Note: Descriptions are shown in the official language in which they were submitted.
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CUTTINGS BED REMOVAL TOOL
Field of the Invention
The present invention relates to the removal of debris from wells drilled in
geological
formations.
Background
While one of the functions of circulating drilling fluid during the drilling
of a well is to
prevent drill cuttings from accumulating in the borehole by carrying them to
the surface,
such circulation may not completely remove all such cuttings (and other
debris) from the
borehole. Moreover, the conventional circulation of drilling fluid during
drilling is
particularly inefficient for cleaning out drill cuttings in many high-angle
and horizontal
wells, sometimes resulting in the formation of a layer of drill cuttings and
other solids
settling along the low side of the high angle and horizontal drill sections;
this is
sometimes known as a cuttings bed. The formation of a cuttings bed can cause
additional
difficulties, for example, by causing increased torque and drag on the drill
string.
Summary
In the following description of the invention, it is to be understood that
although the
reference is made to a borehole and/or well bore and the wall of the borehole
and/or well
bore, it is to be understood that the borehole could be open hole or lined.
For example,
the terms borehole/well bore have been used to include open holes, cased
boreholes and
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the term borehole wall in that case would actually be the inner surface of an
open
borehole wall and any casing or other liner lining the well bore.
In one aspect of the invention, there is provided a cuttings bed removal tool
for use on a
tubular string in a well bore, comprising: a sub having a region of enlarged
outer diameter
over the string diameters indicated by its upper end connection and an
indicator disposed
downhole of the region of enlarged outer diameter and having at least one
bypass port
extending through the indicator to permit passage of fluid in an upward
direction through
the indicator.
In another aspect of the invention, there is provided a cuttings bed removal
system for use
in a well bore, comprising: a tubular string including a maximum outer
diameter and
including a sub having a region of enlarged diameter greater than the maximum
outer
diameter of the tubular string; and, an indicator disposed about the tubular
string
downhole of the region of enlarged diameter and having at least one by pass
port
extending through the indicator.
In another aspect of the invention, there is provided a cuttings bed removal
system for use
in a well bore, the system including a drill string including a sub having an
annular
volume restriction region and an indicator disposed about the drill string
downhole of the
annular volume restriction region and having at least one lateral channel
extending
therethrough.
In yet another aspect of the invention, there is provided a method of reducing
a cuttings
bed, comprising: inserting a tubular string from surface into a well bore,
thereby defining
an annulus between the tubular string and the well bore, the tubular string
including inner
bore, a sub forming an annular restriction region thereabout, and an indicator
disposed
downhole of the annular restriction region, the indicator having at least one
bypass port
extending through the indicator; running the tubular string to a selected
depth; and,
pumping fluid through the tubular string inner bore and into the wellbore
annulus,
circulating the fluid in the wellbore annulus from below the indicator,
through the
indicator bypass ports, and past the sub to surface. The method may further
include the
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steps of retrieving and inspecting the indicator to determine whether
sufficient cuttings
remain to repeat the steps.
It is to be understood that other aspects of the present invention will become
readily
apparent to those skilled in the art from the following detailed description,
wherein
various embodiments of the invention are shown and described by way of
illustration. As
will be realized, the invention is capable for other and different embodiments
and its
several details are capable of modification in various other respects.
Accordingly the
drawings and detailed description are to be regarded as illustrative in nature
and not as -
restrictive.
Brief Description of the Drawings
Referring to the drawings, several aspects of the present invention are
illustrated by way
of example, and not by way of limitation, in detail in the figures, wherein:
Figure 1 is a schematic illustration of a borehole including an assembly for
reducing a
cuttings bed.
Figure 2a is side view of a ported indicator body of an embodiment of the
invention.
Figure 2b is a bottom plan view of the ported indicator body of Figure 2a.
Figure 3a is a side view of an indicator mount of an embodiment of the
invention.
Figure 3b is a cross-section along line I-I of the indicator mount of Figure
3a.
Figure 4 is a side view of an assembly including a bottom sub and ported
indicator
mounting flange of an embodiment of the invention.
Figure 5a is a side view of a top sub of an embodiment of a tool of the
invention.
