Woodside Energy Ltd (Woodside) operates the Enfield field within Production Licence Area WA-28-L. In 2018 the Nganhurra floating production, storage and offtake facility (FPSO) was utilised to flush, isolate and preserve the riser turret mooring (RTM) and the subsea infrastructure, before the FPSO was disconnected and removed from the Enfield field.

The Nganhurra Operations Cessation Environment Plan (EP) was revised and resubmitted on 8th November 2021 (Revision 8) to address the continued presence of the RTM on station to allow market engagement to occur to select a final removal concept. The inspection and preservation of the subsea systems and RTM will be ongoing until the RTM is removed from the title area, the wells are permanently plugged for abandonment, and final decommissioning of the field is completed.

The RTM will be recovered back to shore for disposal. The timing for the RTM removal is highly dependent on the prevailing metocean conditions, which can impact the accessibility of the RTM, and the ability to execute the work. Based on metocean conditions, potential weather windows for field execution are generally between December and April, and even during this period will be limited to days that meet vessel wave height criteria. On this basis, it is anticipated that execution will occur prior to the end of cyclone season 2022/23 with the RTM remaining on location until this time.

The RTM removal activities will be subject to a further EP revision, which will include consultation with relevant stakeholders, anticipated in 2022.

The activities that form the scope of this revised Environment Plan are as follows:
• Inspection Maintenance and Repair (IMR) activities on the RTM while it remains on station until removed from the title area.
• IMR activities on subsea wells and infrastructure within Permit Area WA-28-L, until the wells are permanently plugged for abandonment, and decommissioning of subsea infrastructure commences.

The following activities have been removed from this revision:
• Well intervention (this activity is covered under the Enfield Plug and Abandonment EP accepted by NOPSEMA on 14 October 2021).
• Disconnection of the mooring lines from the RTM and laying them on the seabed (accepted as part of Revision 2).
• Removing the RTM from the title area and repurposing into an Integrated Artificial Reef.

The Petroleum Activities Program within the Operational Area is in Commonwealth waters in the Exmouth Sub-basin. It is located approximately 38 km north of the North West Cape of Western Australia about 2 km to the east of the Enfield reservoir. The water depth across WA-28-L varies from 200 m in the east to over 2000 m to the west. Water depth is approximately 400 to 600 m within the Operational Area.