Potential of Sacramento Valley Gas Province, California
Robert R. Morrison, Willis R. Brown, William F. Edmondson, John N. Thomson, Rex J. Young, 1971. "Potential of Sacramento Valley Gas Province, California", Future Petroleum Provinces of the United States—Their Geology and Potential, Volumes 1 & 2, Ira H. Cram
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The Sacramento Valley is the north half of the Great Valley of California and lies between the Sierra Nevada and Coast Ranges geomorphic provinces. This gas province produces from Upper Cretaceous and Tertiary sandstone deposited in a miogeosynclinal basin. Four tectonic episodes provided structural and strati- graphic complexities that form gas traps today.
Economic conditions tied to the regulated status of the gas market have controlled the rate of new-field discoveries in the past and will do so in the future. Cumulative production is 4.267 trillion cu ft and proved gas reserves are 2.445 trillion cu ft. Economic conditions are expected to improve as market demand provides renewed incentive to explore.
The basin appears to be near the midpoint in its productive life. Many new fields can be expected in presently producing formations, but there is less hope for major accumulations in younger or older rocks. Major structural trends have been delineated, and deeper production is expected along these trends, as well as more subtle structural and stratigraphic traps.
New discoveries are anticipated for the next 25 years, and production should continue into the next century. The estimate of undiscovered recoverable reserves, based on an analysis of currently producing formations, is 4.658 trillion cu ft. If an average recovery factor of 80 percent is assumed, the volume of undiscovered gas in place is estimated to be 5.822 trillion cu ft. The potential of the vast thicknesses of older rocks is largely unknown, and it would be a mistake either to ignore this section or to assign large volumes of reserves to it.
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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.