Note: Descriptions are shown in the official language in which they were submitted.
A DOWNHOLE COUPLING MECHANISM
FIELD OF THE DISCLOSURE
[0001] The disclosure relates to a downhole coupling mechanism for a tubular
assembly for use in oil
and gas wells. Particularly, a downhole coupling mechanism in an anchor and
morphable packer for
use in wells exploited by a hydraulic refracturing process is described.
BACKGROUND
[0002] Hydraulic fracturing, or fracking, is a technique for cracking rock by
the injection of a
mixture of sand and fluid under pressure. This technique enables extraction of
oil or gas contained in
highly compact and impermeable rocks.
[0003] The wellbores for fracking are drilled down to a depth at which rock
layers with hydrocarbon
deposits can be found. The wellbores are then drilled horizontally along the
rock layer. Hydraulic
fracturing of the horizontal wellbores is usually conducted in multiple stages
with fractures created in
the surrounding rock at specific points along the wellbore.
[0004] Two methods of hydraulic fracturing are most commonly used. One of the
most common
techniques requires the well to have a cemented casing and involves a plug and
perforate technique
whereby cement plugs are created to isolate specific sections within the well;
each section is then
perforated and fractured. The plugs are then drilled, and the production stage
of the operation is
begun.
[0005] Another common technique uses a non-cemented casing arrangement where
sliding sleeves
and packers are provided around the outer circumference of the casing string.
Once the casing string
is inserted into the well, the packers are expanded to secure the string in
position and isolate sections
of the well to be fracked. The sleeves are then shifted to an open position by
the pumping of
specifically sized balls into the well. When a sleeve is actuated under the
action of a ball, fracturing
ports are opened, and the isolated zone is fractured and stimulated by fluid
diverted through the open
fracturing ports. The production stage of the operation can then begin.
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[0006] After a few years in operation, the gas or oil production level of a
well may decrease.
Following the initial production period, it is common to stimulate the well by
refracturing.
Refracturing aims to either increase the depth of the original fractures or to
develop a new network
of fractures from which gas or oil may be extracted from rock. Refracturing
often restores well
productivity to close to original levels and thus extends the lifespan of the
well.
[0007] Refracturing is performed in an existing wellbore and is thus
advantageous because it does
not require the steps of drilling and completing a well bore. The process of
refracturing an existing
well is therefore often significantly less costly and more economical than
drilling a new well.
[0008] In wells having a cemented casing, refracturing can be performed by
installing and cementing
a new casing having a smaller diameter than the original casing before a "plug
and perforation"
method of fracturing is used. It is important that the cement layer between
the two casings provides
a high quality seal in order for the process to be effective. In addition, the
perforating step conducted
during the refracturing process must go through two casing walls.
Alternatively, a new casing, or
tubular conduit, provided with an expandable metallic tubular sleeve, or
packer, may be provided
where the sleeve is designed to expand within the original casing of the well
with a plug and
perforation technique subsequently employed again.
[0009] With each of these refracturing techniques, the newly provided casing
has a reduced internal
diameter compared to the initial internal diameter of the well casing.
Generally, efforts are made to
maximize the diameter of the new casing by reducing tolerances between the new
casing and
existing casing to as small as possible. This creates a need for packers that
are thin-walled and are
designed to maintain the greatest inner diameter possible while still
achieving sufficient gripping and
sealing capability on the existing casing.
[0010] A limitation on such thin-walled arrangements is found in forming
threaded couplings
between the components. Such couplings are necessary in order to maintain a
seal, provide sufficient
tensile loading and meet torque ratings. Premium (sealing) threads are not
available in the required
sizes, and the wall is not thick enough to cut a normal ACME or Stub ACME
thread. Additionally,
these screw threaded couplings do not handle radial loads well.
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[0011] Gladstone, GB 2,267,217 discloses a connector with a dowel device for
application in boring
holes for mining or exploration. The device of Gladstone features grooves for
interlocking sections,
but the device is not applicable to refracturing. There is a rotary-drill
casing connector having
interconnecting male and female sleeves incorporating lugs and sockets around
the periphery for the
purpose of transmitting rotary motion and providing segmental abutment faces
for supporting axial
compressive loads. The two sleeves are held together by means of a flexible
multi-stranded steel wire
rope dowel that is inserted manually from the outside via an aperture into a
circular annular cavity,
half of which is formed on the inside face of the female sleeve and half
formed on the outer face of
the male sleeve. The connection is sealed against leakage or ingress of fluids
by a pliable sealing '0'
ring contained in a groove formed in the sleeve such that the seal is
compressed when the parts are
connected together.
