Hydraulic fracturing presents little risk of causing damaging earthquakes, a government study released today concludes, but earthquakes can be caused by other oil and gas activities, particularly injection of waste from drilling.

Carbon capture and storage (CCS) and geothermal energy projects can also lead to man-made earthquakes, says the report from the National Research Council.

The report suggests implementing "best practices" for avoiding such earthquakes and having regulators make plans for when they begin to occur.

"No mechanisms are currently in place for efficient coordination of governmental agency response to seismic events that may have been induced," the report says. "No best practices protocol for addressing induced seismicity is generally in place for each energy technology."

Sites in the United States and Canada with documented reports of quakes caused by or likely related to energy development from various energy technologies. The reporting of small induced seismic events is limited by the detection and location thresholds of local surface-based seismic monitoring networks. Click to enlarge. Map courtesy of National Research Council.

The report will be the subject of a hearing next week in the Senate Energy and Natural Resources Committee. Chairman Jeff Bingaman (D-N.M.) requested the report two years ago.

U.S. Geological Survey 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).

Some state officials have shut down injection wells after earthquakes. But other states have rejected USGS findings linking oil and gas waste injection in their states to earthquakes (EnergyWire, April 16). Scientists are also looking at whether two recent earthquakes near Nacogdoches, Texas, were caused by oil and gas waste injection (EnergyWire, May 21).

Oil and gas producers are exempt from federal environmental laws designed to prevent industrial waste injection wells from triggering earthquakes (EnergyWire, March 22).

Bingaman sought the study of "induced seismicity" because he was troubled that the kind of fears triggered by earthquakes could shake public confidence in the country's growing energy industry.

"Much of public opposition to the deployment of advanced energy technologies in the United States stems from a lack of clear, trusted information regarding the safety of those new energy facilities for the local communities that are their neighbors," Bingaman wrote in a June 2010 letter to Energy Secretary Steven Chu, asking for interagency cooperation on such a study.

The study committee began meeting in September 2010, holding meetings in Washington, Texas and California.

Hydraulic fracturing is a drilling practice in which large amounts of water are jammed underground at high pressure to blast apart deep rock formations that then release oil or gas. Production from shales like the Marcellus in Pennsylvania and the Bakken in North Dakota are dependent on a form of fracking that uses millions of gallons of water and very high pressure.

But the study notes fracking itself has been linked to a low number of earthquakes that could barely be felt at the surface.

"The process of hydraulic fracturing a well as presently implemented for shale gas recovery does not pose a high risk for inducing felt seismic events," the report says.

But a lot of that fluid comes back up as brine, even more toxic than it went down. Some can be reused, but eventually most is injected underground. As drilling is becoming more common in the country amid a domestic drilling boom, a lot more water is being injected than in previous years. Because large amounts of water are injected for a long time, injection can increase pressures underground. In rare circumstances, that can cause earthquakes, the report explains.

CCS could also cause earthquakes because it also involves injecting large amounts of fluid, the report says. But the study notes that the seismic potential of CCS isn't well-understood because there are no large CCS projects in operation.

The report says the earthquake potential of geothermal projects appears to be related to fluid balance considerations and temperature changes produced in the subsurface. And different forms of geothermal resource development appear to have differing potential for causing earthquakes.