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SBM Offshore: FPSO riser receptacle cleaning in Guyana

Marine growth on the FPSO Liza Unity’s riser receptacles prompted operator SBM Offshore to engage OceanTech. The cleaning was successfully completed in just one day.

The Dutch Floating Production Storage and Offloading (FPSO) operator SBM Offshore boasts a global fleet of 16 units, spanning West Africa, Southeast Asia, Brazil, and Guyana. In Guyana, SBM Offshore's FPSO Liza Unity is positioned in the Liza field, approximately 200 kilometres offshore in the Stabroek block. The recoverable oil resources in the block are estimated to be significant, making it one of the most promising offshore developments in the region.

The Liza Unity vessel arrived in Guyana in October 2021 following construction in shipyards in China and Singapore. Moored in a water depth of about 1,650 metres, the FPSO can store around two million barrels of crude oil. Prior to a riser installation project, significant marine growth was identified within the riser receptacles. Consequently, SBM Offshore sought cleaning and inspection assistance from OceanTech.

A clean receptacle surface facilitates the smooth, efficient installation of risers and reduces the risk of complications during the installation operation. In this project, OceanTech was tasked with crafting a bespoke attachment design, customising equipment and tools, and cleaning and inspecting the receptacles in preparation for the riser installations.

Navigating the challenges

Addressing the task of cleaning riser receptacles in Guyanese waters involves navigating several challenges. Despite the region’s calm waters, cleaning operations may face disruptions from high winds and heavy rains during the wet season. The receptacles are also located in underwater or splash zone areas, making access challenging. Limited visibility due to water conditions can impede the effectiveness of cleaning operations, requiring specialised equipment and techniques.

Like many coastal regions, Guyana imposes stringent environmental regulations to safeguard its marine ecosystem. Cleaning activities must adhere to these regulations to minimise the impact on underwater habitats, marine life, and water quality. Site access also poses logistical challenges, requiring careful planning for transporting personnel, equipment, and supplies. 

Liza Unity’s 4-day production and offloading cycle heightened the intricacy of this project. In contrast to conventional operations, the production and offloading cycle on FPSOs unfolds as a seamless, uninterrupted process. This posed a unique challenge for our personnel, who needed to navigate the demanding splash zone environment. They also grappled with dynamic factors like the fluctuating waterline and the vessel's vertical movement. This demanded meticulous planning, coordination, and adaptability offshore.

Successful project completion in one day

At OceanTech, we use cutting-edge, remotely operated robotic solutions to elevate efficiency, safety, and environmental conservation. Our specialist splash zone equipment and cleaning tools are ideal for tasks beyond the capabilities of remotely operated underwater vehicles (ROVs) or divers.

The success of implementation hinges on robust design, thorough engineering, and testing. In this particular endeavour, OceanTech dedicated significant time to designing an attachment solution that leveraged existing towing points. This design facilitated the controlled lowering of our equipment to the splash zone. The project's remote location and considerable distance from our headquarters in Trondheim, Norway, required strategic planning. We opted for a nimble and versatile team of five staff capable of performing multiple roles offshore.

Our toolkit included a specially adapted vertical access tool (VAT), flexi-clean brushes, and high-pressure water jetting. One of our pilots operated these tools remotely from a compact tent positioned topside. Emphasising the importance of lightweight solutions, we made strategic adjustments and customisations. When operating in the North Sea, we typically transport a container. However, logistical constraints and the convenience of Liza Unity’s onboard personnel led us to tailor our equipment for maximum portability. We condensed our entire set of tools and equipment into a single suitcase.

The operation was successfully accomplished within a single day offshore, enabling SBM Offshore to continue production without disruption at Liza Unity. Much of this efficiency is attributed to planning and testing conducted onshore at our Subsea Test Center.

The Subsea Test Center plays a pivotal role in mitigating risks for our clients. For intricate projects, we refrain from offshore operations until the equipment undergoes thorough testing and the team receives training on the operation in seawater, using full-scale mock-ups of the offshore structures.