U.S. patent application number 13/659499 was filed with the patent office on 2014-04-24 for hard stop energizing ring.
This patent application is currently assigned to Vetco Gray Inc.. The applicant listed for this patent is VETCO GRAY INC.. Invention is credited to Detrick Deyon Garner, Chad Eric Yates.
Application Number | 20140110126 13/659499 |
Document ID | / |
Family ID | 49382669 |
Filed Date | 2014-04-24 |
United States Patent
Application |
20140110126 |
Kind Code |
A1 |
Yates; Chad Eric ; et
al. |
April 24, 2014 |
Hard Stop Energizing Ring
Abstract
A wellhead seal assembly that forms a metal-to-metal seal
between inner and outer wellhead members. A metal seal ring has
inner and outer legs separated by a slot. An extension of seal ring
contacts an upward facing shoulder of the inner wellhead member. An
energizing ring with a tapered nose is moved into the slot. The
tapered nose has a downward facing stop shoulder that contacts an
upper end of inner leg when the energizing ring is in its lower
position.
Inventors: |
Yates; Chad Eric; (Houston,
TX) ; Garner; Detrick Deyon; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VETCO GRAY INC. |
Houston |
TX |
US |
|
|
Assignee: |
Vetco Gray Inc.
Houston
TX
|
Family ID: |
49382669 |
Appl. No.: |
13/659499 |
Filed: |
October 24, 2012 |
Current U.S.
Class: |
166/368 ;
166/75.13; 166/88.3 |
Current CPC
Class: |
E21B 33/03 20130101;
E21B 33/04 20130101 |
Class at
Publication: |
166/368 ;
166/88.3; 166/75.13 |
International
Class: |
E21B 33/128 20060101
E21B033/128; E21B 33/03 20060101 E21B033/03 |
Claims
1. A metal-to-metal seal assembly for sealing in a seal pocket
between inner and outer tubular members of a wellhead assembly,
comprising: a seal ring having an axis, and annular inner and outer
legs separated from each other by an annular slot having a run-in
radial width; an annular energizing ring having a nose portion with
a radial thickness greater than the run-in radial width of the seal
ring, and carried in a run-in position with a nose end at an
entrance of the annular slot; an annular stop shoulder on the
energizing ring above the nose end; the seal ring being energized
from the run-in position to a set position by applying an axial
energizing force to the energizing ring, so that the energizing
ring is pressed into the annular slot causing radial plastic
deformation of the annular inner and outer legs of the seal ring
into sealing contact with the inner and outer tubular members
defining the set position; and the annular stop shoulder contacting
an upper end of one of the legs of the seal ring while in the set
position.
2. The assembly according to claim 1, further comprising: a set of
wickers formed in at least one of the seal surfaces, a smooth
cylindrical surface adjoining the set of wickers; and opposing seal
surfaces in the bore and on an exterior portion of the inner
wellhead member.
3. The assembly according to claim 1, wherein the stop shoulder is
perpendicular to the axis.
4. The assembly according to claim 1, wherein the length of the
energizing ring below the stop shoulder to the nose end is less
than the length of the slot in the seal ring.
5. The assembly according to claim 1, wherein continued axial
energy forces applied to the energizing ring after reaching the set
point is directed through the stop shoulder to the seal ring.
6. The assembly according to claim 1, wherein the stop shoulder
engages the upper end of the inner leg of the seal ring.
7. The assembly according to claim 1, wherein a radial thickness of
the energizing ring at the stop shoulder is greater than the radial
thickness of the nose part.
8. The assembly according to claim 1, wherein the stop shoulder is
located between the nose and an upper end of the energizing
ring.
9. The assembly according to claim 1, wherein the nose end is
spaced above a base of the slot while the stop shoulder is
contacting the upper end of said one of the inner and outer seal
legs.
10. A wellhead assembly with an axis, comprising: an outer wellhead
member having a bore; an inner wellhead member in the bore; an
annular space between the inner and outer wellhead members; a seal
member having inner and outer annular legs defining a slot
therebetween, the inner leg having an upper end at a lower
elevation than an upper end of the outer leg; an annular energizing
ring in the slot and having an annular stop shoulder extending
radially inward from the inner surface of the energizing ring
positioned in abutment with the upper end of the inner leg of the
seal member while the energizing ring is in a set position,
preventing further downward movement of the energizing ring in the
slot once the energizing ring reaches the set position.
11. The assembly according to claim 10, further comprising: a set
of wickers formed in at least one of the seal surfaces, a smooth
cylindrical surface adjoining the set of wickers; and opposing seal
surfaces in the bore and on an exterior portion of the inner
wellhead member.
