Decomissioning

The removal of the Brent Alpha topside by the Pioneering Spirit. (Photograph: Allseas)

DUTCH CONTRACTORS HEAVILY INVOLVED IN DECOMMISSIONING WORK

by Paul Schaap, PAS Publicaties

Once again in 2020, Dutch offshore contractors completed a whole series of complex and challenging decommissioning projects, primarily in Western European and Canadian waters. By deploying advanced vessels and innovative techniques, they have now acquired the leading position in this still relatively young market sector. Above all contractors Allseas, Heerema Marine Contractors and Boskalis have played a pioneering role. They will soon be joined by a new Dutch player in the person of OOS International based in Serooskerke in Zeeland.

Just like one year earlier, in 2020, Allseas attracted most attention in carrying out a whole raft of spectacular removal jobs with the single-lift installation/ decommissioning and pipelaying vessel Pioneering Spirit. Having successfully removed topsides from the British Brent field on behalf of Shell in 2017 and 2019 from that company’s Brent Delta and Brent Bravo platforms, weighing 24,200 and 25,000 tonnes respectively, in 2020 it was the turn of the Brent Alpha topside. This topside, weighing 16,000 tonnes, was removed from the sea by the Pioneering Spirit on 21 June, and transported to the Able Seaton Port. Another behemoth removed from the British sector of the North Sea by the same vessel was the 14,200-tonne Ninian Northern topside. This work was undertaken on behalf of CNR International. This particular topside was transported to the Dales Voe terminal operated by Veolia/Peterson on the Shetland Islands.

Allseas also deployed the Pioneering Spirit to remove a series of jackets and topsides from the Danish Tyra field. The largest structures removed by the Pioneering Spirit included the 14,000-tonne Tyra East Alpha topside and

“In Western European waters alone, there are still almost 500 platforms that will have to be removed from the sea, at some point.”

the 7,800-tonne Tyra West Alpha topside, both of which were to be transported to Frederikshaven in Denmark. A number of other structures from the Tyra field were delivered to the Sagro terminal in Flushing.

Among the projects still to be completed are the removal of the 34,000-tonne Brent Charly topside and three large jackets and topsides from the Norwegian Valhall and Hod fields. The total weight of these components is around 33,000 tonnes, and all will be removed by the Pioneering Spirit between 2021 and 2026, and transported to Stord in Norway. Another major challenge will be the removal of the 48,000-tonne Statfjord A topside from the Norwegian sector of the North Sea, on behalf of Equinor. Other projects on the books include work in the Norwegian Gyda field and the Danish Tyra field. Plans are in place, in the near future, to install an innovative lifting system on the stern part of the Pioneering Spirit, that will allow jackets weighing up to 20,000 tonnes to be removed from the sea.

Heerema Marine Contractors (HMC) have also already acquired considerable experience on the decommissioning market. In the period 2014-2018 they deployed their semi-submersible crane vessels Balder, Hermod and Thialf to remove nine platforms from the Greater Ekofisk Area in the Norwegian sector of the North Sea. In total, the work involved the removal of 120,000 tonnes of steel. 2020 once again saw HMC operating in this sea area, with its brand-new Sleipnir, the world’s largest semisubmersible crane vessel. During the month of May, the Sleipnir removed the almost fifty-year-old Ekofisk 2/4 A production platform, and transported it to the AF Decom yard in Vats, in Norway. This was in fact the Sleipnir’s very first decommissioning project ever. The client for this project was the ConocoPhillips oil company. On behalf of the same client, HMC plans to also remove the Ekofisk 2/4 H, 2/4 Q and 2/4 FPP platforms from the sea. After previously setting a lifting record for installation work in the Mediterranean Sea, the vessel went on to set an equivalent record in August, for the decommissioning market. This project involved the removal from the sea of the 10,100-tonne Brent Alpha jacket, which was subsequently delivered to the AF Decom yard in Vats. HMC reported that in the summer period, the Sleipnir went on to remove a total of 43,900 tonnes of steel structures from the sea. Also active this year in the same sector was the Thialf, that carried out the Sable decommissioning project. As part of this project, undertaken on behalf of ExxonMobil Canada, a total of seven platforms had to be removed from Canada’s eastern sea board, and transported by barges to the Able yard in Teesside. Elsewhere, HMC signed contracts with Fairfield Betula Limited for the removal of the Dunlin Alpha topside, weighing 20,000 tonnes, and with Marathon Oil for the removal of the topside and jacket from the Brae Bravo platform. In addition to its

The Sleipnir set a lifting record with the removal of the Brent Alpha jacket. (Photograph: HMC)

The Bokalift 1 with the jacket and topside of the L10-C platform on board, en route for Flushing. (Photograph: PAS Publicaties/maritimephoto.com)

large semi-submersible crane vessels, HMC also deployed the monohull crane vessel Aegir, for platform removal work, for example the removal in 2019 of Wintershall Noordzee’s Kotter- en Loggercomplex from the Dutch sector of the North Sea. This project involved a total of four platforms. In a period of just ten weeks, the Aegir removed 15,000 tonnes of jackets and topsides from the sea, and transported them to the Hoondert Services & Decommissioning yard in Flushing East.

Boskalis, another provider of maritime services, has built up a solid track record over the years, in the offshore platform dismantling market. In the past, this work was mainly carried out using floating sheerlegs but since 2019, the monohull crane vessel Bokalift 1 has also been involved in this specialist field of work. In 2020, for example, the Bokalift 1 removed a series of platforms from the Viking and Vulcan fields in the southern section of the British North Sea sector. This work was undertaken on behalf of ConocoPhillips. Also in 2020, Boskalis deployed the Bokalift 1 for decommissioning work in the Dutch sector of the North Sea, removing the topsides and jackets from the L10-C, L10-D and L10-G platforms from the sea after forty years of gas production on behalf of Neptune Energy, and delivering them to the Hoonert yard in Flushing East.

A new player soon to join the decommissioning market is OOS International. This Dutch offshore contractor has commissioned the construction in China of two advanced semi-submersible dual crane vessels, that are due to be handed over in the near future. The vessels in question are the OOS Serooskerke and the OOS Walcheren, both equipped with two Huisman offshore mast cranes, each with a lifting capacity of 2,200 tonnes. In tandem, these cranes are capable of lifting a maximum load of 4,400 tonnes. On board, the vessels offer accommodation for up to 750 people. Sea trials were completed by the OOS Serooskerke at the end of 2020 and the crane vessel is expected to arrive in the Netherlands imminently.

The decommissioning market is expected to expand steadily over the coming years. In Western European waters alone, there are still almost 500 platforms that will have to be removed from the sea, at some point.

The OOS Serooskerke and the OOS Walcheren under construction. (Photograph: OOS International)