Estimating fracture orientation from elastic-wave propagation: An ultrasonic experimental approach
Estimating fracture orientation from elastic-wave propagation: An ultrasonic experimental approach
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DOI：
10.1029/2012jb009215
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发表时间：
2012-08
影响因子：
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通讯作者：
J. J. S. Figueiredo-J.;J. Schleicher;R. Stewart;N. Dyaur
中科院分区：
文献类型：
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作者：
J. J. S. Figueiredo-J.;J. Schleicher;R. Stewart;N. Dyaur
弹性波在破裂和裂纹介质中的传播取决于不连续面占主导地位的空间方向。因此，纵波速度和横波速度可以提供有关裂缝方向的宝贵信息。本工作的主要目标是基于交叉相关s波地震图和Thomsen参数的分析来估计优选裂缝方向。为此，我们在一个人工各向异性裂缝模型的物理模拟实验中分析了弹性（P和S）波的超声测量。模型的固体基体由环氧树脂组成；小橡胶条模拟裂缝与合规填充。各向异性裂缝模型由三个区域组成，每个区域具有不同的裂缝方向。我们利用s波极化的旋转进行了方向的互相关分析，利用P波和s波测量来评估弱各向异性参数γ和e。横波和纵波源的主导频率为90 kHz和120 kHz。与层间距相比，这些频率对应于较长的波长，表明接近有效介质的行为。综合各向异性参数分析和相互关系分析的结果，我们能够在我们的各向异性裂缝物理模型中估计裂缝的方向。γ参数与相互关联分析结果吻合良好，除此之外，还提供了单独相互关联不能完全解决的有关裂纹方向的额外信息。此外，我们的结果表明，横波受裂缝方向的影响更大，因此可以比纵波包含更多关于裂缝方向的信息。
[1] Elastic-wave propagation in fractured and cracked media depends on the dominant spatial orientation of the discontinuities. Consequently, compressional and shear-wave velocities can give valuable information about the orientation of the cracks. The main goal of this work is to estimate the preferential fracture orientation based on an analysis of cross-correlated S-wave seismograms and Thomsen parameters. For this purpose, we analyzed ultrasonic measurements of elastic (P and S) waves in a physical-modeling experiment with an artificially anisotropic cracked model. The solid matrix of the model consisted of epoxy-resin; small rubber strips simulate cracks with a compliant fill. The anisotropic cracked model consists of three regions, each with a different fracture orientation. We used the rotation of the S-wave polarizations for a cross-correlation analysis of the orientations, and P- and S-wave measurements to evaluate the weak anisotropic parametersγ and e.The shear and compressional wave sources had dominant frequencies of 90 kHz and 120 kHz. These frequencies correspond to long wavelengths compared to the spacing between layers, indicating a nearly effective-media behavior. Integrating the results from cross-correlation with anisotropic parameter analysis, we were able to estimate the fracture orientation in our anisotropic cracked physical model. Theγparameter showed good agreement with the cross-correlation analysis and, beyond that, provided additional information about the crack orientation that cross-correlation alone did not fully resolve. Moreover, our results show that the shear waves are much more strongly influenced by, and can thus contain more information about, crack orientation than compressional waves.