Significant reserves of oil and gas have been established in the western Kansas—western Nebraska region. The major oil and gas provinces of this region are the Central Kansas uplift and the Hugoton embayment, respectively. Of the known oil reserves, approximately 2.2 billion bbl had been produced to 1968. The Central Kansas uplift alone has produced about 2 billion bbl, and of this amount it is estimated that nearly 70 percent was obtained from the Arbuckle Group. In the Kansas part of the Hugoton embayment Wolfcampian rocks had produced 9.4 trillion cu ft of gas to 1968, which accounts for about 60 percent of the 15.5 trillion cu ft produced in the state.
It does not appear, however, that Arbuckle and Wolfcampian rocks will be sources of significant new oil and gas reserves in the western Kansas—western Nebraska region. Both of these units have been explored and developed for more than 40 years, and their productive limits seem to be well defined. Outside the Hugoton embayment, Wolfcampian rocks have been penetrated by many wildcat and development wells which did not find production. Away from the Central Kansas uplift, Arbuckle rocks have been tested on several structures but results have not been encouraging.
Figures & Tables
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.