Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Indirect determination of shear wave velocity in slow formations using full-wave sonic logging technique
This article presents a case study concerning a seismic characterization project. Full-wave sonic logging was used to characterize the shallow compressional wave and shear wave velocity profiles in the site. Anomalous values of the Poisson’s ratio derived from the velocity profiles suggested that the boreholes might have traversed slow formations (i.e. with shear wave velocity smaller than the borehole fluid compressional wave velocity or “mud-wave speed”) and that conventional processing of the sonic logs might have misinterpreted the direct arrivals of fluid acoustic waves as arrivals caused by shear wave propagation in the rock. Consequently, the shear wave velocity profiles provided by the contractor were considered to be unreliable by the project team. To address these problems, a non-conventional determination of the shear wave velocity was implemented, based on the relationship between the Poisson’s ratio of the rock formation and the shape of the first train of sonic waves which arrived to the receivers in the sonic probe. The relationship was determined based on several hundreds of finite element simulations of the acoustic wave propagation in boreholes with the same diameter as used in the perforations. The present article describes how this non-conventional approach was developed and implemented to obtain the shear wave velocity profiles from the raw sonic logs. The approach allows an extension of the range of applicability of full-wave sonic logging to determination of shear wave velocity profiles in formations with low compressional wave velocities. The method could be used to obtain shear wave velocity profiles where compressional wave velocity is as low as slightly larger than the mud-wave speed. A sample sonic log in Log ASCII Standard (LAS) format is provided as supplementary material to this paper via Mendeley Data, together with the FORTRAN source code used to process the log following the approach described in this study.
Indirect determination of shear wave velocity in slow formations using full-wave sonic logging technique
This article presents a case study concerning a seismic characterization project. Full-wave sonic logging was used to characterize the shallow compressional wave and shear wave velocity profiles in the site. Anomalous values of the Poisson’s ratio derived from the velocity profiles suggested that the boreholes might have traversed slow formations (i.e. with shear wave velocity smaller than the borehole fluid compressional wave velocity or “mud-wave speed”) and that conventional processing of the sonic logs might have misinterpreted the direct arrivals of fluid acoustic waves as arrivals caused by shear wave propagation in the rock. Consequently, the shear wave velocity profiles provided by the contractor were considered to be unreliable by the project team. To address these problems, a non-conventional determination of the shear wave velocity was implemented, based on the relationship between the Poisson’s ratio of the rock formation and the shape of the first train of sonic waves which arrived to the receivers in the sonic probe. The relationship was determined based on several hundreds of finite element simulations of the acoustic wave propagation in boreholes with the same diameter as used in the perforations. The present article describes how this non-conventional approach was developed and implemented to obtain the shear wave velocity profiles from the raw sonic logs. The approach allows an extension of the range of applicability of full-wave sonic logging to determination of shear wave velocity profiles in formations with low compressional wave velocities. The method could be used to obtain shear wave velocity profiles where compressional wave velocity is as low as slightly larger than the mud-wave speed. A sample sonic log in Log ASCII Standard (LAS) format is provided as supplementary material to this paper via Mendeley Data, together with the FORTRAN source code used to process the log following the approach described in this study.
Indirect determination of shear wave velocity in slow formations using full-wave sonic logging technique
Francisco Beltran (Autor:in) / Alvaro Yañez-Gonzalez (Autor:in) / María J. Crespo (Autor:in)
2020
Aufsatz (Zeitschrift)
Elektronische Ressource
Unbekannt
Metadata by DOAJ is licensed under CC BY-SA 1.0
Resonant vibration technique for laboratory determination of shear wave velocity
| Engineering Index Backfile | 1966
Wave-velocity logging based on wavelet analysis
| British Library Online Contents | 2007
Shear Wave Velocity via Inversion of Full Waveforms
| British Library Conference Proceedings | 2012
Correlation Study of Shear Wave Velocity in Near Surface Geological Formations in Anchorage, Alaska
| Online Contents | 1997
Determination of Shear Wave Velocity Profile Using SASW Method
| British Library Conference Proceedings | 2002