The University of Southampton
University of Southampton Institutional Repository

Gas hydrate quantification at a pockmark offshore Norway from joint effective medium modelling of resistivity and seismic velocity

Gas hydrate quantification at a pockmark offshore Norway from joint effective medium modelling of resistivity and seismic velocity
Gas hydrate quantification at a pockmark offshore Norway from joint effective medium modelling of resistivity and seismic velocity
Methane emissions from gas hydrate deposits along continental margins may alter the biogeophysical properties of marine environments, both on local and regional scales. The saturation of a gas hydrate deposit is commonly calculated using the elastic or electrical properties measured remotely or in-situ at the site of interest. Here, we used a combination of controlled-source electromagnetic (CSEM), seismic and sediment core data obtained in the Nyegga region, offshore Norway, in a joint elastic-electrical approach to quantify marine gas hydrates found within the CNE03 pockmark. Multiscale analysis of two sediment cores reveals significant differences between the CNE03 pockmark and a reference site located approximately 150 m northwest of CNE03. Gas hydrates and chemosynthetic bivalves were observed in the CNE03 sediments collected. The seismic velocity and electrical resistivity measured in the CNE03 sediment core are consistent with the P-wave velocity () and resistivity values derived from seismic and CSEM remote sensing datasets, respectively. The gradually increases (1.75–1.9 km/s) with depth within the CNE03 pipe-like structure, whereas the resistivity anomaly remains 3 m. A joint interpretation of the collocated seismic and CSEM data using a joint elastic-electrical effective medium model suggests that for the porosity range 0.55–0.65, the gas hydrate saturation within the CNE03 hydrate stability zone varies with depth between 20 and 48%. At 0.6 porosity, the hydrate saturation within CNE03 varies between 23 and 37%, whereas the weighted mean saturation is 30%. Our results demonstrate that a well-constrained gas hydrate quantification can be accomplished by coupling P-wave velocity and CSEM resistivity data through joint elastic-electrical effective medium modelling. The approach applied in this study can be used as a framework to quantify hydrate in various marine sediments.
Effective medium modelling, Gas hydrate, Marine CSEM, Seismic velocity
0264-8172
104151
Attias, Eric
abf34bba-f99f-47f9-ba89-92df1c488a5e
Amalokwu, Kelvin
a88bc1e5-5577-49a6-a503-fcd9ea12d8fe
Watts, Millie
74f8c79a-1eee-4337-ae9e-a2681933ecbe
Falcon-suarez, Ismael Himar
f14858f6-d086-4761-9dc5-ba09bd89d95b
North, Laurence
65837b6b-40f1-4a1c-ba66-ec6ff2d7f84b
Hu, Gao Wei
e763719d-f984-4a89-9867-5fea2fc071b6
Best, Angus I.
cad03726-10f8-4f90-a3ba-5031665234c9
Weitemeyer, Karen
22c524f6-b24d-4d2a-a46d-16b06c70a5d1
Minshull, Tim A.
3b2231bc-f741-463f-8b43-76d41b1cbfec
Attias, Eric
abf34bba-f99f-47f9-ba89-92df1c488a5e
Amalokwu, Kelvin
a88bc1e5-5577-49a6-a503-fcd9ea12d8fe
Watts, Millie
74f8c79a-1eee-4337-ae9e-a2681933ecbe
Falcon-suarez, Ismael Himar
f14858f6-d086-4761-9dc5-ba09bd89d95b
North, Laurence
65837b6b-40f1-4a1c-ba66-ec6ff2d7f84b
Hu, Gao Wei
e763719d-f984-4a89-9867-5fea2fc071b6
Best, Angus I.
cad03726-10f8-4f90-a3ba-5031665234c9
Weitemeyer, Karen
22c524f6-b24d-4d2a-a46d-16b06c70a5d1
Minshull, Tim A.
3b2231bc-f741-463f-8b43-76d41b1cbfec

Attias, Eric, Amalokwu, Kelvin, Watts, Millie, Falcon-suarez, Ismael Himar, North, Laurence, Hu, Gao Wei, Best, Angus I., Weitemeyer, Karen and Minshull, Tim A. (2020) Gas hydrate quantification at a pockmark offshore Norway from joint effective medium modelling of resistivity and seismic velocity. Marine and Petroleum Geology, 113, 104151, [104151]. (doi:10.1016/j.marpetgeo.2019.104151).

Record type: Article

Abstract

Methane emissions from gas hydrate deposits along continental margins may alter the biogeophysical properties of marine environments, both on local and regional scales. The saturation of a gas hydrate deposit is commonly calculated using the elastic or electrical properties measured remotely or in-situ at the site of interest. Here, we used a combination of controlled-source electromagnetic (CSEM), seismic and sediment core data obtained in the Nyegga region, offshore Norway, in a joint elastic-electrical approach to quantify marine gas hydrates found within the CNE03 pockmark. Multiscale analysis of two sediment cores reveals significant differences between the CNE03 pockmark and a reference site located approximately 150 m northwest of CNE03. Gas hydrates and chemosynthetic bivalves were observed in the CNE03 sediments collected. The seismic velocity and electrical resistivity measured in the CNE03 sediment core are consistent with the P-wave velocity () and resistivity values derived from seismic and CSEM remote sensing datasets, respectively. The gradually increases (1.75–1.9 km/s) with depth within the CNE03 pipe-like structure, whereas the resistivity anomaly remains 3 m. A joint interpretation of the collocated seismic and CSEM data using a joint elastic-electrical effective medium model suggests that for the porosity range 0.55–0.65, the gas hydrate saturation within the CNE03 hydrate stability zone varies with depth between 20 and 48%. At 0.6 porosity, the hydrate saturation within CNE03 varies between 23 and 37%, whereas the weighted mean saturation is 30%. Our results demonstrate that a well-constrained gas hydrate quantification can be accomplished by coupling P-wave velocity and CSEM resistivity data through joint elastic-electrical effective medium modelling. The approach applied in this study can be used as a framework to quantify hydrate in various marine sediments.

Text
Attias_et_al_Revised_Manuscript_JMPG_D_19_00591_Clean - Accepted Manuscript
Download (42MB)

More information

Accepted/In Press date: 26 November 2019
e-pub ahead of print date: 3 December 2019
Published date: 1 March 2020
Keywords: Effective medium modelling, Gas hydrate, Marine CSEM, Seismic velocity

Identifiers

Local EPrints ID: 444250
URI: http://eprints.soton.ac.uk/id/eprint/444250
ISSN: 0264-8172
PURE UUID: 3c93a747-e423-4f96-9a37-d42a45fbbe0a

Catalogue record

Date deposited: 06 Oct 2020 18:31
Last modified: 28 Apr 2022 04:52

Export record

Altmetrics

Contributors

Author: Eric Attias
Author: Kelvin Amalokwu
Author: Millie Watts
Author: Ismael Himar Falcon-suarez
Author: Laurence North
Author: Gao Wei Hu
Author: Angus I. Best
Author: Karen Weitemeyer
Author: Tim A. Minshull

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×