By Michel Dran
Thales Industrial Services
A new design of telemetry and berthing aid system (TBAS) to improve safety during floating production system maneuvers has been deployed on the Girassol development offshore Angola.
The system, developed by Thales Industrial Services, is used for tanker mooring and subsequent crude offloading.
Production is due to start at Girassol shortly via subsea wellheads connected to an FPSO (floating production, storage, and offloading) vessel, with the crude then exported to the dedicated tanker in tandem mode or through a loading buoy.
The TBAS for Girassol will be applied to all floating installations. The global system will need to relay the precise position of the FPSO, buoy, and tankers during operation. It will transmit all process data from the buoy to the control unit on the FPSO.
Instructions from the latter will then be transmitted to the tanker or buoy through a permanent radio link, with the capability to also transmit emergency orders from the tanker or buoy back to the FPSO. All units will share the same information to expedite immediate action, if required.
All equipment for the TBAS has been selected and designed to comply with hazardous area safety requirements for the production installation. The contractor, SBM, required four integrated units, each linked to the others by a multi-directional radio-link.
Reliability of the transmission system will be ensured through the redundancy in the radio-link connections, and also the capacity of all four units to collect and transmit all necessary data as required (relay functionality).
The Girassol system can be split into four main components:
- The FTU (FPSO telemetry and berthing aid unit) is a fixed control unit treating all data issued from the CALM (catenary anchor leg) buoy and the two floating vessels. The FTU (floating transport unit) includes monitoring capability such as the man-machine interface, the general situation of the vessels, the buoy, the hawser offloading conditions, alarms, and other factors.
- The BTU (buoy telemetry and berthing aid unit) collects relevant data concerning the hawser offloading process and the buoy equipment (GPS location) so that these are monitored and transferred to the other TBAS units. Also, it manages external or local commands such as cessation of offloading or quick hook release
- The TTU (tanker telemetry and berthing aid unit) comprises one portable telemetry unit relaying the vessel's position and direction. It also delivers all necessary information concerning progress of the operation. The operator is informed in real time about the relative positions of the tanker, buoy, and FPSO.
- The VTU (support vessel telemetry and berthing aid unit) also features one portable telemetry unit, which supplies all data concerning operational progress, including the relative positions of the different floating installations. The VTU, which is integrated in a portable station (laptop), displays a synoptic system position and a synoptic supervision process.
Use and maintenance
All equipment deployed in the Girassol TBAS is easy to use and maintain. The Thales approach is the combination and integration of telemetry and geographic positioning functions into the same system. The heart of the system's architecture is the redundant radio network, which allows all information to be shared and transmitted with high reliability, leading to response times of less than one second for emergency actions.
Operator TotalFinaElf has also commissioned Thales to provide a telemetry system for a CALM mooring system for its Hydra Field development, offshore Tierra del Fuego, Argentina. This will include a berthing aid system (for the tanker/CALM), a load monitoring system, and the control/status monitor of the safety valves.