The Outer High of the Santos Basin, Southern São Paulo Plateau, Brazil: Pre-Salt Exploration Outbreak, Paleogeographic Setting, and Evolution of the Syn-Rift Structures

Paulo Gomes¹, Bill Kilsdonk², Jon Minken², Roberto Barragan², and Tim Grow^2
1Hess Brasil Petroleo Ltda., Rio de Janeiro, Brazil
²Hess Corporation, Houston, TX

In the deepwater Santos Basin multiple geologic elements combine in a very attractive pre-salt exploration play: prolific and mature source rocks are likely; syn-rift structures include huge intra-basinal highs; and the overlying evaporite seal extends throughout most of the area. While all of these have been recognized for some time, reservoir presence and deliverability remain key risks. In addition, different approaches on seismic interpretation and regional geological evaluation have fueled a heated debate between proponents of siliciclastic models and proponents of carbonate reservoir models for the pre-salt section. The most prominent and extensive intrabasinal high in the region is the “Outer High of the Santos Basin”, a regional basement structure which forms a 12,000 sq. km four-way closure at the Aptian level. The geological history of the Outer High involves uplift and erosion of a series of rift shoulders during the Barremian times. The regional uplift event associated to its formation can be linked to a failed seafloor spreading process, which was responsible for the emplacement of a proto-oceanic crust in the Southern Santos. Prior to continental break-up, the Outer High was located 200 km away from both African and Brazilian hingelines. This distal setting, coupled with a positive relief, must have limited siliciclastic input from the margins. A long-lived paleo-high, in clastic-starved environment, favored the development of a broad carbonate platform, during the Lower Aptian. Tectono-eustatic lake/restricted-sea (?) level variations affected the evolving platform, playing a role on reservoir facies development.

The Outer High and adjacent remnant rift structures have been the main stage of a recent and so far successful pre-salt drilling campaign in deepwater Santos Basin. Its huge hydrocarbon potential is yet to be fully unraveled.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery