Note: Descriptions are shown in the official language in which they were submitted.
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Attorney Docket No. 2011-1P-051250U1P4 PCT
CEMENT SET ACTWATORS FOR CEMENT COMPOSITIONS AND
ASSOCIATED METHODS
BACKGROUND
[000 I} The present embodiments relate to subterranean cementing operations
and, in
certain embodiments, to set-delayed cement compositions and methods of using
set-delayed
cement compositions in subterranean formations.
[0002] Cement compositions may be used in a variety of subterranean
operations.
For example, in subterranean well construction, a pipe string (e.g., casing,
liners, expandable
tubulars, etc.) may be run into a wellbore and cemented in place. The process
of cementing
the pipe string in place is commonly referred to as "primary cementing." In a
typical primary
cementing method, a cement composition may be pumped into an annulus between
the walls
of the wellbore and the exterior surface of the pipe string disposed therein.
The cement
composition may set in the annular space, thereby forming an annular she-ath
of hardened,
substantially impermeable cement (i.e.. a cement sheath) that may support and
position the
pipe string in the wellbore and may bond the exterior surface of the pipe
string to the
subterranean formation. Among other things, the cement sheath surrounding the
pipe string
prevents the migration of fluids in the annulus and protects the pipe string
from corrosion.
Cement compositions may also be used in remedial cementing methods to seal
cracks or
holes in pipe strings or cement sheaths, to seal highly pemeable formation
zones or
fractures, or to place a cement plug and the like.
[00031 A broad variety of cement compositions have been used in subterranean
cementing operations. In some instances, set-delayed cement compositions have
been used.
Set-delayed cement compositions are characterized by remaining in a pumpable
fluid state
for at least about one day (e.g., about 7 days, about 2 weeks, about 2 years
or more) at room
temperature (e.g., about 80 F) in quiescent storage. When desired for use,
the set-delayed
cement compositions should be capable of activation and consequently develop
reasonable
compressive strengths. For example, a cement set activator may be added to a
set-delayed
cement composition to induce the composition to set into a hardened mass.
Among other
things, set-delayed cement compositions may be suitable for use in wellbore
applications
such as applications where it is desirable to prepare the cement composition
in advance. This
may allow the cement composition to be stored prior to use. In addition, this
may allow the
cement composition to be prepared at a convenient location before
transportation to the job
site. Accordingly, capital expenditures may be reduced due to a reduction in
the need for on-
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site bulk storage and mixing equipment. This may be particularly useful for
offshore
cementing operations where space onboard the vessels may be limited.
[0004} While set-delayed Cement compositions have been developed heretofore,
challenges exist with their successful use in subterranean cementing
operations. For
example, set-delayed cement compositions prepared with Portland cement may
have
undesired gelation issues which can limit their use and effectiveness in
cementing
operations. Other set-delayed compositions that have been developed, for
example, those
comprising hydrated lime and quartz may be effective in some operations but
may have
limited use at lower temperatures as they may not develop sufficient
compressive strength
when used in subterranean formations having lower bottom hole static
temperatures. In
addition, it may be problematic to activate some set-delayed cement
compositions while
maintaining acceptable thickening times and compressive strength development.
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BRIEF DESCRIPTION OF THE DRAWINGS
1100051 These drawings illustrate certain aspects of some of the embodiments
of the
present methods and compositions, and should not be used to limit or define
the methods or
compositions.
100061 FIG. I illustrates a system for preparation and delivery of a cement
composition to a wellbore in accordance with certain embodiments.
NOM FIG. 2A illustrates surface equipment that may be used in placement of a
cement composition in a wellbore in accordance with certain embodiments.
(00081 FIG. 2B illustrates placement of a cement composition into a wellbore
annulus in accordance with certain embodiments.
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DESCRIPTION OF PREFERRED EMBODIMENTS
[00091 The present embodiments relate to subterranean cementing operations
and, in
certain embodiments, to set-delayed cement compositions and methods of using
set-delayed
cement compositions in subterranean formations. Particular embodiments provide
improved
cement set activators for the activation of cement compositions comprising
pozzolan
materials that have been retarded, have long set times, and/or have
insufficient early strength.
[0010] Embodiments of the set-delayed cement compositions may generally
comprise water, a pozzolan, and hydrated lime. Optionally, the cement
compositions may
further comprise a dispersant and/or a retarder. Advantageously, embodiments
of the set-
delayed cement compositions may be capable of remaining in a pumpable fluid
state for an
extended period of time. For example, the set-delayed cement compositions may
remain in a
pumpable fluid state for at least about I day or longer. Advantageously, the
set-delayed
cement compositions may develop reasonable compressive strengths after
activation at
relatively low temperatures, While the set-delayed cement compositions may be
suitable for
a number of subterranean cementing operations, they may be particularly
suitable for use in
subterranean formations having relatively low bottom bole static temperatures,
e.g.,
temperatures less than about 200 F or ranging from about I 00 F to about 200
F. In
alternative embodiments. the set-delayed cement compositions may be used in
subterranean
formations having bottom hole static temperatures up to 450 F or higher.
[00113 The water used in embodiments may be from any source provided that it
does not contain an excess of compounds that may undesirably affect other
components in
the set-delayed cement compositions. For example. a cement composition may
comprise
fresh water or salt water. Salt water generally may include one or more
dissolved salts
therein and may be saturated or unsaturated as desired for a particular
application. Seawater
or brines may be suitable for use in embodiments. Further, the water may be
present in an
amount sufficient to form a pumpable slurry. In certain embodiments, the water
may be
present in the set-delayed cement compositions in an amount in the range of
from about 33%
to about 200% by weight of the pozzolan. In certain embodiments, the water may
be present
in the set-delayed cement compositions in an amount in the range of from about
35% to
about 70% by weight of the pozzolan. With the benefit of this disclosure one
of ordinary
skill in the art will recognize the appropriate amount of water for a chosen
application.
[0012] Embodiments of the set-delayed cement compositions may comprise a
pozzolan. Any pozzolan is suitable for use in embodiments. Example embodiments
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comprising a pozzolan may comprise fly ash, silica fume, metakaolin, a natural
pozzolan
(e.g., pumice), or combinations thereof.
