Note: Descriptions are shown in the official language in which they were submitted.
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TWO-PART SET-DELAYED CEMENT COMPOSITIONS
BACKGROUND
[0001] 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
tu.bulars, 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 sheath 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
IS subtenlinean fbrmation, Among other thins, 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 permeable formation
zones or
fractures, or to place a cement plug and the like.
100031 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 about 800
17) 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-
site bulk storage and mixing equipment. This may he particularly useful fur
offshore
cementing Operations where space onboard the vessels may be limited.
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[00041 While set-delayed cement compositions have been developed heretolbre,
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 he effective in some. operations hut
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 he 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
[000111 These drawings illustrate certain aspects of some of the embodiments
of the
present method, and should not be used to limit or define the method.
[00021 FIG. illustrates a system for preparation and delivety of a
set-delayed
Seeman composition to a wellbore in accordance with certain embodiments.
[0003] FIG. 2A illustrates surface equipment. that may be used in placement of
a set-
delayed cement composition in a wellbore in accordance with certain
embodiments.
[0004] FIG. 2B illustrates placement of a set-delayed cement composition into
a
wellbore annulus in accordance with eertain embodiments.
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DESC Rirn ON OF PREFERRED EMBODIMENTS
[00051 The example embodiments relate to subterranean cementing operations
and,
more particularly, in certain embodiments, to set-delayed cement compositions
and methods
of using set-delayed cement compositions in subterranean tbrmations.
-5 [00061
Embodiments of the set-delayed cement compositions may generally
comprise %iater, a pozzolanõ and hydrated lime. Optionally, the cement
compositions may
tbrther comprise a dispersant and/or a cement set retarder. Alternatively,
embodiments of the
set-delayed cement composition may comprise two-part set-delayed cement
composition
comprising separate component .Slurries with one component slurry comprising a
pozzolan
and the other component slurry comprising lime. Embodiments of the two-part
set-delayed
cement compositions are discussed in detail below. 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 1 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 hole static temperatures,
e.g:,
temperatures less than about 200" F or ranging from about IOW 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 4500 F or higher.
1.00071 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 punmable 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
he 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.
[0008] Embodiments of the set-delayed cement compositions may comprise a
p0720iall. Any pozzolan is Suitable tbr 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
[0009] Embodiments of the pozzolan may comprise fly ash. A variety of fly
ashes
may be suitable, including fly ash classified as Class C and Class F fly ash
according to
American Petroleum Institute, AN Specification for Materials and 'Vesting fOr
Well
Cements, API Specification 10, Falb 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 tbr a set-delayed
cement
composition comprising Class F fly ash. In some embodiments, lime may he 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, POD/11X A cement additive, commercially
available from
Hatliburton Energy Services, Inc., Houston, Texas.
[0010] Embodiments of the pozzolan may comprise metakaolin. Generally,
metakaolin is a white pozzolan that may be prepared by heating kaolin clay,
for example, to
temperatures in the range of about 600 C to about 8000C.
[00111 Embodiments of the 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, and
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 1
micron to
about 200 microns. The mean particle size corresponds to (150 values as
measured by particle
size analyzers such as those manufactured by MifilVerfl 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,
Malad, Idaho, as 05-325 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
pozzolarts suitable for use for a chosen application,
100121 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 time may be provided as quicklime
(calcium
oxide) which hydrates when mixed with water to form the hydrated lime. The
hydrated lime
may be included in embodiments, 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 10:1 to about 1:1 or a ratio of about 3:1 to about 5:1.
Where present,
the hydrated lime may be included in the 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 time may be present in an amount ranging between any
of andior
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 cememitious 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.
