Reinterpreting the South Atlantic Pre-Salt ‘Microbialite’ reservoirs: petrographic, isotopic and seismic evidence for a shallow evaporitic lake depositional model
The first encounter of the Pre-Salt Aptian ‘Microbialite’ carbonate reservoirs (the Barra Velha Fm) in 2005, in the Parati field, Santos Basin, was followed by additional discoveries such as the multi-billion barrel Lula (Tupi) field. Now, nearly 30 more discoveries have been made in the basin such as Libra and Sapinhoa, with recoverable reserves estimated as >30 BBOE, according to ANP. In addition, discoveries have been made in the adjacent Campos Basin, including the Pão de Açúcar field (Viera de Luca et al., 2017), where the same unit is known as the Macabu Fm., and also in the Kwanza Basin, West Africa (Saller et al., 2016). After deposition in a late rift setting, the Barra Velha Fm and its equivalents were buried by more than 1 km of marine origin evaporites of the Ariri Fm and its equivalents, as the Albian Ocean seeped and poured into the basin.