It is found that high concentrations of salts, including those of radium and barium, are present in the flowback waters from late-end fracking operations, lending fears over potential groundwater contamination. The amounts of the various salts are greater than those in the water-mix used in the fracking operation, and their specific concentrations are consistent as having arisen from an underground aquifer that was set-down during the Paleozoic era. Hydraulic fracturing ("fracking") is the process whereby gas and oil is made to flow from impermeable rock, which is broken-open with water containing various salts and other materials, under high pressures, sometimes as much as 15,000 psi (i.e. one thousand times atmospheric pressure).
Researchers at the University of Pennsylvania http://live.psu.edu/story/63286 analysed samples taken principally from four different sources. These were brines recovered from 40 conventional oil and gas wells in the state; flowback waters from 22 Marcellus gas wells, collected by the Pennsylvania Bureau of Oil and Gas Management; two more samples of Marcellus flowback waters from a previous study; and similar waters from 8 horizontal wells taken by the Marcellus Shale Coalition.
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The results showed that the flowback waters contained a very high degree of salinity, which is inconsistent with the concentrations of salts contained in the waters used for the fracking operations. Rathermore, it appears that these additional elements stem from the Paleozoic era, which was the earliest of three geologic eras of the Phanerozoic eon, and lasted from around 541 - 252 million years B.P. The Paleozoic is subdivided into six geologic periods, which in decreasing order of age are: the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian. The Paleozoic was a period of dramatic geological, climatic, and evolutionary change, and it follows the Neoproterozoic Era of the Proterozoic Eon, and leads-on to the Mesozoic Era.
Specifically the study examined fluids that were brought to the surface within 90 days of fracking. While a fluid equal in volume to one quarter of that used for the fracking operation was recovered, it was found to contain high amounts of a range of elements, most disturbingly radium and barium, which were washed up from some 8,000 feet below the surface. The latter observation might appear to run counter to the view that groundwater contamination is impossible because of the great depths at which fracking is done, and well below the water table.
Attention and concern has so far been given mainly to the chemicals, including corrosive salts and benzene, that are present in the fracking fluid; however, this investigation raises issues over the exhumation of other toxic materials that had previously remained sequestered in the rock over millions of years. The measured levels of radium and barium are significantly greater than those deemed acceptable in drinking water, and so the necessity to dispose properly of the waters from fracking operations is once more stressed, and that account should be taken of the kind of materials that may be washed up from deep underground, as well as the intrinsic composition of the fracking fluid that is injected into the wells in the first place. If the waters are disposed of incautiously, there may be a real risk of water supplies becoming contaminated by substances that are naturally occurring, but nonetheless highly dangerous.
By. Professor Chris Rhodes