Wastewater Disposal, Hydraulic Fracturing, and Seismicity in Southern Kansas

Abstract:

The concurrent appearance of seismicity with the expansion of oil and gas activities in southern Kansas since September 2012 suggests that industrial operations are inducing earthquakes. These earthquakes occur in a portion of the Mississippian Lime Play, an oil and gas field stretching from central Oklahoma to northwestern Kansas. As has been seen in other areas of high-rate wastewater injection, the seismicity appears to be driven by the disposal of produced water by injection into deep sedimentary formations. We focus on an 1800 km^2 region in Harper and Sumner counties where a temporary, 14-station seismic network deployed by the USGS monitors ongoing seismicity. Regional and national networks supplement the temporary network. Earthquake locations and magnitudes are reported on a daily basis and M≥1.5 earthquakes are included in the USGS Comprehensive Catalog (ComCat) with a magnitude of completeness of ~M2.0. The clusters of earthquakes are principally in the crystalline basement, some forming lineations extending up to 10 km. Focal mechanisms indicate normal faulting, consistent with the local tectonic stress field. While some of the clusters of seismicity are located close to high-rate injection wells, others are at least 10km from large injection wells. Additionally, high-rate wells do not always appear to be associated with seismicity. In response to the increased seismicity, on March 29, 2015 the Kansas Corporation Commission placed new limits on the rate of wastewater disposal in 5 areas in southern Kansas. Since this regulation has been in place, earthquake activity has decreased by 40-50%. In the 87 days between January 1, 2015 and March 29, when the order was enacted, there were on average three M≥2 earthquakes and 0.3 M≥3 earthquakes per day in the study area. The earthquake rate in the 87 days following the change in regulations dropped to 1.8 M≥2 and 0.2 M≥3 earthquakes per day in the same region over the same amount of time. The two largest earthquakes (M4.1 and M4.0), however, occurred after the new regulation was put in place.