Patent Grant
7096956
The present invention relates to wellhead equipment and, more particularly, to a wellhead assembly with a tubular hanger adapter to be lowered in a well, then landed within and sealed to a subsea wellhead housing, thereby suspending a tubular string from the wellhead housing, with the hanger sealed to the wellhead housing.
A wellhead housing may be located on the sea floor, so that a casing string may extend downward from the wellhead housing into the well, with the casing string supported in the wellhead housing by a casing hanger. A seal assembly may be installed between the casing hanger at the upper end of the casing string and the wellhead housing. The operator may install the casing string and seal assembly remotely, and in seas of considerable depths.
Running tools have been developed for delivering forces to set and test the downhole seal assemblies, as disclosed in U.S. Pat. No. 4,969,516. Hydraulic pressure may result in axial movement of a piston within a sealed hydraulic chamber in the running tool. Many hydraulically powered running tools are, however, complex and expensive. U.S. Pat. No. 5,044,442 discloses a hydraulic running tool which utilizes annulus pressure. Rams may be closed around a running string, creating a chamber below the rams. An elastomeric seal may be sealed to a portion of the running tool and to the wellhead. The seal and a collar enable pressure to be applied to stroke the tool. Fluid may be pumped downhole through choke and kill lines to set the casing hanger seal.
Other relevant patents include U.S. Pat. Nos. 4,757,860, 5,372,201, and 5,791,418. The '860 patent discloses a running tool for positioning a seal assembly between a casing hanger and a casing head. A first sleeve is connected to the hanger and a second sleeve is threadably connected to the first sleeve, and is movable between one position to support the seal assembly, and a second position for releasing the seal assembly to be lowered for sealing with the casing hanger. The '201 patent discloses a running tool which includes a pressure set seal, where the setting sleeve is sealed to the wellhead. The '418 patent discloses a tool designed to shift an external valve sleeve in a wellhead housing.
The disadvantage of the prior art are overcome by the present invention, and an improved annulus pressure actuated hanger seal assembly and running tool are hereinafter disclosed.
In one embodiment, the seal assembly and running tool of this invention may be used to seal a wellhead housing with one or more hangers in a well, with at least one of the hangers supporting a tubular string in the well. The seal assembly may be lowered with the hanger on a running tool so that the seal assembly is spaced above its set position when the hanger is landed in the wellhead. By manipulation of the running tool string, the seal assembly may be lowered to an initial sealing position. A downward force may thus be applied by set down weight acting on the running tool and transmitted to the seal assembly to initially seal between the bore wall in the wellhead housing and the tubular hanger. A setting piston in the running tool seals with the tool body and moves axially in response to fluid pressure in the annulus about the running string to set the seal assembly. The application of fluid pressure energizes the seal assembly, and may also lock the seal assembly into place so that the integrity of the set seal assembly may be tested.
The annular space between wellhead housing and the tubular hanger may be closed by the seal assembly forming a metal-to-metal seal, and optionally a metal-to-metal seal and a resilient or elastomeric seal, with both the wellhead housing and the hanger.
A locking piston may be provided on the running tool for locking the seal assembly to the hanger, with the setting piston having a larger pressure area than the locking piston. The setting piston preferably is radially outward of the locking piston. Fluid below both the setting piston and the locking piston may be vented to the annulus below the hanger.
The seal assembly preferably forms an initial contact seal between the hanger and the wellhead housing for initially setting the seal assembly. The outer surface sealed by the seal assembly may be substantially cylindrical, and a taper provided on the hanger to force the seal assembly outward when pushed down the taper.
In one subsea application, a blowout preventor is positioned above the wellhead housing, and at least one choke and kill line extends from the surface to the blowout preventor to allow pressure to be applied below the BOP. A connector may connect the blowout preventor to the wellhead housing. Fluid pressure may be applied through the choke and kill lines to the setting piston when the blowout preventor rams are closed.
According to the method, a seal assembly is positioned between a wellhead housing and a tubular hanger for supporting a tubular string in a well. The method includes lowering the seal assembly within the wellhead housing on the running tool to an initial sealing position, and increasing fluid pressure to move the setting piston on the running tool axially to a set position, such that the seal assembly is energized by the application of fluid pressure to the setting piston. An elastomeric seal is preferably provided for at least initial sealing between the wellhead housing and the hanger, and a locking piston supported on the running tool is provided for locking the seal assembly to the hanger.
