Exploration of Geothermal Zone in Mt. Aso West Area in Kyushu, Japan

Abstract

This is an introduction of results of Geothermal Development Promotion Survey done during 1991-1993 in the west half of Aso caldera. Several hot springs and some wells blowing dry steam are distributed across the gently sloping area with an altitude of 400-1000m above sea level. Geological and geochemical survey, electrical and electromagnetic exploration, drilling, heat flow survey and environmental survey have been conducted in support of the project. After such preliminary exploration, it was estimated that favorable heat zones were concentrated within the caldera area. Two deep holes encountered heat zones showing more than 200 degrees centigrade of vapor and water. These two holes hit extraordinary low water levels suggesting imbalance of underground pressure due to the existence of hidden vapor dominant type reservoir.