Bakken formation
The Bakken Formation is a rock unit from the Late Devonian to Early Mississippian age occupying about 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 O. Bakken, a farmer in Tioga, North Dakota, who owned the land where the formation was initially discovered during oil drilling.
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, with a mean of 3.65 billion. Simultaneously the state of North Dakota released a report with a lower estimate of 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.
The application of hydraulic fracturing and directional drilling technologies has caused a boom in Bakken oil production since 2000. By the end of 2010, oil production rates had reached per day, thereby outstripping the pipeline capacity to ship oil out of the Bakken. There is some controversy over the safety of shipping this crude oil by rail due to its volatility.
This was illustrated by the 2013 Lac-Mégantic rail disaster, in which a unit train carrying 77 tank cars full of highly volatile Bakken oil through Quebec from North Dakota to the Irving Oil Refinery in New Brunswick derailed and exploded in the town centre of Lac-Mégantic. It destroyed 30 buildings and killed 47 people. The explosion was estimated to have a one-kilometre blast radius.
As of January 2015, estimates varied on the break-even oil price for drilling Bakken wells. The North Dakota Department of Natural Resources estimated overall break-even to be just below US$40 per barrel. An analyst for Wood Mackenzie said that the overall break-even price was US$62/barrel, but in high-productivity areas such as the Sanish Field and the Parshall Oil Field, the break-even price was US$38–US$40 per barrel.
Geology
The rock formation consists of three members: lower shale, middle dolomite, and upper shale. The shales were deposited in relatively deep anoxic marine conditions, and the dolomite was deposited as a coastal carbonate bank during a time of shallower, well-oxygenated water. The middle dolomite member is the principal oil reservoir, roughly below the surface. Both the upper and lower shale members are organic-rich marine shale.Oil and gas
The Bakken Formation has emerged in recent years as one of the most important sources of new oil production in the United States. Most Bakken drilling and production has been in North Dakota, although the formation also extends into Montana and the Canadian provinces of Saskatchewan and Manitoba. As of 2013, the Bakken was the source of more than ten percent of all US oil production. By April 2014, Bakken production in North Dakota and Montana exceeded. As a result of increased production from the Bakken, and long-term production declines in Alaska and California, during every month from April 2012 through February 2021, North Dakota was the second-most oil-producing state in the US, behind only Texas in volume of oil produced per day, until New Mexico surpassed it in March 2021; as of June 2025, it is the third-most oil-producing state.Bakken production has also increased in Canada, although to a lesser degree than in the US, since the 2004 discovery of the Viewfield Oil Field in Saskatchewan. The same techniques of horizontal drilling and multi-stage massive hydraulic fracturing are used. In December 2012, 2,357 Bakken wells in Saskatchewan produced a record high of. The Bakken Formation also produces in Manitoba, yielding 42.1 thousand barrels per day of crude oil in 2020 and 38.5 in 2023.
Drilling and completion
Most Bakken wells are drilled and completed in the middle member. Many wells are now being drilled and completed in the basal Sanish/Pronghorn member and in the underlying Three Forks Formation, which the North Dakota Department of Mineral Resources treats as part of the Bakken for oil production statistical purposes.Porosities in the Bakken averages about 5%, and permeabilities are very low, averaging 0.04 millidarcys—much lower than typical oil reservoirs, in today's terms an unconventional light tight oil play. However, the presence of vertical to sub-vertical natural fractures makes the Bakken an excellent candidate for horizontal drilling techniques in which a well is drilled horizontally along bedding planes, rather than vertically through them. In this way, a borehole can contact many thousands of feet of oil reservoir rock in a unit with a maximum thickness of only about.
Production is also enhanced by artificially fracturing the rock, to allow oil to seep to the oil well.
