Reactive transport and petrophysical property evolution of the CO2-brine-rock system in porous media during geological CO2 storage

Injecting CO 2 into reservoirs for enhanced oil recovery while concurrently storing CO 2 is an important pathway for CCUS, yet the coupled flow and reaction processes after CO 2 contacts formation brine remain insufficiently resolved. This work develops a CT-informed Darcy scale transport model for the CO 2 -brine-rock system that couples Darcy flow, advection diffusion reaction transport, aqueous speciation, and mineral kinetics with time-dependent porosity evolution and a permeability closure to quantify the hydraulic response during the early stage after CO 2 dissolution. The CT-derived domain reconstructed from core information is used as a continuum template informed by morphology to represent spatial heterogeneity and connectivity. Porosity and permeability are treated as effective time-dependent properties and are fed back to the Darcy flow field, allowing the hydraulic response to evolve consistently with geochemical reactions. This framework enables mechanistic interpretation of stepwise permeability gains through the opening of bottleneck pathways that control rates and quantifies competitive carbonate precipitation among CaCO 3 , BaCO 3 , and MgCO 3 . The simulations reveal a transport sequence from early diffusion near the inlet to advection and diffusion acting together, followed by a quasi-steady state. Carbonic hydration and dissociation adjust ionic inventories, and pH decreases from 6.85 to 5.86, with net acid production tapering as buffering and mixing increase. Mineral reactivity ranks calcite ≫ albite > muscovite. Carbonate precipitation is controlled by brine cation supply and the evolving CO 3 2− pool; CaCO 3 precipitates rapidly because precursors are abundant, and the non-calcic rates follow BaCO 3 > MgCO 3 . Within the simulated window, dissolution driven by acid exceeds space filling precipitation, so effective porosity and permeability increase on average and permeability rises in steps as a few bottleneck pathways are progressively opened. The results clarify the coupled processes governing dissolved and mineral trapping at the porous medium scale and support reservoir evaluation for CO 2 -EOR.