The British would like Norwegian gas. Therefore, gas will soon be exported from the Ormen Lange field via the Langeled sub-sea pipeline. The pipeline will be connected with Statoil’s Sleipner R- platform located between Norway and the UK, and between Sleipner and the UK. Measuring 1,200 km it is the longest sub-sea pipeline in the world.

Platform modifications and new riser pipes

The exporting of gas to the UK poses new demands on the operations of Sleipner; the platform requires modification and new facilities for gas handling purposes, for instance, Sleipner is to connect the gas network of the Norwegian base with the Langeled pipeline from the Ormen Lange field.

Moreover, two new riser pipes are to be designed and installed between the pipeline on the sea bed and the platform. The riser pipes will carry the gas to and from the platform.

Assisted full-service supplier with the project

Vetco Aibel AS, who has been contracted to perform both the platform modifications and the design of riser pipes, contacted FORCE Technology Norway AS for assistance.

To do this job we composed a team of highly experienced engineers specialised in corrosion and supporting constructions. The team was to present the riser pipe design solution and conduct a reanalysis of the platform. The imminent exporting of gas poses new demands on the platform and the re-analysis is thus to verify the platform modifications.

Riser pipes are exposed to significant strain in daily operations, for example, the strong, internal pressure generated by the gas inside the pipelines and the impact of waves and current. FORCE Technology designed the solution on behalf of Vecto Aibel with riser routing along one of the platform legs. We emphasised a pipeline design with few joints, which provides for simple and easy offshore mounting of pipes, and as such is an economic solution.

The re-analysis of the platform was another key element of the project.
The modification of the deck and its facilities involved an expansion of the deck, thus making it heavier, and which altered the strain on the platform too.

By integrating the work with the reanalysis and design development of the platform, FORCE Technology and Vetco Aibel were able to optimise the solution and cut back as much as possible on the necessary modification of the existing platform structures. The final solution ensures the platform integrity relative to future operations while minimising the amount of work that has to be done offshore.

Generally, our design and platform analysis enabled Vetco Aibel to optimise the construction, and it ensured that the platform and riser pipes will take the impact of weight, waves, current, etc. into account in every respect, and it provides for safer and more reliable operations in many years to come.

Solving a task for the offshore industry

The task we performed for Vecto Aibel is an illustrative example of how we advise offshore industry companies on platform modifications and assist in solving associated challenges. Moreover, when it comes to platform integrity management, we are in demand as a collaboration partner.