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Assessment of Undiscovered Resources in the Bakken Formation of the U.S. Williston Basin, North Dakota and Montana

Stephanie B. Gaswirth, Troy Cook, and Kristen R. Marra
U.S. Geological Survey

"The U.S. Geological Survey has completed a geology-based assessment of the undiscovered, technically recoverable petroleum resources in the Devonian-Mississippian Bakken Formation of the U.S. Williston Basin, including North Dakota and Montana. The Bakken Formation was last assessed in 2008 and estimated to have a mean of 3.65 billion barrels (BBO) of recoverable, undiscovered oil. The 2013 assessment incorporates new production data, thermal maturity data, and geologic information to define continuous and conventional assessment units (AUs) in the Bakken Formation. Five continuous AUs are refined as a result of the large amount of new horizontal drilling production, particularly 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 Bakken Total Petroleum System (TPS) encompasses strata from the Devonian Three Forks Formation, Devonian-Mississippian Bakken Formation, and lower part of the Mississippian Lodgepole Formation that may contain Bakken-sourced oil. The TPS is defined by the postulated maximum extent of petroleum fluids within the Bakken and Three Forks Formations. The geologic model for the assessment of the Bakken Formation is that oil generated in the upper and lower Bakken shale members migrated locally into low-permeability and variable-porosity reservoirs of the middle Bakken member, the Pronghorn Member of the Bakken Formation, and dolomitized units of the underlying Three Forks Formation. Locally, oil was also retained in the low-porosity matrix and fractures of the upper and lower Bakken shale members."

AAPG Search and Discovery Article #90169©2013 AAPG Rocky Mountain Section 62nd Annual Meeting, Salt Lake City, Utah, September 22-24, 2013