孔隙压力与水分综合作用的煤岩渗透率演化规律

Evolution law of coal permeability based on comprehensive effect of pore pressure and water

为探究孔隙压力与水分变化引起的煤基质压缩体积变化及其对煤岩渗透率的影响规律,采用液氮吸附实验和压汞实验结合的方法计算煤基质压缩系数,并分析煤岩孔隙结构特征.开展不同含水率条件下孔隙压力升高的煤岩渗流实验,构建考虑水分和孔隙压力综合作用的渗透率模型,体现煤岩孔隙结构和瓦斯渗流的关联性.结果表明:煤基质压缩系数可使煤岩压缩体积变化量化,而且煤岩渗透率与孔隙压力呈指数函数关系.孔隙压力恒定时,渗透率随含水率的增大而减小.对比分析渗透率模型计算的压缩系数与孔隙结构实验计算值,说明孔隙结构对煤岩吸附及渗透特性有控制作用.

In order to explore the variation of coal matrix compression volume caused by pressure changes and its influence on coal permeability,the compressive coefficient of coal matrix was calculated based on the liquid nitrogen adsorption test and mercury intrusion test.The pore structure characteristics of coal were analyzed and seepage tests of coals with different water content conditions were carried out under elevated pore pressure.A permeability model was constructed considering the combined effects of water and pore pressure to reflect the correlation between pore structure and gas seepage.The results show that the compression coefficient can quantify accurately the change of the compression volume of coal.The coal permeability was found exponentially related to the pore pressure.When the pore pressure remains constant,the permeability decreases significantly with the increase of water content.The comparison of the compression coefficient obtained from the proposed model and that from the pore structure test can explain the controlling effect of pore structure on the adsorption and permeability characteristics of coal.