具有越流补给的含水煤层渗流模型求解与典型曲线

Solution and typical curves of seepage model of water-bearing coal seam with leakage recharge

为了分析水层越流补给对煤层气井早期排水的影响,根据不稳定渗流理论,引入越流系数,建立了考虑层间越流现象的煤层中水的渗流数学模型。通过Laplace变换对模型求解,并利用Stehfest反演得到实空间的解,采用新的参数组合,分别绘制了压力和压力导数双对数曲线图版。从物理渗流机理上分析了层间越流对曲线形态的影响,随着越流系数的增大,径向流结束的时间越早;同时提出了利用典型图版拟合确定储层渗透率、表皮系数以及越流系数的方法。典型图版有助于定量评价越流的强弱,对煤层气井后续排采制度的调整具有指导意义。

To study the effects of leaky aquifer on the earlier production of coalbed methane wells,the leaky aquifermodel was established based on transient flow theory.The model was solved under Laplace transform,and Stehfestreverse inversion was used to obtain the real space solution,then dimensionless pressure and pressure derivative typecurves were created in log-log plots with new parameters.Based on physical flow mechanism,the influence of leakyaquifer on curve shape was concluded that the radial flow would end earlier with stronger leakage coefficient.Theway to obtain permeability,skin factor and leakage coefficient by typical curve match was also proposed.Typicalcurves are useful for evaluating leaky aquifer and guiding subsequent production adjustment of CBM wells.