109 ̊ W 108 ̊ W 107 ̊ W 106 ̊ W 105 ̊ W 104 ̊ W 103 ̊ W

46 ̊ N

45 ̊ N

44 ̊ N

43 ̊ N

42 ̊ N

Black Hills

Hartville Uplift

Bighorn Mountains

Billings

Sheridan

Gillette

Casper

MONTANA

WYOMING

NEBRASKA

SOUTH

DAKOTA

NORTH

DAKOTA

CANADA

94

ND MT

WY

ID

UT CO

SD

NE

KS

90

25

90

Powder River Basin

Province

90

0 20 40 MILES

0 30 60 KILOMETERS

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet FS-146-02

November 2002 Printed on recycled paper

National Assessment of Oil and Gas Fact Sheet

Assessment of Undiscovered Oil and Gas Resources of the 

Powder River Basin Province of Wyoming and Montana, 2002

Using a geology-based 

assessment methodology, 

the U.S. Geological Survey 

estimated a mean of 16.5 

trillion cubic feet of undiscovered natural gas, a 

mean of 1.5 billion barrels 

of undiscovered oil, and a 

mean of 86.5 million barrels of natural gas liquids 

in the Powder River Basin 

Province.

Introduction

The U.S. Geological Survey 

(USGS) recently completed an assessment of the potential for undiscovered 

resources in continuous oil and gas 

accumulations of the Powder River 

Basin Province of northeastern Wyoming and southeastern Montana (fig. 

1). The assessment of continuous oil 

and gas resources is based on geologic 

elements such as hydrocarbon source 

rocks (source-rock maturation, hydrocarbon generation and migration), 

reservoir rocks (sequence stratigraphy 

and petrophysical properties), and 

hydrocarbon traps (trap formation 

and timing) in four Total Petroleum 

Systems (TPS) identified in the 

province by the USGS. Six continuous 

assessment units and one conventional 

assessment unit were defined within 

the TPSs. Estimates of the undiscovered oil and gas resources in these 

seven assessment units, along with 

previous estimates of undiscovered oil 

and gas resources in 11 conventional 

plays within the province (Dolton and 

Fox, 1996), are presented in table 1.

Resource Summary

The USGS estimated a mean of 16.5 trillion cubic feet of undiscovered gas, a mean of 1.5 billion barrels of oil, and a mean of 86.5 million 

barrels of total natural gas liquids. Most of the undiscovered gas resource 

(94 percent, or 15.5 trillion cubic feet) is continuous (table 1). Of the 15.5 

trillion cubic feet of continuous gas at the mean, about 14.3 trillion cubic 

feet is estimated to be coal-bed gas in three AUs of the Tertiary–Upper 

Cretaceous Coal-Bed Methane TPS. The Cretaceous Biogenic Gas TPS is 

estimated to contain a mean of 0.78 trillion cubic feet of gas (table 1).

The Mowry TPS is estimated to contain a mean of 198 million barrels 

of undiscovered continuous oil, and the Niobrara TPS is estimated to contain a mean of about 227 million barrels of undiscovered continuous oil, 

together representing about 27 percent (424 million barrels) of the total 

mean undiscovered oil in the province. One-third of the mean undiscovered oil (33 percent, or 522 million barrels) is estimated to be in conventional accumulations of the Upper Minnelusa Sandstone Play (table 1).

Figure 1. Powder River Basin Province of northeastern Wyoming and southeastern Montana.
5.20 43.30 124.20 58.10 0.00 0.00 107.43 27.37 0.0

80.70 629.70 2,513.80 1,131.20 80.13 602.01 2,253.35 1,011.02 5.0

66.90 100.50 151.00 103.60 1,011.94 1,815.71 3,257.89 1,934.09 0.0

66.90 100.50 151.00 103.60 7,232.13 11,635.87 18,721.10 12,132.50 0.0

66.90 100.50 151.00 103.60 0.00 171.67 440.90 197.90 0.0

116.99 189.32 306.38 197.61 103.35 185.50 332.95 197.61 5.5

135.53 217.49 349.03 226.67 119.54 213.10 379.87 226.67 6.4

116.99 189.32 306.38 197.61 341.92 712.15 1,483.26 786.64 0.0

252.52 406.81 655.41 424.28 8,808.88 14,734.00 24,615.97 15,475.41 11.

333.22 1,036.51 3,169.21 1,555.48 8,889.01 15,336.00 26,869.32 16,486.43 17.0

Oil

Oil

Gas

Gas

CBG

CBG

CBG

Continuous Oil and Gas Resources

Total Continuous

Resources

Total Conventional

Resources

Tertiary-Upper Cretaceous

Coal-Bed Methane TPS

Mowry TPS

Niobrara TPS

Cretaceous Biogenic Gas TPS

Wasatch Formation AU

Upper Fort Union Formation AU

Lower Fort Union-Lance

Formation AU

Mowry Continuous Oil AU

Niobrara Continuous Oil AU

Shallow Continuous 

Biogenic Gas AU

gpp

Ft. Union Sandstone AU

Total Undiscovered

Oil and Gas Resources

For Further Information

Supporting geologic studies and reports on the assessment methodology used in the Powder River Basin Province assessments of 

continuous resources are in progress. Assessment results from 1995 

and 2002 are available at the USGS Central Energy Team website:

http://energy.cr.usgs.gov/oilgas/noga/

Powder River Basin Province Assessment Team: 

Romeo M. Flores (Task Leader; flores@usgs.gov), Larry O. Anna, 

Gordon L. Dolton, James E. Fox, Christopher D. French, Ronald R. 

Charpentier, Troy A. Cook, Robert A. Crovelli, Timothy R. Klett, 

Richard M. Pollastro, and Christopher J. Schenk.

Reference Cited

Dolton, G.L., and Fox, J.E., 1996, P

in Gautier, D.L., Dolton, G.L., V

eds., 1995 National Assessme

Resources—Results, method

Geological Survey Digital Dat

Release 2.

FS-146-02.indd 2