A seal assembly and running tool are provided for sealing a casing annulus in a wellhead. More particularly, the seal assembly is axially interconnected with the wellhead while sealing an annulus between the casing hanger and the wellhead.
Various types of seal assemblies and running tools have been devised for sealing a casing annulus. A casing hanger may be positioned within the wellhead, and a running tool may be used to actuate the seal assembly carried on the casing hanger and thereby seal with the casing hanger.
For various reasons, a casing hanger within the wellhead may move axially upward, particularly when the wellhead is part of a production system wherein downhole fluids at elevated temperatures thermally expand the casing string and thus exert a substantial upward force on the casing hanger. Since the casing hanger seal is intended for sealing at a particular location on the wellhead, upward movement of the casing hanger and the seal assembly is detrimental to reliably sealing the casing annulus.
A seal assembly for a casing hanger in a wellhead is disclosed in U.S. Pat. No. 5,287,925. Another type of seal assembly between a wellhead and a tubing hanger seal is disclosed in U.S. Pat. No. 6,598,680. U.S. Pat. No. 6,705,615 discloses yet another version of a seal assembly for use in a wellhead, and U.S. Pat. No. 6,969,070 discloses improvements in a seal assembly. A pressure actuated seal assembly and running tool are disclosed in U.S. Pat. No. 7,096,956.
The disadvantages of the prior art are overcome by the present invention, an improved wellhead seal assembly and running tool are hereinafter disclosed.
In one embodiment, a seal assembly is provided for sealing a casing annulus in a wellhead. A casing hanger is positioned within the wellhead, which is provided with a radially internal groove. A first locking ring is radially movable into the internal groove in the wellhead to axially connect the seal assembly and the wellhead. A second locking ring may interconnect the seal assembly and the casing hanger. Actuating a running tool radially moves each locking ring into the groove in the respective wellhead and the hanger, and thereby axially connects the seal assembly to both the wellhead and the hanger.
These and further features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings.
Referring now to
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In
A feature of the invention is that each of the latch ring 36 and the connecting ring 40 is radially contained by the seal body. Ring 36 is radially contained at its lower end by seal body extension 31 and at its upper end by seal body 45 so that the ring 36 cannot inadvertently come out of its retained position, i.e., no circumferential portion of ring 36 can extend completely outside the seal body due to the stops 44 on the seal body 45 and the body extension sleeve 31. More particularly, the latch ring 36 includes upper and lower protrusions 42 which engage corresponding upper and lower stops 44 on the extension sleeve 31 and body 45 to limit radially outward movement of the latch ring 36. In the absence of this feature, a ring intended to move outward slightly from the supporting body could move appreciably outward of the body, and that part of the ring could then inadvertently get hung up on a component when the assembly is lowered in the well. The C-shaped ring 36 may have upper and lower annular protrusions 42 that may also be C-shaped, while the stops 44 on extension sleeve 31 and seal body 45 may similarly be annular shaped, but may be circular rather than C-shaped. Upper and lower protrusions 42 are fixed on the latch ring 36, and stops 44 are fixed on the extension sleeve 31 and the body 45, so that radially outward movement of C-ring 36 is positively limited. By containing the latch ring 36 while it is run in the well through the riser and one or more BOPs, the reliability of the system is substantially enhanced because the latch ring does not get “hung up” on a component as it is lowered into the wellhead to adversely affect its operability.
It is also desirable to limit connecting or locking ring 40 so that it does not move radially inward until positioned and actuated to connect to the casing hanger. As shown in
As discussed above, upper and lower protrusions on each of the locking rings preferably have the general shape of the C-shaped ring. Substantially ring-shaped stop surfaces supported on the seal body are provided along substantially the length of each upper and lower protrusion, thereby contributing to high reliability when the C-ring is subsequently activated for connection to one of the wellhead and the casing hanger. The stops which are engaged by these protrusions may each have a substantially circular configuration, thereby providing a large contact area between the protrusions and the ring when manipulated from the run-in position to the actuated position.
In the preferred embodiment seal body 48 supports both one or more radially external seals 30 for sealing with an internal surface of the wellhead, and one or more internal seals 33 for sealing with the casing hanger. The seal 30 is a more difficult seal to reliably obtain, and seal 30 may be a combination of a plastic member or a soft metal, such as lead or tin, and one or more radially projecting fingers formed from steel. The seal 33 may be an o-ring carried on the seal body for sealing with the casing hanger. Other seals, such as annular or metal bumps 35 on the seal body, alternatively may be provided for sealing with the casing hanger.
Each of the latch ring and the connecting ring as disclosed herein fit within a groove or recess in the wellhead and the casing hanger, respectively. Most of the discussion involves the use of a groove to receive the respective ring, and an annular groove is suitable for that purpose. In other cases, however, an annular groove may not be necessary, and one or more recesses may be provided in the wellhead and the casing hanger, respectively, to receive the latch ring or the connecting ring. The recesses may have an arcuate shape, or may be otherwise configured to reliably receive the respective ring.
Each of the locking members 36 and 40 as disclosed herein may be a substantially C-shaped locking ring which is retained on the seal body by the stops. C-shaped locking rings are preferred for many applications due to their high reliability, simplistic operation, and their ability to reliably withstand high loads. Other types of locking members may be used for axially interconnecting the seal body to either or both the wellhead and the casing hanger, including radially movable dogs which would fit within the corresponding recesses.
The method of sealing a casing in the wellhead should be apparent from the above description. The casing hanger is positioned within the wellhead, and the casing hanger preferably includes a radially external groove therein. A radially internal groove is provided in the wellhead. The method includes radially moving the latch ring, e.g., by actuating the running tool, to move sleeve 53 so that the locking ring 36 moves into the internal groove in the wellhead to axially connect the seal assembly and the wellhead. According to a preferred embodiment, the method includes radially moving another locking ring into an external groove in the casing hanger and to connect the seal assembly and the casing hanger. The running tool may set the latch ring and the connecting ring once the seal body is in its fully set position.
Each of the latch ring and the connecting ring is supported on the seal assembly in a manner which limits radial movement of the ring beyond the tool body. More particularly, the method includes providing stops on the seal body to prevent premature axial movement of either locking ring with respect to the seal body. A piston on the running tool is moveable in response to fluid pressure in the running tool, and may be used for actuating each locking ring 36 and 40 through the actuation sleeve.
Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.
This application is a U.S. national stage application of PCT Appln. No. PCT/US11/43293 filed on Jul. 8, 2011, which claims the priority of U.S. Provisional Application No. 61/408,755 filed on Nov. 1, 2010, the disclosure of which is incorporated herein by reference for all purposes.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US2011/043293 | 7/8/2011 | WO | 00 | 6/21/2013 |
Publishing Document | Publishing Date | Country | Kind |
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WO2012/060909 | 5/10/2012 | WO | A |
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