Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02686290 2009-11-25
SYSTEM AND METHOD FOR VERIFYING PERFORATING GUN
STATUS PRIOR TO PERFORATING A WELLBORE
TECHNICAL FIELD OF THE INVENTION
[0001] This invention relates, in general, to opening
communication paths through a casing disposed in a wellbore
and, in particular, to systems and methods for verifying
the status of perforating guns prior to perforating the
wellbore.
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BACKGROUND OF THE INVENTION
[0002] Without limiting the scope of the present
invention, its background will be described in relation to
perforating a wellbore, as an example.
[0003] After drilling the various sections of a
subterranean wellbore that traverses a formation,
individual lengths of relatively large diameter metal
tubulars are typically secured together to form a casing
string that is positioned within the wellbore. This casing
string increases the integ rity of the wellbore and
provides a path for producing fluids from the producing
intervals to the surface. Conventionally, the casing
string is cemented within the wellbore. To produce fluids
into the casing string, hydraulic openings or perforations
must be made through the casing string, the cement and a
distance into the formation.
[0004] Typically, these perforations are created by
detonating a series of shaped charges that are disposed
within the casing string and are positioned adjacent to the
formation. Specifically, one or more charge carriers or
perforating guns are loaded with shaped charges that are
connected with a detonator via a detonating cord. The
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charge carriers are then connected within a tool string
that is lowered into the cased wellbore at the end of a
tubing string or other conveyance. Once the charge
carriers are properly positioned in the wellbore such that
the shaped charges are adjacent to the formation to be
perforated, the shaped charges may be fired. If more than
one downhole zone is to be perforated, a select fire
perforating gun assembly may be used such that once the
first zone is perforated, subsequent zones may be
perforated by repositioning and firing the previously
unfired perforating guns without tripping out of the well.
[0005] Typically, once the perforating guns are
assembled, the charge carriers protect the shaped charges
disposed therein against wellbore fluids. It has been
found, however, that perforating guns sometimes develop a
leak, for example during the run in process, and become
partially or completely filled with wellbore fluid. Once
such fluid infiltration has occurred, if such a perforating
gun is fired, there is a high likelihood that the
perforating gun may split. Not only does such an
occurrence result in a failed perforation operation, the
explosive event may damage other wellbore equipment and may
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result in the split perforating gun becoming lodged in the
wellbore. As such, an expensive recovery effort to
retrieve the damaged equipment may be required and the
entire completion may have to be abandoned resulting in the
need to drill a sidetrack well.
[0006] A need has therefore arisen for an apparatus and
method for perforating a cased wellbore that create
effective perforation tunnels. A need has also arisen for
such an apparatus and method that provide for determining
whether a perforating gun has experienced a leak prior to
firing the perforating gun.
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SUMMARY OF THE INVENTION
[0007] The present invention disclosed herein provides
systems and methods for bidirectional communication between
a surface system and a downhole system that enables a
determination of whether a perforating gun has experienced
a leak prior to firing the perforating gun. The systems
and methods of the present invention enable such a
determination by telemetering encoded signals from the
surface system to one or more downhole systems requesting
leak status and other environmental information and by
telemetering encoded signals from the downhole systems to
the surface system including the leak status or other
requested environmental information.
[0008] In one aspect, the present invention is directed
to a method for verifying perforating gun status prior to
perforating the wellbore. The method includes running a
perforating gun having a leak sensor disposed therein to a
target location within the wellbore on a tubing string,
integrating a communication system with the tubing string,
the communication system operable to communicate with the
leak sensor, sending a first telemetry signal via the
communication system to interrogate the leak sensor
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regarding a leak status of the perforating gun, returning a
second telemetry signal from the leak sensor via the
communication system including the leak status of the
perforating gun and determining whether to operate the
perforating gun based upon the leak status information.
[0009] In one embodiment, the leak sensor may be a
moisture sensor. In this embodiment, the method may
include determining whether to operate the perforating gun
based upon moisture status information. In another
embodiment, the leak sensor may be a pressure sensor. In
this embodiment, the method may include determining whether
to operate the perforating gun based upon pressure status
information. In a further embodiment, the communication
system may be an acoustic communication system that is
integratied with the tubing string. In this embodiment, the
method may include sending an acoustic signal encoded with
the leak status request to the leak sensor and returning an
acoustic signal encoded with the leak status information
from the leak sensor.
