Digital Twin: Hybrid Virtual Simulation and Physical Monitoring Strategy for Long-Term Safe Operation of Floating Production Platform-Hybrid Polyester Mooring Lines-Steel Catenary Risers Multibody System in the South China Sea

Abstract As the first self-development ultra-deepwater gas field, the project adopts the floating production platform-subsea production system. The platform is kept in position by sixteen hybrid polyester mooring lines. The gas and other fluids associated to the production process are conveyed to the platform by six steel catenary risers. The field has an operational design cycle of 30 years. With the purpose of ensuring long-term safe operation for offshore structures, this case fuses physical monitoring and virtual simulation to build an integrated platform management system. Monitoring data from the environment, platform, mooring lines and risers are periodically collected from the in-situ sensors. The system applies the Long short-term memory neural network to reconstruct the virtual simulation model of the dynamic response of offshore structures under environmental loads. The system has two main functions: mechanical behavior prediction and mooring strategy adjustment. Combined with the monitoring data of environmental elements in the current operation area, the system can realize real-time prediction and calculation of platform movement, mooring lines tension and riser dynamic configuration, and visualize the health status of offshore structures. In case of severe operational conditions such as typhoon, the platform operators can obtain the platform displacement window and the corresponding mooring tension adjustment strategy through the operating system to maintain the riser stress safety. This case gives a real-time solution for the safe operation of offshore structures with physical monitoring and virtual simulation, which can guide the operators to adjust the platform displacement to maintain the mooring lines and risers in the safety zone for a long time.