用两个不同源距的声波测井全波波形计算纵波和横波波速

The calculation of P- and S-wave velocities from acoustic waveform logs with only two receivers in different ranges

讨论两个不同源距的声波测井全波波形的处理问题。用数值模型模拟SKC -B国产大数控声波全波列测井仪后 ,通过波形的二维谱发现 :测井波形中 ,纵波具有频率选择性 ,但传播速度不随频率改变 ,其幅度比较小 ;横波及伪瑞利波是连在一起的 ,伪瑞利波的幅度比较大 ,速度随频率改变。从这些结果可知 :用实际测井波形计算纵波时差时 ,波形中的干扰对计算结果的影响比较大 ;用实际测井波形计算横波时差时 ,伪瑞利波对计算结果的影响比较大。根据实际测井波形的特点 ,研究了相应的纵波时差和横波时差的处理方法。计算纵波时差时 ,讨论了干扰的影响及其消除方法 ;计算横波的时差时 ,利用伪瑞利波群速度随着频率的降低 ,逐渐接近横波速度的特点 ,改进了直接相位法中横波的处理方法 。

Sonic logging tool SKC-B is simulated with a numerical model in this paper and its two-dimensional spectra of full-waves is used to analyze the frequency characteristics of longitudinal, shear, and Rayleigh waves. Numerical results show that P-wave movemout is affected by the noises contained in the sonic waveform and S-wave movemout is impaired by pseudo-Rayleigh waves. Based on these results, calculation methods of P- and S-wave velocities are constructed.