SALEM, Ohio — Three Miami University scientists have concluded that earthquakes experienced last March, just miles from shale wells in Lowellville, Ohio, can be tied to hydraulic fracturing.
Miami University scientists, Robert J. Skoumal, Michael R. Brudzinski, and Brian S. Currie, studied the seismic activity in Mahoning County’s Poland Township from March 2014, and determined that 77 earthquakes occurred, but only a couple were actually felt.
The study linked the hydraulic fracturing on nearby shale wells drilled by Hilcorp Energy to that seismic activity, which occurred along an unknown fault.
“This activity did not create a new fault, rather it activated one that we didn’t know about prior to the seismic activity,” Skoumal said in a news release.
Some earthquakes were measured at less than magnitude 1 on the seismology scale and one measured a magnitude 3. A quake of magnitude 2.5 to 3 is the smallest generally felt by people.
The study was recently published by the Bulletin of the Seismological Society of America.
Hydraulic fracturing or “fracking” is what oil and gas drilling companies do to extract gas from underground.
Drillers inject a high pressure water mixture into the shale rock, which breaks open the rock and releases the oil and gas trapped inside.
The fracking process results in small seismic activities, but the Ohio researchers’ report says it is rare for fracking to cause larger earthquakes that are felt by humans.
The earthquakes occurred in the Precambrian basement, which is a layer of rock thought to have many pre-existing faults, according to study author Skoumal.
The scientists sifted through the seismic information recorded by the Earthscope Transportable Array, a network of seismic stations, looking for repeating signals similar to the earthquakes reported in Poland Township.
Skoumal said no one knows where the faults are located, so further drilling should include close cooperation by the Ohio Department of Natural Resources, industry officials and the scientific community.
Science is credible
Dr. Jeffrey C. Dick, director of the Natural Gas and Water Resources Institute at Youngstown State University and chair of the geological and environmental sciences department, said the study definitely has enough science behind it to make the findings credible.
“It’s fair and has pure science behind it. There are no political agendas behind it,” said Dick.
Earthquakes are rare
Dick did point out the frequency of earthquakes blamed on hydraulic fracturing is extremely small, as noted in the study. He said there have been four documented in the United States, compared to the more than 45,000 shale wells in the United States.
“You’ve got put things in perspective,” said Dick.
Dick said the oil and gas companies are trying to be more conscious of areas with possible seismic activities, and when it could happen. He said the companies know that if there is seismic activity noted during hydraulic fracturing the company runs the risk of being shut down by the ODNR.
The Ohio Department of Natural Resources said the Hilcorp wells at the Mahoning County site are permitted to recover what was already hydraulically fracked prior to the seismic event, however no hydraulic fracturing may occur.
Last spring, after the ODNR determined the earthquakes had a probable connection to hydraulic fracturing near a previously unknown microfault, stronger permit conditions for drilling near faults or areas of past seismic activity were introduced.
New permits issued by ODNR for horizontal drilling within three miles of a known fault or area of seismic activity greater than a 2.0 magnitude now require companies to install sensitive seismic monitors.
If those monitors detect a seismic event in excess of 1.0 magnitude, activities would pause while the cause is investigated. If the investigation reveals a probable connection to the hydraulic fracturing process, all well completion operations will be suspended.
ODNR has been working on developing new criteria and permit conditions for new applications in light of this change in policy.
The department will also review previously issued permits that have not been drilled.
An ODNR statement said that no one can be 100 percent sure that drilling activities are connected to a seismic event, but the ODNR will take steps to protect human health, safety and the environment,
1,300 wells. More than 1,300 wells have been drilled in Ohio’s Utica and Marcellus shale play, encompassing as many as 16,000 hydraulic fracturing stages from those wells.
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