Effect of laponite particles on the emulsion stability of produced water from polymer flooding

• Laponite particles were used as model solid particles of natural clays.
• Laponite particles significantly affect the emulsion stability.
• Synergy of polymer and laponite particles enhance the emulsionstability.
• Electrostatic repulsion and steric stabilization are the main mechanisms.

In many oilfields, produced water from polymer flooding was more difficult to be treated than produced water from water flooding. The results of simulated experiment showed that the partly hydrolyzed polyacrylamide (HPAM) was present in the produced water, which stabilized the oil droplets in produced water. The addition of HPAM decreased oil–water interfacial tension and increased the viscosity of produced water, the emulsion stability was enhanced when the concentration of HPAM was below 500 mg/L. As the concentration of HPAM was high enough, the flocculating ability of the HPAM caused small oil droplets to coalesce into bigger ones. The addition of laponite particles to simulated polymer flooding water caused the zeta potential and interfacial tension of oil droplets to decrease rapidly, and the formation of stable oil–mineral aggregates (OMA) structures was observed when the concentration of laponite particles was below 150 mg/L. When the concentration of laponite particles was further increased, the zeta potential of oil droplets remained stable, the oil–water interfacial tension increased slightly, and large oil–mineral aggregates formed. These results caused the produced water to become unstable. The concentration of laponite particles determined the emulsion stability of the produced water. It was found that the synergetic effects of the laponite particles and the HPAM enhanced the emulsion stability of the produced water from polymer flooding. The electrostatic repulsion and steric stabilization effect are the main stabilization mechanisms in the polymer flooding water.

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