Dissolution at the pore scale: comparing simulations and experiments

Flow and transport in porous media are usually modeled at the Darcy scale. The system is comprised of representative elementary volumes described by average properties such as porosity, permeability, dispersion coefficients, and reactive surface area. Although this allows large volumes to be simulated efficiently, there are serious difficulties in developing suitable models for the properties of the REV's. When there is rapid dissolution, even the validity of the averaging process is called into doubt by the strong gradients in concentration within a single REV.

Pore-scale modeling overcomes many of the limitations of Darcy-scale models, albeit at much greater computational cost. Nevertheless, it is not yet clear that a single set of parameters – fluid viscosity, ion diffusion coefficients, and surface reaction rates – can consistently describe dissolution of samples with different pore structures. Here we describe some preliminary results of comparisons of numerical simulations with microfluidic experiments, emphasizing uncertainties in the experiments themselves, the numerical modeling of aqueous ion transport, and the characterization of surface reaction rates.