Abstract:

The authors present a method to extract the phase slowness from dispersive waves provided by sonic logging. The dispersion curve can be acquired by maximizing the frequency-slowness coherence value at each frequency. The projection of dispersion curve on slowness axis is the histogram of formation slowness. The method is based on matching a fitting function to the slowness histogram using method of nonlinear least squares. The slowness of edge location in the best fitting function is the true formation slowness. As an example, the method is employed to process both theoretical dipole wave and field sonic logging data. The phase slowness of dipole wave and the formation slowness are almost the same for theoretical dipole wave; the phase slowness of dipole wave matches with the curve of slowness-frequency projection for field sonic logging data. It is reliable and effective for processing dispersive wave data with this method.

Key words: dispersive wave, phase slowness, fitting function, histogram, acoustic logging