Injection of in-situ generated CO2 microbubbles into deep saline aquifers for enhanced carbon sequestration

Carbon sequestration into deep saline aquifers has been considered a promising technology for mitigating heavy atmospheric carbon dioxide (CO2) concentration. When gaseous CO2 is continuously injected into these aquifers, resident brine near a wellbore area is rapidly evaporated while precipitating significant amounts of salt at pores, thereby damaging the aquifer media unfavorable for subsequent CO2 injection. In addition, the continuous injection of CO(2 )at a large volume significantly hinders dissolution of CO2 into brine. In this study, we propose a new method of sequential water injection with gaseous CO2 for in-situ generation of micro-sized CO2 bubbles that minimizes the brine drying-out and simultaneously accelerates CO2 dissolution. We observed that, with this method, a partial volume of CO2 dissolves effectively into the co-injected water during pumping, thereby decreasing the rate of brine drying-out at pores. Another benefit of sequential injection is the significantly increased rate of CO2 hydration induced by the large surface-to-volume ratio of tiny bubbles at micro to nanoscale. To further accelerate CO2 hydration, we investigated reactive dynamics of bubble-driven CO2 hydration at different frequencies of sequential injection and pH levels of the solution. Operation at a higher frequency with higher basicity proved to be the most effective in decreasing the bubble size and therefore accelerating CO2 hydration into brine, which is a more feasible CO2 storage plan.