Note: Descriptions are shown in the official language in which they were submitted.
1 BACKGROUND OF T~E INVENTION
3 1. Field of the Invention:
This invention relates in general to subsea wellhead
6 equipment, and in particular to a casing or tubing hanger
7 having a me-tal-to-metal seal.
9 2. Description of the Prior Art:
11 A typical subsea wellhead assembly includes a
12 wellhead housing mounted within a temporary guide base
13 that is supported on the ocean floor. Large diameter
14 conductor pipe is secured to the wellhead housing and
extends downward into the earth a short distance. A
16 wellhead is mounted inside the wellhead housing and to a
17 permanent guide base which mounts on top of the temporary
18 guide base. Surface casing secured to the wellhead
19 extends a few hundred feet down into the well. The top
of the wellhead is connected to pressure equipment and
21 risers that e~tend to a drilling vessel at the surface.
22 As the well is drilled deeper, a first string of casing
23 may be set to a certain depth. Subse~uently, a second
24 string of casing may be set.
26 In a typical installation, the casing hanger
27 includes a casing hanger body which is secured to the
28 upper end of the casiny string. The body is supported on
29 an annular shoulder in the wellhead. After cementing, a
seal and locking means is lowered into an annular
31 clearance between the casing hanger body and wellhead
32 bore. The seal normally includes an elastomeric ring
33 which is compressed by compression rings between the
34 casing hanger body and the wellhead bore. The locking
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1 means includes a split ring and various wedges, which are
2 actuated by rotation of a running tool to lock the
3 elastomeric seal in compression and to lock the casing
4 hanger in the wellhead. Wickers, which are small
parallel grooves, may be located in the wellhead bore for
6 engagement by the split ring.
8 While successful~ elastomeric seals may not have as
9 long of a life as a metal-to-me-tal seal, particularly if
subjected to heat. Metal seals, and combinations of
11 metal and rubber seals, are commercially available.
12 Improvements, however, are desirable.
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SUMM~RY OF THE INVENTION
3 In this invention, a casing or tubing hanger is
4 provided with a metal-to-metal seal. The casing hanger
5 has a body whi,ch is dimensioned to define an annular
6 clearance between the we]lhead and the body. Locking
7 means is positionable in the annular clearance for
8 locking the body to the wellhead, A deformable metal
9 seal ring is also positioned in the clearance for sealing
10 between the hanger body and the wellhead. The seal ring
11 has inner and outer sidewalls that are cylindrical.
12 Wedge means urges these sidewalls radially apar~ to seal
13 the body to the wellhead.
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15 In the preferred embodiment, the seal ring is "U"
16 shaped, having an upwardly facing cavity between the
17 inner and outer sidewalls. A metal wedge ring, when
18 pressed into the cavity, urges the sidewalls apart.
19 Wickers are preferably formed on the casing hanger body
20 and on the wellhead bore. The metal seal ring embeds
21 into the wickers to provide sealins.
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23 Preferably, the locking means has a split rlng that
24 engages another set of wickers in the bore. Wedges move
A 25 the ring out into engagement. Wedge fingers movably
26 mounted to the hanger body retain the split ring in
27 locking engagement. The wedge fingers are moved into
28 locking engagement by contact with -the metal seal ring
29 prior to its deforma-tion.
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1 BRIEF DESCRIPTION OF THE DRAWINGS
3 Fig. 1 is a partial vertical sectional view of a
4 casing hanger constructed in accordance with this
invention and shown prior to setting.
7 Fig, Z is a view of the casing hanger of Fig. 1,
8 taken from a different vertical section than in Fig. 1
9 and shown with the locking means set and the seal means
prior to setting.
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12 Fig. 3 is a view of the casing hanger of Fig. 1,
13 taken along the same vertical section as in Fig. 2 and
14 showing the seal means and the locking means in the set
position.
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1 DESCRIPTION OF THE PREFERRED EMBODIMENT
3 Referring to Fig. 1, casing hanger 11 is shown
4 located within a subsea wellhead 13. Wellhead 13 has a
bore 15 with an upwardly facing annular shoulder 17. A
6 lower set of wickers 19 are formed in the bore 15 a short
7 distance above shoulder 17. Wickers 19~ are small
8 parallel and circular grooves formed perpendicular to the
9 axis of bore 15. Preferably there are about eight
grooves per inch. An upper set of wickers 21 is located
11 above wickers 19 a selected distance.
