Successful Development of Coiled-Tubing Connectors Using Virtual Testing

Since its introduction in the 1960s, coiled tubing (CT) has evolved from smaller sizes and a few cleanout jobs to larger diameters and heavier grades with higher flow rates. Some of the limiting factors, especially on offshore platforms, are limited crane-weight capability and poor weather conditions, which severely limit the size of the reel that can be lifted. With offshore crane capabilities as low as eight tons on some platforms, a CT reel is often transported in two or more sections, requiring offshore assembly. A conventional method of joining the two strings was to butt weld them, which reduces fatigue life to 35%. Most recently, spoolable connectors, also called cold connections, have gained popularity because of their easy and safe installation. A nonlinear, FEA-based, virtual-test method was developed to quickly and cost effectively design spoolable connectors. Using the virtual test extensively in the development of the spoolable CT connectors, and guided by engineering mechanics principles, we have successfully developed a CT connector tool that exceeds the fatigue life of field butt weld. This CT connector tool has an industry-leading fatigue life and requires a fraction of the developmental cost and time that the conventional procedure of using trial-and-error physical tests requires. The virtual test, selected virtual- test results, physical results from a fatigue machine test, and a full-scale yard test are discussed in this paper.