WHEELING - A West Virginia University professor has joined Chesapeake Energy officials in disputing a notion that natural gas drilling activity contributes to earthquakes, despite officials in Arkansas making such a connection.
The number and magnitude of earthquakes in central Arkansas have declined noticeably since Chesapeake and another company shut down two of its underground injection wells in the area last month, Arkansas officials said.
"We have definitely noticed a reduction in the number of earthquakes, especially the larger ones," said Scott Ausbrooks, geohazards supervisor for the Arkansas Geological Survey. "It's definitely worth noting."
The two Arkansas injection wells are used to dispose of wastewater from gas drilling and fracking. One is owned by Chesapeake and the other by Clarita Operating. The two injection wells at issue dispose of the frack water when it can no longer be re-used by injecting it into the ground.
Similar injection wells are located in West Virginia, and at least one currently is being drilled in Belmont County.
Tim Carr, WVU's Marshall Miller Professor of Energy, said there is no evidence that fracking or fluid injection into underground wells leads to earthquakes.
In noting the action does cause some "micro-seismic" shifting, Carr said, "These are much, much less than having a large truck go by. They are measured with sophisticated downhole tools and are used to map fracture stimulation treatments. No one could ever feel or even detect these events at the surface.
"In terms of inducing earthquakes, fracture stimulation (fracking) would rate very low to non-existent on my list of concerns," Carr added.
In April 2010, a 3.4 magnitude earthquake hit Braxton County, W.Va. In a span of several months the area was hit by five more such quakes. The quakes were small - about a 2.7 magnitude - but large enough to catch the attention of state officials.
Carr attributes the West Virginia tremors to natural activity.
"The earth does move and shake as evidenced by recent events in Japan. Earthquakes in West Virginia are known from throughout history," he said.
In Arkansas, the two energy companies agreed March 4 to temporarily cease injection operations at the request of the Arkansas Oil and Gas Commission. Chesapeake officials have said they do not believe there is a connection between the injection wells and the area's seismic activity.
The commission said preliminary studies showed evidence potentially linking injection activities with nearly 1,000 quakes in the region over the past six months.
A six-month moratorium on new injection wells in the area took effect in January to allow time to determine what relationship, if any, there is between the wells and the earthquakes.
"We remain confident that the facts and science will lead to a more constructive and satisfactory conclusion to this matter," said Danny Games, senior director of corporate development for Chesapeake's Arkansas operations. "The science continues to point to naturally occurring seismicity, but to ensure that we provide the most complete expert analysis, we have agreed with the commission staff to keep our disposal well temporarily closed."
The Center for Earthquake Research and Information recorded around 100 earthquakes in the seven days preceding the shutdown earlier this month, including the largest quake to hit Arkansas in 35 years - a magnitude 4.7 on Feb. 27. A dozen of the quakes had magnitudes greater than 3.0.
In the days since the shutdown, there have been around 60 recorded quakes, with only one higher than a magnitude 3.0. The majority were between magnitudes 1.2 and 2.8, according to the center.
Similar to the Marcellus Shale underlying West Virginia and parts of Ohio, the Fayetteville Shale is a major source of natural gas in Arkansas.