Multi-activity offshore drilling facility having a support for tubular string

• US 6,766,860 B2
• Filed: 02/22/2002
• Issued: 07/27/2004
• Est. Priority Date: 02/22/2002
• Status: Active Grant

• Current Assignee: Transocean Worldwide, Inc. (Transocean Limited)
• Original Assignee: Global Santa Fe Corporation (Transocean Limited)
• Inventors: Bruton, Paul, Archibald, William G.
• Primary Examiner(s): Pezzuto, Robert E.
• Assistant Examiner(s): Beach, Thomas A
• Application Number:
  US10/080,494
• Publication Number:
  US 20030159853A1
• Time in Patent Office: 886 Days
• Field of Search: 166/341, 166/343, 175/5, 175/85, 414/22.57, 414/22.63, 414/22.68
• US Class Current: 166/341
• CPC Class Codes: E21B 19/004 supporting a riser from a drilling or production platform
• CPC Class Codes: E21B 19/143 specially adapted for underwater drilling

Abstract

An offshore drilling rig contains a heavy-duty support cart that straddles the moonpool and rides on rails. A funnel-shaped hole extends through the support cart, and a cutout on one side of the cart provides lateral access to the hole. The cart can be moved to the region of the rotary assembly, where a length of tubulars can be suspended from the cart. For instance, when the BOP is pulled out for installation of the Xmas tree assembly, the BOP and attached riser can be pulled up above the seabed and hung from the support cart, then moved laterally out of the way while the Xmas tree assembly is installed. This lateral movement lowers the possibility of collision between the BOP and Xmas tree assembly. The BOP assembly can then be disassembled and at a later time, or hung until is needed for an adjacent borehole. In a preferred embodiment, the cart is included on multi-activity rigs with more than one load path, hoist, and rotary assembly.

Claims

1. A device for providing lateral separation between two adjacent strings of tubular assemblies suspended from an offshore drilling rig having a working area suspended above the surface of a body of water, comprising:

a heavy-duty cart from which a first tubular assembly can be suspended through a moonpool area, said first tubular assembly extending through said moonpool into said body of water; and

a rail assembly capable of carrying said heavy-duty cart;

ps wherein said cart may translate along said rail assembly to move said first tubular assembly away from a primary load path thereby altering lateral separation between said first tubular assembly and said primary load path so that a second tubular assembly may be advanced into the body of water along said primary load path.

2. The device of claim 1, wherein said cart has an opening through one side through which marine riser pipe can be inserted.

3. The cart of claim 1, wherein said cart can carry a load of greater than 100 metric tons.

4. The cart of claim 1, wherein said cart comprising a substantially rectangular base having an opening therethrough and wherein a side of said cart contains a passageway through which marine riser pipe can be inserted into said opening.

5. The device of claim 1, wherein said first tubular assembly comprises a blow-out protector (BOP) attached to a string of marine riser pipe.

6. An offshore drilling structure comprising:

a working area suspended above the surface of a body of water, said working area comprising a first deck having means for conducting drilling activities along a primary load path and a second deck positioned below said first deck, said second deck having an open moonpool area through which tubular assemblies may be extended from the first deck into said body of water;

a pair of rails positioned on opposing sides of said moonpool area; and

a cart, moveable on said rails, and operative for suspending a first tubular assembly over said moonpool area, said first tubular assembly comprising a blow-out protector (BOP) attached to a string of marine riser pipe;

wherein movement of said cart along said rails alters the lateral separation between said first tubular assembly and said primary load path allowing a second tubular assembly to be advanced along said primary load path.

7. The offshore drilling structure of claim 6, wherein said drilling structure is a semi-submersible drill rig.

8. The offshore drilling structure of claim 6, wherein said cart comprises a substantially rectangular base having an opening therethrough and wherein a side of said cart contains a passageway through which a length of pipe can be inserted into said opening.

9. The offshore drilling structure of claim 8, wherein said opening is substantially funnel-shaped.

10. The offshore drilling structure of claim 6, wherein said cart can carry a load greater than 100 mega-tons.

11. The offshore drilling structure of claim 6, wherein said first deck further includes more than one drilling station operative for conducting drilling activities along said primary load path, wherein a first drilling station comprises a first hoist, which is associated with a first load path and a first rotary table, and a second drilling station comprises a second hoist, which is associated with a second load path and a second rotary table.

12. A method for conducting drilling operations from an offshore structure having a working area suspended above the surface of a body of water, said method comprising the steps of;

advancing a first tubular assembly into said body of water from a first deck of said working area along a primary load path, wherein said first tubular assembly comprises a blow-out protector (BOP) attached to a string of marine riser pipe, and wherein said primary load path extends through an open moonpool area formed in a second deck of said working area to the seabed;

suspending a portion of said first tubular assembly from a cart that straddles said moonpool area, said cart including means for translating along a rail assembly attached to said second deck;

moving said portion of said first tubular assembly along said rail assembly to laterally separate said first tubular assembly from a second tubular assembly extending from said first deck of said working area to the seabed along said primary load path.

13. The method of claim 12, wherein said first tubular assembly comprises a blow-out protector (BOP) attached to a string of marine riser pipe.

14. The method of claim 12, wherein said second tubular assembly comprises a Xmas tree assembly.

15. The method of claim 12, wherein said offshore structure is a semi-submersible rig.