US20140183824A1 - Seal with flexible nose for use with a lock-down ring on a hanger in a wellbore - Google Patents

Abstract

A seal system selectively set between coaxial downhole tubulars seals between the tubulars; the system also locks the tubulars together to resist relative axial movement from thermal expansion. The seal system includes a seal element with a nose ring that couples a lock-down ring to both the inner and outer tubulars. Before inserting the seal system between the tubulars, the lock-down ring is disposed in a groove on the inner tubular. Setting the seal system drives a lower tip of the nose ring between the lock-down ring and inner tubular, thereby urging the lock-down ring radially outward. A portion of the lock-down ring remains in the groove, while an outer radial portion of the lock-down ring inserts into a profile on the outer tubular. Axial movement of a tubular transfers force to the other tubular through the lock-down ring, while a minimal amount of force transfers through the seal system.

Description

BACKGROUND
• 1. Field of Invention
• The present disclosure relates in general to wellhead assemblies, and in particular to a seal and lock-down ring for use between inner and outer wellhead members.
• 2. Description of Prior Art
• Seals are typically provided in an annulus between coaxial wellhead tubular members to isolate internal well pressure. The inner wellhead member is sometimes 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 wellhead housing, a production tree, or tubing head. A packoff or seal typically forms a barrier between the tubing hanger and the outer wellhead member. In other times, the inner wellhead member is a casing hanger landed in a wellhead housing and that has a string of casing that depends down into the well. A seal or packoff usually seals between the casing hanger and the wellhead housing.
• 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 seal has inner and outer legs separated by a slot; in which an energizing ring is inserted that deforms the inner and outer legs apart into sealing engagement with the inner and outer wellhead members. The energizing ring is usually a solid member. The seals with inner and outer legs typically plastically deform when pushed into sealing engagement with the inner and outer wellhead members.
SUMMARY OF THE INVENTION
• Disclosed herein is a seal and lock-down system for use between downhole inner and outer tubulars. In an example the system includes a seal element having a body and inner and outer annular legs projecting from the body that are spaced radially apart to define a gap between the legs, a lock-down ring between the tubulars, and a nose ring on an end of the body of the seal element distal from the legs. In this example the nose ring is elongate and generally parallel with an axis of the tubulars. The nose ring is selectively changeable to a set configuration that is generally oblique with the axis when inserted between the lock-down ring and inner tubular. In one example, when the nose ring is inserted between the lock-down ring and inner tubular, the nose ring substantially occupies the space between the lock-down ring and inner tubular. In an alternate embodiment, when the nose ring is inserted between the lock-down ring and inner tubular, an outer radial portion of the lock-down ring projects into a profile in the outer tubular and an inner radial portion is disposed in a lock-down groove on the inner tubular thereby axially affixing together the inner and outer tubulars. Slots may be included that extend through sidewalls of the nose ring from an end of the nose ring distal from the seal element; and wherein fingers can be defined between adjacent slots. In an example embodiment, the inner radius of the lock-down ring projects radially inward proximate a side of the lock-down ring distal from the seal element. The outer tubular can be a wellhead housing that is part of a wellhead assembly, and the inner tubular can be a casing hanger. In one example, directing the energizing ring against the seal element with an energizing force that urges the nose ring between the lock-ring and the inner tubular, wherein inserting the energizing ring into the gap between the inner and outer legs with an energizing force to the energizing ring, drives the energizing ring into the gap and urges the legs radially outward into sealing contact with the tubulars, and wherein the energizing force for the seal element is greater than the energizing force for the lock-ring.
• Also disclosed herein is a seal system for sealing between coaxial tubulars, where the tubulars are part of a wellhead assembly. In an example, the seal system includes an annular seal element having radially spaced apart inner and outer legs that define a gap therebetween, and that are in sealing contact with opposing surfaces of the tubulars. The seal system further includes a lock-down ring having opposing radial portions in interfering contact with oppositely facing profiles in the tubulars, so that portions of the tubulars adjacent the seal element are axially static, and a nose ring. In this embodiment, the nose ring has an end coupled with an end of the seal element, and a portion spaced from the seal element is wedged between the lock-down ring and one of the tubulars. When wedged as such, the nose ring projects along a path generally oblique to the seal element, and thereby retaining the lock-down ring in interfering contact with the tubulars. The one of the tubulars can be a casing hanger; in this example the portion of the nose ring projects radially inward. A notch can be scored on a radial surface of the nose ring so the nose ring can be changed from an elongate shape to the oblique shape when inserted between the lock-ring and the one of the tubulars. The nose ring can change from an elongate shape to the oblique shape when inserted between the lock-ring and the one of the tubulars, and wherein a force for inserting the nose ring between the lock-ring and the one of the tubulars is less than a force for energizing the seal element. The tubulars can be made up of an inner tubular and an outer tubular with oppositely facing profiles that include an upward facing pedestal defined by a lower surface of a lock-down groove formed along an outer circumference of the inner tubular. The outer tubular can have a downward facing shoulder defined by a profile formed along its inner circumference.
