U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2006–3135

December 2006

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—

2006 Update

Printed on recycled paper

Introduction

The U.S. Geological Survey (USGS) 

has completed an update of the 1995 

assessment (USGS Fact Sheet FS–146–02) 

of the potential for undiscovered resources 

in conventional oil and gas accumulations 

of the Powder River Basin Province of 

northeastern Wyoming and southeastern 

Montana (fig. 1). The 2002 assessment 

of continuous (unconventional) oil and 

gas accumulations were not reassessed. 

The current assessment of conventional 

oil and gas resources, based on geologic 

elements such as hydrocarbon source rocks 

(source rock maturation and hydrocarbon 

generation and migration), reservoir rocks 

(sequence stratigraphy and petrophysical 

properties), and hydrocarbon traps (trap 

formation and timing), includes five Total 

Petroleum Systems (TPS) identified in 

the province by the USGS; eight assessment units (AU) were defined within 

the TPSs. Estimates of the undiscovered 

conventional oil and gas resource in these 

eight AUs, in addition to the estimates 

of undiscovered continuous oil and gas 

resources within the province that were 

reported in USGS Fact Sheet FS–146–02 

are presented in table 1.

Using a geology-based assessment method, the U.S. Geological

Survey estimated means of 16.6 trillion cubic feet of undiscovered 

natural gas, 639 million barrels of 

undiscovered oil, and 131 million 

barrels of natural gas liquids in the 

Powder River Basin Province.

Figure 1.  Powder River Basin Province of northeastern Wyoming and southeastern Montana.

Resource Summary

The USGS estimated means of 

16.6 trillion cubic feet of gas, 639 million 

barrels of oil, and 131 million barrels of 

total natural gas liquids for undiscovered 

continuous and conventional resources in 

the Powder River Basin Province (table 1). 

Most of the undiscovered gas resource 

(93 percent, or 15.5 trillion cubic feet) is 

continuous. Of the 1.16 trillion cubic feet 

of conventional gas at the mean, about 

91 percent, or 1.05 trillion cubic feet is 

estimated to be from the Fall River-Lakota 

and Muddy Sandstones AUs of the Mowry 

TPS. Of the 215 million barrels of conventional oil at the mean: (1) about 30 percent, 

or 64 million barrels, is estimated to be 

from the Fall River–Lakota Sandstone AU; 

(2) about 28 percent, or 61 million barrels, 

is estimated to be from the MinnelusaTensleep-Leo Sandstones AU of the 

Pennsylvanian-Permian TPS; and (3) about 

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

46° N

45° N

44° N

43° N

42° N

Hartville Uplift

Bighorn Mountains

Billings

Sheridan

Gillette

Casper

MONTANA

WYOMING

NEBRASKA

SOUTH

DAKOTA

NORTH

DAKOTA

CANADA

94

MT ND

WY

ID

UT CO

SD

NE

KS

90

25

90

Powder River Basin

Province

90

Black Hills

0 20 40 MILES

0 30 60 KILOMETERS
22 percent, or 47 million barrels is estimated to be from the Muddy Sandstone AU 

(table 1).

The Frontier-Turner, Sussex-Shannon, 

and Mesaverde-Lewis Sandstones AUs 

from the Niobrara TPS are estimated to 

contain means of 25 million barrels of 

conventional oil (12 percent) and 57.0 billion cubic feet of gas (5 percent) of the 

total undiscovered conventional resource 

(table 1).

Table 1. Powder River Basin Province Assessment Results.

[MMBO, million barrels of oil; BCFG, billion cubic feet of gas; MMBNGL, million barrels of natural gas liquids.Results shown are fully risked estimates. For gas accumulations, all 

liquids are included as NGL (natural gas liquids). F95 denotes a 95 percent chance of at least the amount tabulated; other fractiles are defined similarly. Fractiles are additive under the 

assumption of perfect positive correlation. TPS, Total Petroleum System; AU, Assessment Unit. Gray shading indicates not applicable.]

