WELLHEAD LOAD RELIEF DEVICE

Abstract

A wellhead load relief device for reducing riser system induced load effects on a subsea wellhead and a method of installing a subsea wellhead assembly onto a subsea wellhead using the wellhead load relief device. The wellhead load relief device includes: a receptacle for receiving well control equipment, wherein the receptacle has an open top to permit the well control equipment to be received in the receptacle; and an adjustable support mechanism for rigidly supporting well control equipment received in the receptacle. The adjustable support mechanism is located within the receptacle and the adjustable support mechanism has a lateral extent that is adjustable relative to the receptacle. The wellhead load relief device is for providing a load path for forces exerted on the well control equipment to the seabed without going via the subsea wellhead. A subsea wellhead assembly including the wellhead load relief device is also provided.

Claims

1. A wellhead load relief device for reducing riser system induced load effects on a subsea wellhead, the wellhead load relief device comprising: a receptacle for receiving well control equipment, wherein the receptacle has an open top to permit the well control equipment to be received in the receptacle; and an adjustable support mechanism for rigidly supporting the well control equipment received in the receptacle wherein the adjustable support mechanism is located within the receptacle of the wellhead load relief device and wherein the adjustable support mechanism has a lateral extent that is adjustable relative to the receptacle, and wherein the wellhead load relief device is for providing a load path for forces exerted on the well control equipment to the seabed without going via the subsea wellhead.

2. A wellhead load relief device according to claim 1, wherein the adjustable support mechanism is adjustable to change the minimum inner dimension of the receptacle.

3. A wellhead load relief device according to claim 1, wherein the adjustable support mechanism comprises adjustable support elements, and the adjustable support elements comprise beams.

4. (canceled)

5. A wellhead load relief device according to claim 3, wherein each adjustable support element is opposite another support element, and the adjustable support elements are provided at or towards the corners of the receptacle.

6. (canceled)

7. A wellhead load relief device according to claim 3, wherein the adjustable support elements are arranged so that at least some of the adjustable support elements are adjusted together by a single adjustment mechanism, and wherein each adjustable support element is arranged so that it can be adjusted using a remote operated vehicle.

8. (canceled)

9. A wellhead load relief device according to claim 1, wherein the wellhead load relief device comprises a plurality of connectors for latching the wellhead load relief device to a foundation, and wherein the connectors are attached to the receptacle near the bottom of the receptacle.

10-11. (canceled)

12. A wellhead load relief device according to claim 1, wherein the receptacle has an adjustable height.

13. A wellhead load relief device according to claim 1, wherein receptacle has a top part and a bottom part, wherein the top part can be moved relative to the bottom part, wherein the receptacle comprises a telescopic connection between the top and bottom parts that permits the height of the receptacle to be adjusted, and wherein the wellhead load relief device comprises an actuator that can be used to control the extension and retraction between the top part and bottom part of the receptacle.

14-15. (canceled)

16. A wellhead load relief device according to claim 1, wherein the wellhead load relief device comprises a guide for guiding well control equipment into an appropriate position for being lowered into the receptacle and/or guiding the well control equipment into the receptacle, wherein the guide comprises a receptacle extension that extends from and above one side of the receptacle, and wherein the receptacle extension is for guiding the well control equipment into a suitable location above the receptacle to then be lowered into the receptacle.

17. (canceled)

18. A subsea wellhead assembly, the assembly comprising: the wellhead load relief device according to claim 1; a subsea wellhead; and well control equipment attached to the subsea wellhead and located within the receptacle, wherein the adjustable support mechanism supports the well control equipment within the receptacle.

19. A subsea wellhead assembly according to claim 18, wherein the assembly comprises a foundation that is connected to the seabed, and the wellhead load relief device is connected to the foundation.

20. (canceled)

21. A subsea wellhead assembly according to claim 18, wherein brackets are mounted on the well control equipment and are for being the contact points on the well control equipment for the adjustable support mechanism.

22. A subsea wellhead assembly according to claim 18, wherein the well control equipment is a blowout preventer (BOP).

23. A method of installing a subsea wellhead assembly, the method comprising: providing a wellhead load relief device according to claim 1; connecting the wellhead load relief device to the seabed; locating well control equipment within the receptacle; attaching the well control equipment to a subsea wellhead; and adjusting the adjustable support mechanism until it supports the well control equipment within the receptacle.

24. A method of installing a subsea wellhead assembly according to claim 23, wherein adjusting the adjustable support mechanism comprises adjusting the elevation of the adjustable support mechanism relative to the well control equipment and adjusting the lateral position of the adjustable support mechanism.

