ExxonMobil Secures Approval for First Phase of Bass Strait Decommissioning

ExxonMobil, through its Esso-operated venture, has received approval from Australia's National Offshore Petroleum Safety & Environmental Management Authority (Nopsema) for the first stage of decommissioning its Bass Strait assets offshore Victoria. This initial campaign covers the removal of topsides from up to 13 offshore platforms, removal of upper jacket sections from up to 10 steel-piled jackets, and full removal to the seabed of two monotowers, totaling approximately 60,000 tonnes of steel. Activities are scheduled to begin in the third quarter of 2026 and conclude in the first quarter of 2028.

Execution and Recycling Plans

The removal work will be carried out by Allseas' heavy lift vessel Pioneering Spirit, supported by construction support vessels, with operations expected to last about five months starting in Q3 2026. Esso aims to maximize recycling, targeting 95% or more of the mostly steel material to be recycled or reused, and is currently engaging with the Australian Steel Institute. The company emphasizes that decommissioning is a complex, multi-year task to be completed in stages.

Future Decommissioning Stages

The approved environment plan (EP) outlines subsequent phases: concept selection for removing lower jacket sections in 2028-2029, preparation of a new EP for that removal in 2029-2030, contract awards and engineering in 2030, with EP acceptance expected in 2031 and activities commencing in 2032. A separate EP for decommissioning pipelines, umbilicals, and subsea infrastructure is planned for submission between 2026 and 2028.

Asset Context and Operator Transition

The Bass Strait assets include 425 wells, 19 platforms, six subsea facilities, and over 800 km of pipelines, covering developments like West Barracouta, Kipper Compression, Kipper 1b, and Turrum Phase 3. Esso operates the Gippsland basin joint venture with Woodside Energy (50% interest) and the Kipper unit joint venture with Woodside (32.5%) and Mitsui (35%). Woodside is set to take over operatorship of the Bass Strait assets in the second half of this year, subject to regulatory approvals.

Related Well Decommissioning by Woodside

As part of an asset swap with Chevron, Woodside is decommissioning five Julimar Brunello exploration wells. Nopsema approved Woodside's EP to plug and abandon three subsea exploration wells (Julimar East-1, Brunello-1 ST1, Brulimar-1) and remediate the Balnaves Deep-1 well using a mobile offshore drilling unit (MODU). Woodside confirmed the MODU will be the semi-submersible rig Transocean Endurance, with anchor pre-lay starting around May 8 for about 10 days, and well intervention and plugging and abandonment activities commencing around May 13 for approximately 50 days.