Minor Earthquakes Seen Near Texas Injection Wells -Study
Dozens of small earthquakes occurred in central Texas over a two-year period, and 23 of them were close to injection wells where waste water from energy extraction was pumped deep underground for disposal, a new study reported on Monday.
The study used temporary seismographs to detect earthquakes of magnitude 1.5 or higher in a geologic area called the Barnett Shale, a swath of land the size of England that includes Dallas and Fort Worth.
Earthquakes with magnitudes of 1 to 3 would be felt by few people, and only under particularly favorable conditions, according to the U.S. Geological Survey.
Study author Cliff Frohlich of the University of Texas at Austin located 68 earthquakes in this area, more than eight times as many as the U.S. National Earthquake Center found over the same period from November 2009 to September 2011.
Of those, 23 were located within about two miles (3.2 km) of high-volume injection wells that pumped more than 150,000 barrels per month of water underground, Frohlich wrote in the Proceedings of the National Academy of Sciences.
His study did not examine any possible link between earthquakes and hydraulic fracturing - commonly called fracking - where water, sand and chemicals are pumped underground at high pressure to break up rock formations that contain oil and natural gas.
“Drilling never causes earthquakes,” Frohlich said in a telephone interview. “Fracking almost never causes earthquakes … While there are probably millions of hydrofracking jobs, only a few have caused earthquakes and they’ve all been little tiny earthquakes.”