煤层瓦斯运移机制的关键参数表征

 煤层的瓦斯扩散系数、浓度流动系数、初始运移强度系数和衰减系数，是煤体孔隙结构和煤质特性的力学表征。为研究煤层瓦斯运移机制，量化煤层瓦斯运移能力，依据Fick扩散理论和质量守恒方程，建立了描述煤体瓦斯浓度与扩散速率的计算模型，采用变量分离法进行数学求解，并通过数据迭代方法获取煤体内瓦斯的扩散系数和表面浓度流动系数；通过室内4种煤样瓦斯运移实验数据比较发现，煤体瓦斯质量增量与运移时间成负指数关系，且随煤阶升高而增大；瓦斯运移速度和衰减系数取决于煤的吸附能力和煤质组分，且煤种之间差异明显；渗透率与扩散系数成线性关系，与流动系数成二次函数关系，且随煤阶升高整体呈增加趋势。

Key parameters for gas migration mechanism in coal seam

The coefficients of gas diffusion，concentration flow，initial migration strength and attenuation are the mechanical characterization of the pore structure and quality characteristics in coal matrix. In order to investigate the mechanism and to quantify the ability of gas migration in coal seam，a mathematical model about gas concentration and diffusion rate was established based on the Fick′s law and mass conservation equation. The method of variable separation was employed to solve the equation. The coefficients of gas diffusion and gas concentration flow were proposed with the data iterative method. The gas diffusion experiments were carried out for four kinds of coal samples. The results indicated that the mass increment of gas emission had a negative exponential relationship with the test time. The higher the coal rank is，the greater gas quality growth will be. The gas diffusion velocity and the attenuation coefficient were controlled by the pore structure and micro components of the coal matrix. There were obvious differences between the four coal species. The permeability varies linearly with the diffusion coefficient and parabolic with the flow coefficient. The flow coefficient and diffusion coefficient increase with the increasing of coal rank.