
The pre-salt layer is a
diachronous
In geology, a diachronism ( Greek ''dia'', "through" + ''chronos'', "time" + ''-ism''), or diachronous deposit, is a sedimentary rock formation in which the material, although of a similar nature, varies in age with the place where it was deposite ...
series of geological formations on the
continental shelves
A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...
of
extensional basins formed after the break-up of
Gondwana
Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
, characterized by the deposition of thick layers of
evaporites
An evaporite () is a water-soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as ocean ...
, mostly
salt
In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...
. Some of the
petroleum
Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring un ...
that was generated from sediments in the pre-salt layer has not migrated upward to the post-salt layers above due to
salt domes. This is especially common off the coast of
Africa
Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...
and
Brazil
Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
. Total pre-salt oil reserves are thought to be a significant fraction of the
world's oil reserves. According to Brazilian oil and gas company
Petrobras
Petróleo Brasileiro S.A., better known by and Trade name, trading as the portmanteau Petrobras (), is a Brazilian state-owned enterprise, majority state-owned multinational corporation in the petroleum industry headquartered in Rio de Janeiro. ...
, the oil and natural gas reserves lie below an approximately thick layer of salt, which in turn is beneath more than of post-salt sediments in places, which in turn is under water depths between in the
South Atlantic
The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for ...
. Because of this, drilling through the rock and salt to extract the pre-salt oil and gas is very expensive.
Brazil

The
oil reserves
An oil is any chemical polarity, nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobe, hydrophobic (does not mix with water) and lipophilicity, lipophilic (mixes with other oils). Oils are usually flammable ...
found in the pre-salt layer of the
Brazilian coast are within the maritime area considered the
exclusive economic zone
An exclusive economic zone (EEZ), as prescribed by the 1982 United Nations Convention on the Law of the Sea, is an area of the sea in which a sovereign state has exclusive rights regarding the exploration and use of marine natural resource, reso ...
of Brazil. They are reserves with oil considered of medium to high quality, according to the
API scale. The set of pre-salt oil fields extends along the coast from the state of
Espírito Santo
Espírito Santo (; ) is a state in southeastern Brazil. Its capital is Vitória, and its largest city is Serra. With an extensive coastline, the state hosts some of the country's main ports, and its beaches are significant tourist attracti ...
in the north, as far as
Santa Catarina in the south, where the ocean depths range from 1,000 to 2,000 meters, and is found between 4,000 and 6,000 meters deep in the
subsoil
Subsoil is the layer of soil under the topsoil on the surface of the ground. Like topsoil, it is composed of a variable mixture of small particles such as sand, silt and clay, but with a much lower percentage of organic matter and humus. The su ...
, thus reaching up to 8,000 meters below sea level, including a salt layer ranging from 200 to 2,000 meters thick.
''"A produção no pré-sal"''. ''Agência Brasil'', 31/08/2009
/ref>
The current findings from Petrobras
Petróleo Brasileiro S.A., better known by and Trade name, trading as the portmanteau Petrobras (), is a Brazilian state-owned enterprise, majority state-owned multinational corporation in the petroleum industry headquartered in Rio de Janeiro. ...
and other companies in the province of the pre-salt, located in the Brazilian continental shelf
A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...
, implicate reserves of over 50 billion barrels of oil, a volume four times greater than the current national reserves, roughly 14 billion barrels.
In this province, there may be large oil and natural gas reserves located under salt layers that extend for 800 kilometers along the Brazilian coast – from the coast of Santa Catarina to the coast of Espírito Santo
Espírito Santo (; ) is a state in southeastern Brazil. Its capital is Vitória, and its largest city is Serra. With an extensive coastline, the state hosts some of the country's main ports, and its beaches are significant tourist attracti ...
– and are up to 200 km wide.
Some estimates give the total area of the pre-salt as 122,000 km2. Of this total, concessions have already been granted for 41,000 km2, and 71,000 km2 have not yet been tendered.
Pre-salt oil is of good quality, although it is found in reserves that are in deep-sea areas and under thick layers of salt, requiring large-scale investment to extract it.
Since 2006, Petrobras has drilled 11 oil wells in the Santos Basin
The Santos Basin () is an approximately large mostly offshore sedimentary basin. It is located in the south Atlantic Ocean, some southeast of Santos, São Paulo, Santos, Brazil. The basin is one of the Brazilian basins to have resulted from th ...
, near Rio de Janeiro state
Rio de Janeiro () is one of the 27 federative units of Brazil. It has the second largest economy of Brazil, with the largest being that of the state of São Paulo. The state, which has 8.2% of the Brazilian population, is responsible for 9.2% of ...
