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National Assessment of Oil and Gas Project - Williston Basin Province (031) Assessment Units

Published by U.S. Geological Survey | Department of the Interior | Metadata Last Checked: January 27, 2026 | Last Modified: 2021-06-16T00:00:00Z
The Assessment Unit is the fundamental unit used in the National Assessment Project for the assessment of undiscovered oil and gas resources. The Assessment Unit is defined within the context of the higher-level Total Petroleum System. The Assessment Unit is shown here as a geographic boundary interpreted, defined, and mapped by the geologist responsible for the province and incorporates a set of known or postulated oil and (or) gas accumulations sharing similar geologic, geographic, and temporal properties within the Total Petroleum System, such as source rock, timing, migration pathways, trapping mechanism, and hydrocarbon type. The Assessment Unit boundary is defined geologically as the limits of the geologic elements that define the Assessment Unit, such as limits of reservoir rock, geologic structures, source rock, and seal lithologies. The only exceptions to this are Assessment Units that border the Federal-State water boundary. In these cases, the Federal-State water boundary forms part of the Assessment Unit boundary.

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5031 = Williston Basin Province 503101 = Bakken - Lodgepole Total Petroleum System 50310101 = Middle Member Sandstone 50310102 = Lodgepole 50310161 = Elm Coulee - Billings Nose 50310162 = Central Basin - Poplar Dome 50310163 = Nesson - Little Knife Structural 50310164 = Eastern Expulsion Threshold 50310165 = Northwest Expulsion Threshold 503102 = Winnipeg-Deadwood 50310201 = Winnipeg-Deadwood 503103 = Red River 50310301 = Red River Fairway 50310302 = Red River East Margin 50310303 = Interlake-Stonewall-Stony Mountain 503104 = Winnipegosis 50310401 = Winnipegosis 503105 = Duperow 50310501 = Dawson Bay-Souris River 50310502 = Duperow-Birdbear 503106 = Cedar Creek Paleozoic Composite 50310601 = Cedar Creek Structural 503107 = Madison 50310701 = Mission Canyon-Charles 503108 = Tyler 50310801 = Tyler Sandstone 503109 = Shallow Biogenic Gas 50310901 = Shallow Biogenic Gas 503110 = Coalbed Gas 50311081 = Ft. Union Coalbed Gas Assessment Unit Bakken Formation Earth Science Economic geology Energy Resources Geology National Assessment of Oil and Gas Natural Gas Natural Resources Natural gas resources Northern Great Plains Oil Oil sand resources Oil shale resources R.M. Pollastro, L.O. Anna, S.B. Gaswirth Resource Assessment U.S. Geological Survey US30 = Montana US38 = North Dakota US46 = South Dakota USGS USGS World Energy Region 5 USGS:60ca57b0d34e86b938a10779 United States Williston Basin geoscientificInformation noga2000 nogawilliston oilgas

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