July 1 (Bloomberg) -- New technology may help companies exploring for oil in the so-called pre-salt area offshore Brazil, home to the largest crude find in the Americas in three decades, Sanford C. Bernstein & Co said.

Most seismic imaging bounces off salt because of its different properties, “meaning that geophysicists are effectively working blind below salt,” Neil McMahon, a London- based analyst at Bernstein, said in a report today. “Oil companies and seismic acquisition companies have started to develop a host of techniques to improve the situation.”

The pre-salt area runs 800 kilometers (500 miles) along Brazil’s coast and has oil deposits beneath a layer of salt resting as much as 3,000 meters beneath the ocean surface and another 3,000 to 5,000 meters below the seabed. Brazil’s Petroleo Brasileiro SA has estimated that the pre-salt Tupi field may have as much as 8 billion barrels of oil, the largest find in the Americas since Mexico’s Cantarell field in 1976.

“A lot of the challenges of finding and developing oil in the pre-salt, especially in Brazil, can be put down to rock characteristics, and not just the deepwater environment,” McMahon said.

Developments including Petroleum Geo-Services ASA’s GeoStreamer technology may help, the analyst said. That company later this year plans to publish the results of a GeoStreamer survey carried out offshore Brazil, according to McMahon.

“We continue to believe that the exploration in the pre- salt in Brazil is not over,” McMahon said. “The complexity of the geology is becoming a key issue and more wells will be required to complete the pre-salt picture.”

Exxon Mobil Corp., the largest U.S. energy company, on June 3 said it’s taking rock samples from its Guarani well in the BM- S-22 block off the coast of Brazil to see how much oil it holds. Exxon said it plans to follow the evaluation work with a third well in the same geological formation.

To contact the reporter on this story: Joao Lima in Lisbon at jlima1@bloomberg.net

Last Updated: July 1, 2009 08:00 EDT