U.S. patent application number 15/207326 was filed with the patent office on 2017-06-08 for lock ring and packoff for wellhead.
The applicant listed for this patent is Cameron International Corporation. Invention is credited to Hao Bin Huang, Jay P. Painter, Kyle A. Sommerfeld.
Application Number | 20170159399 15/207326 |
Document ID | / |
Family ID | 52808683 |
Filed Date | 2017-06-08 |
United States Patent
Application |
20170159399 |
Kind Code |
A1 |
Sommerfeld; Kyle A. ; et
al. |
June 8, 2017 |
LOCK RING AND PACKOFF FOR WELLHEAD
Abstract
A packoff and a locking assembly installed in a bore of a
wellhead component are provided. In one embodiment, a packoff
includes inner and outer annular seals and an energizing ring
shaped to be wedged between the inner and outer annular seals so as
to apply a radially inward biasing force on the inner annular seal
and a radially outward biasing force on the outer annular seal. In
another embodiment, a locking assembly includes a lock ring that
extends into a recess in a wall of the bore of the wellhead
component and an actuator radially disposed between an inner
component within the bore and the lock ring to retain the lock ring
within the recess. The actuator can have an interference fit with
the inner component to inhibit movement of the actuator between the
lock ring and the inner component. Additional systems, devices, and
methods are also disclosed.
Inventors: |
Sommerfeld; Kyle A.;
(Houston, TX) ; Huang; Hao Bin; (Houston, TX)
; Painter; Jay P.; (Friendswood, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cameron International Corporation |
Houston |
TX |
US |
|
|
Family ID: |
52808683 |
Appl. No.: |
15/207326 |
Filed: |
July 11, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14055702 |
Oct 16, 2013 |
9388655 |
|
|
15207326 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 2200/01 20200501;
E21B 33/03 20130101; E21B 33/04 20130101 |
International
Class: |
E21B 33/12 20060101
E21B033/12; E21B 33/04 20060101 E21B033/04; E21B 33/128 20060101
E21B033/128 |
Claims
1. A system comprising: a wellhead component having a bore; an
inner component disposed within the bore of the wellhead component;
a locking assembly disposed within the bore between the inner
component and the wellhead component to secure the inner component
within the bore of the wellhead component, the locking assembly
including: a lock ring that extends into a recess in a wall of the
bore of the wellhead component; and an actuator radially disposed
between the inner component and the lock ring to retain the lock
ring within the recess; wherein the actuator has an interference
fit with the inner component to inhibit movement of the actuator
between the lock ring and the inner component; and a packoff
disposed in the bore of the wellhead component, the packoff
including: an inner annular seal; and an outer annular seal.
2. (canceled)
3. The system of claim 1, wherein the inner annular seal has a pair
of arms that extend radially inward and the outer annular seal has
a pair of arms that extend radially outward to facilitate sealing
of an annular space by the packoff.
4. The system of claim 1, wherein the inner annular seal is
concentric with the outer annular seal.
5. The system of claim 4, wherein the inner annular seal is axially
aligned with the outer annular seal.
6. The system of claim 1, wherein the packoff includes a landing
ring.
7. The system of claim 6, wherein the landing ring is positioned
within the bore on the actuator of the locking assembly.
8. The system of claim 6, wherein the packoff includes a retaining
ring between the landing ring and the inner annular seal.
9. (canceled)
10. (canceled)
11. The system of claim 1, wherein the inner component is a
hanger.
12. The system of claim 1, wherein the locking assembly includes a
load ring between the lock ring and a shoulder of the inner
component.
13. The system of claim 1, wherein the lock ring cooperates with
the recess in the wall of the bore to preload the inner
component.
14. The system of claim 1, wherein both the locking assembly and
the packoff are configured to be axially set in the bore without
rotation.
15-20. (canceled)
21. A system comprising: a wellhead component having a bore; an
inner component disposed within the bore of the wellhead component;
and a locking assembly disposed within the bore between the inner
component and the wellhead component to secure the inner component
within the bore of the wellhead component, the locking assembly
including: a lock ring that extends into a recess in a wall of the
bore of the wellhead component; and an actuator radially disposed
between the inner component and the lock ring to retain the lock
ring within the recess; wherein the actuator has an interference
fit with the inner component to inhibit movement of the actuator
between the lock ring and the inner component.
22. The system of claim 21, wherein the inner component is a
hanger.
