Local impacts of the Eagle Ford fracking – sciencedaily

Hydraulic fracturing to extract trapped fossil fuels can trigger earthquakes. Most are so small or so far from homes and infrastructure that they can go unnoticed; others can shake windows, cause light fixtures to move, and prevent people from sleeping; some damaged buildings.

Stanford University geophysicists simulated and mapped the risk of notable earthquakes and possible building damage from hydraulic fracturing earthquakes at all potential fracturing sites across the Eagle Ford Shale formation in Texas , which hosted some of the biggest fracking-triggered earthquakes in the United States. States.

Posted on April 29 in Science, the results show that the most densely populated areas – particularly a narrow section of the Eagle Ford nestled between San Antonio and Houston – are at the greatest risk of shaking strong enough to damage buildings or be felt by people. “We found that the risks of nuisance or damage vary widely across space, depending primarily on population density,” said Ryan Schultz, lead author of the study, a doctoral student in geophysics at Stanford.

Social license

Tens of thousands of wells drilled in the vast formation over the past decade have helped fuel the shale boom in the United States and have contributed to a dramatic increase in earthquakes in the central and eastern United States. United from 2009. Although destructive earthquakes are rare, write the authors, “the perceived risks of hydraulic fracturing have both raised public concern and hampered the development of the industry.”

In sparsely populated areas of the southwestern part of the Eagle Ford, researchers found damage was unlikely, even though the fracking caused earthquakes with a magnitude of 5.0. Allowing such powerful earthquakes, however, could jeopardize “social license to function,” they write. The phrase, which emerged in the mining industry in the 1990s and has since been adopted by climate activists, refers to the unofficial acceptance by members of the local community and civil society in general that Oil, gas and mining operations must do business without costly conflicts.

“Seismicity is part of the social license for hydraulic fracturing, but far from the only problem,” said study co-author Bill Ellsworth, a research professor of geophysics at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth). “The complete elimination of hydraulic fracturing seismicity would not change any of the other concerns.”

These concerns include health threats associated with life near oil and gas wells and greenhouse gas emissions associated with the production and use of fossil fuels. California’s recent announcement of its intention to stop issuing new permits for hydraulic fracturing by 2024, for example, is part of an effort to phase out oil extraction and reduce greenhouse gas emissions.

Start with the risk

The researchers say their goal is to make it easier for operators, regulators, local residents and landowners to discuss the risks that are important to them without technical expertise. “The approach we have developed provides the risk of harm or harm as a shared frame of reference and tools to assess it,” said study co-author and geophysics professor Greg Beroza, co-director of the study. Stanford Center for Induced and Triggered Seismicity. (SCITS).

The new risk analysis applies a technique first released last year to determine the whereabouts of people and structures, as well as predictions of the maximum magnitude of earthquakes and geological factors that can amplify or mitigate the impacts. tremors as they move underground. The approach allows you to start with a certain level of risk – such as a 50% chance that 30 households will experience tremors that seem exciting but not scary, based on community questionnaires – and calculate the greatest earthquake magnitude that would keep the risk at or below that level.

The authors propose to use this type of analysis as a starting point for managing the risk of an earthquake caused by fracking using a system known as the traffic light protocol. Adopted in states such as Ohio and Oklahoma to manage seismic risks associated with oil, gas, and certain geothermal energy developments, the traffic light protocols give operators the green light to continue as long as earthquakes remain relatively weak. Larger earthquakes may require an operator to adjust or stop the fluid injections, knowing that the tremors can continue and even intensify after the pumps have stopped.

“If the goal is to treat everyone equally in terms of risk, our analysis shows that action should be taken at lower magnitudes for drilling sites near the towns of North Eagle Ford than for those in the rural areas of the south, ”explained Ellsworth, who is also co-director of SCITS.

According to the researchers, it is “unfair” to set a uniform threshold for the amount of agitation allowed across a large formation like the Eagle Ford. “Single-valued thresholds can allow thresholds that are too permissive in urban areas or too restrictive in rural areas,” said Beroza, Professor Wayne Loel at Stanford Earth. “Instead, if you start with a tolerance for risk, you can set thresholds that vary as the risk changes.

Beroza is also Co-Director of the Southern California Earthquake Center (SCEC).

This research was supported by SCITS.

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Material provided by Stanford University. Original written by Josie Garthwaite. Note: Content can be changed for style and length.

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