Drillships are deployed for exploratory drilling in water depths up to 3200 m. Design variants in the new-generation drillships include flexible internal storage and payload capacity. Their intricate dynamic behavior in severe sea states significantly complicates operating safely and effectively. The current numerical simulation investigation and Analytical technique focuses on the dynamic analysis of drillships under critical environmental sea states while maintaining resilience. The design and operation of drillships, which are intricate and domain-specialized vessels, need attention. The drillship structure is modeled, and its behavior under significant wave amplitude, wave Period, current, and wind velocities emphasis is simulated in the research using the FEA. The current study examines the motion characteristics of a Drillship for different sea states and environmental conditions. Their stability across critical sea states is also assessed. Based on the numerical studies, it is seen that they experience a modest degree of instability due to excessive roll and pitch under extreme environmental loads. While preliminary checks under mild heave motion showed that the coupled heave-pitch motion dominates the design shear and longitudinal bending, they are critically influenced by the pitch motion. The forces of second-order steady drift in the far-field and the near-field are compared in the frequency domain. This investigation covers an extensive spectrum of topics, such as motion-induced Environmental loads, Free Float tests, hydrodynamic forces, RAO based Time and Frequency Domain Analyses. The presented study identifies parameters that influence its strength and stability, and the results are useful for improving the operational safety and reliability of drillships under challenging offshore conditions.

Keywords: Drillship, Environmental loads, Dynamic analysis, Structural responses (RAO), Hydrodynamic Diffraction analysis, Ultra-Deepwater.