The offshore oil and gas industry in Australia has a US $40.5 billion decommissioning liability for its infrastructure. The base case for decommissioning is complete removal of all infrastructure unless there are net environmental benefits from alternative decommissioning options compared to complete removal. Additionally, all impacts and risks need to be of an acceptable level and the approach needs to be consistent with all relevant national legislation.
While the environmental benefits of leaving some infrastructure in situ are well established, regulatory acceptance of in-situ decommissioning options are rare. This is in part because of unaddressed concerns around the long-term fate and consequence of contaminants present in infrastructure. Such contaminants can include naturally occurring radioactive materials and mercury accumulated in internal pipeline films and scales, metals in exotic steel and anode components, and a diverse range of plastic coatings.
A key complication in the ecological risk assessment of these contaminants is that their release may be commensurate with steel and plastic degradation rates, meaning that exposures may only occur long after the decommissioning approach has been determined. This presentation highlights the scope of the offshore oil and gas decommissioning challenge and the push for the development of a contaminants’ assessment framework to support regulators and titleholders. This is discussed as an opportunity to get the risk assessment right to ensure that decommissioning does not create an intergenerational contamination legacy.