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随页岩气开采大力发展,对页岩的认识也逐显重要。页岩作为明显的层状结构岩石,普遍表现出各向异性。为此,基于横观各向同性介质模型,通过测量岩样不同方向的纵波波速和快慢横波波速,计算了长宁区块龙马溪组岩样的刚度系数与弹性系数,并与静载荷试验测定的弹性参数做出对比。试验结果表明,页岩的纵波波速以及快慢横波波速均表现出各向异性,并且随围压升高,波速升高速率变缓。岩样的杨氏模量与泊松比亦表现出各向异性,水平方向上的杨氏模量始终高于垂直方向上的杨氏模量,而3个方向的泊松比不一致。动态加载测试值与静态加载测试值随围压变化趋势一致,并且随围压升高,由孔隙和微裂缝引起各向异性减弱。考虑页岩中微裂缝的存在,通过弥散损伤模型计算龙马溪组页岩的损伤参数,认为在围压作用下微裂缝主要存在于平行层理面方向,围压对垂直层理面的裂缝影响较小。
With the development of shale gas development, the understanding of shale also become increasingly important. Shale generally shows anisotropy as an obvious layered rock. Therefore, based on the transversely isotropic medium model, the stiffness coefficient and elastic coefficient of the Longmaxi Formation in Changning block are calculated by measuring the longitudinal and transverse velocity of the rock specimen in different directions, Elastic parameters to make contrast. The experimental results show that the longitudinal wave velocity and the transverse velocity of shale show anisotropy, and the rate of increase of wave velocity decreases with the increase of confining pressure. The Young’s modulus and Poisson’s ratio of the rock samples also show anisotropy. The Young’s modulus in the horizontal direction is always higher than that in the perpendicular direction, while the Poisson’s ratio in the three directions is not consistent. Dynamic load test values and static load test values with the trend of confining pressure changes, and with the confining pressure increased, caused by the pores and micro-cracks anisotropy weakened. Considering the existence of micro-cracks in shales, the damage parameters of Longmaxi Formation shale are calculated by diffusion damage model. It is considered that the micro-cracks mainly exist in the direction of parallel bedding plane and the confining pressure influences the fracture of vertical bedding plane Smaller.