25. A method of moving well control equipment from a first wellhead to a second wellhead, the method comprising: providing a subsea wellhead assembly comprising a first wellhead, well control equipment mounted on the first wellhead; and a wellhead load relief device according to claim 1; wherein the wellhead load relief device is connected to the seabed; disconnecting the wellhead load relief device from the seabed; disconnecting the well control equipment from the well head; moving the wellhead load relief device with the well control equipment located therein to above a second wellhead; connecting the well control equipment to the second wellhead; and reconnecting the wellhead load relief device to seabed.

26. A method of moving well control equipment from a first wellhead to a second wellhead according to claim 25, wherein the method comprises retracting a lower part of the receptacle relative to the top part before moving the wellhead load relief device to be above a second wellhead.

27. A method of moving well control equipment from a first wellhead to a second wellhead according to claim 25, wherein the method comprises releasing the adjustable support mechanism before the well control equipment is released from the first wellhead and reactivating the adjustable support mechanism after the well control equipment has been attached to the second wellhead.

28. A method of uninstalling well control equipment, the method comprising: providing a subsea wellhead assembly comprising a wellhead, well control equipment mounted on the first wellhead; and a wellhead load relief device according to claim 1, wherein the wellhead load relief device is connected to the seabed; disconnecting the wellhead load relief device from the seabed; disconnecting the well control equipment from the wellhead; and retrieving the well control equipment to the surface; and retrieving the wellhead load relief device to the surface.

29. A method of uninstalling well control equipment according to claim 28, wherein the well control equipment is retrieved to the surface separately to the wellhead load relief device, or wherein the well control equipment is retrieved to the surface together with the wellhead load relief device.

30. (canceled)

Description

[0167] Certain preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0168] FIG. 1 shows a subsea wellhead assembly comprising a wellhead load relief device;

[0169] FIGS. 2 and 3 show a wellhead load relief device;

[0170] FIG. 4 shows a plan view of another wellhead load relief device;

[0171] FIGS. 5 to 10 illustrate a method of installing a subsea wellhead assembly comprising the wellhead load relief device;

[0172] FIGS. 11 and 12 illustrate a method of moving well control equipment from a first wellhead to a second wellhead using a wellhead load relief device; and

[0173] FIGS. 13 to 16 illustrate methods for locating the well control equipment within the wellhead load relief device.

[0174] FIG. 1 shows a subsea wellhead assembly 1. This exemplary assembly 1 comprises four wellheads 2. The wellheads are surrounded by a common foundation, e.g. template 4. On the rightmost wellhead 2 is located a subsea well control equipment, in this case a blowout preventer (BOP) 6. The BOP 6 is located and supported within a wellhead load relief device 8.

[0175] This wellhead load relief device 8 is shown in more detail in FIGS. 2 and 3. The wellhead load relief device 8 comprises a receptacle, e.g. frame, 10 that is made up of an upper part 12 and a lower part 14. The upper part 12 and the lower part 14 are movable relative to each other by means of a telescopic connection between the two parts 12, 14.

[0176] FIG. 2 shows the receptacle 10 in a retracted position and FIG. 3 shows the receptacle in an extended position.

[0177] The wellhead load relief device 8 comprises an adjustable support mechanism. In this example the adjustable support mechanism comprises eight support elements 16 in the form of extendable and retractable arms 16.

[0178] These arms 16 are for contacting and supporting well control equipment 6 received in the receptacle 10 of the wellhead load relief device 8. Each arm 16 can be extended and retracted by use of an ROV.

[0179] The wellhead load relief device 8 also comprises four support pads 18 that are for contacting and supporting the wellhead load relief device 8 on a subsea template 4. The wellhead load relief device 8 also comprises four connectors 20 that are for latching the wellhead load relief device 8 to the template 4 (or some other means/structure that provides a load path to the seabed). The support pads 18 and connectors 20 are used to provide a rigid connection between the wellhead load relief device 8 and the seabed (in this case via the template 4) so that loads can be efficiently transferred from the well control equipment 6 to the template 4 and ultimately into the seabed rather than being directed into the wellhead 2.

[0180] FIG. 4 shows in plan view another exemplary wellhead load relief device 8′. In this example the adjustable support mechanism is provided by two opposite transverse beams 17 that are adjustable in the X-direction. Each transverse beam 17 moves in an opposite direction to the other beam 17 such that when they are moved they move towards or away from each other.

[0181] Each transverse beam 17 comprises two lateral supports 19 that are each independently movable in the Y-direction which is perpendicular to the X-direction. The lateral supports 19 are integrated into the respective transverse beams 17.

[0182] The transverse beams 17 are driven by the same adjustment mechanism, in this case by synchronised worm gears 21.

[0183] The lateral supports 19 are arranged to be driven individually.

[0184] All of the beams and supports 17, 19 may be operated by a ROV class 4 torque tool.

[0185] The device 8′ comprises fixed beams 23 that form part of the receptacle and that provide support and housing for the adjustment means for the transverse beams 17.

