Characterizing the variability of natural gas hydrate composition from a selected site of the Western Black Sea, off Romania

International audience Natural Gas Hydrates (NGH) collected during the Ghass cruise 2015 in the Western Black Sea onboard the R/V Pourquoi pas? are characterized by a suite of techniques. Gas Chromatography and Raman spectroscopy are used for the identification of the nature of the gas source, the h...

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Published in:Marine and Petroleum Geology
Main Authors: Chazallon, Bertrand, Rodriguez, C.T., Ruffine, L., Carpentier, Y., Donval, J.-P., Ker, S., Riboulot, V.
Other Authors: Physique Moléculaire aux Interfaces (PMI), Laboratoire de Physique des Lasers, Atomes et Molécules - UMR 8523 (PhLAM), Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Université de Lille-Centre National de la Recherche Scientifique (CNRS), Géosciences Marines (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)
Format: Article in Journal/Newspaper
Language:English
Published: HAL CCSD 2021
Subjects:
Online Access:https://hal.archives-ouvertes.fr/hal-03249485
https://hal.archives-ouvertes.fr/hal-03249485/document
https://hal.archives-ouvertes.fr/hal-03249485/file/S0264817220305687.pdf
https://doi.org/10.1016/j.marpetgeo.2020.104785
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collection Université de Nantes: HAL-UNIV-NANTES
op_collection_id ftunivnantes
language English
topic [SDE.IE]Environmental Sciences/Environmental Engineering
[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces
environment
spellingShingle [SDE.IE]Environmental Sciences/Environmental Engineering
[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces
environment
Chazallon, Bertrand
Rodriguez, C.T.,
Ruffine, L.
Carpentier, Y.
Donval, J.-P.
Ker, S.
Riboulot, V.
Characterizing the variability of natural gas hydrate composition from a selected site of the Western Black Sea, off Romania
topic_facet [SDE.IE]Environmental Sciences/Environmental Engineering
[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces
environment
description International audience Natural Gas Hydrates (NGH) collected during the Ghass cruise 2015 in the Western Black Sea onboard the R/V Pourquoi pas? are characterized by a suite of techniques. Gas Chromatography and Raman spectroscopy are used for the identification of the nature of the gas source, the hydrate structure and spatial variability of cage occupancies. The nature and source of hydrate forming gases primarily reveal a high methane content (99.6 mol%) and small amount of nitrogen (>0.29 mol%) and CO 2 (0.056 mol%). Isotopic analyses from the hydrate-bound methane and recently published results from Pape et al. (2020) clearly indicate a microbial source of gas supplying the hydrate deposit generated by the reduction of carbon. For the first time, Raman imaging spectroscopy was applied on NGH recovered in the Western Black Sea. The results show a heterogeneous distribution of the encapsulated guest molecules (CH 4 , N 2 and H 2 S), which is associated with a spatial variability of the guest-gas composition at the micron-scale. Some portions of the 2D-Raman images clearly exhibit a relative N 2-enrichment (with a concentration exceeding 6 mol% N 2 at some positions), while H 2 S shows a rather minor contribution on all the spectral maps investigated. A correlation is then established between the composition of the gas in the NGH and its impact on the CH 4 cage occupancy, with a ratio of θ LC /θ SC (large cage/small cage) between ~ 0.5 and 1.26 depending on the positions analyzed. The departure from the expected ratio in pure methane hydrate is attributed to the preferential encasement of N 2 in the large cage of the NGH structure. In addition, the occurrence of carotenoids identified in sediment-rich zones show a minor impact on the CH 4 cage occupancies. The results are discussed within the context of natural gas resource estimates in NGH to emphasize how the measured cage occupancies may impact the volumetric conversion factor commonly used with other geologic parameters to determine the resource ...
author2 Physique Moléculaire aux Interfaces (PMI)
Laboratoire de Physique des Lasers, Atomes et Molécules - UMR 8523 (PhLAM)
Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)
Université de Lille-Centre National de la Recherche Scientifique (CNRS)
Géosciences Marines (GM)
Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)
format Article in Journal/Newspaper
author Chazallon, Bertrand
Rodriguez, C.T.,
Ruffine, L.
Carpentier, Y.
Donval, J.-P.
Ker, S.
Riboulot, V.
author_facet Chazallon, Bertrand
Rodriguez, C.T.,
Ruffine, L.
Carpentier, Y.
Donval, J.-P.
Ker, S.
Riboulot, V.
author_sort Chazallon, Bertrand
title Characterizing the variability of natural gas hydrate composition from a selected site of the Western Black Sea, off Romania
title_short Characterizing the variability of natural gas hydrate composition from a selected site of the Western Black Sea, off Romania
title_full Characterizing the variability of natural gas hydrate composition from a selected site of the Western Black Sea, off Romania
title_fullStr Characterizing the variability of natural gas hydrate composition from a selected site of the Western Black Sea, off Romania
title_full_unstemmed Characterizing the variability of natural gas hydrate composition from a selected site of the Western Black Sea, off Romania
title_sort characterizing the variability of natural gas hydrate composition from a selected site of the western black sea, off romania
publisher HAL CCSD
publishDate 2021
url https://hal.archives-ouvertes.fr/hal-03249485
https://hal.archives-ouvertes.fr/hal-03249485/document
https://hal.archives-ouvertes.fr/hal-03249485/file/S0264817220305687.pdf
https://doi.org/10.1016/j.marpetgeo.2020.104785
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ENVELOPE(-67.450,-67.450,-67.700,-67.700)
ENVELOPE(135.750,135.750,-66.200,-66.200)
geographic Pourquoi Pas
Pourquoi-Pas
Pourquoi-Pas?