[0013] An example of a suitable pozzolan may comprise fly ash. A variety of
fly
ash may be suitable, including fly ash classified as Class C and Class F fly
ash according to
American Petroleum Institute, API Specification for Materials and Testing for
Well
Cements, API Specification 10, Fifth Ed., July 1, 1990. Class C fly ash
comprises both silica
and lime, so it may set to form a hardened mass upon mixing with water. Class
F fly ash
generally does not contain a sufficient amount of lime to induce a
cementitious reaction,
therefore, an additional source of calcium ions is necessary for a set-delayed
cement
composition comprising Class F fly ash. In some embodiments, lime may be mixed
with
Class F fly ash in an amount in the range of about 0.1% to about 100% by
weight of the fly
ash. In some instances, the lime may be hydrated lime. Suitable examples of
fly ash
include, but are not limited to, POZ1v1IX1' A cement additive, commercially
available from
Halliburton Energy Services, Inc., Houston, Texas.
[0014] An example of a suitable pozzolan may comprise metakaolin. Generally,
metakaolin is a white pozzolan that may be prepared by heating kaolin clay to
temperatures
in the range of about 600 to about 800 C.
[0015] An example of a suitable pozzolan may comprise a natural pozzolan.
Natural
pozzolans are generally present on the Earth's surface and set and harden in
the presence of
hydrated lime and water. Embodiments comprising a natural pozzolan may
comprise
pumice, diatomaceous earth, volcanic ash, opaline shale, tuff, arid
combinations thereof. The
natural pozzolans may be ground or unground. Generally, the natural pozzolans
may have
any particle size distribution as desired for a particular application. In
certain embodiments,
the natural pozzolans may have a mean particle size in a range of from about I
micron to
about 200 microns. The mean particle size corresponds to d50 values as
measured by particle
size analyzers such as those manufactured by Malvern Instruments,
Worcestershire, United
Kingdom, In specific embodiments, the natural pozzolans may have a mean
particle size in a
range of from about I micron to about 200 micron, from about 5 microns to
about 100
microns, or from about 10 micron to about 50 microns. In one particular
embodiment, the
natural pozzolans may have a mean particle size of less than about 15 microns.
An example
of a suitable commercial natural pozzolan is pumice available from Hess Pumice
Products,
Inc., Malad, Idaho, as DS-325 lightweight aggregate, which has a particle size
of less than
about 15 microns. It should be appreciated that particle sizes too small may
have mixability
problems while particle sizes too large may not be effectively suspended in
the compositions
and may be less reactive due to their decreased surface area. One of ordinary
skill in the art,
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with the benefit of this disclosure, should be able to select a particle size
for the natural
pozzolans suitable for use for a chosen application.
[00161 Embodiments of the set-delayed cement compositions may comprise
hydrated lime. As used herein, the term "hydrated lime" will be understood to
mean calcium
hydroxide. In some embodiments, the hydrated lime may be provided as quicklime
(calcium
oxide) which hydrates when mixed with water to forrn the hydrated lime. The
hydrated lime
may be included in embodiments of the cement compositions. for example, to
form a
hydraulic composition with the pozzolan. For example, the hydrated lime may be
included in
a pozzolan-to-hydrated-lime weight ratio of about Ithl to about 1: i or a
ratio of about 3:1 to
about 5:1. Where present, the hydrated lime may be included in die set-delayed
cement
compositions in an amount in the range of from about 10% to about 100% by
weight of the
pozzolan, for example. In some embodiments, the hydrated lime may be present
in an
amount ranging between any of and/or including any of about 10%, about 20%,
about 40%,
about 60%, about 80% or about 100% by weight of the pozzolan. In some
embodiments, the
cementitious components present in the set-delayed cement composition may
consist
essentially of the pozzolan and the hydrated lime. For example, the
cementitious components
may primarily comprise the pozzolan and the hydrated lime without any
additional
cementitious components (e.g., Portland cement) that hydraulically set in =the
presence of
water. One of ordinary skill in the art, with the benefit of this disclosure,
will recognize the
appropriate amount of hydrated lime to include for a chosen application.
[0017j Embodiments of the set-delayed cement compositions may comprise a set
retarder. A broad variety of set retarders may be suitable for use in the set-
delayed cement
compositions. For example, the set retarder may comprise phosphonic acids,
such as
ethylenediamine tetra(methylene phosphonic acid), diethylenetriamine
penta(methylene
phosphonic acid), etc.; lignosulfonates, such as sodium lignosulfonate,
calcium
lignosulfonate. etc.; salts such as stannous sulfate. lead acetate. monobasic
calcium
phosphate, organic acids, such as citric acid, tartaric acid, etc.; cellulose
derivatives such as
hydroxyl ethyl cellulose (HEC) and carboxymethyl hydroxyethyl cellulose
(CMHEC);
synthetic co- or ter-polymers comprising sulfonate and carboxylic acid groups
such as
sulfonate-finictionalized acrylamide-acrylic acid co-polymers; borate
compounds such as
alkali borates, sodium metaborate, sodium tetraborate, potassium pentaborate;
derivatives
thereof, or mixtures thereof. Examples of suitable set retarders include,
among others,
phosphonic acid derivatives. One example of a suitable set retarder is Micro
Matrix cement
retarder, available from Halliburton Energy Services, Inc. Generally, the set
retarder may be
present in the set-delayed cement compositions in an amount sufficient to
delay the setting
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for a desired time. In some embodiments, the set retarder may be present in
the set-delayed
cement compositions in an amount in the range of from about 0.01% to about 10%
by weight
of the pozzolan. In specific embodiments, the set retarder may be present in
an amotmt
ranging between any of and/or including any of about 0.01%, about 0.1%, about
1%, about
2%, about 4%, about 6%, about 8%, or about 10% by weight of the pozzolan. One
of
ordinary skill in the art, with the benefit of this disclosure, will recognize
the appropriate
amount of the set retarder to include for a chosen application.
