Scientists Call For Better Monitoring, Transparency With Injection Linked Quakes
Scientists with the University of Colorado Boulder and the U.S. Geological Survey are calling for changes in monitoring and addressing human-caused earthquakes.
Over the past 13 years, many parts of the United States that are not earthquake prone have begun experiencing significant quake activity. In Colorado and other states east of the Rocky Mountains, the earthquakes are linked to injection of wastewater from oil and gas production.
The paper, published Feb. 19 in the journal Science, calls for better monitoring of these earthquakes and injection wells linked to such quakes. The ultimate goal is to use such monitoring to change the wastewater injection activities that cause the quakes, reducing risk to humans and property.
"There are so many of these disposal wells in the United States, roughly 150,000, that even though only a very small fraction result in earthquakes large enough to be felt...the total hazard is significant."
The problem is not a small one. In 2014, Oklahoma – normally a seismic snoozefest -- had more magnitude 3 or greater earthquakes than California. Most of the quakes are relatively small, but in 2011 southern Colorado experienced a human-caused earthquake of a magnitude 5.3, causing significant property damage. In the same year, one in Oklahoma "destroyed a dozen homes," said Arthur McGarr, a U.S. Geological Survey scientist and the lead author of the paper.
"Fortunately nobody was killed but several people were badly injured," McGarr added.
While most injection wells do not cause earthquakes, the boom in unconventional oil and gas drilling and enhanced oil recovery has led to the production of massive amounts of wastewater, and a commensurate growth in the number of injection wells to dispose of that water deep inside the earth, said McGarr.
"There are so many of these disposal wells in the United States, roughly 150,000, that even though only a very small fraction result in earthquakes large enough to be felt…the total hazard is significant. It's a lot more than what nature is providing," said McGarr.
Such quakes are often caused when fluid from a well escapes into unknown faults, lubricating the faults and, eventually causing an earthquake.
The town of Greeley experienced such a quake in May 2014, a magnitude 3.2. While it was not immediately clear if the seismic activity came from an injection well, scientists at the University of Colorado quickly installed a network of earthquake monitors. After these monitors clocked a second quake in late June, the Colorado Oil And Gas Conservation Commission ordered the injection well owners to stop injecting water into the well.
In the case of Greeley, scientists made a link between the quakes and the well. The well operator then plugged the well bottom, aiming to prevent the fluids that escaped and caused the earthquake from doing that in the future. The COGCC also reduced the amount of water the well operator was permitted to inject, another way to minimize the earthquake risk.
In the paper, McGarr and his colleagues highlight the response in Greeley as a model that others should follow. Right now, most of the monitoring for earthquakes is done by injection well operators, and that data is not available to scientists and the public. The paper authors call for such data to be made public.
Monitoring at the site of a first quake could allow for changes in well construction or injection volumes, hopefully limiting future quake risk. This appears to have happened in Greeley, as the quakes have since tapered off.
The scientists also say they are working on a model that will evaluate the risk of human-caused earthquakes, which can be updated as energy production activity changes.