Three‐Dimensional Numerical Study on Dissolution and Precipitation in Diffusion‐Dominated Fractures

Dissolution–precipitation reactions play a critical role in subsurface processes such as carbon mineralization, yet the pore‐scale mechanisms governing clogging and reactive surface utilization in diffusion‐dominated fractures remain poorly constrained. Here, we extend the two‐dimensional LBM3RT framework to a fully three‐dimensional, multi‐component advection–diffusion–reaction lattice Boltzmann model and apply it to a dual‐fracture system comprising a main flow conduit and a dead‐end branch. After verification against analytical diffusion–reaction solutions and previously published 2D crystal‐growth morphologies, we simulate a simplified reaction network in which an in situ mineral dissolves and a secondary mineral precipitates on fracture walls in a diffusion‐dominated dead‐end channel, for example, the conversion of CaCO 3 to BaCO 3 in the presence of soluble barium. Systematic parameter studies show that a lower dissolution rate constant enhances utilization of reactive surfaces. A lower precipitation rate constant reduces clogging tendency. A smaller difference between their equilibrium constants reduces clogging tendency. Increasing the inlet concentration of the mineral‐forming aqueous species deepens the penetration of the precipitation front while lowering the local clogging‐index peak. Enlarging the dead‐end aperture substantially boosts the total precipitation rate and the spatial extent of the reaction front. Finally, including an impermeable passivation layer arrests local dissolution–precipitation but promotes gradual migration of the reaction front toward the fracture tip, thereby improving long‐term access to reactive mineral surfaces. Together, these results demonstrate that LBM3RT provides a mechanistic pore‐scale tool for interpreting reactive transport with complex geochemistry and optimizing injected fluid composition, fracture geometry, and operating conditions in engineered carbon mineralization systems.