Possible Petroleum Resources of Offshore Pacific-Margin Tertiary Basin, Alaska
Roland Von Huene, Ernest H. Lathram, Erk Reimnitz, 1971. "Possible Petroleum Resources of Offshore Pacific-Margin Tertiary Basin, Alaska", Future Petroleum Provinces of the United States—Their Geology and Potential, Volumes 1 & 2, Ira H. Cram
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Tertiary sedimentary rocks in the Alaska Pacific-margin Tertiary basin extend onto the continental shelf, which constitutes approximately 85 percent of the 40,000-sq mi (103,600 sq km) basin. Faunal and litho- logic data from the shelf are insufficient to determine age or to describe the lithology of stratified sedimentary sequences identifiable on continuous seismic-reflec- tion records.
Structures in the Kodiak Tertiary province follow N45°E trends of the Aleutian structural system. The major feature is the Kodiak basin, bounded on the northwest by a zone of discontinuous faults extending from Hinchinbrook Island to Trinity Islands, and on the southeast by an arch at the shelf break exposing in its core upper Miocene and Pliocene strata. As much as 4 km (2.5 mi) of late Tertiary sedimentary beds fills the basin. Additional areas having potential for petroleum lie at greater depths on the upper continental slope.
Major structures offshore in the Gulf of Alaska Tertiary province east of Kayak Island predominantly follow trends of the Alaska Mainland structural system. They are west-trending anticlines 10-20 km (6-12 mi) wide and sediment-filled depressions up to 100 km (62 mi) wide. Strata commonly dip 30° or less in the depressions; however, dips steeper than 30° may have been filtered out by the seismic technique. Crestal areas of folds have been truncated by erosion. An arch is believed to form the shelf edge at most localities. Seismic records in this region are limited to 1 second or less of penetration because of the instrument used.
In the St. Elias transition, west of Kayak Island, structures following both Mainland and Aleutian structural trends are intermixed. The nature of intersection of individual structures is unknown. Structures favorable for petroleum are present, but the geology is more complex than in the area east of Kayak Island or in the Kodiak Tertiary basin, and exploration will be more difficult.
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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.