John E. Stauffer, 1971. "Petroleum Potential of Big Horn Basin and Wind River Basin—Casper Arch Area, Wyoming, and Crazy Mountain Basin—Bull Mountains Basin Area, Montana", Future Petroleum Provinces of the United States—Their Geology and Potential, Volumes 1 & 2, Ira H. Cram
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Area 6 of the northern Rocky Mountain oil province includes the prolifically oil-productive Big Horn basin and Wind River basin-Casper arch in Wyoming and the less productive Crazy Mountain and Bull Mountains basins in Montana. Most of the study area was a part of the Wyoming shelf east of the Cordilleran miogeosyncline during the Paleozoic and Mesozoic Eras, and the present structural features were formed during the Laramide orogeny. The district has produced 2.4 billion bbl (end of 1968) of the 10.9 billion bbl of oil originally in place, and 1.4 trillion cu ft (end of 1967) of the 2.6 trillion cu ft of natural gas in place. More than 80 percent of the oil is contained in Paleozoic rocks. With present technology, only 10 percent of the remaining known oil will be recovered, but secondary recovery may yield more. Structural traps have been drilled extensively; stratigraphic traps, which have had little exploitation, can be expected to add significantly to reserves, especially in the Big Horn basin and Wind River basin-Casper arch structures.
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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.