Pore Network Models to Calculate Transport and Electrical Properties of Single or Dual-porosity Rocks

The objective of the present work is to demonstrate the effect of pore structure on fluid transport and electrical properties of homogeneous or dual-porosity pore structures for drainage conditions. To this end, a pore network numerical simulator is used that calculates multiphase flow and electrical properties taking into account the pore structure specificities. The characteristics of the 3-D pore-network are defined with the requirement that it satisfactorily reproduces the capillary pressure curve, the porosity and the permeability values which were determined experimentally. Gas/oil transport properties are calculated and compared to experimentally determined curves. The simulations show that different input parameters can lead to similarly good reproductions of the experimental capillary pressure. However, only representative network of the real media, in terms of coordination number and average pore radius, gives a good agreement with the measured relative permeabilities. The quantitative effect of pore structure on transport and electrical properties in homogeneous (Fontainebleau) sandstone is demonstrated. The socalled "non-Archie" behavior is confirmed at low water saturation. It is found that the resistivity index and saturation exponent are greatly affected by the pore shape factor (λp) and the wettability. INTRODUCTION The microscopic pore space structure of a porous medium controls the fluid transport and the electrical characteristics of the reservoir rocks. However, the exact solution of the pore scale equations is difficult to obtain, due to the complexity of the real pore space of porous media. Research efforts have focused on ways to simplify the three-dimensional irregular pore system. The simplified equivalent "pore network model", which can be mathematically treated, can take into account essential features of the pore space geometry and topology. The pore networks are flexible models that can account for different phenomena occurring at the pore scale. They permit the calculation of different petrophysical parameters relevant for single phase or multiphase flow (e.g. absolute permeability, relative permeabilities of fluids, formation factor, electrical resistivity index, etc.). Significative efforts have been made for the prediction of macroscopic transport coefficients of the reservoir rocks using pore network models. An extended review of most of these models is given by Sahimi [13]. Several authors have also looked at the