A geotechnical company based in southwest England is developing an autonomous underwater vehicle deployed from an uncrewed surface ship to undertake geotechnical surveys
Recent months have seen several companies unveil uncrewed surface vessels (USVs) intended for the offshore survey space. Others already active in the market have demonstrated the ability of USVs to undertake long-range geophysical survey missions and are already looking at other potential missions for USVs, such as deploying remotely operated vehicles (ROVs), autonomous underwater vehicles (ROVs), and offshore logistics.
But as managing director of Cornwall, UK-based Feritech, a company that specialises in equipment for marine geotechnical surveys, Rob Ferris told OWJ, geophysical surveys – mapping what is on and beneath the seabed using different types of sonar, sub-bottom profilers and magnetometers – from uncrewed vessels is relatively easy compared with uncrewed geotechnical surveys. “No-one is tackling autonomous geotechnical survey,” he said. “The real challenge for the offshore market is autonomous geotechnical investigations, not geophysical surveys.”
Geophysical and geotechnical surveys are used to collect data to understand seabed and subsurface conditions and help understand potential engineering constraints and safety hazards. They help to ensure the success of a project, providing valuable information during the pre-planning stage, helping to optimise engineering solutions. In contrast to geophysical surveys, geotechnical surveys provide sediment samples, and core and cone penetration testing are used to ‘ground truth’ the results of geophysical investigations and provide a detailed record of seabed stratigraphy and soil engineering properties, information that is essential to the design of foundations for structures such as monopile foundations and anchors for floating turbines.
Feritech supplies the offshore industry with a range of seabed geotechnical survey equipment and consumables such as sediment corers, seafloor grabs and cone penetration test (CPT) equipment, a form of in-situ test equipment used to identify the soil type in which a cone penetrometer is pushed into the seabed and data is recorded at regular intervals. It also designs and manufactures winches and launch and recovery systems and, more recently, has begun to focus on autonomous operations. This kind of equipment – long used in the offshore oil and gas sector and in the offshore wind industry – has always been deployed from manned vessels, but as the size and scale of offshore windfarms has grown, and their distance from shore increases, so it has become evident that a new approach is needed.
An oil and gas project of the type for which conventional ship-based geotechnical equipment has long been used, usually has a single structure and a relatively small number of moorings, whereas a commercial-scale floating windfarm will have a very large number of individual mooring systems and anchors, presenting a very different challenge to geotechnical surveys.
“Offshore assets such as floating windfarms require an increasing number of detailed surveys, which often have to be carried out in challenging sea conditions,” Mr Ferris told OWJ. “This is particularly true in the fast-growing floating offshore wind sector, where installation takes place in deep water. There are a number of USVs that have been proposed to carry out geophysical survey work but the concept of autonomous geotechnical surveys is beginning to gain traction. Responding to that demand, we want to design an autonomous solution for geotechnical surveys in deep water.”
In the next 12-18 months, USV companies are planning to begin deploying unmanned surface vessels ranging in size up to 70 m, capable of launching and recovering ROVs and AUVs. But as Mr Ferris points out, an uncrewed vessel able to host subsea units capable of autonomous geotechnical investigations would need to be large – and highly specialised – to accommodate equipment capable of taking samples from the seabed and of surveying a large area. “Although in themselves large units, a USV capable of deploying subsea vehicles with seabed testing solutions could have a huge impact,” said Mr Ferris, “reducing the risks and costs associated with seabed surveys.”
In early 2021, Marine-i, which was created to help the marine technology sector in Cornwall and the Isles of Scilly grow by harnessing the potential of research and innovation, agreed to support Feritech in its plan to develop an autonomous subsea vehicle specially designed for geotechnical survey work.
Feritech engaged with the Marine-i project to get expert help researching and designing the new vehicle. It is collaborating on a structured development programme to define industry standards that the new vehicle would have to meet, specify requirements for tools and create a design solution. This will result in the construction of a pre-commercial prototype for sea trials.
Speaking at the time the agreement was reached, Marine-i programme director Professor Lars Johanning said, “This is exactly the kind of innovative, disruptive technology Marine-i was set up to support. Feritech’s concept could revolutionise the way in which geotechnical survey work is carried out.
“By helping reduce risk and costs for developers, it will help accelerate the growth of floating offshore wind in the Celtic Sea, generating a positive economic impact on the local supply chain. Globally, it would attract interest from clients in a wide range of offshore activities.”
Working with Marine-i, Feritech it is developing sensor and sampling technology capable of being deployed from the subsea unit, which could operate successfully in a range of water depths. It expects to make a patent application for the new technology later in 2021. Mr Ferris said Feritech has also identified a potential partner with whom it could work on a USV capable of deploying the subsea vehicle.
“We need to forget existing geotechnical technology and conventional sampling systems and reinvent the way site investigations are carried out,” he told OWJ. “We want to use miniaturisation to develop much smaller subsystems and combine sampling and innovative sensors with artificial intelligence to provide the same quality data that you get with conventional technology, but at a fraction of the cost.”
Mr Ferris declined to be drawn on exactly what kind of sampling tool and sensors might Feritech is considering, but said the company hopes to begin testing an underwater vehicle combining the new sensors and sampling equipment by the end of 2022 and hopes to bring it to market by the end of 2023.
Mr Ferris’ comments echo those made by Royal Academy of Engineering chair in emerging technologies and ocean engineering Professor Susan Gourvenec in evidence to a House of Commons Environmental Audit Committee (EAC) inquiry on offshore wind technology in 2020.
In her evidence, Professor Gourvenec called for change in the way that windfarm sites are surveyed. She said new approaches were needed for seabed survey and assessments of sites for bottom-fixed foundations, or moorings and anchors for floating wind turbines. She said the size and scale of future offshore windfarms and their distance from shore will pose a challenge for conventional survey technology, and new, more efficient ways to obtain accurate high-resolution seabed data will be required.
“Offshore geotechnical testing tools that can be deployed with reduced vessel support are critical to reduce the cost of offshore renewables developments,” she said, noting that an economic challenge is arising due to the much greater area required for surveys of offshore windfarms.
“A specialist geotechnical vessel could cost in the region of £100,000 (US$122,000) a day and a renewables site investigation will require hundreds of sites to be investigated,” she told the inquiry.
Professor Gourvenec said opportunities for cost reduction of site investigations could include intelligent geotechnical site characterisation tools for remote or autonomous deployment or operation, to upscale capability without upscaling cost; and machine learning techniques to correlate continuous geophysical data with discrete geotechnical data, to optimise development of an engineering ground model of a development area.
“Harnessing the intelligence of sensing, robotics and autonomy, next-generation resiliently engineered systems will enable cheaper, smarter site characterisation,” she told the EAC.