Monitoring CO2 Injection in the Kızıldere Geothermal Field

Abstract

High-enthalpy geothermal systems in Turkey emit significant amounts of non-condensable gases (NCGs), primarily CO2, during energy production. Recent advances in carbon capture and storage technologies have enabled low emissions by re-injecting produced CO2. However, CO2 injection carries risks, necessitating proper evaluation due to potential buoyant migration and leakage. Monitoring is essential before, during, and after CO2 reinjection to ensure the gas is not transported to the surface through fault zones or well cement failure. As part of the GECO H2020 project, 980 tons of CO2 were captured from the K & imath;z & imath;ldere III geothermal power plant and injected as dissolved in effluent water over six months into the K & imath;z & imath;ldere reservoir. This study aims to demonstrate the behavior of injected CO2 by tracking the CO2-effluent fluid mixture, evaluating the chemistry of geofluids from neighboring production wells, analyzing shallow groundwater quality, and monitoring soil CO2 fluxes. The four-year survey established a baseline before CO2 re-injection and observed changes afterward. To determine the movement of injected CO2 within the reservoir, a 2.6 Naphthalene DiSulfonate tracer was injected. The tracer reached all nearby observation wells and confirmed the hydraulic connection between the wells. Monitoring revealed that injected CO2 is predominantly stored as dissolved CO2 in the reservoir water rather than through mineral sequestration. There were no significant changes in shallow groundwater composition and soil CO2 fluxes before, during, and after the CO2 injection. This successful pilot demonstration showed that COQ injection reduces emissions from the power plant and enhances re-injection efficiency by facilitating carbonate dissolution in the reservoir. These findings suggest that similar COQ injection strategies could improve reinjection performance in other geothermal fields with carbonate-bearing reservoir lithologies and enhance natural pumping effects at production wells. Such advancements could lead to reduced operational costs and promote sustainable geothermal energy production with net-zero emissions.