INVESTIGATING OPERATIONAL PARAMETERS ASSOCIATED WITH EARTHQUAKES INDUCED BY HYDRAULIC FRACTURING IN OKLAHOMA

Wastewater disposal is generally accepted to be the primary cause of the increased seismicity rate in Oklahoma within the past decade, but no statewide analysis has investigated the contribution of hydraulic fracturing (HF) to the observed seismicity or the seismic hazard. Utilizing an enhanced seismicity catalog generated with multi-station template matching from 2010-2016 and all available hydraulic fracturing information, we identified 274 HF wells that are spatiotemporally correlated with bursts of seismicity. The majority of HF induced seismicity cases occurred in the SCOOP/STACK plays, but we also identified prominent cases in the Arkoma Basin as well as some more complex potential cases along the edge of the Anadarko Platform. For HF treatments where we have access to injection parameters, modeling suggests poroelastic stresses are likely responsible for seismicity, but we cannot rule out direct pore pressure effects as a contributing factor. In all of the 16 regions we identified, ≥75% of the seismicity correlated with reported HF wells. In some regions, >95% of seismicity correlated with HF wells and >50% of the HF wells correlated with seismicity. Overall, we found ~700 HF induced earthquakes with M ≥ 2.0, including 12 events with M 3.0-3.5. These findings suggest state regulations implemented in 2018 that require operators in the SCOOP/STACK plays to take action if a M > 2 earthquake occurs could have a significant impact on future operations. Using the database of 274 HF wells correlated to the occurrence of seismicity compared with the other HF wells across the 16 regions that did not correlate to seismicity generation, we investigated relationships between operational parameters and seismicity. We found increased prevalence of seismicity with larger injected volumes, deeper formation targets, and use of slickwater versus gel.