A non linear inverse method for high resolution seismic imaging ; Une méthode d'inversion non linéaire pour l'imagerie sismique haute résolution

Fin de rédaction : 30/10/2009 ; Recent innovations in oil industry, both in exploration and production fields, and the development of CO2 subsurface sequestration technics, require high resolution seismic imaging methods. The work presented here is dedicated to the design of such a method, allowing for the fine scale quantitative recovering of the acoustic impedance distribution around a well. This method is an extension to a multidimensionnal framework of the 1D non linear inversion of VSP (Vertical Seismic Profile) seismic data. To perform this generalization, we are faced with two main difficulties. The first one is the intrinsic indetermination of the non linear multidimensionnal inverse problem, which requires the use of regularization terms. The second one is the very high computation cost. Thus, a well suited numerical method is designed. This method uses both Quasi-Newton and Conjugate Gradient optimization methods in a nested optimization loop. Besides, a domain decomposition algorithm is used to perform a distributed computation of the functional gradient through the adjoint state method. The performances of this new seismic imaging method, for both numerical and resolution aspects, are evaluated in a 2D implementation context. In addition, this numerical solving method requires acoustic wave propagation modelling in the subsurface which is obtained using PML (Perfectly Matched Layers) equations. Finally, a stability analysis of these equations adapted to an heterogeneous context is carried on. ; Les développements récents de l'industrie pétrolière en matière d'exploration et de production, et la mise en place de techniques de séquestration souterraine du CO2, nécessitent des méthodes d'imagerie du sous-sol permettant d'obtenir une information structurale et quantitative à fine échelle. Les travaux présentés dans cette thèse s'intéressent au développement d'une telle méthode, permettant d'estimer la distribution d'impédance acoustique autour d'un puits. Elle s'inspire du problème 1D d'inversion de ...