Influence of polymer concentration on the stability of the polymer flooding wastewater: Oil droplets floating behaviour and oil-water interfacial properties

Polymer flooding is considered as a promising technology in enhanced oil recovery process. However, a large amount of oil-in-water (O/W) emulsion with high stability is generated during this process. In order to clarify the stability mechanism of the polymer flooding wastewater, we investigate the effect of polymer concentration on the floating behaviour of the oil droplets and oil-water interfacial properties. The experimental results demonstrate that increasing the polymer concentration can improve the viscosity of system, which results in a low rising velocity of oil droplets. Besides, the hydrophilic polymer molecules can absorb on the oil-water interface, and enhance the electrostatic repulsive force between oil droplets, leading to a low collision efficiency of oil droplets, making oil droplets difficult to approach and coalesce. The viscoelasticity is also improved, indicating that oil-water interfacial film strength is enhanced, and ultimately, the emulsion stability is improved.