Figure 5b is a top plan view of the sub of Figure 5a.
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Figure 6 is an axial section along the length of a borehole including a tool
according to
one aspect of the present invention.
Detailed Description of Various Embodiments
The detailed description set forth below in connection with the appended
drawings is
intended as a description of various embodiments of the present invention and
is not
intended to represent the only embodiments contemplated by the inventor. The
detailed
description includes specific details for the purpose of providing a
comprehensive
understanding of the present invention. However, it will be apparent to those
skilled in
the art that the present invention may be practiced without these specific
details.
A cuttings bed removal tool of the invention may be used to remove waste
solids such as
cuttings and other debris collected on the low side of a drill section. Such
removal may
be accomplished by drilling fluid agitation caused by the tool and physical
contact of the
tool with the waste solids to urge them away from the cuttings bed and out of
the
borehole.
In operation, drilling fluid may be pumped down through a string into which
the tool is
installed and into the wellbore. The string may be a work string or a drill
string and the
fluid may be released into the wellbore through a port in a sub or out through
the drill bit.
The drilling fluid then passes up the borehole annulus between the string and
the wellbore
wall. As the drilling fluid passes the tool, an annular volume restriction
region on the
tool reduces the annular flow area about the tool and causes the annular
velocity of the
drilling fluid flowing back up the borehole annulus to be increased and,
thereby, urges
loose the cuttings bed. The tool further includes a ported indicator formed at
least in part
of a deteriorable material. Remaining debris on the cuttings bed may contact
the
indicator as the tool is drawn uphole causing the indicator to travel along
the cuttings
bed; if any such debris does remain, contact with the indicator may result in
visible
deterioration of the indicator such that viewing the indicator upon removal of
the tool
may provide the user with some indication of the state of the cuttings bed.
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Referring to the embodiment shown in FIG. 1, tool 100 includes a sub 142 for
installation
into a string such as a drill string 102. Tool 100 may include for example, an
upper
connection 143 and a lower connection 144 for installation, as by threaded
connection,
directly or indirectly into the string. Tool 100 may be incorporated into
drill string 102
and connected uphole of a drill bit 124, and, as shown in FIG. 1, it may
include or operate
with a bottom sub 128 for connecting to drill bit 124. However, it is to be
understood
that the tool of the invention is not limited to requiring a bottom sub, sub
142 being able
to connect directly to the drill bit or other structures therebelow or may
have an end
intended to be the lower limit of the string.
Tool 100 includes an inner bore 145 extending axially from upper connection
143 and in
the illustrated embodiment extending to lower connection 144, the inner bore
being
positioned to place the tool into communication with the inner bore 103 of the
string to
which it is attached. As such, fluid, arrows F, pumped through drill string
102 can pass
into and through tool 100 via its bore 145. Inner bore 145 in the illustrated
embodiment
extends through the tool from end to end so that fluid can pass therethrough
into the drill
bit connected therebelow. It is to be understood that the tool lower end could
represent
the lower limit of the string and bore 145 could be open at the tool's lower
end or the
lower end could include ports in communication with bore 145 to allow fluid to
pass
therethrough into the wellbore 101.
Tool 100 includes an enlarged region 140 on its outer surface that creates an
annular
volume restriction, indicated at 146, between region 140 and the wellbore
wall, compared
to the annular volume between the drill string and the wellbore wall, when the
tool and
string are positioned in the wellbore.
Tool 100 further includes an indicator 106 having at least one port 112
therethrough to
allow passage of fluid and cuttings in at least the uphole direction, toward
upper
connection 143. The indicator may be installed in various ways to act in the
annulus
about the tool or the drill string adjacent the tool. For example, in the
embodiment shown
in FIG. 1, indicator 106 is fixed downhole of enlarged region 140. In FIG. 1,
indicator is
secured in a manner to prevent displacement and in a position about a
connection
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between bottom sub 128 and sub 142. In some embodiments, the ported indicator
may be
disposed about the tool sub defining enlarged region 140, and that sub may
itself directly
connect to the drill bit. In further alternative embodiments, instead of being
disposed
about a sub, the ported indicator may connect at its uphole end to the
downhole end of the
top sub, and at its downhole end either to the drill bit or to a another
structure below tool
100.
