Burying carbon dioxide in the ground, considered a promising way to combat climate change, may increase the risk of earthquakes, according to a report.
The process, in which liquefied carbon dioxide is stored in caverns, “may have the potential for causing significant induced seismicity,” the National Research Council said today. Injecting wastewater underground from natural-gas fracking may also trigger earthquakes, while using hydraulic fracturing to get trapped gas doesn’t pose a “high risk,” the report found.
Burying carbon may pose a higher risk of quakes than wastewater disposal because it involves the continuous injection of high volumes of liquefied gas at high pressure, said Murray Hitzman, professor of economic geology at the Colorado School of Mines and chairman of the committee that produced the report.
“Those larger volumes then will increase the pressure in the subsurface over very large areas,” Hitzman said on a conference call. “The bigger the area of the high pressure, the more chance of seeing a fault. The more distance that it moves, the bigger the earthquake.”
The International Energy Agency said in a June 11 report that carbon capture is “the only technology on the horizon today that would allow industrial sectors (such as iron and steel, cement and natural gas processing) to meet deep emissions reduction goals.”
While no large-scale carbon-capture projects are on line, abandoning the technology would “significantly” increase the cost of reaching greenhouse-gas emissions targets, the IEA said.
“Projects that inject or extract large net volumes of fluids over long periods of time such as CCS may have potential for larger induced seismic events,” according to the report. “Insufficient information exists to understand this potential.”
The National Research Council, a nonprofit based in Washington, provides scientific information for government decision-makers under the auspices of the National Academy of Sciences, the National Academy of Engineering and the Institute of Medicine.
Senator Jeff Bingaman, a New Mexico Democrat and chairman of the Energy and Natural Resources Committee, requested the study to assess the potential for seismic events related to energy production. The report covers gas fracking, enhanced recovery of conventional oil and gas, geothermal energy and carbon capture and storage.
In the U.S., fracking by forcing millions of gallons of chemically treated water and sand underground to free trapped gas has been used on 35,000 wells, according to the report. The only confirmed link between fracking and seismic activity was a 2.3-magnitude quake near Blackpool, England, in 2011, the report found.
Evidence linking underground storage of fluids from energy production and earthquakes led regulators to add requirements for water-disposal wells. Researchers think an increase in wastewater wells may be the cause for a sixfold jump in total quakes in the central U.S. from 2000 to 2011.
“If we have more wells, we have more chance of events, and if we have more events there’s more probability of higher magnitude events,” Hitzman said.
Seismic events related to energy development were measured in Alabama, Arkansas, California, Colorado, Illinois, Louisiana, Mississippi, Nebraska, Nevada, New Mexico, Ohio, Oklahoma and Texas, according to the report.
“Although induced seismic events have not resulted in loss of life or major damage in the United States, their effects have been felt locally, and they raise some concern about additional seismic activity and its consequences in areas where energy development is ongoing or planned,” according to the report.
U.S. Geological Survey researchers found that, for three decades prior to 2000, seismic events in the central U.S. averaged 21 a year. They jumped to 50 in 2009, 87 in 2010 and 134 in 2011, according to a study presented April 18 at the annual meeting of the Seismological Society of America.
Last year, Arkansas regulators shut four disposal wells in the Fayetteville Shale, where companies are drilling for gas, after an outbreak of earthquakes near the town of Guy, including a 4.7-magnitude temblor. Drillers must now provide information on the geology of disposal-well sites and avoid known faults when planning the wells.
The Ohio Department of Natural Resources in March proposed rules for wastewater disposal, including bans on drilling into some rock formations and requiring geology reviews before wells are approved. Beginning in March 2011, there have been 12 temblors near a disposal well in Youngstown, including a 4-magnitude quake that struck on New Year’s Eve.
Disposal of wastewater from gas wells involves injection at low pressure into porous aquifers that are chosen to accommodate large volumes of fluid. There are about 151,000 disposal wells for oil and gas production in the U.S., according to the Environmental Protection Agency. Most pose no earthquake hazard, though the long-term effects of an increase in the number of wells are unknown, according to today’s report.
State and federal agencies and research groups are examining the link between energy production and earthquakes, though greater funding may be needed to address “unexpected events,” according to the report.
“We’ve have wastewater disposal wells for many, many, many decades, but they’re increasing in number,” Hitzman said. “One of the differences is we just have a whole bunch more wells out there.”