High-End Testing Frame for Coiled Tubings


Tubulars are involved in most of the activities related to the oil and gas industry. The reliability of any operation can be enhanced by predicting the lifetime of these tubulars and thus avoiding non-productive time and excessive costs.

Thanks to the development of new materials and improvements of the coiled tubing technology with the years, these tubulars have been lately used in more challenging operations, such as drilling. With the need of accurately replicate the actual service loads acting on coiled tubings during its operation in the field, a unique testing facility was designed and built to replicate all the different processes promoting the failure of these kind of pipes.

The main loads acting on coiled tubings are the bending, internal pressure and axial load. Unlike the rest of the tubulars used in the oil and gas industry, coiled tubings work under plastic deformation because of the bending cycles encountered while passing through the reel and gooseneck. The internal pressure, altogether with the alternating bending loads are responsible for the ovality of the pipe, an effect representing the loss of roundness in the coiled tubing. The ovality strongly affects the capacity of the tubing to resist the presence of internal or external pressures. Since the coiled tubing is one piece of pipe which can measure even thousands of meters, it is very common for this tubular to suffer elongation because of the high axial tension load represented by its own buoyed weight when it hangs in the vertical section of a well. Finally, it is important to take into account the friction with the walls of the wellbore as the tubing is deployed. This friction can be represented as an induced torque in the pipe. The idea of using the coiled tubing for drilling applications makes necessary the accurate study of torsion loads in coiled tubings, effect taking place due to the induced torque in the string coming from the drill bit.

The new test facility is able to replicate all these possible loads either separately or at the same time by means of hydraulic cylinders acting directly on the test sample. The results of the first tests applied on coiled tubings are shown and compared with other available results. All these first tests were run with high internal pressure in order to simulate the loads acting in high pressure wells.


Full version of the article can be downloaded here.

Scroll up