Enlarged region 140 of the tool has an outer diameter OD1 less than the inner
diameter of
borehole 101 in which the tool is intended to be used such that fluid can flow
therepast in
the annular area around the enlarged region and the borehole. However, OD1 is
greater
than the average and in some embodiments the maximum outer diameter 0D2 of the
string with which the tool is intended to be used. As will be appreciated, a
drill string
generally includes connections sized with consideration as to the outer
diameter 0D2 of
the string. At least upper connection 143 may be sized to correspond to the
outer
diameter 0D2 of the drill string with which the tool is to be used. In
particular, the size
of upper connection 143 may be selected to correspond and connect to a tubular
of
diameter less than that diameter OD1 of region 140. In the illustrated
embodiment, lower
connection 144 also is sized to correspond and connect to a tubular of outer
diameter less
than that diameter OD1 of region 140. The ends of the tool adjacent to
connections 143,
144 may have an outer diameter 0D3 that substantially corresponds with that
0D2 of the
drill string to which the tool is intended to be connected. In such a tool,
the ends of the
tool have an outer diameter 0D3 less than the outer diameter OD1 at region
140.
Region 140 may be formed in various ways, as by forming an area of increased
wall
thickness on the tool. For example, maximum wall thickness ti at region 140
may be
greater than the maximum wall thickness t2 of the tubulars forming drill
string 102 and
the maximum wall thickness t3 of the tool ends adjacent connections 143, 144.
The enlarged region of the tool, when placed adjacent to the cuttings bed and
in
operation, causes an increase in the annular velocity of fluid passing between
the region
and the borehole wall, which in turn scours the cuttings bed.
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Referring to the embodiment shown in FIGS. 5a and 5b, top sub 542 includes
oversize
region 540 disposed adjacently upstream of a region 550 where ported indicator
body is
to be attached, which is in turn adjacent to the tool's bottom end 548. In
some
embodiments, the top sub may be further provided with cutting edges for
scraping away
the cuttings bed, in circumstances where the cuttings bed is thick enough to
come into
contact with the oversize region. Such cutting edges may be provided by
forming
grooves in the oversize region or, in reverse, forming raised cutting
extensions (such as
inverted stabilizers). Such cutting edges may be disposed substantially
longitudinally,
substantially transversely, or substantially spirally about the oversize
region. In addition,
to further increase cuttings bed removal effectiveness, the annular volume
restriction sub
may be rotatable about its longitudinal axis. For example, as shown in FIG. 5,
top sub
542 is rotatable such as by rotation of the drill string in which it is
installed and includes
spiral channels 544 on oversize region 540, and leading edges 546 on the
raised portion
between channels 544 may function as cutting edges, Leading edges 546 may be
sharpened, hardened, undercut, etc. to enhance their cutting and/or abrasive
properties.
Leading edges 546 may be formed on one or both sides of groove, but in the
illustrated
embodiment are formed on the side of the groove which will have the greatest
contact
with the formation with consideration as to the usual direction of rotation
(i.e. normally
right hand rotation when viewed from above) of the drill string.
In accordance with the invention, the indicator is provided with at least one
passage or
port to allow the flow of fluid from downhole upwardly past the outer surface
of enlarged
region 140 to convey debris from the cuttings bed, and then uphole. The number
and size
of passages or ports may be selected depending on the diameter and composition
of the
indicator, the desired flow rate past the indicator and/or the size of the
cuttings of the
cuttings bed, as would be known by consideration of the drilling and/or
borehole
parameters. The ports may be sized to permit passage therethrough of the
cuttings. The
flow rate that is effective to scour the cuttings bed may depend on factors
such as the
viscosity of the fluid used, the mass of the cuttings, the size of the
borehole, etc., which
would be understood by one skilled in the art. For example, in some
conditions, a flow
rate of 2 m3/min to 3 m3/min may be effective for a 13% inch casing. In the
embodiment
shown in FIGS, 2a and 2b, indicator 206 may be used in high flow rate
conditions,
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having as it does six ports 212 of a selected size; if fewer ports were
desired, then, in
order to maintain a similar flow rate without causing back pressure to be
exerted upon the
formation, the size of the ports should be increased. In practical terms, the
size, shape,
and number of ports may be limited by the diameter and composition of the
indicator. In
addition, for embodiments of the invention that include oversize sub cutting
edges, the
oversize sub channels defined thereby may also be factors in considering size
and number
of indicator ports. For example, if the area defined by the total of the ports
is less than
the total annular area defined between the oversize region and the wellbore
diameter in
which it is intended to be used, then there may be an issue of back pressure
being exerted
upon the formation. In addition, if the area defined by the ports is less than
the annular
area defined by the channels and oversize region, then the annular velocity of
the fluid
flow would be reduced with a resulting reduction of the scouring effect.
