Long Term Use of Acidic Reservoir at Onikobe Geothermal Power Plant.

Abstract

Onikobe Geothermal Power Plant is a single flash type geothermal plant. It has been operated for 18 years since march 1975. At present, Onikobe Geothermal Power Plant has 9 production wells and 6 reinjection wells. 5 of production wells are used, and the hot water after steam-water separation of three of these wells exhibit acidity which is 3 or a fraction more in values. The steam production from these acid wells accounts for approximately 70%of the total steam. Based on our long experience on the hydrochloric acidic reservoir at Onikobe Geothermal Power Plant, it has been verified that a life of production well more than 8 years can be maintained without using special materials (8 years means the average of a life of production well in Onikobe), if the of hot water is 3.4 or so. The stainless steel material has to be used for the well-mouth equipment down to the separator, but this does not pose an economic problem. It is recommended that the use of acidic reservoir is studied with positive attitude in other geothermal regions.