Oceans of knowledge
Integrating the turret mooring system
The Bluewater FPSO vessels are provided with internal turret mooring systems. Some of these systems are disconnectable, allowing the FPSO to sail away from extremely harsh weather events, like a typhoon, or to sail to an onshore shipyard for (future) repairs or upgrades. FPSOs with a disconnectable mooring system are also provided with a Dynamic Positioning (DP) system, to enable positioning of the FPSO using this system during (re)connection. A DP system can also be designed for situations where the FPSO must be kept at station to allow production. In this case a disconnectable riser system needs to be deployed, which can be disconnected very fast (i.e. within a minute) in case of excessive drift of the FPSO. The quick-disconnect turret mooring system is located on an outrigger at the side of the FPSO.
Integrating process topsides
The process topsides enable the separation of the well fluids into oil, water and gas and possibly other contaminants. The separation process is based on the natural oil and water separation that occurs when sufficient retention time is provided. Sufficient heat and demulsifiers will enhance this separation process, which typically requires several stages at different pressure levels. Bluewater’s process systems include separation systems suitable for extremely light oils, as well as systems suitable for very heavy oils. In addition, Bluewater’s process systems sometimes need to handle sour gasses in the well streams, or deal with naphthenates due to commingling of well fluids from different fields.
Floating (Production), Storage & Offloading (F(P)SO)
The Floating Production Storage and Offloading (FPSO) vessel includes all systems to enable offshore production of oil and gas.
The vessel also accommodates large oil tanks for temporary storage until the produced oil can be offloaded into a (shuttle) tanker. Bluewater performs designs for new FPSOs in-house, but only for the company’s own fleet. All these vessels are based on AfraMax size tankers, whose oil storage capacity (approx. 600,000 bbls) is perfectly geared to a trading parcel size of 500,000 bbls. Vessels of this type are particularly suitable for mooring in harsh environments such as the North Sea, and are small enough to limit the mooring loads and thus the costs of mooring systems.
The conversion of a tanker to FPSO involves three main sub-projects: upgrading the tanker hull, integrating a Turret Mooring System and integrating process topsides.
Upgrading the tanker hull
The tanker hull needs to be upgraded to serve as the basis for the FPSO. The hull structures need to be strengthened to provide support to the turret mooring system as well as to the process topsides, and to limit the fatigue damage caused by the continuous impact of waves at the offshore field. The tanker crew facilities need to be increased to accommodate a much larger operating crew. Vessel motions are reduced by increased bilge keels and heading control thruster(s). Limiting the vessel motions at the offshore field will reduce sea sickness of the crew, as well as increase the process efficiency of the topsides to separate oil from water en gas.