Fatigue analysis of off-shore wellheads during drilling operations carried out from semi-submersible units

During drilling operations carried out from floating units, fatigue damage may occur in various locations and particularly in the wellhead, which includes several fatigue hotspots. Different methods are available to assess accumulated fatigue damage at the wellhead. The method recommended by guidelines is the Full Predictive Approach, based on Finite Elements tools to simulate the behaviour of the system under the action of the external sea loads. The latter are modelled on historical data available for the drilling site. A variation of the method is represented by the Semi-predictive Approach which differs because the weather conditions are directly measured with buoys or radars during the drilling operations. In the Measured Response Approach, finally, the actual stress-strain response of the system is directly measured by sensors. The three methods are discussed in more details and a case study is provided with reference to real data collected on the field