A scientific study has linked hydraulic fracturing to 77 minor earthquakes last March around Poland, Ohio, just across the Pennsylvania-Ohio line.
The sequence of seismic events, including a rare “felt” quake of a magnitude 3.0 on the Richter scale, was caused by active “fracking” on two nearby Hilcorp Energy Co. well pads, according to the research published online today in the Bulletin of the Seismological Society of America.
The study found that although it is rare for fracking associated with shale gas extraction to cause earthquakes large enough to be felt on the surface by humans, seismic monitoring advances have found the number of “felt and unfelt” earthquakes associated with fracking have increased over the past 10 years.
Bethany McCorkle, a spokeswoman for the Ohio Department of Natural Resources, said the study findings are consistent with a determination of a “probable” link between fracking and seismic events that the department made shortly after the earthquakes occurred. That determination resulted in the suspension of additional fracking in six wells on one Hilcorp pad and one well on another well pad, and new, tighter, regulations governing the siting of new wells in areas where known geological faults exist or seismic activity has occurred.
A spokesman for Hilcorp said the company would have no comment until it reviewed the study findings.
"Induced seismic events are extremely rare and more often attributed to geothermal heating, dam impoundments and mining operations," said Shawn Bennett, Ohio Oil and Gas Association executive vice president. "However, the Ohio Oil and Gas Association and the broader oil and gas industry takes these events very seriously and is looking at induced seismicity across the nation."
He said the Interstate Oil and Gas Compact Commission has brought together a work group consisting of regulators, including Ohio’s Oil and Gas Division chief, industry and experts in this field, to address the issue.
The researchers, Robert Skoumal, Michael Brudzinski and Brian Currie, used a technique called “template matching” to link fracking activity on certain dates to seismic data recorded by the Earthscope Transportable Array, a network of seismic stations.
“These earthquakes near Poland Township occurred in the Precambrian basement, a very old layer of rock where there are likely to be many pre-existing faults,” said Mr. Skoumal of Miami University of Ohio. “This activity did not create a new fault, rather it activated one that we didn’t know about prior to the seismic activity.”
The study identified 77 deep earthquakes, with magnitudes from 1.0 to 3.0, linked to the fracking done around Poland, just across the Pennsylvania-Ohio line and 15 miles west of New Castle. According to the U.S. Geological Survey, a magnitude 3.0 earthquake produces vibrations similar to those produced by a passing truck.
During the fracking process, millions of gallons of water along with sand and chemicals are pumped down a well and injected under high pressure into a shale formation to crack the rock and release the gas it contains. Those shale formation fractures and water could cause existing faults to slip.
“We just don’t know where all the faults are located,” Mr. Skoumal said in the study news release. “It makes sense to have close cooperation among government, industry and the scientific community as hydraulic fracturing operations expand in areas where there’s the potential for unknown pre-existing faults.”
The peer-reviewed study strengthens the geological links between small and medium-sized seismic events and both fracking and deep wastewater injection disposal wells.
A study published in October 2014 in the journal Seismological Research Letters linked 400 small, deep earthquakes around Canton, Ohio, to fracking in September and October 2013 at three Utica Shale gas wells.
Another study published in March 2014 found that a magnitude 5.0 earthquake in Oklahoma in November 2011 was induced by a nearby wastewater injection well, and that set off additional temblors along the fault that culminated with a magnitude 5.7 quake. Such a quake can rattle and break dishes and windows, and noticeably rock standing vehicles.
Fracking or deep wastewater injection wells have also been linked anecdotally to small seismic events in several other states, including Texas, New Mexico, Arkansas, Kansas and Colorado.
Don Hopey: firstname.lastname@example.org or 412-263-1983. First Published January 5, 2015 2:05 PM