[0012] Reimert, U.S. Patent 4,659,119 discloses a connector assembly including
a pin connector for
receipt by a box connector. An external surface of the pin features a helical
groove, a generally
complementary internal surface of the box features a helical groove of the
same rotational sense and
pitch. A helical latch coil is carried in one of the grooves, extending partly
out of the groove. The
connectors are latched together by stabbing the pin into the box so that the
latch coil is ratcheted into
place, partly extending into the groove of the connector not carrying the
coil. Subsequent mutual
rotation between the connectors in one rotational sense tightens the latched
connection and rotation
in the opposite sense releases the latching. The connector functions without
the need for substantial
rotation or torque.
[0013] Bauer et al., U.S. Patent 4,659,119 disclose a plug connection for
drilling or boring tubes,
rods and worms for earth boring equipment with a male part and a female part,
with a radial coupling
for torque transfer and with an axial coupling having in the overlap zone of
the male and female
parts, and a locking device that can be introduced into an annulus for
transferring axial forces. The
locking device is constructed as a multilink chain that essentially extends
around the entire annulus
and is introduced through the female part into the annulus via a single
opening.
[0014] Lehmann, DE 2310375 discloses a detachable pipe end connection for
locking opposing pipe
ends with different joint designs and engageable gearing featuring a
retractable overrunning pipe end
rotatably fixed and centered, and both of an inserted flexible locking cord in
one of two mutually
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opposite half-grooves in a cavity. The entire tube circumference outside the
coupling region is
blocked and secures and features a flexible locking cord. For insertion or
removal of the flexible
locking cord, window-like openings are provided.
[0015] It would be desirable to provide a coupling mechanism for securing
tubular sections together
in a wellbore over a thin-wall. It would also be desirable to provide a
coupling mechanism for
securing tubular sections that overcomes at least some of the disadvantages of
the prior art.
SUMMARY
[0016] In a first aspect the present disclosure relates to a downhole coupling
mechanism between a
first end of a first tubular section being part of a downhole tool and a
second end of a second tubular
section;
each end including one or more complimentary circumferential grooves machined
in
opposing surfaces to align when the first and second ends are arranged co-
axially one inside the
other;
one or more wires, each wire being located within one of the circumferential
grooves on the
first end and a complimentary one of the circumferential grooves on the second
end, so that each pair
of complimentary grooves contains one wire extending around the circumference
of the surface of
each end;
at least one lug and notch arranged on opposite of the first and second ends
providing
interlocking engagement when the first and second ends are arranged co-axially
one inside the other;
and
a seal arranged between the opposing surfaces when the first and second ends
are arranged
co-axially one inside the other.
The downhole coupling mechanism provides a tensile loading through the wires,
a torque rating via
the interlocking lug and notch, and a seal between the tubular sections
without incorporating a screw-
threaded connection.
[0017] Preferably, the wall thickness of the downhole coupling mechanism when
the first and second
ends are arranged co-axially one inside the other is less than or equal to
about 5%, 10%, 15% or 20%
or so of the outer diameter of the downhole coupling mechanism. More
preferably, the wall thickness
of the downhole coupling mechanism when the first and second ends are arranged
co-axially one
inside the other is less than or equal to about 8%, 10%, 12%, 14%, 16%, 18% or
20% or so of the
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inner diameter of the downhole coupling mechanism. This provides a thin-wall
tubular connection.
In some instances, the inner diameter at the coupling mechanism is greater
than or equal to about
3.00", 3.20", 3.40", 3.50", 3.60", 3.70", 3.80", 3.90", 4.00", 4.10", 4.20",
4.40", 4.60" or so, and
the outer diameter at the coupling mechanism is less than or equal to about
4.00", 4.10", 4.20",
4.40", 4.50", 4.60", 4.70" 4.80", 4.90", 5.00", 5.10", 5.20", 5.40" or so. In
a preferred
embodiment the inner diameter at the coupling mechanism is greater than or
equal to 3.843" (97.61
mm) and the outer diameter at the coupling mechanism is less than or equal to
4.700" (118.44 mm).
The inner diameter provides the clearance through the bore of the downhole
tool.
[0018] Preferably, the seal is arranged in a seating groove that is
circumferential and continuous
around an outer surface. In this way, an o-ring seal may be used that is
restricted in longitudinal
movement in the coupling mechanism. Providing a groove to seat the seal in
also allows use of a
thicker seal. Preferably there are two seals arranged adjacent to each other
on the coupling
mechanism.
