Naphthenic acids in groundwater overlying undeveloped shale gas and tight oil reservoirs

Ahad, Jason M. E.; Pakdel, Hooshang; Lavoie, Denis; Lefebvre, René; Peru, Kerry M.; Headley, John V.

doi:10.1016/j.chemosphere.2017.10.015

Cited by 7 publications

(6 citation statements)

References 56 publications

(75 reference statements)

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“…Despite reported below quantitation levels of NAs in surface river waters of the Athabasca region, many authors recognize that groundwater samples from some areas of Alberta can contain significant levels of WSOs. ,,− In the current work, a brief comparison between OSPW and a group of groundwater samples showed a No Match between the different sources (Figure ). The diagnostic ratio results were able to “distinguish between” the two WSO sources but had difficulty discriminating a natural bitumen-impacted groundwater from an OSPW source.…”

Section: Resultsmentioning

confidence: 51%

Diagnostic Ratio Analysis: A New Concept for the Tracking of Oil Sands Process-Affected Water Naphthenic Acids and Other Water-Soluble Organics in Surface Waters

Brunswick

Shang

Frank

et al. 2020

Environ. Sci. Technol.

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A diagnostic ratio forensics tool, similar to that recognized internationally for oil spill source identification, is proposed for use in conjunction with existing LC/QToF quantitative methodology for bitumen-derived water-soluble organics (WSOs). The concept recognizes that bitumen WSOs bear a chemical skeletal relationship to stearane and hopane oil biomarkers. The method uses response ratios for 50 selected WSOs compared between samples by their relative percent difference and adopted acceptance criteria. Oil sands process-affected water (OSPW) samples from different locations within a single tailings pond were shown to match, while those from different industrial sites did not. Acid extractable organic samples collected over 3 weeks from the same location within a single tailings pond matched with each other; as did temporal OSPW samples a year apart. Blind quality assurance samples of OSPW diluted in surface waters were positively identified to their corresponding OSPW source. No interferences were observed from surface waters, and there was no match between bitumen-influenced groundwater and OSPW samples, as expected for different sources. Proof of concept for OSPW source identification using diagnostic ratios was demonstrated, with anticipated application in the tracking of OSPW plumes in surface receiving waters, together with the potential for confirmation of source.

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Section: Resultsmentioning

confidence: 51%

Diagnostic Ratio Analysis: A New Concept for the Tracking of Oil Sands Process-Affected Water Naphthenic Acids and Other Water-Soluble Organics in Surface Waters

Brunswick

Shang

Frank

et al. 2020

Environ. Sci. Technol.

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“…AEOs were extracted following protocols similar to those described previously. ,, In brief, between 1 and 12 L of water was acidified to pH 4.5 and extracted using loose Strata-X-A solid phase extraction (SPE) sorbent (Phenomenex, Torrance, CA) within several weeks after arriving from the field. The sorbent was then filtered from the aqueous phase under vacuum using precombusted glass fiber filters (450 °C for 4 h) and was subsequently eluted with 10% formic acid in methanol and pure methanol.…”

Section: Methodsmentioning

confidence: 99%

“…Carbon isotope ratios of the CO 2 generated by the pyrolytic decarboxylation of AEOs (δ 13 C pyr ) were determined by thermal conversion/elemental analysis-isotope ratio mass spectrometry (TC/EA-IRMS) at the Delta-Lab of the Geological Survey of Canada (Québec, QC, Canada) using a Delta Plus XL isotope ratio mass spectrometer (Thermo Fisher) following a protocol adapted from Ahad et al The initial applications of this technique separated AEOs into distinct mass fractions using preparative capillary gas chromatography. , However, because no significant isotopic variability was observed between the different mass fractions, here we report δ 13 C pyr values for unfractionated AEOs as done in a previous examination of NAs from undeveloped shale gas and tight oil reservoirs . Briefly, aliquots of AEOs dissolved in methanol were transferred by syringe into a 40 μL rigid silver capsule (IVA-Analysentechnik e.K., Düsseldorf, Germany), dried in an oven at 60 °C for 30 min, and sealed with pliers prior to the analysis by TC/EA-IRMS using a pyrolysis reactor temperature of 750 °C.…”

Section: Methodsmentioning

confidence: 99%

“…4,23 However, because no significant isotopic variability was observed between the different mass fractions, 23 here we report δ 13 C pyr values for unfractionated AEOs as done in a previous examination of NAs from undeveloped shale gas and tight oil reservoirs. 31 Briefly, aliquots of AEOs dissolved in methanol were transferred by syringe into a 40 μL rigid silver capsule (IVA-Analysentechnik e.K., Dusseldorf, Germany), dried in an oven at 60 °C for 30 min, and sealed with pliers prior to the analysis by TC/EA-IRMS using a pyrolysis reactor temperature of 750 °C. The δ 13 C pyr values were analyzed using CO 2 calibrated against international carbonate standards (CO 2 obtained from Oztech Trading Corp., Safford, AZ).…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

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Distinguishing Natural from Anthropogenic Sources of Acid Extractable Organics in Groundwater near Oil Sands Tailings Ponds

Ahad

Pakdel²,

Gammon

et al. 2020

Environ. Sci. Technol.

