含气页岩渗透率的围压敏感性和各向异性研究

Research on confining pressure sensitivity and anisotropy for gas shale permeability

利用MTS岩石力学试验系统研究了牛蹄塘组含气页岩的渗透性能、变形随围压的变化规律和各向异性特征，并利用SEM对试样进行了微观结构观察，揭示了含气页岩渗透率、变形随围压变化的内因。结果表明：1）围压5~40 MPa下，牛蹄塘组含气页岩渗透率范围为5.06×10-7~1.

MTS has been used to study the effects of confining pressure on permeability, deformation and the anisotropic characteristics of Niutitang gas shale. SEM has also been used to observe the sam-ples＇ microstructure, which reveals the real reason of the confining pressure effect. The results show that：1） The Niutitang gas shale permeability is between 5.06×10-7 D and 1.02×10-5 D as the confining pres-sure raises from 0 to 40 MPa;2） The gas shale permeability decreases with the increment of confining pressure, which obeys a power-law relationship, but the volume deformation of shale increases as con-fining pressure gradually increases;3） The gas shale permeability and deformation are anisotropic, that is, under the same confining pressure, the permeability and volume deformation of sample paralleled to bedding plane are both greater than the sample with beddings at an angel of 45 degrees to the plane;4） Obvious sedimentary structure is observed in the gas shale samples, and the pores distribute along the direction of the bedding;5） The volume strain sensitivity to the confining pressure of low permeability gas shale decreases after an initial increase with the increase of confining pressure, and the permeability＆nbsp;sensitivity to the confining pressure is gradually reduced with the increase of confining pressure.