Effect of Capillary Number on the Microstructure of Residual Oil in Strongly Water-Wet Sandstones

Abstract

Summary Changes that occur with increase in capillary number in the detailed structure of residual oil trapped in water-wet sandstone core samples have been investigated. The technique of using a non wetting phase that can be solidified and separated from the porous medium has been applied with styrene monomer as the nonwetting phase and 2% CaCl2 brine as the wetting phase. The size distributions of residual oil blobs, obtained under various flow conditions, were measured by both image analysis and Coulter counter techniques. Specific features of blob shapes and dimensions were checked by optical and electron microscopy. The changes in size distribution and shapes of blobs provide insight into the mechanisms of trapping and mobilization of residual oil.