Multiscale percolation systems (MPSs) were proposed to study invasion processes in porous media with a large pore size distribution, considering the porous section as a polydisperse structure that modifies its geometrical structure when the scale of observation is changed. Multiscale models are nonregular percolation systems and do not have the following limitations common to classical percolation systems: (i) It is not necessary to choose a particular value for the coordination number Z nor to establish a particular distribution law for it and (ii) constrictions appears naturally as pores of smaller diameters connecting pores of greater diameters, as the result of superposing different scales. A fundamental question that arises in this method is related to the conservation of the spatial connectivity between the pores, which is very important if MPS models are to be used for simulating fluid retention and transfer. The present work is focused on this problem. It is shown that, although conserving the classical correlation function at the object level, i.e., pores, the use of a MPS as a representation of a porous medium does not allow for the conservation of the geometrical structure of clusters of connected pores. An improved MPS model is discussed. © 1996 The American Physical Society.

• Received 22 December 1995

DOI:https://doi.org/10.1103/PhysRevE.54.1734