A new independent study concludes that fracking is not likely to cause earthquakes, as fracking opponents frquently allege, but there is a greater likelihood of tremors from waste water injection after the well bores have been fracked.
The U.S. Department of Energy-sponsored study was issued Friday by the nonprofit National Research Council. The 239-page study concludes that the factor most directly correlated with man-made earthquakes is the imbalance of fluid removed from the earth versus fluids pumped underground.
The study comes on the heels of the N.C. House of Representatives passing legislation last week that would legalize fracking in this state within several years. The state Senate will take up the measure this week and is expected to approve it. Meanwhile, Gov. Bev Perdue has remained conspicuously silent as to whether she'll veto the legislation.
Scientists have known since the 1920s that pumping fluids into or out of the earth has the potential to induce seismic events. One of the arguments opponents cited against the N.C. energy bill debated last week was the increased likelihood of of tremors and quakes associated with fracking, also known as hydrofracking.
The terms refer to hydraulic fracturing, a technique that involves pumping millions of gallons of water, sand and chemicals underground at high pressure to break up shale rock formations and release natural gas trapped inside.
The NRC report says that the reported incidents of earth tremors represent a fraction of the tens of thousands of wells drilled, fracked and/or used for waste disposal. The incidents perceptible to the public would be those with a magnitude of 2.0 and above.
The report, "Induced Seismicity Potential in Energy Technologies," cites just one confirmed seismic event associated with fracking. That incident caused a minor 2.8 magnitude quake in Oklahoma.
However, the report cites eight confirmed quakes caused by waste water disposal in three states. The maximum quake registered a magnitude of 4.8.
Injecting fluid wastes underground is illegal in North Carolina, as is fracking and horizontal drilling. The legislation that would legalize fracking and drilling in the state would not legalize undergrond fluid waste disposal.
The report also cites confirmed quakes caused by other energy technologies, including hydrocarbon withdrawal, and secondary oil and gas recovery.
North Carolina is believed to contain 1.7 trillion cubic feet of natural gas in its Triassic Basins, mostly concentrated in the Sanford sub-basin in Lee, Moore and Chatham counties. (For comparison's sake, the gargantuan Marcellus Shale in Pennsylvania and surrounding states has about 84 trillion cubic feet of natural gas.)