[0013] Embodiments of the .set-delayed cement compositions may comprise a
cement set retarder. A broad variety of cement set retarders may be suitable
for use in the
set-delayed cement compositions. For example, the cement set retarder may
comprise
phosphonic acids, such as ethylenedia.mine tetra(rnethylene phosphonic acid),
diethylenetriarnine penta(methylene phosphonic acid), etc.; lignosulfonates,
such as sodium
lignosulfonatc, calcium lignosulfonatc, etc.; salts such as stannous sulfate,
lead acetate,
monobasic calcium Phosphate, organic acids, such as citric add, 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 sulfortate-functionalized acrylamidtktcrylie acid co-polymers;
borate
compounds such as alkali borates, sodium metaborate, sodium tetraborate,
potassium
pentaborate; derivatives thereof or mixtures thereof. Examples of suitable
cement set
retarders include, among others, =phosphonic acid derivatives. One example of
a suitable
cement set retarder is Micro Matrix cement retarder, available *OM
flalliburton Energy
Services, Inc. Generally, the cement set retarder may be present in the set-
delayed cement
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compositions in an amount sufficient to delay the setting for a desired time.
In some
embodiments, the cement 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 cement set retarder may be present in an amount
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 cement
set retarder to include for a chosen application.
[0014] As previously mentioned, embodiments of the set-delayed cement
compositions may optionally comprise a dispersant. Examples of suitable
dispetsants
include, without limitation, sulfonated-formaldehyde-based dispersants (e.g.,
sulfonated
'acetone formaldehyde condensate), examples of which may include Daxtut 19
dispersant
available from Geo Specialty Chemicals, Ambler, Pennsylvania. Other suitable
dispersants
may be polycarboxylated ether dispersants such as Liquiment- 5581F and
Liquitnenel 5141,
dispersants available from BASF Corporation Houston, Texas; or Ethacryr 0
dispersant
available from Comex, Genay, France. An additional example of a suitable
commercially
available dispersant is C'llem-3 dispersant, available from 11011)11dpi]
Energy Services, Inc,
Houston, Texas. The Liquimene 5141.: 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 polyearhoxylated
ether dispersants
may react with certain cement 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.
[0015] In some embodiments, the dispersant. may be included in the sot-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 and/or 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.
[0016] Some embodiments of the set-delayed cement compositions may comprise
silica sources in addition to the pozzolan; for example, crystalline silica
and/or amorphous
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silica. Crystalline silica is a powder that may be included in embodiments of
the set-delayed
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 ga,seous
silicon suboxide,
SiO, which is formed as an intermediate during the process. An example of a
suitable source
of amorphous silica is Silicalite cement additive 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.
[0017.1 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 useful for a particular application
and desired
result.
[00181 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 (ib/gar) to about 20 lb/gal. In certain
embodiments, the
cement compositions may have a density in the range of from about 8 lb/gal to
about 17
lb/gal. Embodiments of the set-delayed cement compositions may be foamed or
unfoamed or
may comprise other means to reduce their densities, such as hollow
microspheresõ
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 to 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
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ordinary skill in the .art, with the benefit of this disclosure, will
recognize the appropriate
density for a particular application.
[00191 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 one day
(e.g., about 1
day, about 2 weeks, about 2 years or more) at room temperature (e.g, about 800
1') in
quiescent storage. For example, the set-delayed cement compositions may remain
in a
purapable 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 1 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 ("130),
as measured on a pressurized consistorneter in accordance with the procedure
for
determining cement thickening times set forth in API RP Practice 1013-2,
Recommended
Practicefir Testing Well Cements, First Edition, July 2005.
[00201 When desired for use, embodiments of the set-delayed cement
compositions
may be activated (e.g., by combination with a cement set 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 aecelerate
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 ranting between any of andior 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.
[00211 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-force
per square inch (psi). Non-destructive methods may employ a UCATm Ultrasonic
Cement
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Analyzer, available from Farm Instrument Company, Houston, TX, Compressive
strength
values may be determined in accordance with API RP 1013-2, RecoMmended
Practice lbr
Testing Well Cements, First Edition, July 2005.
