煤层气三孔双渗流动模型及压力分析

Pressure Transient Analysis for Coal Seams with Triple-porosity/Dual-permeability Model

通过对美国Antrim页岩气藏及一些别的低阶煤层的研究表明,在基质颗粒中也有相当一部分自由气存在。本文建立了低阶煤层中单相煤层气三孔双渗流动的试井模型,并获得了模型在拉氏空间上的解析解以及模型的数值解,讨论了储层外边界条件、弹性储容比、窜流系数以及吸附系数等参数对于压力动态响应的影响。结果表明:外边界条件决定着早期过渡段出现的早晚;窜流系数和弹性储容比影响窜流阶段出现的早晚;而吸附系数对晚期过渡段影响明显。

Reservoir studies on the Antrim shale and other low-rank coal plays show that there is considerable free gas in the matrix block. A triple-porosity/dual-permeability model for single phase coalbed methane in low rank coal seams was developed, for which the analytical solutions in Laplace space and numerical solutions in real space were obtained. And then the effects of outer boundary, inter-porosity flow parameter, storativity ratio and adsorption parameter were discussed. The results indicate that the outer boundary determines the occurrence of early transition section, while the inter-porosity flow parameter and storativity ratio influence the occurrence of interporosity flow, and finally the adsorption parameter has a obvious impact on the late transition section.