Recent Improvements in Subsea Wellhead Fatigue Monitoring Algorithm and Accuracy Using Verification and Calibration Techniques

摘要

Current subsea wellhead fatigue monitoring systems typically measure subsea BOP stack response andrnconvert accelerations directly to the stress on various critical wellhead components using transfer functions.rnThe veracity of this process relies on the accuracy of input data and the numerical modelling of thernriser, subsea stack and wellhead conductor system. Poor representation of a real system could potentiallyrnyield an inaccurate calculation of transfer functions and consequently, imprecise estimation of the stressrnlevels and predicted fatigue damage. The transfer function is strongly influenced by subsea stack systemrnstiffness, which depends on dynamic soil response, stack hydrodynamic added mass and drag, locationrnof the subsea stack fixity point, and stack-conductor system characteristic frequency. The latter two canrnbe measured in the field and compared with predictions from numerical models. This paper evaluates thernsubsea wellhead fatigue monitoring algorithm and accuracy using verification and calibration techniquesrnwith field measurements. Important considerations for verification and calibration (e.g. soil property) arernalso discussed.