U.S. patent application number 13/687758 was filed with the patent office on 2014-05-29 for lockdown system for use in a wellhead assembly.
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 | 20140144650 13/687758 |
Document ID | / |
Family ID | 49679700 |
Filed Date | 2014-05-29 |
United States Patent
Application |
20140144650 |
Kind Code |
A1 |
Yates; Chad Eric ; et
al. |
May 29, 2014 |
LOCKDOWN SYSTEM FOR USE IN A WELLHEAD ASSEMBLY
Abstract
A wellhead assembly having an outer tubular, an inner tubular
inserted into the outer tubular, an annular space between the inner
and outer tubulars, a lock ring in the annular space, and an
activation ring that axially strokes between the lock ring and one
of the tubulars. The lock ring selectively locks together the inner
and outer tubulars when the activation ring slides between the lock
ring and the one of the tubulars. The surface of the activation
ring that contacts lock ring is contoured so that an interface
surface between the activation ring and lock ring when the lock
ring is in its locked position, is offset an angle from an axis of
the wellhead that is less than an offset between the axis of the
wellhead and an interface surface between the activation ring and
lock ring when the activation ring is stroking downward.
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: |
49679700 |
Appl. No.: |
13/687758 |
Filed: |
November 28, 2012 |
Current U.S.
Class: |
166/379 ;
166/75.11 |
Current CPC
Class: |
E21B 33/038
20130101 |
Class at
Publication: |
166/379 ;
166/75.11 |
International
Class: |
E21B 17/02 20060101
E21B017/02 |
Claims
1. A wellhead assembly comprising: an axis; an outer tubular; an
inner tubular inserted into the outer tubular and defining an
annular space between the inner tubular and outer tubular; a lock
ring in the annular space that is moveable from an unlocked
position into a locked position; an activation ring having a
profiled surface that is axially slidable against and in contact
with the lock ring to define a contact interface that is offset an
angle from the axis when the lock ring is in the locked position,
and to define a contact interface that is offset an angle from the
axis when the lock ring is in the unlocked position, so that the
angle when the lock ring is in the locked position is less than the
angle when the lock ring is in the unlocked position.
2. The wellhead assembly of claim 1, wherein a portion of the
profiled surface is curved that is in contact with the lock ring
when the lock ring is in the unlocked position, and wherein a
portion of the profiled surface that is in contact with the lock
ring when the lock ring is in the locked position is substantially
linear.
3. The wellhead assembly of claim 1, wherein the lock ring is set
radially inward from the outer tubular when in the unlocked
position, and wherein the lock ring comprises a protrusion that
engages a depression formed in an inner radial surface of the outer
tubular.
4. The wellhead assembly of claim 1, wherein the lock ring is set
radially outward from the inner tubular when in the unlocked
position, and wherein the lock ring comprises a protrusion that
engages a depression formed in an outer radial surface of the inner
tubular.
5. The wellhead assembly of claim 1, further comprising a seal
assembly that transfers a downward axial force to an upper end of
the activation ring and that is energized by an energizing
force.
6. The wellhead assembly of claim 5, wherein a force applied to the
activation ring that slides the activation ring along the lock ring
and urges the lock ring from the unlocked position to the locked
position, and wherein the energizing force is greater than the
force applied to the activation ring.
7. The wellhead assembly of claim 1, wherein the outer tubular
comprises a wellhead housing and the inner tubular comprises a
tubing hanger.
8. A system for locking together tubulars that are disposed in a
wellhead assembly comprising: a lock ring that axially rests on one
of the tubulars and selectively engages an adjacent tubular thereby
axially locking together the one of the tubulars and the adjacent
tubular; an activation ring axially moveable to between the lock
ring and the one of the tubulars and having a surface in sliding
contact with the lock ring that transitions from a curved profile
to a linear profile as the activation ring moves to between the
lock ring and the one of the tubulars.
9. The system of claim 8, wherein the activation ring contacts the
lock ring along an interface that is offset from an axis of the
wellhead assembly by an angle up to about 5 degrees when the lock
ring is engagement with the adjacent tubular.
10. The system of claim 8, wherein the activation ring contacts the
lock ring along an interface that is offset from an axis of the
wellhead assembly by an angle that ranges from at least about 5
degrees to about 30 degrees when the curved profile is in contact
with the lock ring.
11. The system of claim 8, wherein the one of the tubulars is a
tubing hanger and the adjacent tubular is a wellhead housing.
12. The system of claim 8, wherein the one of the tubulars is
wellhead housing and the adjacent tubular is a tubing hanger.
