多裂缝系统垂直裂缝井不稳定渗流分析

UNSTEADY PERCOLATION ANALYSIS FOR VERTICAL FRACTURED WELL WITH MULTIPLE FRACTURES

高能气体压裂和脉冲压裂能在近井地带形成多条径向裂缝,对此建立了均质油藏和双重介质油藏多裂缝系统垂直裂缝井的物理模型。利用叠加原理,在单裂缝系统压力分布公式的基础上,得到了多裂缝系统垂直裂缝井不稳定渗流压力响应的计算方法,绘制并分析了油藏参数、裂缝条数和裂缝分布影响下的压力动态典型曲线。结果表明:流体在多裂缝系统的流动特征与裂缝条数和裂缝分布有关,当裂缝条数较少并且夹角较大时,压力动态曲线主要分为3个流动阶段:线性流段、椭圆流段和拟径向流段;当裂缝较多或者夹角较小时,由于裂缝之间相互影响,线性流段和椭圆流段之间的过渡段变长,线性流段可能消失;裂缝条数越多,供液能力越强,相同时间下,井底压力下降得越少。

Multiple radial fractures are generated in near bore zone by high energy gas fracturing and pulse fracturing,so the model of vertical fractured well with multiple fractures in homogeneous reservoir and double porosity reservoir is set up in this paper.Based on the pressure distribution formula of single fracture,by using superposition principle,the calculation method of unsteady percolation pressure response for vertical fractured well with multiple fractures is obtained.The typical curves are plotted and analyzed by considering the effect of reservoir parameter,fracture numbers and fracture distribution.The results show the flow characteristic of fluid in multiple fracture system is related to fracture numbers and fracture distribution.When the fracture number is less and angle is larger,the curve of pressure behavior can be divided into three flowing stages,i.e.,linear flow,elliptic flow and pseudo-radial flow.When the fracture number is more and angle is less,transitional section between linear flow and elliptic flow becomes longer,and the linear flow may be missing.At the same time,the more fracture number is,the more the fluid supply capacity,and the less bottom hold pressure will decrease.