METAL TO METAL PACKOFF FOR USE IN A WELLHEAD ASSEMBLY

Abstract

A wellhead assembly having an inner tubular insertable into an outer tubular. A packoff is provided on an outer surface of the inner tubular for sealing between the inner and outer tubulars. The packoff includes an energizing ring, a U-shaped seal member, and a nut for retaining the seal member against the energizing ring. The seal member includes legs that are spaced apart by interaction with the energizing ring. The outer tubular has a bore wall that is profiled so that when the inner tubular is inserted into the outer tubular, an outer leg of the seal member is spaced radially outward from the bore wall until the inner tubular is landed in the outer tubular. When the inner tubular member is landed, a portion of the bore wall adjacent the outer leg tapers radially inward into sealing contact with the outer leg of the seal member.

Description

BACKGROUND

1. Field of Invention

The invention relates generally to wellhead assemblies and in particular to a system and method for sealing between tubulars in a wellhead assembly.

2. Description of Prior Art

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.

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.

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 he 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.

SUMMARY OF THE INVENTION

Provided herein is an example of a wellhead assembly that includes an outer tubular having a bore that defines a bore wall, an inner tubular insertable into the bore and selectively set in a landed position in the bore, a packoff on the inner tubular, and a taper strategically located the bore. When the inner tubular is inserted into the bore, the packoff is in sealing contact with the bore wall when the inner tubular is proximate the landed position, and the packoff is set radially inward from the bore wall when the inner tubular is above a location proximate the landed position. In an embodiment, the packoff includes an energizing ring with a protrusion, a seal element having spaced apart legs that terminate on opposing sides of the protrusion, and a retaining nut threaded to the inner tubular and on a side of the seal element distal from the energizing ring. In this example, the seal elements a generally annular member. One of the legs can be spaced radially outward from the protrusion when the when the inner tubular is above a location proximate the landed position. Further, one of the legs may be wedged between the taper and the protrusion when the when the inner tubular is proximate the landed position. In one example embodiment, one of the legs projects radially outward to define a seal between the outer tubular and the seal element and another one of the legs projects radially inward to define a seal between the inner tubular and seal element. Optionally, the inner tubular is a tubing hanger and the outer tubular is a tithing head. Alternatively, the bore wall projects radially inward at an axial location below the taper to define a shoulder on which the inner tubular lands.

Another example of a wellhead assembly is provided herein that includes an outer tubular having an axial bore, a taper formed in the bore where a surface of the bore projects radially inward, a shoulder formed in the bore below the taper, an inner tubular landed on the shoulder, and a packoff. In this example the packoff has an outer radius in sealing contact with the taper and that is set radially inward from a portion of the bore between the taper and an upper end of the bore. An inner radius of the packoff is in sealing contact with the inner tubular. In one example, the packoff includes an energizing ring, a seal element with legs spaced apart by the energizing ring, and a retaining nut for urging the seal element against the energizing ring, and beads on the legs that form a seal against the inner and outer tubulars. Optionally the seal element can be metal. The energizing ring can also include a protrusion on which the legs are supported. In an example, the inner tubular is a tubing hanger and the outer tubular is a tubing head.

Further disclosed herein is a method of sealing between tubulars in a wellhead assembly. One embodiment of the method includes providing an inner tubular having a packoff circumscribing a portion of the inner tubular, providing an outer tubular having a bore with a taper so that a portion of the bore above the taper has a radius greater than a radius of the packoff, and a portion of the bore below the taper has a radius less than the packoff, and sealing between the packoff and the bore by inserting the inner tubular into the outer tubular at least to a depth that the packoff contacts the portion of the bore having a radius less than the packoff. The method can further include landing the inner tubular in the outer tubular. In this example, the packoff includes an energizing ring with a protrusion, a seal element having spaced apart legs that terminate on opposing sides of the protrusion, a soft metal coating on the seal element, and a retaining nut threaded to the inner tubular and on a side of the seal element distal from the energizing ring.

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 portion of a tubing hanger having a packoff in accordance with the present invention.

FIG. 2 is a side sectional view of the tubing hanger of FIG. 1 landing in a tubing head in accordance with the present invention.

FIG. 3 is a side sectional view of the tubing hanger landed in the tubing head of FIG. 2 in accordance with the present invention.

FIG. 4 is a side partial sectional view of an example embodiment of the tubing hanger of FIG. 1 set in a wellhead assembly in accordance with 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. Accordingly, the improvements herein described are therefore to be limited only by the scope of the appended claims.