[0186] Whilst the remaining figures show an assembly with a device 8 as shown in FIGS. 2 and 3, the assembly could alternatively comprise a well head load relief device of the type shown in FIG. 4, or any other wellhead load relief device with a receptacle and adjustable support members.

[0187] FIGS. 5 to 10 show an exemplary installation method.

[0188] FIG. 5 shows the wellhead load relief device 8 (before the well control equipment 6 is located in the receptacle 10) being lowered by means of a lifting wire 22 connected to a lifting device 24 that is latched onto the receptacle 10. The wellhead load relief device 8 is lowered to a location above the wellhead 2 and then is guided by means of guide posts 26 down onto the template 4 until the wellhead load relief device 8 contacts the template 4 as shown in FIG. 6. The wellhead load relief device 8 may then be latched to the template 4 by the connectors 20 using ROVs. At that point the lifting device 24 may be disconnected from the receptacle 10 and lifted away by the lifting wire 22.

[0189] Once the wellhead load relief device 8 has been latched onto the template 4 well control element 6 can be installed in the receptacle 10 of the wellhead load relief device as shown in FIGS. 7 to 10.

[0190] The well control element (e.g. BOP 6) may be lowered in a known manner until it is just above the height of the top of the receptacle 10 as shown in FIG. 7. The well control element 6 may then be moved laterally above the height of the top of the receptacle 10 until it contacts a receptacle extension 28 as shown in FIG. 8.

[0191] The BOP 6 may then be lowered into the receptacle 10 as shown in FIGS. 9 and 10. Once inside the receptacle 10 the BOP 6 may be connected to the wellhead 2 by connector 30. The support mechanism 16, 17, 19 may be adjusted until it contacts and supports the BOP 6 mounted within the device 8, 8′.

[0192] After the BOP 6 has been installed, if desired the receptacle extension 28 may be removed.

[0193] FIGS. 11 and 12 illustrate a method of using the wellhead load relief device 8 to move the well control equipment 6 from one wellhead 2 to another wellhead 2.

[0194] The method may comprise disconnecting the wellhead load relief device 8 from the template 4 and disconnecting the well control equipment 6 from the well head 2. These steps may be performed in either order or simultaneously.

[0195] The wellhead load relief device 8 may then be lifted with the BOP 6 within the receptacle 10 and moved laterally until the wellhead load relief device 8 with the well control equipment 6 located therein is above a second wellhead 2.

[0196] The protective cover 32 may then be placed back on the template 4 over the first wellhead 2 and the protective cover 34 may be taken off the template 4 to expose the second wellhead 2.

[0197] The wellhead load relief device 8 may then be lowered towards and onto the second wellhead 2. The method may then comprise connecting the wellhead load relief device 8 to the foundation 4 at a position located about the second wellhead 2 and connecting the well control equipment 6 to the second wellhead 2.

[0198] FIGS. 13 to 16 show schematically some alternative arrangements for guiding the well control equipment 6 into the receptacle 10 of the wellhead load relief device 8.

[0199] FIG. 13 shows a receptacle extension 28 that has already been described in relation to FIGS. 5 to 12.

[0200] FIG. 14 shows an arrangement with a funnel 36 that is movable (e.g. slidable) in the axial direction of the wellhead load relief device 8. During installation, the funnel 36 may be located towards the top of the wellhead load relief device 8 to receive a bottom part (e.g. connector 30) of the subsea well control equipment 6. Once part of the wellhead control equipment 6 is received in the funnel 36, the funnel 36 may be lowered into the receptacle 10 and thereby lowering and guiding the well control equipment 6 into the receptacle 10 of the wellhead load relief device 8.

[0201] The guide may comprise one or more foldable latch arms 38 as shown in FIG. 15. During installation, these arms 38 may be located upwards out of the receptacle 10 and may be arranged to receive and attach to a bottom part of the subsea well control equipment 6. Once part of the well control equipment 6 is received by the foldable latch arms 38, the arms may be retracted/collapsed into the receptacle 10 to thereby lower and guide the well control equipment 6 into the receptacle 10 of the wellhead load relief device 8. Guide wires may be threaded through the foldable latch arms 38 to aid in guiding the well control equipment 6 into the receptacle 10.

[0202] As shown for example in FIG. 16, the receptacle 10 may be have an access on one side that allows the well control equipment 6 to be guided in laterally into the receptacle 10 rather than lowering it axially into the receptacle 10. In this case the wellhead load relief device 8 may comprise bumpers 40 on the side of the receptacle 10 opposite the access opening so as to cushion the contact of the well control equipment 6 on the side of the receptacle opposite the access opening. Once the well control equipment 6 contacts the bumpers 40 the well control equipment may be lowered further so it can be latched to a wellhead 2.