Properties of polymer solutions

Abstract

The main solution property which is of interest in polymer flooding applications is the viscosity of the polymer. Polymers are added to the injection brine in a waterflood in order to increase the viscosity of the drive fluid, which in turn improves the oil-water mobility ratio. This leads to improved areal and vertical sweep efficiency. In this chapter, how polymers actually viscosify in aqueous (or other) solutions is discussed. In addition, how this viscometric behaviour is related to the molecular weight of the macromolecule and to polymer-solvent interactions via some simple concepts such as the intrinsic viscosity, [η], the molecular expansion factor, α, etc. is considered. Polymeric solutions, unlike fluids such as water and oil, do not generally show the same viscosity at all flow rates either in a capillary or indeed in a porous medium; water and oil are said to be Newtonian fluids, whereas polymer solutions are generally non-Newtonian. The study of the flow behaviour of non-Newtonian fluids is known as rheology and is a vast area of study in itself (Walters, 1975; Schowalter, 1978; Bird et al., 1987a). In this chapter, a brief review of the properties of non-Newtonian fluids in so far as these properties relate to the flow of polymers in porous media will be presented.