Abstract

This chapter compiled data from the latest history of exploration and investigated the key risks associated with the pre-salt petroleum system processes and elements in the Santos and Campos basins. The discussion goes through the analysis of rock-driven uncertainties, such as reservoir architecture, entrapment geometry, effectiveness of the cap rock, fluid-driven uncertainties represented by the distribution of oil and/or gas around the province, temperature, and hydrological conditions, as well as pressure transmission. The pre-salt reservoirs underwent a complex sedimentological history, and their stratigraphic interpretation is critical for mitigating the risks associated with reservoir connectivity and heterogeneity, as well as transmissibility. The main risks for entrapment are the presence of stratigraphic components of four-way or three-way controlled closures, their integrity affected by faults, and lateral seal presence. The main risks related to the source rocks and their maturation processes are the proportion of black and cracked oils present, the effectiveness of migration, and carbon dioxide (CO₂) contamination observed in some parts of the area. The risk assessment for migration pathways comprises the proper understanding of the northeast–southwest trend of rift extensional faults for upward migration, together with the northwest–southeast transverse faults, and how the fluid circulation through faults was connected to the carrier beds inside the rift section. The most significant region of the pre-salt-oil province is the central high of the Santos Basin, which has been charged by hydrocarbons that were generated in its landward (or internal) and seaward (or external) depocenters. Several external highs are there in the ultra-deep waters of the basin that have great exploration potential and have not yet been tested. These highs are surrounded by depocenters that have potential to hold rich source rocks. A final map of geological success probability summarizes the less risky sweet spots along the westernmost and central areas of the Santos Basin, with the higher success probability extending toward the eastern outboard of Santos and Campos basins.