Fracture Permeability and in Situ Stress in the Dixie Valley, Nevada, Geothermal Reservoir
We have collected and analyzed fracture and fluid flow data from wells both within and outside the producing geothermal reservoir at Dixie Valley. Data from wellbore imaging and flow tests in wells outside the producing field that are not sufficiently hydraulically connected to the reservoir to be of commercial value provide both the necessary control group of fracture populations and an opportunity to test the concepts proposed in this study on a regional, whole-reservoir scale. Results of our analysis indicate that fracture zones with high measured permeabilities within the producing segment of the fault are parallel to the local trend of the Stillwater fault and are optimally oriented and critically stressed for frictional failure in the overall east-southeast extensional stress regime measured at the site. In contrast, in the non-producing (i.e., relatively impermeable:) well 66-21 the higher ratio of S{sub hmin} to S{sub v} acts to decrease the shear stress available to drive fault slip. Thus, although many of the fractures at this site (like the Stillwater fault itself) are optimally oriented for normal faulting they are not critically stressed for frictional failure. Although some of the fractures observed in the non-producing well 45-14 are critically stressed for frictional failure, the Stillwater fault zone itself is frictionally stable. Thus, the high horizontal differential stress (i.e., S{sub Hmax}-S{sub hmin}) together with the severe misorientation of the Stillwater fault zone for normal faulting at this location appear to dominate the overall potential for fluid flow.
- Research Organization:
- USDOE Idaho Operations Office, Idaho Falls, ID; Geophysics Department, Stanford University (US)
- Sponsoring Organization:
- USDOE Office of Geothermal Technologies (EE-12) (US)
- DOE Contract Number:
- FG07-96ID13452
- OSTI ID:
- 12560
- Report Number(s):
- DOE/ID/13452; TRN: AH200120%%356
- Resource Relation:
- Other Information: PBD: 8 Mar 1999
- Country of Publication:
- United States
- Language:
- English
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