Note: Descriptions are shown in the official language in which they were submitted.
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RESE'I'TABLE DOWNHOLE PACKER
This invention relates to a downhole packer, and in
particular but not exclusively to a packer intended for use
in "intelligent" oil and gas wells, that is wells provided
with downhole tools and devices located below the packer
and which may be remotely controlled from surface.
Oil and gas production wells typically comprise a
casing-lined borehole, within which is located a string of
smaller diameter production or "completion" tubing. The
annulus between the casing and tubing is sealed by
provision of one or more packers; a packer will normally be
provided towards the lower end of the tubing and may be set
to seal the annulus after the tubing has been run into the
well.
US Patent No 5,129,454, the disclosure of which is
incorporated herein by reference, describes packers which
provide the facility to pass up to two control lines
through the packer to allow, for example, power cables to
pass down through the packer to an electrical submersible
pump (ESP) provided on the tubing below the packer, the ESP
serving to boost production from relatively low pressure
hydrocarbon-bearing formations. The control lines are
accommodated in short string mandrels mounted to the main
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production fluid-carrying mandrel. The requirement to
accommodate the various mandrels reduces the available flow
area through the packer and thus reduces the flow rate from
the well, and also complicates the sealing and mounting
arrangements for the various packer components.
The packers described in US Patent No 5, 129, 454 are
also resettable, in that the packers may be hydraulically
set, then mechanically unset, and subsequently reset and
unset. This is made possible by the combination of a lost
motion arrangement and various selectively shearable
members: after the initial unsetting of the packer, a set
of compression springs is released and the springs extend
to locate the packer components in position ready to be
hydraulically reset. Setting and resetting the packer
requires shearing of various members, and the lost motion
arrangement protects the screws which must be sheared ~to
permit resetting. The resetting springs are accommodated
in the space between the main and short string mandrels.
UK Patent Application No 2,292,400, the disclosure of
which is incorporated herein by reference, discloses a
packer in which the packer mandrel defines both a main
production fluid-carrying bore and an axial access line
which allows passage of a 1/4" o.d. control line. To
accommodate the line, and also to accommodate two fluid
passageways which extend part-way along the mandrel, the
mandrel is of eccentric form with its o.d. and i.d. offset
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to provide a thickened wall portion.
It is among the objectives of embodiments of the
present invention to provide a downhole packer which
accommodates a plurality of control lines with minimal
reduction in the cross sectional area of the main through
bore.
It is a further objective of an embodiment of the
invention to provide a resettable packer having a main
through bore with a relatively large area through bore.
According to a first embodiment of the present
invention there is provided a downhole packer for sealing
an annulus between first tubing located within larger
diameter second tubing, the packer comprising:
a mandrel for coupling to first tubing, the mandrel
having a wall defining a main through bore and a plurality
of smaller diameter through bores for receiving control
lines;
a seal arrangement located on the mandrel and being
configurable to form an annular seal with a surrounding
larger diameter second tubing; and
a slip arrangement located on the mandrel and being
configurable to engage a surrounding larger diameter second
tubing.
This aspect of the invention permits a plurality of
control lines to pass through the mandrel wall, thus
permitting control and communication with a plurality of
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tools, devices, sensors and the like located below the
packer and as are found in "intelligent" wells.
The packer may be provided in combination with control
lines for communication with an electrical submersible pump
(ESP), or other electrically powered tool or device. In
this case, the control lines comprise power supply cables,
and where the electrical supply is a three phase supply,
the individual phases are carried by respective individual
cables located in respective bores. This allows the bore
diameters to be relatively small; in the arrangement as
described in UK Patent Application No 2,292,400 it would
not be possible to accommodate a conventional ESP power
supply cable in the disclosed axial access line, and this
would require the provision of a packer as described in US
Patent No 5,129,454, that is a packer having separate
fluid-carrying and control line-carrying mandrels. Of
course the present invention may be utilised in other
applications, in which the control lines are not restricted
to electrical power cables, and may carry fluid conduits,
signal carrying members, fibre optic cables and the like.
Preferably, the mandrel is a unitary mandrel, that is
the mandrel is formed from a single piece of material,
typically steel or another appropriate metal alloy.
Preferably, the smaller diameter bores are gun drilled
through the mandrel wall, thus eliminating weak spots and
potential leak paths that would be present if the mandrel
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was formed from multiple parts.
