The Bakken Formation, initially described by geologist J.W. Nordquist in 1953,[1] is a rock unit from the Late Devonian to Early Mississippian age occupying a substantial part of the subsurface of the Williston Basin, in Montana, North Dakota, and Saskatchewan.
It is estimated that there are significant reservoirs of oil shale beneath the Bakken's 200,000 square miles (520,000 kmē). They were first discovered in 1951, but have long frustrated efforts to extract oil. An April 2008 USGS report estimated the amount of technically recoverable oil in the Bakken Formation at 3.0 to 4.3 billion barrels, with a mean of 3.65 billion.[2] The state of North Dakota also released a report that month which estimated that there are 2.1 billion barrels of technically recoverable oil in the Bakken.