表面活性剂对驱油聚合物界面剪切流变性质的影响

利用双锥法研究了表面活性剂十二烷基苯磺酸钠(SDBS)和十六烷基三甲基溴化铵(CTAB)对油田现场用部分水解聚丙烯酰胺(PHPAM)和疏水改性聚丙烯酰胺(HMPAM)溶液的界面剪切流变性质的影响,实验结果表明:HMPAM分子通过疏水作用形成界面网络结构,界面剪切复合模量明显高于PHPAM.SDBS和CTAB通过疏水相互作用与HMPAM分子中的疏水嵌段形成聚集体,破坏界面网络结构,剪切模量随表面活性剂浓度增大明显降低.同时,界面膜从粘性膜向弹性膜转变.低SDBS浓度时,少量SDBS分子与PHPAM形成混合吸附膜,界面膜强度略有升高;SDBS浓度较高时,界面层中PHPAM分子被顶替,吸附膜强度开始减弱.阳离子表面活性剂CTAB通过静电相互作用中和PHPAM分子的负电性,造成聚合物链的部分卷曲,从而降低界面膜强度.弛豫实验结果证实了表面活性剂破坏HMPAM网络结构的机理.

Effects of Surfactants on Interfacial Shear Rheological Properties of Polymers for Enhanced Oil Recovery

The effects of surfactants, namely sodium dodecylbenzenesulfonate (SDBS) and hexadecyltrimethylammonium bromide (CTAB), on the interfacial shear rheological properties of partially hydrolyzed polyacrylamide (PHPAM) and hydrophobically modified polyacrylamide (HMPAM) solutions, which are used in oilfields, were studied using a biconical method. The experimental results show that the interfacial shear complex modulus of HMPAM is significantly higher than that of PHPAM, because an interfacial net structure can be formed by HMPAM molecules through hydrophobic interactions. The SDBS and CTAB molecules can form interfacial aggregates with hydrophobic blocks of HMPAM and destroy the interfacial net structure, which results in a significant decrease in the shear modulus with increasing surfactant concentration. At the same time, the properties of the interfacial film change from viscous to elastic. At low SDBS concentrations, the mixed adsorption film formed by PHPAM and a few SDBS molecules has enhanced strength. However, SDBS molecules can displace PHPAM molecules at the interface and weaken the film at higher surfactant concentrations. The cationic surfactant CTAB neutralizes the negative charge on PHPAM, leading to partial curling of the polymer chain, which decreases the film strength. Relaxation measurements confirmed our mechanism involving destruction of the interfacial net structure of HMPAM by the surfactant.