Biggest Oklahoma Earthquake Ever Linked To Oil Industry
In 2011, a report from the United States Geological Survey linked a series of earthquakes in Oklahoma in January 2011 to a fracking operation underway there.
There was no definitive proof, but it seemed likely that tracking was related to those Oklahoma earthquakes.
On November 5, 2011, a 5.7 earthquake struck near Prague, in central Oklahoma. Fourteen homes were leveled, schools were closed for repairs, and the quake was felt across 17 states. If it had not been centered in open country, the effects could have been much worse. Nevertheless, it worried seismologists, who had believed this area to be seismically safe.
Quake Triggered By Oil Wastewater
Now, a study published this week in the scientific journal Geology reveals that the quake was probably triggered by the injections of wastewater from oil production into wells deep beneath the earth.
Both gas and oil drilling produce massive amounts of toxic wastewater: fracking uses high-pressure water to unlock natural gas from shale formations, while in the case of oil, drillers use water to force oil from wells when it cannot be captured through traditional methods.
The domestic boom in shale gas and oil production in recent years means that the amount of wastewater emerging as a byproduct has increased enormously; most of this wastewater is pumped back into the earth in wells for disposal. And that’s a huge problem, according to the study.
From National Geographic:
Although the controversial practice of fracking has been directly linked to at least two seismic events (small tremors in Garvin County, Oklahoma and Lancashire, England), the wastewater injection that follows fracking is much more likely to set the earth shaking. That’s because injection wells receive far more water than fracking sites, said Katie Keranen, lead author of the Geology study. And unlike at fracking sites, the water is not removed. As pressure builds in these disposal wells, it pushes up against geological faults, sometimes causing them to rupture, setting off an earthquake.
Wastewater Disposal Can Be Even More Disruptive Than Fracking
Keranen and her fellow researchers found that the initial rupture reached within 600 feet of one of the wells that served as a repository for wastewater, and that the majority of the aftershocks from the quake were located within the same level of sedimentary rock as the wastewater injection wells.
Surprisingly the new study also suggested that this effect can occur many years after the fact. Wastewater was first injected into Oklahoma’s Wilzetta oilfields, near the town of Prague, some 18 years prior to the November 2011 big quakes.
Other studies have also found that the injection of wastewater is correlated to an increase in seismic events.
From the BBC:
A comprehensive review in 2012 by the US’ National Academy of Sciences found that “injection for disposal of waste water derived from energy technologies into the subsurface does pose some risk for induced seismicity”.
In April 2012, a study by scientists at the US Geological Survey of the interior of the US found that events of magnitude 3 or greater had “abruptly increased in 2009″ from 1.2 per year in the previous 50 years to more than 25 per year – although a number of gas and oil extraction methods may be implicated in the rise.
John Bredehoeft, a geological expert at the Washington State research firm Hydrodynamics Group, agrees that scientists have long known that wastewater injection cause earthquakes.
Three To Five Million Gallons Of Water
How much water is at issue here? Although tracking itself may or may not be the direct cause of earthquakes, each drill site requires between 3 and 5 million gallons of water per frack, much of which is later disposed of underground.
Is anyone paying attention here?
Unsurprisingly, experts in Oklahoma were skeptical of these findings. A statement released by the Oklahoma Geological Society said its data show the earthquake was likely “the result of natural causes.”
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