A geochemical context for stray gas investigations in the northern Appalachian Basin: Implications of analyses of natural gases from Neogene-through Devonian-age strata

Baldassare, Fred; McCaffrey, Mark A.; Harper, John A.

doi:10.1306/06111312178

Cited by 81 publications

(126 citation statements)

References 34 publications

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“…Gases were sampled from gas wells producing from the Marcellus Formation (Middle Devonian) and Utica Formation (Upper Ordovician) in central Pennsylvania using standard wellhead sampling techniques. Gases produced from these geologic units are dry (<5% C 2+ /∑C 1-5 ) thermogenic gases of high thermal maturity (Baldassare et al, 2014;Stolper et al, 2014a). The C 1 /C 2 ratios of the gas samples from the Marcellus and Utica Shales we analyzed were <100 (Table 2.4), which is within the range expected for thermogenic gases (Bernard et al, 1976;Bernard et al, 1978).…”

Section: Field Site Descriptions and Sampling Methodssupporting

confidence: 54%

“…Our measurements for dominantly-thermogenic gases from the Marcellus and Utica Shales (Burruss and Laughrey, 2010;Baldassare et al, 2014) …”

Section: 2 Preview Of Thesis Contentmentioning

confidence: 99%

“…Carbon ( 13 C/ 12 C) and hydrogen (D/H) isotope ratios of methane are widely applied for distinguishing microbial from thermogenic methane in the environment (Welhan and Lupton, 1987;Whiticar, 1990;Sherwood Lollar et al, 2002;Flores et al, 2008;Sherwood Lollar et al, 2008;Pohlman et al, 2009;Baldassare et al, 2014) as well as for apportioning pathways of microbial methane production (Whiticar et al, 1986;Burke et al, 1988;McCalley et al, 2014). This bulk isotope approach, however, is largely based on empirical observations, and different origins of methane often yield overlapping characteristic isotope signals (Schoell, 1988;Whiticar, 1990; Whiticar, 1999;Pohlman et al, 2009;Etiope and Sherwood Lollar, 2013).…”

Section: Main Textmentioning

confidence: 99%

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The geochemistry of methane isotopologues

Wang¹

2017

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This thesis documents the origin, distribution, and fate of methane and several of its isotopic forms on Earth. Using observational, experimental, and theoretical approaches, I illustrate how the relative abundances of 12 CH 4 , 13 CH 4 , 12 CH 3 D, and 13 CH 3 D record the formation, transport, and breakdown of methane in selected settings.Chapter 2 reports precise determinations of 13 CH 3 D, a "clumped" isotopologue of methane, in samples collected from various settings representing many of the major sources and reservoirs of methane on Earth. The results show that the information encoded by the abundance of 13 CH 3 D enables differentiation of methane generated by microbial, thermogenic, and abiogenic processes. A strong correlation between clumped-and hydrogen-isotope signatures in microbial methane is identified and quantitatively linked to the availability of H 2 and the reversibility of microbially-mediated methanogenesis in the environment. Determination of 13 CH 3 D in combination with hydrogen-isotope ratios of methane and water provides a sensitive indicator of the extent of C-H bond equilibration, enables fingerprinting of methane-generating mechanisms, and in some cases, supplies direct constraints for locating the waters from which migrated gases were sourced. Chapter 3 applies this concept to constrain the origin of methane in hydrothermal fluids from sediment-poor vent fields hosted in mafic and ultramafic rocks on slow-and ultraslow-spreading mid-ocean ridges. The data support a hypogene model whereby methane forms abiotically within plutonic rocks of the oceanic crust at temperatures above ca. 300• C during respeciation of magmatic volatiles, and is subsequently extracted during active, convective hydrothermal circulation. Chapter 4 presents the results of culture experiments in which methane is oxidized in the presence of O 2 by the bacterium Methylococcus capsulatus strain Bath. The results show that the clumped isotopologue abundances of partially-oxidized methane can be predicted from knowledge of 13 C/ 12 C and D/H isotope fractionation factors alone.: Shuhei Ono, Ph.D. Acknowledgments I fear that this section will not do justice to the people I have not the space to thank individually. Alas, here goes. To those whose names are not specifically listed here, thank you too. I wish first to thank Shuhei Ono. The work this thesis represents could not have happened without his bold vision and the license to explore and question that working in his lab afforded. His unbridled optimism, breadth of scientific curiosity, personal integrity, and accessibility to his personnel are traits I one day hope to emulate. I thank him for his nonjudgmental yet appropriately measured support of many of my ideas-even those that led nowhere-, for believing in me even when I found it difficult to do so myself, and for teaching me to change pump oil, build vacuum lines, and drink Icelandic vodka.I also wish to thank my thesis committee members Jeff Seewald, Roger Summons, and John Pohlman, for their in...