100221 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 5tX)0
psi, alternatively,
from about 100 psi to about 4500 psi, or alternatively from about 500 psi to
about 40(K) 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 IF,
[00231 in some embodiments, the set-delayed cement compositions may have
desirable thickening times after activation. Thickening time typically refers
to the time a
such as a set-delayed cement coniposition, 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 1013,1, may be used to measure whether a fluid
is in a
puropable 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 500 F to about 400' F. alternatively, in a range of from
about 800 F to
'about 250' F. and alternatively at a temperature of about 1400 F.
[00241 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, amities such as triethanolamine, diethanolamine;
silicates such as
sodiiim silicate; zinc formate; calcium acetate; Groups IA and HA 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 nanarneters); polyphosphates;
and
combinations 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 sulfite, nod 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,
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phosphate salts, and combinations thereof, Specific examples of polymeric
metaphosphate
salts that may be used include sodium hexametaphosphate, sodium
trimetaphosphate, sodium
tetrametaphosphate, sodium pentametaphosphate, sodium heptametaphosphate,
sodium
oetametaphosphate, and combinations thereof. A specific example of a suitable
cement set
activator comprises a combination of sodium stiltine and sodium
hexametaphosphate. in
particular embodiments, the cement set 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,
[9025] 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 porzolan. 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 tbr a chosen application.
[0026] Embodiments of the set-delayed cement compositions may comprise the use
of two separate component slurries that are combined to form a two-part set-
delayed cement
composition. Embodiments of the two-part set-delayed cement may comprise
providing a
pozzolan slurry and a lime slurry which are kept separate in lieu of adding
cement set
retarders. The two-part set-delayed cement composition may utilize two
individual slurries in
a manner such that neither slurry is able to hydrate and therefore set
independently.
Therefore, each individual slurry of the two-part set-delayed cement
composition should
remain in a set-delayed state (i.e. remaining in a pumpable fluid state for at
least about one
day [e.g., at least about I day, about 2 weeks, about 2 years or morel at room
temperature in
quiescent storage). Embodiments of the two-part set-delayed cement composition
may
comprise two component slunies. One component Slurry comprises a pozzolan and
water.
The other component slurry comprises lime and water. In embodiments: each
Slurry may be
stored at a well site or other storage site until needed. When needed, the two
component
slurries may be mixed together prior to or while pumping downhole. The
combined slurry
may then thicken and set within a desired period of time.
[0027] Advantageously, the use of a two-part set-delayed cement composition
may
allow .for quicker setting at lower temperatures (e.g. temperatures less than
140 1.).
Furthermore, because the reactive components of the two-part set-delayed
cement
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composition are kept separate, additional additives or higher concentrations
of additives (e.g.
additional silica sources, see above) may be added to the two-part set-delayed
cement
composition without risk of premature setting or gelation.
[002S1 Embodiments of the two-part set-delayed cement compositions may
generally comprise two component slurries, a pozzolan slurry and a lime
slurry. Both
component slurries comprise water. Optionally, either component slurry may
further
comprise a dispersant and/or a cement set retarder. Advantageously,
embodiments of the
two-part set-delayed cement compositions may be capable of remaining in a
pumpable fluid
state for an extended period of time. For example, the two-part set-delayed
cement
compositions may remain in a pumpable fluid state for at least about 1 day or
longer.
Advantageously, the two-part set-delayed cement compositions may develop
reasonable
compressive strengths after activating (e.g. by mixing the two component
slurries) at
relatively low temperatures. While the two-part 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 hole
static
temperatures, e.g., temperatures less than about 200" F or ranging from about
100' 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.
