Wintershall L5-C Platform Decommissioning – Dutch North Sea

Engineering support for safe and efficient offshore platform removal

TWD supported HEBO Maritiemservice B.V. in the decommissioning of the Wintershall L5-C offshore platform in the Dutch North Sea. The project involves the removal of both the topside and jacket structure, supporting HEBO’s execution strategy using its heavy lift vessel HEBO Lift 10.

As one of HEBO’s early offshore decommissioning projects, the L5-C removal represented an important opportunity for the company to demonstrate its capabilities in this specialized market. We provided the engineering required to support a safe, efficient, and practical removal operation. The topside has since been successfully removed, with the jacket removal planned as the next stage of the decommissioning campaign.

The engineering package included structural verification, lifting analyses, in-place stability assessments, weight reconciliation, centre of gravity evaluations, and soil load analyses. These studies formed the basis for the safe lift-off, transportation, and removal of the aging offshore structure while accounting for uncertainties related to structural condition, corrosion, marine growth, grout, soil interaction, and available as-built information.

To maximize installation feasibility while minimizing operationally costly structural reinforcements to both jacket and topside structures, we went beyond the limitations of conventional offshore engineering software. By integrating RFEM’s advanced structural analysis capabilities with OrcaFlex’s time-domain simulation of wind, wave, and current loading, we created a fully coupled analysis environment tailored to the project’s specific conditions, unlocking a level of insight that off-the-shelf software simply couldn’t reach.

The workflow also enabled rapid assessment of environmental conditions and weather windows, allowing operational limits to be evaluated far more efficiently than through conventional manual modelling approaches. Because multiple jacket removals are anticipated within the wider Wintershall decommissioning programme, the solution provides a scalable and reusable engineering approach for future projects.

We also received positive feedback that we truly value. Our client highlighted the availability of our engineering team and the quick support provided throughout the offshore operation. In a decommissioning project, things do not always go according to plan, and we are proud to have helped the project team respond to challenges as they arose with practical engineering support.

Project scope

• Development of the Basis of Design and load case determination
• Weight reconciliation and centre of gravity assessments
• Global structural verification of the topside and jacket
• In-place stability and integrity analyses under environmental loading
• Structural assessment and verification of lifting interfaces and padeyes
• Soil load analyses, including pile pull-out and mud-mat effects
• Preparation of engineering reports, calculations, 3D models, and detailed drawings
• Technical support and liaison with Marine Warranty Surveyors (MWS)