Status of Japanese Supercritical Geothermal Project in FY2018

摘要

Japanese scientists have estimated that nationwide potential of "Supercritical Geothermal Resources", which has an origin in subduction of oceanic plates, reaches hundreds GWs in Japan. Power generation using supercritical geothermal resources (supercritical geothermal power generation) in Japan can significantly contribute to energy security and reduction of emission of CO2. Temperature range of the target supercritical rock body is around 400-500 deg-C and depth is expected to be less than several kilometers. The depth of the supercritical rock body is much shallower than the other area in the world, and it brings advantages in accessibility, economy, and safety. However, there are a lot of scientific unknowns about the nature, especially in rock-mechanical and geo-chemical behavior under supercritical conditions. We also need technological breakthroughs, because temperature and pressure conditions in the supercritical geothermal systems are far beyond the current technological limitations and experiences in the foregoing ultra-high temperature geothermal drillings suggests that presence of acidic geothermal fluid should be expected. Japanese government identified the supercritical geothermal power generation as one of the key technologies in their strategy to drastically reduce emission of CO2 in/after 2050 (NESTI2050). Studies mainly to deepen understanding of nature of the supercritical rock body and engineering investigation have been conducted as NEDO-funded feasibility study until FY2017. In FY2018, NEDO has initiated six 2-3 years national projects related to supercritical geothermal development in addition to on-going METI funded two projects. Outline of the supercritical geothermal projects is described in this paper.