Cook Inlet province, which at present is the only productive oil region in Alaska, produced 66 million bbl of oil and 100 billion cu ft of gas in 1968. Commercial discoveries of major fields on the North Slope await solution of logistic problems before production can begin. Cook Inlet province occupies an inter- montane sedimentary basin 900 mi (1,448 km) long and 5-50 mi (8-80 km) wide. It contains the oil-productive nonmarine Tertiary section, which overlies untested late Mesozoic rocks. Current estitmates of oil in place of 2.6 billion bbl may be increased to as much as 7.9 billion bbl. Gas in place, now estimated at 5 trillion cu ft, may total 14.6 trillion cu ft as a result of exploration of the Mesozoic secion and extension of the present restricted area of development. North Slope oil already is estimated to be more than 5 billion bbl on the basis of initial discoveries in only one of three potentially productive geologic zones. Other Tertiary sedimentary areas —e.g., Bristol Bay, the Bering Sea shelf, and the Pacific margin both onshore and offshore—hold less promise, but their potential is by no means negative.
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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.