[0019] Preferably there are two lugs and notches opposite of the first and
second ends. More
preferably the lug and notch are arranged equidistant around the outer
surface. More preferably a
length of the lug that is co-axial with a central axis of the tubular sections
is greater than the wall
thickness of the downhole coupling mechanism. This provides an increased
torque rating over a
screw thread connection of similar thickness.
[0020] Preferably, a plurality of complimentary circumferential grooves are
provided on opposing
surfaces, with each complimentary pair of grooves containing a wire.
Alternatively, there may be a
single groove provided helically around the surface substantially like a screw
thread having a
complimentary screw thread in the opposing surface. In this arrangement there
may be a single wire
wound helically along the connection. Preferably, there are more than three or
four or five or six
pairs of complimentary circumferential grooves. More preferably, there are
more than eight or nine
or ten pairs of complimentary circumferential grooves. There may be more than
eleven or twelve
pairs of complimentary circumferential grooves. In a preferred embodiment
there are fifteen pairs of
complimentary circumferential grooves with fifteen wires. The increased number
of wires increases
the tensile loading of the coupling. Preferably, the wires are continuous
loops. The wires may be of
circular, square, rectangular or custom engineered cross-section. More
preferably each wire has a
diameter in cross-section greater than a depth of a groove into which they
locate. This provides the
required tensile loading through the coupling mechanism.
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[0021] Preferably, the downhole tool is a packer. Alternatively, the downhole
tool may be a liner
hanger. Optionally, the downhole tool may be an anchor. Preferably, the
downhole coupling
mechanism is at a lower end of the downhole tool to connect the tool to a
tubular string located
deeper in a well. This may be considered as a run-in configuration.
[0022] Preferably, the downhole tool includes a plurality of slips arranged on
a wedge formed in a
body of the tool, the slips being movable radially outwards by the action of a
piston moved
longitudinal in a first direction where the slips are held against the body by
at least one retainer band
prior to movement by the piston. Preferably. the retainer band is a wire. More
preferably, the slips
may be held in place against the body with a combination of a retainer wire
and screws or pins. By
having slips directly located against the tool body and the slips retained by
a wire, this anchoring
arrangement for use in anchors, packers and liner hangers may be thin-walled.
[0023] Preferably, a wall thickness of the downhole tool prior to actuating
the slips is less than or
equal to about 5%, 10%, 15% or 20% of the outer diameter of the downhole tool
prior to actuating
the slips. More preferably, a wall thickness of the downhole tool prior to
actuating the slips is less
than or equal to about 8%, 10%, 12%, 14%, 16%, 18% or 20% of the inner
diameter of the downhole
tool prior to actuating the slips. This provides a thin-wall tubular
connection. In some instances, the
inner diameter at the coupling mechanism is greater than or equal to about
3.00", 3.20", 3.40", 3.50",
3.60", 3.70", 3.80", 3.90", 4.00", 4.10", 4.20", 4.40", 4.60" or so, and the
outer diameter at the
coupling mechanism is less than or equal to about 4.00", 4.10", 4.20", 4.40",
4.50", 4.60", 4.70"
4.80", 4.90", 5.00", 5.10", 5.20", 5.40" or so. In a preferred embodiment the
inner diameter at the
coupling mechanism is greater than or equal to 3.843" (97.61 mm) and the outer
diameter at the
coupling mechanism is less than or equal to 4.700" (118.44 mm). The inner
diameter provides the
clearance through the bore of the downhole tool. The outer diameter determines
the borehole size or
installed casing/liner size through which the downhole tool can be run-in.
[0024] Preferably, the downhole tool features a ratchet arranged to prevent
movement of the slips in
a second direction, opposite the first direction. In this way, a ratchet
provides a thin mechanism to
hold the slips in the radially extended position. Preferably the downhole tool
also includes a piston
lock to prevent movement of the piston until actuation of the slips is
required. Preferably the piston is
arranged below the slips in a run-in configuration. In this way, premature
actuation of the slips
during run-in is avoided. Preferably, the piston lock features a sleeve
moveable under pressure to
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release a collet arranged on the piston. As hydraulic force is used, the lock
mechanism can be kept
thin-walled. Preferably, the piston lock sleeve is moved in the second
direction under fluid pressure
pumped from surface through the bore of the downhole tool. More preferably,
the piston is moved to
actuate the slips by continual pumping of fluid through the bore of the
downhole tool.