An example embodiment of a tubing hanger 10 is shown in side sectional view in FIG. 1, wherein the tubing hanger 10 includes a packoff assembly 12. In the example of FIG. 1, the packoff assembly 12 is made up of an energizing ring 14 that is a generally annular member and having a base 16 with a substantially rectangular cross-section. Depending downward from the base 16 is a lower member 18 that in the example of FIG. 1 has a width less than the width of the base 16 and tapers axially inward with distance away from the base 16. The lower member 18 defines a protrusion that extends into a seal element 20 shown disposed on an outer surface of the tubing hanger 10 and just below the energizing ring 14. The seal element 20, which is a generally U-shaped member, has a base 22 which is generally rectangular in cross-section and a pair of legs 24 that project upward and on opposing lateral sides of the lower member 18. Optionally, the leg 24 shown facing outward from an axis A_X of the tubing hanger 10 is spaced apart from the energizing ring 14 to define a gap 25 between the leg 24 and energizing ring 14. Additionally, the spaced apart legs 24 define a space 26. On opposing outer surfaces of the legs 24 are beads 28 that are raised portions on the inner and outer radial surfaces of the seal element 20 and as will be described in more detail below, enhanced formation of a sealing surface between the seal element 20 and another solid member. A group 30 is provided on the outer circumference of the tubing hanger 10 in which the energizing ring 16 and seal element 20 is disposed. A lower groove 32 also on the outer surface of the tubing hanger 10 extends downward from a lower end of the upper groove 30 and as shown in FIG. 1 has a reduced radius over that of the upper groove 30. Threads 34 extend along the face of the lower groove 32 and provide connection between the tubing hanger 10 and a retaining nut 36 shown threaded into placed within the lower groove 32. In one example embodiment, the retaining nut 36 provides axial support for the seal element 20.

FIG. 2 illustrates in side sectional view, one example of the tubing hanger 10 being inserted within a tubing head 40 for assembly of a wellhead assembly (FIG. 4). In this example, the outer radial surface of the tubing hanger 10 is shown sliding into a bowl 42 formed in the tubing head 40. A shoulder 44 is defined at a lower end of the bowl 42 where the inner surface 46 of the bowl 42 extends radially inward towards axis A_X. Above the shoulder 44 is a taper 48 that is defined where the inner surface 46 depends radially inward for an axial distance. As shown, as the tubing hanger 10 is being inserted within the tubing head 40 the beads 28 on the outer leg 24 are set radially inward from the inner surface 46 as long as the beads 28 are at a location above the taper 48.

As shown in FIG. 3, the tubing hanger 10 has landed within the tubing head 40 and the lower lateral edge of the nut 36 is being supported on the shoulder 44. Further, the respective locations of the taper 48 and ridges 28 are strategically disposed so that when tubing hanger 10 is in the landed position of FIG. 3, the ridges 28 are at a depth where the inner surface 46 is set radially inward so that the beads 28 are in compressive contact against the inner surface 46. As such, a sealing surface is formed between the seal element 20 and inner surface 46, the sealing surface against the tubing head 40, in combination with a sealing surface between beads 28 and groove 30 defines a sealing barrier between the tubing hanger 10 and tubing head 40. Further, the gap 25 (FIG. 1) has disappeared due to the radial inward movement of leg 24 against the lower member 18. In this instance, the lower member 18 provides support for legs 24.

A side partial sectional view of an example of a wellhead assembly 50 having the packoff assembly 12 is illustrated in FIG. 4. In this example, the wellhead assembly 50 is made up of a production tree 50 set above the tubing head 40 and over a bore hole 54. In the example of FIG. 4, the bore hole 54 extends through subterranean formation 56. Further included with the wellhead assembly 50 is a string of tubing 58 shown mounted on a lower end of tubing hanger 10 and projecting into the bore hole 54.