(0018) As previously mentioned, embodiments of the set-delayed cement
compositions may optionally comprise a dispersant. Examples of suitable
dispersants
include, without limitation, sulfonated-forrnaldehyde-based dispersants (e.g.,
suifonated
acetone formaldehyde condensate), examples of which may include Daxadg 19
dispersant
available from Geo Specialty Chemicals, Ambler, Pennsylvania. Other suitable
dispersants
may be polycarboxylated ether dispersants such as Liquimentg 558IF and
Liquimentg 514L
dispersants available from BASF Corporation Houston, Texas; or Ethacryrd G
dispersant
available from Coatex, Genay, France. An additional example of a suitable
commercially
available dispersant is CFRT"-3 dispersant, available from Halliburton Energy
Services, Inc,
Houston, Texas. The Liquimentg 5I4L dispersant may comprise 36% by weight of
the
polycarboxylated ether in water. While a variety of dispersants may be used in
accordance
with embodiments, polycarboxylated ether dispersants may be particularly
suitable for use in
some embodiments. Without being limited by theory, it is believed that
polycarboxylated
ether dispersants may synergistically interact with other components of the
set-delayed
cement composition. For example, it is believed that the polycarboxylated
ether dispersants
may react with certain set retarders (e.g., phosphonic acid derivatives)
resulting in formation
of a gel that suspends the pozzolan and hydrated lime in the composition for
an extended
period of time.
[00191 In some embodiments, the dispersant may be included in the set-delayed
cement compositions in an amount in the range of from about 0.01% to about 5%
by weight
of the pozzolan. In specific embodiments, the dispersant may be present in an
amount
ranging between any of ancVor including any of about 0.01%, about 0.1%, about
0.5%, about
1%, about 2%, about 3%, about 4%, or about 5% by weight of the pozzolan. One
of ordinary
skill in the art, with the benefit of this disclosure, will recognize the
appropriate amount of
the dispersant to include for a chosen application.
[0020] Some embodiments of the set-delayed cement compositions may comprise
silica sources in addition to the pozzolan; for example, crystalline silica
and/or amorphous
silica. Crystalline silica is a powder that may be included in embodiments of
the set-delayed
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cement compositions, for example, to prevent cement compressive strength
retrogression.
Amorphous silica is a powder that may be included in embodiments of the set-
delayed
cement compositions as a lightweight filler and/or to increase cement
compressive strength.
Amorphous silica is generally a byproduct of a ferrosilicon production
process, wherein the
amorphous silica may be formed by oxidation and condensation of gaseous
silicon suboxide,
SiO, which is formed as an intermediate during the process. An example of a
suitable source
of amorphous silica is Silicone cement addifive available from Halliburton
Energy
Services, Inc., Houston, Texas. Embodiments comprising additional silica
sources may
utilize the additional silica source as needed to enhance compressive strength
or set times.
[0021] Other additives suitable for use in subterranean cementing operations
also
may be included in embodiments of the set-delayed cement compositions.
Examples of such
additives include, but are not limited to: weighting agents, lightweight
additives, gas-
generating additives, mechanical-property-enhancing additives, lost-
circulation materials,
filtration-control additives, fluid-loss-control additives, defoaming agents,
foaming agents,
thixotropic additives, and combinations thereof. In embodiments, one or more
of these
additives may be added to the set-delayed cement compositions after storing
but prior to the
placement of a set-delayed cement composition into a subterranean formation. A
person
having ordinary skill in the art, with the benefit of this disclosure, should
readily be able to
determine the type and amount of additive usefttl for a particular application
and desired
result.
[0022] Those of ordinary skill in the art will appreciate that embodiments of
the set-
delayed cement compositions generally should have a density suitable for a
particular
application. By way of example, the cement compositions may have a density in
the range of
from about 4 pounds per gallon ("lb/p1") to about 20 Ibigal. In certain
embodiments, the
cement compositions may have a density in the range =of from about 8 lb/pi to
about 17
lb/gal. Embodiments of the set-delayed cement compositions may be foamed or
tmfoamed or
may comprise other means to reduce their densities, such as hollow
microspheres, low-
density elastic beads, or other density-reducing additives known in the art.
In embodiments,
the density may be reduced after storage, but prior to placement in a
subterranean formation.
In embodiments, weighting additives may be used 10 increase the density of the
set-delayed
cement compositions. Examples of suitable weighting additives may include
barite, hematite,
hausmannite, calcium carbonate, siderite, ilmenite, or combinations thereof.
In particular
embodiments, the weighting additives may have a specific gravity of 3 or
greater. Those of
ordinary skill in the art, with the benefit of this disclosure, will recognize
the appropriate
density for a particular application.
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[00231 As previously mentioned, the set-delayed cement compositions may have a
delayed set in that they remain in a pumpable fluid state for at least elle
day (e.gõ at least
about 1 day. about 2 weeks, about 2 years or more) at room temperature (e.g.,
about 80 F) in
quiescent storage. For example, the set-delayed cement compositions may remain
in a
pumpable fluid state for a period of time from about 1 day to about 7 days or
more. In some
embodiments, the set-delayed cement compositions may remain in a pumpable
fluid state for
at least about I day, about 7 days, about 10 days, about 20 days, about 30
days, about 40
days, about 50 days, about 60 days, or longer. A fluid is considered to be in
a pumpable fluid
state where the fluid has a consistency of less than 70 Bearden units of
consistency ("Bc"),
as measured on a pressurized consistometer in accordance with the procedure
for
determining cement thickening times set forth in API RP Practice 10B-2,
Recommended
Practice for Testing Well Cements, First Edition, July 2005.
[0024) When desired for use, embodiments of the set-delayed cement
compositions
may be activated (e.g., by combination with an activator) to set into a
hardened mass. The
term "cement set activator" or "activator-, as used herein, refers to an
additive that activates
a set-delayed or heavily retarded cement composition and may also accelerate
the setting of
the set-delayed, heavily retarded, or other cement composition. By way of
example,
embodiments of the set-delayed cement compositions may be activated to form a
hardened
mass in a time period in the range of from about 1 hour to about 12 hours. For
example,
embodiments of the set-delayed cement compositions may set to form a hardened
mass in a
time period ranging between any of and/or including any of about 1 day, about
2 days, about
4 days, about 6 days, about 8 days, about 10 days, or about 12 days.
