Study tracks Colorado ‘frack-quakes’

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A recent earthquake map from the Colorado Geological Survey shows a cluster of tremors along the northern Front Range.

Findings can help oil and gas operators minimize seismic risks

Staff Report

For nine months, oil and gas companies pumped 250,000 barrels of industrial wastewater deep underground in the fossil fuel sacrifice zone around Greeley, Colorado — and then, the Earth burped.

On the last day of May, 2014, the wastewater triggered a magnitude 3.2 earthquake that for some area residents felt like a truck hitting their house. The quake was the first in the area in about 40 years, fitting a regional pattern of earthquakes linked with fracking.

Now, a new study by scientists with the U.S. Geological Survey and the University of Colorado shows it may be possible to lessen the risk of frack-quakes by controlling the amount of wastewater being pumped into the ground, and by carefully monitoring seismic activity in fossil fuel development areas.

“We were surprised to observe an earthquake right in our backyard, and we knew we needed to know more, so we quickly mobilized seismic monitoring equipment,” said Will Yeck, lead author of the study that appeared in the journal  Seismological Research Letters.

The quake was felt in Boulder, where researchers located its center in the heart of oil and gas country in Weld County, where drillers sometimes dispose of wastewater deep underground — an activity now known to sometimes trigger earthquakes.

CIRES geophysicist Anne Sheehan and other researchers deployed six seismometers   around the earthquake’s epicenter to pinpoint further seismic activity. The scientists shared their findings with state oil and gas regulators and pump operators, helping them understand the real-time seismic data. It quickly became clear that the earthquakes were centered under one specific well: the wastewater disposal well closest to the Greeley earthquake epicenter which happened to be the highest‐rate injection well in northeast Colorado in 2013, according to data compiled by the state.

The real-time tracking enabled the researchers to observe fluctuations in seismic activity as the well was shut down and cemented, said Jenny Nakai, a co-author of the new study and a graduate student in geophysics at CU Boulder. “We could see fluctuations in seismic activity as the well was shut down and cemented.”

Injection stopped on June 24 for a month, and the company that drilled the disposal well took two actions to reduce seismicity: They reduced injection rates and used cement to plug the bottom of the well, impeding fluid interaction with deeper, subsurface faults. Injection resumed a month later at reduced rates, starting at just 5,000 barrels a day mid-July. The injection rates were slowly increased over time.

The team also incorporated historical data from other seismometers in the region, finding that the  Greeley earthquake sequence started about four months after the initiation of high-rate wastewater injection in 2013. The quakes grew stronger over time, in a pattern that’s been observed at  other injection induced earthquake locations as well.

State regulators with the Colorado Oil and Gas Conservation Commission used the findings to change the permitting process, requiring  seismic monitoring at recently permitted commercial disposal wells pumping more than 10,000 barrels per day.

Authors of “Rapid Response, Monitoring, and Mitigation of Induced Seismicity near Greeley, Colorado” in Seismological Research Letters are William Yeck and Harley Benz (U.S. Geological Survey), Anne Sheehan and Jenny Nakai (CIRES and University of Colorado Boulder), and Matthew Weingarten (Stanford University).

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4 thoughts on “Study tracks Colorado ‘frack-quakes’

  1. It is misleading to say that these quakes are linked to fracking. These quakes are related to the disposal of waste water from oil and gas production and have absolutely nothing to do with fracking. This water is produced from all oil and gas wells whether they have been fracked or not. Anyone who has lived on the Front Range for any length of time will remember that the same thing happened – at a much larger scale – years ago when the government was injecting waste water underground at the Rocky Mountain Arsenal. The issue of quakes related to injection wells, particularly the well in question, is being actively monitored and regulated by the COGCC. Please do not try sensationalize this topic to make it somethin it is not

    1. I get the same comment every time I report on this topic, but the fact is, if there were no fracking in Weld County, there would be very little oil and gas production, therefore very little need to inject wastewater, so I stand by my characterization of these quakes being related to fracking. And the story itself is more about how to avoid these types of quakes in the future.

  2. There are thousands of wells that have been hydraulically fractured in the Bakken play, yet no earthquakes. Thousands of wells in the Marcellus, but only two very small earthquakes. In Oklahoma, one play responsible for the upswing in induced earthquakes consisted largely of hydraulically fractured wells, the other (the first play to develop, and the first locus of earthquakes) did not. Oil and gas wells produce water as well, and the amounts vary from play to play, and well to well, and they change through time. Injection of produced formation water (more than 95% of the water being disposed in Oklahoma) is actually a different issue. It is related to oil and gas operations. It is natural water, so it is reasonable to put it back underground.

    It is not clear that there would be no production in Weld County if there were no hydraulic fracturing. Calling them frackquakes looks like just another political designation, meant to drum up support for opposition to hydraulic fracturing. A study by Resources for the Future which polled experts from NGOs, government, Universities and industry clearly indicated that the major risks in development of unconventional resources were generic to oil and gas operations, and not unique to unconventional resources.

    Focusing on the hydraulic fracturing issue diverts attention from the real issue, and hence is likely to drive actions that do not fit the need. The actions taken in Colorado parallel actions taken by the Corporation Commission in Oklahoma, where earthquake rates have declined by one third since last year.

  3. As Miltonian pointed out, this is an injection issue – not a fracking issue. It’s NOT a fact that if there were no fracking in Weld County, there would be very little oil and gas production – that’s just your opinion. Weld county has long had more oil and gas wells than any other county in the state, and have always had to dispose of waste water…nothing to do with fracking.

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