UWA Oceans Institute

Multi-disciplinary research - the key to decommissioning challenges

Sea squirt 


Aging offshore oil and gas infrastructure has drawn attention to the need for options for decommissioning once it reaches the end of its life. In the US and EU, where the oil and gas industry was established early, government and industry have already had to explore this issue including scientific, engineering, economic and regulatory concerns. In Australia, many structures have now been in service for several decades and their removal or re-use is beginning to be explored.

The majority of existing infrastructure contracts, as well as legislative frameworks, favour complete removal of offshore infrastructure as the preferred decommissioning option. It is clear however that there are alternatives including in situ decommissioning whereby part of the subsea structure is left in place. Furthermore, marine science has demonstrated that in many cases artificial reefs have already formed on and around this infrastructure, providing ecosystem services which would be lost if complete removal of pipelines and structures was required. Research from other countries indicates that there may be enhanced benefits from in situ decommissioning and conversion into artificial reefs to provide habitat for marine life or sites for recreational diving. The US for example has adopted a rigs-to-reefs policy to allow for this; whereas in the EU artificial reefs can only be created from new materials rather than decommissioned infrastructure.

From a legal perspective, international law permits in situ disposal for a new use but Australia has yet to engage directly with the legal issues which not only include the circumstances in which in situ decommissioning could and should be permitted, but also the transfer of risk and liability for damage.

From an engineering perspective, the design criteria for in situ decommissioning are less stringent than for the in service life. For in situ decommissioning, it should be shown that the structure is sufficiently stable on the seabed and that there will not be dispersal of the structure that creates either unwanted environmental impacts or a hazard to shipping. In contrast, during the in service operational life, the design criteria are more stringent regarding allowable movements or deformations. These criteria are set by the need for smooth operation of equipment and prevention of damage to containment systems that would lead to hydrocarbon release.

Complete removal certainly poses challenges but is not a showstopper. Most facilities can be removed from the ocean and a solution to almost any challenge can be engineered given sufficient time and resources. The offshore industry has an established track record of developing technology for installation and operation of offshore facilities of extreme scale and in extreme environments, and it is now turning its efforts towards decommissioning – for example, the Pioneering Spirit, a specialised vessel constructed to lift steel platforms from the North Sea.

But just because we can – should we?

Oceans Institute members from the disciplines of both engineering and law have been working on multi-disciplinary publications on these issues. It is clear that further research is needed both in terms of engineering options and potential law reform to allow for in situ decommissioning as well as involvement of the marine sciences, economists and other social scientists including sociologists.

The Oceans Institute is well-placed to conduct this research with expertise across the full range of relevant disciplines.

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