Data Processing for Dipole Acoustic Wave Logging in Unconsolidated Formations
Dipole logging tools are widely used in determining shear wave velocities in poorly consolidated sand formations with formation shear velocities smaller than borehole fluid compressional velocities. The shear velocities are obtained by using borehole dispersed flexural mode waves excited by a dipole acoustic source with a low centre frequency. In practice, sometimes compressional waves with high frequency components are excited by a low frequency dipole source, which usually brings about difficulties in abstracting shear wave velocities and it seems that it is not reasonable apparently in physics. In hard formations, flexural waves with much higher frequency than the source centre frequency are excited. This complicates identifying shear wave events from typical dipole logging. In the paper, we treat both of fast and of slow formations, and we investigate theoretically and numerically the above phenomena. The relations among source spectra, excitation and reception spectra and full waveforms are analyzed in detail for various formations. The results show that waveforms in boreholes are contributions from excitation spectra and source spectra comprehensively. The wave excitation spectra have peaks located at higher frequencies for the fast formation, while they have several peaks with higher frequencies for the slow formations, which contributes differently to shear flexural mode waves and leaky compressinal mode waves. The numerical results are compared with the field dipole logging data that are in good agreement.
Xiumei Zhang Hao Chen Xiuming Wang
State Key Laboratory of Acoustics,Institute of Acoustics,Chinese Academy of Sciences,Beijing 100190,P.R.China
国际会议
The 10th Western Pacific Acoustics Conference(第十届西太平洋声学会议WESPAC X)
北京
英文
1-7
2009-09-21（万方平台首次上网日期，不代表论文的发表时间）