Fatigue Life Evaluation of Subsea Wellhead Connector Based on Finite Element Method

Drilling and work over operations offshore impose fatigue loads on the connector of sub sea wellhead stack due to the riser dynamics. In particular, the connector between them may be subjected to fatigue damage. The fatigue evaluation methodology of sub sea wellhead connectors requires a holistic analysis of the wellhead stack. In this paper, an evaluation methodology including finite element (FE) models, boundary conditions (BC) and stress transfer functions (STFs) for the analysis of wellhead assemblies and their interactions is described. Meanwhile linear and nonlinear models are used for calculating the stress level and STFs. The convergence of model and main results are discussed and analyzed to determine the hotspot. As the fatigue life is based on the local stresses and fatigue resistance is defined by S-N curves, the fatigue life of critical hotspot is evaluated based on the results of FE-analysis.