23. The system of claim 21, wherein the locking assembly includes a
load ring between the lock ring and a shoulder of the inner
component.
24. The system of claim 21, wherein the lock ring cooperates with
the recess in the wall of the bore to preload the inner
component.
25. The system of claim 21, wherein the locking assembly is
configured to be axially set in the bore without rotation.
26. A method comprising: inserting a locking assembly into a bore
of a wellhead component, the locking assembly including a lock ring
and an actuator for controlling the radial position of the lock
ring; positioning the locking assembly so as to be radially between
the wellhead component and an inner component also present within
the bore of the wellhead component; and axially setting the locking
assembly, wherein axially setting the locking assembly includes
applying an axial force to the actuator to move the actuator to a
locked position in which the actuator is wedged behind the lock
ring, moving the actuator to the locked position causes the lock
ring to move radially to extend into a mating recess, and the
actuator is retained in the locked position with an interference
fit.
27. The method of claim 26, wherein applying the axial force to the
actuator to move the actuator to the locked position includes
applying the axial force to the actuator so as to wedge the
actuator between the lock ring and the inner component, the
wellhead component includes the mating recess, and moving the
actuator to the locked position causes the lock ring to move
radially to extend into the mating recess in the wellhead
component.
28. The method of claim 26, wherein applying the axial force to the
actuator includes applying the axial force to the actuator from a
running tool.
29. The method of claim 26, comprising unlocking the locking
assembly, wherein unlocking the locking assembly includes axially
pulling the actuator from behind the lock ring to allow the lock
ring to relax and exit the mating recess.
Description
BACKGROUND
[0001] This section is intended to introduce the reader to various
aspects of art that may be related to various aspects of the
presently described embodiments. This discussion is believed to be
helpful in providing the reader with background information to
facilitate a better understanding of the various aspects of the
present embodiments. Accordingly, it should be understood that
these statements are to be read in this light, and not as
admissions of prior art.
[0002] In order to meet consumer and industrial demand for natural
resources, companies often invest significant amounts of time and
money in finding and extracting oil, natural gas, and other
subterranean resources from the earth. Particularly, once a desired
subterranean resource such as oil or natural gas is discovered,
drilling and production systems are often employed to access and
extract the resource. These systems may be located onshore or
offshore depending on the location of a desired resource.
[0003] Further, such systems generally include wellhead assemblies
mounted on wells through which resources are accessed or extracted.
Such wellhead assemblies can include a wide variety of components,
such as various spools, casings, valves, pumps, fluid conduits, and
the like, that control drilling or extraction operations. In many
instances, casings are coupled to wellheads via hangers installed
in bores of the wellheads. These hangers and other components
within the bores can be retained in various ways, and sealing
packoffs can be used to seal annular spaces within the bores.
SUMMARY
[0004] Certain aspects of some embodiments disclosed herein are set
forth below. It should be understood that these aspects are
presented merely to provide the reader with a brief summary of
certain forms the invention might take and that these aspects are
not intended to limit the scope of the invention. Indeed, the
invention may encompass a variety of aspects that may not be set
forth below.
[0005] Embodiments of the present disclosure generally relate to
locking assemblies and sealing packoffs that can be installed
within a bore of a wellhead. In one embodiment, a locking assembly
includes an actuator that can be driven between a lock ring and
another component within the bore to cause the lock ring to expand
into a recess in a wall of the bore. In another embodiment, a
sealing packoff includes inner and outer annular seals and an
energizing ring arranged such that the energizing ring can be
wedged between the inner and outer annular seals to apply a
radially inward biasing on the inner annular seal and a radially
outward biasing force on the outer annular seal. In at least some
embodiments, the sealing packoff and the locking assembly can be
axially set within the bore without requiring rotation.
[0006] Various refinements of the features noted above may exist in
relation to various aspects of the present embodiments. Further
features may also be incorporated in these various aspects as well.
