Oklahoma state regulators revised protocol developed to reduce the chances of a felt earthquake resulting from well completion activities in Oklahoma’s SCOOP and STACK plays, which account for most of Oklahoma’s new oil and gas activity.
In December 2016, the Oklahoma Corporation Commission’s Oil & Gas Conservation Division (OGCD) and the Oklahoma Geological Survey (OGS) developed a seismicity protocol for the two plays.
OGCD Director Tim Baker said industry had fully cooperated with the previous protocol, but data gathered since late 2016 indicated the need for additional regulation.
“The overall induced earthquake rate has decreased over the past year, but the number of felt earthquakes that may be linked to well completion activity, including hydraulic fracturing, in the SCOOP and STACK has increased,” Baker said. “These events are relatively rare and smaller on average than those linked to injection activity. Most importantly, the risk of such events appears to be manageable.”
The updated seismicity protocol calls for:
• All operators in the defined area will be required to have access to a seismic array that will give real-time seismicity readings.
• The minimum level at which the operator must take action has been lowered from a 2.5 magnitude (M) to 2.0 M. Generally, the minimum level at which earthquakes can be felt is about 2.5 M.
• Some operators will have to pause operations for 6 hours at 2.5 M. Under the previous protocol, the minimum level requiring a pause was 3.0 M.
Baker said more study needs to be done, but it appears operators who have their own seismic arrays and took actions when there were seismic events too small to be felt decreased the risk of having multiple, stronger earthquakes.
OGS Director Jerry Boak agreed protocol changes were necessary, adding the chances are only a step in an ongoing process.
“Ultimately, the goal is to have enough information to develop plans that will virtually eliminate the risk of a felt earthquake from a well completion operation in the SCOOP and STACK,” said Boak.
Monitoring needs
Jake Walter, Oklahoma’s state seismologist, said Oklahoma’s permanent seismic monitoring network needs to be enhanced to control induced seismicity involving both saltwater injection and fracturing jobs.
He said currently the state’s network can record events statewide of 2-2.5 M or stronger. But evaluations typically only happened during normal business hours unless an event is strong.
Walter suggested real-time evaluations daily would be worthwhile.
“We could develop a framework that would enable operators to know before they commence operations just what the estimated seismicity risk could be, what steps to take beforehand, and what to do during operations to minimize seismic hazards,” Walter said.
Contact Paula Dittrick at [email protected].
