CO2-EGS in Hot Dry Rock: Preliminary Results from CO2-Rock Interaction Experiments

Abstract

Carbon dioxide has been identified to possess thermodynamic and transport properties that are suitable for use as "geofluid" to harness geothermal energy from hot dry rock (HDR) where water is scarce. However, limited literature is available on CO2-rock interactions that may affect reservoir performance. CO2-rock interaction experiments were conducted in a flow-through titanium reactor to discover possible geochemical reactions that might affect reservoir performance of a CO2-Engineered Geothermal System (EGS) in hot dry rock (HDR). Granite samples were collected to represent the granitic basement rock postulated to be typically present in HDR. Geothermal reservoir conditions of up to 250 C and 20 MPa were simulated. Preliminary results from Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), Scanning Electron Microscope (SEM), and X-ray fluorescence (XRF) analyses show that at 20 MPa and 200-250 oC reservoir conditions, there are no significant reactions/ dissolutions of minerals in supercritical CO2.