Bakken Shale

The Bakken shale is from the Devonian Mississippian age. The widespread Upper Devonian-Lower Mississippian Bakken formation consists of an upper and a lower shale member with a mixed siliciclastic carbonate middle member, that is usually referred to as a dolomitic sand (or a sandy dolomite). Both the upper and lower shales are organic-rich marine shale of relatively consistent lithology. These shales are both the petroleum source rocks (organic rich) and seal for the reservoir. The Bakken has also sourced the Three Forks Sanish formation, an underlying dolomite, in much of the Williston Basin. In 2008, the USGS estimated technically recoverable reserves from the Bakken could reach as high as 4.3 billion barrels of oil.