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Abstract Due to plastic bending at the reel and guide arch, coiled tubing (CT) elongates with each trip into and out of the well. Laboratory experiments, finite element, numerical and theoretical modeling were performed to determine the magnitude of this elongation. The elongation for loads above an axial transition load are permanent while the elongation for loads below this load can be removed by a bending cycle. Theoretical modeling shows that rotation of the CT in the well and axial loading while bending significantly increases the axial elongation.
Abstract For many years, coiled tubing has been successfully operated from floating facilities. With recent advances relating to the understanding of plastic fatigue of coil, there are evolving concerns associated with the fatigue of a continually moving reel. This paper quantifies reel motion with respect to the relative position of the reel, heave amplitude and period and the effect of running rates. A fatigue computer model is used to assess the operating limits and time to failure in a hypothetical case and a heave animation simulator is used to optimise rig-up configurations. Real and potential operating solutions are offered and a definition of maximum operating heave is addressed.
The installation of flowlines in ever deeper and remote areas requires the usage of specific technologies in order to carry out pre-commissioning operations. As the water depth increases, the weight of the conventional equipment to be deployed to perform the required operations becomes a major issue and alternate solutions are thus required. An option lies in using Coiled Tubing. Coiled Tubing consists of continuous pipe that has been coiled around a reel and can be deployed and recovered according to operational needs.
So far, offshore operation of coiled tubing has been limited to small diameters and to short operational duration. The pre-commissioning operations can require the Coiled Tubing to be deployed several times for durations sometimes exceeding a month, and also requires larger diameters (typically 3.5”). As the duration of operations increases, a suitable way of assessing the fatigue of Coiled Tubing and of mitigating is required.
In order to address these challenges, SAIPEM has initiated an extensive fatigue campaign aiming at characterizing the fatigue behavior of Coiled Tubing under combined Plastic and Elastic fatigue. This testing campaign is being performed on actual coiled tubing samples made of CT-80 steel. The paper will present an overview of the testing matrix as well as an insight on the results obtained during this fatigue testing campaign.
In addition, in order to mitigate fatigue during offshore operations, SAIPEM has also developed an innovative bend stiffener design in order to control the stress levels in the Coiled Tubing at the hang-off location on the ship. This bend stiffener design allows for safe and easy operation of Coiled Tubing offshore while allowing the deployment of all required equipment and doesn't interfere with the deployment and recovery of the coiled tubing. A feedback on the utilization and performance of such equipment offshore will be provided.
The use of coiled tubing (CT) to conduct well-intervention services is well established. According to industry experts, its use continues to grow at an Additional Technical Papers average rate of 10% per year, even as other services show declines in the last year. As with all technology, the appropriate and effective use of any selected technique is a fundamental prerequisite for success. If these specialized techniques are to be used effectively, candidate selection, along with effective prejob planning and project evaluation, plays a much more important role in today's intervention and completion activities. The combined use of sound engineering planning, the speed and convenience of CT, and creative integration with other complementary equipment can provide today's engineer with the tools to return even the toughest well to profitable production.