Investigation of the Effect of Local Buckling and VIV Fatigue on Failure Probability of Subsea Pipelines in Iranian South Pars Gas Field

Abstract

Free-span occurs normally in a pipeline at uneven seabed, dynamic seabed and pipeline crossing. Free spanning in pipeline causes Vortex Induced Vibration (VIV) fatigue, fracture and bursting. In this paper, a pipeline located in South Pars Gas Field is assessed against local buckling and VIV fatigue using probability of failure theory based on the recommended methodology by Det Norske Veritas (DNV) corresponding to different soil classes and different span length to pipeline diameter and also different water depths by applying First-Order Reliability Method (FORM) and Monte-Carlo Sampling (MCS), separately. Furthermore, the simultaneous effect of local buckling and VIV fatigue is assessed in terms of probability of failure. Finally, in order to determine the effect of each parameter on failure probability, sensitivity analysis is carried out using the alpha index.