U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2008–3092

November 2008

Assessment of Undiscovered Oil and Gas Resources of the

Williston Basin Province of North Dakota, Montana, and 

South Dakota, 2008

Printed on recycled paper

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

Geological Survey estimated mean undiscovered volumes 

of 3.8 billion barrels of undiscovered oil, 3.7 trillion cubic 

feet of associated/dissolved natural gas, and 0.2 billion 

barrels of undiscovered natural gas liquids in the Williston 

Basin Province, North Dakota, Montana, and South 

Dakota.

Introduction

The U.S. Geological Survey (USGS) completed an assessment 

of the undiscovered oil and gas resources in conventional and 

continuous accumulations of the Williston Basin Province of North 

Dakota, eastern Montana, and northwestern South Dakota (fig. 1). 

The assessment is based on geologic elements of a total petroleum 

system (TPS) that include (1) source-rock distribution, thickness, 

organic richness, maturation, petroleum generation, and migration; 

(2) reservoir-rock type (conventional or continuous), distribution, 

and quality; and (3) character of traps and time of formation 

with respect to petroleum generation and migration. Detailed 

National Assessment of Oil and Gas Fact Sheet

Fargo

Minot

Pierre Gillette

Bismarck

Sheridan

Jamestown Dickinson

Williston

Rapid City

Grand Forks

Glendive

Miles 

City

Sidney

0 50 MILES

0 50 KILOMETERS

MT

CANADA

WY SD

ND

108° 107° 106° 105° 104° 103° 102° 101° 100° 99° 98° 97°

49°

48°

47°

46°

45°

44°

CANADA

UNITED STATES

NORTH DAKOTA

MONTANA

SOUTH DAKOTA

WYOMING

Williston Basin 

Province

POPLAR

DOME

BROCKTON-FROID FAULT ZONE

CEDAR CREEK

ANTICLINE

BILLINGS

ANTICLINE

LITTLE KNIFE

ANTICLINE

NESSON

ANTICLINE

Figure 1. Williston Basin 

Province of North Dakota, 

Montana, and South Dakota. 

framework studies in stratigraphy and structural geology and the 

modeling of petroleum geochemistry, combined with historical 

exploration and production analyses, were used in estimating the 

undiscovered, technically recoverable oil and gas resources of the 

entire stratigraphic section in the U.S. part of the basin. Using this 

framework, the USGS defined 11 TPSs and 19 assessment units 

(AU) within them, and undiscovered oil and gas resources were 

quantitatively estimated within each AU (table 1). The assessment 

of the Bakken Formation is included here, and it was also published 

previously as USGS Fact Sheet 2008-3021.

Resource Summary

The USGS estimated means of 3,844 million barrels of oil 

(MMBO), 3,705 billion cubic feet of gas (BCFG), and 202 million 

barrels of total natural gas liquids (MMBNGL) for undiscovered 

continuous and conventional resources in the Williston Basin Province (table 1). 

The assessment indicates that most of the undiscovered oil 

and gas resides within the Bakken Formation as a continuous 

reservoir with a mean of 3,645 MMBO, whereas undiscovered oil 

from conventional reservoirs 

has a mean of 197 MMBO. All 

of the undiscovered continuous 

gas resides in the Bakken with 

a mean of 1,848 BCFG, and 

in coalbed gas with a mean of 

882 BCFG.

Most of the undiscovered 

conventional oil resides in the 

Mission Canyon–Charles AU 

with a mean of 45 MMBO, 

and the Red River Fairway AU 

with a mean of 30 MMBO. 

The remainder from Paleozoic 

AUs is estimated to contain 

a mean of 122 MMBO. 

Undiscovered conventional gas 

resources reside in Paleozoic 

and shallow biogenic gas AUs 

with a mean of 975 BCFG.
For Further Information

Supporting geologic studies and reports on the assessment 

method used in the Williston Basin Province assessments of 

conventional resources are in preparation. Assessment results are 

available at the USGS Central Energy Team website at URL http://

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

Williston Basin Province Assessment Team: Lawrence O. 

