Santos Basin: the outlook for a new petroleum province on the southeastern brazillan continental shelf

Abstract

The prospectable area of the Santos Basin totals 130 000 km² (180 x 700 km), between the Cretaceous hinge line and the 2 000 m isobath. Sedimentary thickness may reach 10 to 12 km at depocenters. Although neither the structural framework of the basin nor its rift phase sediments have been well-researched, the tectonic style is judged to be transtensional. Five distinct salt tectonics provinces can be characterized in the post-tilt section and sharply influence the stratigraphic package of the basin. Hydrocarbons recovered from this basin at water depths as great as 400 m, approximately, are especial/y prone to the production of very light oils and gas; at greater water. depths less mature oils are expected to be found. Geochemical and geological data suggest that a pre-salt section is the main source rock. In areas at a water depth of less than 400m, the two main targets are Lower Albian oolitic calcarenites and Upper Turonian turbidite sandstones, widely spread throughout the area and both located at depths that usually exceed 4 500 m. The Upper Cretaceous and Tertiary turbidite sandstones on the continental slope and adjacent deep basin a/so form important plays. Basin exploration began at the end of the sixties, and from 1976 through 1986 included the participation of foreign firms operating under risk contracts. In 1984, Pecten discovered the Merluza gas field. In 1987 expectations were further boosted by PETROBRÁS' discovery of the Tubarão oil and gas field, which has helped make this area one of the main exploratory targets in the Brazilian Continental margin.