1. Field of the Invention
This invention relates in general to wellhead assemblies and in particular to a seal with a bellows style nose ring and radially drivable lock rings that improve lockdown to a casing hanger.
2. Brief Description of Related Art
Seals are used between inner and outer wellhead tubular members to contain internal well pressure. The inner wellhead member may be a casing hanger located in a wellhead housing. The casing hanger supports a string of casing extending into the well. A seal or packoff seals between the casing hanger and the wellhead housing. Alternatively, the inner wellhead member could 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 Christmas tree, or a tubing head. A seal or packoff seals between the tubing hanger and the outer wellhead member.
A variety of seals located between the inner and outer wellhead members have been employed in the prior art. Prior art seals include elastomeric and partially metal and elastomeric rings. Prior art seal rings made entirely of metal for forming metal-to-metal seals (“MS”) are also employed. 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 prior art metal-to-metal seal has a seal body with inner and outer walls separated by a cylindrical slot, forming a “U” shape. An energizing ring is pushed into the slot in the seal to deform the inner and outer walls apart into sealing engagement with the inner and outer wellhead members. The inner and outer wellhead members may have wickers formed thereon. The energizing ring is typically a solid wedge-shaped member. The deformation of the inner and outer walls of the seal exceeds the yield strength of the material of the seal ring, making the deformation permanent.
Thermal growth between the casing or tubing and the wellhead may occur, particularly with wellheads located at the surface, rather than subsea. The well fluid flowing upward through the tubing heats the string of tubing, and to a lesser degree the surrounding casing. The temperature increase may cause the tubing hanger and/or casing hanger to move axially a slight amount relative to the outer wellhead member. During the heat up transient, the tubing hanger and/or casing hanger can also move radially due to temperature differences between components and the different rates of thermal expansion from which the component materials are constructed. If the seal has been set as a result of a wedging action where an axial displacement of energizing rings induces a radial movement of the seal against its mating surfaces, then sealing forces may be reduced if there is movement in the axial direction due to pressure or thermal effects. A reduction in axial force on the energizing ring results in a reduction in the radial inward and outward forces on the inner and outer walls of the seal ring, which may cause the seal to leak. A loss of radial loading between the seal and its mating surfaces due to thermal transients may also cause the seal to leak. One approach to preventing this type of movement is through the use of lockdown C-rings on the seal that rest in a machined pocket on the energizing ring. The C-ring engages the hanger when the seal is set, locking the seal to the hanger. Another approach has been to use the sealing element itself as a locking mechanism. In these approaches, lockdown is thus provided by the seal. Further, a lockdown style hanger may be utilized to lock the casing hanger in place. This requires an extra trip to lower the lockdown style hanger.
A need exists for a technique that addresses the seal leakage problems described above by providing additional lockdown capacity in a cost-effective way. The following technique may solve one or more of these problems.
These and other problems are generally solved or circumvented, and technical advantages are generally achieved, by preferred embodiments of the present invention that provide a casing hanger seal with a bellows style nose ring and radially drivable lock rings, and a method for using the same.
In an embodiment of the present invention, a wellhead assembly with an axis is disclosed. The assembly includes an outer wellhead member having a bore, and an inner wellhead member located in the bore. A seal ring is disposed between the inner and outer wellhead members and is in sealing engagement with the inner and outer wellhead members. A bellows style portion is disposed on a lower end of the seal ring, and the bellows style portion is axially contractible. The assembly also includes at least two lock rings disposed on the bellows style portion such that axial contraction of the bellows style portion will urge each lock ring into radial engagement with at least one of the inner wellhead member and the outer wellhead member.
In another embodiment of the present invention, a wellhead seal assembly is disclosed. The assembly includes a seal ring for sealing between inner and outer wellhead members, and a bellows style portion on a lower end of the seal ring. The bellows style portion is axially contractible and has outer surfaces and inner surfaces. The bellows style portion comprises an undulation that forms apexes and gaps between adjacent apexes. The gaps in the bellows style portion exist prior to setting and diminish in size when the bellows style portion collapses during setting. Inner and outer lock rings are disposed in the gaps such that axial contraction of the bellows style portion will urge the inner lock rings into radial engagement with the inner wellhead member and the outer lock rings into radial engagement with the outer wellhead member. A lower end of bellows style portion is adapted to land on a shoulder of the inner wellhead member and, when the seal ring is energized, the bellows style portion collapses to urge the inner and outer lock rings into radial engagement.
In still another embodiment of the present invention, a method for sealing an inner wellhead member to an outer wellhead member is disclosed. The method provides a seal assembly having a bellows style portion carried on a lower end and inner and outer lock rings located within gaps of the bellows style portion. The method lands the seal assembly between the inner and outer wellhead members, and applies an axial force to the seal assembly to axially contract the bellows style portion. The axial force urges the inner and outer lock rings disposed on the bellows style portion into engagement with the inner and outer wellhead members in response to the axial contraction of the bellows style portion. The method sets the seal assembly to seal between the inner and outer wellhead members.
