Geochemical Monitoring of Surface Water Injected into the Sumikawa Geothermal Wells, Northeast Japan

Abstract

A large volume of river water was injected into geothrmal at Sumikawa. northeast Japan and the subsequently discharged fluids were analyzed for their chemical and isotopic compositions to study the geochemical characteristics of the reservoir. Fluids from well SB-1 have been monitored to the greatest extent. The flowrate of the fluid increased rapidly both in steam and water for a period of 400 hours after the start of the discharge and then became almost constant until 4000 hours. The and electrical increased for the first 400 hours and then continued a slight increase. On the basis of the flowrate of fluid discharged and the chemical variation. most of the injected water was discharged by 1500 hours after the start of the discharge; the increases of and EC after this period were due to returns of recycled thermal water reinjected into other wells.