GB2193520A

GB2193520A - Well-head sealing

Info

Publication number: GB2193520A
Application number: GB08714780A
Authority: GB
Inventors: David James Armstrong; Cecil Claude Goonetilleke; Charles Sterling Johnson
Original assignee: NAT OILWELL; National Oil Well
Current assignee: NAT OILWELL; National Oil Well
Priority date: 1986-06-27
Filing date: 1987-06-24
Publication date: 1988-02-10
Also published as: GB8714780D0; GB8615797D0

Abstract

Apparatus for sealing a casing hanger or casing to an element of a well head comprises an annular metal seal 7 for interposition between said casing hanger or casing and said element of a well head, said seal 7 comprising an annular body 8 having two generally axially extending annular seal members 9, 10 radially spaced from each other, and further comprising an annular expansor ring 11 adapted, to be received between said seal members when said seal and said expansor ring are urged together, thereby to force the seal members into sealing engagement respectively with a said casing hanger or casing and with a said element of a well head. The metal seal may be of generally U-shaped or V-shaped profile or may be of generally H-shaped or X- shaped profile. The annular seal members 9, 10 may be adapted to undergo axial foreshortening to ensure efficient sealing. <IMAGE>

Description

SPECIFICATION Well-head sealing This invention relates to a method of and apparatus for sealing a casing hanger or casing to an element of a well head. The term 'element of a well head' is intended to include a casing head of a well head assembly, a spool of a well head assembly and indeed a casing hanger itself. The last mentioned case therefore embraces sealing between conventionally arranged casing hangers or between casing and a casing hanger.

According to a first aspect of the present invention there is provided a method of sealing a casing hanger or casing to an element of a well head as defined above, in which method said sealing is effected by means of an annular metal seal interposed between said casing hanger or casing and said element of a well head, said seal comprising an annular body having two generally axially extending annular seal members radially spaced from each other, and in which method an annular expansor ring is located between said seal members, and sealing load is applied to the combination of said expansor ring and said seal, thereby to force the seal members into sealing engagement respectively with the casing hanger or casing and with said element of a well head.

According to a second aspect of the present invention there is provided apparatus for sealing a casing hanger or casing to an element of a well head as defined above, which apparatus comprises an annular metal seal for interposition between said casing hanger or casing and said element of a well head, said seal comprising an annular body having two generally axially extending annular seal members radially spaced from each other, and further comprising an annular expansor ring adapted, to be received between said seal members when said seal and said expansor ring are urged together, thereby to force the seal members into sealing engagement respectively with a said casing hanger or casing and with a said element of a well head.

Although the seal members may be downwardly directed or upwardly directed it is preferred that they be upwardly directly. Preferably said seal members diverge upwardly from each other and preferably said expansor ring has a generally wedge-shaped profile for cooperating therewith. Generally however it is envisaged that any suitable profiles may be adopted for the expansor ring and for the seal members to achieve a sealing separation of the seal members when the expansor ring or a part thereof is introduced between said seal members.

In a simple embodiment of the seal of the present invention the annular metal seal may have a generally U-shaped or V-shaped profile.

In order to provide even more secure sealing, the annular metal seal may be provided with generally axially extending seal members to both sides of its annular body thereby to produce an annular metal seal having. e.g. a generally H-shaped or X-shaped profile. In this latter case two separate means will normally be provided to achieve sealing separation of the respective seal members e.g. in the form of oppositely directed expansor rings each having a generally wedge-shaped profile.

Such a 'double' metal seal not only affords better sealing with respective surfaces of said casing hanger or casing and said element of a well head but also may provide-an intermediate region e.g. between upper and lower seal members which region can be pressurized to test the integrity of sealing.

In one embodiment of the seal of the present invention, an annular metal seal may comprise an annular body having two axially extending annular seal members, radially spaced from each other, at least one of said seal members being provided with means whereby said seal member can undergo axial fore-shortening to ensure efficient sealing. It is envisaged that the seal members need not be of the same axial length, in which case only the longer of the two members need be provided with the axial fore-shortening means.

