In the central and eastern United States, felt earthquakes likely triggered by fluid injection from oil and gas production or wastewater disposal have dramatically increased in frequency since the onset of the unconventional shale gas and oil boom. In the Rome Trough of eastern Kentucky, fracture stimulations and wastewater injection are ongoing and occur near areas of historical seismic activity. Unlike in surrounding and nearby states (Ohio, West Virginia, and Arkansas), in Kentucky, no seismic events related to subsurface fluid injections have been reported as felt or detected by regional seismic networks, including the Kentucky Seismic and Strong-Motion Network.
Oil and gas development of the deep Cambrian Rogersville Shale in the Rome Trough is in a very early stage, and will require horizontal drilling and high-volume hydraulic fracturing. To characterize natural seismicity rates and the conditions that might lead to induced or triggered events, the Kentucky Geological Survey is conducting a collaborative study, the Eastern Kentucky Microseismic Monitoring Project, prior to large-scale oil and gas production and wastewater injection. A temporary network of broadband seismographs was deployed near dense clusters of Class II wastewater-injection wells and near the locations of new, deep oil and gas test wells in eastern Kentucky. Network installation began in mid-2015 and by November 2015, 12 stations were operating, with data acquired in real time and jointly with regional network data. Additional stations were installed between June 2016 and October 2017 in targeted locations. The network improved the monitoring sensitivity near wastewater-injection wells and deep oil and gas test wells by approximately an entire unit of magnitude: With the temporary network, the detectable magnitudes range from 0.7 to 1.0, and without it, the detectable magnitudes range from 1.5 to 1.9.
Using the real-time recordings of this network in tandem with the recordings of other temporary and permanent regional seismic stations, we generated a catalog of local seismicity and developed a calibrated magnitude scale. At the time this report was prepared, 151 earthquakes had been detected and located, 38 of which were in the project area, defined as the region bounded by 37.1°N to 38.7°N latitude and 84.5°W to 82.0°W longitude. Only six earthquakes occurred in the Rome Trough of eastern Kentucky, none of which were reported in regional monitoring agency catalogs, and none of which appear to be associated with the deep Rogersville Shale test wells that were completed during the time the network was in operation or with wastewater-injection wells.
Report of Investigations 5
Digital Object Identifier (DOI)
We wish to acknowledge the state of Kentucky for funding the majority of this study, including funding for the acquisition of new seismic instrumentation, without which the scope of the study would have been severely reduced, and former KGS associate Director Jerry Weisenfluh, who permitted and encouraged us to undertake this investigation. We also thank Cimarex Energy Co. for their generous loan of six complete seismograph stations for the duration of this project, Nanometrics for the contribution of one complete seismic station, and the University of Kentucky Department of Earth and Environmental Sciences for their financial assistance. We are grateful to Pioneer Natural Resources for funding Andrew Holcomb’s research assistantship while he was a student in the Department of Earth and Environmental Sciences.
Eastern Kentucky Microseismic Monitoring Project recordings and metadata are available upon request; contact Seth Carpenter. Kentucky Seismic and Strong-Motion Network, operated jointly by the Kentucky Geological Survey and the University of Kentucky Department of Earth and Environmental Sciences, recordings are continuously archived at Incorporated Research Institutions for Seismology’s Data Management Center (ds.iris.edu/ds/nodes/dmc; last accessed 02/21/2018) and at the Kentucky Geological Survey (doi:10.7914/SN/KY).
Carpenter, N. Seth; Holcomb, Andrew S.; Wang, Zhenming; Hickman, John B.; and Woolery, Edward W., "Seismic Monitoring and Baseline Microseismicity in the Rome Trough, Eastern Kentucky" (2019). Kentucky Geological Survey Report of Investigations. 41.