聚合物弱凝胶在高盐中低渗条件下的渗流特性 及影响因素*

为提高长庆高盐油藏采收率,以长庆油田油藏地质特征和流体性质为模拟对象,研究了聚合物弱凝胶的渗流特性及影响因素,分析了作用机理。结果表明,影响聚合物弱凝胶渗流特性的因素较多。随聚合物浓度、相对分子质量、注入水矿化度和Cr³⁺浓度增加,聚合物弱凝胶的阻力系数(Fr)和残余阻力系数(F(rr))增大,驱替过程中注入压力增加;随岩心渗透率减小,Fr和F(rr)增加,注入压力增加。不同类型聚合物交联生成的弱凝胶对岩心的封堵效果不同。与相同浓度的聚合物溶液相比,尽管聚合物弱凝胶视黏度略为减小,但其Fr和F(rr)较大,且F(rr)大于Fr,液流转向能力良好。水稀释引起弱凝胶分子链舒展和吸水水化膨胀是造成弱凝胶分子聚集体尺寸增大、岩心孔隙内滞留和封堵作用增强的主要原因。图6表9参25。

Seepage Characteristics and Influencing Factors of Polymer Weak Gel under High Salinity,Medium and Low Permeability Conditions

In order to improve the recovery factor of Changqing high-salinity oil reservoir,the seepage characteristics and influencing factors of polymer weak gel were studied,and the action mechanism was analyzed basing on the geological characteristics and fluid properties of Changqing oilfield.The results showed that there were many factors influencing the seepage characteristics of polymer weak gel.With the increase of polymer concentration,relative molecular mass,injection water salinity and Cr3+concentration,the drag coefficient(Fr)and residual resistance coefficient(Frr)of polymer weak gel increased,and the injection pressure increased.As the core permeability decreased,the Fr and Frr increased,and the injection pressure increased.Weak gels formed by different types of polymers had different blocking effects on the core.Although the apparent viscosity of polymer weak gel was lower than that of polymer solution at the same concentration,the Fr and Frr of polymer weak gel were larger.Moreover,the Frr was greater than Fr,which indicated excellent flow steering ability.The main reason for the increase in the size of weak gel molecular aggregate was molecular chain stretching and water swelling of weak gel as a result of water dilution,which led to enhanced retention and plugging in the core.