Sometimes it’s not who you know, it’s who you get to know.

In late 2006, documentary filmmaker Rachel Boynton was trekking through the oil-rich Niger Delta region of southern Nigeria, and gaining zero traction with masked militants who were regularly blowing up pipelines to disrupt the global economy and protest the official corruption and income disparity arising from the exploitation of their nation's precious natural resource.

Getting the militants on camera would be vital to the real-life drama of Big Men, her chronicle of the petroleum-fueled pursuit of wealth and status in Africa, which opens Friday in New York and later on around the country.

“There was an email address that all the journalists were using to contact the militants, and I was basically getting the answer, ‘We don’t know who you are. Good luck,’ ” Boynton says. “I was traveling around with Sebastian Junger, who was writing an article for Vanity Fair, and he was getting the same responses,” she recalls. “Then, one day they wrote back to Sebastian, ‘We’ll give you whatever you want. Just send us a signed copy of your book.’ They must have Googled him.”

Junger, of course, is the author of A Perfect Storm, among other best-sellers; he’s also a swashbuckling war correspondent and a celebrated filmmaker. He’s rich and famous--a quintessential big man. “I took that as a lesson: Oh, OK, I get it,” Boynton says. “It was clear that in order to gin up some street cred here, I needed to bring on a high-powered, well-recognized executive producer, hopefully from Hollywood, who can legitimize me.”

And so, after consulting with her husband, feature film director Steven Shainberg, Boynton decided to approach Brad Pitt, a socially conscious actor who occasionally throws his star power behind worthy causes, including documentaries. Pitt—a big man in Hollywood—agreed to sign on as an executive producer. “And voilà!” Boynton says. The Nigerian oil militants quickly fell into line.

A gang calling themselves the “Deadly Underdogs”--whose ski mask-wearing members brandish machine guns, sing war songs, dance war dances and basically preen for Boynton’s camera, the militant equivalent of performance art--are actually secondary characters in her documentary. The dysfunctional oil economy of Nigeria--from which high government officials and other well-connected types looted or wasted nearly half a trillion dollars of the people’s money from 1960 to 1999, according to reliable estimates--serves as context for her story, which might otherwise be titled “A Tale of Two Countries.”

The central narrative of Big Men takes place in Ghana, some 200 miles to the west. Boynton somehow convinced Dallas oilman James Musselman and his British-born colleague Brian Maxted--the chief executive officer and chief operating officer, respectively, of a privately held exploration company called Kosmos Energy--to let her shadow them with cameras and microphones as they drilled their way through layers of Ghanaian politics and bureaucracy, and the white-hot core of Wall Street, in order to reap the financial rewards of an amazing discovery. Kosmos had raised $825 million in private equity investment from Warburg Pincus and the Blackstone Group and located the country’s first known oil reserves: a multi-billion barrel, deep-sea deposit, 40 miles off the Ghanaian coast in the Atlantic Ocean and dubbed the Jubilee Field.

“Rachel is very persuasive,” Musselman tells me from Dallas, explaining why he allowed Boynton such an unusual degree of access after she made her pitch in the form of a PowerPoint presentation at Kosmos’s North Dallas headquarters. “She was passionate about the story. I thought it was a good story that just got better, frankly, as time went on.”

Musselman, a tall, rangy Texan who hails from a family of ranchers--that is, another big man--adds that he hoped the adventures of the plucky Kosmos would serve as a refreshing counterpoint to the public perception of oil companies as greedy, faceless giants. “We don’t enjoy great reputations a lot of the time. I thought this was a good story to show how in Ghana, we could transform the lives of a whole lot of people for the better. And I thought her contrast back to Nigeria was really good.” (The jury is still out, of course, on whether oil is transforming Ghanaian lives for the better.) Musselman continues: “I’d seen some of her previous work and I thought she’s gonna do a good job. It wouldn’t be any kind of expose’ or anything bad. I trusted her.”

For Boynton--who obtained equally intimate access for her first film, Our Brand Is Crisis, about American political consultants who give state-of-the-art advice to a presidential campaign in violence-plagued Bolivia--the trust issue is pretty simple.

“In my book, you get people to trust you by being trustworthy,” she says. “You don’t expect things to happen overnight. You understand where they’re coming from. I’m extremely straightforward. What you see is what you get. When people get to know me they have a little more confidence that I will do my utmost to fulfill my promises. If you tell me to turn off the camera, I will. And if you don’t want me around, just tell me, and I won’t be there.”

In Musselman’s case, that was never a problem. At one point in the movie--at a particularly touchy moment during the Wall Street meltdown of late 2008, when the price of oil was plunging, a new and hostile Ghanaian government was throwing up bureaucratic roadblocks, and Kosmos was also facing separate financial stresses and offering itself for sale to the highest bidder--Musselman advises Boynton: “You probably ought to mount a camera here [in his office] fulltime because it’s gonna be nuts.”

Sometimes, he says, he simply forgot that the camera was rolling and the microphone was hot, as when he’s caught musing, during the bidding process, about the possibility of going quietly to Exxon Mobil and confiding the dollar figure that would let the oil Goliath preempt the process. “And they could go to the safe and pull it out and pay you as you left,” he says to jolly laughter from Maxted and Kosmos general counsel Bill Hayes. “You want that in hundreds or twenties?”

At another point in May 2011, five months after he has been deposed as Kosmos’s CEO by the board of directors (after apparently unfounded allegations surfaced that the company had violated the Foreign Corrupt Practices Act), Musselman is shown standing on the crowded floor of the New York Stock Exchange. He watches glumly as his successor, Maxted, is happily perched on the balcony, basking in all the glory as he presides over the company’s Initial Public Offering. “This kinda sucks,” Musselman remarks--notwithstanding that he’s Kosmos’s biggest individual shareholder, with around 3 percent of a company that had opened its public career with a $6 billion market capitalization.

In Musselman's case, the thrill is probably less about money than the adrenalin rush of a wildly successful gamble. But the nature of greed, ambition, and how savagely human beings can compete with one another for scarce and valuable resources, is a constant theme of Boynton’s film. A lingering shot at the beginning of Big Men--of a swarm of fierce-looking African wasps buzzing around a pipeline valve--and later, of an army of red ants quickstepping through a muddy trench (with the sound of their insect legs amped up to monster-movie levels)--are disturbing visual metaphors.

“You got a room full of hungry people, you throw in a loaf of bread, and everybody’s trying to find a way to get to it,” says one of Boynton’s commentators, public interest lawyer Kyeretwie Opoku, who is a member of the Ghana National Petroleum Corporation, the regulatory body for the country’s nascent oil industry. “Sudden wealth is what drives industry, just because everybody wants a piece of it.”