Effects of Aqueous-Phase Salinity on Water-in-Crude Oil Emulsion Stability

The stability and morphology of water-in-crude oil emulsions were investigated as functions of aqueous-phase salinity. First, the aqueous phase at the initial ionic strength, and then at 10 and 100 times dilution, was emulsified with two crude oils at several water-oil ratios to study salinity effects on emulsion stability. Temperature was adjusted to investigate the relationship between film drainage velocity and oil viscosity. The stability of emulsion was determined through bottle tests designed to attain phase separation. An optical microscope equipped with a digital camera was used to corroborate onset of phase separation. Our results show that phase separation occurs more easily when temperature is increased. We conclude that low ionic strength conditions, typical of low-salinity water flooding, favor water-in-oil emulsion stability.