State-of-the-Art Portable Measurement and Defect Detection Technology for Coiled Tubing String

Abstract

AbstractMost coiled tubing (CT) string failures in the field can be traced back to some initial defects, such as mechanical damage, a corrosion pit, a manufacturing defect, etc. Because of the ductility of CT, the introduction of these initial defects doesn’t normally cause failure at the onset. However, over the course of the service life, these initial defects evolve or grow until they reach a critical stage, leading to eventual failure. To assess the serviceability of a CT string, the industry has largely relied on periodic pipe inspection using magnetic flux leakage (MFL). Since MFL signals arise from a complex combination of defect geometry, defect severity, and material anomaly, etc. in the pipe wall, they are very difficult to interpret. A "snapshot" inspection of the string may not provide adequate information to fully evaluate its integrity and/or future serviceability.To improve assessment of CT string serviceability, a new approach has been developed. The "continuous" inspection approach involves MFL monitoring of the CT string during utilization. With the continuous MFL monitoring from "new" pipe state through its entire service life, the MFL signal directly attributed to defects can be isolated and tracked, leading to an improved evaluation of the CT string’s condition and future serviceability. In conjunction with the theoretical fatigue life tracking, a new pipe Degradation Parameter is used to improve the management of aging coiled tubing.The state-of-the-art portable measurement and defect detection technology for CT strings uses MFL to detect the existence of defects and to measure wall thickness. It uses eddy current technology to measure the outside diameter (OD) of the pipe. MFL measurements are used to evaluate the defects over successive operations. Wall thickness and OD measurements are used in a real-time software to update the CT working envelope and the fatigue life. By integrating these features into a small portable device suitable for real-time inspection, this technology significantly improves the ability to monitor overall pipe integrity.