Stress-Associated Intrinsic and Scattering Attenuation from Laboratory Ultrasonic Measurements on Shales
Stress-Associated Intrinsic and Scattering Attenuation from Laboratory Ultrasonic Measurements on Shales
复制标题
页岩实验室超声测量中与应力相关的固有衰减和散射衰减
DOI：
10.1007/s00024-017-1705-9
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发表时间：
2017-05
影响因子：
2
通讯作者：
Yan Zhang
中科院分区：
文献类型：
--
作者：
Junhua Hu;Li-yun Fu;Wei Wei;Yan Zhang
地震衰减对应力引起的岩石物理状态的细微变化很敏感。在这项研究中，应力和频率相关的衰减量化通过超声波测量三个不同取向的圆柱形页岩样品在各种轴向应力。作为对单次散射模型的改进，弹性蒙特卡罗方法被用来研究多次散射衰减，通过合并边界反射和波转换。结果表明，随着轴向应力的增加，各方向的本征衰减减小，而散射衰减在垂直于层理的方向略有减小，但在其他方向则大幅度非线性增加。这些差异是由不同的衰减机制造成的。本征衰减和散射衰减在与层理成45°的方向上最大，而在垂直于层理的方向上最小。由于横波波长较短，横波的衰减比纵波的衰减大，对应力变化也更敏感。正如从砂岩实例中所预期的，页岩中的散射衰减比固有衰减明显更大并且对应力变化更敏感。散射衰减的频率依赖性表明，具有最大散射衰减的峰值频率与轴向应力无关，但是在具有不同非均质性和各向异性尺度的单个岩石的不同方向上变化。S-尾波的峰值频率比P-尾波小，散射衰减峰值大。总之，页岩中的超声波衰减的应力和频率依赖性在各个方向上有很大不同，表明显着的各向异性和非均质性。
Seismic attenuation is sensitive to stress-induced subtle changes in the physical state of rocks. In this study, the stress- and frequency-associated attenuation is quantified through ultrasonic measurements on three differently oriented cylindrical shale samples under various axial stresses. As an improvement to the single-scattering model, the elastic Monte Carlo method is employed to investigate multiple-scattering attenuations by incorporating the boundary reflections and wave conversions. Our results show that, as the axial stress increases, the intrinsic attenuation decreases in all directions, while the scattering attenuation decreases slightly in the direction perpendicular to the bedding but increases largely and nonlinearly in other directions. These discrepancies result from different attenuation mechanisms. Both the intrinsic and scattering attenuation are found to be largest in the direction 45° to the bedding, but least in the perpendicular direction. TheS-wave attenuation is larger and more sensitive to stress changes thanP-wave attenuation due to its shorter wavelength. As expected from sandstone examples, the scattering attenuation in shales is significantly larger and more sensitive to stress changes than the intrinsic attenuation. The frequency dependence of scattering attenuation suggests that the peak frequency with the maximum scattering attenuation is independent of axial stresses, but varies in different directions of an individual rock with different heterogeneity and anisotropy scales. The peak frequency ofS-coda is smaller and its peak scattering attenuation is larger thanP-coda. In conclusion, the stress and frequency dependence of ultrasonic attenuations in shales differ largely in various directions, indicating significant anisotropy and heterogeneity.
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影响因子：
20.6
作者：
A. Ishimaru
通讯作者：
A. Ishimaru
影响因子：
2.8
作者：
H. Sato
通讯作者：
H. Sato
影响因子：
--
作者：
K. Yoshimoto
通讯作者：
K. Yoshimoto
影响因子：
5.2
作者：
CHENG, CH;JOHNSTON, DH
通讯作者：
JOHNSTON, DH
影响因子：
2
作者：
HERRAIZ, M;ESPINOSA, AF
通讯作者：
ESPINOSA, AF