Coupling time-domain analysis for pipeline end termination installation based on pipelaying
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ORIGINAL ARTICLE
Coupling time‑domain analysis for pipeline end termination installation based on pipelaying Duanfeng Han1 · Kuo Huang1 · Yingfei Zan1 · Lihao Yuan1 · Zhaohui Wu2 Received: 26 February 2019 / Accepted: 7 October 2019 © The Japan Society of Naval Architects and Ocean Engineers (JASNAOE) 2019
Abstract To study the dynamic characteristics of the pipeline end termination (PLET) installation operation based on pipelaying under full coupling effect, a numerical model for PLET installation based on S-laying with the vessel–cable–PLET–pipeline coupling in time domain is proposed in this study. The whole model mainly consists of four parts, which are the pipelaying vessel, the abandonment and recovery (A&R) cable, the pipeline and the PLET. The finite element method is proposed for the pipeline and the cable, while the hydrodynamic forces on the PLET are simulated by the Morison equation. The pipelaying vessel is controlled by a dynamic positioning system. The proposed model is validated by OrcaFlex software and then used to carry out numerical simulations of PLET installation based on practical operations. The static and dynamic responses of each part in different operation phases and under different wave and current directions are analyzed. The results show that the PLET position in different phases as well as the direction of wave and current during installation has great effect on forces and motions of the system parts. Moreover, the dynamic responses of different parts are apparently connected, so the coupling effect cannot be ignored. Keywords Pipeline end termination installation · Pipelaying · Numerical simulation · Coupling · Time domain
1 Introduction Pipeline end termination (PLET) is an important part of underwater production system in offshore oil and gas engineering. Generally, it is a subsea structure located at the end of a pipeline and is designed to connect the pipeline with other underwater facilities [1–3]. The installation for a PLET is a process during which the PLET is carried from sea surface to the seabed with the pipeline. There are several ways to carry out the installation, by lifting or based on pipelaying. The latter is better at saving the cost of multiple facilities [4]. The S-laying technique still occupies a dominant position in the current pipelaying market due to its particular advantages such as higher efficiency, lower costs, and better adaptability to different sea states and various water depths.
* Yingfei Zan [email protected] 1
College of Shipbuilding Engineering, Harbin Engineering University, Harbin 150001, China
Offshore Oil Engineering Co., Ltd., Tianjin 300461, China
2
The PLET installation based on S-laying can be simplified as a pipeline abandonment operation based on S-laying with a PLET fixed to the junction of the pipeline and the cable. The PLET is lifted by a buoy connected to it. As shown in Fig. 1, the cable connects the PLET to the vessel, and the pipeline begins to contact with the seabed at the touchdown point (TDP). Controllin
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