Swivel device

Ships – Mooring device – Having ship-mounted turret

Reexamination Certificate

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Details

C441S005000

Reexamination Certificate

active

06302048

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a swivel device for use in a ship equipped for carrying out production/ drilling, etc., in connection with submarine oil/gas wells, said ship being formed with a vertically through-going shaft accommodating a turret rotatably mounted to the ship's hull around a vertical rotational axis, about which the ship may turn when the turret is moored to the seabed by means of anchor lines, preferably in the form of mooring chains.
Through the shaft which is surrounded by the turret, it is possible to lower down and draw up a riser production tubing string, and at a lowermost shaft portion widened through a conical transition portion it is possible to accommodate a so-called STL-buoy which is an immersed buoyancy body moored to the seabed and having transition pieces for risers each extending to a well head.
In the mooring arrangement of the turret, at least one mooring chain might be included, said mooring chain having a fixed length and, for the attachment of its upper end to the turret, is assigned an attachment hook, the other chains included in the mooring arrangement having changeable length and each being assigned thereto a guide pulley at the level of the hook(s) and, preferably, also an individual winch disposed at a higher level than the attachment hook(s) as well as an individual locking means for locking the respective, longitudinally changeable mooring chain in stretched, tensioned, shortened condition.
The turret may, in addition to its rotatable mounting around a vertical axis, be raisable/lowerable for temporarily uncovering and making available underlying structure, e.g. said attachment hooks for some of the mooring chains.
The turret's mounting device for the relative rotatability between ship and turret may, intermediate ship's hull and turret, comprise an upper combined roller-ball bearing and a lower roller bearing, each roller having a vertical axis.
Alternatively to a physical mooring to the seabed, the ship may be positioned on the field through so-called dynamic positioning as previously known.
SUMMARY OF THE INVENTION
By means of the present invention one has aimed at, through simple means, to provide a swivel device adapted to put a ship of the kind described above in a position to carry out production as well as drilling, possibly simultaneously.
In accordance with the invention, this object is realized by means of a swivel device distinguishing itself through the features as defined in the claims.
According to the invention, spaced radially inwardly of the turret, within said vertically through-going shaft, is disposed a first pipe substantially concentrically with the turret, the outside of said first pipe together with the inner side of the turret defining a vertically through-going annulus for the accommodation of a larger or smaller number of production risers, vertically directed passage possibility for drill pipes being available in the central bore of the first pipe.
If one wishes to have a possibility of connecting the shop temporarily to a STL buoy which, for its connection to the ship, requires a cavity therein having an upwardly conically tapering cavity portion in the bottom of said vertically through-going shaft, such a tapering portion may be formed from the end of a second pipe taking a substantially concentrical positioning within said first pipe. In this case, it is the bore of said second pipe that forms the central, separate passage possibility for drill pipe(s) and downhole accessories. Vertically above the vertically through-going shaft, the ship will normally be equipped with a rig structure in which a top driven rotary system for a drilling string is disposed.


REFERENCES:
patent: 4305341 (1981-12-01), Stafford
patent: 4436048 (1984-03-01), Gentry et al.
patent: 4648848 (1987-03-01), Busch
patent: 4698038 (1987-10-01), Key et al.
patent: 4701143 (1987-10-01), Key et al.
patent: 5359957 (1994-11-01), Askestad
patent: 5755607 (1998-05-01), Boatman et al.
patent: 5823837 (1998-10-01), Boatman et al.
patent: 5860840 (1999-01-01), Boatman et al.
patent: 6014939 (2000-01-01), Gusmeri et al.
patent: 371668 (1990-06-01), None
patent: 2118903 (1983-11-01), None
patent: 2285028 (1995-06-01), None

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