Dedicated to decommissioning

Elaine Maslin

December 1, 2016

The offshore lifting market for decommissioning has been relatively small so far, but it won’t stay that way. Elaine Maslin looks at some new concepts edging into the market.

OOS’ Serooskerke. Image from OOS.

With more than 40 years of oil and gas production under its belt, the UK North Sea has reached the time in its life where some of its more than 400 facilities are being removed.

However, while a large chunk of the infrastructure in place is mature – many facilities are well beyond their design life – the topsides and jacket removals market is less so.

To date, topsides removal has used a piece-small approach, whereby modules are removed, piece by piece, largely due to what is available on the market.

The top end offshore heavy lifting market is served by just a few semisubmersible crane vessels owned by even fewer companies, namely Heerema Marine Contractors (HMC), with the Thialf (14,200-tonne lifting capacity) and Saipem, with the S7000 (up to 14,000-tonne).

A monumental change came earlier this year, with the introduction of Allseas’ Pioneering Spirit twin hull, mega lifting vessel to the market. The unit, which performed its first job lifting out the Yme mobile offshore production unit offshore Norway (OE: September 2016), brings an up to 48,000-tonne topsides lifting capacity and up to 25,000-tonne jacket lifting capacity to the market (OE: April 2016). HMC is also building the two, 10,000-tonne crane (20,000-tonne combined) capacity Sleipnir.

But, it’s not all about big lifts. Of the approximately 600 platforms in the Northwest Europe – including Norway, UK, Denmark, Netherlands, and Germany – about half have topsides weighing less than 1600-tonne, according to an Oil & Gas UK database. About 200 are under 1000-tonne, 375 under 3000-tonne and just over 400 are under 4000-tonne.

However, even for smaller lifts, there are a limited number of heavy lift vessels and for many years this has been the status quo, with the exception of the occasional float over installation for the larger structures.

“It’s very clear there isn’t the toolbox to do it whatever size you’re looking at,” says Lynne Nordby, senior manager specialized tonnage, Maersk Broker, at Decom Offshore, in Aberdeen earlier this year. “Even for the smaller piece meal, we are still looking at quite a reduced market of vessels. We haven’t got all the tools in the toolbox.” But, that could soon change. Existing and prospective vessel operators are taking note and there are an increasing number of concepts eager to join this market, for the small and mid-range lifts.


OOS’ Walcheren. Image from OOS.

Overdulve Offshore Services (OOS) is a relatively new entrant to the market. In August, the company ordered two new semisubmersible combined accommodation and crane (SSCV) vessels from Chinese shipyard China Merchants Heavy Industry (CMHI).

The OOS Serooskerke (named after a village in the Netherlands) and OOS Walcheren (a former Dutch island, now part of the mainland) will be capable of lifting and positioning with two 2200-tonne capacity cranes, with combined 4400-tonne capacity, using Huisman Equipment-supplied cranes. The cranes will be used for decommissioning subsea structures, foundations, moorings, floating and heavy lift platforms for offshore wind structures in deepwater.

The vessels will each provide beds for 750 people, and will be DP3 capable and able to perform subsea lifting in up to 3000m water depth, OOS says.

The engineering and construction phase is estimated to be completed in Q2 2019 for the first SSCV (OOS Serooskerke) and Q3 2019 for the second SSCV (OOS Walcheren)

And yet, moving into decommissioning wasn’t OOS’ initial intention. OOS, founded and led by Dutchman Leon Overdulve, bought two newbuild semisubmersible crane and accommodation vessels, which had been due to work off Angola for Sonangol, but had been left stranded by the failure of Marine Subsea & Consafe, a partnership. OOS has since secured an opportunity with Petrobras offshore Brazil, which the units were a good fit for.

The two units, OOS Gretha and OOS Prometheus, built at CIMC Raffles in 2012 and 2013, started work in 2014 as accommodation vessels, with OOS Gretha, which has two Huisman 1800-tonne cranes, as well as accommodation for 618 people, also doing regular heavy lift work. OOS Prometheus has 400 beds and a 1100-tonne crane.

While the cranes on OOS Gretha made the unit costlier to run, challenging its economics as an accommodation unit, running the OOS Prometheus alongside and supplementing the accommodation unit contracts with heavy lifting work proved profitable. This gave Overdulve the idea that they could also be profitable as heavy lifting vessels in a wider market, by increasing the crane and accommodation capacity, thus creating the OOS Serooskerke and OOS Walcheren.

“We can operate and manage a unit like OOS Gretha for US$170,000 a day. So, I thought, why are these heavy lift semis in the world so expensive? We looked into the decommissioning market. Only 5-10% (of topsides needing lifting out) are heavier than 10,000-tonne. We saw huge potential for medium-size heavy lifting. We re-engineered the OOS Gretha design to have larger cranes and more accommodation.”

After a couple of studies with oil majors, using the concept, the firm was told the Gretha would make the tender list. For one particular Gulf of Mexico spar decommissioning project, with its deepsea capacity, the Gretha would remove deepwater umbilicals and perform preparation works for topsides removals, as a flotel, before removing the topsides in five lifts. This would include a system to keep the five separate sections in their respective places during the lift program. This would all happen over six months, Overdulve says.

