Injection‐induced seismicity in Carbon and Emery Counties, central Utah

Abstract

Utah is one of the top producers of oil and natural gas in the United States. 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 Carbon and Emery Counties, central Utah, where seismicity has increased during the same period. Previous studies have attributed this seismicity to coal mining. Here, we present evidence for wastewater injection being a major cause of the increased seismicity. We show that, in the coal mining area, seismicity rate increased significantly 1–5 years following the wastewater injection, and the earthquakes, mostly with magnitudes <3.0, are concentrated in areas seismically active prior to the injection. Using simple analytical and numerical models, we show that the injection in central Utah can sufficiently raise pore pressure to trigger seismicity within 10–20 km of the injection wells, and the time needed for the diffusion of pore pressure may explain the observed lag of seismicity increase behind the commencement of injection. The b‐value of these earthquakes increased following the wastewater injection, which is consistent with these events being injection‐induced. We conclude that the marked increase in seismicity rate in central Utah is induced by both mining activity and wastewater injection, which raised pore pressure along preexisting faults.

Small Earthquakes Matter in Injection‐Induced Seismicity

“…We use three b-values low, average, and high (0.8, 1.0, and 1.2, respectively) and keep a consistent at a = 3. A range of b-values has been calculated for induced seismicity from low (<1.0) b-values (Goebel et al, 2017) to high (>1.0) b-values (e.g., Bachmann et al, 2012;Brown & Liu, 2016;Goebel et al, 2017;Mousavi et al, 2017;Ogwari et al, 2018). We include all earthquakes of magnitude 1.0 and larger.…”

Low‐Magnitude Seismicity With a Downhole Distributed Acoustic Sensing Array—Examples From the FORGE Geothermal Experiment

“…Natural seismicity in Utah exhibits both strike‐slip and normal faulting with tens of M3+ events occurring per year (Arabasz et al., 2016). In the broader context, induced earthquake cases have been noted in association with both coal mining (Arabasz et al., 2005; Pechmann et al., 2008) and subsurface injection operations (Brown & Liu, 2016). Focusing slightly closer to the FORGE project, in the Marysvale volcanic field, swarm activity dominates the seismic activity, is typically associated with events in the upper crust, and is thought to be related to either hydrothermal or volcanic activity (Arabasz et al., 2007).…”

A Simple Relation to Constrain Groundwater Models Using Surface Deformation

“…Groundwater models in locations of wastewater injection are important to determine the cause of induced seismicity and plan mitigation strategies. In these models, literature values of hydrogeologic parameters are frequently used for the specific aquifer formation or type of formation (e.g., Keranen et al 2014 ; Brown and Liu 2016 ). Some injection‐induced seismicity areas may have core samples available for laboratory testing (e.g., Brown et al 2017 ).…”