Origin of fractured cretaceous conventional and unconventional reservoirs, southern Powder River basin, Wyoming

Conference · Sun Aug 01 04:00:00 EDT 1993 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:6684601

Mitchell, G C; Rogers, M H

Cretaceous conventional and unconventional fractured reservoirs in the southern Powder River basin, Wyoming, are associated with small throw (10 to 30 ft) normal faults. The faults are nearly vertical, trend northwest-southeast and northeast-southwest, and probably are basement derived. The faults are most easily identified in Cretaceous marine shales and are exposed at the surface in Tertiary units. Erosion and subsequent deposition of Cretaceous sandstones, limestones, and shales affected by the extensional normal faults form stratigraphic traps. The reservoirs are interbedded with, or composed of, mature source rocks have generated and expelled significant hydrocarbons. Overpressuring from the maturation and expulsion processes is still present and has preserved open fractures and porosity in reservoirs from the Lower Cretaceous Fall River through the Upper Cretaceous Niobrara formations. The faults have offset thin sandstone reservoirs forming permeability barriers. The faulting and associated fractures have provided pathways for organic acids that assisted formation of secondary perosity in Upper Cretaceous sandstones. The fracturing of mature source rocks provides areally extensive unconventional reservoirs. Fracturing associated with the extensional normal faults provides significant exploration and exploitation potential for the use of horizontal drilling techniques to evaluate multiple, fractured, overpressured conventional, and unconventional reservoirs that may contain large reserves.

• OSTI ID: 6684601
• Report Number(s): CONF-930947--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Journal Volume: 77:8
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
CARBONATE ROCKS
DEVELOPED COUNTRIES
DIRECTIONAL DRILLING
DRILLING
GEOLOGIC DEPOSITS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOLOGIC TRAPS
LIMESTONE
MINERAL RESOURCES
MONTANA
NORTH AMERICA
PETROLEUM DEPOSITS
POWDER RIVER BASIN
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
SOURCE ROCKS
USA
WATERSHEDS
WYOMING