Reinjection Plan for the Takigami Geothermal Field Oita Prefecture, Japan

Abstract

The Takigami geothermal area is located in the southwestern par to the Oita prefecture, Kyusyu island, Japan. Idemitsu Geothermal Co. Ltd. Has been exploration this area since 1978. From the results of exploration, the Takigami area is characterized by the following features. (1) the Takigami geothermal area is regionally divided into the eastern and western parts; the boundary between the regions is approximately the Noiine normal fault, which striked north south and dips to the west. (2) the temperature of the reservoir fluid of the western part if higher (230 to about 250°C) than that of the eastern part. (3) the reservoir top of the eastern part is situated at a shallower depth (0 to about 600 m S.L.) than that of western part (-800 to about -15,00 m S. L.) (4) the permeability of the eastern part if considerably higher than that of the western part. In particular, the northern area of the east par is very high. As a result of these features, we plan to establish the western and southeastern parts as the production area and the northern eastern part (hereafter called the "northern area") as the reinjection area.