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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

Dynamic Responses of a novel Floating Column with Dry-well and Storage Platform under stochastic
wave condition
Yan Li1,2

Zhimin Zhao1,2

Yougang Tang1,2 Jianhao Xu3 Yaolong Li1,2

Ruoyu Zhang1,2

1. State Key Laboratory of Hydraulic Engineering Simulation and Safety, School of Civil Engineering, Tianjin University,Tianjin, China2. Tianjin Key Laboratory of Coastal and Ocean Engineering, School of Civil Engineering, Tianjin University,Tianjin, China
3. Shanghai Waigaoqiao Shipbuilding CompanyShanghai, China

their working area and connection type to the seafloor, there are twomain kinds of offshore oil and gas platforms. One kind is the fixed
platform, such as jacket, gravity-based platform, etc. They are directly
supported by the piles or other structures which are injected stably inthe seabed. Due to the continuous structure to the seafloor and its
construction cost, the fixed platform is usually adopted in the shallow
water areas. On the other hand, when the offshore oil development
steps into the deep water areas, the fixed platforms are seldom adopted
because of the establish cost and safety factors. Therefore, the floating
structures positioned by anchor and mooring lines become the mostcommon choice.
The Floating Production Storage and Offloading system (FPSO) is oneof the most prevailing structure for the deep-water oil fielddevelopment due to their large storage capacity, when comparing withother floating platform such as semi-submersibles, TLPs and SPARs(Lee et.al, 2021). The first-generation FPSOs are the modifications ofoil tankers, so most of the in-operation FPSOs are ship-type ones.
Although their storage capacity meets the requirement of offshore oiland gas development, the ship-type FPSO also has several
disadvantages which challenge the safe and efficient operation. For
example, due to the single-axis symmetrical structure, theenvironmental loads on the ship are different under the various incident
wave direction. To be specific, the beam wave will induce larger wave
loads than the longitudinal wave. In order to reduce the resulting
loading on the whole system, the single point mooring (SPM) system isusually adopted (Dong et.al, 2021). Although the safety could beensured, the SPM system is much more expensive than the multi-point
mooring system.
On the other hand, the ship-type FPSO usually has relatively poor
hydrodynamic feature, especially the large heave motion. Because ofthis reason, the subsea and flexible risers are chosen in most of thedeepwater oilfield development, which means higher cost than adopting
the steel catenary risers (SCRs) steel lazy wave risers (SLWRs).
Towards this end, many attempts are performed to improve the motion
response of the FPSOs, and this has become one of the key issues in theoffshore engineering.

ABSTRACT
Compared with those offshore oil development platforms using wet
wellhead, dry wellhead has advantages of drilling, production andmaintenance management. At present, the TLP and SPAR platforms
which use dry wellhead have poor liquid storage capacity. On the other
hand, the vertical motion of FPSO platform with strong storage
capacity is too extreme to meet the requirements of dry wellheadsystem. In present work, a floating column with dry-well and storage
platform (FCDS platform) is proposed based on the FWPSO platform.
After adding an extension cylinder and the new damping structure to
the bottom of the platform, the hydrodynamic performance isinvestigated by the numerical algorithm. Taking the sea scenarios in theSouth China Sea into account, a time-domain coupling analysis wasadopted to simulate the dynamic performance of the buoy-mooring
system. The maximum horizontal displacement and the maximum
tension of the mooring line are compared and analyzed. The results
show the FCDS platform with "chain-polyester-chain" type mooring
system can meet the motion response requirements and the mooring
system can also meet the requirements of the specification.

KEY WORDS: FPSO; dry wellhead; mooring; dynamic response;
damping structure.

INTRODUCTION
The crude, which is one of the major energy resources, has played an
important role in the society development. As the onshore oil storage
becomes less and less, more attentions are paid on the offshore areas.
According to previous surveys (Yacovitch et al., 2020; Kaiser, 2020),
the offshore oil has reached about 30% of the whole production in 2019,and it will be undoubtedly increasing and become the major contributor
in the following years.
For the offshore oil and gas development, the facilities and equipment
are located on the offshore platforms. According to the water depth of816