Polymer retention in porous media
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When polymers are added to displacement fluids, the objective is usually to viscosify the injection brine using the properties of the transported polymer as discussed in Chapter 3. However, there may be significant interactions between the transported polymer molecules and the porous medium. Such interactions will cause the polymer to be retained by the porous medium and will lead to the formation of a bank of injection fluid wholly or partially denuded of polymer. Clearly, this bank of fluid will have a viscosity which is much lower than the injected polymer solution, and this will generally lead to a reduction in the efficiency of the polymer flood. However, this polymer retention on the porous medium may also cause some reduction of the rock permeability, which can contribute to the oil recovery mechanism, as is discussed further below. However, overall, the retention of polymer tends to reduce oil recovery despite the permeability reduction contribution. In fact, it is the author’s observation that the level of polymer retention is one of the key factors in determining the economic viability of a polymer flood. Thus, it is of great importance to establish the correct retention levels for a given proposed field polymer flood. The conditions under which such laboratory measurements should be made are extremely important so that relevant figures for retention are available for the simulation assessment of the polymer flood.
KeywordsPorous Medium Relative Permeability Polymer Adsorption Permeability Reduction Polymer Flood
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