The headlines were clear: fracking causes earthquakes. Yesterday an important study came out in Science that found a strong link between the injection of wastewater into deep underground wells and nearby earthquakes. Hydraulic fracturing—used in the process of developing shale gas and oil wells—also involves pumping millions of gallons of water and chemicals underground, in an effort to essentially pry fossil fuels out of tight layers of rock. Therefore, fracking causes quakes. Right?
Not exactly. The Science study, led by researchers from Columbia University’s Earth Institute, looked at deep wastewater disposal wells, which are different than the shale gas wells where fracking actually takes place in the way that a landfill is different from a garbage can. Injection wells are designed to hold the wastewater created by drilling many wells—for that reason, far more water goes into a deep injection well than into a fracked gas or oil well. The researchers found that the pressure created by pumping millions upon millions of gallons underground seemed to put extra pressure on nearby fault lines—so much so that when major quakes struck thousands of miles away, like the March 2011 quake in northern Japan that caused an epic tsunami, the resulting seismic waves could trigger swarms of small quakes near the injection sites. It’s the injection wells—not the fracking per se—that are specifically linked to those temblors in this study.
Does that mean fracking is off the hook? Not really. Many of the fluid-injection wells studied by the Science researchers—in Texas, Oklahoma, Colorado, Arkansas and Ohio—have been in operation much longer than shale gas and oil fracking has been active. But each shale gas well can produce several million gallons of wastewater, and in much of the country, that wastewater is disposed by being pumped into one of the more than 30,000 deep disposal wells around the country. As the oil and gas industry likes to point out, underground disposal wells are an accepted way to dispose of wastewater, and they’ve been used for decades. But as the shale gas and oil boom ramps up, the industry will be producing vast amounts of wastewater tainted with sometimes toxic fracking chemicals. It’s worrying to know that there is growing scientific evidence linking those fluid-injection wells to earthquakes—even if so far the quakes that have been linked to the wells have all been relatively minor.
The good news from this research is that we may be slowly getting closer to the holy grail of seismology: accurately predicting when quakes will strike. The fact that the seismic waves from a distant but powerful quake triggered swarms of small quakes near the studied well sites—which were then followed by a moderately sized temblor around those well sites—demonstrates that the faults near the injection sites were already critically stressed. Such “remote triggering” can offer scientists an indication that the injection sites have passed a critical seismic threshold, leaving the area in greater danger from a larger quake. It’s not exactly an earthquake weather forecast, but since we remain utterly unable to predict when temblors will strike with any precision, it’s certainly a start.
As the authors put it in the conclusion of their article, the Science study “underlines the importance of improved seismic monitoring in areas of subsurface fluid injection.” In other words, if we’re going to keep injecting millions upon millions of gallons of fracking wastewater into underground wells as the shale gas and oil boom continues, we need to ensure that we keep close track of the seismic side effects. That something to consider as the Environmental Protection Agency continues its long, drawn out review of hydraulic fracturing.
Or better yet, the industry can work on ways to clean, recycle and reuse wastewater from wells, eliminating the need for the deep injection wells. Recycling wastewater would also help allay the concerns that fracking will stress the water supplies of already arid areas. In states like Pennsylvania, which lack the geology needed for deep injection wells, recycling wastewater may be the only way to ensure that fracking has anything close to a sustainable future. And companies are exploring ways to effectively recycle that wastewater, though the reuse is generally more expensive and more cumbersome than simply injecting it into the deep wells.
I know it seems pedantic to point out that it is the deep injection wells, not fracking itself, that has been linked to these earthquakes—especially since it is the wastewater created by fracking that is now flowing into many of those wells, putting more pressure on fault lines. Why not just make the leap: fracking causes quakes? But when it comes to an issue as white-hot as fracking—with both sides utterly convinced of their righteousness— a little pedantry can help.