Hydraulic-Fracture Triggered Earthquakes in Oklahoma
Oklahoma Geological Survey
In December 2016, the Oklahoma Corporation Commission (OCC) instituted a “stoplight” protocol for mitigating seismicity possibly associated with hydraulic fracturing during production well completion. The OCC is able to track completion activities due to a new program, implemented in October 2016, requiring operators to file at least 48 hours notice that they intend to complete a well. The Oklahoma Geological Survey (OGS) monitors seismicity throughout the state, utilizing permanent and temporary seismometers operated by OGS and other agencies, while maintaining an earthquake catalog. The catalog is complete down to M2.2 since mid-2014, throughout most of the state and OGS continues to install additional temporary seismometers across the western portion of the state. Over the last year, out of greater than 3,000 completions we find only a small percentage (< 5%) of hydraulic fracturing well stimulations produce a regionally-detected earthquake on the state network through a simple spatio-temporal correlation (5 km and 10 days since start). There are several characteristics of these events that challenge current mitigation practices including earthquakes that continue after flowback has begun and relatively more seismically-active faults that may be activated by several different well completions at different leases over several months. We present our latest findings related to seismologically discriminating between earthquakes directly triggered by hydraulic fracturing and others that may be related to background tectonic activity or wastewater injection. The findings have implications for regulatory and corporate oversight of safe hydraulic fractures.
Dr. Walter, a Geophysicist at the Oklahoma Geological Survey, has been the State Seismologist since November 2016. Prior to joining the state survey, he was a research scientist at the Institute for Geophysics at the University of Texas at Austin. Walter’s research interests include ice sheet and glacier dynamics, tectonic tremor and slow slip, earthquakes, and seismic triggering of earthquakes. Walter earned his BA in geology at the University of Colorado at Boulder and his PhD in Earth Sciences at the University of California, Santa Cruz.