The pre-salt layer is a diachronous series of geological formations on the continental shelves of extensional basins formed after the break-up of Gondwana, characterized by the deposition of thick layers of evaporites, mostly salt. Some of the petroleum that was generated from sediments in the pre-salt layer has not migrated upward to the post-salt layers above due to salt domes.[1] This is especially common off the coast of Africa and Brazil. Total pre-salt oil reserves are thought to be a significant fraction of the world's oil reserves.[2][3] According to Brazilian oil and gas company Petrobras, the oil and natural gas reserves lie below an approximately 2,000 metres (6,600 ft) thick layer of salt, which in turn is beneath more than 2,000 metres (6,600 ft) of post-salt sediments in places, which in turn is under water depths between 2,000 and 3,000 metres (6,600 and 9,800 ft) in the South Atlantic. Because of this, drilling through the rock and salt to extract the pre-salt oil and gas is very expensive.
- ^ Idel Waisberg (December 3, 2011). "Brazil's Pre-Salt Layer". Retrieved April 9, 2014.
- ^ Brainard, Lael; Martinez-Diaz, Leonardo, eds. (2009). Brazil As an Economic Superpower?: Understanding Brazil's Changing Role in the Global Economy. Brookings Institution. p. 33. ISBN 9780815703655.
- ^ Selley, R.C., ed. (1997). African Basins. Elsevier. p. 180. ISBN 9780080540825.