Shear-wave velocities derived from VSPs and full-waveform acoustic logs

Abstract

This paper describes a case history from a hard rock (limestones, dolomites and anhydrites) region of Michigan. Shear wave velocities have been derived from a nine component zero offset VSP and compared to shear wave velocities from two full waveform acoustic logs (Welex and Elf). In order to investigate the shear wave birefringence (azimuthal anisotropy) which effects the shear wave's vertical propagation, we used the "propagator matrix" technique as described in Nicoletis et al. (1988) and Lefeuvre (1990). Then the picked times obtained by correlation have been corrected in the birefringent areas to compute the fast and the slow velocities. Although there exists some differences between the three velocity sets, there is a good fit between the velocities from the shear wave VSP and those from the two logs.