Research On Critical Depth of Water For a Deep Sea Semi-Submersible Drilling Platform Based On Dynamic Positioning

Wang, Lei (School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Yang, Huan (School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Zhang, Shen (School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University)

OnePetro 

ABSTRACT:

Dynamic Positioning System (DPS) is an essential requirement for marine vessels and in many offshore platform operations, in order to maintain desired position and heading in the presence of environmental disturbances from wind, waves, and current. Based on DPS, in operating condition, this paper makes time domain simulation of a semi-submersible platform’s motion induced by environment loads in different directions and thrusters in three different kinds of service conditions (all thrusters available, arbitrary one thruster unavailable and two thrusters on the same switchboard unavailable) by means of DPSEMI program, from which the critical depth of water of this platform in operating condition when DP can meet the demand of precision for station-keeping is obtained. This paper also compares the critical depth of water in different ocean environment conditions and different thruster service conditions, analyses the station-keeping ability of DPS, brings up some new opinions about critical depth of water and points the way out for the research in the future.



INTRODUCTION

Dynamic Positioning System (DPS) is an essential requirement for marine vessels and in many offshore platform operations, in order to maintain desired position and heading in the presence of environmental disturbances from wind, waves, and current (Mahfouz, 2005). A great number of offshore platform operations are carried out using DPS, such as drilling, underwater pipe laying, offloading, and diving support (Tannuri, 2010). A DPS mainly consists of three primary units: the sensors unit, the control and monitoring unit and the actuators unit (Brink, 1981). Only when the value of horizontal motion of vessels is less than certain critical value can vessels meet the demand of precision for station-keeping. In other words, only when vessels operate in the condition of the water depth more than a critical water depth, can DPS work effectively (Brink,1981).