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Polymer flooding technology is a promising method to improve the oil recovery rate. However, a large amount of polymer in the oil recovery wastewater makes the wastewater appear high viscosity. In this study, the effect of ultrasonic treatment, ozone treatment and ultrasonic-assisted ozone treatment on viscosity and polymer concentration of the wastewater was investigated experimentally. Firstly, with the ultrasonic treatment of 10 minutes, the viscosity and polymer concentration of wastewater was reduced by 96.56% and 55.64% respectively. With the ozone treatment of 10 minutes, the viscosity and polymer concentration of wastewater was reduced by 13.44% and 82.60% respectively. This indicates that ultrasound is more efficient for viscosity reduction while ozone is more efficient for polymer degradation. With the treatment of 1-minute ozonation and 3-minutes ultrasound sequentially, the viscosity and polymer concentration of wastewater were reduced by 95.80% and 75.64% respectively. Moreover, when the wastewater was treated by 3-minutes ultrasound and 1-minute ozonation sequentially, the viscosity and polymer concentration of wastewater were reduced by 95.14% and 92.31% respectively. In conclusion, ultrasonic-assisted ozone is an effective way for polymer degradation and viscosity reduction, which is much helpful for the treatment of oil recovery wastewater form polymer flooding. [ABSTRACT FROM AUTHOR]

Properties of crude oil are affected by its own components and the external environment. During the transportation of crude oil, aging oil is easy to be formed, which performs ultra-high viscosity. This makes it difficult to be transported effectively. In addtion, the viscosity of aging oil is difficult to be reduced by chemical agent and traditional methods. In this study, the aging oil from Daqing Oilfield is treated by ultrasound and the corresponding viscosity reduction is evaluated by measuring the viscosity-temperature curve. The effects of treatment duration, ultrasonic power density and vibration mode are investigated. The results show that the viscosity of aging oil decreases with increasing the ultrasonic power density and treatment duration obviously. Typically, the viscosity of aging oil at 20℃ decreases from 13657 mPa·s to 3039 mPa·s when the treatment duration is 2 minutes. Comparing with the aging oil treated by horn ultrasonic transducer, the aging oil treated by radial ultrasonic transducer shows lower viscosity. In addition, the viscosity reduction effect of aging oil caused by ultrasound can be kept for a long period (e.g., a few days), but it disappears after the aging oil is reheated. [ABSTRACT FROM AUTHOR]