Heerema Marine Contractors' Thialf crane vessel; Source: DNO

Heerema’s giant vessel removes North Sea platform

Norwegian oil and gas company DNO has wrapped up the last major offshore operation under its multi-year decommissioning programme in the North Sea, thanks to the completion of another activity related to a platform removal campaign for a field off the UK. This was carried out by Heerema Marine Contractors’ second-largest semi-submersible crane vessel (SSCV), Thialf.

Heerema Marine Contractors' Thialf crane vessel; Source: DNO

Back in 2019, DNO assumed operatorship and working interest in the Schooner and Ketch fields in the UK and the Oselvar subsea field in Norway, three end-of-life fields whose decommissioning had been deferred by the previous operator. To this end, DNO handed out a decommissioning contract for up to twenty-one wells on the Schooner and Ketch fields on the UK Continental Shelf (UKCS ) to Well-Safe Solutions in June 2019.

Furthermore, DNO completed the plugging and abandonment (P&A) of the nine Ketch wells and the three Oselvar wells in 2021, followed by the 12 Schooner wells in 2022. The Norwegian player picked Heerema Marine Contractors in January 2022 for the integrated engineering, preparation, removal, and disposal (EPRD) of the Ketch and Schooner platforms.

Both platforms were installed by Heerema in the 1990s and were tied back to the Murdoch complex, which was also expected to be removed by the company. The Ketch and Schooner fields are located in the Southern Basin of the UKCS in license block 44/28a and license block 44/26a, respectively. The Murdoch installation acted as both fields’ Installation Control Centre (ICC).

The Schooner and Ketch fields, located in the UK Southern North Sea, ceased production in August 2018, with 20 platform wells and a single subsea well. Moreover, the Ketch and Oselvar production facilities were removed and dismantled last year and it is expected that about 95 per cent of the removed materials will be recycled.

In an update on Monday, 5 June 2023, DNO revealed that the wellhead platform production facilities were removed from the Schooner field offshore UK. According to the company, the heavy lift was conducted using Heerema Marine Contractors’ Thialf semi-submersible crane vessel.

While the 1,200-tonne platform deck was lifted aboard the vessel on 17 May, the jacket was removed on 23 May after the piles had been cut three metres below the seabed. Based on DNO’s statement, the deck and jacket have since been transported to the Hoondert Yard in the Netherlands for dismantlement and recycling.

Chris Spencer, DNO’s Chief Operating Officer, commented: “We have conducted these operations in a safe, cost-efficient and environmentally responsible manner, coordinating five tier-one contractors and displaying our capabilities as a full life-cycle offshore operator.”  

Heerema carried out multiple decommissioning jobs last year. One of these was completed in August 2022 by its Thialf vessel, which removed the Kinsale Alpha topside in the Celtic Sea. This came after the Dutch contractor’s Sleipnir vessel completed the removal and disposal of the Dunlin Alpha topsides in June 2022.