Preferably also, the mandrel has an outside diameter
and the main through bore has a inside diameter, said
outside diameter and said inside diameter being offset to
5 provide a relatively thick wall portion in which the
smaller diameter through bores are formed.
Preferably also, the smaller diameter through bores
are circumferentially spaced about the main through bore.
Preferably also, the packer is adapted to be
hydraulically set, most preferably by bore pressure. The
packer may comprise a setting arrangement including a
setting piston which is axially movable in response to
elevated pressure; and most preferably includes at least
two linked setting pistons. The two or more setting
pistons are preferably axially spaced, and thus may provide
a relatively high setting force in response to a given
setting pressure, without significantly increasing the
diameter of the setting arrangement, and thus permitting
provision of a relatively large area main through bore.
Preferably also, the packer may be released from the
set configuration, or unset, to release the seal
arrangement and the slip arrangement from the set
configuration, and allow retrieval or at least movement of
the packer. Conveniently, this is achieved by means of a
releasable coupling, typically a shear member, between a
packer body mounted on the mandrel and comprising elements
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of the seal arrangement and the slip arrangement, and the
mandrel.
Preferably also, the packer is resettable, that is the
packer is adapted to be set, unset and then reset without
requiring retrieval to the surface. The packer preferably
further comprises a lost motion arrangement, including
means f or biassing a packer body mounted on the mandrel and
comprising elements of the seal arrangement and slip
arrangement towards a configuration ready for resetting the
seal and slip arrangements, following initial unsetting of
the packer. The biassing means may comprise a spring, and
most preferably a spring mounted concentrically on the
mandrel. The use of a concentric spring allows the
diameter of the main through bore to be maintained
relatively large. Most preferably, the spring is initially
restrained by a releasable coupling, which may also serve
to retain the seal and slip arrangements in the set
configuration.
Preferably also, the packer may be released from the
reset configuration, or unset, to release the seal
arrangement and the slip arrangement from the reset
configuration, and allow retrieval of the packer.
Conveniently, this is achieved by means of a further
releasable coupling, typically a further shear member,
between the packer body and the mandrel.
This and other aspects of the present invention will
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now be described, by way of example, with reference to the
accompanying drawings, in which:
Figure 1 is a schematic half-sectioned view of a
downhole packer in accordance with a preferred embodiment
of the present invention;
Figure 2 is a top view of the packer of Figure 1;
Figures 3a to 3h are sectional views of the packer of
Figure 1 in a run-in configuration;
Figures 4a to 4h are sectional views of the packer of
Figure 1 in a first set configuration;
Figures 5a to 5h are sectional views of the packer of
Figure 1 in a first unset configuration;
Figures 6a to 6h are sectional views of the packer of
Figure 1 in a second set configuration;
Figures 7a to 7h are sectional views of the packer of
Figure 1 in a second unset configuration; and
Figures 8, 9 and 10 are top views of packers in
accordance with other embodiments of the present invention.
Reference is first made to Figures 1 and 2 of the
drawings, Figure 1 being a schematic illustration of a
downhole packer 10 in accordance with an embodiment of the
present invention, and Figure 2 being an enlarged plan view
of the packer 10. The packer 10 is intended to be utilised
in "intelligent" well applications, and allows six control
lines to pass through the packer 10 to facilitate control
of tools and devices below the packer 10. In use, the
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packer 10 is mounted in a tubing string (not shown) and
accordingly the packer includes top and bottom connectors
12, 13. Extending the length of the packer 10, between the
connectors 12, 13, is a one-piece mandrel 14 which, as will
be described, defines a main through bore 16, for carrying
production fluids, and six smaller diameter secondary
through bores 18, for acoommodating control lines. Mounted
externally of the mandrel 14 is a body 20 which includes
resilient packer elements 22, slips 24 and the arrangement
which permits setting and unsetting of the packer 10, as
described below.
Reference is now also made to Figures 3a to 3h, which
illustrate the components of the packer 10 in greater
detail. The Figures are arranged in sequence, with Figure
3a illustrating the upper end of the packer 10, through to
Figure 3h illustrating the lower end of the packer 10, and
the components of the packer 10 will, where possible, be
introduced in sequence from the top of the packer 10
towards the bottom.
