I attended the Floating Offshore Wind 2024 (FOW24) conference this week and heard everyone talking about their concerns with current requirements of acquiring geotechnical samples at every potential seabed anchor point.
This is the current requirement that grants insurance cover for offshore wind developers, so that when operational challenges occur, such as placing the anchor points and costs start to overrun, they stay protected because they have done what is required.
The challenge for floating wind developers however, is the fact that geotechnical samples are expensive. Not only is there a cost per sample location, but if there is bedrock near surface or high risk of boulders, then additional costs per location would apply.
Floating offshore wind turbines (FOWTs) are tethered to the seabed using mooring systems. These systems connect the floating turbine to the seabed and allow the turbine to move within a certain range.
Different types of anchors can be used to tether FOWTs to the seabed, including:
Drag embedment anchors
These are made of steel plates that are welded together and secure the turbine by embedding themselves into the seabed. They are the cheapest option and the anchors can be recovered.
Suction buckets
These are steel structures that open at the bottom and rest on the seabed. They create a vacuum to anchor the turbine, but they work best on sandy or sandy-loam seabeds.
Driven or drilled piles
These are large, hollow metal cylinders that are hammered into the seabed. They can also be drilled into rocky or hard soils.
Dead or gravity anchors
These are massive concrete structures that are placed on the seabed. They are usually only used in specific situations to minimize their impact.
These types of mooring systems are nothing new, as the oil and gas industry has been using them for decades to secure semi-submersible floating drilling/production rigs in position.
But floating wind farms can be made up of tens or hundreds or turbines, dramatically increasing the development costs, possibly beyond financial viability,
I believe RockWave can help with this, even though our focus is not on geotechnical information, instead we are obsessed with creating the most data-driven imaging solutions that form the truest represention of the subsurface.
These datasets, because they are processed and optimised to the highest standard, can be used to gain an understanding of the soil conditions at locations away from physical geotechnical samples, using machine learning and seismic inversion to infer elastic and geotechnical soil properties (pseudo-CPT) for integration within a quantitative ground model....
... potentially reducing the offshore geotechnical requirements (and costs!).... assuming DNV agree to this approach. From their website:
DNV is calling for industry partners to collaborate in delivering a recommended practice that provides clear guidance on the expectations for projects adopting a holistic approach to improve ground characterization for offshore wind developments. This initiative will be part of the ambitious joint industry project (JIP) Ground Investigation for Floating Wind (GIFT)
And then there is Repurposing...
Sometimes, ultra-high resolution seismic (UHRS) does not give us all the answers. Even when it is acquired and processed to its full potential, the raw data lacks information about soil conditions important to engineers of offshore wind developers. Our expertise processing deep exploration 2D/3D seismic datasets has helped us demonstrate to industry how we can repurpose these to enhance understanding of bedrock and channel systems at floating wind sites.
You can do things with these datasets beyond what is possible with conventional 2D and 3D UHRS approaches.
Read more about that here.
Contact seismic@rockwave.xyz if you would like to know more about our seismic solutions that could help you reduce costs of geotechnical campaigns at floating offshore wind sites.
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