System for and method of restraining a subsurface exploration and production system

Abstract

A system for and method of limiting and controlling the unintended subsurface release of an exploration or production riser system is provided including one or more means for anchoring the riser or casing stack at one or more pre-determined points upon the length of the riser, and/or on the housing of an associated buoyancy chamber or the like, and/or on a particular portion of the riser as dictated by the operational environment, and/or on an anchor portion secured in the sea floor; and a network of restraining members disposed on the anchoring means. A lower anchoring portion includes one or more anchors disposed in communication with a wellhead, or with the sea floor or below the sea floor mud line, or with a well casing portion. A network of restraining members forms an essentially continuous connection from the buoyancy member portion to said bottom anchor portion. In a particular, though, non-limiting embodiment of the invention, a means for anchoring the system using pairs of anchors disposed at one or more predetermined points along the riser portion of the system is provided. Also disclosed is a variety of means and devices by which a surface vessel or a rig, etc., servicing a subsea well equipped with the present system may absorb or deflect impact forces originating from portions of the system that unexpectedly break free and rush upwards toward the surface vessel or rig.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an offshore exploration and production system in which a floating mobile offshore drilling unit is connected to an upper riser stack and a blowout preventer assembly; the blowout preventer assembly is in turn connected to a conventional self-standing casing riser. The self-standing casing riser employs a buoyancy device to support the casing riser from a sea-floor wellhead.

FIG. 2 is a side view of a self-standing casing riser employing a buoyancy device without an upper riser and blowout preventer assembly, wherein the casing riser is extended from a sea-floor wellhead, with a mobile offshore drilling or production unit or disposed overhead.

FIG. 3 is a side view of an offshore exploration and production system, with an upper riser and blowout preventer assembly, shown while undergoing catastrophic failure or release along a length of the casing riser, illustrated here by upward lines of force.

FIG. 4 is a side view of an offshore exploration and production system, depicted without an upper riser and blowout preventer assembly, undergoing catastrophic failure or unintentional release along the self-standing casing riser, further illustrating potential impact points of the buoyancy device into the overhead floating unit.

FIG. 5 is a side view of a self-standing casing riser employing a buoyancy device but without a riser and blowout preventer assembly, supporting the casing riser from a sea-floor wellhead, with an example of the restraining devices of the present invention.

FIG. 6 is a side view of an offshore exploration and production system in which a floating mobile offshore unit is connected to an upper riser and blowout preventer assembly, which is, in turn, connected to a self-standing casing riser. In an example of the present invention, both the floating unit and the self-standing casing riser employ independent restraining and control systems.

FIG. 7 is a side view of an offshore exploration and production system in which a floating mobile offshore drilling or production unit is mechanically connected to an upper riser and blowout preventer assembly; the blowout preventer assembly is in turn connected to a self-standing casing riser. In a further example of the present invention, one or more restraining and control devices are connected between the floating unit and the upper riser.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a method for restraining and, at least to some degree, controlling the unintended subsurface release of exploration and production riser systems, in which the method comprises the steps of disposing one or more means for anchoring a riser system to either the sea floor or an underwater wellhead system; and disposing a network of associated restraining members in communication with the anchoring means.

Also provided is a system for restraining and controlling the unintended subsurface release of a riser system, the system generally comprising one or more restraining elements disposed along the length of the riser stack at predetermined points along the sea floor or beneath the mud line.

Also disclosed is a system for and method of restraining and controlling the unintended subsurface release of a subsurface riser system, in which a receiving station having one or more means for absorbing or deflecting force carried by an unintentionally released system component is disposed in a fluid transport system.

Claims

1. A method for restraining the release of a subsurface riser system, said method comprising the steps of: disposing one or more anchoring members at one or more predetermined points along a length of said riser system; anddisposing one or more restraining members in communication with said one or more anchoring members.

2. The method of claim 1, wherein said step of disposing one or more anchoring members further comprises a step of disposing one or more anchoring members in communication with an associated buoyancy member.

3. The method of claim 2, wherein said step of disposing one or more anchoring members further comprises a step of disposing one or more anchoring members on at least one surface of said buoyancy member.

4. The method of claim 2, wherein said step of disposing one or more anchoring members further comprises a step of disposing one or more anchoring members on at least one longitudinal portion of an upper riser segment disposed above said buoyancy member.

