes data from Madden, Lost Cabin, and Lysite fields. Graphs are based on production data from IHS Energy Group (2005). Undiscovered Petroleum Resources—Waltman Shale Total Petroleum System—Wind River Basin Province, Wyoming on current EURs. The minimum and median estimates for petroleum trapped in the manner described above. However, sizes (grown) of undiscovered accumulations were strongly similar sonic velocity decreases were observed in essentially influenced by the limited cumulative production from known all wells investigated in this study that penetrated the shale in fields. The maximum estimate of 15 MMBO far exceeds the the Waltman Fractured Shale Continuous Oil AU, indicating size of the largest field discovered to date (Fuller Reservoir that overpressuring conditions may involve a significantly field; ~ 2.3 MMBO). However, this maximum is significantly larger area than previously thought. On the other hand, the smaller than the analog Sirikit oil field (Thailand), which has anomaly might be due to some other phenomenon, such as the produced more than 100 MMBO. velocity decrease being in response to the organic richness of the shale (Passey and others, 1990); however, this possibility was not investigated as part of this study. Waltman Fractured Shale Continuous Oil AU (50350361)
The Waltman Fractured Shale Continuous Oil AU (fig. Assessment of Undiscovered 6) encompasses about 745,000 acres, and includes areas Resources–Summary of Results within the Upper Fort Union Sandstones Conventional Oil and Gas AU where thermal maturity at the base of the Waltman Shale Member is at an Ro level of 0.60 percent or greater. Results of the assessment of undiscovered, technically This assessment unit was defined based on interpretations in recoverable resources in the Upper Fort Union Sandstones Jorjorian and others (1989) and Katz and Liro (1993) who Conventional Oil and Gas AU (50350301) are shown in described the potential for hydrocarbon (oil) saturation and table 1. Mean estimates of the total undiscovered petroleum entrapment within the Waltman member in areas near Madden resources AU indicate the potential for 12 MMBO, 24 BCF of anticline. Jorjorian and others (1989) recognized decreasing gas, and 1.4 million barrels of natural gas liquids. sonic velocities in the shale relative to overlying and Numerous positive aspects of the Waltman Shale TPS underlying units (fig. 9) and suggested that this sonic anomaly favor the presence of undiscovered resources in conventional resulted from overpressure due to generation of oil and an accumulations. The Waltman Shale Member is a good source inability for the oil to be expelled from the shale because of rock with TOCs as high as 6.2 percent and averaging about the lack of porous conduits for hydrocarbon migration. In 2.7 percent (Katz and Liro, 1993). Thermal maturity values following this concept, the authors defined the assessment unit at the base of the shale are well within the oil window (equal to include those areas within the Upper Fort Union Sandstones to or greater than 0.65 percent) and may exceed 1.10 percent Conventional Oil and Gas AU in which thermal maturity Ro in untested, deep basin areas (Johnson and others, 1996b). at the base of the Waltman Shale is mostly within the oil The petroleum system has a history of production from generation window (Ro of 0.65 percent or greater). However, marginal lacustrine (deltaic) and fluvial sandstone reservoirs, because of limited thermal maturity data, the south boundary and numerous progradational successions within the Shotgun of the AU was extended to the 0.60 percent isoreflectance Member place porous sandstone in contact with lacustrine (Ro) line as defined by Johnson and others (1996b) (fig. 6). shale source rocks; well-developed clinoforms within these This AU was not quantitatively assessed because current data successions might provide conduits for oil migration up are insufficient for proving or disproving the presence of depositional dip into sandstone reservoirs. In addition, there
Table 1. Waltman Shale Total Petroleum System assessment results. [MMBO, million barrels of oil; BCFG, billion cubic feet of gas; MBNGL, thousand 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 represents 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. Gray shade indicates not applicable]
Total Petroleum Systems Total undiscovered resources (TPS) Field Oil (MMBO) Gas (BCFG) NGL (MBNGL) and Assessment Units (AU) type Waltman ShaleTPS Upper Fort Union Sandstones Oil 3 11 25 12 6 21 54 24 330 1,250 3,370 1,470 Conventional Oil and Gas AU 50350301 Gas 0.00 0.00 0.00 0.00 0 0 0 0 0 0 0 0
