存在动态非达西效应的复合油藏试井分析方法

Well Test Analysis Method for Composite Reservoir with Dynamic Non-Darcy Flow Effect

为准确描述低渗油藏注水井附近储层渗流变化规律及影响因素,提出一种存在动态非达西效应的复合油藏试井分析方法。该方法首先考虑内区渗流方式为达西流,外区渗流方式为启动压力梯度效应和动态渗透率效应构成的非达西流。其次采用数值法进行离散求解,计算得到注水井井底压力。然后绘制井底压力响应典型曲线图版,典型曲线主要分为井储段、过渡段、内区径向流段、外区低渗流段和边界反映段共5个流动段。最后对启动压力梯度、动态渗透率参数进行敏感性分析,并对比不同渗流规律的压力响应。以长庆油田某注水井为例,进行试井解释。结果表明:该注水井周围的渗透率较大,外区受启动压力梯度和动态渗透率的共同影响,存在启动压力梯度、渗透率较小,符合现场实际。常规油藏注水井复合试井分析方法以及低渗油藏单区试井分析方法均为该方法的一种特例。

In order to accurately describe the change law and influencing factors of reservoir seepage flow near injection wells in low permeability reservoirs,a well test analysis method for composite reservoir with dynamic non-Darcy effect outside injection wells was constructed.Firstly,Darcy flow is considered as the inner seepage mode,and non-Darcy flow as the outer seepage mode composed of starting pressure gradient effect and dynamic permeability effect.Secondly,numerical method is used for discrete solution to calculate the bottom-hole pressure of the injection well,and then the typical curve of bottom-hole pressure response is drawn.Typical curves are divided into 5 flow sections:wellbore storage section,transition section,inner radial flow section,outer low seepage flow section and boundary reflection section.Finally,sensitivity analysis of starting pressure gradient and dynamic permeability parameters is carried out,and pressure response of different seepage laws is compared.Taking an injection well in Changqing Oilfield as an example,the well test results show that the permeability around the injection well is larger,and the outer zone is affected by the combination of starting pressure gradient and dynamic permeability,and there is a starting pressure gradient in the outer area,and the permeability is smaller,which is consistent with the field practice.This method is a relatively general numerical pressure calculation method,among which the conventional injection well composite well test analysis method and low permeability reservoir single zone test analysis method are special cases of this method.