TYPE OF PLATFORMS (FLOATER)
Tension Leg Platform (TLP)
– Tension Leg Platforms (TLPs) are floating facilities that are tied down to the seabed by vertical steel tubes called tethers.
– This characteristic makes the structure very rigid in the vertical direction and very flexible in the horizontal plane. The vertical rigidity helps to tie in wells for production, while, the horizontal compliance makes the platform insensitive to the primary effect of waves.
– Have large columns and Pontoons and a fairly deep draught.
TYPE OF PLATFORMS (FLOATER)
Tension Leg Platform (TLP)
– TLP has excess buoyancy which keeps tethers in tension. Topside facilities , no. of risers etc. have to fixed at pre-design stage.
– Used for deep water up to 1200 M
– It has no integral storage.
– It is sensitive to topside load/draught variations as tether tensions are affected.
TYPE OF PLATFORMS (FLOATER)
n SEMISUB PLATFORM
– Due to small water plane area , they are weight sensitive. Flood warning systems are required to be in-place.
– Topside facilities , no. of risers etc. have to fixed at pre-design stage.
– Used for Ultra deep water.
– Semi-submersibles are held in place by anchors connected to a catenary mooring system.
TYPE OF PLATFORMS (FLOATER)
n SEMISUB PLATFORM
– Column pontoon junctions and bracing attract large loads.
– Due to possibility of fatigue cracking of braces , periodic inspection/ maintenance is prerequisite
TYPE OF PLATFORMS (FLOATER)
n SPAR:
– Concept of a large diameter single vertical cylinder supporting deck.
– These are a very new and emerging concept: the first spar platform, Neptune, was installed off the USA coast in 1997.
– Spar platforms have taut catenary moorings and deep draught, hence heave natural period is about 30 seconds.
– Used for Ultra deep water depth of 2300 M.
– The center of buoyancy is considerably above center of gravity , making Spar quite stable.
– Due to space restrictions in the core, number of risers has to be predetermined.
TYPE OF PLATFORMS (FLOATER)
n SHIP SHAPED VESSEL (FPSO)
– Ship-shape platforms are called Floating Production, Storage and Offloading (FPSO) facilities.
– FPSOs have integral oil storage capability inside their hull. This avoids a long and expensive pipeline to shore.
– Can explore in remote and deep water and also in marginal wells, where building fixed platform and piping is technically and economically not feasible
– FPSOs are held in position over the reservoir at a Single Point Mooring (SPM). The vessel is able to weathervane around the mooring point so that it always faces into the prevailing weather.
To be Cont....
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