ИСТИНА

Oil is the one of the most important source of energy and raw materials for chemical industry. However an increase in exploitation of highly viscous heavy oil leads to search for methods of reducing its viscosity to 200−400 mPa·s (in accordance with the existing technological requirements). One of the most promising and ecologically attractive concepts is the formation of oil/water (o/w) emulsions by using suitable surfactants. This study showed that the nature of different additives and conditions of emulsification radically changes the rheological properties of heavy oil: the transition from Newtonian behavior, typical for heavy oils, to viscoplastic flows inherent for concentrated emulsions takes place. The minimum values of the apparent viscosity (below 200 mPa·s at 25 °C) and the yield stress (approx. 1 Pa) were reached for emulsions with 25% of water stabilized by mixtures of non-ionic and anionic surfactants (synergetic effect). Emulsions with the share of water higher than 25 vol % can exist only with polymer stabilizers, e.g., hydroxyethyl cellulose, which slightly increases the viscosity. Thus the minimum value of the apparent viscosity (50−90 mPa s at 25 °C) was reached for emulsions containing 50 vol % of water. With decreasing temperature the effect of emulsification increases. The maximum result at 0 °C (decreasing the viscosity by 3 times in comparison with crude oil at 40 °C) was obtained for emulsions stabilized by the mixture of non-ionic surfactant and stabilizing agent. Nevertheless, the minimum viscosity of the obtained emulsions was below the necessary level (< 200 mPa·s at high shear stresses), which is acceptable for tube transportation of oil.