TAHLEQUAH — A University of Tulsa geology professor insists that despite what some might be claiming, a rise in injection wells has led to a rise in earthquake occurrences around the state.
The Tahlequah Rock and Mineral Society held its regular monthly meeting Tuesday evening, and the featured speaker was Bryan Tapp. With the record-breaking quake two weeks ago in Pawnee, Tapp said there’s been an increased focus on Oklahoma fault lines and geological changes the state has been undergoing. Tapp pointed to a dramatic uptick in earthquake occurrences in the past six years and said that in those six years, there has also been a dramatic increase in the use of injection wells.
“The earthquake is Pawnee was an unexpected and unfortunate one that set all kinds of records,” Tapp said. “In this part of the country, the chances are seemingly small that we’ll see damage from the earthquakes. Before the Pawnee earthquake, we felt that the 5.6 earthquake in Meeker-Prague was about the limit of what we’d expect in the mid-continent region, so this 5.8 has a few people on edge.”
From 1882 to 1999, Oklahoma had 1,579 recorded earthquakes; from 2000 to 2008, there were 307, and in 2009, there 50. From there, the numbers skyrocket: in 2010, there were 106, then 1,400 in 2011, 980 in 2012, 2,500 in 2013, 5,416 in 2014, and 5,691 in 2015. Year to date, Oklahoma has recorded 2,960 earthquakes, and Tapp speculated this number may be an indication the rate of earthquakes could be going down.
“We’ve been through a phased step-down of volume throughout most of the area of interest in the Mississippi play,” Tapp said. “A 40 percent reduction in volume [of injection wells] was enforced toward the beginning of summer, and we’re waiting to see if that has a significant impact in reducing the number of earthquakes. They were tracking downward with volume, indicating we were starting to see that impact. I’m interested to see after the Pawnee incident if we tick back up or if we’ll continue to move downward.”
Tapp said 2015 seems to be the peak for earthquakes in Oklahoma, and he hopes it stays that way. In 2006, Oklahoma had 204,000 oil wells and 55,000 gas wells, and those number have risen to over 500,000 and 130,000, respectively.
Tapp talked about trigger-induced seismicity and said some experts are starting to think the Meeker-Prague incident in 2011 was trigger-induced. He said not only has the number of earthquakes increased, but the area in which they occurs has shifted — incidentally, to the areas with an increase in injection wells.
“Injection into the deep Arbuckle seems to be causing enough pressure that we’re seeing these induced earthquakes,” Tapp said. “The majority of earthquakes we’re seeing are related to that deep wastewater injection. What’s happening at the state level is, there was that reduction in volume [of injection wells], and that was a temporary order. If that continues to show a decrease in earthquakes, we’ll probably remain at a reduced volume as long as we are recovering. We’re doing what needs to be done. We’re seeing a reduction in [oil] prices as well, and that’s reducing volumes. Companies are moving away from these dewatering plays simply because they are no longer economical, so that seems to be self-limiting.”
Dusty Rhodes, vice president for TRAMS, said the group tries to host events like these every other month, and the public is welcome to learn more about some of the ecological issues in the area.
“The past tells you a lot about what happened, and history repeats itself,” Rhodes said. “If this keeps happening, we might do earthquake preparedness. On our webpage, we provide all kinds of links and information people.”
Anyone wanting more information regarding TRAMS can visit its website at www.tramsok.webs.com. The group generally meets the third Tuesday of the month at the Tahlequah Public Library.