结构异性煤体渗透率特性

 煤渗透率是研究瓦斯渗流特性及运移规律的关键参数, 而煤体结构各向异性导致渗透率具有明显的方向性。利用煤岩瓦斯渗流试验系统, 对不同变质程度煤样试件在面割理和端割理方向上, 进行不同瓦斯压力下的渗透率测试, 并根据等效驱替原理, 建立各向异性煤体渗透率的计算模型, 数值分析了煤体渗流的定向性特征。结果表明:在煤体面割理和端割理方向, 渗透率均随瓦斯压力增大成负指数减小;面割理方向的瓦斯渗透率与端割理方向相差可超过1 个量级, 且煤的变质程度越高, 差别越明显。随瓦斯压力增大, 煤的瓦斯渗流定向性系数峰值增大, 煤层瓦斯渗透定向性增强。在相同瓦斯压力下, 煤的变质程度越低, 煤层瓦斯渗透定向性越弱。

Permeability characteristics of structurally anisotropic coal

The coal permeability is a key parameter for the gas seepage characteristics and the migration law, and the structural anisotropy of the coal seam makes the permeability obvious orientation dependent. In this paper the gas permeability of raw coal specimens is measured in directions of face cleats and butt cleats under different gas pressures by a coal and rock permeability testing system. According to the equivalent displacement principle, the calculation model for the permeability of anisotropic coal is established and the directional characteristics of gas seepage are numerically simulated. It is shown that the structural anisotropy of coal has a great influence on the gas permeability of coal, the permeability in the direction of face cleats is larger than that in the direction of butt cleats, and the difference of coal permeability in the two directions reaches one order of the magnitude, and the more degraded the coal is, the greater the difference is. With the increase of the coal rank, the permeability decreases both in the directions of raw coal face cleats and butt cleats. With the increase of the gas pressure, the permeability decreases exponentially and the directionality coefficient peak increases and the directionality of gas seepage in the coal seam enhances. And under the same gas pressure, the lower the coal rank is, the weaker the directionality of gas seepage will be. This study provides some insight for optimizing the design and the layout of the gas drainage borehole in the coal seam, improving the gas drainage effect and achieving optimal extraction.