Chemical and Phase Equilibrium Calculations Applied to Dissolution and Precipitation of Multiple Solid Phases

Abstract Mineralization stands out as the most reliable method for carbon dioxide (CO2) storage, transforming CO2 into stable carbonate minerals that remain locked away from the atmosphere. This high security has sparked interest in enhancing CO2 mineralization within geological formations. However, effective enhancement demands a robust thermodynamic model that integrates chemical and phase equilibria (CPE). In this paper, we introduce a CPE model built upon the Pitzer activity and Peng-Robinson fugacity models, solving it through Gibbs free energy minimization. The CPE model can model complex systems involving multiple hydrocarbon phases, an aqueous phase, and several solid phases, marking a significant advance in fluid modeling for carbon capture, utilization, and storage (CCUS) technologies. We applied the CPE model to analyze experimental data, particularly the enhanced dissolution of basalt minerals using sodium formate solutions. Our case studies highlight the model's versatility. One case demonstrated the model's capability to represent seven distinct phases, including an oleic, a gaseous, an aqueous, and solid phases, during CO2 injection into a depleted oil reservoir. In another novel application, the CPE model analyzed ligand-promoted basalt dissolution, revealing that metal-formate compounds in the aqueous solution lowered the chemical potentials of dissolved solids, thereby enhancing mineral dissolution. These findings confirm the CPE model's potential to drive forward CO2 mineralization strategies.