Reliability of Subsea Pipelines

The subsea industry is having to face increasingly more challenges to develop hydrocarbon reserves in the marginal and more in accessible fields around the world. These challenges include those associated with deep water, high pressure/ high temperature, aggressive environments and economic restrictions. All of these put increasing demand on the achievement and improvement of reliability at every stage of the system life cycle. The reliability depends strictly on the design rules and the associated parameters that have been used in system design. So the evaluation of reliability requires an understanding of design methodologies and what design parameters can cause and increase unreliability in a designed system. This study provides a comparison of DNV and API Design Methodologies for Subsea Pipelines and discusses the rules and parameters for designing subsea pipeline by each method. Reliability of both DNV and API designed subsea system is evaluated using corresponding Limit State Equations. The results that have been achieved are applied to a realistic model and suggestions are made for a more reliable method.