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Researchers affirm injection wells' link to earthquakes, praise Okla. response

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Researchers affirm injection wells' link to earthquakes, praise Okla. response

New research into injection wells in Texas, Oklahoma and North Dakota reinforced the link established in earlier studies between the underground injection of wastewater from hydraulic fracturing and earthquakes.

The report backed previous research by the U.S. Geological Survey that showed a rapid increase in earthquakes in areas where injection wells have been used near fault lines.

"The researchers found that the increased pressure that is caused by storing produced water inside geologic formations raises the risk of induced seismicity," according to a University of Texas news release. "The risk increases with the volume of water injected, both at the well and regional scale, as well as the rate of injection." The report was published Oct. 31 in the journal Seismological Research Letters by researchers from the University of Texas, San Diego State University and the University of Oklahoma.

The report looked into water from hydraulic fracturing that is stored not only in the Permian, Eagle Ford and Oklahoma, but also the Bakken Shale of North Dakota. The results were not consistent, with seismic activity varying with geology. The researchers found that 56% of wells used to dispose of produced water in Oklahoma are potentially associated with earthquakes, with the next closest area being the Eagle Ford, at 20%.

The link between injection waste wells and earthquakes has been a source of discussion for several years, as earthquakes in the Arbuckle formation in Oklahoma and the Ellenburger formation in north Texas increased substantially as more injection wells were created.

A 2017 report by a task force of the Academy of Medicine, Engineering and Science of Texas said there appeared to be a significant link between injection wells and earthquakes in the Barnett Shale, saying that "between 1975 and 2008 there were, on average, one to two earthquakes per year of magnitude greater than M3.0. Between 2008 and 2016, the rate increased to about 12 to 15 earthquakes per year on average."

Similar events have since occurred in the prolific Permian Basin of West Texas and the Eagle Ford Shale in southern Texas, increasing concern over the issue.

The study said Oklahoma's tendency to store water in deeper geologic formations frequently connected to faults has increased the seismic risk. In other regions, the wastewater is stored at shallower depths, which has limited the risk that they will disrupt fault lines.

"If we want to manage seismicity, we really need to understand the controls," said Bridget Scanlon, a senior research scientist at the University of Texas' Bureau of Economic Geology and lead author of the report.

The report credited the Oklahoma Corporation Commission, which issued directives intended to reduce the risk of earthquakes in 2015, for making the right moves in requesting reduction of injection rates and volumes. The study showed a 70% reduction in the number of earthquakes over magnitude 3.0 between 2015 and 2017.

"Everything they (the OCC) did is supported by what we have in this article," said Kyle Murray, an adjunct professor at the University of Oklahoma and a co-author. "The decisions they made, the directives that they put out, are supported by statistical associations we found."