Earthquakes are on the rise in Oklahoma and Texas, and media reports have made sure to link hydraulic fracturing, or fracking, operations to quakes rocking parts of the country. But connecting fracking to earthquakes is frustrating scientists working on the issue.
“We’re not talking at all about fracking,” Dr. Matthew Hornback, a scientist at Southern Methodist University who recently released a study on quakes in North Texas, told Congress Tuesday.
“In fact, it’s been driving us crazy, frankly, that people keep using it in the press,” Hornback told lawmakers during a hearing.
Hornback and fellow SMU researchers found that wastewater injection wells, not fracking itself, are behind the rise in earthquakes in North Texas. Oil and gas companies take brine and other substances out of the ground when extracting fuels and then inject the waste from that process back into the ground.
The huge increase in oil and gas drilling has forced billions of wastewater underground in recent years. The EPA and states regulate the disposal of wastewater into underground wells — before 1985 companies could dispose of this water in state waterways.
Underground wastewater storage is an improvement over disposing of such waste in waterways, but the large increase in wastewater storage is being linked to increases in magnitude three and larger earthquakes. The U.S. Geological Survey notes that from “1973–2008, there was an average of 21 earthquakes of magnitude three and larger in the central and eastern United States.”
“This rate jumped to an average of 99 M3+ earthquakes per year in 2009–2013, and the rate continues to rise. In 2014, alone, there were 659 M3 and larger earthquakes,” the survey notes.
Wastewater injection, however, should not be confused with fracking itself. Fracking is the well-stimulation process that allows for oil and gas companies to extract resources from shale formations, while wastewater injection is the disposal process for water produced during extraction. As the USGS notes, fracking “does not appear to be linked to the increased rate of magnitude 3 and larger earthquakes.”
USGS researcher William Ellsworth told the Associated Press that “deep injection of the wastes still is the principal culprit,” adding that the “controversial method of hydraulic fracturing or fracking, even though that may be used in the drilling, is not physically causing the shakes.”
But are these earthquakes cause for alarm? The EPA says there are more than 170,000 Class II injection wells in the country — Class II wells are for the injection of “brines and other fluids associated with oil and gas production, and hydrocarbons for storage.”
Of those wells, the USGS says that only 40,000 of these wells are used for “waste fluid disposal wells for oil and gas operations.” Of these, only “a small fraction of these disposal wells have induced earthquakes that are large enough to be of concern to the public,” USGS states.
EPA data shows there are as many as 844,000 injection wells of all classes in the country. Most of these are Class V wells that store non-hazardous waste in shallow, low-tech storage areas.
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