Fracture Evaluation by Vertical Electric Profiling

Abstract

For Hot Dry Rock (HDR) geothermal energy development, it is necessary to establish techniques for creating artificial fractures and for evaluating a man-made circulation system as geothermal reservoirs. In this study, we have developed the Fluid Flow Tomography (FFT) technique using the Vertical Electric Profiling (VEP/hole-to-surface) method in which a casing pipe of fracturing well can be used for a current electrode. The fluid flow behavior was continuously detected and monitored with 30 stations on the ground surface during massive hydraulic fracturing operations. The VEP method provides lateral distribution of major fractures with time, while the crosshole (hole-to-hole) survey gives informations on fracture depths connected among the injection and production wells. Therefore, we can image the fluid front with time variations and major fractures in three-dimentions by the joint use of VEP (hole-to-surface) and crosshole (hole-to-hole) surveys on the HDR project.