13. The system of claim 8, wherein an upper end of the activation
ring is in axial contact with a seal assembly, where the seal
assembly is energized with an axial force that exceeds a force
applied to slide the activation ring from a position above the lock
ring to a position adjacent the lock ring.
14. A method of locking together tubulars in a wellhead assembly
comprising: providing a lock ring on a lateral surface of one of
the tubulars; applying a force onto the lock ring in a direction
oblique with an axis of the wellhead assembly to radially urge the
lock ring towards an adjacent tubular; changing the direction of
the force to be substantially perpendicular to the axis and
engaging the lock ring with the adjacent tubular; and retaining the
lock ring in engagement with the adjacent tubular by continuing to
apply the force in a direction substantially perpendicular to the
axis.
15. The method of claim 14, further comprising providing an
activation ring having a contact surface that transitions from a
curved portion to a linear portion.
16. The method of claim 15, wherein the step of applying a force
onto the lock ring in a direction oblique with an axis of the
wellhead assembly comprises axially urging the activation ring so
the curved portion slides against a side of the lock ring.
17. The method of claim 15, wherein the step of applying a force
onto the lock ring in a direction perpendicular to an axis of the
wellhead assembly comprises axially urging the activation ring so
the linear portion slides against a side of the lock ring.
18. The method of claim 15, wherein the step of continuing to apply
the force in a direction substantially perpendicular to the axis
comprises retaining the activation ring adjacent the lock ring so
the linear portion is in contact with a side of the lock ring.
Description
BACKGROUND
[0001] 1. Field of Invention
[0002] The invention relates generally to a system and method for
locking together tubulars in a wellhead assembly.
[0003] 2. Description of Prior Art
[0004] Wellheads used in the production of hydrocarbons extracted
from subterranean formations typically comprise a wellhead assembly
attached at the upper end of a wellbore formed into a hydrocarbon
producing formation. Wellhead assemblies usually provide support
hangers for suspending production tubing and casing into the
wellbore. The casing lines the wellbore, thereby isolating the
wellbore from the surrounding formation. The tubing typically lies
concentric within the casing and provides a conduit therein for
producing the hydrocarbons entrained within the formation.
[0005] Wellhead assemblies also typically include a wellhead
housing adjacent where the casing and tubing enter the wellbore,
and a production tree atop the wellhead housing. The production
tree is commonly used to control and distribute the fluids produced
from the wellbore and selectively provide fluid communication or
access to the tubing, casing, and/or annuluses between the tubing
and casing. Valves assemblies are typically provided within
wellhead production trees for controlling fluid flow across a
wellhead, such as production flow from the borehole or circulating
fluid flow in and out of a wellhead.
[0006] Seals are used between inner and outer wellhead tubular
members to contain internal well pressure. The inner wellhead
member may 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 production tree, or a tubing head. A packoff or
seal seals between the tubing hanger and the outer wellhead member.
Alternately, the inner wellhead member might be an isolation sleeve
secured to a production tree. A seal or packoff seals between the
isolation sleeve and a casing hanger located within the wellhead
housing.
[0007] A variety of seals of this nature have been employed in the
prior art. Prior art seals 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. The seals may
be set by a running tool, or they may be set in response to the
weight of the string of casing or tubing. One type of prior art
metal-to-metal seal has inner and outer walls separated by a
conical slot. An energizing ring is pushed into the slot to deform
the inner and outer walls apart into sealing engagement with the
inner and outer wellhead members. The deformation of the inner and
outer walls exceeds the yield strength of the material of the seal
ring, making the deformation permanent. Sometimes a lockdown ring
is provided in the annular space between the tubulars, which is put
into a position that locks the tubulars to one another when the
seal is set.
SUMMARY OF THE INVENTION
[0008] Provided herein is an example of a wellhead assembly. In one
example, a wellhead assembly includes an axis, an outer tubular, an
inner tubular inserted into the outer tubular and defining an
annular space between the inner tubular and outer tubular, and a
lock ring in the annular space that is moveable from an unlocked
position into a locked position. The wellhead assembly of this
embodiment also includes an activation ring having a profiled
surface that is axially slidable against and in contact with the
lock ring to define a contact interface that is offset an angle
from the axis when the lock ring is in the locked position, and to
define a contact interface that is offset an angle from the axis
when the lock ring is in the unlocked position, so that the angle
when the lock ring is in the locked position is less than the angle
when the lock ring is in the unlocked position. Optionally, a
portion of the profiled surface is curved that is in contact with
the lock ring when the lock ring is in the unlocked position, and a
portion of the profiled surface that is in contact with the lock
ring when the lock ring is in the locked position is substantially
linear. In one example embodiment, the lock ring is set radially
inward from the outer tubular when in the unlocked position, and
the lock ring comprises a protrusion that engages a depression
formed in an inner radial surface of the outer tubular.
