In the most recent phase of the Hornsea 3 Offshore Wind Farm, AMS Trenchless was once again contracted by Orsted to execute the landfall drilling. This continued the long-standing partnership in which AMS previously completed the landfall drilling for Hornsea 1 and Hornsea 2. Hornsea 3 is the largest and most technically challenging project AMS has executed to date.
Hornsea 3 is being built in the North Sea.
Hornsea 3 is being built in the North Sea, approximately 120 km off the coast of Norfolk and 160 km off the coast of Yorkshire. The wind farm will consist of 197 offshore wind turbines within an area of approximately 696 km². Upon completion, the wind farm will be able to generate at least 2,9 GW of green electricity, sufficient to power more than 3 million households. As the main contractor for the landfall works, AMS initially started with the construction of four boreholes of 830 meters each. However, due to deviations identified during the preliminary surveys, the length of each borehole was increased to 950 meters.
HDD installations
In close cooperation with the client, AMS mobilized a full maritime fleet alongside the HDD (Horizontal Directional Drilling) installations. This consisted of support vessels, multicats, crew transfer vessels, and a jack-up barge (JUB). Creating a stable working platform at sea was crucial to the success of the project. AMS personnel remained on board during the operations to limit the number of transports to and from shore and to minimize delays caused by weather conditions during transfers.
On board the JUB, AMS developed and fabricated various custom solutions, including an outrigger chute, duct rollers, a stinger, and securing systems for pipe retrieval, tool changes, and the installation of casing pipes. Prior to departure, all Orcaflex analyses, fabrication designs, and seafastening engineering were fully executed by AMS.
Limiting the environmental impact was a key objective for both Orsted and AMS. To avoid towing pipelines from the coast to the offshore extraction site, it was decided to use fully extruded casing pipes for all four boreholes.
These casing pipes were delivered in four full lengths and stored in a protected offshore storage location until the relevant borehole was ready for installation. Subsequently, the pipes were towed individually from the storage location to the JUB and deployed in a timely manner for the retrieval operations. After all design, fabrication, engineering, and sea-securing works had been completed, the vessels were mobilized to the offshore exit point. AMS had meanwhile already started the pilot drilling, allowing the drill pipes to be retrieved quickly and the widening phase (reaming) to begin.
During execution, the project faced exceptionally bad weather during the summer months. To limit the impact of this, AMS mobilized a second 250-ton HDD installation. This allowed the teams to remain productive at times when they would otherwise have been halted due to weather conditions. Despite the efforts of Orsted, AMS, and all subcontractors, it was decided during the final drilling to temporarily switch the project to winter mode at the end of 2024 and complete the remaining work in April 2025.
During the preparations for the resumption, the limited availability of vessels made it apparent that an earlier mobilization was necessary. Despite the shorter preparation time, AMS, the subcontractors, and Orsted succeeded in mobilizing all offshore resources according to the adjusted program, without incidents, accidents, or safety issues.
The works in 2025 were successfully completed when the last casing pipe was installed on 9 April 2025. The demobilization of the vessels, the removal of the sea-fastening devices, and the restoration of the decks were subsequently carried out fully according to schedule.
This project was the largest assignment AMS has ever realized and was made possible by the close collaboration with Orsted throughout all project phases. With Hornsea 3, AMS has proven its ability to successfully execute large-scale and technically complex directional drilling for offshore energy infrastructure.