Thermal stability of oil-in-water Pickering emulsion in the presence of nanoparticle, surfactant, and polymer

• Pickering emulsion needs improved thermal stability for oilfield application.
• Novel nanoparticle-surfactant-polymer stabilized o/w emulsions are formulated.
• Polyacrylamide enhances nanoparticle and surfactant association at droplet surface.
• Partially hydrophobic clay nanoparticles provide improved thermal stability.
• Salt NaCl further promotes thermal stability of nanoparticle stabilized emulsion.

Pickering emulsion offers potential applications in several fields including oil and gas industry due to their enhanced stability. Oil-in-water (o/w) emulsions are usually stabilized by surfactant or nanoparticle or by both but show poor thermal stability which limits their use for high-temperature applications. In this work, a novel formulation of o/w emulsion stabilized using nanoparticle-surfactant-polymer system is investigated for the formulation of thermally stable Pickering emulsion. The conventional oilfield polymer polyacrylamide (PAM), surfactant, sodium dodecylsulfate (SDS), and nanoparticles such as, SiO2, clay, and CuO in varying concentration are used. It is observed that the nanoparticle in the presence of surfactant and polymer synergistically interacted at the oil–water interface. The effect of temperature, pH, and salinity on the interfacial tension is investigated to understand the thermal stability. The emulsion system with partially hydrophobic clay nanoparticles in the presence of PAM and SDS shows higher thermal stability as compared to fully hydrophilic SiO2 nanoparticles. In the presence of salt, NaCl (1.0 wt%), the thermal stability of clay and SiO2 stabilized emulsions is observed to be further promoted at higher temperatures. Scanning electron microscopy (SEM) images confirm the existence of a structured and rigid layer of nanoparticle at the oil–water interface.

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