Full-Scale Fatigue Testing With 130K Yield Tubing

Abstract Coiled tubing (CT) is widely used in the well-intervention business as a practical and cost-effective means of servicing wells. Since CT’s inception, the use of continuous steel tubular has been the primary means of conduit for the applications required. The performance of CT has vastly improved throughout the years because of advancements in the tubing material and manufacturing processes, as well as extrapolated models predicting low-cycle tubing fatigue life. Because of these developments, CT has expanded to meet the increased demands of deeper and more rigorous wells. Utilization of new higher- strength grades of tubing plays one of the most essential roles for performing in these critical well applications. This paper presents results from full-scale fatigue tests performed at several pressures on newly developed 130,000-psi (130K) minimum yield strength tubing. CT made with this new 130K material was cycled to failure in a real-world full-scale fatigue test setup. The collected fatigue-life values will help modify and validate the existing fatigue model used for CT job designs as well as lead to the development of a potential new model with further refinement for critical applications. This full-scale testing also verifies the correlation between tubing life observed in controlled, short-stroke lab-scale fatigue tests and real-world applications.