Lynda Stokes admits to being frustrated as she waits for Texas regulators to offer a solution to the swarm of small earthquakes that shook the area near her home in Reno in recent months.
“I see what the other states have done — they close the wells and the earthquakes go away,” said Stokes, the mayor of the Parker County community just north of Azle. “And yet Texas just turns its face.”
The Texas Railroad Commission isn’t the only state energy regulator grappling with whether wastewater disposal wells used in natural gas drilling cause earthquakes. Agencies in Colorado, Ohio, Arkansas, Oklahoma and, most recently, Kansas have had to respond to seismic events that are new to them or have become far more frequent.
And some states have concluded that there’s a direct link between the injection wells and the seismic activity.
In Austin, Railroad Commission officials are interviewing candidates for a staff seismologist to spearhead research into the link between disposal wells and seismic activity, and a House subcommittee was created in January with a similar purpose. In Oklahoma, the state energy agency has proposed closer monitoring of injection wells.
Ohio and Arkansas, meanwhile, moved relatively rapidly when faced with unexpected quakes near disposal wells. Arkansas permanently closed four injection wells after a swarm of quakes in 2011, and Ohio’s governor stepped in to order a well in Youngstown shut down after it was linked to quakes.
Quakes up sharply
There’s doubt about how to deal with the risk related to injection wells, but there’s no question that the number of quakes is rising.
In January, the U.S. Geological Survey said “the number of earthquakes has increased dramatically over the past few years within the central and eastern United States.” Seismic monitoring networks recorded nearly 450 quakes of magnitude 3.0 or more — big enough to be felt at the surface — from 2010 to 2013.
In just the central U.S., roughly between the Appalachians and the Rockies, an average of 21 quakes of 3.0 magnitude or more occurred each year from 1970 to 2000, USGS researchers reported. That increased to an average of 29 from 2001 to 2008. After that, it leapt to 151 a year.
The rise in quakes coincides with increased underground disposal of wastewater associated with hydraulic fracturing, the oil and natural gas production technique that has boosted U.S. output but has had environmental effects.
The Azle area, which has a number of injection wells, was the latest region to experience quakes, with more than 30 starting in November. Dallas/Fort Worth Airport and the Cleburne area both had a spate of small quakes in 2009, which stopped after nearby injection wells were closed.
Still, the Railroad Commission has stopped short of acknowledging a link between seismic events and injection wells.
“Commission staff has not identified a definitive correlation between seismic activity … and injection wells in Texas,” Railroad Commission spokeswoman Ramona Nye told the Star-Telegram in an email response to questions about the agency’s position.
She said hiring a seismologist will “allow the Commission to strengthen its ability to follow new research, as well as coordinate an exchange of factual, scientific information with the research community.” The agency has received 21 applications, Nye said, “and interviews are ongoing.”
And unlike some other states, the agency does not require a seismic survey before a disposal well can be built, Nye said. Instead, it looks for the proper conditions to prevent groundwater contamination.
The mere existence of faults “does not necessarily indicate” that a disposal well will trigger seismic activity, she said. But part of the seismologist’s job, she said, will be to evaluate the impact of oil and gas activity on known faults.
Stokes, who was among more than 30 Azle-area residents who traveled to Austin in January to urge the commission to act, thinks there’s been plenty of research already.
“The fact of the matter is they have 60 years of studies,” she said, and nearly all say “it’s more than probable that these injection wells are causing” quakes.
And she knows the consequences of the temblors. A crack in Reno City Hall runs from the linoleum floor up a wall to the ceiling. It wasn’t there before the quakes started, she said, and “every time we get a pretty good earthquake, it gets a little wider.”
The reaction in other states has been far from uniform.
The most highly regarded study of the link between wastewater injection wells and earthquakes is also the oldest. It was done at the Rocky Mountain Arsenal outside Denver, and Ken Morgan, director of the TCU Energy Institute, calls it “the gold standard.”
In 1962, the well started disposing of wastewater from chemical weapons production. From 1962 to 1966, the amount of fluid injected in any given month corresponded to earthquake frequency nearby.
Injection at the arsenal well was halted for about a year starting in 1963. Earthquake frequency slowed sharply. When injection resumed in 1964 — at greater volumes — quakes surged to higher levels.
By 1966, more than 700 quakes had occurred within 5 miles of the well. Injection was permanently ended that year, but smaller bursts of seismic activity continued until 1972.
The Colorado Oil and Gas Conservation Commission today requires a seismic review before it will issue a permit for a disposal well.
In 2010 and 2011, more than 1,300 small earthquakes occurred near Greenbrier, Ark., a farming community about 40 miles north of Little Rock. The area had previously experienced quakes, including a swarm in the 1980s.
The Arkansas Geological Survey, along with the University of Memphis Center for Earthquake Research and Information, installed seismic monitors around eight injection wells. Researchers determined that 98 percent of the 2010-11 quakes were within 3.7 miles of two particular wells.
Scientists then discovered a previously unknown geological fault, dubbed the Guy-Greenbrier fault for the two cities that bookend it.
