Note: Descriptions are shown in the official language in which they were submitted.
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ARTICULATED PLUNGER ROD PUMP
Field of the Invention
[0001] The present invention relates to reciprocating rod pumps and improved
components of
a rod pump system.
Back2round
[0002] Horizontal well drilling has been a significant development in the
evolution of the
tools and techniques to recover and lift reservoir products to the surface.
However,
horizontal well drilling continues to pose significant challenges associated
with producing oil
and gas to surface. These methods are analogous in many ways to creating a
pipeline located
several hundred meters below the surface of the earth. While in pipeline
flow/production
operations, there are booster pumps and compressor stations strategically
located along the
line in order to aid movement of the product along the line, such flow
enhancements are not
available downhole. Intervention techniques such as pipeline pigging are also
available to
assist in surface pipeline productivity. None of these techniques are
available or practical for
use in the production of horizontal oil wells.
[0003] In conventional rod pumping activities, it is well known that rod and
tubing wear
associated with reciprocating rod pumps can lead to premature failure of a rod
pumping
system. Excessive tubing wear can also lead to costly well workovers and high
operating
costs. All this is well known in vertical rod pumping systems and is even more
relevant in
high angle rod pump applications. The challenges of pumping at high angles and
solutions to
those challenges are not well understood to date.
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[0004] To efficiently produce horizontal wellbores, operators continually
require deeper
landing depths and higher (more horizontal) angles for their rod pump systems.
This
minimizes the back pressure residing against the formation and results in the
well producing
in a "pumped-off' state. In addition, the flow complexity of multi-phase
flowing conditions
in the region of the wellbore transitioning from substantially horizontal to
substantially
vertical results in complex, turbulent and disorganized flow which
dramatically impacts
pumping efficiency. Therefore, landing pumps as deep as practical and
preferably
horizontally in the wellbore is advantageous. Drilling activities of these
wells to
accommodate pump landing depths may incorporate a tangent section where the
build rates
of the horizontal remains constant and therefore creates a linear but deviated
section of
wellbore in which the rod pump is landed and can reciprocate. As reservoir
pressure declines,
the rod pump landing depth is moved downward, chasing the declining fluid
level. This often
results in pumps being landed beyond the end of the tangent section in the
wellbore, in a
section where there may be large build rates. Operation of a conventional rod
pump at high
angle build rates beyond the tangent segment of the wellbore can result in
substantial wear to
the components of the rod pumping system. Numerous components can suffer the
effects of
this type of application including, but not limited to the pump barrel,
plunger, valve rod, or
plunger seals.
[0005] When landed in a high angle section, the stiffness of the plunger in
comparison to that
of the barrel can lead to the barrel deflection being substantial enough that
the plunger will
not easily pass through the barrel, causing exaggerated rod loads,
particularly on the upward
stroke of the pump. This exaggerated loading condition will lead to a high
stress due to
bending residing in the valve rod at the terminal top end of the rod pump.
This condition can
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result in the plunger becoming stuck in the pump barrel and the valve rod
ultimately failing
and parting near the rod pump top or within the pump barrel.
[0006] Therefore, there is a need in the art for modified rod pumps which
mitigates some or
all of the difficulties associated with the prior art.
Summary Of The Invention
[0007] The present invention relates to a downhole rod pump system and more
particularly
improvements to a rod pump system for more efficient operation in high angle
or horizontal
conditions, such as below a conventional tangent section leading into the
substantially
horizontal portion of said wellbore. The system may be deployed in conjunction
with
conventional, unconventional or enhanced oil recovery techniques such as steam-
assisted
gravity drainage, miscible flood, or steam (continuous or cyclic), gas or
water injection.
