Pore‐Scale Modeling of Fracture Evolution Driven by Dual‐Mineral Dissolution With Contrasting Reactivity and Morphology

Predictive models for reactive flow in fractured media often adopt single‐mineral simplifications, neglecting feedback between mineralogical heterogeneity and hydrological evolution. This study investigates the pore‐scale dynamics of fracture evolution in dual‐mineral systems characterized by contrasting mineral reactivities and morphologies across varying Péclet and Damköhler numbers, using pore‐scale reactive transport simulations. The results show that dual‐mineral systems can accelerate total dissolution rates by suppressing local saturation buildup through ion‐partitioned saturation control. However, this enhanced chemical reactivity does not necessarily result in permeability enhancement. Reactivity contrast sustains hydraulic resistance when the slower‐reacting phase persists, limiting effective aperture widening even under fast bulk dissolution conditions. We identify a mineral‐size‐dependent permeability reversal phenomenon, where systems with smaller mineral clusters initially restrict flow due to dense clustering but eventually achieve higher permeability than large‐cluster systems upon complete dissolution. An empirical phase diagram is developed to characterize armored, compact, and uniform dissolution regimes, and a sigmoid function is proposed to capture the asymptotic evolution of permeability. Mineral surface area evolution also deviates from conventional porous media models, exhibiting near‐flat responses in the uniform regime due to a balance between mineral removal and newly exposed surface area. Finally, it is shown that conventional upscaled reaction rate relationships underestimate dissolution of the slow‐reacting phase when its surface is newly exposed to undersaturated fluid. These findings highlight that predicting fracture alterations in subsurface environments requires accounting for the coupled effects of pore‐scale mineral morphology, reactivity contrasts, and evolving porosity‐permeability, surface area, and reaction rate relationships.