CHARLESTON, W.Va. -- Chesapeake Energy is skeptical there's any connection between a small earthquake in Braxton County and its underground disposal of wastewater.
The company said Friday that the epicenter of last week's earthquake was 6 miles from its disposal well and 3 miles below its disposal zone.
Ten small quakes shook central West Virginia in 2010, ranging in magnitudes from 2.2 to 3.4. Three quakes occurred in one day.
Media outlets say the Department of Environmental Protection then worked with Chesapeake Energy to reduce the amount of fluid it was putting into underground wells, and the quakes stopped.
"While we will work with DEP as they continue to study [last week's] event, we know that natural seismicity has long been observed in this part of Appalachia," Chesapeake said.
The company noted 25 earthquakes have been reported within 100 miles of the recent seismic activity since the year 2000, including a magnitude-2.5 quake in Braxton County in October 2000, before the well was drilled.
Chesapeake recently began increasing the volume of its underground injections, said DEP spokeswoman Kathy Cosco. The 2.8-magnitude quake last week about 10 miles from Gassaway suggests there is some kind of connection, she said, but without seismic monitors, it's difficult to prove.
But Chesapeake says it's kept the underground injection volume at the reduced level.
The company's injection well in Braxton County was used to dispose of more than 10.6 million gallons of wastewater from hydraulic fracturing, a technique that creates fissures in shale formations and allows natural gas to escape for capture.
The well was initially licensed to inject fluid at a rate of 2,100 pounds per square inch of surface pressure, but the DEP cut that to just 200 pounds per square inch in August 2010 after the quakes.
Michael Hohn, director of the West Virginia Geological and Economic Survey, said initial interest in installing seismic monitors died after the quakes stopped.
In 2009, Chesapeake shut down two underground injection sites in Texas after a series of small quakes.
D&L Energy voluntarily shut down its underground injection well near Youngstown, Ohio, on Dec. 30 after a 10th earthquake rattled the area Christmas Eve.
When an 11th earthquake occurred New Year's Eve, Ohio Gov. John Kasich ordered a moratorium on all wastewater injection wells within a roughly five-mile radius.