[0025) In some embodiments, the set-delayed cement compositions may set to
have
a desirable compressive strength after activation. Compressive strength is
generally the
capacity of a material or structure to withstand axially directed pushing
forces. The
compressive strength may be measured at a specified time after the set-delayed
cement
composition has been activated and the resultant composition is maintained
under specified
temperature and pressure conditions. Compressive strength can be measured by
either
destructive or non-destructive methods. The destructive method physically
tests the strength
of treatment fluid samples at various points in time by crushing the samples
in a
compression-testing machine. The compressive strength is calculated from the
failure load
divided by the cross-sectional area resisting the load and is reported in
units of pound-forte
per square inch (psi). Non-destructive methods may employ a 'MAIN ultrasonic
cement
analyzer, available from Fann Instrument Company, Houston, TX. Compressive
strength
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values may be determined in accordance with API RP 1013-2, Recommended
Practice Jiff
Testing Well Cements, First Edition, July 2005.
[0026] By way of example, the set-delayed cement compositions may develop a 24-
hour compressive strength in the range of from about 50 psi to about 5000 psi,
alternatively,
from about 100 psi to about 4500 psi, or alternatively from about 500 psi to
about 4000 psi.
In some embodiments, the set-delayed cement compositions may develop a
compressive
strength in 24 hours of at least about 50 psi, at least about 100 psi, at
least about 500 psi, or
more. In some embodiments, the compressive strength values may be determined
using
destructive or non-destructive methods at a temperature ranging from 100 F to
200 F.
[0027] In some embodiments, the set-delayed cement compositions may have
desirable thickening times after activation. Thickening time typically refers
to the time a
fluid, such as a set-delayed cement composition, remains in a fluid state
capable of being
pumped. A number of different laboratory techniques may be used to measure
thickening
time. A pressurized consistometer, operated in accordance with the procedure
set forth in the
aforementioned API RP Practice 10B-2, may be used to measure whether a fluid
is in a
pumpable fluid state. The thickening time may be the time for the treatment
fluid to reach 70
Be and may be reported as the time to reach 70 Be. In some embodiments. the
cement
compositions may have a thickening time of greater than about 1 hour,
alternatively, greater
than about 2 hours, alternatively greater than about 5 hours at 3,000 psi and
temperatures in a
range of from about 50 F to about 400 F, alternatively, in a range of from
about 80 F to
about 250 F, and alternatively at a temperature of about 140 F.
[0028] Embodiments may include the addition of a cement set activator to the
set
delayed cement compositions. Examples of suitable cement set activators
include, but are
not limited to: zeolites, amines such as triethanolamine, diethanolamine;
silicates such as
sodium silicate; zinc formate; calcium acetate; Groups IA and 11A hydroxides
such as
sodium hydroxide. magnesium hydroxide, and calcium hydroxide; monovalent salts
such as
sodium chloride; divalent salts such as calcium chloride; nanosilica (i.e.,
silica having a
particle size of less than or equal to about 100 nanometers); polyphosphates;
and
cornbinations thereof. In some embodiments, a combination of the polyphosphate
and a
monovalent salt may be used for activation. The monovalent salt may be any
salt that
dissociates to form a monovalent cation, such as sodium and potassium salts.
Specific
examples of suitable monovalent salts include potassium sulfate, and sodium
sulfate. A
variety of different polyphosphates may be used in combination with the
monovalent salt for
activation of the set-delayed cement compositions, including polymeric
metaphosphate salts,
phosphate salts, and combinations thereof. Specific examples of polymeric
metapbosphate
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salts that may be used include sodium hexametaphosphate, sodium
trimetaphosphate, sodium
tetrametaphosphate, sodium pentametaphosphate, sodium heptatnetaphosphate,
sodium
octametaphosphate, and combinations thereof. A specific example of a suitable
cement set
activator comprises a combination of sodium sulfate and sodium
hexametaphosphate. In
particular embodiments, the activator may be provided and added to the set-
delayed cement
composition as a liquid additive, for example, a liquid additive comprising a
monovalent
salt, a polyphosphate, and optionally a dispersant,
[0029] As discussed above, zcolites may be included as activators in
embodiments
of the set-delayed cement compositions. Zeolites are generally porous alumino-
silicate
minerals that may be either natural or synthetic. Synthetic zeolites are based
on the same
type of structural cell as natural zeolites and may comprise aluminosilicate
hydrates. As used
herein, the term "zeolite" refers to all natural and synthetic forms of
zeolite. An example of a
suitable source of zeolite is Valfor-100 zeolite or AcIvere 401 zeolite
available from the
PQ Corporation, Malvern, Pennsylvania.
[0030] Embodiments of the set-delayed cement compositions may comprise a
cement set activator comprising a zeolite, a combination of zeolites, a
combination of zeolite
and a non-zeolite activator, a combination of zeolites and a non-zeolite
activator, a
combination of zeolites and a combination of non-zeolite activators, or
combinations thereof.
Embodiments comprising zeolite may comprise any zeolite. Examples of zeolites
include
mordenite, zsm-5, zeolite x, zeolite y, zeolite a, etc. Furthermore,
embodiments comprising
zeolite may comprise zeolite in combination with a cation such as Ne,K, Ca.
Mg2+, etc.
Zeolites comprising cations such as sodium may also provide additional cation
sources to the
set-delayed cement composition as the zeolites dissolve. An example of a
zeolite comprising
a cation (e.g., Na) is the afore-mentioned Valfoi"' 100 zeolite. Without being
limited by
theory, it is believed that zeolites increase the surface area of the pozzolan
without increasing
their particles size. Increased surface areas for the pozzolan may allow for a
faster
dissolution rate of silica, the free silica is able to react with calcium
species, such as those
from hydrated lime, to form calcium-silicate-hydrate gels. Increasing the
surface area
without altering the particle size is advantageous because it allows for
greater reactivity
without affecting other properties such as viscosity or pumpability. Sodium
zeolites may also
exchange sodium for calcium in solution thereby increasing the pH and
increasing the rate of
dissolution of silica in the slurry.
