Effects of Na–montmorillonite particles on the emulsification stability of polymer flooding produced water

Simulation experiments were conducted to investigate the effects of Na–montmorillonite (Na–Mt) on the emulsion stability of polymer flooding water. To study the stabilization mechanisms of Na–Mt particles in the emulsion system, the oil/water interfacial properties were investigated by measuring the zeta potential, interfacial tension and dilational viscoelasticity. The features of Na–Mt particles adsorbed on oil droplets were observed under optical microscopy. The results indicated that, with the increase of Na–Mt particles up to 200 mg/L, the zeta potential became more negative, the interfacial tension decreased greatly, dilational viscoelasticity was enhanced and a stable oil–mineral aggregate (OMA) structure appeared, therefore, the polymer flooding produced water was stabilized. With further increases of Na–Mt particle concentrations, the zeta potential of oil droplets remained stable, the interfacial tension slightly increased, and the dilational viscoelasticity decreased. In this system, a larger OMA structure was apt to form, which could favor the treatment of polymer flooding produced water.