A split lock ring may expand by rotation of the running string to move a setting sleeve to a locked position, while rotation of the running string in an opposing direction moves the setting sleeve to an unlocked position. An anti-rotation key may be provided for allowing a running string to be rotated and the setting sleeve moved axially without rotating either the running tool or the hanger. A retaining ring carried on the setting sleeve may secure the seal assembly in place when the hanger is being run in a well, then release the fully installed seal assembly. Rotation of the running string to the right also releases the seal assembly to move downward.
A running tool is provided for setting a seal assembly between a wellhead housing and a tubular hanger for supporting a tubular string in a well. The running tool includes a running tool body for lowering the seal assembly within wellhead housing, and a setting piston supported on the running tool body for moving the seal assembly axially to a set position, such that the seal assembly may be lowered and energized by the application of fluid pressure to the setting piston. Fluid pressure in the assembly surrounding the running string acts on the setting piston for moving the seal assembly to the set position. The setting piston seals on a radially inward surface and a radially outward surface of the tool body. An elastomeric seal on the seal assembly is preferably also provided for sealing between the wellhead housing and the hanger, and allows fluid pressure to also act directly on the seal assembly. A locking piston supported on the running tool may lock the seal assembly to the hanger.
These and other 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.
The running tool 30 supports the hanger 10 by a split lock ring 32 (see
One or more rotation keys 36 as shown in
One or more release dogs 12 may each be carried by a window 11 in the actuating sleeve 34, and are moved in response to axial movement of the actuating sleeve 34. The release dogs 12 may be radially expanded to hold the seal assembly 20 in place while the hanger is being run, then release inward to allow the released seal assembly 20 to be moved to the set position. While the tool is locked to the hanger, the release dogs 12 may be in the radially outward position to hold the seal assembly 20 in place.
Once the hanger 10 has been landed, the running string 42 may be rotated to the right to allow the tool to be released from the hanger. While rotating the central stem 40 to the right, the actuating sleeve 34 may be rotated to move to the unlock or up position. While the actuating sleeve is moved to the unlock or up position, the release dogs 12 also move up until they are radially retracted into a groove 13 in the body of the tool. Once the release dogs 12 enter this groove, the lower part of the setting piston 72 releases, and the seal assembly 20 may move downward with the setting piston. The weight of the running string 42 acting on the top of the tool 30 and on the setting piston 72 then pushes the seal assembly 20 to an initial contact seal on the hanger 10 and the bore wall of the wellhead housing 50.
The setting piston 72 may thus move downward with the seal assembly 20 until the seal assembly contacts the hanger, thereby generating a contact seal between the OD of the hanger and the ID of the wellhead housing. This initial seal may be between a rubber or elastomeric portion of the seal assembly and both the hanger 10 and the wellhead housing 50. With the rams 56 of the BOP 54 closed, fluid pressure may be applied through the choke and kill line 60 below the rams. Fluid pressure acting on the setting piston further moves the setting piston downward, with pressure assist from the sealing assembly 20, which is also subject to this fluid pressure. Fluid pressure on the lower face of the piston created during this movement may be vented through port 73 in locking piston 70, then downward to the annulus below the set hanger. During downward movement of locking piston 70, fluid pressure is similarly vented to this annulus. As pressure is applied, the setting piston 72 moves the seal assembly in place. The setting piston 72 applies a substantial setting force to set the seal assembly 20. The set seal assembly 20 preferably forms a metal-to-metal seal with both the wellhead housing 50 and the hanger 10.
