The important public concern about carbon capture and storage is whether stored CO2 will leak to groundwater sources and eventually back into the atmosphere or not, since CO2 at high concentration is hazardous. Besides, if it leaks back, then it means the process would not be working as a climate change mitigation method. During underground CO2 storage, the containment of CO2 will be crucially dependent on the cap rock integrity above the CO2. Thus, it is important to assess how the CO2 might impact cap rocks, since this could control the ultimate longevity of CO2 storage. The objective of this research is to identify the geochemical reactions of the dissolved CO2 in the synthetic formation water with the rock minerals of the Sayindere formation in laboratory. It is also aimed to assess the potential impacts of geochemical processes on the integrity of the Sayindere cap rock in the long term by using mathematical models and simulation techniques. Sayindere formation, a clayey carbonate, is the cap rock of the Caylarbasi field, which is near to a CO2 source-cement factory. In previous studies, the Caylarbasi field has been studied as an optimum site for the possible CO2 storage in Turkey. The experimental work consists of static and dynamic experiments. In the static experiment, original core is put into the core holder filled with CO2 saturated synthetic formation water. The system is under a pressure of 100 bars and a temperature of 90° C, representing the field conditions. In the dynamic experiment, the core is ground and packed and CO2 saturated synthetic formation water is injected through the unconsolidated core. In the dynamic experiment, X-Ray Diffraction analysis of the grinded core sample will be made prior to and after the experiment. So far, the static experiment has been carried out. Thin Section and Scanning Electron Microscope analyses for mineral identification and composition prior to and after the experiment have been carried out. Cations available in water are analyzed by Inductively Coupled Plasma-Optical Emission Spectroscopy and anions are analyzed by Ion Chromatography. Bicarbonate ion concentrations are determined by titration. The mineralogical investigation and fluid chemistry analysis of the static experiment show that calcite was dissolved from the cap rock as a result of CO2- water- rock interaction. Presently, the dynamic experiment is being carried out and the geochemical modeling of Sayindere cap rock geochemical evolution is being investigated using ToughReact software.


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