The Campos Basin is one of 12 coastal sedimentary basins of Brazil. It spans both onshore and offshore parts of the South Atlantic with the onshore part located near Rio de Janeiro. The basin originated in Neocomian stage of the Cretaceous period 145–130 million years ago during the breakup of Gondwana. It has a total area of about , with the onshore portion small at only .[
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Etymology
The basin is named after the Campos dos Goytacazes city.
Description
The Campos Basin is bound on the south by the Cabo Frio High, separating the basin from the Santos Basin and on the north by the Vitória High, forming the boundary with the Espírito Santo Basin. Campos Basin contains the Paraiba do Sul River delta.[
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Tectonic history
The South Atlantic margin developed on Archean stable consisting of hard and resistant rocks and partly on the Neoproterozoic mobile belts composed of less resistant .[Clemente, 2013, p.3] The Precambrian basement of the Santos Basin is exposed as the Araçuaí Belt along the Brazilian coast, most notably in the of Rio de Janeiro, of which Sugarloaf Mountain is the most iconic. The ancient rocks consist of a Neoproterozoic to Cambrian high-grade metamorphic core of and gneisses, formed during the collision of Gondwana in the Pan-African-Brasiliano orogeny.[Owen, 2014, p.36] Basalts similar to the Paraná and Etendeka traps, exposed to the west in the Paraná Basin, have been found underlying the Santos Basin.[Peate, 1997, p.220] The Tristan da Cunha hotspot, known as the Tristan hotspot, is considered the driver behind the formation of these .[Beasley et al., 2010, p.31]
During the Early Cretaceous, the former continent Gondwana, as southern part of Pangea, starting to break-up, resulting in a sequence of bordering the present-day South Atlantic. The Pelotas-Namibia spreading commenced in the Hauterivian, around 133 million years ago and reached the Santos Basin to the north in the Barremian. Seafloor spreading continued northwards to the Campos Basin in the Albian, at approximately 112 Ma.
Five tectonic stages have been identified in the Brazilian basins:[Contreras, 2011, p.7]
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Pre-rift stage – Jurassic to Valanginian
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Syn-rift stage – Hauterivian to Barremian
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Sag stage – Late Barremian to Aptian
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Post-rift stage – Albian
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Drift stage – Late Albian to Holocene
Stratigraphy
Oil reservoirs include formations deposited during the Aptian and pre-Aptian continental rift phase, of post-salt Albian-Cenomanian shallow-water marine carbonates and deepwater , and in of the open marine drift phase of Late Cretaceous and early Tertiary period ages.[
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The Namorado Field "location was selected based on seismic interpretation of a structural high at the top of the Macaé Formation (Albian )" at a depth of about ,[ and the reservoirs are marine turbidite deposits transgressing over the Albian limestone shelf.][
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The stratigraphy starts with basalt flows dated at 120 Ma, overlain by the Lagoa Feia Group, consisting of the organic-rich lacustrine "green shales" followed by Lacustrine plain limestones and continental sandstones and conglomerates, transitioning into marine sediments with evaporites, limestones, and limestone altered dolomites.[ The shallow marine limestones of the Macaé Formation follow, then the Namorado turbidite sandstones, and finally the Campos Formation, consisting of the turbidite sandstone Carapebus Member and the prograding slope and shelf Ubatuba Formation.][
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Exploration
The off-shore oil exploration in the Campos Basin began in 1968.[ The first exploratory well was drilled in 1971. The first field to be discovered was Garoupa Field in 1974, at a shallow water depth of , followed by Namorado in 1975 in of water.][Bacoccoli et al., 1980] The first oil production started in 1977 from Enchova Field, at a water depth of .[ The largest fields, listed by their year of discovery year, include Linguado Field (1978), Carapeba Field (1982), Vermelho Field (1982), Marimba Field (1984),][Horschutz et al., 1992, pp.137–152] Albacora Field (1984), Marlim (1985), Albacora-Leste (1986), Marlim Sul (1987), Marlim Leste (1987), Barracuda Field (1989), Caratinga Field (1989), Espadarte Field (1994), Roncador field (1996), Jubarte Field (2002), Cachalote (2002), and Badejo Field (2008). The largest Marlim field is located in the northeast of the basin, offshore in water depths ranging from .[Fraga et al., 2003]
By 2003, 41 oil and gas fields were discovered, which ranging at distances from from the coast and at water depths varying from . Of these fields, 37 are being developed by Petrobras. By 2003, the oil production from the basin had reached 1.21 million per day. The production comes from a variety of reservoirs including siliciclastic , fractured , , (limestones). The total cumulative production from the Campos Basin by 2003 was 3.9 billion barrels of oil with remaining reserves of 8.5 billion barrels.[Bruhn et al., 2003]
In February 2010, a new 65 million barrel discovery was made by Petrobras near the Barracuda oil field.[Flower 2010]
In 2020, the Enchova, Enchova Oeste, Marimbá, Piraúna, Bicudo, Bonito, Pampo, Trilha, Linguado, and Badejo concessions were sold by Petrobras to Trident Energy. These concessions are located in the shallow part of the Campos Basin, offshore Rio de Janeiro state.
See also
Bibliography and further reading
Brazil general
Campos Basin geology
Campos Basin exploration
External links
