Shear wave logging in elastic formations
Shear wave logging in elastic formations
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DOI：
10.1121/1.397015
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发表时间：
1988-12
影响因子：
2.4
通讯作者：
D. Schmitt
中科院分区：
文献类型：
--
作者：
D. Schmitt
本文分析了在被（多层）弹性地层包围的充满流体的井眼中，偶极子源和四极子源所产生的模式的色散和衰减。位移-应力矢量采用Thomson-Haskell方法在各层间传播。只研究了良好键构型。在时域上，研究了震源中心频率对离散波数法计算合成全波形微震图的影响。无论地层（快或慢）和结构如何，弯曲和螺旋模式的低频部分都遵循原始地层横波特征。它们的高频部分表现得像单极源激发的斯通利波。因此，基模对中频和高频的内层特性非常敏感。在入侵区存在的情况下，波形的内部动力学可以显著地改变，而有用的基本模态的起始能量向较低的频率转移。当井眼下套管时，则发生相反的现象。对于最后一种配置，由于基模的泄漏特性，只有在较低的源中心频率下，多极源才能记录到缓慢的地层横波。这种行为强调了实际测井工具需要有用的低频能量。
The analysis of the dispersion and attenuation of the modes generated both by a dipole and a quadrupole source in a fluid‐filled borehole surrounded by a (multilayered) elastic formation is performed. The displacement‐stress vectors are propagated through the layers using the Thomson–Haskell method. Only the well‐bonded configuration is investigated. In the time domain, the effects of the source center frequency on synthetic full waveform microseismograms computed using the discrete wavenumber method are investigated. Whatever the formation (fast or slow) and the configuration, the low‐frequency part of both the flexural and screw modes follows the virgin formation shear wave characteristics. Their high‐frequency parts behave like that of the Stoneley wave excited by a monopole source. As a result, the fundamental modes are very sensitive to the properties of the inner layers at intermediate and high frequencies. In the presence of an invaded zone, the internal dynamics of the waveforms can be significantly modified, while the useful starting energy of the fundamental modes is shifted toward lower frequencies. The reverse phenomenon occurs when the borehole is cased. For this last configuration, it is only with low source center frequencies that multipole sources can log a slow formation shear wave due to the leaky character of the fundamental modes. Such behaviors emphasize the need for useful low‐frequency energy for the actual logging tools.