COGCC expert doubts New Castle quakes linked to gas activity
February 2, 2017
RIFLE — A top engineer with Colorado's oil and gas regulatory agency told a roomful of concerned residents Thursday that small, recent earthquakes near New Castle do not appear linked to injection wells that are part of the natural gas fracking process.
"There's nothing that draws my attention as an indicator," said Stuart Ellsworth, engineering manager for the Colorado Oil and Gas Conservation Commission.
"There was no excessive injecting and no continuous injecting," he said of wastewater wells in the area. "I can't jump to say that these are induced events."
The Garfield County Energy Advisory Board held a community program on underground waste injection and its relationship to recent New Castle seismic events. The meeting lasted more than an hour, and though the more than 40 people attending had little objection to Ellsworth's presentation, the earthquakes have residents in and around New Castle rattled.
"I'm interested in anything that has potential of being caused by oil and gas," Dave Devanney, co-chair of Battlement Concerned Citizens, said after the meeting. "When I hear that there has been increased seismic activity coinciding with increased activity of the oil and gas industry, I want to learn more."
The Energy Advisory Board invited Ellsworth to speak to review the COGCC underground injection program, but his presentation quickly switched focus to the relationship between recent New Castle earthquakes and adjacent underground injection activity. Just days before he was to speak, the New Castle area was hit with its third earthquake since October. At a magnitude of 3.3 on the Richter Scale, it was Garfield County's biggest earthquake in a decade — though still considered minor.
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He does not believe the quakes are correlated to injection wells.
Among his primary reasoning not to be concerned over recent seismic activity is the fact that Garfield County's nearby injection wells do not drill into basement rock. He explained that basement rock is highly fractured and thus injecting wastewater into it can cause seismic activity. In fact, the injection wells near the earthquake drill to around 8,189 feet, nearly 9,000 feet above the basement depth at 17,800 feet.
He referenced human induced earthquakes in Rangely in 1960s, which established that deep water well injection can cause earthquakes. In that instance, the Rocky Mountain Arsenal injected into the granite basement rock, which induced mutliple nearby earthquakes. He also drew comparisons between the seismic activity in New Castle and a dramatic earthquake upsurge in recent years in Oklahoma, further showing that the New Castle quakes are not human induced.
"I want to disconnect your brains from what's happening in Oklahoma and what's happening here," Ellsworth said. "Oklahoma is injecting into rock that's highly fractured."
He also pointed to what he termed excessive injecting in Oklahoma, which is not something he sees in Garfield County. Some Oklahoma wells have injected more than 300,000 barrels of water per month. All of the wells in Garfield County inject less than 100,000 barrels a month.
"Induced events tend to be critically stressed over time," he added.
Oklahoma currently has 11,000 injection wells, and earthquake tracking sites often show a few small quakes daily. Colorado has 943 total injection wells.
The meeting ended without much comment from concerned residents, but they intend to keep an eye on in it.
"I think it is just something we will have to wait and see," Grand Valley Citizen Alliance President Leslie Robinson said following the presentation. "We appreciated the outreach by the COGCC in sending their expert to talk to us. We just don't know the future, but it's good that everyone is on top of it and it's always good to learn more. It will definitely be something we'll be monitoring."
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