The offshore industry has been very successful at reducing occupational safety incidents with a dramatic improvement in lost time and recordable incidents statistics. However, major accidents have proven much more resistant to reduction. The methods that have delivered the occupational safety improvements have not worked as well for major accidents. Risk assessment is a powerful approach, but to date it has been more successful at design stage to ensure facilities have suitable layout and separations, provide safe refuges, and protect escape and evacuation against a range of possible hazard events.

The author describes in this paper an integrated approach that addresses risks effectively during operations stage with the intent of providing practical risk management tools for offshore drilling, production operations, and support activities. This is built around the now well-known bow tie methodology, but it extends the model in several important directions.


The O&G industry reports occupational accidents in a standard manner and presents these in company annual financial or sustainability reports. This data has been compiled by the author and is plotted over the period 1994–2012. Some companies report Lost Time Injuries others report Total Recordables. These trend in similar manners, but Total Recordables are greater by a factor between 2–3. The graph, shown in Figure 1, has both types of data included, so it should only be used to demonstrate the trends.

Major accidents are more difficult to trend as specific process safety metrics have only recently been agreed in the industry (e.g. API 754, OGP 456 recommended practices). These are not yet publicly reported and the timeframe when they are will be very short. Instead it is possible to use insurance statistics - these are not perfect as they do not show uninsured losses (e.g. Macondo). However, data from Marsh (2011) is available and has been trended in 5 year averages over the period 1972–2011. This appears in Figure 2. The peak in this figure is due to Piper Alpha. There is no obvious downwards trend. A similar result is obtained for the US process industry as assessed by Wharton Business School for the EPA RMP-Star offsite impacts accident dataset (Kleindorfer et al, 2007).

While this lack of improvement was not expected by industry or the regulators, it appears to be a clear trend. It seems that an approach relying heavily on safety management systems and emergency response is less effective for major accidents, whether this is wrapped in a safety case (e.g. EU Seveso Directive) or not (e.g. USA OSHA PSM or EPA RMP). There is diversity in global offshore regulations and the approach adopted in the North Sea appears to be delivering significant improvements in major accidents. At a qualitative level there were 2 total loss events over 8 years (Alexander Kielland in 1980 and Piper Alpha in 1988) and none in the subsequent 25 year period with focused major accident regulations. On a quantitative level the UK maintains loss of containment statistics for 3 hole sizes - where major is the only one with the potential for total loss. Results for the period 1996–2012 are shown in Figure 3. Major leaks had declined by close to an order of magnitude between 1996 (20/yr) to 2011 (2/yr) but unfortunately bumped up to closer to 6 in 2012. Other leaks (Minor and Significant) showed a clear downwards trend. Results in Norway are broadly similar.

A key question then is what is different about the North Sea regulatory environment for major accidents compared to the USA and elsewhere? DNV believes this is due to a focus on Barriers. In the UK, risk assessment is used to identify Safety Critical Elements (SCE), and for each of these specific Performance Standards (PS) define the required functionality and reliability to deliver the desired risk target. Further, Written Schemes define the set of maintenance, inspection, training and competence programs needed to keep the SCE at their PS specifications for the entire facility lifecycle. This goes well beyond the requirements of Safety Management Systems and Emergency Plans. SCE / barriers are the specific means to prevent a major accident from occurring or mitigate its consequence should an accident sequence commence.

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