Regulators with the Oklahoma Corporation Commission (OCC) are preparing to order another round of wastewater disposal wells to halt or curtail their operations, after a 4.7-magnitude earthquake -- the second of such magnitude in less than two weeks and tied for third-strongest in state history -- struck north-central Oklahoma on Monday.
Meanwhile, Oklahoma Gov. Mary Fallin is forming a fact-finding work group tasked with finding ways for produced water to be recycled or reused, rather than injecting it into underground disposal wells.
OCC spokesman Matt Skinner told NGI's Shale Daily on Wednesday that the commission is preparing to order an unspecified number of injection wells in two areas of the state to halt operations, and for other well operators to reduce the volume of wastewater for disposal. Additional details are to follow, possibly as early as Thursday.
According to the U.S. Geological Survey (USGS), an earthquake that measured 4.7 magnitude on the Richter scale struck at 3:43 a.m. CST Monday about three miles west of Medford, OK. Another 20 earthquakes of 2.5-magnitude or greater have been detected by USGS since the Medford quake; the most recent was a 2.8-magnitude temblor that struck 17.4 miles east of Cherokee, OK at 12:20 a.m. CST on Wednesday.
Two significant earthquakes hit Oklahoma on Nov. 19 (see Shale Daily, Nov. 20; Nov. 19). The first was another 4.7-magnitude temblor, with an epicenter eight miles southwest of Cherokee, OK. The second earthquake registered 4.0-magnitude and was centered more than nine miles north of Crescent, OK.
At a magnitude of 4.7, Monday's temblor near Medford and the Nov. 19 quake near Cherokee are tied for the third-largest in the state's history. The largest was a 5.6-magnitude temblor that struck the Prague area on Nov. 6, 2011. It spawned a 4.8-magnitude aftershock two days later.
According to the USGS, there have been 47 earthquakes of all magnitudes in Kansas and Oklahoma over the last seven days. Of those, 33 registered 2.5-magnitude or higher.
Skinner said to date this year, the commission has ordered 325 wells to shut down, and more than 200 additional wells to reduce their depth to avoid injecting near the crystalline basement.
Separately Tuesday, Fallin said the Water for 2060 Produced Water Working Group would discuss the challenges of treating produced water and look into opportunities for its potential use. Two possible uses for recycled water are industrial consumers or crop irrigation. The work group will focus primarily on produced water in north-central Oklahoma.
"Opening appropriate and environmentally responsible avenues for beneficial use of reclaimed produced water will require coordination across industry sectors and regulatory agencies," Fallin said. "In addition to the opportunities to save fresh water by reusing and recycling oil- and gas-produced water, I'm equally interested in looking at alternatives to deep well disposal of this resource.
"What a win-win for all if we can turn wasted water into a useful resource, while at the same time reducing seismic activity caused by deep well injection."
Fallin's office said J.D. Strong, director of the Oklahoma Water Resources Board, will serve as chairman. "Other members will represent agriculture, power generators, public water supply systems, oil and gas associations, industrial and commercial water users and environmental non-governmental organizations, along with the Oklahoma Department of Environmental Quality and the OCC," the office said.
The governor's office added that nearly 1.5 billion barrels of produced water were disposed underground in Oklahoma in 2014.
For months, the OCC has been taking action to reduce the number and intensity of earthquakes in the state, ordering some disposal wells to shut down operations and others to reduce the volume of wastewater they accept. The watershed moment came in April, when the OGCD issued new rules for injection well operators working in "areas of interest" that inject into the Arbuckle Formation, the state's deepest formation (see Shale Daily, April 2).
The OCC shut down two wells and ordered volumes to be cut at another three in September and ordered 13 wells to change operations in October (see Shale Daily, Oct. 19; Sept. 21). The operators of two wells voluntarily shut down their operations in July, and a third agreed to cut intake volumes by half (see Shale Daily, July 29).
Last March, the OGCD directed operators of 347 disposal wells targeting the Arbuckle to prove that they were not injecting oil and gas waste into basement rock below it. The directive was expanded to include another 211 disposal wells earlier this month. The wells are all within "areas of interest," which include 21 of the state's 77 counties that have seen increased seismicity (see Shale Daily, July 20; April 2).
Scientists with the Oklahoma Geological Survey (OGS) reported in April that the state was being hit by earthquakes at a rate about 600 times greater than historic background data (see Shale Daily, April 22). Seismicity increased from an average of one-and-a-half earthquakes of 3.0 magnitude or greater to about two-and-a-half such earthquakes every day in 2014.
According to the OGS, the earthquakes are primarily occurring within the crystalline basement. The majority of the state's nearly 900 injection wells target the Arbuckle formation, which closely overlies the crystalline basement.
Last fall, Oklahoma regulators shut in a disposal well that was thought to have been drilled too deep following a spate of seismic activity in the area (see Shale Daily, Oct. 31, 2014).
A recently released report by industry-based Energy In Depth said less than 1% of wastewater disposal wells in the United States used by the oil and gas industry have a potential link to induced seismicity (see Shale Daily, Nov. 19).