Stress and permeability heterogeneity within the Dixie Valley geothermal reservoir: Recent results from well

To understand causes for localized variations in stress and permeability in a geothermal reservoir associated with the Stillwater Fault Zone (SFZ), we collected borehole televiewer, temperature and flowmeter logs and conducted a hydraulic fracturing test in a well (82-5) that penetrated the SFZ within the known boundaries of the geothermal field but which failed to encounter significant permeability. Although stuck drill pipe prevented direct access to the SFZ, bore-hole breakouts and cooling cracks indicate a ~90° rotation in the azimuth of the least horizontal princi-pal stress (Shmin) in well 82-5 at about 2.7 km depth; similar rotations were observed in a producing well located ~0.6 km to the northeast. This rotation, to