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Horizontal Drilling Potential of the Middle Member Bakken Formation, North Dakota

Julie A. LeFever, North Dakota Geological Survey, P.O. Box 8156, Grand Forks, ND 58202-8156, phone: 701-777-2441, fax: 701-777-2857, [email protected]

The Bakken Formation has once again become the focus of activity in the Williston basin. Horizontal drilling of the middle member began in 2001 and has been restricted to Richland County, Montana until recently. As the success rate increased in Montana, activity has increased in North Dakota.

The stratigraphy in the main play area is relatively simple with each successively higher member of the Bakken Formation onlapping the underlying Three Forks Formation. These units pinch out to the south. A bottom seal is formed by the impermeable Three Forks Formation while the overlying Lodgepole Formation forms the top seal. A well developed mappable trend is readily apparent in the middle member on wireline logs over this area.

Technology has finally caught up to the Bakken Formation. The ability to fracture stimulate these horizontal wells is what makes this play work. The zone generally has between 7 to 12% porosity, permeabilities of .01 to .02 mD, and 70 to 80% oil saturation.

The facies that produce in Montana are present basinwide. Additional production potential occurs in North Dakota as the Bakken thickens towards its depositional center. Localized accumulations of the “Sanish Sand” that occur at the base of the Bakken also increases the potential pay section. Already a significant producer at Antelope Field, the “Sanish Sand” interval is untested and occurs throughout the “Bakken Fairway.” Detailed mapping of all of the zones will be required to determine the best location to tap into the oil resources of the Bakken Formation.