Esso’s Bass Strait platforms decommissioning proposal goes public

Esso Australia has made public its initial proposal for the decommissioning of 10 steel piled platform jackets in Bass Strait. Work is expected to begin in 2027.

The initial environmental plan (EP) is being facilitated by the National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) after Esso voluntarily sought public comment for the project plans.

The EP relates only to steel piled platforms, an operation Esso has designated Campaign #1. EPs for pipelines, umbilicals, and concrete gravity platforms will be submitted separately.

Activities cover proposed decommissioning end states for platform jackets at Halibut A, Fortescue A, Cobia A, Mackerel A, Kingfish A, Kingfish B, West Kingfish, Flounder A, Bream A, and Whiting.

The plan proposed for Halibut, Fortescue, Cobia, Mackerel, Kingfish A & B, West Kingfish and Flounder is to cut the steel jackets above the sea floor ensuring there will be a minimum of 55 m clearance below mean sea level.

For Whiting and Bream, the plan is to cut the jackets as close to the seabed as practicable without large scale dredging.

The EP said there are two options still under consideration for disposal of the removed upper sections of the steel jackets. They may be transported to an onshore reception center for dismantling and onshore recycling/disposal, or selected sections can be arranged adjacent to the lower sections of the jackets remaining in place entirely within the title area.

The latter disposal option refers to Halibut, Cobia, Mackerel, the two Kingfish jackets, West Kingfish, and Flounder.

Execution activities to achieve these end states will be the subject of another EP, which is planned for submission in 2025.

Campaign #1 decommissioning also includes the Perch and Dolphin monotowers where the plan is to fully remove the structures. These operations do not form part of the scope of the current EP.

Esso has completed about $600 million (Aus.) of decommissioning works in Bass Strait, including removal of the Seahorse and Tarwhine infrastructure, completion of well plug and abandonment activities at Blackback and Whiting, and progressing similar plug and abandonments on Kingfish B and Mackerel. Another $150 million (Aus.) has been committed to further the plug and abandonment work.

Earlier this year the company entered a multi-year agreement with DOF Subsea to charter a multi-purpose supply vessel to support early decommissioning work on Perch and Dolphin infrastructure before moving on to other topside and subsea work scopes.

In June Esso called for technical submissions from heavy lift contractors for platform removal activities.

The EP relating to the 10 steel platforms opened for public comment Aug. 1 and will close Aug. 31.

Esso will review the EP in the light of any submissions received and submit a revised EP to NOPSEMA.