Oklahoma officials are beefing up their regulation of the injection of wastewater from oil and gas into deep layers of rock that scientists blame for an explosion of earthquakes.
As Reveal reported in February, Oklahoma recorded more than three times as many earthquakes as California in 2014, and so far, 2015 has been even worse. As of March 25, Oklahoma recorded 201 earthquakes of magnitude 3.0 or greater, compared with California’s 18, according to the Advanced National Seismic System global earthquake catalog.
The oil industry largely has denied any link among drilling, wastewater injection and earthquakes, despite numerous peer-reviewed scientific studies connecting them. And in Oklahoma, until now, the state’s oil and gas regulator had set a relatively high bar for when it would intervene to halt wastewater injection because of seismic concerns.
But new directives announced today set a much lower threshold for action and place the onus on well operators in areas that have had earthquakes to prove that they aren’t injecting into the dangerous layer of rock where geologic faults lie. That so-called crystalline basement is just below the Arbuckle formation, the layer that many wastewater disposal wells in Oklahoma target because of its ability to absorb fluid.
As Joe Wertz of StateImpact Oklahoma reports:
The directives expand the definition of “areas of interest” – a term the agency uses to describe locations of concentrated seismic activity – and require operators to prove to the commission that their wells aren’t in contact with granite basement rock. Fluid injection into basement rock has been identified by researchers as a major risk factor for triggering earthquakes.
“This is a way of quickly getting our hands around the issue, particularly in those areas that have seen huge increases in seismicity,” says commission spokesman Matt Skinner.
An “area of interest” previously was defined as a 6-mile radius around any earthquake magnitude 4.0 and greater. The new definition lowers the threshold to any area with two or more quakes within a quarter-mile, one of which was over magnitude 3.0. That greatly expands the regulator’s reach, because there were 28 times as many earthquakes between magnitude 3.0 and 4.0 than at magnitude 4.0 or above in 2014, according to the global earthquake catalog.Disposal well operators in the expanded areas of interest have been given 30 days to conduct well depth tests, though many have done so already. Operators whose wells are touching the basement will have to inject solid material into the well until it no longer reaches the layer. Operators of wells not in compliance by April 18 will have to cut their disposal volumes in half.
Skinner told Wertz that officials are worried by warnings that the increase in smaller earthquakes is sure to mean an increase in larger, more dangerous events. A team of researchers reported in late January that one section of faults in Oklahoma reactivated by wastewater injection was capable of producing a magnitude 6 earthquake.
“Statistically it’s quite clear that the more earthquakes you have, with an increase in magnitude, the greater your chance for a major quake,” Skinner told Wertz. “We don’t look at this as something we have time for.”
While the new directives target some of the activities that concern scientists most, earthquakes aren’t likely to stop in Oklahoma anytime soon. Already this week, residents have endured more than a dozen quakes, three of them of magnitude 4.0. And even if all wastewater disposal stopped tomorrow, scientists aren’t sure how quickly – or even if – the earthquake activity could be stopped. The largest Midwest quake in recent years, a magnitude 5.7 in 2011, was centered near Prague, Oklahoma, close to injection wells that had been in operation for 17 years without incident.
This story was edited by Amy Pyle and copy edited by Nikki Frick.