Abstract
An artificial fracture made by hydraulic fracturing plays an important role as a heat exchanger in Hot Dry Rock geothermal system. An estimation on distribution of fracture width before hydraulic fracturing is necessary in designing HDR system. A laboratory test was carried out to estimate the width of an artificial fracture. A cubic rock specimen, Inada granite, was set into a rigid steel frame, and hydraulic pressure was applied to make a fracture. After hydraulic fracturing, water was injected. A flow rate of injected water was increased step by step. An injection pressure, flow rate and displacements of free surfaces were measured during these injection tests. Unlikely to similar experiments done before, the displacements of the free surfaces which was parallel to fracture were measured. Based on the experiment result, the distribution of fracture width and pressure along the fracture was estimated by using combine analysis of analytical and Finite Element Method. By the analysis proposed in this paper, the distribution of fracture width and pressure, which had been hard to be measured, could be estimated successfully.
