NUMERICAL INVESTIGATION OF THE DEPENDENCE OF RESIDUAL OIL SATURATION ON GEOMETRY, WETTABILITY, INITIAL OIL SATURATION AND POROSITY

Oil/water drainage and imbibition processes have been numerically investigated for a set of sandstone samples including Berea, Fontainebleau and Bentheimer samples. The pore scale structures of the sandstone samples have been digitized using high resolution microCT. The primary drainage and first imbibition process was computed numerically with a pore scale simulator which is based on a two-phase lattice Boltzmann method including interactions with the solid pore wall. To cope with the large computational demand the simulations were run on high performance computing hardware. Residual oil saturation after imbibition Sor was calculated for complete water-wet rock surface (zero water contact angle) to investigate the effect of different geometries represented by different kinds of sandstone samples. The calculated results compare well with recently published high quality laboratory data. The change of Sor with variation of the degree of water wettability was investigated for the samples by changing the water contact angle on the pore surface. It was found that the weaker water wetness results in smaller Sor which is consistent with the experimental investigations recently reported in literature. The dependence of Sor on the initial oil saturation was calculated and the results are consistent with experimental data and published correlations. Finally the residual oil was calculated for several Fontainebleau samples with different porosity. It was found that Sor decreases with porosity and the variation of Sor agrees well with published experimental data.