[0025] Preferably, the downhole tool includes a morphable element. The
morphable element may be
considered as a packer element. More preferably, the morphable element is a
sleeve arranged on the
tool body, sealed thereto and providing an annular chamber, that when fluid is
introduced to the
chamber, expands the sleeve to seal against a borehole wall or a tubular in
which the packer element
is located. The borehole wall or tubular, which may be casing, liner or
similar may be considered as
an outer substantially cylindrical structure. Preferably, the morphable
element is above the slips in
the run-in configuration. More preferably, the piston lock is released, and
the piston moves at a fluid
pressure above a setting pressure for the morphable element. In some
instances, the morphable
element is metal and the setting pressure morphs the sleeve against the outer
substantially cylindrical
structure. In this way, pressure does not have to be held in the bore when the
anchor mechanism and
the morphable element are set.
BRIEF DESCRIPTION OF THE FIGURES
[0026] Figure 1 is a schematic plan view of a downhole coupling mechanism as
described herein.
[0027] Figure 2A is a cross-sectional view through a first tubular section of
the downhole coupling
mechanism of Figure 1. Figure 2B is a cross-sectional view through a second
tubular section of the
downhole coupling mechanism of Figure 1.
[0028] Figure 3A is a cross-sectional view through an anchor including the
downhole coupling
mechanism of Figure 1, and Figure 3B is an exploded view of section A of
Figure 3A.
[0029] Figures 4A and 4B are cross-sectional views of the piston of the anchor
of Figure 3 shown in
locked (Figure 4A) and unlocked (Figure 4B) configurations.
[0030] Figure 5 is a schematic view of an anchor including the coupling
mechanism of Figure 1
according to an alternative embodiment described herein.
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[0031] Figure 6 is a cross-sectional view through a packer suitable for use
with the downhole
coupling mechanism of Figure 1.
DETAILED DESCRIPTION
[0032] In the description that follows, it is understood that the drawings are
not necessarily to scale.
Certain features of the downhole coupling mechanism for a tubular assembly for
use in oil and gas
wells as described herein may be shown exaggerated in scale or in somewhat
schematic form, and
some details of conventional elements may not be shown in the interest of
clarity and conciseness. It
is to be fully recognized that the different teachings of the embodiments
discussed below may be
employed separately or in any suitable combination to produce the desired
results.
[0033] Accordingly, the drawings and descriptions are to be regarded as
illustrative in nature, and
not as restrictive. Furthermore, the terminology and phraseology used herein
is solely used for
descriptive purposes and should not be construed as limiting in scope.
Language such as "including,"
"comprising," "having," "containing," or "involving," and variations thereof,
is intended to be broad
and encompass the subject matter listed thereafter, equivalents, and
additional subject matter not
recited, and is not intended to exclude other additives, components, integers
or steps. Likewise, the
term "comprising" is considered synonymous with the terms "including" or
"containing" for
applicable legal purposes. All numerical values in this disclosure are
understood as being modified
by "about." All singular forms of elements, or any other components described
herein including
without limitations components of the apparatus are understood to include
plural forms thereof. The
downhole coupling mechanism for a tubular assembly for use in oil and gas
wells will now be
described with reference to the following figures, by way of example only.
[0034] Referring to Figure I, the drawings illustrate a downhole coupling
mechanism, generally
indicated by reference numeral 10 as described herein. Coupling mechanism 10
features a first
tubular section 12 and a second tubular section 14 connected via a tensile
load arrangement 16, a
torque arrangement 18 and a seal arrangement 20. Arrangements 16, 18, 20 allow
the tubular
sections 12, 14 to be fixed together without a screw threaded connection and
can thus find
application in small diameter bores and casing strings used downhole.
[0035] The first tubular section 12 is considered as an end piece to a
downhole tool 22. The
downhole tool 22 may be an anchor, packer, liner hanger or similar tool used
within a wellbore.
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Figure 2A illustrates a tubular member 24 forming a portion of a downhole tool
22 and having a first
tubular section 12 at a first end 26 thereof. Tubular section 12 has a smooth
circumferential inner
surface 28. The outer surface 30 is provided with a series of grooves 32. Each
groove 32 is
preferentially square in cross-section though may be of any cross-sectional
shape such as circular, v-
grooved, dovetailed or a hooked profile. Each groove 32 is provided into the
outer surface 30 to
provide a continuous groove depth around a circumference of the outer surface
30. There are a
number of grooves 32. In a preferred embodiment, there are fifteen grooves but
there may be any
number ranging typically from 3 to 20. A greater number is preferred. The
series of parallel grooves
32 are perpendicular to the bore 34 through the tool 22 and provide a
continuous circumferential
profile on the outer surface 30. The shape is entirely circumferential in
that, a cross-sectional view as
shown in Figure 2A, would be identical for every cross-section around the
tubular section 12. This is
in contrast to a screw thread arrangement that would provide a single groove
helically wound on the
outer surface. A single wire may be fed around such a helical groove.
