Geothermal Resources of Takigami Pield in Oita Prefecture, Japan

Abstract

Idemitsu Geothermal Co., LTD. (IGC), founded in 1979, has started nationwide exploration of the geothermal resources and has made much progress in the Takigami area in the southwest part of Oita prefecture.

Takigami area is the northeast part of Hohi geothermal region, which is known to have many geothermal manifestations such as hot sprin~s, fumaroles. However, Takigami area is exceptionally characterized by no-existence of surface manifestation. IGC has carried out various kinds of survey in and around this area to clarify the geothermal system and to estimate the geothermal potential in the past 9 years. In addition to these field surveys, more than 20 wells have been drilled and used to evaluate the capability to generate electricity, based upon the long term discharge I injection tests including three dimensional model matching with downhole pressure monitoring. This paper describes the geological structure based upon the subsurface information from drilled wells and geological field surveys.