Large reserves of oil and gas have been discovered and produced in the Texas and Oklahoma Panhandles, and it is anticipated that significant new gas and some additional oil reserves will be found there in the future.
Approximately 1.4 billion bbl of the known recoverable oil reserves had been produced to January 1, 1968. Total gas production (including associated, dissolved, and nonassociated gas) is estimated to be 38.8 trillion cu ft. Approximately 99 percent of the established oil and gas reserves is in rocks which range from Chesteran (Mississippian) to Leonardian (Permian) in age. As a result, exploration of these strata has been extensive. Continued exploitation in the form of infill drilling in proved areas and extensions to partially defined fields, both stratigraphic and structural, may result in the discovery of additional oil and gas reserves. These new reserves will be small in relation to those now established. Most of the new gas reserves are expected to be found within the almost continuous carbonate section below the Chesteran. Only 37 basement tests have been drilled, and the majority of these are concentrated in the shallower western parts of the Anadarko and Dalhart basins.
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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.