Tube wave
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Definition
In borehole geophysics, a tube wave is an interface wave traveling along the steel-cased borehole at a relatively fixed velocity, about 1430 m/s, as reported by Gal'Perin (1974).[1] Tube wave occurs when a Rayleigh wave encounters the wellbore and perturbs the wellbore fluid.[2] It propagates along the cylindrical fluid-solid boundary of the borehole and has no spherical divergence.[1] Tube waves often have larger amplitudes than that of body waves in the surrounding rocks due to little energy loss during their propagation.[1],[2]
Tube wave modes
The classic tube wave can be observed as the lowest order trapped mode.[3] The higher modes of tube waves may be generated depending on the rock properties and source frequency.[4] The fundamental tube wave mode is often called Stoneley wave.[4] However, tube wave is a solid-liquid interface wave, the term Scholte wave is more appropriate than Stoneley wave.[4]
Applications
In some applications, tube waves could be considered as a useful seismic signal.[5] We can use the information obtained from tube waves to determine some properties of the rock formation near the borehole.[5] Due to the coupling property of tube wave with the rock formation where it travels through, tube wave can perturb the formation across open fractures intersecting the borehole.[2] This effect is called squeezing effect. This effect can generate secondary tube waves traveling both up and down the wellbore from the fractures.[2] Therefore, tube waves can be used to study the presence of open fractures.[2] In addition, the length and the width of the fractures can be qualitatively assessed based on the amplitude of the tube waves.[2]
However, in vertical seismic profile (VSP), tube waves are considered as the most damaging noise because of their coherency feature.[1] They interfere with the reflected body waves which occur later in time on VSP data.[2]
References
- ↑ 1.0 1.1 1.2 1.3 Gadallah, M.R.; Fisher, R. (2008). Exploration Geophysics. Springer Science and Business Media. p. 76.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 "Tube wave". http://www.glossary.oilfield.slb.com/Terms/t/tube_wave.aspx. Retrieved May 15, 2018.
- ↑ Schoenberg, M.; Marzetta, T.; Aron, J.; Porter, R.P. (1981), "Space–time dependence of acoustic waves in a borehole", Journal of the Acoustical Society of America 70 (5): 1496-1507
- ↑ 4.0 4.1 4.2 Daley, T.M.; Gritto, R.; Majer, E.L.; West, P. (2003), "Tube-wave suppression in single-well seismic acquisition", Geophysics 68 (3): 883-869
- ↑ 5.0 5.1 White, J.E. (1965), "Seismic waves: Radiation, transmission, and attenuation", McGraw-Hill
External links
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