Construction et manipulation de maillages - Application aux géosciences

Abstract : Geomodeling is considered by oil companies as a critical aspect of hydrocarbon prospection. Indeed building geological models of subsurface allow them to estimate location and capacity of oil reservoirs in studied territories. Modeling stage consists in studying seismic volume in order to highligt horizons (interface between two depositional events), faults (fracturation of rocks) and bodies (cluster of rocks with same physical properties). Those geological objects are within two problematics treated in this thesis: building the structural model containing horizons and faults, and reconstruction of bodies based on seismic attributes. Structural modeling is based on interpreted data, point clouds or set of polylines, representing geological objects. First, each fault is built independently by triangulating projection of its set of polylines in its regression plane. Generated coarse mesh is then smoothed using subdivision schemes. A second step consists in extrapolating and clipping operations applied to fault surfaces in order to build a coherent fault network. During last step, point clouds representing horizon are interpolated in order to complete holes in horizon surfaces due to the noise surrounding the faults in seismic data The interpolation process takes faults into account thanks to our partial neighboring. We also show the effects on surface quality of the filling strategies used in the interpolation process. Body reconstruction is done by isosurface extraction on seismic attributes. In order to deal with the heavy trend in size increase of volumetric datasets, we present in this thesis a parallel, bloc-wise extension of the tandem algorithm, which simplifies on the fly an isosurface being extracted. Our approach minimizes the overall memory consumption using an adequate bloc splitting and merging strategy and with the introduction of a component dumping mechanism that drastically reduces the amount of memory needed for particular datasets such as those encountered in geophysics. As soon as detected, surface components are migrated to the disk along with a meta-data index (oriented bounding box, volume, etc) that will allow further improved exploration scenarios (small components removal or particularly oriented components selection for instance).
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Submitted on : Tuesday, November 29, 2011 - 3:08:34 PM
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Guilhem Dupuy. Construction et manipulation de maillages - Application aux géosciences. Géométrie algorithmique [cs.CG]. Université de Pau et des Pays de l'Adour, 2008. Français. ⟨tel-00646256⟩

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