Pore network modelling of two-phase flow in porous rock: the effect of correlated heterogeneity

Using large scale computer simulations and pore network models of porous rock, we investigate the effect of correlated heterogeneity on two-phase flow through porous media. First, we review and discuss the experimental evidence for correlated heterogeneity. We then employ the invasion percolation model of two-phase flow in porous media to study the effect of correlated heterogeneity on rate-controlled mercury porosimetry, the breakthrough and residual saturations, and the size distribution of clusters of trapped fluids that are formed during invasion of a porous medium by a fluid. For all the cases we compare the results with those for random (uncorrelated) systems, and show that the simulation results are consistent with the experimental data only if the heterogeneity of the pore space is correlated. In addition, we also describe a highly efficient algorithm for simulation of two-phase flow and invasion percolation that makes it possible to consider very large networks. (C) 2001 Elsevier Science Ltd. All rights reserved.