This document discusses a seismic survey conducted in the Mid-Atlantic Ridge to explore seabed minerals. It provides background on the geological features of the survey area, including the Mohn's Ridge slow spreading ridge. It then describes the 2D seismic acquisition using a source vessel and towed streamer, and the processing sequence applied to the data. The document presents some preliminary seismic section examples and interpretations, noting imaging challenges from the 2D nature and short offsets. It concludes by acknowledging the project partners and highlighting the improved geological understanding from the survey.

1. Deep Sea Mining Summit 2023:
Seismic For Exploring Seabed Minerals At The
Mid-Atlantic Ridge
Phil Hayes & Gulsah Metin
Shearwater GeoServices

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Introduction
• Introduction to Marine Minerals
• Introduction to Shearwater
• The ATLAB-3 Survey:
• Geological Background
• Seismic Acquisition & Processing
• Seismic Data Examples
• Learning from the 2D Seismic Processing & Preliminary Interpretation
• Summary / Next Steps?

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• Seafloor Massive Sulphides (SMS)
• Located at spreading axis
• Active mounds vs. Passive mounds
• 300m diameter, 150m thickness, 25+m tall
• Zn, Cu, Co, S, Fe, Rare Earth minerals
• Mining required
• Manganese Crusts
• Crusts grow on hard substrates of volcanic
Origin (layer on top of Seamounts/Ridges)
• Mn, Co, Zn, Ni, Rear Earth minerals (Dy, Nd, Sc)
• Mining required
• Manganese Nodules
• Ni, Co, Cu, Mn
• No mining required, “just” pick up (will be the first resource to be exploited)
What are Marine Minerals?

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• Why?
• Energy transition
• Energy security / Geopolitics
• Environmental and public concerns on land-based mining
• Lower grade of minerals in existing fields
• Status
• ISA, International Seabed Authority (www.isa.org.jm)
• ISA Issued licence required
• 31 exploration licenses active
• Handful of coastal states have initiated activity on proximal continental shelves:
Papa New Guinea, Japan, Cook Islands. A few others to follow (Norway…)
Why Marine Minerals? Status?
Exploration areas – International Seabed Authority (isa.org.jm)

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• Norwegian Government
• Program launched H2 2021
• Impact Assessment -> H1 2023
• Opening for exploration licences -> H2 2023
• First production 2028/2029?
Timeline for Marine Minerals in Norway

6. Introduction to Shearwater

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Innovation, Technology, and Collaboration from Sensor to Image

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Leveraging Complementary Activities
Marine Acquisition
A global fleet with efficient operations
at scale offering the full range of marine
acquisition surveys
Shearwater is a marine geophysical company that innovates collaboratively from sensor to image. The process of
development is a continuous loop, between people, technology and platform, involving hardware and software
Software
The most modern seismic processing
software in the industry.
Technology
Innovation and collaboration at every
step from sensor design to Final image
Processing & Imaging
A truly integrated service for your
processing and re-processing projects

9. EXPLORATION
Depth
~2-4 km
Detectable Feature Size
> ~10 m
Frequency
125-250 Hz
Sample Rate
2-4 ms
CCUS
Depth
~1-2 km
Detectable Feature Size
~3-10 m
Frequency
250-500 Hz
Sample Rate
1-2 ms
SHALLOW FOCUS
Depth
< ~500 m
Detectable Feature Size
< ~3 m
Frequency
> 1 kHz
Sample Rate
< 1 ms

10. Atlab 3: Geological Background

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• Uneven topography. Dissimilarities between the flanks:
• Western flank shows oceanic core complexes and major normal faults with significant rotation
• Eastern flank shows less topographical relief
Geological Background (I)
Mohn’s
Treasure

