孔隙结构控制下的煤体渗透实验研究

Permeability experiments of pore structure in coal matrix

煤层为典型的双重孔隙介质体,其渗透能力受孔隙和裂隙结构参数控制。通过建立描述煤体孔隙和裂隙渗透率统一数学模型,将煤体内气体渗流分为孔隙控制型、裂隙控制型和孔隙-裂隙联合控制型3类;借助6组煤样气体渗流实验数据和孔隙裂隙的测试统计,讨论了不同孔隙特征的渗透率差异原因。研究发现,孔隙和裂隙的结构参数决定了煤体的压缩系数和孔渗指数,进而决定了其渗流类型,影响煤体渗透率敏感性的关键因素是裂隙的密度和尺度,微孔中的气体分子受范德华力影响导致渗透率的应力敏感性几乎无法体现。

Coal seam is typical double porosity medium,whose permeability is controlled by the structural parameters of pores and fractures.A unified mathematical model of porosity and permeability for gas flow in a double porosity medium was established.Lots of gas seepage phenomena in coal body were divided into three types: pore control,fracture control and pore-fracture combination control.With the gas seepage experimental data of six groups of coal samples and their test statistics of the porosity and fracture,the reasons of the permeability difference in the coal samples were discussed.The study found that the structural parameters of the pores and fractures determined the compression coefficient and permeability index of coal body,and then determined the type of gas seepage.The key factors affecting the permeability of coal seam were the density and the scale of pores and fractures.However,the stress sensitivity was almost impossible to be reflected in the micro pores because of the Van der Waals force between gas molecules and other particles.