[0036] The first tubular section 12 also features lugs 36. Lugs 36 are
protrusions or tongues
extending from the end face 38 of the section 12. These are best seen with the
aid of Figure 1. In a
preferred embodiment, two lugs 36 arranged equidistant around the end face 38
are provided.
However, there may be any number of lugs 36. Each lug 36 is preferentially
square in cross-section
with rounded edges to assist in assembly. Each lug 36 is of the same thickness
as the wall thickness
40 of the section 12 so that the inner 28 and outer surfaces 30 extend over
the lugs. A protrusion
length 42, coaxial with the bore 34, is also greater than the wall thickness
40.
[0037] Figure 2B illustrates the second tubular section 14 being the
complimentary mating section to
the first tubular section 12. The second tubular section 14 also has a
cylindrical body and a series of
grooves 44. Grooves 44 match the grooves 32 in number, depth, and position
along the section 14,
but are now arranged on the inner surface 46. A longitudinally arranged access
window 48 is
machined through the section 14 over the grooves 44.
[0038] Adjacent to the grooves 44 are two further grooves 50a, 50b. The
further grooves 50a, 50b are
wider and deeper than the grooves 44, but they are also continuous around the
inner surface 46 and
are neither helical nor provide a thread. Though two further grooves 50a, 50b
are shown there may
be a single further groove or more than two further grooves, but there will
always be fewer further
grooves 50 than grooves 44.
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[0039] When considered from an end face 52 of the second tubular section 14,
there are the grooves
44, the further grooves 50 and then a stop edge 54. Stop edge 54 is provided
by a reduction in the
inner diameter of the tubular section 14 providing a circumferential rim or
lip arranged perpendicular
to the bore 56. The stop edge 54 has a width greater than or equal to the wall
thickness 40 of the first
tubular section 12. Machined into the stop edge 54 is a notch 58. There are
two notches 58 preferably
equidistantly machined around the edge 54, the number and dimensions of each
notch 58 match the
lugs 36 on the first tubular section 12. The second tubular section 14 may
form part of tubing such as
casing or liner. The second tubular section 14 may be considered as a bottom
sub for connection to
other downhole tools and components.
[0040] Returning to Figure 1, the coupling mechanism 10 is illustrated in an
assembled form. The
second tubular section 14 has been slid over the first tubular section 12
until the end face 38 has
abutted the stop edge 54. The sections 12 and 14 have been aligned so that the
lugs 36 fit in the
notches 58. Prior to engagement, seals 60a, 60b have been located in the
further grooves 50a, 50b.
Upon engagement, grooves 44 will be coaxial with grooves 32. Separate wires 62
are each located in
one of the groove pairs 32,44 and joined to provide individual wire loops in
each groove 44 via the
access window 48.
[0041] The grooves 32,44 with corresponding wires 62 provide the tensile load
arrangement 16. In a
preferred embodiment there are fifteen grooves 32, 44 with corresponding wires
62. However,
preferably there are more than three wires. More preferably, there are more
than eight wires. There
may be more than eleven wires. The increased number of wires increases the
tensile loading of the
coupling 10. The wires 62 are preferentially of square cross-section and may
be considered as a
square locking wire. Wire having a circular, triangular, rectangular or other
cross-sections may also
be used. Each wire 62 has a diameter in cross-section, perpendicular to the
axis of the bores 34, 56,
greater than a depth of a groove 32, 44 into which they locate. This ensures
that the wires 62 lie
between the first and second tubular sections 12, 14. In the embodiment shown,
the wires 62 are
sized to fill both grooves 32,44 so as to prevent relative longitudinal
movement of the tubular
sections 12,14. This provides the required tensile loading through the
coupling mechanism 10.
[0042] The seals 60a, 60b, within the further grooves 50a, 50b, that are sized
to protrude from the
further grooves 50a, 50b and be compressed against the outer surface 30 of the
first tubular section
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12 provides the seal arrangement 20. The seal arrangement 20 prevents the
egress of fluid through
the coupling mechanism 10.
[0043] The combination of the lugs 36 and notches 58 provide the torque
arrangement 18. The length
42 of the lugs 36 provides abutting surfaces between the lugs 36 and notches
58 that are parallel with
the axis of the bores 34, 56. As this length 42 is greater than a wall
thickness 64 of the coupling
mechanism 10, this gives a torque rating to the coupling mechanism 10 greater
than the torque rating
of a screw threaded connection of similar thickness.
