In Japan, the development of renewable energies is expected against not only the global warming but also the disaster of nuclear power plant and an energy policy which showed a plan of the electricity generation for each energy in 2030 was announced. Geothermal energy is desired to install power generation more than 1.5GWe under this new policy, which is almost three times of the current installed capacity. However, achievement of the political goal is so high when conventional geothermal power generation is applied using natural geothermal resources. We are developing a new heat recovery technology in JOGMEC on the base of the super-critical CO2(ScCO2) and EGS technology creating an artificial heat exchange layer in a high-temperature area. In ScCO2 geothermal power generation, CO2 in the supercritical state is used for two purposes. The first is to create an artificial heat exchange surface (artificial reservoir), and the other is as a heat recovery medium. The first artificial reservoir creation utilises the property that supercritical substances, whether water or CO2, have very low viscosity and penetrate fine cracks. In Japan's HDR technology development (Hijiori Project), which was carried out until the early 2000s, no damage was caused by induced earthquakes during the creation of the artificial reservoir, but in other countries the occurrence of earthquakes was a major problem. Since ScCO2 forms fine cracks, it is expected to have the effect of suppressing induced earthquakes that occur during fracturing. For this use, basic experiments such as rock testing have been completed, and small-scale field experiments are being carried out. ScCO2 is used as a working fluid. Short circuit was formed and observed in the Hijiori project, which connected between the injection and production wells directly. ScCO2 may be possible to prevent the occurrence of short circuits by changing the conditions of injection of ScCO2, or by adding additives. The recovery rate, which shows the rate of reproduced fluid against the injected fluid, was less than 50% in the Hijiori project. ScCO2 is also expected for the working fluid that escapes to react with the rocks and become solidified. Since much is unknown about the method of using ScCO2 to extract geothermal fluids, basic experiments and studies are being conducted.

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