The world’s largest semi-submersible crane vessel Sleipnir has installed the Tolmount platform in the Southern North Sea. The project consisted of installing the 2350-metric-tonne jacket and 2500-metric-tonne topsides constructed by Rosetti Marino.

Sleipnir travelled to the Tolmount Field located 40 km off the coast of Hull, UK, with a water depth of around 51 metres on October 7. Installation began on October 12 when the jacket was safely lifted from the Heerema barge H-408. After finalising jacket and pile installation, Sleipnir lifted and installed the 2500-metric-tonne topsides on October 13, which took 5 hours, to complete the Tolmount Platform project.

NUI Tolmount Platform

The Tolmount jacket and topside arrived at the Tolmount field following a 5390-km journey from Rosetti’s yard in Ravenna, Italy. The Tolmount Platform will be a Normally Unattended Installation (NUI), located in the vicinity of the 42/28d-13 appraisal well and will handle wet gas production from four platform wells.

The Premier Oil operated Tolmount field development is on track to deliver first gas in the second quarter of 2021 and will be an important energy supplier for the UK.

Rosetti Marino managed the construction and installation of the low-carbon design jacket and topsides on behalf of client Premier Oil. The project involved more than 1,100,000 manhours, was executed LTI free, and was completed over a duration of 26 months.

‘The close collaboration with Rosetti Marino has been a highlight of the Tolmount project. Despite challenges introduced by the ongoing pandemic, we worked together to find creative solutions, which were handled with total professionalism and high regard for safety,’ says Michel Hendriks, Heerema Transport and Installation Director.


Sleipnir has a wide range of sustainability measures, including dual-fuel functionality allowing the vessel to run on LNG, a cleaner fuel than standard MGO. During the Tolmount installation, the vessel ran on LNG. Heerema plans to go carbon neutral in 2020.

Despite summer coming to a close, Heerema’s Sleipnir continues to be busy in the North Sea. Before the Tolmount installation, the Sleipnir completed its second project in the wind sector this season. The work included the transportation and installation of two jackets for client Ørsted for the Hornsea 2 wind farm, which is located approximately 89 km off the Yorkshire coast in the North Sea.