The production of oil and natural gas through hydraulic fracturing methods creates only a low risk for inducing earthquakes that can be felt by people, the National Research Council, an arm of the National Academy of Sciences, concludes in a new study. Only a very small fraction of natural resource extraction activities has caused noticeable earthquakes, and these are related to wastewater storage activities subsequent to, and separate from, the fracking process itself, the report notes.
Wastewater Storage the Key
Although the hydraulic fracturing (fracking) process itself is unlikely to induce earthquakes, the underground disposal of fracking wastewater presents a higher risk of small earthquakes, the study concludes. These risks, the study notes, can be mitigated by carefully choosing where and how to store wastewater underground, or by disposing it above ground.
Minor Seismic Events
“A string of small seismic events in Arkansas, Ohio, Oklahoma, and Texas in the past several years has been related to waste water disposal associated with oil and gas production. These seismic events have brought the issue of induced (human-caused) seismicity firmly into public view,” the study noted.
“Although only a very small fraction of injection and extraction activities at hundreds of thousands of energy development sites in the United States have induced seismicity at levels that are noticeable to the public, seismic events caused by or likely related to energy development have been measured and felt in Alabama, Arkansas, California, Colorado, Illinois, Louisiana, Mississippi, Nebraska, Nevada, New Mexico, Ohio, Oklahoma, and Texas,” the study reported.
Even with the higher risk of earthquakes associated with underground wastewater storage, the earthquakes have been sufficiently minor to cause no loss of life or significant property damage.
“Induced seismic events associated with these energy technologies have not resulted in loss of life or significant damage in the United States,” explained a National Academies press release accompanying the study.
Contributing Factors ‘Well Understood’
“The basic mechanisms that can induce seismicity related to energy-related injection and extraction activities are not mysterious and are presently well understood,” the study reported. “Only a very small fraction of injection and extraction activities among the hundreds of thousands of energy development wells in the United States have induced seismicity at levels that are noticeable to the public.”
“The factor most directly correlated with induced earthquakes is the total balance of fluid introduced or removed underground,” the press release explained. “Because oil and gas development, carbon capture and storage, and geothermal energy production each involve net fluid injection or withdrawal, all have at least the potential to induce earthquakes that could be felt by people. However, technologies designed to maintain a balance between the amounts of fluid being injected and withdrawn, such as most geothermal and conventional oil and gas development, appear to produce fewer induced seismic events than technologies that do not maintain fluid balance.”
The study identified the factors necessary to cause seismic events.
“For such activities to cause these events, a certain combination of conditions has to exist simultaneously:
“a. significant change in net pore pressure in a reservoir;
“b. a pre-existing, near-critical state of stress along a fracture or fault that is determined by crustal stresses and the fracture or fault orientation; and
“c. fault-rock properties supportive of brittle failure.”
Study Debunks Activist Myths
Environmental activist groups have pushed the notion that hydraulic fracturing causes earthquakes, in an effort to convince state legislatures to ban or severely restrict energy production.
“The National Research Council has convincingly shot down yet another alarmist myth about energy production,” said Jay Lehr, science director for The Heartland Institute, which publishes Environment & Climate News. “Hydraulic fracturing does not cause earthquakes.
“In certain circumstances, post-fracking water storage techniques can cause an increase in very minor earthquakes, but these minor side effects have nothing to do with the fracking process itself. And even these minor impacts are becoming better understood and are increasingly being averted,” Lehr observed.
“Just as importantly, natural gas is a clean-burning energy source that produces almost no emissions. It offers a win-win option for both the economy and the environment,” Lehr explained.
James M. Taylor ([email protected]) is managing editor of Environment & Climate News.