Improved efficiencies and experience may help to ease the cost of decommissioning Australia’s ageing offshore oil and gas infrastructure, a new report suggests.
The Department of Industry, Science, and Resources recently commissioned consultancy, Xodus Group, to explore the nation's overall decommissioning liabilities.
The report — Australian Offshore Oil & Gas Decommissioning Liability Estimate 2025 — estimates the industry will spend A$43.6bn through to 2070, rising to A$66.8bn when factoring in inflation.
This includes all fixed and floating facilities, rigid and flexible lines, subsea infrastructure and wells.
It added that around 55% of the decommissioning spend will occur before 2040, with 61% of the liability focused on Western Australia, 23% in Victoria and 16% off the Northern Territory.
The decommissioning of wells represents the single largest portion of the decommissioning liability, with an estimated cost of A$17.9bn, the report added, followed closely by pipeline decommissioning, with an estimated liability of A$17.85bn.
The report noted that decommissioning practice and technology have already improved since 2020, a trend that could continue, yielding benefits along the way.
There is an opportunity for further improvements in efficiency, it added, through operator cooperation when decommissioning, in addition to further technological advances and industry investment in onshore disposal and recycling.
“Possible cost reductions primarily relate to the opportunity for efficiencies, technological development and future infrastructure investments,” it stated.
These include:
Single and multiple operator campaigns to distribute the costs of equipment and vessels across multiple assets.
A dedicated disposal yard for deconstruction and cleaning.
Domestic steel recycling to reduce the amount of steel which is exported for recycling.
Aligning decommissioning campaigns with offshore wind construction to reduce vessel mobilisation rates.
Implementing new technologies and/or engineering practices to ensure that the most appropriate and efficient methodology, vessels, and equipment are used to perform decommissioning activities. Here, it cites the example of changes in the commonly accepted removal methodologies for certain infrastructure types.For example, reverse s-lay was previously considered the only methodology for recovery of pipelines — however, cut and lift now remains the most accepted method for pipeline removal.
Other findings in the report highlight the sheer magnitude of the task now facing contractors and operators across the board, with at least 2.7 million tonnes of infrastructure set to be removed, including a large portion of steel, with huge potential for local recycling.