These refinements and additional features may exist individually or
in any combination. For instance, various features discussed below
in relation to one or more of the illustrated embodiments may be
incorporated into any of the above-described aspects of the present
disclosure alone or in any combination. Again, the brief summary
presented above is intended only to familiarize the reader with
certain aspects and contexts of some embodiments without limitation
to the claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These and other features, aspects, and advantages of certain
embodiments will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0008] FIG. 1 is a block diagram of a system having a wellhead with
various components installed at a well in accordance with one
embodiment of the present disclosure;
[0009] FIG. 2 is a section view of a wellhead having locking
assemblies for securing components within a bore of the wellhead
and packoffs for sealing annular spaces within the bore in
accordance with one embodiment;
[0010] FIG. 3 is a detail view of one locking assembly and one
packoff of the wellhead of FIG. 2 in accordance with certain
embodiments;
[0011] FIGS. 4 and 5 are detail views of the locking assembly
depicted in FIG. 3 and generally depict unlocked and locked states
of the locking assembly in accordance with one embodiment;
[0012] FIG. 6 depicts another locking assembly similar to that of
FIG. 3 but including a spring in an actuator of the locking
assembly in accordance with one embodiment;
[0013] FIG. 7 depicts the packoff of FIG. 3 in a relaxed state as
it is being positioned within the bore of the wellhead and before
it is set in accordance with one embodiment; and
[0014] FIG. 8 is a detail view of a portion of the packoff of FIG.
3 and depicts the setting of annular seals of the packoff with
energizing rings in accordance with one embodiment.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0015] Specific embodiments of the present disclosure are described
below. In an effort to provide a concise description of these
embodiments, all features of an actual implementation may not be
described in the specification. It should be appreciated that in
the development of any such actual implementation, as in any
engineering or design project, numerous implementation-specific
decisions must be made to achieve the developers' specific goals,
such as compliance with system-related and business-related
constraints, which may vary from one implementation to another.
Moreover, it should be appreciated that such a development effort
might be complex and time consuming, but would nevertheless be a
routine undertaking of design, fabrication, and manufacture for
those of ordinary skill having the benefit of this disclosure.
[0016] When introducing elements of various embodiments, the
articles "a," "an," "the," and "said" are intended to mean that
there are one or more of the elements. The terms "comprising,"
"including," and "having" are intended to be inclusive and mean
that there may be additional elements other than the listed
elements. Moreover, any use of "top," "bottom," "above," "below,"
other directional terms, and variations of these terms is made for
convenience, but does not require any particular orientation of the
components.
[0017] Turning now to the present figures, a system 10 is
illustrated in FIG. 1 by way of example. The system 10 is a
production system that facilitates extraction of a resource, such
as oil or gas, from a reservoir 12 through a well 14. A wellhead 16
is installed on the well (e.g., attached to the top of casing and
tubing strings in the well). As shown here, the wellhead 16
includes at least one tubing head 18 and casing head 20. The
wellhead 16 also includes various inner components 22 inside the
wellhead, such as annular plugs and casing and tubing hangers. The
components 22 inside the wellhead 16 can also include locking
assemblies and packoffs, examples of which are described in greater
detail below. The depicted system 10 also includes a tree 24 (e.g.,
a Christmas tree) to facilitate resource production from the well
14.
[0018] An example of a wellhead 30 is generally depicted in FIG. 2
in accordance with one embodiment. This wellhead 30 includes casing
heads 32 and 34 connected to a casing system 36. As depicted, the
casing system 36 includes five tubular strings (e.g., a production
tubing string, intermediate casings, a surface casing, and a
conductor pipe) and control lines in the annulus between the two
innermost tubular strings, but other embodiments include different
casing arrangements. Hangers are connected to the top of various
tubular strings (e.g., all of the strings besides the conductor
pipe) of the casing system 36 to allow the strings to be suspended
from the wellhead 30.
[0019] The casing head 32 is illustrated as a multi-bowl casing
head that receives hangers for multiple tubular strings, including
a production tubing string and intermediate casing strings. This
allows a single casing head to support multiple casing strings,
rather than using separate heads (e.g., a tubing head 18 and other
casing heads 20) for each string. But separate tubing and casing
heads could be used for supporting individual strings in other
embodiments. Various locking assemblies 38 and packoffs 40 are
disposed within the bore 42 of the wellhead 30 to secure the
hangers and inhibit fluid leakage. In at least some embodiments,
the locking assemblies 38 and the packoffs 40 are constructed for
use in high and low temperatures and for high pressure within the
wellhead 30 exceeding 20 ksi.