Waltman Fractured Shale Continuous Oil AU 50350361 Oil Not quantitatively assessed Total Undiscovered Oil and Gas Resources 3 11 25 12 6 21 54 24 330 1,250 3,370 1,470 Assessment of Undiscovered Oil and Gas in the Wind River Basin Province, Wyoming also are large areas in the basin, particularly in the deep basin, Blackstone, Jr., D.L., 1990, Rocky Mountain foreland struc- where the Shotgun Member might not have been adequately ture exemplified by the Owl Creek Mountains, Bridger tested. Range, and Casper arch, central Wyoming, in Specht, R.W., However, not all characteristics of the TPS are necessarily ed., Wyoming Sedimentation and Tectonics: Wyoming positive for undiscovered petroleum accumulations. Geological Association Guidebook, 41st Field Conference, Transformation ratios based on hydrous pyrolysis kinetics of p. 151–166, 2 pls. a Type-II kerogen calculated at several locations throughout Brown, R.G., and Shannon, L.T., 1989, Madden (Greater)– the basin are generally less than 20 percent; peak generation Long Butte, in Cardinal, D.F., Miller, Terry, Trotter, J.F., (transformation ratio of 0.50) may only have occurred in the and Stewart, W.W., eds., Wyoming Oil and Gas Fields deep basin west of Madden anticline. These data indicate Symposium—Bighorn and Wind River Basins: Casper, that the Waltman Shale Member as a source rock may not Wyoming, Wyoming Geological Association, p. 293–295. have reached its full potential for hydrocarbon generation and expulsion in much of the basin. Additionally, although Dunleavy, J.M., and Gilbertson, R.L., 1986, Madden anti- progradational successions in areas south and west of mature cline—Growing giant, in Noll, J.H., and Doyle, K.M., eds., Waltman source rocks might provide effective conduits for Rocky Mountain oil and gas fields: Wyoming Geological petroleum migration, oil-stained outcrops at Castle Gardens Asociation, 1986 Symposium, Casper, Wyoming, p. 107- and Signor Ridge (Palacas and others (1994) also might 157. signal the potential for leakage of hydrocarbons out of the system. This leakage could be due to factors such as the lack Evans, J.G., 1989, Haybarn, in Cardinal, D.F., Miller, Terry, of adequate seal or trap development, or oil generation and Trotter, J.F., and Stewart, W.W., eds., Wyoming Oil and expulsion that preceded trap formation. In addition, in the past Gas Fields Symposium—Bighorn and Wind River Basins: 20–30 years, only one field (Fuller Reservoir) has produced Casper, Wyoming, Wyoming Geological Association, enough oil to exceed the USGS minimum field size of 500,000 p. 228–229. barrels. Flemings, P.B., and Nelson, S.N., 1991, Paleogeographic evo- In summary, data indicate that the Waltman Shale TPS lution of latest Cretaceous and Paleocene Wind River Basin: does have the potential for undiscovered oil accumulations The Mountain Geologist, Volume 28, No. 2/3, p. 37–52. exceeding 500,000 barrels, although fields might tend to be small or moderate in size. Future exploration might target Flores, R.M., Roberts, S.B., and Perry, W.J., Jr., 1994, Paleo- deeper horizons where thermal maturity of the Waltman Shale cene paleogeography of the Wind River, Bighorn, and Member exceeds 0.70 percent, and progradational successions Powder River Basins, Wyoming, in Flores, R.M., Mehring, (clinoform packages) in close contact with lacustrine shale K.T., Jones, R.W., and Beck, T.L., eds., Organics and the provide conduits for migration into marginal lacustrine, Rockies Field Guide: Wyoming State Geological Survey, deltaic, and fluvial reservoir sandstones. Public Information Circular No. 53, p. 1–16. Green, G.N., and Drouillard, P.H., 1994, The digital geologic map of Wyoming in ARC/INFO format: U.S. Geological Acknowledgments Survey Open-File Report 94–0425, scale 1:500,000. Gries, Robbie, 1983, North-south compression of Rocky The authors thank Doug Nichols (U.S. Geological Mountain foreland structures, in Lowell, J.D., and Gries, Survey [USGS]), Steve Condon (USGS), Paul Lillis (USGS), Robbie, eds., Rocky Mountain foreland basins and uplifts: and Dick Keefer (USGS) for their thoughtful reviews. Their Rocky Mountain Association of Geologists Guidebook, comments and suggestions greatly improved the organization October 3, 1983, Symposium, Steamboat Springs, Colo- and clarity of the manuscript. rado, p. 9–32. Hollis, S.H., 2001, Upper Fort Union (Paleocene) deposition on the north flank of Madden