[0008] In one aspect, the invention may comprise rod pump system comprising an
articulating plunger assembly for use in a reciprocating rod pump, the
articulating plunger
comprising:
(a) at least two plunger segments, each comprising a pin end and a box end,
wherein the
pin end has an external threaded portion and the box end has an internally
threaded portion;
(b) a ball and socket articulating connector, formed between the pin end of
one plunger
segment and the box end of another plunger segment, which articulating
connector
comprises:
i. a collar rigidly attached to the pin end, the collar and pin end together
defining a
socket, the collar comprising an internal shoulder which abuts an external
shoulder on the pin
end, such that the uppermost end of the collar does not contact the plunger
segment;
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ii. a plunger nipple comprising a ball and a shank, wherein the ball is
adapted to fit
and rotate within the socket, and the shank comprises an external thread which
rigidly
engages the box end thread of a plunger segment, wherein the ball comprises a
travel limiting
abutment which contacts a lower surface of the pin end at the rotational
travel limit of the
ball within the socket, and the shank and collar are configured so as to not
contact each other
at the travel limit.
[0009] In another aspect, the invention may comprise a rod pump system
comprising a top
rod articulating joint for connecting between a reciprocating rod string and a
valve rod
comprising:
(a) a rod sub configured to connect to the rod string and having a lower
bearing surface;
(b) a swivel sub having an upper bearing surface and lower internal
threaded portion
and a collar (110) which engages the rod sub to retain the swivel sub, which
can freely rotate
within the collar (110);
(c) a rod bushing having a lower end adapted to connect to a valve rod and
a threaded
upper end which rigidly engages the swivel sub internal threaded portion; and
(d) at least one pin, disposed longitudinally within the swivel sub and the
upper end of
the rod bushing.
Brief Description of the Drawin2s
[0010] The following drawings form part of the specification and are included
to further
demonstrate certain embodiments or various aspects of the invention. In some
instances,
embodiments of the invention can be best understood by referring to the
accompanying
drawings in combination with the detailed description presented herein. The
description and
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accompanying drawings may highlight a certain specific example, or a certain
aspect of the
invention. However, one skilled in the art will understand that portions of
the example or
aspect may be used in combination with other examples or aspects of the
invention.
[0011] Figure 1 shows a cross-sectional view of one embodiment of a rod pump
assembly of
the present invention.
[0012] Figure 2 displays a travelling assembly having 3 plunger segments
deflecting in a
working state.
[0013] Figure 3 is a partial section view showing a ball and socket
articulating connector in a
deflected position.
[0014] Figure 4A is an enlarged depiction of the ball and socket joint of
Figure 3. Figure 4B
is a sectional view of a collar in isolation. Figure 4C is a view of a plunger
nipple in
isolation.
[0015] Figure 5 is a detailed view of box D in Figure 1, showing a transverse
section view of
the top section of an articulated assembly within the rod pump system
[0016] Figure 6 is a detailed view of box C in Figure 1, showing one
embodiment of a top
articulating joint assembly.
[0017] Figure 7 shows an exploded view of the top articulating joint assembly
of Figure 6.
[0018] Figure 8 displays a transverse cross section of a swivel sub hex head
in the top
articulating joint assembly of Figure 6.
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Detailed Description
[0019] The present invention relates to rod pump systems generally, and in
some
embodiments, more particularly to a system comprising an articulated plunger,
which may be
used in circumstances resulting in high angle conditions, which may result in
relatively large
deflections of the pump barrel. The articulated plunger has at least one, and
preferably
multiple deflection points along its length.
[0020] The guidelines and standard practices governing the art of rod pumping
within the
energy market are well known, and are typically governed by the American
Petroleum
Institute (API) standards. A component of such guidelines is a standardization
of the threaded
connections which make up the various fittings and standard components of a
typical rod
pump system. These standards and guidelines provide consistency and
standardization,
however they can present significant difficulty when innovation is desired. It
is an object of
some embodiments of the present invention to conform to standardized threaded
connections.
The claimed invention described herein comprises embodiments of a rod pump
system which
may be configured to suit many different wellbore configurations and fluid
compositions, and
the components of the system. As described herein, the term "longitudinal" or
"axial" refers
to a direction, axis or plane parallel to the longitudinal center axis of the
pump assembly. The
term "transverse" or "radial" refers to a direction, axis or plane which is
perpendicular to the
longitudinal direction, axis or plane. The terms "up", "above", "down" or
"below" (or the
like) are used for convenience to refer to the relative configuration of
components when the
pump assembly is viewed in a vertical configuration, but is not intended to
limit the use of
the pump assembly vertically, horizontally, or at any deviated angle.
