Yukon-area oil operations cut following earthquakes
Staff from Tulsa-based Citizen Energy and the Oklahoma Corporation Commission on Monday cut pressure and volume at an oil well near Yukon following a series of small earthquakes, the commission said.
The largest of the earthquakes measured a magnitude 2.9, according to the Oklahoma Geological Survey. The quakes are believed to be caused by hydraulic fracturing operations, commission spokesman Matt Skinner said.
"There are no Arbuckle disposal wells in that area," he said. "The quakes are all located around the location of a well completion operation."
Representatives from Citizen Energy did not return a phone call from The Oklahoman on Monday.
Late Thursday, Citizen Energy management ordered a series of two-hour pauses to study the well after the earthquake activity was experienced in the area, Skinner said. Hydraulic fracturing was restarted Friday. The completion pressure and volume were cut by 50 percent Monday morning after earthquake activity continued.
Oklahoma's ongoing earthquake swarm over the past five years has widely been attributed to saltwater disposal operations, where ancient saltwater produced along with oil and natural gas has been pumped deep underground for disposal. Research and regulators have focused on wells that pump water into or through the Arbuckle rock layer, which is the deepest sedimentary rock layer underlying Oklahoma.
Far fewer earthquakes have been attributed to hydraulic fracturing, or fracking.
The Corporation Commission in December 2016 issued new rules for when and how well operators must respond to fracking-related earthquakes.
Under those rules, operators are required to contact Corporation Commission staff if there is an earthquake of magnitude 2.5 or greater. A mandatory six-hour shut-in is required for such quakes rated at magnitude 3.0 or greater. At magnitude 3.5, the well is required to undergo a hard shutdown, not to resume until after the company and Corporation Commission hold a technical meeting to discuss the well.
The Corporation Commission and Oklahoma Geological Survey in June said regulators had contacted oil and gas operators about 27 seismic events greater than magnitude-2.5 since the protocols were released in December.
No fracking-related earthquake has been recorded at magnitude 3.5 or greater, Skinner said Monday.