WICHITA — State regulators have expanded their investigation into what’s causing a recent string of earthquakes in eastern Wichita.
Regulators say the earthquakes are most likely naturally occurring, but want to make sure oil and gas operations aren’t contributing.
The earthquakes began around Thanksgiving, with three happening in the span of four days. The trend continued with a couple of days of quakes, then a break, then a couple of days of quakes, then a break. That lasted until Dec. 30, when the largest quake, a 3.9 magnitude, shook Wichita.
“You have an earthquake and everyone looks at the closest (oil and gas) well and blames it on the well,” said Rick Miller, a senior scientist with the Kansas Geological Survey. “Well, that’s not how it works.”
He said it’s not unheard of for there to be earthquakes in northeast Wichita. A known fault line sits nearby and people have recorded earthquakes there as far back as 1919.
For Miller, seeing earthquakes happening there again made sense.
“The real question,” he said, “is there anything that we can have an influence on that might have hit a pressure point for this particular fault?”
Since the beginning of November, the area in and around Wichita has experienced more than two dozen earthquakes.
None of them have been big enough to cause any damage. They’ve also appeared to have come to a stop. There haven’t been any major earthquakes in the area since the beginning of the year.
But the seismic activity that did happen was enough to trigger the state’s seismic action plan. The plan was created in 2014 in response to the massive increase in the number of earthquakes happening in Harper and Sumner counties in south-central Kansas.
The action plan requires regulators at the Kansas Corporation Commission to look at how much wastewater oil and gas operations are injecting into the ground within a six-mile radius of any string of earthquakes.
“Just because there have been natural earthquakes doesn’t mean that there couldn’t be induced earthquakes in that same area,” said Ryan Hoffman, director of the conservation division of the KCC.
When investigating the connection between oil and gas operations and earthquakes, regulators look for two things: A large increase in the total amount of wastewater being pumped into the ground in an area, or wells with irregular bursts in the amount being pumped underground.
The investigation into the Wichita earthquakes found only six wastewater disposal wells within the six-mile boundary. They were all located a few miles north of Wichita near K-254.
Data showed that during the last five years, all six wells combined were consistently pumping about 9,000 barrels of wastewater a day. That’s a relatively small quantity compared to what regulators found around the spike of earthquakes in Harper and Sumner Counties in 2015 and 2016. There, regulators found groups of dozens of wells each pumping as much as 15,000 barrels of wastewater a day.
In the case of Harper and Sumner counties, earthquake experts were able to clearly see that the number of earthquakes mirrored almost exactly the rise and fall of how much wastewater was being injected.
“What we saw there was nothing like what we see in Sedgwick County in terms of the large number of injection wells that were disposing of large volumes,” Hoffman said.
Ultimately, state regulators determined that the six wells investigated near Wichita did not contribute to the recent string of earthquakes. But the state’s investigation concluded before the largest of the earthquakes had even hit.
While the state still doesn’t suspect oil and gas operations played a role, it has decided to expand its investigation beyond what’s required in the state’s seismic action plan. It’s now gathering data from all wastewater injection wells within a 15-mile radius.
Miller, the expert from the Kansas Geological Survey, said he’s in favor of expanding the investigation. He said the geology of the area is complicated, and a large underground ridge nearby could be directing the pressure created from the wastewater pumping in unexpected directions.
“We don’t know that’s what’s going on,” he said. “We’re not suggesting it is going on, but we want to look at all possibilities.”
Hoffman said he doesn’t think the state’s seismic action plan needs to be changed or expanded officially.
He also says he doesn’t expect to find anything in the expanded investigation, but in a state with a history of links between oil and gas operations and earthquakes, it’s worth having more data than less.
“If there was something that caused those earthquakes,” Hoffman said, “we want to be able to make sure it doesn’t happen again.”