Transducer Technology for Deep Borehole Geothermal Environments

摘要

Hydraulic-fracturing experiments, as a part of the Los Alamos Dry Hot Rock Geothermal Energy Program, were conducted in the Jemez Mountains 40 miles (60 km) west of Los Alamos, New Mexico on the western rim of the Valles Caldera. Pressurization was accomplished in a 2040-m-deep borehole in the Precambrian basement rock at a bottomhole temperature of 145 exp 0 C. Instrumentation was designed to measure breakdown and crack-extension parameters in the borehole. In situ measurements of pressure, temperature, and acoustic velocities required brute-force techniques in the high-pressure, high-temperature environment during long-term tests of up to 12 hours. Special armored logging cable of high-temperature Tefzel, enclosing shielded pairs, provided communication between a downhole instrumentation sonde and a recording facility at the surface. Lack of suitable downhole signal conditioning limited the number of data channels that could be employed for the in situ measurements.