Fluid–CO₂ injection in a hypersaline volcanic systems: a reactive transport and experimental evaluation with application to the Tuzla Geothermal Field, Türkiye

Abstract This study evaluates the CO 2 sequestration capability of the Tuzla Geothermal Field (TGF) in northwest Türkiye under reservoir conditions (200 °C and 4.4 MPa). While ongoing studies at TGF have investigated CO 2 co-injection primarily for geothermal heat extraction, the present study focuses on the associated potential for long-term CO 2 storage. To this end, CO 2 –brine–rock interactions were examined through batch reactor experiments and reaction path modeling using the PhreeqC geochemical tool. The experiments revealed complex dissolution/precipitation reactions that altered reservoir properties, with mineralogical analyses (XRD, XRF, SEM, and EDS) showing the formation of secondary phases such as calcite, kaolinite, and Ca-rich aluminosilicates. These results indicate that the Tuzla reservoir rocks provide sufficient divalent cations to support mineral trapping under reservoir conditions. Overall, our findings highlight that, in addition to its promise for heat extraction, CO₂ co-injection at TGF offers an opportunity for permanent geological storage, thereby strengthening the dual benefits of this approach.