Structural Configuration Selection and Optimization of 7th Generation Semi-Submersible Drilling Unit

The 7th generation semi-submersible drilling unit (CSDU) represents a significant step forward for the ultra deepwater drilling units in terms of equipment specifications, operational efficiency, flexibility and reliability. Due to significant Variable Deck Load (VDL) increase, the 7th generation CSDU to be designed with larger main dimensions and particulars compared with its previous generations, which brings up a big challenge of the structural design. This paper presents the structural configuration selection and optimization design based on the profound investigation on the load-resistance characteristics of the overall structures and considering the stress distribution variation of the deck box with the integration of different lower hull configurations. This paper also investigates the effects of different types of upper and lower hull joints on the structural strength and fatigue in way of the main connection regions and provides the major connection optimization design. The optimized configuration and major connections have been used in the structural design of the 7th generation semi-submersible drilling unit.