Earthquake between 4.3 to 4.5 magnitude in Oklahoma led to injection wells being shut down

An earthquake estimated between magnitude 4.3 to 4.5 that hit Oklahoma shortly after midnight on Wednesday has led oil and gas officials to shut down four injection wells used to dispose of drilling waste from horizontal hydraulic fracturing, the leading method for producing oil and gas in the U.S., Mike Soraghan reports for Energywire. Another 10 wells have had disposal volumes cut by 25 percent. The earthquake occurred near Pawnee (Best Places map) which in September had the largest quake ever recorded in the state.

"The quake occurred close to Osage County, home of the Osage Nation, where Environmental Protection Agency has jurisdiction over disposal wells," Soraghan writes. "EPA directed the operators of 26 wells to limit volume to the average injected in the last 30 days. Another six must reduce volumes to 75 percent of their 30-day average."

Oklahoma had more earthquakes in 2015—903 of magnitude 3.0 or higher—than the combined total of every state except Alaska. Prior to the oil and gas boom of 2009, Oklahoma averaged two earthquakes of magnitude 3.0 or higher per year. The United States Geological Survey in March for the first time released maps of potential man-made earthquakes. USGS has attributed Oklahoma's increased seismic activity to injection wells. (Read more)