Formation of concentrated emulsions in heavy oil

The addition of aqueous solutions of some surfactants with high hydrophilic-lipophilic balance (HLB = 11-40) into heavy oil leads to the formation of concentrated oil-in-water emulsions. The basic oil sample is a Newtonian fluid in a wide temperature range and its viscosity is 4 Pa s at room temperature, which is too high for its transportation. So, the goal of the work was the creation of emulsions with an acceptable level of viscosity. The morphology and rheological properties of the formed emulsions have been studied. All the emulsions demonstrate visco-plastic behavior. Their yield stress and apparent viscosity at high shear stresses are determined by the HLB of the surfactant used, the regime of mixing and the content of water in the emulsion. The higher the HLB value, the more effective is its influence on the rheology of the emulsions. It was found that the optimal properties are provided by creating multiple emulsions of the water/oil/water type. In these emulsions, thin channels of aqueous phase are the outer continuous medium and the dispersed phase is the ultra-disperse invert emulsion, existing as rather large droplets and fine inclusions in the aqueous channels. The values of the yield stress in the best obtained emulsions lie in the range from 0.6 to 22 Pa and the apparent viscosity at high stresses was reduced by not less than 10 times (in the limiting case by 50 times) in comparison with the crude oil, wherein the content of water as a continuous phase can be reduced to 20%.