Halokinetic analysis of the Frade field area, Campos Basin, Brazil: Salt tectonics within an offshore strike-slip setting

The Frade field, located within the Campos Basin in the southeastern Brazilian margin, is a key oil field that produces from Oligo-Miocene turbidite reservoirs that derived their structural positioning due to the presence of an underlying salt diapir. The evolution of the Frade salt structure was examined using well data, selected 2D lines, and a 3D volume that were interpreted in detail focusing on the Aptian evaporite interval and its influence on the overburden. Analysis of the salt-sediment interaction indicated a complex deformation history that included five main stages of deformation, some assisted by tectonic reactivation episodes. (1) Post-Albian reactivation of a nearby north-northwest-south-southeast basement fault caused the Albian carbonate interval to fault, forming a west-northwest-east-southeast shear zone with a dextral strike-slip component This movement initiated thin-skinned tectonics that offset the Albian carbonates and formed a pull-apart basin that accommodated a thick Late Cretaceous interval, which weakened the overburden and allowed for the initial formation of the F'rade salt diapir. (2) Renewed diapir growth thickened and redistributed the Cenomanian-Maastrichtian sedimentary package proximal to the Frade salt anticline. (3) An initial and localized collapse of the Frade salt anticline occurred during early Paleogene extension. (4) Paleogene shortening caused the salt to flow, resulting in salt withdrawal in the southeast and diapir rejuvenation near its present-day apex, forming several inversion structures. In addition, the Paleogene shortening resulted in a low-relief anticlinal structure that rotated the turbidites into geometries favoring hydrocarbon accumulation. (5) A return to an extensional regime occurred during the late Oligocene/early Miocene. The results of this study provide a new insight into the development of strike-slip salt tectonic structures and show for the first time within the Campos Basin an Albian-level pull-apart basin that formed in association with salt tectonics.