Tennet awards Heerema and Allseas offshore converter transport and installation contracts

Transmission system operator Tennet has signed multi-year framework agreements with Heerema Marine Contractors and Allseas for the transport and installation of multiple 2GW offshore platforms.

Heerema’s Sleipnir semi-submersible crane vessel will be deployed for the 2GW programme (pic credit: Heerema)

The contracts include 14 confirmed 2GW converter stations to be installed in the Dutch and German parts of the North Sea, with potential for expansion under the terms of the agreements.

The framework agreements cover at least 28 timeslots up to 2031 – 14 slots for the transport and installation of a jacket and 14 slots for the transport and installation of a topside.

Tennet awarded Dutch firm Heerema about 60% of the available slots, with the remainder going to Allseas, which is headquartered in Switzerland.

Heerema will deploy the Sleipnir semi-submersible crane vessel (SSCV), as well as an owned floatover barge. Allseas will use its single-lift installation vessel Pioneering Spirit for the installation of the jackets and topsides.

The vessels have been used several times in recent years to install jackets and topsides for Tennet in the Dutch and German North Sea.

“With this agreement, we secure global marine transport and the heaviest offshore installation capacity in the market for our HVDC partners while expanding transport capacity in the market,” said Tim Meyerjürgens,Tennet’s chief operating officer.

The awarded slots are not linked to specific 2GW projects, Tennet said. Rather, the HVDC suppliers building the jackets and topsides for Tennet (Hitachi Energy/Petrofac, GE/Sembcorp, GE/McDermott and Siemens/Dragados) can choose from the suppliers, whereby Heerema and Allseas can install both jackets and topsides.

Boskalis will act as a subcontractor to Allseas, building one or two new transport vessels specifically for the 2GW programme. These “will meet the most stringent future legislation standards on sustainability and emissions”, Tennet said.