Discussion of “Characteristics of an Open Tube Wave Attenuation System”

The tube wave, or low‐frequency manifestation of the Stoneley wave, has been modeled previously using the quasi‐static approximation; I extend this method to include the effect of the formation matrix compressibility, which tends to marginally increase the tube‐wave attenuation. Using the Biot theory of poroelasticity, I develop a fully dynamic description of the Stoneley wave. The dispersion relation derived from Biot’s equations reduces in the low‐frequency limit to the quasi‐static dispersion relation. Comparisons of the quasi‐static and dynamic theories for typical sandstones indicate the former to be a good approximation to at least 1 kHz for oil and water infiltration. At higher frequencies, usually between 5 and 20 kHz for the formations considered, a maximum in the Stoneley Q is predicted by the dynamic theory. This phenomenon cannot be explained by the quasi‐static approximation, which predicts a constantly increasing Q with frequency. Instead, the peak in Q may be understood as a transition from dispersion dominated by bore curvature to a higher frequency regime in which the Stoneley wave behaves like a wave on a flat fluid‐porous interface. This hypothesis is supported by analytical and numerical results.

Download Full-text

Tube wave attenuation by polarization filtering

10.1190/1.1822278 ◽

1992 ◽

Author(s):

Allan J. Campbell

Keyword(s):

Wave Attenuation ◽

Polarization Filtering ◽

Tube Wave

Download Full-text

Acoustic characterization of fracture permeability at Chalk River, Ontario

Canadian Geotechnical Journal ◽

10.1139/t83-055 ◽

1983 ◽

Vol 20 (3) ◽

pp. 468-476 ◽

Cited By ~ 8

Author(s):

Frederick L. Paillet

Keyword(s):

Wave Amplitude ◽

Acoustic Analysis ◽

Wave Attenuation ◽

Close Correlation ◽

Wave Mode ◽

Acoustic Energy ◽

Shear Mode ◽

Fracture Permeability ◽

Keywords Fracture ◽

Tube Wave

This study was undertaken to test recently formulated acoustic-analysis methods for fracture interpretation. The study area was selected because surface outcrops of igneous and metamorphic rocks have numerous, interconnected fractures and major lithology changes. In-situ acoustic-refraction data were obtained by digitally recording the entire pressure signal received by a conventional acoustic borehole logging system. The acoustic energy source had a centerband frequency of 34 kHz, and data were obtained at 60 and 90 cm source/receiver spacing. Borehole geometry produces waveforms with strong shear arrivals and high amplitudes associated with the fundamental guided fluid mode known as the tube wave. Waveforms refracted across fractures that are open on the borehole have shear mode excitation and tube-wave attenuation effects similar to previously described effects for isolated fractures in very uniform lithologies. Independent permeability data for the Chalk River boreholes are available in the form of effective-fracture apertures determined by straddle packer isolation and injection tests. The best correlation between the permeabilities measured by packer tests and acoustic data is obtained by integrating the difference between local tube-wave amplitude and an average amplitude from many adjacent stations. This synthetic amplitude-deficit log shows close correlation with zones of large measured permeabilities; however, there are some quantitative differences. These are attributed to: (1) differing radii of investigation, (2) effects of fracture interconnectivity, and (3) drilling damage in highly weathered and fractured zones. The tube-wave-amplitude method also does not seem applicable to depths less than about 50 m where the tube-wave mode is relatively unexcited. Keywords: fracture permeability, borehole acoustics, fracture hydrology.

Download Full-text

Experimental testing of semirigid corrugated baffles for the suppression of tube waves in vertical seismic profile data

Geophysics ◽

10.1190/geo2017-0636.1 ◽

2019 ◽

Vol 84 (3) ◽

pp. D131-D149 ◽

Cited By ~ 1

Author(s):

Andrew Greenwood ◽

J. Christian Dupuis ◽

Anton Kepic ◽

Milovan Urosevic

Keyword(s):

Wave Attenuation ◽

Experimental Testing ◽

Low Cost ◽

High Amplitude ◽

Seismic Profile ◽

Vertical Seismic Profile ◽

Vsp Data ◽

Scale Experiment ◽

Tube Wave ◽

The Cost

Multichannel borehole hydrophone strings are a low-cost, low-risk, alternative to borehole clamping geophones. Vertical seismic profile (VSP) data collected with hydrophones, however, suffer from high-amplitude coherent tube-wave noise. This reduces the usable data to the first arrivals and traveltimes for check-shot surveys. To significantly reduce tube-wave noise from VSP data acquired with hydrophones, we have designed and tested a novel tube-wave attenuation baffle. The effectiveness of the baffle was first verified in a laboratory-scale experiment and then in a borehole drilled into a hardrock environment. The laboratory experiments tested the performance of four different baffle topologies, whereby the best performing topology was the semirigid corrugated pipe baffle. This design reduced the amplitude of the tube wave with more than 40 dB and was logistically easy to deploy. The field experiment investigated the effectiveness of three different semirigid corrugated pipe baffle topologies in a PQ (123 mm) diamond drillhole in Western Australia. Here, we found that the semirigid corrugated pipe baffle was effective in disrupting tube-wave propagation. The 100 mm diameter baffle achieved an impressive 60 dB of tube-wave attenuation, whereas the 50 mm baffle had a modest attenuation of 10–15 dB. This suggests that the performance of this new type of baffle is best when the diameter of the baffle is closely matched to the diameter of the borehole. The results of these experiments have signiﬁcant implications because hydrophone arrays with a large number of receivers are comparatively inexpensive and simpler to deploy than borehole geophone counterparts. The development of hydrophone arrays that are free of interfering borehole modes could allow VSPs to be acquired in situations in which seismic-polarity information is not required and could help VSP gain traction in cases in which the cost of acquisition has precluded its use until now.

Download Full-text