Metal Chevron Seal

Abstract

A well tool has an elongate, metal outer tubing and an elongate, metal inner tubing received in the outer tubing to move axially with respect to the outer tubing. A metal annular seal assembly is provided between the outer and inner tubings residing in a seal chamber of the outer or inner tubing. The seal assembly has a center ring, a chevron seal ring on each side of the center ring and an end ring at each axial end of the seal assembly. The seal chamber is tight to the seal assembly.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase Application under 35 U.S.C. §371 and claims the benefit of priority to International Application Serial No. PCT/US2013/067336, filed on Oct. 29, 2013, the contents of which are hereby incorporated by reference.

BACKGROUND

Downhole conditions in a well present numerous sealing challenges. For example, components of many well tools must be able to move relative to one another and be sealed against fluid communication. Polymer seals are typically used in such applications, because they do not damage adjacent metallic sealing surfaces when passed over the surfaces. Additionally, polymer seals can provide effective sealing, and can be reinforced or provided with back-up rings to seal against high pressure differentials. For example, typical chevron seals, having a polymer O-ring that energizes multiple, polymer, chevron cross-sectioned seal rings on each side, will have a more ridged back-up ring on each end.

A seal chamber in a metal component carrying a polymer chevron seal stack must be longer than the chevron seal stack, long enough to accommodate the differential thermal expansion of the polymer seal stack and metal component assembly. When sealing, the chevron rings on the high pressure side of the seal stack are not compressed with the pressure differential. They can become misaligned and deform in the long chamber as the sealing surfaces move relative to one another. Additionally, the O-ring can roll in various places along its circumference and, due to the high temperature, take a set in its deformed condition. When the pressure is reversed and the sealing surfaces move in the opposite direction, the chevron seal stack shifts to the opposite end of the chamber. The chevron rings deformed in the first pressure cycle will remain partially deformed, and the chevron rings on the new high pressure side will be loose and can become misaligned and deform. As this is repeated over and over, the elastomeric parts become deformed to the point they will no longer seal, and the seal begins to leak.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic side view of an example well with a well tool.

FIG. 2 is a side cross-sectional view of a well tool incorporating an example seal assembly.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring first to FIG. 1, a well 10 includes a substantially cylindrical wellbore 12 that extends from a wellhead 14 at the surface 16 downward into the Earth into one or more subterranean zones of interest 18 (one shown). The subterranean zone 18 can correspond to a single formation, a portion of a formation, or more than one formulation accessed by the well 10, and a given well 10 can access one, or more than one, subterranean zone 18. In certain instances, the formations of the subterranean zone are hydrocarbon bearing, such as oil and/or gas deposits, and the well 10 will be used in producing the hydrocarbons and/or used in aiding production of the hydrocarbons from another well (e.g., as an injection or observation well). The concepts herein, however, are applicable to virtually any type of well. A portion of the wellbore 12 extending from the wellhead 14 to the subterranean zone 18 is lined with lengths of tubing, called casing 24.

The depicted well 10 is a vertical well, extending substantially vertically from the surface 16 to the subterranean zone 18. The concepts herein, however, are applicable to many other different configurations of wells, including horizontal, slanted or otherwise deviated wells, and multilateral wells.

A tubing string 20 is shown as having been lowered from the surface 16 into the wellbore 12. The tubing string 20 is a series of jointed lengths of tubing coupled together end-to-end and/or a continuous (i.e., not jointed) coiled tubing, and includes one or more well tools (e.g., one shown, well tool 22). The string 20 has an interior, center bore that enables communication of fluid between the wellhead 14 and locations downhole (e.g., the subterranean zone 18 and/or other locations). In other instances, the string 20 can be arranged such that it does not extend from the surface 16, but rather descends into the well on a wire, such as a slickline, wireline, e-line and/or other wire.

The well tool 22 is of a type having an inner tubing nested in an outer tubing, so that the tubings can move axially relative to one another. The well tool 22 has a sealing arrangement that allows the tubings to move while maintaining a seal between the tubings under high temperature and high pressure differential. In certain instances, the seal formed by the seals can be gas tight. The well tool 22 can be a number of different tools incorporating inner and outer tubings that move relative to one another. In certain instances, the tool 22 is a valve where the inner and outer tubings define walls of pressure chamber that, by pressure in the chamber, drives the tubings to move axially relative to one another in actuating the valve. Other types of valves, as well as other types of tools, are within the concepts herein.

Referring to FIG. 2, an example well tool 100 that can be used as well tool 22, is shown in a half side cross-sectional view. The example well tool 100 is generally elongate and tubular, and centered around the longitudinal center axis A-A. Only the upper half of the side cross-sectional view is shown, and the lower half of the side cross-sectional view is identical. The well tool 100 is of a type having an elongate, metal outer tubing 102 receiving an elongate, metal inner tubing 104, so that the outer tubing 102 and inner tubing 104 can move axially with respect to each other. In this example, the outer tubing 102 concentrically receives the inner tubing 104. The outer tubing 102 and the inner tubing 104 are sealed to each other by an annular, metal seal assembly 106 that is shown carried in a seal chamber 108 of the outer tubing 102. Although shown with the seal chamber 108 and the seal assembly 106 associated with the outer tubing 102, in certain instances, the inner tubing 104 may additionally or alternatively have a seal chamber and seal assembly of the same or different configuration. In certain instances, end walls 118 of the seal chamber 108 are defined by additional components 124 affixed to the outer tubing 102, as shown in the figure, but the seal chamber 108 could alternatively be partially cut from the material of the tubing.

