P. T. Kinnison, 1971. "Future Petroleum Potential of Powder River Basin, Southeastern Montana and Northeastern Wyoming", Future Petroleum Provinces of the United States—Their Geology and Potential, Volumes 1 & 2, Ira H. Cram
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The Powder River basin in northeastern Wyoming and southeastern Montana is an asymmetric structural depression, deepest along the west flank. All but 6 percent of its 42,000-sq mi (108,780 sq km) area has oil potential. Pre-Pennsylvanian strata offer possibilities for production, especially in the Ordovician Red River or Bighorn, which have been only partly tested. Good recoveries from the upper Minnelusa (Lower Permian) probably can be extended beyond the areas of present production. Lower Mesozoic sedimentary rocks have limited potential because good source beds are absent and trapping conditions are poor. The Cretaceous System, which has yielded two thirds of the oil already produced in the Powder River basin, offers the best prospects for the future. All formational units except the Lance have been productive, but 90 percent of the oil has come from the upper Inyan Kara (Fall River) and Muddy-Newcastle zones. Although only a small fraction of the volume of Cretaceous sedimentary rocks appears to offer favorable reservoir potential, it is estimated that total oil in place is 6 billion bbl; 10 billion bbl is the speculative figure. Cumulative production to the date of this report is a scant 349 million bbl.
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The geology of the entire United States, including the continental shelf and slope, was studied by petroleum geologists to determine its petroleum potential. Prospective areas of the 11 regions were assessed qualitatively and, usually, quantitatively.
The prospective basinal area covers approximately 3.2 million sq mi (statute; 8.3 million sq km) and contains approximately 6 million cu mi (25 million cu km) of sedimentary rock above basement or 30,000 ft (9,144 m). Other less prospective areas are, in the aggregate, large.
The prospective area has not been explored adequately. Many high-potential areas are indicated by the geology and extent of exploration, particularly in parts of Alaska, California, Colorado, Louisiana, Mississippi, Montana, New Mexico, North Dakota, Oklahoma, Texas, Utah, and Wyoming, and in parts of the offshore of Alaska, California, Louisiana, and Texas. The prospective Atlantic, Florida, and Alaska continental shelves, and the entire continental slope, barely have been touched by drilling, and other prospective areas and depths on land and the continental shelf remain largely unexplored.
Estimates of potential crude oil reserves of the basinal area only, exclusive of known reserves, range from 227 to 436 billion bbl of original oil in place. The potential probably exceeds the mean of 332 billion bbl. Approximately 32 percent of the oil in place would be recoverable at known rates of recovery. Ultimately, the rate of recovery may reach 60 percent.
Estimates of potential natural gas reserves exclusive of known reserves range from 595 to 1,227 trillion cu ft of recoverable natural gas. The gas potential also probably exceeds the mean of 911 trillion cu ft.
The ultimate petroleum potential of the United States, including known reserves, may exceed 432 billion bbl of crude oil, 1,543 trillion cu ft of natural gas, and 49 billion bbl of natural gas liquids.
Finding and developing the large petroleum potential will require a great amount of drilling because a significant percentage of the visualized undiscovered crude oil and natural gas is in stratigraphic traps, combination stratigraphic and structural traps, reefs, and complex structural situations. Estimates of future domestic demand call for accelerated exploration. To the extent that policies of industry and government militate against accelerated exploration, particularly drilling, a high percentage of the petroleum resources of the United States will not be reduced to possession.