Pore-network modeling of reactive transport and mineral dissolution in porous media

Abstract

This thesis proposes and demonstrates a new pore-network modeling approach including topology evolution to simulate single-phase reactive transport and mineral dissolution in porous media. The approach couples transport and reaction kinetics using a pore-network model that implements a single heterogeneous chemical reaction describing the dissolution of calcite by acidic solutions. The network geometry is updated based on the dissolution process happening at the mineral surface that enlarges pores and throats. Importantly, a new algorithm to describe the merging of pores and throats resulting from solid dissolution is introduced to guarantee conservation of the main variables of interest during the merging process. Surface areas and throat conductances are accurately conserved upon merging using a novel application of correction factors and effective properties. The fluid flow field is also updated due to the new pore-network configuration. A wide range of pore-networks are used to study the reactive transport problem. The main results include the mapping and exploration of different dissolution regimes through porositypermeability evolution curves, acid concentration profiles in the pore network, and the use of statistical criteria to differentiate regimes.