Woodside Energy, an Australian petroleum exploration and production company, has safely and successfully lifted the 83 m-long Nganhurra Riser Turret Mooring (RTM) onto a barge off the North West Cape in Western Australia.
Following the successful lift, the RTM is now transitioning to the Australian Marine Complex (AMC) near Perth. Upon arrival, it will be cleaned and deconstructed for recycling and reuse – more than 95% of the RTM is expected to be eligible for this.
In a world-first, the heavy lift vessel Heerema Aegir, with three supporting tugs, lifted the 2,500 tonne RTM onto a 120 m barge where it was secured ahead of its journey to the AMC. Woodside has presented the removal as a demonstration of its abilities to manage activities in the sensitive marine environments where it operates.
The Nganhurra RTM brought subsea production lines from the Enfield oil field to a floating production storage and offloading facility. Enfield ceased production in November 2018 and the RTM is being removed as part of decommissioning activities at the field, which also includes the permanent plugging and abandonment of 18 former production wells.
The decommissioning concept for the Nganhurra RTM was matured over more than two years of careful planning and detailed engineering, undertaken in conjunction with a range of specialist contractors.
In-field preparatory activities included remote operated vehicle inspections, removal of redundant equipment and installation of a purpose-built lifting point.
Following an assessment of the forecast weather and sea-state, the remaining mooring lines were cut, and the RTM was towed to a sheltered location to ensure the lifting operation could be executed safely. After the RTM is unloaded at AMC, it will be cleaned of marine growth and deconstructed for recycling and reuse opportunities, supporting local employment and contracting opportunities.