Abstract: Ultrasonic was applied with viscosity reduction intensifier to reduce the viscosity of heavy oil under the conditions of not adding water. The SARA of heavy oil before and after treatment was analyzed. The effect of intensifier concentration, reaction time and ultrasonic power on the viscosity reduction of heavy oil was studied. The changes in viscosity and flow property of heavy oil before and after treatment and the recovery of viscosity were analyzed by MCR 302 rheometer. The infrared spectroscopy and gas chromatography was used to analysis the structure changes. The experimental results show that the intensifier concentration has the biggest effect on viscosity reduction of heavy oil, followed by reaction time and ultrasonic power. The higher the intensifier concentration, the better the effect for viscosity reduction. With the increase of the treatment time and ultrasonic power, the effect for viscosity reduction increases and then decreases slightly. There is a synergistic effect between ultrasonic and intensifier for the process, which leads to chain scission of long chain macromolecules, aromatic rings and other heteroatoms, hydrogenation and ring opening reactions. The combination use of ultrasonic and intensifier can reduce the viscosity of heavy oil under normal temperature conditions, improve the flow properties and the quality of heavy oil.

Key words: heavy oil, ultrasonic, intensifier, synergetic effect, viscosity reduction