Quantitative collision risk assessment of a fixed-type offshore platform with an offshore supply vessel

Abstract

Offshore installations are designed to withstand against potential collisions from offshore supply vessels (OSV). Quantitative risk assessment (QRA) provides an overall picture of expected collision frequencies and consequences for the design life of a platform and subsequently estimates the damage repair cost. However, the main challenge of the QRA study is how well various uncertainties are implemented into the model. This study aimed to introduce and demonstrate an advanced and efficient QRA model for the collision between an OSV and a jacket type offshore platform. A set of fifty collision scenarios were selected using probabilistic sampling techniques, and vessel motion analyses were performed to determine collision load characteristics. Extensive nonlinear structural crashworthiness analyses were conducted using advanced computational modelling techniques, and the repair cost of the damaged brace and column members were calculated. Probability exceedance diagrams were established for different consequence parameters, and asset risks were calculated. A comparison study of the design values of damage parameters and repair costs were carried out in association with the NORSOK and HSE risk acceptance criteria. A sensitivity study was carried out to study the effects of various collision load parameters on the structural consequences. The methods and insights developed in this study could be applied to both new and existing offshore platforms and practically useful for the platform owners to aid in their decision-making process towards the risk-based safety analysis of offshore platforms.