According to a new study in the journal, Science, an increase in the number of earthquakes in central Oklahoma likely arises from the use of underground injection wells to dispose of treated wastewater from oil and gas fracking operations. The study, funded in part by the U.S. Geological Survey (“USGS”)and the National Science Foundation (“NSF”), focused on Oklahoma earthquakes and injection well practices. The research was led by Cornell University and included researchers from the University of Colorado, Boulder.
A prior USGS/NSF funded study last year had linked injection wells to an increase in small to moderate “induced” earthquakes in Oklahoma, Arkansas, Ohio, Texas and Colorado. Seismologists at Columbia University authoring that study identified three quakes in Oklahoma, Colorado and Texas that they conclude were triggered at injection well sites by major earthquakes. “The fluids (in wastewater injection wells) are driving the faults to their tipping point,” said Nicholas van der Elst of Columbia’s Lamont-Doherty Earth Observatory, who led that study.
Wastewater flows back from a well during drilling and fracking operations. While some of the wastewater is treated and recycled, often leftover treated wastewater is re-injected underground. The wastewater is forced into deep geological formations for storage. The Colorado Oil and Gas Conservation Commission shut down an injection well after two earthquakes shook the Greeley area within weeks of each other in late May and June this year.
According to the U.S. Geological Survey, prior to 2008, Oklahoma averaged about two earthquakes per year with a magnitude of 3.0 or greater. However, there has been a reported 40-fold increase in seismic activity in Oklahoma since 2008, according to the study. The state had 109 temblors measuring magnitude 3.0 or greater in 2013 alone–more than 5,000% above normal–and there have already been more than 200 such quakes this year. This dramatic increase occurred contemporaneously with greater oil and gas fracking operations. Oklahoma is now the second-most seismically active state behind California in the continental U.S.
The study’s hydrogeological models demonstrated that underground pressure elevated due to injected wastewater. Under increased pressure, the injected wastewater migrates into preexisting faults. This practice can trigger earth movement in the preexisting faults or other areas of geological weaknesses, allowing slip planes to move, sliding by one another and resulting in a shift in position. Katie Keranan, a geophysics professor at Cornell and the study’s lead author, allowed that even small changes in underground pressure can cause a fault to rupture and trigger an earthquake.
The Los Angeles Times, in a copyrighted story, reported that “four high-rate disposal wells in southeast Oklahoma City probably induced a group of earthquakes known as the ‘Jones swarm,’ which accounted for 20% of the seismicity in the central and eastern United States between 2008 and 2013.”
The Jones swarm, named for a small town east of Oklahoma City, included more than 100 earthquakes of magnitude 3.0 or greater during that five-year period. The four wells dispose of more than 4 million barrels of fluid monthly.
The L.A. Times story also cited industry officials who say additional studies are needed to confirm conclusively any link between the surge in earthquakes and drilling operations. In a released statement, Oklahoma Independent Petroleum Assn. President Mike Terry called the Science report “just one part of continuing research into the increase of seismic activity in Oklahoma,” and, “a rush to judgment based on one researcher’s findings provides no clear understanding of the causes.”
Terry said disposal wells have been used in the state for more than 50 years and “have met and even exceeded current disposal volumes during that time.” Oil and natural gas are produced in 70 of Oklahoma’s 77 counties, so “any seismic activity within the state is likely to occur near oil and gas activity,” he said.
Portions of this article were based upon stories reported in the Denver Business Journal, The Los Angeles Times and Reuters U.S. Edition.
To review the study appearing in Science, “Sharp increase in central Oklahoma seismicity since 2008 induced by massive wastewater injection,” please click here.