Subsalt seen as promising exploration frontier for Brazil
Dayse Abrantes
Peter Howard Wertheim
Discoveries point toward huge light-oil reserves
Brazil’s subsalt exploration is focused in the Santos, Campos and Espirito Santo basins. It is expected to spread to the eastern margin Jequitinhonha and Camamu-Almada basins, Petrobras Corporate Executive Manager Francisco Nepomuceno Filho, told Offshore magazine in an exclusive interview.
All these basins, even the Campos, still are unexplored for subsalt targets. But, the subsalt section congregates all the elements considered essential for the existence of oil and gas accumulations, added Nepomuceno.
Although private sector geologists say that there may be another Campos basin subsalt, with more than 10 Bbbl of light oil reserves, Petrobras was first to affirm that Campos basin subsalt section still has billions of barrels of light oil potential to be explored, said Nepomuceno.
“Due to the urgent necessity of importing light oil to be blended at Petrobras’ old refineries with heavy crude (the bulk of Brazil’s oil output) and because of the huge tertiary/upper cretaceous oil discoveries that occurred during the ’70s, ’80s, and first half of the ’90s, Brazilian exploration remained predominantly concentrated at the Campos basin Tertiary and Upper Cretaceous reservoirs. Campos and other basins subsalt exploration was sporadic,” he explained.
“Since 2004, however, subsalt exploration has become an important exploration focus, both in the Campos basin as in the adjacent Espírito Santo and Santos basins. Based upon their interpretation Petrobras geologists and geophysicists expected to find porous-permeable reservoirs and good quality oil, as actually occurred,” added Nepomuceno.
Along the coastline from Santa Catarina state, south of Brazil to Paraíba and Pernambuco states, in northeastern region, there are sedimentary basins with a total sedimentary area of near 770,000 sq km (297,299 sq mi), with water depths up to 3,000 m (9,842 ft).
From south to north, the following gives the areas of each sedimentary basin: Santos, 350,000 sq km (13,514 sq mi); Campos, 115,000 sq km (44,402 sq mi); Espírito Santo/Mucuri, 120,000 sq km (46,332 sq mi); Cumuruxatiba, 39,000 sq km 15,058 sq mi); Jequitinhonha, 23,000 sq km (8,880 sq mi); Camamu-Almada, 23,000 sq km (8,880 sq mi); Jacuipe, 13,000 sq km (5,019 sq mi); Sergipe-Alagoas, 46,000 sq km (17,761 sq mi); and Pernambuco-Paraiba, 40,000 sq km (15,444 sq mi).
Seismic surveys have been conducted predominantly in the Campos, Santos, and Espírito Santo/Mucuri basins, and more recently in the Jequitinhonha, Camamu-Almada, and Sergipe-Alagoas basins. In the other basins, due to the fact that there were no exploration concessions available in the ANP Bid Rounds, there is less available seismic data.
Santos basin subsalt discovery
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Volume 67 Issue 1
January 2007
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