钻采工作液用聚丙烯酰胺溶液的表观黏度影响因素与分子链破坏机制

Influence factors of apparent viscosity and molecular chain failure mechanism of polyacrylamide solution used in drilling and production

研究几种油田常见离子(Na^(+)、K^(+)、Ca^(2+)、Mg^(2+)、Fe^(2+)、Fe^(3+)、S^(2-))以及溶解氧对聚丙烯酰胺溶液黏度的影响规律,考察聚丙烯酰胺分子链的破坏机制。结果表明:金属离子均会造成聚丙烯酰胺水溶液黏度下降,二价离子因使得聚合物发生分子内缩聚,导致分子链收缩,因而影响程度强于一价离子,其中以Fe^(2+)与S^(2-)对聚丙烯酰胺溶液黏度的影响最为显著;S^(2-)主要通过氧化降解反应机制,引发聚丙烯酰胺分子链断裂、聚合物溶液黏度下降;Ca^(2+)/Mg^(2+)、Fe^(2+)对聚合物凝胶黏度的影响规律类似,二价离子致使聚合物分子内缩聚,分子链收缩,聚合物黏度降低;Fe^(3+)主要是与聚丙烯酰胺分子链上的羧酸基团结合且难以再次电离,大分子链开始聚集,分子间产生交联-絮凝反应,导致聚合物溶液黏度下降。

The effects of several conventional ions(Na^(+)、K^(+)、Ca^(2+)、Mg^(2+)、Fe^(2+)、Fe^(3+)、S^(2-)and dissolved oxygen)on the viscosity of polyacrylamide were studied,and the damage mechanism of polyacrylamide molecular chain was investigated.The results show that the above ions can reduce the viscosity of polyacrylamide aqueous solution.Divalent ions cause intramolecular polycondensation of the polymer,resulting in molecular chain shrinkage,so the influence degree is stronger than that of monovalent ions.Among them,Fe^(2+)and S^(2-)present the most significant effect on the viscosity of the solution.S^(2-)lead to the fracture of HPAM skeleton mainly through oxidative degradation mechanism,resulting in a significant decrease in the viscosity of HPAM solution.Ca^(2+)/Mg^(2+)and Fe^(2+)show similar influence on the viscosity of the polymer gel.The divalent ions cause the intramolecular polycondensation of the polymer,the molecular chain shrinkage,and the viscosity of the polymer decreases.Fe^(3+)is mainly combined with carboxylic acid groups on the molecular chain of polyacrylamide,and it is difficult to ionize again.Macromolecular chains begin to aggregate,cross-linking flocculation reaction occurs between molecules,and the viscosity of polymer solution decreases.