Televiewer Measurement of the Orientation of in situ Stress at the Fenton Hill Hot Dry Rock Site, New Mexico

Abstract

The in situ stress at Fenton Hill has been determined in drill hole EE-3A by observations of wellbore breakouts on imagery obtained with a televiewer logging tool. Wellbore shape, tool off centering, and tool misalignment cause geometric distortions which have been treated by comparing imagery from two logging runs made six months apart. The comparison establishes that wellbore degradation in drill hole EE-3A is due to breakouts, which grow larger with time. The azimuth of the axis of minimum horizontal principal stress is estimated to be 110.7 +/- 10.3 deg E of true N at a depth of 11,500 ft increasing with depth at a rate of 1 deg per 50 ft. This method of measuring the orientation of horizontal principal axes is considerably more accurate than previous methods tried at Fenton Hill. The results agrees generally with other stress indicators. The results support the concept that direction of reservoir growth during hydraulic stimulation favors the intermediate axis over other principal axes of stress.