Mineral Carbonation in an Enhanced Geothermal System Using CO2 as Heat Transmission Fluid

Abstract

There is growing interest in the novel concept of operating Enhanced Geothermal Systems (EGS) with CO2 instead of water as heat transmission fluid. Initial studies on fluid dynamics and heat transfer have suggested that CO2 may achieve larger rates of heat extraction, and can offer geologic storage of carbon as an ancillary benefit. Fluid-rock interactions in EGS operated with CO2 are expected to be vastly different in zones with an aqueous phase present, as compared to the central reservoir zone with anhydrous supercritical CO2. We have performed chemically reactive transport (TOUGHREACT ) modeling to investigate fluid-rock interactions and CO2 mineral carbonation of an EGS operated with CO2. Several mineral compositions at the EGS sites of Desert Peak and Solutz were taken to (1) investigate mineral dissolution/precipitation and associated porosity changes, (2) evaluate impacts on reservoir growth and longevity, and (3) figure tradeoffs between sustaining geothermal energy recovery and CO2 mineralization (geologic storage).