Integrate Carbon Sequestration in Enhanced Geothermal System Through Surface Dissolution

Abstract

Abstract Enhanced geothermal system (EGS) provides a pathway for geothermal energy development beyond traditional regional constraints, offering a cost-effective and carbon-free energy solution. The potential to integrate carbon capture and sequestration (CCS) within geothermal operations; however, remains an open question to be investigated. This study examines the feasibility of CO2 geological sequestration within enhanced geothermal frameworks. We investigated CO2 storage incorporating a surface dissolution strategy under normal operational conditions of EGS, utilizing thermodynamic models and reservoir simulation. Our findings demonstrate the viability of storing CO2 in geothermal reservoirs, as indicated by the net mass of CO2 storage and the plume migration distance. Hydraulically fractured geothermal reservoirs can accommodate CO2 plume migration, even in ultra-tight reservoirs with permeabilities as low as 0.01 millidarcies (mD). A comprehensive sensitivity analysis, including parameters such as rock porosity, reservoir permeability, thickness, well arrangement, and fracture design, revealed optimal conditions for CO2 sequestration and identified key mechanisms in CO2 storage. Further exploration into CO2 storage in an actual EGS reservoir highlighted the benefits of a complex fracture network, which enhances interactions between wells, fractures, and the matrix. Additionally, we addressed critical issues in implementing CCS with EGS, including sourcing CO2 from direct air capture (DAC) facilities integrated with geothermal power plantsand problems associated with in-situ sequestration. Leveraging geothermal heat, built facilities, and generated energy to operate DAC facilities is a beneficial approach. The advantages are further accentuated when carbon credits are considered. In geological storage, the buildup of injection pressure is a pivotal factor for storage operations within ultralow permeability reservoirs. Another challenge is the exsolution of CO2 from brine during the production process in geothermal operations. The produced CO2, flowing alongside the production well, necessitates separation and cycling back into the system. This research exemplifies the innovative integration of EGS with CCS. By revealing new avenues for CO2 sequestration, we position EGS as a valuable adjunct to conventional CCS techniques. The synergy of technologies underscores an innovative path toward a more sustainable energy landscape.