Willy Røed

On the use of the hybrid causal logic method in offshore risk analysis

In the Norwegian offshore oil and gas industry risk analyses have been used to provide decision support for more than 20 years. The focus has traditionally been on the planning phase, but during the last years a need for better risk analysis methods for the operational phase has been identified. Such methods should take human and organizational factors into consideration in a more explicit way than the traditional risk analysis methods do. Recently, a framework, called hybrid causal logic (HCL), has been developed based on traditional risk analysis tools combined with Bayesian belief networks (BBNs), using the aviation industry as a case. This paper reviews this framework and discusses its applicability for the offshore industry, and the relationship to existing research projects, such as the barrier and operational risk analysis project (BORA). The paper also addresses specific features of the framework and suggests a new approach for the probability assignment process. This approach simplifies the assignment process considerably without loosing the flexibility that is needed to properly reflect the phenomena being studied.

Bayesian approaches for detecting significant deterioration

Risk indicators can provide useful input to risk management processes and are given increased attention in the Norwegian petroleum industry. Examples include indicators expressing the proportion of test failures of safety and barrier systems. Such indicators give valuable information about the performance of the systems and provide a basis for trend evaluations. Early warning of a possible deterioration is essential due to the importance of the systems in focus, but what should be the basis for the warning criterion? This paper presents and discusses several Bayesian approaches for the establishment of a warning criterion to disclose significant deterioration. The Norwegian petroleum industry is the starting point for this paper, but the study is relevant for other application areas as well.

A practical approach for the evaluation of acceptable risk in road tunnels

In many European countries it is common to adopt quantitative criteria in evaluation of acceptable risk in road tunnels. Such criteria, usually expressed by FN-criteria and IR-values, will easily lead to a regime that is difficult to adopt in practice, as the use of such criteria requires extensive analyses and documentation for all types of tunnels. In this paper, a more practical approach for the evaluation of acceptable risk in road tunnels is presented, in which quantitative risk acceptance criteria are used for some road tunnels, while qualitative criteria are used for others. This means that varying degrees of effort and documentation are necessary for the evaluation of acceptable risk in road tunnels. The approach suggested is inspired by challenges in Norway.