Sayindere cap rock integrity during possible CO2 sequestration in Turkey

Abstract

Abstract One way to reduce the amount of CO 2 in the atmosphere for the mitigation of climate change is to capture the CO 2 and inject it into geological formations. The most important public concern about carbon capture and storage (CCS) is whether stored CO 2 will leak into groundwater sources and finally into the atmosphere. To prevent the leakage, the possible leakage paths and the mechanisms triggering the paths must be examined and identified. It is known that the leakage paths can be due to CO 2 - rock interaction and CO 2 –well interaction. The objective of this research is to identify the geochemical reactions of the dissolved CO 2 in the synthetic formation water with the rock minerals of the Sayindere cap rock by laboratory experiments. It is also aimed to model and simulate the experiments using ToughReact software. Sayindere formation is a regionally extensive cap rock for many oil fields in southeastern Turkey. The mineralogical investigation and fluid chemistry analysis of the experiments show that calcite was dissolved from the cap rock core as a result of CO 2 -water-rock interaction. Using the reactive transport code TOUGHREACT, the modeling of the dynamic experiment is performed. Calcite, the main primary mineral in the Sayindere is dissolved first and then re-precipitated during the simulation process. The decreases of 0.01% in the porosity and 0.03% in permeability of the packed core of the Sayindere cap rock are observed in the simulation. The simulation was continued for 25 years without CO 2 injection. However, the results of this simulation show that the porosity and permeability are increased by 0.001% and 0.004%, respectively due to the CO 2 -water-rock mineral interaction. This shows that the Sayindere cap rock integrity must be monitored in the field if application is planned.