Insight of Syn-Tectonic Crystalline Reservoirs. Effect of Inherited Structures on Fracture Networks (e.g. Elba Island)

Because of the potential reservoir that may represent fractured basement rocks, notably the igneous rocks, knowledge about the development of brittle structures and fracturation networks in such rocks must be enhanced. Formation of igneous intrusive complexes is often associated to large-scale tectonic structures, which may develop structural inheritance within the rocks, this latter controlling strongly the geometry of the brittle structures. This study aims to characterize in an extensional setting the complex relationship between major structures, fracturation density and matrix porosity, taking into account the structural inheritance of the studied complexes. The two Late-Miocene intrusive plutons of Elba Island (Italy) are each a syn-tectonic granitic pluton set up in the footwall of a low-angle normal fault, and are good examples of field analogue of a basement reservoir linked to a major tectonic structure. The main observations are that the potential fractured reservoir is located mainly on the edge of the pluton, and its geometry is controlled by the dynamic of flow of the magmatic supplies and by the induced structures: shear planes due to the contact effect of the host rock on the granite during its emplacement and in the roof of the pluton, structures associated to the detachment fault.