低渗非达西渗流煤层气羽状井开发机理研究

建立了非均质各向异性双重介质煤层气定向羽状水平井开采的较完整的数学模型，模型考虑了与气体吸附、解吸、扩散相耦合的三维气、水两相渗流；考虑了储层的压力敏感性；考虑了煤层本身所具有的低渗透特性，即低渗透地层启动压力梯度的影响；考虑了井筒内的压降损失。通过数值模拟分析了煤层气羽状水平井的增产机理，指出羽状水平井的主支和分支在地层中广泛均匀延伸，使整个控制区域地层压力均匀、快速下降，增大了气体解吸扩散的机会，是羽状分支水平井促使煤层气产量提高的根本原因；启动压力梯度的存在使煤层中羽状水平井的降压效果变差，从而使煤层气的产量减少。

Development Mechanism of Low Permeable Coalbed Methane from Multilateral Horizontal Pinnate Well with Non Darcy Seepage Flow Characteristic

A rather whole mathematical model of multilateral horizontal pinnate well for CBM recovery is developed.The coalbed is considered as dual medium and the factors including heterogeneity and anisotropy of stratum,sensitivity of permeability to pressure,friction and acceleration loss in well bore and start-up pressure derivative in low permeability coalbed are considered in this model.The mechanism of multilateral horizontal pinnate well for CBM recovery is analyzed by using of simulation technique.It is pointed that whole pinnate well bore spreading widely and evenly in coalbed makes stratum pressure dropped evenly and fast,which increases the chance of desorption and diffusion in area controlled.The above is the basic reason that horizontal pinnate well can increase production.The existence of start-up pressure gradient can make depressurization effect of horizontal pinnate well get worse,which promotes gas production reducing.