anticline, Wind River Basin, References Cited Wyoming, in Stilwell, D.P., ed., Wyoming gas resources and technology: Wyoming Geological Association Guidebook, Ainsworth, R. Bruce, Sanlung, Montree, and Duivenvoorden, 52nd Field Conference, p. 194. S. Theo C., 1999, Correlation techniques, perforation strate- gies, and recovery factors—An integrated 3-D reservoir Hunt, J.M., 1996, Petroleum geochemistry and geology (2nd modeling study, Sirikit Field, Thailand: American Asso- edition): W.H. Freeman and Company, New York, New ciation of Petroleum Geologists Bulletin, v. 83, no. 10, p. York, United States, 743 p. 1535–1551. Undiscovered Petroleum Resources—Waltman Shale Total Petroleum System—Wind River Basin Province, Wyoming
IHS Energy Group, 2005, [includes data current as of Decem- Keefer, W.R., 1970, Structural geology of the Wind River ber, 2000] PI/Dwights Plus U.S. Production Data: Engle- Basin, Wyoming: U.S. Geological Survey Professional wood, Colo., database available from IHS Energy Group, Paper 495-D, 35 p. 15 Inverness Way East, D205, Englewood, Colorado 80112, U.S.A. Keefer, W.R., 1997, Stratigraphy and correlation of Cretaceous and Paleocene rocks, northern Wind River Basin, Wyoming: Johnson, R.C., and Rice, D.D., 1993, Variations in composi- U.S. Geological Survey Oil and Gas Investigations Chart tion and origins of gases from coal bed and conventional OC–146–A, 2 sheets. reservoirs, Wind River Basin, Wyoming, in Keefer, W.R., Metzger, W.J., and Godwin, L.H., eds., Wyoming Geologi- Keefer, W.R., and Johnson, R.C., 1997, Stratigraphy and cor- cal Association Special Symposium on Oil and Gas and relation of Cretaceous and Paleocene rocks, west-central Other Resources of the Wind River Basin, Wyoming, 1993: Wind River Basin, Wyoming: U.S. Geological Survey Oil Wyoming Geological Association, Casper, Wyoming, and Gas Investigations Chart OC–146–B, 2 sheets. p. 319–335. Keighin, C.W., and Flores, R.M., 1994, Characteristics of Johnson, R.C., Finn, T.M., Keefer, W.R., and Szmajter, R.J., oil-saturated fluvial channel sandstone reservoirs, Paleo- 1996a, Geology of Upper Cretaceous and Paleocene gas- cene upper Fort Union Formation, south-central Wind River bearing rocks, Wind River Basin, Wyoming: U.S. Geologi- Basin, Wyoming, in Flores, R.M., Mehring, K.T., Jones, cal Survey Open-File Report 96-090, 120 p. R.W., and Beck, T.L., eds., Organics and the Rockies Field Guide: Wyoming State Geological Survey, Public Informa- Johnson, R.C., Finn, T.M., Crovelli, R.A., and Balay, R.H., tion Circular No. 53, p. 99–108. 1996b, An assessment of in-place gas resources in low-per- meability Upper Cretaceous and Lower Tertiary sandstone Lewan, M.D., 1997, Experiments on the role of water in petro- reservoirs, Wind River Basin, Wyoming: U.S. Geological leum formation: Geochimica et Cosmochimica Acta, v. 61, Survey Open-File Report 96-264, 204 p. p. 3691–3723. Johnson, R.C., Roberts, S.B., and Nichols, D.J., 2005, New Liro, L.M., 1993, Sequence stratigraphy of a lacustrine sys- stratigraphic and palynologic studies of the Paleocene tem: Upper Fort Union Formation (Paleocene), Wind River Waltman Shale Member, Wind River Basin, Wyoming— Basin, Wyoming, USA, in Weimer, Paul, and Posamentier, Implications for basin depositional environments [abs.]: Henry, eds., Siliciclastic Sequence Stratigraphy—Recent American Association of Petroleum Geologists, Rocky Developments and Applications: American Association of Mountain Section Jackson Hole Meeting, Jackson, Wyo- Petroleum Geologists Memoir 58, p. 317–333. ming, Abstracts with Programs, p. 34. Liro, L.M., and Pardus, Y.C., 1990, Seismic facies analysis Jorjorian, Thomas, Liro, L.M., and Katz, B.J., 1989, Geo- of fluvial-deltaic lacustrine systems—Upper Fort Union chemical and well-log investigation of an actively generat- Formation (Paleocene), Wind River Basin, Wyoming, in ing source rock sequence—Waltman Shale, Wind River Katz, B.J., ed., Lacustrine Basin Exploration—Case Studies Basin, Wyoming [abs.]: American Association of Petroleum and Modern Analogs: American Association of Petroleum Geologists Bulletin, v. 73, no. 9, p. 1162. Geologists Memoir 50, p. 225–242. Katz, B.J., and Liro, L.M., 1993, The Waltman Shale Member, Love, J.D., Christiansen, A.C., and Ver Ploeg, A.J., compilers, Fort Union Formation, Wind River Basin—A Paleocene 1993, Stratigraphic chart showing Phanerozoic nomencla- clastic lacustrine source system, in Keefer, W.R., Metzger, ture for the state of Wyoming: Wyoming State Geological W.J., and