Bakken Shale Overview

Map of Bakken Shale Play Reservoirs in the Williston Basin.

The Bakken Shale Play is an oil and gas formation located in Northeast Montana and Northwestern North Dakota in the Williston Basin. Oil was initially discovered in the Bakken Shale Play in 1951, but until recently it was considered an insignificant source of oil.

However, new drilling technology has made Bakken oil accessible through hydraulic fracturing and horizontal well drilling. The U.S. Geological Survey has estimated the Bakken Shale Formation could yield 4.3 billion barrels of oil.

Geology of the Bakken Shale Play

Map of the Williston Basin with major North Dakota and Montana structures shown.

The Bakken shale is a rock formation from the Late Devonian – Early Mississippian age. The formation consists of three layers: an upper shale layer, middle dolomite, and a lower layer of shale. The shale layers are petroleum source rocks as well as seals for an oil reservoir in the dolomite layer known as the Three Forks or Sanish Formation. The North Dakota Industrial Commission, in a 2010 study estimates the underlying Three Forks Formation could yield 1.9 billion barrels of reserves.