As noted above, the packer mandrel 14 defines a main
through bore 16 and six smaller diameter secondary through
bores 18. The secondary through bores 18 are accommodated
in a relatively thick portion of the packer wall 26, this
being provided by offsetting the internal diameter of the
main through bore 16 from the mandrel outside diameter 28.
However, the thickened portion of the packer wall 26 does
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not extend to the ends of the mandrel 14, as is apparent
from Figures 3b and 3g, to facilitate coupling of the
control lines to the respective bores 18. The packer body
20 is mounted on the larger diameter section of the mandrel
14, the uppermost element of the body 20 being an upper
gauge ring 30 which is pinned and threaded to the mandrel
14. The gauge ring 30 serves to restrain the upper end of
the packer elements 22, the lower end of the elements 22
abutting the upper end of a setting sleeve 32 which is
coupled to a pair of hydraulic setting pistons 34, 35
(Figures 3d and 3e) , as will be described. The setting
sleeve 32 is restrained against downward movement relative
to the mandrel 14 by a locking ring 36, but of course may
be moved upwardly relative to the mandrel 14 to allow
energising of the packer elements 22. The sleeve 32 is in
two parts 32a, 32b, which are threaded together, the
lowermost part 32b being threaded to a sleeve 38 forming
part of the slip setting arrangement as will be described.
The lower part of the sleeve 32b also abuts the upper end
of a compression spring 40, the lower end of the spring
abutting a sleeve 42 which is coupled to the setting
pistons 34, 35 via a sleeve 44 forming a lower part of the
slip setting arrangement.
As noted above, the sleeve 44 of the slip setting
arrangement is also coupled to the setting pistons 34, 35
and defines a cam face 46 for radially extending the slips
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24. The sleeve 38 also defines a cam face 48 for acting on
the upper end of the slips 24, the slips being contained
within a cage 50 which is pinned to the sleeve 38. The
slips 24 are provided with cone-shaped compression springs
5 (not shown) which tend to urge the slips 24 towards the
retracted position, thus facilitating unsetting of the
packer 10 and in particular disengagement of the slips 24
from the surrounding casing.
As noted above, two setting pistons 34, 35 are
10 provided, these being formed by sleeves 52a, 52b, 52c which
are threaded and pinned together and in sealed sliding
contact with the mandrel outside diameter. The lower wall
of the annular fluid chamber 54, 55 associated with each
piston 34, 35 is formed by a respective seal ring 56, 57,
each ring being restrained on the mandrel 14 by respective
locking rings 58. Each fluid chamber 54, 55 is in
communication with the main through bore 16 via a
respective fluid port 62, 63. The pistons 34, 35 are
initially fixed relative to the mandrel 14 by a shear screw
64 (Figure 3f) which couples the pistons 34, 35 to a lower
body assembly 66, arranged to permit unsetting and
resetting of the packer 10, as will be described. A
secondary shear screw 65 also couples the pistons 34, 35 to
the assembly 66, however in the packer run-in
configuration, the shear screws 65 does not serve to
restrain the pistons 34, 35, the screw head being located
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in an axial slot 67 in the piston sleeve 52c.
As will be described, upward movement of the pistons
34, 35 relative to the assembly 66 is conserved by
provision of a ratchet 68 arrangement comprising catches 70
mounted on the sleeve 52c and a toothed outer face of a
sleeve 72 forming the upper part of the assembly 66.
The sleeve 72 is initially restrained relative to the
mandrel 14 by a shear wire 74 (Figure 3f) . A secondary
shear wire 75 is also provided and restrains a spring
support 76 which abuts the upper end of a pre-loaded spring
78 which tends to bias the assembly ~6 towards a lower
relative position on the mandrel 14. However, as noted
above, the assembly is initially restrained against such
movement by the primary shear wire 74.
Figures 3a to 3h illustrate the packer in its run-in
configuration, that is with the packer elements 22 and the
slips 24 retracted. The initial setting of the packer 10
will now be described, also with reference to Figures 4a to
4h, which illustrate the packer 10 in its first set
configuration.
Once the packer 10 has been positioned at the desired
location in the well bore, the pressure within the main
through bore 16 is increased. This increase in fluid
pressure is communicated, via the ports 62, 63, to the
pistons 34, 35. Once the fluid pressure exceeds a
predetermined level, the primary shear screw 64 will fail,
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allowing the pistons 34, 35 to move upwardly relative to
the mandrel 14. This movement is transmitted, via the
spring 40, to the setting sleeve 32, and energises the
packer elements 22, such that they are radially expanded to
form a seal with a surrounding casing. Also, the piston
movement is transmitted to the slip setting sleeve 44 which
pushes the slips upwardly and outwardly. The movement of
the pistons 34, 35 is conserved by the ratchet 68, such
that on bleeding off bore pressure the packer 10 remains in
the set configuration.