100291 Embodiments of the pozzolan slurry comprise a pozzolan. Any pozzolan is
suitable fOr use in embodiments. Example embodiments comprising a pozzolan may
comprise fly ash, silica fume, metakaolin, diatomaceous earth, a natural
pozzolan (e.g.,
pumice), or combinations thereof. in a two-part set-delayed cement composition
embodiment, the pozzolan may be a non-hydraulic pozzolan, i.e. a pozzolan that
will not
react when mixed with water in the absence of hydrated lime to form a
cementitious
material. By way of example, some types of Class C fly ash may not be suitable-
for use in a
two-parr set-delayed cement composition embodiment, because Class C fly ash
may
comprise lime and will therefore react when mixed with water to become
eertientitious,
100301 Embodiments of the pozzolan slurry may comprise fly ash. A variety of
fly
ashes may be suitable, inclading, fly ash classified as 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 and may thus be
unsuitable fOr use
in the pozzolan slurry as it may undesirably set when mixed with the water.
Class F fly ash
generally does not contain a sufficient amount of lime to induce a
cementitious reaction,
therefore, should remain in a pumpable fluid state when mixed with water,
Suitable
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examples of fly ash include, but are not limited to, POZMIX1. A cement
additive,
commercially available from Hall ihurain Energy Services, Inc., Houston,
Texas.
[00311 Embodiments of the pozzolan slurry may comprise metakablin. Generally,
metakaolin is a white pozzolan that may be prepared by heating kaolin clay,
for example, to
temperatures in the range of about 6000C to about g000 C.
100321 Embodiments of the pozzolan slurry may comprise a natural pozzolan.
Natural pozzolans are genemlly present on the Earth's surface and set and
lhattlen in the
presence of hydrated lime and water. Embodiments comprising a natural pozzolan
may
comprise pumice, diatomaceous earth, volcanic ash, opaline shale, tuff, and
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 1 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 WO large may not be
effectively
suspended in the compositions and may be less reactive dud to their decreased
surface area.
One of ordinary skill in the art, 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,
[0033] Embodiments of the pozzolan slurry comprise water. The water used in
embodiments of the pozzolan slurry may be from any source provided that it
does not
contain an excess of compounds that may undesirably affect other components in
the
pozzolan slurry. For example, the pozzolan slurry 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
he 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 individually present
in the
pozzolan slurry in an amount in the range of .1Tom about 33% to about 200% by
weight of the
pozzolan. In certain embodiments, the water may be present in the pozzolan
slurry in an
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amount in the range of from about 35% to about 85% 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 fir a chosen application. Embodiments of the pozzolan slurry
may comprise
additives suitable for use in subterranean cementing operations. Any additive,
including
additional silica sources, may be added to the pozzolan slurry. Examples of
additives
include, but are not limited to: weighting additives, lightweight additives,
gas-generating
additives. Mechanical-property-enhancing additives, lost-circulation
materials, filtration-
control additives, fluid-loss-control additives, defoaming agents, foaming
events, thixotropic
additives, dispersants, cement set activatotslaccelerators, cement set
retarders, and
combinations thereof. In embodiments of the pozzolan slurry, one or more of
these additives
may be added to the pozzolan slurry before or after storing. Additionally one
or more of
these additives may be added to the pozzolan slurry before or after mixing the
pozzolan
slurry with the lime slurry. A person having ordinary skill in the art, with
the benefit ofthis
disclosure, should readily be able to determine the type and amount of
additive useful fbr a
particular application and desired result.
[0034] Embodiments of the lime slurry 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 form the. hydrated Hine. The hydrated lime may be included in
embodiments of
the lime slurry to form a hydraulic composition with the pozzolan. For
example, the hydrated
lime may be included in a poz.zolan-to-hydrated-lime weight ratio of about
10:1 to about 1:1
or a ratio of about 3:1 to about 5:1, based on the combined mix of both
component slurries.
Where present, the lime slurry may comprise an amount of hydrated lime between
about
10% to about 100% by weight of the pozzolan present in the pozzolan slurry. In
some
embodiments, the hydrated lime may be present in the lime slurry 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 the pozzolan shirty. In
some
embodiments, the cementitions components present in the two-part set-delayed
cement
composition may consist essentially of the pozzolan and the hydrated lime. For
example, the
cementitious components may primarily comprise the pozzolan (e.g., pumice) and
the
hydrated lime without any additional cementitions 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.
