Research on Optimal Design of Dual Derrick for the 7th Generation Ultra-Deepwater Offshore Platform

Abstract

To solve the problem of small safety factor and heavy structure of dual derrick of the 7th generation ultra-deepwater offshore platform, the optimal design of the dual derrick is studied. Using ANSYS software, the mechanical property of dual derrick under the storm self-storage condition is analyzed. Taking the mass and safety factor of the dual derrick as the target and the beam section parameters as the design variable, after the single factor optimization, the response surface method is used to establish the comprehensive optimization mathematical model of the section parameters. The optimal combination of the section parameters is obtained. The results show that the safety factor of the original design of the dual derrick in the storm self-storage condition is less than 1.67 as required by API Spec 4F, and the bottom leg of the derrick is the most dangerous. Compared with the original scheme, the final optimization scheme of dual derrick reduces the mass by 19.11% and increases the safety factor by 23.81%, which meets the requirements of operating conditions.