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| Titel |
Characterization of methane hydrates and free gas deposits at Nyegga CNE03 pockmark, using marine CSEM and seismic joint-interpretation |
| VerfasserIn |
Eric Attias, Karen Weitemeyer, Martin Sinha, Tim Minshull, Marion Jegen-Kulcsar, Christian Berndt |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250101061
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| Publikation (Nr.) |
 EGU/EGU2015-81.pdf |
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| Zusammenfassung |
| In recent years, gas hydrate deposits have attracted growing interest from both academic and
industry research, due to their potential as an unconventional energy resource and as a
geohazard to various marine infrastructures, and to their possible role in climate change.
Methane hydrates are known to be widespread in seafloor sediments at water depths
ranging from 130 to 2,000 m along offshore continental margins. They are normally
found close to the seafloor and are often present in pockmarks that are underlain by
chimney-like structures. The Nyegga region is situated on the west Norwegian continental
slope and characterized by an extensive pockmark field. The Nyegga pockmarks are
characterised by bathymetric troughs, seep-associated organisms, and rich methane-derived
authigenic carbonate rocks. A controlled-source electromagnetic (CSEM) survey
was performed at the CNE03 pockmark, where high-resolution three-dimensional
seismic data was previously collected and analyzed. The aim of this CSEM study is to
characterize the hydrate and free gas distribution within and around the CNE03 pockmark.
Two-dimensional CSEM joint-inversions were computed using the data acquired by both
ocean bottom electrical field receivers (OBE) and a 3-axis towed receiver (Vulcan). Our
OBE-Vulcan inversion results confirm the existence of a distinctive resistivity anomaly
structure at the CNE03 pockmark, suggesting a shallow anomaly at the underlying
chimney center, likely to result from the presence of gas hydrates. Furthermore, a
deeper and latterly extensive resistivity anomaly emerged from the inversions of
the OBE data, most probably due to the existence of a free gas layer beneath the
base of the gas hydrate stability zone (BGHSZ). The CSEM inversion results are
consistent with a seismic velocity model for the NW–SE survey line; both support the
presence of gas hydrate and free gas accumulations within the CNE03 chimney-like
structure. Several more resistivity anomalies were detected near to CNE03, which are
currently being investigated. This work will contribute to an accurate estimate of the
amount of methane hydrate and free gas both beneath the pockmark and over a larger
regional scale, providing valuable information for future exploration of gas hydrate
deposits.
Keywords: CSEM, 2D joint-inversion, Nyegga, Chimney, Pockmark, Methane hydrate. |
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