Evaluation of Methane Sources in Groundwater in Northeastern Pennsylvania

Molofsky, Lisa J.; Connor, John A.; Wylie, Albert S.; Wagner, Tom; Farhat, Shahla K.

doi:10.1111/gwat.12056

Cited by 226 publications

(306 citation statements)

References 29 publications

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“…Multiple regression P = 0.0034 P = 0.053 P = 0.45 Pearson r P = 0.003 P = 0.36 P = 0.11 Spearman ρ P = 0.004 P = 0.95 P = 0.21 (−24.98‰ δ 13 C-CH 4 ) exceeded the values observed for ethane (−31.2‰ δ 13 C-C 2 H 6 ), an isotopic reversal (Δ 13 C = 6.22‰) characteristic of Marcellus or other deeper gas compared with gases from Upper Devonian sequences (14,28). Helium is an inert noble gas with a radiogenic isotope, 4 He, that is a major component of thermogenic natural gas.…”

Section: Resultsmentioning

confidence: 81%

“…In most natural gases, the isotopic composition (δ 13 C) of C 3 > C 2 > C 1 (i.e., δ 13 C of ethane is heavier than methane). In thermally mature black shales, however, this maturity trend reverses, creating diagnostic isotopic reversals in which the δ 13 C-CH 4 becomes heavier than δ 13 C-C 2 H 6 (Δ 13 C = δ 13 C-CH 4 − δ 13 C-C 2 H 6 > 1) (14,15,28,30,32).…”

Section: Resultsmentioning

confidence: 99%

“…4. Stable isotope signatures (‰ VPDB) of methane (δ 13 C-CH 4 ) vs. δ 13 C for methane minus ethane (Δ 13 C = δ 13 CH 4 − δ 13 C 2 H 6 ); 6 of 11 drinking water samples exhibited isotopic reversals and δ 13 C-CH 4 values consistent with Marcellus production gas (14,28,55). In contrast, five drinking water samples and the salt spring at Salt Springs State Park (filled square) had δ 13 C-CH 4 and Δ 13 C < 0 consistent with Upper Devonian production gases (14,55).…”

Section: Resultsmentioning

confidence: 99%

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Increased stray gas abundance in a subset of drinking water wells near Marcellus shale gas extraction

Jackson

Vengosh²,

Darrah³

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

505

475

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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 (δ 13 C-CH 4 , δ 13 C-C 2 H 6 , and δ 2 H-CH 4 ), hydrocarbon ratios (methane to ethane and propane), and the ratio of the noble gas 4 He to CH 4 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.carbon, hydrogen, and helium isotopes | groundwater contamination | geochemical fingerprinting | fracking | hydrology and ecology

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Section: Resultsmentioning

confidence: 81%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Increased stray gas abundance in a subset of drinking water wells near Marcellus shale gas extraction

Jackson

Vengosh²,

Darrah³

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

505

475

View full text Add to dashboard Cite

show abstract

“…2). Likewise, the 1,701 drinking water wells collected by gas companies before drilling in adjacent Susquehanna County between 2008 and 2011 and analyzed in commercial laboratories (27) varied from a high (90th percentile) of 1.8 mg/L for valleys to a low of 0.017 mg/L for uplands. A steady decrease in dissolved methane was observed for at least one impacted household well (Well 1) with ample time series data, subsequent to the remediation of the Welles 3, 4, and 5 series gas wells (Fig.…”

Section: Resultsmentioning

confidence: 99%

Evaluating a groundwater supply contamination incident attributed to Marcellus Shale gas development

Llewellyn¹,

Dorman²,

Westland³

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

257

241

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High-volume hydraulic fracturing (HVHF) has revolutionized the oil and gas industry worldwide but has been accompanied by highly controversial incidents of reported water contamination. For example, groundwater contamination by stray natural gas and spillage of brine and other gas drilling-related fluids is known to occur. However, contamination of shallow potable aquifers by HVHF at depth has never been fully documented. We investigated a case where Marcellus Shale gas wells in Pennsylvania caused inundation of natural gas and foam in initially potable groundwater used by several households. With comprehensive 2D gas chromatography coupled to time-of-flight mass spectrometry (GCxGC-TOFMS), an unresolved complex mixture of organic compounds was identified in the aquifer. Similar signatures were also observed in flowback from Marcellus Shale gas wells. A compound identified in flowback, 2-n-Butoxyethanol, was also positively identified in one of the foaming drinking water wells at nanogram-per-liter concentrations. The most likely explanation of the incident is that stray natural gas and drilling or HF compounds were driven ∼1–3 km along shallow to intermediate depth fractures to the aquifer used as a potable water source. Part of the problem may have been wastewaters from a pit leak reported at the nearest gas well pad—the only nearby pad where wells were hydraulically fractured before the contamination incident. If samples of drilling, pit, and HVHF fluids had been available, GCxGC-TOFMS might have fingerprinted the contamination source. Such evaluations would contribute significantly to better management practices as the shale gas industry expands worldwide.

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“…This contrasts with the little information on hydrochemical aspects associated with the potential methane leakage during such an operation. Some papers deal with the stable isotopes of carbon, hydrogen and helium, which are meant to distinguish between man-made sources and natural occurrences (Taylor et al 2000;Breen et al 2007;Osborn and McIntosh 2010;Osborn et al 2011;Stuart 2012;Jackson et al 2013;Molofsky et al 2013;McMahon et al 2013). There are reports on elevated concentrations of arsenic, selenium and strontium in groundwater near fracking sites in the Barnett Shale formation of north Texas but it is not known whether the contaminants have a near-surface origin or are derived from a deep source (Fontenot et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Modelling the hypothetical methane-leakage in a shale-gas project and the impact on groundwater quality

Schwartz

2014

Environ Earth Sci

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The hypothetical leakage of methane gas caused by fracking a 1,000-m deep Cretaceous claystone horizon at Damme, Germany, is simulated in a TOUGH-REACT reactive-transport model with 5,728 elements. A hypothetical leakage zone connects the Cretaceous horizon with a Quaternary potable-water aquifer (q1). Methane gas rises up to the q1 horizon in less than 2 days in all calculated scenarios. The simulations include the major constituents of groundwater as well as the seven most hazardous trace components that are natural constituents of groundwater (As, Cd, Cr, Ni, Pb, Se and U). The general trend is characterised by depletion of the natural hazardous components with decreasing acidity and oxygen fugacity in the relevant pH range (7-9). Nevertheless, the concentrations of elements whose dominant aqueous species are negatively charged in this pH range (Cr and Se) rise against the general trend due to desorption reactions. Slight enhancement effects are produced by the dissolution of contaminant-bearing oxides such as Cr-bearing goethite. In summary, the geological risks of a fracking operation are minor. The technical risks are more important. This is especially the case when rising methane gas gets into contact with fracking fluid that accidentally escapes through faulty well seals.

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Evaluation of Methane Sources in Groundwater in Northeastern Pennsylvania

Cited by 226 publications

References 29 publications

Increased stray gas abundance in a subset of drinking water wells near Marcellus shale gas extraction

Increased stray gas abundance in a subset of drinking water wells near Marcellus shale gas extraction

Evaluating a groundwater supply contamination incident attributed to Marcellus Shale gas development

Modelling the hypothetical methane-leakage in a shale-gas project and the impact on groundwater quality

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