National Assessment of Oil and Gas Fact Sheet

2005 Assessment of Undiscovered Oil and Gas Resources 

in Hanna, Laramie, Shirley Basins Province, Wyoming

Introduction

The U.S. Geological Survey (USGS) recently 

completed an assessment of the undiscovered oil 

and gas potential of the Hanna, Laramie, Shirley 

Basins Province of the Rocky Mountain region 

(fig. 1) as part of a national oil and gas assessment 

effort. The assessment of the petroleum potential 

of the province was based on the general geologic 

elements used to define a total petroleum system 

(TPS)—hydrocarbon source rocks (source rock 

maturation, hydrocarbon generation and migration), reservoir rocks (sequence stratigraphy and 

petrophysical properties), and hydrocarbon traps 

(trap formation and timing). By using this geologic 

framework, the USGS defined five TPSs containing seven assessment units (AUs) and quantitatively 

estimated the undiscovered resources for three of 

the seven AUs (table 1).

Resource Summary

Assessment of the undiscovered oil and gas 

resources for the three AUs—Tensleep-Casper Oil 

and Gas AU, Mesozoic–Cenozoic Conventional 

Oil and Gas AU, and Niobrara Continuous Oil 

AU—resulted in estimated means of 298 billion 

cubic feet of nonassociated gas and associated gas 

in oil fields, 94 million barrels of oil, and 14 million barrels of natural gas liquids (table 1). All of 

Application of a geology-based assessment 

methodology by the U.S. Geological Survey 

resulted in estimated means of 298 billion 

cubic feet of undiscovered natural gas, 94 

million barrels of undiscovered oil, and 

14 million barrels of undiscovered natural 

gas liquids in the Hanna, Laramie, Shirley 

Basins Province, Wyoming. 

the undiscovered gas is conventional. The Mesozoic–Cenozoic Conventional 

Oil and Gas AU contains an estimated mean of 207 billion cubic feet of gas, 

representing nearly 70 percent of the total mean undiscovered gas resource 

(298 billion cubic feet) for the province. Two continuous gas and two coalbed gas AUs were not quantitatively assessed owing to a lack of data.

Figure 1. Map of the Hanna, Laramie, Shirley Basins Province (Province 5030) of the Rocky 

Mountain region (outlined in red).

Hanna

Laramie

Rawlins

Saratoga

Riverside

Elk Mountain

Medicine Bow

Grand County

Carbon

Larimer

Natrona

Routt Jackson

Converse

Albany

COLORADO

WYOMING

HANNA

BASIN

LARAMIE

BASIN

SHIRLEY

BASIN

L A

R

A

M I E

R

A

N

G E

M E D I C I N E

B O W

M O U N T A I N S

25

107° 106°

41°

42°

0 20 MILES

WY

CO

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet FS-2005-3125

January 2006 Printed on recycled paper
For Further Information

Geologic studies of total petroleum systems and assessment units, as well as reports on the methodology used in assessing 

resources, for the Hanna, Laramie, Shirley Basins Province of the Rocky Mountain region are available at the USGS Central Energy 

Team Web site: http://energy.cr.usgs.gov/oilgas/noga/.

Hanna, Laramie, Shirley Basins Province Assessment Team

T.S. Dyman (Task Leader: dyman@usgs.gov), S.M. Condon, T.S. Ahlbrandt, R.R. Charpentier, T.A. Cook, T.R. Klett, M.D. 

Lewan, P.G. Lillis, M.J. Pawlewicz, R.M. Pollastro, and C.J. Schenk.

Table 1. Hanna, Laramie, Shirley Basins Province assessment results.

[MMBO, million barrels of oil; BCFG, billion cubic feet of gas; MBNGL, thousand barrels of natural gas liquids; MAS, minimum accumulation size assessed 

(MMBO or BCFG); Prob., probability (including both geologic and accessibility probabilities) of at least one accumulation equal to or greater than the MAS or, 

for continuous-type resources, at least one additional cell of equal to or greater than the minimum estimated ultimate recovery; Accums., accumulations. 

Results shown are fully risked estimates. For gas accumulations, all liquids are included as NGL (natural gas liquids). F95 represents a 95 percent chance of 

at least the amount tabulated; other fractiles are defined similarly. A single major commodity and its coproducts were assessed for continuous-type 

assessment units. Fractiles are additive under the assumption of perfect positive correlation. Totals reflect rounding to nearest whole number. Shading 

indicates not applicable]

Total petroleum Total undiscovered resources

system (TPS) MAS Prob. Oil (MMBO) Gas (BCFG) NGL (MBNGL)

and assessment (0–1) F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean

units (AUs)

Conventional oil and gas resources

 Phosphoria TPS

Tensleep-Casper Oil and Gas AU

Oil accums. 0.5 1 6 19 39 20 6 18 42 20 190 650 1,590 740

Gas accums. 3.0 16 47 101 52 460 1,380 3,220 1,550

Total 1 6 19 39 20 22 66 143 72 650 2,030 4,810 2,290

 Mowry-Hanna Composite TPS

Mesozoic-Cenozoic Conventional Oil and Gas AU 

Oil accums. 0.5 1 7 31 79 36 17 75 208 89 1,620 7,320 21,610 8,910

Gas accums. 3.0 25 99 278 118 460 1,920 5,770 2,360

Total 1 7 31 79 36 42 174 486 207 2,080 9,240 27,380 11,270

 Total undiscovered conventional oil and gas resources

Oil accums. 13 50 119 56 23 94 250 110 1,810 7,970 23,200 9,650

Gas accums. 42 146 379 170 920 3,300 8,990 3,910

Total 13 50 119 56 64 240 629 279 2,730 11,270 32,190 13,560

Continuous oil and gas resources

 Mowry-Hanna Composite TPS

Hanna Basin Continuous Gas AU—Not quantitatively assessed

 Niobrara TPS

Niobrara Continuous Oil AU

Oil accums. 0.5 1 14 33 76 38 6 16 43 19 0 0 0 0

Gas accums. 3.0

Total 1 14 33 76 38 6 16 43 19 0 0 0 0

 Niobrara Biogenic Gas TPS

Niobrara Biogenic Gas AU—Not quantitatively assessed 

 Mesaverde-Hanna Coalbed Gas TPS

Medicine Bow–Ferris–Hanna Coalbed Gas AU—Not quantitatively assessed

Mesaverde Coalbed Gas AU—Not quantitatively assessed

 Total undiscovered continuous oil and gas resources

Oil accums. 14 33 76 38 6 16 43 19 0 0 0 0

Gas accums.

Total 14 33 76 38 6 16 43 19 0 0 0 0

 Total undiscovered oil and gas resources

Oil accums. 28 83 195 94 29 110 292 129 1,810 7,970 23,200 9,650

Gas accums. 42 146 379 170 920 3,300 8,990 3,910

Total 28 83 195 94 70 256 671 298 2,730 11,270 32,190 13,560