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

Attias, Eric; Weitemeyer, Karen; Minshull, Tim A.; Best, Angus I. ORCID: https://orcid.org/0000-0001-9558-4261; Sinha, Martin; Jegen-Kulcsar, Marion; Hölz, Sebastian; 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. https://doi.org/10.1093/gji/ggw188

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Official URL: http://dx.doi.org/10.1093/gji/ggw188

Abstract/Summary

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.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1093/gji/ggw188
ISSN:	0956-540X
Additional Keywords:	Gas hydrates; CSEM; 2D inversion; Anisotropy; Seismic Tomography; Pipe structures
Date made live:	27 May 2016 09:03 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/513716

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1093/gji/ggw188

ISSN:

0956-540X

Additional Keywords:

Gas hydrates; CSEM; 2D inversion; Anisotropy; Seismic Tomography; Pipe structures

Date made live:

27 May 2016 09:03 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/513716