| Guaratiba Group | |
| Period: | Aptian |
| Age: | Hauterivian-Early Aptian ~ |
| Type: | Group |
| Prilithology: | Limestone (coquina), marl, shale, siltstone |
| Otherlithology: | Sandstone, conglomerate |
| Subunits: | Piçarras Fm., Itapema Fm., Barra Velha Fm. |
| Underlies: | Ariri Formation |
| Overlies: | Camboriú Formation |
| Thickness: | up to 4200m (13,800feet) |
| Map: | Santos basin map.png |
| Coordinates: | -26.1°N -86°W |
| Region: | Santos Basin, South Atlantic |
| Namedfor: | Guaratiba |
The Guaratiba Group (Portuguese: Grupo Guaratiba) is a geological group of the Santos Basin offshore of the Brazilian states of Rio de Janeiro, São Paulo, Paraná and Santa Catarina. The group forms the pre-salt layer in the petroleum-rich basin and hosts the biggest oil fields of Brazil, as Tupi, Júpiter and many more. The group contains, depending on the definition, three to four formations and dates to the Early Cretaceous period; Hauterivian to Early Aptian epochs. The total thickness of the group, representing the first phase of sedimentation after the break-up of Gondwana in the Santos Basin, is estimated at 4200m (13,800feet).
The formation is named after Guaratiba, a neighbourhood in the west of Rio de Janeiro.
The Guaratiba Group is 4200m (13,800feet) thick and subdivided into three formations, four if the underlying basalts of the Camboriú Formation are included,[1] and five if the salt layer of the Ariri Formation is included,[2] from old to young the Piçarras, Itapema, and Barra Velha Formations.
The conglomerates and sandstones of the formation are representative of an alluvial environment. The coquinas represent a shallow lacustrine environment. Similar to the Atafona Formation of the Campos Basin, the sandstones, stevensite-bearing siltstones and shales represent an alkaline lacustrine environment affected by volcanic activity. The shales represent deeper lacustrine waters in more distal areas. The alternation of the two facies implies a series of alluvial progradation-retractions into the Early Cretaceous carbonate lakes. The low textural and compositional maturity of conglomerates and sandstones implies the basin was supplied from areas close to the basin margins.[3]
The formation hosts the important pre-salt reservoir rocks of the Santos Basin.[5] [6]
| Field | Year | Operator | Reserves (in place unless otherwise noted) | class=unsortable | Notes |
|---|---|---|---|---|---|
| Sagitário | 2013 | ||||
| 2011 | 8000- (recoverable) | ||||
| 2010 | 3058abbr=unitNaNabbr=unit | ||||
| 2008 | 3000- | ||||
| 2008 | |||||
| 2008 | 1600e6oilbbl 17abbr=unitNaNabbr=unit | ||||
| 2008 | 1100- | ||||
| 2007 | 459e6oilbbl | ||||
| 2006 | 8000e6oilbbl | ||||