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US university study on gas migration in region of shale gas extraction
This is a recent peer-reviewed paper from the Duke University scientists published in the prestigious Proceedings of the National Academy of Sciences. of the United States of America.
Higher Levels of Stray Gases Found in Water Wells Near Shale Gas Sites
This new American scientific study casts considerable doubts on the universal assertions of the gas industry that large scale hydraulic fracturing cannot contaminate surface fresh water aquifers. The industry says that the surface water and their gas production fracking zones are separated by hundreds of meters of "impenetrable" geological strata. Any contamination of the drinking water by fugitive gasses or toxic fracking chemicals is, therefore, impossible. . It should be noted that this study analysed the results from the Pennsylvanian shale gas deposits which are typically located in the depths of several kilometers. Australian coal seam gas strata are usually only several hundred meters deep and thus the chance of the biosphere contamination is much greater. THOSE IMPENETRABLE BARRIERS MAY NOT BE SO IMPENETRABLE AFTER ALL!
DURHAM, NC – Some homeowners living near shale gas wells appear to be at higher risk of drinking water contamination from stray gases, according to a new Duke University-led study.
The scientists analyzed 141 drinking water samples from private water wells across northeastern Pennsylvania’s gas-rich Marcellus Shale basin.
They found that, on average, methane concentrations were six times higher and ethane concentrations were 23 times higher at homes within a kilometer of a shale gas well. Propane was detected in 10 samples, all of them from homes within a kilometer of drilling.
“The methane, ethane and propane data, and new evidence from hydrocarbon and helium content, all suggest that drilling has affected some homeowners’ water,” said Robert B. Jackson, a professor of environmental sciences at Duke’s Nicholas School of the Environment. “In a minority of cases the gas even looks Marcellus-like, probably caused by poor well construction.”
The ethane and propane data are “particularly interesting,” he noted, “since there is no biological source of ethane and propane in the region and Marcellus gas is high in both, and higher in concentration than Upper Devonian gases” found in formations overlying the Marcellus shale.
The full text of the highly technical original article is here: US university study on gas migration in region of shale gas extraction
We include only a copy of the abstract.
Horizontal drilling and hydraulic fracturing are transforming energy production, but their potential environmental effects remain controversial. We analyzed 141 drinking water wells across the Appalachian Plateaus physiographic province of northeastern Pennsylvania, examining natural gas concentrations and isotopic signatures with proximity to shale gas wells. Methane was detected in 82% of drinking water samples, with average concentrations six times higher for homes <1 km from natural gas wells (P = 0.0006). Ethane was 23 times higher in homes <1 km from gas wells (P = 0.0013); propane was detected in 10 water wells, all within approximately 1 km distance (P = 0.01). Of three factors previously proposed to influence gas concentrations in shallow groundwater (distances to gas wells, valley bottoms, and the Appalachian Structural Front, a proxy for tectonic deformation), distance to gas wells was highly significant for methane concentrations (P = 0.007; multiple regression), whereas distances to valley bottoms and the Appalachian Structural Front were not significant (P = 0.27 and P = 0.11, respectively). Distance to gas wells was also the most significant factor for Pearson and Spearman correlation analyses (P < 0.01). For ethane concentrations, distance to gas wells was the only statistically significant factor (P < 0.005). Isotopic signatures (δ13C-CH4, δ13C-C2H6, and δ2H-CH4), hydrocarbon ratios (methane to ethane and propane), and the ratio of the noble gas 4He to CH4 in groundwater were characteristic of a thermally postmature Marcellus-like source in some cases. Overall, our data suggest that some homeowners living <1 km from gas wells have drinking water contaminated with stray gases.