Will fracking kill the wind industry in the southern plains states?
Television and newspapers have picked up the recent report and associated maps released by the U.S. Geological Survey (USGS) Report entitled “One-year seismic hazard forecast for the Central and Eastern United States from induced and natural earthquakes” 28 March 2016. The conclusions of the report caused consternation from informed investors operating wind power plants in Oklahoma, Kansas and northern Texas.
The objective of the report is to provide a prediction for induced seismicity in the Central US through 2016. The results of the modelling that was undertaken show that there will be an increase in the frequency of earthquakes as a result of wastewater disposal injection (not hydraulic fracturing). While the expected frequency of earthquakes is expected to increase, the maximum magnitude of the potential earthquakes is expected to remain constant, since the magnitude of earthquakes is controlled by the seismic framework of the region.
The maps prepared showed that the chance of damage due to induced earthquakes in the Oklahoma and Kansas was similar or higher than those occurring naturally in Coastal California. The primary concern with induced seismicity is the effect on existing unreinforced masonry buildings that were not designed with seismic standards in mind, and are sensitive to the high frequencies generated by the shallow induced earthquakes.
In our role as independent engineer for project financing, DNV GL has reviewed the design basis and calculations for many of the operating wind power plants in the Central US. The turbine foundations that DNV GL has reviewed are designed to a much higher seismic load than that considered in the USGS report since the design standard requires the consideration of a much longer exposure period. Even with a higher frequency of earthquake ground motion, the seismic plus operational loads are less than the extreme wind loads that typically control the design. Given the predicted ground motion included in the USGS report, we believe that even with the increased occurrence of earthquakes in the area, seismic loading should still be well within the design envelope for wind turbines and foundations.
The good news is that fracking will not kill the wind industry. The expected increase in the frequency of earthquakes in Kansas and Oklahoma will not even have an impact on the design or the cost of building wind turbine foundations.
Figure 1: USGS Map: http://www.usgs.gov/blogs/features/files/2016/03/Yellow-Map-Chance-of-Earthquake.jpg