Amorphous Diffusion Bonding: New Technology Towards a Seamless Reeled Tubing System

Abstract

Abstract A new Amorphous Diffusion Bonding (ADB) technology is being developed to overcome the known problems involved in shop welding and field weld repairs of coiled tubing and their poor fatigue properties. The objective of the technology is to join long lengths of seamless tubing prior to reeling using a high speed diffusion bonding system in conjunction with a thin film of amorphous metal. The new technology is part of an overall project to develop a high fatigue resistance seamless coiled tubing. The key technology of ADB involves finished ends of tubulars being butted together with an amorphous thin film filler metal between the ends. The amorphous film at elevated temperatures creates a diffusion of atoms across the interface and encourages a mutual diffusion of the filler metal and joining metal in the local area of contact. Extensive laboratory testing has been carried out during a feasibility study including metallurgical examination and small scale bend and reverse bend fatigue testing. Additionally, a small amount of full scale fatigue testing has been undertaken and further testing has been scheduled for the future. The results indicate a bonded joint that is/has; homogeneous with the parent metal; no deformation; a small smooth upset; resistance to fatigue equal to that of the parent metal. From the tests carried out to-date the indications are that the bonded joint has a superior fatigue life to that of the TIG welded joint by an order of magnitude in excess of three and it is evident that this can be improved on. This paper centers on whether Amorphous Diffusion Bonding is a valuable and applicable contribution to seamless reeled tubing systems within the oil industry. Introduction Major changes in how we conduct our business in the oil industry can't come just from one company. This is why a JIP was formed from invited oil companies and the service sector that share similar objectives, i.e. to join in a fundamental research program initially on fatigue resistant steels for coiled tubing. Only in this way can the views across the whole spectrum of the industry, including those of the service companies, be considered under one "umbrella" and thus help to create a "step change" in the area of Reeled Tubing Systems. The project concept is to research and characterise the present steels then formulate new steels that will substantially increase the performance levels over that of present steels. If the new steels are produced in seamless reeled tubing this will be a major change and there might be a distinct possibility that not just one steel could be considered but the whole range of API OCTG including CRA steels. It is well known that present welding methods being used have severe limitations in field application, quality control and fatigue characteristics. Therefore in order to advance reeled tubing technology, a method of circumferential butt welding tubulars that has a high fatigue performance and repeatability will have to be developed. Status of Present Technology The total acceptance and application of coiled tubing for drilling and workover operations is being limited by the inability to circumferentially butt weld present coiled tubing materials with a high degree of success and thereby retain an acceptable fatigue life.P. 591^