Alternatively, the lock ring is set radially outward from the inner
tubular when in the unlocked position, and the lock ring has a
protrusion that engages a depression formed in an outer radial
surface of the inner tubular. In an alternate embodiment, the
wellhead further includes a seal assembly that transfers a downward
axial force to an upper end of the activation ring and that is
energized by an energizing force. The force applied to the
activation ring that slides the activation ring along the lock ring
may urge the lock ring from the unlocked position to the locked
position, and the energizing force can be greater than the force
applied to the activation ring. In one example, the outer tubular
is a wellhead housing and the inner tubular is a tubing hanger.
[0009] Also provided herein is a system for locking together
tubulars that are disposed in a wellhead assembly. In this example
the system includes a lock ring that axially rests on one of the
tubulars and selectively engages an adjacent tubular thereby
axially locking together the one of the tubulars and the adjacent
tubular. Also included is an activation ring axially moveable to
between the lock ring and the one of the tubulars and having a
surface in sliding contact with the lock ring that transitions from
a curved profile to a linear profile as the activation ring moves
to between the lock ring and the one of the tubulars. In an example
embodiment of the system, the activation ring contacts the lock
ring along an interface that is offset from an axis of the wellhead
assembly by an angle up to about 5 degrees when the lock ring is
engagement with the adjacent tubular. Optionally, the activation
ring contacts the lock ring along an interface that is offset from
an axis of the wellhead assembly by an angle that ranges from at
least about 5 degrees to about 30 degrees when the curved profile
is in contact with the lock ring. The one of the tubulars can be a
tubing hanger and the adjacent tubular can be a wellhead housing.
In an alternate example, the one of the tubulars can be a wellhead
housing and the adjacent tubular can be a tubing hanger.
Optionally, an upper end of the activation ring is in axial contact
with a seal assembly, where the seal assembly is energized with an
axial force that exceeds a force applied to slide the activation
ring from a position above the lock ring to a position adjacent the
lock ring.
[0010] Yet further provided herein is a method of locking together
tubulars in a wellhead assembly. One example embodiment of the
method includes providing a lock ring on a lateral surface of one
of the tubulars, applying a force onto the lock ring in a direction
oblique with an axis of the wellhead assembly to radially urge the
lock ring towards an adjacent tubular, changing the direction of
the force to be substantially perpendicular to the axis and
engaging the lock ring with the adjacent tubular, and retaining the
lock ring in engagement with the adjacent tubular by continuing to
apply the force in a direction substantially perpendicular to the
axis. The method may further include providing an activation ring
having a contact surface that transitions from a curved portion to
a linear portion. In one example, the step of applying a force onto
the lock ring in a direction oblique with an axis of the wellhead
assembly involves axially urging the activation ring so the curved
portion slides against a side of the lock ring. In an optional
embodiment, the step of applying a force onto the lock ring in a
direction perpendicular to an axis of the wellhead assembly
includes axially urging the activation ring so the linear portion
slides against a side of the lock ring. In an example, the step of
continuing to apply the force in a direction substantially
perpendicular to the axis includes retaining the activation ring
adjacent the lock ring so the linear portion is in contact with a
side of the lock ring.
BRIEF DESCRIPTION OF DRAWINGS
[0011] Some of the features and benefits of the present invention
having been stated, others will become apparent as the description
proceeds when taken in conjunction with the accompanying drawings,
in which:
[0012] FIGS. 1A and 1B are side sectional views of an example of
coupling together tubulars in a wellhead assembly in accordance
with the present invention.
[0013] FIGS. 2A-2C are side sectional detailed views of operation
of a locking mechanism of FIGS. 1A and 1B in accordance with the
present invention.
[0014] FIG. 3 is a side partial sectional view of an example
embodiment of the wellhead assembly of FIGS. 1A and 1B set over a
wellbore in accordance with the present invention.
[0015] While the invention will be described in connection with the
preferred embodiments, it will be understood that it is not
intended to limit the invention to that embodiment. On the
contrary, it is intended to cover all alternatives, modifications,
and equivalents, as may be included within the spirit and scope of
the invention as defined by the appended claims.
DETAILED DESCRIPTION OF INVENTION
[0016] The method and system of the present disclosure will now be
described more fully hereinafter with reference to the accompanying
drawings in which embodiments are shown. The method and system of
the present disclosure may be in many different forms and should
not be construed as limited to the illustrated embodiments set
forth herein; rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey its
scope to those skilled in the art. Like numbers refer to like
elements throughout.
