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Injection Well Closed During Investigation Into What Caused Earthquakes In Weld County

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DENVER (CBS4)- The commission investigating seismic activity near wastewater disposal sites in Weld County met Friday afternoon to discuss developments since it ordered an injection well temporarily shut down.

The Colorado Oil and Gas Conservation Commission on Monday directed High Sierra Water Services, the owner of the injection site, to halt the disposal of wastewater into the well east of the Greeley-Weld County Airport. The company agreed to stop injection for 20 days so COGCC can study data to determine if a 2.6-magtitude earthquake was related.

(credit: CBS)

(credit: CBS)

Representatives from COGCC, High Sierra and University of Colorado seismologists attended the meeting.

“There have been quite a few earthquakes so we have been tracking the seismic activity, how many per day and how big they are,” said Seismologist Anne Sheehan.

The CU scientists, who tracked the small quake on Monday, also picked up a larger 3.4-magnitude quake near Greeley on May 31.

“In light of the findings of CU’s team, we think it’s important we review additional data, bring in additional expertise and closely review the history of injection at this site in order to more fully understand any potential link to seismicity and use of this disposal well,” COGCC director Matt Lepore said.

Companies use wastewater injection wells to dispose of some of the water used in the drilling process, which extracts oil and gas from below the earth’s surface. When water doesn’t stay in rock layers and flows to the surface, companies must dispose of that water properly. One option is to re-inject the water back into the ground through a Class II UIC injection well, the Colorado Geological Survey says.

There are 309 of those wells in Colorado, and approximately 145,000 in the United States, according to August 2013 CGS numbers. COGCC administers the wells.

COGCC said the well — labeled by High Sierra as C4A — was permitted in March 2013. Injection began a month later. Wells are analyzed for geologic factors, including proximity to water supplies, before permits are issued.

Since the well was shut down there still have been earthquakes. They stopped on Thursday but resumed Friday on a very small scale. There is no determination of cause just yet.

Back in the 1960s a 12,000 foot injection well was drilled at the Rocky Mountain Arsenal. After that a series of earthquakes occurred.

Les Ainsworth remembers when the most severe struck, “The building started shaking and I actually thought the building was going to fall down and I fell to my knees.”

More recently in Oklahoma some 270 earthquake have been recorded since the first of the year measuring 3.0 or bigger.

“Oklahoma is quite concerning because we have a seismicity rate comparable to California,” said Sheehan.

In Oklahoma they are also trying to determine if the earthquakes there are natural or caused by drilling-related activity.

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