Could Shale Gas Power the World?

Natural gas from shale rock promises to provide cleaner, abundant energy for the U.S. and the world. But there's a catch. It could come with significant environmental and social costs. Can the energy industry deliver the goods so that everyone benefits?

  • Jeff Riedel for TIME

    A suspected leak from a wastewater pond on Don and Carol Johnson's farm meant their cows had to be quarantined

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    It's water that's at the heart of the environmental impact of shale-gas drilling. To understand why, you need to understand how horizontal well drilling and hydraulic fracturing work. The name isn't accidental —as much as 5 million gal. (19 million L) of water is used in a typical hydraulically fractured (or hydrofracked) well in the Marcellus. First a drilling rig will dig a vertical hole several thousand feet deep, gradually bending until the concrete-encased well reaches the shale layer. After burrowing horizontally for as much as a mile (1.6 km), the drillers lower a perforating gun down to the end of the well. That gun fires off explosions underground that pierce the concrete and open up microfractures in the shale. The drillers then shoot millions of gallons of highly pressurized water, mixed with sand and small amounts of additives known as fracking chemicals, down the well, widening the shale fractures. Natural pressure forces the liquids back up the well, producing what's known as flowback, and the gas rushes from the fractures into the pipe. The grains of sand included in the fracking fluid keep the shale cracks open — like stents in a clogged blood vessel — while the well produces gas for years, along with a steadily decreasing amount of wastewater from deep inside the shale.

    Many environmental activists worry that fracking fluid could somehow contaminate nearby groundwater. Even though fracking chemicals make up only perhaps 0.5% of the overall drilling fluid, in a 5 million–gal. (19 million L) job, that would still amount to some 25,000 gal. (95,000 L). It's not always clear what those chemicals are, because the industry isn't required to release the precise makeup of its fracking formulas — and drilling-service companies like Halliburton have been reluctant to reveal the information. (It's not for nothing that a provision in the 2005 energy bill that prevents the Environmental Protection Agency from regulating hydraulic fracturing has been nicknamed the Halliburton loophole.) Gas companies compare fracking additives to household chemicals, but some environmentalists and scientists believe the formulas can contain toxic ingredients. When the fracking fluid mixes with the shale, it may also become contaminated with radioactivity —the Marcellus is slightly radioactive — while growing increasingly brackish. "You bring everything the fluid encounters down there back to the surface along with the gas," Michel Boufadel, an environmental engineer at Temple University, told TIME last year.

    The chance that fracking fluid could directly escape through the deep fractures created by the process and contaminate groundwater appears remote. The Marcellus Shale is separated from aquifers by thousands of feet of rock, much of it impermeable, and the gas industry argues that there has never been a proven case of water contamination through hydraulic fracturing. "I don't think it's scientifically plausible to suggest that could happen," says Don Siegel, a hydrogeologist at Syracuse University. In a 2009 study, the Ground Water Protection Council, a consortium that includes industry and state regulators, reported that the chance of aquifer contamination was extremely low, echoing the results of a 2004 EPA review of hydraulic fracturing. But that EPA report has been criticized, and the science is open enough that the agency is beginning a comprehensive new study of the relationship between hydraulic fracturing and drinking water.

    Of greater concern is what may be happening closer to the surface. Wells need to be properly cemented to prevent any gas or fluid from escaping before it's collected. Cementing is one of the trickiest parts of drilling — a bad cement job helped lead to the Deepwater Horizon blowout last year — and it can and does fail over time. That seems to be what happened in the northeastern Pennsylvania town of Dimock, where the state government has said poor cementing around well casings by the drilling company Cabot allowed methane to contaminate the water wells of 19 families. Methane isn't dangerous to drink, but in high enough concentrations it can cause water to burn and even explode — which is exactly what happened to one Dimock family's well in 2009. (Cabot has denied that it caused the methane contamination, which the company claimed was naturally occurring, but it did offer the affected residents compensation.) "We were never forewarned about this risk," says Craig Sautner, one of 14 affected Dimock residents still suing Cabot. "I worry that this took years off our lives."

    Beyond well problems, there's the threat of spills like those that struck the Burnetts and the Johnsons. The gas industry says such accidents are rare. "We drill 35,000 wells a year, and 95% are fractured," says Lee Fuller, executive director of Energy in Depth, a gas trade group. "We need to put this in a context that reflects all the successes as well as the failures." Still, in 2010 the Pennsylvania department of environmental protection issued 1,218 violations, out of 1,944 inspected Marcellus wells, for offenses ranging from littering to spills on drill sites. Wells have blown out, and explosions from methane contamination have destroyed homes. Shale-gas drilling is an industrial process, and the more wells that are drilled, the more often something will go wrong — and in a populated state like Pennsylvania, those accidents will be felt.

    Even if everything goes right, hydraulic fracturing can produce over 1 million gal. (3.8 million L) of toxic, briny wastewater over the lifetime of an individual well. In western states like Texas, companies can store the wastewater in deep underground control wells, but Pennsylvania's geology makes that difficult. As a result, drillers have had to ship much of their wastewater to municipal treatment plants —and as a recent New York Times investigation showed, those plants are often incapable of screening all drilling-waste contaminants. Although Pennsylvania has begun to tighten treatment regulations and gas companies are recycling increasing amounts of wastewater — reusing it in additional frack jobs — the problem is still one of the biggest challenges in drilling. "There are only a few thousand wells now, but there will be far more," says Anthony Ingraffea, a structural engineer at Cornell University. "What will life be like when there are 100,000 wells here?"

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