Effects of thermal sulfate reduction on permeability distributions of the Norphlet Formation

Conference · Fri Mar 01 04:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5574601

Dunn, T L; Surdam, R C ^[1]

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1. Univ. of Wyoming, Laramie (United States)

Framework grain coatings are common in the Norphlet. Clay coatings are present throughout the depth range (16,000 to 22,000 ft) over which significant variations of permeability occur. Pyrobitumen coatings occur within the deep, low-permeability interval (approximately 18,000-20,000 ft) and the deeper (greater than 20,000 ft), more permeable interval. Both types of coatings may be important in preserving porosity during portions of the burial history of the Norphlet sandstones; however, their occurrence does not correlate with observed variations in permeability. Diagenetic reactions associated with thermal sulfate reduction provide a mechanism for the dissolution of carbonate cements in deep zones characterized by enhanced permeabilities. Protons generated from dissociation of H{sub 2}S produced during sulfate reduction results in the dissolution of carbonate cements. To be effective, this process must remove cements that precipitated after grain coatings. Uncoated quartz grains produce quartz overgrowths. Vertical permeability distributions within the Norphlet suggest that early and intermediate diagenetic carbonate and sulfate cements, sourced from the intercalated, interdunal pond strata, were redistributed throughout the dune sands. Portions of carbonate cements were either dissolved or the extent of their precipitation was reduced as thermal decarboxylation was closely followed by the initiation of sulfate reduction. Hence, variations in Norphlet permeability distributions are in part the result of diagenetic reactions associated with thermal sulfate reduction and, therefore, can be predicted using kinetic modeling of sulfate reaction.

• OSTI ID: 5574601
• Report Number(s): CONF-910403--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Journal Volume: 75:3
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
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58 GEOSCIENCES
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BUILDING MATERIALS
CALCITE
CARBONATE MINERALS
CEMENTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CLAYS
DEVELOPED COUNTRIES
DIAGENESIS
DISSOLUTION
FEDERAL REGION VIII
GEOLOGIC DEPOSITS
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KINETICS
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MINERALOGY
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OXYGEN COMPOUNDS
PERMEABILITY
PETROLEUM DEPOSITS
POROSITY
REACTION KINETICS
REDUCTION
RESERVOIR ROCK
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
SULFATES
SULFUR COMPOUNDS
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WYOMING