Diagenesis of sandstones in Permian upper Minnelusa Formation, West Mellott field, Powder River Basin, Wyoming
Dolomite-anhydrite-sandstone cycles of the Permian upper Minnelusa Formation, Wyoming, record multiple progradations of marine, siliciclastic sabkha, and eolian sediments. Heterogeneity in the sandstones, studied in five cores from present-day depths between 7,100 and 7,300 ft, is partly the result of diagenetic alterations. The earliest alternation was the formation of clay coatings on the detrital grains, particularly in siliciclastic sabkha and related eolian sandstones. Quartz cement formed small overgrowths, particularly in the siliciclastic sabkha sandstones. Carbonate clasts in the sandstones were pervasively dolomitized, as were the adjacent carbonate beds, possibly by reflux associated with brines that formed during the evaporitic stage of the next sedimentary cycle. The sandstones were then partially cemented with anhydrite (or gypsum). Clay coatings and partial cementation by anhydrite did not completely prevent a progressive loss of intergranular volume by pressure solution with burial. The illitization of early clay coatings was also a progressive process with burial. Late-stage dissolution of anhydrite produced irregularly distributed secondary sandstone porosity that ranged to approximately 30%; dissolution was most complete in the upper parts of eolian-dune and reworked-eolian sandstones, resulting in excellent reservoir properties. Late-stage dissolution of potassium feldspars also occurred, as evidenced by the lack of compaction of the partially dissolved grains. Hydrocarbons then migrated into and occupied the secondary porosity of the upper arts of eolian-dune sandstones and reworked-eolian sandstones at West Mellott.
- OSTI ID:
- 5955769
- Report Number(s):
- CONF-880301-
- Country of Publication:
- United States
- Language:
- English
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ALKALINE EARTH METAL COMPOUNDS
ANHYDRITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CALCIUM SULFATES
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CATAGENESIS
CHALCOGENIDES
DOLOMITE
EXPLORATION
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GEOLOGY
HETEROGENEOUS EFFECTS
IRON COMPOUNDS
IRON SULFIDES
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MINERAL RESOURCES
MINERALS
MONTANA
NATURAL GAS DEPOSITS
NORTH AMERICA
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PALEOZOIC ERA
PERMIAN PERIOD
PETROLEUM DEPOSITS
PETROLEUM GEOLOGY
POWDER RIVER BASIN
PYRITE
QUARTZ
RESERVOIR ROCK
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
SILICATES
SILICON COMPOUNDS
SILICON OXIDES
SULFATE MINERALS
SULFATES
SULFIDE MINERALS
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
USA
WYOMING