Allseas will play a key construction role in the realisation of the Porthos carbon capture and storage (CCS) project in the Port of Rotterdam, the first development of its kind in the Netherlands.

Porthos, a partnership between EBN, Gasunie and the Port of Rotterdam Authority, will transport CO2 from industrial sites in the port area to empty gas fields in the Dutch North Sea, where it will be permanently stored up to 4 kilometres beneath the seabed.

Allseas selected for construction of subsea pipeline

Allseas has been selected to construct the subsea pipeline. Starting 2025, the work includes installation, burial and commissioning of the 16-inch CCS pipeline connecting a compressor station on the Maasvlakte with the P18-A platform approximately 20 kilometres offshore.

Pipelay will be executed by Allseas’ dynamically positioned S-lay vessel Lorelay, with construction support from Oceanic. The vessels can position precisely and safely in the busy waters around Rotterdam, the busiest and largest port in Europe.

Allseas’ first carbon capture pipeline

“We are delighted that the Porthos partnership recognised Allseas’ offshore installation capability as being key to the success of this landmark project,” says Allseas Chief Executive Pieter Heerema.

“Back in the mid-1980s, as the world’s first pipelay vessel operating fully on dynamic positioning, Lorelay installed some of the earliest gas and oil pipelines in the Dutch North Sea. The fact that almost four decades later, the same vessel will install the first carbon capture pipeline is a testament to our ongoing innovation and continuous improvement of our vessels’ capabilities.”

Porthos expected to reduce CO2 emissions by about 2%

Operational by 2026, Porthos is expected to reduce the Netherland’s annual CO2 emissions by about 2%. The pipeline will transport about 2.5 million tonnes of CO2 per year for 15 years to the North Sea storage site.

The EU has recognised Porthos as an important “Project of Common Interest” in meeting climate targets and awarded a €102 million subsidy to accelerate development.

Porthos project

Porthos is developing a project in which CO2 from industry in the Port of Rotterdam is transported and stored in empty gas fields beneath the North Sea.

The CO2 that will be transported and stored by Porthos, will be captured by various companies. The companies will supply their CO2 to a collective pipeline that runs through the Rotterdam port area. The CO2 will then be pressurised in a compressor station.

The CO2 will be transported through an offshore pipeline to a platform in the North Sea, approximately 20 km off the coast. From this platform, the CO2 will be pumped in an empty gas field. The empty gas fields are situated in a sealed reservoir of porous sandstone, more than 3 km beneath the North Sea.

Porthos will store around 37 Mton CO2, approximately 2.5 Mton CO2 per year for 15 years.

Storage

The collected CO2 is stored in the pores of the sandstone substratum, which used to contain natural gas. For millions of years, this gas was hermetically trapped under high pressure between a nonpermeable layer of caprock and sealing plane faults. The local pressure in this field, which gradually decreased during gas extraction, will once again rise as a result of CO2 injection. The reservoir will be consistently monitored and checked to ensure that local pressure never exceeds the values recorded when gas extraction first started.

The CO2 from the pipeline will be injected into the depleted gas field under P18-A via a well. This well is a metal casing that is anchored to the rock all the way down to the reservoir in the substratum. To make the existing facility suited for CO2 injection, the well will be fitted with a new inner tube. The wells will also have monitoring equipment that is used to check the local pressure and temperature during CO2 injection. Once CO2 injection has been completed – when the reservoir is full and at the correct ultimate pressure – the wells will be sealed with plugs.

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