SEAL WITH FLEXIBLE NOSE FOR USE WITH A LOCK-DOWN RING ON A HANGER IN A WELLBORE

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 of FIG. 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 of FIG. 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 of FIG. 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 of FIG. 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 view FIG. 1 is one example of a portion of a wellhead assembly 10 that includes a pair of coaxial tubulars 12, 14. In the example, tubular 14 is an inner tubular and proximate an axis A_x of the wellhead assembly 10. Further in the example, tubular 12 is an outer tubular which circumscribes tubular 14. Examples exist, where tubular 12 is a wellhead housing, and tubular 14 is a casing hanger. Optionally, tubular 14 may also be a tubing hanger, wherein tubular 12 may be a casing hanger. A seal assembly 16 is shown being inserted into an annulus 18 formed between the tubulars 12, 14. The seal assembly 16 includes a seal element 19 shown having an elongate outer leg 20 oriented substantially parallel with axis A_x. Seal element 19 further includes an inner leg 24, which like outer leg 20 is elongate and projects along a path generally parallel with axis A_x. Between legs 20, 24 an annular gap 26 is defined that is elongate in an axial direction. Optional wickers 30, 31 are formed respectively on portions of the outer and inner surfaces 28, 22. Seal element 19 further includes a body 31 on which the legs 20, 24 mount; and the body 31 defines a bottom of the gap 26.

Shown threadingly mounted to an end of the body 31 opposite from legs 20, 24 is an annular nose ring 32 that is elongate in an axial direction and depends from body 31 deeper into the annulus 18. Other means for mounting the nose ring 32 to the body 31 may be employed, such as a C-ring (not shown) and/or threaded fasteners. A lock-down groove 34 is illustrated circumscribing the inner tubular 14 formed into the outer surface 28, and spaced downward from nose ring 32. A wall of the lock-down groove 34 that is distal from an opening of the annulus 18, projects radially outward to define a pedestal 36. In the example of FIG. 1, the pedestal 36 provides a support ledge on the tubular 14 shown supporting a lock-down ring 38. An example embodiment of the lock-down ring 38 extends substantially the length of the lock-down groove 34, such as a “C” ring. In the example of FIG. 1, the radial section of the lock-down ring 38 has an outer surface substantially parallel with axis A_x. While a portion of the inner surface of the lock-down ring 38 proximate pedestal 36 is substantially parallel with axis A_x, the inner surface tapers radially outward with distance away from pedestal 36. The angle of the taper changes to define a transition 39, where angle of the taper between the transition 39 and the pedestal 36 is more oblique to axis A_x than the angle of the taper between transition 39 and the end of the lock-down ring 38 distal from pedestal 36. Optionally, the lock-down ring 38 can fully circumscribe lock-down groove 34. Further illustrated in FIG. 1 is a profile on the inner surface 22 of tubular 12 that projects radially inward to define a shoulder 40, wherein shoulder 40 is opposite from and faces pedestal 36.