12. The assembly according to claim 10, wherein the stop shoulder
is perpendicular to the axis.
13. The assembly according to claim 10, wherein the length of the
energizing ring below the stop shoulder to the nose end is less
than the length of the slot in the seal ring.
14. The assembly according to claim 10, wherein continued axial
energy forces applied to the energizing ring after reaching the set
point is directed through the stop shoulder to the seal ring.
15. The assembly according to claim 10, wherein the stop shoulder
is located between the nose and an upper end of the energizing
ring.
16. The assembly according to claim 10, wherein the nose end is
spaced above a base of the slot while the stop shoulder is
contacting the upper end of said one of the inner and outer seal
legs.
17. A method for sealing an annular space in a wellhead assembly
between inner and outer wellhead members, comprising: providing
wickers on at least one of the inner and outer wellhead members;
providing a seal member having inner and outer annular walls
defining a slot therebetween, and an annular energizing ring and
having an annular stop shoulder, inserting the seal member between
the inner and outer members; inserting energizing ring into the
slot by a downward force on the energizing ring, causing the inner
and outer legs to move radially into sealing engagement with the
inner and outer wellhead members and into engagement with the
wickers; continuing to apply the downward force after the stop
shoulder contacts an upper end of one of the legs, and directing
the downward force through said one of the legs to the wickers.
18. The method according to claim 17, wherein the inner leg is
contacted by the stop shoulder and wickers are on the inner
wellhead member
Description
FIELD OF THE INVENTION
[0001] This invention relates in general to wellhead assemblies and
in particular to an energizing ring profile that allows increased
seal setting load capacity when a U-seal is locked down.
BACKGROUND OF THE INVENTION
[0002] Seals are used between inner and outer wellhead tubular
members to contain internal well pressure. The inner wellhead
member may be a casing hanger located in a wellhead housing and
that supports a string of casing extending into the well. A seal or
packoff seals between the casing hanger and the wellhead housing.
Alternatively, the inner wellhead member could be a tubing hanger
that supports a string of tubing extending into the well for the
flow of production fluid. The tubing hanger lands in an outer
wellhead member, which may be a wellhead housing, a Christmas tree,
or a tubing head. A seal or packoff seals between the tubing hanger
and the outer wellhead member.
[0003] A variety of seals located between the inner and outer
wellhead members have been employed in the prior art. FIG. 1 shows
a portion of a seal assembly in the prior art within a wellhead
housing 101. Housing 101 is typically located at an upper end of a
well and serves as an outer wellhead member. An energizing ring 103
is typically forced downward by a running tool or the weight of a
string to force it into a slot 105 defined by a U-type metal seal
ring 107. Located below the seal ring 107 is a lower extension 109
that rests on a shoulder 111 formed on an inner wellhead member,
such as a hanger 113. As it is forced downward, the energizing ring
deforms inner and outer walls of the seal ring 107 apart into
respective sealing engagement with inner and outer wellhead members
113, 101. The energizing ring is typically a solid wedge-shaped
member. The deformation of the inner and outer walls exceeds the
yield strength of the material of the seal ring 107, making the
deformation permanent. Prior art seals may also include elastomeric
and partially metal and elastomeric rings. Prior art seal rings
made entirely of metal for forming metal-to-metal seals are also
employed.
[0004] However, energizing rings of the prior art have a setting
load capacity below the full capability of the running tool. In the
event that the seal is set with the full force of the running tool,
the outer leg of the seal ring 107 will buckle, causing the seal to
fail.
[0005] Additionally, cyclic pressure tests of the wellhead cause
low-cycle fatigue in the wellhead seal. When the seal is
pressurized from above the energizing ring, the energizing ring is
forced deeper into the seal pocket which can likewise cause the
seal to fail.
[0006] A need exists for a technique that addresses the seal
setting problems described above. In particular a need exists for a
technique to prevent structural damage to the seal ring caused by
too much setting force and low-cycle fatigue.
SUMMARY OF THE INVENTION
[0007] In an embodiment of the present technique, a seal assembly
is provided that forms a metal-to-metal seal and has features that
enhance sealability in the seal assembly. The seal ring has inner
and outer walls separated by a slot and has a bottom portion that
contacts an upward facing shoulder of a hanger. A metal energizing
ring has a tapered nose that may be pushed into the slot during
installation to deform the inner and outer walls into sealing
engagement with inner and outer wellhead members having wickers
formed thereon. A radial gap exists between the outer wall of the
seal and the inner wall of the mating housing. Such a gap is
required for installation in the field and is sufficiently large to
require plastic deformation of the seal body, but not the energizer
ring.
