NETWORK MODELING OF PORE STRUCTURE AND TRANSPORT-PROPERTIES OF POROUS-MEDIA

A methodology is presented for the simultaneous prediction of absolute permeabilities, formation resistivity factors and drainage capillary pressure curves of sandstones by employing a network model of pore structure based on bond-correlated site percolation concepts. The model is a regular cubic lattice consisting of pore throats and pore bodies, having respective pore size distributions. Information about the pore structure, obtained from mercury porosimetry and photomicrographic analysis, is utilized to select the pore throat and pore body size distributions in a manner such that the resulting model (i) matches the porosity of the medium and (ii) satisfactorily simulates the drainage capillary pressure curve of the porous medium under consideration. Assumptions made about the cross-sectional shape of the pore throats and their effect on the network model predictions are discussed. Details of the methodology used in the simulation of transport properties with microscopic pore structure parameters are also presented and discussed. The problem of fluid and electric current flow through the simulated porous medium is reduced to an electric analogue-linear network problem and is numerically solved using a conjugate gradients method for computing the absolute permeability and the formation resistivity factor. Good agreement between the predicted and the measured values is observed for a number of sandstone samples having widely different transport properties.