The mechanism of ultrasonic and chemical synergistic demulsification

The complex and stable emulsion formed during tertiary oil recovery can significantly reduce oil recovery efficiency, making effective oil-water separation a critical challenge. In this study, a novel demulsifier was synthesized for emulsions with high wax content. Subsequently synergistic experiments were conducted in combination with ultrasonic treatment to evaluate and compare their combined effectiveness. The mechanism of oil-water separation was ultimately elucidated through a comprehensive comparison of interfacial tension, viscosity, and microscopic morphology analyses. The results indicate that when the demulsifier is used alone, the dehydration rate of oil samples exhibits an “N”-shaped change with increasing temperature under different demulsifier concentrations, and the maximum dehydration rate is 31.33%. When ultrasound and the demulsifier are used in combination, given a constant ultrasound power, the dehydration rate increases and then decreases with the increasing concentration of the demulsifier, and the dehydration rate can reach 45.56%. The demulsifier reduces the viscosity of emulsion and disrupts the molecular structure of wax crystals. Meanwhile, ultrasonic irradiation generates high temperature, high pressure, shock wave, and micro-jet, which enhance the dispersion of demulsifier molecules and accelerate collisions between droplets. The synergistic effect of these two mechanisms can amplify the demulsification effect, outweighing the emulsification effect. This ultimately lowers the interfacial tension at the oil-water interface, thereby facilitating more effective separation of oil and water.