5. The method of claim 2, wherein said step of disposing one or more anchoring members further comprises a step of disposing one or more anchoring members on at least one longitudinal portion of a lower riser segment disposed beneath said buoyancy member.

6. The method of claim 1, wherein said step of disposing one or more anchoring members further comprises a step of disposing one or more anchoring members on at least one portion of an associated well casing.

7. The method of claim 1, wherein said step of disposing one or more anchoring members further comprises a step of disposing one or more anchoring members on at least one portion of an associated sea floor.

8. The method of claim 7, wherein said step of disposing one or more anchoring members further comprises a step of disposing one or more anchoring members on at least one portion of the sea floor disposed beneath the mud line.

9. The method of claim 1, wherein said step of disposing one or more restraining members further comprises a step of disposing a restraining member between a first predetermined point and a second predetermined point disposed along a length of the riser system.

10. The method of claim 1, wherein said step of disposing a restraining member further comprises a step of disposing at least one restraining member between a buoyancy member and a predetermined point along a length of said system.

11. The method of claim 1, wherein said step of disposing one or more restraining members further comprises a step of disposing at least one restraining member between a predetermined point along a length of said riser system and a wellhead disposed in communication with said system.

12. The method of claim 1, wherein said step of disposing one or more restraining members further comprises a step of disposing at least one restraining member between a predetermined point along a length of said riser system and a predetermined point disposed beneath a wellhead associated with said system.

13. The method of claim 1, wherein said step of disposing one or more restraining members further comprises a step of disposing at least one restraining member between a predetermined point along a length of said riser system and a predetermined point disposed beneath the sea floor mud line.

14. The method of claim 1, wherein said step of disposing one or more anchoring members further comprises a step of disposing at least one anchoring member between a first predetermined point and a second predetermined point located along one or more lengths of said riser system, wherein said first predetermined point and said second predetermined point are disposed in functionally close proximity to one another, thereby constituting an effective anchoring pair.

15. The method of claim 14, wherein said step of disposing one or more restraining members further comprises a step of disposing at least one additional restraining member between said first predetermined point and said second predetermined point of said anchoring pair.

16. A system for restraining the release of a subsurface riser system, said system comprising: one or more anchoring members disposed at one or more predetermined points along a length of said riser system; andone or more restraining members disposed in communication with said one or more anchoring members.

17. The system of claim 16, wherein said system further comprises one or more anchoring members disposed in communication with an associated buoyancy member.

18. The system of claim 17, wherein said system further comprises one or more anchoring members disposed on at least one surface of said buoyancy member.

19. The system of claim 17, wherein said system further comprises one or more anchoring members disposed on at least one longitudinal portion of an upper riser segment disposed above said buoyancy member.

20. The system of claim 17, wherein said system further comprises one or more anchoring members disposed on at least one longitudinal portion of a lower riser segment disposed beneath said buoyancy member.

21. The system of claim 16, wherein said system further comprises one or more anchoring members disposed on at least one portion of an associated well casing.

22. The system of claim 16, wherein said system further comprises one or more anchoring members disposed on at least one portion of an associated sea floor.

23. The system of claim 22, wherein said system further comprises one or more anchoring members disposed on at least one portion of the sea floor disposed beneath the mud line.

24. The system of claim 16, wherein said system further comprises at least one restraining member disposed between a first predetermined point and a second predetermined point disposed along a length of the riser system.

25. The system of claim 16, wherein said system further comprises at least one restraining member disposed between a buoyancy member and a predetermined point along a length of said system.

26. The system of claim 16, wherein said system further comprises at least one restraining member disposed between a predetermined point along a length of said riser system and a wellhead disposed in communication with said system.

27. The system of claim 16, wherein said system comprises at least one restraining member disposed between a predetermined point along a length of said riser system and a predetermined point disposed beneath a wellhead associated with said system.

28. The system of claim 16, wherein said system further comprises at least one restraining member disposed between a predetermined point along a length of said riser system and a predetermined point disposed beneath the sea floor mud line.

29. The system of claim 16, wherein said system further comprises at least one anchoring member disposed between a first predetermined point and a second predetermined point located along one or more lengths of said riser system, wherein said first predetermined point and said second predetermined point are disposed in functional proximity to one another, thereby constituting an effective anchoring pair.

30. The system of claim 29, wherein said system further comprises at least one additional restraining member disposed between said first predetermined point and said second predetermined point of said anchoring pair.