“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 start-ups in a Brazilian industry long dominated by the state-run behemoth, Petrobras, and multinational giants.

This is not the first time that Mello, 58, has worked in the Solimoes basin, a swath of jungle twice the size of Maryland and located 2,500 miles northwest of Rio. More than 30 years ago, he was a young geologist there with Petrobras.

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

Mello gets revved up just talking about oil, particularly Amazon crude.

In his office on the 10th floor of a sleek tower, he has a mounted telescope that he uses to track the oil-producing platform vessels being towed out to sea.

And he waxes on about the importance of oil to modern life — not just for motor fuel, he pointed out, but as a component of pretty much every object in his office.

“I dream oil 23 hours a day. I don’t sleep. My mind is rrrrrr,” he said, making the sound of a motor.

“Oil is life, my friend,” Mello added, noting that carbon dioxide — that byproduct of combustion and bane of climate scientists — is used to produce food for plants.

“People think oil is pollution,” he said. “That is a big mistake.”

Of course, such views are widely contested. And Mello’s nonstop narration of all his plans, big and small, prompt some observers in the oil industry to describe him as “agitated,” “unconventional” and “egotistical.”

Mello seems to relish the nicknames bestowed on him in industry publications because of his work discovering oil, including Mr. Go Deep and the Oil Detective.

‘The best oil we have’

Cleveland Jones, a petroleum engineer who teaches at the State University of Rio de Janeiro, believes that 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.