Research & Commentary: Analysis of Oklahoma Geological Survey Data Shows Large Decrease in Seismicity Since 2015

Published October 25, 2017

While Oklahoma has a long history of seismicity, the state has seen a significant increase in the number of earthquakes since 2013. This spate of earthquakes has led to public confusion as to whether hydraulic fracturing, commonly called “fracking,” is the direct cause of these earthquakes. Some state lawmakers even called for an outright moratorium on fracking in Oklahoma in 2015. 

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.

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. The U.S. Geological Survey 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 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. Another study, published in Science in 2014, found only four of the roughly 4,500 injection wells in Oklahoma had most likely induced seismic activity, while an OGS analysis released in October 2017 found only 282 of 23,000 measurable earthquakes in Oklahoma between 2011 and 2016 occurred within two kilometers of a fracking well within a week of the well’s stimulation.

“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.”

Sensible precautions such as those taken in Oklahoma can reduce the risk of increased induced seismicity. As already noted, in many cases these precautions are already being taken by drillers without any government mandates. Flatly, concerns about induced seismicity are overblown and do not provide justification for banning fracking or over-regulating it out of existence.

The following documents provide more information on hydraulic fracturing and seismic activity.

Fracking Facts: The Science, Economics, and Legal Realities
Hydraulic fracturing, commonly known as fracking, has been employed in the United States since the 1940s. Although innovation has improved the precision of the process, the essentials are the same. Utilizing horizontal drilling, a mixture of mostly water, sand, and trace amounts of chemicals, are used to create fissures in underground shale deposits to allow oil and natural gas trapped in hard rock to move toward the surface to be collected. Activists have blamed fracking and the processes associated with it for emissions of pollutants, earthquakes, and even groundwater contamination, though independent evidence consistently shows these allegations to be false. Leigh Thompson of the Texas Public Policy Foundation argues the evidence supporting fracking bans looks slim when attention is drawn to the facts.

Fracking and Earthquakes
Fracking is responsible for some of the greatest growth in oil and gas production the United States has ever experienced. Yet, as U.S. energy extraction increases, so have concerns about the safety of fracking, with The New York Times linking the practice to “Scores of earthquakes.” Research shows, however, the risk of earthquakes caused by fracking is minimal and can be fixed with modest siting regulations, bonding requirements, and wastewater recycling. Jillian Melchoir of the Independent Women’s Forum writes that it is essential to understand what the science is actually revealing about energy extraction and induced seismicity and to create balanced public policy that allows safe energy extraction to continue.

Injection Wells and Earthquakes: Quantifying the Risks
This report from StatesFirst, a partnership between the Ground Water Protection Council and the Interstate Oil and Gas Compact Commission, states data from the U.S. Geological Survey and several peer-reviewed studies show out of an estimated 40,000 disposal wells across the United States, only 218 of them have been linked to or suspected of being a possible cause of seismicity. This means only 0.15 percent of all Class II injection wells and 0.55 percent of all federally regulated disposal wells in the United States have been tangentially associated with a seismic event of any size.

The Human-Induced Earthquake Database
This database, administered by researchers at the University of Durham and the University of Newcastle upon Tyne in the United Kingdom, is the largest and most up-to-date database of earthquake sequences proposed to have been induced or triggered by human activity since the 1800s. Of these, fracking has been conclusively linked to only 4 percent, or just 29 earthquakes overall, as of July 2017. 

Hydraulic Fracturing a Game-Changer for U.S. Energy and Economies
In this Policy Study from The Heartland Institute, Heartland Research Fellow Isaac Orr explains the advantages and disadvantages of smart drilling and its alternatives. Orr reviews the background and potential of hydraulic fracturing in the United States and puts that potential in the context of the supply of and demand for oil and gas. He addresses the environmental impacts of hydraulic fracturing, both positive and negative, as well as the public safety issues raised by activists, such as potential harm to drinking water supplies. Orr also discusses how oil and gas production is regulated at the state and national levels and suggests appropriate policies for the industry.

Hydraulic Fracturing: Critical for Energy Production, Jobs, and Economic Growth
Increased energy production on private lands in the United States has been one of the most promising economic success stories in recent years. A large part of the success is due to an energy-extraction process known as hydraulic fracturing. Misconceptions about hydraulic fracturing, also called fracking, abound. The Heritage Foundation’s Nicolas Loris explains hydraulic fracturing is safe when regulated effectively and says fracking greatly increases the nation’s energy production, thus promoting job creation.


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