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Distinguishing between naphthenic acids (NAs) associated with oil sands process-affected water (OSPW) and those found naturally in groundwaters in contact with the bituminous McMurray Formation poses a considerable analytical challenge to environmental research in Canada’s oil sands region. Previous work addressing this problem combined high-resolution Orbitrap mass spectrometry with carbon isotope values generated by online pyrolysis (δ13Cpyr) to characterize and quantify the acid extractable organics (AEOs) fraction containing NAs in the subsurface near an oil sands tailings pond. Here, we build upon this work through further development and application of these techniques at two different study sites near two different tailings ponds, in conjunction with the use of an additional isotopic toolsulfur isotope analysis (δ34S) of AEOs. The combined use of both δ13Cpyr and δ34S allowed for discrimination of AEOs into the three end-members relevant to ascertaining the NA environmental footprint within the region: (1) OSPW; (2) McMurray Formation groundwater (i.e., naturally occurring bitumen), and; (3) naturally occurring non-bitumen. A Bayesian isotopic mixing model was used to determine the relative proportions of these three sources in groundwater at both study sites. Although background levels of OSPW-derived AEOs were generally low, one sample containing 49–99% (95% credibility interval) OSPW-derived AEOs was detected within an inferred preferential flow-path, highlighting the potential for this technique to track tailings pond seepage.

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“…Acid extractable organics (AEOs) in groundwater samples were analysed to determine the occurrences, distributions and sources of naphthenic acids (NAs) in the subsurface (Ahad et al, 2018). As classically defined by CnH2n+ZO2, the most abundant NAs detected in the majority of groundwater samples' AEOs were straight-chain (Z = 0) or monounsaturated (Z = -2) C16 and C18 fatty acids.…”

Section: Presence Of Naphthenic Acids (Nas)mentioning

confidence: 99%

Assessing potential impacts of shale gas development on shallow aquifers through upward fluid migration: A multi-disciplinary approach applied to the Utica Shale in eastern Canada

Rivard

Bordeleau

Lavoie

et al. 2019

Marine and Petroleum Geology

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Potential impacts of shale gas development on shallow aquifers has raised concerns, especially regarding groundwater contamination. The intermediate zone separating shallow aquifers from shale gas reservoirs plays a critical role in aquifer vulnerability to fluid upflow, but the assessment of such vulnerability is challenging due to the general paucity of data in this intermediate zone. The ultimate goal of the project reported here was to develop a holistic multi-geoscience methodology to assess potential impacts of unconventional hydrocarbon development on freshwater aquifers related to upward migration through natural pathways. The study area is located in the St. Lawrence Lowlands (southern Quebec, Canada), where limited oil and gas exploration and no shale gas production have taken place. A large set of data was collected over a ~500 km 2 area near a horizontal shale gas exploration well completed and fracked into the Utica Shale at a depth of 2 km. To investigate the intermediate zone integrity, this project integrated research results from multiple sources in order to obtain a better understanding of the system hydrodynamics, including geology, hydrogeology, deep and shallow geophysics, soil, rock and groundwater geochemistry, and geomechanics. The combined interpretation of the multidisciplinary dataset demonstrates that there is no evidence of, and a very limited potential for, upward fluid migration from the Utica Shale reservoir to the shallow aquifer. Microbial and thermogenic methane in groundwater of this region appear to come from the shallow, organic-rich, fractured sedimentary rocks making up the regional aquifer. Nonetheless, diluted brines present in a few shallow wells close to and downstream of a normal fault revealed that some upward groundwater migration occurs, but only over a few hundred meters from the surface based on the isotopic signature of methane. The 3 methodology developed should help support regulations related to shale gas development aiming to protect groundwater.

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Naphthenic acids in groundwater overlying undeveloped shale gas and tight oil reservoirs

Cited by 7 publications

References 56 publications

Diagnostic Ratio Analysis: A New Concept for the Tracking of Oil Sands Process-Affected Water Naphthenic Acids and Other Water-Soluble Organics in Surface Waters

Diagnostic Ratio Analysis: A New Concept for the Tracking of Oil Sands Process-Affected Water Naphthenic Acids and Other Water-Soluble Organics in Surface Waters

Distinguishing Natural from Anthropogenic Sources of Acid Extractable Organics in Groundwater near Oil Sands Tailings Ponds

Assessing potential impacts of shale gas development on shallow aquifers through upward fluid migration: A multi-disciplinary approach applied to the Utica Shale in eastern Canada

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