U.S. EPA permits for disposing of oil and gas drilling waste underground might not be providing enough information to determine whether a well used for disposal has caused earthquakes, a U.S. Geological Survey official said yesterday in a Senate hearing.

"Without more precise and complete data, it will be very difficult to assess the hazard potential from the tens of thousands of UIC [Underground Injection Control] wells that are currently in operation," Bill Leith, senior science adviser for earthquake and geologic hazards at USGS, told the Energy and Natural Resources Committee hearing.

Underground disposal of drilling waste is regulated by state officials in most states, though not Pennsylvania and a handful of others. The permitting standards, though, are set by EPA, under the Underground Injection Control provisions of the Safe Drinking Water Act.

Leith was testifying about a new report by the National Research Council about man-made earthquakes caused by energy production (Greenwire, June 15).

One of his fellow witnesses, Stanford geophysics professor Mark Zoback, said it might be a good idea to test injection sites for their earthquake potential when regulators consider permit applications from industry.

"Perhaps it should be, at least in some parts of the country," Zoback said.

Federal regulations currently require such seismic testing for some sorts of wastewater injection, such as hazardous waste from manufacturing. But it is not required for wastewater from oil and gas drilling. There are hundreds of times more wells receiving oil and gas waste than there are wells receiving manufacturing waste, and industry says it would be cost-prohibitive to apply the same rules.

It is well-understood among scientists that injecting wastewater underground -- whether from energy production or something else -- can lubricate faults and create earthquakes.

Hydraulic fracturing and carbon capture and storage also can lead to "induced seismicity," or man-made earthquakes. But the small number of quakes linked to fracturing itself have been almost too small to be felt, and there is no carbon storage project large enough to cause a quake.

Fracturing in shale formations requires millions of gallons of water to be forced down well bores to crack the rock and release gas. Much of that comes back up, laden with salt and more toxic than it went down. Drillers dispose of it most commonly in deep underground wells. When the fluid is injected into or near a fault, it can trigger an earthquake.

Such earthquakes are rare, and there has never been death or serious injury from such a quake.

As oil and gas drilling has increased in the past few years, there have been increasing numbers of earthquakes linked to underground injection of oil and gas waste.

"With the vast numbers, there are so many and many with large amounts of injection, occasionally there will be an event," said Murray Hitzman, the Colorado School of Mines professor who chaired the study on man-made earthquakes for the council, which is part of the National Academies.

Oil and gas waste disposal has been linked to earthquakes in Arkansas, Colorado, Ohio and Texas. Scientists have linked Oklahoma's largest-ever earthquake, a magnitude-5.6 event in November, to brine injection from drilling. The earthquake injured two people and damaged 14 homes. But state officials have rejected the Oklahoma findings as premature.

USGS scientists raised the profile of the issue earlier this year with research finding a "remarkable" rash of earthquakes in the middle of the country that they linked to underground injection of waste brine from oil and gas production (EnergyWire, March 29).

Leith said that of all the high-profile earthquakes in the eastern and central United States last year, only the August quake in Virginia is "unequivocally" natural in origin.

He said better permitting information is needed to give useful information to local regulators about the earthquake risks of particular operations. Hitzman noted that many operations don't have a lot of testing done before drilling to see whether there are faults in the area.

For now, the experts said, one key concept is to not inject waste directly into known underground faults, which ranking member Lisa Murkowski (R-Alaska) said seemed "pretty obvious."

"This may seem like a no-brainer," Zoback said. "But that would go a long way toward making a rare occurrence even more rare."