Interfacial effects in the entrapment and displacement of residual oil

Qualitiative theories are developed to explain the roles of surface tension and the two surface viscosities during the entrapment of residual oil by water and during the subsequent displacement of residual oil by surfactant solutions. The results are in agreement with available experimental data concerning the effects to be observed as the oil‐water surface tension is reduced. Limited data suggest an order of magnitude criterion for the critical surface tension above which no residual oil can be recovered. The two surface viscosities do not affect the entrapment of residual oil, but they are predicted to play a major role in the displacement of residual oil by surfactant solutions.