E. H. Rainwater, 1971. "Possible Future Petroleum Potential of Lower Cretaceous, Western Gulf Basin", Future Petroleum Provinces of the United States—Their Geology and Potential, Volumes 1 & 2, Ira H. Cram
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Lower Cretaceous sedimentary rocks probably underlie most of the western Gulf basin, though they are deeply buried in much of the area and have not been penetrated by wells. Average thickness of strata in the productive and prospective belts is about 4,000 ft (1,220 m); the area is 177,000 sq mi (458,430 sq km), and the volume of sedimentary rock is approximately 130,000 cu mi (541,700 cu km). A nonprospective belt, with an area of 86,000 sq mi (222,740 sq km) and a sedi- mentary-rock volume of about 40,000 cu mi (166,680 cu km), is updip from the proved belt. A speculative zone, which extends basin ward from the prospective belt to the outer edge of the continental shelf, has an area of 77,000 sq mi (199,430 sq km); its sedimentary- rock volume may be more than 50,000 cu mi (208,350 cu km).
The sedimentary section is composed of carbonate and terrigenous clastic rocks; much of the sediment was deposited in environments favorable for the generation and accumulation of oil and gas. Approximately 300 fields in Texas, Louisiana, Arkansas, Mississippi, and Alabama have produced about 1.5 billion bbl of oil and 10.5 trillion cu ft of gas from Lower Cretaceous sandstone and carbonate rocks. The ultimate recovery from the fields and their extensions, and from new discoveries within the productive belt, will be more than double the amount already produced. In the more seaward, unexplored province, especially in the Mississippi and Rio Grande embayments and in the East Texas basin, numerous accumulations will be found in limestone reefs, shell mounds, porous dolomite, and deltaic sandstone. The petroleum potential of the thick and widespread Lower Cretaceous in the western Gulf Coast is very great.
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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.