Oklahoma focuses on induced seismicity remedies

Oklahoma state regulators directed five companies to limit operations at nine disposal wells north of Medford after more than 24 earthquakes in 4 days with the strongest recent tremor being 4.1 magnitude on Nov. 7.

Tim Baker, director of the Oklahoma Corporation Commission's Oil and Gas Conservation Division, said the agency developed a response that called for volumes at six nearby disposal wells to be cut by certain percentages based on how close the wells were to the center of the seismic activity.

Directives were sent to well operators SandRidge Exploration Production LLC, Kirkpatrick Oil Co. Inc., Primexx Operating Corp., Union Valley Petroleum Corp., and Special Energy Corp.

Wells within 3 miles of the center of recent earthquake activity must reduce wastewater disposal volumes by half; wells within 3-6 miles must cut volumes 25%, and all others within 10 miles of the center should be "on notice to prepare for possible future changes."

The Oklahoma Oil and Gas Association supported the commission's actions.

"It's a good, measured response," said Chad Warmington, OOGA president. "As long as it's being driven by good data of where the earthquakes are occurring, taking in the injection well data, looking at where the injections are and trying to balance out the injections, I think it's the right approach."

Medford is in Grant County in north-central Oklahoma and south of the Kansas state line. Previously, the area had experienced a decline in seismic activity over 3 months, said Jeremy Boak, director of the Oklahoma Geological Survey.

Boak spoke during an induced seismicity workshop in Houston on Nov. 4. The workshop was sponsored by the Research Partnership to Secure Energy for America (RPSEA).

"Since July, we've had about a 20% reduction in the frequency of earthquakes," Boak said, adding that he does not know if the apparent lull stemmed from actions already recommended for industry by the Corporation Commission or whether it was because there is less oil and gas activity given lower commodity prices.

"We still need to look at the area where the reduction is happening and see what's going on," Boak said.

Overall, seismic activity in Oklahoma has slowed since July, but the reduction has not been uniform, he said.

The state averaged 4.8 earthquakes/day of magnitude 2.8 or greater during July. That number has decreased to 3.5/day.

Isolated areas see increase

Although the overall rate dropped, Boak noted that isolated areas-including Cushing and parts of Logan County-have experienced increases. The biggest reduction was in Grant and Alfalfa counties, he said.

Grant, Alfalfa, and Logan counties were the most seismically active this year, representing most of the state's 28 earthquakes of 4.0 or greater, he said.

RPSEA Chairman Paul Doucette, who also is GE Oil & Gas government relations manager, told the RPSEA workshop participants that, "We've got a tremendous group of people who really care about the industry... We see public-private partnerships continuing to play a role in safe, sustainable development."

But Doucette noted earthquakes are a serious issue for oil and gas companies to address.

"We see induced seismicity as the Achilles heel of the industry," Doucette said.

F. Rall Walsh, a postgraduate student at Stanford University, presented research on unconventional development and induced seismicity. Walsh works with Stanford University professor Mark Zoback who was unable to attend the RPSEA workshop.

Walsh said scientists and regulators are gaining a better understanding of earthquakes but they need more information, particularly any information that could help determine how to reduce future induced seismicity.

Stanford researchers believe a large amount of water being injected is driving the process. Walsh said some natural faults are prone to earthquakes while others are not. Many faults have yet to be mapped.

Researchers believe a possible solution could involve less injection in areas where the fluid has direct contact with faults, but the problem is that nobody knows the location of all the faults.