Itajaí-Açu Formation

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.

Not to be confused with Açu Formation.
Itajaí-Açu Formation
Stratigraphic range: Cenomanian-Maastrichtian
~100–66 Ma
TypeGeological formation
Unit ofFrade Group
UnderliesMarambaia Formation
OverliesItanhaém Formation
Thicknessup to 2,000 m (6,600 ft)
Lithology
PrimaryShale
OtherSandstone
Location
Coordinates26°6′S 43°43′W
RegionSantos Basin, South Atlantic
Country Brazil
Type section
Named forItajaí-Açu River

Location of 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,[1] 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 nanofossils and planktonic foraminifera indicate a Late Cretaceous age (Cenomanian-Maastrichtian).[2]

Petroleum geology

The formation, mainly its Ilhabela Member, is the main post-salt reservoir rock of the Santos Basin.[3][4] The formation also is the main post-salt source rock and a seal for the post-salt reservoirs.[5]

Fields with Itajaí-Açu reservoirs
Field Year Operator Reserves (in place)
Notes
Panoramix2009Repsol176 million bbl (28.0 million m3)
[3]
Piracucá2009Petrobras321.4 million bbl (51.1 million m3)
[3][6]
Cedro2005Petrobras95.76 million bbl (15.2 million m3)
[3][7]
Lagosta2003El Paso Corp.0.173 trillion cu ft (4.9 billion m3)
[3][8]
Uruguá2003Petrobras174.27 million bbl (27.7 million m3)
1 trillion cu ft (28 billion m3)
[3][8]
Carapiá2002Petrobras63.52 million bbl (10.1 million m3)
[3][8]
Mexilhão2001Petrobras532.23 million bbl (84.6 million m3)
3.4 trillion cu ft (96 billion m3)
[3][9][10]
Tambuatá1999Petrobras212.8 million bbl (33.8 million m3)
[3][9]
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See also

References
  1. Kiang Chang et al., 2008, p.32
  2. Clemente, 2013, p.23
  3. "Santos Basin Fields". Archived from the original on 2017-09-07. Retrieved 2017-09-07.
  4. Juarez, 2013, p.7
  5. Contreras, 2011, p.77
  6. Piracucá Field
  7. Petrobras BS-400 gas find confirms E&P expansion plans
  8. Vieira, 2007, p.9
  9. Juarez, 2013, p.14
  10. Vieira, 2007, p.8

Bibliography
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