金属阳离子对聚丙烯酰胺溶液黏度的影响及其降黏机理研究

聚丙烯酰胺(HPAM)是油田常用的驱油聚合物,用油田污水配制HPAM溶液易导致其黏度明显降低,影响驱油效果。依据埕东油田污水实测的各种金属阳离子含量来配制HPAM溶液,测得各金属阳离子对其黏度影响由大到小的顺序为:Na⁺>Fe²⁺>Ca²⁺>K⁺>Mg²⁺;通过红外光谱和扫描电镜分析金属阳离子导致HPAM溶液降黏的机理,Na⁺、K⁺、Ca²⁺、Mg²⁺主要是通过与HPAM链上的羧酸根阴离子静电引力相互作用,降低HPAM分子表面原有的电荷密度,造成分子链卷曲,同时减弱了极性基团的溶剂化能力,释放大量的"束缚水",从而使黏度显著降低;Fe²⁺离子主要是与水中溶解氧共同作用,引发自由基反应,导致HPAM骨架水解断裂,致使黏度显著降低。

Effect of metal ions on the viscosity of polyacrylamide solution and the mechanism of viscosity degradation

Hydrolyzed polyacrylamide(HPAM) is a kind of polymer used for displacement of reservoir oil,while the oilfield sewage used to prepare HPAM may reduce its viscosity and impact the displacement efficiency.In this work,the HPAM solution was prepared according to the metal ions composition in Chengdong Oilfield sewage and the effect of metal ions on the viscosity of HPAM solution was investigated.It was found that the influencing extent of various metal ions on the viscosity of HPAM solution is in the order of Na+ > Fe2+ > Ca2+ > K+ > Mg2+.IR and SEM characterization results suggested that Na+,K+,Ca2+ and Mg2+ interact with the carboxylate anions,which may decrease the HPAM molecular charge density,make the polymer curl,reduce the solvation ability of polar groups,and release a large number of "bounded" water;these lead to the degradation of HPAM solution viscosity.On the other side,the viscosity degradation by Fe2+ is attributed to its interaction with oxygen in sewage,which initiates a free-radical reaction and causes the disintegration of the polymer chains.