[0044] The tensile load arrangement 16, torque arrangement 18 and seal
arrangement 20 of the
coupling mechanism 10 can all be formed over relatively small wall
thicknesses. The coupling
mechanism 10 is suitable for slim hole arrangements where a maximum bore 34,
56 is required to be
maintained. The wall thickness 64 of the made-up coupling mechanism 10 is less
than or equal to
10% of the outer diameter 66 of the coupling mechanism 10. Also, the wall
thickness 64 is less than
or equal to 12% of the inner diameter 68 of the coupling mechanism 10. This
provides a thin-wall
tubular connection. In a preferred embodiment, the inner diameter 68 is
greater than or equal to
3.843" (97.61 mm) and the outer diameter 66 is less than or equal to 4.700"
(118.44 mm). The inner
diameter 68 provides clearance through the bore 34, 56 of the downhole tool
22.
[0045] By providing such a small relative wall thickness over the tubing
diameter, the coupling
mechanism 10 finds use on downhole tools used in refracturing operations such
as anchors, liner
hangers and packers and provides particular advantages. An embodiment of a
suitable anchor 70
with the coupling mechanism 10 is now described with reference to Figures 3A,
3B, 4A and 4B.
[0046] Figure 3A is a cross-section view of a downhole tool 22 being an anchor
70 incorporating the
coupling mechanism 10 according to an embodiment described herein. The figure
is provided in the
standard downhole format with the right side being the lower end 72 of the
tool 22 that is run into the
wellbore first before the upper end 74 of the tool 22 shown on the left side
of the figure. Figure 3B is
an exploded view of a section of the anchor 70 of Figure 3A so that the
features are clearer.
[0047] Anchor 70 features a substantially tubular body 76 with a maximum outer
diameter 78 and
minimum inner diameter 80. At the lower end 72 a coupling mechanism 10 is
provided as described
herein for connecting the anchor to another downhole component (not shown).
The first tubular
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section 12 is part of an inner mandrel 82 that is connected at the upper end
74 to a J-housing 84 as is
known in the art.
[0048] At the upper end 74 of the inner mandrel 82, the diameter is tapered to
provide a downward
facing wedge 86 around the mandrel 82. Slips 88 are arranged around the
mandrel 82 and initially
held in place using a retaining wire 90 wrapped around the outside of the
slips 88. Use of a retaining
ring 90 advantageously removes the requirement for mounts for the slips 88
that would increase the
wall thickness 79 of the tool 22. The slips 88 abut a spacer ring 92 that can
be moved upwards by
action of a piston 102 so as to force the slips 88 up the wedge 86 moving them
radially outwards to
contact an inner surface 94 of the outer tubing 96. Movement of the slips is
initially prevented by
location of a shear pin 98 in the wedge 86 at the front of the slips 88. This
arrangement provides
anchoring of the downhole tool 22 to the outer tubing 96.
[0049] A piston locking assembly 100 is used to prevent premature actuation of
the anchor 70
especially during run-in. The piston locking assembly 100 sits between the
spacer ring 92 and the
coupling mechanism 10. Figure 4A shows the piston locking assembly 100 in a
run-in configuration.
[0050] Piston locking assembly 100 includes the piston 102 being a cylindrical
body arranged around
the mandrel 82. At the upper end it is connected to the spacer ring 92 via a
wire and groove
arrangement as per the tensile load arrangement 16 described hereinbefore.
Four wires are illustrated
but there could be any number. Behind the spacer ring 92 is a locking ring 104
whose outer surface
106 is threaded to attach to an inner surface 108 of the piston 102. The inner
surface 110 of the
locking ring 104 is also threaded with a complementary left hand thread 112
along the outer surface
114 of the mandrel 82 that extends to the wedge 86. At a lower end of the
piston 102 are collet
fingers 116 that are directed inwardly and locate in a recess 118 formed on
the outer surface 114 of
the mandrel 82. Recess 118 is located below a port 120 through the mandrel 82.
[0051] Below the piston 102 is a locking element 122. This is a ring having an
upwardly directed lip
124 at its upper end, extending the outer surface 126 at the upper end. The
locking element 122 also
has a circumferential groove 134 around the outer surface 126 towards a lower
end. A piston housing
128 slides over the locking element 122 and a portion of the piston 102. The
piston housing 128 is
fixed to the inner mandrel 82 and/or a second tubular portion 14 at the lower
end. The locking
element 122 is moveable between the housing 128 and mandrel 82 but is sealed
130 to both and
initially held in place via a shear pins 132 through the housing 128 locating
in the groove 134.