In various embodiments, the indicator may be secured about the tool or a drill
string sub
by use of an indicator mount, including at least one port corresponding to and
to be
aligned with at least one of the indicator ports. Referring to FIGS. 2 and 3,
indicator 206
and indicator mount 316 may be provided with apertures 252 and 352,
respectively, for
accepting fasteners, such as bolts, for joining the two parts. It is to be
understood that the
engagement of the indicator and the indicator mount may be achieved in many
ways (and
indeed in some embodiments these parts may comprise a single integral unit).
In
embodiments such as that shown in FIGS. 2 and 3 these attachment points may
include
such attachments as weld points, threaded bores, etc. Further, while the
illustrated
indicator mount 316 comprises a rigid ported flange having an outside diameter
substantially less than the diameter of indicator edge 222, it is to be
understood that in
some embodiments the indicator mount may be similarly dimensioned to the
indicator
edge, if it is desired to utilize the indicator mount as a means for engaging
against and
displacing cuttings from the cuttings bed. In addition, while indicator mount
316
includes ports 320 alignable with ports 212 on indicator body, it is to be
understood that
it is not necessary to have a one-to-one correlation of such ports. In
embodiments such as
that shown in part in FIG. 4, indicator mount 416 may be attached (such as by
welding,
threading, etc.) onto bottom sub 428, with bottom sub region 438 being
provided as a
base for the ported indicator body (not shown). For this purpose, in
embodiments having
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separately-formed indicator mounts for engagement to a sub such as is shown in
FIGS. 3a
and 3b, mount 316 is provided with a central aperture 318 having an internal
diameter
corresponding to the external diameter of the region of such a sub upon which
the mount
is to be attached. Similarly, referring back to FIG. 2b, indicator 206 is
provided with a
corresponding central channel 208. Of course, in some embodiments, the tool
may
include an integrally-formed indicator. In various embodiments, the bottom sub
may be
sized and configured for the drill bit in use including, by way of example,
being provided
with a connector and having appropriate dimensions for accommodating
connection to
the drill bit; for embodiments such as that shown in part in FIG. 4, bottom
sub 428 may
be provided with threaded connector 432 for attaching to the drill bit having
a
complementary threaded connection (not shown). The bottom sub may also be
provided
with a connector element for connecting to the top sub; for example, bottom
sub 428 in
FIG. 4 is provided with a connector element 434 for connection to the top sub
(not
shown).
In operation, contact of the indicator with the cuttings bed may result in
visible changes
to the surface of the indicator. Referring back to FIG. 1, the tool 100
includes a ported
indicator 106 for mounting on a drill string 102 uphole of a drill bit 124.
