The effects of gas-fluid-rock interactions on CO2 injection and storage: Insights from reactive transport modeling

The effects of gas-fluid-rock interactions on CO 2 injection and storage: insights from reactive transport modeling Yitian Xiao a *, Tianfu Xu b , and Karsten Pruess b a b ExxonMobil Upstream Research Company, Houston TX 77027, USA Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA Abstract Possible means of reducing atmospheric CO 2 emissions include injecting CO 2 in petroleum reservoirs for Enhanced Oil Recovery or storing CO 2 in deep saline aquifers. Large-scale injection of CO 2 into subsurface reservoirs would induce a complex interplay of multiphase flow, capillary trapping, dissolution, diffusion, convection, and chemical reactions that may have significant impacts on both short-term injection performance and long-term fate of CO 2 storage. Reactive Transport Modeling is a promising approach that can be used to predict the spatial and temporal evolution of injected CO 2 and associated gas-fluid-rock interactions. This presentation will summarize recent advances in reactive transport modeling of CO 2 storage and review key technical issues on (1) the short- and long-term behavior of injected CO 2 in geological formations; (2) the role of reservoir mineral heterogeneity on injection performance and storage security; (3) the effect of gas mixtures (e.g., H 2 S and SO 2 ) on CO 2 storage; and (4) the physical and chemical processes during potential leakage of CO2 from the primary storage reservoir. Simulation results suggest that CO 2 trapping capacity, rate, and impact on reservoir rocks depend on primary mineral composition and injecting gas mixtures. For example, models predict that the injection of CO 2 alone or co-injection with H 2 S in both sandstone and carbonate reservoirs lead to acidified zones and mineral dissolution adjacent to the injection well, and carbonate precipitation and mineral trapping away from the well. Co-injection of CO 2 with H 2 S and in particular with SO 2 causes greater formation alteration and complex sulfur mineral (alunite, anhydrite, and pyrite) trapping, sometimes at a much faster rate than previously thought. The results from Reactive Transport Modeling provide valuable insights for analyzing and assessing the dynamic behaviors of injected CO2, identifying and characterizing potential storage sites, and managing injection performance and reducing costs. Keywords: CO2 injection and storage, gas-fluid-rock interactions, reactive transport modeling, ccs.