基于磁化改性清水剂的油田含聚污水油水分离方法研究

How to treat the oily wastewater produced from polymer flooding (OWPF) effectively is an important problem for oilfield production. Viscous flocs could be formed when OWPF was treated by cationic polymer, which could lower the efficiency of treatment. When OWPF was treated by non-ionic polyether demulsifier using N, N-dimethylethanolamine as acceptor (DMEAxnmp) , the oil in OWPF could float on water and there was no viscous floc. However, the cost of DMEAxnmp was high and its separation rate of oil from water was slow. Therefore, in this project, magnetic water clarifier, called M-DMEAxnmp, will be prepared by graft reaction using DMEAxnmp and Fe3O4 microsphere. During the reaction, DMEAxnmp will be grafted onto the Fe3O4 microsphere. Magnetic water clarifier can be reused and its molecular weight is much higher than the DMEAxnmp. It can resolve the two disadvantages of DMEAxnmp. The effects of size of Fe3O4 microsphere, structure of DMEAxnmp and amount of graft on the flocculation and reuse performance of M-DMEAxnmp will also be investigated. At the same time, the interaction between oil and M-DMEAxnmp will be studied, to attain its separation mechanism.

如何有效处理聚驱后含油污水（含聚污水）是油田生产急需解决的重要问题之一。阳离子清水剂处理含聚污水时会导致粘性油泥的产生，影响正常生产，采用以N’N-二甲基乙醇胺为起始剂的聚醚（DMEAxnmp）型非离子清水剂可将含聚污水中油滴破乳形成浮油，避免粘性油泥的产生。但使用DMEAxnmp时存在成本高、油水分离速度慢等缺点。为此，本项目拟以DMEAxnmp为原料，将其接枝到纳米Fe3O4上合成系列能有效处理含聚污水用的磁化清水剂（M-DMEAxnmp），利用其可循环使用和增大分子量两大优点有效解决DMEAxnmp成本高、油水分离速度慢的问题；并拟考察纳米Fe3O4大小、DMEAxnmp结构、DMEAxnmp在纳米Fe3O4上的接枝量等因素对M-DMEAxnmp油水分离效果和循环使用次数的影响；同时利用双偏振干涉测量技术（DPI）研究 M-DMEAxnmp和原油间相互作用，揭示其实现油水分离的机理。

如何有效处理聚驱后含油污水（含聚污水）是油田生产急需解决的重要问题之一。阳离子清水剂处理含聚污水时会导致粘性油泥的产生，影响正常生产，采用以N’N-二甲基乙醇胺为起始剂的聚醚（DMEA）型非离子清水剂可将含聚污水中油滴破乳形成浮油，避免粘性油泥的产生。但使用DMEA时存在成本高、油水分离速度慢等缺点。本项目对DMEA进行了磁化改性，得到的磁化改性清水剂M-DMEA为一种不规则核壳结构物质，粒径为160~260 nm，内层为Fe3O4，外层为DMEA，外层带正电，磁化强度为55.2 emu/g。M-DMEA处理油田含聚污水（含油量为8724mg/L，聚合物浓度为82 mg/L）的最佳条件为：M-DMEA的粒径应该小于220nm，M-DMEA浓度2-2.5 g /L，温度65 oC，超声时间为6 min,此时除油率为92.3%（解决了DMEA油水分离速度慢的问题）。M-DMEA随着循环使用次数的增加，除油率降低，经过三次循环（降低了DMEA的使用成本）后，第四次的除油率仅有71.2 %，这是因为M-DMEA经循环使用后会吸附含聚污水中聚合物，粒径变大、活性变低。动态界面张力实验和吸附实验发现 M-DMEA会自发运动到油水界面，导致油水界面张力降低，同时与原本存在于油水界面的活性物质发生吸附作用；三相接触角实验表明，M-DMEA无法稳定吸附在界面，M-DMEA在界面吸附了活性物质后，会连同活性物质一起发生脱附，油水界面变得不稳定，有利于油水分离；微观动力学实验表明M-DMEA浓度的增大，温度升高，都有利于水中油滴聚并速率常数k增大。综上得到M-DMEA清水机理如下：在含聚污水中加入M-DMEA后，M-DMEA运动至油水界面与稳定油水界面的活性物质产生吸附作用，因 M-DMEA自身不能稳定存在于油水界面，它会携带吸附的活性物质一起脱离油水界面。油水界面失去活性物质后稳定性变差，油滴发生聚并，待体积增大到一定值，因密度差发生油水分离。