Wastewater Injections After Earthquake

Energy Pipeline: Water Injection Company Allowed to Resume Wastewater Injections After Earthquake

A Greeley company whose wastewater injection well was linked to a 3.4 magnitude earthquake two months ago has been able to resume injecting after plugging about 400 feet of the well to keep water from flowing into a possible fault.

The Colorado Oil and Gas Conservation Commission, announcing July 17 that NGL Water Services could resume limited operations, also is investigating the company for potentially violating its limits on volumes on the well.

"We've been working closely with COGCC throughout all of this, and we don't believe we're in violation of any operations of our wells," said Doug White of NGL. "So we're continuing to work with them through their questions and possible concerns."

Injection wells, in which companies inject water produced from drilling activities deep underground, have long been connected to earthquake activity, though 99 percent of the injection wells across the country have been uneventful.

Once the earthquake hit on May 31, researchers from the University of Colorado placed seismic monitors in the general area of several injection wells to pinpoint better the potential source of the quake. They narrowed it to an injection well east of the Greeley-Weld County Airport. On June 23, after a 2.6 magnitude quake in the same spot, the COGCC ordered the company to stop injections for 20 days for further study. Monitoring revealed continued seismic activity.

The COGCC stated that flow rate testing on the well showed a "high permeability zone near the bottom of the well that created a preferred pathway for injected wastewater," according to a news release. Put simply, water was able to slip through pathways to allow geologic structures to move.

COGCC is reviewing its injection permit standards for clarity, said Todd Hartman, spokesman for the agency.

"We continually strive to make sure that our rules are effective at ensuring that oil and gas development is done safely," Hartman wrote in an email response to questions. "The issues with this well were highly technical in nature, and the company was cooperative in taking remedial action. Nonetheless, we are already looking at our injection permits to be sure that our expectations and requirements are clear."

The May 31 earthquake was located northeast of Greeley, and it was the first that was felt by residents in some time.

Further analysis of the seismic activity in the area since the well began accepting high volumes of wastewater in August 2013, revealed a year-long pattern of seismic activity, said Anne Sheehan, a geophysics professor at CU leading the research into the well. Based on the May 31 quake, Sheehan said her team was able to review data for the prior year to find a seismic match. The first detectible seismic activity came within months of high pressure injection that started.

"There was a detectible earthquake in November of 2013, but it was not felt," Sheehan said. "We were able to find more than a dozen prior earthquakes in the area. One was bigger than magnitude 2, and that was felt by one family close to the epicenter. There was kind of a correlation with earthquakes with the well."

In mid-July, NGL, with approval and oversight from the COGCC, plugged 410 feet of the basement of the well, shaving it to 10,360 feet to seal off the preferential pathway and to increase the distance between the zone of injection and "basement" rock, the release stated.

"These measures are expected to mitigate the potential for future seismic events," the release stated. Sheehan said there's been less seismic activity since it was plugged, but it's not totally quiet.

Sheehan said she wanted to study it quickly because in many cases, the biggest earthquake activity occurs after a well has been shut down. That was the case with the earthquakes at the Rocky Mountain Arsenal in the ‘60s.

Source: The Tribune

Read More Related Content On This Topic - Click Here

Media

Taxonomy

• Sludge Separation
• Pipes Design