[0031] Zeolites may be added to the set-delayed cement compositions in a
number
of ways. One embodiment comprises a method wherein the zeolites are added
directly to the
set-delayed cement compositions in an amount sufficient to activate or
accelerate the setting
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of the cement composition. An alternative embodiment is to induce the growth
of the zeolite
crystals directly on the pozzolan. The pozzolan may be a nutrient source for
zeolite crystals
and be induced to grow zeolite crystals either as a film or as an integral
part of the particle if
the pozzolanic particles were placed under zeolite synthesis conditions.
Various seeding
methods such as pulsed laser deposition. secondary growth, vacuum deposition,
etc. may be
used to produce a variety of zeolites (e.g., zsm-5, zeolite x, etc.) on the
pozzolan. The
synthesized zeolites may form crystals, film, and/or integrate directly into
the pozzolan. The
pozzolan with the zeolite disposed thereon may be provided and used in
preparation of a set-
delayed cement composition.
[0032] The cement set activator should be added to embodiments of the set-
delayed
cement composition in an amount sufficient to induce the set-delayed
composition to set into
a hardened mass. In certain embodiments, the cement set activator may be added
to the
cement composition in an amount in the range of about 0.1% to about 20% by
weight of the
pozzolan. In specific embodiments, the cement set activator may be present in
an amount
ranging between any of and/or including any of about 0.1%, about 1%, about 5%,
about
10%, about 15%, or about 20% by weight of the pozzolan. One of ordinary skill
in the art,
with the benefit of this disclosure, will recognize the appropriate amount of
the cement set
activator to include for a chosen application.
[00333 While the preceding may describe the use of zeolites as activators in
set-
delayed cement compositions, it is to be understood that zeolites may be used
in other
cement systems comprising a pozzolan to accelerate the set time of the cement
composition
and to enhance the development of early compressive strength. In some
embodiments, a
zeolite may be used in a cement composition comprising a pozzolan and water.
In other
embodiments, the cement composition may further comprise hydrated lime and
other
optional additives, such as those described above. The disclosure of the
zeolite used herein is
not to be limited to set-delayed pozzolan cement compositions but may be used
for any
pozzolan cement composition regardless of whether the cement composition may
be
categorized as "set-delayed."
[0034] As will be appreciated by those of ordinary skill in the art,
embodiments t-,if
the set-delayed cetrieht compositions may be used in a variety of subterranean
operations,
including primary and remedial cementing. In some embodiments, a set-delayed
cement
cotnposition may he provided that comprises water, a pozzolan, hydrated lime,
a set retarder,
and optionally a dispersant. The set-delayed cement composition may be
introduced into a
subterranean formation and allowed to set therein. As used herein, introducing
the set-
delayed cement composition into a subterranean formation includes introduction
into any
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portion of the subterranean formation, including. without limitation, into a
wellbore drilled
into the subterranean formation, into a near wellbore region surrounding the
wellbore, or into
both. Embodiments may further include activation of the set-delayed cement
composition.
The activation of the set-delayed cement composition may comprise, for
example, the
addition of a cement set activator to the set-delayed cement composition.
[0035} In some embodiments, a set-delayed cement composition may be provided
that comprises water, a pozzolan, hydrated time, a set retarder, and
optionally a dispersant.
The set-delayed cement composition may be stored, for example, in a vessel or
other suitable
container. The set-delayed cement composition may be permitted to remain in
storage for a
desired time period. For example, the set-delayed cement composition may
remain in
storage for a time period of about 1 day or longer. For example, the set-
delayed cement
composition may remain in storage for a time period of about I day, about 2
days, about 5
days, about 7 days, about 10 days, about 20 days, about 30 days, about 40
days, about 50
days, about 60 days, or longer. In some embodiments, the set-delayed cement
composition
may remain in storage for a time period in a range of from about 1 day to
about 7 days or
longer. Thereafter, the set-delayed cement composition may be activated, for
example, by
addition of a cement set activator, introduced into a subterranean formation,
and allowed to
set therein.
[0036) In primary cementing embodiments, for example, embodiments of the set-
delayed cement composition may be introduced into an annular space between a
conduit
located in a wellbore and the walls of a wellbore (and/or a larger conduit in
the wellbore),
wherein the wellbore penetrates the subterranean formation. The set-delayed
cement
composition may be allowed to set in the annular space to form an annular
sheath of
hardened cement. The set-delayed cement composition may form a barrier that
prevents the
migration of fluids in the wellbore. The set-delayed cement composition may
also, for
example, support the conduit in the wellbore.
[0037] In remedial cementing embodiments, a set-delayed cement composition may
be used, for example, in squeeze-cementing operations or in the placement of
cement plugs.
By way of example, the set-delayed composition may be placed in a wellbore to
plug an
opening (e.g., a void or crack) in the formation, in a gravel pack, in the
conduit, in the
cement sheath, and/or between the cement sheath and the conduit (e.g., a
microannulus).
[0038] An embodiment con-tprises a method of cementing in a subterranean
formation comprising: providing a cement cotnposition comprising water, a
pozzolan,
hydrated lime, and a zeolite activator; introducing the cement composition
into a
subterranean formation; and allowing the cement composition to set in the
subterranean
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formation, wherein the zeolite activator accelerates compressive strength
development of the
cement composition
[0039] An embodiment comprises an activated set-delayed cement composition
comprising: water, a pozzolan, hydrated lime, a set retarder, and a zeolite
activator.
[00401 An embodiment comprises a cementing system comprising: a set-delayed
cement composition comprising water, a pozzolan, hydrated lime, and a set
retarder, a zeolite
activator for activation of the set-delayed cement composition; mixing
equipment for mixing
the set-delayed cement composition and the zeolite activator to form an
activated cement
composition; and pumping equipment for delivering the activated cement
composition into a
wellbore.
[0041] Referring now to FIG, 1, preparation of a cement composition (which may
be set delayed or non-set delayed) in accordance with example embodiments will
now be
described. FIG. 1 illustrates a system 2 for preparation of a cement
composition and delivery
to a wellbore in accordance with certain embodiments. As shown, the cement
composition
may be mixed in mixing equipment 4, such as a jet mixer, re-circulating mixer,
or a batch
mixer, for example, and then pumped via pumping equipment 6 to the wellbore.
