酸化返排液/原油乳状液的破乳脱水研究

酸化返排液与原油混合可形成稳定性强的乳状液,影响原油的脱水及原油沉降罐的安全运行。通过室内实验考察温度、破乳剂加量、pH值及降黏剂加量对乳状液黏度和破乳效果的影响,并采用显微镜观察不同阶段乳状液微观形态变化。实验表明:酸化返排液与原油混合成的乳状液其黏度随温度升高先急剧下降,后平缓下降,在温度低于40℃时乳状液稳定性较强,温度50~60℃时,随着温度升高,乳状液脱水率上升幅度不大,综合选取破乳温度为50℃;添加破乳剂有利于降低乳状液黏度,但效果不明显,破乳剂加量越大,乳状液破乳效果越好,当破乳剂加量达到150 mg/L后,随破乳剂用量加大,乳状液脱水率上升幅度不大,综合选取破乳剂加量为150 mg/L;调节酸化返排液pH值至6.0~7.0有利于乳状液破乳,pH值越高,油水界面变得棱角分明,脱出水的原油结构更加紧密;加入降黏剂后,乳状液脱水速度明显加快。研究结论对指导油田酸化改造后,井口初期返出的乳状液实施破乳具有借鉴作用。

Study on demulsification and dehydration of emulsion of returned acidizing fluids and crude oil

The emulsion that is mixed with returned acidizing fluids and crude oil has strong stability, which may have a great influence on the crude oil dehydration and the safe operation of crude setting tank. The effects of temperature, demulsifier dosage, pH value, viscosity reducer dosage on the viscosity of emulsion and demulsification performance are studied, and the microscopic changes of emulsion at different times are observed. It is indicated by experiments that the viscosity of emulsion mixed with returned acidizing fluids and crude oil declines significantly firstly and then decreases gradually with the increasing temperature; when the temperature is lower than 40℃, the emulsion has stronger stability, however, between the temperature of 50-60℃, the dehydration rate does not increase significantly with the increasing temperature. So it is concluded that the best demulsification temperature is 50℃. It is also found that emulsion viscosity could be decreased by adding demulsifier, but not significantly; the more the dosage of demulsifier is, the better the demulsification performance is, and the dehydration rate is not remarkably increased when the demulsifier dosage is more than 150 mg/L. So it is concluded that the best demulsifier dosage is 150 mg/L. Moreover, it is beneficial for demulsification performance to adjust the returned acidizing fluids pH value to 6.0-7.0. With the increasing pH value, the oil water interface grows suddenly angular and the structure of crude oil after dewatering is more tight. Finally, the dehydrating speed is improved obviously by using viscosity reducer. These conclusions can be used as references to the demulsification and dehydration of emulsion that is flowed back early after the implementation of acidification.