聚醚结构对油水界面性能及稠油降黏效果的影响

为深入认识化学驱稠油乳化降黏的作用机制,考察了3种不同结构的聚醚与稠油的界面张力和界面扩张流变性质,测定了聚醚溶液与稠油形成的乳状液的稳定性、粒径和黏度。结果表明,聚醚类表面活性剂具有较长的柔性氧乙烯(EO)链和氧丙烯(PO)链,能形成界面“亚层”,油水界面膜以弹性为主,易与稠油形成稳定的O/W乳状液,显著降低稠油黏度。聚醚的相对分子质量和EO/PO比是影响油水界面张力的主要结构因素,而界面膜强度主要由相对分子质量控制。随聚醚相对分子质量增加,界面膜强度增大,乳状液稳定性增强。聚醚结构、加量和油水体积比对乳状液粒径的影响较小,均在300~500 nm之间变化。相对分子质量分别为8400、12600、14600的3种聚醚均具有良好的稠油降黏效果,当油水体积比为1∶1时,聚醚质量分数在0.2%~0.5%范围内的降黏率>98%。聚醚的相对分子质量和EO/PO比对降黏效果的影响较小。

Effect of Polyether Structure on the Interfacial Property and Viscosity Reduction of Heavy Oil

In order to deeply understand the mechanism responsible for the emulsifying viscosity reduction for heavy oil in chemical flooding,the interfacial tension and dilational rheological parameters between heavy oil and three polyether solutions with different structures were studied.The stability,particle size and viscosity of the emulsion that was formed by polyether solution and heavy oil were also investigated.The results showed that long flexible ethylene oxide(EO)and propylene oxide(PO)chains in polyether molecule could form a sub-layer at interface,resulting in an oil-water interfacial film with strongly elastic nature.Therefore,it was easy for polyether solution to form stable O/W emulsion with heavy oil and obviously decrease viscosity.The molecular weight and the ratio of EO/PO played the major role in affecting interfacial tension and the strength of interfacial film was mainly controlled by molecular weight.The polyether with larger molecular weight showed higher interfacial film strength and more stable O/W emulsion with heavy oil.The structure and dosage of polyether and oil-water volume ratio showed little influences on particle size of emulsion,which varied from 300 nm to 500 nm.The three polyether solutions with molecular weight of 8400,12600 and 14600 had good viscosity reduction effect on heavy oil.At oil-water volume ratio of 1∶1,the rate of viscosity reduction was over 98%when the dosage of polyether was 0.2%—0.5%.The molecular weight and the ratio of EO/PO had little effect on viscosity reduction.