FIG. 2 illustrates a side sectional view of the seal assembly 16 being inserted deeper within the annulus 18 and wherein outer and inner radial surfaces of the legs 20, 24 are in respective sealing engagement with the inner and outer surfaces 22, 28. Further, an energizing ring 42 which is inserted into the gap 26 provides a radial force for sealingly engaging legs 20, 24 with inner and outer surfaces 20, 28. An axial force F applied to energizing ring 42 further downwardly urges the seal element 19 and nose ring 32 so that nose ring 32 is in contact with lock-down ring 38. In this example, nose ring 32 is shown having a flexible portion that deforms when wedged between lock-down ring 38 and inner groove 34 in inner tubular 14. When deformed, nose ring 32 is in a configuration generally oblique to the axis A_x, which is in contrast to the elongate configuration of FIG. 1 that is generally parallel with axis A_x. Lock-down ring 38 is shown being urged radially outward at least partially out of lock-down groove 34 and into interfering contact with tubular 12 while remaining in interfering contact with tubular 14. More specifically, a surface of lock-down ring 38 distal from seal element 19 rests on and is in contact with the pedestal 36 of tubular 14. Urging the lock-down ring 38 radially outward in the example of FIG. 2, further positions a surface of lock-down ring 38 proximate seal element 19 into engaging contact with shoulder 40. As such, relative axial movement between tubulars 12, 14 is arrested by the presence of the interfering lock-down ring 38. Additionally, substantially all axial forces resulting from respective axial movements of the tubulars 12, 14 are transferred through the lock-down ring 38. Thus, forces on the seal element 19 that result from forces that transfer between the tubulars 12, 14, can be minimized. The compound angle created by the transition 39 on the lock-down ring 38 also reduces relative movement between the seal assembly 16 and the inner tubular 14. The more oblique surface between the transition 39 and pedestal 36 urges the lower terminal portion of the nose ring 32 radially inward, where it is wedged between the lock-down ring 38 and outer surface 28 of inner tubular 14. Strategically profiling the inner surface of the lock-down ring 38 and outer surface 28, in combination with the flexible nose ring 32, directs forces from the lock-ring 38 to the nose ring 32 in a direction oblique to the axis A_x, instead of parallel to the axis A_x. Obliquely directing forces from the lock-ring 38 to the nose ring 32, rather than directing the forces axially, creates a force coupling the nose ring 32, and attached seal assembly 16, to the inner tubular 14, As such, during episodes of thermal expansion of the casing or casing hanger, seal integrity may be maintained between tubulars 12, 14 by bypassing the resulting axial forces through lock-down ring 38. Bending of the nose ring 32 may be facilitated by scoring an inner radial surface of lock-down ring 38 with a notch 43, wherein notch 43 may extend along an entire circumference of nose ring 32 or along a portion thereof.

Referring now to FIG. 3, shown in perspective view is an alternate embodiment of nose ring 32A, that includes axial slots 44 that extend from an end of the nose ring 32A distal from its attachment with seal element 19 into a mid-portion of the body of nose ring 32A. The slots 44 can each have the same length, or as have different lengths as shown. Positioning of the slots 44 define elongate fingers 46 between adjacent slots 44, where the absence of material due to slots 44 reduces the force required for deforming sidewalls of the nose ring 32A, thereby facilitating its deformed setting position as illustrated in FIG. 2. In an example, the axial force required for positioning the nose ring 32, 32A into the setting position illustrated in FIG. 2 is less than the axial force required for energizing the seal element 19. In this example, the nose ring 32 would be in the set position of FIG. 2 and between the lock-down ring 38 and inner tubular 14 before the energizing ring 42 would set the legs 20, 24 into sealing contact with the inner and outer tubulars 14, 12.

FIG. 4 provides a side partial sectional view one example of the seal assembly 16 set between tubulars 12, 14. The tubulars 12, 14 are part of the wellhead assembly 10, which is shown mounted on a surface 48 of a formation through which a wellbore 50 is formed. Casing 52 depends downward from tubular 14, and a production tree 54 is shown mounted on tubular 12. A main bore 56 extends through wellhead assembly 10 and into communication with wellbore 50, wherein a swab valve 58 is disposed in main bore 56 for controlling access into the wellbore 50. Also, wing valves 60 are shown set in lines that mount to the production tree 54.

Shown in a plan view in FIG. 5 is an alternate embodiment of lock-down ring 38A and shown having slots 62 formed axially from an outer terminal radius of lock-down ring 38A approximately to a mid-portion of the body of the lock-down ring 38A. In this example, slots 64 are formed axially through lock-down ring 38A from its inner diameter that extend radially outward approximately to a mid-portion of the body of lock-down ring 38A. In the example of FIG. 5, slots 62 are offset from slots 64, however, alternate embodiments exist where slots 62, 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

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; anda 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 of claim 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 of claim 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 of claim 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 of claim 4, wherein fingers are defined between adjacent slots.

6. The seal system of claim 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 of claim 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 of claim 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; anda 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 of claim 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 of claim 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 of claim 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 of claim 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; anda 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 of claim 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 of claim 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 of claim 14, wherein the one of the tubulars comprises a casing hanger and the another one of the tubulars comprises a wellhead housing.