Abstract Oil production in offshore regions involves the transportation of oil and gas in submarine pipelines, which are vulnerable to geological processes triggered by subsurface oil production like fault reactivation. The fault reactivation process can lead to phenomena that impact the seabed, like subsidence and fluid exudation, and can trigger instability of submarine slopes, which can result in environmental and economic damage. The present work addresses a coupled hydromechanical numerical modeling of a hypothetical case involving fault reactivation caused by oil reservoir production and its impact on an overlying submarine slope. The hypothetical case was simulated using a finite element model. The case involves a reservoir which is cut by a fault zone that reaches the seabed. The slope instability studied was induced by the injection and production of fluids in the reservoir. The fault zone is assumed to be a sealing region and a geomechanical and pressure field discontinuity within the reservoir. Int this work was used the Mohr-Coulomb elastoplastic model with Perzyna viscoplastic regularization to represent the behavior of the fault zone and the overlying submarine slope. Results showed that the fault reactivation, caused by the reservoir production, developed shear stress and shear plastic strain along the fault and through the submarine slope, causing horizontal and vertical displacements in the slope mass and acting as a trigger factor for slope stability. Pore pressure increase at the bottom of the slope structure correlated with the injection pressure artificially increased into the reservoir. pipelines seabed exudation slopes damage MohrCoulomb Mohr Coulomb stability

Abstract This paper presents the results of a petrographic and diagenetic study of the laminated limestones of the upper part of the Aptian to Albian Crato Formation, northeast of Brazil. The applied techniques were optical microscopy, cathodoluminescence and scanning electron microscopy (SEM) coupled to a wavelength-dispersive spectrometer (WDS). Petrographic analysis has revealed that most of the laminated limestones are calcilutites with a dominance of a micritic matrix, indicating a low-energy depositional environment. Microstructures such as microfaults, microfractures, microslumps, and loop bedding were observed. Based on textural, structural and paleontological features, seven microfacies were recognized: massive limestone, limestone with parallel laminations, limestone with undulated laminations, limestone with slumps, limestone with loop bedding, limestone with ostracods and limestone with peloids. In addition, the processes of cementation, dissolution, replacement, recrystallization and compaction, which are related to different diagenetic stages, were also recognized. The diagenetic constituents found in the sections include calcite, pyrite, silica and sulfates. We can conclude that a large part of the microstructures (microfaults, microfractures, microslumps and loop bedding) can be related to local seismicity, probably due to the reactivation of the Patos Shear Zone. The diagenetic constituents indicate an early to late diagenesis (eogenetic, mesogenetic and telogenetic stage).