Thermal Characterization of Pockmarks Across Vestnesa and Svyatogor Ridges, Offshore Svalbard
The Svalbard margin represents one of the northernmost gas hydrate provinces worldwide. Vestnesa Ridge (VR) and Svyatogor Ridge (SR) west of Svalbard are two prominent sediment drifts showing abundant pockmarks and sites of seismic chimney structures. Some of these sites at VR are associated with ac...
Published in: | Journal of Geophysical Research: Solid Earth |
---|---|
Main Authors: | , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
American Geophysical Union
2020
|
Subjects: | |
Online Access: | https://hdl.handle.net/10037/20565 https://doi.org/10.1029/2020JB019468 |
id |
ftunivtroemsoe:oai:munin.uit.no:10037/20565 |
---|---|
record_format |
openpolar |
spelling |
ftunivtroemsoe:oai:munin.uit.no:10037/20565 2023-05-15T14:26:59+02:00 Thermal Characterization of Pockmarks Across Vestnesa and Svyatogor Ridges, Offshore Svalbard Riedel, M. Villinger, H. Freudenthal, T. Pape, T. Bünz, Stefan Bohrmann, G. 2020-11-10 https://hdl.handle.net/10037/20565 https://doi.org/10.1029/2020JB019468 eng eng American Geophysical Union Journal of Geophysical Research (JGR): Solid Earth info:eu-repo/grantAgreement/RCN/SFF/223259/Norway/Centre for Arctic Gas Hydrate, Environment and Climate/CAGE/ Riedel M, Villinger, Freudenthal T, Pape T, Bünz S, Bohrmann G. Thermal Characterization of Pockmarks Across Vestnesa and Svyatogor Ridges, Offshore Svalbard. Journal of Geophysical Research (JGR): Solid Earth. 2020;125(12) FRIDAID 1867558 doi:10.1029/2020JB019468 2169-9313 2169-9356 https://hdl.handle.net/10037/20565 openAccess Copyright 2020 The Author(s) VDP::Mathematics and natural science: 400::Geosciences: 450::Marine geology: 466 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Marin geologi: 466 Journal article Tidsskriftartikkel publishedVersion 2020 ftunivtroemsoe https://doi.org/10.1029/2020JB019468 2021-06-25T17:57:56Z The Svalbard margin represents one of the northernmost gas hydrate provinces worldwide. Vestnesa Ridge (VR) and Svyatogor Ridge (SR) west of Svalbard are two prominent sediment drifts showing abundant pockmarks and sites of seismic chimney structures. Some of these sites at VR are associated with active gas venting and were the focus of drilling and coring with the seafloor‐deployed MARUM‐MeBo70 rig. Understanding the nature of fluid migration and gas hydrate distribution requires (among other parameters) knowledge of the thermal regime and in situ gas and pore fluid composition. In situ temperature data were obtained downhole at a reference site at VR defining a geothermal gradient of ~78 mK m −1 (heat flow ~95 mW m −2 ). Additional heat probe data were obtained to describe the thermal regime of the pockmarks. The highest heat flow values were systematically seen within pockmark depressions and were uncorrelated to gas venting occurrences. Heat flow within pockmarks is typically ~20 mW m −2 higher than outside pockmarks. Using the downhole temperature data and gas compositions from drilling we model the regional base of the gas hydrate stability zone (BGHSZ). Thermal modeling including topographic effects suggest a BGHSZ up to 40 m deeper than estimated from seismic data. Uncertainties in sediment properties (velocity and thermal conductivity) are only partially explaining the mismatch. Capillary effects due to small sediment grain sizes may shift the free gas occurrence above the equilibrium BGHSZ. Changes in gas composition or pore fluid salinity at greater depth may also explain the discrepancy in observed and modeled BGHSZ. Article in Journal/Newspaper Arctic Svalbard Svalbard margin University of Tromsø: Munin Open Research Archive Svalbard Svyatogor Ridge ENVELOPE(5.783,5.783,78.233,78.233) Journal of Geophysical Research: Solid Earth 125 12 |
institution |
Open Polar |
collection |
University of Tromsø: Munin Open Research Archive |
op_collection_id |
ftunivtroemsoe |
language |
English |
topic |
VDP::Mathematics and natural science: 400::Geosciences: 450::Marine geology: 466 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Marin geologi: 466 |
spellingShingle |
