OKLAHOMA CITY -- Oklahoma oil-and-gas regulators are making their most far-reaching directive yet in response to the spike in earthquakes in the state by asking the operators of nearly 250 injection wells to reduce the amount of wastewater they inject underground.
The Oklahoma Corporation Commission released a plan Tuesday that covers more than 5,200 square miles in northwest Oklahoma. It calls for a reduction of more than 500,000 barrels of wastewater daily, or about 40 percent less than previous levels.
The Sierra Club also filed a lawsuit against three Oklahoma energy companies the same day. The group blames an increasing number of earthquakes on wastewater disposal from hydraulic fracturing operations at Chesapeake Operating, Devon Energy Production Co. and New Dominion. Devon spokesman John Porretto said it would be inappropriate to discuss the litigation. The other companies didn't immediately reply to requests for comment.
The number of earthquakes with a magnitude 3.0 or greater has skyrocketed in Oklahoma, from a few dozen in 2012 to more than 900 last year. Scientists have linked the quakes to the underground disposal of wastewater from oil-and-gas production.
A 5.1 magnitude earthquake shook northwest Oklahoma and was felt in seven other states Saturday, the U.S. Geological Survey said, the third-strongest temblor ever recorded in the state where the power and frequency of earthquakes has dramatically increased in recent years.
The earthquake centered about 17 miles north of Fairview in northwestern Oklahoma occurred at 11:07 a.m. and was reportedly felt across Arkansas, Iowa, Kansas, Missouri, Nebraska, New Mexico and Texas, the USGS said.
At least 10 smaller quakes ranging in magnitude from 2.5 to 3.9 were recorded in the same area by late Saturday afternoon, according to the USGS. A magnitude 3.1 quake occurred near Crescent, about 75 miles east of Fairview, the USGS said.
Oklahoma's stronger and more frequent earthquakes have been linked to the injection into the ground of the briny wastewater left over from oil and gas production. The 10 earthquakes Saturday were in the same lightly populated area near Fairview, a town of about 2,600 that's about 100 miles northwest of Oklahoma City. The area has had several quakes of magnitude 4.0 since the start of the year.
Regulators have recommended reducing the volume or shutting down some of the disposal wells. Gov. Mary Fallin last month approved the use of nearly $1.4 million in state emergency funds for state agencies working to reduce the number of earthquakes linked to the wastewater disposal.
Oil and gas operators in Oklahoma, where the industry is a major economic and political force, have resisted cutting back on their injections of wastewater.