Iterative optimization process of an offshore anchoring system

 The discovery of oil reserves at great depths has necessitated technological advancements in various engineering fields. Among the most affected systems is the anchoring system, which must be capable of maintaining the position of an offshore platform, meeting various design criteria that establish limits for unit displacement, line tension, vertical forces on anchors, line arrangement, among others. Additionally, the widespread availability of large-scale computational resources motivates the analysis of a considerable number of environmental conditions, with projects currently requiring the analysis of over 5000 combinations of waves, winds, and currents affecting the unit. Paradoxically, there is a pursuit of more economical projects that reduce installation costs, extend the unit's lifespan, and mitigate fatigue failures in the lines. In this context, this work presents a case study utilizing optimization techniques aimed at minimizing the percentage of offset from the neutral position of an anchoring system project for an FPSO (Floating Production, Storage, and Offloading Systems) platform. The design problem is modeled in the Synapse Offshore program and solved with the genetic algorithm (HDGA). Design variables refer to anchor radius, length of the segment near the fairlead, and length of the first polyester segment. The analyzed attributes refer to the percentage of tension in the lines, percentage of maximum load applied to the anchors, and neutral yaw delta angle. The study addresses an FPSO platform with 24 lines grouped into 4 clusters. The results, although limited to an FPSO platform, indicate that it is possible to find an optimal solution to the problem that respects the established restrictions and ISO rules without compromising system operation and ensuring safety. The analyses used simulations in the time domain for 10,800 seconds using Dynasim as the solver, a program developed by Petrobras, conducted with a set of 56 environmental conditions selected from the analysis of approximately 1700 environmental conditions for the case analyzed in deep waters. After the optimization process, the solutions for each analysis were reanalyzed iteratively, considering changes in the initial conditions to achieve the project's goal. In conclusion, the results of this study highlight the effectiveness of optimization techniques in offshore engineering, offering valuable insights for the design and operation of anchoring systems in challenging environments.