Indicator 106
includes at least one port 112 and is attached to drill string 102. The
diameter D of
indicator 106 is selected to be small enough to fit within the borehole 101
and large
enough that outer surface 114 may contact solid debris on the cuttings bed
when it is run
down to the depth of the cuttings bed; for compressible indicators, this may
mean that the
diameter D of the indicator may be about the same as the diameter of the
borehole in
which it is intended to be used (or, for those indicators that can be
sufficiently
compressed to fit into the borehole, diameter D may be even slightly greater
than the
diameter of the borehole), whereas non-compressible indicators may require a
diameter
slightly less than that of the borehole in which the tool is intended to be
used. In order to
provide the indication function, at least some portion of outer surface 114
includes
material selected to deteriorate with suitable abrasive contact, as would
occur when the
ported indicator comes into contact with the cuttings bed. While in some
embodiments it
may be desirable that the outer surface of the ported indicator may be
deteriorable,
sufficiently flexible that it can be fairly easily unstuck from the borehole,
yet sufficiently
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rigid to cause displacement of cuttings bed solids as the ported indicator is
run along the
cuttings bed, it is up to the user whether or not the entire ported indicator
should be
constructed of the same material. For example, referring to FIG. 2, the
indicator 206 may
include central channel 208 (to accommodate a drill string), body 210 having
ports 212,
and edge 222 (at which the diameter of the indicator is at its greatest) of
outer surface
214, all of which may be constructed of a suitable material that is both
deteriorable yet
rigid enough that it may apply a dislodging force to settled debris with which
at least
edge 222 comes into contact during movement of the tool. Edge 222 may be
annular
such that the entire of circumference of the borehole may be checked with one
pass of the
indicator. For example, without limitation, an indicator may include a painted
surface
from which paint will be abraded by contact with the cuttings bed. In another
example,
without limitation, the indicator may include such components as a synthetic
or natural
rubber or polymeric swab cup (also called a packer cup); using this example,
while the
rubber of the swab cup indicator outer surface could be scratched, torn, or
otherwise
damaged by contact with cuttings on the cuttings bed, it is also sufficiently
rigid to
possibly urge such debris away from the cuttings bed as the outer surface
travels along
the cuttings bed but can be dislodged relatively easily should it become stuck
in the hole.
Of course, depending on the thickness of the cuttings bed, the diameter of the
indicator
body and the material(s) from which it is composed, the body may come into
contact with
the debris and may similarly urge away the cuttings and/or be damaged by such
contact.
In some embodiments, a second edge, comprising a rigid and more durable
material, may
be provided between the first edge and region 140 to scrapingly dislodge
cuttings from
the cuttings bed. Such a second edge may, by way of example, comprise a steel
flange.
Such a second edge may be provided on the indicator or as a part on the tool
adjacent the
indicator but spaced from the indicator.
Another cuttings bed removal tool is shown in FIG. 6 including an upper end
543 and a
lower end 544 and an enlarged region 540 therebetween. Enlarged region 540
includes
an outer diameter 0D5 that is larger than the maximum outer diameter of the
string 502
to which it is to be attached during use. The tool of Figure 6 further
includes an indicator
extension 506 including ports 512 therethrough. The tool further includes an
inner
longitudinal bore 545 that extends from the upper end to the lower end to
permit fluid
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flow through the tool from the upper end out of the lower end. In the
illustrated
embodiment, one or more fluid outlets 547 are provided laterally from inner
bore 545
through body to the tool's outer surface. Two such fluid outlets 547 are shown
in FIG. 6.
Such fluid outlets may extend to open on outer surface between the lower end
of region
540 and upper end 543. In the illustrated embodiment, for example, outlets 547
open
between the area of maximum outer diameter of region 540 and upper end 543 and
in
particular on a shoulder between end 543 and region 540. Outlets 547 may be
angled to
discharge fluid therethrough in a direction toward upper end, which in use
will be an
uphole direction. Outlets 547 may include nozzles 549 such that fluid
discharged
therethrough tends to jet with force therethrough. As such, fluid discharged
through
outlets 547 may apply a jetting force. Such a tool may be useful in holes
where an extra
jetting force, in addition to fluid circulation upwardly from below indicator
extension
506, may be desired to remove the cuttings bed.
While the illustrated embodiments disclose the engagement of the ported
indicator about
the subs, it is to be understood that the ported indicator itself may comprise
a sub being
bracketed between upper and lower subs. Such a ported indicator sub may be
provided
with connector elements with which it may attach to such upper and lower subs.
Of course, it is to be understood that the cuttings bed removal tool may be
formed in
other ways. While the embodiments of FIGS. 1 to 5 illustrate that the tool may
be
formed in sections that are connected together such as by the threaded
connections to
facilitate manufacture and assembly, other connections (such as welded
connections, etc.)
could be used, or the tool could have a unitary construction such as that
shown in FIG. 6.
