Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Investigation on hydrodynamic response characteristic of 10000-ton topside floatover installation ofthe jacket platform in South China Sea
LI Xinchao1, LI Huailiang1, YU Wentai1, BAI Xiaodong2, LUO Hanbing2
1

Offshore Oil Engineering Co., Ltd., Tianjin, China;

2 Department of Naval Architecture and Ocean Engineering, Tianjin University, Tianjin, China

floatover method has great advantages over the lifting method when it
comes to the mega topsides exceeding the capacity of the lifting crane.
The floatover method allows that more than 20000-ton mega topsides arefabricated and outfitted onshore. The integrated topsides are then placedon the barge deck in one piece and finally transferred onto thesubstructures by the tide, the ballasting system, or the active jackingsystem. Besides the capacity, there are plenty of benefits and strengths of
the integrated topside floatover method. More flexibility of the bargechoice, less long-term offshore hook-up operations, and reductions ofschedule interfaces make the floatover method a much safer and morecost-efficient method than the lifting method (Gros and Lescurat, 1982;
ONeill et al., 2000; Seij and Groot, 2007; Wang et al., 2010).

ABSTRACTThe relative long wave and depth water in South China Sea poses great
difficulties to the applications of the main floatover barge HYSY228 forthe 10000-ton mega topsides. This study aims at evaluating theworkability of the floatover operations in the South China Sea. Numericalinvestigations on the dynamic response of the floatover installation forthe 10000-ton topsides are presented. The numerical model of thefloatover system is built based on the prototype T-shaped barge
HYSY228. Two critical floatover phases are considered: pre-matingphase and mating phase. The loads on Leg Mating Unit(LMU) andfenders at pre-mating phase are discussed. Various intermediate matingstages with different drafts and different engagements of the LMU areanalyzed. It is found that fender forces, LMU horizontal motions andLMU loads meet the design requirements. But the LMU vertical load isclose to the design value, which threatens the safety of the floatover
operations. The study provides valuable suggestions on the topside
floatover installation for the jacket platform in the South China Sea.

The floatover method consists of the stages of standby, entrance, premating, load transfer and exits. The interaction between the topsides, thesubstructure, the Leg Mating Unit (LMU), the Deck Support Unit (DSU),
the mooring system and the ballast system, are quite complex. Bai et al.
(2020, 2021) approximated the continuous floatover installation process
into several quasi-steady-state stages, and conducted experimental andnumerical simulations of several intermediate stages for the jacket
platform. The time-domain analysis was carried out to investigate thecollision forces on LMUs. Chen et al. (2017) constructed a numericalmodel for the dynamic response analysis of the floatover installation andused a state-space approach to carry out a time-domain analysis of theload transfer conditions to investigate the collision forces between thebarge and topsides. Li et al. (2015) used ANSYS to establish a threedimensional structural finite element model of the LMU and carried outa non-linear static analysis of the large deformation of the LMU and theequivalent forces of the external sleeve. They pointed out that the force
characteristics of the LMU during load transfer are crucial to thestructural design of the LMU. Liu et al. (2018) introduced the power
positioning floatover installation technology and the study pointed outthat the fenders seriously affected the lateral movement characteristics ofthe power positioning floating bracket installation vessel. Li et al. (2018)carried out a model test for the 10,000-ton topsides using a twin barge
floatover method, and analyzed the motion response of the floatoversystem and the force characteristics of the LMU under different wave
directions. It was found that the wave direction is crucial to the floatover
installation and the design of the floating buttress system should fully
consider the influence of the wave direction.

KEYWORDS: Floatover; South China Sea; motions; mating unit
loads
INTRODUCTION
With the development of China's oil and gas resources in the South China
Sea, high requirements for offshore engineering have been put forward.
The weight of topside has also developed from a few thousand tons tomore than 10,000 tons. It is critical to ensure safety, improve efficiency
and save costs for the offshore installation of mega topsides.
The topsides installation of the offshore platform is one of the expensive
and important tasks. The topsides installation methods include the lifting
method and the floatover method. In the lifting method, the individual
module or the integrated topsides are lifted up by the floating crane vessel
and matted with the substructures. Lifting the individual functional
module separately and welding modules together are time-consuming anduneconomical. Lifting the integrated topsides installation requires a large
floating crane and an extended crane radius. Those factors result in a great
limitation of the lifting operations and constraint the application. The680