Demulsification of Water-in-Oil Emulsions: Effects of Crude Oil Composition and Ultrasonic Treatment Mode

Abstract

This study examines the microstructure and rheology of 30 wt % water-in-oil emulsions prepared with distilled water as the dispersed phase and either resin–paraffin or high-resin–paraffin crude oils as the dispersion medium. Crude oils from the Khanty-Mansi Autonomous Okrug, Russia exhibit higher viscosity, a higher content of oxygenated fragments and high-molecular-weight n-alkanes in the saturate fraction, and lower interfacial tension compared to crude oils from Tomsk Oblast, Russia. Continuous ultrasonic treatment (UST) increases emulsion dispersion and viscosity while decreasing pseudoplasticity, but does not affect sedimentation stability. In contrast, pulsed UST—with controlled variations in field intensity, number of cycles, and operating time—enables identification of optimal conditions for reducing aggregation stability. Treatment of the Tomsk Oblast emulsion under these optimized conditions reduces its dispersion and increases its pseudoplasticity; subsequent thermostating at 50°C indices its complete demulsification.