Allseas on offshore pipelay duty as Porthos takes over North Sea gas assets for CCS revamp

Switzerland-headquartered offshore pipeline installation, heavy lift, and subsea construction contractor Allseas is putting an offshore pipeline in place for a development that aims to become the first offshore CO2 transport and storage project in the European Union (EU). To this end, a gas field and its infrastructure off the coast of the Netherlands have changed hands and will be repurposed to enable carbon capture and storage (CCS).

Allseas has confirmed that its Lorelay pipe-laying vessel has begun offshore pipelay activities in Rotterdam Harbour for the Port of Rotterdam CO2 transport hub and offshore storage (Porthos) project, a joint venture between EBN, Gasunie, and the Port of Rotterdam Authority in the Dutch North Sea.

The Swiss player underlines that the campaign got underway with a pull-in of the 16-inch CO2 pipeline to the Maasvlakte side, marking the start of the 20-kilometer offshore pipeline that will transport CO2 captured from local industry to depleted gas fields beneath the North Sea for permanent storage.

Aside from this, Porthos’ CO2 infrastructure also entails around 30 kilometers of onshore pipeline, a compressor station, an injection platform, and former wells and gas fields. The initial stretch of the pipeline is said to demand pinpoint positioning, tight marine coordination, and 24/7 communication with port authorities, as it is operating a few hundred meters from the shoreline in the Maasgeul.

Allseas highlights its role as the main offshore contractor for this CCS development, described as the first of its kind in the Netherlands. The firm’s scope covers installation, burial, and commissioning of the offshore pipeline, insulated to retain heat and coated with a thick layer of concrete to prevent it from floating.

This comes shortly after Valaris announced the return of the Valaris 123 rig to the Porthos carbon transport and storage project to carry out its offshore activities. Porthos has now confirmed the acquisition of TAQA’s P18-A gas production platform and its associated wells and decommissioned gas fields under the Dutch North Sea, which are going to be given a new lease on life soon.

This is portrayed as an important step in the transition from natural gas extraction to large-scale CO2 storage at the asset, where the existing infrastructure will be reused, enabling the gas production platform to be converted into a CO2 injection platform and made more sustainable with solar panels and wind turbines.

Moreover, CO2 from the Rotterdam port industry is expected to be permanently stored in the former gas fields, more than 3 kilometers below the seabed, via four wells. Porthos, which will store around 37 million tons of CO2, about 2.5 million tons of CO2 per year for 15 years, is slated to come online next year.

“TAQA is carrying out the transformation work on behalf of Porthos – a collaboration that combines technical expertise with a shared ambition for climate solutions. The conversion is expected to be completed by the end of 2025; the Porthos project will be operational in the course of 2026,” underlined Porthos.

Aside from Allseas and Valaris, several other players are working on bringing this project to life, including Expro, MAN Energy Solutions, and KCI.

Allseas recently expanded its fleet with two newbuild offshore construction vessels (OCVs) to boost its offshore capabilities.