Carbon capture and storage likely to cause earthquakes

of less than 1 percent every thousand years to be effective.

“The bar is much higher in this case,” Zoback said.

Where to put it
The areas where CCS is already practiced successfully follow a very specific geologic profile.

Ideally, the reservoirs themselves are formed from porous, weakly cemented materials that slow pressure build-up, but are isolated from the surface by an impermeable rock layer.

The North Sea’s Sleipner gas field, for example, makes use of the Utsira formation — a porous sandstone structure under impermeable shale.

It is an open question as to whether there are enough low-risk geologic formations to engage in CCS at the necessary level.

The authors say that approximately 3,500 Utsiras would be necessary to contribute significantly to reductions. Some scientists, however, say fewer would suffice.

“Of course, you need to pick sites carefully,” said Sally Benson, Stanford professor of energy resources engineering and director of Stanford’s Global Climate and Energy Project. “But finding these kinds of locations does not seem infeasible.”

She argues that only 600 such sites would be necessary, and that existing formations in Texas and the Gulf Coast, the Middle East, the North Sea, and Western Australia provide promising sequestration reservoirs. Pressure build-up in other areas can also be managed, she says, by controlling injection rates and well design.

Zoback says there will continue to be a use for CCS at a small scale, in regions that are near both CO2-producing plants and ideal geologic formations.

“But for the U.S. and the world to be considering CCS one of the potential solutions to the greenhouse gas problem — it’s a very high risk endeavor,” he said. “We need options that are practical, don’t cost literally trillions of dollars and aren’t vulnerable to moderate size earthquakes.”

The issue of triggered earthquakes is also the subject of a new report from the National Research Council, which concludes that, “continued research will be needed to examine the potential for induced seismicity in large-scale carbon capture and storage projects.”

Zoback testified on Tuesday before the Senate Committee on Energy and Natural Resources, in hearings on “Induced Seismicity Potential in Energy Technologies.”

— Read more in Mark D. Zobacka and Steven M. Gorelickb, “Earthquake triggering and large-scale geologic storage of carbon dioxide,” Proceedings of the National Academy of Sciences (18 June 2012) (doi: 10.1073/pnas.1202473109); and Mark D. Zoback, “Managing the seismic risk posed by wastewater disposal,” Earth (17 April 2012); also see the National Research Council report, Induced Seismicity Potential in Energy Technologies