Extensional tectonic influence on lower and upper cretaceous stratigraphy and reservoirs, southern Powder River basin, Wyoming

Journal Article · Thu Apr 01 04:00:00 EST 1993 · Mountain Geologist; (United States)

OSTI ID:6180581

Mitchell, G C; Rogers, M H

The southern Powder River basin has been influenced significantly by an extensional system affecting Lower Cretaceous, Upper Cretaceous and Tertiary units. The system is composed of small throw, nearly vertical normal faults which are identified in the Cretaceous marine shales and that we believe are basement derived. Resultant fractures were present at erosional/depositional surfaces, both marine and nonmarine, that, in part, controlled erosion and subsequent deposition of Lower and Upper Cretaceous rocks. The normal faults also affected coal deposition in the Tertiary, now exposed at the surface. The erosion and resultant deposition formed extensive stratigraphic traps in Cretaceous units in both conventional and unconventional reservoirs. These reservoirs are interbedded with mature source rocks that have generated and expelled large amounts of hydrocarbons. Resulting overpressuring in the Fall River through the Niobrara formations has kept fractures open and has preserved primary porosity in the reservoirs. The normal faults offset thin sandstone reservoirs forming permeability barriers. Associated fractures may have provided vertical pathways for organic acids that assisted development of secondary porosity in Upper Cretaceous sandstones. These normal...faults and fractures provide significant potential for the use of horizontal drilling techniques to evaluate fractured, overpressured conventional and unconventional reservoirs.

• OSTI ID: 6180581
• Journal Information: Mountain Geologist; (United States), Journal Name: Mountain Geologist; (United States) Vol. 30:2; ISSN MOGEA2; ISSN 0027-254X
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
011000 -- Coal
Lignite
& Peat-- Reserves
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& Exploration
02 PETROLEUM
020200* -- Petroleum-- Reserves
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& Exploration
58 GEOSCIENCES
580000 -- Geosciences
CRETACEOUS PERIOD
DEVELOPED COUNTRIES
FRACTURED RESERVOIRS
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOLOGIC TRAPS
GEOLOGY
MESOZOIC ERA
MINERAL RESOURCES
MONTANA
NORTH AMERICA
OIL FIELDS
PETROLEUM DEPOSITS
PETROLEUM GEOLOGY
POROSITY
POWDER RIVER BASIN
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
SHALES
STRATIGRAPHY
TECTONICS
USA
WATERSHEDS
WYOMING