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[0021] In one aspect, the invention may comprise a rod pump system as shown in
Figure 1.
In one embodiment, an upper portion of the pump assembly includes a top
articulated joint
(10) connected between the rod string (1) and the valve rod (12). The valve
rod (12) extends
downward through the rod pump top guide (14) and an upper housing (16). The
upper
portion of the rod pump may include a sliding valve assembly (2), as described
in Applicants
co-owned US Patent No. 10,329,886, entitled "Rod Pump System", the entire
contents of
which are incorporated herein by reference, where permitted.
[0022] A seating cup assembly (18) is attached to the upper housing (16) and
includes
seating cups which land the rod pump into a pump seating nipple (112) (not
shown) as is
well-known in the art. The pump barrel (20) extends downwards from the seating
cup
assembly and terminates at the lower end of the rod pump with a standing valve
assembly
(22).
[0023] In some embodiments, the upper portion of the rod pump may also include
a bushed
barrel assembly for centralizing and guiding the valve rod (12) as it enters
and exits the pump
barrel (20). Such an assembly is also described in Applicants co-owned US
Patent No.
10,329,886, entitled "Rod Pump System".
[0024] The valve rod (12) attaches to a plunger (100) which reciprocates
within the pump
barrel (20). The plunger is comprised of a plurality of plunger segments
(102), connected by
articulating connectors (108), as described further below. The upper end of
the plunger (100)
attaches to the lower end of the valve rod (12) by a threaded connection to a
top plunger
adapter (101) this item number is missing in the drawings. The uppermost
plunger segment
comprises a box end female thread, while the top plunger adapter comprises a
male pin
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threaded end. The top plunger adapter then connects to the valve rod by means
of a top
plunger cage (202).
[0025] The bottommost plunger (100) segment is attached to a traveling valve
assembly (24).
The standing valve and traveling valve assemblies (22, 24) may comprise any
suitable
standing or traveling valve assemblies. In some embodiments, the standing and
traveling
valves are configured as described in Applicants co-owned US Patent No.
10,329,886,
entitled "Rod Pump System".
[0026] As is well known in the art, the plunger (100) is bored through end-to-
end to allow
flow of production fluids through from the pump barrel (20) below the
travelling valve (24)
to the plunger bore (3) above the travelling valve.
[0027] The plunger (100) is articulated, meaning that it is capable of bending
slightly along
its length to accommodate deflection in the pump barrel (20). In one
embodiment, the
articulated plunger (100) comprises at least two plunger segments (102),
joined in a manner
which permits some deflection between two adjacent segments, and which
tolerates the
forces transmitted through the plunger (100) during pumping operations. As
used herein,
"deflection" means that the longitudinal, central axes of adjacent plunger
segments are not
co-axial and parallel, but rather a small angle is created between the two
axes. Accordingly,
an articulating connector (108) is disposed between and attached to the at
least two plunger
segments, and permits at least one deflection point relative to one or both of
the at least two
plunger segments as may be seen in Figure 2. In some embodiments, this
articulating
connector (108) may provide up to about 5 of deflection between adjacent
plunger segments.
[0028] In some embodiments, at least one segment, and preferably each segment,
is
configured to restrict the annular space between the plunger segment and the
inner surface of
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the pump barrel. This restriction may be provided by ring seals or a close
tolerance between
the outer surface of the plunger segment and the pump barrel. In some
embodiments, at least
one segment defines at least one circumferential groove housing a seal (106)
for sealingly
and slidably engaging the pump barrel bore. Preferably, each plunger segment
(102) defines
a plurality of seal grooves each housing a fluid-energized seal (106). The
seal need not be an
0-ring or be a fluid-tight seal; small gaps when installed may be tolerated,
so long as there is
significant resistance to fluid flow around and past the plunger (100).
