Rheology, particle size distribution, and asphaltene deposition of viscousasphaltic crude oil-in-water emulsions for pipeline transportation

The rheology of an asphaltic heavy crude oil-in-water emulsions stabilized by an anionic (RN) and a nonionic (TEP) surfactants individually or in a mi xture has been studied. The investigated crude oil has a non-Newtonian, tim e dependent, shear thickening, rheopectic behavior with a relatively high y ield stress. The relatively high yield stress of this crude oil is attribut ed to the presence of a relatively high asphaltene and resins content. The viscosity of the crude oil decreases when it is emulsified with synthetic f ormation water in the form of an oil-in-water type of emulsion using a noni onic or an anionic surfactant. It has been found that, the maximum oil cont ent required for forming an oil-in-water emulsion of acceptable viscosity i s the 60% oil-containing emulsion. However, the 70% oil-containing emulsion is not an oil-in-water type of emulsion but it is rather a complicated mix ture of oil-in-water-in-oil type of emulsion. The presence of the anionic a nd the nonionic surfactants together has a synergistic effect in decreasing the total surfactant concentration required to stabilize the emulsion and to form low viscosity emulsion. It has been emphasized that the nonionic su rfactant has a positive contribution in forming emulsions with low viscosit y. Meanwhile, the anionic surfactant contributes in stabilizing the emulsio n at lower concentrations. Flocculation point measurements showed that the added surfactants caused no sign of asphaltene deposition. This implies tha t it is safe to use the investigated surfactants in forming oil-in-water em ulsion for viscous asphaltic crude oils without any fear of asphaltene depo sition.