Coiled Tubing Working Life Prediction

ABSTRACT Failure of coiled tubing, due to the repeated bending and plastic deformation of coiled tubing on and off the reel and gooseneck, is of great concern in coiled tubing operations. This paper discusses the coiled tubing working life based on one of the coiled tubing life models published in the literature, and compares the results with other models. Certain agreements are found among these models. A group of curves is presented to illustrate the coiled tubing working life affected by coiled tubing size and wall thickness, internal pressure, yield strength, reel diameter, gooseneck radius, operation condition (corrosion) and butt- welded connection (stress concentration). The results show that coiled tubing life can be greatly increased by increasing CT wall thickness and CT strength, while the coiled tubing working life decreases under high internal pressure, corrosion, and butt-weld conditions. These curves can be easily used in estimating coiled tubing life for the field use.