[0017] It is to be further understood that the scope of the present
disclosure is not limited to the exact details of construction,
operation, exact materials, or embodiments shown and described, as
modifications and equivalents will be apparent to one skilled in
the art. In the drawings and specification, there have been
disclosed illustrative embodiments and, although specific terms are
employed, they are used in a generic and descriptive sense only and
not for the purpose of limitation. Accordingly, the improvements
herein described are therefore to be limited only by the scope of
the appended claims.
[0018] FIG. 1A is a side sectional view of one example embodiment
of a wellhead assembly 10 that includes a portion of a wellhead
housing 12 adjacent a tubing hanger 14. The wellhead housing 12 and
tubing hanger 14 are generally tubular members that are spaced
apart. An example of a seal assembly 16 is illustrated set within
an annulus 18 that is between the tubing hanger 14 and wellhead
housing 12. The embodiment of the seal assembly 16 includes an
annular seal ring 20 insertable into the annulus 18. The seal ring
20 of FIG. 1A has an inner leg 22, which as provided in the
sectional view is an elongate member that extends generally
parallel with an axis A.sub.X of the wellhead assembly 10. The
example of the seal ring 20 also includes an outer leg 24; which
also extends substantially parallel with the axis A.sub.X and is
longer than the inner leg 22. The outer leg 24 is set radially
outward from the inner leg 22 to define an annular space 26 set
between the inner and outer legs 22, 24. The inner and outer legs
22, 24 are connected to one another on their respective lower ends
by a cross piece that also defines a lower surface of the space 26.
An energizing ring 28 is shown having a lower end inserted into an
upper end of the space 26. In an example, axially urging the seal
assembly 20 into annulus 18 then inserting energizing ring 28 into
space 26 urges legs 22, 24 radially outward from one another
thereby creating a pressure barrier in the annulus 18. A ring-like
collar 30 is shown circumscribing a portion of the energizing ring
28 and threadingly engaged with an upper end of the outer leg
24.
[0019] Further illustrated in the example of the wellhead assembly
10 of FIG. 1A is an annular activation ring 32, which is set in the
annulus 18 below the seal assembly 20. In the example of FIG. 1A,
the lower end of the seal assembly 20 rests on an upper end of the
activation ring 32. Below the activation ring 32 is a lock ring 34
for axially locking together the wellhead housing 12 and tubing
hanger 14. Referring now to FIG. 2A, illustrated in detailed
sectional view is an example of the activation ring 32 and lock
ring 34. In the example of FIGS. 1A and 2A, the lock ring 34 is in
an unlocked configuration, thus the wellhead housing 12 and tubing
hanger 14 may move axially with respect to one another. As shown in
FIG. 2A, a surface of the activation ring 32 facing axis A.sub.X
defines an inner surface 36 that is shown having a transition 38
where a radius of the surface 36 changes. Opposite the inner
surface 36 is an outer surface 40 shown having a lower portion 42
that transitions into an upper portion 44. The transition 46 at the
upper end of upper portion 44 defines where a change in length of
radius of the outer surface 40 takes place.
[0020] Profiles 48 are shown formed on the outer surface 40 and
above transition 46 to define a handle 50 for raising and lowering
the activation ring 32 within the annulus 18 (FIG. 1A). In the
example of FIG. 2A, a line L.sub.1 is shown extending tangentially
across upper portion 44 illustrating in the example of FIG. 2A that
the outer surface 40 is generally linear along upper portion in the
axial direction. In contrast, outer surface 40 along lower portion
42 is curved and in some portions thereof maintains a consistent
radius. A line L.sub.2 is shown tangentially across a portion of an
inner surface of the lock ring 34. In one example embodiment, the
line L.sub.2 is at about 20 degrees to about 35 degrees offset from
axis A.sub.X.
[0021] Still referring to FIG. 2A, an outer surface 54 of the lock
ring 34 is shown having protrusions 56 that extend radially outward
and away from inner surface 52. Referring back to FIG. 1A, the
protrusions 56 are profiled to correspond to depressions 58 shown
formed along an inner surface 60 of the wellhead housing 12 and
adjacent lock ring 34. Further illustrated in FIG. 1A are wickers
62, 64 shown respectively formed on the inner surface 60 of the
wellhead housing 12 and an outer surface 66 of the tubing hanger
14. In an embodiment, the wickers 62, 64 are ridge-like members
formed in the surfaces 60, 66, so that when the seal 20 is set in
the annulus 18, the wickers 62, 64 deform respective outer surfaces
of the inner leg 22 and outer leg for enhancing the sealing
function of the seal assembly 20.
