Support structure for mudline suspension wellhead

• US 4,401,398 A
• Filed: 05/26/1981
• Issued: 08/30/1983
• Est. Priority Date: 05/26/1981
• Status: Expired due to Fees

• Current Assignee: BJ Services Co. USA (Baker Hughes Company)
• Original Assignee: Western Services International Incorporated
• Inventors: Remson, Donald R.
• Primary Examiner(s): Leppink, James A.
• Assistant Examiner(s): Hjorth, Beverly E.
• Application Number:
  US06/266,967
• Time in Patent Office: 826 Days
• Field of Search: 405/195, 405/201, 405/228, 405/203, 175/7, 175/9, 175/220, 166/367
• US Class Current: 405/201
• CPC Class Codes: E21B 15/003 adapted to be moved on their substructure, e.g. with skidding means; adapted to drill a plurality of wells
• CPC Class Codes: E21B 19/002 specially adapted for underwater drilling E21B19/09, E21B19/143 take precedence
• CPC Class Codes: E21B 7/136 from non-buoyant support E21B7/124 takes precedence

Abstract

A support structure (20) for supporting the freestanding portion of a mudline suspension wellhead includes first and second support arms (56) attached to and extending from an offshore drilling platform (24). The structure is aligned below a cantilevered type drilling derrick (40). A gantry (60) is supported by and slidable relative to these arms. A cradle structure (66) is mounted for lateral movement on the gantry. Structure is provided for positioning the gantry along the longitudinal length of the arms and for positioning the cradle along the longitudinal length of the gantry. Movement of the cradle structure relative to the gantry and of the gantry relative to the support arms defines a zone between the support arms and between the drilling platform and the outermost point of travel of the gantry in which the cradle may be selectively positioned. The gantry and cradle are aligned relative to the wellhead, and structure (290, 320) associated with the cradle is provided for clamping the wellhead thereto.

Claims

1. A structure for attachment to an offshore drilling platform for supporting the freestanding portion of a mudline suspension wellhead comprising:

first and second support arms attached to and extending from the platform, said arms being independently hingeable from said platform and movable from a stored position against said platform to a working position extending from said platform,

a gantry supported by and slidable relative to said arms when said arms are in the working position,

a cradle structure mounted for lateral movement on said gantry,

means for positioning said gantry along the longitudinal length of said arms when said arms are in the working position and for positioning said cradle along the longitudinal length of said gantry to selectively align said gantry and cradle structure relative to the wellhead, and

means associated with said cradle structure for clamping said wellhead.

2. The structure according to claim 1 wherein said means for moving said gantry includes:

sheave means mounted at the end of each said arm with first cable means extending from said gantry around said sheave means and to said platform,

second cable means attached between said gantry and said platform, and

means for drawing in said first and second cable means to move said gantry toward and away from said platform.

3. The structure according to claim 1 wherein said means for moving said cradle along the longitudinal length of said gantry includes:

sheave means mounted near the opposite ends of said gantry,

cable means having one end attached to said cradle and engaged around said sheave means, and

means for drawing the opposite end of said cable means to move said cradle along said gantry.

4. The structure according to claim 1 wherein said arms include an inwardly facing channel member, each said channel member forming an inwardly facing track, and wherein said gantry includes a plurality of rollers extending from the ends thereof for engagement within the tracks formed by said channels for movement along said channel members.

5. Structure for supporting a wellhead positioned to one side of a drilling platform, comprising:

a frame structure comprising first and second support arms independently hingeable to and extending from the platform,

a gantry supported by said frame structure and movable to and from said drilling platform by movement on said frame structure,

a cradle structure mounted for movement on said gantry substantially transverse to the movement provided by said gantry relative to said frame structure,

means for positioning said gantry relative to said frame structure and for positioning said cradle relative to said gantry to selectively align said cradle structure relative to the wellhead, and

means associated with said cradle structure for clamping said wellhead.

6. The structure according to claim 5 wherein said means for moving said gantry includes:

sheave means mounted at the end of each said arm with first cable means extending from said gantry around said sheave means and to said platform,

second cable means attached between said gantry and said platform, and

means for drawing in said cables to move said gantry toward and away from said platform.

7. The structure according to claim 5 wherein said means for moving said cradle along the longitudinal length of said gantry includes:

sheave means mounted near the opposite ends of said gantry,

cable means attached to said cradle and around said sheave means, and

means for drawing said cables to move said cradle along said gantry.

