Conjugate fracture pairs in the Molina Member of the Wasatch Formation, Piceance basin, Colorado: Implications for fracture origins and hydrocarbon production/exploration
The sandstones of the Molina Member of the Wasatch Formation in the Piceance basin of northwestern Colorado contain a suite of fractures that have a conjugate-pair geometry. The fractures are vertical and intersect at an acute angle of between 20 and 40 degrees. Although direct evidence of shear is rare, the fracture surfaces commonly display small steps. The fracture geometries suggest that the maximum compressive stress during fracturing was in the plane of the acute angle of the conjugate fractures: the steps are interpreted as broken-face manifestations of very low angle en echelon fractures, formed within exceptionally narrow zones of incipient shear. In contrast to the highly anisotropic permeability enhancement created by subparallel vertical extension fractures in the underlying Mesaverde Formation, the conjugate pairs in the Molina sandstones should create a well connected and relatively isotropic mesh of fracture conductivity. Increases in stress magnitudes and anisotropy during production drawdown of reservoir pressures should cause shear offsets along the fractures, initially enhancing permeability.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE Assistant Secretary for Fossil Energy, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 474852
- Report Number(s):
- SAND-97-1106C; CONF-9706100-1; ON: DE97005901; TRN: AHC29711%%22
- Resource Relation:
- Conference: Natural fracture systems in the Southern Rockies, Durango, CO (United States), 13-14 Jun 1997; Other Information: PBD: [1997]
- Country of Publication:
- United States
- Language:
- English
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