This paper describes the implementation of the Advisory Hull Monitoring System (AHMS) onboard the existing Bonga FPSO (Nigeria) during operations and production. AHMS has been developed for FPSOs in the Monitas Joint Industry Project as a fully automated system, which explains and advises on the fatigue lifetime consumption of the hull of FPSOs. The explanations and advice offered are based on a comparison between the design and the actual predicted lifetime consumption by replacing the design parameters including environmental and operational conditions with the measured data. The system differentiates between the contributions of environmental and operational conditions as well as hydro-mechanic and structural responses. The AHMS system comprises hardware and software for smart data gathering and processing. AHMS hardware includes strain- type sensors on deck and inside the Water Ballast Tanks (WBTs) and/or void spaces and interfaces with external systems including the Computer Loading Instrument (CLI), Gyro and metocean system. AHMS has generally been installed onboard newly built floaters including the Usan FPSO (Nigeria), Clov FPSO (Angola), Ichthys FPSO (Australia) and Moho Nord FPU (Congo). Being in operation since 2005, the Bonga FPSO has lived 14 of its 20-year design life. Given the constraints inherent in her design, deployment of the AHMS for the FPSO's hull fatigue life monitoring therefore presented unique installation challenges to overcome as would be expected for ageing brownfield assets. To add to this challenge, the installation was carried out during production and so required strict adherence to the stringent safety requirements of Simultaneous Operations (SIMOPs) on a live plant. This paper describes in detail, the AHMS hardware, the complexity and challenges of their installation for the Bonga FPSO and highlights lessons learned for typical brownfiled retrofit of this nature. OCTOPUS MONITAS, the software of the AHMS system for the smart data processing, calculates onboard fatigue lifetime consumption of the hull and explains the differences against design predictions. Methodology of the software is herein described, and the first set of measurements taken from the Bonga FPSO as well as preliminary results produced by the software are similarly presented.

A high-fidelity FPSO Structural Digital Twin (SDT) based on Reduced Basis Finite Element Analysis (RB-FEA) coupled with inspection data and physical sensor measurements (advisory hull monitoring system) is presented to demonstrate a complete FPSO "digital thread" that combines operational data feeds, detailed structural analysis based on as-is asset condition, and automated structural integrity reporting. This lays the groundwork for a philosophical shift for asset lifecycle management by enabling the use of "as-measured" conditions in lieu of assumed "design-conditions" for a more accurate, and robust understanding of asset health. We demonstrate the deployment of this methodology for the Bonga FPSO and discuss the value that it brings during day-to-day operations.

An active subsea field in the Gulf of Mexico has adopted a thermoplastic composite pipe (TCP) water injection jumper for its waterflood upgrade. The TCP spool is lightweight and flexible — relative to the traditional steel-only spool segments used in subsea jumpers. As such, the flow-induced vibration (FIV) threat from internal fluid flow must be assessed for the intended service. A three-tiered approach is used to assess the level of FIV threat expected in this TCP subsea jumper application. A high-level screening based on widely used industry guidelines indicates a high susceptibility to FIV fatigue failure for the steel product in the jumper, with no applicability to the TCP material. A comprehensive screening based on structural finite element analysis and computational fluid dynamics shows that the vibration levels and stress cycling due to FIV will be acceptable for the intended water injection application and a 30-year design life, when adopting a factor of safety of 10 for subsea service.

The Auger Tension Leg Platform (TLP), which was installed in 1994, is Shell’s first TLP in the Gulf of Mexico (GoM). The Auger TLP was designed during the time when the industry had not yet been able to fully investigate the global dynamic characteristics of TLPs, especially the high frequency dynamic responses of tendons, and the design tensions of the Auger tendons were not calibrated to scaled wave basin model tests like the later TLP projects since the Auger TLP. Based on the accumulated experience from more than two decades’ operation and a number of studies conducted on the Auger TLP global performance, it is revealed that the Auger tendon tension is conservative given the current operational limit; however, the extra conservatism has not been fully quantified due to the lack of model test data. With the recorded Auger global motions and tendon tensions from the on-board measurement system, the performance of the Auger TLP in extreme storms is becoming fully unveiled by calibrating the analytical predictions (both time-domain analysis and frequency-domain analysis) with the measurement data. Thus, the objectives of this paper are (i) to calibrate the TLP minimum tendon tension design recipe based on the high-fidelity field measurement data from Tropical Storm Cindy 2017 and Hurricane Laura 2020 using both time-domain and frequency-domain simulations, and (ii) to propose the new allowable vertical center of gravity (VCG) and the new tendon pretensions for the Auger TLP for the extreme storm conditions. It is concluded that the current allowable VCG can be increased or the current required tendon pretension can be decreased without compromising the safety to the platform during the extreme storm conditions.

An active subsea field in the Gulf of Mexico has adopted a thermoplastic composite pipe (TCP) water injection jumper for its waterflood upgrade. The jumper assembly is composed of a TCP span attached to steel piping on either end. The TCP spool is lightweight and flexible relative to the traditional steel-only M-shaped subsea jumpers. As such, the flow-induced vibration (FIV) threat from internal fluid flow must be assessed for the intended service. A three-tiered approach is used to assess the level of FIV threat expected in this TCP subsea jumper application. A high-level screening based on widely used industry guidelines indicates a susceptibility to FIV fatigue failure for the steel piping in the TCP jumper assembly. A comprehensive screening based on structural finite element analysis and computational fluid dynamics shows that the vibration levels and stress cycling due to FIV will be acceptable for the intended water injection application and a 30-year design life, when adopting a factor of safety of 10 for subsea service. We evaluate the effect of doubling the length of the steel piping on either end of the TCP span, as a means to increase the overall span of the TCP jumper assembly. Lastly, we draw a comparison between a traditional all-steel M-shaped jumper and the TCP jumper in terms of FIV fatigue life, for the same operating conditions and the same total suspended span.