Diagenesis of upper Cretaceous Teapot sandstones, Powder River basin, Wyoming
The Upper Cretaceous Teapot sandstones of Well Draw field, Converse County, Wyoming, are turbidite fan deposits bounded stratigraphically by marine shales. They presently occur from 6360 to 7200 ft (1920 to 2195 m), dipping to the northwest. Cored samples selected from nonbioturbated A bedsets show that the sandstones are fine to very fine-grained feldspathic litharenites. Major authigenic minerals include carbonate cement, quartz overgrowths, and clay minerals. The clay minerals originated either as alteration rims on detrital silicates or as precipitated from pore fluids. Alteration rims typically consist of illite, smectite, mixed layer illite/smectite, and lesser chlorite. Feldspars are altered to kaolinite. Precipitated clays occur as thin, unoriented, grain coating chlorite and kaolinite; pore lining mixed layer illite/smectite and lesser chlorite oriented with (001) normal to the pore wall; and unoriented, poorly crystalline, pore filling chlorite. The diagenetic sequence is: compaction and limited quartz overgrowth development; complete calcite cementation and precipitation of grain-coating clays; dissolution of carbonate cement; precipitation of pore lining and later pore filling clays; and development of second stage quartz overgrowths. Development of silicate alteration rims occurred throughout the diagenetic history. Dissolution of carbonate cement produced the majority of present-day porosity; however, this secondary porosity was reduced by precipitation of clays minerals. In the downdip sandstones, hydrodynamic flow and an increase in the abundance of detrital labile grains have caused an increased abundance of clay mineral precipitates, reducing the reservoir potential. The pore fluids which controlled sandstones diagenesis were likely provided by dewatering and diagenesis of enclosing shales.
- Research Organization:
- Texas A and M Univ., College Station
- OSTI ID:
- 6641957
- Report Number(s):
- CONF-8405216-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 68:4; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CLAYS
FEDERAL REGION VIII
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
GEOLOGY
ILLITE
KAOLIN
MINERAL RESOURCES
MINERALS
NORTH AMERICA
OIL FIELDS
OXYGEN COMPOUNDS
PETROLEUM DEPOSITS
POROSITY
RESERVOIR ROCK
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
SHALES
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SMECTITE
USA
WYOMING