"I am not against carbon dioxide sequestration by any means and it certainly has a role," Zoback said. "What I am asking people to consider is whether or not it should really be one of the key components of a strategy for reduction of greenhouse gas."
Even if earthquakes are induced, he said it would not be an issue of immediate safety. It would take a fairly large earthquake to create a rupture that would send carbon dioxide pouring back out on the surface and that situation should be fairly easy to avoid. To get big earthquakes, you need big faults and locations such as that would be ruled out during the selection process.
The problem Zoback foresees is that the seismicity could create small pathways through the rock by which carbon dioxide would gradually seep back into the air.
"If the carbon dioxide permeates back out of the reservoir, the effort to keep it out of the atmosphere will have been futile," he said. In addition to failing to solve the problem, a lot of time and money would turn out to have been wasted.
There are two sequestration projects already underway around the world, in Norway and Algeria, and so far they appear to be working as planned. But Zoback said 3400 such projects would be needed worldwide by midcentury to deal with the volume of carbon dioxide that we will be generating.
"Finding that many ideal sites around the globe is not impossible, but it is going to be a tremendous challenge," he said. And while some view the issues associated with injecting gas into the subsurface as mainly a technical challenge, Zoback thinks that challenge may not be an easy one to engineer around.
"My main concern is to get these geological
|Contact: Louis Bergeron|