Phase-field modeling of coupled reactive transport and pore structure evolution due to mineral dissolution in porous media

Abstract

Based on the phase-field method, a fluid–solid coupling modeling method was proposed to simulate the reaction transport in porous media at the pore scale and realize the dynamic tracking of the fluid–solid interface. We skillfully combined the phase-field module in COMSOL with the Heaviside function to realize the numerical solution of the model. The feasibility and reliability of the model are verified by comparing it with the results of previous studies on the related benchmark problems (the dissolution process of a single calcite crystal). To further explore the practicability of the model, we simulate the dissolution process in two-dimensional porous media generated by random circles under different transport conditions and reaction rates. The results show that the solute can be transported downstream of the model region under advection-dominated transport conditions, which are common in engineering applications, and the dissolution reaction in the medium takes place synchronously. When diffusion is the main transport mode which often occurs in natural conditions, and the reaction is relatively fast, the solute is difficult to transport downstream of the model region, mineral dissolution mainly occurs near the solute inlet, and mineral disappearance is carried out in a horizontal push mode. The permeability-porosity relationship is predicted by the Kozeny-Carman law for different transport conditions and reaction rates. The results show that the Kozeny-Carman law is more accurate in predicting permeability over a porosity range of 15% for advection-dominated reactive transport, considering specific surface area variation.