Simulation of mercury porosimetry on correlated grids: Evidence for extended correlated heterogeneity at the pore scale in rocks

A modification of invasion percolation is used to simulate rate-controlled mercury injection experiments on porous media displaying both uncorrelated and correlated disorder. The correlations are generated by a fractional Brownian motion with a cutoff. The introduction of correlated heterogeneity has a marked effect on the behavior of the capillary pressure curve and accounts quantitatively for the features of the experimental curves for sedimentary rock samples. This result suggests that correlated heterogeneity, which is common in porous rock at reservoir scales, persists down to the pore scale. It casts doubt on the use of network models with uncorrelated disorder and classical percolation concepts to model flow behavior at the pore scale in sedimentary rocks.