Yet another scientific study of Oklahoma’s earthquakes and their connection to the energy industry claims it’s the depth of wastewater injection wells that is critical to reducing the number of the seismic events.
The journal Science reported this week that a “major” study by the University of Bristol and involving the University of Southampton, Delft University of Technology and Resources for the future came up with the determination. The scientists say their study shows “conclusively that Oklahoma’s seismicity is strongly linked to fluid injection depth.”
Lead author of the study, Dr Thea Hincks, Senior Research Associate at the University of Bristol’s School of Earth Sciences, said: “Our new modelling framework provides a targeted, evidential basis for managing a substantial reduction in induced seismicity in Oklahoma, with extensive possibilities for application elsewhere in the world. This marks a step forward in understanding the evolution of seismicity in the Oklahoma region.”
Hincks and others used a powerful computer model that incorporated injection well records and earthquake data from the U.S. Geological survey. They examined the connections between injection volume, depth, and location as well as geological features over a six-year period.
They came to the conclusion that the joint effects of depth and volume are critical. But injection volume becomes more influential and more likely to cause earthquakes at depths where layered sedimentary rocks meet crystalline basement rocks. Deeper wells allow easier access for fluids into the fractured basement rocks that seem to be more prone to earthquakes.
By raising injection well depths to above the basement rocks in key areas could significantly reduce the annual energy released by the quakes, according to the team of scientists. One suggested it could cut the number of Oklahoma’s earthquakes every year by half.
Anyone who lives in and around Oklahoma knows very well the number of quakes that have rattled the region in recent years. Once scientists concluded that some of Oklahoma’s more than 10,000 injection wells were linked to the quakes, the Oklahoma Corporation Commission began asking operators to either shut down some wells or reduce their operations.
It appears to be working in many areas as the number of strong earthquakes in recent months has dropped.