Recent Exploration and Development of the Okuaizu Geothermal Field, Japan

Abstract

The Okuaizu Geothermal field is located on the northern part of Honshu in Japan. The Okuaizu Geothermal Company Ltd. (OAG), a subsidiary of Mitsui Mining and Smelting Co..Ltd.(MMS), has done geological, geochemical and geophysical surveys since 1983. and has drilled 20 wells during 1984-1988. In a period of numerous flow tests, downhole pressure, temperature and spinner surveys have been conducted and fluid samples from wells and hot springs have been analyzed. There are two major production zones controlled by the fault system in the Okuaizu Geothermal field: one is the Chinoikezawa zone and the other is the Sarukurazawa zone. In 1987. a simultaneous flow test of five wells in the Chinoikezawa zone was made for four months and the total consistent steam flow rate was more than 200 t/h at a separating pressure of G.5kg/'dfG. In 1988, a simultaneous flow test of three wells drilled into the Sarukurazawa zone will be held. The computer simulation indicates that it will be possible to expand production to 100 MWc, meanwhile OAG plans a 55MWe development in the near future.