• Further described herein is a system for sealing between tubulars in a wellhead assembly. In an example the system includes a seal element that is selectively inserted between the tubulars, and a lock-down ring selectively disposed on an profile on an outer surface of a one of the tubulars. The lock-down ring can be selectively urged to a position towards another one of the tubulars and into interfering contact with an oppositely facing profile on the another one of the tubulars. Further included in this example is a nose ring on an end of the seal element that selectively inserts between the lock-down ring and the one of the tubulars into a setting position to urge the lock-down ring into the interfering contact, so that forces resulting from relative axial movement of the tubulars are applied to the lock-down ring and bypass the seal element. In an example, the interfering contact of the lock-down ring maintains the portions of the tubulars adjacent the seal in relative static positions. Optionally, when the nose ring is in the setting position the nose ring substantially occupies the space between the lock-ring and the one of the tubulars. In an example, the one of the tubulars is a casing hanger and the another one of the tubulars is a wellhead housing.
BRIEF DESCRIPTION OF DRAWINGS
• 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:
• FIG. 1 is a side sectional view of an example of a seal system being inserted between a pair of downhole tubulars in accordance with an embodiment of the present invention.
• FIG. 2 is a side sectional view of the seal system ofFIG. 1 being set and energized into a sealing and lock-down configuration in accordance with an embodiment of the present invention.
• FIG. 3 is a side perspective view of an example of nose ring from the seal system ofFIG. 1 in accordance with an embodiment of the present invention.
• FIG. 4 is a side partial sectional view of an embodiment of the seal system and tubulars ofFIG. 1 in a wellhead assembly in accordance with an embodiment of the present invention.
• FIG. 5 is a plan view of an example of a lock-down ring from the seal system ofFIG. 1 in accordance with an embodiment of the present invention.
• 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
• 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.
• 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.
• Shown in a sectional viewFIG. 1 is one example of a portion of awellhead assembly10 that includes a pair ofcoaxial tubulars12,14. In the example, tubular14 is an inner tubular and proximate an axis A_xof thewellhead assembly10. Further in the example, tubular12 is an outer tubular which circumscribes tubular14. Examples exist, where tubular12 is a wellhead housing, and tubular14 is a casing hanger. Optionally, tubular14 may also be a tubing hanger, wherein tubular12 may be a casing hanger. Aseal assembly16 is shown being inserted into anannulus18 formed between thetubulars12,14. Theseal assembly16 includes aseal element19 shown having an elongateouter leg20 oriented substantially parallel with axis A_x. Seal element19 further includes aninner leg24, which likeouter leg20 is elongate and projects along a path generally parallel with axis A_x. Betweenlegs20,24 anannular gap26 is defined that is elongate in an axial direction.Optional wickers30,31 are formed respectively on portions of the outer andinner surfaces28,22.Seal element19 further includes abody31 on which thelegs20,24 mount; and thebody31 defines a bottom of thegap26.
• Shown threadingly mounted to an end of thebody31 opposite fromlegs20,24 is anannular nose ring32 that is elongate in an axial direction and depends frombody31 deeper into theannulus18. Other means for mounting thenose ring32 to thebody31 may be employed, such as a C-ring (not shown) and/or threaded fasteners. A lock-downgroove34 is illustrated circumscribing the inner tubular14 formed into theouter surface28, and spaced downward fromnose ring32. A wall of the lock-downgroove34 that is distal from an opening of theannulus18, projects radially outward to define apedestal36. In the example ofFIG. 1, thepedestal36 provides a support ledge on the tubular14 shown supporting a lock-down ring38. An example embodiment of the lock-down ring38 extends substantially the length of the lock-downgroove34, such as a “C” ring. In the example ofFIG. 1, the radial section of the lock-down ring38 has an outer surface substantially parallel with axis A_x. While a portion of the inner surface of the lock-down ring38proximate pedestal36 is substantially parallel with axis A_x, the inner surface tapers radially outward with distance away frompedestal36. The angle of the taper changes to define atransition39, where angle of the taper between thetransition39 and thepedestal36 is more oblique to axis A_xthan the angle of the taper betweentransition39 and the end of the lock-down ring38 distal frompedestal36. Optionally, the lock-down ring38 can fully circumscribe lock-downgroove34. Further illustrated inFIG. 1 is a profile on theinner surface22 oftubular12 that projects radially inward to define ashoulder40, whereinshoulder40 is opposite from and facespedestal36.
