Identification of geopressured occurrences outside of the Gulf Coast
The work focused on the occurrences of geopressures in Appalachia and selected California basins. In the former region, where geopressures have been observed, the pressure gradients for the most part were only slightly above normal as in the case of the Oriskany formation of Devonian age; this unit was also characterized by extremely high salinity. The one notable exception was in the Rome trough of West Virginia where Cambrian beds at depths below 10,000 feet display very high geopressures, approaching the lithostatic gradient, and the waters are only moderately saline. Though the geothermal gradient throughout Appalachian is relatively low, even in the Rome trough, the pressure, temperature and salinity values in this area indicate that the methane content of the Cambrian formation waters is in the range of 30 to 35 SCF/barrel. The two California areas researched included the contiguous Sacramento and San Joaquin Valleys. In the first, geopressures have been principally encountered in the Forbes formation of Cretaceous age, often at very shallow depths. Further waters are invariably characterized by very low salinity, far below the salinity of normal sea water, while the geothermal gradient in apparently higher in geopressured than in normally pressured zones. In the San Joaquin Valley, geopressures are particularly noteworthy in at least two formations of Miocene age at depths generally greater than those of the Forbes. The formation waters are likewise low in salinity; however, the geothemal gradient, especially in the geopressured zones on the west side of the valley, can be extremely high, up to twice as much as the normal temperature gradient. In view of these conditions, it is estimated that in the western San Joaquin Valley the methane content of geopressured formation waters will range from 30 to 40 SCF/barrel while in the Sacramento Valley, the methane content is estimated to be 20 to 25 SCF/barrel.
- Research Organization:
- Science Applications, Inc., McLean, VA (USA)
- DOE Contract Number:
- AC08-80NV10133
- OSTI ID:
- 6481456
- Report Number(s):
- DOE/NV/10133-2; ON: DE81027583
- Country of Publication:
- United States
- Language:
- English
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03 NATURAL GAS
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GEOPRESSURED SYSTEMS
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METHANE
ABUNDANCE
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SALINITY
TEMPERATURE GRADIENTS
TENNESSEE
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ALKANES
CENTRAL REGION
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