Mineralogical Heterogeneity Controls Dissolution-Front Instability and Reactive-Transport Scaling in Porous Media

Abstract

Mineral dissolution in multicomponent porous media involves coupled mineral–water reactions, solute transport, and evolving pore topology. However, most continuum reactive-transport models still rely on constitutive relations developed for single-mineral media, and the influence of insoluble mineral phases remains poorly understood. Here, we use three-dimensional pore-scale reactive transport simulations to investigate how the insoluble mineral fraction affects dissolution patterns and the evolution of hydraulic and reactive properties. Mineralogical heterogeneity has regime-dependent effects on dissolution-front stability. At relatively low Péclet numbers, moderate insoluble mineral fractions enhance concentration heterogeneity and promote wormholing, whereas larger fractions disrupt connected reactive pathways and suppress flow focusing. At relatively high Péclet numbers, insoluble phases monotonically weaken preferential channel development and drive dissolution toward a more uniform pattern. Mineralogical heterogeneity also alters permeability evolution. As the insoluble mineral fraction increases, the permeability–porosity relationship becomes progressively more linear in log–log space and approaches a power-law form, while the maximum permeability–porosity exponent decreases and shows a converging trend. We further find that the reactive surface area and bulk dissolution rate can be described by empirical porosity-based relationships, which remain consistent across the tested Péclet numbers, Damköhler numbers, and random mineral distributions. These results improve our understanding of dissolution processes in mineralogically heterogeneous porous media and provide empirical relationships for continuum-scale reactive transport modeling.