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13 The casing hanger 11 includes a hanger body 23 that
14 has an axial passage 25 having threads 27 at the lower
end for securing to the upper section of a string of
16 casing 29, which could be tubing if hanger 11 is used as
17 a tubing hanger. Body 23 has an exterior flange 31
18 located intermediate the upper and lower ends of the body
19 23. Flange 31 extends radially outward and contacts the
wellhead bore 15. Flange 31 has a plurality of vertical
21 slots 32 extending radially outward and spaced
22 circumferentially around the flange. The flange 31 has a
23 reacting surface 33 on the lower side which is inclined
24 so that it faces downwardly and outwardly. The wall of
the hanger body 23 above flange 31 and below the reacting
26 surface 33 is cylindrical and spaced inwardly from the
27 bore 15, defining annular clearances between bore 15 and
28 hanger body 23. ~ set of wickers 35 are formed on the
29 upper end of the hanger body 23 on the ex-terior surface
in alignmen-t with the wickers 21 formed in the wellhead
31 bore 15. Wickers 35 are of the same size and type as the
32 wickers 21 and 19.
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1 Hanger body 23 is supported in the wellhead 13 by a
2 locking means that includes a split ring 37. Split ring
3 37 is a circular ring that will move from a ~adially
4 inward position shown in Fig. 1 to a radially outward
position shown in Fig. 2. Passages (not shown) in the
6 split ring 37 allow fluid to flow through the ring. The
7 exterior surface of split ring 37 is cylindrical and
8 contai~s a plurality of wickers 39, which align with the
9 wickers 19 in the wellhead bore 15. A retaining pin 40
(Fig. 2~, orients the split ring 37 with the hanger body
11 23, but allows radial movement with respect thereto.
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13 The casing hanger 11 has reacting means for moving
14 the split ring radially outward when the casing hanger 11
is seated upon the wellhead shoulder 17. The reacting
16 means includes the reacting surface 33 and also three
17 wedge shaped rings 41, 43 and 47. The inner ring 41 is
lB stationarily carried by the body 23 by means of threads.
19 Inner ring 41 has passages (not shown) that allow fluid
to flow upward through ring 41. An outer ring 43 is
21 slidably carried on the cylindrical outer wall of the
22 inner ring 41. Outer ring 43 is secured to the inner
23 ring 41 by means of a shear pin 45. The outer surface of
24 outer ring 43 is cylindrical and contacts the wellhead
bore 15. The lower surface of the outer ring 43 is
26 tapered for contacting the tapered shoulder 17. The
27 upper surface of the outer ring 43 is tapered for mating
28 contact with the tapered lower edge of the split ring 37.
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As can be seen by comparing Fig's. 2 and 3, the
31 weight of the string 29 will shear the pin 45, causing
32 the hanger body 23 and inner ring 41 to move downward a
33 short distance with respect to the outer ring 43. This
34 downward movement causes the reacting surface 33 and the
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1 upper edge of the outer ring 43 to urge the split ring 37
2 radially outward for engaging wickers 39 with wickers 19.
3 When moving outwardly, pin 40 (Fig. 2) will move
4 outwardly within its enlarged slot or cavity.
6 The split ring 37 is maintained in the ou-tward
7 position by retaininy ~leans which includes an expandable
8 ring 47 and a plurality of wedging fingers 49.
9 Expandable ring 47 is split to allow radial movement
outward as can be séen by comparing Fig's. 1 and 2.
11 Expandable ring 47 has a tapered lower edge carried on a
12 tapered upper edge of inner ring 41 and retained by a pin
13 48. Pin 48 locates in an enlarged slot in inner ring 41
14 to allow radial movement. The upper edge of the
expandable ring 47 is tapered and mates slidingly with
16 the lowered tapered edge of the split ring 37.
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18 Each wedging finger 49 is integrally formed with a
19 collar 51 at the top. Collar 51 is secured to the hanger
body 23 above flange 31 by means of a shear pin 53. Each
21 wedge finger 49 (only one shown) extends through one of
22 the slots 32 spaced around the flange 31. Each wedge
23 finger 49 extends within the inner diameter of split ring
24 37 and is axially movable between the expandable position
shown in Fig. 1 and the lower position shown in Fig. 2.
26 Each wedge finger 49 has a tapered su,rface on lts lower
27 end, which slides between the expandable ring 47 and the
28 hanger body 23 when moved to its downward position as
29 shown in Fig. 2. The wedge fingers 49 force the upper
ring 47 radlally outward in-to tight contact with the
31 lower edge of the split ring 37, to retain the split ring
32 in the engayed posikion shown in Fig. 2. The fingers 49
33 and upper ring 47 cause the split ring 37 to positively
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1 lock the body 23 to the wellhead 13 to prevent any axial
2 movement.
