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Phenomenological study of seismic anisotropy in Shales

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Authors
Pervukhina, Marina
Golodoniuc, P.
Dewhurst, D.
Date
2013
Type
Conference Paper

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Pervukhina, M. and Golodoniuc, P. and Dewhurst, D. 2013. Phenomenological study of seismic anisotropy in Shales, in Proceedings of the 75th European Association of Geoscientists and Engineers Conference and Exhibition, Jun 10-13 2013, pp. 2631-2635. London: European Association of Geoscientists and Engineers.
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75th European Association of Geoscientists and Engineers Conference and Exhibition 2013 Incorporating SPE EUROPEC 2013: Changing Frontiers
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Department of Exploration Geophysics
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Abstract

Copyright © (2012) by the European Association of Geoscientists & Engineers All rights reserved. Elastic anisotropy is important for a number of geophysical applications, including seismic interpretation, fluid identification and 4D seismic monitoring. Due to their strongly anisotropic properties, the presence of shales in the subsurface may cause significant errors in depth obtained from surface seismic data, in normal and dip moveout correction, migration and amplitude versus offset analysis. Here we analyze Thomsen's anisotropy parameters and anellipticities of 37 shales with different mineralogical compositions, maximum overburden stress experienced, silt and clay fractions, porosities and other petrophysical parameters. The shales extracted from depths below 4000 m exhibit the largest values of Pand S-wave anisotropies, while negative delta values are mostly observed for shales extracted from shallow depths. The observed diversity of Thomsen's anisotropy parameters and anellipticities can be explained with (1) intrinsic anisotropy of wet clay packs, (2) governed by compaction anisotropic distribution of discontinuities and (3) effects of aligned silt inclusions on shale elastic properties.