沁水煤田承压破碎无烟煤气体渗透特性试验研究

Experimental study on gas permeation characteristics of pressure-bearing crushed anthracite coal in Qinshui coalfield

充分掌握采空区垮落带瓦斯运移规律,对提高煤层气抽采效率具有重要意义。为揭示老空区抽采中后期破碎无烟煤的瓦斯渗透规律,利用自主设计研发的破碎煤岩体压实-渗透试验装置,对0.32~0.63 mm粒径破碎无烟煤开展试验。研究结果表明:以动态渗透过程中气体压力及流量的变化趋势为依据,气体在破碎无烟煤中的渗透可划分为两种模式;老空区煤层气抽采中后期低雷诺数下破碎无烟煤中气体运移存在拟启动压力梯度,且空隙率越小所需要的拟启动压力梯度越大;破碎无烟煤渗透率与气体压力呈对数正相关,且随空隙率降低呈指数函数减小;随着轴向应力的增加,破碎无烟煤由弹性变形转化为非弹性变形,此时空隙率对轴向应力的敏感程度降低。

It is of great significance to understand the gas migration rule in the caving zone in order to improve the extraction efficiency of coalbed methane.In this study,self-designed gas permeability test equipment for crushed coal and rock mass was developed.By virtue of this equipment,we carried out compaction-permeability tests on crushed anthracite of 0.32~0.63 mm particle size.The results show that:The dynamic gas flow process in crushed anthracite can be divided into two representative types(type Ⅰ and type Ⅱ)before the stable adsorption equilibrium is achieved.There is a quasi-threshold pressure gradient of gas migration in the crushed anthracite at low Reynolds number.And the quasi-threshold pressure gradient decreases with the growth of porosity.The permeability of crushed anthracite is logarithmically positively correlated with the gas pressure;the permeability decreases exponentially with the decrease of void ratio.With the increase of axial stress,the crushed anthracite is transformed from elastic deformation to inelastic deformation,and the sensitivity of permeability to axial stress decreases at this time.