The risk of anthropogenic earthquakes created by fluid injection and completion of horizontal wells is managed using maps of recent seismicity and by creating buffer zones around previously mapped faults. In Madison and Fayette Counties, Ohio, faults were identified in 1969 using analogue paper-recorded seismic reflection technology. These faults were located primarily by mapping a prominent “Conasauga reflector” from a shale within the subsurface Cambrian section. The faults were associated with an apparent abrupt increase of the regional dip to the east. The appearance of these faults on subsequent structural maps guides regulation of horizontal drilling activity in Ohio. A time-migrated, nominal 60-fold, mini-hole-sourced, seismic section using a digital recorder with 24-bit sigma delta technology was acquired over what was reported to be the best constrained of these faults; it revealed no detectable fault or significant change in the regional dip. A synthetic seismogram derived from a sonic log acquired at a nearby well enabled identification of a seismic facies change that was likely mistaken for faulting using the earlier technology. Regulations should consider acquisition parameters and vintage of seismic surveys used to identify faults for induced seismicity risk management.

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