Unlocking geothermal potential: Activating calcite-filled veins using chelating agents to improve granitic rock permeability

Chemical stimulation of geothermal reservoirs using environmentally friendly chelating agents has emerged as a promising method to complement hydraulic stimulation. While hydraulic techniques have been the primary approach for enhancing permeability, numerous basement rock types worldwide contain infilled veins with calcium-bearing minerals (e.g., calcite) that present a significant opportunity for achieving higher permeability improvements through chemical methods. In this study, flooding experiments were performed on fractured granitic rocks with calcite-filled veins at 200 °C using a 20 wt.% N,N-bis(carboxymethyl)-L-glutamic acid (GLDA) solution at a pH of 4. The GLDA solution selectively dissolved calcite, reactivating mineral-filled veins, which provided superior fluid-flow pathways compared to the initial artificial fractures. Reactivated veins resulted in dramatic permeability enhancements, reaching up to three orders of magnitude within two hours of stimulation. These results demonstrate the feasibility and effectiveness of chelating agents-assisted chemical stimulation by activating calcite-filling veins.