Computational simulation reveals material uncertainties reduce coiled tubing fatigue life from 39 to 14 operating cycles, highlighting the need for stochastic structural safety assessments.
The increasing demand for safer and more cost-effective offshore drilling has encouraged the adoption of coiled tubing (CT) systems. Their structural design requires low-cycle fatigue (LCF) assessment because the associated deformations reach the plastic regime. However, uncertainties in material properties can significantly affect fatigue-life predictions, while geometric, material, and contact nonlinearities require computationally expensive finite element (FE) analyses. This paper presents a methodology combining a detailed FE model with uncertainty quantification to predict the LCF life of a critical CT section passing through the reel and gooseneck. The strain history is obtained from the FE model, and fatigue life is evaluated using the Ramberg–Osgood and Coffin–Manson models, under parameter uncertainties. Monte Carlo simulations combined with Bootstrap resampling provide stochastic LCF predictions. The results show that the nominal fatigue life of 39 operating cycles decreases to 14 cycles when uncertainties are considered.
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Corbani et al. (2026) studied this question.
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