[0008] In an illustrated embodiment, the energizing ring has a 90
degree shoulder extending from the inside surface of the energizing
ring positioned to abuttingly contact the top of the inner leg of
the seal ring when the seal is fully energized. As the nose travels
into the slot, the outer and inner legs of the metal seal ring are
forced into sealing engagement with the inner and outer wellhead
members. Once the seal has been fully set, the shoulder on the
energizing ring prevents the nose of the energizing ring from
entering the seal ring any further by transferring the setting load
into the inner leg of the seal ring and subsequently into the
wickers.
[0009] In an example embodiment, the seal assembly also comprises
the energizing ring that engages the slot. The retainer nut rests
in a machined gap on the outer surface of the energizing ring. The
outer leg of the seal ring is threadedly connected with the
retainer ring. The engagement ensures that the seal assembly
remains intact as one integral structure during landing, setting,
and retrieval operations.
[0010] The combination of stored energy provided for by the
energizing ring, the hard stop shoulder configuration of the
energizing ring, and the compressible elastomeric seal below the
seal ring, advantageously provide enhanced setting capacity and
resilience to the wellhead seal assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a sectional view of a seal assembly of the prior
art with an energizing ring without a hard stop shoulder set in the
seal;
[0012] FIG. 2 is a sectional view of the seal assembly of FIG. 2
landed between outer and inner wellhead members in an unset
position in accordance with an embodiment of the invention;
[0013] FIG. 3 is a sectional view of the nose of an energizing ring
after entering a slot of a seal ring and deforming walls of the
seal ring, in accordance with an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Referring to FIG. 2, an embodiment of the invention shows a
portion of a wellhead assembly that includes a high pressure
wellhead housing 101. In this example, the housing 101 is located
at an upper end of a well and serves as an outer wellhead member of
the wellhead assembly. Housing 101 has a bore 115 located therein.
In this example, an inner wellhead member is a casing hanger 113,
which is shown partially in FIG. 2 within bore 115. Alternately,
wellhead housing 101 could be a tubing spool or a Christmas tree,
and casing hanger 113 could instead be a tubing hanger, plug,
safety valve, or other device. Casing hanger 113 has an exterior
annular recess radially spaced inward from bore 115 to define a
seal pocket 117. Wickers 119 are located on a portion of the
wellhead bore 115 and wickers 121 are located on a portion of the
cylindrical wall of seal pocket 117. The wickers comprise
triangular grooves parallel to each other. In this example, the
profiles of each set of wickers 119, 121 are shown as continuous
profiles on the bore 115 and seal pocket 117. However, the wickers
119, 121 may be configured in other arrangements. For instance, the
wickers may be only on the bore 101 or only on the casing hangar
113.
[0015] Continuing to refer to FIG. 2, a metal-to-metal seal
assembly 123 is lowered between the housing 101 and casing hanger
113 and located in seal pocket 117. Seal assembly 123 includes a
seal ring 125 formed of a metal such as steel. Seal ring 125 has an
inner wall 127 that is an inner seal leg 129 for sealing against
the cylindrical wall of casing hanger 113. Seal ring 125 has an
outer wall surface 131 comprised of outer seal leg 133 that seals
against wellhead housing bore 115. One of the seal legs is shorter
than the other. In this embodiment, the upper end of inner leg 129
is lower than the upper end of outer leg 133. Each wall surface
127, 131 is cylindrical and smooth and engages the wickers 119, 121
when deformed against the bore 115 of the housing 101 and seal
pocket 117 of the casing hanger 113. The wickers 119, 121 enhance
the grip to aid in the prevention of axial movement of the seal
assembly once set.
[0016] In the example FIG. 2, seal ring 125 is uni-directional,
having an upper section only; however, a seal ring that is
bi-directional may optimally be used. The upper section has a slot
135 defined between inner and outer legs 129, 133. The inner and
outer surfaces forming slot 135 comprise generally cylindrical
surfaces, that when viewed in an axial cross-section are generally
parallel and each follow a straight line.
[0017] An annular energizing ring 137 engages slot 135 on the upper
side. As shown, the energizing ring 137 has an axis A.sub.R that
substantially coincides with an axis (not shown) of the wellhead
assembly. Energizing ring 137 is forced downward into slot 135 by a
running tool (not shown). Alternatively, seal assembly 123 and
energizing ring 137 may be part of a string that is lowered into
bore 115, the weight of which forces energizing ring 137 into slot
135. Energizing ring 137 can be formed of metal, such as steel. The
mating surfaces of energizing ring 137 and outer seal leg 133 may
be formed at a locking taper. Energizing ring 137 has a greater
radial thickness than the radial breadth of slot 135.
