pH值对原油乳状液稳定性的影响

研究了pH值对原油乳状液稳定性的影响, 测定了胶质和沥青质在油水界面上的聚集和铺张情况, 不同pH值下油水界面张力以及胶质和沥青质模拟乳状液的稳定性变化, 并且完成了不同pH值下的乳状液化学破乳以及电场破乳实验。沥青质相对胶质更易在界面上聚集和铺展, 形成高黏弹性的界面膜。pH值为酸性或碱性时都能有效降低油水界面张力, 增加乳状液稳定性, 使其化学破乳脱水困难, 而破乳实验也验证了这一观点。随着pH值从2增加到10, 胶质模拟乳状液和沥青质模拟乳状液稳定性变化大, 变化趋势则刚好相反, 胶质模拟乳状液稳定性增加, 油水分离速度减慢;沥青质模拟乳状液稳定性减弱, 体系电导率0.21～1.8mS/cm。因此pH<7时, 沥青质稳定能力强, 而胶质稳定能力弱, 电脱水过程中电脱装置正常工作;pH>7时, 结果相反, 表明电脱装置短路现象与沥青质、胶质稳定能力变化相关。

Effect of pH on the stability of crude oil emulsions

The effect of pH on stability of crude oil emulsions was studied. The aggregation and spreading behaviors of resins and asphaltenes on oil-water interface were measured. In addition, the interfacial tension (IFT) and conductivity of model emulsions stabilized by the resin and asphaltene respectively were measured under different pH values. The results indicate that the asphaltenes are easier to aggregate and spread to form high viscoelasticity film than resins. When pH in the acidic range or in the basic range, the IFT both decreases, which enhances the stability and demulsification difficulty of emulsions, and the demulsification experiments are in agreement with it. It has a remarkable change in the stability of resin-stabilized and asphaltene-stabilized emulsions, respectively. When the pH increases from 2 to 10, and their change trends are opposite, pH 2 to 10, the stability of resin-stabilized emulsion increased, the oil-water separation speed slower, the stability of asphaltene-stabilized emulsions decreases, change of the conductivity:0.21—1.8mS/cm. Therefore, when pH < 7, asphaltenes film is strongest, resins film is weakest, the electric dehydrator works normally during the electric dehydration process; however, the results are opposite when pH > 7, all of these demonstrate that the short circuit has a relationship with the change of stability of asphaltenes and resins.