Geology And Geophysics

Oil Recovery in the Bakken formation



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The Bakken formation is a rock unit that is a part of the Williston Basin. It is roughly 8,000 feet beneath the surface and covers a 200,000 square mile area encompassing parts of Northeastern Montana, Western North Dakota, Southeastern Saskatchewan, and a small portion of Manitoba. It developed over about twenty-five million years from the late Devonian period (about 383 million years ago) to the early Missipian subperiod (about 358 million years ago).

The formation is comprised of three different distinct rock layers, or members. The bottom member is shale, the middle is dolomite, and the top, closest to the surface is another layer of shale. Above the Bakken Formation is the Lodgepole Formation, and it sits above the Three Forks Formation. The formation was first completely described by geologist J.W. Nordquist in 1953 and named after Henry Bakken, a farmer in Tioga, North Dakota who owned the land where the formation was first discovered.

The Bakken formation is most well-known for the massive oil reserves found primarily in the middle dolomite layer and the Three Forks Formation below. It is also famous for being a prolific source for source rock, a type of rock capable of producing  the hydrocarbons necessary to make the petroleum system function. The oil that is extracted from this formation is highly sought after sweet crude oil.

Sweet crude oil contains lower amounts of sulfur, making it more ideal for processing into gasoline, kerosene, and high-quality diesel. As of 2013, the Bakken formation alone provides more than ten percent of all United States oil production and has made North Dakota the second largest by volume producer of crude oil in the United States beat only by Texas. It is also the home of the Elm Coulee oil field on the Montana side of the Williston Basin which is one the highest-producing onshore oil fields.

How much oil could be recovered  from the formation as been widely revised over the past fifty years.  A paper originally published in 1974 suggested that the formation could generate 10 billion barrels of oil (BBbls) in total but only 3 BBbls would be recoverable. This number rose to 92 BBbls then again to 132 BBbls in the early 1980's, through a few more fluctuations to an estimated 300 BBbls in 2006.

Each new published paper comes  with its own controversy, as new computer models and geological study techniques become available. The most recent was in April of 2013. The United States Geological Survey puts the new estimates at 3.65 BBbls  of recoverable oil (an increase from a 2008 survey) as well as 6.7 trillion cubic feet of undiscovered,  recoverable natural gas and 0.53BBbls of undiscovered, recoverable natural gas liquids.

Despite certain confident calculations, as recently as 2007 the formation was thought to only be a relatively poor source for recoverable oil and natural gas. This was because these resources are trapped in a layer of highly impermeable rock. Recent advances in drilling technology, however, have allowed oil industry workers to unlock previously inaccessible deposits. Horizontal drilling creates a 90 degree turn in the well so that it runs laterally through the layer some distance, increasing its "pay zone," or the amount of area a well can use for collection purposes.

Hydraulic fracturing, or "fracking," is the process of pumping liquids down a well into subsurface rocks with a high enough pressure to fracture them, thus increasing porosity and oil flow to the well through the rocks. These techniques combined allowed technicians working in the formation to maximize the amount of oil recoverable by the more than 190 active wells peppering the basin where the formation is found.

The greatest social effect seen by the presence  of the formation was the North Dakota Oil boom of 2006 that started with the discovery of the Parshall Oil Field. With the jobs and income that new oil rigs create, North Dakota reduced its unemployment to the lowest in the country and saw a billion-dollar budget surplus.

On a local level, certain counties at the heart of oil production country saw their residents' average income more than double since the beginning of the boom. Royalties paid to local land and mineral rights owners have possibly created thousands of millionaires from once regular ranchers and farmers. Though the area sees the same social turbulence and strain on infrastructure that population and job booms can bring (stress on social services, higher crime rates, lack of housing) recent surveys suggest that the towns and counties are starting to catch up, thus painting a highly optimistic economic future for residents in the area.

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ARTICLE SOURCES AND CITATIONS
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  • InfoBoxCallToAction ActionArrowhttp://www.undeerc.org/bakken/lithology.aspx
  • InfoBoxCallToAction ActionArrowhttp://discoverygeo.com/Papers/Bakken%20History%20Headington.pdf
  • InfoBoxCallToAction ActionArrowhttp://www.nd.gov/ndic/ic-press/bakken-form-06.pdf
  • InfoBoxCallToAction ActionArrowhttp://www.usgs.gov/newsroom/article.asp?ID=1911
  • InfoBoxCallToAction ActionArrowhttp://geology.com/articles/horizontal-drilling/
  • InfoBoxCallToAction ActionArrowhttp://geology.com/articles/hydraulic-fracturing/
  • InfoBoxCallToAction ActionArrowhttp://online.wsj.com/news/articles/SB10001424052702304072004577328100938723454?mod=googlenews_wsj&mg=reno64-wsj&url=http%3A%2F%2Fonline.wsj.com%2Farticle%2FSB10001424052702304072004577328100938723454.html%3Fmod%3Dgooglenews_wsj
  • InfoBoxCallToAction ActionArrowhttp://www.reuters.com/article/2012/10/03/us-usa-northdakota-millionaires-idUSBRE8921AF20121003
  • InfoBoxCallToAction ActionArrowhttp://www.npr.org/2011/12/02/142695152/oil-boom-puts-strain-on-north-dakota-towns