Oklahoma has a long history of seismicity, but, since 2013, the Sooner State has seen a significant increase in the number of earthquakes within its borders. This spate of earthquakes has led to public confusion as to whether hydraulic fracturing, commonly called “fracking,” is the direct cause of these earthquakes, with some state lawmakers even calling for an outright moratorium on fracking back in 2015, despite roughly 20 percent of the jobs in the state being supported by oil and natural gas development.
A new analysis of Oklahoma Geological Survey (OGS) data undertaken by Energy in Depth shows the amount of monthly earthquakes in the Sooner State has decreased 86 percent from its peak in June 2015. Concurrently, there has been an 11 percent increase in oil production and 81 percent increase in the number of operation oil rigs in the state over the past calendar year. These numbers help reinforce what the scientific literature has long shown: Fracking is not the cause of the increases in induced seismicity.
Researchers at the University of Alberta released a study in June concluding fracking has had a limited impact on earthquakes in the United States and Canada. Further, a database tracking earthquake sequences proposed to have been induced or triggered by human activity since the 1800s, administered by researchers at two universities in the United Kingdom, shows only 29 earthquakes have conclusively been linked to fracking. The U.S. Geological Survey (USGS) itself, on its “Myths and Misconceptions” page for induced seismicity, says, under “Fact 1”: “Fracking is NOT causing most of the induced earthquakes.”
Instead of blaming fracking, research suggests the additional earthquakes are likely linked to an increase in the number of wastewater injection wells, which are separate from the fracking process, with most of the wastewater being injected into those wells also being unrelated to fracking activity. “More than 95 percent of wastewater injected in disposal wells located in Oklahoma’s most seismically active areas is produced water, which is co-produced with oil and gas whether a well has been hydraulically fractured or not,” writes Seth Whitehead, author of the Energy in Depth piece. “This produced water is also known as brine or formation water and is typically ancient ocean water. It is not used fracking fluid, sometimes called flowback.” (Most wastewater injection wells are not exclusive to hydraulic fracturing and are used by conventional drilling sites.)
Whitehead also notes the number of earthquakes in Oklahoma that reached magnitude-3.0 (M3) or higher declined by 76 percent between September 2016 and September 2017. M3 is roughly the magnitude needed for an earthquake to be felt on Earth’s surface. USGS equates the vibrations from an M3 earthquake to be “similar to [vibrations produced by] the passing of a truck.” It is also important to remember that the moment magnitude scale, which measures earthquake intensity, is logarithmic, with each whole number on the scale being 10 times as large as the preceding number. Therefore, for example, an M6 quake is 100 times as powerful as an M4 and 1,000 times as powerful as an M3 quake.
In a major study, the Environmental Protection Agency concluded most injection wells do not cause earthquakes and “very few” earthquakes produced by those that do can be felt by humans.
Specific to Oklahoma, another study, published in Science in 2014, found only four of the roughly 4,500 injection wells in the state had most likely induced seismic activity. A 2015 Energy in Depth report notes only 89 of the more than 10,700 injection wells in Oklahoma had “potentially” been linked to seismic activity.
“Oklahoma regulators have implemented measures that have either shut in or reduced volumes of injection in roughly 700 disposal wells, reducing wastewater injection volumes 40 percent from 2014 levels,” Whitehead wrote. “Though these more than a dozen directives — which included increased monitoring, well plugging, and volume reductions for hundreds of injection sites near seismic events — have resulted in a ‘significant economic impact,’ they have been largely supported by industry and have proven effective.”
Oklahoma has shown that sensible precautions can reduce the risk of increased induced seismicity. Flatly, concerns about induced seismicity are overblown and do not provide justification for banning fracking or over-regulating it out of existence.
Timothy Benson (tbenson@heartland.org) is a policy analyst with The Heartland Institute, a free-market think tank headquartered in Arlington Heights, Ill.
