ABSTRACT
Most current seismicity in the southern U.S. midcontinent is related to oil and gas operations (O&G Ops). In Texas, although recorded earthquakes are of low-to-moderate magnitude, the rate of seismicity has been increasing since 2009. Because of the newly developed Texas Seismological Network, in most parts of Texas, recent seismicity is reported on a daily basis with a magnitude of completeness of ML 1.5. Also, funded research has allowed the collection of O&G Op information that can be associated with seismicity. Although in the Dallas–Fort Worth area, recent seismicity has been associated mostly with saltwater disposal (SWD), in the South Delaware Basin, West Texas, both hydraulic fracturing (HF) and SWD have been found to be causal factors. We have begun to establish an O&G Op database using four different sources—IHS, FracFocus, B3, and the Railroad Commission of Texas—with which we can associate recent seismicity to HF and SWD. Our approach is based on time and epicentral location of seismic events and time, location of HF, and SWD. Most seismicity occurs in areas of dense HF and SWD-well activity overlapping in time, making association of seismicity with a specific well type impossible. However, through examination of clustered seismicity in space and time, along with isolated clusters of spatiotemporal association between seismicity and O&G Ops, we are able to show that a causation between HF and seismicity may be favored over causation with SWD wells in areas of spatially isolated earthquake clusters (Toyah South, Reeves West, Jeff Davis Northeast, and Jeff Davis East). Causality between SWD and seismicity may be inferred for isolated cases in Reeves South and Grisham West.
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