Enhanced Geothermal Systems (EGS) comparing water with CO2 as heat transmission fluids

This paper summarizes our research to date into operating EGS with CO2. Our modeling studies indicate that CO2 would achieve more favorable heat extraction than aqueous fluids. The peculiarthermophysical properties of CO2 give rise to unusual features in the dependence of energy recovery on thermodynamic conditions and time. Preliminary geochemical studies suggest that CO2 may avoid unfavorable rock-fluid interactions that have been encountered in water-basedsystems. To more fully evaluate the potential of EGS with CO2 will require an integrated research programme of model development, and laboratory and field studies