The top geologists in Oklahoma and Colorado say scientists at the U.S. Geological Survey were too quick to conclude that disposal of oil and gas waste is linked to a rise in the number of earthquakes in the middle of the country.
"It's unfortunate that they've jumped to this conclusion," said Colorado state geologist Vince Matthews. "There really needs to be a good scientific understanding."
Colorado and Oklahoma both had significant earthquakes last year. They also figure prominently in the findings of Bill Ellsworth and fellow USGS scientists that a rash of midcontinent earthquakes in the past 11 years or so is man-made and that the earthquakes appear to be linked to such oil and gas activity.
In interviews, Matthews and Oklahoma state geologist G. Randy Keller stressed that injection of industrial waste can cause earthquakes. That proved notoriously true in Colorado at the Rocky Mountain Arsenal.
And they say the science may yet show underground injection of oil and gas wastewater may have unleashed earthquakes, but the data are not yet there to prove it.
But Keller said his office got so many inquiries after the USGS study hit the news last month that he put out a "position statement" on man-made earthquakes.
"It is unlikely that all of the earthquakes can be attributed to human activities," the position statement says. "We consider a rush to judgment about earthquakes being triggered to be harmful to state, public and industry interests."
Keller also noted that activists who oppose drilling and hydraulic fracturing had seized on such findings.
"There's not a lot of calm reflection," Keller said.
But Ellsworth is standing by the conclusions of his research and says that some of the state geologists' positions stem from a misperception "that needs to be corrected."
The two state geologists are not the only ones sent scrambling by the USGS study, which is to be presented this week at the annual meeting of the Seismological Society of America in San Diego.
David Hayes, the Obama administration official who is No. 2 at the Interior Department, posted an article on the department website last week seeking to "clarify a few points" about the USGS investigation of man-made earthquakes (EnergyWire, April 12). USGS is part of the Interior Department.
"While it appears likely that the observed seismicity rate changes in the middle part of the United States in recent years are manmade, it remains to be determined if they are related to either changes in production methodologies or to the rate of oil and gas production," he wrote.
But in the days between Hayes' article and Ellsworth's research becoming news, a higher-ranking USGS official drew a stronger link than Hayes between drilling injection and quakes.
"There's a large number of those so-called excess earthquakes occurring in southern Colorado and they're associated with production of coalbed methane," Bill Leith, associate coordinator of the USGS Hazards Program, said in an April 4 presentation at the U.S. Geological Survey National Center in Reston, Va. In Oklahoma, he said, an increase in earthquakes has been "spatially associated" with drilling injection.
"It's a very significant phenomenon in seismicity of the United States," Leith said, "although it's localized and the earthquakes have not been all that large."
Seismic surge corresponds to shale boom
Ellsworth and his team concluded that a "remarkable" increase in the number of earthquakes in the middle of the country since 2001 is "almost certainly manmade." And all of the potential causes they explore in the published abstract relate to drilling, or more specifically, deep underground injection of drilling waste (EnergyWire, March 29).
The USGS abstract says nothing about hydraulic fracturing, a process essential for production of oil and gas from shale. Many people, particularly critics of drilling, use the term "fracking" to mean all aspects of drilling. But hydraulic fracturing is a process done at a specific time in the production of oil and gas.
In fracturing, sand and chemical-laced water are injected underground at high pressure to crack open shale formations and release oil and gas. Much of the water comes back up as a briny, toxic soup and must be disposed of. Generally, the brine is permanently injected into deep disposal wells that are known, in rare circumstances, to lubricate faults and unleash earthquakes.
The scientists found the frequency of earthquakes started rising in 2001 across a broad swath of the country between Alabama and Montana. There were 50 earthquakes greater than magnitude 3.0 in 2009, the abstract states, then 87 quakes in 2010. The 134 earthquakes in the zone last year represented a sixfold increase over 20th-century levels.
The rise in seismic activity corresponds to a nationwide surge in shale drilling. According to the federal Energy Information Administration, shale gas production grew, on average, nearly 50 percent a year from 2006 to 2010.
The USGS findings were quickly cited by critics of the drilling industry. The Environmental Working Group called it "another piece of evidence that shows we have to proceed carefully."
There are 181 injection wells in the Oklahoma county where the magnitude-5.7 quake occurred in November. But Keller and Matthews said injection well operators in Oklahoma and Colorado do not have to use pressure to keep wastewater down, as was the case with wells blamed for earthquakes last year in Arkansas and Ohio.
"It just flows under the force of gravity," Keller said.
Matthews said another important difference is that the 2001 earthquakes in southern Colorado stopped, even though the injection did not. In Arkansas, earthquake activity has fallen sharply since state officials banned injection in the region where a "swarm" of quakes had taken place.
In an email exchange with EnergyWire, Ellsworth said Keller and Matthews are incorrectly putting too much emphasis on whether wastewater is injected under pressure or whether the earthquakes stop after the injections stop.
"The implication is that injection under pressure is a necessary condition for inducing earthquakes. This is not true. This perception is widely held and needs to be corrected," Ellsworth said.
He noted that some of the injections at Rocky Mountain Arsenal were not under pressure, and the quakes continued for a year after injection stopped.
Keller will also be at the earthquake meeting in San Diego, though he will not be talking about man-made earthquakes.
But his colleague at the Oklahoma Geological Survey, Austin Holland, is scheduled to discuss his findings that hydraulic fracturing itself might be linked to much smaller earthquakes in southern Oklahoma.
The quakes, which struck on Jan. 18 in a rural area near Elmore City, peaked at magnitude 2.8 and caused no deaths or property damage (E&E PM, Nov. 2, 2011).