Total Petroleum Systems

(TPS)

and Assessment Units (AU)

Total undiscovered resources

Field

type

Oil (MMBO) Gas (BCFG) NGL (MMBNGL)

F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean

Conventional Oil and Gas Resources

Pennsylvanian-Permian

Composite TPS

Minnelusa-Tensleep-Leo AU Oil 21.38 56.48 112.13 60.51 0.87 2.52 5.85 2.83 0.02 0.08 0.25 0.10

Gas 3.34 7.26 13.39 7.32 0.17 0.41 0.86 0.44

Mowry TPS

Fall River-Lakota Sandstone AU Oil 18.14 58.58 127.53 64.05 18.58 64.98 162.77 74.70 1.03 3.81 10.25 4.48

Gas 104.85 507.46 1,257.06 574.51 9.72 49.36 131.97 57.47

Muddy Sandstone AU Oil 10.95 40.62 106.81 47.34 31.03 122.43 360.08 149.14 2.71 10.89 32.87 13.43

Gas 52.61 214.07 564.62 248.77 4.93 20.79 58.58 24.85

Niobrara TPS

Frontier-Turner Sandstones AU Oil 2.46 9.12 21.37 10.18 8.72 34.44 93.45 40.47 0.59 2.41 6.97 2.91

Sussex-Shannon Sandstones AU Oil 2.75 7.97 16.98 8.67 2.25 7.09 17.30 8.09 0.17 0.55 1.45 0.65

Mesaverde-Lewis Sandstones AU Oil 1.55 5.19 13.20 6.00 1.90 6.97 19.84 8.41 0.13 0.48 1.44 0.59

Tertiary-Upper Cretaceous 

Coalbed Methane TPS

Eastern Basin Margin Upper

Ft. Union Sandstone AU Gas 0.00 0.00 107.43 27.37 0.00 0.00 0.00 0.00

Paleozoic-Mesozoic TPS

Basin Margin AU Oil 4.79 16.30 36.76 17.93 3.46 12.58 32.89 14.66 0.11 0.44 1.23 0.53

Total Conventional 

Resources 62.02 194.26 434.78 214.68 227.61 979.80 2,634.68 1,156.27 19.58 89.22 245.87 105.45

Continuous Oil and Gas Resources

Tertiary-Upper Cretaceous 

Coalbed Methane TPS

Wasatch Formation AU CBG 1,011.94 1,815.71 3,257.89 1,934.09 0.00 0.00 0.00 0.00

Upper Fort Union Formation AU CBG 7,232.13 11,635.87 18,721.10 12,132.50 0.00 0.00 0.00 0.00

Lower Fort Union-Lance

Formation AU CBG 0.00 171.67 440.90 197.90 0.00 0.00 0.00 0.00

Mowry TPS

Mowry Continuous Oil AU Oil 116.99 189.32 306.38 197.61 103.35 185.50 332.95 197.61 5.56 10.91 21.37 11.86

Niobrara TPS

Niobrara Continuous Oil AU Oil 135.53 217.49 349.03 226.67 119.54 213.10 379.87 226.67 6.43 12.53 24.40 13.60

Cretaceous Biogenic Gas TPS

Shallow Continuous

Biogenic Gas AU Gas 341.92 712.15 1,483.26 786.64 0.00 0.00 0.00 0.00

Total Continuous

Resources 252.52 406.81 655.41 424.28 8,808.88 14,734.00 24,615.97 15,475.41 11.99 23.44 45.77 25.46

Total Undiscovered 

Oil and Gas Resources 314.54 601.07 1,090.19 638.96 9,036.49 15,713.80 27,250.65 16,631.68 31.57 112.66 291.64 130.91

The Basin Margin AU of the 

Paleozoic-Mesozoic TPS is estimated to 

contain a mean of 18 million barrels and 

14.7 billion cubic feet of total undiscovered conventional resource (table 1).

The Eastern Basin Margin–Upper 

Ft. Union Sandstone AU of the Tertiary–

Upper Cretaceous Coalbed Methane TPS 

is estimated to contain a mean of 27.4 billion cubic feet of total undiscovered 

conventional gas resource (table 1).

For Further Information

Supporting geologic studies and 

reports on the assessment method used in 

the Powder River Basin Province assessments of conventional resources are in 

preparation (2006). Assessment results 

are available at the USGS Central Energy 

Team website, http://energy.cr.usgs.gov/

oilgas/noga.

Powder River Basin Province Assessment Team

Lawrence O. Anna (Task Leader; lanna@usgs.gov), Ronald R. Charpentier, Troy A. Cook, Timothy R. Klett, Richard M. 

Pollastro, and Christopher J. Schenk.