Such a metal seal may include means, e.g. in the form of one or more annular shoulders on a radially inner surface thereof, for load-bearing purposes. Said means whereby the seal member(s) can undergo axial fore-shortening may comprise a portion of said annular seal member which is of generally zig-zag or concertina shape in section. It is possible that the seal member may simply include a thinned web portion capable of bending, deforming or distorting under axial load.

An advantage of using two such seal members at least one of which is provided with said axial fore-shortening means is that, when a force is applied to the seal and the seal members are driven into a sealing position, any discrepancy between the respective engagements by said first and second members will be compensated for by axial fore-shortening of that seal member which is the first to engage, until the other seal member is properly engaged.

The method and apparatus of the present invention are applicable both to surface (i.e.

land-based or platform-based) and to subsea systems. The method and apparatus have particular utility in contingency or tie-back well head systems.

It is envisaged that in applying the method and apparatus of the present invention to such a contingency pack off or tie-back system, either or both of the slip and guide ring could be provided with an upper profile to function as a said expansor ring for the lower half of a said 'double' seal.

An embodiment of a method and apparatus according to the present invention will now be described, by way of example only, by reference to the accompanying drawings, in which: Fig. 1 is a vertical cross-section of a contingency pack-off or tie back well head system; Fig. 2 shows an alternative arrangement of metal seal for use with a contingency pack-off or tie back well head system of the type shown in Fig. 1; Fig. 3 is a side elevation and half-section of an alternative metal seal and expansor ring; and Fig. 4 shows an alternative metal seal and expansor ring, preferred for casing of smaller diameter.

Referring to the drawings, a well head 1 has disposed therewithin a length of casing 2. The casing 2 is supported within the well head 4 by means of a segmented generally cylindrical annular slip 3 having upon a radially inner face thereof means engaging with the outer surface of said tube 2 and having a frusto-conical radially outer surface, and by means of a segmented generally cylindrical annular guide ring 4 having a frusto-conical radially inner surface generally complementary to the frusto-conical surface of said slip 3 and which is supported upon an annular shoulder 5 provided on said well head.

The guide ring 4 provides a support surface 6 for an annular metal seal 7. The annular metal seal 7 comprises an annular body 8 provided with generally axially extending and upwardly directed seal members 9,10. The seal members 9 and 10 define between them an annular space having a generally downwardly convergent profile. An annular expansor ring 11 is located generally intermediate of the seal members 9,10 and thereabove. The annular expansor ring 11 is provided with a downwardly convergent frusto-conical profile, adapted to co-operate with sealing surfaces of generally corresponding profile provided on said seal members 9,10. Bolt means 12 are provided for holding seal 7 loosely in engagement with ring 11, in order to facilitate assembly of the well head.To cause sealing of the casing to the well head axial pressure is applied downwardly upon annular expansor ring 11 thereby to force apart the seal members 9,10 and to cause them respectively to seal between casing 2 and ring 11 and between 11 and well head 1.

Referring now to Fig.2 of the accompanying drawings there is shown an arrangement wherein said seal is generally X-shaped in profile. That is to say, the seal 7 of this embodiment is provided with an annular body 8 as in the embodiment of Fig. 1. Likewise it is provided with axially extending and upwardly directed seal members 9,10. In addition however the seal 7 of this embodiment is provided with a pair of axially extending and downwardly directed further seal members 13,14. It will be seen that a further annular expansor ring 15 is provided. For this purpose the said further annular expansor ring 15 is supported upon the support surface 6 of a said guide ring 4.

Referring to Fig. 3 of the accompanying drawings, a metal seal 20 provided with a pair of axially extending circumferential seal members 21,22 is in sealing engagement with an expansor ring 23. Each seal member is provided with a portion which extends generally axially and which is of zig-zag or concertina section, whereby each seal member may undergo axial foreshortening under axial load.

The seal 20 is provided with annular shoulders 24 on a radially inner surface thereof for transmitting the load of a further tube (not shown).

Referring to Fig. 4 of the accompanying drawings, an expansor ring 26 is shown, equivalent to support ring 23.A metal seal 27 equivalent to metal seal 20 is also provided.

