Wastewater disposal linked to earthquakes

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WASHINGTON -- A 2011 Oklahoma earthquake has been tied by researchers to the disposal of wastewater from oil production, the latest study suggesting the energy boom from advances such as fracking is increasing temblors.

A series of quakes in November 2011 followed an 11-fold bump in seismic activity across the central U.S., as disposal wells are created to handle the increase in hydraulic fracturing, or fracking, for oil and gas, geologists at the University of Oklahoma, Columbia University and the U.S. Geological Survey said in the journal Geology Tuesday.

The wastewater that triggered the earthquakes came from conventional wells in the Hunton formation, said Katie Keranen, assistant professor at Oklahoma and co-author of the report. The findings are a cautionary note for disposal of the millions of gallons of fluids from hydraulic fracturing, she said.

"It has little to do with where the water comes from," Ms. Keranen said in an interview. "What really matters is how you're getting rid of the water."

A spate of earthquakes in the central U.S. in recent years is "almost certainly" man-made, and may be caused by oil-and-gas wastewater disposal, U.S. Geological Survey researchers said a year ago. For the three decades until 2000, seismic events in the nation's midsection averaged 21 a year. They jumped to 50 in 2009, 87 in 2010 and 134 in 2011.

Concerns over earthquakes prompted the U.K. to temporarily halt fracking. The ban ended late last year when the government adopted standards, including a rule that would suspend operations when unusual seismic activity is detected.

Concerns have also emerged in the Netherlands. Natural gas extraction in the country's Loppersum area has created at least 1,800 faults in the region's subsoil, gas consortium NAM reported.

The 5.7-magnitude earthquake near Prague, Okla., on Nov. 6, 2011, was the state's biggest and may be the largest linked to the injection of water from drilling process, the report Tuesday found. The state's geological survey disagreed with the finding, and said it was likely "the result of natural causes." The trembler destroyed 14 homes, damaged other buildings, injured two people and buckled pavement, according to the report.

In fracking, water, sand and chemicals are injected into deep shale formations to split underground rock and free trapped gas. Much of that water comes back to the surface for disposal. Wastewater is also produced from conventional oil wells to boost production.

Fluids from conventional oil extraction in Oklahoma had been pumped into abandoned wells for 17 years before the quake, according to the study.

The Oklahoma Geological Survey maintains the "interpretation that best fits current data" is that the earthquakes in 2011 were naturally occurring, according to an agency statement.

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New York Times contributed.


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