In some
embodiments, the mixing equipment 4 and the pumping equipment 6 may be
disposed on
one or more cement trucks as will be apparent to those of ordinary skill in
the art. In some
embodiments, a jet mixer may be used, for example, to continuously mix the
lime/settable
material with the water as it is being pumped to the wellbore. In set-delayed
embodiments, a
re-circulating mixer and/or a batch mixer may be used to mix the set-delayed
cement
composition, and the activator may be added to the mixer as a powder prior to
pumping the
cement composition downhole.
[0042] An example technique for placing a cement composition into a
subterranean
formation will now be described with reference to FIGS. 2A and 213. FIG. 2A
illustrates
surface equipment 10 that may be used in placement of a cement composition in
accordance
with certain embodiments. It should be noted that while FIG. 2A generally
depicts a land-
based operation, those skilled in the art will readily recognize that the
principles described
herein are equally applicable to subsea operations that employ floating or sea-
based
platforms and rigs, without departing from tbe scope of the disclosure. As
illustrated by FIG.
2A, the surface equipment 10 may include a cementing unit 12, which may
include one or
more cement trucks. The cementing unit 12 may include mixing equipment 4 and
pumping
equipment 6 (e.g., FIG. 1) as will be apparent to those of ordinary skill in
the art. The
cementing unit 12 may pump a cement composition 14 through a feed pipe 16 and
to a
cementing head 1$ which conveys the cement composition 14 downhole.
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[00431 Turning now to FIG 2B, the set-delayed or non-set-delayed pozzolanic
cement composition 14 may be placed into a subterranean formation 20 in
accordance with
example embodiments. As illustrated, a wellbore 22 may be drilled into the
subterranean
formation 20. While wellbore 22 is shown extending generally vertically into
the
subterranean formation 20, the principles described herein are also applicable
to wellbores
that extend at an angle through the subterianean formation 20, such as
horizontal and slanted
wellbores. As illustrated, the wellbore 22 comprises walls 24. In the
illustrated embodiment,
a surface casing 26 has been inserted into the wellbore 22. The surface casing
26 may be
cemented to the walls 24 of the wellbore 22 by cement sheath 28. In the
illustrated
embodiment, one or more additional conduits (e.g., intermediate casing,
production casing,
liners, etc.), shown here as casing 30 may also be disposed in the wellbore
22. As illustrated,
there is a wellbore annulus 32 formed between the casing 30 and the walls 24
of the wellbore
22 and/or the surface casing 26. One or more centralizers 34 may be attached
to the casing
30, for example, to eentralin the casing 30 in the wellbore 22 prior to and
during the
cementing operation.
[0044] With continued reference to FIG. 28, the cement composition 14 may be
pumped down the interior of the casing 30. The cement composition 14 may be
allowed to
flow down the interior of the casing 30 through the casing shoe 42 at the
bottom of the
casing 30 and up around the casing 30 into the wellbore annulus 32. The cement
composition
14 may be allowed to set in the wellbore annulus 32, for example, to form a
cement sheath
that supports and positions the casing 30 in the wellbore 22. While not
illustrated, other
techniques may also be utilized for introduction of the pozzolanic cement
composition 14,
By way of example, reverse circulation techniques may be used that include
introducing the
cement composition 14 into the subterranean formation 20 by way of the
wellbore annulus
32 instead of through the casing 30.
[00451 As it is introduced, the cement composition 14 may displace other
fluids 36,
such as drilling fluids and/or spacer fluids that may be present in the
interior of the casing 30
and/or the wellbore annulus 32. At least a portion of the displaced fluids 36
may exit the
wellbore annulus 32 via a flow line 38 and be deposited, for example, in one
or more
retention pits 40 (e.g., a mud pit), as shown on FIG. 2A, Referring again to
FIG. 2B, a
bottom plug 44 may be introduced into the wellbore 22 ahead of the cement
composition 14,
for example, to separate the cement composition 14 from the fluids 36 that may
be inside the
casing 30 prior to cementing. After the bottom plug 44 reaches the landing
collar 46, a
diaphragm or other suitable device should rupture to allow the pozzolanic
cement
composition 14 through the bottom plug 44. In FM. 2B, the= bottom plug 44 is
shown on the
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landing collar 46. In the illustrated embodiment. a top plug 48 may be
introduced into the
wellbore 22 behind the cement composition 14. The top plug 48 may separate the
cement
composition 14 from a displacement fluid 50 and also push the cement
composition 14
through the bottom plug 44.
[00461 The exemplary cement compositions disclosed herein may directly or
indirectly affect one or more components or pieces of equipment associated
with the
preparation. delivery, recapture, recycling, reuse, and/or disposal of the
disclosed cement
compositions. For example, the disclosed cement compositions may directly or
indirectly
affect one or more mixers, related mixing equipment, mud pits, storage
facilities or. units,
composition separators. heat exchangers, sensors, gauges, pumps, compressors,
and the like
used generate, store, monitor, regulate, and/or recondition the exemplary
cement
compositions. The disclosed cement compositions may also directly or
indirectly affect any
transport or delivery equipment used to convey the cement compositions to a
well site or
downhole such as, for example, any transport vessels, conduits, pipelines,
trucks, tubulars,
and/or pipes used to compositionally move the cement compositions from one
location to
another, any pumps, compressors, or motors (e.g., topside or downhole) used to
drive the
cement compositions into motion, any valves or related joints used to regulate
the pressure or
flow rate of the cement compositions, and any sensors (i.e.. pressure and
temperature),
gauges, and/or combinations thereof, and the like. The disclosed cement
compositions may
also directly or indirectly affect the various downhole equipment and tools
that may come
into contact with the cement compositions such as, but not limited to,
wellbore casing,
wellbore liner, completion string, insert strings, drill string, coiled
tubing, slickline, wireline,
drill pipe, drill collars, mud motors, downhole motors and/or pumps, cement
pumps, surface-
mounted motors and/or pumps, centralizers, turbolizers, scratchers, floats
(e.g., shoes,
collars, valves, etc.), logging tools and related telemetry equipment,
actuators (e.g.,
electromechanical devices, hydromechanical devices, etc.), sliding sleeves,
production
sleeves, plugs, screens, filters, flow control devices (e.g., inflow control
devices, autonomous
inflow control devices, outflow control devices, etc.), couplings (e.g.,
electro-hydraulic wet
connect, dry connect, inductive coupler, etc.), control lines (e.g.,
electrical, fiber optic,
hydraulic, etc.), surveillance lines, drill bits and reamers, sensors or
distributed sensors,
downhole heat exchangers, valves and corresponding actuation devices, tool
seals, packers,
cement plugs, bridge plugs, and other wellbore isolation devices, or
components, and the
like.
