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Porosity and free gas estimates from controlled source electromagnetic data at the Scanner Pockmark in the North Sea

Porosity and free gas estimates from controlled source electromagnetic data at the Scanner Pockmark in the North Sea
Porosity and free gas estimates from controlled source electromagnetic data at the Scanner Pockmark in the North Sea
We present porosity and free gas estimations and their uncertainties at anactive methane venting site in the UK sector of the North Sea. In the Scan-ner Pockmark area in about 150m water depth, we performed a multi-disciplinary experiment to investigate the physical properties of fluid flowstructures within unconsolidated glaciomarine sediments. Here we focus onthe towed controlled source electromagnetic (CSEM) data analysis with con-straints from seismic reflection and core logging data. Inferred backgroundresistivity values vary between 0.6–1 Ωm at the surface and 1.9–2.4 Ωm at150 mbsf. We calibrate Archie’s parameters with measurements on cores, andestimate porosities of about 50±10% at the seafloor decreasing to 25±3% at 150 mbsf which matches variations expected for mechanical compaction ofclay rich sediments. High reflectivity in seismic reflection data is consistentwith the existence of a gas pocket. A synthetic study of varying gas contentin this gas pocket shows that at least 33±8% of free gas are required to causea distinct CSEM data anomaly. Real data inversions with seismic constraintssupport the presence of up to 34±14% free gas in a 30–40 m thick gas pocketunderneath the pockmark within the stratigraphic highs of a till layer abovethe glacial unconformity in the Aberdeen Ground Formation.
1750-5836
Gehrmann, Romina
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Provenzano, Giuseppe
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Böttner, Christoph
e35e2e9c-3e87-48b2-a5bb-a68cd68266be
Moreno, Hector Marin
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Bayrakci, Gaye
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Tan, Yee Y
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Yilo, Naima Karolina
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Djanni, Axel T.
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Weitemeyer, Karen
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Minshull, Timothy
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Bull, Jonathan
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Karstens, Jens
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Berndt, Christian
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Gehrmann, Romina
1ee547b2-aa53-4d38-9d36-a2ccc3aa52e2
Provenzano, Giuseppe
0da03494-44a8-4536-8833-6cd4feb75882
Böttner, Christoph
e35e2e9c-3e87-48b2-a5bb-a68cd68266be
Moreno, Hector Marin
3fe1141c-c2f4-475a-89ea-bec8a87388bd
Bayrakci, Gaye
0f436a50-6297-4ed1-9c12-797f16cbc9c4
Tan, Yee Y
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Yilo, Naima Karolina
317f9415-f7ab-4277-acf0-51064751b995
Djanni, Axel T.
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Weitemeyer, Karen
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Minshull, Timothy
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Bull, Jonathan
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Karstens, Jens
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Berndt, Christian
29364362-5d52-4b1b-82b9-e799fcc4d7ed

Gehrmann, Romina, Provenzano, Giuseppe, Böttner, Christoph, Moreno, Hector Marin, Bayrakci, Gaye, Tan, Yee Y, Yilo, Naima Karolina, Djanni, Axel T., Weitemeyer, Karen, Minshull, Timothy, Bull, Jonathan, Karstens, Jens and Berndt, Christian (2021) Porosity and free gas estimates from controlled source electromagnetic data at the Scanner Pockmark in the North Sea. International Journal of Greenhouse Gas Control, 109, [103343]. (doi:10.1016/j.ijggc.2021.103343).

Record type: Article

Abstract

We present porosity and free gas estimations and their uncertainties at anactive methane venting site in the UK sector of the North Sea. In the Scan-ner Pockmark area in about 150m water depth, we performed a multi-disciplinary experiment to investigate the physical properties of fluid flowstructures within unconsolidated glaciomarine sediments. Here we focus onthe towed controlled source electromagnetic (CSEM) data analysis with con-straints from seismic reflection and core logging data. Inferred backgroundresistivity values vary between 0.6–1 Ωm at the surface and 1.9–2.4 Ωm at150 mbsf. We calibrate Archie’s parameters with measurements on cores, andestimate porosities of about 50±10% at the seafloor decreasing to 25±3% at 150 mbsf which matches variations expected for mechanical compaction ofclay rich sediments. High reflectivity in seismic reflection data is consistentwith the existence of a gas pocket. A synthetic study of varying gas contentin this gas pocket shows that at least 33±8% of free gas are required to causea distinct CSEM data anomaly. Real data inversions with seismic constraintssupport the presence of up to 34±14% free gas in a 30–40 m thick gas pocketunderneath the pockmark within the stratigraphic highs of a till layer abovethe glacial unconformity in the Aberdeen Ground Formation.

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More information

Accepted/In Press date: 20 April 2021
e-pub ahead of print date: 12 May 2021

Identifiers

Local EPrints ID: 449200
URI: http://eprints.soton.ac.uk/id/eprint/449200
ISSN: 1750-5836
PURE UUID: 07806c21-57b8-4fce-a348-2dbbaff78fd8
ORCID for Romina Gehrmann: ORCID iD orcid.org/0000-0002-3099-2771
ORCID for Timothy Minshull: ORCID iD orcid.org/0000-0002-8202-1379

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Date deposited: 19 May 2021 18:17
Last modified: 20 May 2021 01:48

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Contributors

Author: Romina Gehrmann ORCID iD
Author: Giuseppe Provenzano
Author: Christoph Böttner
Author: Hector Marin Moreno
Author: Gaye Bayrakci
Author: Yee Y Tan
Author: Axel T. Djanni
Author: Karen Weitemeyer
Author: Jonathan Bull
Author: Jens Karstens
Author: Christian Berndt

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