Brazil on Thursday said it will auction concessions to drill and explore an offshore oil field believed to hold up to 12 billion barrels of crude, the country\'s largest find. The tender process for the Libra oil field will take place in mid-October, said National Oil Agency (ANA) director Magda Chambriard, changing an originally scheduled date in late November. \"I have worked in the oil industry for 30 years and have never seen anything like it,\" she said. \"Something this size will raise eyebrows all over the world.\" Libra, discovered in 2010, is within the vast Santos Basin, located some 180 kilometers off the coast of Rio de Janeiro. Oil in the Santos basin, first discovered in 2007, lies under a thick layer of salt between five and seven kilometers below the ocean surface. Brazil\'s first oil field auction in five years -- 142 land and ocean oil blocs in unexplored regions in north and north-eastern Brazil -- in mid-May raked in a record $1.4 billion. The ANA estimates that Libra holds between 26 and 42 billion barrels of crude. Chambriard said that its recoverable reserves of between eight and 12 billion barrels are based on an estimated 30 percent on-site recovery rate. The estimates, completed in May, are based on data obtained by drilling in the area and updates previous estimates, she said. By way of comparison, the so-called Marlim field, which is the most productive one Brazil now has operating -- at 600,000 barrels per day -- has a recoverable oil volume of 2 billion barrels, Chambriard said. Another, called Roncador, has 2.5 billion, she added. But Libra is another thing altogether. Libra, which covers 1,500 square kilometers, will be auctioned off as a single bloc under 2010 legislation that increases the government\'s control over the pre-salt reserves and its share of the profits. The next pre-salt oil bloc auction will not likely be held until 2015, Chambriard said. Brazil currently consumes some 800 million barrels of crude a year, so in the Libra reserve alone \"there is enough oil to satisfy the current consumption rate for 12 years,\" said Florival Carvalho, a senior ANP official. Brazil currently extracts some 300,000 barrels per day from the pre-salt region. By 2017 Petrobras expects to extract 962,500 barrels per day from the underwater area -- tripling its current production -- and by 2020 they expect that more than half of the company\'s total production will come from the pre-salt region. In 2012 Petrobras produced an average of 1.98 million barrels per day, a figure they hope to double by 2020.