Print this pageStructural Anisotropy and Implications for the Oil and Gas Distribution Along the Campos and Santos Basin, Brazil
The Campos and Santos basins have evolved over a complex basement, controlled by different stretching rates, kinematics and rheology. Both basins show the same geodynamic evolution, beginning with mechanical subsidence in the Neocomian and Barremian, evolving to a sag phase in the Aptian and a further thermal subsidence during the Late Cretaceous and Cenozoic. The opening of the South Atlantic propagated from south to north and was controlled by stress trajectories applied over a NE-striking basement, nucleating new NE and NS faults. Additionally, different strain rates were accommodated in transverse NW and EW faults. The lithospherical attenuation was strongly influenced by imprinting of the Walvis giant-plume. Such processes lead to deformation partitioning, with the Cabo Frio Region working as a supraregional accommodation zone. During the post-rift phase, despite the determinant role of thin-skinned gravitational and overburden post-rift processes, some rearrangement and tenuous modification of the structural geometry of deep crustal blocks are also observed. These processes are evidenced by reactivation of some rift blocks, igneous activities along structural trends during the Paleogene and the uplift of the adjacent Serra do Mar range. The regional anisotropy is fairly observed not only in magnetic, gravimetric and seismic data, but also in remote sensing and onshore geological maps. Such post-rift events have generated tectonic instability, renewed structural domains, changed depocenters and controlled HC charge and entrapment processes. Some NW listric faults worked as thin-skinned transfer faults related to different extension rates during the gravitational halokinesys, as observed in the area of the Marlim and Albacora fields. Two regional EW-striked faults, which show a clear spatial relationship with the Cenozoic igneous activity in the onshore area, are clearly related to the distribution of fields in the central part of the Campos basin. Some NW faults control the hydrocarbon occurrences in the Santos basin, as observed along the offshore continuity of the Guapiara Fault Zone. The relationship between regional features and known HC fields suggests a genetic and spatial correlation between the tectonic framework and hydrocarbon pools distribution.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil