Fracking Wells Link to Quakes: Study

Wednesday, June 24, 2015 @ 08:06 AM gHale

Fast pumping of oil and gas industry waste fluids deep underground — at rates exceeding 300,000 barrels a month — links to the national surge in earthquakes, a new study said.

Rapid pumping made quakes 1.5 to 2 times more likely, according to an University of Colorado and U.S. Geological Survey. And the number of quakes near wells is increasing, reaching 650 a year, up from a handful in the 1970s.

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The researchers looked at 187,757 waste disposal and “enhanced recovery” injection wells across the central and eastern United States. They found quakes occurred within 9 miles of 10 percent of those wells after companies injected fluids into the ground.

In Colorado, the industry operates eight waste disposal wells where companies inject fluids at rates greater than 300,000 barrels a month, state regulators said.

Oil and gas companies run 920 injection wells statewide — 350 for disposal of drilling wastewater and 570 for accelerating extraction of oil and gas from deep rock, state records show.

Colorado’s Oil and Gas Conservation Commission (COGCC) has required companies to install seismic monitors at each of the eight high-rate injection wells, a state spokesman said. The COGCC has borrowed 11 seismic monitoring devices from the USGS to detect quakes.

“High-rate injection wells are more likely to have earthquakes associated with them,” said study co-author Shemin Ge, a CU geology professor who helped direct the research.

“At the end of the day, pressure is really the ultimate culprit weakening rock and creating earthquakes. If you have a high rate of injection, that definitely creates higher pressure,” Ge said. “It would be safer to inject at lower rates, not putting so much in during such a short time.”

The findings add to a growing body of research on industry-induced quakes.

A sharp increase in the frequency of earthquakes in the central and eastern United States since 2009 traces back to the domestic oil and gas boom. Most are relatively small magnitude quakes, but the increase includes damaging quakes between 2011 and 2012 that ranged between magnitudes 4.7 and 5.6 in Oklahoma, Texas, Arkansas and Colorado. Industry-related quakes in Colorado were near Trinidad and Greeley and in northwestern Colorado.

The USGS began redrafting earthquake hazard maps for the nation to account for the surging quakes.

The issue of induced earthquakes is complex, USGS and CU scientists acknowledged, saying their analysis looked at natural geologic faults, tectonic activity, geographical location and stage of production.

“This is really a call for detailed studies of a lot of these cases. We need to know more,” Denver-based USGS scientist and study co-author Jonathan Godt said. “If you live near one of these wells associated with earthquakes, your obvious interest is what is going to happen. We need to know more to be able to answer that question.”

“This study shows that the high-rate injection wells are more likely to be associated with earthquakes,” Godt said. “To understand how you should regulate that, you would need to know more about the hydrologic and geologic setting.”

Colorado Department of Natural Resources officials said the eight high-rate injection wells are in Weld County.

A 10,770-foot-deep industry waste disposal well east of the Greeley-Weld County Airport where a 3.2 magnitude quake shook the area last year is operating after a shutdown — but with seismic sensors around it that show minimal activity.

“The latest report of activity was in Greeley over a year ago, and the state immediately halted the underground injection well, which immediately stopped any seismic activity,” said Doug Flanders, spokesman for the Colorado Oil and Gas Association. “The company adjusted its well pressure, and since then there have been no issues with the well.”

State regulators set limits on injection that vary by well, taking into account local conditions, specified in permits, state spokesman Todd Hartman said.

“It is very important to permit injection activities with a strong regulatory review and standards to confirm that injection is managed to reduce the risk of inducing the likelihood of earthquake events,” he said.

“Operators are being required to place monitors when they are operating a high-rate well. … Injection rate (volume per month in this case) might be a valid marker for additional monitoring. At the same time, we know other factors such as pressure, geology and rock mechanics are also important criteria.”