Ultrasonic Treatment Improves the Synergistic Modification Effect of EVA and Asphaltenes on Nanyang Crude Oil

The synergistic effect of asphaltenes and PPDs (Pour Point Depressants) on improving the low-temperature rheological properties of waxy crude oils has been extensively studied. Based on these studies, exploring a feasible method to improve the synergistic effect between PPDs and asphaltenes is greatly significant for the safe and economical transportation of waxy crude oils. This paper investigates the effects of different ultrasonic treatment durations (0–30 s, fixed at 20 kHz and 900 W) on the low-temperature fluidity of Nanyang crude oil with/without 100 ppm of EVA. The results of the pour point test, rheological test, DSC test, and microscopic observation show that ultrasonic treatment slightly improves the low-temperature fluidity of Nanyang crude oil without EVA PPDs. However, ultrasonic treatment has a very significant improvement effect on the low-temperature fluidity of Nanyang crude oil containing 100 ppm of EVA, and this effect is improved with the increase of ultrasonic treatment time. This indicates that ultrasonic treatment and EVA have a synergistic effect on the fluidity improvement of Nanyang crude oil. Combined with the results of the asphaltene dispersibility test, the mechanism of the synergistic effect of ultrasonic treatment and EVA on the fluidity improvement of Nanyang crude oil is discussed. Ultrasonic treatment improves the dispersibility of asphaltenes in Nanyang crude oil through cavitation and mechanical vibration, promotes the adsorption of asphaltenes by EVA, and improves the synergistic effect between EVA and asphaltenes. The discovery of this phenomenon enriches the research on the synergistic modification effect of PPDs and asphaltenes on waxy crude oil and provides insights into the application of ultrasonic treatment technology to improve the fluidity of waxy crude oil.