Godwin, L.H., eds., Wyoming Geological Survey Map Series no. 41, 1 pl. Association Special Symposium on Oil and Gas and Other Love, J.D., and Christiansen, A.C., 1985, Geologic Map of Rresources of the Wind River Basin, Wyoming, 1993: Wyoming: U.S. Geological Survey and Wyoming State Wyoming Geological Association, Casper, Wyoming, Geological Survey, scale 1:500,000. p. 163–174. Magoon, L.B., and Dow, W.G., 1994, The petroleum system, Keefer, W.R., 1961, Waltman Shale and Shotgun Members in Magoon, L.B., and Dow, W.G., eds., The petroleum of Fort Union Formation (Paleocene) in Wind River Basin, system—From source to trap: American Association of Wyoming: American Association of Petroleum Geologists Petroleum Geologists, AAPG Memoir 60, p. 3–24. Bulletin, v. 45, no. 8, p. 1310–1323. Keefer, W.R., 1965, Stratigraphy and geologic history of the uppermost Cretaceous, Paleocene, and lower Eocene rocks in the Wind River Basin, Wyoming: U.S. Geological Survey Professional Paper 495-A, 77 p. 0 Assessment of Undiscovered Oil and Gas in the Wind River Basin Province, Wyoming
Nichols, D.J., 1994, Palynostratigraphic correlation of Paleo- Palmer, A.R., and Geissman, John, comps., 1999, Geologic cene rocks in the Wind River, Bighorn, and Powder River time scale, Product Code CTS004, Geological Society of Basins, Wyoming, in Flores, R.M., Mehring, K.T., Jones, America. R.W., and Beck, T.L., eds., Organics and the Rockies Field Guide: Wyoming Geological Survey, Public Information Passey, Q.R., Creaney, Stephen, Kulla, J.B., Moretti, F.J., and Circular No. 33, p. 17–29. Stroud, J.D., 1990, A practical model for organic richness from porosity and resistivity logs: American Association of Nuccio, V.F., and Finn, T.M., 1994, Structural and thermal Petroleum Geologists Bulletin, v. 74, no. 12, p. 1777-1794. history of the Paleocene Fort Union Formation, central and eastern Wind River Basin, with emphasis on petroleum Phillips, S.T., 1983, Tectonic influence on sedimentation, potential of the Waltman Shale Member, in Flores, R.M., Waltman Member, Fort Union Formation, Wind River Mehring, K.T., Jones, R.W., and Beck, T.L., eds., Organics Basin, Wyoming, in Lowell, J.D., and Gries, Robbie, eds., and the Rockies Field Guide: Wyoming State Geological Rocky Mountain Foreland Basins and Uplifts: Rocky Survey, Public Information Circular No. 33, p. 53–68. Mountain Association of Geologists, Denver, Colorado, p. 149–160. Nuccio, V.F., Finn, T.M., and Johnson, R.C., 1996, Thermal maturity data used for the assessment of gas resources in Ray, R.R., 1982, Seismic stratigraphic interpretation of the the Wind River Basin, Wyoming: U.S. Geological Survey Fort Union Formation, western Wind River Basin—example Open-File Report 96-064, 57 p. of subtle trap exploration in a nonmarine sequence, in Hal- bouty, M.T., ed., The deliberate search for the subtle trap: Osborn, Amy, 2001, Surface and subsurface geology of the American Association of Petroleum Geologists, Memoir 32, Shotgun Member of the Fort Union Formation (Paleocene), p.169–180. Madden field, Wyoming: Golden, Colorado, Colorado School of Mines, master’s thesis, Golden, Colorado, 167 p. Robertson, R.D., 1984, Haybarn Field, Fremont County, Wyo- ming—An upper Fort Union (Paleocene) stratigraphic trap: Palacas, J.G., Flores, R.M., Keighin, C.W., and Anders, D.E., The Mountain Geologist, v. 21, no. 2, p. 47–56. 1994, Origin of oil in oil-stained sandstones in the upper part of the Fort Union Formation (Paleocene), Castle Gar- Specht, R.W., 1989, Fuller Reservoir, in Cardinal, D.F., dens and Signor Ridge areas, Wind River Basin, Wyoming, Miller, Terry, Trotter, J.F., and Stewart, W.W., eds., Wyo- in Flores, R.M., Mehring, K.T., Jones, R.W., and Beck, T.L., ming Oil and Gas Fields Symposium—Bighorn and Wind eds., Organics and the Rockies Field Guide: Wyoming State River Basins: Wyoming Geological Association, Casper, Geological Survey, Public Information Circular No. 33, p. 179–181. p. 83–97. Wyoming Oil and Gas Conservation Commission accessed March 1, 2005, http://wogcc.state.wy.us Undiscovered Petroleum Resources—Waltman Shale Total Petroleum System—Wind River Basin Province, Wyoming 1
Appendix A. Basic input data (Seventh Approximation data form [part]) used in estimates of the numbers and sizes of undiscovered petroleum accumulations in the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit (50350301) in the Walt- man Shale Total Petroleum System, Wind River Basin Province, Wyoming. Complete data input form is in Klett and Lee, Chap. 12, this CD–ROM.
