Hydraulic fracturing, or fracking, is a widespread technique used by the oil and gas industry to obtain natural gas from shale rock, a type of sedimentary rock that contains hydrocarbons that cannot be recovered using conventional techniques. The process involves drilling thousands of feet into the Earth’s subsurface and injecting a special mixture of water, sand and chemicals to crack the rock and release the gas.
Hydraulic fracturing (fracking) gas drilling concept illustration.
Since approximately one quarter of the fluid returns to the surface through the process, the chemical composition of the returning fluid is of interest to researchers. Studies have shown previously that the wastewater liquid that flows back after fracking contains elements that were not part of the initial solution.
A new paper co-authored by Associate Director Lee Kump (Penn State) accepted for publication in Applied Geochemistry studied four separate fracking locations in the Marcellus Formation located in Pennsylvania, USA – a sedimentary rock formation rich in untapped natural gas reserves – in order to determine the origin and concentrations of these foreign elements.
Chemical analysis showed that the fluids that flowed back within 90 days of fracking comprised high levels of salinity, along with radium and barium. Their analysis showed that the initial solution was contaminated not as a result of the fracking process, itself, but from the contact with ancient deposits of evaporated seawater from the Paleozoic era, at approximately 8,000 feet below the surface. The high concentration of salts and radioactive elements in flow-back wastewaters are harmful to human health, and even when diluted, are still many times above their drinking water limits.
The study also underscored the importance of proper disposal of these flow-back fluids to mitigate their impact on the environment.
“There is a growing interest in reusing the flow-back water as fracking fluid so that the natural brine and radiation is returned to where it originated,” says Kump. “Doing so will help to keep the brine from potentially ending up in drinking water, and it also reduces the water demand on the fracking process itself.”
This study was funded by the Pennsylvania Department of Environmental Protection.