5.6 Mag Oklahoma Quake Matches Record

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Oklahoma registered one of its biggest earthquakes on Sept. 3 even after state regulators have beefed up limits on disposing oilfield waste and the rate of tremors had started to slow somewhat from unprecedented levels last year.

The tremor in central Oklahoma was felt from Texas to Illinois, measuring 5.6 in magnitude and tying a state record set in 2011, according to the U.S. Geological Survey. The number of earthquakes measuring 3.0 or higher reached 890 last year, followed by 375 this year through June 22. At that rate, the number of earthquakes would fall to less than 800 this year, still a far cry from only two in 2008.

As oil production surged in the state, with the Scoop and Stack areas among the most coveted new plays in the country, so too did the disposal of wastewater from fracked fields that scientists have tied to earthquake activity. Several producers, and now the U.S. Environmental Protection Agency, are facing lawsuits because of seismic activity allegedly linked to oilfield wastewater disposal in Oklahoma and other states.

“Without studying the specifics of the wastewater injection and oil and gas production in this area, the USGS cannot currently conclude whether or not this particular earthquake was caused by industrial-related, human activities,” the agency said Saturday in a statement. “However, we do know that many earthquakes in Oklahoma have been triggered by wastewater fluid injection.”

Disposal Wells

The which regulates oil and gas activity in the state, has been issuing restrictions for more than a year aimed at cutting down on the amount of wastewater injected into underground wells. There are about 35,000 active wastewater disposal wells, though only a few dozen have been linked to quakes, according to a Bloomberg Intelligence report in May, citing the USGS.

The Sept. 3 earthquake, near a complex of oil-storage facilities, led the regulator to order the suspension of about 37 wastewater-disposal wells. The commission was contacting the operators of the wells in a 500-square-mile area around the town of Pawnee, Gov. Mary Fallin said in a Twitter post. Oil storage and pipeline facilities at Cushing, 25 miles (40 kilometers) south of Pawnee, were undamaged, according to the commission and four of the companies that operate there.

The quake was followed by at least eight others measuring as much as 3.6, according to the USGS.

Fracking Boom

Oklahoma, a region previously not known for intense seismic activity, began having a significant number of earthquakes in 2009, the same year area oil companies began using fracking to shatter deep rock layers to extract oil and gas. Fracked wells produce large quantities of wastewater, which drilling companies inject into ultra-deep disposal wells.

Saturday’s tremor hit the area about 7:02 a.m. Oklahoma time, the USGS said. It was also felt in Kansas, Missouri, Texas, Arkansas, Tennessee, Iowa, Illinois and Indiana, according to USGS’s reporting system for members of the public.

Officials for Enterprise Products Partners LP, Kinder Morgan Inc., Magellan Midstream Partners LP and Enbridge Inc., which operate petroleum terminals, pipelines and storage facilities in Cushing, said their sites sustained no damage and that operations were normal. Last week, the crude storage levels at Cushing stood at nearly 64 million barrels, according to the Energy Information Administration data.

Cushing Terminal

“Following the earthquake, Enbridge employees were directed to conduct visual inspections of tanks, manifolds and other facilities,” spokeswoman Jennifer Smith said in an e-mail. “The Cushing terminal is currently operating normally.”

A spokesman for the Oklahoma Corporation Commission, Matt Skinner, offered similar comments.

Tremors were also felt at the Cooper Nuclear Station in Brownville, Nebraska, about 350 miles north of Pawnee, but operations were unaffected and no damage was reported, said Drew Niehaus, a spokesman based at the plant.

Oil and gas explorers that injected wastewater in the state include SandRidge Energy Inc., Chesapeake Energy Corp. and Range Resources Corp.

“Evidence linking oil and gas activity to earthquakes is mounting, along with legal and policy challenges,” Peter Pulikkan and Rob Barnett, analysts at Bloomberg Intelligence, wrote last month in a report.

(With assistance from Lananh Nguyen)