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Geological Background (II)
• Mohn's Ridge: Slow spreading ridge:
• Irregular flanks
• Exposed lower crustal and upper
mantle
• Hydrothermal deposits
• Deep rooted detachment faults
• Long term hydrothermal circulation
• Conceptual profile of the Mohn’s
Treasure showing the rotated fault
(F8) and an idealized fault plane
steepening at depth as a result of the
flexural rotation (Buck, 1988).
Section across the northern sector of the ultraslow-spreading Mohn’s Ridge. From Johansen et al., 2019
Conceptual profile: (From Reimers, 2017, 2020)

13. ATLAB-3: Seismic Acquisition & Processing

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Towed Streamer: Seismic Acquisition
2D seismic: 1 Source / 1 Streamer. Acquiring multiple 2D lines (challenges for 3D structure)
Obstruction
deviation

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Towed Streamer: Seismic Acquisition
2D seismic: 1 Source / 1 Streamer. Acquiring multiple 2D lines (challenges for 3D structure)
3D seismic: Multiple Sources / Multiple Streamers. Acquiring a regular pattern of lines (frontier areas)
start
end
Obstruction
deviation

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• Deploying recording equipment onto the Seabed, with a source vessel
• Long Offsets  FWI
• Low frequencies  FWI / Broadband Imaging
• Wide Azimuths  Better illumination in complex geological plays
 Better Velocity Model Building
 Better Imaging
• Flexible  Deployment around/under platforms
Ocean Bottom: Seismic Acquisition

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• Rugose seabed with significant challenges in geometry
• Seismic were acquired during the turn lines. Maximise the amount of useable seismic data.
~200km of data acquired across 8 sail lines
• Note: Data acquired during sail line turns (Yellow) were acquired using a 20m shot point interval
• Seq 8 broken into 2 lines due to an air gun source issue
ATLAB-3: Seismic Acquisition
Loki’s Castle
Mohn’s Treasure

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• Input raw shots
• Reformat to SW Reveal format
• Reversible Spherical Divergence correction
• N+1 Shot mute
• Direct Arrival Mute
• Noise Attenuation (Tug Noise, Tail Noise)
• Source De-signature & De-bubble
• Source-Side De-ghost
• Phase-only Q Compensation
ATLAB-3: Seismic Processing Sequence
• Common Offset Regularization
• Redatum to MSL (Source side only)
• PreSTM velocity scanning
• Isotropic Kirchhoff PreSTM
• Stack (no mute required)
• Amplitude-only Q Compensation
• Time Variant Filter
• SEG-Y Output

19. ATLAB-3: Seismic Data Examples

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• Compared to the presentation shown at the workshop session, only limited seismic sections are
shown.
• Please contact phayes@shearwatergeo.com / sfrivik@shearwatergeo.com for further details.
Seismic Examples

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5km
700m
Final PreSTM Seismic Example (Contact authors for details)

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Loki’s Castle
3km 3km
500m
700m
Example of 3D illumination differences

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SW
NE
Seq-02
SW
NE
Base of Post-volcanic sedimentary cover / Erosional surface
Mixed sediments and volcanics (?) / truncated
Syn-tectonic mixed sediments and volcanics (?)
Syn-volcanic fault systems
Sideswipe (?)
Volcanics (?)
Volcanics (?)
Preliminary Interpretation & Learning

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• ATLAB-3 Seismic Acquisition and Processing have begun to improve understanding of this interesting and challenging part of the
world.
• Acquisition and processing of data acquired during turn lines were processed to a good standard > turn line acquisition could be
considered as part of any future 3D acquisition campaign.
• The 2D nature and the short offset of the acquisition led to a series of processing and imaging challenges, in particular the velocity
analysis and imaging.
• Increased seismic resolution.
Summary / Where Next?

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• The Shearwater UK & Norway Teams:
• Gulsah Metin
• Svein Arne Frivik
• Bengt Larssen
• Javier Martin
• Francesco Borraccini
• Rich Bartlett
• Stefano Panepinto
Acknowledgements: Shearwater

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• Thanks to the ATLAB-3 partners for the effort of getting the data acquired and in particular Professor
Ståle Johnsen at NTNU for leading the consortium.
Acknowledgements: ATLAB-3 Consortium
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