Numerical Reservoir Simulation of CO2 Storage in Saline Aquifers: Assessment of Trapping Mechanisms, Geochemistry, O2 Impurities and Brine Salinity

It is a challenge in experimental studies today to accurately predict the trapping mechanisms in saline aquifers that influence the long-term CO2 storage capacities. The inability in current experimental studies to quantify the effects of combined processes of solubility, hysteresis, and mineralization as a means of affecting saline aquifer properties that influence CO2 trapping mechanisms makes this topic interesting. A systematic framework in CMG-GEM compositional simulation studies is proposed in this article to assess the effects of gradually modelled trapping mechanisms on CO2 storage performance. Simulation studies are conducted under identical constraints, trapping mechanisms, as well as operational factors in a sequential process that activates (i) solubility, (ii) solubility + hysteresis, and (iii) solubility + hysteresis + mineralization. The findings demonstrate distinct differences in trapping process behaviors as well as simulation stability under various modes: hysteresis effects largely improve immobile reserves as well as decrease plume migration, and, on the other hand, mineralization adds long-term dynamics of capacity increase as well as porosity-permeability alterations, especially in carbonate reservoirs. Through long-term post-injection simulations (up to 1000 years), the findings demonstrate that various trapping processes trigger over distinct time periods—years for immobile reserves, decades for dissolution, and centuries in the case of mineralization. This contribution is able to point out the computational efficiency as well as defective model behavior of concern to various physics levels, providing a practical guide to modelers in making a well-informed decision on what constitutes a minimum set of physics in long-term trustworthy CO2 storage.