Maritime Developments Limited (MDL) is reinventing offshore SURF decommissioning with its Wheeled Horizontal Lay System (WHLS)—an innovative, portable solution that overcomes deepwater recovery challenges by reducing friction and tension through wheel-based design, enabling safer, more efficient and sustainable operations.
ALEXANDER WILSON, MDL Flexlay Solutions
In the evolving landscape of offshore energy, decommissioning of aging infrastructure presents both a challenge and an opportunity. As more offshore fields approach the end of their productive life, the volume of infrastructure requiring removal or repurposing is growing rapidly.
This escalation heightens the importance of finding decommissioning solutions that are not only efficient and cost-effective, but also environmentally responsible—minimising ecological impact, reducing carbon emissions and aligning with broader sustainability and net-zero goals. Maritime Developments Limited (MDL) has risen to this occasion with its innovative Wheeled Horizontal Lay System (WHLS), a game-changer in subsea decommissioning operations that enhances efficiency, reduces operational costs and minimises environmental impact.
CRACKING THE CAPSTAN CODE: INNOVATION IN ACTION
In the world of offshore flex-lay recovery, portable solutions are widespread—until you add water depth into the equation. As recovery operations move into deeper environments, the list of viable equipment options shrinks rapidly. The limiting factor? The capstan effect, Fig. 1.
The capstan effect describes the exponential increase in tension that occurs as a product is pulled over a curved surface—such as a chute—due to friction. A key issue in such operations is the friction between the chute and the product, which can significantly limit recovery capacity and increase the risk of product damage. In deepwater environments, the submerged weight of the product further compounds this effect, often pushing the limits of the pulling equipment on deck before the product even reaches the surface.
This challenge became particularly evident during a project with Brazilian operator Ocyan, who initially planned to use MDL’s Horizontal Lay System (HLS) to recover flexible risers. However, early analysis revealed that the capstan effect, intensified by deepwater conditions, would create tension levels beyond safe operating limits. MDL responded by engineering a breakthrough solution.
The Wheeled Horizontal Lay System (WHLS) was developed to directly address this issue. By replacing the sliding friction of a chute with the rolling contact of a rotating wheel, the WHLS drastically reduces resistance and minimises tension build-up. This allowed the operation to proceed safely and efficiently—and established a new benchmark for subsea recovery.
The system’s modular design also means it can be deployed on vessels of opportunity, offering operators a more flexible, cost-effective and environmentally responsible alternative to traditional methods—especially in deepwater and late-life field scenarios, Figs. 2 and 3.
TECHNICAL FEATURES AND BENEFITS OF THE MDL WHLS
The system employs a wheel mechanism that establishes a two-point contact with the product, reducing minimum bend radius requirements and minimising the risk of damage. Unlike traditional chute-based methods, which can cause wear and tear, the WHLS enables a controlled, frictionless recovery process. This is particularly crucial for retrieving valuable components that may be repurposed or recycled, supporting a more sustainable decommissioning approach, Fig. 4.
The adjustable wheel is designed to accommodate a wide range of product diameters, ensuring proper alignment with the firing line of the product. This flexibility ensures the system can adapt to different sizes while maintaining the required precision for optimal performance. The tensioner, which is the core of the WHLS, delivers the pulling or deployment power. The wheel system helps optimise the tensioner’s full line-pull capacity by reducing friction, enabling it to perform at its maximum potential. With MDL’s unique range of tensioners, the system can be hand-picked for the scope and basin, achieving capacities of up to 162 tonnes. This tailored solution maximises efficiency and ensures reliable operation in a variety of environments.
To further improve operational efficiency, the WHLS incorporates a retractable hang-off beam that extends over the work platform; aided by overhead davits, the system facilitates safe removal of end terminations or mid-line connections and buoyancy modules during product retrieval. A low-tension roller directs the product into the low-tension side of the tensioner for optimal alignment. Additionally, horizontal and vertical rollers can be adjusted to align the product with the tensioner’s centreline, ensuring greater control and efficiency.
The integrated Hydraulic Power Unit (HPU) further reduces the overall footprint of the system while minimising the need for hose and cable lines on deck, enhancing operational safety and optimising mobilisation. With a compact and portable design, the WHLS allows for rapid deployment, making it an optimal solution for various decommissioning projects. The system can be transported in modules by road to the destination port, where it is assembled off the critical path on the quayside. Once assembled, it is installed aboard the vessel in a single lift, followed by a second lift for the tensioner. This streamlined process optimises project schedules while significantly reducing mobilisation and demobilisation times, Fig. 5.
Additionally, the WHLS system is highly versatile, making it ideal not only for decommissioning but also for the installation of flexibles. This adaptability makes it a smart solution for contractors looking to diversify their operations, offering increased operational flexibility and reducing the need for additional equipment for different project types.
SHAPING THE FUTURE OF OFFSHORE ASSET RETIREMENT
By integrating a wheel into the HLS design, the WHLS effectively addresses longstanding friction-related challenges in product recovery. This innovation not only increases recovery capacity but also offers a safer, more adaptable, and cost-effective solution for offshore decommissioning projects. Drawing on the capstan effect, the system enhances control during recovery operations without the need for excessive force or costly support vessels. Its portability, ease of installation and operational flexibility make the WHLS an ideal choice for handling products safely and efficiently, while minimising the risk of damage and eliminating reliance on expensive construction vessels.
Beyond its technical capabilities, MDL’s WHLS represents a broader shift towards more sustainable and economically viable decommissioning solutions. By facilitating the use of existing vessels and reducing dependency on specialised fleets, the WHLS contributes to a more responsible approach to offshore asset retirement. As the energy sector continues to navigate the complexities of decommissioning, MDL's WHLS stands out as a beacon of ingenuity and progress, setting a new benchmark for efficiency and sustainability in offshore operations.
ABOUT MARITIME DEVELOPMENTS
Established in 1999, Maritime Developments (MDL) provides tailored back-deck consultancy, equipment and personnel packages for the global energy sectors from its bases in the UK, France, USA and Brazil.
MDL provides front-end customer support for project specification; full suite of SURF handling back-deck equipment for sale or hire; and expert personnel support, alongside its Asset Maintenance & Engineering services providing design, engineering, manufacture and equipment support. It is also the only company in the pipelay rental market to supply DNV/Lloyd’s design-verified equipment.
The company operates health, safety, environmental and quality management systems that have been certified to the internationally recognised standards, ISO 45001, ISO 14001 and ISO 9001. WO
ALEXANDER WILSON is the head of Sales for MDL’s Flexlay Solutions. With over a decade overseeing various stages of MDL operations, his vast experience spans drafting, project engineering, delivery management and technical sales. This in-depth understanding of offshore operations and expertise on MDL technology, coupled with technical background and unique problem-solving perspective, enables project teams looking to maximise their operations’ success across the complete field lifecycle.