03 June 2024

LMR completes drilling under sea wall

German company LMR Drilling GmbH specialises in complex drilling projects including the installation of underground cables and pipelines. The HDD drilling under the sea wall was one such project where maximum accuracy and minimum surface disturbance was essential. The drilling was successful; LMR has now almost completed the work and the site is being prepared to lay the CO₂ sea pipeline next year. LMR Project Manager Jorn Stoelinga on the work: “In close consultation with all parties involved, we found an innovative solution to an unexpected situation.”

Preparing for drilling
Back in 2020, LMR tendered for Porthos’ European tender for the underground crossing of the seawall in preparation for the actual CO₂ pipeline. Finally, in September ’23, LMR was able to start preparations for the horizontal directional drilling: constructing the access road and carrying out the so-called UXO drilling. Stoelinga: “UXO drilling involves detecting potentially explosive remnants of war. As a precaution and for maximum safety, we carried out this detection drilling; now we know for sure that in a radius of one metre around the borehole no World War II explosives were left behind in the ground.”

Successful drilling
In March this year, the team started building the chain, welding the casing pipe and the actual drilling. “About five years ago, we drilled a similar well 100 metres away, on the First Maasvlakte. Remarkably, when the casing was struck at the Porthos site on the Second Maasvlakte, the ground was just different.”

Positioned under the North Sea floor
“The drilling under the hard seawall went well,” Stoelinga continues. “As did pushing the HDPE pipe into the casing pipe and retrieving the pipe from the bottom of the North Sea from the sea. There, we did encounter a difficulty: the ground was different from what had been calculated beforehand. As a result, the pipe at sea behaved differently than expected and was not flat enough under the seabed. In close consultation with Porthos experts and the other parties involved, we found a good solution for working from the ship and getting the casing pipe within the desired profile. Great to think out an innovative plan together and then implement it in practice. The pipe now has the desired position and depth location.”

Ready for the offshore connection
The casing pipe has been laid down under the seabed and will soon be covered with sand. It will then be ready, awaiting the withdrawal of the CO₂ sea pipeline, scheduled for early 2025. LMR has provisionally sealed the jacket pipe on land; the dead man’s bed, as the sheet pile walls are called that absorb the pushing and pulling forces of the drill, will be removed very soon. By coordinates, the pipe will soon be found. Stoelinga: “It was a great job for LMR. We have made the landfall and next year, as a subcontractor to Allseas, we can pick up where we have finished now.”

Also watch the video of the drilling under the seawall: