- Copyright ©2006. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.
The injection of CO2 into deep saline aquifers is a potential option for greenhouse gas mitigation. However, several key issues, such as underground storage time and the fate of the injected CO2, must be studied before this option becomes economically and socially acceptable. In the current study, a one-dimensional reactive mass-transport model was used to predict the long-term chemical behavior of a deep saline aquifer following CO2 injection, far away from the injection site and representative of basin-scale migration and long-term fate. The dissolution of the injected CO2 into brine causes a sharp drop in pH, and consequently, the acidic brine aggressively reacts with aquifer minerals. Our model also predicts the dissolution of aluminosilicate minerals with the formation of secondary minerals and the precipitation and dissolution of carbonate minerals and is consistent with laboratory-scale CO2 core-flooding experiments. However, the extent and development of reaction fronts depend on the reaction rates used. For example, our modeling results indicate that the transport of carbon can be significantly retarded with respect to the flow of the brine itself, and a significant amount of injected CO2 is immobilized because of mineral trapping. The precise locations and patterns of the carbon reactive transport are sensitive to the reaction rates used, illustrating the need for improved knowledge of reaction kinetics, particularly the in-situ rates of dissolution and precipitation of aluminosilicate minerals, in evaluating mineral trapping of CO2 in deep geological formations.
Brian Strazisar works in the Environmental Sciences Division at the National Energy Technology Laboratory. He has worked on several aspects of carbon sequestration science. His projects have focused on CO2 capture from power plants, sequestration in deep saline aquifers, and monitoring of leakage from sequestration sites. Brian holds a B.S. degree in chemistry from the University of Pittsburgh and a Ph.D. from Cornell University.Chen Zhu is an associate professor of hydrogeochemistry at Indiana University–Bloomington. He received an M.S. degree from the University of Toronto, a Ph.D. from the Johns Hopkins University, and a postdoctoral fellowship from Woods Hole Oceanographic Institution. He coauthored (with Greg M. Anderson) the popular book Environmental Applications of Geochemical Modeling published by the Cambridge University Press.
Sheila W. Hedges is a research chemist in the Geosciences Division of the U.S. Department of Energy's National Energy Technology Laboratory. Hedges' current research focus is gas-water-rock interaction studies of potentially important reactions in geological CO2 sequestration in deep saline aquifers. She received her Ph.D. and her M.S. degree in physical chemistry from North Carolina State University.