Dynamic CO₂ Storage Potential assessment via Reactive Transport

Geological CO₂ storage is a pivotal technology for achieving carbon neutrality. However, current assessments of storage potential predominantly rely on static volumetric methods or short-term simulations of dissolution processes. They often fail to adequately quantify the dynamic trapping capacity, particularly the actual contribution of mineral trapping, the dominant mechanism that ensures long-term permanence and enhanced security over centennial to millennial timescales.  This study developed a reactive transport modeling-based assessment framework to quantify the dynamic evolution and contribution of different trapping mechanisms, especially mineral trapping, over centennial timescales following CO₂ injection. A multiphase flow and reactive transport model, coupling CO₂-water-rock interactions, was established to simulate a 1000-year post-injection period for a typical reservoir A in China. The model integrates site-specific hydrogeological parameters and mineral reaction kinetics calibrated against experimental data. The simulation clearly reveals the sequential dominance of trapping mechanisms. Following injection cessation, the proportion of free-phase CO₂ decreases rapidly, while dissolution trapping increases significantly within the first century. Mineral trapping, the precipitation of carbonates such as calcite and dolomite, begins to contribute around 500 years and continues to grow, becoming the dominant mechanism for long-term security. This study proposes "effective mineral trapping capacity" as a time-dependent dynamic metric. In reservoir A, the amount of CO₂ immobilized through mineral reactions over a millennium far exceeds estimates based on short-term reactions, highlighting the necessity of long-term simulations to reveal the true storage potential. Besides, the simulation predicts the spatial evolution of CO₂ plume, trapping mechanism, formation pressure, and the impact of mineral reactions on porosity. This work provides a quantitative assessment of dynamic CO₂ mineralization potential through high spatio-temporal resolution reactive transport modeling. The findings elucidate the time-varying dominance of CO₂ trapping mechanisms for the design and risk management of CCUS project. Furthermore, it provides a transferable methodological framework for capacity evaluation and project optimization in similar or reactive reservoirs. This contributes to advancing the substantive deployment of long-term gigaton-scale, secure geological storage.