[0010] In another aspect, the present invention is
directed to a method for verifying perforating gun system
status prior to perforating a welibore. This method
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includes running the perforating gun system to a target
location within the wellbore on a tubing string, the
perforating gun system including a plurality of perforating
guns each having a leak sensor disposed therein,
integrating a communication system with the tubing string,
the communication system operable to communicate with the
leak sensors, sending first telemetry signals via the
communication system to interrogate the leak sensors
regarding a leak status of each of the perforating guns,
returning second telemetry signals from the leak sensors
via the communication system including the leak status of
each of the perforating guns and determining whether to
operate the perforating gun system based upon the leak
status information.
[0011] In a further aspect, the present invention is
directed to a system for verifying perforating gun status
prior to perforating a wellbore. The system includes a
perforating gun having a leak sensor disposed therein. The
perforating gun may be deployed on a tubing string and
positioned at a target location within the wellbore. A
communication system is integrated with the tubing string.
The cornmunication system is operable to communicate with
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the leak sensor. A surface controller is operable to send
a first telemetry signal via the communication system to
interrogate the leak sensor regarding a leak status of the
perforating gun, receive a second telemetry signal from the
leak sensor via the communication system including the leak
status of the perforating gun and determine whether to
operate the perforating gun based upon the leak status
information.
[0012] In yet another aspect, the present invention is
directed to a method for verifying an environmental
condition relative to a perforating gun disposed in a
wellbore. The method includes running the perforating gun
having at least one environmental sensor associated
therewith to a target location within the wellbore on a
tubing string, integrating a communication system with the
tubing string, the communication system operable to
communicate with the environmental sensor, sending a first
telemetry signal via the communication system to
interrogate the environmental sensor regarding an
environmental condition relative to the perforating gun and
returning a second telemetry signal from the environmental
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sensor via the communication system including the
environmental condition relative to the perforating gun.
[0013] In one embodiment, the environmental sensor may
include one or more of a moisture sensor, a pressure
sensor, a high speed pressure sensor, a temperature sensor,
an accelerometer, a shock load sensor, a liner displacement
sensor, a depth sensor and a fluid sensor. These
environmental sensors may be disposed interior of the
perforating gun, exterior of the perforating gun or in the
vicinity of the perforating gun. In another embodiment,
the communication system may be an acoustic communication
system that enables sending of an acoustic signal encoded
with the environmental condition request and returning an
acoustic signal encoded with the environmental condition
information.
(0014] In an additional aspect, the present invention is
directed to a system for verifying an environmental
condition relative to a perforating gun disposed in a
wellbore. At least one environmental sensor is associated
with the perforating gun which is positioned at a target
location within the wellbore on a tubing string. A
communication system is integrated with the tubing string.
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The communication system is operable to communicate with
the environmental sensor. A surface controller is operable
to send a first telemetry signal via the communication
system to interrogate the environmental sensor regarding an
environmental condition relative to the perforating gun and
receive a second telemetry signal from the environmental
sensor via the communication system including the
environmental condition relative to the perforating gun.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0015] For a more complete understanding of the present
invention., including its features and advantages, reference
is now made to the detailed description of the invention,
taken in conjunction with the accompanying drawings in
which like numerals identify like parts and in which:
[0016] Figure 1 is a schematic illustration of an
offshore oil and gas platform operating a system for
verifying the status of perforating guns prior to
perforating a wellbore that embodies principles of the
present invention;
[0017] Figure 2 is a partial cut away view of a
perforating gun for use in a system for verifying the
status of perforating guns prior to perforating a wellbore
that embodies principles of the present invention; and
[0018] Figure 3 is a flow chart illustrating a method
for verifying the status of perforating guns prior to
perforating a wellbore that embodies principles of the
present invention.
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DETAILED DESCRIPTION OF THE INVENTION
[0019] While the making and using of various embodiments
of the present invention are discussed in detail below, it
should be appreciated that the present invention provides
many applicable inventive concepts which can be embodied in
a wide variety of specific contexts. The specific
embodiments discussed herein are merely illustrative of
specific ways to make and use the invention, and do not
delimit the scope of the invention.
[0020] Referring initially to figure 1, a system for
verifying the status of perforating guns prior to
perforating a wellbore is operating from an offshore oil
and gas platform that is schematically illustrated and
generally designated 10. A semi-submersible platform 12 is
centered over a submerged oil and gas formation 14 located
below sea floor 16. A subsea conduit 18 extends from deck
20 of platform 12 to wellhead installation 22 including
subsea blow-out preventers 24. Platform 12 has a hoisting
apparatus 26 and a derrick 28 for raising and lowering pipe
strings such as work sting 30.
