From Brazil's mountainous coastline near São Paulo, the azure blue of the South Atlantic shimmers towards the horizon.

The idyllic, forested shoreline has long held the key to the Brazilian economy, offering an export point for sugar, coffee and wood from the interior. Now, however, the waters themselves may be about to dispense an even richer treasure.

Deep beneath the ocean lies what could be one of the world's largest oil discoveries - at least five billion barrels' worth, but probably far more.

As oil prices soar to record highs of $139 per barrel (and likely more to come), it promises to transform Brazil into one of the world's biggest producers, with profound implications for the country's economy and society.

The man who made the discoveries is in little doubt about their significance. “It's an extraordinary position for Brazil to be in,” Guilherme Estrella, the director of exploration and production at Petrobras, said. “We have opened a new frontier in oil.”

The discoveries in the Santos Basin roughly 300kilometres (186 miles) offshore have been made in five fields spanning an area about 100 kilometres across.

Petrobras, the Brazilian state oil company that is leading the operation alongside Britain's BG Group and Repsol, of Spain, considers that one field alone - Tupi - probably contains between five billion and eight billion barrels of oil (Brazil's existing, proven oil reserve base is 14 billion barrels).

It would be the largest single oil discovery since the Kashagan field was identified in Kazakhstan in the mid-1990s.

Moreover, the potential for further discoveries is breathtaking. There has been speculation that a neighbouring field - Carioca - could contain as much as 33 billion barrels of oil.

Four others - Parati, Bemte-Vi, Jupiter and Caramba - are believed to hold vast reserves and there are other areas where exploration has not yet begun.

“Tupi is just a small part of this, so anyone can imagine what the real [total] estimate could be,” Mr Estrella said. He refused to be drawn on exact numbers until further appraisals had been carried out.

Globally, such repeated, giant discoveries have not been made since the 1970s and Mr Estrella can barely contain his excitement at what this could mean for Brazil.

“We have created a concrete base on which we can plan our economic and social development for decades,” he said.

Nevertheless, exploiting these vast reserves of oil and gas will not be easy. Not only do they lie a long way offshore in waters that are 2,000 to 3,000 metres deep, but the oil itself lies at least a further 2,000 metres beneath that under a thick layer of salt rock.

Extracting oil at such extraordinary depths and pressures represents an unprecedented challenge.

“We need to develop new technologies, new equipment, new materials,” Mr Estrella said. He believes that automation and the use of robots could provide a large part of the solution.

Present industry estimates suggest that it could cost at least $50 billion (£25 billion) and take the best part of a decade to develop Tupi alone.

Cost and expertise are not the only challenges. With sudden oil wealth comes the threat of corruption - an affliction already well-recognised in Latin America's largest country - and concern that by exploiting this resource, Brazil could become a leading contributor to global warming.

Yet it is hard to deny Brazil's good fortune. Not only are global crude prices soaring, while many of the world's leading exporters are struggling to maintain production, Brazil has just become a net exporter and its current production of 1.9 million barrels per day is set to grow by 7.5 per cent per year, leaving aside the Santos Basin.

With global demand continuing to grow, the discoveries put Brazil in an immensely powerful position.

There has been talk - dismissed by many - of membership of Opec, the oil cartel, and Mr Estrella speaks, only half-joking, of permanent membership of the United Nations Security Council being the logical next step. It is an illustration of just how influential Brazil, the land of samba and football, is about to become.

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