Wells – Processes – Placing or shifting well part
Reexamination Certificate
2001-12-04
2004-05-25
Tsay, Frank (Department: 3672)
Wells
Processes
Placing or shifting well part
C166S123000, C166S153000
Reexamination Certificate
active
06739398
ABSTRACT:
FIELD OF THE INVENTION
An improved liner hanger running tool is provided for hanging a liner from a casing within a wellbore. The liner hanger running tool includes improvements to a running tool release mechanism, a retrievable packoff bushing, and a packer setting assembly. The packer setting assembly may be used in other downhole sealing applications.
BACKGROUND OF THE INVENTION
When drilling a well, a borehole is typically drilled from the earth's surface to a selected depth and a string of casing is suspended and then cemented in place within the borehole. A drill bit is then passed through the initial cased borehole and is used to drill a smaller diameter borehole to an even greater depth. A smaller diameter casing is then suspended and cemented in place within the new borehole. This is conventionally repeated until a plurality of concentric casings are suspended and cemented within the well to a depth which causes the well to extend through one or more hydrocarbon producing formations.
Rather than suspending a concentric casing from the bottom of the borehole to the surface, a liner is often suspended adjacent to the lower end of the previously suspended casing, or from a previously suspended and cemented liner, so as to extend the liner from the previously set casing or liner to the bottom of the new borehole. A liner is defined as casing that is not run to the surface. A liner hanger is used to suspend the liner within the lower end of the previously set casing or liner. Typically, the liner hanger has the ability to receive a tie back tool for connecting the liner with a string of casing that extends from the liner hanger to the surface.
A running and setting tool disposed on the lower end of a work string may be releasably connected to the liner hanger, which is attached to the top of the liner. The work string lowers the liner hanger and liner into the open borehole so that the liner extends below the lower end of the previously set casing or liner. The borehole is filled with fluid, such as a selected drilling mud, which flows around the liner and liner hanger as the liner is run into the borehole. The assembly is run into the well until the liner hanger is adjacent the lower end of the previously set casing or liner, with the lower end of the liner typically slightly above the bottom of the open borehole.
When the liner reaches the desired location relative to the bottom of the open borehole and the previously set casing or liner, a setting mechanism is conventionally actuated to move slips on the liner hanger from a retracted position to an expanded position and into engagement with the previously set casing or liner. Thereafter, when set down weight is applied to the hanger slips, the slips are set to support the liner.
The typical liner hanger may be actuated either hydraulically or mechanically. The liner hanger may have a hydraulically operated setting mechanism for setting the hanger slips or a mechanically operated setting mechanism for setting the slips. A hydraulically operated setting mechanism typically employs a hydraulic cylinder which is actuated by fluid pressure in the bore of the liner, which communicates with the bore of the work string. When mechanically setting the liner hanger, it is usually necessary to achieve relative downhole rotation of parts between the setting tool and liner hanger to release the hanger slips. The hanger slips are typically one-way acting in that the hanger and liner can be raised or lifted upwardly, but a downward motion of the liner sets the slips to support the hanger and liner within the well.
To release the running tool from the set liner hanger, the setting tool may be lowered with respect to the liner hanger and rotated to release a running nut on the setting tool from the liner hanger. Cement is then pumped down the bore of the work string and liner and up the annulus formed by the liner and open borehole. Before the cement sets, the setting tool and work string are removed from the borehole. In the event of a bad cement job, a liner packer and a liner packer setting tool may need to be attached to the work string and lowered back into the borehole.
The packer is set utilizing a packer setting tool. Packers for liners are often called “liner isolation” packers. A typical liner isolation packer system includes a packer element mounted on a mandrel and a seal nipple disposed below the packer. The seal nipple stings into the tie back receptacle on top of or below the previously set and cemented liner hanger. A liner isolation packer may be used, as explained above, to seal the liner in the event of a bad cement job. The liner isolation packer is typically set down on top of the hanger after the hanger is secured to the outer tubular, and the packer is set by the setting tool to seal the annulus between the liner and the previously set casing or liner.
Generally, the deeper a well is drilled, the higher the temperature and pressure which is encountered. Thus, it is desirable to have liner packers which will ensure quality cementing of the liner so as to provide a high safety factor in preventing gas from the formation from migrating up the annulus between the liner and outer casing.
During the cementing operation, fluid such as drilling mud in the annulus between the liner and outer casing is displaced by cement as the cement is pumped down the flow bore of the work string. First, the drilling mud and then the cement flows around the lower end of the liner and up the annulus. If there is a significant restriction to flow in the annulus, the flow of the cement slows and a good cementing job is not achieved. Any slowing of the cementing in the annulus allows time for the gas in the formation to migrate up the annulus and through the cement to prevent a good cementing job.
Running Tool Release Mechanism
As a practical matter, the liner hanging running tool must include a release mechanism so that, once the liner is reliably set to the lower end of the casing, the running tool can be released from the liner hanger and retrieved to the surface. Conventional liner hanger running tool releasing mechanisms include hydraulically actuated mechanisms, and release mechanisms that are manipulated by left-hand rotation of the running string. The left-hand rotation of the running string is, however, generally considered undesirable since it may result in an unintended disconnection of one of the joints of the running string, thereby causing separation of the running string and a fishing operation to retrieve the running tool, which may have been damaged by the unintended disconnection. For various reasons, hydraulically operated running tool release mechanisms may fail to operate, or may prematurely release the running tool from the liner hanger.
Accordingly, improvements in release mechanisms are desired which will reliably release the running tool from the set liner only when intended, particularly when retrieving is easily accomplished and premature disengagement of the running tool from the liner is highly unlikely.
Packoff Bushing
A liner hanger packoff bushing conventionally seals between the liner hanger and the running tool, and thus between the liner and the running string or work string, which conventionally may be drill pipe. A packoff bushing is particularly required during cementing operations so that fluid pumped through the drill pipe continues to the bottom of the well and then back up into the annulus between the well bore and the liner to cement the liner in place. During cementing operations, the seal body of the packoff bushing is fitted in the annulus between the liner hanger and the running tool, and includes OD seals for sealingly engaging the liner hanger and ID seals for sealingly engaging the running tool. Packoff bushings are preferably retrievable with the running tool to prevent having to drill out the bushings after the cementing operation is complete. Also, a packoff bushing is preferably lockable to the liner hanger by locking within a profile to prevent the bushing from moving axially with r
Reimert Larry E.
Yokley John M.
Browning & Bushman P.C.
Dril-Quip Inc.
Helmreich Loren G.
Tsay Frank
LandOfFree
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