Development of hot dry rock technology at the Hijiori test site

Since 1985, the New Energy and Industrial Technology Development Organization (NEDO) has conducted a Hot Dry Rock project at the Hijiori test site, Yamagata prefecture. The objective of this project is to develop and test technologies such as borehole logging, hydraulic fracturing, fracture mapping and reservoir evaluation, which are essential for the development of a Hot Dry Rock power generation system. In 1991, heat was successfully extracted from a shallow reservoir at a depth of 1800 m for three months using one injection well (SKG-2) and three production wells (HDR-1, HDR-2 and HDR-3). About 80% of the injected water was recovered from these production wells. The thermal output of hot water and steam reached about 8 MW. Since 1992, a deep reservoir at a depth of 2200 m has been developed. In 1995 and 1996, heat extraction tests were conducted using one injection well (HDR-1) and two production wells (HDR-2 and HDR- 3). A long-term circulation test, lasting about two years, is planned to evaluate the reservoir, starting in 2000. # 1999 CNR. Published by Elsevier Science Ltd. All rights reserved.