U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2018–3001

April 2018

National and Global Petroleum Assessment

Assessment of Continuous Gas Resources in the Phosphoria Formation 

of the Wyoming Thrust Belt Province, Wyoming, Idaho, and Utah, 2017

Using a geology-based assessment methodology, the U.S. Geological Survey estimated mean undiscovered, technically recoverable resources 

of 198 billion cubic feet of continuous gas in the Phosphoria Formation of the Wyoming Thrust Belt Province, Wyoming, Idaho, and Utah.

Introduction

The U.S. Geological Survey (USGS) quantitatively assessed 

the potential for undiscovered, technically recoverable continuous 

gas resources in shales of the Lower Permian Phosphoria Formation 

within the Wyoming Thrust Belt Province (fig. 1). The Wyoming Thrust 

Belt developed by east-directed compression associated with steeply 

dipping subduction during the latest Jurassic to Late Cretaceous Sevier 

Orogeny (Lamerson, 1982; Webel, 1987). Compression resulted in a 

series of stacked thrust sheets that are progressively younger to the east. 

The major thrusts in the Wyoming Thrust Belt Province are the ParisWillard, Meade, Crawford, Absaroka, Hogsback-Darby, and Prospect 

(fig. 1). The purpose of this assessment is to estimate potentially 

recoverable shale-gas resources remaining within Phosphoria 

Formation shales following structural deformation.

Total Petroleum System and Assessment Unit

The USGS defined the Phosphoria Total Petroleum 

System (TPS) and the Phosphoria Shale Gas Assessment 

Unit (AU) within this TPS. The Phosphoria TPS includes 

petroleum generated from organic-rich, Lower Permian 

Phosphoria Formation shales, specifically the Meade 

Peak Member and Retort Tongue. Organic-rich shales 

of the Phosphoria Formation contain marine Type IIS 

organic matter (Lillis and Selby, 2013) and have total 

organic carbon content averaging 4 weight percent and 

reaching a maximum of 13 weight percent (Claypool 

and others, 1978). Organic-rich shales of the Meade 

Peak Member are up to 60 meters thick, and the Retort 

Tongue is up to 30 meters thick (Maughan, 1984). 

Phosphoria Formation shales are largely in the drygas to postmature zone in terms of thermal maturity 

(Edman and Surdam, 1984; Burtner and Nigrini, 1994). 

In conventional accumulations in the Wyoming Thrust 

Belt Province, Phosphoria-sourced condensate is known 

from the Tip Top, Dry Piney, and Hogsback Fields 

(Edman and Cook, 1992). Gas is known to be present 

in the Phosphoria Formation at the Cave Creek (Utah), 

Whitney Canyon-Carter Creek (Wyoming), Yellow Creek 

(Wyoming), and Thomas Canyon (Wyoming) Fields 

(Ver Ploeg and De Bruin, 1982).

The assessment input data are summarized 

in table 1. Well drainage areas, success ratios, and 

estimated ultimate recoveries are taken from U.S. shalegas analogs.

Geologic Model for Assessment

Organic-rich shales of the Lower Permian Phosphoria Formation are interpreted to have reached thermal 

maturity for oil generation through burial by Mesozoic 

sediments prior to the formation of most thrust structures related to the 

Sevier Orogeny (Warner, 1982; Burtner and Nigrini, 1994). Much of the 

oil from the Phosphoria Formation was generated prior to thrust development and migrated eastward into structural traps in what are now the 

Laramide basins in Wyoming, Montana, and Colorado (Sheldon, 1967; 

Lillis and Selby, 2013). Following migration, any oil retained within 

the Phosphoria Formation shales in the Wyoming Thrust Belt Province 

would have cracked to gas because of deeper burial from progressive 

thrust loading throughout the Sevier and Laramide deformations. Thrust 

loading has placed the Phosphoria Formation shales in the Wyoming 

Thrust Belt Province within the thermal window for dry gas or postmature for gas generation (Edman and Surdam, 1984). Gas in these 

Phosphoria Formation shales may have high percentages of hydrogen 

sulfide. There is significant geologic uncertainty on the retention of 

oil in the Phosphoria Formation shales following migration and on the 

retention of gas within the shales during thrust displacement.