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100351 Embodiments of the lime slurry comprise water. The water used in
embodiments of the lime slurry may be from any source provided that it does
not contain an
excess of compounds that may undesirably affect other components in the lime
shirty. For
example, the lime slurry 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 he 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 individually present in the lime slurry
in an amount
in the range of from about 33% to about 200% by weight of the lime. In certain
embodiments, the water may be present in the lime slurry in an amount = in the
range of from
about 35% to about 70% by weight of the lime. With the benefit of this
disclosure one of
ordinary skill in the art will recognize the appropriate amount of water .for
a chosen
application,
[00361 Embodiments of the lime slurry may comprise additives suitable for use
in
subterranean cementing operations. Any additive, including additional silica
sources, may be
added to the lime slurry. Examples of such additives include, but are not
limited to:
weighting additives, lightweight additives, gas-generating additives,
mechanical-property-
enhancing additives, lost-circulation materials, filtration-control additives,
fluid-loss-control
additives, defbaming agents, foaming agents, thixotropic additives,
dispersants, cement set
activators/accelerators, cement set retarders, and combinations thereof. In
embodiments of
the lime slurry, one or more of these additives may be added to the lime
slurry before or after
storing. Additionally one or more of these additives may be added to the lime
slurry before
or after mixing the lime slurry with the pozzolan slurry. 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 useful for a particular application and desired result,
[0037] Embodiments of the two-part set-delayed cement compositions may
comprise a cement set retarder as described above. Any cement set retarder
described in
embodiments of the set-delayed cement compositions above may also be suitable
for
embodiments of the two-part set-delayed cement compositions. Cement set
retarders may be
added to one or both component slurries or may be added to the combined
slurry. Amongst
.other reasons, cement set retarders may be added to increase thickening time.
In some
embodiments, the cement set retarder may be present in the component slurries
(either
individually or in both) or in the combined slurry of the two-part 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 cement set retarder may be present in
an amount
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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 -for
the
pozzolan slurry or by weight of the lime for the lime slurry. One of ordinary
skill M the art,
with the benefit of this disclosure, will recognize the appropriate amount of
the cement set
retarder to include for a chosen application.
[0038] As previously mentioned, embodiments of the two-part set-delayed cement
compositions may optionally comprise a dispersant as described above. Any
dispersant
described in embodiments of the set-delayed cement compositions may also be
suitable for
embodiments of the two-part set-delayed cement compositions. In some
embodiments, the
dispersant may be included in one or both of the component slurries or in the
combined
slurry of the two-part set-delayed cement compositions in an amount in the
range of from
'about 0.01% to about 5% by weight of the pozzolan or the hydrated lime. In
specific
embodiments, the dispersant may be present in an amount ranging between any of
and/or
including any of about 0.01%, about 0A%, about 0.5%, about 1%, about 2%, about
3%,
about 4%, or about 5% by weight of the pozzolan or the hydrated lime. 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.
[0039] Embodiments may include the addition of a cement set activator to the
two-
part set-delayed cement compositions as described above. The cement set
activator may be
included to accelerate setting times, amongst other reasons. Any cement set
activator
described in embodiments of' the set-delayed cement compositions may also be
suitable for
embodiments of the two-part set-delayed cement compositions. Any cement set
activator
may be added to either one or both of the component slurries as well as to the
combined
slurry in an amount sufficient to accelerate the setting of the combined two-
part. set-delayed
composition if added to only a component slurry, the acceleration of the set
time should
happen when the component slurries are mixed). In embodiments, the cement set
activator
may be added to the component slurries (either individually or both) or to the
combined
slurry of the two-part set-delayed 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 the component slurries (either individually or in
both) or in the
combined slurry of the two-part set-delayed cement composition 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.