[0018] The annular energizing ring 137 has a downwardly facing
90.degree. hard-stop shoulder 139 formed on its inner wall 141
positioned to abuttingly contact the top edge of the inner leg 129
of the seal ring 125 when the energizing ring is fully engaged in
the seal ring in the set position. When fully set, the nose or
lower end of the energizing ring 137 will be spaced above the base
of slot 135.
[0019] In an embodiment of the invention, a retaining nut 143 is
carried in a gap 145 formed in the outer surface of upper
energizing ring 137. Retaining nut 143 is threadedly connected to
the outer leg 133 of the seal ring 125. The top edge of the
retaining nut forms an upward facing shoulder 147. On the upper end
of the outer seal leg 133. Retaining nut 143 has a 90 degree
downwardly facing shoulder 149 on its outer surface which makes
abutting contact with the top edge 151 of the seal ring 137 when
the retaining nut is attached to the seal ring. When in position,
retaining nut 143 is positioned to prevent energizing ring 137 from
moving out of its run-in position during landing, setting, and
retrieval operations.
[0020] Energizing ring 137 has a nose 161 or engaging portion that
engages slot 135. Energizing ring 137 has an inner surface 141 and
an outer surface 153 for engaging the opposite inner sidewalls of
slot 135 in seal ring 125. Inner and outer surfaces 141, 153 may be
straight surfaces as shown, or optimally curved surfaces.
[0021] In the example embodiment of FIG. 2, a lower extension 155
secures by threads to the lower portion of seal ring 125. The lower
extension 155 extends down and comprises a landing nose 157 to
facilitate landing on an upward facing shoulder 159 formed on the
interior of the casing hanger 113. The shoulder 159 provides a
reaction point during setting operations.
[0022] Referring to FIG. 3, an enlarged sectional view of the nose
161 of the energizing ring 141 is shown in the set position. The
nose 161 may have a vent 163 to prevent hydraulic locking and may
have a first tapered surface or portion. The inner and outer legs
129, 133 of the seal ring 125 have chamfers at their upper ends and
proximate the opening of the slot 135. In embodiments of the
invention, vent passages or penetration holes 163 (FIG. 5) may be
incorporated across wedge member 161 and through upper energizing
ring 137 so that a hydraulic lock condition does not prevent axial
make-up of the energizer and seal system.
[0023] As force is applied to the energizing ring 137 (FIG. 2), the
force on the energizing ring 137 and the reacting force from the
shoulder 159 (FIG. 3) cause the nose 161 to enter into the slot 135
and thereby deform the legs 129, 133 of the seal ring 125 against
the wickers 119, 121 of the housing 101 and hanger 113. Once the
legs 129, 133 are set and the energizing ring is in the set
position, the hard-stop shoulder 139 makes contact with the top
edge of the inner seal leg 129, thereby preventing the energizing
ring 137 from moving any further into the slot 135 by transferring
the load from the running tool to the upwardly facing shoulder 159
of casing hangar 113 through the energizing ring hard-stop shoulder
139 into the seal ring 125, and thus into the lower extension 155
and the wickers 119, 121. The lower end of energizing ring 137 does
not contact the base of slot 135 when fully set.
[0024] In an example of operation of the embodiment shown in FIGS.
2-3, a running tool or string (not shown) is attached to seal
assembly 123 and lowered into the seal pocket 117 Seal assembly 123
may be pre-assembled with energizing ring 137, retaining nut 143,
seal ring 125, and extension 155 all connected as shown in FIG. 2.
The outer wall 131 of outer seal leg 133 will be closely spaced to
wickers 119 on the wellhead bore 115. The inner wall 127 of inner
seal leg 129 will be closely spaced to the wickers 121 on the
cylindrical wall of seal pocket 117. By pushing the energizing ring
137 downward (such as by the running tool) with sufficient force to
insert the nose 161 in the slot 135, engagement of nose 161 with
the slot 135 causes the inner and outer seal legs 129, 131 to move
radially apart from each other as shown in FIGS. 4 and 5. The inner
wall 127 of inner seal leg 129 will embed into wickers 121 in
sealing engagement while the outer wall 131 of outer seal leg 133
will embed into wickers 119 in sealing engagement.
[0025] In an additional embodiment (not shown), the wellhead
housing 101 could be a tubing spool or a Christmas tree.
Furthermore, the casing hanger 113 could instead be a lockdown
hanger, tubing hanger, plug, safety valve or other device.
[0026] While the invention has been shown in only one of its forms,
it should be apparent to those skilled in the art that it is not so
limited but is susceptible to various changes without departing
from the scope of the invention. For example, the seal could be
configured for withstanding pressure in two directions, if desired,
having two energizing rings. In addition, each energizing ring
could be flexible, rather than solid.
* * * * *