• FIG. 2 illustrates a side sectional view of theseal assembly16 being inserted deeper within theannulus18 and wherein outer and inner radial surfaces of thelegs20,24 are in respective sealing engagement with the inner andouter surfaces22,28. Further, an energizingring42 which is inserted into thegap26 provides a radial force for sealingly engaginglegs20,24 with inner andouter surfaces20,28. An axial force F applied to energizingring42 further downwardly urges theseal element19 andnose ring32 so thatnose ring32 is in contact with lock-down ring38. In this example,nose ring32 is shown having a flexible portion that deforms when wedged between lock-down ring38 andinner groove34 ininner tubular14. When deformed,nose ring32 is in a configuration generally oblique to the axis A_x, which is in contrast to the elongate configuration ofFIG. 1 that is generally parallel with axis A_x. Lock-down ring38 is shown being urged radially outward at least partially out of lock-downgroove34 and into interfering contact with tubular12 while remaining in interfering contact withtubular14. More specifically, a surface of lock-down ring38 distal fromseal element19 rests on and is in contact with thepedestal36 oftubular14. Urging the lock-down ring38 radially outward in the example ofFIG. 2, further positions a surface of lock-down ring38proximate seal element19 into engaging contact withshoulder40. As such, relative axial movement betweentubulars12,14 is arrested by the presence of the interfering lock-down ring38. Additionally, substantially all axial forces resulting from respective axial movements of thetubulars12,14 are transferred through the lock-down ring38. Thus, forces on theseal element19 that result from forces that transfer between thetubulars12,14, can be minimized. The compound angle created by thetransition39 on the lock-down ring38 also reduces relative movement between theseal assembly16 and theinner tubular14. The more oblique surface between thetransition39 andpedestal36 urges the lower terminal portion of thenose ring32 radially inward, where it is wedged between the lock-down ring38 andouter surface28 ofinner tubular14. Strategically profiling the inner surface of the lock-down ring38 andouter surface28, in combination with theflexible nose ring32, directs forces from the lock-ring38 to thenose ring32 in a direction oblique to the axis A_x, instead of parallel to the axis A_x. Obliquely directing forces from the lock-ring38 to thenose ring32, rather than directing the forces axially, creates a force coupling thenose ring32, and attachedseal assembly16, to theinner tubular14, As such, during episodes of thermal expansion of the casing or casing hanger, seal integrity may be maintained betweentubulars12,14 by bypassing the resulting axial forces through lock-down ring38. Bending of thenose ring32 may be facilitated by scoring an inner radial surface of lock-down ring38 with anotch43, whereinnotch43 may extend along an entire circumference ofnose ring32 or along a portion thereof.
• Referring now toFIG. 3, shown in perspective view is an alternate embodiment ofnose ring32A, that includesaxial slots44 that extend from an end of thenose ring32A distal from its attachment withseal element19 into a mid-portion of the body ofnose ring32A. Theslots44 can each have the same length, or as have different lengths as shown. Positioning of theslots44 defineelongate fingers46 betweenadjacent slots44, where the absence of material due toslots44 reduces the force required for deforming sidewalls of thenose ring32A, thereby facilitating its deformed setting position as illustrated inFIG. 2. In an example, the axial force required for positioning thenose ring32,32A into the setting position illustrated inFIG. 2 is less than the axial force required for energizing theseal element19. In this example, thenose ring32 would be in the set position ofFIG. 2 and between the lock-down ring38 and inner tubular14 before the energizingring42 would set thelegs20,24 into sealing contact with the inner andouter tubulars14,12.
• FIG. 4 provides a side partial sectional view one example of theseal assembly16 set betweentubulars12,14. Thetubulars12,14 are part of thewellhead assembly10, which is shown mounted on asurface48 of a formation through which awellbore50 is formed.Casing52 depends downward from tubular14, and aproduction tree54 is shown mounted ontubular12. Amain bore56 extends throughwellhead assembly10 and into communication withwellbore50, wherein aswab valve58 is disposed inmain bore56 for controlling access into thewellbore50. Also,wing valves60 are shown set in lines that mount to theproduction tree54.
• Shown in a plan view inFIG. 5 is an alternate embodiment of lock-down ring38A and shown havingslots62 formed axially from an outer terminal radius of lock-down ring38A approximately to a mid-portion of the body of the lock-down ring38A. In this example,slots64 are formed axially through lock-down ring38A from its inner diameter that extend radially outward approximately to a mid-portion of the body of lock-down ring38A. In the example ofFIG. 5,slots62 are offset fromslots64, however, alternate embodiments exist whereslots62,64 are aligned or spaced apart at different angular locations than as shown.
• 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.

