Ns. Ahmed et al., Stability and rheology of heavy crude oil-in-water emulsion stabilized by an anionic-nonionic surfactant mixture, PET SCI TEC, 17(5-6), 1999, pp. 553-576
The stability and rheology of an Egyptian Heavy crude ail-in-water emulsion
s stabilized by an anionic (TDS) and a nonionic (NPE) surfactants individua
lly or in a mixture have been studied. The study reveals that, the viscosit
y of the crude oil decreases when it is emulsified with water in the form o
f an oil-in-water type of emulsion. The stability of the oil-in-water emuls
ion increases as the surfactant concentration and speed of mixing of the em
ulsion increases. Fresh water and synthetic formation water have been used
to study the effect of aqueous phase salinity on the stability and viscosit
y of the emulsion. Surfactant dissolved in synthetic formation water has be
en utilized to find out the possibility of injecting the surfactant into a
well bore to effect emulsification in the pump or tubing for enhancing the
production of heavy crude oils as oil-in-water emulsion. The study revealed
that, the viscosity of the emulsion containing fresh water is always less
than that containing formation water, these findings have been correlated w
ith the crude oil/water interfacial tension (IFT) measurements. The decreas
ed IFT value results in a decrease in the average particle size of the disp
ersed crude oil leading to an increase in the emulsion viscosity. It has be
en found that, the presence of the anionic and the nonionic surfactants tog
ether has a synergistic effect in decreasing the total surfactant concentra
tion required to stabilize the emulsion and to form low viscosity emulsion.
It has been emphasized that, the nonionic surfactant has a positive contri
bution in forming emulsions with low viscosity. Meanwhile, the anionic surf
actant contributes in stabilizing the emulsion at lower concentrations. The
flow behavior of the emulsion stabilized by the binary surfactant mixture
was found to be pseudoplastic (shear thinning) behavior.