Effects of Surfactants and. Alkalis on the Stability of Heavy-Oil-in-Water Emulsions

In this work, the effects of combining a surfactant/alkali on the stability of heavy-oil-in-water emulsions are analyzed by use of bottle testing, spinning-drop interfacial-tension (IFT) meters, microscopes, conductivity meters, zeta-potential analyzer Turbiscan laboratory expert stabilizer, and Anton Paar rheometer. The experimental results showed that the formulated surfactant (BS 12 and OP-10) had an optimal mass ratio (1:2), and the water-separation rates initially decreased sharply as the concentrations of the surfactant increased, before decreasing moderately until reaching a minimum value. The formulated alkali solution exerted a positive synergistic effect in tandem with the surfactant at low alkali concentrations. In this way, an increasing number of petroleum soaps are produced by reactions between the alkali solutions and the active components in heavy crude oil. However, the effect was reversed at high alkali concentrations, where the compression of the alkali on the electric double layer was more significant. Images of the emulsions taken with a microscope showed that the sizes of the oil droplets were the smallest when the alkali concentration was 0.2% and mass ratio of NaOH and TEA (triethanolamine) was 1:1, which indicated that the amount of petroleum soap produced reached the maximum at this point. In addition, TEA, as a type of surface-active molecule, can form cross-multiple adsorption and hydrogen-bonding structure with surfactant and petroleum soap at the water/oil interface. When the oil/water ratio was 7:3, the water-separation rate reached its lowest point 5.33% for 3 hours. In addition, the emulsion stabilized by the surfactant and the compositional alkali possesses salt tolerance and temperature resistance. When the concentration of the bivalent salt (CaCl2 and MgCl2) increased to 0.01mol.L-1, the water-separation rate was less than 20%, and when the temperature increased from 30 to 60 degrees C, the growth of back-scattering (BS) value was less than 2%.