In the case of metal seal 27 however, loadtransmission occurs not via annular shoulders in said metal seal but via a plurality of separate elements including a split locking ring 28 and upper and lower actuators 29,30 therefor.

The method and apparatus of the present invention provide a satisfactory system for sealing a casing hanger or casing to an element of a well head as hereinbefore defined.

It is to be understood that the invention may be performed and embodied, other than as has been particularly described. The invention includes within its scope all such modifications and variations as would be apparent to one skilled in the art.

Claims

1. A method of sealing a casing hanger or casing to an element of a well head as hereinbefore defined, in which method said sealing is effected by means of an annular metal seal interposed between said casing hanger or casing and said element of a- well head, said seal comprising an annular body having two generally axially extending annular seal members radially spaced from each other, and in which method an annular expansor ring is located between said seal members, and sealing load is applied to the combination of said expansor ring and said seal, thereby to force the seal members into sealing engagement respectively with the casing hanger or casing and with said element of a well head.

2. A method according to Claim 1, in which the seal members are downwardly directed.

3. A method according to Claim 1, in which the seal members are upwardly directed.

4. A method according to Claim 3, wherein said seal members diverge upwardly from each other and said expansor ring has a generally wedge-shaped profile for co-operating therewith.

5. A method according to Claim 1, wherein the annular metal seal is provided with generally axially extending seal members to both sides of its annular body.

6. A method according to Claim 5, wherein the annular metal seal has a generally Hshaped profile.

7. A method according to Claim 5, wherein the annular meal seal has a generaly X-shaped profile.

8. A method according to Claim 1, wherein at least one of said seal members is provided with means whereby said seal member can undergo axial foreshortening to ensure effective sealing.

9. A method according to Claim 8, wherein said means whereby seal- member can undergo axial foreshortening comprises a portion of said annular seal member which is of generally zig zag shape in section.

10. A method according to Claim 8, wherein the annular metal seal includes two axially extending annular seal members radially spaced from each other, each of said seal members being provided with said means whereby said seal members can undergo axial foreshortening.

11. Apparatus for sealing a casing hanger or casing to an element of a well head as hereinbefore defined, which apparatus comprises an annular metal seal for interposition between said casing hanger or casing and said element of a well head, said seal comprising an annular body having two generally axially extending annular seal members radially spaced from each other, and futher comprising an annular expansor ring adapted, to be received between said seal members when said seal and said expansor ring are urged together, thereby to force the seal members into sealing engagement respectively with a said casing hanger or casing and with a said element of a well head.

12. Apparatus according to Claim 11, in which the seal members are downwardly directed.

13. Apparatus according to Claim 11, in which the seal members are upwardly directed.

14. Apparatus according to Claim 13, wherein said seal members diverge upwardly from each other and said expansor ring has a generally wedge-shaped profile for co-operating therewith.

15. Apparatus according to Claim 11, wherein the annular metal seal is provided with generally axially extending seal members to both sides of its annular body.

16. Apparatus according to Claim 15, wherein the annular metal seal has a generally H-shaped profile.

17. Apparatus according to Claim 15, wherein the annular meal seal has a generally X-shaped profile.

18. Apparatus according to Claim 11, wherein at least one of said seal members is provided with means whereby said seal member can undergo axial foreshortening to ensure effective sealing.

19. Apparatus according to Claim 18, wherein said means whereby seal member can undergo axial foreshortening comprises a portion of said annular seal member which is of generally zig-zag shape in section.

20. Apparatus according to Claim 18, wherein the annular metal seal includes two axially extending annular seal members radially spaced from each other each of said seal members being provided with said means whereby said seal members can undergo axial foreshortening.

21. A method of sealing a tubing hanger or tubing to an element of a well head as hereinbefore defined, substantially as hereinbefore described with reference to the accompanying drawings.

22. Apparatus for sealing a tubing hanger or tubing to an element of a well head as hereinbefore defined, substantially as hereinbefore described with reference to the accompanying drawings.

23. The features hereinbefore disclosed, or their equivalants, in any novel selection.