The hydraulic fracturing plan is an attempt to get ahead of rapid development in the SCOOP and STACK formations in west central and south central Oklahoma. Almost half the 78 rigs drilling in Oklahoma are in those two areas.
Regulators and scientists began looking at hydraulic fracturing operations after several small earthquakes were reported south and west of the Oklahoma City area earlier this year. Those areas were outside the large, regional plans to reduce wastewater injection into deep Arbuckle disposal wells that have been linked to induced seismicity.
The Oklahoman reported earlier this month that regulators with the Oklahoma Corporation Commission were working on the hydraulic fracturing plan.
The guidance document, which was mailed to operators on Friday, establishes a "traffic light" system for dealing with earthquakes potentially linked to hydraulic fracturing operations. Different actions are required after reported earthquakes greater than magnitude-2.5; magnitude-3.0; and magnitude-3.5. The guidelines set up a 2-kilometer (1.25 miles) radius around an earthquake.
The guidelines are similar to those developed in Canada and Ohio for dealing with earthquakes linked to hydraulic fracturing. The Oklahoma guidelines escalate from informal conversations to a pause of operations for at least six hours. The "red light" — at earthquakes greater than magnitude-3.5 — involves a suspension of operations and a formal technical conference with regulators.
Hydraulic fracturing has long been known to induce earthquakes of very small magnitudes, known as microseismicity. Those quakes are rarely felt at the surface.
However, the earthquakes recorded earlier this year near Blanchard and Calumet ranged from magnitude-3.0 to 3.4. Both areas are in SCOOP and STACK plays.
Hydraulic fracturing, or fracking, is a different process than disposing the wastewater that comes up with oil and natural gas. Fracking is used to enhance the production of a well by injecting a mix of water, sand and chemicals under high pressure to blast new fissures in the rock, releasing additional hydrocarbons.
Wastewater does flow back during hydraulic fracturing jobs, but the volumes are far below the wastewater volumes that come up during ongoing production.
OGS reviews new data
Jeremy Boak, director of the Oklahoma Geological Survey, said old and new data prompted the plan to mitigate risks related to hydraulic fracturing. He said seismic activity related to hydraulic fracturing "can be more precisely defined and rapidly implemented."
"Then-state seismologist Austin Holland did some work on small earthquakes some years ago in what is now widely known as the SCOOP and STACK, and showed some of them might have been related to hydraulic fracturing," Boak said Tuesday in a news release. "More recent small events outside the AOI (area of interest) might also be linked to hydraulic fracturing.
"While the data indicates that seismicity related to the SCOOP and STACK would be far less frequent and much lower in magnitude than the activity we are addressing in the main earthquake region of the state that has been linked to wastewater disposal, we have enough information to develop a plan aimed at reducing the risk of these smaller events as operations commence."
Chad Warmington, president of the Oklahoma Oil and Gas Association, said the new hydraulic fracturing guidelines were a good example of states being in the best position to regulate energy activities "using transparent data and sound science."
"The new guidelines to manage and mitigate anomalous seismic events will help to protect and maximize the development of Oklahoma's abundant natural resources for years to come," Warmington said Tuesday in a statement. "As the data indicates, these seismic events have been small, rare and manageable. OKOGA operators in Oklahoma are actively monitoring their operations and adjusting in real time if they identify geologic risk factors, using methods that have proven effective in Ohio and British Columbia. The OCC's new protocol will complement operators' efforts."
Ongoing disposal well response
In Oklahoma, regulators have previously focused on the growing body of research linking the state's increase in earthquakes to large volumes of wastewater into the Arbuckle layer. They continue to work on details of a stricter disposal well plan to deal with damaging earthquakes that hit the Cushing and Pawnee areas in the past few months.
A study released last month by Stanford University researchers indicated the state's rate of earthquakes tied to wastewater disposal could decrease by the end of the year and approach historic levels of "background" seismicity. But the research cautioned that "potentially damaging earthquakes cannot be ruled out during the next few years."
Various explanations for the decline in Oklahoma's earthquake rate have been suggested by experts, including the recent regulatory actions to curtail wastewater injections. Low oil prices have also led to lower production in areas such as the Mississippi Lime, a play in north central Oklahoma that has higher levels of wastewater coming up with oil and gas.
Oil and gas produced from the STACK and SCOOP plays have much less wastewater than production from the Mississippi Lime. Operators in the SCOOP and STACK are either recycling the wastewater or injecting it into other disposal formations, not the deep Arbuckle layer.
Tim Baker, director of the Corporation Commission's Oil and Gas Conservation Division, said production in the Mississippi Lime and Hunton Dewatering play resulted in an "unprecedented" amount of saltwater already in the formation coming up with oil and gas. He said production from the SCOOP and STACK aren't capable of generating those volumes of wastewater.
"There is broad agreement among researchers that disposal of these large amounts of water into the state's deepest formation (the Arbuckle) can be linked to the high earthquake rate in parts of the AOI (area of interest)," Baker said Tuesday in a news release. "By comparison, the SCOOP and STACK plays have very small amounts of produced water."
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