Petrography stable-isotope geochemistry and diagenesis of Miocene sandstones, Vermilion Block 31, offshore Louisiana
Sandstones from three conventional cores between depths of 11,140 and 14,910 ft (3345 and 4545 m) currently have an average composition of Q/sub 86/F/sub 10/R/sub 4/, but have lost approximately 5% feldspar to replacement by carbonates and to dissolution. Like other deeply buried Gulf Coast sandstones, plagioclase is being albitized and K-feldspar is dissolving. Patterns of feldspar distribution in the deeper cores suggest that tight cementation by calcite retarded feldspar diagenesis and that waters of different composition or temperature must have invaded different sandstone beds in close proximity. Calcite, quartz, and chlorite are most responsible for causing deterioration of reservoir quality. Calcite volume averages 4.8% and occludes all pores in samples containing more than 5% calcite. Textural relations and isotopic data indicate that calcite precipitated over a broad temperature range and from fluids of variable composition during burial. The /sup 87/Sr//sup 86/Sr ratio of cements is consistent with the derivation of the Sr from coeval, or only very slightly older skeletal material, prior to extensive silicate reactions.
- Research Organization:
- Univ. of Texas, Austin (USA)
- OSTI ID:
- 6180744
- Report Number(s):
- CONF-8810362-
- Journal Information:
- AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States), Journal Name: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States) Vol. 72:9; ISSN AABUD
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
020200* -- Petroleum-- Reserves
Geology
& Exploration
ALKALINE EARTH METAL COMPOUNDS
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CHEMISTRY
DIAGENESIS
FEDERAL REGION VI
GEOCHEMISTRY
GEOLOGIC DEPOSITS
LOUISIANA
MINERAL RESOURCES
MINERALS
NORTH AMERICA
OFFSHORE SITES
OXYGEN COMPOUNDS
PETROLEUM DEPOSITS
POROSITY
RESERVOIR ROCK
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
USA