铁离子对水解聚丙烯酰胺溶液流变性能影响研究

针对还原性物质使驱油水解聚丙烯酰胺(HPAM)体系黏度损失严重的问题,利用室内物理模拟方法,定量和定性地分析了Fe~(2+)和Fe~(3+)对HPAM溶液零剪切黏度、动态黏弹性以及瞬时拉伸流变性能的影响,分析了2种铁离子影响HPAM溶液黏度的机理。结果表明:Fe~(2+)主要通过氧化还原反应以及水解的化学行为使HPAM分子链断裂,溶液黏度、流变性能大幅降低,同时,溶液中Fe~(2+)的存在,不仅会使HPAM溶液弹性模量和损耗模量都急剧下降,也使HPAM溶液拉丝直径变小,拉伸断裂时间缩短,最终使HPAM分子与分子间的链缠结机会减小,缠结程度减弱,分子变得易于流动。Fe~(3+)对HPAM溶液流变性能影响较小,其主要作用是使HPAM絮凝并沉淀。

Research work with respect to effects of iron ion on rheological performance of hydrolytic polyacrylamide solution

Considering the problem that reducing substances cause serious viscosity loss of hydrolytic polyacrylamide (HPAM) solution used as oil displacement agent in crude oil field, the effects of Fe2+ and Fe3+ on the zero shear viscosity, dynamic viscoelasticity and rheological performance under instant extension were qualitatively and quantitatively analyzed with laboratory physical simulation method; then the mechanism for the effect of two kinds of iron ion on the viscosity of HPAM solution was examined. Results showed that the presence of Fe2+ in the solution mainly causes the break of the molecular chain of HPAM via redox reaction and chemical behavior of hydrolysis, which results in significant decline of viscosity and rheological performance of the HPAM solution. Meanwhile, the presence of Fe2+ in the HPAM solution not only causes the elastic modulus and loss modulus both fall sharply; but also reduces the filament diameter of HPAM solution and accelerates the break of the filament. Finally, degree of entanglement between polymer molecules reduces, and the molecules become easy to flow. Effect of Fe3+ on the rheological performance of HPAM solution is rather small, and its main functions are flocculation and precipitation of HPAM.