驱油用超高分子量聚丙烯酰胺拉伸流变性能研究

Study on elongational rheological behavior of ultra-high molecular weight HPAM using for polymer flooding

关键词:  部分水解聚丙烯酰胺  拉伸黏度  聚合物驱油  拉伸应变

Key words:  HPAM  elongational viscosity  polymer flooding  tensile strain

摘要:

聚合物溶液的流变行为对其在油藏多孔介质中的驱油效果影响较大。系统分析了聚合物含量、温度、多种金属离子及机械剪切作用对驱油用超高分子量部分水解聚丙烯酰胺(U-HPAM)及常规中等分子量部分水解聚丙烯酰胺(M-HPAM)溶液拉伸流变性能的影响。实验结果表明:提高聚合物含量能够促进HPAM分子链间纠缠,聚合物的拉伸黏度增加,同时U-HPAM对拉伸黏度的增强幅度远大于M-HPAM；温度升高、外加金属离子(Na⁺、Ca²⁺、Mg²⁺、Fe³⁺和Fe²⁺)含量增大及机械剪切作用增强都会削弱聚合物分子链间纠缠,导致拉伸黏度降低；U-HPAM受温度及Na⁺、Ca²⁺、Mg²⁺、Fe³⁺等的影响明显小于M-HPAM,而Fe²⁺及机械剪切对两类HPAM影响程度相似。渗流及岩心驱替实验表明,U-HPAM比M-HPAM具有更强的调剖能力,在强非均质油藏中更能发挥其高效驱油能力。 

Abstract:

The rheological properties of polymer have profound effects on the displacement efficiency of polymer in reservoir porous medium. This paper investigated the effects of polymer concentration, temperature, metal ions, and mechanical shear on the elongational rheological behavior of ultra-high molecular weight HPAM (U-HPAM) and normal medium molecular weight HPAM (M-HPAM). It was found that the intermolecular entanglement and elongational viscosity increased with HPAM concentration, and U-HPAM exhibited superior ability to enhance the elongational viscosity than M-HPAM. The intermolecular entanglement was reduced by increasing temperature, increasing Na⁺, Ca²⁺, Mg²⁺, Fe³⁺, Fe²⁺ concentrations and enhancing mechanical shear, which correspondingly decreased the elongational viscosity. Temperature and additional Na⁺, Ca²⁺, Mg²⁺, Fe³⁺ had severe impact on the elongational behavior of M-HPAM more than that of U-HPAM, while the additional Fe²⁺ and mechanical shear had the similar effects on the elongational behavior of M-HPAM and U-HPAM. Seepage and core displacement experiments exhibited that U-HPAM had better profile control ability than M-HPAM, and it could play a better role in oil displacement in strong heterogeneous formation.