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f0047] To facilitate a better understanding of the embodiments, the following
examples of certain aspects of some embodiments are given. In no way should
the following
examples be read to limit, or define, the entire scope of the disclosure.
EXAMPLES
Example 1
[0048] Four samples were prepared to test the effectiveness of sodium zeolite
A as
an activator of lime-pozzolan cement compositions. The sodium zeolite A used
for the
experiment was Val for 100 zeolite from the l'Q Corporation, Malvern,
Pennsylvania.
Valfor 100 zeolite has a median particle size of 5 microns and a high surface
area (i.e., 71.4
m2/g). Two lime-pozzolan cement formulations were prepared with and without
sodium
zeolite A. The formulation with sodium zeolite A had a density of 14.0 lb/gal
and was
comprised of 304 grams of pumice (DS-325 lightweight aggregate), 45 grams of
hydrated
lime, 25 grams of sodium zeolite A (Valfor 100), 1.9 grams of dispersant
(Liquiment
5581F dispersant), and 158.5 grams of water. The formulation without sodium
zeolite A had
a density of 14.0 lb/pi and was comprised of 304 grams of pumice (DS-325
lightweight
aggregate), 45 grams of hydrated lime, 1.9 grams of dispersant (Liquiment
5581F), and
145.5 grams of water. The strength development of the samples was monitored
via a Fann
UCAT" ultrasonic cement analyzer at test temperatures of 80 F and 100 F. The
UCAT" was
used to determine the compressive strengths of the samples after twenty-four
hours as well
as the time for the samples to develop compressive strengths of 50 psi and 500
psi. The
UCAT" determines the compressive strength rate as a function of time. The rate
of strength
development was calculated as the slope of the initial linear part (starting
from the onset of
the strength development) of the compressive strength versus time graph. The
results of
these tests are set forth in Table 1 below.
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Table 1
Comparison of Lime-Pox/Ann Cement with and without a Zeolite Activator
Test Zeolite (% by Time to 50 psi Time to 500 24-
Hour
Temperature weight of (hr:min) psi Compressive
pumice + (hr:min) Strength
(psi)
hydrated lime)
80 F 7.20% 4:23 17:10 688
80 F = 0.00% 20:03 69
100 F 7.20% 2:41 8:30 1562
100 F 0.00% 7:22 29:30 374
Example 2
[0049] A sample of pumice was treated with sodium hydroxide and sodium
chloride
to produce zeolite on the pumice. The zeolite synthesis was carried out by
mixing 300 grams
of pumice (DS-325 lightweight aggregate) with 1.25 liters of 30% NaCI solution
that
contained 25 grams of Na011. After mixing was completed, the sample was placed
in a
sealed plastic container and heated at 85 C for 17 hours. After treatment, the
solids were
filtered and washed several times with deionized water and then dried. The
solids were used
to form a Ihne-pozzolan set-delayed cement composition comprising 250 grams of
zeolitized
pumice, 50 grams of hydrated lime, 349 grams of dispersant (Liquiment 5141.,
dispersant),
3.13 grams of set retarder (Micro Matrix* cement retarder), and 207.4 grams of
water. As a
control, a lime-pozzolan set-delayed cement composition was prepared that did
not comprise
the zeolitized pumice. The control composition comprised 250 grams pumice (DS-
325
lightweight aggregate), 50 grams of hydrated lime, 3.49 grarns of dispersant
(Liquiment*
5141, dispersant), 3.13 grams of set retarder (Micro Matrix cement
retarder), and 154.9
grams of water, The strength development of the samples was monitored via UCA
at a test
temperature of 100 F. The UCA'M was used to determine the compressive
strengths of the
experimental sample and the control after seventy-two hours as well as the
time for the
experimental sample and the control to develop compressive strengths of 50 psi
and 100 psi.
The UCATM determines the compressive strength rate as a function of time. The
rate of
strength development was calculated as the slope of the initial linear part
(starting from the
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onset of the strength development) of the compressive strength versus time
graph, The
results of these tests are set forth in Table 2 below.
Table 2
Comparison of Lime-Pozzolan Cement with and without a Zeolitized Pumice
Activator
Test Pozzolan Time to 50 psi Time to 100 psi 72-Hour
Temperature (hr:min) (hr:min) Compressive
Strength (psi)
100 F Zeol itized 58:45 62:24 331
pumice
100 F pumice --*
* After 78 hours the slurry had not set.
Example 3
[0050} Several samples of set-delayed cement compositions were prepared. The
samples comprised pumice (DS-325 lightweight aggregate), 20% hydrated lime,
and 60%
water. The density of each sample was 13.5 lb/gal. In addition to the base
composition, a
varying amount of dispersant (Liquiment* 5581F dispersant), cement retarder
(Micro
Matrix* cement retarder), and activator (activator type varied by sample) were
added to
individual samples. The activator types chosen were sodium zeolite A (Valfoe
100 zeolite),
hydrated sodium zeolite A (Advera 401 zeolite), divalent salt (CaCl2), and
cement (API
Class A). The dispersant was added as a percentage by weight a the pumice
(bwoP). The
cement retarder was added in units of gallons per 46 lb. sack of pumice
(galisk). Each
activator comprised 10% of the samples by weight of the pumice and the
hydrated lime
(bwoP HL). The strength development and initial set times of the samples were
monitored
via UCATh at a test temperature of 80 F. The UCe was used to determine the
compressive
strengths of the experimental sample and the control after twenty-four hours.
The UCAlm
determines the compressive strength rate as a function of time. The rate of
strength
development was calculated as the slope of the initial linear part (starting
from the onset of
the strength development) of the compressive strength versus time graph. The
results of
these tests are set forth in Table .3 below.
