Hydraulic and earth engineering – Marine structure or fabrication thereof – With work deck vertically adjustable relative to floor
Patent
1992-01-14
1994-02-22
Taylor, Dennis L.
Hydraulic and earth engineering
Marine structure or fabrication thereof
With work deck vertically adjustable relative to floor
405203, 405227, 52725, 527263, E02B 1700
Patent
active
052881741
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a jackable oil rig designed for operations at large ocean depths, and comprising at least one leg and a deck with a jack system, the leg (or the legs) comprising a number of corner columns together with transverse stays, and where each corner column comprises a substantially annular outer pipe in which a substantially annular inner pipe is arranged, and the annular space between the inner wall of the outer pipe and the outer wall of the inner pipe is filled with a hardenable material such as concrete, capable of transferring forces between the pipes, the outer diameter of the outer pipe being approximately constant over the whole length of the column. The oil rig according to the present invention is especially suitable for operations at ocean depths down to 200 meters.
The present invention also relates to a corner column. The invention thus has particular application to jackable platforms which are employed especially as service platforms for more localized rigs, but can also be used for boring and the production of oil and gas.
For the extraction of oil and gas at sea it is usual to employ jackable platforms. Such platforms usually have three or more independent legs which can stand at varying depths of water. At shallower ocean depths such as in the Gulf of Mexico it is usual that the platforms stand at from 20 to 60 meters, and the platform legs are often anchored on the bottom by means of steel and concrete bases, (mat support rig). With such bases the jackable platforms are braced and have better fatigue properties.
In the region of the North Sea, jackable platforms have been used for depths of up to 80-90 meters. In this region, however, the environment is much harsher and the platform constructions are therefore stronger than in the Gulf of Mexico.
The jackable platforms can be moved from place to place within the operational water depths in so far as such occur with floating platforms and drilling ships. The jackable platforms stand however fastened to the bottom and are therefore much less exposed to movements, something which is especially important for the connection of the boring and production pipes between the bottom of the ocean and the deck of the platform. Consequently, it is simpler to carry out the necessary operations in the well such as different measurements, logging, washing and other maintenance from a jackable rig. When the boring and production pipes are coupled up, there is less danger of disruptions by virtue of bad weather than for floating platforms.
Besides, jackable platforms are cheaper to produce than floating platforms since the shape of the hull is simple and since there are employed as a rule well developed, well tested and reasonable jack systems, and in addition it is not necessary to mount anchoring systems. Thereby the running of the platform also becomes more reasonable.
Most jackable platforms have the drilling rig placed on a projection on the deck. This allows the platform to move the drilling rig in over another permanent platform so that the drill stem can be guided through its structure. Consequently, the permanent platform does not need to have its own boring equipment since it will then pay to hire in the drill work from a special platform in preference to supplying the permanent platform with equipment which has a much shorter service life. However, heavy demands are placed on the relative movements between a permanent platform and the jackable platform because these are generally connected with rigid drill pipes, production pipes and others. Such problems increase with increasing depths of water since the jackable platforms have larger deflections than the specially constructed permanent platforms.
Several jackable platforms have moreover been reconstructed in order to be able to produce oil and gas directly, and since the type of platform is mobile, such reconstructions can be easily carried out on land and also the rig can be moved without any problems to a new field after the oil field is empty.
The main problem with
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Foss Gunnar
Kjersem Geir L.
Rundhovde Sture
Hand Francis C.
Offshore Innovation Limited A/S
Taylor Dennis L.
LandOfFree
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