Petroleum Potential of Paradox Region
Richard C. Schneider, Bruce To HILL, James R. Taylor, 1971. "Petroleum Potential of Paradox Region", Future Petroleum Provinces of the United States—Their Geology and Potential, Volumes 1 & 2, Ira H. Cram
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The Paradox region, within the Colorado Plateau physiographic province, contains such major features as the San Juan, Blanding, Henry Mountain, and Kaiparowits intermontane basins, the San Rafael swell, and the Monument and Circle Cliffs uplifts.
Permian carbonate rocks and sandstone have the greatest potential for future production. The Pennsylvanian section, now the most productive part of the Paleozoic sequence, is second in potential, followed in order of decreasing potential by the Mississippian, Devonian, and Cambrian sections. Ordovician and Silurian rocks are absent in the area.
Permian, Pennsylvanian, Mississippian, and Devonian shelf-carbonate rocks in the area between the Cordi- lleran geosyncline and the Uncompahgre uplift show much promise for future prolific production from strati- graphic and structural traps. These carbonate rocks probably will be more productive in the western Paradox region than elsewhere in the area. Large accumulations of oil may be found in Mississippian and Devonian carbonate rocks on structures in the Paradox fold and fault belt. Many stratigraphic traps and some structural traps are expected to be present in sequences of very porous and permeable Permian sandstone in southeastern Utah and in northwestern New Mexico.
Mesozoic and Tertiary sequences within the area are predominantly sandstone, siltstone, and shale; they show limited potential for future exploratory success. Cretaceous rocks have been eroded or are near the surface in most localities. Where the Cretaceous is buried in the San Juan basin, it has been drilled extensively to develop the prolific San Juan basin oil and gas fields. Jurassic and Triassic sequences have been explored extensively in the Blanding basin without success. These sequences generally are buried in the San Juan, Henry Mountain, and Kaiparowits basins but may lack associated source rocks, Mesozoic and Tertiary strata are potentially productive in the virtually unexplored Rio Grande trough and San Luis Valley.
Obstacles to finding new production are: (1) the relatively high costs of exploration in large parts of the region; (2) the poor surface accessibility in some areas, which limits the acquisition of sufficient seismic control to map the subsurface structure; (3) the inability to acquire acreage and explore in areas where shallow production already is established; and (4) the prohibition of exploration in national parks and monuments.
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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.