Numerical simulation of fault damage zones and their impact on the structural evolution of Pre-salt carbonate reservoirs

Abstract

Our work employs numerical models to investigate the impacts of the early and late faulting stages on the development of fault damage zones (DZs) in conditions analogous to Pre-salt. DZs exhibit contrasts in geomechanical and petrophysical properties compared to the surrounding host rock. Numerous studies have explored the characterization of DZs by modeling fault formation processes. Most Brazilian Pre-salt reservoirs have early faults associated with depositional tectonic development overprinted by late faults that formed at greater depths. Both faulting events can markedly affect the present-day DZ widths. Previous studies have investigated the development of DZ during the early faulting stage. However, the late faulting stage and its impact on DZs have not been explored. Thus, our goal is to investigate the impact of both the early and late faulting stages in the structural evolution of DZs in carbonate rocks through geomechanical analyses. The results indicate that burial during the late faulting stage increases confinement and enhances the integrity of the rock far from the DZ, while the DZs triggered during the early fault formation remains unchanged. In addition, for the late faulting stage, we assess the role of fault roughness on the DZ by adopting friction coefficients to represent smooth or rough surfaces. The results show that rough fault surfaces contribute to lower fault displacements.