ABSTRACT

Offshore decommissioning is a high-stakes undertaking. Australian law requires removal of all infrastructure from the field, unless in situ decommissioning environmental outcomes are ‘equal or better’ than full removal. So how do we measure ‘equality’ or ‘better-ness’ when it comes to decommissioning options? How do we compare a 6-month removal campaign to a degradation pathway that lasts 1000 years? How should this case be presented effectively, in the right terms? This paper introduces a methodology that incorporates all the right criteria; legislation and stakeholder views, the principles of ecologically sustainable development, the environmental impacts and risks of decommissioning, indirect consequences and control measures. This method can be used to compare two or more decommissioning options – usually the full removal case, and one or more in situ decommissioning options. An assessment against 11 criteria is performed for each decommissioning option, establishing its environmental impact profile independently against measures that are relevant to decommissioning. Comparison of these profiles between decommissioning options allows us to identify where the options provide ‘equal’ environmental outcomes, or when to identify one as ‘better’. This methodology has the advantage of using fit-for-purpose criteria that enable consideration of short-term and very-long-term effects, via the principles of ecologically sustainable development and other factors like indirect consequences. This approach also, importantly, addresses key requirements of the Environment Regulations and Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act).