Experimental Investigation and Numerical Simulation of CO 2 –Brine–Rock Interactions during CO 2 Sequestration in a Deep Saline Aquifer

CO 2 mineralization is a long-term and secure solution for geological CO 2 storage that primarily depends on the CO 2 –brine–rock interaction during CO 2 sequestration in subsurface formations. In this study, lab experiments were conducted to investigate the CO 2 –brine–rock interaction over short timescales, and numerical simulations were performed to reveal dynamic interactions and equilibrium interactions by applying TOUGHREACT and PHREEQC, respectively. In the experiments, the main ions of HCO 3 − and Ca 2+ were detected in the solution, and calcite dissolution and dawsonite precipitation were observed from SEM images. The simulation results showed that the CO 2 dissolution and the solution pH were affected by the temperatures, pressures, types of solutions, and solution concentrations and were further influenced by mineral dissolution and precipitation. The results of the equilibrium simulation showed that the dissolved minerals were albite, anhydrite, calcite, Ca-montmorillonite, illite, K-feldspar, and chlorite, and the precipitated minerals were dolomite, kaolinite, and quartz, which led to HCO 3 − , K + , and Na + being the main ions in solutions. The results of the dynamic simulation showed that calcite and dolomite dissolved in the early period, while other minerals began to dissolve or precipitate after 100 years. The dissolved minerals were mainly albite, kaolinite, K-feldspar, and chlorite, and precipitated minerals were Ca-montmorillonite, illite, and quartz. Anhydrite and pyrite did not change during the simulation period, and the main ions were HCO 3 − , Na + , Ca 2+ , and Mg 2+ in the simulation period. This study provides an effective approach for analyzing the CO 2 –brine–rock interaction at different stages during CO 2 storage, and the results are helpful for understanding the CO 2 mineralization processes in deep saline aquifers.