论文部分内容阅读
在考虑井筒储存和表皮效应影响的情况下,建立了存在启动压力梯度的低渗透煤层气流动数学模型,利用Laplace变换和Green函数方法求得了煤层气井的无因次井底压力的Laplace空间解析解,并通过数值求解绘制了典型样板曲线。通过对特征曲线的分析发现:在定产量生产的情况下,启动压力梯度对初期压力动态无显著影响;在生产的中后期,启动压力梯度值越大,则压力及其导数曲线上升趋势越明显,这代表启动压力梯度对煤层渗流的影响也就越严重,压力导数曲线上的径向流水平直线段消失;弹性储容比和介质间窜流系数主要影响煤基质孔隙向裂隙发生窜流的时间。
Taking into account the influence of wellbore storage and skin effect, a mathematical model of low permeability coalbed methane flow with start-up pressure gradient is established. Laplace transform and Green’s function method are used to obtain the Laplace space analytical solution of dimensionless bottomhole pressure of coalbed methane wells. , And draws a typical sample curve by numerical solution. Through the analysis of the characteristic curves, it is found that in the case of constant production, the starting pressure gradient has no significant effect on the initial pressure dynamic. In the middle and late production stage, the larger the starting pressure gradient value, the more obvious the upward trend of the pressure and its derivative curve , Which means that the more serious the influence of the start-up pressure gradient on the seepage of coal seam, the disappearance of the horizontal straight-line section of the radial flow on the pressure derivative curve. The elastic reservoir ratio and interchannel cross-flow coefficient mainly affect the flow of coal matrix pores to fissures time.