RIO DE JANEIRO —

Márcio Mello often talks of eureka moments.

The veteran geoscientist's biggest came when he decided his petroleum-research firm should become an oil producer, taking advantage of the rich sedimentary basins that have lured oil companies to Brazil.

"This is very funny, because one day I was here and I just had the idea," said Mello, recounting his thought process with bubbling enthusiasm. "I say, 'Why don't I fulfill my dream and build my own oil company? Why am I finding oil for the other ones?' "

It was an expensive gamble, Mello said, but he had an easy explanation: "You know, Brazil is like that, where everything is possible."

His company was buoyed by an initial public offering in 2010 that netted $1.5 billion and an alliance with Russia's TNK-BP. Now HRT Oil & Gas is drilling in one of the most challenging and isolated spots on Earth: the heart of the Amazon.

Mello represents a new breed of Brazilian oilmen, and his company's arrival heralds the entry of startups in a Brazilian industry long dominated by the state-run behemoth, Petrobrás, and multinational giants.

This isn't the first time Mello, 58, has worked in the Solimões basin, a swath of jungle 2,500 miles northwest of Rio. More than 30 years ago, he was a young geologist there with Petrobrás.

"I was there in 1979, drilling a well, and I dreamed that one day I would be back. I always have the Amazon in my mind, and I knew there was a huge potential."

Cleveland Jones, a petroleum engineer who teaches at the State University of Rio de Janeiro, thinks Mello's focus on the Amazon could be misdirected, given that Brazil's energy future appears to be under the waves far off Rio's coast.

"There's a lot of potential there. Why go crazy somewhere else?" he said.

But energy analysts say Mello happens to be right about the Amazon.

Magda Chambriard, director of the National Petroleum Agency, regulator of Brazil's oil industry, called the crude produced in the jungle "the best oil we have in Brazil" because it requires far less refining than the heavy oil pumped offshore.

Jean-Paul Prates, director of the Center for Strategies in Natural Resources and Energy in Natal, in northeastern Brazil, said geologists have known for years that the Amazon has "excellent potential" for oil and natural-gas production. Petrobráas pumps more than 100,000 barrels a day there.

Prates said with so many multinational oil companies drilling off the coast of Brazil, it made sense for Mello to make his mark elsewhere.

"That's why Márcio is trying to get into that niche and say, 'We're the jungle company,' " Prates said.

What oil-industry observers agree on is the difficulty of drilling in virgin forest. "The only really big obstacle or challenge, let's say, is the jungle itself," Prates said.

Mello talks a lot about that, too. HRT did not build roads into the Solimões, Mello said, opting instead for helicopters to fly in workers and drilling equipment. The company is laying flexible pipelines to carry oil over hills and around vegetation. The crude would be conveyed to floating terminals and transported by river to the first big city, Manaus.

A handful of wells are operating now, and HRT foresees as many as a dozen online by the end of the year, with production expected to hit 50,000 barrels a day in 2014. With 2,500 workers, it is not a small operation.

Yet, HRT's activities have not met with the kind of bitter protests oil companies face in the Ecuadorean or Peruvian Amazon.

"The footprint on oil drilling — the way HRT is doing it — is significantly less than what is usually produced in the oil sector," said Virgílio Viana, chief executive of the Foundation for a Sustainable Amazon, or FAS, an environmental organization.

Mello is already looking farther afield.

HRT is gearing up to produce off the coast of Namibia, and Mello said he wants to drill in Colombia. The goal is to turn his company into an international player.

"That is our dream," he said. "You cannot perform this dream standing in one place."