Shear-Wave Processing of Sonic Log Waveforms in a Limestone Reservoir
Abstract
Sonic full waveforms were recorded in a shale-limestone interval with an experimental 12-channel acoustic logging device. Well-defined shear (pseudo-Rayleigh) waves were observed throughout most of the 142 m interval and were used to distinguish lithologic boundaries and zones of fracturing as interpreted by acoustic borehole televiewer and standard geophysical logs. The high signal-to-noise ratio of the waveforms permitted meaningful shear velocities to be obtained by 12-fold semblance calculations in all but the washed-out intervals in this well. A correlation of changes in the Vp/Vs ratio with depth aided in identifying some compositional changes in the well, but such a correlation could not be used to distinguish fracturing in the limestone. Shear-wave amplitudes, however, were effective for identifying lithologic changes, as well as fractures, from the sonic log. Shear amplitudes were lower in the shale than in the limestone, and shear-wave attenuation increased in fractured zones. There was no strong correlation between the degree of fracturing and the attenuation of Stoneley waves. In general, shear-wave processing of sonic logs is recommended for interpretation of lithology and fracturing in any well in which full waveforms are recorded and shear waves propagate. Reprints.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1988
- Accession Number
- ADA198190
Entities
People
- David Goldberg
- William T. Gant
Organizations
- Columbia University