Vessel Motion Based Laying Criteria for Rigid and Flexible Pipes in Deepwater

摘要

The traditionally used lay criteria for the installation of rigid and flexible pipes as well as umbilicals based on environmental characteristics are often used with difficulty and inaccuracy. It has been shown that in deepwater, the behavior of the bottom part of a catenary (minimum bend radius, minimum and maximum axial load) is very well correlated to the heave velocity of the vessel at the location of the hang-off point. In addition, the top tension is well correlated to the heave acceleration at this point. The paper describes how the latter has been demonstrated and the lay criteria determined, as well as the method used to apply it during installation operations. Several softwares are used onboard: one is for statistical analyses of motion measurements of a MRU (Motion Recording Unit); another one is a vessel motion predictor software that compares calculated motions for present and forecasted weather conditions. The lay parameters and criteria further depend on the measured current profile which is also used to predict the top angle.