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

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Tonkul S., EROL S., Baba A., Regenspurg S.

Geothermal Energy, vol.14, no.1, 2026 (SCI-Expanded, Scopus) identifier identifier

  • Publication Type: Article / Article
  • Volume: 14 Issue: 1
  • Publication Date: 2026
  • Doi Number: 10.1186/s40517-025-00372-3
  • Journal Name: Geothermal Energy
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, Environment Index, Geobase, Directory of Open Access Journals
  • Keywords: CO2 sequestration, High enthalpy, PhreeqC, Reactive transport modeling, Saline systems, Tuzla
  • Middle East Technical University Affiliated: Yes

Abstract

This study evaluates the CO2 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 CO2 co-injection primarily for geothermal heat extraction, the present study focuses on the associated potential for long-term CO2 storage. To this end, CO2–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.