The Role of Coalescence Phenomena and Interfacial Rheological Properties in Enhanced Oil Recovery: An Overview

Abstract

Experiments conducted recently in both laboratory cores as well as in some oil fields suggested that the poor efficiency of oil recovery might be due to emulsion stability problems in the low tension surfactant or micellar processes. Thus, an important opportunity for improving surfactant/polymer or caustic system performance for enhanced oil recovery lies in learning to what extent the coalescence phenomena and hence stability of emulsions flowing through the porous media affect oil recovery processes. Earlier studies had concluded that low interfacial tensions and therefore a high capillary number must be achieved to obtain displacement of all residual oil in surfactant/polymer flooding processes. Largely ignored has been the role played by the coalescence of oil ganglia and hence emulsion stability. It has been shown recently in our laboratory and at other institutions that low interfacial tension promoted considerable emulsification and that emulsion formation and coalescence can significantly affect the results of laboratory oil‐recovery tests. Rapid coalescence could be correlated with low interfacial viscosity but not with low interfacial tension for the systems studied. This paper attempts to present an assessment of the factors that influence the coalescence‐rupture processes, which in turn may affect oil bank formation and emulsion stability in surfactant/polymer and caustic systems. The scope of this paper is intentionally limited to a preliminary discussion of coalescence and its correlation with interfacial properties and displacement processes. Further investigation is needed to clarify and establish conclusively the role of coalescence phenomena and emulsion stability in the basic mechanisms of oil recovery processes involving the use of chemicals.