Sonic logging of compressional-wave velocities in a very slow formation
- Shell Research B.V., Rijswijk (Netherlands)
- Nederlandse Aardolie Maatschappij B.V., Assen (Netherlands)
Borehole sonic waveforms are commonly acquired to produce logs of subsurface compressional and shear wave velocities. To this purpose, modern borehole sonic tools are usually equipped with various types of acoustic sources, i.e., monopole and dipole sources. While the dipole source has been specifically developed for measuring shear wave velocities, the authors found that the dipole source has an advantage over the monopole source when determining compressional wave velocities in a very slow formation consisting of unconsolidated sands with a porosity of about 35% and a shear wave velocity of about 465 m/s. In this formation, the recorded compressional refracted waves suffer from interference with another wavefield component identified as a leaky P-wave, which hampers the determination of compressional wave velocities in the sands. For the dipole source, separation of the compressional refracted wave from the recorded waveforms is accomplished through bandpass filtering since the wavefield components appear as two distinctly separate contributions to the frequency spectrum: a compressional refracted wave centered at a frequency of 6.5 kHz and a leaky P-wave centered at 1.3 kHz. For the monopole source, the frequency spectra of the various waveform components have considerable overlap. It is therefore not obvious what passband to choose to separate the compressional refracted wave from the monopole waveforms.
- OSTI ID:
- 175954
- Journal Information:
- Geophysics, Journal Name: Geophysics Journal Issue: 6 Vol. 60; ISSN GPYSA7; ISSN 0016-8033
- Country of Publication:
- United States
- Language:
- English
Similar Records
3-D sonic wavefields with a dipping interface
Low-frequency P-wave logging for improved compressional velocity in slow formation gas zones
Sonic well tool transmitter receiver array including an attenuation and delay apparatus
Conference
·
Fri Dec 30 23:00:00 EST 1994
·
OSTI ID:80165
Low-frequency P-wave logging for improved compressional velocity in slow formation gas zones
Conference
·
Sat Dec 30 23:00:00 EST 1995
·
OSTI ID:542814
Sonic well tool transmitter receiver array including an attenuation and delay apparatus
Patent
·
Tue Aug 06 00:00:00 EDT 1991
·
OSTI ID:5799541