苏里格气田椭圆状孤立砂体产能方程的建立

Establishment of the deliverability equation of elliptic isolated sandbody in Sulige gas field

目前二项式产能方程的建立是基于一种圆形水平、等厚和均质的气层,气体径向流入井底的模型。而苏里格气田有效砂体则以孤立状分布为主,砂体规模较小,形态呈椭圆或长椭圆状,当压力传播至砂体宽度边界之后,将不再满足纯径向流的渗流规律,目前推导的产能方程存在较大误差。根据该气田实际的砂体特征,将整个渗流过程分为两段,即在投产初期比较短的时间内,当压力未传播至砂体宽度边界之前,表现为近井区径向流;当压力传播到砂体宽度边界之后则表现为远井区单向流。由此建立了新的渗流物理模型,并推导出了远井区单向流的产能方程,然后根据物质守恒原理与近井区径向流的产能方程合并,得出了苏里格气田孤立砂体新的产能方程。现场应用表明该方程具有较高的计算精度。

At present, the establishment of the binomial deliverability equation is based on a horizontal circular, equal thick and homogeneous gas reservoir model in which gas flows into well bottom in the form of radial flow. The efficient sand body in the Sulige gas field, developed in relatively small size and ellipse or long ellipse shape, is always distributed isolatedly. When pressure is propagated to sandbody width boundary, it will not meet the seepage law for pure radial flow, as a result, there is a bigger error by the current deduced deliverability equation; The seepage process can be divided into two stages in accordance with the actual characteristics of sandbody in the Sulige gas field, i.e., in the short term of early operation, it behaves as radial flow near wellbore before the pressure is propagated to sandbody width boundary and as unidirectional flow far from wellbore after the pressure is propagated to sandbody width boundary. A new percolation physical model is established and the deliverability equation of unidirectional flow far from wellbore is deduced, which is then combined with that of radial flow near wellbore according to material conservation theory, thus to get a new deliverability equation for isolate sandbody in the Sulige gas field. The field application shows that this equation has higher accuracy.