After one-month technical delay, Allseas resumes pipelaying at first Dutch offshore CCS project

July 17, 2025, by Nadja Skopljak

Allseas has resumed pipelaying for the first offshore carbon capture and storage (CCS) project in the Netherlands after a one-month break caused by a technical issue.

Allseas’ purpose-built offshore construction vessel (OCV) Oceanic was in charge of a special unexploded ordnance (UXO) survey along the 20-kilometer pipeline route for the Porthos (Port of Rotterdam CO2 Transport Hub and Offshore Storage) project, after which the pipelay vessel Lorelay started installing the 16-inch pipeline.

Due to a technical issue with onboard tensioning equipment, Lorelay paused the work on May 7 to go to port for inspection, repair, and full system testing.

With all systems cleared and operational, the installation of the 20-kilometer offshore pipeline restarted on July 11.

Other offshore activities continued during the pause, ensuring no impact on the project schedule. During this time, Lorelay supported the installation of the riser and clamp systems at the P18-A platform, where CO2 will be injected into depleted gas fields.

Once pipelay is complete, the pipeline will be trenched and buried along its full route for added stability and protection.

Porthos, the first large-scale CO2 transport and storage project to be realised in the EU, is designed to transport CO2 captured from industry through the Port of Rotterdam to depleted gas fields in the North Sea, approximately 20 kilometers off the coast, where it will be permanently stored at a depth of more than 3 kilometers beneath the seabed.

The final investment decision (FID) for the project was reached in October 2023.

Allseas is the main offshore contractor for Porthos, in charge of the installation, burial and commissioning of the 16-inch pipeline, connecting the future compressor station, located at the Maasvlakte, with the TAQA-owned P18-A platform offshore. The offshore pipeline is provided with a plastic insulation coating to retain the heat in the pipe and a concrete weight coating for stability on the seabed.

MAN Energy Solutions is to deliver three integrally geared compressor trains, and KCI is in charge of engineering the modification of the P18-A platform, transforming the facility into a platform for permanent offshore CO2 storage. Expro will supply tubular running services (TRS).

Developed by a joint venture of EBN, Gasunie, and the Port of Rotterdam Authority, Porthos is expected to enable the Rotterdam port industry to emit about 10% less CO2 and contribute to CO2 reductions of around 17% for the industry in 2030.