HYDRAULIC FRACTURING INDUCED SEISMICITY IN OKLAHOMA

Since 2009, there has been a large increase in seismicity throughout the state of Oklahoma. Wastewater injection wells have been a suspected cause of the widespread rise of earthquakes in the state (Ellsworth et al., 2015). However, hydraulic fracturing activities have been reported to cause earthquakes in selected areas in Oklahoma (Holland, 2013; Darold et al., 2014). Both hydraulic fracturing and wastewater injection wells have been linked to seismicity. While numerous studies have been conducted to examine the relationship between wastewater injection and earthquakes, analysis of hydraulic fracturing wells has not been systematically conducted in Oklahoma. In areas where wastewater disposal is rare (e.g., southern Oklahoma), it is relatively easy associate earthquakes with hydraulic fracturing, while in areas where wastewater injection is ongoing (e.g., north-central Oklahoma) new criteria needs to be developed to separate earthquakes related to hydraulic fracturing versus wastewater disposal. In this study, we systematically analyze the correlation between hydraulic fracturing wells and earthquakes to understand the geological conditions and operational parameters likely to cause earthquakes during hydraulic fracturing. We examine earthquake and hydraulic fracturing well operations from January 2011 to July of 2017 in five different geologic zones around the state. We analyze the spatiotemporal density of the earthquakes nearby each hydraulic fracturing well to identify possible associations, starting with the aforementioned south area of the state where wastewater wells are scarce. These initial findings will aid our analysis in other regions where hydraulic fracturing and high volume wastewater wells are nearly co-located. Finally, we segregate several productive earthquake sequences to analyze the influence of operational parameters (injection volume, duration) on those sequences.