[0021] A wellbore 32 extends through the various earth
strata including formation 14. A casing 34 is cemented
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within wellbore 32 by cement 36. Work string 30 includes
various tools such as a plurality of perforating guns 38
disposed in a generally horizontal portion of wellbore 32
and a communication system including communication nodes
42, 44, 46, 48, 50. In the illustrated embodiment, a
surface communication node or controller 40 provides a user
interface including, for example, input and output devices
such as one or more video screens or monitors, including
touch screens, one or more keyboards or keypads, one or
more pointing or navigation devices, as well as any other
user interface devices that are currently known to those
skilled in the art or are developed. The user interface
may take the form of a computer including a notebook
computer. In addition, surface controller 40 may include a
logic module having various controllers, processors, memory
components, operating systems, instructions, communication
protocols and the like for implementing the systems and
methods for verifying the status of perforating guns of the
present invention. Surface controller 40 is coupled to a
bidirectional communication link that provides for
communication between surface controller 40 and a node 42
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that is positioned in the well as part of or attached to
work string 30.
[00221 The bidirectional communication link includes at
least one communication path from surface controller 40 to
node 42 and at least one communication path from node 42 to
surface controller 40. In certain embodiments,
bidirectional communication may be achieved via a half
duplex channel which allows only one communication path to
be open in any time period. Preferably, bidirectional
communication is achieved via a full duplex channel which
allows simultaneous communication over multiple
communication paths. This can be achieved, for example, by
providing independent hardwire connections or over a shared
physical media through frequency division duplexing, time
division duplexing, echo cancellation or similar technique.
In either case, the communication link may include one or
more electrical conductors, optical conductors or other
physical conductors.
[0023] Each of communication nodes 42, 44, 46, 48, 50
includes a transmitter, a receiver and a logic module that
includes, for example, various fixed logic circuits,
controllers, processors, memory components, operating
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systems, instructions, communication protocols and the like
for implementing the systems and methods for verifying the
status of perforating guns of the present invention. In
addition, each communication node 42, 44, 46, 48, 50 also
includes a power supply such as a battery pack which may
include a plurality of batteries, such as nickel cadmium,
lithium, alkaline or other suitable power source, which are
configured to provide proper operating voltage and current.
[0024] In one embodiment, communication nodes 42, 44,
46, 48, 50 are operable to transmit and receive acoustic
signals that are propagated over work string 30. In this
case, the transmitters and receivers of communication nodes
42, 44, 46, 48, 50 preferably include one or more
transducers in the form of stacks of piezoelectric ceramic
crystals. It should be noted that a single transducer may
operated as both the transmitter and the receiver of a
given communication node. Any number of communication
nodes may be operated in the system of the present
invention with the number determined by the length of work
string 30, the noise in the wellbore, the type of
communication media used and the like. As illustrated,
communication nodes 44, 46, 48 serve as repeater that are
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positioned to receive the acoustic signals transmitted
along work string 30 at a point where the acoustic signals
are of a magnitude sufficient for adequate reception. Once
the acoustic signals reach a given node, the signals are
converted to an electrical current which represents the
information being transmitted and is fed to the logic
module for processing. The current is then sent to the
transducer to generate acoustic signals that are
transmitted to the next node. In this manner,
communication from node 40 to node 50 as well as from node
50 to node 40 is achieved.
[0025] When it is desired to perforate casing 34, work
string 30 is lowered through casing 34 until the
perforating guns 38 are properly positioned relative to
formation 14. To verify the condition of perforating guns
38 prior to the perforating operation, an interrogation
command may be sent from surface controller 40 to sensors
disposed in perforating guns 38. For example, as discussed
in greater detail below, each perforating gun 38 may
include one or more sensors such as moisture sensors,
pressure sensors or other leak sensors. Preferably, each
of these sensors is individually addressable and
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communicates with communication node 50 via a wired
connection but a short range wireless connection such as an
electromagnetic communication link could alternatively be
used.
[0026] Accordingly, when surface controller 40 sends
interrogation commands to determine the leak status of
perforating guns 38 to one or more of the sensors, the
commands are received by communication node 42 and
retransmitted as encoded acoustic signals along work string
30 which are received by communication node 44.
Communication node 44 acts as a repeater to receive,
process and retransmit the commands via acoustic signals
along work string 30 which are received by communication
node 46. Likewise, communication node 46 forwards the
commands to communication node 48 via acoustic signals
along work string 30 and communication node 48 forwards the
commands to communication node 50 via acoustic signals
along work string 30. Communication node 50 then sends the
commands to interrogate each of the sensors in perforating
guns 38. The sensors obtain the desired data regarding the
leak status of each perforating gun 38 and provide this
information to communication node 50. Communication node
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50 converts this information to acoustic signals that are
sent to communication node 48 along work string 30.
Communication nodes 48, 46, 44 act as repeaters, each
receiving, processing and retransmitting the information in
the form of acoustic signals along work string 30.
