Abstract
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.
