Mechanical Degradation Onset of Polyethylene Oxide Used as a Hydrosoluble Model Polymer for Enhanced Oil Recovery

Water soluble polymers such as polyacrylamide are used in polymer flooding, which is an advanced technique of Enhanced Oil Recovery (EOR). It aims at improving crude oil displacement in reservoir by pushing it with a viscous injected fluid. Polymer flood is challenged by mechanical degradation of long macromolecules during intense flows. Many studies reported that above a critical extensional rate \hbox{$\varepsilon^{\mathrm{\cdot }}_{\mathrm{c}}$}, polymer chains can break and lose their rheological properties. The molecular weight (M) dependence of \hbox{$\varepsilon^{\mathrm{\cdot }}_{\mathrm{c}}$} for dilute solutions in laminar flows was shown to follow a power law: \hbox{$\varepsilon^{\mathrm{\cdot }}_{\mathrm{c}}$} ≈ Mw–k. An experimental study has been performed to investigate the onset of mechanical degradation in both laminar and turbulent flows and for both dilute and semi dilute polyethylene oxide aqueous solutions. It reveals that the exponent k strongly depends on the concentration and flow regimes and also on solvent quality. Results show that mechanical degradation mainly affects long chains, that it is favoured at high concentrations, under poor solvent conditions. They also evidence that the extensional viscosity at low strain rates decreases to the same extent as shear viscosities due to mechanical degradation. However, the decrease of the extensional viscous properties at high strain rates is much more pronounced