Host: Japan Association of Mineralogical Sciences
The chemical equilibrium for calcite, anhydrite and quartz of HDR geothermal fluid is calculated using SOLVEQ-CHILLER. In early stage of circulation, the equilibrium temperature of calcite was about 100°C and those of anhydrite and quartz were about 250°C in production well, HDR-2a. However, after thermal breakthrough occurred, the equilibrium temperature of anhydrite and quartz decreased and the log(Q/K) of calcite at 80°C increased rapidly. This is corresponds to the calcite precipitation in surface installations and the temperature fell down in well HDR-2a. And calcite precipitated with CO2 gas release in pipeline.