Oklahoma oil and gas regulators are scrambling to deal with increasing seismic activity. The Oklahoma Corporation Commission ordered six wastewater disposal wells shut down after the state’s strongest earthquake since 2011, a magnitude-4.7 quake near Cherokee, close to the Kansas border. The quake was felt from Dallas to Kansas City. A second 4.0- quake was centered near Crescent, close to Oklahoma City. There were a total of eight earthquakes. The Commission also ordered the owners of 23 other wells to reduce injection rates by 25 to 50 percent.
Oklahoma regulators have now conceded that earthquakes there are caused by disposal wells, after much earlier debate. Oklahoma is now the most seismically active area of the country. The state has had more than 790 quakes of magnitude 3 or greater this year, compared to 585 last year.
Cherokee is in Alfalfa County, where 225 million barrels of waste water was disposed of last year, more than 10 times what was injected in 2010. It sits over the Mississippi Lime, an oil play that requires disposal of 10 barrels of water for every barrel of oil produced.
Meanwhile in Texas, the Texas Railroad Commission has yet to concede that injection wells cause seismic activity. After scientists at Southern Methodist University published a study earlier this year connecting earthquakes near Azle, Texas to two injection wells in the vicinity, the RRC held hearings to determine whether those wells, operated by XTO and Enervest, should be shut in or restricted. After the hearings, the RRC concluded that there was not sufficient evidence to connect the quakes to the injection wells and declined to modify the injection well permits. Separately, a study group formed as a result of a law passed by the Texas legislature last year to investigate quakes in Texas should have its report ready by the end of this year. The study is being led by the UT Bureau of Economic Geology in collaboration with other Texas universities.