“Given the strong spatial and temporal correlation between the two wells and seismic activity on the fault, it would be an extraordinary coincidence if the recent earthquakes were not triggered by the fluid injection. For these reasons, I conclude that fluid injection triggered the recent seismicity,” one of the researchers, Steve Horton, wrote in a study published in 2012.
The Arkansas Oil and Gas Commission voted in March 2011 to close two of the wells for more than three weeks and later ordered four wells permanently closed.
It issued a permanent moratorium on new injection wells around that fault, required that new wells be 1 to 5 miles from known faults, and stepped up monitoring of wastewater injection volumes and pressures.
While the quakes tapered off after the closings, more than 70 were recorded the next October and November. Researchers said that was expected based on the experience at the Rocky Mountain Arsenal well, where the largest quake, magnitude 5.3, happened a year and a half after the well was shut.
In 2013, about a dozen small quakes were recorded around Clinton, Ark., about 25 miles north of Greenbrier. Several quakes have also hit northern Arkansas this year.
Starting in March 2011, the area around Youngstown in northeast Ohio experienced 11 small quakes over several months. According to a report from the Ohio Department of Natural Resources, all were within a mile of an injection well that had gone into operation in December 2010, just three months before the first temblor.
State regulators and geologists inspected the injection well 35 times from April 26 to Dec. 15, 2011. Each showed that the well, which was 9,184 feet deep, was operating within its allowed volume and pressure. The Youngstown area had no record of seismic activity.
In November 2011, a newly appointed head of the agency, James Zehringer, asked for additional data, and the state teamed with the Lamont-Doherty Earth Observatory at Columbia University to install seismic monitors in the area.
Having more monitors in a given area allows researchers to pinpoint the epicenter of a quake (its location on the earth’s surface) and a quake’s focus (the underground location where the earth moved). Those monitors went into operation Dec. 1.
On Dec. 24, a 2.7-magnitude quake hit the area. The newly installed seismometers pinpointed the quake’s focus 2,454 feet beneath the injection well, and on Dec. 29, state regulators asked its operator to suspend activities.
Personnel with the Ohio Department of Natural Resources witnessed the well’s shutdown the next day. But a day after that, the area experienced a 4.0-magnitude quake, and Gov. John Kasich quickly suspended the operation of three deep injection wells in the area.
Construction on an additional injection well in the area was halted, said Mark Bruce, a department spokesman. All four wells remain out of operation today.
In March 2012, the agency announced new rules for wastewater disposal, saying they were among the most stringent in the nation. It banned new wells from being drilled into the area’s basement rock formation, where the problematic Youngstown well injected its wastewater.
The rules also require injection well operators to submit extensive geological data before drilling and to add pressure- and volume-monitoring devices, including automatic shut-off switches.
Bruce said operators of new injection wells in deeper formations can also be required to install or allow the department to install seismic monitors nearby. Those monitors will record seismic activity for two months before injection begins and for at least 12 months afterward, Bruce said.
The state has 25 seismic monitoring stations in six counties and plans 12 more this spring, covering two more counties, Bruce said. That allows regulators to build a base line of seismic activity.
“If we pick up activity, we can ask how it fits in” with injection operations, he said. Early results show that some areas have very small seismic events, perhaps magnitude 1.5, that predate injection wells, he said, and no wells have been closed because of the results of that monitoring, he said.
Oklahoma has seen more than 200 earthquakes in the past year, according to data from the U.S. Geological Survey, including 20 in the past month. That continues a string of quakes that have shaken the state since 2009, mostly in central Oklahoma, including a 5.7-magnitude temblor near Prague on Nov. 5, 2011, the largest in state history.
Last year, the USGS and the Oklahoma Geological Survey noted an upswing in frequency of quakes of 3.0 or greater, the magnitude at which people are likely to feel it. From 1975 to 2008, according to a study released Oct. 22, the state experienced one to three 3.0 quakes a year.
But from 2009 to the middle of 2013, it saw about 40 a year, the study said.
“The analysis suggests that a contributing factor to the increase in earthquake triggers may be from activities such as wastewater disposal — a phenomenon known as injection-induced seismicity,” the report said.
In January, the Oklahoma Corporation Commission proposed more stringent monitoring of disposal wells, aimed at giving researchers more data. It was the first action by the agency, which regulates the oil and gas industry, to address quakes and energy activities.
In what would be something of a replay of the Rocky Mountain Arsenal well, a seismologist with the Oklahoma Geological Survey has proposed intentionally injecting fluid into a formation known to be earthquake-prone.
On Feb. 17, Kansas Gov. Sam Brownback appointed a task force to examine the tie between earthquakes and injection wells. The USGS recorded a 3.8-magnitude quake in December and a 3.9-magnitude quake in early February, both near the Oklahoma border.
Its first meeting is set for April 16.
“Recent seismic activity in south-central Kansas has raised concerns that fluid injection might be related,” Brownback said in a prepared release. He called the issue “a matter of public safety”
His appointees to the task force include the head of the Kansas Geological Survey, the director of the state’s energy regulator and an official with the Kansas Department of Health and Environment.