Oil displacement using polymers

Earlier parts of this book have discussed the various aspects of polymer structure, stability, solution behaviour, in-situ rheology and transport in porous media that are relevant to their ultimate task of improving oil recovery. In this chapter, an attempt is made to pull these strands together by describing the main mechanisms of polymer oil displacement processes in reservoir systems. For this purpose, the main multiphase flow equations that may be used in the design and simulation of polymer floods are developed, along with some simpler solutions for certain limiting cases. 

In simulating field polymer floods, an important issue which may have to be considered is the thermal effect of injecting fairly cool water (say at 70-100°F) into hotter reservoir systems. This may cause a temperature gradient across the flooded zone which is cool at the injectors and hot in the main bulk of the reservoir. Since certain important polymer properties depend on temperature (e.g. the solution viscosity—and that of oil and reservoir brine—and the chemical degradation rate), simulation models should take this effect into account when it is important. In addition, the cooler zone close to the injector will affect the local apparent viscosity and hence the injectivity of the polymer solution. In order to perform such calculations, the simulator must include a heat balance equation from which temperature distributions are found. This has not been done on a routine basis until recently (Sorbie etal, 1982 Clifford and Sorbie, 1985 Scott etai, 1985 Scott et ai, 1987), and the effect of the temperature on polymer flooding efficiency will be discussed later in this chapter. 

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OIL DISPLACEMENT USING POLYMERS Table 8.2. Fluid properties in the Brent Sands simulations. 

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