Origin, Geological Controls and Interactions of CO ₂ With Hydrocarbons and Pre‐Salt Reservoirs, Santos Basin, Brazil

ABSTRACT Knowledge on the origin and the main geological controls on the occurrence of CO 2 in the pre‐salt reservoirs of the Santos Basin has had significant improvement in the last decade. However, the influence of CO 2 on the petroleum system needs more investigations, especially, related to the segregation of components in the oil column, or changes in the reservoir diagenesis. Anticipation of possible interactions CO 2 ‐fluids‐rock is critical to evaluate prospects, considering implications for development and production. Aiming to contribute to the improvement in predictions on the interactions CO 2 ‐fluids‐rock, this study was developed to investigate the relationship between the origin and CO 2 distribution with alterations in the petroleum column and reservoir diagenesis in the Santos Basin. New results of noble gas analyses corroborate the strong mantle signature of the contemporary CO 2 . Phase split in the petroleum column, already depicted in laboratory experiments, was identified in accumulation of Júpiter. High CO 2 is found preferentially along a NE–SW trend and seems to increase towards SE. Similar traps can have highly variable contents of CO 2 suggesting active sinking. Episodes of CO 2 flux through reservoir play an important role in diagenesis promoting the corrosion of calcite cement and precipitation of quartz, anhydrite and dawsonite. Results of this investigation have shown significant influence of CO 2 on the phase segregation of petroleum column and on diagenesis of pre‐salt reservoirs in the Santos Basin.