OKLAHOMA CITY -- State oil and gas officials here are doubling the number of disposal wells under scrutiny for signs they could be causing earthquakes.
As part of that scrutiny, officials at the Oklahoma Corporation Commission (OCC) also could order about nine wells, and possibly many more, to shut down and be temporarily reworked because they permitted companies to drill too deep.
About 380 wells already must record daily the volume of drilling waste they inject deep underground and the pressure they use. They are in "areas of interest" because they're within 6 miles of where a magnitude-4 earthquake has occurred.
But yesterday, OCC made public its plan to expand areas of interest to include wells within 6 miles of an earthquake swarm. The agency defines a swarm as two earthquakes within a quarter-mile of each other, if one of the quakes is magnitude 3 or greater. That will put another 350 wells that inject into the Arbuckle formation under that extra scrutiny.
Officials say they're concentrating at first on the Arbuckle formation. Hundreds more wells could come under scrutiny when they move on to other formations.
The companies that own those wells will also have to demonstrate to the agency that they are not injecting in, or too close to, the granite bedrock zone known as the "basement."
"There is general agreement among seismologists that fluid disposal into or in communication with the crystalline basement rock presents a potential risk for induced seismicity," Tim Baker, director of the OCC's Oil and Gas Conservation Division, wrote in a letter sent to companies that own the affected wells.
Under that directive, at least nine wells could be required to close temporarily to be "plugged back" -- changed to inject at a shallower depth. Even though they have valid permits allowing them to inject just above the basement layer, officials fear that the fluid they inject could affect basement rock.
The nine wells are those that are known to be injecting into zones near the basement. Closer examination could reveal many more injecting into the basement or too close.
The changes stop far short of the moratorium on high-volume disposal wells that some drilling critics have demanded. They also do not require operators to reduce volumes or pressures, so long as they comply.
Gov. Mary Fallin (R) yesterday signaled her support for the measures being undertaken by the commission.
"The Oklahoma Corporation Commission today took appropriate and necessary action to ensure there are no disposal wells below a certain depth in an area we believe is vulnerable to seismic activity," Fallin said in a statement.
Dealing with the 'swarms'
The changes are the latest in a series of incremental moves the OCC has taken in response to growing swarms of earthquakes in the state. The agency calls its approach the "traffic light" system.
In 2014, Oklahoma had 585 earthquakes of magnitude 3 or greater, three times more than California.
The U.S. Geological Survey and many academic researchers say the surge in earthquakes is linked to disposal of oil and gas waste fluid. The Oklahoma Geological Survey (OGS) has been equivocal, acknowledging that disposal can cause quakes but sharply rejecting most specific correlations by outside scientists.
When OGS did cautiously join with outside scientists in a 2013 statement linking quakes and disposal, the state seismologist was called into a meeting with University of Oklahoma President David Boren and Continental Resources Inc. founder Harold Hamm (EnergyWire, March 3). Hamm, a major donor to the school, rejects the idea that the quakes are linked to oil and gas activity.
But in a forum last week, the state seismologist, Austin Holland, linked many of the state's quakes to oil and gas activity.
"It appears quite likely most of the seismicity we're seeing in northern and north-central Oklahoma is most likely due to this wastewater disposal," Holland said. "It's hard to explain this as a natural variation."
State officials say the basics of their "traffic light" system of dealing with disposal wells came together in May 2014. In Oklahoma, eight disposal wells have received the conditional "yellow light" permits. Some wells, proposed for "red light" areas, haven't been permitted at all (EnergyWire, March 9).
Companies under the extra scrutiny could appeal the staff's actions and get a hearing before an administrative law judge. So far, though, none has.
Traffic lights signal disposal wells' link
The OCC has continued permitting high-volume wells, and the seismic activity has intensified. Last year, there was an average of 1.6 quakes a day of magnitude 3 or greater. This year, the rate has been 2.26 a day.
Older wells have continued to operate, even though they've been linked by seismologists to a quake sequence called the "Jones Swarm" and the state's largest recorded earthquake, a magnitude-5.7 rupture in November 2011.
The traffic light approach is a tacit acknowledgment that disposal wells could be linked to man-made earthquakes. But officially the agency says it has no position on the cause and doesn't need to take one.
"While a direct, definitive link of oil and gas activity to the current major seismic events in Oklahoma has not been be established," states a posting on the agency website, "the Oklahoma Corporation Commission is not waiting for one."
The traffic light approach traces back to a National Academy of Sciences report in 2012. Illinois adopted a similar system when it wrote a state law governing shale gas drilling in 2013.