FRAGMENTATION AND MIGRATION OF INVASION PERCOLATION CLUSTERS - EXPERIMENTS AND SIMULATIONS

Experimental studies of two fluid displacement processes in porous med ia involving extensive fragmentation of invasion percolationlike struc tures are described. In the first process, a two-dimensional porous ce ll Saturated with a wetting fluid was slowly invaded by air. The air f ormed a fractal structure that fragmented when the pressure of the wet ting fluid increased and the air was driven out of the system. In the second process, a fractal air structure migrated through a two-dimensi onal porous medium saturated with wetting fluid. The structure was dri ven by increasing buoyancy forces and fragmented. The fragments migrat ed, fragmented, and coalesced with other fragments. The processes were simulated using new site-bond invasion percolation models that captur ed the displacement mechanisms and reproduced the fragmentation events , and good agreement was found. In both processes, the fractal dimensi onality of the fragments was equal to the dimensionality D approximate to 1.82 of the initial invasion percolationlike structures. The fragm ent size distributions measured in both processes and the dynamics of the migration process could be described by simple scaling forms.