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Dispersions and Attenuations Phenomena on Sandstones Poisson’s RatioNormal access

Authors: L. Pimienta, J. Fortin and Y. Guéguen
Event name: 79th EAGE Conference and Exhibition 2017
Session: Rock Physics II - Pressure effects and Brittleness Prediction
Publication date: 12 June 2017
DOI: 10.3997/2214-4609.201700570
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 1.19Mb )
Price: € 20

When acquiring and interpreting seismic data at the field scale, one aims to gain insights on the rocks travelled through as well as the saturating fluid. One interesting property for such studies is the Vp/Vs ratio that allows insights independently of the density effects. Assuming the media to be isotropic, this ratio directly relates to Poisson’s ratio, an intrinsic property of the rock. Over the last decades, dispersion and attenuation effects were shown to occur on Vp and Vs, but Poisson’s ratio is often assumed to be independent of the measuring frequency. In this study, provided that dissipation phenomena are observed on the elastic constants, it is shown theoretically that the same is expected for Poisson’s ratio. Moreover, measurements on a viscoelastic material and a poroelastic rock confirm this observation. For the rock sample, the measured dispersion/attenuation phenomena are large when fluid pressure is high or confining pressure is low. At the field scale, Vp/Vs ratio would indeed be a clear proxy of a high fluid pressure, and the ratio in attenuations could be a very interesting asset.

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