Does oil and gas drilling cause earthquakes?

 

Just before 11 p.m. on November 5, 2011, the biggest earthquake in Oklahoma’s history hit the small town of Prague. It buckled a highway, exploded windows, collapsed homes and left terrified residents clutching their beds as they waited for the shaking to stop. Ripples from the 5.7 magnitude quake were felt as far as 800 miles away, and smaller temblors continued to rock the area the next day.

The quake shook the house of University of Oklahoma seismologist Katie Keranen, who rushed to Prague the next morning and installed three seismometers, just in time to record the aftershocks. Her recordings showed the quake had originated in the near-by Wilzetta fault, long thought to be inactive.

But less than 650 feet from the fault were old oil wells, used by the oil industry to dispose of chemical-laden water deep underground. When Keranen looked at the wellhead’s records, she found that the pressure in the well had risen 10-fold from 2001 to 2006. These findings, published March 26 in the journal Geology, led her to conclude that the wells had triggered the earthquake.

The findings raise questions about the safety of deep injection wells, which have been used by the oil industry long before the recent natural gas boom, but have increased along with the proliferation of hydraulic fracturing. In 2011, a group of USGS scientists documented “a remarkable increase” in seismic activity in the oil and gas regions of the Plains. “A naturally-occurring rate change of this magnitude is unprecedented outside of volcanic settings or in the absence of a main shock, of which there were neither in this region,” they noted, although they couldn’t conclusively link the increase to oil and gas activity. A 2012 study by researchers at University of Texas at Austin found that the majority of earthquakes recorded between fall 2009 and 2011 in Northern Texas occurred within a few kilometers of a highly-active injection well.

How do injection wells cause quakes? As wastewater is pumped underground, it gradually fills up crevices in the rock previously occupied by oil, until more and more pressure is needed to send the water down into the well. As pressure increases, it can trigger near-by faults, like the Wilzetta, to jump. “When you overpressure the fault, you reduce the stress that’s pinning the fault into place and that’s when earthquakes happen,” Heather Savage, a Columbia University geophysicist who co-authored the study on the Prague quake with Keranen, said in a news release.

But industry reps, and the Oklahoma Geological Survey, disagree. According to Bloomberg, the state agency “maintains the ‘interpretation that best fits current data’ is that the earthquakes in 2011 were naturally occurring.” And when reporter Michael Behar, who wrote a story for Mother Jones on the topic, asked an oil company executive with wells near the Wilzetta Fault about the Prague earthquake, “he informed me that people claiming to know the true source of the Oklahoma quakes are ‘either lying to your face or they’re idiots.’”

The outright denial is what makes the results of a February 2013 study so interesting. Conducted by the Washington D.C.-based non-partisan, non-profit environmental think tank Resources for the Future, the researchers asked 215 experts from academia, government, oil and gas industry and the non-profit world to identify their top environmental risks of oil and gas development. The researchers then identified areas of consensus—risks everyone can agree on—and controversy—risks that certain groups prioritized, but not others. Earthquakes fell into the second category, but not for reasons you’d expect: Industry experts actually were much more concerned about injection well-induced earthquakes than government or NGO experts. So contrary to quotes they give to reporters, many oil and gas industry experts are not only aware of the connection between injection wells and seismic activity, they’re worried about it.

Because of the increasing evidence of seismic risk, one energy policy analyst thinks the days of deep injection wastewater wells could be numbered. “I don’t know anybody who says that underground injection is the future of this industry,” Benjamin Salisbury, a senior energy policy analyst at FBR Capital Markets Corp. told Bloomberg. “We are going to wastewater treatment and recycling for a plethora of reasons.”

Emily Guerin is the assistant online editor at High Country News.

Photo courtesy Flickr user martinluff.

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