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10040] Those of ordinary skill in the art will appreciate that embodiments of
the
two-pan set-delayed cement compositions generally Should have a density
suitable for a
particular application. By way of example, the combined two-part set-delayed
cement
compositions may have a density in the range of from about 4 pounds per gallon
(Ibigar) to
about 20 lb/gal. In certain embodiments, the combined two-patt set-delayed
cement
compositions may have a density in the range of from about 8 lb/gal to About
17 lb/gal.
Embodiments of the two-part set-delayed cement compositions may be foamed or
unlbamed
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 fbrmation.
In embodiments, weighting additives may be used to increase the density of the
two-part set-
delayed cement compositions. Examples of suitable weighting additives may
include barite,
hematite, hausmannite, calcium carbonate, siderite, iimenite, 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.
[0041] As previously mentioned, the component slurries of the two-part set-
delayed
cement compositions may have a delayed set in that they remain in a pumpable
fluid State for
at least one day (e.g.. about I day, about 2 weeks, about 2 years or more) at
room
temperature (e4., about 80" F) in quiescent storage. For example, the
component slurries of
the two-part 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
component: slurries of the two-part 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 fbrth in API RP
Practice 10B-2,
Recommended Pmealeelbr Testing Well Cemenn, First Edition, July 2005.
[0042] When desired for use, embodiments of the two-part set-delayed cement
compositions may be activated (e.g., by combining the pozzolan and lime
slurries) to set into
a hardened mass. By way of example, embodiments of the two-part 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 two-part set-
delayed
cement compositions may set to form a hardened mass in a time period ranging
between any
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of andior including any of about I day, about 2 days, about 4 days, about 6
days, about 8
days, about 10 days, Or about 12 days.
[00431 In some embodiments, the two-part 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 two-part
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 (1-ms-sectional area resisting the load and is reported in
units of pound-three
per square inch (psi). Non-destructive methods may employ a UCATs` Ultrasonic
Cement
Analyzer, available from Faim Instrument Company, Houston, TX. Compressive
strength
values May be determined in accordance with API RP 10B-2, Recommended Practice
fir
&sling Well Cemons, First Edition, July 2005.
[0044] By way of example, the two-pan 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 two-part 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.
[00451 In some embodiments, the two-part set-delayed cement compositions may
have desirable thickening times after activation, Thickening time typically
refers to the time
fluid, such as a set-delayed i:ttnent 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
athrementioned API RP Practice 1013-2, 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 Bc, In some embodiments, the
two-part set-
delayed 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 between
about 1,000 psi to about 20,000 psi and temperatures in a range of from about
50Q F to about
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400'F, alternatively, in a range of from about 80' F to about 2500 F, and
alternatively at a
temperature Of about 1400 F.
[0046] Embodiments of the two-part set-delayed cement. composition may be used
to displace a prior placed fluid (i.e. embodiments of the two-part set-delayed
cement
composition may be used as a spacer fluid). The pozzolan slurry of the two-
part set-delayed
cement composition, comprising a pozzolan and water, may be similar in
composition to
conventional spacer fluids. Because of this similarity, the pozzolan slurry
may be used as a
spacer fluid in embodiments, The pozzolan slurry may be used to displace a
drilling mud,
separate cement from a drilling mud, displace another treatment fluid,
separate the drilling
mud from a treatment fluid, and/or separate cement from a treatment fluid,
Advantageously,
the use of the pozzolan slurry as a spacer fluid may condition the
subterranean formation
with part of the same composition that ultimately May be used as the annular
Sealant.
Therefore, the risk of incompatibilities 'between sealant and Spacer fluid may
be reduced.
