August 21, 2025 [Pipeline Technology Journal]- The Porthos CO2 transport and storage project has reached a critical milestone with the completion of laying and entrenching of an approximately 20-kilometer-long offshore pipeline at the bottom of the North Sea, Port of Rotterdam announced on August 14, 2025.
Expected to transport CO2 captured from the industries at the Rotterdam port to designated storage reservoirs under the North Sea, the project is part of the Netherlands’ broader strategies to meet its Net Zero emission goals by 2050.
The 20-kilometer pipeline stretches across the bottom of the North Sea, connecting the compressor station on the Maasvlakte to the platform P18-a located above the depleted gas field, where the captured CO2 will be stored safely and permanently at a depth of more than 3 kilometres below the seafloor.
Allseas completed the pipelaying work on the Dutch CO2 transportation and storage pipeline late last month, bringing the project closer to completion. During the pipelaying, the pipes were first welded together on a pipe-laying ship before being lowered to the seafloor.
After the pipeline was completely laid, it was then sunk in trenches that had already been prepared along the entire route. A layer of Sand was then added to provide cover for extra stability and protection.
Designed to store up to 37 million tonnes (Mton) of CO2 upon becoming operational, equivalent to 2.5 million tonnes annually for 15 years, the construction of the infrastructure began in early 2024 following the completion of the final investment decision in 2023.
According to the project’s details, the pipeline is expected to be operational in 2026, with the transportation of captured CO2 taking place in three phases. The first phase involves the “free-flow” of the CO2 into the reservoirs enabled by the initial low pressure of the depleted gas fields.
The second phase, known as the “gas-phase injection,” involves using compressors up to 75 barg. In the final phase, the system switches to “dense-phase injection,” which involves the use of colder CO2 and pressures rising to 135 barg.
