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Abstract

Shear and compressional velocities of acoustic waveforms in the earth formations surrounding a well bore are measured by analyzing the waveforms propagated through different lengths of substantially the same formation intervals. Phase analysis techniques applied to waveforms windowed for compressional waves are used to determine the propagation velocity of the compressional waves through the differential path lengths. The waveforms are then windowed for shear waves, the discrete fourier transforms of the windowed waveforms are taken, and the cross-spectral magnitude and phase for each frequency is computed as the product of the discrete fourier transform sample of one with the conjugate of the other. Several different moveouts are calculated, the resultant phases from each analyzed, and a band specified where the zero phase moveouts are roughly consistent. This ultimately specifies a final, accurate shear window moveout for determining, using phase analysis techniques, the shear propagation velocity characteristics of the respective earth formation intervals.

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