Emulsification of heavy crude oil in water by natural surfactants

The factors affecting the stability of a heavy crude oil-in-water emulsion stabilized by sodium carbonate (Na2CO3) as a natural surfactant were studied. An Iranian heavy crude oil, namely West Paydar, was used as the oil phase of the emulsions. Tap water was used as the aqueous phase. Various concentrations of sodium chloride were employed to study the effect of aqueous phase salinity on the stability and interfacial tension of the emulsions. The stability and viscosity of O/W emulsions and their viability for the transportation of heavy crude oil through the pipeline were investigated. The diverse factors affecting the properties of emulsions were investigated. The study reveals that the stability of the oil-in-water emulsions was increased versus surfactant concentration due a decrease in the crude oil-water interfacial tension. The natural surfactant was responsible for the very low values of interfacial tensions observed and for the stabilization of the viscous crude oil-in-water emulsions. By increasing the surfactant concentration in the aqueous phase, as well as the speed and duration of homogenization, the emulsion stability was increased. There was a limit of 60 vol.% for the crude oil content in the emulsions, beyond that the emulsions were inverted into water-in-oil emulsions. Zeta potential measurements revealed that the zeta potential of emulsion droplets decreased by the concentration of sodium carbonate in the aqueous phase. (C) 2012 Elsevier B.V. All rights reserved.