Optionally, a soft metal, such as silver, may be set over the seal element 20 provide a lubricating coating for when the tubing hanger 10 is being landed within the tubing head 40. One example of operation, the packoff assembly 12 (FIG. 1) is formed onto the tubing hanger 10 by first sliding the energizing ring 14 into upper groove 30 and then adding the annular seal element 20 into upper groove 30 so that the lower member 18 extends between the legs 24 for providing support for the legs 24. In one example, the outer leg 24 of the seal element is sized to have an outer circumference just less than the inner circumference of the radius of the inner surface 46 so that during landing, up until the seal element 20 contacts the taper 48, the seal element 20 is spaced radially inward from the inner surface 46. Reducing the amount of sliding contact between the seal element 20 and inner surface 46 reduces chances of damage before the tubing hanger 10 is landed within the tubing head 40. After installing the seal element 20, the retainer nut 36 is screwed into place thereby locking the packoff assembly 12 to the tubing hanger 10. Again, as the tubing hanger 10 is being landed within the tubing head 40 the strategic location of the taper 40 then engages the seal element 20 to create the seal between the tubing hanger 10 and tubing head 40. Although the energizing ring 14 may lift slightly during engagement of the seal element 20 with inner surface 46, the energizing ring 14 provides a backup force for legs 22 and prevent legs 24 from collapsing. Optionally, outer diameter of the seal element 24 is electively changed to fit a particular size of the bowl 42. Moreover, in one example, the seal element 24 includes a flexible material, such as metal, so that when landing in tubing heads having asymmetric bowls 42, the elasticity and flexibility of the seal element 24 can from a full seal around the entire circumference of the interface between the tubing hanger 10 and tubing head 40. An example of using a seal element 24 made from a metallic material over that of an elastomer is the ability to be deployed in lower depth but higher temperature wells.

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 wellhead assembly comprising: an outer tubular having a bore that defines a bore wall;an inner tubular insertable into the bore and selectively set in a landed position in the bore;a packoff on the inner tubular;a taper strategically located in the bore, so that when the inner tubular is inserted into the bore, the packoff is in sealing contact with the bore wall when the inner tubular is proximate the landed position, and the packoff is set radially inward from the bore wall when the inner tubular is above a location proximate the landed position.

2. The wellhead assembly of claim 1, wherein the packoff comprises an energizing ring with a protrusion, a seal element having spaced apart legs that terminate on opposing sides of the protrusion, and a retaining nut threaded to the inner tubular and on a side of the seal element distal from the energizing ring.

3. The wellhead assembly of claim 2, wherein the seal element is a generally annular member.

4. The wellhead assembly of claim 3, wherein one of the legs is spaced radially outward from the protrusion when the when the inner tubular is above a location proximate the landed position, and wherein the one of the legs is wedged between the taper and the protrusion when the when the inner tubular is proximate the landed position.

5. The wellhead assembly of claim 2, wherein one of the legs projects radially outward to define a seal between the outer tubular and the seal element and wherein another one of the legs projects radially inward to define a seal between the inner tubular and seal element.

6. The wellhead assembly of claim 1, wherein the inner tubular is a tubing hanger and wherein the outer tubular is a tubing head.

7. The wellhead assembly of claim 1, wherein the bore wall projects radially inward at an axial location below the taper to define a shoulder on which the inner tubular lands.

8. A wellhead assembly comprising: an outer tubular having an axial bore;a taper formed in the bore where a surface of the bore projects radially inward;a shoulder formed in the bore below the taper;an inner tubular landed on the shoulder; anda packoff having, an outer radius in sealing contact with the taper and set radially inward from a portion of the bore between the taper and an upper end of the bore, and an inner radius in sealing contact with the inner tubular.

9. The wellhead assembly of claim 8, wherein the packoff comprises an energizing ring, a seal element with legs spaced apart by the energizing ring, and a retaining nut for urging the seal element against the energizing ring, and beads on the legs that form a seal against the inner and outer tubulars.

10. The wellhead assembly of claim 9, wherein the seal element comprises metal.

11. The wellhead assembly of claim 9, wherein the energizing ring comprises a protrusion on which the legs are supported.

12. The wellhead assembly of claim 8, wherein the inner tubular comprises a tubing hanger and the outer tubular comprises a tubing head.

13. A method of sealing between tubulars in a wellhead assembly comprising: providing an inner tubular having a packoff circumscribing a portion of the inner tubular;providing an outer tubular having a bore with a taper so that a portion of the bore above the taper has a radius greater than a radius of the packoff, and a portion of the bore below the taper has a radius less than the packoff; andsealing between the packoff and the bore by inserting the inner tubular into the outer tubular at least to a depth that the packoff contacts the portion of the bore having a radius less than the packoff.

14. The method of claim 13, further comprising landing the inner tubular in the outer tubular.

15. The method of claim 13, wherein the packoff comprises an energizing ring with a protrusion, a seal element having spaced apart legs that terminate on opposing sides of the protrusion, a soft metal coating on the seal element, and a retaining nut threaded to the inner tubular and on a side of the seal element distal from the energizing ring.