Pore-network modeling of particle dispersion in porous media

Abstract Coupling with the random walk particle tracking method and pore-network modeling simulation, this work systematically analyzed dispersion of particles with different particle sizes in pore-network models with variable heterogeneity. The newly developed pore-network model has been verified against results from the published papers. Effect of particle size on dispersion coefficient varies and depends upon the heterogeneity of porous media. Dispersion coefficient of particles is found to be greatly affected by particle size in a homogeneous model; however, for a heterogeneous model, throat velocity difference caused by heterogeneity plays an important role on particle dispersion. Comparing particle dispersion coefficient with and without size-exclusion effect in a homogeneous model, for large particles (i.e., 5 × 10 − 7 m), size-exclusion effect needs to be considered, especially at late times. In other words, without size-exclusion, particle dispersion coefficient is overestimated, while the size-exclusion effect becomes more important as flow rate increases. In the heterogeneous models, however, size-exclusion effect of particles (i.e., 5 × 10 − 7 m) can be neglected. Effects of the widely used uniform distribution and volumetric distribution profiles on particle dispersion have been compared in different pore-network models. The dispersion difference between volumetric and uniform distributions increases with particle size and heterogeneity of the pore-network model. For a homogeneous model, dispersion coefficient with uniform distribution leads to a larger value than that with volumetric distribution; however, as heterogeneity increases, dispersion coefficient with volumetric distribution shows a larger value.