US Geological Survey


Date of this Version



Published in PROCEEDINGS. Twenty-Second Workshop on Geothermal Reservoir Engineering Stanford University, Stanford. California, January 27-29, 1997 SGP-TR- 155


An extensive suite of spinner flowmeter, high-resolution temperature and borehole televiewer logs were acquired in a 2.7-km-deep well drilled into a fault-hosted geothermal reservoir at Dixie Valley, Nevada. Localized perturbations to wellbore temperature and flow were used to identify hydraulically conductive fractures. Comparison of these data with fracture orientations from the borehole televiewer logs indicates that hydraulically conductive fractures in crystalline rocks within and adjacent to the producing fault zone have an orientation distinct from the overall fracture population. In conjunction with in-situ stress measurements from this well, Coulomb analysis indicates that these permeable fractures are critically stressed, potentially active normal faults in the current west-northwest extensional stress regime at Dixie Valley.