Sun, Mingyuan (Shanghai JiaoTong University) | Ding, Jinhong (Shanghai JiaoTong University) | Yuan, Meng (COSCO Shipping Specialized Carriers Co. Ltd) | Yang, Qi (Shanghai JiaoTong University) | Ni, Chongben (Shanghai JiaoTong University) | Chen, Xinquan (Shanghai JiaoTong University)
The numerical simulation of J-lay pipelaying is an essential process for the offshore pipeline installation to investigate the motion behavior of the pipelaying vessel, and to assess the dynamic loads and stresses on the pipeline. A series of model tests for a light J-lay vessel and pipelaying were completed to figure out the vessel seakeeping performance and the configuration of the pipelaying. With the great match between the numerical simulation and the model test results, a series of coupled dynamic analysis for the pipelaying operation was completed to evaluate the light J-lay vessel motion and dynamic loads and stresses on the pipeline in a specified sea state.
The subsea pipeline is a necessity to offshore petroleum industry for it connecting offshore facilities and transporting petroleum to terminals. The most common methods to install subsea pipelines and risers are S-lay and J-lay according to the pipelaying devices mounted on the vessel. It has been decades since the J-lay method is employed in offshore pipelaying and is proven as an optimal way to install pipelines and risers in deep water (van der Heijden & Bulter, 1992; Springmann and Hebert, 1994; Heerema & Allseas Group S.A., 2005; Wang et al, 2012).
Some inherent advantages of J-lay method were well known because the pipelines and risers are laid in the water almost vertically in J-lay operation (Pamler & King, 2008). Firstly, the required tension is lower because the pipe being laid only need tension to limit the bending in the sagbend. Secondly, the huge stinger structure is omitted for J-lay vessels. Thirdly, by the vertically laying way, the horizontal load on the vessel by pipeline can be dramatically reduced compared with S-lay. Finally, the touchdown point is closer to the J-lay vessel. Thus, positioning the vessel to lay the pipe accurately could be easier.
Numerical simulation is a feasible way to study the motion characteristic of the J-lay vessel in waves, and the response of the pipeline being laid under the effect of wind, wave, and current (Wang et al, 2010; Kang et al, 2015; Lenci et al, 2005; Gong et al, 2014). The motion characteristic of the pipelaying vessel can be assessed by the hydrodynamic analysis. Meanwhile, the response of the pipelaying vessel and the pipeline in wind, wave, and current can be simulated in the coupled analysis.