Nullerical Studies of Body Wave Amplitudes in Full Waveform Acoustic Logs

Abstract

The amplitudes of P and S head waves in a full waveform acoustic log microseismogram are studied numerically as a function of borehole and formation parameters. The technique used is contour integration around the respective branch cuts in the complex wavenumber plane (Tsang and Rader, 1979). The results showed that the P wave amplitude depends on the Poisson's ratio, but the S wave amplitude does not. The well accepted geometric spreading factor for P and S waves in the "far field" is only valid for a limited range of source-receiver spacings, and the onset of "far field" depends on the Poisson's ratio as well as the wavelength. The wave shape factor I[subscript e] for the P wave as defined by Lebreton et al. (1978) has a direct relationship to in situ attenuation.