[0022] FIG. 1B illustrates in side sectional view an example of the
lock ring 34 set in a locked position and in engagement with the
depressions 58 on the wellhead housing 12. Further illustrated in
FIG. 1B is that a lower end of the lock ring 34 rests on a shoulder
67 defined where the outer surface 66 of the tubing hanger 14 juts
radially outward and away from axis A.sub.X. Engaging the
protrusions 56 with the depressions 58 axially retains the lock
ring 34 in place. Also, by contacting the shoulder 67 with lower
end of the block ring 34, the tubing hanger 14 is prevented from
moving axially upward with respect to the wellhead housing 12 by
the axially static lock ring 34. Further in the example of FIG. 1B,
the lock ring 34 engages the profiles 58 by being moved radially
outward from axis A.sub.X by downward axial movement of the
activation ring 32. Thus, retaining the activation ring 32 in the
position of FIG. 1B, the tubing hanger 14 is axially constrained to
the wellhead housing 12.
[0023] A detailed example of interaction between the activation
ring 32 and lock ring 34 in the locked position is illustrated in
side sectional view in FIGS. 2B and 2C. In FIG. 2B, shown is an
example of the activation ring 32 having a force F applied to its
upper end thereby slidingly urging the activation ring 32 to a
position adjacent the lock ring 34 (FIG. 2C). In one example, the
activation ring 32 and lock ring 34 are substantially coaxial when
the lock ring 34 is in the locked position. In the example of FIG.
2B, the lower curved portion 42 of the activation ring 32 is in
contact with the inner surface 52 of the lock ring 34. As such, a
resultant force F.sub.R is exerted against the lock ring 34 and
shown being in a direction generally oblique to the axis A.sub.X.
With further downward movement of the activation ring 32, the
direction of resultant force F.sub.R rotates from its oblique
orientation and to one that is close to being substantially
perpendicular to axis A.sub.X (FIG. 2). In the example of FIG. 2B,
a portion of line L.sub.3 extends along a contact interface between
the activation ring 32 and lock ring 34. Similarly, line L.sub.4 in
FIG. 2C is drawn along a contact interface between the activation
ring 32 and lock ring 34 when the activation ring 32 is
substantially adjacent lock ring 34. As shown, line L.sub.4 is at
an offset angle from axis A.sub.X that is less than an offset angle
between L.sub.3 and axis A.sub.X (FIG. 2B).
[0024] An advantage of the curved lower surface 42 is that the lock
ring 34 may be urged radially outward into its locked configuration
with the wellhead housing 12 by a stroke distance of the activation
ring 32 that is shorter than a corresponding stroke distance in
instances where the lower portion 42 is linear. Moreover, by
transitioning the outer surface 40 of the activation ring 32 from a
curved lower portion 44 to a linear upper portion 44, the resultant
force F.sub.R has a reduced axial component exerted from the lock
ring 34 onto the activation ring 32. As such, more force from the
lockdown system may be distributed towards retaining the tubing
hanger 14 rather than maintaining the lock ring 34 in its locked
position.
[0025] FIG. 3 is a side partial sectional view of one example of
the wellhead assembly 10 shown set over a wellbore 68, where the
wellbore 68 extends through a formation 70. In the example of FIG.
3, an example of a lockdown assembly 71 is schematically
illustrated for locking the tubing hanger 14 to the wellhead
housing 12. In the example of FIG. 3, the lockdown assembly 71
includes examples of the activation ring and lockdown ring as
described above. Further illustrated in FIG. 3 is a string of
tubing 72 that depends downward into the bore hole 68 from the
tubing hanger 14.
[0026] An additional advantage of the lockdown assembly illustrated
herein is that by transitioning the outer surface of the retaining
ring 32, axial forces required for retaining the lockdown ring 34
in its locked position are reduced that in turn allows for higher
preloads on a seal assembly 20 (FIG. 1A). Thus, the lock ring 34
can be set at an axial force below that which may initiate
energizing of a seal set in the annulus 18.
[0027] The present invention described herein, therefore, is well
adapted to carry out the objects and attain the ends and advantages
mentioned, as well as others inherent therein. While a presently
preferred embodiment of the invention has been given for purposes
of disclosure, numerous changes exist in the details of procedures
for accomplishing the desired results. These and other similar
modifications will readily suggest themselves to those skilled in
the art, and are intended to be encompassed within the spirit of
the present invention disclosed herein and the scope of the
appended claims.
* * * * *