Study On Demulsification Of Crude Oil Emulsions Via Ultrasonic Irradiation

The Rheologic properties of the crude oil emulsion and demulsification on it with the methods of thermo-chemical and ultrasonic chemical were studied in this paper. The effects of water content ratio, shear rate and heating temperature on the rheologic properties of crude oil emulsion were analyzed. The effects of the demulsification were investigated with some controllable factors changed, including temperature, demulsifier dosage, ultrasonic power, irradiating time and water content.The results show that the viscosity of the crude oil emulsion increases with the raise of the emulsion water content at initial stage, and it begins to decrease after the phase inversion point. The temperature of the crude oil emulsion can greatly influence its viscosity, and with the increase of temperature the viscosity declines. In addition, viscosity-temperature curve gradually converges to s point from divergence at varied shear rate. The dehydrating ratio of crude oil emulsion ascents according as the raise of temperature and sediment time though the tendency becomes slow gradually. The ultrasonic power and irradiating time are the two most important factors which can affect the dehydrating ratio of the emulsion. Both of the ultrasonic power and irradiating time have an optimum range against the crude oil emulsion used in this paper. The dehydrating ratio declines when these two factors exceed the respective optimum range. Demulsifier dosage also has a critical concentration. In the end, the dehydrating ratio of crude oil emulsion increases with the ascent of demulsifier dosage until a certain point, namely it also has a critical concentration. Exceed this point the dehydrating ratio falls down. This phenomenon is not only applicable for the thermo-chemical method but also the ultrasonic chemical technology.For the crude oil emulsion used in this experiment, the dehydrating rate can reach about 96.45 % for the thermo-chemical method under the conditions of 75℃of heating temperature, 100 mg/L of demulsifier dosage and 200 min settling time. But for the ultrasonic chemical method, the best dehydrating rate was about 97.65 % when the conditions were 75℃of heating temperature, 50 mg/L of demulsifier dosage, 100 W of ultrasonic power, 10~30 min irradiating time and 60 min settling time.The results show that ultrasonic has good flexibility on crude oil emulsion. It can not only increase the speed of demulsification and reduce the settling time but also improve the efficiency of demulsifier and cut down the dosage of demulsifier. So it is an effective demulsifying method. The dehydration effect is better for the high water content crude oil emulsion than that of emulsion with lower water content by ultrasonic irradiation.This paper provides a certain partial theory basis and abundant experiment data for the improvement of crude oil dehydration process in oil field.