In an embodiment of the method of the invention, the tool is made up and run
in to the
top of the cuttings bed. The borehole may be previously drilled, the drill
sting removed
and then another string including a tool according to the present invention
run into the
hole. In some embodiments, the exact location of the cuttings bed may not be
positively
known, but may be estimated or determined from the angle/trajectory of the
well. At the
upper end of the cuttings bed, if drilling fluid is not already being
circulated through the
tool, circulation of drilling fluid is begun and the tool is worked down
through the
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cuttings bed to a desired depth. At a desired depth the tool has passed down
through at
least a portion of a cuttings bed and disrupted the bed such that at least
some of the
cuttings have been moved with the circulating fluid uphole of the tool. To
most rapidly
clear the cuttings bed, the circulation rate should be as high as possible
while trying to
avoid problematic well conditions, such as, for example, the generation of a
back
pressure issue. As the drilling fluid continues to be circulated, the tool is
then slowly
pulled back up towards surface such as to the depth previously believed to be
the top of
the cuttings bed. The drilling fluid continues to be circulated at this depth
until the hole
above the tool is substantially clear of drill cuttings. Depending on the
length of the
cuttings bed, it may be necessary to repeat this procedure over several depths
to clean out
the borehole in a stepwise fashion; alternatively, the procedure may be
repeated several
times over the entire length of the cuttings bed to achieve this purpose. In
some
embodiments, the tool may be pulled to surface while circulating to urge the
cuttings
along the well. As a check, the tool may be pulled to surface to examine the
indicator for
damage or wear thereto as would be caused by existence of cuttings bed over
which the
outer edges of the indicator have passed, which are those cuttings not
conveyed with the
fluid through the indicator ports and/or those not conveyed past the enlarged
region. Of
course, it is to be understood that embodiments of the method of the invention
are not
limited to the apparatus illustrated in these figures.
Another embodiment of the inventive method may include the following, repeated
as
necessary to achieve the desired reduction of the cuttings bed:
(a) inserting a string from surface into a well bore, thereby defining an
annulus between the drill string and the well bore, the drill string including
a drill string inner bore, a sub having an enlarged region forming an
annular restriction around the sub, and an indicator disposed downhole of
the enlarged region, the indicator having at least bypass port extending
through the indicator;
(b) running the string to a selected depth, such as a depth at which it is
suspected that at least a portion of a cuttings bed is located uphole of the
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ported indicator. While running through the cuttings bed, a drill bit may
be operated/rotated to disrupt the cuttings bed and/or fluid circulation may
be carried out to move the cuttings up through the ports of the indicator;
and,
(c) pumping
fluid through the string inner bore and into the wellbore annulus,
so that fluid is circulated in the wellbore annulus from below the indicator,
through the indicator ports, and past the sub to surface. The circulation
may be continued as the tool is pulled to surface to move cuttings
ahead/uphole of it substantially without settling. Using a tool such as that
of FIG. 6, pumping fluid also discharges fluid though the lateral outlets
above the enlarged region. Such laterally directed fluid may act to jet out
debris from the crevices of borehole wall.
Cuttings carried to surface by the circulating fluid may be disposed (such as
into a shale
bin) or subjected to whatever processing may be desired.
In addition, some embodiments of the method of the invention may include the
further
step of retrieving the tool to the surface and visually inspecting it to
determine whether
the indicator was damaged by cuttings during such retrieval and thus whether
enough of a
cuttings bed remains to justify repeating the method. In various embodiments,
the drill
bit may also be used to loosen the accumulated cuttings sufficiently to allow
the tool to
be brought down to the desired depth.
The previous description of the disclosed embodiments is provided to enable
any person
skilled in the art to make or use the present invention. Various modifications
to those
embodiments will be readily apparent to those skilled in the art, and the
generic
principles defined herein may be applied to other embodiments. Thus, the
present
invention is not intended to be limited to the embodiments shown herein, but
is to be
accorded the full scope consistent with the claims, wherein reference to an
element in the
singular, such as by use of the article "a" or "an" is not intended to mean
"one and only
one" unless specifically so stated, but rather "one or more". All structural
and functional
equivalents to the elements
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of the various embodiments described throughout the disclosure that are know
or later
come to be known to those of ordinary skill in the art are intended to be
encompassed by
the elements of the claims.
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