From the Colorado Oil and Gas Conservation Commission (Todd Hartman):
The Colorado Oil and Gas Conservation Commission has required operators of a wastewater injection site in Weld County to make changes to their well and adjust their disposal activities after determining actions at the location are potentially related to low-level seismic activity nearby.
On June 23, the COGCC directed NGL Water Solutions DJ LLC* to stop disposing wastewater into the well for a 20-day period while the agency worked with the operator and a team of University of Colorado researchers to determine whether deep injection at the site may be tied to recent seismic activity detected within the general vicinity. Following a 3.2 magnitude event on May 31, seismometers placed by CU recorded other small earthquakes, including one of magnitude 2.6 on June 23.
Since the shutdown, the COGCC has further analyzed data associated with the injection well, as well as seismic data recorded by a local network of instruments placed and maintained by CU geophysicists. While seismic activity in the area around the well continued during the shutdown period, it occurred at a lower energy level, according to the CU researchers.
Flow rate tests conducted by NGL indicated a high permeability zone near the bottom of the well that created a preferred pathway for injected wastewater. As a result of the findings, NGL, with approval and oversight from the COGCC, has plugged the basement of the well from a depth of 10,770 feet to 10,360 feet in order to seal off the preferential pathway and to increase the distance between the zone of injection and “basement” rock. These measures are expected to mitigate the potential for future seismic events.
Beginning Friday, July 18 the COGCC will allow NGL to resume limited injections, at lower pressures and lower volumes, under continued seismic monitoring, to ensure the facility is operating safely. Specifically, the operator will be permitted to inject at an initial maximum rate of 5,000 barrels per day with a maximum pressure of 1,512 psi. After 20 days, the maximum injection rate may be increased to 7,500 barrels a day at the same pressure.
Continued use of the injection well will be reviewed and may be halted if seismic events within a 2.5-mile radius of the well occur at or above a magnitude of 2.5 – the U.S. Geological Survey’s default threshold for displaying seismic events. CU geophysicists will continue to monitor the location, and the COGCC has required NGL to install a permanent seismometer near the well to allow for real-time monitoring. The company is also required to provide access to the monitor and all its data to the COGCC and any third parties authorized by the agency.
“We are proceeding with great care, and will be tracking activities at this site closely,” said Matt Lepore, director of the COGCC. “We’re moving slowly and deliberately as we determine the right course for this location.”
The COGCC is also reviewing a potential violation of the operator’s permitted injection volumes. The matter remains under investigation and any further information on possible enforcement would be contained in a Notice of Alleged Violation from the agency. Such a determination could result in financial penalties against the company.
The well, SWD C4A, is located east of the Greeley-Weld County Airport. It was permitted by COGCC in March 2013 and injection began in April of 2013.
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