Numerical simulation of CO2 sequestration stability in carbonate-bearing saline aquifers: Effects of mineral dissolution

Geological sequestration is a key technology for the long-term and safe storage of CO2, but subsurface migration may pose significant leakage risks. This study develops a two-dimensional fully coupled thermo-hydro-chemical (THC) numerical model for CO2 storage in carbonate-bearing saline aquifers, incorporating Darcy flow, unsteady heat conduction and convection, nonlinear acid-rock reactions, pore structure evolution, and reaction heat. The model is verified using experimental results and applied to assess how geological features, temperature, and CO2 partial pressure (pCO2) influence the risk of leakage. Results show that high-permeability features (e.g., fractures) significantly accelerate wormhole formation, increasing leakage risk; low-temperature conditions lead to higher leakage potential, while high temperatures may destabilize the reservoir. Elevated pCO2 substantially increases wormhole growth rates, making it a critical factor in leakage risk. The study highlights the importance of identifying and avoiding high-permeability zones and optimizing injection strategies to enhance storage security. The developed model offers a theoretical basis for optimizing site selection, designing injection strategies, and implementing monitoring protocols in CO2 storage operations.