Hydrogen sulfide is found to varying degrees in crude petroleum. The gas is flammable, corrosive, poisonous, and explosive; thus, oil with higher levels of H2S presents challenges such as "health and environmental risks, corrosion of wellbore, added expense with regard to materials handling and pipeline equipment, and additional refinement requirements." Bakken oil has historically been characterized as "sweet", meaning that it has little or no H2S. However, increased concentration of H2S over time has been observed in some Bakken wells, believed to be due to certain completion practices, such as hydraulic fracturing into neighboring formations, that may contain high levels of H2S. Some other formations in the Williston Basin have always produced "sour" crude oil, and because sweet oil brings a higher price, oil transporters suspect that some sour oil is being blended into sweet Bakken crude. H2S in crude oil is being investigated as a possible cause of the explosive nature of the Lac-Mégantic rail disaster. Pipeline transport operator Enbridge no longer accepts crude with more than five parts per million H2S, citing safety concerns.
Increased US oil production from hydraulically fractured tight oil wells in formations such as the Bakken was mostly responsible for the decrease in US oil imports since 2005. The US imported 52% of its oil in 2011, down from 65% in 2005. Hydraulically fractured wells in the Bakken, Eagle Ford, and other tight oil targets enabled US crude oil production to rise in September 2013 to the highest output since 1989.
History of Bakken oil resource estimates
Oil in place
A research paper by USGS geochemist Leigh Price in 1999 estimated the total amount of oil contained in the Bakken shale ranged from, with a mean of. While others before him had begun to realize that the oil generated by the Bakken shales had remained within the Bakken, it was Price, who had spent much of his career studying the Bakken, who particularly stressed this point. If he was right, the large amounts of oil remaining in this formation would make it a prime oil exploration target. Price died in 2000 before his research could be peer-reviewed and published. The drilling and production successes in much of the Bakken beginning with the Elm Coulee Oil Field discovery in 2000 have proven correct his claim that the oil generated by the Bakken shale was there. In April 2008, a report issued by the state of North Dakota Department of Mineral Resources estimated that the North Dakota portion of the Bakken contained of oil in place.Recoverable oil
Although the amount of oil in place is a very large oil resource, the percentage that can be extracted with current technology is another matter. Estimates of the Bakken's recovery factor have ranged from as low as 1%—because the Bakken shale has generally low porosity and low permeability, making the oil difficult to extract—to Leigh Price's estimate of 50% recoverable. Reports issued by both the USGS and the state of North Dakota in April 2013 estimated up to 7.4 billion barrels of oil can be recovered from the Bakken and Three Forks formations in the Dakotas and Montana, using current technology. The flurry of drilling activity in the Bakken, coupled with the wide range of estimates of in-place and recoverable oil, led North Dakota senator Byron Dorgan to ask the USGS to conduct a study of the Bakken's potentially recoverable oil. In April 2008 the USGS released this report, which estimated the amount of technically recoverable, undiscovered oil in the Bakken formation at, with a mean of 3.65 billion. Later that month, the state of North Dakota's report estimated that of the of oil in place in the North Dakota portion of the Bakken, were technically recoverable with current technology.In 2011, a senior manager at Continental Resources Inc. declared that the "Bakken play in the Williston basin could become the world's largest discovery in the last 30–40 years," as ultimate recovery from the overall play is now estimated at. This considerable increase has been made possible by the combined use of horizontal drilling, hydraulic fracturing, and a large number of wells drilled. While these technologies have been consistently in use since the 1980s, the Bakken trend is the place where they are being most heavily used: 150 active rigs in the play and a rate of 1,800 added wells per year.
An April 2013 estimate by the USGS projects that of undiscovered oil can be recovered from the Bakken and Three Forks formations and 6.7 trillion cubic feet of natural gas and 530 million barrels of natural gas liquids using current technology.
The Energy Information Administration, the statistics service of the Department of Energy, estimated in 2013 that there were 1.6 billion barrels and 2.2 trillion cubic feet of technically recoverable oil and natural gas in the Canadian portion of the Bakken formation. Crescent Point Energy and other operators are implementing waterfloods in the Bakken Formation of the Viewfield Oil Field in Saskatchewan. Some believe that waterflooding can raise the recovery factor at Viewfield from 19 percent to more than 30 percent, adding 1.5 to two billion barrels of additional oil.