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Atténuation et dispersion des ondes P en milieu poreux partiellement saturé: approche expérimentale

Abstract : In order to analyse the role of partial saturation on direct P-waves phase velocity and attenuation, we performed a laboratory experiment in the kiloHertz range to avoid scale effects between field studies and traditional ultrasonic laboratory measurements. This experiment consists in a sand-filled tank equiped with accelerometers and water capacitance probes, were seismic propagation is generated by hitting a steel ball on a granite plate. Several imbibition/drainage cycles were performed between the water and gas residual saturations. Seismic data were processed by a Continuous Wavelet Transform using the complex Morlet wavelet which was numerically validated using a viscoelastic 2D code for wave propagation (Specfem2D). Phase velocity of direct P-wave decreases with the increase of water content, which is quite consistent with Biot-Gassmann-Wood (BGW) limit of the Biot's theory for both imbibition and drainage. This behaviour indicates that the fluid mixture (gaz and water) can be considered as an effective fluid, which is typical of field seismic applications. In this experiment, attenuation is very strong and cannot be fully explained by the macroscopic fluid flow of Biot's theory. It is necessary to introduce a viscoelastic contribution linked to the grain to grain overall losses, which are described by a constant Q-model. Moreover, hysteresis between imbibition and drainage are observed and explained by introducing an effective permeability of the mixture depending on water and gas relative permeabilities.
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Contributor : Julien Barrière <>
Submitted on : Friday, September 21, 2012 - 11:46:42 PM
Last modification on : Tuesday, February 2, 2021 - 2:52:03 PM
Long-term archiving on: : Saturday, December 22, 2012 - 3:40:23 AM

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  • HAL Id : tel-00734463, version 1

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Julien Barrière. Atténuation et dispersion des ondes P en milieu poreux partiellement saturé: approche expérimentale. Géophysique [physics.geo-ph]. Université de Pau et des Pays de l'Adour, 2011. Français. ⟨NNT : 2011PAUU3025⟩. ⟨tel-00734463⟩

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