驱油剂对三元复合驱含油污水中油滴稳定性的影响

三元复合驱技术已在大庆油田成功进行工业化应用。三元复合驱含油污水中由于含有残余的化学药剂,导致其很难处理,从而限制了三元复合驱技术的推广。本文首先采用室内实验制备模拟三元复合驱含油污水,然后通过沉降实验研究驱油剂对油滴稳定性的影响,最后结合驱油剂对油水界面张力、油滴Zeta电位、油滴粒径大小的影响来阐释驱油剂对油滴稳定性的作用机制。结果表明：油滴的稳定性随着NaOH浓度的增大先增大后减小,当NaOH浓度由0增大到400mg/L时,NaOH与原油中的酸性物质反应生成表面活性剂增强油滴的稳定性;当NaOH浓度大于400mg/L时,NaOH本身作为电解质压缩双电层,使油滴的稳定性减小。油滴的稳定性随着表面活性剂浓度的增大而增大,这是因为表面活性剂可以吸附在油滴表面,使油水界面张力减小,同时增大油滴表面的Zeta电位,从而使油滴的稳定性增强。油滴的稳定性随着聚合物浓度的增大先减小后增大,当聚合物的浓度小于300mg/L时,聚合物的桥接、絮凝作用起主导作用,聚合物分子可以吸附到油滴表面,将油滴连接到一起,同时聚合物分子可以压缩液滴表面的双电层,从而有利于油滴的聚结;当聚合物的浓度大于300mg/L时,体系的黏度增大,油滴的运动速度减小,此时聚合物分子占满油滴表面,表现出空间位阻作用,从而使油滴的稳定性增强,不利于油滴的聚结。

Effect of oil displacement agent on oil droplet stability in alkali/surfactant/polymer flooding oily wastewater

Alkali/surfactant/polymer (ASP) flooding technology has been used successfully in the Daqing oilfield, but the water produced from ASP flooding is difficult to treat due to the existence of oil displacement agents, which restricts the promotion of ASP flooding technology. The simulated ASP flooding produced water was prepared in the lab; then the effect of displacement agent on oil droplets stability was studied by settling experiment; the effect of oil displacement agent on oil-water interfacial tension, Zeta potential and oil droplet size explained the mechanism of the oil displacement agent on the stability of the oil droplet. The simulation experiment results showed that the stability of oil droplets increased first and then decreased with increasing NaOH concentration. When the NaOH concentration was increased from 0 to 400mg/L, NaOH reacted with acidic substances in the crude oil to form surfactant that enhanced the stability of the oil droplets. When the concentration of NaOH was greater than 400mg/L, NaOH itself acted as an electrolyte to compress the double layer, reducing the stability of the oil droplets. The stability of the oil droplets increased with the increase of the surfactant concentration, due to the surfactant absorbed on the surface of oil droplets, which could reduce the interfacial tension and increase the Zeta potential of oil droplets, so that the stability of oil droplets increased. The stability of oil droplets first decreased and then increased with the increase of polymer concentration. When the concentration of the polymer is less than 300mg/L, the bridging and flocculation of the polymer plays a leading role. The polymer molecules can absorb on the surface of the oil droplets and link the oil droplets together. At the same time, the polymer can compress the double layer of the surface of the droplet, which is beneficial to the coalescence of the oil droplets. The viscosity of the system increases and the movement speed of the oil droplets decreases when the concentration of the polymer is greater than 300mg/L. At the same time, the polymer molecules occupy the surface of the oil droplets, showing the steric hindrance, which makes the stability of the oil droplets increase and is not conducive to the coalescence of oil drops.