Brazil awarded 72 onshore natural gas and shale gas exploration blocks Thursday in a controversial auction marked by complaints from environmentalists about a lack of regulation.

The National Petroleum Agency, or ANP, said in a statement that the auction generated $72 million in revenue, awarding 72 of the 240 concessions on offer.

Forty-nine blocks were snatched by state-run oil giant Petrobras either alone or as part of a consortium.

An ANP spokeswoman said four of the 11 foreign companies that took part in the auction were awarded blocks: France's GDF Suez, Colombia's Petrominerales, Panama's Trayectoria Oil & Gas and GeoPark from Bermudas.

ANP head Magda Chambriard stressed that the licensing round aimed to "sow the culture" of natural gas drilling in Brazil.

Blocks on offer covered 168,348 square kilometers (65,000 square miles) in the states of Amazonas, Acre, Alagoas, Bahia, Goias, Maranhao, Mato Grosso, Parana, Piaui, Sao Paulo, Sergipe and Tocantins.

The sale, initially planned for two days, marked the third round of energy auctions this year in Brazil, which in 2007 discovered huge so-called pre-salt oil reserves deep below the Atlantic Ocean, bedrock and hot salt beds.

The total reserves could hold more than 100 billion barrels of high-quality recoverable crude and turn Brazil into one of the world's top exporters.

The auction raised concern because it also involved shale gas drilling, which has the potential to contaminate surface or groundwater and cause air pollution.

"Drilling with hydraulic fracturing techniques raises a major controversy in all countries over the huge environmental impacts and led some European countries like France to ban it," the SocioAmbiental Institute noted at a recent public hearing.

But Chambriard stressed that Brazil was working on regulations to ensure that such exploration would meet environmental standards.

Source: AFP