压裂气井非达西流动模拟研究

A STUDY OF NON- DARCY FLOW SIMULATION IN FRACTURED GAS WELLS

在压裂气井中，低粘气体在高导流支撑裂缝中的渗流阻力降低，渗流速度加快，气体渗流入井的流动由达西流变为非达西流。目前基于达西流动假设所制作的预测压裂井生产动态的典型图版，对压裂气井生产动态的计算结果与实际相差较大。为此在引入非达西因子的基础上，首次推导建立了压裂气井中真实气体在地层—裂缝中非达西渗流的数学模型，采用有限差分法得到了该模型的数值方程和求解方法，推导了非达西因子的数值计算法，模拟计算了压裂气井生产过程中的非达西因子和井底、地层及支撑裂缝中的压力动态。计算表明压裂气井中存在的非达西渗流对压力动态和生产动态有显著影响，在低导流能力、高产压裂气井中非达西流的影响更为显著。文中的模型和方法可应用于气井压裂后动态预测和气藏整体压裂数值模拟。

The resistance to flow of low viscosity gas in fractured wells with high conductivity fractures decreases and flow velocity rapidly increases, non-darcy flow near wellborn occurs. There is a big gap between the production performance prediction on the fractured wells using the typical curves developed by darcy flow law and practice. On the basis of the non-darcy flow factor, this paper presents the non-darcy flow mathematical model of real gas in the reservoir and fracture. The corresponding numerical model and solution methodology is derived by the finite difference method and the numerical algorithm of non-darcy flow factor is derived. The pressure performance at buttonhole, formation and propped fractures and non-darcy factors in the fractured gas well production are simulated and calculated. The results show the non-darcy flow exited in the fractured wells has much effect on the pressure and production performance. The effect has more notable in the lower conductivity or higher productivity well. The model and methodology can be applied to the performance prediction in a fractured well.