Communication node 42 receives the acoustic signals send
from communication node 44 and processes the information
such that it can be forwarded to surface controller 40 for
analysis.
[0027] If the sensors report that no leaks have been
identified within perforating guns 38, then the
communication system may be used in a similar manner to
enable, arm and fire perforating guns 38 using, for
example, one or more electronic or hydraulic firing heads.
Thereafter, the shaped charges within perforating guns 38
are sequentially fired, either in an uphole to downhole or
a downhole to uphole direction. Upon detonation, the
liners of the shaped charges form jets that create a spaced
series of perforations extending outwardly through casing
34, cement 36 and into formation 14, thereby allow fluid
communi.cation between formation 14 and wellbore 32.
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[0028] In the illustrated embodiment, wellbore 32 has an
initial, generally vertical portion and a lower, generally
deviated portion which is illustrated as being horizontal.
It should be noted, however, by those skilled in the art
that the system for verifying the status of perforating
guns of the present invention is equally well-suited for
use in other well configurations including, but not limited
to, inclined wells, wells with restrictions, non-deviated
wells and the like. In addition, even though figure 1 has
been described with reference to an offshore environment,
it should be understood by one skilled in the art that the
principles described herein are equally well-suited for an
onshore environment.
[0029] As should be understood by those skilled in the
art, any of the functions described with reference to a
logic module herein can be implemented using software,
hardware, including fixed logic circuitry, manual
processing or a combination of these implementations. As
such, the term "logic module" as used herein generally
represents software, hardware or a combination of software
and hardware. For example, in the case of a software
implementation, the term "logic module" represents program
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code and/or declarative content, e.g., markup language
content, that performs specified tasks when executed on a
processing device or devices such as one or more processors
or CPUs. The program code can be stored in one or more
computer readable memory devices. More generally, the
functionality of the logic modules may be implemented as
distinct units in separate physical grouping or can
correspond to a conceptual allocation of different tasks
performed by a single software program and/or hardware
unit. The logic modules can be located at a single site
such as implemented by a single processing device, or can
be distributed over plural locations such as a notebook
computer or personal digital assistant in combination with
other physical devices that communication with one another
via wired or wireless connections.
[0030] Referring next to figure 2, therein is depicted a
perforating gun for use in the system for verifying the
status of perforating guns of the present invention that is
generally designated 100. Perforating gun 100 includes a
carrier 102 having a plurality of recesses, such as recess
104, defined therein. Radially aligned with each of the
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recesses is a respective one of the plurality of shaped
charges, such as shaped charge 106.
[0031] The shaped charges are retained within carrier
102 by a support member 108 which includes an outer charge
holder sleeve 110 and an inner charge holder sleeve 112.
In this configuration, outer tube 110 supports the
discharge ends of the shaped charges, while inner tube 112
supports the initiation ends of the shaped charges.
Disposed within inner tube 112 is a detonating cord 116.
In the illustrated embodiment, the initiation ends of the
shaped charges extend across the central longitudinal axis
of perforating gun 100 allowing detonating cord 116 to
connect to the high explosive within the shaped charges
through an aperture defined at the apex of the housings of
the shaped charges. In this configuration, carrier 102 is
sealed to protect the shaped charges disposed therein
against wellbore fluids.
[0032] Each of the shaped charges, such as shaped charge
106, is longitudinally and radially aligned with a recess,
such as recess 104, in carrier 102 when perforating
apparatus 100 is fully assembled. In the illustrated
embodiment, the shaped charges are arranged in a spiral
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pattern such that each shaped charge is disposed on its own
level or height and is to be individually detonated so that
only one shaped charge is fired at a time. It should be
noted, however, by those skilled in the art that alternate
arrangements of shaped charges may be used, including
cluster type designs wherein more than one shaped charge is
at the same level and is detonated at the same time,
without departing from the principles of the present
invention.
[00331 As discussed above, perforating guns for use in
the system for verifying the status of perforating guns of
the present invention, such as perforating gun 100, include
one or more sensors used to obtain and provide information
relative to environmental factors that surround perforating
gun 100. In the illustrated embodiment, perforating gun
100 includes a plurality of sensors such as sensor 120
positioned on the exterior of support member 108, sensor
122 positioned on the interior of support member 108,
sensor 124 positioned on the interior of carrier 102 and
sensor 126 positioned on the exterior of carrier 102. As
discussed above, sensors 120, 122, 124, 126 are preferably
coupled to communication node 50 via a wired connection but
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other communication means are also possible and considered
within the scope of the present invention.
