Williston Basin

The Williston Basin is a large intracratonic sedimentary basin in eastern Montana, western North and South Dakota, and southern Saskatchewan known for its rich deposits of petroleum and potash. The basin is a geologic structural basin but not a topographic depression; it is transected by the Missouri River. The oval-shaped depression extends approximately convert|475|mi|km north-south and convert|300|mi|km east-west.

The Williston Basin lies above an ancient Precambrian geologic basement feature, the Trans-Hudson Orogenic Belt that developed in this area about 1.8-1.9 billion years ago, and that created a weak zone that later led to sagging to produce the basin. [Gibson, R.I., 1995, Basement tectonics and hydrocarbon production in the Williston Basin: An interpretive overview: 7th Int'l. Williston Basin Symposium, 1995 Guidebook, p. 3-11] The Precambrian basement rocks in the center of the basin beneath the town of Williston, North Dakota lie about convert|16000|ft|m below the surface.

rejuvenated several basement structures in the Williston Basin to produce anticlines that serve as oil traps today. [Geologic Atlas of the Rocky Mountain Region, Rocky Mountain Association of Geologists, Denver, CO, 1972: p. 81-85, 88-89, 94-97, 168, 184]

Natural resources

Petroleum

. The basin's oil and gas fields are found in a wide range of geologic ages, as indicated by the generalized stratigraphic column. [Peterson, J., Williston Basin Province, "in" U. S. Geological Survey 1995 National Assessment of United States Oil and Gas Resources, Digital Data Series DDS-30, Release 2, CD-ROM]

Oil was first found in the Williston Basin along the Cedar Creek Anticline in southeastern Montana, in the 1920s and 1930s. [ [http://www.fossil.energy.gov/programs/oilgas/publications/eor_co2/Williston_Basin_Document.pdf Oil Exploration History of Williston Basin] ] The basin did not become a major oil province until the 1950s when large fields were discovered in North Dakota. Production peaked in 1986, but in the early 2000s significant increases in production began because of application of horizontal drilling techniques, especially in the Bakken Formation. [Diagenesis and Fracture Development in the Bakken Formation, Williston Basin: Implications for Reservoir Quality in the Middle Member, by Janet K. Pitman, Leigh C. Price, and Julie A. LeFever, U.S. Geological Survey Professional Paper 1653, 2001]

Cumulative basin production totals about convert|3.8|Goilbbl|m3 of oil [ [http://www.fossil.energy.gov/programs/oilgas/publications/eor_co2/Williston_Basin_Document.pdf Cumulative oil production] ] and convert|470|Gcuft|m3 of natural gas [ [http://www.searchanddiscovery.net/documents/2006/06088houston_abs/abstracts/burke.htm Cumulative gas production] ] . Oil production in 2007 averaged about convert|120|Moilbbl/d|m3/d in North Dakota and convert|95|Moilbbl/d|m3/d in Montana, making them #8 and #10, respectively, among United States oil producing states. [ [http://tonto.eia.doe.gov/dnav/pet/pet_crd_crpdn_adc_mbbl_m.htm Oil production by US state, 2007] ] The largest oil fields are listed in the following table, showing estimated ultimate recoveries. [Peterson, J., Williston Basin Province, "in" U. S. Geological Survey 1995 National Assessment of United States Oil and Gas Resources, Digital Data Series DDS-30, Release 2, CD-ROM]

Potash

The Canadian portion of the basin holds important deposits of potash, and is home to the Potash Corporation of Saskatchewan.

Coal

The Williston Basin holds large coal deposits, primarily in the Fort Union Formation of mostly Paleogene age.

References