Australia’s offshore energy regulator is assessing Woodside’s updated cessation environment plan (EP) for the Nganhurra operations offshore Western Australia after the company submitted a revised plan for the floating production, storage and off take (FPSO) facility in December 2019.
Following further stakeholder consultation, Woodside elected to withdraw its initial EP and submit a revision to the National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA).
Located in the Enfield field within production licence area WA-28-L, the company addressed alternatives for removal of the riser turret mooring (RTM) from the field for onshore disposal in its updated EP.
The revised EP provides a more comprehensive evaluation of the impacts and risks associated with repurposing the RTM into an integrated artificial reef (IAR), as well as further consideration of the practicability of onshore disposal.
The activities that form the scope of the revised EP plan include the implementation of an inspection regime during preservation period until all wells are abandoned and subsea infrastructure is decommissioned.
It also includes the inspection, monitoring, maintenance and repair (IMMR) activities to ensure integrity of subsea infrastructure.
Woodside outlined that it would undertake IMMR of the RTM while it remains on station, disconnect mooring lines from RTM and lay on seabed, remove RTM from the title area, tow the RTM to the proposed integrated artificial reef (IAR) site, and augment the RTM by installing addition purpose-built reef modules to complete the IAR.
The RTM removal would be completed between December 2020 and the end of April 2021, with it estimated to take 30 days.
In addition, well intervention activities may commence from 2021, and is estimated to take about 10-20 days per well.
However, Woodside has noted that if undertaken as a campaign, the cumulative duration is expected to be 18 months (including mobilisation and demobilisation) and may be performed over multiple campaigns.
“For the purpose of this EP, two operational areas have been defined to allow impacts and risks to be evaluated separately for activities conducted within WA-28-L and activities associated with towing, installation on the seabed, stabilisation and modification of the RTM on the seabed, and placement of reef modules to form an IAR,” Woodside outlined in its EP.
“The activities of towing the RTM outside of WA-28-L and installing it on the seabed as an IAR have been included as part of the petroleum activity program on the basis that these constitute impacts and risks associated with the petroleum activity.”
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