[0034] Sensors 120, 122, 124, 126 may be of the same
type or different types and may be moisture sensors,
humidity sensors, pressure sensors including high speed
pressure sensors or fast gauge sensors, temperature
sensors, accelerometers, shock load sensors, liner
displacement sensors, depth sensors, fluid sensors, CO2
sensors, H2S sensors, CO sensors, thermal decomposition
sensors, casing collar locators, gamma detectors or any
other types of sensors that are operable to provide
information relating to the perforating gun environment.
Sensors 120, 122, 124, 126 and similar sensors associated
with the perforating gun system may be used for monitoring
a variety of environmental conditions relative to the gun
string such as the depth and orientation of the guns in the
wellbore; the condition of the guns prior to firing
including leak status, pressure, thermal decomposition and
moisture; whether the guns fired properly including gun
pressures, accelerations and shock loads; the near wellbore
reservoir parameters including temperatures, hydrostatic
pressures, peak pressures and transient pressures as well
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as other environmental conditions that are known to those
skilled in the art.
[0035] The operation of one embodiment of the present
invention will now be described as process 200 with
reference to figure 3. Once the perforating guns 38 are
positioned at the target location in the wellbore (step
202) and prior to detonating the shaped charges, the system
of the present invention is operable to perform a variety
of gun condition verifications such as those described
above and including perforating gun depth and orientation
verification and perforating guns condition verification.
This verification is accomplished using the surface
controller in conjunction with the communication nodes
positioned along the work string to interrogate the sensors
associated with the perforating guns for the desired
information. As an example, an interrogation command
requesting the leak status of one of the perforating guns
is sent to one of the downhole sensors via the
communication nodes and the work string and that downhole
sensor responds with the requested information also via the
communication nodes and the work string (step 204) Next,
the surface controller determines whether all the sensors
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have been interrogated (decision 206) If all of the
sensors have not been interrogated, an interrogation
command requesting the leak status of another of the
perforating guns is sent to another of the downhole sensors
and that downhole sensor responds with the requested
information (step 208) . This process continues until all
of the sensors have been interrogated (decision 206).
[0036] Once all of the sensors have been interrogated,
the surface controller determines whether all of the
perforating guns are dry (decision 210). If all of the
perforating guns are dry, the surface controller may
proceed with the remainder of the firing sequence including
sending the appropriate enable, arm and fire commands via
the communication nodes to a suitable firing head (step
212). If all of the perforating guns are not dry, the
surface controller determines whether remedial action can
be taken to allow the perforating event to occur (decision
214). Such remedial action may include repeating the
verification process to determine if the out of range
condition persists, identifying which guns have an out of
range condition and removing those guns from the firing
sequence or the like. If in performing such remedial
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action the surface controller determines that the
perforating event should occur, then the surface controller
may proceed with the remainder of the firing sequence (step
212). If in performing such remedial action it is
determined that the perforating event may not occur, then
the process ends.
[0037] During the perforating event, the sensors
associated with the perforating guns may continue gather
and transmit information. Specifically, sensors such as
the above described accelerometers, pressure sensors, high
speed pressure sensors, temperature sensors and the like
are used to obtain a variety of perforating gun and near
wellbore reservoir data. For example, the high speed
pressure sensors are operably to obtain pressure data in
the millisecond range such that the pressure surge and
associated pressure cycles created by the perforating event
can be measured. Likewise, the accelerometers are operable
to record shock data associated with the perforating event.
Use of this and other data provide for a determination of
the intensity level of the detonation associated with the
perforating guns. During, immediately after or at a later
time, this information is communicated from the sensors to
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the surface controller over the communication system. This
information may be used to determine the quality of the
perforating event such as whether the initiator was
detonated, whether any of the shaped charges within the
perforating gun were detonated, whether all of the shaped
charges within the perforating gun were detonated or
whether only some of the shaped charges within the
perforating gun were detonated. This information will
allow the operator in substantially real time to determine,
for example, if a zone should be reperforated.
[0038] Likewise, following the perforating event, the
sensors associated with the perforating guns may continue
gather and transmit information. Specifically, sensors
such as the above described pressure sensors, temperature
sensors, fluid sensors and the like are used to obtain a
variety of near wellbore reservoir data. This data may be
useful in designing the next phase of the completion such
as whether to perform an acid job or a facture stimulation.
[0039] While this invention has been described with a
reference to illustrative embodiments, this description is
not intended to be construed in a limiting sense. Various
modifications and combinations of the illustrative
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embodiments as well as other embodiments of the invention,
will be apparent to persons skilled in the art upon
reference to the description. It is, therefore, intended
that the appended claims encompass any such modifications
or embodiments.
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