DEEP INJECTION AND INDUCED SEISMICITY IN OKLAHOMA AND PENNSYLVANIA: A COMPARISON OF RISK FACTORS

Induced seismicity is an increasing problem in many states with deep injection wells, specifically class II injection wells. A common misconception is that the fracking process is causing the increase in seismicity when, in reality, it is the disposal of waste fluids associated with conventional and unconventional drilling. In recent years, Oklahoma has had a dramatic rise in seismic activity. So much so that the USGS has added Oklahoma to the yearly assessment of earthquake hazard zones within the US. Unlike the booming injection well industry of Oklahoma, Pennsylvanian class II injection is in its infancy. This study compares several seismic risk factors related to the class II disposal well industry in Oklahoma and Pennsylvania. These factors include well density, injection volume, injection rate, proximity between the bottom of the injection well and basement rock, and pre-existing faults. This study concludes that elevated induced seismicity occurs when injection well density is high, injection rate and volume are high, and depth of injection is in close proximity to pre-existing fault in basement rock. Although Pennsylvania’s current deep well injection program is low risk, factors governing induced seismicity should shape future program decisions.