Floating Wind & Deepwater Oil & Gas – Two Worlds Collide

Over the last few years, the energy trilemma has pivoted away from energy transition to energy security and affordability. As a result, offshore oil & gas exploration and production activity, including deepwater activity, has been relatively healthy. Construction, operational support and decommissioning activity has supported the deployment of large anchor handlers and MSVs.

At the same time, the global floating offshore wind forecast has “moved to the right” due to cancelled projects, disappointing auctions, cost increases and political headwinds. Within the offshore wind sector, floating wind remains an emerging technology. The 2035 commissioned floating wind capacity forecast is ~5GW, rising to ~14GW by 2040.

Despite this less positive floating wind forecast than previously presented, floating wind projects will drive demand (and shortages) for the largest AHTSs and MSVs.

Depending on oil & gas demand for large AHTSs, shortages could appear by 2029-2031 and shortages in large MSV supply could emerge as early as 2030-2031. These are the finding of a new floating wind vessel forecast by Intelatus global partners.

The Variability of Floating Wind Projects

A commercial scale floating wind farm will be made up of a group of turbines supported by floating structures, moored to the seabed by a station keeping system, with generated electricity passed along dynamic array cables, often to a bottom-fixed offshore substation. On the face of it, this sounds simple. It is not – there are many challenges to address, including:

• What turbine to use: The western OEMs are currently favoring 15MW turbines for bottom-fixed projects, although Siemens is likely to release a 20MW+ turbine in the next decade (again for bottom-fixed projects). Chinese OEMs are pushing the boundaries with 16-25MW turbines, some of which are designed specifically for floating wind. Turbine size will drive the size of array cable to be used, which we anticipate being predominantly installed by large MSVs.

• What structure to deploy: There are over 100 floater concepts, loosely grouped as semi-subs, barges, spars and TLPs. All four concepts have been demonstrated with semi-submersibles being the most popular. Structures can be built from steel (plate structures suited to shipyards or tubular structures suited to bottom-fixed wind monopile factories) or concrete. Large waterfront sites, such as those used to build large offshore oil & gas structures, are needed to construct or assemble these huge structures. Deepwater quays and ultra large cranes are required for mating the turbine to the floating structure and wet storage is needed to marshal assembled turbines featuring 220-300m diameter rotors. Facility size and throughput is an issue, with floating offshore wind installation campaigns calling for 20-30 floaters delivered per year.

• What permanent mooring system to deploy: Water depth and soil type are the first factors to consider. A large concentration of operational and planned floating wind farms is in ≤140m of water, although the future U.S. Pacific and western Mediterranean sites are expected to see much deeper water.

  Conventional catenary, buoyant semi-taut and taut mooring systems featuring combinations of chain and fiber rope are forecast to be deployed at scale in floating wind, and to a lesser extent some single point mooring systems.

  Assuming a three-point mooring system, redundancy calculations generally offer three choices: (1) a 3 x 1 mooring line featuring large diameter chains and fiber ropes, generally bigger than those seen on oil & gas projects, which constrain the number of vessels that can technically lay these mooring lines; (2) a 3 x 2 mooring line, featuring smaller diameter chain and rope than the 3 x 1 scenario, opening up the number of vessels that can lay the mooring line; and a 3 x 3 mooring line featuring even smaller diameter chain and rope and making more vessels technically capable of laying the mooring line. The anchor handlers required to lay these moorings are also those involved in deepwater oil& gas projects.

  Another engineering decision is whether to anchor each mooring line with an individual anchor or share/mutualize anchors, as has been demonstrated at the Hywind Tampen project in Norway, currently the world largest floating wind array.

  Anchor choice is another variable, with the focus to date on suction anchors installed by MSVs or AHTSs equipped with large subsea cranes and drag embedment anchors installed by anchor handlers.

Floating wind projects will rely on vessels built predominantly for oil & gas projects.

As noted above, floating wind projects will rely on large AHTSs and MSVs to pre-lay moorings, tow & hook-up the floating turbines and lay array cables.

The large MSV segment is relatively simple to group in terms of AHC crane size and back deck. To meet the offshore construction schedules of commercial floating projects, Vessels with large back decks, of 2,000 square meters and more, equipped with AHC cranes with capacities of 400 tonnes or more will be required to ensure offshore productivity.

Large AHTSs are more complicated. Not only are high bollard pull vessels required (those with 300 tonnes and more bollard pull) but vessels with large back decks, large chain lockers, large capacity fiber rope winches and high-capacity chain handling equipment. The latter point is often under-looked, but many of today’s anchor handlers are equipped with chain haulers, gypsies, etc. that can handle 76-165mm chain seen in most oil & gas projects, but not the 175-220mm chain anticipated for many floating wind projects.

In addition to large MSVs and AHTSs, floating wind projects will also require smaller support MSVs and AHTSs, where supply is greater.

Is Anyone Building?

Whereas there is new building in the 250t AHC crane MSV segment, there are no 400t AHC conventional MSVs under construction. The same goes for large AHTS. Without a specific long-term charter to back an investment, the economics required to build such vessels are generally missing. Without investment, as floating wind demand grows, vessel supply will become tighter, which will push rates up.

However, there are some moves to build new large anchor handlers.

In Brazil’s deep waters, the world’s largest floating production system market, Petrobras was considering long-term chartering two new build 140m 300t bollard pull mooring pre-lay vessels with larger capabilities than its current 120t torpedo anchors connected by 120mm chain and fiber rope systems. There was talk that the vessels were being specified with both oil & gas and floating projects in mind. The original specification called for vessels capable of carrying 8x160t torpedo anchors (1,500sqm deck) with 150t AHC crane and ≥2,500cbm chain lockers. After industry feedback, the design has now been revised to 4x120t torpedo anchors (840sqm back deck), 4 chain lockers that can store ≥142mm chain, and a 20t crane. The revised specification is suited to oil & gas projects but sub-optimal for commercial scale floating wind projects.

In an interesting move, South Korea’s Hana Shipping recently announced that it is building the world’s first purpose built floating wind installation vessel at China’s Jiangsu Dajin Heavy Industry Co., Ltd. The 127m vessel features a Kongsberg deck machinery package, including a 500t towing/anchor handling winch with three drums and chain handling equipment for 220mm chain, and a MacGregor 400t AHC crane. The vessel will be delivered in 2028 and is intended to be deployed for mooring and cable laying for floating wind projects offshore Ulsan in South Korea.

It is to be seen whether more owners will follow Hana’s example. However, without new vessel investment (and the conditions to support an investment), suitable large AHTS and MSV supply will become an increasingly rare commodity.