GEORGE MITCHELL IS almost 93 years old, but he’s still drilling for oil and gas.

A native of Galveston, Texas – next to the port city of Houston – Mitchell lives in a suite in one of his hotels on the Galveston sea front. He’s just had knee surgery (too much tennis, he concedes) and so gets about on a small, motorized vehicle. He has lived here since his wife, Cynthia, died after a long battle with Alzheimers last year. “A terrible disease,” he says, shaking his head.

The son of a Greek immigrant who shined shoes for a living, Mitchell is a billionaire several times over. But when he talks about how he made his fortune, the money itself appears to be of little interest to him. He could have made far more than he did, he admits, but he had already made enough. By the time he sold his company, Mitchell Energy and Development Corporation, for $3.5 billion in 2002, there were other achievements that mattered more to him.

Described by those who know him as “a visionary”, Mitchell is, in large part, responsible for the natural gas boom that has transformed the US energy industry over the past decade, after he spent several years honing the technique known as hydraulic fracturing (or simply “fracking”) to extract natural gas from shale rock.

A geologist by training, he and his brother set up a small company in Houston shortly after the second World War.

“Houston had to be the place to go,” he insists, “because they couldn’t get material to drill wells during the war.” Up until that point, all steel production had been directed toward the war effort, and Mitchell saw an opportunity open up as the war came to an end. They started small. He did the geology late at night (the logs he needed to determine where the oil and gas deposits were located were too expensive, so he borrowed them overnight for a small fee), they leased some land and set about drilling their first wells.

Forty years later, in the early 1980s, Mitchell’s company had become one of the biggest in Texas. But he had a problem. He figured he had about 10 years of gas supply left in his existing land leases and needed to find a new source. He knew there was gas locked in the Barnett Shale, an area around which he had been operating for several decades, but nobody knew how to release it. So he told his staff that they had to find a way.

“The industry didn’t give a damn about the Barnett,” says Dan Steward, another geologist who Mitchell drafted in to work with him on what, at that time, was seen as a lost cause. “George always pushed technology.”

And he pushed his people too. “He’s about as nice a man as you could meet, but if he disagrees with you he can cuss you out like he was a sailor,” Dan laughs.

It took seven years of experimenting and several million dollars, but Mitchell and his team figured out how to make it work. Unlike traditional deposits of gas and oil, shale gas is locked within the cells of the rock. In other words, it is highly dispersed throughout the rock, rather than bunched in a concentrated bubble. To release it, they had to break open the shale, thus allowing it to make its way to the atmosphere.

Hydraulic fracturing in and of itself was not new. It had first appeared in conventional drilling in the 1940s, where mud was pumped into oil wells at high pressure to release the deposits below. But what Mitchell’s team eventually figured out was that, by pumping a mix of water, sand and some chemicals into the shale-rock formations at high pressure, they could fracture the shale. The sand kept the fracture open enough to allow the gas to flow.

It took several modifications, but with every improvement they made, Mitchell and his team edged closer to the goal of making it economically viable to produce shale gas. By switching to fresh water from a gel substance they had initially started out using, they managed to slash the cost of each fracturing procedure from $365,000 to $80,000. They were also figuring out how to release more and more gas with each attempt.

By the time Mitchell sold his company to Devon Energy in 2002, the rest of industry was finally starting to take notice.

What Devon added to the mix was a technique known as horizontal drilling. Instead of just drilling a hole straight down into the ground for several thousand metres, once the drill got to a certain point, they turned it sideways, and continued to drill horizontally. Now, they could fracture the rock at several points along this new well bore, both along its horizontal stretch and its vertical stretch. And that’s when the shale gas boom really began to take off.