Claims (17)

What is claimed is:

1. A seal system for use between downhole inner and outer tubulars comprising:

a seal element having a body and inner and outer annular legs projecting from the body that are spaced radially apart to define a gap between the legs;

a lock-down ring between the tubulars; and

a nose ring on an end of the body of the seal element distal from the legs that has an elongate side having an inserting configuration that is generally parallel with an axis of the tubulars, and selectively changeable to a set configuration that is generally oblique with the axis when inserted between the lock-down ring and inner tubular.

2. The seal system ofclaim 1, wherein when the nose ring is inserted between the lock-down ring and inner tubular, the nose ring substantially occupies the space between the lock-down ring and inner tubular.

3. The seal system ofclaim 1, wherein when the nose ring is inserted between the lock-down ring and inner tubular, an outer radial portion of the lock-down ring projects into a profile in the outer tubular and an inner radial portion is disposed in a lock-down groove on the inner tubular thereby axially affixing together the inner and outer tubulars.

4. The seal system ofclaim 1, further comprising slots that extend through sidewalls of the nose ring from an end of the nose ring distal from the seal element.

5. The seal system ofclaim 4, wherein fingers are defined between adjacent slots.

6. The seal system ofclaim 1, wherein the inner radius of the lock-down ring projects radially inward proximate a side of the lock-down ring distal from the seal element.

7. The seal system ofclaim 1, wherein the outer tubular comprises a wellhead housing that is part of a wellhead assembly, and wherein the inner tubular comprises a casing hanger.

8. The seal system ofclaim 1, wherein directing the energizing ring against the seal element with a nose ring energizing force urges the nose ring between the lock-ring and the inner tubular, wherein inserting the energizing ring into the gap between the inner and outer legs with a seal energizing force on the energizing ring, drives the energizing ring into the gap and urges the legs radially outward into sealing contact with the tubulars, and wherein the seal energizing force is greater than the nose ring energizing force.

9. A seal system for sealing between coaxial tubulars that are part of a wellhead assembly comprising:

an annular seal element having radially spaced apart inner and outer legs that define a gap therebetween, and that are in sealing contact with opposing surfaces of the tubulars;

a lock-down ring having opposing radial portions in interfering contact with oppositely facing profiles in the tubulars, so that portions of the tubulars adjacent the seal element are axially static; and

a nose ring having an end coupled with an end of the seal element and a portion spaced from the seal element that is wedged between the lock-down ring and one of the tubulars and projects along a path generally oblique to the seal element, and thereby retaining the lock-down ring in interfering contact with the tubulars.

10. The seal system ofclaim 9, wherein the one of the tubulars comprises a casing hanger, and wherein the portion of the nose ring projects radially inward.

11. The seal system ofclaim 9, wherein a notch is scored on a radial surface of the nose ring so the nose ring can be changed from an elongate shape to the oblique shape when inserted between the lock-ring and the one of the tubulars.

12. The seal system ofclaim 9, wherein the nose ring changes from an elongate shape to the oblique shape when inserted between the lock-ring and the one of the tubulars, and wherein a force for inserting the nose ring between the lock-ring and the one of the tubulars is less than a force for energizing the seal element.

13. The seal system ofclaim 9, wherein the tubulars comprise an inner tubular and an outer tubular, and oppositely facing profiles in the tubulars comprise an upward facing pedestal defined by a lower surface of a lock-down groove formed along an outer circumference of the inner tubular and a downward facing shoulder defined by a profile formed along an inner circumference of the outer tubular.

14. A system for sealing between tubulars in a wellhead assembly comprising:

a seal element selectively inserted between the tubulars;

a lock-down ring selectively disposed on an profile on an outer surface of a one of the tubulars, and selectively urged to a position towards another one of the tubulars and into interfering contact with an oppositely facing profile on the another one of the tubulars; and

a nose ring on an end of the seal element that selectively inserts between the lock-down ring and the one of the tubulars into a setting position to urge the lock-down ring into the interfering contact, so that forces resulting from relative axial movement of the tubulars are applied to the lock-down ring and bypass the seal element.

15. The system ofclaim 14, wherein the interfering contact of the lock-down ring maintains the portions of the tubulars adjacent the seal in relative static positions.

16. The system ofclaim 14, wherein when the nose ring is in the setting position the nose ring substantially occupies the space between the lock-ring and the one of the tubulars.

17. The system ofclaim 14, wherein the one of the tubulars comprises a casing hanger and the another one of the tubulars comprises a wellhead housing.

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