Brazil's giant state oil company, Petrobras, has uncovered a "giant" deep-water offshore oil well that could double the reserves of this energy-hungry nation.

The find, announced yesterday, has come from the floors of the South Atlantic, in the Campos Basin, 63 miles off the coast of Rio de Janeiro state.

Tests still are being conducted, but officials of Petrobras and the Ministry of Mines and Energy have hopes that this newest well will be Brazil's largest, producing a potential 15,000 barrels a day.

The deep-water well, said to be the world's deepest, lies more than 3,000 feet (943 meters) below the ocean's surface. It represents a giant leap forward for this petroleum-importing nation.

Labeled only "3-rjs-319," the well is believed to sit on the edge of an oil-rich shelf containing up to 2 billion barrels of oil.

Fully tapped, the Campos Basin could double Brazil's 2-billion-barrel oil reserve, enough to last about 40 days.

In the last decade, Brazil invested heavily in a national highway system and made itself over into one of the world's largest automobile manufacturers. Virtually all transport of food and consumer goods was by truck over the sprawling interior of this country, as large as the continental United States.

These factors weighed heavily during the heyday of Organization of Petroleum Exporting Countries price hikes in the 1970s, which left Brazil's oil-guzzling economy with a near $10 billion petroleum import tab and swelled the country's foreign debt, now standing at $103 billion.

Just five years ago, Brazil imported almost 90 percent of its petroleum. Today, the government has managed to curb consumption while increasing domestic oil production to nearly half of the million barrels a day Brazil needs. The nation now produces more petroleum than three OPEC countries -- Ecuador, Gabon and Qatar -- and has edged close to Argentina in total output.

At the same time, Brazil has tapped its vast rivers, boosting hydroelectric power 500 percent in the last 20 years. Also, fuel alcohol distilled from sugar cane now amounts to the energy equivalent of 300,000 barrels a day of petroleum.

Authorities admit that this nation of 131 million is still a long way from energy self-sufficiency.

"We are heartened by this find, but not euphoric. There is still a long way to go," said a mines and energy official in Brasilia.