ICE 2022


Recently shot 3D surveys over the southward extension of the External High beyond the EEZ in the Santos Basin unveiled the existence of a structural style yet unknown in the prolific Pre-Salt section. Very large positive and negative flower structures of great relief and amplitude can be observed. Vertical faults that cut through the upper brittle crust are seen offsetting the salt wall as if it were an elastic/brittle body. An unprecedented view of the intensively broken, faulted, uplifted and twisted outer continental crust can be observed. Amidst this complex style, very large structural closures, such as the Puri Prospect (> 1000 km2 of 4-way closure) occur completely sealed by salt, despite the intense deformation. Some of such structures consist of inverted Pre-Salt grabens due to transpression. Typical Pre-Salt reservoir seismic facies can be seen at the crests of the structures. Planar, parallel reflectors indicative of the carbonate ramp model of microbialite deposition and travertine cones/buildups related to hydrodynamically active syn-rift faults can be visualized right beneath the base of salt. Another important feature revealed by the 3D surveys is the presence of thick, deep-seated grabens filled by sedimentary strata adjacent to or underneath such highs. Their existence is important as they may contain the so-needed source rocks of the External Kitchen. All Pre-Salt section was deposited in a syn-rift setting, being its typical extensional structural style strongly overprinted by an overlapping to later strike-slip deformation. The age of the strike-slip tectonism is deduced to be late syn-rift to syn-salt deposition. For the first time, a glimpse into the highly complex deformation history of the last lapses of continental separation can be attained. The External High is the most important feature of both Santos and Campos basins because, being a >600 km continuous feature, it plays the role of the main focusing high for both surrounding Internal and External Kitchens. It acts just like the backbone and the surrounding depressions of the ribs. The External High controls the location of most of the Pre-Salt and Post-Salt producing fields. These very large structural highs mapped at the base of the salt upon this newly identified extension of the External High show great potential for future discoveries of large accumulations.