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Similarly, the piston 102 is moveable between the housing 128 and mandrel 82
but is sealed 136 to
both and initially held in place by virtue of the collet fingers 116 located
in the recess 118 and locked
in place by the lip 124 of the locking element 122.
[0052] In the run-in configuration, shown in Figures 3A, 3B and 4A, the slips
88 are held in position
at the bottom of the wedge 86 by the retaining wire 90. The spacer ring 92
abuts the slips 88 and is
held to the piston 102 with the locking ring 104 sitting adjacent the spacer
ring 92 and connecting to
the mandrel 82 and piston 102. The collet fingers 116 and in the recess 118.
The locking element 122
is positioned so that the lip 124 is over ends of the collet fingers 116 and
supports them in the recess
118. The locking element 122 is prevented from moving off the fingers 116 as
it is held in place by
shear pin 132 located through the housing 128 and locating in the groove 134.
In this configuration,
the tool 22 can be run in the outer tubing 96, and if it encounters ledges
such as at casing collars, it
cannot be activated.
[0053] When the anchor 70 requires setting, pressure is applied through the
bore 138 from the
surface. The pressurized fluid enters the tool 22 through the port 120. The
pressure acts on the
locking element 122 until the pressure is sufficient to shear the pins 132
allowing the element to
move downward until the lip 124 is clear of the collet fingers 116. This
releases the collet fingers
116 so that they come out of the recess 118. Fluid pressure now acts on the
piston 102 moving it
upwards. The piston 102 acts on the locking ring 104, spacer ring 92 and
ultimately the slips 88.
With sufficient pressure the slips 88 move upwards along the wedge 86 and
radially outwards so that
they contact and grip the inner surface 94 of the outer tubing 96. On movement
the slips 88 will
contact and shear the shear pins 98 while breaking the retaining wire 90. Due
to the close tolerance
between the slips 88 and the outer tubing 96, the slips 88 will never clear
the width of the spacer ring
92 and thus will only move upwards and outwards. The anchor set arrangement is
illustrated in
Figure 4B. Advantageously, pressure does not have to be held to keep the
anchor in the set
configuration due to the locking ring 104 arrangement on the mandrel 82 that
acts as a ratchet when
the piston 102 moves.
[0054] The overall outer diameter 78 of the anchor 70 in the run-in
configuration is less than or equal
to the overall outer diameter 66 of the coupling mechanism 10. Thus, the
anchor 70 is suitable for
slim hole applications. Additionally, the minimum inner diameter 80 of the
anchor 70 is equal to the
minimum inner diameter 68 of coupling mechanism 10 by virtue of the inner
tubular section 12 of
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the coupling mechanism 10 being formed on the same mandrel 82 as the anchor
70. Thus, the wall
thickness 64, 79 of the anchor 70 and coupling mechanism 10 are substantially
the same.
[0055] Figure 5 illustrates an alternative embodiment for the slips 88A that
provides a mechanical
constraint to prevent the slips 88A from unwanted movement until actuation.
Those like parts to
Figures 3 and 4 are given the same reference numbers and suffixed 'A,' for
clarity. Figure 5 shows
an anchor 70A where at the lower end 72A there is arranged a coupling
mechanism 10A as described
herein for connecting the anchor to another downhole component (not shown).
[0056] At the upper end 74A of the inner mandrel 82A, the diameter is tapered
to provide a
downward facing wedge 86A around the mandrel 82A. Slips 88A are arranged
around the mandrel
82A and initially held in place using three retaining wires 90A wrapped around
the outside of the
slips 88A in the same manner as for Figures 3 and 4. However, where the slips
88 abutted a spacer
ring 92 in the earlier embodiment, the slips 88A now have tabs 91 extending
from a lower end 93.
Typically, there is a tab 91 on each section of the slip 88A. Spacer ring 92A
is extended to provide
mating recesses 95 for the tabs 91. The spacer ring 92A is connected to the
piston 102A in an
identical manner as before with the addition of a securing band 97, between a
lower shoulder 99 of
the spacer ring 92A and the end face 101 of the piston 102. The securing band
97 (shown in
transparency in Figure 6) of soft metal lies over the interlocking arrangement
of tabs 91 and recesses
95 to prevent movement radially outwards when the piston 102 is actuated.
Further, the shear pin 88
on the wedge 86 is now a pin or screw 88A, located in a front tab 103 of each
slip 88A. This secures
the front or nose of the slips 88A to the mandrel 82A to provide added
security to the slips and
prevent unwanted movement until actuation is desired. Anchor 70A is operated
in the same manner
as anchor 70.
