Modeling Reactive Transport in Clay Fractures

Since fractures may become the primary pathways for flow in clay rocks, it is essential to understand how they behave when infiltrated by reactive fluids. The clay matrix bordering the fracture plays an important role in mediating chemical processes in the fractures, but deciphering such fracture-matrix systems is rendered difficult because of the anomalous transport behavior of ions in clays. In this study, we present a 2D model based on CrunchClay that considers reactive flow in the fracture coupled to reaction-diffusion in the clay matrix bordering the fracture. CrunchClay simulates multicomponent diffusion of ions through clay and clay-rock by treating the charge and transport characteristics of the electrical double layer (EDL). The model is based on a global implicit solve of the reaction-diffusion equation with explicit consideration of two co-existing continua: a bulk water continuum and an EDL continuum in which electrostatic effects are treated. The model is applied to the problem of contaminant transport within a single fracture.