Wells – Processes – Assembling well part
Reexamination Certificate
1999-12-22
2004-03-09
Tsay, Frank (Department: 3672)
Wells
Processes
Assembling well part
C166S208000
Reexamination Certificate
active
06702029
ABSTRACT:
This invention relates to a tubing anchor, such as a liner hanger, that is a arrangement for locating and sealing a section of liner downhole relative to an existing casing. The invention also relates to a method and apparatus for use in providing such an anchor or hanger.
In oil and gas exploration and extraction, it is conventional to line the bores drilled to access subsurface hydrocarbon-bearing formations with steel tubing. The upper section of a bore is typically lined with steel “casing”, while the lower section of the bore is provided with “liner”, which is hung off the lowermost section of casing. The liner is secured and sealed to the casing using a liner hanger comprising an arrangement of slips and elastomer seals, which seals may also serve to energise the slips.
Conventional liner hangers are relatively complex and expensive and occupy a significant annular space, necessary to accommodate both the gripping slip segments which support the weight of the liner and resist the differential pressure forces which may be generated across the liner/casing overlap and the elastomeric seals which prevent pressure leakage past the overlap. Accordingly, there may be a significant loss in bore diameter at the liner: for example, accommodation of a 7″ diameter liner normally requires provision of a 9⅝″ diameter casing, and a 5″ liner a 7″ casing.
The maintenance of the integrity of the elastomeric seals used in conventional liner hangers has also proved problematic, particularly in high pressure high temperature wells, which are becoming increasingly more common.
In the majority of cases, the liner section will be cemented in place, by pumping cement slurry down through the liner and back up the annular space between the liner and the borehole wall. Recent developments have resulted in the provision of mechanisms which allow the liner to be rotated during the cementing process, to improve cement coverage around the liner and the subsequent bond between the liner and the bore wall. These mechanisms typically consist of bearings which isolate the slip and seal sections of the liner hanger while the casing is rotated from surface via the liner running tool assembly.
In addition, circulating ports are provided in the liner hanger to allow fluid displaced from the annulus by the cement slurry to bypass the liner hanger mechanism to the point where returning cement can also pass the liner hanger before the liner is finally set, thus ensuring that the annulus is filled with uncontaminated cement slurry.
The provision of these bearings and circulating ports add further complexity to an already complex system.
It is among the objectives of embodiments of the present invention to provide a liner hanger arrangement which obviates and mitigates at least some of these disadvantages. In particular, embodiments of the present invention provide relatively simple liner hangers which occupy only a very limited volume and which utilise metal-to-metal seals.
It is among the objective of other embodiments of the present invention to provide a downhole method and apparatus for anchoring tubing, particularly expandable tubing, to a section of existing casing.
According to one aspect of the present invention there is provided a method of installing a liner in a drilled bore below a section of bore previously lined with casing the method comprising the steps of:
running a length of liner into the bore such that at least an upper end of the liner is positioned in overlapping relation with at least a lower end of the casing; and
plastically deforming a portion of the liner such that an external face of said portion forms an interference fit with an internal face of a portion of the casing to provide at least one of hanging support for the liner and a fluid-tight seal between the liner and casing.
The invention also relates to liner and casing for use in the method. In one embodiment of the invention, at least the portion of liner to be expanded is of a relatively ductile material.
the plastic deformation of the portion of liner to create an interference fit with the casing and provide hanging support for the liner obviates the requirement to provide slips or the like on the liner, and also a mechanism to energise the slips, and thus the liner outside diameter may be relatively close to the inside diameter of the casing. The creation of fluid-tight seal obviates the requirement to provide conventional elastomeric seals requiring petting and energising.
Preferably, said portion of liner is deformed by rolling expansion, that is an expander member is rotated within the liner with a face in rolling contact with an internal face of said portion. The expander member may describe the desired diameter and is preferably urged radially outwardly into contact with the liner. Such rolling expansion causes compressive plastic deformation or yield of the liner and a localised reduction in wall thickness resulting in a subsequent increase in liner diameter.
Preferably, said deformed portion of the liner is annular.
Preferably, the portion of liner is deformed to create a pressure-tight seal between the liner and casing. Most preferably, the seal formed is a metal-to-metal seal. Conveniently, the portion of liner includes a relatively soft material, such as a relatively soft metal, which is plastically deformed during the expansion of the liner portion. The soft metal may be provided as an annular coating or insert. In other embodiments other sealing materials may be utilised, such as elastomers, or the relatively soft material may be provided on the casing.
The portion of liner may be deformed to extend into or otherwise engage a preformed profile in the casing. A step of a method in accordance with an embodiment of the invention may involve deforming the casing to define the profile prior to running the liner into the bore. Alternatively, the portion of casing may also be deformed together with the liner, and the deformation of the casing may be elastic or plastic. The liner may be deformed at two or more axially spaced locations. Thus, the liner, and possibly also the casing, may be deformed to define a plurality of axially spaced profiles.
The liner may be initially secured in the casing, at least against relative rotation, by deforming the liner, in particular by radially extending circumferentially spaced areas of the liner to form corresponding areas of interference fit between the liner and the casing. Preferably, these areas are then extended circumferentially to form annular areas of interference fit between the liner and casing.
The portion of the liner may carry relatively hard material on its external face, which material will tend to bite into the opposing faces of the liner and casing to provide a more secure coupling therebetween. The material is preferably in the form of relatively small discrete particles or pieces, such as balls, chips or the like of relatively hard metal such as tungsten carbide. The hard material may be held in a matrix of softer material.
The method may further comprise the step of cementing the liner in the bore. This may be achieved by pumping cement from surface to the lower end of the liner, preferably through a combined running and cementing string and tool, directing the cement into the annulus between the liner and the bore wall and displacing well fluid from the annulus to substantially fill the annulus with cement. Preferably, the portion of the liner is expanded once the cement is in place in the annulus; the displaced well fluid may therefore pass between the upper end of the liner and the lower end of the casing. Preferably, the liner is rotated as the cement is passed into the annulus; thus, there is preferably a releasable coupling between the running tool and the liner to permit transfer of torque therebetween.
Preferably, the liner is run into the bore on a running tool carrying an expander including a body and at least one radially extendable member mounted thereon, the running tool being rotatable to move the member around the porti
Abercrombie Simpson Neil Andrew
Metcalfe Paul David
Moser, Patterson & Sheridan L.L.P.
Tsay Frank
Weatherford / Lamb, Inc.
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