The full-length NDE inspection of coiled tubing is now well established, and it is expected that NDE will play an increasing role in setting quality standards for used coiled tubing. Nondestructive Evaluation (NDE) methods are currently being documented into the API Recommended Practice for Care, Maintenance and Inspection of Coiled Tubing in order to set baseline requirements for inspection, and should form an integral part of a string management programme. Non-contact electromagnetic techniques for wall thickness measurement, ovality measurement, and flaw detection are in use in such tools, and have resulted in the following: detection of internal corrosion, section removal from the bed-wrap, downhole, and mid sections of tubes, scrapping entire tubes, and the detection of heavily fatigued areas in high strength tubing.
This paper indicates the type and value of the information that has been collected by performing NDE inspection, and presents the results of some recent inspections in detail. The paper also indicates the need for universal rules for derating sections of tubing in terms of both wall condition and consumed fatigue life.
The development of a universal vocabulary for the problems associated with coiled tubing in use that is consistent with current API terminology is also discussed.