IMechE - Offshore Decommissioning: Getting structures out of the sea

One of the defining engineering achievements of the latter half of the twentieth century was the installation of offshore oil and gas structures in oceans around the world. Today, the industry faces the equally complex challenge of safely and efficiently removing these assets after decades of exposure to harsh marine environments. This presentation provides a high-level overview of the key challenges associated with offshore decommissioning and the solutions currently being applied.

The removal process broadly mirrors installation and is typically divided into two principal phases: topside removal and substructure removal. The presentation will outline the key preparation activities required for the removal of both the topside and the substructure, including isolation, cleaning, and structural assessments. It will also examine the main factors that influence the selection of an appropriate decommissioning strategy, such as platform age, structural condition and original design philosophy. The discussion will then review the range of removal methods available, together with the associated technologies and specialist vessels used to carry out decommissioning operations.

Through selected case studies, the webinar will illustrate the practical realities of decommissioning diverse types of offshore structures, including variations in end states and associated environmental considerations. It will also examine key global regulatory differences and how these influence decommissioning strategies and outcomes. With tens of billions of pounds expected to be spent on decommissioning in the UK over the coming decades, this session will explore the key cost drivers and how operators provision for these long‑term liabilities.

As the energy sector moves towards a more integrated landscape, the webinar will discuss the future of decommissioning, including how established practices from oil and gas decommissioning can be applied to inform best practice across other offshore energy technologies.