| Santos Basin | |
|---|---|
| Bacia de Santos | |
  | |
 Location of the basin offshore Brazil | |
| Coordinates | 26°6′22″S 43°43′45″W / 26.10611°S 43.72917°W |
| Etymology | Santos |
| Location | South America |
| Region | Southeast, South |
| Country |  Brazil |
| State(s) | Rio de Janeiro, São Paulo, Paraná, Santa Catarina |
| Cities | Cabo Frio, Rio de Janeiro, Guarujá, Santos, Itajaí, Balneário Camboriú, Florianópolis |
| Characteristics | |
| On/Offshore | Both, mostly offshore |
| Boundaries | Cabo Frio, Florianópolis Highs, Serra do Mar |
| Part of | Brazilian Atlantic margin basins |
| Area | ~352,000 km2 (136,000 sq mi) |
| Hydrology | |
| Sea(s) | South Atlantic Ocean |
| River(s) | Ribeira de Iguape |
| Geology | |
| Basin type | Passive margin on rift basin |
| Plate | South American |
| Orogeny | Break-up of Gondwana |
| Age | Barremian-recent |
| Stratigraphy | Stratigraphy |
| Field(s) | Tupi, Libra, Júpiter, others |
The Santos Basin (Portuguese: Bacia de Santos) is an approximately 352,000 square kilometres (136,000 sq mi) large mostly offshore sedimentary basin. It is located in the south Atlantic Ocean, some 300 kilometres (190 mi) southeast of Santos, Brazil. The basin is one of the Brazilian basins to have resulted from the break-up of Gondwana since the Early Cretaceous, where a sequence of rift basins formed on both sides of the South Atlantic; the Pelotas, Santos, Campos and Espírito Santo Basins in Brazil, and the Namibia, Kwanza and Congo Basins in southwestern Africa.
Santos Basin is separated from the Campos Basin to the north by the Cabo Frio High and the Pelotas Basin in the south by the Florianópolis High and the northwestern boundary onshore is formed by the Serra Do Mar coastal range. The basin is known for its thick layers of salt that have formed structures in the subsurface due to halokinesis. The basin started forming in the Early Cretaceous on top of the Congo Craton as a rift basin. The rift stage of the basin evolution combined with the arid Aptian climate of the southern latitudes resulted in the deposition of evaporites in the Late Aptian, approximately 112 million years ago. The phase of rifting was followed by a thermal sag phase and drift stage in the widening of the South Atlantic Ocean. This process led to the deposition of a more than 20 kilometres (66,000 ft) thick succession of clastic and carbonate sediments.
One of the largest Brazilian sedimentary basins, it is the site of several recently (2007 and later) discovered giant oil and gas fields, including the first large pre-salt discovery Tupi (8 billion barrels), Júpiter (1.6 billion barrels and 17 tcf of gas), and Libra, with an estimated 8 to 12 billion barrels of recoverable oil. Main source rocks are the lacustrine shales and carbonates of the pre-salt Guaratiba Group and the marine shales of the post-salt Itajaí-Açu Formation. Reservoir rocks are formed by the pre-salt Guaratiba sandstones, limestones and microbialites, the Albian limestones of the Guarujá Formation and the Late Cretaceous to Paleogene turbiditic sandstones of the Itanhaém, Juréia, Itajaí-Açu, Florianópolis and Marambaia Formations. The mobile salt of the Ariri Formation forms regional seals, as well as the shales of the post-salt sedimentary infill. In 2014, the total production of only the sub-salt reservoirs accumulated to more than 250 thousand barrels per day (40×103 m3/d). In 2017, the Santos Basin accounted for 35% of Brazil's oil, with the northern neighbour Campos Basin at 55%.