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Prise en compte d’une anisotropie variable en modélisation géologique 3D par la méthode implicite du potentiel : application aux structures plissées

Abstract : Three-dimensional geological modelling methods aim at building relevant and coherent underground numerical models based on field-collected data. So-called implicit methods, which have been increasingly used, allow to construct a potential field from contact and orientation data of observed geological units. These numerical models allow to extract isopotential surfaces and interpret them as geological surfaces. In this framework, the “Potential Field Method”, introduced over 20 years ago by MINES ParisTech and BRGM, use geostatistical tools, like the means of co-kriging interpolation, to construct these potential fields. Despite having been extensively used, these modelling methods still exhibit some limitations when confronted to complex models. Non-cylindrical folds, mineralized veins or channel networks, among other geological structures, present a clearly identifiable and spatially variable preferential orientation, called anisotropy. Often, the amount and/or spatial distribution of available data do not allow a unique and accurate representation of the variable anisotropy. This PhD work aims at overcoming these limitations through the integration of anisotropy data as an input to the implicit method. Two approaches have been developed and studied: (1) A first approach takes advantage of first or second derivative data to locally constrain the anisotropy of the potential field. This approach was developed in the framework of polyphase foldings, an iconic example of the variable anisotropy problematic due to its inherent requirement of surface curvature constraints. For this approach, benefits of different input data are compared. (2) A second approach suggests to interpret the potential field as the convolution between a white noise and a gaussian kernel. This allows to mathematically and explicitly describe the anisotropy properties, which can either be interpolated from sampled data or built based on geologist’s interpretation. Finally, applications of either methods are compared and their respective advantages and drawbacks, in regard of the target applications, are discussed.
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Submitted on : Thursday, January 13, 2022 - 3:49:10 PM
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  • HAL Id : tel-03525009, version 1

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Laure Pizzella. Prise en compte d’une anisotropie variable en modélisation géologique 3D par la méthode implicite du potentiel : application aux structures plissées. Géophysique [physics.geo-ph]. Université Paris sciences et lettres, 2020. Français. ⟨NNT : 2020UPSLM075⟩. ⟨tel-03525009⟩

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