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Table 3
Comparison of Different Types of Activators
UCAnr Data
Cement Activator
Dispersant 24-Hour
Retarder (10%
(% bwop) Initial Set Compressive
(gal/sk) bwoP+HL)
(hr:min) Strength (psi)
524 (316)*; tested
0.575 0.015 Zeolite NaA 12:09 same day as mixed
778 (343)*; tested
one day after
0.625 0.015 Zeolite NaA 7:03 mixing
Hydrated
0.625 0.015 Zeolite NaA 7:56 603
0.725 0.015 CaC12 53:52
0.725 0.015 Cement 15:33 71
0.50 0.020 Zeolite NaA 11:46 580 (230)*
250 psi at 30:30
0,55 0.025 Zeolite NaA 24:43 500 psi at 36:05
0.55 0.025 Zeolite NaA (100 F) 11:20 965 (678)*
* Values in parentheses are crush values for UCAT" samples.
Example 4
[0051} Two set-delayed cement composition samples were prepared. The samples
comprised pumice (DS-325 lightweight aggregate), 20% hydrated lime, 65% water,
2%
weight additive (Micromax weight additive), 0.6% dispersant (Liquiment* 5581F
dispersant), and 0.04 galisk cement retarder (Micro Matrix* cement retarder).
Additionally,
one experimental sample comprised 10% bwoPIIIL sodium zeolite A activator
(Valfor 100
zeolite). The density of each sample was 13.5 lb/gal. The strength development
of the
samples was monitored via UCA at a test temperature of I 00 F. The UCArm was
used to
determine the time to 50 psi and the time to 500 psi of the experimental
sample and the
control. The LICA determines the compressive strength rate as a ftmction of
time. The rate
of strength development was calculated as the slope of the initial linear part
(starting from
the onset of the strength development) of the compressive strength versus time
graph. The
results of these= tests are set forth in Table 4 below.
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Table 4
Comparison of Lime-P=01AR Cement with and without a Zeolite Activator
Activator UCAT" Data
(10% Time to 50 psi Time to 500 psi
bwoP+HL) (hr: min) (hr:min)
50:00+*
Zeolite NaA 38:25 56:65
* Had not set by 50 hours.
Example 5
[00521 Seven experimental samples of set-delayed cement compositions were
prepared. The samples comprised 609 grams fly ash (Magnablend Class F fly ash,
available
from Magnablend inc.. Waxahachie, Texas), 21 grams silica fume, 3.5 grams
cement friction
reducer (CFR-3'" cement friction reducer, available from Halliburton Energy
Services inc.,
Houston, Texas), and 317 grams water. In addition to the base composition, a
varying
amount of hydrated sodium zeolite A activator (Advere 401 zeolite) was added
to each
experimental sample. The strength development of the samples was monitored via
UCAr" at
a test temperature of 150 F. The UCATu was used to determine the compressive
strengths of
the experimental samples after twenty-four hours. The UCArm determines the
compressive
strength rate as a function of time. The rate of strength development was
calculated as the
slope of the initial linear part (starting from the onset of the strength
development) of the
compressive strength versus time graph. The results of these tests are set
forth in Table 5
below.
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Table 5
Zeolite Concentration versus Compressive Strength
Zeolite Activator (grams) 24-Hour
Compressive Strength at 150 F
(Psi)
49 1220
42 990
35 1140
28 1110
14 980
7 1090
0 1010
[00531 Additionally the strength development of the zeolite sample comprising
49
grams from Table 5 above, was additionally measured by the UCAI'l at test
temperatures of
100 F and 120 F. The results of these tests are set forth in Table 6 below.
Table 6
Zeolite concentration versus Compressive Strength at 100 F, 120 F, and 150 F
Zeolite Activator 24 Hour Comp. 24-hour Comp. 24-Hour Comp.
(grams) Strength at 100 F Strength
at 120 F Strength at 150 F
(Psi) (psi) (psi)
49 620 770 1220*
0 Did Not Set 60 1010
*Permeability 0.013 md
00541 lt should be understood that the compositions and methods are described
in
terms of "comprising," "containing," or "including" various components or
steps, the
compositions and methods can also "consist essentially of' or "consist of' the
various
components and steps. Moreover, the indefinite articles "a" or "an," as used
in the claims,
are defined herein to mean one or more than one of the element that it
introduces.
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[00551 For the sake of brevity, only certain ranges are explicitly disclosed
herein.
However, ranges from any lower lirnit may be combined with any upper limit to
recite a
range not explicitly recited, as well as, ranges from any lower limit may be
combined with
any other lower limit to recite a range not explicitly recited, in the same
way, ranges from
any upper limit may be combined with any other upper limit to recite a range
not explicitly
recited. Additionally, whenever a numerical range with a lower limit and an
upper limit is
disclosed, any number and any included range falling within the range are
specifically
disclosed. In particular, every range of values (of the form, ¶from about a to
about b," or,
equivalently, "from approximately a to b," or, equivalently, "from
approximately a-h")
disclosed herein is to be understood to set forth every number and range
encompassed within
the broader range of values even if not explicitly recited. Thus. every point
or individual
value may serve as its own lower or upper limit =combined with any other point
or individual
value or any other lower or upper limit, to recite a range not explicitly
recited.
[00561 Therefore, the present embodiments are well adapted to attain the ends
and
advantages mentioned as well as those that are inherent therein. The
particular embodiments
disclosed above are illustrative only, and they may be modified and practiced
in different but
equivalent manners apparent to those skilled in the art having the benefit of
the teachings
herein. Although individual embodiments are discussed, all combinations of all
those
embodiments are covered by the disclosure. Furthermore, no limitations are
intended to the
details of construction or design herein shown, other than as described in the
claims below.
Also, the terms in the claims have their plain, ordinary meaning unless
otherwise explicitly
and clearly defined by the patentee. It is therefore evident that the
particular illustrative
embodiments disclosed above may be altered or modified and all such variations
are
considered within the scope and spirit of those embodiments. If there is any
conflict in the
usages of a word or term in this specification and one or more patent(s) or
other documents
that may be incorporated herein by reference. the definitions that are
consistent with this
specification should be adopted.
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