If it becomes necessary to release or unset the packer
10, the string in which the packer 10 is mounted is pulled
upwardly. Due to the engagement of slips 24 with the
casing, the upper portion of the packer body 20 will tend
to remain fixed relative to the casing, and if sufficient
force is applied to the packer mandrel 14 from the upper
portion of the string, the primary shear wire 74 will fail.
The weight of the packer body 20, and also the action of
the springs 40, 78 and any remaining pulling force, then
move the packer element and slip setting parts of the
packer body 20 to the position on the mandrel 14 as
illustrated in Figures 5a to 5h of the drawings, causing
the packer elements 22 and the slips 24 to retract . It
will be noted that in this first unset configuration, the
lower body assembly 6~ moves to a lower position on the
mandrel 14, however due to the ratchet 68 the upward
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portion of the packer body 20 assumes a similar position to
when the packer was in the initial running configuration.
When it is desired to set the packer 10 once more,
elevated bore pressure will again tend to lift the pistons
34, 35 relative to the mandrel 14. Due to the changes in
the relative positions of the pistons 34, 35 and the lower
body assembly 66, the secondary shear screw 65 now occupies
the lower end of the slot 67 in the sleeve 52c, such that
movement of the pistons 34, 35 will only occur when the
pressure has reached a level sufficient for the screw 65 to
fail. Following failure of the screw 65, the packer
elements 22 are energised and the slips 24 extended, as in
the initial setting. As before, the ratchet 68 conserves
the movement of the pistons 34, 35 relative to the lower
body assembly 66, and the packer may assume the
configuration as illustrated in Figures 6a to 6h of the
drawings.
In this second set configuration, the packer body 20
is restrained against axial movement relative to the
mandrel 14 by the secondary shear wire 75. Accordingly, if
axial force is applied to the packer 10 sufficient to shear
the wire 75, the packer 10 will once more move to a set
position, as illustrated in Figures 7a to 7h of the
drawings. The packer body 20 is urged to assume this unset
configuration by virtue of its own weight and by the action
of the springs 40, 78, the body 20 being retained on the
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mandrel 14 by a lower retaining ring 80.
Those of skill in the art will thus appreciate that
the packer 10 may conveniently be set, released and reset
in a bore, and ultimately released to allow retrieval of
the packer 10.
Reference is now made to Figure 8 of the drawings,
which illustrates the top view of a packer 90 in accordance
with another embodiment of the present invention. The
illustrated packer 90 is operated in a similar manner to
the packer 10 described above, and also defines similar
internal and external diameters. However, rather than
providing six similar diameter secondary through bores 18,
the packer 90 provides five secondary through bores 92,
comprising three through bores 92a for accommodating cables
carrying a single phase of a three phase electrical supply
to an electric submersible pump (ESP) located below the
packer 90. The two remaining bores 92b may accommodate
smaller diameter control lines.
Reference is now made to Figure 9 of the drawings,
which illustrates a packer 100 in accordance with a further
embodiment of the present invention. The illustrated
packer 100 is provided with a body 20 as described above,
but comprises a conventional monobore mandrel 102,
demonstrating that the body 20 may be used in applications
in addition to those where communication is required
through the packer for control and operation of ESPs and
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the like.
Finally, reference is made to Figure 10 of the
drawings, which illustrates a packer 110 in accordance with
a still further embodiment of the present invention. The
5 packer 110 is of greater internal and external diameter
than the packers 10, 90, 100 described above, however the
general structure and operation of the packer is
substantially the same. The primary difference lies in the
number and configuration of secondary through bores 112
10 provided in the packer mandrel 114, this larger diameter
packer 110 accommodating seven secondary through bores 112,
three capable of accommodating the cabling necessary to
power a three-phase ESP, and a further four smaller
diameter through bores being provided to accommodate other
15 control lines.
It will be event to those of skill in the art that the
above described embodiments are merely exemplary of the
present invention, and that various modifications and
improvements may be made thereto without departing from the
scope of the present invention.
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