聚合物驱剖面返转规律及返转机理

利用室内并联岩心物理模拟实验及渗流力学的基本定律,对聚合物驱油过程中的剖面返转规律及返转机理的研究表明,油层非均质性是剖面返转的主要原因,随着渗透率级差的增大及返转时机提前,低渗透层累积吸液比例下降。在固定渗透率级差条件下,随着聚合物分子量及浓度的增大及返转时机提前,低渗透层累积吸液比例下降及聚合物驱波及效率下降。剖面返转的根本原因在于聚合物溶液在高、低渗透层中的动态阻力系数表现规律不同,高渗透层中阻力系数呈对数式上升。低渗透层中阻力系数呈指数式上升。即高、低渗透层中阻力系数变化率不同,高渗透层中阻力系数变化率不断下降,低渗透层阻力系数变化率不断上升,在注聚合物初期,高渗透层中阻力系数变化率大于低渗透层阻力系数变化率,当二者相等的时候,吸水剖面开始发生返转。

Section inversion rules and inversion mechanism of polymer flooding

The section inversion rules and inversion mechanism during polymer flooding were studied by using physical simulation experiment of indoor parallel core and the basic principles of seepage mechanics. The study result showed that reservoir heterogeneity resulted in the section inversion. With the increase of permeability ratio and advancement of inversion opportunity, the cumulative imbibition rate of low-permeability layer decreases. Under the condition of fixed permeability ratio, the cumulative imbibition rate of low-permeability layer and the sweep efficiency of polymer flooding decrease with the increase of molecular weight and concentration of polymer and the advancement of inversion opportunity. The section inversion lies on the different change laws of dynamic resistance coefficient of polymer solution in the high and low permeability layers. In the high permeability layer, the resistance coefficient rises in the logarithm form. While in the low permeability layer, the resistance coefficient rises in the index form. In the high permeability layer, the changing rate of resistance coefficient decreases constantly, while in the low permeability layer, the changing rate of resistance coefficient continuously increases. In the primary stage of polymer flooding, the changing rate of resistance coefficient in the high permeability layer is bigger than that in the low permeability layer. When those are equal, the water injection profile begins to invert.