Reactive transport modeling for CO2 geological sequestration

One way to reduce carbon dioxide (CO2) releases to the atmosphere, is to capture it from power plants and then inject it into deep geological formations. Understanding water-gas-mineral reactions is the core of assessing the long term storage and risks in geological sequestration. Because of various limitations of laboratory and field tests, reactive transport modeling has been one important supplementary or independent tool to study the water–gas–mineral reactions at different components of geological sequestration. In this paper, we reviewed the applications of reactive transport modeling to three aspects of CO2 geological sequestration: the behavior of CO2 in storage formation, the storage security issues related to caprock integrity or wellbore cement degradation, and the change of the shallow groundwater in response to the potential leakage of CO2. Key finding are summarized and further research needs are identified. The lack of the detailed mineralogical composition information at the storage formation, caprock and overlying aquifers is currently the first obstacle for quantitative prediction of geochemical evolution. The thermodynamic properties of relevant minerals under high temperature and pressure have to be refined. Reliable reaction rates of minerals dissolution/precipitation at field are still the bottle neck of the calculating the long term mineral trapping of CO2. Issues related to relatively fast reactions such sorption and ion exchange need special attention when the impact of CO2 leakage on shallow groundwater was evaluated. The role of organic compounds in water-gas-mineral reactions needs further study.