WASHINGTON — Fracking, the controversial drilling technique that is driving Americas energy boom, has been around for decades. But it was only in the last decade that the process of blasting underground rocks with water and chemicals was refined enough to deliver a long sought oil and gas bounty and stir a furious debate over its health and environmental consequences.
The fracking revolution began in an underground rock formation known as the Barnett Shale outside of Fort Worth, Texas. Thats where a wildcatter named George Mitchell, the son of an immigrant Greek goat herder, began searching in the 1980s for the right cocktail of water, sand and chemicals that would crack shale a mile underground and free the natural gas trapped inside. His company finally found the formula in the late 1990s, and it took a few years after that for others in the American oil industry to catch on to the transformative power of the new techniques.
It took a long time to get to the starting line, but once we got there its really gone pretty fast, said Pulitzer-Prize winning author and historian Daniel Yergin.
This is a technical triumph, what George Mitchell did, said Jim Henry, a 78-year-old drilling pioneer in Midland, Texas.
Formally known as hydraulic fracturing, fracking starts with a rig on the surface drilling through layers of earth and rock to a hydrocarbon-rich rock formation, often one to two miles below the ground. Instruments guide the drilling crew to whats known as the kickoff point within the deep formation. Thats where the crew instructs the drill bit to move sideways, drilling a horizontal shaft that can stretch thousands of feet.
Thats called horizontal drilling, and it allows the rig to tap a huge area. It makes the wells far more economical than the traditional method of just drilling straight down into the earth.
Next a perforating gun with explosive charges is lowered by wire to the rock formation. It sets off a charge that pierces the pipe and creates minuscule fractures within the shale rock.
Then the fracking really starts. Between 3 million and 6 million gallons of chemical-spiked water is injected down the well to the rock formation at enormous pressure, thousands of pounds per square inch.
The force of the water is like a baseball hitting a piece of glass and shattering it, except the rock can take days to crack. Sand is sent down the pipe to prop open the paper-thin cracks.
The fracking fluid is 99 percent sand and water and 1 percent additives, said Robert Montgomery, a production engineer in Williamsport, Pa., with Anadarko Petroleum.
Oil and gas flow through the cracks into the hole the drill has made, and pressure brings it to the surface.
The exact makeup of the chemical cocktail depends on the driller and the well. Its often protected as a trade secret. The list often includes hydrochloric acid, used at the start of the fracking process to dissolve debris.
Other common chemicals include ethylene glycol (used in antifreeze) to help stabilize the mixture, glutaraldehyde to kill bacteria in the pipe, potassium chloride to reduce friction so the water goes faster and dimethylformamide to fight corrosion.
Some polluted water rises back to the surface, at times with low levels of radiation. It can be stored in a pit or tanks, and there are increasing efforts to recycle and reuse it. The waste is often trucked to disposal wells and injected thousands of feet underground.
Kevin Hurst, a former assistant director for energy research and development in the Obama White House, said there needs to be more research about the health and environmental impacts of the shale boom. There is a widespread perception of the risks, but a lack of information on how likely those risks are and the consequences, said Hurst, who chaired a recent working group taking a look at whats scientifically known about fracking for the Union of Concerned Scientists.
Among the key issues is whether the chemicals contaminate groundwater. The drilling industry maintains they dont, noting that the water table is typically only a few hundred feet underground while the chemicals are injected more than a mile below the surface. Cement is used to seal the steel drilling pipe from surrounding earth and rocks, with the cement thickest at the water table.
The Environmental Protection Agency in 2011 linked fracking chemicals to groundwater contamination in central Wyoming. But this past summer the EPA withdrew from further investigation and turned the investigation over to the state of Wyoming, which had been critical of the EPAs testing methodology and conclusions, and questioned whether the contamination came from fracking. The EPA also backed off a claim of water contamination in Texas, and closed a high-profile investigation in Pennsylvania.
Preliminary results of a Department of Energy study in western Pennsylvania found no evidence of groundwater contamination. Results of a broader EPA study arent expected until 2016.
Scientists are also looking at earthquakes associated with shale development.
There is a growing body of research linking modest quakes in multiple states to deep injection of fracking waste fluids down disposal wells. That includes Oklahomas biggest recorded earthquake, a 5.7 quake in 2011.
Methane is another major issue, but its not clear how much of a threat it poses. A Duke University study linked methane in some residential Pennsylvania water wells to fracking in the Marcellus shale. A 2010 documentary, Gasland, which was nominated for an Academy Award and aired on HBO, became a popular vehicle for fracking critics, particularly a scene where a man is shown setting fire to water flowing from his tap.
Methane, while not known to be toxic, is flammable as well as a potent greenhouse gas. A recent University of Texas study, sponsored by oil companies and the Environmental Defense Fund, concluded that the methane emissions from natural gas drilling sites were lower than previously feared. Fracking critics maintain those findings are based on inadequate data.
Pennsylvania State University geoscientist Terry Engelder, an industry consultant, argues that the risk is far less than the public perception, and that most methane complaints are unfounded. Those that are related to fracking result from bad cement seals letting methane escape, he said.
Recovery of any energy comes with a risk, and the way that risk manifests itself with the gas industry is that not all cement jobs are perfect, he said. The view I would take is that the industry is trying its level best to get it right.
Fracking critic Tony Ingraffea, a Cornell University engineering professor, calls the industrys safety claims outlandish.
Ingraffea asserted that between 5 percent to 10 percent of the wells that the industry drilled since 2007 atop the Marcellus shale formation in Pennsylvania experienced initial leaks. Ingraffea said more will leak as they age, and he is researching on how many. The shale boom is so huge that even a small percentage of errors could pose considerable issues.
Engelder said the biggest risk for the fracking boom could be a bad public image.
He said it is in everyones best interest to figure out how many of the anecdotal reports of harm from fracking represent real health and environmental issues. Engelder said he supported the state of Pennsylvania paying for a health study when he was on the governors Marcellus Shale Advisory Commission. But the states politicians decided to kill the plan, Engelder said.
We have to solve this particular problem of understanding whether or not public health is affected by this process. And that is really, really, really important, Engelder said.
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