Design Optimization of Braces for Three-Legged Minimum Jacket Offshore Structure

The innovative design of offshore structures has developed rapidly in line with the increasing demand for energy from oil and gas in the world. One of the innovations is the effort to use a modified or minimum jacket structure. The minimum jacket structure is a concept that is very suitable to use in shallow water marginal fields, because the structural design is more economical in terms of cost, reusable, and easier to move than the conventional jacket. This study presents design optimization of the existing jacket platform in terms of brace pattern (configuration) and dimension selection with the objective function being to minimize the weight of the jacket platform. The optimization process was carried out with 2 steps of optimization scenarios which are selecting the most optimal jacket brace configuration among various variations and determining the most optimal jacket brace dimensions through a static in-place analysis of the jacket structure. The brace configuration variations considered are V-brace, N-brace, and K-brace patterns. The second optimization step is the determination of the brace dimensions including outside diameter (OD) and wall thickness (WT) by considering 12 model variations. The results showed that the optimization result on the existing minimum jacket has complied with the whole criteria and yielded a lighter structure weight of 3,542.11 kips. This optimized minimum jacket structure became 15.9% lighter than the weight of the existing initial jacket structure, which is 4,211.96 kips.