However, as of April , the agency has increased its estimate to 7 billion barrels of recoverable oil. The Bakken Shale was formed during the Late Devonian to Early Mississippian age nearly million years ago and consists of three members: lower shale, middle dolomite and upper shale. The shales were deposited in deep anoxic water conditions. Anoxic waters are areas of sea water, fresh water or groundwater that are depleted of dissolved oxygen.
The majority of the oil resides in the middle dolomite area, which is located roughly two miles below the surface. While the drilling and completion techniques of horizontal drilling and hydraulic fracturing have unlocked this oil resource, the combination of the following characteristics make it a world class play: distribution of source rock, the thickness of the shale interval, the organic maturation and the character of trap styles.
The foot thick shale interval is oil wet and over-pressured causing it to fault and fracture. The shale itself sources the middle dolomite and because the impermeable layer on top of the Bakken is so tight, oil has been forced down into two additional formations, the Three Forks carbonate and the Sanish Sand. However, by the end of , thousands of successful wells made it one of the most important crude oil sources in the history of North America. Throughout history, most great oil and gas fields have been discovered.
The Bakken Formation was unlocked through innovation. Throughout history, most great oil and gas fields were "discovered. Bakken Drilling Horizontal drilling and hydraulic fracturing: Advances in drilling and well stimulation made the Bakken Formation a viable oil and gas resource. Find Other Topics on Geology.
Maps Volcanoes World Maps. Oil and Gas Rights. What is LNG? Natural Gas Investing. Shale Gas Resources. Uses of Natural Gas. Haines, Seth S. Haines, S. Geological Survey Fact Sheet —, 4 p. Gaswirth, Stephanie B. Pollastro, R.
Attribution: Energy Resources Program. Pollastro, Richard M. Year Published: Diagenesis and fracture development in the Bakken Formation, Williston Basin; implications for reservoir quality in the middle member The middle member of the Bakken Formation is an attractive petroleum exploration target in the deeper part of the Williston Basin because it is favorably positioned with respect to source and seal units.
Pitman, Janet K. Year Published: A resource evaluation of the Bakken Formation Upper Devonian and Lower Mississippian continuous oil accumulation, Williston Basin, North Dakota and Montana The Upper Devonian and Lower Mississippian Bakken Formation in the United States portion of the Williston Basin is both the source and the reservoir for a continuous oil accumulation - in effect a single very large field - underlying approximately 17, mi2 46, km2 of North Dakota and Montana.
Schmoker, J. Year Published: Developing an oil generation model for resource assessment of the Bakken Formation, U. Krystinik, K. Filter Total Items: 3. Date published: May 2, Date published: November 10, Attribution: Region 5: Missouri Basin. Date published: April 10, Filter Total Items: 6. List Grid. December 31, This technology allows for quick and efficient fracture stimulation by minimising fluid use and downhole trips. The thickest portion of the Bakken 46m is in north-western North Dakota and it thins evenly south-eastwards toward the margins of the Williston Basin.
The upper and lower members consist of hard, siliceous, black organic-rich shales. These form effective seals for the middle member, which consists of five highly variable lithologies, from several argillaceous siltstones to fine-grained sandstone and limestone, all with low primary permeability 0.
The other important reservoir target, the Three Forks Formation, consists of shales, dolostones, siltstones, and sandstones with a maximum thickness of 76m. Depositionally, the Three Forks Formation consists of shallow marine to terrestrial sediments that transition from highly oxidising conditions to the anoxic conditions of the lower Bakken.
The middle Bakken sedimentation is associated with the drop in sea level and influx of sedimentary material into near-shore tidal basins and lower shoreface environments. Anoxic conditions resumed during the deposition of the upper shale member, followed by oxidising water conditions during the deposition of the overlying Lodgepole Formation.
Without hydraulic fracturing, under regulation of the states, this resource could not be produced. Water and sand make up most of the frac treatments with additives to give the fluids special properties, like cross-linked gels to better transport proppants into the formation. Proppants, typically sand or ceramics, are used to hold the fractures open and allow reservoir fluids to flow to the wellbore.
The upper Bakken shale member was first targeted for production at the Elkhorn Ranch Field in Vertical wells were fracture-stimulated with sand and oil. The first horizontal wells were completed in , however the play ended in the s because of low oil prices. The drilled program was a huge success with ultimate recoveries approaching , barrels of oil. In , EOG Resources utilised horizontal drilling combined with hydraulic fracturing to recover significant oil from the middle Bakken interval at the Ross Field in North Dakota.
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