Reassessment of Undiscovered Resources in the Bakken Formation, Williston Basin, North Dakota and Montana

Gaswirth, Stephanie; Marra, Kristen; Cook, Troy

The U.S. Geological Survey (USGS) is reassessing the undiscovered, technically recoverable oil and gas resources of the U.S. Williston Basin in the Devonian-Mississippian Bakken Formation in North Dakota and Montana. The Bakken Formation was last assessed by the USGS in 2008, and required a revaluation due to improved geologic knowledge of the Bakken Formation, as well as production information related to the substantial increase in the number of Bakken wells since 2008.

In 2008, five unconventional (continuous) assessment units and one conventional assessment unit (AU) were defined for the Bakken Formation. These AU lines were based on structural elements, source rock maturity of the Upper Bakken Shale, and resistivity data. For unconventional oil resources, the USGS estimated a total mean resource of 3.65 BBO, and 4 MMBO for conventional resources.

The reassessment of the Bakken Formation redefines the AUs based on updated thermal maturity data, structural controls, and the mapped extent of Bakken source rocks. Continuous assessment units are refined given a large amount of new production data since 2008, especially in the areas of the central basin, northeast Montana, and northwest North Dakota. The Parshall and Sanish fields have also been substantially developed since 2008, providing longer production histories and more robust estimated ultimate recovery (EUR) data. The new estimation of undiscovered technically recoverable resources for the redefined Bakken Formation AUs will be completed in 2013.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013