Part 8 Activity Description Overview
Santos Ltd (Santos) is proposing to decommission the Mutineer, Exeter, Fletcher, Finucane field. The revision of the Mutineer Exeter Cessation of Production (CoP) Environment Plan, is to enable the continued operation of the Mutineer, Exeter, Fletcher and Finucane (MEFF) facilities in cessation phase and execute the removal of infrastructure from above the seabed. This revision now includes final seabed decommissioning activities on title, within WA-54-L, WA-26-L and WA-27-L to address sections s572 and s270 of the Offshore Petroleum and Greenhouse Gas Storage Act 2006 (OPGGS Act). The permit areas are within Commonwealth waters, approximately 160 km north of Dampier, in water depths ranging from 130 – 160m.
Cessation phase commenced when production ceased in 2018, flushing activities were completed and the FPSO departed the field. Removal of the Direct Turret Mooring (DTM) and Mid Water Arches (MWA’s), was completed in Q1 2023. Removal of the remaining subsea equipment is planned to be executed in 2025/2026 with completion planned by the end of 2026.
The reservoirs remain isolated from the subsea production system at the Xmas trees (XTs). All well valves will remain isolated unless they are required to be operated to allow decommissioning activities. Wells are being plugged and abandoned under a separate EP accepted by NOSPEMA in February 2024.
The petroleum activities covered in this EP includes the following activities and will address inspection, monitoring, maintenance and repair (IMMR) activities on subsea equipment in the title area until removed, or decommissioned under this EP:
• removal of subsea equipment normally located on the seabed during production;
• abandonment in situ of six deeply buried steel anchors and the corresponding buried steel mooring chains of approximately 580 m / ~100t per mooring leg.
Individual IMMR campaigns may take approximately 14 days. Decommissioning of the seabed assets may take up to 12 months cumulative duration. However, unfavourable weather and operational delays this could extend the estimated project durations.
All activities could be undertaken at any time of the year, continuous over a 24-hour period and are expected to be conducted over multiple and concurrent campaigns during these time frames.
The activities may be supported by one, or a combination of the following ‘vessels’:
• tugs including Anchor Handling Tugs (AHT);
• barges;
• crew transfer vessel;
• Heavy Lift Vessel (HLV); and
• Dive Support Vessel (DSV) and rescue vessel
Helicopters and support vessel may be used to transfer crew and equipment to and from vessels and assist in emergency as required.