Infrastructure / Energy futureUSGS says Bakken Formation holds large recoverable oil, gas reserves

Here is a trivia question: What U.S. state is practically identical in size to Japan? Answer: Montana (which is slightly larger). Japan’s area is 374,744 sq. km.; Montana’s area is 376,555 sq. km. The populations occupying these similar areas are not similar, though: There are 127,000,000 Japanese living on the Japanese islands, while Montana is populated — sparsely populated — by 945,000 inhabitants. Why engage in this trivial pursuit? Because North Dakota and Montana have an estimated 3.0 to 4.3 billion barrels of undiscovered, technically recoverable oil in an area known as the Bakken Formation of the Williston Basin, according to a just-released assessment by the U.S. Geological Survey (USGS). This latest assessment shows a twenty-five-fold increase in the amount of oil that can be recovered compared to the agency’s 1995 estimate of 151 million barrels of oil. The assessment also identified 1.85 trillion cubic feet of associated/dissolved natural gas, and 148 million barrels of natural gas liquids. New geologic models applied to the Bakken Formation, advances in drilling, and production technologies, and recent oil discoveries have resulted in these substantially larger technically recoverable oil volumes. About 105 million barrels of oil were produced from the Bakken Formation by the end of 2007.

               The Bakken Formation of the Williston Basin / Source: Imageshack

Technically recoverable oil resources are those producible using currently available technology and industry practices. The USGS Bakken study was undertaken as part of a nationwide project assessing domestic petroleum basins using standardized methodology and protocol as required by the Energy Policy and Conservation Act of 2000. The Bakken Formation estimate is larger than all other current USGS oil assessments of the lower forty-eight states and is the largest continuous oil accumulation ever assessed by the USGS. A continuous oil accumulation means that the oil resource is dispersed throughout a geologic formation rather than existing as discrete, localized occurrences. The next largest continuous oil accumulation in the United States is in the Austin Chalk of Texas and Louisiana, with an undiscovered estimate of 1.0 billions of barrels of technically recoverable oil. The USGS estimate of 3.0 to 4.3 billion barrels of technically recoverable oil has a mean value of 3.65 billion barrels. Scientists conducted detailed studies in stratigraphy and structural geology and the modeling of petroleum geochemistry. They also combined their findings with historical exploration and production analyses to determine the undiscovered, technically recoverable oil estimates. USGS worked with the North Dakota Geological Survey, a number of petroleum industry companies and independents, universities, and other experts to develop a geological understanding of the Bakken Formation. These groups provided critical information and feedback on geological and engineering concepts important to building the geologic and production models used in the assessment.

Five continuous assessment units (AU) were identified and assessed in the Bakken Formation of North Dakota and Montana: the Elm Coulee-Billings Nose AU, the Central Basin-Poplar Dome AU, the Nesson-Little Knife Structural AU, the Eastern Expulsion Threshold AU, and the Northwest Expulsion Threshold AU. At the time of the assessment, a limited number of wells have produced oil from three of the assessments units in Central Basin-Poplar Dome, Eastern Expulsion Threshold, and Northwest Expulsion Threshold. The Elm Coulee oil field in Montana, discovered in 2000, has produced about 65 million barrels of the 105 million barrels of oil recovered from the Bakken Formation.