Study On Dynamic Positioning Capability Analysis Method Of Deepwater Drilling Ship

As the dynamic positioning (DP) system has been more and more widely used in deepwaterengineering equipments, dynamic positioning analysis has become a key technique. Consideringthe characteristics of deepwater drilling ship, this thesis will study on the dynamic positioningcapability analysis including environmental loads calculation method, frequency-domainanalysis method and time-domain analysis method.Firstly, a new improved block method is studied based on the wind tunnel test which iscapable to consider the shield effect. Based on this method, a wind force calculation programnamed “WindC” is developed. The wave drift force of the drilling ship is calculated bySESAM/WADAM which is based on3D linear potential theory; Furthermore, the effect on wavedrift force due to moon pool is studied. The current force is studied by wind tunnel test. Secondlythruster optimal allocation and optimization theory are studied, and a dynamic positioninganalysis program named DPA which is based on SQP(Sequences Quadratic Program) isdeveloped. DPA is capable to consider most thruster type and forbidden angles. Thirdly, equationof motions and theory of controls are studied in time-domain analysis. Time-domain simulationsoftware SIMO developed by MARINTEK is used to calculate the accuracy of dynamicpositioning capability and time series results of dynamic positioning system. Time-domainanalysis is a convincing complement for method of frequency-domain analysis.Finally, as an example, dynamic positioning capability of Bully Drilling Ship is calculatedby use of methods mentioned above. Environmental forces, including wind forces, wave driftforces and current forces, are calculated. Then frequency-domain analysis of dynamicpositioning capability is taken by using DPA, and time-domain analysis of dynamic positioningcapability is taken by using SIMO. The calculation results of environmental forces and dynamic positioning capability are close to those calculated by foreign designer Gusto.In conclusion, the achievements of this thesis are capable to be used for dynamicpositioning capability analysis of deepwater drilling ship, and provide the tenical method todesign drilling ship and its thrusters.