有效流动单元划分方法与流场动态变化特征

Dividing principle and method of effective flow units and the characteristics of flow field

为了研究不同开发阶段非均质油藏内部渗流规律,反映不同开发阶段地层中流体流动规律及分布特征,揭示流场变化与储层特征间的内在联系,对克服启动压力梯度、对产量有贡献的压力梯度控制区进行研究,建立有效流动单元划分原理及方法。首先,基于水动力学原理及流线簇方程,提出流量贡献率、流量非均匀分布曲线和流量强度差异系数3个概念,以流量非均匀分布曲线的导数为1作为区分高速与低速流动区的划分准则,并绘制不同井网模式下划分图版,划分高速与低速流动区。其次,基于流管模型并结合两相渗流理论,求取恒速注水单条流线的平均含水饱和度,建立平面饱和度分布模型,将含水率大于极限含水率的流管视为无效循环区,将储层划分为高速流动无效区、高速流动有效区、低速流动有效区和死油区4类有效流动单元,通过对反五点井网恒速注水理想模型并结合实际油藏的模拟计算,证明通过有效流动单元的划分能够揭示剩余油形成机理和分布特征。

Flow dynamics and fluid saturation distribution vary in different stages of development of heterogeneous reservoirs. The dividing principle and method of effective flow units were established in order to study the close relationship between variation of flow field and reservoir characteristics, and to figure out the characteristics of zones contributing to oil production. First of all, the concept of the contribution rate of flow（CRF）, nonuniform distribution curve（NDC） and the difference coefficient of flow intensity（DCFI） was proposed on the basis of water dynamics theory and streamline cluster equation. Dividing principle between high and low velocity flow area is that the value of derivative function is 1. Charts of divided flow units of different kinds of well patterns were presented. Secondly, based on the flux-tube model and two-phase flow theory, mathematical model was derived for planar water saturation distribution during constant rate water flooding. The ineffective flow area was divided by the streamline of which water saturation is higher than extreme water cut. The effective flow units of reservoir were divided by high velocity ineffective flow, high velocity effective flow, low velocity effective flow and dead oil area. Numerical simulation was conducted using data of a reservoir with inverted 5 spots pattern. The effective flow units were verified to be capable of uncovering mechanism and distribution of remaining oil.