There is no evidence that hydraulic fracturing has been causing earthquakes to the extent the public and the media seem to believe, but the link does appear to exist. Most recently, the Pennsylvania Department of Environmental Protection (DEP) reports that between three and five “micro” earthquakes in three towns were likely caused by fracking at four wells within a 5-mile radius of the reported epicenters. The wells were drilled into the Utica shale formation. According to the DEP, the earthquakes, all of which occurred on April 25, 2016, had magnitudes between 1.8 and 2.3. Events of this size are rarely felt by people but are recorded by seismic monitors. The Pennsylvania Seismic Network said it registered four earthquakes while monitors at two other labs recorded three and five events, respectively.
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Larger seismic events, exceeding magnitude 4.0, in Alberta, Canada, have been linked to fracking for natural gas in the Duvernay shale formation. But the most notable swarms of earthquakes recorded in Oklahoma over the past several years are believed to be associated with the underground injection of wastewater from oil and gas development, not fracking.
Zipper Fracturing
According to the DEP report, the earthquakes were likely caused by natural gas hydraulic fracturing being conducted by Hilcorp Energy Company. Hilcorp was using a technique known as “zipper fracturing,” or hydraulic fracturing operations that are carried out concurrently two horizontal wellbores that are parallel and adjacent to each other. When the DEP contacted Hilcorp on April 25, the company voluntarily stopped activities and later reported they would discontinue hydraulic fracturing and stimulation operations at the well pad indefinitely.
DEP’s Recommendations
Recommendations in the DEP report include discontinuation of the practice of zipper fracturing during any future completions when there is less than a ¼ mile between lateral portions of adjacent wellbores.
The report also includes recommendations specific to Hilcorp’s operations. These include maintaining operation of the company’s seismic network in the towns where the earthquakes occurred; notification to the DEP of seismic events of magnitude 1.0 and greater within 6 miles of the wellbore within 10 minutes of occurrence; and cessation of fracking following events of magnitude 1.5 or greater within 3 miles of the wellbore along with submittal to the DEP of how fracking activities will be modified.
On November 16, 2016, the DEP approved a seismic monitoring plan submitted by Hilcorp, which described how the recommendations set forth in the DEP report will be implemented.
The DEP has also recommended that the above terms apply to any new permits requested by Hilcorp and that other operators follow similar plans within the affected townships.
DEP’s report is here.