Depocenter Migration in the Santos Basin and Its Importance to Oil and Gas Exploration

Mario Luis Assine, Hung Kiang Chang, Fernando Santos Correa, Julio Setsuo Tinen, Eduardo De Mio, and Joel Carneiro Castro
University State São Paulo, Rio Claro, Brazil

Recent important discoveries of gas and oil fields during the last few years have called attention to the Santos Basin, offshore Southeast Brazil. The basin is located south of the Campos Basin, the most prolific Brazilian oil province. The two basins divided by the Cabo Frio Arch present many similarities in their structural and stratigraphic evolution. Tertiary section is well developed in both basins, however the Upper Cretaceous record is significantly more preserved in the Santos Basin, characterized by thick Santonian to Maastrichtian progradational siliciclastic clinoforms. The accommodation space was generated by salt basinward withdrawal, which in consequence caused the rafting of the Albian carbonate sequences and overlying Cenomanian to Turonian marine shales and turbidites. Because the withdrawal of Aptian evaporites, the deltaic clastic wedges downlap the unconformity with rift sequences, putting directly in contact rift source-rocks and Cretaceous reservoirs. Progradation was not simultaneous along the basin. In order to understand the way of depocenter migration, a sequence stratigraphic analysis was carried out using 2D seismic lines and well data. Isopach and several lithologic ratio maps based on 60 wells were produced for each sequence. The maps show clearly a northward depocenter migration during the Late Cretaceous along the Santos Basin in direction to the Campos Basin, where the Tertiary section is well developed. Early Tertiary section is also important in the northern portion of the Santos Basin, represented by prominent deltaic progradation and associated turbidite systems.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005