Assessment of undiscovered oil and gas resources of the Powder River Basin Province of Wyoming and Montana— 2006 update

National Assessment of Oil and Gas Fact Sheet

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.

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.

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 Minnelusa-Tensleep-Leo Sandstones AU of the Pennsylvanian-Permian TPS; and (3) about 22 percent, or 47 million barrels is estimated to be from the Muddy Sandstone AU (table 1).

Table 1. Powder River Basin Province Assessment Results.

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).

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.

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.

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