Prospect for storage of impure carbon dioxide streams in deep saline aquifers-A convective dissolution perspective

Secure and permanent storage of CO2 in deep saline aquifers by solubility trapping depends highly on the rate at which it dissolves in formation brine by convective dissolution. A commonly-held belief is that injection of impurities along with CO2 retards the evolution of convective dissolution, thereby, negatively impacting solubility trapping of CO2. Injection of impurities along with CO2 provides an exceptional prospect for low-cost Carbon Capture and Storage (CCS) technologies and can potentially accelerate large scale implementation of geological storage of CO2. In this study, convective dissolution of CO2 streams with different portion of H2S impurities, which leads to solubility trapping of CO2 in deep saline aquifers, is studied using non-linear numerical simulations. We have shown that the rate of dissolution of an impure CO2 stream with H2S impurities less than 30 mol% is nearly similar to that of a pure CO2 stream. It was also shown that an impure CO2 stream may lead to different convective mixing dynamics at early and late periods of dissolution process. These findings suggest that an impure CO2 stream can be engineered to improve the rate of dissolution and thus solubility trapping of CO2 leading to higher storage security and efficiency.