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Titre : | Geomechanical simulations infilling using inverted seismic properties : Heterogeneities study and impact on modeling. |
Auteurs : | Valérie GALIN |
Type de document : | Mémoire de fin d'études |
Année de publication : | 2017 |
Résumé : | This study questions the role of the geophysical material properties distributions in defining the material properties for static geomechanical simulations based on the finite-element method. Outputs of prestack seismic inversions and some assumptions on 3D volumetric mass distribution enable the computation of dynamic Young's modulus and Poisson's ratio required in the theory of poro-elasticity. Geomechanical studies are then conducted in 2D, on the particular case of the Dalia field, Angola (block17). It aims at estimating the stress changes within and around this turbiditic reservoir made of unconsolidated sandstone of Miocene age in which fluid pressure is modified by production. The fluid pressure variation comes from reservoir simulation obtained using sugar-box grids which are coarser than the seismic sampling. The three main findings are as follows: The distribution of the reservoir information carried by the reservoir model dominates the seismic information. Because of this it is crucial to check the consistency between seismic and reservoir model infilling at the beginning of the proposed workflow. The finite-element mesh has to be selected to ensure appropriate sampling of the heterogeneity captured by the seismic information and accuracy of the stress predictions. It implies a mesh size one tenth of the seismic wavelength. The corners of the reservoir grids may introduce undesired stress singularities in the stress distribution. A smoothing algorithm has been applied successfully to eliminate these heterogeneities showing angular shapes. Such smoothing may introduce in some cases a decrease in the depletion force applied to the reservoir. This pitfall is found to be dependent on the size of the heterogeneity,the finer reservoir beds being most at risk. This new workflow linking seismic data and reservoir data for geomechanical simulations could also be implemented for future 3D studies performed using Total-Geosciences proprietary softwares. It will imply an increase in the computational power necessary for such kind of simulations given the relatively fine mesh size it implies to capture properly the reservoir heterogeneities seen by seismic. |
Spécialité : | Géologie |
Numéro de promo : | 77 |