Oklahoma hopes to cut off a sharp spike in earthquakes with new directions limiting how much wastewater can be pumped underground, changing tack from an earlier policy in hopes of reassuring residents after several years of bigger and more urban quakes.
The Oklahoma Corporation Commission released a new plan on Tuesday, directing oil and gas producers to reduce the amount of water they inject into wells by 40 percent. The guidelines would directly impact about 250 wells, and reduce well input by 500,000 barrels per day.
Seismologists have linked a sudden increase in strong quakes to the practice of injecting wastewater underground, which can create dangerous tensions in geological fault lines. The limestone Arbuckle formation, which lies beneath Oklahoma, may be especially vulnerable to new tensions.
Although oil companies have been injecting wastewater back underground for decades, new technology has sped up the process, likely increasing the rate and strength of quakes in Oklahoma and neighboring Kansas.
Since 2012, the number of quakes rated 3.0 or higher has gone from a few dozen per year to more than 900. Recently, more have been felt in Oklahoma City, bringing new attention to the problem. A 5.1 quake hit northern Oklahoma this weekend, the state's third-largest in history.
Although the tremors are still relatively small, "It’s a trend that’s unsettling," Cornell University Professor Katie Keranen told the Associated Press. "You have the ingredients you need to have a larger earthquake."
Meanwhile, the amount of injected wastewater in Oklahoma's most susceptible counties has more than tripled since 2014.
Originally, state regulators focused on wells' depth, ordering drilling companies not to put water in the Arbuckle formation's "basement" without issuing rules about the amount of water. By mid-January, the state government requested reductions at just over 100 wells; this week's regulations will impact almost 250.
Oil and gas producers, however, say that the new rules could make business difficult.
"A lot of people say we just need the earth to stop shaking, and I understand that," Kim Hatfield, the president of Crawley Petroleum, told the Associated Press. "But the fact of the matter is that without the ability to dispose of wastewater, we cannot produce oil and gas in the state of Oklahoma, and this is our lifeblood." Ms. Hatfield is a member of Oklahoma Governor Mary Fallin's task force to study the sudden jump in earthquakes.
Some scientists, however, hope that Oklahoma can follow Kansas' example: after its own spurt in seismic activity, Kansan regulators restricted the amount and speed of underground injections, and believe it may have contributed to fewer quakes this year.
This report includes material from the Associated Press.