Analyse de sensibilité et estimation de paramètres de transport pour une équation de diffusion, approche par état adjoint

L'identification des coefficients d'une équation aux dérivées partielles (EDP) entre dans le cadre des problèmes inverses. L'analyse de la sensibilité des mesures de la solution de l'EDP par rapport aux coefficients à estimer est alors une technique efficace d'aide à la résolution du problème. En quantifiant le nombre de degrés de liberté identifiables de fa on stable, elle permet de guider le choix d'une paramétrisation des coefficients de l'EDP adaptée au problème, mais également de tester des dispositifs de mesure plus performants pour l'inversion. Dans ce travail, l'EDP est une équation de diffusion en milieu poreux. Des outils efficaces tels la décomposition en valeurs singulières, pour l'analyse de sensibilité, et la méthode de l'état adjoint, pour le calcul des dérivées, sont mis en oeuvre

An efficient finite volume discretization to simulate flows on 3D discrete fracture network for transient flow analysis and equivalent permeability upscaling

The organization of natural fracture networks induces flow paths that control fluid flows in reservoirs. Taking into account all heterogeneities is computationally very costly, therefore, equivalent multi-porosity and multi-permeability models have to be used. We present an innovating discretization procedure allowing to simulate flow on 3D Discrete Fracture Networks involving over 100.000 fractures. We then demonstrate how to improve the computation of an equivalent permeability tensor by combining analytical and clever-meshed numerical solutions

Prediction of flexible pipe annulus composition by numerical modeling: identification of key parameters

This article describes recent improvements made in the design process of offshore flexible pipes. These improvements consider the more precise complex geometry and architecture of the flexible pipes, while considering their corrosive environment (high pressure, high temperature, acid gases (CO2, H2S), sea water, etc.) and the relevant physics. MOLDITM, the design software that was developed 20 years ago to predict flexible pipes annulus environment, has been constantly upgraded to increase its representativeness: use of chemical potential or fugacity to better describe the mass transport, improvement of the thermodynamic module to better describe the interaction between chemical species and allow to model the purging through gas release valves. Recently, a major advance has been made allowing to cope with flooded annulus flexible pipes. When the annulus is flooded, the tortuosity produced by the presence of steel wires inside the annulus can take a major importance. Therefore, a new model, named 3DIFF, has been developed to describe the 3-dimensional characteristics of the annulus and its impact on fugacity profile across the structure. Depending on permeation properties of each layer, the result is that the presence of water can produce a fugacity gradient within the annulus. This heterogeneity must be considered during the design process to be fully representative of service conditions and allow to select flexible pipes materials with confidence. Experimental devices used to generate permeation database are under constant evolution to study even more complex mechanisms such as the diffusion process in a flooded tortuosity or the compression effects of polymeric material on their permeation properties