[0020] By way of example, a friction locking assembly 38 and a
packoff 40 are illustrated in FIG. 3 as installed in an annular
space 44 in the bore 42 (between the casing head 32 on the one hand
and an inner component in the form of a hanger 48 coupled to an
additional inner component 52, such as an annular plug, on the
other). As shown in this figure, the hanger 48 is positioned on a
landing shoulder 50 within the bore 42. The landing shoulder 50 can
be formed integrally with the casing head 32, i.e., as a tapered
edge of the bore wall 46, or can be a separate component installed
within the bore 42 (as is the case in FIG. 3). The hanger 48 can be
threaded onto the component 52 or coupled in some other suitable
fashion.
[0021] The depicted locking assembly 38, which is shown in greater
detail in FIGS. 4 and 5, includes a lock ring 54, an actuator 56,
and a load ring 58. The components of the locking assembly 38 can
be formed of metal or of any other suitable material. The lock ring
54 is disposed radially about a neck 60 of the hanger 48 and
includes ridges 62 along its outer circumference. The bore wall 46
of the casing head 32 has mating recesses 64 for receiving the
ridges 62 of the lock ring 54. In the presently depicted
embodiment, the load ring 58 also includes a recess 70 for
receiving a distal end 72 of the actuator 56.
[0022] The locking assembly 38 is shown in its unlocked state in
FIG. 4, with the actuator 56 positioned above the lock ring 54,
which is withdrawn from the recesses 64. This unlocked state allows
the locking assembly 38 to move axially within the bore 42, such as
during installation of the locking assembly 38 and the hanger 48 in
the casing head 32.
[0023] Once the locking assembly 38 and the hanger 48 are axially
positioned at their intended locations within the bore 42 (i.e.,
with the hanger 48 on landing shoulder 50 and the lock ring 54
adjacent the recesses 64), the actuator 56 can be pushed toward the
landing shoulder 50 so that the actuator 56 is radially positioned
between the lock ring 54 and the neck 60 of the hanger 48. This
locked state is depicted in FIG. 5.
[0024] A tapered interface 68 of the lock ring 54 and the actuator
56 causes the lock ring 54 to expand radially as the actuator 56 is
driven between the lock ring 54 and the neck 60. To facilitate this
radial expansion, the lock ring 54 is provided as a split ring
(e.g., a C-ring) in at least some embodiments. The expansion of the
lock ring 54 results in the movement of the ridges 62 into the
recesses 64, which inhibits axial movement of the hanger 48 within
the bore 42.
[0025] The locking assembly 38 of at least some embodiments can be
set using only axial motion to secure the hanger 48 (or some other
component) inside the bore 42. Unlike other locking assemblies that
require rotation of an element (such as a threaded ring) within
bores to set the locking assemblies and secure components within
the bores, the presently depicted locking assembly can be set by
axially driving (e.g., with a running tool) the actuator 56 between
the lock ring 54 and the hanger 48 to cause the lock ring 54 to
engage the recesses 64. Rotation of components within a bore can
increase the risk of damage to the bore and other components. By
axially setting the locking assembly 38, such an increased risk of
damage from rotation can be avoided. Axial setting also allows the
use of less complicated tooling in installing the locking assembly
38, which can reduce installation time and expense. The locking
assembly 38 can also be unlocked via axial force, such as by
engaging recess 74 on the actuator 56 and pulling the actuator 56
away from the load ring 58 to allow the lock ring 54 to relax and
retract from the recesses 64.
[0026] Further, when in its locked position, the locking assembly
38 provides a preload on the hanger 48. This preload in some
instances can be equal to the expected loading on the hanger 48
from wellbore fluids in the wellhead 30 during operation. As
depicted in FIG. 4, the ridges 62 and recesses 64 have mating
tapered edges. As the lock ring 54 is driven into engagement with
the recesses 64 by the actuator 56, the mating engagement of the
upper tapered surfaces of the ridges 62 and the recesses 64 in FIG.
4 cause the lock ring 54 to be driven downward and to apply a
compression force on the load ring 58, thus applying a preload on
the hanger 48. It will be appreciated that the amount of preload
depends on the geometries of the lock ring 54, the load ring 58,
and the recesses 64, which can vary between different
embodiments.
[0027] In some prior art designs, locking assemblies in wellheads
are retained by providing devices, such as springs, above the
locking assemblies to load against the locking assemblies and
inhibit axial movement. In other prior art designs, threaded
connections are used to retain locking assemblies at a desired
location. But in contrast to such prior art designs, in at least
some embodiments of the present disclosure friction alone is used
to retain a locking assembly 38 in the locked position without the
need for rotation or other retention mechanisms.
