Crown Estate Round 6: Turning Oil & Gas Seismic Data into an Advantage for Offshore Wind Developers

With The Crown Estate's Round 6 leasing round expected to launch in 2027, developers have an opportunity to build their understanding of prospective offshore wind sites before applications begin.

Crown Estate Offshore Wind Leasing Round 6 - PDA Zones (from https://www.thecrownestate.co.uk/our-business/marine/offshore-wind/round-6)

One of the biggest challenges is what lies beneath the seabed. Unforeseen ground

conditions can create significant technical, operational and commercial risks for offshore wind projects. Unexpectedly hard ground, shallow bedrock or buried geological features can affect foundation installation, forcing changes to installation methods or causing delays while the problem is investigated. For transport and installation (T&I) contractors, conditions that fall outside agreed assumptions and operational limits can mean suspending work, with potential consequences for vessel time, schedules and costs. The precise contractual consequences depend on the circumstances and project contracts.

Understanding these risks earlier can make a real difference. Developers will often defer substantial expenditure on site-wide subsurface investigations until after a leasing award. But wouldn't it be valuable to know beforehand if bedrock m

ight lie within the penetration depth of a typical 30 m monopile? Such a discovery could have significant implications for foundation selection, installation methods and project economics — even if further investigation is needed to establish the actual ground conditions and engineering solution.

RockWave is helping developers make more of the data that already exists by repurposing oil and gas (O&G) seismic data to reveal valuable detail about the shallow subsurface.

Map showing location of RockWave's Repurposed O&G seismic data optimised for Offshore Wind Developers scoping applications to the Crown Estate's Round 6 lease round in 2027.

From ScotWind to Round 6

In 2021, RockWave repurposed the UK government-funded Mid North Sea High (MNSH) 2015 2D seismic dataset for use in the ScotWind application process. See the original post here.

Working with Atkins (as they were known at the time - now AtkinsRéalis), the data was used to map Quaternary sediment thickness and identify potential geohazards, including buried depressions, tunnel valleys, faults and gas pockets. This provided additional insight into subsurface conditions and helped inform future survey planning and potential foundation considerations. The developers behind the Ossian project, within ScotWind area E1, used the repurposed dataset as part of their application work.

Traditional O&G seismic processing is designed to investigate deeper geological targets, potentially sacrificing useful information from the shallow subsurface. RockWave returns to the raw seismic field data and designs a processing workflow to maximise detail within the depth range relevant to offshore wind foundations and anchors.

The resulting data can provide valuable regional coverage and deeper penetration than typical ultra-high-resolution surveys. It complements the higher-density investigations required to develop engineering ground models, providing a stronger geological foundation from which to plan and optimise subsequent geophysical and geotechnical surveys — and make better-informed decisions about where investigation budgets are spent.

Why shallow subsurface detail matters

Repurposed seismic can support early-stage development in four key ways:

• Mapping sediment thickness: Understanding the distribution of Quaternary sediments helps establish an initial geological model and identify changes in ground conditions across a site.

• Identifying potential geohazards: Buried valleys, faults and gas pockets can be highlighted for further investigation, helping developers identify areas of uncertainty.

• Planning future surveys: Regional seismic interpretation can help target higher-resolution geophysical surveys and geotechnical investigations where they are most needed.

• Informing foundation concepts and costs: An early understanding of geological conditions can flag potential engineering challenges, including the possibility of shallow bedrock or unexpectedly hard layers that may affect foundation installation.

  
  

Repurposed seismic does not replace site-specific investigation or determine final foundation designs. Its value is in providing an earlier, broader evidence base to help developers understand uncertainty and plan the next stage of work.

BGS Quaternary maps: A useful first look

The British Geological Survey (BGS) recently digitised its offshore Quaternary geology maps, making an important national-scale geological reference dataset more accessible to offshore developers.

The BGS Offshore Quaternary 250K dataset brings together legacy maps originally published between 1984 and 1992 at a scale of 1:250,000. While digitisation improves accessibility, the underlying geological interpretations have not been updated using new data or analysis.

These maps provide a useful first look at regional Quaternary geology, but they are not a substitute for higher-resolution subsurface interpretation.

During the 2021 ScotWind project, RockWave's repurposed Mid North Sea High seismic data was used to update the BGS geological interpretation in the relevant area, adding detail on sediment thickness and potential geohazards.

Updated Quaternary thickness map using RockWave's Repurposed seismic data, showing significantly enhanced resolution compared to the published BGS Quaternary maps.

More recently, BGS announced Seabed GeoMaP, a three-year project funded by The Crown Estate to improve geological mapping of the UK Continental Shelf, including seabed and shallow subsurface information. This is a positive development, combining existing geological information and marine survey data with new analytical techniques.

However, the announcement does not yet specify the seismic data, processing methods or resolution that will be available. With Round 6 approaching, developers may need answers sooner.

RockWave's repurposed seismic data can help bridge that gap, providing more detailed insight into shallow subsurface conditions where suitable coverage exists. For developers preparing their applications, the opportunity is to build on existing geological mapping and investigate what additional information is already available over their sites.

Existing seismic data across UK offshore regions

RockWave already has repurposed seismic datasets available across several UK offshore regions:

• North Sea: Mid North Sea High 2D

• UK Celtic Sea: Southwest Approaches 2D

• Irish Celtic Sea: Geopartners NCS 2D

• Irish Sea: SLB legacy 2D

• East Shetland Basin: ESB 2D

Depending on the location and available coverage, these datasets can help developers investigate sediment thickness, potential geohazards and geological variability before planning more detailed site investigations.

There is also the possibility of adding a high-resolution velocity model derived from recorded seismic refractions. RockWave calls this DCR, providing a further source of subsurface information to complement the repurposed seismic interpretation.

With Repurposed seismic data it is possible to use the refractions recorded by long-offset hydrophone cables to generate a high resolution velocity model that captures information about the density of subsurface strata.

Explore the available coverage on our repurposed seismic data page.

Make more informed decisions ahead of Round 6

With Round 6 expected to launch in the first half of 2027 and the potential for around 6 GW or more of new offshore wind capacity, developers have a timely opportunity to review the subsurface information already available over their prospective sites.

RockWave's ScotWind experience demonstrates how existing O&G data can be repurposed to support offshore wind development, helping developers build an earlier understanding of ground conditions and plan future investigations more effectively.

Before commissioning more data, find out what you already have beneath your site.

Explore RockWave's repurposed seismic coverage or contact Alastair MacLeod and Matt Swan to discuss your Round 6 requirements.