Hydrocarbon exploration in Western Oregon and Washington
Continuing development of the Mist gas field and stepout discovery wells affirm the hydrocarbon prospectivity of western Oregon and Washington. Reservoir sandstones in the Mist area are in the Cowlitz Formation of middle to late Eocene age. Reservoir-quality sandstones have average porosities of 25% and average permeabilities of 200 md. The reservoir sands are wellsorted feldspathic-quartzose sandstones and are less susceptible to diagenetically formed pore-filling authigenic minerals than are the more lithic sandstones of other horizons and less well-sorted depositional environments. Potential hydrocarbon source rocks consist of marine shale to coaly facies. Organic matter is predominately terrestrially derived. Mist gas field pools are small and have variable gas types, suggesting to some workers that the gas is generated from rocks immediately adjacent to the reservoir. Gas wetness and delta/sup 13/C values indicate that gas from the Bruer, Flora, and Newton pools is probably thermally generated. Shales encasing the Mist gas field sandstone reservoirs are thermally immature, having vitrinite reflectance values less than 0.4%. Thermal gas most likely would have been generated downdip within nearby depocenters and migrated into the reservoir. The integration of paleogeographic models for mineralogic provenance, well-sorted sand accumulation, and thermal maturation within Cenozoic depocenters provides an exploration strategy for defining areas of highest hydrocarbon potential in western Oregon and Washington.
- Research Organization:
- Mobil Oil Corp, Dallas, TX
- OSTI ID:
- 5358926
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 69:4; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
020200* -- Petroleum-- Reserves
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03 NATURAL GAS
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CENOZOIC ERA
CHEMISTRY
EXPLORATION
FEDERAL REGION X
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC MODELS
GEOLOGY
MATURATION
MINERAL RESOURCES
MINERALOGY
NATURAL GAS DEPOSITS
NORTH AMERICA
OREGON
PETROLEUM DEPOSITS
RESERVOIR ROCK
RESOURCES
ROCKS
SEDIMENTARY ROCKS
SHALES
TERTIARY PERIOD
USA
WASHINGTON