A handful of oil and gas waste disposal wells with names like "Deep Throat" and "Flower Power" have been linked by seismologists to an increasingly strong earthquake swarm around Oklahoma City.
Their peer-reviewed paper, released Thursday and published in the journal Science, finds that wells with "exceedingly high" injection volumes likely changed underground pressures and triggered earthquakes more than 20 miles away.
The paper focuses on four high-volume wells in southeast Oklahoma City and a seismic swarm that started near the suburb of Jones, Okla., in 2009.
"We view the expanding Jones earthquake swarm as a response to regionally increased pore pressure from fluids injected at the SE OKC wells," the study says.
But New Dominion LLC, the oil producer that owns the four wells, says it operates the wells safely and called the findings "irresponsible" in a statement.
State officials responsible for regulating oil and gas operations have a copy of the study and are "carefully studying" the findings, said Matt Skinner, spokesman for the Oklahoma Corporation Commission.
Lead author Katie Keranen said the importance of the study is not tying specific earthquakes to particular wells, but showing that high-volume wells can trigger earthquakes miles away from the point of injection. In the past, correlations have generally depended on showing that wells are close to epicenters and that the quakes correspond in time with the start or increase in injection.
"If you have a high-rate well, it can have a strong influence at greater distances," Keranen, a Cornell University geophysicist, said in an interview. "This can affect larger areas than we had appreciated."
The quakes in the Jones swarm have been persistent but small. They've rarely gotten as strong as magnitude 4. But the study warns that the longer the smaller quakes keep spreading, the greater the likelihood that they could rupture a fault capable of a magnitude-6 or -7 quake, which would cause serious damage and possibly casualties.
"The increasing proximity of the earthquake swarm to the Nemaha fault presents a potential hazard for the Oklahoma City metropolitan area," the study said.
Jay Hanas, a professor at the University of Oklahoma Health Sciences Center, shares the concern that the current small earthquakes could lead to a much larger earthquake.
"There's obviously something very sensitive going on in this area," Hanas said.
Beyond the prospect of a big earthquake, the constant shaking has a lot of people mad about damage to the homes they own.
Troy Westmoreland, who lives 2 miles outside Edmond, a suburb north of Oklahoma City, said the state needs to be more aggressive about dealing with disposal wells.
"If they can prove it, then they need to do what they can to shut it down or change their methods," said Westmoreland, who attended a town hall meeting on the quakes last month in Edmund that drew more than 400 people (EnergyWire, June 27).
4 wells tied to 20% of central U.S. quakes
The Jones swarm, which produced hundreds of "felt" earthquakes in the past several years, is part of a big surge of seismicity in the state. There's been a fortyfold increase during the period of 2008 to 2013, the study says, compared with 1976 to 2007.
It's also a major reason that Oklahoma has had more earthquakes magnitude 3 or higher than California in the last nine months (EnergyWire, May 7).
The four New Dominion wells, the study says, "likely" triggered 20 percent of the earthquakes in the central United States from 2008 to 2013. In that region, there have also been earthquakes linked to injection in Arkansas, Colorado, Kansas and Texas.
Wastewater disposal rates have varied across the state in recent years as some companies ramped up recycling, while others developed production methods involving huge amounts of water.
In central Oklahoma, waste fluid disposal volumes nearly doubled from 2004 to 2008, a change that the study says tracks with the increase in earthquakes.
A chunk of that increase is from New Dominion. The Tulsa company pioneered large-scale "dewatering" -- a production method requiring a lot of wastewater disposal -- in Oklahoma.
Dewatering wells, the study says, can bring up as much as 1,000 times more water than oil. The water production is 200 times greater than that of conventional wells.
The four New Dominion wells in southeast Oklahoma City all inject an average of more than a million barrels a month (each barrel is 42 gallons). The Deep Throat and Flower Power wells are on the same site as another well named "Sweetheart." A little more than 3 miles away, the company's more mundanely named "Chambers No. 1" injects the highest volumes in the state.
The only other wells of comparable size are near another fast-growing earthquake swarm in northern Oklahoma, the paper says. And the authors say 85 other high-volume wells to the northeast of the Jones swarm likely have some involvement in the surge in earthquakes.
But the paper focuses on the wells in southeast Oklahoma City. The wastewater and pressure rippled outward from the wells and ruptured previously dormant faults, triggering earthquakes miles away. The front of the Jones swarm, the paper says, corresponds closely to the expanding pressure changes rippling away from the four big wells.
New Dominion decries study's 'false assumptions'
New Dominion has long rejected any links between earthquakes and its operations.
In a statement released the same day as Keranen's study, the company stated that "an initial review reflects it is premised on certain false assumptions." The statement, issued by spokesman Jack Money, doesn't say what those assumptions are but says Keranen did not consult with the company's geologist.
"At best, these incorrect assumptions are irresponsible," the statement said. It added a hint at legal action, saying the company is withholding further comment while it "consults legal counsel."
The company has been familiar with Keranen's research for years. New Dominion's vice president of exploration, Jean Antonides, has previously dismissed any connection between the company's wells and earthquakes.
Antonides didn't respond to a request for comment when the findings about the four company wells were presented at a conference of seismologists in May (EnergyWire, May 2). But he commented extensively on Keranen's findings that disposal wells farther east from Oklahoma City, where New Dominion is a dominant operator, likely triggered the state's largest recorded earthquake in November 2011 (EnergyWire, July 24, 2012).
He has also complained that researchers have not asked the company for injection data it is willing to share (EnergyWire, Dec. 3, 2012).
Antonides, a geologist, has authored a paper asserting a link between the Oklahoma earthquakes and changing levels of water in area aquifers caused by sudden rainfall after prolonged drought.
The Oklahoma Geological Survey (OGS) has also dismissed links between the Jones swarm and drilling activity. In February, OGS issued a statement saying, "A direct link to oil and gas activity ... cannot be established." OGS Director Randy Keller said yesterday that his agency is still evaluating the paper.
Keranen began studying the Jones swarm while she was a professor at the University of Oklahoma, before departing for Cornell last year.
She was also among the first to link the damaging magnitude-5.7 quake in November 2011 east of Oklahoma City to disposal wells near the epicenter (EnergyWire, April 19, 2012).
She co-authored the study released last week with colleagues from the University of Colorado and Geoff Abers of the Lamont-Doherty Earth Observatory at Columbia University.
Scientists have known for decades that underground injection of waste fluid -- from drilling or other industrial activities -- can lubricate faults and unleash earthquakes. In addition to dewatering, the hydraulic fracturing techniques that have powered the nation's oil and gas boom also create vast amounts of toxic waste fluid to be disposed of.
Researchers have linked such deep disposal wells to earthquakes in Arkansas, Colorado, Ohio and Texas. In some instances, wells were shut down. But in others, state officials disagreed with the researchers' findings.
Correction: The original version of this article misstated the ratio of oil to water from "dewatering wells." They bring up much more water than oil.