What’s an industry to do? Most companies have tried to respond with science – a “fact attack,” if you will. By and large, these facts are accurate, if not as sensational as the fears they attempt to assuage. But in certain circumstances it might be wise to heed the warnings.
Such is the case with induced seismicity. While major earthquakes that cause devastation are almost always caused by forces beyond human control, there are increasing incidents where industrial operations, whether they be fracturing, waste disposal, or damming a river, have been known to cause seismic events that register high enough on the Richter scale to be felt by nearby populations.
At a recent Geophysical Society of Houston luncheon, Julie Shemeta, owner of MEQ Geo Inc. and consulting seismologist discussed the challenges in addressing supposed induced seismicity events.
Shemeta recently participated in a study by the National Research Council (NRC) funded by the US Department of Energy to study the potential for induced seismicity in geothermal, oil and gas, and carbon capture and sequestration. Some of the concern in the US is based on a report by the US Geological Survey showing an uptick in seismic events felt in areas like the midcontinent region that are typically tectonically quiet. A 2011 earthquake in Prague, Okla., for example, registered a magnitude of 5.6, destroyed 14 homes, buckled a federal highway, and left two people injured, according to Columbia University’s Earth Institute. These types of seismic events have triggered considerable study and more than a few harsh reactions from legislators and regulators. Some have suggested that the Prague incident might be linked to oil and gas wastewater disposal in the region.
While no events have yet led to the types of earthquakes that make global headlines, many in the industry feel that it is not too early to begin monitoring the possibility of these events. Iain Weir-Jones, president and founder of Weir-Jones Engineering Group, said that a baseline survey of ambient reservoir noise is the best way to determine the extent of seismicity induced by oil and gas operations.
Part of the problem is the uncertainty inherent in the subsurface. Shemeta showed examples where events continue to happen months and even years after activity has subsided. She also discussed a situation in a coalbed methane operation in the Raton basin in Colorado and New Mexico where wastewater is being disposed of at a depth considerably shallower than the seismic events.
“You can’t prevent it; all you can hope to do is operate in a way that minimizes the adverse effects on your own operations and those of your neighbors,” Weir-Jones said. “If you know what’s going on, you can take the appropriate steps to mitigate the problem.” To view the NRC study, visit http://www.nap.edu/catalog.php? record_id=13355.