PERCEIVED RISK OF INDUCED SEISMICITIY JUST AS POWERFUL AS ACTUAL RISK, PROJECT OPERATORS SAY

Tamar Hallerman
GHG Monitor
05/11/12

Operators of some large-scale CO2 storage projects say that while they are largely not concerned about potential induced seismicity that could occur as a result of CO2 injection into the subsurface, public opinion of perceived risk could shape their worries as much as actual geologic risk. Over the last six months, several lower-magnitude earthquakes have occurred in the Midwest that have been attributed to the injection of wastewater into the subsurface from shale gas fracking operations. The events have caused some in the carbon capture and storage industry to express concern that public sentiment stemming from the wastewater-induced earthquakes could translate to worries regarding CO2 storage operations, GHG Monitor previously reported (Vol. 7, Issue 3).

Overall, geologic studies have shown that the risk for earthquakes above a micro level, or 3.0 on the Richter scale, is fairly low for CO2 injection operations. However, geologists also point out that the subsurface injection of any type of fluid—common in the CO2 storage, geothermal and oil and gas industries—creates hundreds and thousands of earthquakes all the time, but most of those are too small to be felt at the surface. A multi-year study being conducted at Lawrence Livermore National Laboratory as a part of the National Risk Assessment Partnership has helped clarify that CO2 sequestration will not likely have a large seismic impact as long as site operators properly assess surrounding geology and properly take risk into account before injecting into the subsurface.

Operators Not Very Concerned on Technical Level

Speaking during a panel event at the Eleventh Annual Carbon Capture, Utilization and Sequestration Conference last week in Pittsburgh, several officials representing major CO2 injection projects said they are largely not concerned about the potential seismic effects of their operations. “If you look at the statistics, most injection wells are not seismically active,” said Jean-Philippe Nicot, a research scientist at the University of Texas’ Bureau of Economic Geology, which is helping run large-scale injection operations at the Southeast Regional Carbon Sequestration Partnership. “If they are, it is basically bad luck in most cases. In most cases, operators are [monitoring] so that the pressure doesn’t go very high,” subsequently lowering the likelihood of any microseismic events occurring, he said.

Stephen Bourne, a geophysicist with Shell Canada, which is spearheading the development of the Quest CCS project in Alberta, said that the company took seismicity concerns seriously during its planning stages for the project. “In the case of the Quest project, this is recognized as a potential threat to containment, and indeed we had an extensive assessment of this and vigorous discussion with the external experts that reviewed our [monitoring and verification] plans,” he said. Bourne added that due to the risk mitigation efforts undertaken by the company, “the technical risk is considered to be essentially non-significant.” 

Perceived Risk by Public Equally Important, Operators Say

But project operators speaking during the panel event also said that the perceived risk of the possibility of microseismic events among members of the public is just as important to their projects as the actual technical risk. “I think it’s important to distinguish the empirical risk from the perceived risk from local landowners living above the storage site who would perceive a threat that injection will raise pressure in the aquifer and that may create small earthquakes that shake the ground enough to be troublesome,” Bourne said. “We take perceived risk just as seriously as the actual technical risk assessment.” He said part of Shell’s strategy is to conduct extensive public outreach efforts in the time before injection to provide the “necessary reassurance” that there is no real threat of microseismic events

Rob Finley is director of the Advanced Energy Technology Initiative at Illinois State Geological Survey who is also overseeing large-scale injection of CO2 in the Mt. Simon formation of Illinois as part of the Midwest Geological Sequestration Consortium. He said the perceived risk of induced seismicity from CO2 injection is also of key concern for his project. “The perceived risk is just as important as the actual risk to us,” he said. “By monitoring and getting the data [from the injection well], we gain the data to allow us to address and understand what is actually occurring at the site.” Finley added that the Consortium installed three tetrahedral microseismic sensors in its injection well to test for microseismic events.

Extensive Public Outreach Needed

All speakers on the panel emphasized the need for extensive outreach efforts to help the public understand the geologic risks associated with CO2 injection. Previously, several prominent geophysicists argued that microseismic activity as a result of CO2 injection could ultimately be the Achilles heel for carbon sequestration (GHG Monitor Vol. 7, Issue 3), particularly if it leads to public skepticism of the technology. Public opposition helped topple plans for Germany’s only remaining CCS project late last year after local politicians organized grassroots campaigns focusing on the potential leakage and seismic events that could occur as a result of CO2 storage in the area.

Bill Foxall, a seismologist at Lawrence Livermore who has conducted research on the topic, said in an interview with GHG Monitor that while microseismic events are often inevitable for large-scale storage projects, they can be minimized by risk assessment, site characterization and monitoring work before, during and after injection. “In many cases, it won’t be a major issue as long as [developers] plan their operations accordingly,” he said. “But like anything else, you’ve got to do an adequate risk analysis to see what the significance of seismicity will be, and it’s going to vary quite a bit from place to place. In most cases, it will dictate the long-term injection strategy at a project.”