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对煤层气的流动机理进行了分析。结果表明 ,煤层中的甲烷气主要以吸附的方式储集在煤基质中 ,煤层割理系统提供渗流通道。煤层气在煤基质中的吸附遵循朗格缪尔等温方程 ;煤层气由煤基质向割理系统的扩散遵循Fick第一定律 ;煤层气在割理系统的流动遵循达西定律。借鉴美国现有模型 ,结合我国现场实际情况 ,建立了二维煤层气垂直井的非平衡拟稳态井底渗流数学模型。现场实例模拟计算表明 ,该模型能够用于煤层气单井数值模拟。
The mechanism of CBM flow is analyzed. The results show that the methane gas in the coal seam is mainly stored in the coal matrix by adsorption and the coal seam cutting system provides the seepage channel. The adsorption of CBM in the coal matrix follows the Langmuir isotherm equation. The diffusion of coalbed methane from the coal matrix to the cleat system follows Fick’s first law. The flow of CBM in the cleat system follows Darcy’s law. With reference to the current American model and the actual situation in our country, a mathematical model of non-equilibrium quasi-steady state bottom hole seepage of 2D vertical coalbed methane wells is established. Simulation results show that the model can be used for single well numerical simulation of CBM.