A new study published in October purports to link seismic activity in Oklahoma to wastewater injection wells. Besides rates and pressures, Bridget Scanlon, hydrogeologist and lead author of the study, suggested injection depth may influence seismicity potentials. However, Scanlon limited her study to deep wastewater injection wells in Oklahoma.
The study examined the correlation between seismicity and wastewater injection wells in Oklahoma’s Arbuckle Formation—located adjacent to the basement. Additionally, the study noted seismic activity appeared to decrease in connection with reduced wastewater injection rates. According to the study, wastewater injection wells are the culprit of the increased seismic activity in Oklahoma, not hydraulic fracturing.
Similar studies on wastewater injection wells focused their research on regional areas, not exceptional study areas like the Arbuckle Formation. These studies revealed seismicity is rare considering the extensive injection activity that has occurred in close proximity to active faults. The USGS emphasized only a small fraction of wastewater disposal wells have induced seismicity. In fact, Thomas Goebel, researcher and lecturer at the University of California, emphasized the specific geologic setting and nearby faults makes some areas more susceptible to seismicity.
The National Research Council reiterated hydraulic fracturing “does not pose a high risk for inducing felt seismic events.” A combination of many factors including injection rate, total volume, the presence of faults, large stresses, and the pathway of the injected fluids are necessary for injection to induce felt earthquakes. In fact, Keith B. Hall, Director of the Mineral Law Institute, emphasized “[t]he vast majority of injection operations, including those associated with the oil and gas industry, do not trigger earthquakes.”
Although Scanlon noted the Oklahoma Corporation Commission reduced wastewater injection rates by 40 percent in the Arbuckle Formation in 2015, Oklahoma regulators are cognizant about cooperating with producers. When setting fracking and injection regulations, fracking proponents argue regulators need to keep in mind the benefits of fracking such as, access to an abundant source of domestic energy, fewer CO2 emissions than coal, and economic benefits like providing jobs, revenues, and taxes for local governments.
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