考虑次生裂缝的页岩气藏有限导流缝网模型

The Finite-conductivity Fracture Networks Model in Shale Gas Reservoirs with Consideration of Induced Fractures

为了考虑次生裂缝对页岩气井压力响应特征的影响,建立了耦合多重运移机制的页岩气藏有限导流缝网流动模型,并开展了压力动态特征的研究。首先,通过Laplace空间源函数、局部坐标转换及叠加原理得到耦合吸附解吸、扩散、渗流的气藏解析解。然后,基于有限差分方法及交汇单元流量分配变换,推导得到裂缝单元的数值解。耦合气藏及裂缝两部分的流动,半解析计算求解得到了考虑次生裂缝影响的压力响应曲线,并对次生裂缝组数、导流能力、裂缝角度等反映次生裂缝特征的参数进行了敏感性分析。结果表明,该模型存在10个典型流动阶段,能有效表征次生裂缝对曲线形态的影响,对页岩气压力动态特征的研究具有重要指导意义。

In order to analyze the influence of secondary induced fractures on the pressure response of shale gas wells,a finite conductivity fracture network flow model of shale gas reservoir with coupling multiple migration mechanism has been established,and the pressure dynamic characteristics have been studied.Firstly,the analytical solution of pressure in shale gas reservoir has been obtained by employing Laplace space source function,local coordinate transformation and superposition principle.Then,based on the finite difference method and the flow distribution transformation of intersection element,the numerical solution of fracture element has been derived.By coupling the flow of gas reservoir and fracture,the pressure response curve considering the influence of secondary fracture was drawn,and the influences of characteristic parameters(such as the number of secondary fracture groups,secondary fracture angle,and fracture conductivity,etc.)were analyzed.The results show that there are 10 typical flow stages,which can effectively characterize the influence of secondary fractures.In addition,the presented model will be helpful for understanding the transient performance of multi-stage fractured horizontal wells with consideration of induced fractures.