OOS, he says, will be able to perform these jobs on a turnkey basis. Indeed, it’s already found a partner, Modern American Recycling Services (MARS) in Louisiana, which has disposal yards based on scrapping for zero cost – MARS makes its cash back by turning the steel quickly into scrap steel to re-sell. Historically, MARS has disposed of barges and ships, but it entered the platform decommissioning market in 2010, opening a new yard in Gibson, about 76mi outside New Orleans. Last September, MARS also secured a lease on land in Denmark for a yard there. The new site, at Port of Frederikshavn, is due to start operations in 2017, and will cover 270,000sq m with 381m of water front.

Overdulve, who has worked offshore since he was 17 and has worked in Nigeria, the Middle East and Brazil, is eyeing a global market. “Right now, in Thailand, there are 80 small units to be removed, but especially in Asia, there are a lot of small units.” Because of the deep draft of the units (26m, due to not having retractable thrusters), very shallow waters will not be accessible (“there is always a piece of the market you cannot cover,” Overdulve says). Norway might also be too expensive. “But still, there’s 60-70% of the decommissioning market we could cover,” he says. “It is a big enough pie.”

Twin marine lifter

The Twin Marine Lifter concept. Image from SDTM.

Meanwhile, a single lift system, for which a newbuild contract was placed with China’s CIMC Raffles, as OE went to press, is being marketed by Shandong Twin Marine (SDTM). Some may recognize it as the SeaMetric concept, developed in the late-2000s. Norway-based SeaMetric had a Brent Delta topsides removal study with Shell and a long-term agreement with Fairfield Energy and started building its system in 2007, but various issues meant the project didn’t come to fruition. SeaMetric went into liquidation in 2010 and the company Twin Marine Heavylift took its place.

In the UK, The Decommissioning Co. (TDC) is marketing the Twin Marine Lifter (TML) technology, now owned by joint venture Shandong Twin Marine. TML is capable of installing and removing topsides weighing up to 34,000-tonne and 16,000-tonne jackets.

The system consists of three DP3 vessels, each 206m-long and 42m-wide. Two have skid mounted lifting arms centrally balanced on the vessels, facing to starboard on one and to port on the other, so they can maneuver each side of a platform and lift the topsides free together, placing it down on to an identical third vessel.

TML would be water depth independent and able to work in up to 3m significant wave height, verified through 1:40 scale model test done in the Marintek/SINTEF ocean laboratory in Trondheim, says Mark McAllister, a director of SDTM and TDC chairman, at Decom Offshore in Aberdeen. It would be able to remove almost all North Sea topside types in a single lift and any North Sea jacket in no more than two lifts, he says.

Prior to the execution of an operation, first the topsides (and jacket) is prepared for lifting by installation of lifting interface points and any required local strengthening, etc. Then, the two lifting vessels position in towards the jacket. On the inboard side of each vessel is a buoyancy tank on each lift arm. On the outboard side, there is a ballast tank on each lift arm. Seawater is dumped from the inboard buoyancy tanks to get the lifting arms into position. Then, water is pumped from the buoyancy tanks to counter balance (ballast) tanks until 95% of the weight of the topsides is taken by the vessels, SDTM says.

Each TML arm can take individual loads to make up the total weight of the lifted object and to suit the strength of the main structure of the lifted topside. When all is cleared for lift-off there’s a second stage of dumping seawater in less than 10 seconds that lifts off the topside from the jacket.

Jacket lifts are done using winches where the 1600-tonne hooks are running from the tip of each of the arms and connected through a diver-less operation to lifting points clamped to the jacket legs.

SDTM was incorporated in April 2016 and design enhancement initiated to reflect the latest rules and regulations. This work was completed in October 2016 and submitted to the yard (to be named soon) as part of the TML construction contract.

TDC was started in 2011, led by McAllister and Terry Kimber, both of whom worked at Fairfield Energy, the former as CEO, up until 2011. Their work looking at decommissioning ideas for Fairfield’s Dunlin platform led them to believe there would be better solutions to benefit the market, not just in terms of technology, but also commercially, through work with insurance companies. This led them to the TML system.

Platform installation and removal is offered by SDTM at a price fixed for several years in advance and underpinned by an insurance package developed with Munich Re and in cooperation with Aon. This means that the insurer is involved at every step of the project, from yard selection, detail and fabrication design phases, during construction, assembly, commissioning, load testing, sea trials and full scale offshore testing, SDTM says.

The result is a performance guarantee for the TML system, which underpins the price guarantee related to the contract. This helps remove some of the uncertainty around decommissioning costs, which is a burden to operators who may need to arrange decommissioning liability – funds that could be spent elsewhere.

During the Decom Offshore event, McAllister said the system will be available for the 2020 spring season.

The Nessie concept. Image from Seaways Engineering. 


