Two-dimensional evaluation for dynamic positioning performance of offshore platform under complex sea conditions

In the actual engineering, the dynamic positioning of offshore platform is carried out by arranging different thrusters in different positions and adjusting propeller rotational speed and spatial azimuth angle to provide various thrust and torque, or changing the direction of thrust and torque. A special study on the dynamic positioning performance of the offshore platform should be conducted if it is necessary to obtain not only the final resultant forces and resultant moments on the offshore platform, but also the magnitude of each component force provided by each thruster and the spatial azimuth angle of each azimuth thruster. In this study, a dynamic positioning two-dimensional (2-D) simulation evaluation software DPTSE is designed and developed. Combined with the specific parameters of Offshore Platform 981, the thrust allocation strategy and the detailed layout of eight azimuth thrusters, the dynamic positioning process of the offshore platform in the South China sea under different environment loads are simulated and evaluated. The study demonstrates that second order wave drift forces, despite their complexity, enable faster positioning convergence (6 min) compared to steady current forces (110 min) due to their oscillatory nature and lower mean values. Under combined environmental loading, the DPTSE software successfully maintains platform positioning within acceptable limits while providing detailed thruster-level analysis that enables operators to optimize energy consumption and prevent individual thruster overloading. This research provides offshore engineers with a practical tool for preliminary DP system evaluation and thruster allocation optimization, offering significant value for platform design verification and operator training in realistic South China Sea environmental conditions.