InfrastructureCarbon capture and storage likely to cause earthquakes

Stanford geophysicists say earthquakes triggered by underground CO2 storage, while probably too small to cause major damage, could release stored CO2 into the atmosphere.

Carbon capture and storage, or CCS, is a major component of the world’s greenhouse gas reduction strategy. Involving injecting and storing carbon dioxidein underground geologic reservoirs, the method is used at several oil and gas exploration sites worldwide to prevent the gases from entering the atmosphere.

A Stanford University release reports that significantly reduce emissions, however, CCS would need to operate on a massive scale, potentially sequestering upward of 3.5 billion metric tons of CO2 each year. A new technical hurdle may mean CCS will not be able to get anywhere near that volume.

In a paper appearing in the journal PNAS, Stanford geophysics Professor Mark Zoback and environmental Earth science Professor Steven Gorelick argue that, in many areas, carbon sequestration is likely to create pressure build-up large enough to break the reservoirs’ seals, releasing the stored CO2.

“Almost all of our current climate mitigation models assume CCS is going to be one of the primary tools we use,” said Zoback. “What we’re saying is, not so fast.”

Induced seismicity
Intraplate earthquakes — earthquakes that occur far from the boundaries between tectonic plates — can occur nearly anywhere in continental interiors, due to what the researchers describe as “the critically stressed nature of the Earth’s crust.” Small pressure build-ups near potential faults reduce friction, increasing the likelihood of a fault slip.

The release notes that it has been known for a half-century that human activities can increase pressure to the point of inducing small temblors. In the 1960s, the injection of wastewater into a well near Denver triggered a series of small earthquakes. Last year, similar quakes were induced in Arkansas, Ohio and on the border of Colorado and New Mexico.

Reviewing field stress measurements and laboratory studies of shear displacements, Zoback and Gorelick say injection of massive quantities of CO2 would be likely to produce the same result.

Zoback has previously described wastewater-induced quakes as manageable, low-risk events. Carbon injection is unlikely to trigger large, destructive earthquakes, the professors argue, but “the implications are different if you’re trying to store carbon for thousands of years.” Zoback said.

Zoback and Gorelick state that even a fault slip of a few centimeters could allow stored CO2 to reach the surface – a serious concern, since the researchers argue that carbon repositories need a leak rate