Numerical modeling of the CO2 injection in the Kızıldere geothermal field using multiple inter-well tracer tests

Many geothermal power plants in Turkey emit high amounts of non-condensable gas (NCG), consisting mainly of CO2. Thus, it is crucial to mitigate the NCG emissions by re-injecting the captured gas back into the reservoir. In this study, a numerical sector reservoir model is developed to inspect how the reinjected NCG dissipates in the reservoir for successful sequestration. To accurately characterize the flow characteristics in the reservoir, chloride concentrations observed at the production wells were matched. Furthermore, two multi-well slug tracer tests (one with NCG injection well and one from the northernmost shallow injection well by using different naphthalene-sulphonates) results have been used to calibrate the numerical model. Consequently, a high degree of quantitative and qualitative characterization of the reservoir section near the injection site has been achieved. Using the calibrated model, the impact of CO2-brine injection has been studied for different injection scenarios with varying injection rates and durations. The results of the CO2-charged brine injection showed that approximately 20 % of the injected CO2 circulates in the reservoir, ensuring reduced CO2 emissions. It has been estimated that 200 Mt of CO2 emission can be safely removed if all injection wells are used for NCG re-injection.