The Colorado Oil and Gas Conservation Commission now has a plan for future earthquakes after two small quakes rattled an area in Weld County that officials later determined were likely caused by a nearby injection well.
The commission said NGL Water Solutions was not in violation of its state permit or any state rules at the time of the earthquakes, which occurred on May 31 and June 23.
Immediately after the second quake, the commission asked the company to shut down the operation while a study was conducted. The solution was a system to monitor wells for seismic activity so injection can be shut down or temporarily halted if the monitors detect inclined seismic activity.
Under the new system, underground injections wells receive a green light if the seismic activity is a magnitude 1 to 2 on the Richter Scale, which means it can’t be felt above the surface, the Greeley Tribune reported.
An amber light means operations must be modified and is given to moderate quakes, which can be felt but don’t cause structural damage. A red light, which suspends operations, is given when seismic activity can be felt at the surface and causes problems.
Both of the summer earthquakes were small. The first was a 3.2-magnitude quake and the second a 2.6, which means both could be felt for several miles. Neither was strong enough to cause significant structural damage.
Injections wells are used to dispose of wastewater produced from drilling activity. Companies inject the wastewater into the wells, which are typically much deeper than those drilled for oil and gas. If there are faults or fissures underground, the water can fill the fissure and act as a lubricant, which can lead to shifting that causes earthquakes.
“We have worked with the parties to rectify the situation and have successfully managed it with physical changes made to the well and continued close monitoring,” said Todd Hartman, a spokesman for the commission.
Dave Neslin, who was the director of the commission from 2007 to 2012 and has continued to work on oil and gas issues since joining a law firm in 2012, said seismic activity around injection wells is rare.
There are about 800 injection wells in Colorado, but only a small handful had seismic activity related to them, he said.
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