Geothemial Development Promotion Survey in Western Part of Unzen Area, Kyushu Island, Southwest Japan

Abstract

NEDO has been undertaking a Geothermal Development Promotion Survey since FY 1980 in the promising geothermal areas all over Japan. The survey in Western Part of Unzen Area was commenced in FY 1984 and completed in FY 1986. Western Part of Unzen Area is situated on the western breast of the Unzen volcano in the Shimabara Peninsula of Kyushu Island, southwest Japan. Obama spa of high temperature lies west of the area. Unzen spa lies east of the area, accompanied with fumarolic areas of large scale. The survey applied in the area were geological and alteration mapping, geochemical prospecting, gravity survey, electro-magnetic survey, and drillings. As a result, high temperatures of 248.4 8 230.3 , and 238.2 were recorded at N59-UZ-1, N60-UZ-3 , and N61-UZ-7 respectivity, in the northeast part of the area. The high temperature zone in the area presumably extends in the northwest direction from Unzen spa. A large promising reservoir was confirmed by the discharge test at N61-UZ-7, which produced 5.0 t/h of steam and 19.9 t/h of hot water.