Prediction of fracture networks at depth in low-permeability reservoir rocks, Piceance and Washakie basins, western United States
- Geological Survey, Denver, CO (USA)
Comparison of fracture networks in surface rocks with those of correlative, fracture-controlled petroleum reservoir rocks at depth in the Piceance and Washakie basins indicates both simple and complex relations among the networks. Documented subsurface networks at two sites in the Piceance basin, Colorado - the C-a mine in Eocene oil shales and the US Department of Energy's Multiwell Experiment (MWX) site in Upper Cretaceous strata - differ greatly despite similar surface networks in Paleocene-Eocene strata. At the C-a mine the subsurface fracture network to depths of at least 950 ft closely resembles that at the surface and shows systematic changes in fracture spacing and aperture with depth. At the MWX site, however, the fracture network in Cretaceous reservoir rocks at depths of 4,000 to 8,000 ft is wholly unlike that at the surface. Among exposed, laterally equivalent Cretaceous strata along the basin rim, those to the west are cut by young fracture sets correlative with sets in the Paleocene-Eocene surface rocks around the MWX site, whereas those along the eastern margin are cut by the same older sets as found at depth. In the Washakie basin, Wyoming, subsurface fracture data are not available. Only the youngest fracture sets in exposed, reservoir-equivalent strata can be correlated from the east to the west rim of the basin; the older sets cannot. These results suggest, for the older sets, either different timing of fracture events or rotation of the regional stress field across the basin, such that equivalent sets have unlike orientations between the two rims. Successful prediction of the subsurface fracture network at the C-a mine is due in part to minimal lithologic variability and relatively shallow mining depths. At the MWX site, subsurface prediction is complicated by the different burial and tectonic histories of the different parts of the Piceance basin.
- OSTI ID:
- 5570760
- Report Number(s):
- CONF-8910195--
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (USA), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Vol. 73:9; ISSN AABUD; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
020200* -- Petroleum-- Reserves
Geology
& Exploration
BITUMINOUS MATERIALS
CARBONACEOUS MATERIALS
COLORADO
CRETACEOUS PERIOD
ENERGY SOURCES
FEDERAL REGION VIII
FOSSIL FUELS
FUELS
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
MATERIALS
MESOZOIC ERA
MINERAL RESOURCES
NATIONAL ORGANIZATIONS
NORTH AMERICA
OIL SHALES
PERMEABILITY
PETROLEUM DEPOSITS
POROSITY
RESEARCH PROGRAMS
RESERVOIR ROCK
RESOURCES
SEDIMENTARY BASINS
TECTONICS
US DOE
US ORGANIZATIONS
USA