The bellows style portion on the nose ring provides a mechanism of locking down the hanger in addition to those in the prior art. The radially drivable lock rings provide additional transfer of upward axial force by the casing hanger into radial force to limit casing hanger movement. Thus, lockdown capacity is advantageously increased by sharing upward forces on the hanger among the present invention and these mechanisms of the prior art. Still further, the disclosed embodiments provide a debris tolerant lockdown seal. In addition, the present invention may also advantageously save the time and money associated with having to re-trip in order to install a lockdown hanger.
So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, are attained, and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof which are illustrated in the appended drawings that form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and are therefore not to be considered limiting of its scope as the invention may admit to other equally effective embodiments.
The present invention will now be described more fully hereinafter with reference to the accompanying drawings which illustrate embodiments of the invention. This invention may, however, be embodied 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 the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and the prime notation, if used, indicates similar elements in alternative embodiments.
In the following discussion, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be obvious to those skilled in the art that the present invention may be practiced without such specific details. Additionally, for the most part, details concerning well drilling, running operations, and the like have been omitted in as much as such details are not considered necessary to obtain a complete understanding of the present invention, and are considered to be within the skills of persons skilled in the relevant art.
Referring to
An extension 32 extends downward from outer leg 26 and may form a portion of a threaded connection 34. However, it is not necessary that the connection be threaded. Extension 32 has a downward facing shoulder 36 that rests on an upward facing shoulder 38 formed on a nose ring 37. In the illustrated embodiment, nose ring 37 includes an annular extension forming a mating portion of threaded connection 34. Threaded connection 34 connects nose ring 37 to seal ring 25. Lower portion 21 defines a downward facing annular shoulder 39 of nose ring 37 and rests on upward facing shoulder 19 of hanger 18. During setting operations, upward facing shoulder 19 provides a reaction point to set the seal assembly. In this embodiment, nose ring 37 includes a bellows style portion 40 to increase lockdown capacity of the seal assembly. The bellows style portion 40 may have a zig-zag or triangle wave shaped cross section or undulation 44 having a “V” or “U” shape as shown in
Referring to
Referring again to
Residual effects of the manufacturing process may leave surfaces 42, 46 (
Inner and outer lock rings 90, 92 may be formed of any suitable material such that inner and outer lock rings 90, 92 may contract or expand as described in more detail below. In an exemplary embodiment, inner and outer lock rings 90, 92 are formed of an elastomer material allowing for deformation of inner and outer lock rings 90, 92. In another exemplary embodiment, inner and outer lock rings 90, 92 are formed of a thermoplastic material, such as Teflon or the like, also allowing for deformation of inner and outer lock rings 90, 92. In still another exemplary embodiment, inner and outer lock rings 90, 92 may be formed of a metal such as carbon steel, brass, or the like, again allowing for some deformation of inner and outer lock rings 90, 92 under sufficient loading. Lock rings 90, 92 may be split rings having a slot formed therein for radial expansion/contraction. Lock rings 90, 92 may also be continuous rings formed of a material allowing for expansion/contraction.
Referring to
Continuing to refer to
The engagement by lock rings 90, 92 with hanger 18 and housing 10 provides a rigid stop for the seal assembly, allowing the seal to be fully set, as shown in
In another embodiment, bellows style portion 40 portion of nose ring 37 may be made of a material with a different coefficient of thermal expansion than hanger 18 and housing 10. This may allow bellows style portion 40 to thermally expand at a greater rate, increasing the radial force applied against outer profile 43 of hanger 18 and bore 12 of housing 10 by lock rings 90, 92. The different coefficients of thermal expansion may further add to the lockdown capacities of bellows style portion 40 and inner and outer lock rings 90, 92.
Thus, lockdown capacity is advantageously increased by sharing upward forces on the hanger among the present invention and mechanisms of the prior art. In addition, the present invention may also save the time and money associated with having to re-trip in order to install a lockdown hanger. Further, with the present invention there is no need for additional locater grooves in the housing, thus allowing for greater misalignment during operation. The bellows style portion on the nose ring also provides a mechanism of locking down the hanger, with radially moving lock rings. The radially drivable lock rings provide additional transfer of upward axial force by the casing hanger into radial force to limit casing hanger movement. Thus, lockdown capacity is advantageously increased by sharing upward forces on the hanger. Still further, the disclosed embodiments provide a debris tolerant lockdown seal.
It is understood that the present invention may take many forms and embodiments. Accordingly, several variations may be made in the foregoing without departing from the spirit or scope of the invention. Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.
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Number | Date | Country |
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2135416 | Aug 1984 | GB |
2489593 | Oct 2012 | GB |
Entry |
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Search Report from corresponding GB Application No. GB1221350.0 dated Feb. 11, 2013. |
U.S. Appl. No. 13/114,916, filed May 24, 2011 by Ford, et al. |
Number | Date | Country | |
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20130140042 A1 | Jun 2013 | US |