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Anisotropies microstructurales composites dans les roches réservoir: Conséquences sur les propriétés élastiques et relation à la déformation

Abstract : From diagenesis to tectonic stress induced deformation, rock microstructures always present some anisotropy
associated with a preferential orientation, shape or spatial arrangement of its constituents. Considering the consequences
anisotropy has on directional transport properties and compliance, as the geological history it carries,
this approach has received a particular attention in numerous works. In this work, the microstructural features
of various sedimentary rocks were investigated through direct observations and laboratory measurements in naturally
deformed and undeformed blocks, samples being considered as effective media. All investigated samples
were found to be anisotropic with respect to the physical properties we measured (i.e. ultrasonic P-wave velocity,
magnetic susceptibility, electrical conductivity). Considering that P-wave velocities can be described by a second
order tensor, we applied to the velocity data the same inversion procedure as the one routinely used in magnetic
studies, which provided an efficient tool to estimate and compare these 3d anisotropies with respect to the original
sample geographical position. In each case, we tried to identify as thoroughly as possible the microstructural
source of the observed anisotropies, first by the mean of existing models, then through direct observations (optic
and electronic microscopy). Depending on the rock investigated, anisotropy was found to be controlled by pore shape, intergranular contact distribution, preferentially oriented microcracks interacting with compaction pattern
or pressure solution cleavages interacting with each other. The net result of this work is that P-wave velocity
anisotropy can express the interaction between different microstructural features as well as their evolution during
deformation.
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Contributor : Laurent Louis <>
Submitted on : Tuesday, August 24, 2004 - 7:53:44 PM
Last modification on : Wednesday, December 9, 2020 - 3:11:55 PM
Long-term archiving on: : Friday, April 2, 2010 - 8:51:55 PM

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  • HAL Id : tel-00006750, version 1

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Laurent Louis. Anisotropies microstructurales composites dans les roches réservoir: Conséquences sur les propriétés élastiques et relation à la déformation. Géologie appliquée. Université de Cergy Pontoise, 2003. Français. ⟨tel-00006750⟩

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