Akademik Veri Yönetim Sistemi
JEOLOJI MUHENDISLIGI DERGISI, cilt.49, sa.3, ss.43-80, 2025 (Scopus)
Carbon dioxide (CO2) sequestration into geological formations is one of the most reliable methods for mitigating CO2 emissions. Geothermal reservoirs are excellent candidates for CO2 trapping due to considerable fracture pore volume, which provides safe and permanent storage. The stability of the target reservoir rock and caprock is a critical topic during long-term CO2 sequestration. This study examines the geochemical changes resulting from reactions between geothermal reservoir rock and CO2-saturated brine. The ultimate aim is to understand the efficiency of CO2 sequestration in a metamorphic geothermal reservoir regarding its geochemical impact. The study involves batch experiments on core samples taken from depths of 1900 m and 3000 m in the Kızıldere geothermal reservoir in western Turkey. We exposed crushed core samples to CO2-saturated geothermal brine at a temperature of 95 °C and a pressure of 10 bar for 21 days. Experimental changes in the concentrations of major elements (Mg2+, Ca2+, Al3+, Fe2+, SiO2, and Cl-) were simulated using PHREEQC software. Kinetic rates and activation energy were utilized as tuning parameters to align simulation outcomes with experimental observations. The behavior of Mg2+ and Ca2+ exhibited an increasing trend, while SiO2, Al3+, and Fe2+ demonstrated a decreasing trend. Consequently, the interaction between CO2-saturated brine and reservoir rock resulted in the precipitation of K-feldspar and kaolinite minerals, whereas other minerals, such as biotite, quartz, magnesite, and siderite, exhibited slight dissolution. The mineral assemblage remained consistent, while the abundance of the minerals exhibited slight variations. The study indicates that a high concentration of cations may facilitate the trapping of CO2 within metamorphic rocks. Furthermore, solubility trapping was determined to be more significant than mineral trapping in the batch experiments.