As recently as 2005, most exploration offshore Brazil took place above the huge salt sheets that blanket much of the area.

Then Petrobras drilled its Tupi discovery. Suddenly the term “presalt” (what Gulf of Mexico explorers call “subsalt”) was on everyone’s lips.

At a technical session Monday at the Offshore Technology Conference, Marcio Mello from HRT Petroleum gave a talk about recent presalt discoveries and the prognosis for this region in the future. The prognosis, according to Mello, is excellent.

The region formed 146 million years ago as South America split away from Africa. As the continent drifted farther west, a large shallow lake formed, with lots of organic matter. Seawater eventually entered this lake and deposited layers of salt. Salt, Mello said, is one of the best sealing mechanisms there is.

Petrobras is sitting pretty on these reserves, having exclusive ownership of 10 blocks in the Santos Basin and sharing partnerships on an additional 17. Altogether the company has licensed 7,917 sq miles (13,000 sq km) of acreage.

So why chase the presalt? Mello had several reasons. First of all, the geology in the postsalt region differs from the Campos to the Santos to the Espiritu Santo basins. Presalt, they are one continuous province.

Secondly, an analysis of the oil present shows that most of the oil in this deeper section is lacustrine in nature, meaning it is very high-quality oil. Thirdly, the source rocks are rich and thick and contain massive amounts of organic manner. And though there are different producing reservoirs, they are generally characterized by good porosity and permeability. Even the Coquinas, which is a carbonate reservoir, has 20 to 30% porosity.

These reservoirs also are not high-pressure or high-temperature, despite their depth. Mello said that salt is a good conductor of temperature, so the temperature moves up through the salt body, leaving the temperature in the Tupi reservoir at generally less than 212 Fahrenheit.

In all, these characteristics equal “super-giant reservoirs,” Mello said. The oil is 28 to 30 degrees API, and Petrobras is expecting initial flow rates at 15,000 to 20,000 barrels per day.

“This is not expensive,” Mellos said. “You do need money and logistics. But the technology required is not a big deal.”