Researchers from Duke University have published a second study concerning water impacts of gas drilling in Pennsylvania. Based on 426 samples of groundwater in 6 counties, Professor Jackson states: "These results reinforce our earlier work showing no evidence of brine contamination from shale gas exploration." today.duke.edu/2012/07/marcellus.
The study found elevated salinity in some samples but concludes that natural causes and not gas drilling produced the raised level. The research cautioned that natural pathways were a feature of the geology in some areas that could facilitate gas migration if mistakes are made in cementing or drilling. The Duke paper does not identify when, how, or from precisely what geology the salinity came. The discussion about natural flows and pathways will be controversial.
One reviewer of the paper, Standford geophysicist Mark Zoback said: "Frankly, I think some degree of vertical hydraulic conductivity in the crust over geologic time is reasonable, but why dense brines would rise and mix with near surface aquifers is not clear. [Duke's] supposition 'therefore it implies a greater tendency for leakage from hydraulically fracturing in the shale' is illogical. Production from the Marcellus would lower the pressure and cause flow into the Marcellus, not out of it."
The implication of Professor Zoback's comment is that if natural flow were taking place over geologic time of brine production of that brine would reduce the natural flow.
The paper was authored by Duke professors Jackson and Vengosh and graduate student Warner, appears in the online edition of the Proceedings of the National Academy of Sciences, and was funded by Duke's Nicholas School of the Environment.
Let's see what the media does with this paper.