4 The collar 51 and the wedge fingers 49 are moved
downwardly by force of a seal ring 55, which also serves
6 to seal the casing hanger ll. Seal ring 55 is a "U"
7 shaped, soft metal ring, which deforms when set to form a
8 metal~to-metal seal. Seal ring 55 is preferably formed
9 of a low carbon steel with a hardness of about 150
Brinnell. Seal ring 55 has inner and outer sidewalls 57
11 and 59 which are cylindrical and concentric with the axis
12 of the wellhead 13. Prior to deformation, the inner and
13 outer sidewalls 57 and 59 are dimensioned such that the
14 seal ring 55 can slide without restriction into the
annular space between the hanger body 23 and the bore 15.
16 Seal ring 55 has a closed bottom 61 that is located in a
17 plane perpendicular to the axis of the sidewalls 57 and
18 59. A rectangular cavity 63 is formed in seal ring 55
19 and faces upwardly. Cavity 63 is annular and has a
closed bottom defined by bottom 61. Cavity 63 has a
21 tapered and enlarged portion 65 on its upper end.
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23 A metal wedge ring 67 has its lower edge carried in
24 the enlarged portion 65 of cavity 63 by means of a shear
pin 69. Wedge ring 67 is annular, and will not deform
26 under normal operation, rather serves to deform the seal
27 ring 55. Wedge ring 67 has an inner sidewall 71 and an
28 outer sidewall 73 that are cylindrical, parallel and
29 concentric wi-th the axis of the seal ring 55. The
cross-sectional dimension between sidewalls 71 and 73 is
31 greater than the dis-tance across cavity 63. A plurality
32 of passages 75 extend through the top and bottom of the
33 wedge ring 67 to allow the displacement of liquid when
34 the wedge ring is pressed into the cavity 63, as shown in
Fig. 3.
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1 In operation, the string of casing or tubing will be
2 secured to the lower end of the casing hanger body 23 and
3 lowered through risers (not shown) extending from a
4 drilling vessel into the wellhead 13 by means of a
handling tool (not shown). Seal ring 55 and wedge ring
6 67 could be lowered with the same handling tool during
7 the same run, or they could be lowered in a second or
8 subsequent run. When the outer ring 43 contacts the
9 wellhead shoulder 17, further downward movement caused by
the weight of string 29 will shear pin 45, causing the
11 split ring 37 to move outward into engagement with the
12 wickers 19. Then, if the string 29 is casing, cement
13 will normally be pumped downward through the passage 25
14 and through the casing 29 to cement the casing 29 into
the well. Liquid in the well will be displaced from the
16 annulus between the casing 29 and the wellbore through
17 passages (not shown) located in inner ring 41, upper ring
18 ~7, and split ring 37. The displaced liquid will flow
1~ through the slots 32 and to the surface.
21 Once the cement has set, the handling to~l (not
22 shown), moves the seal 55 downward without rotation,
23 causing its bottom 61 to contact the collar 51, pushing
24 the expandable ring 47 outwardly to retain the split ring
37 in the locked and engaged position. Shear pin 53 will
26 shear at this time. Then, the handling tool applies
Z7 force without rotating -to the wedge ring 67. This force
28 deforms the seal ri.ng 55, forcing the inner sidewall 57
29 radially inward and the outer sidewall 59 radially
outward. Shear pin 69 will shear. The wedging Eorce
31 will cause the soft metal of the seal ring 55 -to
32 sealingly embed within the wickers 21 and 35. Any fluid
33 that tends to leak past the seal ring 55 will be trapped
34 in the wickers 21 and 35.
1 The invention has significant advantages. The
2 locking portions of the casing hanger assembly positively
3 lock the casing hanger body to the wellhead. This
4 prevents any axial movement of the hanger body relative
to the wellhead that might otherwise occur due to the
6 thermal changes. The lack oE movement of the hanger body
7 relative to the wellhead avoids flexing of the metal
8 seal, which could deteriorate the seal. The metal seal
9 has a large cylindrical surface which provides good
sealing, enhanced by the wickers. The soft metal seal
11 does not deform the wellhead, enabling the casing hanger
12 to be pulled and another substituted in the same place.
13 The cooperation between the locking means and the seal
14 means enables the casing to be lowered into place,
cemented, locked and sealed all in a single run, if
16 desired.
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18 While the invention has been shown in only one of
19 its forms, it should be apparent to those skilled in the
art that it is not sa limited but is susceptible to
21 various changes without departing from the scope of the
22 invention.
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