The present disclosure relates generally to a tubing hanger for use with a subsea wellhead, and in particular, a mechanism for sealing a tubing hanger in a subsea wellhead.
Tubing hangers are employed in subsea wellheads used in, for example, oil and gas wells. The tubing hanger supports the tubing, or “string”, which extends down into the production zone of the well. The tubing hanger can be installed in the wellhead at the well location. Tubing hanger installation can be performed by various means, such as, for example, by employing a tubing hanger running tool that positions the tubing hanger into the wellhead. Tubing hangers are generally locked into place in the wellhead in order to reduce undesired movement of the tubing hanger relative to the wellhead.
The annulus between the tubing hanger and the wellhead housing employs a seal barrier. One of the seals that forms such a barrier is a metal seal that often functions by forming a forced contact with the sealing surface on the tubing hanger and wellhead housing.
When a tubing hanger is installed into or removed from a wellhead, seals formed between the tubing hanger and wellhead can sometimes be damaged. For example, during installation of the tubing hanger into the wellhead, seals that form part of the tubing hanger can contact portions of the wellhead through which they pass. The interference of the seal with the wellhead during installation can damage the seal.
Additionally, some tubing hanger designs may rely on the landing and/or locking movement of the tubing hanger relative to the wellhead in order to energize the seals. Such tubing hanger designs can make it difficult for operators to reposition the tubing hanger in the wellhead and/or verify that the tubing hanger is correctly positioned in the wellhead without risk of damaging the seals.
The present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the issues set forth above.
An embodiment of the present disclosure is directed to a wellhead assembly. The wellhead assembly comprises a wellhead housing comprising a throughbore having a recessed sealing area and a tubing hanger positioned in the throughbore. A seal is positioned between the wellhead housing and the tubing hanger, the seal being positioned so as to form a gap between the seal and the wellhead housing. The wellhead assembly can further include a seal energizer capable of moving relative to the seal in a manner that forces the seal against the wellhead housing to bridge the gap.
Another embodiment of the present disclosure is directed to a method of installing a tubing hanger into a throughbore of a wellhead housing, the tubing hanger having a seal and a seal energizer. The method comprises installing the tubing hanger in the throughbore with the seal in a de-energized position so that substantially no interference occurs between the wellhead housing and the seal during the installing. The tubing hanger is positioned so that the seal is proximate a recessed sealing area in the wellhead housing. The seal is then energized so that a portion of the seal is pushed into a sealing contact with the recessed sealing area.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Tubing hanger 102 can include a seal 110, which can be positioned between the wellhead housing 106 and the tubing hanger 102. Seal 110 can be positioned so as not to physically contact the wellhead housing 106 while entering the bore. As more clearly shown in
Tubing hanger 102 can also include a seal energizer 114. As will be discussed in greater detail below, seal energizer 114 is capable of moving relative to the seal 110 in a manner that forces the seal 110 against the wellhead housing 106 to bridge the gap 112 and provide the desired sealing contact.
The seal 110 can be an annular seal capable of sealing an annulus formed in throughbore 104 between a perimeter of the tubing hanger 102 and the wellhead housing 106. As shown in the embodiment of
Referring to
Recessed sealing area 122 can have any suitable dimensions that allow the desired sealing to occur. In one embodiment, the recess has a depth, D2, ranging from about 0.01 inch to about 0.3 inch.
The width, D1, of the gap 112 can be equal to the depth, D2, of the recessed sealing area 122 plus the width, D3, where D3 is the width of a clearance gap 123 between seal 110 and the major wall surface 124 of the throughbore 104 that surrounds the recessed sealing area 122. Clearance gap 123 can be wide enough to allow seal 110 to pass through throughbore 104 during installation without substantial interference with the wellhead housing 106.
Seal 110 can be made of any suitable material capable of providing a sufficient seal between the tubing hanger 102 and the wellhead housing 106. The material for seal 110 can be chosen to meet any desired specifications or design criteria. For example, the material can be chosen to provide a desired deformation of the seal, to have desired stress and strain characteristics, durability, and/or the ability to withstand pressure loads without losing sealing capability. In an embodiment, the seal is a metal seal. In other embodiments, the seal comprises a non-metal material, such as a polymer.
Seal 110 can be designed to have any suitable shape that will function to provide the desired seal.