IDENTIFICATION INFORMATION Assessment Geologist: S.B. Roberts Date: 9/21/2005 Region: North America Number: 5 Province: Wind River Basin Number: 5035 Total Petroleum System: Waltman Shale Number: 503503 Assessment Unit: Upper Fort Union Sandstones Conventional Oil and Gas Number: 50350301 Based on Data as of: IHS Energy Group (2005), Wyoming Oil and Gas Conservation Commission (2005) Notes from Assessor: Uinta Green River Conventional Oil and Gas Assessment Unit (50200501) as partial analog.
CHARACTERISTICS OF ASSESSMENT UNIT
Oil (<20,000 cfg/bo overall) or Gas (>20,000 cfg/bo overall): Oil
What is the minimum accumulation size? 0.5 mmboe grown (the smallest accumulation that has potential to be added to reserves)
No. of discovered accumulations exceeding minimum size: Oil: 1 Gas: Established (>13 accums.) Frontier (1-13 accums.) X Hypothetical (no accums.)
Median size (grown) of discovered oil accumulations (mmbo): 1st 3rd 2nd 3rd 3rd 3rd Median size (grown) of discovered gas accumulations (bcfg): 1st 3rd 2nd 3rd 3rd 3rd
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
UNDISCOVERED ACCUMULATIONS No. of Undiscovered Accumulations: How many undiscovered accums. exist that are > min. size?: (uncertainty of fixed but unknown values)
Oil Accumulations: minimum (>0) 1 mode 3 maximum 15 Gas Accumulations: minimum (>0) mode maximum
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): minimum 0.5 median 1.5 maximum 15 Gas in Gas Accumulations (bcfg): minimum median maximum Assessment of Undiscovered Oil and Gas in the Wind River Basin Province, Wyoming
Appendix A. Basic input data (Seventh Approximation data form [part]) used in estimates of the numbers and sizes of undiscovered petroleum accumulations in the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit (50350301) in the Walt- man Shale Total Petroleum System, Wind River Basin Province, Wyoming. Complete data input form is in Klett and Lee, Chap. 12, this CD–ROM.—Continued
Assessment Unit (name, no.) Upper Fort Union Sandstones Conventional Oil and Gas, 50350301
AVERAGE RATIOS FOR UNDISCOVERED ACCUMS., TO ASSESS COPRODUCTS (uncertainty of fixed but unknown values) Oil Accumulations: minimum mode maximum Gas/oil ratio (cfg/bo) 1000 2000 3000 NGL/gas ratio (bngl/mmcfg) 30 60 90
Gas Accumulations: minimum mode maximum Liquids/gas ratio (bliq/mmcfg) Oil/gas ratio (bo/mmcfg)
SELECTED ANCILLARY DATA FOR UNDISCOVERED ACCUMULATIONS (variations in the properties of undiscovered accumulations) Oil Accumulations: minimum mode maximum API gravity (degrees) 30 45 55 Sulfur content of oil (%) 0.05 0.15 0.5 Depth (m) of water (if applicable)
minimum F75 mode F25 maximum Drilling Depth (m) 600 1500 2000 2100 2800
Gas Accumulations: minimum mode maximum Inert gas content (%)
CO2 content (%) Hydrogen-sulfide content (%) Depth (m) of water (if applicable)
minimum F75 mode F25 maximum Drilling Depth (m)
Volume Title Page