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Lawrence County Earthquake

A series of low-magnitude earthquakes that began on April 25 at 4:17 am in North Beaver, Union, and Mahoning Townships showed a marked temporal/spatial relationship to hydraulic fracturing activities at Hilcorp’s North Beaver NC Development well pad. 

The Pennsylvania Seismic Network registered four earthquakes. (OhioSeis recorded three earthquakes, and Lamont-Doherty Cooperative Seismic Network recorded five.) The final magnitude of the earthquakes ranged from 1.8 to 2.3 on the Richter Scale, putting them in the category of microseismic events, which are likely to go unnoticed by humans and only recorded by sensitive seismic monitors.

The Hilcorp pad, which includes four wells drilled into the Utica Shale Formation, lies within a five-mile radius of the reported epicenters. Hydraulic fracturing activities began at the pad on March 30. 

Hilcorp was using a technique known as “zipper fracturing,” or hydraulic fracturing operations that are carried out concurrently at two horizontal wellbores that are parallel and adjacent to each other. When 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. 

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. This applies to Hilcorp’s Utica gas wells in North Beaver, Union, and Mahoning Townships. Zipper fracturing is allowed when there is more than ¼ mile distance between lateral portions.

In addition, it is recommended that Hilcorp maintain operation of its own seismic network within these townships. The seismic network will allow for the accurate detection of local, low-magnitude events.

A seismic event reporting schedule and operator response plan is also included in DEP’s recommendations:

  • For seismic events of 1.0 or greater magnitude occurring within 6 miles of the wellbore path, the company should notify DEP within 10 minutes via email and within one hour by telephone.
  • For any succession of three seismic events of 1.5 to 1.9 magnitude that occurs within a three-consecutive-day period and within a 3-mile radius of the wellbore path, Hilcorp should notify the DEP within 10 minutes via email and within one hour by telephone. Actions taken for this magnitude range of seismic events include suspension of stimulation operations, submittal of seismic data to DEP for review and a plan detailing modifications to stimulation operations.
  • Finally, for any seismic event of 2.0 or greater magnitude that occurs within a 3-mile distance of a wellbore path, Hilcorp should notify the DEP within 10 minutes via email and within one hour by telephone.  Actions taken include cessation of stimulation operations, flowing back of the well, submittal of seismic data to DEP for review and a plan detailing any potential modification to stimulation operations.

On November 16, 2016, DEP approved a seismic monitoring plan submitted by Hilcorp implementing the recommendations set forth in the DEP report.

DEP has also recommended that these terms apply to any new permits requested by Hilcorp and that other operators follow similar plans within the referenced townships.