Evaluation of CO2 sequestration in saline formations based on geochemical experiments and modeling

This paper presents results of a recently completed study in collaboration with the U.S. Department of Energy's (DOE) National Energy Technology Laboratory (NETL) to conduct research on the feasibility of CO2 sequestration in deep saline formations. The objectives of the study were to: (1) investigate the potential for long-term sequestration of CO2 in a deep, regional host rock formation; and (2) evaluate the compatibility of overlying caprock with injected CO2 with regard to its effectiveness as a barrier against upward migration of the injectate. Experiments were conducted using rock samples from different potential host formations and overlying caprocks, as well as certain pure mineral specimens to evaluate specific mineral reactions. Reaction vessels containing a pure solid phase or mechanical mixture of phases, and liquid were pressurized with CO2 or a mixture of either N-2 and CO2, or N-2, CO2, and SO2. The duration of the experiments was one to three months at pressures consistent with deep reservoirs, and temperatures of either 50degreesC (typical) or 150degreesC (elevated). It was concluded from the experiments and geochemical modeling calculations that the potential for adverse effects of CO2 injection into capped, sandstone formations is low.