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
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.
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.
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.
seismic event reporting schedule and operator response plan is also included in
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
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.