Australian energy giant Woodside Energy has removed the decommissioned Nganhurra riser turret mooring (RTM) from Australian water, which is now in transit to the shore for recycling and reuse.
The Nganhurra RTM has been lifted onto a barge approximately 38 kilometers north of the North West Cape in Western Australia and is transiting to the Australian Marine Complex (AMC) near Perth where it will be cleaned and deconstructed in preparation for recycling and reuse.
In a world-first, Heerema Marine Contractors ‘ heavy lift vessel Heerema Aegir, with three supporting tugs, lifted the 2,500-tonne RTM onto a 120-meter barge where it was secured ahead of its journey to the AMC.
After the RTM is unloaded at AMC, it will be cleaned of marine growth and deconstructed for recycling and reuse opportunities. More than 95% of the structure will be recycled or reused.
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The Nganhurra RTM is about 83 meters long and brought subsea production lines from the Enfield oil field to a floating production storage and offloading (FPSO) 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.
Woodside said it had explored a number of concepts for decommissioning the RTM before selecting the current concept, which has been matured through more than two years of planning and detailed engineering, undertaken in conjunction with a range of specialist contractors.
In-field preparatory activities included remotely operated vehicle (ROV) 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.