Peridynamic theory coupled with PHREEQC for reactive transport modeling in heterogeneous and discontinuous porous media

Abstract

Modeling reactive transport in discontinuous and heterogeneous porous media is key to the understanding of geochemical systems. Integral formulations of conservation equations can be an alternative approach to solving transport problems in such complex media compared to the classical local (differential) formulations. A prominent example is Peridynamics. However, it has been developed only for advection–dispersion transport with a simple bimolecular reaction, which is of limited utility in complex geochemical problems in real environments. This study integrates bond-based Peridynamics with advanced geochemical modeling (PHREEQC), enabling accurate simulation of reactive transport in heterogeneous porous systems, overcoming limitations in grid-based discretization methods. The sequential non-iterative approach is introduced to address the coupling between the transport of chemical species (solved by Peridynamics) and geochemical reactions (solved by PHREEQC). The proposed model is verified with a set of benchmarks. A series of cases is studied to show the model’s capabilities in the prediction of reactive transport in porous media with fractures and heterogeneities (e.g., permeable and impermeable inclusions). The current model can be used to quantify the impact of the permeable/non-permeable inclusions on non-uniform solution migration and sharp fronts of mineral precipitation/dissolution without any refinements and modifications at the interface. The PD reactive transport also captures the influences of fractures in accelerating the solute transport and enhancing the mineral reaction rate. The current multi-physics nonlocal reactive transport formulations can be easily extended to study more complex problems, such as reactive flow–mechanical process coupled behavior and accurate description of the mineral dissolution/precipitation interface at the micro-scale.