Abstract
The objective of this study was to create a microfluidic model of complex porous media for studying single and
multiphase flows. Most experimental porous media models consist of periodic geometries that lend themselves to
comparison with well-developed theoretical predictions. However, most real porous media such as geological
formations and biological tissues contain a degree of randomness and complexity that is not adequately represented
in periodic geometries. To design an experimental tool to study these complex geometries, we created microfluidic
models of random homogeneous and heterogeneous networks based on Voronoi tessellations. These networks
consisted of approximately 600 grains separated by a highly connected network of channels with an overall porosity
of 0.11–0.20. We found that introducing heterogeneities in the form of large cavities within the network changed
the permeability in a way that cannot be predicted by the classical porosity-permeability relationship known as the
Kozeny equation. The values of permeability found in experiments were in excellent agreement with those
calculated from three-dimensional lattice Boltzmann simulations. In two-phase flow experiments of oil
displacement with water we found that the surface energy of channel walls determined the pattern of water invasion,
while the network topology determined the residual oil saturation. These results suggest that complex network
topologies lead to fluid flow behavior that is difficult to predict based solely on porosity. The microfluidic models
developed in this study using a novel geometry generation algorithm based on Voronoi tessellation are a new
experimental tool for studying fluid and solute transport problems within complex porous media.
