Injection Induced Seismicity in Carbon and Emery Counties, Utah

Abstract:

Utah is one of the top producers of oil and natural gas in the country. Over the past 18 years, more than 4.2 billion gallons of wastewater from the petroleum industry has been injected into the Navajo Sandstone, Kayenta Formation, and Wingate Sandstone in two areas in Carbon and Emery County, Utah. We found that the seismicity rate increased significantly 3 to 5 years following the commencement of wastewater injection. The increased seismicity consists almost entirely of earthquakes with magnitudes of less than 3 and is localized in areas seismically active prior to the injection. We suggest that the marked increase in the seismicity rate was induced by pore pressure increase along pre-existing faults in these areas. We have used simple groundwater models to estimate the change in pore pressure, calculate the pore pressure diffusion rate, and evaluate the observed time gap between the start of injection and the onset of the increased seismicity in the areas surrounding the injection wells.