No matter what other problems may or may not be linked to hydraulic fracturing, or fracking, the disposal of wastewater from oil and gas drilling almost certainly is primarily responsible for the recent spate of earthquakes in Oklahoma, normally a seismologically quiet state.
That’s the conclusion of a report issued April 21 by the Oklahoma Geological Survey (OGS), in which the state geologist Richard D. Andrews and Dr. Austen Holland, the state seismologist, said the rate of earthquakes near major oil and gas drilling operations that produce large amounts of wastewater demonstrate that the quakes “are very unlikely to represent a naturally occurring process.”
Andrews and Holland concluded that the “primary suspected source” of the quakes is not hydraulic fracturing, or fracking, in which water and chemicals are injected under high pressure to crack shale to free oil and gas trapped inside. It said the source is more likely the injection of wastewater from this process in disposal wells, because water used in fracking cannot be re-used.
“The OGS considers it very likely that the majority of recent earthquakes, particularly those in central and north-central Oklahoma, are triggered by the injection of produced water in disposal wells,” the statement said. It warned that residents should prepare for “a significant earthquake.”
Oklahoma recorded 585 earthquakes with a magnitude of 3 or greater, the equivalent of the force felt in Oklahoma City at the time of the terrorist bombing in 1995. This is a significant increase from 109 earthquakes of the same magnitude in 2013. Before 2008, when fracking became a popular drilling technique in the state, there were fewer than two earthquakes in Oklahoma each year, on average.
Andrews’ and Holland’s report draws the same conclusions as a study last year by Katie Keranen, an assistant professor of seismology at Cornell University, who found that injecting fracking wastewater into underground disposal sites tends to widen cracks in geological formations, increasing the chances of earthquakes.
Keranen’s study, in turn, reinforces similar conclusions in a previous study by the U.S. Geological Survey, which found that earthquakes in central and eastern parts of the United States between 2010 and 2013 also coincided with the disposal of fracking wastewater.
What’s important about Andrews’ and Holland’s conclusion is that they represent the state of Oklahoma, where energy is an important industry, providing about one-quarter of the state’s jobs. Last autumn, Gov. Mary Fallin, a Republican, dismissed the problem as speculative and urged further study.
But in a statement coinciding with Andrews’ and Holland’s report, Fallin said their ability to link wastewater disposal with earthquakes was significant and promised unspecified action. “Oklahoma state agencies already are taking action to address this issue and protect homeowners,” she said.
The state’s energy industry also supports further study of the state’s recent uncharacteristic seismic activity. “Oklahoma’s oil and natural gas producers have a proven history of developing the state’s oil and natural gas resources in a safe and effective manner,” Kim Hatfield, regulatory committee chairman for the Oklahoma Independent Petroleum Association, said in a statement.