The seal assembly 106 contacts both the inner diameter of the outer tubing 102 and the outer diameter of the inner tubing 104 in the seal chamber 108. The seal assembly 106 is configured to prevent axial passage of fluids between the outer tubing 102 and the inner tubing 104 both from the left side of the view towards the right side of the view and from the right side of the view towards the left side of the view. Thus, for example, when the well tool 100 residing in a wellbore and axis A-A is generally aligned with the longitudinal axis of the wellbore, the seal assembly 106 is configured to prevent axial passage of fluids both uphole and downhole between the outer tubing 102 and the inner tubing 104.

The seal assembly 106 is a metal chevron-type seal assembly, having a plurality of metal chevron seal rings 110 that contact and form the primary seal between the outer tubing 102 and the inner tubing 104. In certain instances, the chevron rings are entirely metal, and can be coated or constructed from metal selected to prevent galling with the metal of the tubing. Each of the chevron seal rings 110 is generally chevron shaped, or V-shaped, in cross-section, having a thickest section at the vertex of the V-shape and tapering towards the ends of the V-shape. The V-shape of the chevron seal rings 110 allows the rings to nest within each other as shown in FIG. 2. The tapered ends allow the rings to be more flexible to radial loads at their ends.

The innermost chevron seal rings 110 are nested into V-shaped recesses 114 on opposing sidewalls of a center ring 112. In the example, six chevron seal rings 110 are symmetrically arranged about the center ring 112, with three chevron seal rings 110 oriented with their vertex towards the left side of the view (e.g., uphole), and three chevron seal rings 110 oriented with their vertex towards the right side of the view (e.g. downhole). Fewer or more chevron seal rings 110 could be provided, and they need not be symmetrically arranged about the center ring 112. The chevron seal rings 110 are held tightly nested within each other and nested into the center ring 112 by an end ring 116 at each end of the seal assembly 106, which itself abuts the end walls 118 of the seal chamber 108. The end rings 116 each have a generally V-shaped nose 120 adapted to nest into the chevron seal rings 110 and a flat outer wall 122 that presses flush and square against the flat end walls 118 of the seal chamber 108. In certain instances, the center ring 112 and or the end rings 116 are metal (entirely or substantially).

The chevron seal rings 110 are shown in a radially uncompressed state, to illustrate that the seal rings 110 are designed to provide an interference fit with the outer tubing 102 and the inner tubing 104. In practice, the ends of the chevron seal rings 110 would not overlap with the outer tubing 102 and inner tubing 104, as shown, but would flex radially inward. In other words, the free outer diameter of the seal rings 110 is greater than the inner diameter of the outer tubing 102 where the chevron rings 110 contact and seal (i.e., the sealing surface, typically of a controlled, fine surface finish). The free inner diameter of the seal rings 110 is smaller than the diameter at the bottom of the seal chamber 108 (i.e., the sealing surface of the inner tubing 104, also typically of a controlled, fine surface finish). As a result, when the seal assembly 106 is installed into the seal chamber 108 between the outer tubing 102 and inner tubing 104, the outer ends of the chevron seal rings 110 elastically deform radially inward and apply a contact pressure on the sealing surfaces of the outer tubing 102 and the inner tubing 104. This contact pressure provides an initial seal between the chevron rings 110 and the outer tubing 102 and inner tubing 104. As a pressure differential develops in the fluid on each side of the seal assembly 106, the pressure acts on the interior of the chevron seal rings 110 to pressure energize the rings to increase the contact pressure and form a tighter seal.

The seal assembly 106 is shown in an assembled, axially uncompressed, state, where the center ring 112, chevron seal rings 110, and end rings 116 are tightly nested, abutting, with no gaps and the rings not substantially axially elastically or plastically deformed. The seal assembly 106, in this state, is at its assembled, axially uncompressed stack length. The axial distance (length) between end walls 118 of the seal chamber 108 is sized relative to this stack length, so as to be tight to the seal assembly 106. When tight, there is no substantial gap between the end walls 118 and the seal assembly 106. For example, because both the seal assembly 106 and seal chamber 108 are metal, there will be no or insubstantial differential thermal expansion. Thus, the seal chamber 108 need not include a gap to account for the differential thermal expansion between an entirely or substantially polymer seal assembly and the surrounding metal. Nominal gaps may be provided, though, to account for tolerances and to facilitate assembly of the seal assembly 106 into the seal chamber 108. In certain instances, the axial length between the end walls 118 is no longer than the assembled, uncompressed stack length of the seal assembly 106 (of course, accounting for tolerances and ease of assembly). Having the seal chamber 108 tight to the seal assembly 106 holds the seal assembly 106 together, keeping the rings tightly nested within and abutting each other and supporting the rings against misalignment. When the tubings move back and forth relative to one another, there is no relative movement or separation of the seal rings. In certain instances, the axial length between end walls 118 is a fixed length because the components 124 affix to specified locations on the tubing. In certain instances, one or both end walls 118 of the seal chamber 108 can be axially adjustable on the tubing, so that the seal assembly 106 can be clamped and the components 124 fixed, with the end walls 118 pressing on the seal assembly 106. For example, one or both of the components 124 can be threaded into or onto the tubing, so that it can be axially tightened against the seal assembly 106. In this configuration, no nominal gaps are needed to account for tolerances and ease of assembly.