[0029] As a result of having a sufficient effective sealing elements, the seal
between the
plunger segment and the pump barrel provides sufficient resistance to fluid
movement that it
is suitable for this application. On the plunger downstroke, production fluid
below the
traveling valve should be forced into the production path within the plunger
segments, and
not leak out between the plunger and the pump barrel. The overall sealing
ability produced
by the multiple seal grooves and seals is designed to incorporate the
equivalent seal area
length as is well known in the art.
[0030] Other plunger finishes as are well known in the art may be utilized in
this design. For
example, spray metal, chrome plating, nitriding, or other advanced materials
such as nickel
based alloys, stainless steel, etc. may be employed. Any combination of
plunger type and
finish considered suitable by those skilled in the art may also be utilized.
[0031] As shown in Figure 3, in some embodiments, the articulating connector
(108)
comprises a collar (110) and a plunger nipple (112) having a ball (114)
portion and a shank
(116). The collar is threaded onto the lower end of a plunger segment, while
the plunger
nipple is threaded into the upper end of an adjacent plunger segment. The
connector is
hollow to allow passage of production fluids, and sealed to contain those
fluids.
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[0032] In some embodiments, the collar (110) is fixed to the plunger segment
with a straight
close tolerance threaded connection, leaving a small gap between the upper end
of the collar
(110) and an external shoulder (120). An internal shoulder (122) on the
socket, below the
threaded portion, abuts a corresponding shoulder (124) on the plunger pin.
Additionally, an
inner bore surface (126) on the collar (110), above shoulder (122), is close
tolerance fitted
around an outer surface (128) on the plunger pin (130). In some embodiments,
the
combination of this close tolerance fitment and the internal abutment permits
isolation of the
large, static connection stresses from the large alternating stresses carried
by the thicker
portion of the collar wall below the internal abutment.
[0033] The pin (130) defines a partial hemispherical socket and the collar
(110) also defines
a partial hemispherical socket, which combine to retain the plunger nipple
(112) ball, as is
shown in the Figures. The diameter of the collar (110) socket is larger than
the diameter of
the pin (130) socket.
[0034] The plunger nipple (112) comprises a ball (114) and a shank (116)
portion, which
comprises external threads to engage a box threaded end of a plunger segment.
An upper
portion of the ball (114) has a diameter matching the diameter of the pin
socket, while a
lower portion of the ball has a larger diameter, matching the diameter of the
collar (110)
socket. A seal (132), such as an 0-ring, may be provided between an upper
portion of the
ball and the pin socket to provide a seal and to prevent fine solids from
infiltrating the socket.
Alternatively, or additionally, an 0-ring seal may be provided on a lower
portion of the ball,
in the region of the collar (110) socket. Alternatively, a polished metal-on-
metal surface seal
may be used. A secondary metal seal may be formed in the socket by an internal
abutment
metal-on-metal shoulder between the collar (110) and the plunger segment.
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[0035] In some embodiments, a travel limiting shoulder (134) is formed around
the surface
of the ball, which limits rotation of the ball within the socket by abutting
against the pin (130)
end of the plunger segment. The lower end of the collar (110) has a flared
opening, allowing
for pivoting movement of the shank. In preferred embodiments, the ball
shoulder travel stop
(134) is configured such that shank does not contact the collar (110) at the
travel limits of the
ball within the socket, as is illustrated in Figure 4. The shank itself may
have a reduced
diameter or relief and/or the flared opening may have some additional relief
in the area of
potential contact. This mitigates against unwanted contact between the two
faces, which
contact could introduce external forces and stresses.
[0036] The ball itself comprises a reduced diameter band (136), which may be
machined flat,
around the circumference of the ball, just below the ball shoulder (134).
Preferably this band
is located at about the equator of the ball. This band also modifies contact
and stress transfer
between the plunger nipple (112) and the collar (110), making the articulating
connector
more robust. Additionally, this reduced outside diameter is desired to permit
passage of the
plunger nipple (112) through the collar (110) internal shoulder during
assembly.
[0037] The articulating plunger joint connection is assembled by first
installing a seal, such
as an o-ring, into the groove on the upper portion of the ball; which is then
passed through
the inside of the collar (110), leading with the male thread end until the
lower hemispherical
phase of the articulating joint connector meets with the internal socket of
the collar (110).
