OBSERVING INJECTION-INDUCED SURFACE DEFORMATION IN THE US MIDCONTINENT WITH INTERFEROMETRIC SAR (INSAR): NEW METHODS FOR MONITORING INDUCED SEISMICITY

Fluid injection into deep formations is a commonly used method for disposing of brine and hazardous/nonhazardous wastewater as well as for enhanced oil recovery (EOR). In Kansas, the Cambrian-Ordovician Arbuckle Group saline aquifer is the primary reservoir used for injection, despite recent increases in earthquakes in the state and across the midcontinent that have been linked to large volume injection operations. Monitoring these operations is complicated due to the large number of wells (49 Class I and > 2000 Class II wells injecting into the Arbuckle in Kansas) and interactions that may occur between these injection sites. Additionally, while Class I (hazardous and non-hazardous waste injection) wells are strictly monitored by state and federal agencies, injection volumes for Class II wells are self-reported and often based off oil production figures and estimated oil-water ratios. Interferometric Synthetic Aperture Radar (InSAR) is a powerful tool for monitoring ground deformation associated with earthquakes, volcanoes, landslides, and different anthropogenic activities, and can be utilized to for surface deformation surrounding injection sites. We are using C-band (~5.6 cm wavelength) Sentinel-1 SAR data to observe areas in central Kansas that have large numbers of Class I and II injection wells and look for signatures of surface deformation. These observations are integrated with a comprehensive 3D reservoir-geomechanical model for the region, as well as regional seismicity to look for patterns. Despite the pitfalls that surround InSAR processing in the midcontinent, we are able to demonstrate coherence across multiple months and observe potential deformation signatures. With elastic source modeling, it is possible that InSAR-based approaches will constitute a viable methodology for future monitoring of injection operations in Kansas and the rest of the midcontinent.