[0057] A further embodiment of a downhole tool 22 that can use the coupling
mechanism 10 is a
packer 140, as illustrated in Figure 6. Packer 140 features three tubular
parts, a mandrel 142, a
bottom section 144, and a sleeve member 146. Each part is machined as a single
piece, and the
bottom section 144 forms the first tubular section 12 of the coupling
mechanism 10. The mandrel
142 provides a downward facing ledge 148 perpendicular to an axis of the
central bore 150 on its
outer surface 152. There is a port 154 through the mandrel 142. The mandrel
142 has an end face 156
at its lower end that is perpendicular to the axis of the central bore 150.
The bottom section 144 is
arranged at the lower end of the mandrel with a portion 158 extending over the
mandrel 142 and
presenting an upward facing end face 160 that is perpendicular to the axis of
the central bore 150.
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The bottom section 144 has an upward facing ledge 162 that is perpendicular to
the axis of the
central bore 150. The lower end of the bottom section 144 forms the first
tubular section 12 of the
coupling mechanism 10. A tubular section with first and second end faces 164,
166 respectively
forms the sleeve member 146.
[0058] The sleeve member 146 is slid over the mandrel 142 in order to abut the
ledge 148 with the
first end face 164. The ledge 148 and face 164 are joined together. The bottom
section 144 is then
slid over the end of the mandrel 142 so the portion 158 sits on the mandrel
and the end face 160
abuts the second end face 166 of the sleeve member 146. The faces are joined
together. This
connection also sees the ledge 162 of the bottom section 144 abutting the end
face 156 of the
mandrel 142. The ledge 162 and face 156 are joined together. The mandrel 142
and bottom section
144 are made of a hardened steel that does not yield under pressure. The
sleeve member 146 is made
of a ductile metal that yields under pressure. The joints are formed by
welding or other suitable
techniques known to those skilled in the art to provide a pressure tight seal
between the components.
[0059] The packer 140 is run into the well in the configuration shown in
Figure 6. At the desired
location, fluid pressure is increased from the surface, or via a running tool
inside the packer 140, so
that fluid under pressure enters the port 154. This fluid reaches a chamber
168 created between the
outer surface 152 of the mandrel 142 and the inner surface 170 of the sleeve
member 146. The
ductile metal of the sleeve member 146 yields and expands. The sleeve member
146 morphs against
the inner surface 94 of the outer tubing 96 and creates a metal to metal seal.
As the sleeve member
146 undergoes elastic and plastic deformation during morphing, the packer 140
holds a seal between
the packer 140 and the outer tubing 96 thereby maintaining a seal across the
annulus between both.
[0060] The overall outer diameter 172 of the packer 140 in the run-in
configuration is less than or
equal to the overall outer diameter 66 of the coupling mechanism 10. Thus, the
packer 140 is
suitable for slim hole applications. Additionally, the minimum inner diameter
174 of the packer 140
is equal to the minimum inner diameter 68 of the coupling mechanism 10 by
virtue of the inner
tubular section 12 of the coupling mechanism 10 being formed in the same piece
as the bottom
section 144. Thus, the wall thickness 64, 176 of packer 140 and coupling
mechanism 10 are
substantially the same.
[0061] The anchor 70 may be used along with the packer 140 on a string.
Advantageously the anchor
70 may be located above the packer 140 as the anchor 70 does not require
holding pressure in use.
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This is the reverse of typical packers where the slips are used to expand the
packer element and thus
pressure must be held by the anchor to keep the packer element expanded in
use.
[0062] The principle advantage of the downhole coupling mechanism described
herein is that it
provides a coupling mechanism for securing tubular sections together in a
wellbore over a thin wall
not achievable using a screw-threaded connection and not achievable by the
means provided
previously. A further advantage of at least one embodiment of the downhole
coupling mechanism
described herein is that it provides an anchor for securing tubular sections
together in a wellbore over
a thin wall not achievable previously. A still further advantage of at least
one embodiment of the
downhole coupling mechanism described herein is that it provides a packer for
securing tubular
sections together in a wellbore over a thin wall not achievable previously.
The downhole coupling
mechanism described herein features novel means for attaching a mandrel to a
bottom section while
maintaining a seal, tensile loading and torque ratings. The downhole coupling
mechanism described
herein provides wire set in grooves to hold tensile, and then provides for
using torque shoulders to
handle the torque.
[0063] It will be appreciated to those skilled in the art that various
modifications may be made to the
description herein provided without departing from the scope thereof. For
example, the grooves and
further grooves in the downhole coupling mechanism may be reversed.
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