OKLAHOMA CITY – State Rep. Cory Williams, D-Stillwater, called Tuesday for a moratorium on oil and gas wastewater disposal wells in the 16 counties the Oklahoma Corporation Commission has identified as “areas of interest” because of earthquake activity.
State Seismologist Austin Holland of the Oklahoma Geological Survey (OGS) announced Monday that saltwater disposal wells quite likely triggered most of the earthquakes that have occurred in central and northern Oklahoma over the past two and a half years.
“Based on observed seismicity rates and geographical trends following major oil and gas plays with large amounts of produced water, the rates and trends in seismicity are very unlikely to represent a naturally occurring process,” the OGS wrote in a statement issued Tuesday.
[http://wichita.ogs.ou.edu/documents/OGS_Statement-Earthquakes-4-21-15.pdf ]
The Corporation Commission, which regulates the oil and gas industry, Gov. Mary Fallin and major oil producers in Oklahoma “have consistently said they would re-evaluate this issue if scientific evidence demonstrated that there was a connection between disposal wells and earthquakes,” Williams said. “Well, the science on induced seismicity is in. It’s time to take swift action to protect the lives and property of this state’s citizens.”
Approximately 4,500 Class II wastewater disposal wells have been drilled in this state, and about 3,200 of them “are injecting at any given time,” Corporation Commission spokesman Matt Skinner said Tuesday.
Initially the commission zeroed in on saltwater disposal wells in eight counties where earthquakes have occurred at a high frequency: Alfalfa, Garfield, Noble, Payne, Lincoln, Oklahoma, and especially Grant and Logan counties.
Since that time the commission has extended its focus to eight other counties, too: Woodward, Pawnee, Seminole, Garvin, Stephens, Love, Carter and Marshall. [http://www.occeweb.com/News/2015/03-25-15%20Media%20Advisory%20-%20TL%20and%20related%20documents.pdf]
The number of disposal wells in those 16 counties totals “more than 1,000,” Skinner said.
The seismicity rate in Oklahoma in 2013 was 70 times greater “than the background seismicity rate observed in Oklahoma prior to 2008,” the OGS wrote in its report. “While unlikely, this rate could have been potentially explained by natural variations in earthquake rates from naturally occurring swarms.”
Now, though, the seismicity rate is “about 600 times greater than the background seismicity rate and is very unlikely the result of a natural process,” the OGS reported.
Historically the Oklahoma Geological Survey recorded on average about 1½ earthquakes each year in Oklahoma that were gauged at Magnitude-3 or greater.
In 2013 the OGS logged on average about two Magnitude-3+ earthquakes each week and this rate continued to rise during 2014, to a year-end total of 580 Magnitude-3+, or almost 1.6 per day, according to the OGS. “Currently the OGS is reporting on average about 2½ M3+ earthquakes each day,” the agency said.
The Oklahoma Geological Survey deems it “very likely” that the majority of recent earthquakes, particularly those in central and north-central Oklahoma, “are triggered by the injection of produced water in disposal wells.”
The primary suspected source of triggered seismicity “is not from hydraulic fracturing, but from the injection/disposal of water associated with oil and gas production,” the OGS added.
The Corporation Commission’s Oil and Gas Conservation Division (OGCD) issued directives last month to disposal well operators that are injecting into the Arbuckle formation in the “areas of interest” in the 16 affected counties. Those operators were given a deadline of April 18 to prove to the OGCD that their disposal wells were not extending below the Arbuckle formation.
The Arbuckle is “the favorite disposal zone” for oil and gas producers – approximately 900 disposal wells inject into the Arbuckle – and lays just above “basement” rock, Skinner said.
“There is broad agreement among seismologists that injecting below the Arbuckle poses a potential risk of causing earthquakes, as it puts the well in communication with the solid ‘basement’ rock,” the commission wrote in a media advisory last month.
Seven disposal wells injecting into the Arbuckle “have been identified as too deep and will have to be plugged back,” Skinner said Tuesday. Any operators who cannot show that their disposal wells do not extend below the Arbuckle and who don’t have an approved well-plugging plan will be required to reduce their disposal volumes by 50%, the Corporation Commission has mandated.
“There will no doubt be more steps to take, and all options available to the Commission are on the table,” the agency claims on its website. “There is no issue that has a higher priority for this agency, and the continuing work and commitment of OGS is central to this effort,” the OCC concluded.
Meanwhile, the U.S. Geological Survey recently issued a preliminary Oklahoma seismic hazard map for 2015 that includes a colored zone that identifies 10 counties in central and north central Oklahoma that have experienced a high frequency of M-3+ earthquakes since 2010. The final version of that map will be issued in coming months.
The seismic hazard map is a guide that’s utilized by mortgage and homeowners insurance companies to establish insurance rates based on earthquake risk; by home loan lenders; and to establish building codes.
“There is no greater action this Legislature or the Corporation Commission could take to preserve lives and property than a moratorium on injection wells in the 16-county area,” Williams said. “Failure to act is tantamount to complicity.”
Legislator Calls for Moratorium on Oil/Gas Disposal Wells In ‘Areas of Interest’ Where ‘Quakes Are Occurring
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