Earlier this month, the British shale gas company, Cuadrilla Resources Ltd., made an unlikely admission: It concluded the fracking it was doing in the Bowland Shale formation in Lancashire probably caused several slight earthquakes that occurred last spring.
The company stated in press release that it was likely the fracking triggered "a number of minor seismic events." The company is now taking preventive measures, including the use of an early detection system to monitor quakes.
Although most energy companies tend to downplay so-called "shalequakes," the reality is hard to argue. (See Quaking Over the Search for Energy.) As Austin Holland, a seismologist at the Oklahoma Geological Survey, explained, "By definition, when fracking occurs so do 'microseismic' events, or really, really small earthquakes."
Microseismic events are too slight to feel. Even "minor" earthquakes, such as Caudrilla's, which measured 2.3 on the Richter scale, or a cluster that occurred in Oklahoma earlier this year, which only ranged as high as 2.8, are felt by relatively few.
The more significant question is whether hydraulic fracturing can trigger larger earthquakes -- ones that measure 3 or greater, and have potential to create minor to severe property damage.
Three seismologists interviewed for this post all said yes. But they also noted that the odds of such an event happening is rare, and further noted that the risk can be mitigated.
"Almost all of the earthquakes that are associated with fracking are very small," Dr. Peggy Hellweg of the University of California Berkeley's Seismological Laboratory told IU. The greatest risk is from a potential large earthquake triggered by an unknown fault.
"Drilling and high pressure applied on a fault could trigger an earthquake if the fault is close to failure," she says. "As far as I know, fracking isn't done on known faults, but there are undiscovered faults. There are millions of undiscovered faults."
There are numerous examples of California earthquakes that happened on unknown faults, including the 1971 San Fernando earthquake, the 1983 Coalinga earthquake, and the 1994 Northridge quake. None of the three, however, was linked to fracking.
But fracking involves the injection of fluid into the ground under high pressure. And generally speaking, pumping fluid into the ground can induce seismicity. Geologists blamed filling a reservoir, for example, for a large 1967 earthquake in India, says John Vidale, director of Pacific Northwest Seismic Network in Seattle. "We think you can trigger an earthquake of any size," he says. "It's just that the biggest ones are very rare."
Vidale says fracking could've triggered the 5.6 quake earlier this month in Oklahoma. It might have been a quake waiting to happen, and pushed to reality by the fluid pumped into the ground.
The energy industry seems to understand the concerns raised by fracking. "Every new well that has to be drilled means the company has to prove itself in front of the public," says Steve Everley, spokesman for D.C.-based Energy in Depth, the information arm of the Independent Petroleum Association of America, a trade group.
"There have been incidents," Everley says. "No industry is perfect." But he maintains the industry largely owns up to accidents and learns from them, adding, "There's always room to improve."
The industry founded Energy in Depth to educate people about onshore energy sources and associated technologies, including fracking. "This is an increasing part of what we're doing," he says. "It's become part of our operations."
Earthquakes aside, environmental groups have been focusing their muster on instances of the hydraulic fracturing process leading to contaminated water. The Environmental Protection Agency has been studying the effect of fracking on drinking water (it's not looking at shalequakes), and is expected to release another in a series of reports next year.
"Natural gas plays a key role in our nation's clean energy future, and the Obama Administration is committed to ensuring that we continue to leverage this vital resource responsibly," the agency stated in a press release earlier this month.
Environmental groups point to other potential environmental hazards, such as emissions, land degradation, and the disruption of wildlife habitats.
The US Department of Energy released a final report Nov. 18, making several "best practices" recommendations for shale gas companies, including reducing air pollution and disclosing the exact makeup of their fracking fluids. Companies can now voluntarily reveal their fluid compositions at FracFocus.org.
The industry has had some high-profile scrutiny. PBS, 60 Minutes, and the BBC have all highlighted concerns about the industry. The movie, Gasland, called attention to what it dubbed the "Halliburton loophole," which exempts the industry from being regulated under the 2005 Safe Drinking Water Act. It's called the Halliburton loophole because former Vice President Dick Cheney, who used to be chief executive of oil and gas company Halliburton Co. (NYSE: HAL), spearheaded the exemption for the energy industry.
Everley says environmental groups have created mostly hysteria around the exemption, arguing that the industry is exempt because of geology rather than politics. The geology of shale sites varies in different states, so it's preferable that each site is regulated by the state in which it is located, he contends.
The industry isn't exempt from other federal regulations, however, and has a slew of federal and state regulations with which it complies.
While fracking has risks, it also has upsides. Fracking is creating jobs and is helping to develop a long-term supply of affordable energy. That energy is reducing our dependence on foreign oil, which in turn can help contribute to our national security.
Perhaps the key question that needs to be answered is whether the risks involved with fracking outweigh rewards -- or if the rewards are greater than the risks. In truth, an accurate answer might be different in different places, depending on geology, geography, and population density.