CMC系列高分子表面活性剂与原油超低界面张力形成机理的研究

采用动态激光光散射及环境扫描电镜研究了羧甲基纤维素系列高分子表面活性剂与大庆原油形成超低界面张力的机理.结果表明,CMC系列高分子表面活性剂具有与低分子量表面活性剂相比拟的表/界面活性,其水溶液的表面张力可达2835mN/m,界面张力达到10^-110mN/m.碱的加入可显著降低高分子表面活性剂与原油的界面张力,在适当条件下界面张力达到超低值(10^-3mN/m),可望作为三次采油的驱油剂.等效烷烃模型研究表明,用碱与原油酸性组分的作用来解释碱能使界面张力下降至超低值的传统观点是不完善的,加入碱能使高分子表面活性剂胶束解缔,胶束数量增多,胶束粒径减小,单分子自由链增加,有利于高分子表面活性剂向界面迁移和排布,这是高分子表面活性剂和碱复配体系与原油界面张力下降至超低值的主要原因.

Mechanism of Forming Ultra-low Interfacial Tension of Polymeric Surfactants Based on Carboxy Methyl Cellulose

The interfacial activity of polymeric surfactants based on carboxy methyl cellulose with Daqing crude oil was studied by dynamic laser scattering, environmental scanning electron microscope, spinning drop interfacial tensiometer and surface tensiometer. The results show that polymeric surfactants based on CMC have same excellent surface(interfacial) activity as low molecular weight surfactants. The surface tension of 0.5% copolymer aqueous solution is 28—35 mN/m, the interfacial tension(IFT) with Daqing crude oil is 10-1—10 mN/m. And IFT decreases sharply after alkali is added into polymeric surfactant solutions. At the appropriate conditions, IFT of some systems reach 10-3 mN/m. The studies on equal-alkane model show, the standpoints that the action of alkali and acid components in crude oil leads to the lowest IFT are not perfect yet. The analyses by ESEM and dynamic laser scattering indicate that the micelles of polymeric surfactants disaggregate by adding alkali into solution, which leads to decrease size of micelles. And the number of mono-molecules also goes up. These changes contribute polymeric surfactants to move to and arrange in the interface of oil/water, which is the main reason of the decreasing of IFT to the lowest value.