[0028] For example, the actuator 56 of the locking assembly 38
depicted in FIG. 5 is installed on the neck 60 of the hanger 48
with an interference fit. Friction caused by the interference fit
at the interface 66 between these two components retains the
actuator 56 in its locked position. In another embodiment generally
depicted in FIG. 6, the actuator 56 has a recess 76 and a spring
78. In its natural, unflexed state the spring 78 is slightly wider
than the depth of the recess 76, which causes the spring 78 to bow
in the middle when the actuator 56 is moved into its locked
position. This, in turn, causes the ends of the spring 78 to press
against the neck 60 of the hanger 48, allowing friction between the
spring 78 and the hanger 48 to retain the actuator 56 in its locked
position.
[0029] Returning now to FIG. 3, the packoff 40 is depicted directly
above the locking assembly 38. Like the locking assembly 38, the
packoff 40 is configured to be run into the bore 42 and set through
axial movement without requiring rotation. And while depicted here
together, it will be appreciated that each of the locking assembly
38 and the packoff 40 could be used separately without the
other.
[0030] The packoff 40 includes an inner annular seal 80 and an
outer annular seal 82. These annular seals can be formed of metal
(enabling metal-to-metal sealing against other metal components) or
of any other suitable material. As illustrated, the inner and outer
annular seals 80 and 82 have cross-sectional profiles that include
arms that extend outwardly from a central portion to seal against
other components. But the annular seals 80 and 82 can be provided
with different shapes in other embodiments.
[0031] The packoff 40 also includes an energizing ring 84. As
discussed in greater detail below, the energizing ring 84 is shaped
to be wedged between the inner annular seal 80 and the outer
annular seal 82 to deflect and energize these seals by applying
radially inward and outward biasing forces, respectively, to the
seals. In FIG. 3, the outer annular seal 82 is depicted as resting
on a landing ring 88 that is positioned in contact with the
actuator 56 of the locking assembly 38. The inner annular seal 80
is shown as resting on a retaining ring 90. Although provided in
FIG. 3 as a separate component, the retaining ring 90 could instead
be integrated as part of the landing ring 88.
[0032] In one embodiment, the packoff 40 could include only one
pair of annular seals (e.g., inner and outer annular seals 80 and
82). But multiple pairs of annular seals (each pair having a
respective energizing ring) can be used in series in the packoff 40
to provide multiple pressure barriers. For instance, the packoff 40
in FIG. 3 includes an additional pair of annular seals, namely
inner annular seal 94 and outer annular seal 96. The inner and
outer annular seals 94 and 96 are identical to the seals 80 and 82
in the present embodiment, but could vary in others. The packoff 40
includes an additional energizing ring 98 that is shaped to be
wedged between the inner and outer annular seals 94 and 96 to apply
a radially inward biasing force on the seal 94 and a radially
outward biasing force on the seal 96. The outer annular seal 96 is
depicted as resting on the energizing ring 84 and the inner annular
seal 94 is depicted as resting on a retaining ring 100, which could
instead be provided as an integral portion of the energizing ring
84.
[0033] While the packoff 40 is depicted here as having only two
sets of inner and outer annular seals with associated energizing
rings, further sets of seals and energizing rings could be
connected in series with those described above. Each pair of inner
and outer annular seals (e.g., seals 80 and 82; seals 94 and 96)
can be provided as concentric ring seals that are axially aligned
with one another (i.e., both intersecting a shared axial plane
through the wellhead 30), as generally depicted in the present
figures. But in other embodiments the seals could be provided in
different arrangements, such as being axially offset from one
another. The packoff 40 of FIG. 3 also includes an actuator 106 and
an associated lock ring 108 above the uppermost energizing ring
(here ring 98) for retaining the packoff 40 in its installed
position.
[0034] Installation and setting of the packoff 40 may be better
understood with reference to FIGS. 7 and 8. Before being installed
in the wellhead 30, the packoff 40 is in a relaxed state in which
its inner and outer annular seals are withdrawn into the radial
profile of the packoff 40 to reduce or eliminate contact by these
seals against the wall 46 or the inner component 52 as the packoff
40 is run into the annular space 44 of the bore 42. In FIG. 7, the
packoff 40 is depicted as having been run into the bore 42 until
the landing ring 88 contacts the actuator 56 of the locking
assembly 38. But the packoff 40 is shown here as still being in its
relaxed state (the same state the packoff 40 is in before it is
inserted into the bore 42) prior to energizing the inner and outer
seals with the energizing rings.
