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Wastewater disposal method may limit earthquakes caused by fracking

Oil and gas production, which includes fracking, generates large volumes of wastewater, which is often injected into the ground as a means of disposal to avoid polluting surface waters. Photo by UCR
Oil and gas production, which includes fracking, generates large volumes of wastewater, which is often injected into the ground as a means of disposal to avoid polluting surface waters. Photo by UCR

July 28 (UPI) -- Oil and gas companies can prevent earthquakes by reducing the rate of wastewater injections, according to a new study.

To extract oil and gas trapped deep in rock deposits, fossil fuel companies use hydraulic fracturing, or the the injection of high-pressure fluids deep into Earth's crust.

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Because these injection fluids are filled with toxic chemicals, the resulting wastewater must be disposed of safely.

Most operations blast the dirty water deep underground at old injection sites, but numerous studies -- from Middle America and Appalachia to Sichuan, China -- have linked the practice with increases in regional earthquakes.

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For the latest study, published Wednesday in the journal Nature, scientists combined field studies and geological models to predict the impacts of wastewater injection on local faults systems.

Scientists began by studying the effects of wastewater injections across the Val d'Agri oil field in southern Italy, the largest onshore oil field in western Europe. The injections triggered hundreds of small earthquakes.

"The earthquakes were detected within hours of injection," study co-author James Dietrich said in a press release.

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"The cause and effect relationship was clear," said Dietrich, distinguished professor emeritus of geophysics at the University of California, Riverside.

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Using seismic data and records of wastewater injection activity, researchers built a model to predict the effects of injections on local fault systems.

Using the model, scientists were able to accurately reproduce seismic events recorded between 1993 and 2016.

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Both the model and lab experiments helped Dietrich and his research partners demonstrate the knock-on effects of small shifts in fault pressure caused by wastewater injections.

After demonstrating the accuracy of their new model using historical data, scientists simulated the effects of different wastewater injection rates on the rate of earthquakes across the Val d'Agri oil field.

The analysis showed a lower injection rate was both sustainable and did not induce earthquakes.

The model's predictions were confirmed in field tests, where the lower injection rate was credited with reduced seismic activity across the Val d'Agri.

In order to combat climate change, most policy makers agree that fossil fuel extraction must be phased out in favor of green energy.

But that won't necessarily spell the end of wastewater injections and human-caused earthquakes -- many carbon capture technologies sequester carbon dioxide by injecting it deep underground.

"One of the big impediments to this is that gigantic volumes of fluids injected into the ground will probably trigger earthquakes," Dieterich said. "How can that be managed? We've learned a little here that may help along those lines, and for related problems like fracking."

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