Network modelling of wettability and pore geometry effects on electrical resistivity and capillary pressure

Recent research efforts have focused on using simple non-circular cross-sec tional pore shapes to honour the physics observed at the pore scale. For ex ample, there is evidence to suggest variations of wettability occur at this level. These pores can exhibit water-wet and oil-wet regions, depending on the physics of wetting films; and hence the porous medium maybe of mixed-w ettability character. For low water saturations, electrical resistivity can not be physically simulated at the pore scale using cylindrical tubes, even though wetting film thickness' and pore constrictions are taken into accou nt. A three-dimensional network model that investigates the petrophysical chara cteristics, electrical resistivity and capillary pressure, is presented. Th e influence of saturation history is also modelled. Key pore geometrical at tributes such as pore shape, aspect ratio, pore coordination number (pore c onnectivity) and pore size distribution are included in the model. In addit ion, pore constrictions are introduced which may result in phase trapping v ia snap-off within the tube itself. Analysis of our developing network model starting from representing the por e shape as circular is presented. Using a simple non-circular cross-section al pore shape we show bulk water retained in the crevices give rise to pred ictions that are in close agreement with electrical resistivity and capilla ry pressure trends observed in experiments. Numerical results are presented and compared with experimental data. (C) 1999 Elsevier Science B.V. All ri ghts reserved.