Shale Games


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"Don't frack with our water." "Support American Energy: Let's Frack!"

You've probably seen the bumper stickers with their various twists on the F-word pun. Once an issue makes it onto bumpers it's already become controversial and polarizing, and excavating the truth out the mountain of opinions becomes a more daunting task. While one chorus tells us that hydraulic fracking is the drilling method that will help solve our energy problems—while turning the U.S. into another Saudi Arabia—another says it's an environmental hazard that's irreparably tearing up the earth and mucking up the water supply.

Do a Google search on the word and you'll find millions of opinions. "But If you look at the literature in peer-reviewed journals, you'll see maybe ten good papers," says Avner Vengosh, a professor of geochemistry and water quality at Duke University's Nicholas School of the Environment. "There is a huge discrepancy between what we talk about and what we know." He and a handful of other researchers are trying to increase the "what we know" so that the public and policy makers can make a more informed risk analysis.

Professor Avner Vengosh. Image: Duke University

In many areas of the U.S., a gas-laden layer of shale sits thousands of feet below the surface. Harvesting natural gas with a well is nothing new. George Westinghouse, for instance, had a natural gas well on his estate in the nineteenth century. The difference between his well and the ones that are now divorcing the price of natural gas from that of oil, is a matter of direction. Until the 1990s, most wells were vertical, or, at best, diagonal. When Westinghouse wanted more gas, he had to build another vertical well, not far from the first. Frack wells, though, snake through the shale layer horizontally for nearly a mile, harvesting orders magnitude more gas.

To do so, first, a 24-inch diameter hole is drilled straight down for a few hundred feet to prevent a blow out of the well. Inside that, another hole is drilled down to just below the fresh water supply. It's fit with another casing (13 and 3/8 inch diameter, if you must know) and cement is pumped down, and out through the bottom. It comes up and seals the space between the casing and the hole, and protects the water from the well. Inside, another casing continues the descent down through thousands of feet of earth to below the aquifer. A quarter of a mile before it hits the shale layer, it begins to curve. Once it does hit the rock containing the transparent gold, the bit continues through it, boring horizontally for several thousand feet. Cement is again pumped in, sealing the pipe from the shale. The entire well is outfitted with some 80 tons of pipe.

Hydraulic fracturing taps shale with horizontal pipe that can run for thousands of feet, a mile below the surface.

A perforating gun is then sent to the end of the line. When discharged, it perforates (hence the name) the bore and the cement, and sends small holes into the shale. Then it's time to fracture (hence the name) the shale. A mixture of water, sand, and chemicals is pumped into the well at high pressure. As the frack fluid breaks apart the shale, the sand lodges itself into the fissures in the rock, keeping them open so the gas can escape into the bore and back to the surface.

The environmental concerns are all about the water. The fracturing part of fracking requires millions of gallons of the stuff. Half of that stays underground; but the other half comes back to the surface. "In general, a frack job might be 10 million gallons," says Gary Gartenberg, a mining engineer who now works for Robson Foresnic, Lancaster, PA. "If you get 5 million back, where do you get rid of it?" Much of it goes into sealed tanks, to sit for eternity. Some can be recycled. Though the chemicals are only a quarter percent of the fracking fluid, many of them are proprietary. Their make up and toxicity is unknown to the public, worrying environmentalists.

Vengosh says that the public focus on the frack water is misguided. The percentage of chemicals in the water is small enough that it's less dangerous than other industrial run off. What's of greater concern is the naturally occurring water from the formation that comes up with it. It's highly radioactive and ten times as saline as seawater. If it gets dumped into a river it's not too good for river life. "So I worry more about the naturally occurring stuff than the manmade stuff," he says.

The sheer quantity of water is another issue. On many sites, water is shipped in by the truckload. In essence, that water is gone forever once used. This, and other hazards, could be mitigated by recent development of the "waterless frack." The Canadian company Gasfrack, Calgary, AB, Canada, for instance, has developed a method of using propane instead of water. "It will definitely reduce the need for water," says Vengosh, "so it will have some positive consequences, but it's not the final solution." The aquifer will be no less at risk, and the method is sure to have it's own dangers. "You're pumping that stuff at high pressure," says Gartenberg. "I hope someone like me—a smoker—doesn't come along."

The most visible worry is the leaching of gas into the water supply. Pictures of homeowners igniting their water as it flows out of the tap have galvanized environmentalists against fracking. Unfortunately, those photos don't come pared with photos of the same activity before fracking stared in the area. In fact, in unfracked lands with natural gas resources, water from wells only 300 feet can have methane. "A lot of times you find that the people have been siphoning gas off their water for 13 years—they've been heating their house with it," says Gartenberg. "Is it possible that fractures will propagate a mile up to the surface? Most engineers would feel the same way I do. There are so many layers and formations. It's too dense and too thick. And you've got to remember that the layer above the shale is going to be impermeable. That's what traps the gas there in the first place." He recommends that both the industry and residents living above soon to be fracked shale sample the water before drilling begins.

Vengosh, though, has used isotropic fingerprints to distinguish between naturally occurring methane and methane contaminated by shell gas. In a 2011 paper, he showed that methane contamination of water indeed occurred more frequently near fracking wells.

But Vengosh doesn't think such worries warrant bans on fracking. "If you stop it and go back to coal, damage will be done—coal is extremely not clean. One has to see the big picture, and what it means for everyone."

"It's like most things in engineering life, says Gartenberg. "If you follow the rules, follow the codes, and do it right, there are no problems."

Michael Abrams is an independent writer.

There is a huge discrepancy between what we talk about and what we know.

Prof. Avner Vengosh, Duke University

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November 2012

by Michael Abrams, ASME.org