[pt] As zonas de falha são compostas por um núcleo, onde a maior parte da deformação é acomodada, e uma zona de dano, com deformação menos intensa. A zona de dano pode atuar como caminho de fluxo preferencial devido à presença de fraturas, ou como barreira devido às bandas de deformação. Portanto, sua caracterização é essencial para a adoção de estratégias de produção adequadas em campos de petróleo. Os métodos geofísicos geralmente utilizados, porém, dificilmente permitem a identificação das zonas de dano devido à baixa resolução sísmica. Como alternativa, empregam-se observações em afloramentos superficiais. Contudo, há uma grande dispersão de dados, que pode estar relacionada a uma variedade de fatores, como as propriedades da rocha protólita e os mecanismos de deformação atuantes. Neste sentido, este trabalho apresenta duas metodologias baseadas no método dos elementos finitos (MEF) para analisar a formação e evolução das zonas de dano em escala de reservatório. Na primeira abordagem, a zona de falha é totalmente representada através de um meio contínuo, enquanto que na segunda, a falha é representada como um plano por meio de uma descontinuidade. Em ambas aproximações, a zona de dano é estabelecida através das regiões plastificadas. Os resultados numéricos obtidos se aproximaram das observações de campo e possibilitaram a identificação das vantagens e limitações das duas abordagens baseadas no MEF. Por fim, os resultados também permitiram identificar os principais parâmetros geomecânicos que influenciam o desenvolvimento das zonas de dano, bem como os diferentes mecanismos de deformação que ocorrem ao longo da zona de dano. / [en] Fault zones are composed of two structural domains: the fault core, which accommodates most of the deformation, and a damage zone, with less intense deformation. The damage zone may act as a preferential flow path due to the presence of fractures, or as a barrier due to deformation bands. Therefore, the characterization of geological fault zones is essential for the adoption of adequate production strategies in oil fields. Generally, geophysical methods are used to characterize geological faults in the field. However, they hardly allow the identification of damage zones due to low seismic resolution. Alternatively, damage zones are analyzed through surface outcrops. Nonetheless, there is a wide dispersion of data in this type of study, which may be related to various factors, such as the properties of the host rock and the acting deformation mechanisms. Therefore, it is interesting to carry out this type of study in conjunction with numerical modeling to understand better the damage zone formation process. In this study, we present two methodologies based on the finite element method (FEM) to analyze the formation and evolution of damage zones at a reservoir scale. In the first methodology, the entire fault zone is represented through a continuum medium, while in the second methodology, the fault core is represented as a plane through a discontinuity. In both approaches, the damage zone is defined through the regions where plastic deformations were triggered. The numerical results obtained were close to field observations. They enabled the identification of the advantages and limitations of the two approaches based on the MEF. Finally, the results also allowed to identify the main parameters that influence the development of the damage zones and the different deformation mechanisms that occur along the damage zone.

Les zones de failles concentrent la migration de fluides et la déformation dans la croûte supérieure. Les propriétés hydrauliques des formations argileuses en font des excellents sites de stockage et des roches mères performants. Les zones de failles peuvent jouer deux rôles contraires dans la circulation de fluides, soit elles s’expriment sous forme de drains, soit elles constituent une barrière, et souvent les deux rôles sont combinés au sein d’une même zone de failles. Les processus de migration des fluides dans les zones de failles affectant les argiles sont peu connus. Cette étude s’est focalisée sur la structure, les paléo-circulations, les circulations actuelles lors de tests d’injection et les propriétés pétro-physiques de la zone de failles présente dans le laboratoire de recherche souterrain de Tournemire dans les argilites Toarciennes. La structure de la zone de failles a été caractérisée par des forages et reconstituée en 3D par modélisation numérique, permettant de définir des faciès de déformation. L’architecture de la zone de failles se caractérise par une imbrication de facies de déformations plus ou moins intenses sans claire organisation en cœur et zone endommagée comme observée dans les roches plus dures. Les zones intactes, fracturées et les brèches sont respectivement caractérisées par des porosités matricielles comprises entre 9.5-13.5, 10-15 et 13-21%. La circulation de fluide se concentrant aux limites de la brèche et au niveau des zones de failles «immatures» ou secondaires comprises dans les zones fracturées. Lors de son activité, la zone de failles a déjà été affectée par au moins deux phases de circulations de fluides. / Fault zones concentrate fluids migration and deformations in the upper crust. The shale hydraulic properties make them excellent storage sites and hydrocarbon reservoirs/source rocks. Fault zones can play two roles in the fluid circulation; drains or barriers, in general, both roles are combined within the same fault zone. What are the conditions that promote the fluid circulation along the fault zones in shales and what are the fault zone impacts on the formation properties are relatively poorly explored key questions. This study focused on characterizing the relationships between fault architecture, paleo-fluid as well as current fluid circulations through the analysis of fault calcite mineralization, injection tests and petrophysical properties conducted on a fault zone outcropping underground in the Tournemire research laboratory nested in the Toarcian shale. The fault zone structure was characterized using boreholes data and reconstructed in 3D through modeling to define different deformation facies. No clear facies organization is observed, a fault core and a fault damage zone being difficult to define as it is in hard rocks. The intact, fractured and breccia facies are characterized by a porosity of 9.5-13.5, 10-15 and 13-21%. Large fluid flowrate concentrated along a few “channels” located at the breccia boundaries and in the secondary fault zones that displayed fractured facies and limited breccia fillings. Detailed microstructural and geochemical analysis at the breccia/fractured zones interface revealed that fluids circulated out of the main shear zones, in micro-more or less inherited fractures highlighting a decoupling between fault slip and fluid migrations.