Geochemical modelling of fluid – rock interactions in Akköy and Edremit geothermal fields (western Anatolia) as prospective CO2 storage sites

Date

2024-5-15

Author

Elidemir, Sanem

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Lithogeochemical and hydrogeochemical characterizations of two geothermal fields located in western Anatolian region (Akköy – Denizli and Edremit – Balıkesir) are performed to simulate the CO2-fluid-rock interactions in the systems through geochemical modelling studies. Drill cuttings obtained from the fields are investigated in terms of their petrographic features, mineral compositions and elemental variations with depth. Calcareous rocks (marble/limestone/calcschist) and granitic rocks constitute the dominant rock fragments in the samples of Akköy and Edremit, respectively. Main mineral phases in Akköy include quartz, calcite and clay minerals whereas in Edremit, along with quartz, feldspars, micas, carbonates and amphiboles are the dominant phases. Hydrogeochemical analyses reveal that the hot waters are of Na+K-HCO3-SO4 type in Akköy and of Na+K–SO4 type in Edremit field. The results have led to the geochemical assessment of two fields as potential sites for CO2 storage in the context of CO2-fluid-rock interactions with the utilization of geochemical simulations performed by PHREEQC software. Modelling studies of Akköy samples point to ankerite as the principal carbonate phase that can trap CO2. In Edremit, mineral trapping mainly occurs through the precipitation of dolomite. Clay mineral abundance seems to prolong the reaction times and smectite presence, in particular, increases the propagation distance. Due to the mineralogical differences, the reactions in Edremit samples are shorter both temporally and spatially than in Akköy. The geochemical outcome of a CO2 addition to a system (e.g. trapping mechanisms) seems to be closely interconnected to the composition and assemblage of minerals in the reservoir.

Subject Keywords

CO2 Storage, Fluid-Rock Interactions, Geochemical Modelling, Lithogeochemistry, Hydrogeochemistry

URI

https://hdl.handle.net/11511/109858

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Graduate School of Natural and Applied Sciences, Thesis