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Assessment of Undiscovered Oil and Gas Resources of the Williston Basin Province of North Dakota, Montana, and South Dakota, 2008

Anna, Lawrence 1; Pollastro, Richard M.1; Gaswirth, Stephanie B.1; Lillis, Paul 1; Roberts, Laura N.1; Cook, Troy 1
1 USGS, Lakewood, CO.

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. The assessment is based on geologic elements and associated processes that define a total petroleum system (TPS), including (1) stratigraphic and structural geology framework; (2) source rock distribution, thick¬ness, organic richness, maturation, petroleum generation, and migration; and
3 reservoir type (conventional or continuous), distribution, and quality. These elements combined with burial history modeling, and petroleum geochemistry and historical exploration and production analyses, were used in estimating the undiscovered, technically recover¬able oil and gas resources within the Cambrian to Tertiary strata of the U.S. part of the basin.

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 natural gas liquids (MMBNGL) for undiscovered continuous and conventional resources in the 10 TPSs and 19 assessment units that were defined in the Williston Basin Province. The assessment indicates that most of the undiscovered oil resource is within the Bakken Formation as a continuous reservoir with a mean of 3,645 MMBO, whereas undiscovered oil from conventional reservoirs has a much lesser mean of 197 MMBO. All of the undiscovered continuous gas resides in the Bakken as associated gas with a mean of 1,848 BCFG, and in Tertiary coalbeds with a mean of 882 BCFG. Most of the undiscovered conventional oil is in the Mississippian Madison Group with a mean of 45 MMBO, and the Ordovician Red River Formation with a mean of 30 MMBO. Oil from other Paleozoic reservoirs is estimated at a mean of 122 MMBO. Undiscovered conventional gas resources from Paleozoic and Tertiary reservoirs are estimated at a mean of 976 BCFG.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009