Fracking Unlikely to Cause Earthquakes, Says NRC Study

Jul 2012

Fracking is unlikely to cause earthquakes, according to a recent study by the National Research Council (NRC). Induced Seismicity Potential in Energy Technologies, National Research Council, June 15, 2012. The study was commissioned by the U.S. Department of Energy (DOE), after Sen. Jeff Bingaman (D-NM) requested in 2010 that the DOE use the NRC to study the potential for seismicity induced by energy development.

Hydraulic fracturing (fracking) involves the injection of fluids into underground shale formations to release trapped natural gas, and wastewater from fracking operations is sometimes disposed of using underground injection wells. Both types of injection have led to concerns that fracking can cause earthquakes.

The NRC study found that fracking “as presently implemented . . . does not pose a high risk for inducing felt seismic events.” Out of the approximately 35,000 fracking wells that exist in the United States, only one case of “felt seismicity” (in Oklahoma in 2011) has been reported where fracking is suspected, but not confirmed, as the cause of the seismicity. And globally only one case of “felt induced seismicity” (in Blackpool, England, in 2011) has been confirmed as caused by fracking. The study noted that these low numbers were likely due to “the short duration of injection of fluids and the limited fluid volumes used in a small spatial area.”

In contrast, the study found that the disposal of wastewater into underground injection wells “does pose some risk for induced seismicity, but very few events have been documented over the past several decades relative to the large number of disposal wells in operation.” This may be because most “disposal wells typically involve injection at relatively low pressures into large porous aquifers that have high natural permeability, and are specifically targeted to accommodate large volumes of fluid.” Factors that determine the probability of a seismic event include the volume of fluid injected, the injection rate, the injection pressure, and the proximity to existing faults and fractures. Where seismicity is detected, “[r]educing injection volumes, rates, and pressures have been successful in decreasing rates of seismicity associated with waste water injection.” The study cautioned that the “long-term effects of a significant increase in the number of waste water disposal wells for induced seismicity are unknown,” and that “[f]urther research is required.”