Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering ConferenceShanghai, 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

Time-Domain Analysis of Positioning Capability of DP Assisted Mooring System of a Drilling and OilProduction Vessel
Jinhui He1,2，Haibin Zhang1，Renchuan Zhu2，Huayong Tian3
1. Offshore Engineering Department, Marine Design & Research Institute of China, Shanghai, China
2. State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering,
Shanghai Jiaotong University, Shanghai, China
3. Sing Tong Marine & Offshore Pte Ltd, Nantong, China

offshore industry.
At present, the drilling and oil-production vessel has only beensuccessfully applied in the West African Sea area because of the mild
environmental conditions, but its application in the South China Sea area
has just started. The main reason is that the environmental conditions in
the South China Sea are more complicated and stronger than those inWest Africa, with far greater wave height and wind speed than those inWest Africa. Also, the dominant environmental factors and dominantdirection in the South China Sea change significantly with seasons. It isa severe challenge for positioning capability and development of thevessel.

ABSTRACTIn this thesis, the time-domain analysis of dynamic positioning assisted
single point mooring positioning capability of a drilling and oilproduction vessel is studied. The vessel has a larger displacement thanregular drillship for oil production and is also designed for drill and wellrepair. Therefore the vessel can be considered as combination of adrillship and FPSO, and three hypothetical positioning systems, thedynamic positioning system, single point mooring positioning systemand dynamic positioning assisted single point mooring positioning
system are proposed and their capacities at South China Sea are studied.
The time-domain analysis of the vessel with three positioning systems iscarried out, and the dynamic positioning assisted single point mooring
positioning is recommended.

The drilling operation has a much higher requirement than oilproduction operation. For drilling operation, the deflection angle ofriser shall not be over than 5° or 6°, so the positioning drift range
should be kept in 1%~3% of water depth, 15m~45m for 1,500m waterdepth. Positioning system is the key system for the safety of the drillingand oil-production vessel.

KEY WORDS:

time-domain analysis, drilling vessel, dynamic
positioning, single point mooring positioning, dynamic positioning
assisted single point mooring positioning

In this thesis, based on the design environmental conditions of the South
China Sea, three hypothetical positioning systems, the dynamic
positioning system, single point mooring positioning system anddynamic positioning assisted single point mooring positioning system
are proposed and their capacities at South China Sea are studied.

INTRODUCTION
With the development of "shale gas revolution" in the United States,
profound changes have taken place in the global energy pattern. The
crude oil price has gone very low for a very long time before 2022.
Therefore, the exploitation of offshore oil and gas resources has sufferedtremendous cost pressure.
The drilling and oil-production vessel is a unit combining two functionsof drilling and oil & gas production, which can be used for progressive
development of successive oilfields without other drilling units. Thevessel can carry out drilling operation meanwhile the oil & gas
production does not need to be stopped, which makes incomparable
economy performance compared with traditional offshore oil & gas
resources exploitation units. Therefore, the drilling and oil-production
vessel has become a very important developing equipment in the field ofocean engineering, and the related research is the frontier topic in theMETHODS

A time-domain analysis method is applied in this thesis. For this analysis,
the equation of motion as follow should be solved.
𝑴𝑥 𝑪𝑥 𝑫𝟏 𝑥 𝑫𝟐 𝑓 𝑥
𝑲 𝑥 𝑥 𝒒 𝑡, 𝑥, 𝑥
(1)
Where,

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