The Azimuth Determination Research Of The Main Fractures In Hot Dry Rock Reservoir By Proximity Similar Microseismic Doublets

HDR(hot dry rock) resource is a kind of geothermal energy which is renewableclean energy. In the past couple of decades, it was sleeping underground all the timebecause HDR was buried deeply and the exploitation need high technical level. With thedevelopment of economy and technique, some developed countries successively beganto do some research and experiment on exploitation of HDR. These researches showthat Hydrofracturing method is one of the effective ways to exploit the HDR resources.The principle is making artificial fracture in HDR, water becomes artificial heatreservoir with absorbing the heat from surrounding rock when it flows. In order toimprove the utilization ratio and mining ratio of HDR energy, the shape, position,especially the main fractures’ distribution of artificial heat reservoir must be fullyknown. The traditional drilling and geophysical prospecting methods are incapable inthese problems due to burying deeply. However, according to the research of Prof. KojiNagano of Muroran Institute of Technology, cepstrum analytic method which is basedon AE(acoustic emission) and signal processing technology can be used to explore thedeep fractures’ distribution and orientation.Therefore, I used the AE date induced by hydrofracturing test in Soultz HDRgeothermal field from1995to1996in France as research object. Properties ofmicroseismic wave are restored through coordinate axis transformation; Proximitysimilar microseismic doublets are detected by cepstrum analysis; Then the arrival timeintervals of P-wave were obtained through Time-Quefrency analysis andthree-dimensional diagram of Time-Quefrency-Cepstrum; Finally, the relativehypocenter coordinates were calculated by arrival time intervals of P-wave, and thus thedirection of main fractures’ forward motion in artificial fracture network. The thesis hasbeen got the following results:1. It’s feasible to detect the direction of main fractures’ forward motion in artificialheat reservoir in hydrofracture HDR by proximity similar microseismic doublets;2. The main fractures’ length represented by proximity similar microseismicdoublets are11.6266m,10.3082m,32.1894m,19.9995m and12.9015m which arecalculated by relative hypocenter coordinates, realizing quantitative evaluation of mainfractures in artificial heat reservoir. 3. The main fractures’ azimuth represented by proximity similar microseismicdoublets are142Degrees,145Degrees,127Degrees,116Degrees and56Degrees,which provides reliable basis for analyzing local crustal stress and designing theproduction well.