Once the seal has landed and is sealed to the wellhead housing 50 and the hanger 10, fluid pressure may be increased until the locking sleeve 14 connected to the locking piston 70 locks the seal assembly to the hanger and the seal is tested. Once the seal assembly 20 has been set, the locking piston 70 and the locking sleeve 14 may thus continue to move downward. When shear pins 17 in the seal assembly 20 are sheared, the lock ring 98 as shown in
The surfaces being sealed by the seal assembly of the present invention may be provided in a well below a BOP or other closure device. Pressure from above is supplied to the setting piston 72 to force the seal downward. In a preferred application as disclosed above, an elastomeric member of seal assembly 20 engages the bore of a cylindrical inner wall of the subsea wellhead housing, although the seal could in other applications engage the bore of a surface housing. The hanger 10 has a radially external sealing surface with a taper for forcing the seal assembly radially outward to seal with the wellhead housing. The preferred seal assembly includes both an elastomeric seal which, in a preferred embodiment, initially seals with the wellhead housing, and another radially internal elastomeric seal for gas-tight sealing engagement with the tubular hanger. In some applications, it may not be necessary to provide a second elastomeric seal for sealing with the hanger, since one or more annular bumps on the ID of the seal assembly may form a reliable metal-to-metal seal with the outer surface of the hanger.
Release locks 16 may initially fix the seal assembly 20 to the tool 30, with the seal assembly 20 held in place by one or more shear pins 17. The tool 30 may have two or more pistons and sleeves for installing the seal assembly. A locking piston 70 may be used to lock the seal assembly to the hanger, and a setting piston 72 with a larger area may generate the setting force to assist in the final setting of the seal assembly. In the embodiment shown, locking piston 70 is connected to sleeve 14 which contacts the seal assembly during the final locking operation. The upper end of the locking piston 70 may be connected to a plate which is in engagement with the sleeve 14. This plate includes apertures for allowing axial movement of bolts at the upper end of the setting piston to move relative to the plate. An outer sleeve 15 may surround the inner components of the running tool for protection.
As disclosed above, the setting piston 72 on the running tool may be actuated to move the seal assembly to the set position. As shown in
Another significant feature of the invention is that this design operates in response to fluid pressure in the annulus about the running tool. This fluid pressure may conventionally be applied subsea through choke and kill lines to the BOP. With the BOP ram closed, fluid pressure may thus be controlled in the annulus about the running tool. By avoiding operation of the tool in response to fluid pressure in the work string and/or the central stem or mandrel of the tool, the cost of balls, seats, plugs or other sealing members passing through or spaced below the running tool are avoided. Also, significant savings are realized in the time savings by the operator to run in and use such sealing devices.
In the embodiment disclosed above, the annular seal assembly seals to the exterior surface of a casing hanger, but in other applications the setting piston may force the seal assembly in an annulus between the wellhead housing and an exterior surface of a tubular, or to a plug member, such as a tree cap or a dummy hanger. A preferred embodiment allows fluid on the back side of both the setting piston and the locking piston to be vented to the area inside the running tool body and below the hanger. As disclosed herein, the setting piston is radially outward of the locking piston, although in an alternate embodiment the locking piston might be provided exterior of the setting piston. A preferred embodiment allows the seal assembly to be locked in place once the setting piston has fully set the seal, although in alternate embodiments the locking piston might be eliminated.
In the above described embodiments, fluid pressure was applied from choke and kill lines to the annulus surrounding the running string and then to the setting piston and seal assembly to set the seal assembly. In other applications, fluid pressure to the setting piston may be supplied through the annulus surrounding the running string from other flow lines extending, for example, from a rig spaced from the subsea well. In this application, the BOP may be located subsea or on the surface.
While preferred embodiments of the present invention have been illustrated in detail, it is apparent that other modifications and adaptations of the preferred embodiments will occur to those skilled in the art. The embodiments shown and described are thus exemplary, and various other modifications to the preferred embodiments may be made which are within the spirit of the invention. Accordingly, it is to be expressly understood that such modifications and adaptations are within the scope of the present invention, which is defined in the following claims.
The present application claims the benefit of Application 60/476,933 filed Jun. 10, 2003.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3693714 | Baugh | Sep 1972 | A |
| 4561499 | Berner et al. | Dec 1985 | A |
| 4674576 | Goris et al. | Jun 1987 | A |
| 4757860 | Reimert | Jul 1988 | A |
| 4766956 | Smith et al. | Aug 1988 | A |
| 4969516 | Henderson et al. | Nov 1990 | A |
| 5044442 | Nobileau | Sep 1991 | A |
| 5372201 | Milberger | Dec 1994 | A |
| 6557638 | Cunningham et al. | May 2003 | B1 |
| Number | Date | Country | |
|---|---|---|---|
| 20040251031 A1 | Dec 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60476933 | Jun 2003 | US |
