EFFECTS OF SURFACE VISCOELASTICITY IN THE ENTRAPMENT AND DISPLACEMENT OF RESIDUAL OIL

Qualitative analyses are developed to explain the role that surface viscoelasticity could be playing during the entrapment and displacement of residual oil. The characteristic time of a simple surface fluid, which is a measure of the memory of the interface for past stress-deformation behavior, is taken to be a measure of the degree of surface viscoelasticity. The approach taken is similar to that used by Slattery (1974, 1979), in two prior qualitative analyses of displacement. The entrapment of residual oil in the smaller pores of an oil-wet rock would be enhanced by reducing the degree of surface viscoelasticity. We predict a similar effect during a free or forced displacement of oil by water in a water-wet structure. No conclusions can be drawn for a restricted displacement of oil by water in a water-wet rock. For values of the interfacial tension less than the critical value, the rate of displacement of residual oil will increase as the degree of surface viscoelasticity is decreased.