Stability and rheology of heavy crude oil-in-water emulsion stabilized by an anionic-nonionic surfactant mixture

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.