Geologic description of middle Devonian Chert Reservoir, Block 31 field, Crane County, Texas
Block 31 field is a large anticlinal structure that produces from six pay zones. The first miscible gas-injection enhanced oil recovery project has been operated by ARCO since 1952 in the middle Devonian reservoir, which is the main producing interval in the field. The middle Devonian unit was deposited as a siliceous, calcareous ooze in a basin-slope environment in the ancient Tobosa basin. Sedimentation buried earlier fault blocks, as the slope deposits aggraded and prograded mainly from the west and south. Subsequent diagenesis converted the ooze into calcareous chert. Reservoir quality of the chert depends on degree of compaction and quartz cementation. Gray, dense, glassy chert at the base of the sequence is nonporous except for small, incipient fractures in the brittle matrix. Creamy white, evenly laminated, microporous, calcareous chert, which alternates with and overlies the dense chert in the lower half of the middle Devonian interval, has porosity of 10-30% and permeability as great as 10 md. The upper half of the reservoir interval consists mainly of light-gray and white, partially porous, heterogeneous, calcareous chert. This rock type has porosity of 5-20%, but permeability is usually less than 3 md. Patchy silica cement, discontinuous low-permeability laminae, and thin beds of dense limestone reduce its effectiveness as a reservoir.
- OSTI ID:
- 6634026
- Report Number(s):
- CONF-880301-
- Resource Relation:
- Conference: Annual meeting of the American Association of Petroleum Geologists, Houston, TX, USA, 20 Mar 1988
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CHERT
GEOLOGY
PETROLEUM DEPOSITS
TEXAS
CATAGENESIS
DEVONIAN PERIOD
EXPLORATION
LAMELLAE
LIMESTONE
POROSITY
QUARTZ
RESERVOIR ROCK
SEDIMENTATION
SILICA
CARBONATE ROCKS
CHALCOGENIDES
FEDERAL REGION VI
GEOLOGIC AGES
GEOLOGIC DEPOSITS
MINERAL RESOURCES
MINERALS
NORTH AMERICA
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PALEOZOIC ERA
RESOURCES
ROCKS
SEDIMENTARY ROCKS
SILICON COMPOUNDS
SILICON OXIDES
USA
020200* - Petroleum- Reserves
Geology
& Exploration