Integration of Reactive Transport Simulation with Rock Physics Modeling for the Estimation of Time-Lapse Seismic Properties of Basalt during CO ₂ Sequestration

Geological carbon sequestration is an effective strategy to mitigate climate risks caused by anthropogenic CO2 emissions. Many conventional geological reservoirs rely on physical trapping of CO2, with minimal mineral trapping, which poses long-term leakage risks, particularly under seismic or tectonic movements. Basalt formations are increasingly favored, as they reduce these risks by promoting rapid CO2 mineralization and converting it into stable carbonate minerals. This results in altering reservoirs’ mineralogical and petrophysical properties and consequently the elastic properties. This study integrates reactive transport simulation with rock physics modeling to estimate the time-lapse seismic properties of the Wallula basalt. A guided effective medium modeling framework is used to incorporate cementing, pore-filling, and fracture-filling morphologies of secondary mineralization. Results indicate that mineralization extends up to ∼150 m from the injection well, while buoyancy drives upward CO2 migration. The mineralization is dominated by calcite, dolomite, and a very compliant mineral smectite. Secondary mineral precipitation in cementing morphologies increases the overall stiffness of the reservoir, whereas in pore-filling and fracture-filling morphologies, it leads to a reduction. The combined hybrid morphology model shows an overall decrease in elastic properties near the well and at the top of the reservoir, attributed to higher secondary mineral precipitation. Sensitivity analysis indicates that the porosity and secondary mineral volume exert the strongest control on seismic properties, highlighting their importance in reducing uncertainty.