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Winter 2012 Vol. 12 Number 2

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On Shaky Ground?

Graphic depicting oil extraction, ©Hemera/Thinkstock

To produce much of the energy that powers our daily lives -- from the natural gas that heats our homes to the petroleum that runs our cars -- a step that injects or withdraws large volumes of liquid deep beneath the Earth's surface is often involved. One unfortunate side effect of this step is the possibility of causing an earthquake. In the past several years, earthquakes related to energy projects have drawn heightened public attention, particularly in areas where development is ongoing or planned. In response, Congress requested that the U.S. Department of Energy call upon the National Research Council to examine the issue.

Hydraulic fracturing, carbon capture and storage, geothermal energy, and conventional oil and gas development all have components of production that involve underground fluid injection, while oil and gas development and geothermal energy production also withdraw fluid. Hydraulic fracturing, commonly known as fracking, pumps a chemical mixture into wells and results in natural gas flowing up the well along with wastewater. Although some of this wastewater can be recycled, it is often disposed of through deep underground injection at a location separate from the production site. Currently, commercial carbon capture and storage involves liquefying carbon dioxide produced at power plants and pumping small volumes of the mixture over long periods of time at high pressure deep underground for permanent storage.

The committee that examined the potential for man-made earthquakes that result from these activities found that hydraulic fracturing has a low risk for inducing earthquakes that can be felt by people, but the underground injection of wastewater produced from this and other energy technology processes has a higher risk of causing earthquakes. Furthermore, carbon capture and storage may cause earthquakes, but there is limited information to understand to what extent because no large-scale projects are in operation that can inject the large volumes necessary to reduce greenhouse gas emissions.

The factor most directly correlated with induced earthquakes is the total balance of fluid introduced or removed underground, the committee said. Because most of the energy technologies explored in the study involve net fluid injection or withdrawal, they all have the potential to cause an earthquake that could be felt by people. Technologies designed to maintain a fluid balance between those being injected and withdrawn -- as is the case with most geothermal and oil and gas development -- appear to produce fewer seismic events than technologies that do not balance the fluids.
-- Jennifer Walsh

Induced Seismicity Potential in Energy Technologies . Committee on Induced Seismicity Potential in Energy Technologies, Division on Earth and Life Studies (2012, approx. 300 pp.; ISBN 0-309-25367-5; available from the National Academies Press, tel. 1-800-624-6242; $57.00 plus $5.00 shipping for single copies).

The study was chaired by Murray W. Hitzman, Fogarty Professor of Economic Geology in the department of geology and geological engineering at the Colorado School of Mines in Golden. The study was sponsored by the U.S. Department of Energy.

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Copyright 2012 by the National Academy of Sciences