Abstract
When offshore oil and gas infrastructure is no longer needed, it is either removed, partially removed, left in place, or left in place but repurposed. These processes are collectively referred to as decommissioning. Australian legislation requires oil and gas companies to develop acceptable plans for the safe removal of all offshore infrastructure at the end of a project’s life. Over the next 50 years, the liability for this decommissioning in Australia is expected to exceed US$45 billion. Unlike countries such as Norway, the United Kingdom and the Netherlands, Australian decommissioning activities are in their infancy, with only three cases (to date) in Commonwealth waters where infrastructure has been left in place or partially removed as part of decommissioning. Differences between the Australian marine environment and that of other regions around the world where decommissioning-related research is better progressed include very low sedimentation rates, both tropical and temperate habitats, different species composition, low primary production, and frequent tropical cyclones, as well as unique sociodemographic and cultural characteristics. Accordingly, the outcomes of the decision support tools used in other regions to identify preferred decommissioning options may not be equally applicable in Australia. Here we describe research to support risk and impact assessment for offshore decommissioning in Australia, where full removal of infrastructure is the “base case” regulatory default, but other options including partial removal and/or repurposing might provide similar or better outcomes when environmental, social, economic and seafood safety aspects are considered. Based on our review we propose an integrated framework for research needs to meet legislative requirements for decommissioning and identify research gaps that need to be addressed to inform decision-making for decommissioning in the Australian context.
Highlights
Decommissioning is the process of plugging and abandoning oil and gas wells removing or repurposing infrastructure at the end of its useful life
We suggest that decommissioning research activities in Australia should address three key elements and interdependencies—ecological considerations, contaminants and socioeconomics, in a manner that integrates decision support tools
Repurposing offshore oil and gas infrastructure in a “rigs to reefs” program in this region was successful because: (i) the operators’ stakeholder engagement and consultation process identified recreational fishing as a community value; (ii) surveys of contaminant levels showed that they were below thresholds of concern (Kennicutt et al, 1996a), and unlikely to be affecting benthic biodiversity (Montagna et al, 2002) or fisheries productivity (McDonald et al, 1996); and (iii) the platforms were known to provide habitat for Red Snapper, a commercially important species (Ajemian et al, 2015)
Summary
Decommissioning is the process of plugging and abandoning oil and gas wells removing or repurposing infrastructure at the end of its useful life. During the operational phase, discharging produced water (PW; see Box 1 for acronyms and definitions of terms used in this paper) containing high concentrations of organic carbon and nutrients such as ammonia affects the productivity of the surrounding ecosystem. Generalisations about the ecological value of decommissioned oil and gas infrastructure from other well studied regions may manifest differently in Australian waters because: (1) Australia’s large marine estate contains a large number of different temperate and tropical marine habitats at the continental scale (Figure 1); (2) species assemblages in Australia are distinct from northern hemisphere regions which have been the focus of decommissioning research to date (notably the Gulf of Mexico, California, the North Sea, and the Adriatic Sea; see section “Status of Decommissioning Research Internationally and in Australia”); (3) the low rate of sedimentation in the Australian marine environment (e.g., Blom and Alsop, 1988; Baker et al, 2008), a consequence of comparatively low primary production and low riverine discharge, may affect the persistence of environmental contaminants around offshore infrastructure; BOX 1 | Glossary and acronyms. (i) consider research needs for evaluating environmental risk and impacts for decommissioning options in Australia, relative to the unique aspects of its biodiversity, marine environment and sociodemographic and cultural characteristics (ii) develop a general framework that identifies the information needed to make environmentally sound decisions about decommissioning options (and that considers linkages between these aspects)
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