Figure 1. Map showing the location of the Phosphoria Shale Gas Assessment 

Unit (AU) in the Wyoming Thrust Belt Province, Wyoming, Idaho, and Utah.

GREAT

 SALT 

 LAKE

EASTERN

GREAT

BASIN

PROVINCE

SOUTHWESTERN

WYOMING PROVINCE

WIND RIVER

BASIN

PROVINCE

IDAHO-SNAKE

RIVER

DOWNWARP

PROVINCE

UINTA-PICEANCE

BASIN PROVINCE

BIGHORN BASIN

PROVINCE

43°

42°

41°

Base map from U.S. Department of the Interior National Park Service

EXPLANATION

Phosphoria Shale Gas AU

Province boundary

Thrust faults

PARIS-WILLARD

THRUST FAULTS

MEADE

THRUST

FAULT

PROSPECT

THRUST

FAULT

HOGSBACK-DARBY

THRUST FAULTS

ABSAROKA

THRUST

 FAULT

CRAWFORD

THRUST

FAULT

IDAHO

UTAH COLORADO

WYOMING

NEVADA

MONTANA

Map

area

WYOMING

THRUST BELT

PROVINCE

–114° –113° –112°

UTAH

NEVADA

IDAHO

WYOMING

COLORADO

SALT LAKE 

CITY

Pocatello

Green River

–111° –110° –109° –108°

Tip Top Field

Hogsback Field

Dry Piney Field

0 25 50 KILOMETERS

0 25 50 MILES

Hogback

Ridge

Field

Whitney

Canyon-Carter

Creek Field

Thomas Canyon

Field

Yellow Creek Field

Cave Creek Field
ISSN 2327-6916 (print) 

Phosphoria Formation Assessment Team

Christopher J. Schenk, Tracey J. Mercier, Marilyn E. Tennyson, Cheryl A. Woodall, Thomas M. Finn, Janet K. Pitman, Stephanie B. Gaswirth, 

Kristen R. Marra, Phuong A. Le, Timothy R. Klett, and Heidi M. Leathers-Miller

For More Information

Assessment results are also available at the USGS Energy Resources Program website at https://energy.usgs.gov.

ISSN 2327-6932 (online) https://doi.org/10.3133/fs20183001

References Cited

Burtner, R.L.; and Nigrini, Andrew, 1994, Thermochronology of the 

Idaho–Wyoming Thrust Belt during the Sevier Orogeny—A new, 

calibrated, multiprocess thermal model: American Association of 

Petroleum Geologists Bulletin, v. 78, no. 10, p. 1586–1612.

Claypool, G.E., Love, A.H., and Maughan, E.K., 1978, Organic geochemistry, incipient metamorphism, and oil generation in Black shale 

members of Phosphoria Formation, western interior United States: 

American Association of Petroleum Geologists Bulletin, v. 62, no. 1, 

p. 98–120.

Edman, J.D., and Surdam, R.C., 1984, Influence of overthrusting on 

maturation of hydrocarbons in Phosphoria Formation, Wyoming–

Idaho–Utah Overthrust Belt: American Association of Petroleum 

Geologists Bulletin, v. 68, no. 11, p. 1803–1817.

Edman, J.D.; and Cook, Lance, 1992, Tip Top field—U.S.A., 

Wyoming–Utah–Idaho Overthrust Belt, Wyoming, in Beaumont, 

E.A., and Foster, N.H., comps., Structural traps VII: Tulsa, Okla., 

American Association of Petroleum Geologists, Treatise of Petroleum Geology, Atlas of Oil and Gas Fields, p. 1–27.

Lamerson, P.R., 1982, The Fossil basin and its relationship to the 

Absaroka thrust system, Wyoming and Utah, in Powers, R.B., ed., 

Geologic studies of the Cordilleran Thrust Belt, volume I: Denver, 

Colo., Rocky Mountain Association of Geologists, p. 279–340.

