Méthode des éléments spectraux pour la propagation d'ondes sismiques en milieu géologique fluide-solide avec pas de temps locaux et couches absorbantes parfaitement adaptées C-PML

Ronan Madec 1
1 Magique 3D - Advanced 3D Numerical Modeling in Geophysics
LMAP - Laboratoire de Mathématiques et de leurs Applications [Pau], Inria Bordeaux - Sud-Ouest
Abstract : In the petroleum industry, many oil research is made offshore. Finite difference or finite element methods are usually used to numerically simulate seismic results of petroleum campaigns. In this manuscript, we used the spectral element method (Komatitsch and Tromp, 2002) which is a finite element method with a high degree polynomial interpolation. When studying offshore seismic propagation, geological models used are composed of two types of medium: a fluid part (ocean) and a solid part (ocean bottom). As we are interested in the solid part where the oil reservoirs can be, we want to reduce the computational cost on the fluid part which is less important. To do so, we use different time steps in the fluid and in the solid. In most of the case, velocity wave in the fluid is smaller than in the solid, therefore, the stability condition (CFL), which depends on the maximum velocity and the time step, allow us to take a bigger time step in the fluid while preserving the numerical stability of the computation. My work in this thesis has consisted in introducing a local time stepping technique and in insuring coupling between fluid and solid by conserving energy on the interface. In order to make more realistic simulations, I also introduced absorbing boundary conditions called Perfectly Match Layer (PML) for fluid-solid models. Such boundary conditions have the ability to absorb waves and then avoid artificial unrealistic reflections of the boundaries in order to simulate semi-infinite models.
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Submitted on : Tuesday, August 24, 2010 - 11:35:00 PM
Last modification on : Sunday, April 7, 2019 - 3:00:02 PM
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Ronan Madec. Méthode des éléments spectraux pour la propagation d'ondes sismiques en milieu géologique fluide-solide avec pas de temps locaux et couches absorbantes parfaitement adaptées C-PML. Modélisation et simulation. Université de Pau et des Pays de l'Adour, 2009. Français. ⟨tel-00511418⟩

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