粘弹性聚合物溶液提高驱油效率机理研究

Mechanism of enhancing oil displacement efficiency by viscoelastic polymer solution

为了了解聚合物溶液的粘弹性在多孔介质中对残余油的作用机理,描述油藏条件下以第一法向应力差为主要特征的聚合物溶液的流变性,采用上随体Maxwell本构方程,对粘弹性聚合物溶液在油藏孔隙模型——波纹管模型中的流动及其驱替残余油膜的机理进行了油藏工程方法分析,在理论上从力学的角度提出了聚合物驱提高驱油效率的机理。研究结果表明,粘弹性聚合物溶液产生的第一法向应力和剪切应力对油膜的携带作用大于相同粘度的牛顿流体,从而可携带部分残余油膜流动;聚合物溶液的粘弹性越强,作用于残余油膜的第一法向应力越大,对残余油膜的携带力越强,驱油效率越高;多孔介质越不规则,产生的第一法向应力越大,越有利于聚合物发挥粘弹性效应。

In order to research the action mechanism of viscoelastic polymer solution on residual oil in porous medium, the rheological properties of polymer solution characterized by first normal stress of polymer solution under reservoir conditions were described. The flowing and oil displacement mechanism of viscoelastic polymer solution in undulating tube model conducted by upper-convected Maxwell model were analyzed by reservoir engineering method. The mechanism of enhanced oil displacement efficiency of polymer solution was presented from mechanics angle. The results show that the dragging force on oil film of first normal stress and shear stress from viscoelastic polymer solution is larger than that of Newtonian fluid. The stronger the viscoelastisity is, the larger the first normal stress and the dragging force on oil film are, and the higher the enhanced oil recovery is. The more irregular the pore media is, the larger the first normal stress is and the stronger the viscoelastisity is.