. All these oil wells have been successful. At the prospects of Tupi and Iara alone, which are located in the BM-S-11 block, Petrobras already estimates that there are 8 to 12 billion barrels of recoverable oil. This block alone can almost double the current Brazilian oil reserves
An oil is any chemical polarity, nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobe, hydrophobic (does not mix with water) and lipophilicity, lipophilic (mixes with other oils). Oils are usually flammable ...
.
Angola
The first pre-salt discoveries in Angola
Angola, officially the Republic of Angola, is a country on the west-Central Africa, central coast of Southern Africa. It is the second-largest Portuguese-speaking world, Portuguese-speaking (Lusophone) country in both total area and List of c ...
were the Denden-1 well in Block 9 in 1983, operated by Cities Services at the time, and the Baleia-1A well on Block 20 in 1996, operated by Mobil
Mobil Oil Corporation, now known as just Mobil, is a petroleum brand owned and operated by American oil and gas corporation ExxonMobil, formerly known as Exxon, which took its current name after history of ExxonMobil#merger, it and Mobil merge ...
(now ExxonMobil
Exxon Mobil Corporation ( ) is an American multinational List of oil exploration and production companies, oil and gas corporation headquartered in Spring, Texas, a suburb of Houston. Founded as the Successors of Standard Oil, largest direct s ...
). Both blocks are now operated by the U.S.-based Cobalt International Energy. The Danish company Maersk Oil made the first recent pre-salt discovery in the Kwanza Basin in late 2011 with the Azul well on Block 23. Maersk continues to study the results of the well and plans to appraise it.
Cobalt International has had the most success with pre-salt exploration in Angola, making multiple pre-salt well discoveries in Blocks 20 and 21 ( Cameia, Mavinga, Lontra
''Lontra'' is a genus of otters from the Americas.
Species
These species were previously included in the genus ''Lutra'', together with the Eurasian otter
The Eurasian otter (''Lutra lutra''), also known as the European otter, Eurasian river ...
, Bicuar, and Orca
The orca (''Orcinus orca''), or killer whale, is a toothed whale and the largest member of the oceanic dolphin family. The only extant species in the genus '' Orcinus'', it is recognizable by its black-and-white-patterned body. A cosmopol ...
). In January 2011, Angola announced that it awarded 11 pre-salt offshore blocks in the Kwanza basin, following a closed licensing round in which a few selected International Oil Companies (IOCs) were invited. IOCs that were awarded blocks include Petrobras
Petróleo Brasileiro S.A., better known by and Trade name, trading as the portmanteau Petrobras (), is a Brazilian state-owned enterprise, majority state-owned multinational corporation in the petroleum industry headquartered in Rio de Janeiro. ...
, Maersk Oil, Cobalt International, BP, Repsol
Repsol S.A.
El Nuevo Herald, 2012-05-31[Originally an init ...]
, TotalEnergies
TotalEnergies SE is a French multinational integrated energy and petroleum company founded in 1924 and is one of the seven supermajor oil companies. Its businesses cover the entire oil and gas chain, from crude oil and natural gas explorati ...
, Eni
Eni is an Italian oil and gas corporation.
Eni or ENI may refer to:
Businesses and organisations
* Escuela Nacional de Inteligencia, the Argentine intelligence academy
* Groupe des écoles nationales d’ingénieurs (Groupe ENI), a French engi ...
, ConocoPhillips
ConocoPhillips Company is an American multinational corporation engaged in hydrocarbon exploration and production. It is based in the Energy Corridor district of Houston, Texas.
The company has operations in 15 countries and has production in t ...
, and Statoil
Equinor ASA (formerly Statoil and StatoilHydro) is a Norwegian multinational energy company headquartered in Stavanger, Norway. It is primarily a petroleum company operating in 36 countries with additional investments in renewable energy. In th ...
. Some of those companies have slowed their investments in Angola's pre-salt reserves, and some wells have been closed and abandoned. The combination of disappointing results and geological complexity, compounded by the low-oil-price environment, has resulted in reduced investment in Angola's pre-salt areas.
References
External links
*
*
*
* {{cite web , url=http://www.midiaindependente.org/pt/blue/2010/08/476211.shtml , title=Regulatory political conferencing of geological for exploitation pre-salt , date=August 2010 , access-date=2012-04-24 , archive-url=https://web.archive.org/web/20170909233542/https://midiaindependente.org/pt/blue/2010/08/476211.shtml , archive-date=2017-09-09 , url-status=dead
Geology of the Atlantic Ocean
Geology of Angola
Geology of Brazil