A depositional setting for the Mist gas field reservoir sands
- ARCO Oil and Gas Co., Bakersfield, CA (United States)
The depositional origin of the upper Eocene Clark and Wilson (C and W) sandstone member (informal) of the Cowlitz Formation near Mist, Oregon, is controversial. Previous workers have suggested a deep-water setting for the C and W sands. However, recent interpretations of integrated surface and downhole data from Oregon's Mist gas field suggest a wave-dominated deltaic to shallow-marine depositional environment for the C and W sandstone. Sedimentary structures, lithofacies associations, mapped sand geometries, and petrographic examinations indicate that strong wave processes reworked a progradational delta-front environment during a transgression, winnowing fines and controlling C and W sandstone deposition. These well-sorted arkosic sands were deposited following an abrupt relative sea level regression; they onlap an underlying basaltic rock suite and were sourced largely from batholithic masses and Idaho and Washington. Outcrop mapping, studies of continuous cores, and electric-log interpretation show that the Clark and Wilson consists of a 400 to 800-ft-thick series of five stacked, massive-to-hummocky bedded, coarsening- and thickening-upward sandstones separated by minor bioturbated siltstones and lignites. Extensive subsurface mapping delineates individual sandstone bodies that exhibit sheet-like geometries and lateral continuity over areas as great as 60 mi{sup 2}. The authors interpret the siltstone and lignite deposits to represent restricted marine or brackish-water deposition behind a high-energy C and W shoreline.
- OSTI ID:
- 5219150
- Report Number(s):
- CONF-9103128--
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Vol. 75:2; ISSN AABUD; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
030200* -- Natural Gas-- Reserves
Geology
& Exploration
CENOZOIC ERA
DEPOSITION
DEVELOPED COUNTRIES
EOCENE EPOCH
FEDERAL REGION X
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GEOLOGY
GEOMETRY
MAPPING
MATHEMATICS
MINERAL RESOURCES
NATURAL GAS DEPOSITS
NORTH AMERICA
OREGON
PETROGRAPHY
RESERVOIR ROCK
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
STRATIGRAPHY
TERTIARY PERIOD
USA