ICE 2022


The offshore Santos and Campos basins located in the southeastern margin of Brazil have been focusing extensive hydrocarbon exploration after large discoveries made in the sedimentary package known as pre-salt. In our conception, the structural architecture of those basins that control facies distribution during and after rifting is consequence of the change in the extension direction along the Eastern Brazilian margin in the Early Cretaceous: initial E-W extension in the Hauterivian/Barremian was followed by distal NW-SE opening in the Aptian as the tectonic activity migrated offshore. During initial rifting when world class source rocks and coquina reservoirs were deposited in the basins, the trend of the Brazilian margin was strongly controlled by basement heterogeneity, which also determined the NE-SW direction of rift propagation. In this way, because the initial E-W extension was oblique to the direction of rift propagation, oblique rifting dominated Santos basin, with a transition to suborthogonal in the southern Campos basin. Consequently, a complex structural framework resulted with the alternance of prominent highs and lows controlled by transfer zones, which kinematics depended on the orientation with respect to the regional extension. Those transfer zones compartmentalized the basins along the strike during the initial rifting; however, some regional structures formerly interpreted as developed during the syn-rift probably evolved during post-rift times in the Late Cretaceous. The tectonism along the margin tended to rejuvenate eastward during the Aptian as the opening direction changed from E-W to NW-SE. Therefore, previous existing structures were reactivated and developed in the internal, initial rift, but the external rift became the locus of the main tectonic activity as the margin evolved until final break up took place. Our interpretation has important consequences on the distribution of reservoirs and source rock facies of the so-called pre-salt in the proximal/internal and distal/external rifts.