潞安矿区煤层渗透率的各向异性特征实验研究

Experimental study on anisotropic characteristics of coal seam permeability in Lu’an mining area

为了研究原位煤体渗透性的各向异性特征,以山西潞安常村矿3号煤层圆柱试样为对象,利用TCQT-Ⅲ型低渗煤层气相驱替增产试验装置,对煤样进行加载,并以氮气注入压力2.0MPa的条件下,分析垂直层理和平行层理2个方向的煤体变形和渗透率变化特征。实验结果表明:煤样在加载过程中,平行和垂直层理煤样渗透率均随着有效应力的增大而减小,平行层理方向的渗透率始终大于垂直层理方向,应力加载初期渗透率急剧下降,最后逐渐趋于平缓;径向应变的增加量与渗透率呈正相关性,且平行层理相关性大于垂直层理;沿平行层理方向的裂隙度大于沿垂直层理方向,沿垂直层理方向的应变量大于沿平行层理方向;应变增加量均随有效应力的增加而逐渐减小。研究结果可为煤层井网布置及优化提供参考。

In order to study the anisotropic characteristics of in-situ coal permeability,taking the cylinder samples from No.3 coal seam of Changcun Mine in Lu’an Shanxi as the objects,the TCQT-Ⅲ test device of gas phase displacement for increasing production of low permeability coal seam was used for the loading of coal samples,and the change characteristics of coal deformation and permeability in the vertical bedding and parallel bedding directions were analyzed with the injection pressure of nitrogen as 2.0 MPa.The results showed that during the loading process of coal samples,both the permeability of coal samples with vertical bedding and parallel bedding decreased with the increase of effective stress,and the permeability in the parallel bedding direction was always larger than that in the vertical bedding direction.The permeability decreased sharply in the initial period of stress loading,and gradually tended to be flat at last.The increment of radial strain presented the positive correlation with the permeability,and the correlation of parallel bedding was larger than that of vertical bedding.The fracture degree along the parallel bedding direction was greater than that along the vertical bedding direction,and the strain along the vertical bedding direction was greater than that along the parallel bedding direction.Both the increment of strain decreased gradually with the increase of effective stress.The results can provide reference for the layout and optimization of coal seam well pattern.