Permeability and Relative Permeability in Rocks

Important features of the topology of the pore space of rocks can be usefully quantiied by analyzing digitized images of rock cross sections. One approach computes statistical correlation functions using modern image processing techniques. These correlation functions contain information about porosity, speciic surface area, tortuosity, formation factor, and elastic constants, as well as the uid permeability and relative permeability. The physical basis of this approach is discussed and examples of the results for various sandstones are presented. The analysis shows that Kozeny-Carman relations and Archie's empirical laws must be modiied to account for nite percolation thresholds in order to avoid unphysical behavior in the calculated relative permeabilities.