[0047] In embodiments wherein the poz2Aan component slurry of the two-part set-
delayed cement composition may be used as a spacer fluid, the density of the
pozzolan slurry
may be adjusted by the addition of water and/or a viscosifier. The water and
viscosifiers may
he added in any amount to achieve the appropriate density to provide a
suitable theological
hierarchy for a given application. An example of a suitable viscosifier is SA-
l015
suspending agent available from Halliburton Energy Services, Houston, TX.
Additionally,
weighting agents may be added to adjust the density as may be appropriate to
maintain a
suitable theological hierarchy. One of ordinary skill in the art, with the
benefit of this
disclosure, will recognize the appropriate density and method Of density
adjustment
necessary for a chosen application.
[0048] Moreover, in embodiments wherein the pozzolan Slurry may be used as a
spacer fluid, the spacer fluid may be foamed with a foaming additive and/or a
gas. The
spacer fluid may be foamed, for example, to provide a spacer fluid with a
reduced density.
The as used for fiaarning the composition may be any suitable gas flar
foaming, including,
but not limited to: air, nitrogen, or combinations thereof. Generally, the gas
should be
present in an amount sufficient to form the desired amount or quality of foam.
Foaming
additives may be included in embodiments to, for example, facilitate foaming
and/or
stabilize the resultant foam formed therewith. Examples- of suitable foaming
additives
include, but are not limited to: mixtures of an ammonium salt of an alkyl
ether sulfate, a
cocoamidopropyl betaine surfactant, a cocoamidopropyl dimethylamine oxide
surfactant,
sodium chloride, and water, mixtures of an ammonium salt of an alkyl ether
sulfate
surfactant, a cocoamidopropyl hydrox,ysultaine surfactant, a cocoamidopropyl.
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dimethylamine oxide surfactant, sodium chloride, and water; hydrolyzed
keratin; mixtures of
an etboxylated alcohol ether sulfate surfactant, an alkyl or alkene
amidopropyl betaine
surfactant, and an alkyl or alkene dimethylamine oxide surfactant; aqueous
solutions of an
alpha-oleftnic sulfonate surfactant and a betaine surfactant; and combinations
thereof. An
example Of a suitable foaming additive is ZONESEALANTrm 2000 agent, available
from
Halliburton Energy Services, Houston, TX.
[0049] ft is to be understood, that any additive, component, or embodiment
disclosed
herein may additionally be used or combined with embodiments of the two-part
set-delayed
cement composition. For example, previously described additives such as
weighting agents,
lightweight additives, gas-generating additives, mechan ica 1-property-
enhancina additives,
lost-circulation materials, filtration-control additives, fluid-loss-control
additives, defoaming
'agents, foaming agents, thixotropic additives, dispersants, cement set
retarders, cement set
activators/accelerators, additional silica sources, and the like, and
combinations thereof may
all be used with embodiments of the pozzolan slurry, lime slurry, and the
combined slurry of
the two-part set-delayed cement compositions in the same manner as previously
described.
The two-part set-delayed cement composition embodiment is therefore inclusive
of every
additive, component, or other embodiment that may be used in combination;
including the
use of cement set activators and cement set. retarders. For example, the two-
part set-delayed
cement composition may comprise a cement set activator to accelerate setting
time and
enhance early strength, additionally or alternatively, the two-part set-
delayed cement
composition may comprise a cement set retarder to delay thickening time. Any
additive,
component: or embodiment disclosed herein may be added to one or both of the
component
slurries or to the combined slurry of the two-part set-delayed cement
compositions.
Moreover, any additive, component, or embodiment disclosed herein that is used
with the
pozzolan slurry, the lime slurry, or the combined slurry may also be used with
embodiments
of the two-part set-delayed cement composition that comprise a spacer fluid.
[0050] As will be appreciated by those of ordinary skill in the art
embodiments of
the set-delayed cement compositions including the two-part set-delayed cement
compositions may be used in a variety of subterranean operations, including
primary and
remedial cementing. In some embodiments, a set-delayed cement composition (in.
the two-
part set-delayed cement composition embodiments, this may he a combined two-
part set-
delayed cement composition) may be provided that. comprises water, a pozzolan,
hydrated
lime, a cement 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
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introduction into any 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, addition of a cement set accelerator to the set-delayed
cement
composition or the mixing of the two component slurries of the two-part set-
delayed cement
composition.
