Numerical Study of CO 2 Geological Storage in Saline Aquifers without the Risk of Leakage

The purpose of this study is to reduce the risk of leakage of CO 2 geological storage by injecting the dissolved CO 2 solution instead of the supercritical CO 2 injection. The reservoir simulation method is used in this study to evaluate the contributions of the different trapping mechanisms, and the safety index method is used to evaluate the risk of CO 2 leakage. The function of the dissolved CO 2 solution injection is performed by a case study of a deep saline aquifer. Two scenarios are designed in this study: the traditional supercritical CO 2 injection and the dissolved CO 2 solution injection. The contributions of different trapping mechanisms, plume migrations, and the risk of leakage are evaluated and compared. The simulation results show that the risk of leakage via a natural pathway can be decreased by the approach of injecting dissolved CO 2 solution instead of supercritical CO 2 . The amount of the CO 2 retained by the safe trapping mechanisms in the dissolved CO 2 solution injection scenario is greater than that in the supercritical CO 2 scenario. The process of CO 2 mineralization in the dissolved CO 2 solution injection scenario is also much faster than that in the supercritical CO 2 scenario. Changing the injection fluid from supercritical CO 2 to a dissolved CO 2 solution can significantly increase the safety of the CO 2 geological storage. The risk of CO 2 leakage from a reservoir can be eliminated because the injected CO 2 can be trapped totally by safe trapping mechanisms.