As the tubings 102 and 104 move axially relative to each other, the rings of the seal 100 do not separate and remain tightly nested. The vertex of the innermost chevron seal rings 110 being tightly nested in the V-shaped recesses of the center ring 112, holds the innermost chevron seal rings 110 in alignment and supports the rings against rolling or canting. Similarly, the adjacent chevron seal rings 110, tightly nested in the V-shaped recesses of the innermost chevron seal rings 110, are held in alignment and supported against rolling or canting, as are the remaining chevron seal rings 110 with each other. The seal assembly 106 is further held in alignment, and held against rolling or canting, by the end rings 116 tightly nested in the V-shaped recesses of the outermost chevron seal rings 110, and the flat end 122 of the end rings 116 being pressing flush and square against the flat end walls 118 of the seal chamber 108.

A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made. Accordingly, other embodiments are within the scope of the following claims.

Claims

1. A well tool, comprising:

an elongate, metal outer tubing;

an elongate, metal inner tubing received in the outer tubing to move axially with respect to the outer tubing; and

a metal annular seal assembly between the outer and inner tubings residing in a seal chamber of the outer or inner tubing and contacting the other of the outer or inner tubing, the annular seal assembly comprising a center ring, a chevron seal ring on each side of the center ring and an end ring at each axial end of the seal assembly, and the seal chamber being tight to the axial ends of the annular seal assembly.

2. The well tool of claim 1, where there is no substantial gap between the seal chamber and the ends of the seal assembly.

3. The well tool of claim 1, where the annular seal assembly has an assembled, uncompressed stack length and the seal chamber is no longer than the assembled, uncompressed stack length.

4. The well tool of claim 1, comprising a plurality of chevron seal rings on each side of the center ring.

5. The well tool of claim 1, where the annular seal assembly is entirely metal.

6. The well tool of claim 1, where the seal chamber is defined between components coupled to one of the outer tubing or inner tubing, and where the components are axially movable to clamp the seal assembly.

7. The well tool of claim 1, where a free inner diameter of the chevron seal rings is smaller than a diameter of the inner tubing contacted by the chevron seal rings when sealing.

8. The well tool of claim 7, where a free outer diameter of the chevron seal rings is greater than a diameter of the outer tubing contacted by the chevron seal rings when sealing.

9. The well tool of claim 8, where the contact force of the chevron seal rings on the seal surface of the seal chamber and the seal surface the outer tubing forms an initial seal.

10. The well tool of claim 9, where the chevron seal rings are pressure energized to increase the contact force of the chevron seal rings against the seal surface of the seal chamber and the seal surface of the outer tubing when subjected to an axial fluid pressure differential.

11. A method, comprising:

supporting a metal chevron seal assembly tightly between end walls of a seal chamber of a first elongate, metal tubing in a well; and

sealing, with the metal chevron seal assembly, between first tubing and a second, elongate metal tubing nested with the first tubing, while the tubings are moving relative to one another.

12. The method of claim 11, where supporting the metal chevron seal assembly comprises supporting the metal chevron seal between end walls of the seal chamber having no substantial gap between the metal chevron seal and the end walls.

13. The method of claim 12, where the metal chevron seal assembly is entirely metal.

14. The method of claim 11, where supporting the metal chevron seal assembly comprises supporting the metal chevron seal between end walls spaced no farther apart than an assembled, uncompressed stack length of the metal chevron seal.

15. The method of claim 11, comprises adjusting a component defining an end wall of the seal chamber to clamp the metal chevron seal assembly.

16. A well device for use in a well, comprising:

a first and second nested metal tubing; and

an annular seal chamber associated with the first tubing and comprising an annular metal chevron seal assembly in the seal chamber, the seal chamber having no substantial gap between the axial ends of the seal assembly and the seal chamber.

17. The device of claim 16, where the annular metal chevron seal assembly has an assembled, uncompressed stack length and the seal chamber is no longer than the assembled, uncompressed stack length.

18. The device of claim 16, where the annular seal chamber comprises end walls that support the annular metal chevron seal against rolling.

19. The device of claim 16, where the annular metal chevron seal is entirely metal.

20. The device of claim 16, where the annular metal chevron seal is a two way seal to seal against pressure from two directions.