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Section: Field Site Descriptions and Sampling Methodssupporting

confidence: 54%

“…Our measurements for dominantly-thermogenic gases from the Marcellus and Utica Shales (Burruss and Laughrey, 2010;Baldassare et al, 2014) …”

Section: 2 Preview Of Thesis Contentmentioning

confidence: 99%

Section: Main Textmentioning

confidence: 99%

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The geochemistry of methane isotopologues

Wang¹

2017

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“…S1 for the (i) impacted household wells, (ii) annular space of Welles 2, 3, 4, and 5 gas wells, and (iii) predrill private household wells from the region (16). Notably, methane isotopic characteristics are consistent between gas sampled from the annular spaces of Welles 2, 3, 4, and 5 gas wells and groundwater sampled from the impacted homeowner wells.…”

Section: Resultsmentioning

confidence: 81%

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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“…To unambiguously address such concerns, it is essential to assess the natural occurrence of methane and its spatial distribution, the variability of methane concentrations and the sources of methane in shallow groundwater prior to unconventional energy development to establish a baseline. In the last 5 years, an increasing number of publications have addressed the questions of occurrence and sources of methane in shallow groundwater in natural gas producing regions (Osborn et al, 2011a, b;Warner et al, 2013;Darrah et al, 2012Darrah et al, , 2014Molofsky et al, 2013;Siegel et al, 2015;Vengosh et al, 2013;Brantley et al, 2014;Baldassare et al, 2014;McPhilips et al, 2014;McIntosh et al, 2014;Vidic et al, 2013;Hamilton et al, 2015). These studies have contributed a wealth of baseline data for gas occurrences in shallow groundwater in many regions of North America.…”

Section: Introductionmentioning

confidence: 99%

Redox controls on methane formation, migration and fate in shallow aquifers

Humez¹,

Mayer²,

Nightingale³

et al. 2016

Hydrol. Earth Syst. Sci.

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Abstract. Development of unconventional energy resources such as shale gas and coalbed methane has generated some public concern with regard to the protection of groundwater and surface water resources from leakage of stray gas from the deep subsurface. In terms of environmental impact to and risk assessment of shallow groundwater resources, the ultimate challenge is to distinguish (a) natural in situ production of biogenic methane, (b) biogenic or thermogenic methane migration into shallow aquifers due to natural causes, and (c) thermogenic methane migration from deep sources due to human activities associated with the exploitation of conventional or unconventional oil and gas resources. This study combines aqueous and gas (dissolved and free) geochemical and isotope data from 372 groundwater samples obtained from 186 monitoring wells of the provincial Groundwater Observation Well Network (GOWN) in Alberta (Canada), a province with a long record of conventional and unconventional hydrocarbon exploration. We investigated whether methane occurring in shallow groundwater formed in situ, or whether it migrated into the shallow aquifers from elsewhere in the stratigraphic column. It was found that methane is ubiquitous in groundwater in Alberta and is predominantly of biogenic origin. The highest concentrations of biogenic methane ( > 0.01 mM or > 0.2 mg L −1 ), characterized by δ 13 C CH 4 values < −55 ‰, occurred in anoxic Na-Cl, Na-HCO 3 , and Na-HCO 3 -Cl type groundwaters with negligible concentrations of nitrate and sulfate suggesting that methane was formed in situ under methanogenic conditions for 39.1 % of the samples. In only a few cases (3.7 %) was methane of biogenic origin found in more oxidizing shallow aquifer portions suggesting limited upward migration from deeper methanogenic aquifers. Of the samples, 14.1 % contained methane with δ 13 C CH 4 values > −54 ‰, potentially suggesting a thermogenic origin, but aqueous and isotope geochemistry data revealed that the elevated δ 13 C CH 4 values were caused by microbial oxidation of biogenic methane or postsampling degradation of low CH 4 content samples rather than migration of deep thermogenic gas. A significant number of samples (39.2 %) contained methane with predominantly biogenic C isotope ratios (δ 13 C CH 4 < −55 ‰) accompanied by elevated concentrations of ethane and sometimes trace concentrations of propane. These gases, observed in 28.1 % of the samples, bearing both biogenic (δ 13 C) and thermogenic (presence of C 3 ) characteristics, are most likely derived from shallow coal seams that are prevalent in the Cretaceous Horseshoe Canyon and neighboring formations in which some of the groundwater wells are completed. The remaining 3.7 % of samples were not assigned because of conflicting parameters in the data sets or between replicates samples. Hence, despite quite variable gas concentrations and a wide range of δ 13 C CH 4 values in baseline groundwater samples, we found no conclusive evidence for deep thermogenic gas migration into shallow aqu...

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A geochemical context for stray gas investigations in the northern Appalachian Basin: Implications of analyses of natural gases from Neogene-through Devonian-age strata

Cited by 81 publications

References 34 publications

The geochemistry of methane isotopologues

The geochemistry of methane isotopologues

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

Redox controls on methane formation, migration and fate in shallow aquifers

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