8. The structure according to claim 5 wherein said arms include an inwardly facing channel member, each said channel member forming an inwardly facing track, and wherein said gantry includes a plurality of rollers extending from the ends thereof for engagement within the tracks formed by said channels for movement along said channel members.

9. The structure according to claim 5 further comprising support cables for attachment between the ends of said gantry and the platform to provide lateral stability to said arms.

10. In a cantilevered type drilling rig wherein a drilling derrick is movable from a skidded in position over a main platform and a cantilevered position wherein the derrick is skidded out from the platform, a structure for supporting the wellhead of a drill string worked by the drill rig in its cantilevered position, comprising:

a frame structure comprising first and second support arms independently hingeable to and extending from the platform,

a gantry supported by said frame structure and slidable to and from said drilling platform by movement on said frame structure,

a cradle structure mounted for movement on said gantry transverse to the movement provided by said gantry relative to said frame structure,

means for positioning said gantry relative to said frame structure and for positioning said cradle relative to said gantry to relatively align said cradle structure relative to the wellhead, and

means associated with said cradle structure for clamping said wellhead.

11. The structure according to claim 10 wherein said means for moving said gantry includes:

sheave means mounted at the end of each said arm with first cable means extending from said gantry around and sheave means and to said platform,

second cable means attached between said gantry and said platform, and

means for drawing in said cables to move said gantry toward and away from said platform.

12. The structure according to claim 11 further comprising support cables for attachment between the ends of said gantry and said cradle storage structure to provide lateral stability to said arms.

13. The structure according to claim 10 wherein said means for moving said cradle along the longitudinal length of said gantry includes:

sheave means mounted near the opposite ends of said gantry,

cable means having an end attached to said cradle and around said sheave means, and

means for drawing the opposite end of said cable means to move said cradle along said gantry.

14. The structure according to claim 10 wherein said arms include an inwardly facing channel member, each said channel member forming an inwardly facing track, and wherein said gantry includes a plurality of rollers extending from the ends thereof for engagement within the tracks formed by said channels for movement along said channel members.

15. A structure for attachment to an offshore drilling platform for supporting the freestanding portion of a mudline suspension wellhead comprising:

a cradle storage structure mounted to said platform,

first and second support arms attached to and extending from said cradle storage structure, said arms being independently hingeable from said cradle storage structure for selectively hinging said arms against the drillingn platform,

a gantry supported by and slidable relative to said arms and receivable onto the cradle storage structure for storage thereof,

a cradle structure mounted for lateral movement on said gantry,

means for positioning said gantry along the longitudinal length of said arms and for positioning said cradle along the longitudinal length of said gantry to selectively align said gantry and cradle structure relative to the wellhead, and

means associated with said cradle structure for clamping said wellhead.

16. The structure according to claim 15 further comprising support cables for attachment between the ends of said gantry and said cradle storage structure to provide lateral stability to said arms.

17. A structure for attachment to an offshore drilling platform for supporting the freestanding portion of a mudline suspension wellhead comprising:

first and second support arms attached to and extending from the platform,

a gantry supported by and slidable relative to said arms,

cradle storage structure mounted between said platform and said arms, for receiving said gantry, said arms being hingeable from said cable storage structure for selectively hinging said arms against the drilling platform,

cradle structure mounted for lateral movement on said gantry,

means for positioning said gantry along the longitudinal length of said arms and for positioning said cradle along the longitudinal length of said gantry to selectively align said gantry and cradle structure relative to the wellhead,

means associated with said cradle structure for clamping said wellhead, and

a first stabilizing cable attached between the end of said gantry adjacent said second support arm and said cradle storage structure adjacent the point of attachment of said first arm to said storage structure and a second cable attached between the end of said gantry adjacent said first support arm and to said storage structure adjacent the attachment of said second arm to said storage structure.

18. A method for supporting the freestanding portion of a mudline suspension wellhead from an offshore platform having a cantilevered type drilling rig, comprising:

mounting a frame structure comprising first and second support arms independently hingeable to the platform below the cantilevered rig,

positioning the support arms such that the arms are in a woking position extending outwardly from the platform,

mounting a movable gantry for sliding engagement on the support arms,

mounting a slidable cradle structure on the gantry for movement along the longitudinal length of the gantry,

moving the gantry on the support arms toward and away from the platform to align the gantry with the wellhead,

moving the cradle on the gantry to align the cradle with the wellhead, and

clamping the wellhead within the cradle.

19. The method according to claim 18 further comprising:

applying a tension to the wellhead prior to clamping the wellhead in the cradle.