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The reservoir characterization of the Brazilian Santos Basin's pre-salt carbonates is a major challenge due to the faciological and depositional complexity, providing high lateral and vertical heterogeneities, and consequently, the formation of static/dynamic intraformational seals. Regarding this context, there is a massive pre-salt accumulation known as the Iara Cluster. During the early development stage, this cluster was split into three distinct accumulations named Berbigão, Sururu, and Atapu. This study aims to characterize the geological and hydrodynamic factors that affect the Iara Cluster reservoir compartmentalization. To achieve this objective, we applied an integrated analysis based on 3D seismic interpretation, well logs, pressure formation and fluid geochemistry analysis. The spatial distribution of the reservoir range's five main seismic patterns indicates potential stratigraphic-structural barrier zones. The well log analysis correlated with formation pressure data enabled the identification of several irregular oil-water contacts and free water levels. Small relative variations are associated with the perched-water phenomenon, while large variations are related to compartmentalization. The formation pressure analysis shows the hydraulic compartmentalization of the reservoirs in the Berbigão Field. Sururu and Atapu fields' oil zones are possibly connected by a dynamic sealing zone or a common aquifer, which provides a pressure balance on a geological time scale, since their oil gradients are similar. Our analyzes identified stratigraphic components in reservoir trapping associated with reservoir quality lateral obliteration. Dissimilarities in the oil sample composition and properties indicate different petroleum charge histories along with the distinct CO 2 contamination timing. The Berbigão oil-associated gas formed in earlier stages of maturation than the Sururu and Atapu samples. The results integration through a risk matrix revealed areas with a greater chance of compartmentalization and perched-water phenomenon. Our study highlights the importance of multidisciplinary analysis to comprehend complex carbonate reservoirs connectivity, and offers input to de-risk new ventures' pre-salt reservoir quality. • Four compartmentalized reservoir segments were identified in the Iara pre-salt cluster. • We identified irregular free water levels in the same oil zone, indicating a phenomenon known as perched-water effect. • A stratigraphic-structural trapping is pointed out as a significant trapping mechanism of pre-salt reservoirs. • The gas geochemical analysis indicates the contribution of different generation kitchens in the area. [ABSTRACT FROM AUTHOR]

The absence of expressive hydrocarbon columns and high CO 2 content observed in the pre-salt of Santos Basin reservoirs over the last decade reveal the risk of hydrocarbon charge and contamination to be a relevant concern in exploration activities in the basin. Therefore, this study was focused on elucidation of the source potential, basin depocenters, and CO 2 occurrence in the pre-salt of the Santos Basin, aimed at reducing risk of upcoming exploration activities. Based on geochemical analysis, our study revealed that Late Barremian-Early Aptian fine-grained rock intervals, rich in organic matter, from the Itapema Formation and secondarily, from the Piçarras Formation, are likely the main source rocks of the Santos Basin. Seismic interpretation revealed five wide pre-salt depocenters. The Main Depocenter, followed by the Central and North depocenters, could be the major hydrocarbon sources for pre-salt reservoirs. Based on the CO 2 distribution data, low amounts of the contaminant (under 5%) were detected in the post-salt and proximal pre-salt reservoirs, with intermediate values (from 10 to 50%) in the main pre-salt accumulations. High CO 2 amounts (over 50%) were encountered mainly in a northeast to southwest trend, linking Peroba-Júpiter-Libra areas, and could be related to a deep-seated fault system associated with mantle contamination. Accordingly, the northern and central parts of the Central Santos sub-basin have a low risk of hydrocarbon charge and contamination, whereas its eastern portion has a high risk because of the absence of an expressive hydrocarbon column and elevated CO2 content. The Southwest Santos sub-basin presented a high risk for pre-salt discoveries because of salt windows which limit the top seal for pre-salt-sourced hydrocarbons. In the Southeast Santos sub-basin, the risk of hydrocarbon charge and contamination is significant because of the absence of mapped depocenters and its location on a crustal domain favorable to mantle CO 2 access. • Fine-grained rock intervals from the Itapema and secondarily, Piçarras Formation, are likely the main source of the Santos Basin. • Five broad pre-salt depocenters and other local depocenters mapped could act as pre-salt hydrocarbon source. • High mantle CO 2 in pre-salt reservoirs, can be linked to igneous intrusions, and migrated along deep-seated faults. • The northern, central, and southwestern of the basin have a low to moderate risk of hydrocarbon charge and contamination. • The eastern, central-eastern, and southern of the basin have a high risk of hydrocarbon charge and contamination. [ABSTRACT FROM AUTHOR]