A Highly Resolved Direct Numerical Simulation Model of Reactive Transport at the Pore Scale

Abstract:

A direct numerical simulation pore scale reactive transport model is presented that is comprised of high performance tools and algorithms for incompressible Navier-Stokes flow, advective-diffusive transport and multicomponent geochemical reactions. Simulation domains are constructed from highly resolved microtomographic images of sediment and rock samples using implicit functions to represent the mineral surface locally on a grid. A Cartesian grid embedded boundary method, whereby interfacial surfaces are described by a cut-cell approach, is used to directly account for the surface area available for reaction—rather than treating the reactive surface area as a continuum-scale parameter. Adaptive mesh refinement is used effectively as a multiscale approach with high resolution used to resolve small pore spaces while a coarser mesh is employed in large pore spaces. Simulations of dissolution experiments on limestone and on fractured dolomite are used to demonstrate the simulation capability, which is used to investigate the effect of transport processes on effective reaction rates, including mixing processes and transport limitations to reactive surfaces.