Quadrilateral mesh-based reactive transport modeling in non-orthogonal random fracture-matrix systems

Reactive transport modeling (RTM) is a critical tool for understanding complex fluid-rock interactions in fractured rock systems. However, applying RTM in such systems remains challenging due to the wide disparity of scales spanning from millimeters to kilometers. While existing RTM codes effectively address fracture-matrix interactions at smaller scales, few can handle irregular fracture networks on larger scales while explicitly incorporating matrix processes. To bridge this gap, we introduce a novel discrete fracture-matrix (DFM) reactive transport model based on the MIN3P code, utilizing an anisotropic quadrilateral mesh. This approach enables coarser discretization along fractures (advection-dominated zones) and refined discretization perpendicular to fractures (diffusion-dominated zones), significantly improving computational efficiency without compromising accuracy. The model’s capabilities are demonstrated through simulations of conservative tracer transport and dissolved oxygen migration in fractured crystalline rock at both intermediate (hundred-meter) and large (kilometer) scales. Comparative analyses with traditional triangular mesh methods reveal that the proposed approach achieves comparable or superior accuracy while drastically reducing computational demands. The model’s ability to efficiently simulate large-scale fractured rock systems makes it a powerful tool for applications such as assessing geochemical stability in crystalline rock with extensive fracture networks.