Hybrid modeling of heterogeneous geochemical reactions in fractured porous media

Quantitative modeling of geochemical reactions at the Darcy scale is challenging due to their dependence on pore-scale characteristics that often cannot be averaged out. We propose a hybrid pore-scale/continuum-scale algorithm to bridge the gap between the pore-scale mechanisms of reactive transport and the Darcy-scale observations of their impact. These two scales are coupled by introducing extra nodes at the pore/continuum interfaces, in which the continuity of both concentrations and mass fluxes is enforced. Our algorithm is applicable to highly localized transport phenomena that can be adequately described by Darcy-scale equations in most of a computational domain except for small regions (e.g., reaction fronts) wherein pore-scale simulations are necessary. We employ the proposed hybrid algorithm to model transient reactive solute transport involving fracture cementation.