Solutions to Oklahoma’s Earthquakes Continue to Evolve

bigstock Seismological Device Sheet S 136225652
bigstock Seismological Device Sheet S 136225652

Oklahoma’s ever-developing approach to dealing with earthquakes is having a positive effect. However, advocates for the oil and natural gas industry say they expect more directives to continue to come their way.

The Oklahoma Oil & Gas Association, a trade industry that represents most of the state’s largest producers, has been working closely with regulators, researchers and companies in advancing actions that are based on science and research, says Executive Vice President Arnella Karges.

“The majority of Oklahoma legislators understand it is a technical and complicated issue, and Oklahoma Corporation Commissioners are relying on science in creating policies and regulations,” Karges says. “Legislators also believe the Corporation Commission is the proper agency to handle seismicity regulations.”

Since early 2014, the industry has actively worked with the state’s Coordinating Council on Seismic Activity and the Water for 2060 Produced Water Working Group to find solutions to reduce seismicity and the amount of produced wastewater injected deep into the Arbuckle Formation.

Through the oil and gas industry’s help in providing the Oklahoma Geological Survey proprietary seismic research in oil and gas plays, wastewater injection deep into the Arbuckle Formation has been identified as the primary culprit that could be triggering much of the seismicity. The earthquakes primarily occur in north and central Oklahoma, which is home to the Mississippian Lime play. The Mississippian Lime is known for producing a large amount of salty, briny wastewater along with oil and gas. Oklahoma Corporation Commission (OCC) regulations require that wastewater be disposed of. Before the dramatic uptick in seismicity the state has experienced since 2011, injection deep underground was the preferred environmental solution to disposing of wastewater.

OCC Restricts Wastewater Injection and Small Earthquakes Slow Down

Since 2015, the OCC has issued directives to restrict the amount of wastewater being injected into a large area of interest of about 15,000 square miles identified as the primary area where earthquakes could occur. Since May, wastewater injection has been reduced by as much as 1 million barrels a day in those areas.

The effect of the reduction has been a sharp decrease in the number of earthquakes, as reported by Dr. Jeremy Boak, director of the Oklahoma Geological Survey. As of summer 2016, earthquakes at 3.0 magnitude or higher had been reduced in the state by about 15 percent from the year before.

However, on Sept. 3, 2016, the state’s largest quake, a 5.8 magnitude, struck Pawnee, Oklahoma, causing the most significant damage of any of the previous quakes. The location of the quake was on the outskirts of the area of interest identified by researchers. Researchers concluded that, somehow, the pressure created by the injection wells is pushing faults that are relatively far away.

In early November, another strong earthquake, a 5.0 magnitude, struck Cushing, Oklahoma, the site of the world’s largest commercial oil storage hub. In the wake of these two large seismic events, the OCC issued more directives aimed at shutting down more wells and increasing the areas of interest for watching seismicity. The impact has been not only a reduction in wastewater disposal, but also in oil and gas production from the Mississippian Lime play, the Oklahoma Oil & Gas Association reports.

Researchers Continue to Worry About Large Quakes

Stanford Geophysicist Cornelius Langenbruch and his colleague Dr. Mark Zoback recently released a peer-reviewed study in Science Advances that confirms the decline of small earthquakes in Oklahoma. The study further solidifies the “clear relation” between wastewater disposal volumes and earthquake rates.

The state’s 180-day moving average of 2.8 magnitude or greater earthquakes peaked at approximately 4.5 per day in summer 2015, declining to about 2.3 a day in fall 2016.

The researchers told Tulsa World that the state’s seismicity should return to its typical background levels with the regulatory cap on injection volumes. But effects from years of injecting so much saltwater into disposal wells could impact Oklahomans for several more years.

They concluded that Oklahoma is “almost certain” to have a damaging earthquake in the next five years, with heightened risks of a large quake probable to continue for a decade even with the declining frequency. Karges says the Coordinating Council on Seismic Activity and oil and gas companies are taking this recent study seriously, but they are also encouraged by the sharp decline in earthquakes from 2015 levels.

“We’ve been seeing how regulators have been balancing the amount of disposed produced water volumes, and it seems to be working,” she says. “Dr. Zoback presented information that shows the probability of earthquakes continuing to decrease in 2017 by a substantial amount.”

Langenbruch says elevated risks will remain in the earthquake zone for the next five to 10 years for a quake capable of damaging buildings, not ruling out the possibility for multiple large quakes.

Karges says the oil and gas industry will continue to support directives from the OCC, Oklahoma Geological Survey and other researchers to reduce seismicity as long as regulators follow science-based approaches to changes in wastewater disposal.

OCC to Issue Guidelines on Completions Processes

In December 2016, Oklahoma regulators announced they will release industry guidelines and best practices on the small number of earthquakes that are possibly linked to hydraulic fracturing. This concern is a departure from what has been their primary focus on the connections to wastewater disposal wells used in oil and gas development.

“This is part of a continuous, ever-evolving approach when it comes to seismicity,” the OCC’s Matt Skinner. “The bulk of our concern is obviously up in the main earthquake areas like Cushing and Pawnee. But we have been providing data and working with the Oklahoma Geological Survey on the issue of hydraulic fracturing and seismicity. It is something we hope to complete work on soon, but quite frankly, our highest priority is up in the main earthquake area.”

Karges says the OCC guidelines will likely reflect internal controls oil and gas companies are already using to watch for seismic events during hydraulic fracturing jobs. Many of the association’s members are among the most active drillers in the SCOOP and STACK plays, which are located in south-central and southwestern Oklahoma and do not have the same produced water quantities as the Mississippian Lime.

In the meantime, the Oklahoma Oil & Gas Association is expecting the OCC to continue issuing additional wastewater reduction directives over a large area.

“They [the OCC] have responded to the immediate needs,” Karges says. “We are still expecting a larger directive for the Cushing and Pawnee areas.”

Potential Legislative Action Considered

Karges says she doesn’t expect much new legislation regarding earthquake response from the Oklahoma Legislature during the 2017 session. However, she said it is possible legislators will look at reducing or prohibiting wastewater from coming into Oklahoma for disposal from other states.

“Only a very negligible amount of wastewater disposal is made up from outside the state,” she says.

“And, in coming up with any new regulations, legislators must consider interstate commerce laws.”

She also says the Water for 2060 Produced Water Working Group has been considering potential regulations regarding recycling and reuse of produced water with possible tax incentives offered for recycling. However, many regulatory issues that are not already in place must be addressed, including transportation, ownership of the water, etc.

“On all those issues, Oklahoma needs to have a better regulatory framework,” Karges says.


About the author: Cindy Elliott Allen is a veteran Oklahoma journalist who has spent most of her career as a reporter, editor and publisher of community newspapers in Oklahoma, Arkansas and Kansas. She most recently has concentrated on writing about the oil and natural gas industry and has served as a Communications Specialist for Devon Energy and as a Strategic Communications Adviser for the Oklahoma Oil & Gas Association. She also writes about public policy and politics on her blog,




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