AT EXACTLY 10:53 P.M. on Saturday, November 5, 2011, Joe and Mary Reneau were in the bedroom of their whitewashed and brick-trimmed home, a two-story rambler Mary’s dad custom-built 43 years ago. Their property encompasses 440 acres of rolling grasslands in Prague, Oklahoma (population 2,400), located 50 miles east of Oklahoma City. When I arrive at their ranch almost a year later on a bright fall morning, Joe is wearing a short-sleeve shirt and jeans held up by navy blue suspenders, and is wedged into a metal chair on his front stoop sipping black coffee from a heavy mug. His German shepherd, Shotzie, is curled at his feet. Joe greets me with a crushing handshake—he is 200 pounds, silver-haired and 6 feet tall, with thick forearms and meaty hands—and invites me inside. He served in Vietnam, did two tours totaling nine years with the Defense Intelligence Agency, and then, in 1984, retired a lieutenant colonel from the US Army to sell real estate and raise cattle. Today, the livestock are gone and Joe calls himself “semiretired” because “we still cut hay in the summers.”
On that night in November, just as he and Mary were about to slip into bed, there was “a horrendous bang, like an airliner crashing in our backyard,” Joe recalls. Next came 60 seconds of seismic terror. “The dust was flying and we were hanging onto the bed watching the walls go back and forth.” Joe demonstrates by hunching over and gripping the mattress in their bedroom. He points to the bathroom. “The mirror in the vanity exploded as if somebody blew it out with a shotgun.” When the shaking stopped, Joe surveyed the damage. “Every corner of the house was fractured,” he says. The foundation had sunk two inches. But most frightening was what Joe discovered in the living room: “Our 28-foot-tall freestanding chimney had come through the roof.” It had showered jagged debris onto a brown leather sofa positioned in front of their flat-screen TV. Joe shows me the spot. “It’s Mary’s favorite perch. Had she been here…” He chokes up.
The earthquake registered a magnitude 5.7*—the largest ever recorded in Oklahoma—with its epicenter less than two miles from the Reneaus’ house, which took six months to rebuild. It injured two people, destroyed 14 homes, toppled headstones, closed schools, and was felt in 17 states. It was preceded by a 4.7 foreshock the morning prior and followed by a 4.7 aftershock.
The quake baffled seismologists. The only possible culprit was the Wilzetta Fault, a 320-million-year-old rift lurking between Prague and nearby Meeker. “But the Wilzetta was a dead fault that nobody ever worried about,” says Katie Keranen, an assistant professor of geophysics at the University of Oklahoma. We’re driving in her red SUV, just south of the Reneaus’ property, when she stops to point out where the quake tore open a footwide fissure across State Highway 62. The United States Geological Survey (USGS) maintains a database of seismically risky areas. Its assessment of the Wilzetta Fault, Keranen notes, was “zero probability of expected ground motion. This fault is like an extinct volcano. It should never have been active.”
When the Wilzetta mysteriously and violently awakened, Keranen wanted to know why. So she partnered with scientists from the USGS and Columbia University’s Lamont-Doherty Earth Observatory. The morning after the initial foreshock, Keranen’s team scrambled to install three seismometers around Prague. They did so in time to capture the quake system in unprecedented detail. She says, “We got this beautiful image of the fault plane.” Within a week, her team and other scientists had placed a total of 25 devices around the fault zone. One is buried in the Reneaus’ backyard. Now, having completed a yearlong study (just published in the journal Geology), Keranen’s research indicates the Oklahoma earthquakes were likely attributable to underground injection of wastewater derived from “dewatering,” separating crude oil from the soupy brine reaped through a drilling technique that allows previously inaccessible oil to be pumped up. “Pretty much everybody who looks at our data accepts that these events were likely caused by injection,” Keranen concludes.
“We still feel tremors weekly,” complains Joe Reneau. “They rattle our windows.” The couple hasn’t bothered to rehang family photos in their living room. Instead, the framed snapshots are stacked in tidy piles on a coffee table.
“The Wilzetta was a dead fault that nobody ever worried about.” Then the drillers came. And so did a swarm of quakes.
Such seismic activity isn’t normal here. Between 1972 and 2008, the USGS recorded just a few earthquakes a year in Oklahoma. In 2008, there were more than a dozen; nearly 50 occurred in 2009. In 2010, the number exploded to more than 1,000. These so-called “earthquake swarms” are occurring in other places where the ground is not supposed to move. There have been abrupt upticks in both the size and frequency of quakes in Arkansas, Colorado, Ohio, and Texas. Scientists investigating these anomalies are coming to the same conclusion: The quakes are linked to injection wells. Into most of them goes wastewater from hydraulic fracking, while some, as those in Prague, are filled with leftover fluid from dewatering operations.
The impact of fossil fuels is no secret, but until now the short list of dirty energy’s villains never included water. Together, oil and gas extraction and production generate about 878 billion gallons of wastewater annually, roughly what tumbles over Niagara Falls every two weeks. More than a third is injected back into disposal wells. With natural gas production on the rise—it has jumped 26 percent since 2007, chiefly because fracking now makes it economically viable to pursue gas trapped in shale deposits—and unconventional practices such as dewatering ramping up domestic oil development, the wastewater deluge is expected to get worse. Operators are injecting more water than ever into drilling wells, while boring new wells to accommodate the overflow. Yet nobody really knows how all this water will impact faults, or just how big an earthquake it could spawn. In the West, small quakes don’t often cause much damage because of stricter seismic regulations but also because the underground formations—buckled, with younger rock—absorb all but the biggest events. Induced quakes, however, are happening primarily in flatter states, amid more rigid rock, making them more destructive—a stone makes a bigger splash when it’s hurled into a glassy pond than a river of raging whitewater.
