2025 Geophysical Survey

Objectives

The 2025 survey will provide high-resolution mapping and characterization of the seafloor and sub-seafloor geology and structures, with relevance for OWF instalation.

The 2024 results will be expanded by increasing the spatial data density in 10 times and acquiring additional data sets, for the PAER areas of Figueira da Foz and Leixões.

Aims

Methods

>> Full mapping of seafloor, including bathymetry and backscatter

<< Multibeam echosounder (MBES)

>> Characterization of the shallow geology up to 25 m bsf

<< Sub-bottom profiler (SBP)

>> Characterization of the the deep geology up to 50 m bsf

<< Ultra-high resolution (UHR) single-channel system (SCS)

>> Characterization of the deep geology up to 100 m bsf

<< 2D UHR multi-channel seismic system (MCS)

>> Classification of seafloor features, infrastructures, targets, debris or obstructions

<< Side-scan sonar (SSS)
<< Transverse gradiometer/magnetometer (TVG/MAG)

>> Determination of the geotechnical properties of the shallow sediment layers

<< Sediment sampling and laboratory analysis

>> Identification, mapping and risk assessment of geohazards* and anthropogenic hazards**

<< All data

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*Geohazards: geological features with potential to pose risk to one or more aspects of the proposed activity or development at a site.
Examples: boulders, channels, faults, mass transport deposits (MTDs), fluid bearing sediments, gas traps, etc.

**Anthropogenic hazards: man-made objects on the seafloor or buried that may pose risk to the proposed activities or development.
Examples: shipwrecks, aircraft crashes, sunken cargo, archeological sites, undetermined obstructions, military ordnances, etc.

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Aims & Methods

>> Full mapping of seafloor, including bathymetry and backscatter
<< Multibeam echosounder (MBES)

>> Characterization of the shallow geology up to 25 m bsf
<< Sub-bottom profiler (SBP)

>> Characterization of the the deep geology up to 50 m bsf
<< Ultra-high resolution (UHR) single-channel system (SCS)

>> Characterization of the deep geology up to 100 m bsf
<< 2D UHR multi-channel seismic system (MCS)

>> Classification of seafloor features, infrastructures, targets, debris or obstructions
<< Side-scan sonar (SSS)
<< Transverse gradiometer/magnetometer (TVG/MAG)

>> Determination of the geotechnical properties of the shallow sediment layers
<< Sediment sampling and laboratory analysis

>> Identification, mapping and risk assessment of geohazards* and anthropogenic hazards**
<< All data

______

*Geohazards: geological features with potential to pose risk to one or more aspects of the proposed activity or development at a site.
Examples: boulders, channels, faults, mass transport deposits (MTDs), fluid bearing sediments, gas traps, etc.

**Anthropogenic hazards: man-made objects on the seafloor or buried that may pose risk to the proposed activities or development.
Examples: shipwrecks, aircraft crashes, sunken cargo, archeological sites, undetermined obstructions, military ordnances, etc.

Survey details

Operation

The execution of the 2025 geophysical survey was contracted to Ocean Infinity.

Ocean Infinity uses an innovative fuel-efficient vessel fleet where a skeleton crew ensures all the onboard operations for geophysical and geotechnical data acquisition. Data QC, processing and payload are conducted real-time in a remote control center.

Vessels 7803, 7805 and 7808 of the Armada fleet, class 78, will be used to collect all types of geophysical and geotechnical data during the 2025 geophysical survey.

This solution allows to acquire all types of geophysical data (MBES, SSS, SBP, SCS or MCS, TVG/MAG) at single pass on each survey line.

The project team will closely participate in real-time monitoring and decision-making processes at the Ocean Infinity’s Gothenburg operational center.

Vessel 7805 of the Armada fleet

Geophysical survey

Survey lines for geophysical data acquisition were planned to provide high horizontal resolution, with main lines spaced of 150 m and cross lines spaced of 300 m.

A final highly detailed Geomodel will be produced, including seismostratigraphic interpretation and hazard assessment.

Example of planned lines for geophysical data acquisition, comparing 2024 and 2025 surveys.
Detail for the Leixões area: thick lines – 2024 survey; thin lines– 2025 survey (10 times increase in line density).

Planning

The 2025 survey is organized in 4 lots:

Lot 1 – Geophysical survey

>> Lot 1a – Leixões

  • 170 main lines
  • 149 cross lines
  • total length – 6761 km

>> Lot 1b – Figueira da Foz

  • 225 main lines
  • 180 cross lines
  • total length – 13 723 km

Lot 2 – Geotechnical survey

>> Lot 2a – Leixões

  • seabed grab samples: 68 stations
  • Vibrocores: 34 stations
  • ‘deep’ push seabed CPTs: 14 stations

>> Lot 2b – Figueira da Foz

  • seabed grab samples: 138 stations
  • Vibrocores: 69 stations
  • ‘deep’ push seabed CPTs: 29 stations

Geotechnical investigation

All geotechnical datasets are processed for laboratory testing, processing and reporting.

Sediment and ecological analyses include:

  • Identification of trace metal concentration (As, Cd, Cu, Cr, Hg, Pb, Ni, Zn)
  • Identification of the concentration of persistent organic pollutants (PAHs, PCBs, HCBs)
  • Characterization of benthic macrofauna.

Geotechnical results will support decisions on layout and design of foundations/anchors of floating wind turbine generators (WTG).

Survey partners

>> Survey contractor

>> Seismic data acquisition

>> Geotechnical consulting

>> Survey management consulting

>> Seismic processing and interpretation
(Geomodel)