Abstract Organic-rich gas shales are often composed of thin laminated structures and, thus, may be considered as transversely isotropic material. The shale's anisotropic properties are affected by many factors, including confining pressure, water content, total organic content (TOC), etc. In this work, ultrasonic velocity measurements were performed at various confining pressures and water content conditions to study the effects of confining pressure and water content on anisotropic properties at Eagle Ford shale. The test results show that Eagle Ford shale has weak elastic anisotropy. In addition, the results confirm that transversely isotropic media is an appropriate model to characterize Eagle Ford shale. Both the compressional (P) and shear (S) wave velocities increase as the confining pressure increases, especially at low confining pressure range. The horizontal elastic modulus, vertical elastic modulus and shear modulus also increase with the increase in confining pressure. Varying the confining pressure show minimal to no effect on the horizontal and vertical Poisson's ratio. On the other hand, the increase in the confining pressure decreases both P- and S-wave anisotropy. The study shows that P-wave anisotropy is more sensitive to confining pressure than S-wave anisotropy. The imbibed water significantly decreases P- and S- wave velocities. For a given sample at the same confining pressure, the decrease of P-wave/S-wave velocity is proportional to the unit increase of water content, which is defined as water content impact factor. Increasing water content also significantly reduces horizontal Young's modulus, vertical Young's modulus and shear modulus. Water makes the shale softer. The study shows that increase in the water content decreases the horizontal Young's modulus, the vertical modulus as well as the shear modulus by 8%, 11% and 15%, respectively. Both horizontal and vertical Poisson's ratio increase with increasing water content. Rock samples tested confirm that the increase in water content increases the P- and S-wave anisotropies by approx. 2.1% and 2.6%, respectively. The presence of water narrows the difference of V P and V P ( 90 0 ) at small angle of the near vertical range and, therefore, decreases the near vertical P-wave anisotropy.

中文翻译：

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含水量对富有机质页岩横向各向同性性质的影响

摘要 富有机质页岩通常由薄层状结构组成，因此可以认为是横向各向同性的物质。页岩的各向异性性质受围压、含水量、总有机物含量（TOC）等多种因素的影响。 本文在不同围压和含水量条件下进行超声速度测量，研究围压的影响和含水量对 Eagle Ford 页岩各向异性特性的影响。试验结果表明，鹰福特页岩弹性各向异性较弱。此外，结果证实横向各向同性介质是描述 Eagle Ford 页岩特征的合适模型。纵波 (P) 和横波 (S) 波速度都随着围压的增加而增加，特别是在低围压范围内。水平弹性模量、垂直弹性模量和剪切模量也随着围压的增加而增加。改变围压对水平和垂直泊松比的影响很小甚至没有影响。另一方面，围压的增加同时降低了 P 波和 S 波的各向异性。研究表明，纵波各向异性比横波各向异性对围压更为敏感。吸收的水显着降低了 P 波和 S 波速度。对于相同围压下的给定样品，纵波/横波速度的降低与单位含水量的增加量成正比，定义为含水量影响因子。增加含水量也会显着降低水平杨氏模量、垂直杨氏模量 s 模量和剪切模量。水使页岩变软。研究表明，含水量的增加使水平杨氏模量、垂直模量以及剪切模量分别降低了 8%、11% 和 15%。水平和垂直泊松比都随着含水量的增加而增加。测试的岩石样品证实，含水量的增加会使 P 波和 S 波各向异性增加约 10 倍。分别为 2.1% 和 2.6%。水的存在缩小了 VP 和 VP ( 90 0 ) 在近垂直范围的小角度上的差异，因此降低了近垂直 P 波的各向异性。分别为 11% 和 15%。水平和垂直泊松比都随着含水量的增加而增加。测试的岩石样品证实，含水量的增加会使 P 波和 S 波各向异性增加约 10 倍。分别为 2.1% 和 2.6%。水的存在缩小了 VP 和 VP ( 90 0 ) 在近垂直范围的小角度上的差异，因此降低了近垂直 P 波的各向异性。分别为 11% 和 15%。水平和垂直泊松比都随着含水量的增加而增加。测试的岩石样品证实，含水量的增加会使 P 波和 S 波各向异性增加约 分别为 2.1% 和 2.6%。水的存在缩小了 VP 和 VP ( 90 0 ) 在近垂直范围的小角度上的差异，因此降低了近垂直 P 波的各向异性。