Itajaí-Açu Formation

Not to be confused with Açu Formation.

Itajaí-Açu Formation
Stratigraphic range: Cenomanian-Maastrichtian ~
Type	Geological formation
Unit of	Frade Group
Underlies	Marambaia Formation
Overlies	Itanhaém Formation
Thickness	up to 2,000 m (6,600 ft)
Lithology
Primary	Shale
Other	Sandstone
Location
Coordinates	26°6′S 43°43′W
Region	Santos Basin, South Atlantic
Country	Brazil
Type section
Named for	Itajaí-Açu River
Location of the Santos Basin

The Itajaí-Açu Formation (Portuguese: Formacão Itajaí-Açu) is a geological formation of the Santos Basin offshore of the Brazilian states of Rio de Janeiro, São Paulo, Paraná and Santa Catarina. The predominantly shale with interbedded turbiditic sandstones formation dates to the Late Cretaceous period; Cenomanian-Maastrichtian epochs and has a maximum thickness of 2,000 metres (6,600 ft). The formation is a reservoir rock of the fields in the Santos Basin.

Etymology

The formation is named after the Itajaí-Açu River, Santa Catarina.

Description

The Itajaí-Açu Formation consist mainly of turbidites, formed at the base of the Brazilian marginal continental slopes. The sands of this formation, called Ilhabela Member, host vast amounts of oil in the Santos Basin.

The Itajaí-Açu Formation is 1,545 to 2,000 metres (5,069 to 6,562 ft) thick, and comprises a thick interval of dark grey clayey rocks, interbedded with the clastics of the Santos and Juréia Formations. Within this formation, the Ilhabela Member includes the turbiditic sandstones occurring along the section. The sedimentary environment is thought to be marine talus to open basin. Biostratigraphic data from palynomorphs, calcareous nannofossils and planktonic foraminifera indicate a Late Cretaceous age (Cenomanian-Maastrichtian).

Petroleum geology

The formation, mainly its Ilhabela Member, is the main post-salt reservoir rock of the Santos Basin. The formation also is the main post-salt source rock and a seal for the post-salt reservoirs.

Fields with Itajaí-Açu reservoirs

Field	Year	Operator	Reserves (in place)	Notes
Panoramix	2009	Repsol	176 million bbl (28.0 million m3)
Piracucá	2009	Petrobras	321.4 million bbl (51.1 million m3)
Cedro	2005	Petrobras	95.76 million bbl (15.2 million m3)
Lagosta	2003	El Paso Corp.	0.173 trillion cu ft (4.9 billion m3)
Uruguá	2003	Petrobras	174.27 million bbl (27.7 million m3) 1 trillion cu ft (28 billion m3)
Carapiá	2002	Petrobras	63.52 million bbl (10.1 million m3)
Mexilhão	2001	Petrobras	532.23 million bbl (84.6 million m3) 3.4 trillion cu ft (96 billion m3)
Tambuatá	1999	Petrobras	212.8 million bbl (33.8 million m3)

See also

• Campos Basin

References

Bibliography

• Clemente, Pilar (2013), Petroleum geology of the Campos and Santos basins, Lower Cretaceous Brazilian sector of the South Atlantic margin, Danmarks Tekniske Universitet, pp. 1–33, retrieved 2017-09-04
• Contreras, Jorham (2011), Seismo-stratigraphy and numerical basin modeling of the southern Brazilian continental margin (Campos, Santos, and Pelotas basins) (PhD thesis) (PDF), Ruprecht-Karls-Universität Heidelberg, pp. 1–171, retrieved 2017-09-04
• Juarez Feijó, Fávio (2013), "Santos Basin: 40 Years from Shallow to Deep to Ultra-Deep Water" (PDF), Search and Discovery, 10553: 1–49, retrieved 2017-09-04
• Kiang Chang, Hung; Assine, Mario Luis; Santos Corrêa, Fernando; Setsuo Tinen, Julio; Campane Vidal, Alexandre; Koike, Luzia (2008), "Sistemas petrolíferos e modelos de acumulação de hidrocarbonetos na Bacia de Santos" (PDF), Revista Brasileira de Geociências, 38: 29–46, doi:10.25249/0375-7536.2008382S2946 (inactive 1 November 2024), retrieved 2017-09-04{{citation}}: CS1 maint: DOI inactive as of November 2024 (link)
• Vieira, Juliana (2007), Brazil Round 9 - Santos Basin (PDF), ANP, pp. 1–73, archived from the original (PDF) on 2017-02-03, retrieved 2017-09-04