Evaluation of SO2 impurity effects on CO2 sequestration capacity and leakage risk: reservoir simulations with an accurate solubility model

Geological carbon sequestration (GCS) and CO 2 -based energy storage in deep saline aquifers are crucial strategies for mitigating climate change. The presence of impurities (like SO 2 ), commonly found in captured CO 2 gas, can alter the gas solubility in brine and the phase density, affecting the overall storage capacity. Despite these important effects, previous fluid models have demonstrated limited accuracy, particularly in describing the solubility of captured CO 2 gas containing SO 2 at in-situ aquifer conditions. In this study, we develop an accurate CO 2 –SO 2 –water solubility model and integrate it into a reservoir simulator to evaluate the influence of SO 2 impurities on CO 2 sequestration capacity and leakage risks. This model has been validated against experimental data, confirming its reliability in predicting gas solubility under reservoir conditions. Furthermore, comparisons of simulation results between pure CO 2 injection and CO 2 -SO 2 co-injection reveal that co-storage can enhance stable storage capacity by up to 31.06% and reduce leakage by up to 22.96%. These findings indicate that CO 2 –SO 2 co-injection is a promising strategy for achieving more secure sequestration and effective subsurface SO 2 disposal.