|« Back to Article|
Report: 2011 quake in Oklahoma likely caused by oil drilling
Associated Press : March 26, 2013
WASHINGTON — An unusual and widely felt 5.6-magnitude quake in Oklahoma in 2011 probably was caused when oil drilling waste was pushed deep underground, a team of university and federal scientists said.
That would make it the most powerful quake to be blamed on deep injections of wastewater, according to a study published Tuesday by the journal Geology. The waste was from traditional drilling, not from the hydraulic fracturing technique, or fracking.
Although the wastewater came from conventional wells, Katie Keranen, assistant professor at the University of Oklahoma and co-author of the report, said the findings are a cautionary note for disposal of the millions of gallons of fluids from hydraulic fracturing.
“It has little to do with where the water comes from,” Keranen told Bloomberg News. “What really matters is how you're getting rid of the water.”
Not everyone agrees with the scientists' conclusion: Oklahoma's state seismologists say the quake was natural.
A National Academy of Sciences study last year documented 60 small injection-induced quakes in the United States in the last 90 years, mostly in Texas, California, Colorado, Oklahoma and Ohio.
The Nov. 6 earthquake near Prague, Okla., injured two people, damaged 14 houses and was felt for hundreds of miles in 14 states, according to the U.S. Geological Survey.
The study by geophysicists at the University of Oklahoma, Columbia University and the USGS says that a day earlier there was a slightly smaller quake in an old oil well used to get rid of wastewater, right along a fault line. That smaller quake triggered the bigger one, and a third smaller aftershock.
The location of the tremors right at the spot where wastewater was stored, combined with an increased well pressure, makes a strong case that the injections resulted in the larger quake, they said.
In a statement, the Oklahoma Geological Survey said the interpretation that best fits the data is the quake “was the result of natural causes” but needs further study. The state officials cited new 3-D seismic data, a time lag between injection and the quakes, and the orientation of the faults to say it was natural, not induced.