Fragmentation and migration of invasion percolation clusters: Experiments and simulations

Abstract

Experimental studies of two fluid displacement processes in porous media involving extensive fragmentation of invasion percolationlike structures are described. In the first process, a two-dimensional porous cell saturated with a wetting fluid was slowly invaded by air. The air formed a fractal structure that fragmented when the pressure of the wetting fluid increased and the air was driven out of the system. In the second process, a fractal air structure migrated through a two-dimensional porous medium saturated with wetting fluid. The structure was driven by increasing buoyancy forces and fragmented. The fragments migrated, fragmented, and coalesced with other fragments. The processes were simulated using new site-bond invasion percolation models that captured the displacement mechanisms and reproduced the fragmentation events, and good agreement was found. In both processes, the fractal dimensionality of the fragments was equal to the dimensionality D\ensuremath{\approx}1.82 of the initial invasion percolationlike structures. The fragment size distributions measured in both processes and the dynamics of the migration process could be described by simple scaling forms.