geographic_facet Pourquoi Pas
Pourquoi-Pas
Pourquoi-Pas?
genre Methane hydrate
genre_facet Methane hydrate
op_source ISSN: 0264-8172
Marine and Petroleum Geology
https://hal.archives-ouvertes.fr/hal-03249485
Marine and Petroleum Geology, 2021, 124, pp.104785. ⟨10.1016/j.marpetgeo.2020.104785⟩
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doi:10.1016/j.marpetgeo.2020.104785
PII: S0264-8172(20)30568-7
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spelling ftunivnantes:oai:HAL:hal-03249485v1 2023-05-15T17:12:12+02:00 Characterizing the variability of natural gas hydrate composition from a selected site of the Western Black Sea, off Romania Chazallon, Bertrand Rodriguez, C.T., Ruffine, L. Carpentier, Y. Donval, J.-P. Ker, S. Riboulot, V. Physique Moléculaire aux Interfaces (PMI) Laboratoire de Physique des Lasers, Atomes et Molécules - UMR 8523 (PhLAM) Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Centre National de la Recherche Scientifique (CNRS) Université de Lille-Centre National de la Recherche Scientifique (CNRS) Géosciences Marines (GM) Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER) 2021-02 https://hal.archives-ouvertes.fr/hal-03249485 https://hal.archives-ouvertes.fr/hal-03249485/document https://hal.archives-ouvertes.fr/hal-03249485/file/S0264817220305687.pdf https://doi.org/10.1016/j.marpetgeo.2020.104785 en eng HAL CCSD Elsevier info:eu-repo/semantics/altIdentifier/doi/10.1016/j.marpetgeo.2020.104785 hal-03249485 https://hal.archives-ouvertes.fr/hal-03249485 https://hal.archives-ouvertes.fr/hal-03249485/document https://hal.archives-ouvertes.fr/hal-03249485/file/S0264817220305687.pdf doi:10.1016/j.marpetgeo.2020.104785 PII: S0264-8172(20)30568-7 http://creativecommons.org/licenses/by-nc/ info:eu-repo/semantics/OpenAccess CC-BY-NC ISSN: 0264-8172 Marine and Petroleum Geology https://hal.archives-ouvertes.fr/hal-03249485 Marine and Petroleum Geology, 2021, 124, pp.104785. ⟨10.1016/j.marpetgeo.2020.104785⟩ [SDE.IE]Environmental Sciences/Environmental Engineering [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces environment info:eu-repo/semantics/article Journal articles 2021 ftunivnantes https://doi.org/10.1016/j.marpetgeo.2020.104785 2023-01-03T23:44:31Z International audience Natural Gas Hydrates (NGH) collected during the Ghass cruise 2015 in the Western Black Sea onboard the R/V Pourquoi pas? are characterized by a suite of techniques. Gas Chromatography and Raman spectroscopy are used for the identification of the nature of the gas source, the hydrate structure and spatial variability of cage occupancies. The nature and source of hydrate forming gases primarily reveal a high methane content (99.6 mol%) and small amount of nitrogen (>0.29 mol%) and CO 2 (0.056 mol%). Isotopic analyses from the hydrate-bound methane and recently published results from Pape et al. (2020) clearly indicate a microbial source of gas supplying the hydrate deposit generated by the reduction of carbon. For the first time, Raman imaging spectroscopy was applied on NGH recovered in the Western Black Sea. The results show a heterogeneous distribution of the encapsulated guest molecules (CH 4 , N 2 and H 2 S), which is associated with a spatial variability of the guest-gas composition at the micron-scale. Some portions of the 2D-Raman images clearly exhibit a relative N 2-enrichment (with a concentration exceeding 6 mol% N 2 at some positions), while H 2 S shows a rather minor contribution on all the spectral maps investigated. A correlation is then established between the composition of the gas in the NGH and its impact on the CH 4 cage occupancy, with a ratio of θ LC /θ SC (large cage/small cage) between ~ 0.5 and 1.26 depending on the positions analyzed. The departure from the expected ratio in pure methane hydrate is attributed to the preferential encasement of N 2 in the large cage of the NGH structure. In addition, the occurrence of carotenoids identified in sediment-rich zones show a minor impact on the CH 4 cage occupancies. The results are discussed within the context of natural gas resource estimates in NGH to emphasize how the measured cage occupancies may impact the volumetric conversion factor commonly used with other geologic parameters to determine the resource ... Article in Journal/Newspaper Methane hydrate Université de Nantes: HAL-UNIV-NANTES Pourquoi Pas ENVELOPE(135.783,135.783,-66.083,-66.083) Pourquoi-Pas ENVELOPE(-67.450,-67.450,-67.700,-67.700) Pourquoi-Pas? ENVELOPE(135.750,135.750,-66.200,-66.200) Marine and Petroleum Geology 124 104785