Deep Water Riser System Design and Management

Abstract

Abstract The risk of a fatigue failure of a critical weld in a marine riser employed in deep water, harsh environment operations is judged to be high. This paper describes how the dynamic excitation caused by vortex shedding can be quantified and used to predict fatigue accumulation while drilling. Estimation of the initial riser fatigue state is of considerable importance, for this good record keeping by the rig owner is required. The paper concludes that wells can be drilled in harsh environments without the use of vortex suppression devices so long as fatigue accumulation is monitored. Drilling contractors play a key role in maintaining accurate records of riser fatigue history and managing an appropriate inspection programme. The fatigue accumulation predictions are only as good as the models used in the analysis, which at this stage must be treated with some care. P. 25