For its part, industry is doing its best to avoid discussing the issue publicly, even as its leading professional guild, the Society of Petroleum Engineers, recognized the matter was serious enough to call its first-ever meeting devoted to “injection induced seismicity.” Held in September, the SPE’s 115-member workshop sought to “better understand and mitigate potential risks.” When I reached out to SPE coordinator Amy Chao, she told me, “I appreciate your interest but press is not allowed to attend in any fashion.” My requests to speak with geophysicists at leading oil and gas companies implicated in injection-induced earthquakes were also ignored or denied. I did manage to speak with Jean Antonides, vice president of exploration for New Dominion, which operates one of the wells near the Wilzetta Fault. He informed me that people claiming to know the true source of the Oklahoma quakes are “either lying to your face or they’re idiots.”
Nonetheless, there’s growing concern among state officials. After a spate of quakes linked to injection wells shook northern Arkansas, the state’s oil and gas commission declared a moratorium on underground wastewater disposal activities within a 1,000-square-mile area encompassing the towns of Guy and Greenbrier and required seismic-risk studies in the greater Fayetteville Shale area. Affected residents filed a class-action lawsuit against Chesapeake Energy and BHP Billiton Petroleum—the first time anyone has sued oil and gas companies for causing an earthquake. After an injection well was linked to quakes in Youngstown, Ohio, Gov. John Kasich issued an executive order requiring operators to conduct seismic studies before the state will issue well permits. So far, Ohio is alone in this regard; no other state—or the federal government—requires any type of seismic-risk assessment for all of its injection wells. And that worries scientists: “Nobody is talking to one another about this,” says William Ellsworth, a prominent USGS geophysicist who’s published more than 100 papers on earthquakes. Among other mishaps, Ellsworth worries that a well could pierce an unknown fault “five miles from a nuclear power plant.”
THE EPA CLASSIFIES AND REGULATES underground injection wells—some 700,000 and counting—based on what goes into them. There are six categories. Class VI wells sequester carbon dioxide; Class V wells store nonhazardous fluids; nuclear waste is stashed in Class IV wells; Class III wells are used in mining salt, uranium, copper, and sulfur; industrial chemicals get stored in Class I wells. Wastewater from oil and gas operations is discharged—typically by injecting it under pressure—into Class II wells.
There are at least 155,000 Class II wells in the United States. Of these about 80 percent are involved in recovering hydrocarbons, predominantly through slick-water hydrofracking, a technique developed by Halliburton. Fracking fluid—water blended with lubricants, thickeners, disinfectants, and other compounds—is pumped into well bores at extremely high pressures. Eventually, the fluid reverses course and—along with millions of gallons of salt water that resides underground—ascends to the surface. The “flowback,” now laden with natural gas, is collected, the gas is extracted, and the residual fluid is pumped into disposal wells. There are roughly 40,000 of these, and they can be up to 13,000 feet deep.
The extraction process itself doesn’t generally produce earthquakes. This is because of something known as pore pressure, a measurement of how much stress a fluid exerts into the “pores” of surrounding rock. The whole aim of fracking is to rapidly increase pore pressure just long enough to cleave fissures into sediment and free trapped gas, after which time pore pressure equalizes, easing the subterranean stress. Only rarely is pore pressure high enough in a fracking well to cause an earthquake that can be felt at the surface.
But while fracking wells are intended to withstand high pore pressure, wastewater disposal wells are not. When pore pressure spikes in disposal wells, it can move rock. Disposal wells are drilled into vast, permeable formations—think giant sponges—where there’s plenty of space for water to spread out. But because water is heavy, the more of it that is sluiced into a well, the more it weighs on the rock below. And as Scott Ausbrooks, a geologist with the Arkansas Geological Survey, points out, “Water does not like to be squeezed.” Eventually it finds an escape route, “just like a room of people. The more you put in, the more crowded it gets, and at some point, people are going to start being pushed out the doors.”
ANIMATED GIF: FRACKED UP?
Drillers inject high-pressure fluids into a hydraulic fracturing well, making slight fissures in the shale that release natural gas. The wastewater that flows back up with the gas is then transported to disposal wells, where it is injected deep into porous rock. Scientists now believe that the pressure and lubrication of that wastewater can cause faults to slip and unleash an earthquake.
Illustration: Leanne Kroll. Animation: Brett Brownell
With the oil and gas boom generating record amounts of wastewater, these rooms are getting increasingly jam-packed. Exactly how much? The EPA tracks volumes but wouldn’t provide them; agency officials declined numerous requests for interviews. Companies are also pumping into denser rock, or into deeper formations that are inherently unstable. “There’s much more injection going on today where there wasn’t injection before,” says Cliff Frohlich, associate director of the Institute for Geophysics at the University of Texas-Austin, who recently identified a cluster of wells at the Dallas/Fort Worth International Airport as the likely culprit for nearby earthquakes.
Too much wastewater in a disposal well forces liquid downward and outward, he adds. It can meander for months, creeping into unknown faults and prying the rock apart just enough to release pent-up energy. Frohlich describes this as the “air hockey” effect. A puck on an air hockey table won’t move even if the table is tilted upward a few degrees. “It would just sit there,” he says. “But when you turn on the air, it reduces the friction and the puck will slide. There are faults most everywhere. Most of them are stuck, because rock on rock is pretty sticky. But if you pump a fluid in there to reduce the friction, they can slip.”
*It should be noted that the United States Geological Survey used two different techniques to estimate the earthquake magnitude at 5.6. The Global Centroid-Moment-Tensor Project at Lamont-Doherty Earth Observatory of Columbia University used different methods to measure it at 5.7. As Justin Rubinstein of the USGS told us, this type of variance is not unusual, and the measurements are considered consistent.