REVIEW OF 15 YEARS EXPERIENCE OF THE OGACHI HOT DRY ROCK PROJECT WITH EMPHASIS ON GEOLOGICAL FEATURES

摘要

The Ogachi hot dry rock (HDR) experiments, which lasted from 1986 to 2001, are reviewed. The Ogachi site, situated on a horst in the central part of a caldera, has two artificial reservoirs at depths of 700 m and 1000 m. The characteristics of the two reservoirs are different in that the lower one, which extends to the NNE is 30 times larger in volume than the upper one extending to the east. Water recovery during circulation tests was at best 25% using two wellbores. The reason for these features was discussed mainly from geological standpoints.