Comparison of Riser Fatigue Methodologies Based on Measured Motion Data

摘要

In-situ riser structural monitoring has been used by a number of operators and drilling contractors tornsupport drilling operations. The measurements have been used to understand the level of accuracy presentrnin the up-front fatigue analysis and to confirm the integrity of the drilling systems, especially duringrnextreme environmental events. However, the field data analysis requires detailed understanding of drillingrnriser modeling, loading conditions, operations, sensor characteristics and signal processing. Severalrnmethods have been developed to calculate stresses and fatigue damages in the riser using measured motionrndata. Careful selection of the analysis approach will determine the system configuration and validity ofrnthe measured results.rnMode shape matching has been widely used for the data analysis where riser response is dominated byrnVortex Induced Vibration (VIV). Another riser fatigue method has been recently developed and is basedrnon analytical transfer functions used to convert measured accelerations into curvature. Another methodrnconsiders FEA-based transfer functions. Some of these methods perform fatigue calculations in timerndomain while some others in frequency domain.rnEach method exhibits benefits and limitations depending on the characteristics of the measured riserrnresponse. Selecting the most appropriate fatigue methodology depends on the riser response and instrumentationrnsystem design.rnIn this paper, three fundamentally different riser fatigue methods utilizing measured motion data arerndescribed and compared with each other. The advantages and disadvantages of each approach arernevaluated and recommendations are provided for when each method should be considered.