Determination of in-Situ Stress to Predict Direction of Hydraulically Created Fractures for Development of Hot Dry Rock Geothermal Reservoir in Japan

摘要

It is very important to know the underground stress state to design and complete a Hot Dry Rock geothermal reservoir because the direction of the hydraulic fractures depends on the earth stress. The hydraulic mini fracturing technique was introduced to determine the in-situ stress state without assuming the borehole axis to be parallel to one of the principal stresses. Small scale hydraulic fracturing tests were conducted to verify this technique at an underground power plant and microseismic activities were monitored for fracture mapping. The direction of the fracture propagation was estimated from the in-situ stress state and compared with the fracture plane mapped by microseismic activities. 2 refs., 7 figs., 1 tab. (ERA citation 10:041590)