Another concept, based on an established idea, is being offered by California’s Seaways Engineering International: the “novel extended semisubmersible” (Nessie). The Nessie is a box-section semisubmersible with six columns and a gate at the aft end. “It’s basically a floating dry dock, without the bottom,” says Joe Glass, managing director (UK), Seaways, with inherent stability, due to its deep draft and huge displacement.

Seaways has an outline design for two versions, one, measuring 220m by 120m, for jackets weighing up to 18,000-20,000-tonne, with a capability to carry up to 300,000-tonne in total. A smaller unit, measuring 60m x 60m, would be for smaller southern North Sea type platforms in the 3000-4000-tonne range.

The idea is that the vessel moves to within 100m of a structure to be removed, propelled by a DP system or moved using tugs. There it would stabilize and be anchored using a 12-point mooring system, if it didn’t have DP. Then, it ballasts down, to move under the platform to be removed – using laser positioning for accuracy – and its gate is opened to allow it to slot under the platform.

If it’s moored, winches on the mooring lines will be used for positioning, Glass says. Ballasting would either be via ballast pumps or compressed air, using an open tank methodology (water is allowed in through open holes in the hull and compressed air is pumped in to de-ballast). The gate is likely to be a latch gate, also operated using ballasting. Once under the platform, the Nessie slowly de-ballasts, to lift the pre-cut topsides off, resting on 40 strategically placed strand jacks.

Next, the Nessie is rigged up to the pre-prepared jacket (using remotely operated vehicles), also pre-cut, and de-ballasts further to lift it free. It is then swung around to horizontal, during which time it’s emptied of air to make it neutrally buoyant, where it is secured for transport. The rigging for each jacket removal would be designed for each jacket, due to the array of different designs out there, Glass says. They wouldn’t be looking to perform operations in above 1-1.5m wave height, he adds.

Glass says that the cost would be low compared to building other more complex units and it could also be built in more yards, using a simple flat plate design. Seaways estimates a unit could be built in 20 months. Seaway is at an early design phase with the Nessie, however.

Glass has a long history in the industry, working on dive support vessels as a chief engineer in the early 1980s, during which time he met Seaway’s CEO and owner Craig Lang. Lang also has a history with offshore heavy engineering, having designed a multipurpose semisubmersible (MPSS), back in the 1980s, and which was approved by Shell. Several versions of the MPSS are in operation worldwide, including the Shell/BP Na Kika host facility, BP’s Thunder Horse, BP’s Atlantis, Chevron’s Blind Faith, the Ichthys LNG project, Petrobras P51 and others. Lang’s inventions also include the Apache reel ship and steel risers in catenary.

He describes using hydraulic motion control as a “money pit.” “The deep draft [on the Nessie] works with the pontoons to dampen any movement. The deletion of crane booms further reduces risk and costs related to hoisting. Other semisubmersible crane vessels are built to support the crane and then the crane is built to support the load and that idea is expanded again and again. It is that kind of thinking we avoid.”

Video: The Nessie concept animated

Damen does decom

The Damen Decommissioning series. Image from Damen.

Dutch firm Damen Shipyards Group is also offering a decommissioning concept. It unveiled its offering, called the Damen Decommissioning Series, earlier this year.

It is a split stern monohull concept, which would be used for platform removal, and subsea cleaning and other removal work. The design is based on research carried out at Damen by one of its undergraduate interns. Justin Rietveld, studying Maritime Technology at the Rotterdam Mainport University of Applied Sciences, was assigned to investigate the potential niche markets for new vessel designs in the oil and gas decommissioning sector.

“This research started off with the idea of developing a decommissioning vessel based on Damen’s existing portfolio,” Rietveld says. “However, we soon found out that this market needs more.

“This ship will be able to reverse up to a jacket, where it will be ballasted to sink below the platform. Upon de-ballasting, the vessel will rise up to pick up the platform.”

The preliminary estimations of the vessel’s capabilities show that it will be able to perform decommissioning of fixed platforms of up to 1600-tonne in weight. The concept design includes modular add-ons, such as a crane, accommodation modules or helideck, which could be temporarily installed, so that the vessel could be used for other purposes. Adding a temporary platform to create a solid stern could also enable use of the increased deck space for transporting and installing monopiles and foundations for the offshore wind industry, Damen says.

SkyJack’s the limit

A SkyJack unit. Photo from SkyJack Marine. 

Dutch firm SkyJack Marine prepared another concept, a twin self-elevating semisubmersible platform, using two SkyJack 16000 units. The SkyJack was designed for bringing heavy structures, such as concrete tunnels, wind turbine foundations, etc., from the quay to the water and vice versa. But, the firm saw it could also be used for removing topsides.

The unit is based on a 70m-long, 40m-wide, monohull pontoon with four jacking systems, using a hydraulically controlled heavy duty pinning system, and four 55-80m tall, 3m-diameter spudlegs.

It would be limited to below a certain water depth, with maximum pile length below the barge at 28m. But, because it’s on legs, it is less limited by wave conditions for lifting operations. Maximum operational wave height is 2m, the firm says, with maximum wind speed at 14m/s.