Wells – Above ground apparatus – Inner member anchor or seal with lateral port
Reexamination Certificate
2000-10-25
2003-12-16
Neuder, William (Department: 3672)
Wells
Above ground apparatus
Inner member anchor or seal with lateral port
C166S096100, C166S088200, C285S123100, C285S382000
Reexamination Certificate
active
06662868
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the clamping of concentric well casings, where an inner well casing is to be clamped in position relative to an outer well casing, to achieve a desired relative axial position between the casings, for operational reasons axial fixing between coaxial well casings over a range of positions may be required at various times during drilling and/or production from wells, and the present invention makes it possible to clamp one or more casings within another at any desired position and subsequently to unclamp the casings for disassembly, or to change their relative positions and then reclamp the casings in a new relative position. As the clamping mechanism is preinstalled and can be externally activated, the blowout preventers can remain in place throughout the installation, clamping or release of the subsequently installed casing.
BACKGROUND OF THE INVENTION
In oil and gas wells, it is conventional to pass a number of concentric tubes or casings down the well. An outermost casing is fixed in the ground, and the inner casings are each supported in the wellhead or in the next outer casing by casing or tubing hangers.
These casing hangers may take the form of a body with interengaging internal shoulders on the outer casing and a body with external shoulders on the inner casing hangers, located at fixed positions on each previously installed casing.
There are however applications where a fixed position casing hanger is unsatisfactory, because the hang-off point of one casing on another may require to be adjustable.
The invention has particular application for such casing and tubing hangers, which require adjustment.
Where drilling or production wellheads have to accommodate a casing or tubing without predetermined hang-off point, it has been known to use casing slip-type support mechanisms.
It is also known from European patent number EP251595B2 to use an adjustable landing ring on a surface casing hanger to accommodate a space-out requirement.
It is furthermore known that where production wellheads have to accommodate casing or tubing with a tension load greater than the running weight, retractable shoulders or internal wedge mechanisms have been used to allow passing of the casing or tubing hanger, and re-tensioning to a predetermined point.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a pre-installed clamping arrangement for clamping a subsequently installed tubular well casing of a first diameter within a previously installed tubular casing of larger internal diameter, the arrangement comprising a sleeve associated with the large diameter casing, the sleeve having a collar at one end which has an external tapered surface, the arrangement also including an annular component with an internal tapered surface, the sleeve and annular component being relatively axially moveable between a first position in which the tapered surface of the annular component exerts minimal or no radial force on the collar and a second position in which the tapered surface of the annular component exerts sufficient radial force to distort the collar into the bore of the larger diameter casing, to grip the well casing of smaller diameter, the arrangement also including a removable device for maintaining the surfaces in the first position, and separate means for urging the annular component axially against the collar.
The sleeve may be of one piece with the large diameter casing, but more probably will be a separate component which could either be threaded onto the casing or be located in a suitable locating and receiving area on the casing.
The clamping arrangement preferably also provides a sealing function across the interface between the tapered surfaces, either through the metal/metal contact between the tapered surfaces, or through a separate seal body. Where the sleeve is a separate component from the larger diameter casing, there may be a metal/metal seal between the tapered surfaces and, in addition, a separate seal between the sleeve and the casing.
The device for maintaining the surfaces in the first position is preferably a spacer ring. The spacer ring may be removable, or may be a ring which can be moved axially by rotating it on a thread.
The sleeve can be formed as part of a casing hanger used for supporting a casing in a well.
The annular component can be a wellhead spool, and means can be provided to move the annular component axially in a direction away from the sleeve. This means for moving can comprise a chamber between the sleeve and the annular component, and the chamber can be pressurized to urge the wellhead component away from the sleeve.
The means for urging the annular component axially against the collar can comprise radially extending bolts extending through threaded bores in the annular component and each ending in a tapered dog, and recesses around the larger diameter casing, the recesses having inclined flanks and being positioned so that when the bolts are screwed in, the dogs enter the recesses and make contact with the inclined flanks, and as the bolts are screwed further in, the annular component is drawn further towards the sleeve.
The internal bore of the larger diameter casing may have a constant internal diameter, and the sleeve can be located between the larger diameter casing and the annular component, and when the arrangement is in use, the sleeve is in abutment with the larger diameter casing.
According to a second aspect of the present invention, there is provided a pre-installed clamping arrangement for clamping a subsequently installed tubular well casing of a first diameter within a previously installed tubular casing of larger internal diameter, wherein the larger diameter casing has a wall thickness which is sufficiently thin to allow the casing wall to be distorted inwards to grip the smaller diameter casing, the arrangement also comprising a compression unit which includes a compression collar surrounding the larger diameter casing, a compression ring axially movable relative to the collar and means for producing relative axial movement between the ring and the collar, the compression ring and compression collar having oppositely directed axially tapered annular surfaces, so that relative axial movement between the collar and ring produces a reduction in the internal diameter of the unit to distort the larger diameter casing inwards to grip the smaller diameter casing.
The tubular annular walls of oil well casings have to withstand substantial pressures, and it is this requirement to withstand certain pressures which generally determines the wall thickness of the casings. In most cases, casing walls will be too thick to allow inward deflection to grip an internal component. However by making the walls thin enough to allow such deflection, it becomes possible to achieve the advantageous clamping arrangement of the invention. It will be a matter of trial and error, or of relatively straightforward calculation, to determine the appropriate casing wall thickness for any particular application. Factors which have to be taken into account are the gap between the larger and smaller diameter casings (this gap has to be bridged when the clamp is tightened), the overall diameter of the casings and the material of which they are made. It is desirable to maintain deflection of the casing wall in the elastic range, thereby allowing the casing to expand to it's original diameter once the clamping or compression force has been removed. This allows the clamping arrangement to be reversed or disengaged relatively quickly and easily without any permanent alteration to the casing. The clamping system can, of course, plastically deflect the casing should such be required by a particular application. One such application would be clamping more than one inner casing. In such a case, it is likely that the outer casing would be plastically deformed because of the greater clamping force required to adequately grip the most inner casing.
The casing may be divided axially into diff
Dougherty Jennifer
Neuder William
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