Second leg 118 of seal 110 comprises a distal portion 128 having a first width, w1; a proximal portion 130 having a second width, w2; and a tapered portion 132 between the proximal portion 130 and distal portion 128, where w1 is less than w2. As shown in
The dimensions of seal 110 can be any suitable dimensions that are sufficient to provide the desired sealing contact. Referring to
A description of the seal energizing and de-energizing systems will now be described with reference to
Seal energizer 114 can be configured to move relative to the seal 110 in any suitable manner. For example, seal energizer 114 can be configured to slide back and forth in an axial direction on the tubing hanger body 120. The force employed to move seal energizer 114 can be applied by any suitable means using hydraulic, mechanical or electrical devices.
A locking mechanism 136 can be employed to hold the seal energizer in place in relation to the seal when the seal is energized. In an embodiment, the locking mechanism can be a C-ring, which can be biased to move under the seal energizer 114 when seal energizer 114 is positioned to engage seal 110, as illustrated in
The operation of the seal energizer 114 can be independent from the operation of landing and locking the tubing hanger 102. For example, tubing hanger 102 can be positioned into throughbore 104 and locked into place prior to energizing the seal 110. Thus, the motion of positioning the tubing hanger in the wellhead housing during the landing and locking processes is not necessarily employed to energize the seal 110. Any suitable landing and locking mechanisms can be employed. An exemplary landing mechanism 150 and locking mechanism 152 is illustrated in
In an embodiment, tubing hanger 102 can comprise a suitable mechanism for de-energizing the seal 110. De-energizing seal 110 can involve disengaging energizer tip 134 of seal energizer 114 from seal 110. As mentioned above, a suitable de-energizing mechanism 140 is illustrated in
In an embodiment, the de-energizing mechanism 140 can be configured to unlock the locking mechanism 136. For example, de-energizing mechanism 140 can include a tapered portion 142 (
In an embodiment, the de-energizing mechanism 140 can de-energize seal 110 using pressure from a single pressure port 145. As illustrated in
A method of installing the tubing hanger of the present application into a wellhead will now be described. The tubing hanger can include a seal 110 and a seal energizer 114, similarly as described herein. The tubing hanger 102 can be installed in a throughbore 104 of a wellhead housing 106. During installation, the seal can be in a de-energized position, similar to the seal 110 illustrated in
The tubing hanger 102 can be positioned so that the seal 110 is proximate the recessed seal area 122 in the wellhead housing 106. The seal 110 can then be energized so that a portion of the seal 110, such as second leg 118, is pushed into a sealing contact with the recessed sealing area 122.
The process of energizing seal 110 can be accomplished using any suitable technique that results in the desired sealing contact between the seal 110 and wellhead housing 106. In an embodiment, energizing the seal 110 comprises actuating seal energizer 114, as disclosed above. Other exemplary techniques for energizing seals are well known in the art and can be employed in place of or in addition to actuating seal energizer 114.
As discussed above, seal energizer 114 can be designed to push against the second leg 118 of the seal 110 at a point above the seal-wellhead housing interface 133 where the second leg 118 contacts the wellhead housing 106. This can allow for increased elasticity of the seal 110 at the interface 133, relative to the elasticity that would be achieved if the seal energizer 114 pushed against the seal 110 at the portion of the second leg 118 that interfaced with the wellhead housing 106 when seal 110 is energized.
In an embodiment, the method of the present application can further comprise positioning a locking mechanism 136 to constrain the seal energizer 114 in place in relation to the seal 110 while the seal is energized. Suitable locking mechanism designs other than the design illustrated in
In an embodiment, the method of the present application can further comprise de-energizing the seal by forcing the locking mechanism 136 from its locked position so that it no longer supports the seal energizer 114. The seal energizer 114 can then be forced to a position so that it no longer energizes the seal. In an embodiment, forcing the locking mechanism 136 and forcing the seal energizer 114 can both be accomplished using pressure from a single pressure port. In other embodiments, pressure from different pressure ports can be used, as can any other suitable means for applying the force to drive the locking mechanism 136 and the de-energizing of seal energizer 114.
Although various embodiments have been shown and described, the present disclosure is not so limited and will be understood to include all such modifications and variations as would be apparent to one skilled in the art.
The present disclosure claims benefit of U.S. Provisional Patent Application No. 61/090,462, filed Aug. 20, 2008, and U.S. Provisional Patent Application No. 61/090,000, filed Aug. 19, 2008, both of which applications are hereby incorporated by reference in their entirety.
Number | Date | Country | |
---|---|---|---|
61090462 | Aug 2008 | US | |
61090000 | Aug 2008 | US |