l2-floating platforms [compatibility mode]

7/28/2019 L2-Floating Platforms [Compatibility Mode]

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Lecture 2Floating Platforms & Drilling Rigs

Arun S Chandel

[email protected]

09997200339

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FLOATING

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Stability of Floating Vessels

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Tension Leg Platform (TLPs)

¾ Tension Leg Platforms (TLPs)are floating facilities that are tieddown to the seabed by verticalsteel tubes called tethers.

¾ This characteristic makes the

direction and very flexible in thehorizontal plane.

e ver ca r g y e ps o ein wells for production, while, thehorizontal compliance makes the

latform insensitive to the

primary effect of waves.

¾ Have large columns and

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.



Tension Leg Platform (Contd.)

¾ TLP has excess buoyancy whichkeeps tethers in tension.

to side movement (up to 20 feet),with little vertical movement.

¾ Topside facilities, no. of risers etc.have to fixed at pre- design stage.

.

¾ It has no integral storage.

¾ It is sensitive to topside load.

¾ Variations as tether tensions are

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.



Tension Platform

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SPAR

¾ Concept of a large

cylinder supporting deck.

¾ These are a very new and

spar platform, Neptune, wasinstalled off, was installed off the USA coast in 1997.

¾A spar is a deep-draftfloating caisson, which is ahollow cylindrical structure

similar to a very large buoy.Its four major systems arehull, moorings, topsides, and

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SPAR Platform (Contd.)

¾ The number of wells, surface wellhead spacing, and facilities weightdetermine the size of the centerwell and the diameter of the hull.

¾ In the classic or full c linder hull forms the u er section iscompartmentalized around a flooded centerwell containing the differenttype of risers. This section provides the buoyancy for the spar.

for oil storage.

¾ The bottom section (keel) is compartmentalized to provide buoyancy- , .

¾ The topsides configurations follow typical fixed platform designpractices. The decks can accommodate a full drilling rig (3,000 hp) or a

wor over rig -1, p p us u pro uction equipment. Pro uctioncapacities range up to 100,000 BOPD and 325 MMscfgpd.

¾ Installation is performed in stages similar to those of other deepwater

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production systems, where one component is installed while another is

being fabricated. Installation schedules heavily depend upon thecompletion status of the hull and topsides.



SPAR Characteristics

-Applicable in 1,500 ft. to 10,000 ft. water depths

-Cost relatively insensitive to water depth, most competitive in very deep water

-Hull cost is relatively insensitive to deck payload

-Platform motions are mostly lateral (minimal heave)

-Uses standard shipyard and offshore deck construction

-Hull is initially transported by towing in a horizontal, self-floating position

-Wells can be pre-drilled or drilled from the platform

-Production risers are steel pipe with surface trees

-Hull can be configured for significant liquids storage if this is advantageous

-Particularly applicable in remote locations which lack infrastructure

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-Economical to relocate to other sites, in both deeper and shallower water



Ship shaped vessel (FPSO)

¾ Ship-shape platforms are calledFloating, Production, Storage and

¾FPSOs have integral oil storagecapability inside their hull. This

avoids a long and expensivepipeline to shore.¾ Can explore in remote and deep

water and also in marginal wells,

piping is technically andeconomically not feasible FPSOsare held in osition over the

reservoir at a Single Point Mooring(SPM).¾ The vessel is able to

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weat ervane aroun t e moor ngpoint so that it always faces intothe prevailing weather.



Ship shaped vessel (FPSO)



DRILLING RIGS

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Self Elevating Jack-ups

¾ Primarily used for drillingoperations.

sometimes rectangular, shapedbox section barge fitted with three(sometimes four) moveable legswhich enable the vessel to standon the sea bed.

¾Can work in water depths of .

¾Transported in long sea passagesusing submersible heavy lift ships.¾Thrusters unit enable the vessel

to maintain position whilst thelegs are lowered to the sea bedand the hull is jacked into

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pos t on, c ear o wave act on.



Self Elevating Jack-ups

¾ The base of each leg is fittedwith a “SPUD CAN” whichcons s s o a p a e or s

designed to spread the load andprevent over penetration of the

.

¾ High pressure jets of water or

compressed air may be used toremove loose debris in thevicinity of the spud cans whilstthe legs are manoeuvred into

,as “SPUDDIND IN”.

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Drilling Barges

¾ Drilling barges are usedmostly for inland, shallow water

r ng. s yp ca y a es

place in lakes, swamps, rivers,and canals.

¾ Drilling barges are large,floating platforms, which must

be towed by tugboat fromlocation to location.

¾ Suitable for still, shallow

,able to withstand the watermovement experienced in largeo en water situations.

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Drillships

¾ Ships designed to carry outdrilling operations. These boatsare specially designed to carrydrilling platforms out to deep-sea

locations.

,addition to all of the equipmentnormally found on a large ocean

ship, a drilling platform anderr c oca e on e m e o

its deck.

¾In addition drillshi s contain a

hole (or 'moonpool'), extendingright through the ship downthrough the hull, which allow for

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the boat, down into the water.



Drillships

¾ Drillships are often used to drillin very deep water, which canoften be quite turbulent.

¾ Drillships use what is known as'dynamic positioning' systems.

¾ Drillships are equipped withelectric motors on the underside

of the ships hull, capable of prope ng e s p n anydirection. These motors areintegrated into the shipscom uter s stem which uses

satellite positioning technology, inconjunction with sensors locatedon the drilling template, to ensure

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drill site at all times.



Semi Submersible Rigs

¾ Semisubmersible rigs are the mostcommon type of offshore drilling rigs,combining the advantages of su mers e r gs w t t e a ty to r

in deep water.

¾ Semisubmersible rigs work on theprinciple of 'inflating' and 'deflating' of its lower hull. Topside facilities , no. of

risers etc. have to fixed at pre-designsta e.

¾ Semi-submersibles are held in placeby anchors connected to a catenary

. ,

combined with the submerged portionof the rig, ensure that the platform isstable and safe enough to be used in

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ur u en o s ore wa ers.




¾ Used for Ultra deep water.

¾These rigs consist of platforms

with two hulls positioned on topof one another.

¾ The upper hull contains theliving quarters for the crew, as well

as the actual drilling platform.

¾ The lower hull works much likethe outer hull in a submarine -

from one place to another, thelower hull is filled with air - makingthe entire rig buoyant.

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¾ When the air is let out of the lowerhull, the rig does not submerge to

. ,

partially submerged, but still floatsabove the drill site.

¾When drilling, the lower hull, filledwith water, provides stability to the

rig. Semisubmersible rigs can be

than the rigs mentioned above.

¾ Column pontoon junctions and

rac ng attract arge oa s.

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An d Fi n a l l y …. .

22DEEPWATER HORIZON!

l2-floating platforms [compatibility mode]

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