Asymmetric Modes of Elastic Wave Propagation in a Fluid-Filled Borehole
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1985.5 Stephen.pdf
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435.09 KB
Format
Adobe PDF
Checksum (MD5)
9f599636f839140880cdcf0b09a24644
Author(s)
Jinzhong, Zhang
Cheng, C. H.
Date Issued
1985
Publisher
Massachusetts Institute of Technology. Earth Resources Laboratory
Series/Report no.
Earth Resources Laboratory Industry Consortia Annual Report;1985-04
Abstract
A numerical investigation of asymmetric modes of elastic wave propagation in a
fluid-filled borehole is treated in this paper. The dispersion curves of guided waves
(called flexural waves) and synthetic microseismograms are presented. The guided
waves are found to be highly dispersive, with the phase velocities decreasing from
the formation shear wave velocities in both hard and soft formations. They have
much lower cut-off frequencies than the pseudo-Rayleigh waves in axisymmetric
modes of propagation. We found that under conditions of low frequency (2-3 kHz)
and long source-receiver separation (3-4 m), the flexural wave is the prominent
arrival in a microseismogram generated with an asymmetric source, traveling with a
phase velocity equal to the formation shear wave velocity, while the compressional
wave arrival before that is generally suppressed. The results of this study may be
meaningful for designing a shear wave logging tool.
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