More Evidence Shows Drilling Causes Earthquakes

More Evidence Shows Drilling Causes Earthquakes
A Chesapeake natural gas rig is worked on in the North Texas Barnett Shale bedrock deposit near Kennedale, Tex., in 2009
Photograph by Matt Nager/Bloomberg

A recent study (abstract here) published in the journal Geology is getting a lot of attention for  conclusions it draws about whether oil and natural gas drilling is causing earthquakes. In particular, the study examines the biggest quake in the history of Oklahoma, a 5.7 shaker that hit the tiny town of Prague on Nov. 6, 2011. Ripples from the earthquake were felt across 17 states.

According to the study’s authors, the culprit isn’t the actual drilling itself but the injection of wastewater back into the ground afterward. Even though wastewater had been injected into old wells around Prague since the early 1990s, the authors argue that as crevices previously containing oil filled with water, from 2001 to 2006, the amount of pressure needed to keep pushing water underground rose tenfold, or 1,000 percent. The resulting pressure change triggered a “jump” in a nearby fault line known as the Wilzetta fault, and then—boom, earthquake. The well the study examined was not drilled using the controversial hydraulic fracturing techniques, commonly known as fracking.

A review of the study by Columbia University’s Lamont-Doherty Earth Observatory quotes one of the study’s authors, geologist Heather Savage of Columbia, saying, “When you overpressure the fault, you reduce the stress that’s pinning the fault into place and that’s when earthquakes happen.”

There have been a lot of earthquakes recently in parts of the U.S. that traditionally haven’t seen so many, including Arkansas, Texas, Ohio, and Colorado—all states where fracking activity just happens to have increased substantially in the past decade. The Geology study estimates that during the last four years, the number of earthquakes in the middle of the U.S. was 11 times higher than the average rate over the previous 30 years.

The notion that injecting water deep into the ground causes earthquakes is nothing new, or even very surprising. Whether you support or oppose fracking, is it difficult to fathom that pumping billions of gallons of water and other fluids down into the earth over several decades might one day cause things to shift around, especially when those structures have been virtually untouched for millions of years?

The results of research by the U.S. Geological Survey released last year essentially concluded that a sharp rise in seismic activity in the middle of the U.S. was the result of injecting water into deep underground wells. There is also growing concern that gas-drilling in the Netherlands has led to some recent earthquakes.

Anti-fracking groups are hoping the increasing amount of evidence demonstrating a link between wastewater injection and earthquakes will slow the push into fracking. So far, however, such links don’t seem to be gaining much traction. Even as Texas rewrites its drilling laws, the state isn’t looking at the connection. Nor is California, which is no stranger to earthquakes.

Fracking proponents tend to argue that the evidence is still inconclusive, and that to limit fracking would carry economic consequences far greater than the damage a few earthquakes might do. In an online debate posted in December by Tufts University, Bruce McKenzie Everett, an associate professor at Tufts’s Fletcher School of International Affairs and a 20-year veteran of ExxonMobil, argued: “If we stopped right now, or placed a moratorium on new fracking, the price of natural gas would go up. This means electricity prices would go up, heating prices would go up.”

In New York, where state regulators are studying the pros and cons of tapping huge gas deposits, the Department of Environmental Conservation dismissed the risk of earthquakes, although it did hire a Columbia geologist to look into it.

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