Factors Influencing on Stability of Water-in-crude Oil (W/O) Emulsions

Abstract

Water-in-crude oil (W/O) emulsions were prepared from two crude oils, Upper Zakum (UZ) and Hout (HT), of which density and API degree were similar. The W/O emulsions were subjected to natural settling test to determine the mass% water resolved and settling model of water particles in W/O emulsions was proposed. Three fractions obtained from the crude oils, asphaltene (APS), i.e., pentane insoluble fraction, deasphalting oil, i.e., pentane soluble fraction containing resin (R), and waxlike oil, i.e., pentane soluble fraction not containing resin, were mixed with liquid paraffin–toluene or toluene to prepare model W/O emulsions. These model emulsions were centrifuged to elucidate factors influencing on the mass% water resolved and the stability of model W/O emulsions. The results of natural settling test showed that the mass% water removed and increase in water particle size in W/O emulsion of HT were higher than those of UZ, suggesting higher stability of W/O emulsion of UZ compared with HT, with respect to coalescence of water particles in W/O emulsions. The results of centrifugation of model W/O emulsions indicated that ASP and R in UZ crude oil and ASP in HT crude oil may act as stabilizers of model W/O emulsions, and suggested capability of ASP and/or R for the stabilization of W/O emulsions through enhancement of oil-water interfacial film strength.