CUSHING, Okla./HOUSTON (Reuters) - Oklahoma regulators are cracking down harder on saltwater disposal wells near the vitally important Cushing crude storage hub, where a rash of quakes have stoked concerns its tanks and pipelines may not be designed to handle a major seismic event.
The state's oil and gas regulator late on Monday said all saltwater disposal wells within a 10-mile radius of Cushing could face new limits. It has also basically halted approvals for new disposal wells for the time being and ordered 13 wells to shut in or reduce the amount of water they inject deep into the earth.
Once considered an area of "moderate seismic risk", Oklahoma now experiences as many as two magnitude 3.0 or higher earthquakes a day, up from just two a year in 2008. The uptick has been attributed to the disposal of saltwater, a normal byproduct of oil drilling, into deep wells.
In September, in a bid to curb the frequency of the quakes, the Oklahoma Corporation Commission (OCC), which regulates the state's oil industry, ordered drilling companies to shut or reduce usage at half a dozen saltwater wells near Cushing. Just one month later, a pair of earthquakes registering at 4.4 and 4.5 struck near Cushing, renewing safety concerns among residents and regulators alike.
While the OCC is not currently issuing new permits for disposal wells near Cushing, there are still an estimated 3,500 wells operating in the state. These play an important role servicing the oil and gas industry that has long been key to the economy of the Sooner State.
But shutting these wells has the potential to quell the tectonic disruption in Oklahoma, scientists interviewed by Reuters said.
"In most cases the seismicity would decrease at some rate and eventually it would go away. Sometimes it can take only weeks to a month, but there are always weird cases where it may take longer," Egill Hauksson, a geophysics professor at California Institute of Technology, said.
The largest earthquake to strike Oklahoma was in 2011, 40 miles from Cushing near Prague, Oklahoma. It was a 5.6, strong enough to cause potential damage to oil infrastructure.
Some of the 7,889 residents in the town of Cushing say this is a concern as the hub is home to an estimated 54 million barrels of stored oil and the delivery point for the widely traded West Texas Intermediate (WTI) futures contract.
(Reporting By Liz Hampton in Houston and Heide Brandes in Cushing; Editing by Terry Wade and Chizu Nomiyama)