| Abstract |
There are many geothermal areas in Japan. These areas are located tectonically active regions. In these areas we can access hot rock at relatively shallow depth, but there are many natural joints in the rock. Original Hot Dry Rock (HDR) geothermal energy system designed by Los Alamos National Laboratory (LANL) considered extracting heat from deep and low permeability rock. Therefore, we thought that we needed some new technologies for constructing the HDR system in Japan. We designed an HDR heat extraction model of multiple reservoirs and multiple production wells. For realizing the HDR model, we had conducted field experiments at Ogachi from 1989 to 2002. In these experiments, we developed new technologies, for example, a multiple reservoir creation method without open-hole packers, an electrical reservoir evaluation method, a numerical simulation code for predicting heat extraction, a temperature monitoring method by using a fiber optic thermometer, and so on. Using these technologies, we succeeded to produce hot water and steam at a temperature of 165 degree C in some water circulation tests between two 1,000 m class wells through artificially created two reservoirs. Unfortunately, we could not apply the multiple production wells system because of financial problems. The water recovery rate in the water circulation tests was relatively small of 25 to 32 % comparing with that of other HDR programs such as LANL. However, we simulated that the water recovery would increase 44 % if we had another production well. If we had four production wells and use down-hole pump, we expected to be able to get the recovery more than 80 %. We considered that the basic technologies for constructing HDR system in Japanese thermal and geological condition had been developed. Now we are applying some of these technologies to the Australian HDR program in Cooper Basin for improving the technologies and contributing the program. |