Fitness for Service of Subsea Pipelines

As offshore activities move to deeper scenarios, rigid pipelines and flexible pipes used to connect sea-floor wells to platforms are subjected to several failure mechanisms due to environmental and operational loads. Rigid deep-water pipelines are particularly susceptible to collapse due to the ambient external pressure, as it will be thoroughly discussed in this chapter. Rigid risers and moderate to shallow water pipelines are also prone to other failure mechanisms, such as fatigue and burst, respectively, but they will not be the focus of the chapter presented herein. On the other hand, flexible pipes are more complex structures comprising layers of metallic and polymeric materials, which can suffer from several failure mechanisms and modes. This chapter gives a general overview of methods to access the integrity against collapse of rigid pipelines with corrosion defects and dents. A brief description of an innovative method to assess the relative risk of flexible pipes in operation is also presented, considering possible defects observed during periodic inspections. All methods presented herein can be used to establish a risk-based inspection routine for those subsea assets.