For the first time, a team of state regulators and geologists have identified hydraulic fracturing as a “probable” trigger for earthquakes, confirming suspicions that a series of tremors in Poland Township were the result of fracking operations.
“ODNR geologists believe the sand and water injected into the well during the hydraulic-fracturing process may have increased pressure on an unknown microfault in the area,” the agency responsible for regulating the state’s oil and gas industry said in a statement.
On March 23, The Vindicator reported that geologists outside of an Ohio Department of Natural Resources investigation were considering the theory that fluid from a fracking well at the Carbon Limestone Landfill could have seeped into an unknown fault extending upward from the Precambrian basement, causing the ground to shake March 10.
ODNR’s investigation turned up no link to the Precambrian formation, but it did indicate that fracking aggravated a small, previously undetected fault in the overlying Paleozoic rock.
Rick Simmers, chief of ODNR’s oil and gas division, said it wasn’t clear whether the fluid leaked into the fault or whether it created pressure that caused the fault to move.
The precise depth of the March 10 quake also remains unknown, but ODNR’s review of seismic data, Hilcorp records and other information all pointed to fracking as the most likely cause, he said.
“The data started to focus in on the well itself, but, in a way, that gave us more and more evidence that the events were related to the hydraulic fracturing,” Simmers said in an interview.
Though there is a moratorium on drilling at the site, Hilcorp Energy Co. will be allowed to recover oil and gas from five previously drilled wells, as long as seismic monitoring occurs.
Hilcorp said in a statement that it “is currently reviewing the Ohio Department of Natural Resources’ latest announcement regarding drilling-permit conditions. While we take the time necessary for understanding how these conditions impact Ohio operations, we remain fully committed to public safety and acting in a manner consistent with being a good corporate citizen in the communities where we operate.”
ODNR’s findings prompted the agency to take the unprecedented step of changing its permit conditions to require drillers in certain areas to monitor seismic activity.
The requirements — the first of their kind — will require companies seeking horizontal-drilling permits within three miles of known faults or in the vicinity of seismic events greater than a 2.0 magnitude to install “sensitive” seismic monitors.
If the latter detect movement of a magnitude of more than 1.0, drilling and related activities would have to stop while the quakes are investigated. Drilling would be suspended if fracturing is determined to be the cause.
Officials said additional monitoring during the drilling process would provide a range of new data points, giving regulators a more-comprehensive picture of existing faults in underlying rock formations.
“Not only will this reasonable course of action help to ensure public health and safety, but it will also help us to expand our underground maps and provide more information about all types of seismicity in Ohio,” ODNR Director James Zehringer said in a statement.
Geologists saw the new conditions as “reasonable,” but expressed some concern that they do not go far enough to map the geology of an area that has seen its share of earthquakes in recent years.
As many as 109 earthquakes were linked to a Youngstown injection well that shot fracking wastewater into the Precambrian basement.
Investigations by ODNR and Columbia University’s Lamont-Doherty Earth Observatory into those events also found previously unknown faults in Mahoning County.
Mike Brudzinski, a professor of seismology at Miami University in Oxford, said the monitoring requirement would be effective in monitoring seismic pressure at a site, but it would provide only a “local” snapshot of geological conditions.
“ODNR needs to think about, ‘Is there a way we can do more characterization of the overall fault network?’” he said.
In an email exchange with The Vindicator, Thomas Serenko, the state’s chief geologist, indicated that public seismic mapping data is lacking in Mahoning County because the companies that perform the expensive and detailed surveys hold the information as proprietary.
Ohio law does not authorize ODNR to require that companies turn that data over to state regulators, ODNR spokesman Mark Bruce said.
Additionally, requiring the tests could have a cooling effect on the state’s drilling industry, Brudzinski said, but regulators should work with companies to defray the cost and share the data.
Ray Beiersdorfer, a geology professor at Youngstown State University, said the burden should be on companies to turn over information to ODNR when they encounter a potential problem. “I suggest that the drilling companies have to prove there are no faults in the area by making their seismic reflection data available to ODNR,” he said.
But Bruce said seismic reflection data don’t always reveal small dangers such as the “microfault” encountered at the Hilcorp wells.
“[Hilcorp] had seismic reflection data,” he said, “but they didn’t see this fault.”
Brudzinski took issue with ODNR’s use of the term “microfault,” saying the agency took “a lot of geological leeway” in its word selection. “It’s not a term that has a lot of specific meaning,” he said.
According to Simmers, the term referred to the length of the roughly east-to-west oriented fault, but Beiersdorfer agreed that the word is rarely used and can have various connotations.
Beiersdorfer did, however, credit ODNR with responding “in a timely fashion to these earthquakes,” drawing a contrast to the agency’s drawn-out review of the injection-well quakes.
According to agency spokesmen, ODNR’s investigation is now finished, and all its data and findings are publicly available upon request.
Meanwhile, industry representatives emphasized the need for “perspective” when responding to ODNR’s findings.
Thomas E. Stewart, vice president of the Ohio Oil and Gas Association, characterized the Poland quakes as a “rare and isolated event that should not cast doubt about the safety of hydraulic fracturing.”
“Though we understand the public’s concern, we encourage an abundance of caution and perspective when evaluating this incident. Ohio has benefited greatly from a robust oil and gas industry, and this should not curtail development,” he said in a statement.
According to ODNR, there have been more than 800 wells drilled in the Utica and Marcellus shale plays, which have included as many as 16,000 fracking stages.