United by cultural and trade ties as well as a common language, Angola and Brazil are close allies. Now their common geology could double their oil output.
The implications of the shared geological history between Angola – currently producing 1.8m barrels per day (bpd) – and Brazil – 2.1m bpd – is exciting petroleum geologists and oil companies.
During the Lower Cretaceous period, some 125m years ago, Angola and Brazil were part of the supercontinent of Pangea.
When continental drift started and Africa and South America began to separate from each other, extensive rift valleys formed similar to the East Africa rift system.
These valleys contained large lakes full of plant and animal material that would eventually form source rocks capable of generating oil and gas.
With continued continental separation, the sea flooded the rift valleys and, owing to the effects of evaporation, thick layers of salt were deposited.
These salt layers are up to 2km thick in parts of the Lower Cretaceous sedimentary basins of Angola and Brazil.
These impervious salt layers act as a seal above the porous sandstone and limestone reservoirs that contain the oil and gas generated by the lake sediments.
Brazil's tupi discovery
In 2007, the discovery of the giant Tupi field beneath the salt in the Santos Basin transformed Brazil's oil industry.
Petrobras, Brazil's state oil company, drilled the Tupi-1 well in 2,100m of water to a depth of 5,200m below the sea floor.
It cost almost $250m, but the reward was a well capable of producing 20,000bpd and the discovery of a field with recoverable oil reserves of about 6.5bn barrels.
The rift that made oil for Angola and Brazil
The Tupi discovery – renamed Lula after Brazil's President Luiz Inácio Lula da Silva – opened up a fairway of pre-salt oil and gas fields in the Santos and Campos basins.
Oil industry analysts such as Wood Mackenzie and IHS estimate Brazil's pre-salt reserves to hold as much as 30bn barrels.
Brazil's current production now includes more than 300,000bpd from pre-salt fields.
Petrobras says that the pre-salt discoveries could double Brazil's production within 15 years.
Angola and Brazil face each other across the Atlantic Ocean, some 7,000 km apart, but their common geological history suggests that both countries could benefit from pre-salt deposits.
Brazil's Tupi find prompted an enormous interest from oil companies, leading to the examination of geological and geo- physical data in Angola.
About two-thirds of Angola's daily oil production now comes from its deep off- shore blocks.
In 2011, Angola's state oil company Sonangol awarded 11 pre-salt blocks to companies including BP, Cobalt International Energy, Eni, Total, Repsol, ConocoPhillips and Statoil.
A year later, Maersk Oil announced the results of its Azul-1 well in Block 23, drilled specifically to evaluate a pre-salt prospect.
Azul-1 produced 3,000bpd of oil and confirmed that there was an effective working petroleum system in the pre-salt sediments of the deep-water Kwanza Basin.
Shortly afterwards, Cobalt announced the success of its first well drilled in the Kwanza Basin, Cameia-1, which tested at 5,000bpd of high-quality oil.
Cobalt says the well could produce more than 20,000bpd.
Brazilian and Angolan companies are also sharing their expertise.
Petrobras has stakes in six Angolan blocks, and Brazilian bank BTG Pactual agreed to buy 50% of Petrobras's African holdings in 2013.
Sonangol bought Starfish Oil and Gas, which held the rights to three blocks in Brazil, in 2010.
As the oil industry keenly watches the results of more drilling in Angola, a key question arises about whether the success of Brazil's pre-salt oil play can be repeated in Angola.
Would that mean that Angola can also double its oil production?
The answer lies in the geology. Petroleum geology is not precise because of the technology geologists use to search for oil and gas in ancient strata lying at depths of some 4-5km beneath the sea floor.
The drilling targets are defined by seismic waves that must penetrate the thick salt layer and then be reflected back to the surface to be recorded as seismic lines.
As with all oil and gas exploration in little-explored sedimentary basins, much risk is involved. Yet by the end of 2014, the answers to questions on Angola's future production will be much clearer. ●
*Tako Koning is a Canadian senior petroleum geologist living and working as a consultant in Luanda, Angola.