Offshore production system with drilling/workover rig

• US 20040244986A1
• Filed: 05/12/2004
• Published: 12/09/2004
• Est. Priority Date: 06/04/2003
• Status: Active Grant

• Current Assignee: Single Buoy Moorings of America Incorporated (Single Buoy Moorings)
• Original Assignee: Single Buoy Moorings of America Incorporated (Single Buoy Moorings)
• Inventors: Rosen, Leon D., Poldervaart, Leendert, Cann, Bram Van
• Granted Patent: US 7,172,479 B2
• Time in Patent Office: Days
• US Class Current: 166/367
• CPC Class Codes: B63B 21/507 with mooring turrets
• CPC Class Codes: E21B 19/004 supporting a riser from a drilling or production platform

Abstract

An offshore hydrocarbon production system includes a vessel (12) with a turret (16), and a fluid swivel (50) on the turret that is connected to risers (41-43) that extend to the sea floor (26), wherein a drilling/workover rig (60) on the vessel can lower tubing (65) toward the sea floor without danger that the tubing will wrap about the risers when the hull weathervanes. The rig is mounted on the turret. Pipes (54) that extend from the rotatable part of the fluid swivel to fittings (55) on the hull (14), are supported on a gantry (80) that is fixed to the hull and having a gantry middle portion (106) that extends over the turret. The gantry middle portion extends higher than the top (88) of the rig.

Claims

1. An offshore production system for use in a sea location over a sea floor (26), which includes a floating hull (14) rotatably connected to a turret (16) to allow the hull to rotate about a primarily vertical turret axis (18) about the turret, a mooring system (20) that moors the turret to the sea floor to limit turret rotation, a fluid swivel device (50, 50A) that has a plurality of fluid swivels that have rotatable swivel parts (85) that rotate with the hull about said turret axis and that have nonrotatable swivel parts (84) centered on said turret axis, a plurality of risers (41-43) extending from wells in the sea floor to the nonrotatable swivel parts, and a plurality of conduits (54, 54A) that extend from the rotatable swivel parts to the vessel hull, comprising:

a tubing-supporting rig (60, 134) mounted on said turret at a location horizontally spaced from said turret axis, to avoid rotation about the turret axis of the rig and of any tubing extending down from the rig toward the sea floor, with respect to the risers, to thereby prevent the tubing from wrapping about the risers as the hull weathervanes.

2. The system described in claim 1 including:

a gantry (80, 80A) fixed to said hull and having a portion (106, 144) extending high enough over said turret to lie above said rig;

said rotatable parts of said fluid swivel are supported on said gantry.

3. The system described in claim 2 wherein:

said turret has a top deck part (90, 130); and

including

a nonrotating structure (120) that extends upward from said top deck part to one of said nonrotatable parts of said fluid swivel device to prevent said nonrotatable parts from rotating.

4. The system described in claim 1 including:

at least one rotatable pipe (54, 54A) that extends from said rotatable part of said fluid swivel device to said hull (14);

a gantry (80) having opposite ends fixed to said hull at opposite sides of said turret, and having a middle (106) that supports said rotatable pipe, said middle having a portion that lies above said rig.

5. The system described in claim 1 wherein:

said rig has a primarily vertical tube-supporting rig axis (94) that is spaced from said turret axis (18);

said plurality of risers have parts (108) lying at a bottom of said turret, that are centered on a primarily vertical riser axis (92);

said turret has a periphery lying at a predetermined turret radius (R) from said turret axis;

said riser axis (92) is horizontally spaced from said rig axis (94) of said rig by at least said turret radius (R).

6. The system described in claim 5 wherein:

said turret has a top deck (90), and a plurality of said risers have upper ends (52a) lying at about the level of said turret top deck and extending primarily horizontally and away from said rig by a distance (D) of at least one-half the radius (R) of said turret to said rotatable swivel parts.

7. The system described in claim 1 including:

a manifold (122) on said turret, that has an input connected to a plurality of said risers and that has an output connected to a single one of said nonrotatable swivel parts.

8. The system described in claim 1 including:

a swivel output pipe (54) extending from the rotatable swivel part of one of said fluid swivels to said hull, said pipe having a part that lies over said turret at a greater height than a top (88) of said rig.

9. An offshore production system that includes a vessel hull (14), a nonrotatable turret (16) that is moored to the sea floor and that is supported on said hull by a bearing arrangement (110) that allows said vessel hull to weathervane about said turret about a turret axis (18), at least one fluid swivel device (50) with rotatable (85) and nonrotatable (84) swivel parts, and at least one riser (41-43) that extends up from the sea floor and through said turret to said nonrotatable swivel part, comprising:

a gantry (80, 80A) having an end (100, 102, 140) mounted on said vessel hull and having a gantry middle portion (106, 144) that lies over said turret, said rotatable swivel part lying above said turret deck and being attached to said gantry middle portion.

10. The system described in claim 9 including:

a tube-supporting rig (60, 134) mounted on said turret, said turret having a top deck (90) and said rig projecting a plurality of meters (B) above said turret top deck, the rig having a rig top (88, 132) lying a predetermined horizontal distance (E) from said turret axis;

said gantry middle portion has a gantry part lying above the height of said rig top above said turret top deck, so said gantry part moves over said rig top when the vessel hull weathervanes.

11. A method for use with a rig (60, 134) on a vessel (12) of an offshore production system wherein the vessel includes a hull (14) and a turret (16) mounted on the hull where the turret is moored to the sea floor and at least one riser (41-43) extends from about the sea floor to a fluid swivel (50, 50A) on the turret, wherein the fluid swivel includes a nonrotatable part (84) attached to the turret and a rotatable part (85) that is connected by a swivel output pipe (54) to a fitting (55) on the hull, and wherein the hull can weathervane about the turret, the method allowing the rig to lower a tube to about the sea floor without danger that the tube will wrap about the riser, if the riser or tube is not withdrawn when the vessel weathervanes, comprising:

mounting the rig on the turret;

mounting the swivel output pipe (54, 54A) so it extends above a top (88, 132) of the rig in its extension between the fluid swivel and the fitting (55) on the hull.

12. The method described in claim 11 including:

establishing a gantry (80) with ends (100, 102) that are fixed to said hull and with a gantry part (106, 144) that lies over said turret and that is fixed to said swivel output pipe, including positioning a gantry part that lies over said turret and that extends higher above said turret that said rig.