--> ABSTRACT: Deep Water Siliciclastic Depositional Systems of Sergipe Sub-basin - Exploratory Perspectives - Sergipe-Alagoas Basin, Northeastern Offshore Brazil, by Cunha, Roberto Carlos R.; Jardim, Celso M.; Nobrega, Mirnis A.; Almeida, Camilla B.; Souza, Paulo Henrique G.; #90135 (2011)

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Deep Water Siliciclastic Depositional Systems of Sergipe Sub-basin - Exploratory Perspectives - Sergipe-Alagoas Basin, Northeastern Offshore Brazil

Cunha, Roberto Carlos R.1; Jardim, Celso M.1; Nobrega, Mirnis A.1; Almeida, Camilla B.1; Souza, Paulo Henrique G.2
(1)E&P-Exploration, Petrobras, Rio de Janeiro, Brazil. (2) International R&R, Petrobras, Rio de Janeiro, Brazil.

The Sergipe-Alagoas Basin, located at the northeastern offshore Brazil, has more than forty years of exploration and production, mostly from land and shallow water oil and gas fields. Despite the huge database and knowledge on these areas, only in the last ten years systematic efforts have been made to unravel its deep water and ultra-deep water domains. Detailed mapping of a recent 3-D seismic survey in the Sergipe sub-basin allowed disclosing the deep water depositional system in the post-rift section. Provenance studies and previous works on shallow water areas highlighted the transfer of significant sand volume to the basin from a narrow (less than 40 km) prograding shelf developed since the Upper Cretaceous. Four major depositional sequences can be distinguished, separated by unconformities dated by seismic and well data correlation as Santonian, Campanian, Maastrichtian and Lower Paleogene. In these sequences moderate to high amplitude reflectors are visualized with very distinct internal geometries of submarine turbidite channels and lobes developed in base of slope and basin floor environments, as well as transparent to chaotic seismofacies interpreted as mass transport complexes (MTC). The seismic character changes as the sequences become younger, with a more pronounced impedance contrast and particular features here associated to drifts produced by bottom currents accelerated along the NW-SE oriented canyons observed in the sequences mapped. The recent discovery of light oil and gas/condensate accumulations in Upper Cretaceous sandstones in the deep southern and northern sectors of the sub-basin brings new perspectives to the exploration of a formerly interpreted sand-poor deep water basin.

 

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.