Finally, the collar (110) is threaded to the pin end of a plunger segment
until the internal
abutment features meet and the prescribed torque is applied. On the bottom
end, the male
threaded connector is rigidly connected to an adjacent plunger component.
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[0038] In some embodiments, the same basic plunger body can be employed with
one
instance or multiple instances and in either condition being easily
interchangeable with
standard pump componentry. Therefore, in some embodiments, the articulating
plunger is
configured to utilize identical plunger bodies throughout the assembly. As
shown in Figure 5,
the top of the upper most plunger segment (102) is fitted with an adapter
(200) which then
allows connection to a standard plunger top cage (202) and ultimately the
valve rod (12).
The plunger segments may have non-standard threads, in which case the adapter
(200) may
have standard API threads to allow connection to a standard plunger top cage.
[0039] In some embodiments, the invention comprises atop rod articulating
joint, which
permits rotation and back spin of the rod string above the pump while
preventing rotation of
the pump internals. The rod articulation joint must provide a robust and
rotatable connection
which does not mechanically release due to unthreading of the internal
connection.
Therefore, in some embodiments, a pump top articulating joint is configured to
incorporate
anti-rotation connection features to prevent the pre-mature release of the
threaded
connections during normal pumping operations.
[0040] In some embodiments, a top articulating joint (10) connects between the
bottom of the
rod string (1) and the top of the valve rod (12). The top articulating joint
(10) allows for
deflection between the rod string and the valve rod, and also swivels to allow
free rotation of
the rod string without rotating the valve rod. This functionality may reduce
stresses due to
bending on the upstroke of the rod string at the top face of the fixed valve
rod guide (14), and
help mitigate uneven wear of the rod string centralizers (not shown).
[0041] A collet-style rod bushing (302) is connected to the top of the valve
rod (12) and
secured by a rod bushing nut (304). The rod sub (306) is threaded into the rod
string (1)
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which extends to the pumping unit on surface. A swivel sub (308) has a crowned
upper
surface (310) which bears on a lower surface (312) of the rod sub (306). The
lower end of
the swivel sub is threaded to the rod bushing (302) and has an exposed
shoulder (314). A
collar (316) rigidly threads onto the rod sub (306) and has a lower lip (318)
which retains the
swivel sub by bearing on the shoulder (314). The swivel sub may be equipped
with a hex
head to receive a socket wrench for ease of assembly.
[0042] There is sufficient clearance within the collar (316) to allow the
swivel sub (308) to
pivot slightly in relation to the rod sub (306), while still being retained by
the collar lower lip
(318). In addition, the swivel sub (308) may freely rotate within the collar
(316).
[0043] In some embodiments, at least one spring pin (320) is installed axially
through the
swivel sub (308) and into the top of the rod bushing (302) male thread end
after the
components are torqued together. The spring pins mechanically lock together
the swivel sub
and the rod bushing and thereby prevent the components from unthreading in
pumping
operation.
[0044] The articulating rod joint is assembled by first passing the top pin
end connection of
the rod bushing (302) through the bottom of the collar (316) and the threading
the swivel sub
(308) onto the top end of the rod bushing (302) after passing it through the
top end of the
collar (316). The connection is then torqued together, subsequently two holes
are drilled,
which holes pass through the swivel sub length and into the pin end connection
of the rod
bushing. The spring pins (320) inserted into the holes and locked in place.
Next, the sub-
assembly comprised of rod bushing (302), collar (316) and swivel sub (308) is
threaded and
torqued onto the rod sub (306) which in turn connects to the rod string (1) to
surface. On the
bottom end, the rod bushing nut (304) is passed over the valve rod (12) which
in turn is
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threaded into the rod bushing (302) internal thread. Finally, the rod bushing
nut (304) is
passed over the collet end and threaded and torqued onto the rod bushing (302)
external
thread which locks the rod bushing assembly onto the pump valve rod (12).