Anna (Task Leader; lanna@usgs.gov), Richard M. Pollastro (Bakken Formation Task Leader), Stephanie B. Gaswirth, Michael D. 

Lewan, Paul G. Lillis, Laura N.R. Roberts, Christopher J. Schenk, 

Ronald R. Charpentier, Troy A. Cook, and Timothy R. Klett.

Total Petroleum System 

and Assessment Unit

Field 

Type

Total Undiscovered Resources

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

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

Bakken–Lodgepole TPS

Elm Coulee–Billings Nose AU Oil 374 410 450 410 118 198 332 208 8 16 29 17

Central Basin–Poplar Dome AU Oil 394 482 589 485 134 233 403 246 10 18 35 20

Nesson–Little Knife 

Structural AU Oil 818 908 1,007 909 260 438 738 461 19 34 64 37

Eastern Expulsion 

Threshold AU Oil 864 971 1,091 973 278 469 791 493 20 37 68 39

Northwest Expulsion

Threshold AU Oil 613 851 1,182 868 224 411 754 440 16 32 64 35

Coalbed Gas TPS

Fort Union Coalbed Gas AU Gas 368 791 1,701 882 0 0 0 0

Total Continuous

 Resources 702 1,422 3,645 2,730 148

Bakken–Lodgepole TPS

Middle Sandstone Member AU Oil 1 4 8 4 0 1 3 2 0 0 0 0

Gas 0 0 0 0 0 0 0 0

Lodgepole AU

Oil 2 7 18 8 1 4 11 5 0 0 1 0

Gas 0 0 0 0 0 0 0 0

Winnipeg–Deadwood TPS

Winnipeg–Deadwood AU

Oil 1 4 10 5 3 9 24 11 0 0 1 0

Gas 56 161 358 178 3 8 20 9

Red River TPS

Red River Fairway AU

Oil 12 29 51 30 11 28 55 30 1 3 6 3

Gas 58 155 314 167 11 30 67 33

Red River East Margin AU

Oil 0 2 4 2 0 0 1 0 0 0 0 0

Gas 0 0 0 0 0 0 0 0

Interlake–Stonewall–Stony 

Mountain AU

Oil 9 22 44 24 8 22 47 24 1 2 5 2

Gas 0 0 0 0 0 0 0 0

Winnipegosis TPS

Winnipegosis AU

Oil 4 11 22 11 2 6 14 7 0 1 1 1

Gas 0 0 0 0 0 0 0 0

Duperow TPS

Dawson Bay–Souris River AU

Oil 2 5 12 6 1 3 6 3 0 0 0 0

Gas 0 0 0 0 0 0 0 0

Duperow–Birdbear AU

Oil 13 26 44 27 9 20 38 22 1 2 4 2

Gas 0 0 0 0 0 0 0 0

Cedar Creek Paleozoic Composite TPS

Cedar Creek Structural AU Oil 6 19 41 20 3 12 28 13 0 1 2 1

Gas 0 0 0 0 0 0 0 0

Madison TPS

Mission Canyon–Charles AU

Oil 13 43 85 45 9 33 72 36 1 3 7 3

Gas 0 0 0 0 0 0 0 0

Tyler TPS

Tyler Sandstone AU

Oil 4 14 31 15 1 3 7 3 0 0 0 0

Gas 0 0 0 0 0 0 0 0

Shallow Biogenic Gas TPS

Shallow Biogenic Gas AU Gas 48 418 1,091 475 0 0 0 0

Total Conventional

 Resources 197 976 54

Total Undiscovered 

 Oil and Gas Resources 3,844 3,705 202

Continuous Oil and Gas Resources

Table 1. Williston 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 represents a 95-percent 

chance of at least the amount tabulated; other fractiles are defined similarly. TPS, total petroleum system; AU, assessment unit. 

Gray shading indicates not applicable] 

Conventional Oil and Gas Resources