July 22 (Bloomberg) -- A Brazilian oil well drilled by Exxon Mobil Corp. in the country’s so-called pre-salt offshore fields which showed no sign of oil was “a mistake,” Brazilian Energy Minister Edison Lobao said today.

Petroleo Brasileiro SA, the state-controlled oil company, recommended the well be drilled in a different location, Lobao said today in an interview in Brasilia.

“The dry well occurred because they drilled in the wrong place. It was a mistake,” he said. “There is no risk with the pre-salt.”

Exxon failed to find oil or natural gas in the offshore Guarani well in the sub-sea block known as BM-S-22. Nelson Narciso Filho, director of Brazil’s National Petroleum Agency, said on June 14 that the dry well was a “one off.”

“We are working with Petrobras and Hess to evaluate the results of the BM-S-22 drilling program in order to plan a location of a third well to help us further evaluate the BM-S- 22 block,” Patrick McGinn, a spokesman for Exxon Mobil’s Houston-based exploration business, said today.

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 (9,843 feet) beneath the ocean surface and another 3,000 to 5,000 meters below the seabed.

Petrobras is developing the Tupi field in the pre-salt region, the largest oil discovery in the Americas since 1976, with BG Group Plc and Galp Energia SGPS SA.

Petrobras Comment

“Petrobras will not comment the subject because it is not the operator of the block BM-S-22,” the company said today in an emailed response to questions about Lobao’s remarks.

Conflicts aren’t uncommon among partners in major oil projects. Exxon Mobil disagreed with London-based BP Plc’s decision to use an unfamiliar platform design at the Thunder Horse field in the Gulf of Mexico, Stuart McGill, a former Exxon Mobil senior vice president, said in 2006.

BP, operator of the deepwater project, ignored Exxon Mobil’s plea to rely on platform designs the company had experience with in similar environments. Subsequent equipment malfunctions and bad weather that nearly sank the vessel delayed output from Thunder Horse by three years.

Petrobras fell 5 centavos, or 0.2 percent, to 31.77 reais in Sao Paulo trading at 2:15 p.m. New York time. The shares have risen 39 percent this year.

To contact the reporter on this story: Maria Rabello in Brasilia Newsroom at mrabello@bloomberg.netHelder Marinho in Rio de Janeiro at hmarinho@bloomberg.net

Last Updated: July 22, 2009 15:30 EDT