Patent Application
20170145775
The field of the invention is sealing systems for a liner hanger/packer assembly and more particularly where the polished bore is above the liner top packer and has a metal to metal seal to the packer body.
Boreholes are completed with a liner string connected to an existing string. Typically the liner string is run in with a running tool to the desired overlapping position with the existing string so that a liner hanger can be set and the running tool released. The hanger has spaces between the gripping members so that when cement is pumped through the liner and darts are launched to displace the cement out of a shoe at the lower end of the liner the fluid in the annulus can be displaced through those spaces. After that the liner top packer is set.
In existing designs there is a polished bore receptacle associated with the liner top packer and the seal between the mandrel for the packer and the polished bore has in the past been one or more resilient elastomer o-rings. The polished bore has also been located below the liner top packer and a string to the surface known as a tieback string was extended into the polished bore receptacle and sealed with a metal to metal seal.
The elastomer seals over a long period of time can leak and the present invention addresses this issue in a liner hanger/packer application with a metal to metal seal to a polished bore from the packer mandrel. The tieback string connects to the same polished bore with a metal to metal seal so that from the liner string to the surface there are only metal to metal seals. The polished bore is also located uphole from the liner top packer so that the tieback string and the polished bore can have a larger diameter so as not to restrict production flow unduly. The prior design located the polished bore below the packer seal which caused a flow restriction. These and other aspects of the present invention will become more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.
Generally related to polished seal bores and/or metal to metal seals are U.S. Pat. No. 5,662,341 and US US20110147015.
A liner string has a hanger/packer near its upper end for connection and sealing to a surrounding tubular. A polished bore assembly is located above the packer and is pushed down after the liner hanger is set to slide over a metal to metal seal on the packer body. A surface string is then tied into the polished bore with another metal to metal seal against the polished bore. The liner string has just metal to metal seals going up to the surface for well pressure containment. Elastomer seals to the polished bore are eliminated. Placement of the polished bore above the packer body allows for a larger diameter polished bore so as to minimize restriction to future production flow. The liner top packer seal is also metal to metal as offered by Baker Hughes Incorporated under the ZX trademark.
Referring to
Several features are different than past designs and bear some emphasis. First there are no elastomer seals between the mandrel 24 and the assembly 16. The location of the assembly 16 uphole from the liner top packer 14 allows the use of a larger bore 26 for the tieback string that will next to secured to bore 26 to make a connection to the surface with another metal to metal seal as illustrated schematically at 32 after the running tool that is not shown is pulled out of the hole. The use of a metal to metal seal 18 against the bore 26 provides only metal to metal seals from the liner attached at 10 to the surface while eliminating the use of elastomer o-rings or similar seals in a liner hanging application as described. The feature of moving the seal bore assembly 16 over the metal to metal seal assembly 18 allows fluid passages to remain open between them for running in to expedite that process.
In short, for operators that are hesitant to rely on elastomer seals between a mandrel and the polished bore 26 for what could turn out to be many years during the life of the well, the above described assembly presents only metal to metal seals from the liner string to the surface. Positioning the polished bore above the liner top packer also allows use of a larger polished bore for the tieback string to reduce flow restrictions during production.
Those skilled in the art will appreciate that the running tool is manipulated to extend dogs to bear on the assembly 16 indirectly for setting the liner hanger 12 in a known manner followed by a release of the running tool and the performance of the cementing job in a known manner. The liner top packer 14 is also set with pressure on a ball dropped into the running tool in a known manner.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below:
