This work aims to collaborate with the understanding of the natural fracture system of the Quintuco Formation as a Tight Oil reservoir in the southeastern sector of the Neuquén basin. A mesoscopic study was carried out on 126 meters of cores, recognizing seven types of natural fractures: Tension fractures (Mode I); Shear fractures (Mode II-III), Stylolites (Mode IV), Deformation bands, Irregular fractures (Vugs) and bedding-parallel veins (BPV). Rheological control of the lithology on the deformation mechanisms developed is recognized. The analysis of the structural diagenesis led to the following succession of deformation events: 1°) the horizontal stylolites were generated by lithostatic loading; 2°) sub-horizontal shear stresses formed the deformation bands; 3°) a migration event is recorded by bitumen in the deformation bands and finally, 4°) an opening and cementation event, with mosaic calcite precipitation. Associated with this last calcite mosaic cementation event, two types of fluid inclusions were identified, one aqueous and one rich in light hydrocarbons, which would indicate a second hydrocarbon migration event. Considering the geological evolution of the Quintuco Formation and its subsidence history, togetherwith the trapping temperatures obtained by microthermometry (114°-125°C), two possible ages of formation of the fractures are interpreted: one associated with the burial peak during the Upper Cretaceous; and another one of exhumation during the late Paleogene. Analyzing the fracture types identified, the recognized paragenetic scheme and the hydrocarbon migration events, it is possible to suggest that the fracture generation was during the Paleogene.