Bakken Shale
| Bakken Formation Stratigraphic range: Late Devonian to Early Mississippian |
|
|---|---|
| Type | Geological formation |
| Unit of | Three Forks Group |
| Underlies | Madison Limestone |
| Overlies | Wabamun Formation, Big Valley Formation, Torquay Formation |
| Area | 200,000 square miles (520,000 km2) |
| Thickness | up to 40 metres (130 ft) |
| Lithology | |
| Primary | Shale, Dolomite |
| Other | Sandstone, Siltstone |
| Location | |
| Region |
Williston Basin of central North America |
| Country |
 United States,  Canada
|
| Type section | |
| Named for | Henry Bakken |
| Named by | J.W. Nordquist, 1953 |
 Map of Bakken Formation reservoirs in the US portion of the Williston Basin (Saskatchewan is north border). Prior to 2007, most oil came from the Elm Coulee Oil Field. |
|
The Bakken Formation /ˈbɑːkən/ is a rock unit from the Late Devonian to Early Mississippian age occupying about 200,000 square miles (520,000 km2) of the subsurface of the Williston Basin, underlying parts of Montana, North Dakota, Saskatchewan and Manitoba. The formation was initially described by geologist J.W. Nordquist in 1953. The formation is entirely in the subsurface, and has no surface outcrop. It is named after Henry Bakken, a farmer in Tioga, North Dakota, who owned the land where the formation was initially discovered, during drilling for oil.
Besides the Bakken formation being a widespread prolific source rock for oil when thermally mature, significant producible oil reserves exist within the rock unit itself. Oil was first discovered within the Bakken in 1951, but past efforts to produce it have faced technical difficulties.
In April 2008, a USGS report estimated the amount of recoverable oil using technology readily available at the end of 2007 within the Bakken Formation at 3.0 to 4.3 billion barrels (680,000,000 m3), with a mean of 3.65 billion. Simultaneously the state of North Dakota released a report with a lower estimate of 2.1 billion barrels (330,000,000 m3) of technically recoverable oil in the Bakken. Various other estimates place the total reserves, recoverable and non-recoverable with today's technology, at up to 24 billion barrels. A recent estimate places the figure at 18 billion barrels. In April 2013, the U.S. Geological Survey released a new figure for expected ultimate recovery of 7.4 billion barrels of oil.
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