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Controlled-source electromagnetic and seismic delineation of sub-seafloor fluid flow structures in a gas hydrate province, offshore Norway

Controlled-source electromagnetic and seismic delineation of sub-seafloor fluid flow structures in a gas hydrate province, offshore Norway
Controlled-source electromagnetic and seismic delineation of sub-seafloor fluid flow structures in a gas hydrate province, offshore Norway
Deep sea pockmarks underlain by chimney-like or pipe structures that contain methane hydrate are abundant along the Norwegian continental margin. In such hydrate provinces the interaction between hydrate formation and fluid flow has significance for benthic ecosystems and possibly climate change. The Nyegga region, situated on the western Norwegian continental slope, is characterized by an extensive pockmark field known to accommodate substantial methane gas hydrate deposits. The aim of this study is to detect and delineate both the gas hydrate and free gas reservoirs at one of Nyegga's pockmarks. In 2012, a marine controlled-source electromagnetic (CSEM) survey was performed at a pockmark in this region, where high-resolution three-dimensional seismic data were previously collected in 2006. Two-dimensional CSEM inversions were computed using the data acquired by ocean bottom electrical field receivers. Our results, derived from unconstrained and seismically constrained CSEM inversions, suggest the presence of two distinctive resistivity anomalies beneath the pockmark: a shallow vertical anomaly at the underlying pipe structure, likely due to gas hydrate accumulation, and a laterally extensive anomaly attributed to a free gas zone below the base of the gas hydrate stability zone. This work contributes to a robust characterization of gas hydrate deposits within sub-seafloor fluid flow pipe structures.
CSEM, seismic, 2D inversion, Gas Hydrate, Pockmarks
0956-540X
1093-1110
Attias, Eric
abf34bba-f99f-47f9-ba89-92df1c488a5e
Weitemeyer, Karen
22c524f6-b24d-4d2a-a46d-16b06c70a5d1
Minshull, Tim A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
Best, Angus I.
cad03726-10f8-4f90-a3ba-5031665234c9
Sinha, Martin
794c3012-d0e8-4d2f-b328-c8cfd56c5976
Jegen, Marion
c4a9eace-f47f-4a5d-a4ac-47aa3477e374
Holz, Sebastian
18a1f9d4-219c-4649-a2a1-8529cd2510c7
Berndt, Christian
29364362-5d52-4b1b-82b9-e799fcc4d7ed
Attias, Eric
abf34bba-f99f-47f9-ba89-92df1c488a5e
Weitemeyer, Karen
22c524f6-b24d-4d2a-a46d-16b06c70a5d1
Minshull, Tim A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
Best, Angus I.
cad03726-10f8-4f90-a3ba-5031665234c9
Sinha, Martin
794c3012-d0e8-4d2f-b328-c8cfd56c5976
Jegen, Marion
c4a9eace-f47f-4a5d-a4ac-47aa3477e374
Holz, Sebastian
18a1f9d4-219c-4649-a2a1-8529cd2510c7
Berndt, Christian
29364362-5d52-4b1b-82b9-e799fcc4d7ed

Attias, Eric, Weitemeyer, Karen, Minshull, Tim A., Best, Angus I., Sinha, Martin, Jegen, Marion, Holz, Sebastian and Berndt, Christian (2016) Controlled-source electromagnetic and seismic delineation of sub-seafloor fluid flow structures in a gas hydrate province, offshore Norway. Geophysical Journal International, 206 (2), 1093-1110. (doi:10.1093/gji/ggw188).

Record type: Article

Abstract

Deep sea pockmarks underlain by chimney-like or pipe structures that contain methane hydrate are abundant along the Norwegian continental margin. In such hydrate provinces the interaction between hydrate formation and fluid flow has significance for benthic ecosystems and possibly climate change. The Nyegga region, situated on the western Norwegian continental slope, is characterized by an extensive pockmark field known to accommodate substantial methane gas hydrate deposits. The aim of this study is to detect and delineate both the gas hydrate and free gas reservoirs at one of Nyegga's pockmarks. In 2012, a marine controlled-source electromagnetic (CSEM) survey was performed at a pockmark in this region, where high-resolution three-dimensional seismic data were previously collected in 2006. Two-dimensional CSEM inversions were computed using the data acquired by ocean bottom electrical field receivers. Our results, derived from unconstrained and seismically constrained CSEM inversions, suggest the presence of two distinctive resistivity anomalies beneath the pockmark: a shallow vertical anomaly at the underlying pipe structure, likely due to gas hydrate accumulation, and a laterally extensive anomaly attributed to a free gas zone below the base of the gas hydrate stability zone. This work contributes to a robust characterization of gas hydrate deposits within sub-seafloor fluid flow pipe structures.

Text
Geophys. J. Int.-2016-Attias-gji_ggw188.pdf - Accepted Manuscript
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Accepted/In Press date: 16 May 2016
e-pub ahead of print date: 20 May 2016
Published date: 1 August 2016
Keywords: CSEM, seismic, 2D inversion, Gas Hydrate, Pockmarks
Organisations: Ocean and Earth Science, Geology & Geophysics, Marine Geoscience

Identifiers

Local EPrints ID: 395478
URI: http://eprints.soton.ac.uk/id/eprint/395478
ISSN: 0956-540X
PURE UUID: 47f94af2-ed4f-4dc4-b77f-13eeed6f35aa
ORCID for Tim A. Minshull: ORCID iD orcid.org/0000-0002-8202-1379

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Date deposited: 27 May 2016 08:53
Last modified: 17 Dec 2019 01:53

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Contributors

Author: Eric Attias
Author: Karen Weitemeyer
Author: Tim A. Minshull ORCID iD
Author: Angus I. Best
Author: Martin Sinha
Author: Marion Jegen
Author: Sebastian Holz
Author: Christian Berndt

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