Viscosity of mixtures of polymers and microemulsions — the Huggins interaction coefficient

Microemulsions used in enhanced oil recovery are usually used in conjunction with a polymer solution that provides mobility control by reducing the permeability of the formation and/or increasing the viscosity of the injected fluid. Microemulsions, which are mixtures of at least four components — water, oil, surfactant and cosurfactant (and, usually, inorganic salts) are complex even in the absence of polymer and consequently, studies of their phenomenon tend to be phenomenological. An approach found to be useful to circumvent this has been to consider the microemulsion particles dispersed in their external phase to be macromolecules which retain their integrity when diluted with external phase or when mixed with polymers. Thus the dispersed phase components are treated as a pseudocomponent. If this approach is followed, many features of the phase diagram of polymer-microemulsion mixtures can be rationalized. It is therefore of some interest to determine whether a similar approach can be used to understand or predict the viscosity of mixtures in which a simple mixing rule for viscosities can be utilized to gain further insight into the polymer-microemulsion interaction.