Using InSAR to link surface deformation from deep fluid injection with earthquakes in central Kansas, USA: Overcoming challenges specific to the US Midcontinent

Abstract:

The Cambrian-Ordovician Arbuckle Group saline aquifer is a widely used reservoir for deep fluid injection for storage of brine, hazardous/nonhazardous wastewater, and for enhanced oil recovery. Central Kansas has experienced a profound uptick in earthquakes over recent years while volumes of fluid injected into the Arbuckle have also increased. Monitoring these injection operations is also challenging due to the large number of wells (49 Class I and > 2000 Class II wells injecting into the Arbuckle in Kansas) and the volumes from Class II wells being entirely self-reported and based on oil production figures. Interferometric Synthetic Aperture Radar (InSAR) is a powerful tool to image surface deformation from various natural and anthropogenic sources, and thanks to the success of the Sentinel-1 mission, there exists a very complete freely available archived dataset for the past 5+ years. Significant challenges exist with the processing of InSAR data within the US midcontinent due to regional climate and land use patterns. Kansas experiences severe weather events that can not only delay radar phases, but also scatters C-Band radar signals via large hail. Despite these challenges, we have found that C-Band Sentinel-1 can resolve coherent surface deformation in the vicinity of one of the highest volume Class I injection wells in Kansas in the City of Hutchinson. Additionally, this deformation signal temporally correlates with well injection records and appears to predate the occurrence of ongoing earthquake activity in Hutchinson that started in 2017. We are currently working to improve our time-series data coverage and automate our processing workflow to mitigate issues with weather and land use. InSAR is a powerful tool for earth observation, and should prove useful to regulators and stakeholders hoping to monitor injection activities and their effects on seismicity.