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Combined interpretation of marine controlled source electromagnetic and reflection seismic data in the German North Sea: a case study

Combined interpretation of marine controlled source electromagnetic and reflection seismic data in the German North Sea: a case study
Combined interpretation of marine controlled source electromagnetic and reflection seismic data in the German North Sea: a case study
This paper focuses on the combined analysis and interpretation of controlled source electromagnetic (CSEM) and multichannel reflection seismic (MCS) data along one profile in the German North Sea with the goal to reduce ambiguities in interpretation. The shallow water environment of the North Sea is characterized by a complex geological development which includes rifting, several ice age cycles, a propagating shelf margin, mass-transport deposits and salt dome formation. Seismic and electromagnetic methods are sensitive to different physical properties of the seabed and therefore complement each other. We analyse the MCS data with a migration velocity tomography and an amplitude variation with offset analysis and discuss seismic velocities and densities. For true amplitude recovery the amplitude distortions are calibrated with in situ logging data. The CSEM data are analysed in 2-D, for which, for the first time, data were included that were acquired while the instrument was towed on the seafloor in addition to the stationary sites. The CSEM inversions are constrained by seismic horizons. The joint interpretation focuses on two seismic reflectors: One can be interpreted as an unconformity marking a lithological change from fresh water-bearing glacial deposits to compacted sediments below, and the other one as a layer of fine-grained deposits potentially capping patchy shallow gas occurrences. This exemplary case study shows how the combination of both methods can benefit by interpreting complex geology and eliminating ambiguous explanations.
Electrical properties, Europe, Marine electromagnetics, Inverse theory, Acoustic properties, Controlled source seismology
0956-540X
218-230
Gehrmann, Romina A.S.
1ee547b2-aa53-4d38-9d36-a2ccc3aa52e2
Schnabel, Claudia
e0bc82cb-1f28-4b4e-b31f-d9b0070eec9a
Engels, Martin
7da68be4-0918-41b6-88ed-23b86bbad308
Schnabel, Michael
d3ee2aa9-47bc-49af-8fe0-c59d2f7d50ce
Schwalenberg, Katrin
2d6f4b27-eb47-4c1c-9b26-11ae3dfbf6dc
Gehrmann, Romina A.S.
1ee547b2-aa53-4d38-9d36-a2ccc3aa52e2
Schnabel, Claudia
e0bc82cb-1f28-4b4e-b31f-d9b0070eec9a
Engels, Martin
7da68be4-0918-41b6-88ed-23b86bbad308
Schnabel, Michael
d3ee2aa9-47bc-49af-8fe0-c59d2f7d50ce
Schwalenberg, Katrin
2d6f4b27-eb47-4c1c-9b26-11ae3dfbf6dc

Gehrmann, Romina A.S., Schnabel, Claudia, Engels, Martin, Schnabel, Michael and Schwalenberg, Katrin (2019) Combined interpretation of marine controlled source electromagnetic and reflection seismic data in the German North Sea: a case study. Geophysical Journal International, 216 (1), 218-230. (doi:10.1093/gji/ggy408).

Record type: Article

Abstract

This paper focuses on the combined analysis and interpretation of controlled source electromagnetic (CSEM) and multichannel reflection seismic (MCS) data along one profile in the German North Sea with the goal to reduce ambiguities in interpretation. The shallow water environment of the North Sea is characterized by a complex geological development which includes rifting, several ice age cycles, a propagating shelf margin, mass-transport deposits and salt dome formation. Seismic and electromagnetic methods are sensitive to different physical properties of the seabed and therefore complement each other. We analyse the MCS data with a migration velocity tomography and an amplitude variation with offset analysis and discuss seismic velocities and densities. For true amplitude recovery the amplitude distortions are calibrated with in situ logging data. The CSEM data are analysed in 2-D, for which, for the first time, data were included that were acquired while the instrument was towed on the seafloor in addition to the stationary sites. The CSEM inversions are constrained by seismic horizons. The joint interpretation focuses on two seismic reflectors: One can be interpreted as an unconformity marking a lithological change from fresh water-bearing glacial deposits to compacted sediments below, and the other one as a layer of fine-grained deposits potentially capping patchy shallow gas occurrences. This exemplary case study shows how the combination of both methods can benefit by interpreting complex geology and eliminating ambiguous explanations.

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Gehrmann et al 2018 - Version of Record
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More information

Accepted/In Press date: 30 September 2018
e-pub ahead of print date: 10 October 2018
Published date: 1 January 2019
Additional Information: This article has been accepted for publication in Geophysical Journal International ©: 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Keywords: Electrical properties, Europe, Marine electromagnetics, Inverse theory, Acoustic properties, Controlled source seismology

Identifiers

Local EPrints ID: 426337
URI: https://eprints.soton.ac.uk/id/eprint/426337
ISSN: 0956-540X
PURE UUID: 533c2ccb-7310-440c-9593-fa94b9ddeeb0
ORCID for Romina A.S. Gehrmann: ORCID iD orcid.org/0000-0002-3099-2771

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Date deposited: 23 Nov 2018 17:30
Last modified: 20 Jul 2019 00:33

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Contributors

Author: Claudia Schnabel
Author: Martin Engels
Author: Michael Schnabel
Author: Katrin Schwalenberg

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