[0035] In this relaxed state, the energizing ring 84 is spaced
axially apart from the landing ring 88, the energizing ring 98 is
spaced axially apart from the ring 84, and the actuator 106 is
spaced axially apart from the ring 98. The packoff 40 can be held
together with retaining wires 110 and shear pins 112 while in its
relaxed state to facilitate handling and to enable the packoff 40
to be run into the bore 42 as a single unit (e.g., in a single
operation by a running tool coupled to the actuator 106). One or
more shear rings can be used with or instead of the shear pins 112
in other embodiments. The packoff 40 can first be axially run into
the bore 42 to the position depicted in FIG. 7. Further axial force
can then be applied to the packoff 40 (e.g., to the actuator 106)
to break the shear pins 112 and cause tapered portions 118 of the
energizing rings 84 and 98 to be driven downward and wedged between
the inner and outer annular seals. This, in turn, causes the
tapered portions 118 to energize the seals by driving the inner
annular seals 80 and 94 radially inward against the inner component
52, as represented by arrows 124 in FIG. 8, and driving the outer
annular seals 82 and 96 radially outward against the wall 46 (which
may include recesses for receiving the seals, like in FIG. 8), as
represented by arrows 126. Sealing contact is made by the inwardly
extending pairs of arms of inner annular seals 80 and 94 and by the
outwardly extending pairs of arms of outer annular seals 82 and
96.
[0036] In one embodiment, the shear pins 112 are designed to shear
in a staggered fashion. For instance, to avoid energizing the
annular seals 94 and 96 before they are positioned at their desired
axial location in the bore 42, the shear pin 112 through the
retaining ring 90 can be configured to break first to allow
energizing ring 84 to energize the seals 80 and 82. As the
energizing ring 84 is driven axially downward between the seals 80
and 82, the seals 94 and 96 move into their desired axial position.
The shear pin 112 through the retaining ring 100 can be configured
to break next, allowing the energizing ring 98 to be driven axially
downward to then energize the seals 94 and 96. The shear pin 112
holding the energizing ring 98 to the actuator 106 can then be
broken to drive the lock ring 108 toward a recess in the inner
component 52. Other techniques for timing the energizing of the
seals and the movement of the various components of the packoff 40
(e.g., using shear rings) may also be used in full accordance with
the present techniques.
[0037] The packoff 40 can be removed from the bore 42 by pulling
the actuator 106 to release the lock ring 108. As the actuator 106
moves up the bore 42, the retaining wires 110 cause the energizing
rings 84 and 98 to be pulled from the seals, allowing the seals to
relax and the packoff 40 to be removed from the bore 42. And as
noted above with respect to the locking assembly 38, the ability to
axially set and remove the packoff 40 without requiring rotation
can reduce the risk of damage to components of the wellhead and
allow simpler tooling to be used.
[0038] In addition to simplifying installation by being axially set
within a bore, the disclosed locking assemblies 38 and packoffs 40
can also enable the use of a shorter wellhead assembly. For
example, by omitting separate retention devices above the locking
assemblies 38, packoffs 40 can be installed closer to (e.g., in
contact with) the locking assemblies 38. The seals of the packoffs
40 can also be axially set with a lower setting load and have lower
preload requirements compared to wedge seals used in some other
arrangements. This allows the packoffs 40 to omit both the longer,
rotatable actuators (and threads) and the crushable spacers between
seals of a previous arrangement, providing further space savings.
In one comparison, the axial length of a combination of one locking
assembly 38 and one packoff 40 (as depicted in FIG. 3) was
determined to be thirty-five percent less than a locking
assembly--packoff combination of a previous design. And a wellhead
can include multiple locking assemblies and packoffs (see, e.g.,
FIG. 2), allowing the aggregate reduction in axial length to be
even more substantial.
[0039] While the aspects of the present disclosure may be
susceptible to various modifications and alternative forms,
specific embodiments have been shown by way of example in the
drawings and have been described in detail herein. But it should be
understood that the invention is not intended to be limited to the
particular forms disclosed. Rather, the invention is to cover all
modifications, equivalents, and alternatives falling within the
spirit and scope of the invention as defined by the following
appended claims.
* * * * *