Table 1. Key input data for one continuous assessment unit in the Phosphoria Formation, 

Wyoming Thrust Belt Province, Wyoming, Idaho, and Utah.

[AU, assessment unit; %, percent; EUR, estimated ultimate recovery per well; BCFG, billion cubic feet of 

gas. Well drainage area, success ratio, and EUR are from U.S. shale-gas analogs. The average EUR input 

is the minimum, median, maximum, and calculated mean. Shading indicates not applicable]

Assessment input data—

Continuous AU

Phosphoria Shale Gas AU

Minimum Mode Maximum Calculated

mean

Potential production area of AU (acres) 1,000 2,000,000 8,000,000 3,333,667

Average drainage area of wells (acres) 80 120 200 133

Success ratio (%) 5 15 35 18

Average EUR (BCFG) 0.04 0.07 0.1 0.071

AU probability 0.6

Table 2. Results for one continuous assessment unit in the Phosphoria Formation, Wyoming Thrust Belt Province, Wyoming, Idaho, and Utah.

[AU, assessment unit; BCFG, billion cubic feet of gas; NGL, natural gas liquids; MMBNGL, million barrels of natural gas liquids. Results shown are fully risked 

estimates. For gas accumulations, all liquids are included in the NGL 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. Shading indicates not applicable]

Total petroleum system and assessment unit (AU) AU

probability

Accumulation

type

Total undiscovered resources

Gas (BCFG) NGL (MMBNGL)

F95 F50 F5 Mean F95 F50 F5 Mean

Phosphoria Total Petroleum System

Phosphoria Shale Gas AU 0.6 Gas 0 130 669 198 0 1 7 2

Total undiscovered continuous resources 0 130 669 198 0 1 7 2

Lillis, P.G.; and Selby, David, 2013, Evaluation of the rhenium-osmium 

geochronometer in the Phosphoria petroleum system, Bighorn Basin 

of Wyoming and Montana, USA: Geochimica et Cosmochimica 

Acta, v. 118, p. 312–330.

Maughan, E.K., 1984, Geologic setting and some geochemistry of 

petroleum source rocks in the Permian Phosphoria Formation, in

Woodward, Jane; Meissner, F.F.; and Clayton, J.L., eds., Hydrocarbon source rocks of the Greater Rocky Mountain Region: Denver, 

Colo., Rocky Mountain Association of Geologists, p. 281–294.

Sheldon, R.P., 1967, Long-distance migration of oil in Wyoming: Rocky 

Mountain Association of Geologists, The Mountain Geologist, v. 4, 

p. 53–65.

Ver Ploeg, A.J., and De Bruin, R.H., 1982, The search for oil and gas 

in the Idaho–Wyoming–Utah salient of the overthrust belt: Laramie, 

Wyo., Geological Survey of Wyoming, Report of Investigations 

No. 21, 108 p., 2 pls., scale 1:316,800.

Warner, M.A., 1982, Source and time of generation of hydrocarbons in 

the Fossil Basin, western Wyoming Thrust Belt, in Powers, R.B., ed., 

Geologic studies of the Cordilleran Thrust Belt, volume II: Denver, 

Colo., Rocky Mountain Association of Geologists, p. 805–815.

Webel, Suzanne, 1987, Significance of backthrusting in the Rocky 

Mountain Thrust Belt, in Miller, W.R., ed., The thrust belt revisited: 

Jackson Hole, Wyo., Wyoming Geological Association, 38th Annual 

Field Conference, Guidebook, p. 37–53.

Undiscovered Resources Summary

The USGS quantitatively assessed the 

potential for continuous gas resources within the 

organic-rich shales of the Phosphoria Formation 

in the Wyoming Thrust Belt Province (table 2). 

The estimated mean total for undiscovered 

shale gas resource is 198 billion cubic feet of 

gas (BCFG) with an F95–F5 range from 0 to 

669 BCFG and 2 million barrels of natural gas 

liquids (MMBNGL) with an F95–F5 range from 

0 to 7 MMBNGL. Values of 0 at the F95 fractiles reflect geologic risk for the retention of gas 

within shales of the Phosphoria Formation.