[0045] While the illustrated embodiment of the rod articulating joint
comprises a collet style
valve rod bushing connection, alternative embodiments of the rod articulating
joint may be
furnished with any style of valve rod bushing as required by the application
or desired by the
operator.
[0046] As will be apparent to those skilled in the art various modifications
of this design may
be employed without departing significantly from the aspects of this
invention. For example,
alternate materials may be selected for the base components provided that the
mechanical
properties of the same meet the minimum basic requirements expected of the
components in
application.
Definitions and Interpretation
[0047] The description of the present invention has been presented for
purposes of
illustration and description, but it is not intended to be exhaustive or
limited to the invention
in the form disclosed. Many modifications and variations will be apparent to
those of
ordinary skill in the art without departing from the scope and spirit of the
invention.
Embodiments were chosen and described in order to best explain the principles
of the
invention and the practical application, and to enable others of ordinary
skill in the art to
understand the invention for various embodiments with various modifications as
are suited to
the particular use contemplated. To the extent that the following description
is of a specific
embodiment or a particular use of the invention, it is intended to be
illustrative only, and not
limiting of the claimed invention.
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[0048] The corresponding structures, materials, acts, and equivalents of all
means or steps
plus functional elements in the claims appended to this specification are
intended to include
any structure, material, or act for performing the function in combination
with other claimed
elements as specifically claimed.
[0049] References in the specification to "one embodiment", "an embodiment",
etc., indicate
that the embodiment described may include a particular aspect, feature,
structure, or
characteristic, but not every embodiment necessarily includes that aspect,
feature, structure,
or characteristic. Moreover, such phrases may, but do not necessarily, refer
to the same
embodiment referred to in other portions of the specification. Further, when a
particular
aspect, feature, structure, or characteristic is described in connection with
an embodiment, it
is within the knowledge of one skilled in the art to combine, affect or
connect such aspect,
feature, structure, or characteristic with other embodiments, whether or not
such connection
or combination is explicitly described. In other words, any element or feature
may be
combined with any other element or feature in different embodiments, unless
there is an
obvious or inherent incompatibility between the two, or it is specifically
excluded.
[0050] It is further noted that the claims may be drafted to exclude any
optional element. As
such, this statement is intended to serve as antecedent basis for the use of
exclusive
terminology, such as "solely," "only," and the like, in connection with the
recitation of claim
elements or use of a "negative" limitation. The terms "preferably,"
"preferred," "prefer,"
"optionally," "may," and similar terms are used to indicate that an item,
condition or step
being referred to is an optional (not required) feature of the invention.
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[0051] The singular forms "a," "an," and "the" include the plural reference
unless the context
clearly dictates otherwise. The term "and/or" means any one of the items, any
combination
of the items, or all of the items with which this term is associated.
[0052] As will be understood by one skilled in the art, for any and all
purposes, particularly
in terms of providing a written description, all ranges recited herein also
encompass any and
all possible sub-ranges and combinations of sub-ranges thereof, as well as the
individual
values making up the range, particularly integer values. A recited range
(e.g., weight
percents or carbon groups) includes each specific value, integer, decimal, or
identity within
the range. Any listed range can be easily recognized as sufficiently
describing and enabling
the same range being broken down into at least equal halves, thirds, quarters,
fifths, or tenths.
As a non-limiting example, each range discussed herein can be readily broken
down into a
lower third, middle third and upper third, etc. As will also be understood by
one skilled in
the art, all language such as "up to", "at least", "greater than", "less
than", "more than", "or
more", and the like, include the number recited and such terms refer to ranges
that can be
subsequently broken down into sub-ranges as discussed above. In the same
manner, all ratios
recited herein also include all sub-ratios falling within the broader ratio.
[0053] The term "about" can refer to a variation of 5%, 10%, 20%, or
25% of the
value specified. For example, "about 50" percent can in some embodiments carry
a variation
from 45 to 55 percent. For integer ranges, the term "about" can include one or
two integers
greater than and/or less than a recited integer at each end of the range.
Unless indicated
otherwise herein, the term "about" is intended to include values and ranges
proximate to the
recited range that are equivalent in terms of the functionality of the
composition, or the
embodiment.
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