VDP::Mathematics and natural science: 400::Geosciences: 450::Marine geology: 466 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Marin geologi: 466 Riedel, M. Villinger, H. Freudenthal, T. Pape, T. Bünz, Stefan Bohrmann, G. Thermal Characterization of Pockmarks Across Vestnesa and Svyatogor Ridges, Offshore Svalbard |
topic_facet |
VDP::Mathematics and natural science: 400::Geosciences: 450::Marine geology: 466 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Marin geologi: 466 |
description |
The Svalbard margin represents one of the northernmost gas hydrate provinces worldwide. Vestnesa Ridge (VR) and Svyatogor Ridge (SR) west of Svalbard are two prominent sediment drifts showing abundant pockmarks and sites of seismic chimney structures. Some of these sites at VR are associated with active gas venting and were the focus of drilling and coring with the seafloor‐deployed MARUM‐MeBo70 rig. Understanding the nature of fluid migration and gas hydrate distribution requires (among other parameters) knowledge of the thermal regime and in situ gas and pore fluid composition. In situ temperature data were obtained downhole at a reference site at VR defining a geothermal gradient of ~78 mK m −1 (heat flow ~95 mW m −2 ). Additional heat probe data were obtained to describe the thermal regime of the pockmarks. The highest heat flow values were systematically seen within pockmark depressions and were uncorrelated to gas venting occurrences. Heat flow within pockmarks is typically ~20 mW m −2 higher than outside pockmarks. Using the downhole temperature data and gas compositions from drilling we model the regional base of the gas hydrate stability zone (BGHSZ). Thermal modeling including topographic effects suggest a BGHSZ up to 40 m deeper than estimated from seismic data. Uncertainties in sediment properties (velocity and thermal conductivity) are only partially explaining the mismatch. Capillary effects due to small sediment grain sizes may shift the free gas occurrence above the equilibrium BGHSZ. Changes in gas composition or pore fluid salinity at greater depth may also explain the discrepancy in observed and modeled BGHSZ. |
format |
Article in Journal/Newspaper |
author |
Riedel, M. Villinger, H. Freudenthal, T. Pape, T. Bünz, Stefan Bohrmann, G. |
author_facet |
Riedel, M. Villinger, H. Freudenthal, T. Pape, T. Bünz, Stefan Bohrmann, G. |
author_sort |
Riedel, M. |
title |
Thermal Characterization of Pockmarks Across Vestnesa and Svyatogor Ridges, Offshore Svalbard |
title_short |
Thermal Characterization of Pockmarks Across Vestnesa and Svyatogor Ridges, Offshore Svalbard |
title_full |
Thermal Characterization of Pockmarks Across Vestnesa and Svyatogor Ridges, Offshore Svalbard |
title_fullStr |
Thermal Characterization of Pockmarks Across Vestnesa and Svyatogor Ridges, Offshore Svalbard |
title_full_unstemmed |
Thermal Characterization of Pockmarks Across Vestnesa and Svyatogor Ridges, Offshore Svalbard |
title_sort |
thermal characterization of pockmarks across vestnesa and svyatogor ridges, offshore svalbard |
publisher |
American Geophysical Union |
publishDate |
2020 |
url |
https://hdl.handle.net/10037/20565 https://doi.org/10.1029/2020JB019468 |
long_lat |
ENVELOPE(5.783,5.783,78.233,78.233) |
geographic |
Svalbard Svyatogor Ridge |
geographic_facet |
Svalbard Svyatogor Ridge |
genre |
Arctic Svalbard Svalbard margin |
genre_facet |
Arctic Svalbard Svalbard margin |
op_relation |
Journal of Geophysical Research (JGR): Solid Earth info:eu-repo/grantAgreement/RCN/SFF/223259/Norway/Centre for Arctic Gas Hydrate, Environment and Climate/CAGE/ Riedel M, Villinger, Freudenthal T, Pape T, Bünz S, Bohrmann G. Thermal Characterization of Pockmarks Across Vestnesa and Svyatogor Ridges, Offshore Svalbard. Journal of Geophysical Research (JGR): Solid Earth. 2020;125(12) FRIDAID 1867558 doi:10.1029/2020JB019468 2169-9313 2169-9356 https://hdl.handle.net/10037/20565 |
op_rights |
openAccess Copyright 2020 The Author(s) |
op_doi |
https://doi.org/10.1029/2020JB019468 |
container_title |
Journal of Geophysical Research: Solid Earth |
container_volume |
125 |
container_issue |
12 |
_version_ |
1766300521650454528 |