Analysts have predicted that North Sea decommissioning costs over the next 40 years could exceed £47.5 billion (US $75.3 billion), and it is estimated that around 150 assets will be decommissioned in the Gulf of Mexico in the next five years.

Decommissioning is one of the most complex phases in the asset lifecycle, and managing the safety of employees and operational risk poses a number of major issues for operators and project support partners.

In some cases, installations that have been producing for 30 years have had the same core workforce on it since hookup and commissioning. It is important to realize that for these individuals in particular, decommissioning is not “business as usual.”

A multidisciplined Stork Technical Services employee uses rope access to carry out air gouging on a leg of the NW Hutton platform during a North Sea decommissioning project. (Image courtesy of Stork Technical Services)

Changing risks

A platform’s risk profile changes when production has ceased and the installation moves into the engineering down, and cleaning, and module process and utility separation phases. The move from production to active reduction in the hydrocarbon inventory changes the working practices, and other specialist service providers – such as waste handling specialists and heavy lift contractors – become involved in the project.

An important difference from “steady state” producing operations to the decommissioning process is that the physical operating environment is constantly changing, which introduces the opportunity for injury. For example, eye injuries from debris and dust can increase as people access areas that have not been entered for a number of years. Dropped objects like detached cable trays, also pose a serious risk because corrosion can increase as the heat supply drops with cessation of production.

With separation, lifting, and removal taking place in various areas across the installation, safety escape routes might not be as available as they were during the operational phase. In fact, it is not uncommon for them to change on a daily basis. Work also will be carried out in modules that have been partly decommissioned, and efforts could be required to ensure safe operations.

Introducing new people, processes, equipment, and changes to the installation’s operating philosophy means everyone has an even greater role in ensuring that safety remains the primary focus and the highest HSEQ standards are maintained during decommissioning.

The introduction of many new personnel who are unfamiliar with the installation often can be perceived as a potential risk by the existing platform team. But personnel new to the installation can offer a different perspective and see potential hazards that were not immediately obvious to the incumbent platform team. Feedback from new personnel should be actively encouraged.

Given that decommissioning involves a wide range of complex and potentially hazardous work scopes, it is crucial for both contractors and operators to recognize the level of upfront inspection, engineering, and planning required before work takes place on site. For example, in-depth site surveys of cold cutting options, access methods, waste removal, and asbestos, as well as extensive nondestructive testing, are often carried out to give a clear picture of what activity the project could entail.

Clarifying work scopes, developing methodology and work practices, and quantifying the resources required will help ensure decommissioning is delivered in the safest, most efficient, and most cost-effective manner.

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