100511 In some embodiments, a set-delayed cement composition may be provided
that comprises water, a pozzoltin, hydrated lime, a cement set retarder, and
optionally a
dispersant. The set-delayed cement composition may be stored, for example, in
a vessel or
other suitable container. In alternative embodiments a two-part set-delayed
cement
composition may be provided that comprises a lint part comprising a pozzolan
and water
component slurry and a second part comprising a hydrated lime and water
component slurry.
The first and second parts may individually stored and combined prior to or
while pumping
downhole. The set-delayed cement compositions may be permitted to remain in
storage for a
desired time period. For example, the set-delayed cement compositions may
remain in
storage for a time period of about I day, about 2 weeks, about 2 years, or
longer. For
example, the set-delayed cement compositions 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 up to about 2 years.
In some
embodiments, the set-delayed cement composition may remain in storage for a
time period in
a range of from about I day to about 2 years or longer, Thereafter, the set-
delayed. cement
composition may he activated, for example, by mixing the two-component
slurries together,
introduced into a subterranean formation, and Allowed to set therein.
100521 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 4 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.
f00531 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 art
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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
microarmulus).
100541 An embodiment comprises a method of cementing comprising: providing a
pozzolan slurry comprising a pozzolan and water; providing a time slurry
comprising
hydrated lime and water; allowing the pozzolan slurry and the time slurry to
remain separate
'for about one day or longer; mixing the pozzolan slurry and the lime slurry
to limn a cement
composition; and allowing the cement composition to set.
[0055] An embodiment comprises a method of displacing a fluid in a
subterranean
formation comprising: providing a pozzolan slurry comprising a pozzolan and
water;
providing a lime slurry comprising hydrated lime and water; introducing at
least a portion of
the pozzolan slurry into a wellbore that penetrates a subterranean formation
such that the
pozzolan slurry displaces at least one fluid from the Webore; activating the
set-delayed
cement composition by mixing at least a portion of the pozzolan slurry and at
least a portion
of the lime slurry to form a cement, composition; introducing the cement
composition into a
subterranean formation; and allowing the cement composition to set in the
subterranean
formation.
[0056] An embodiment comprises a system for cementing comprising: a pozzolan
slurry comprising a pozzolan and water; a lime slurry for combination with the
pozzolan
slurry to form a cement composition comprising hydrated lime and water.
[0057] Referring now to FIG. I, preparation of a set-delayed cement
composition in
accordance with example embodiments will now be described. FIG. 1 illustrates
a system 2
for preparation of a set-delayed cement composition and delivery to a wellbore
in accordance
with certain embodiments. As shown, the set-delayed 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 limesettable material
with the
water as it is being pumped to the wellbore. In two-part set-delayed
embodiments, mixing
equipment (e.g., a jet mixer, re-circulating mixer, and/or a batch mixer) may
be used to mix
the combined two-part set-delayed cement composition slurry.
[0058] An example technique lOr placing a set-delayed 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 set-
delayed cement
composition in accordance with certain embodiments. It should be noted that
while FIG. 2A
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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 the scope of
the disclosure.
As illustrated by MG. 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.õ FIG. I) as will be apparent to
those of ordinary
skill in the art. The cementing unit 12 may pump a set-delayed cement
composition 14
through a feed pipe 16 and to a cementing head 18 which conveys the set-
delayed cement
composition 14 downhole..
[00591 Turning now to FIG. 213, the set-delayed 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 welltwe
22 is shown extending generally vertically into the subterranean formation 20,
the principles
described herein are also applicable to wellborns that extend at an angle
through the
subterranean 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 wellborn 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 easing
26. One or more centralizers 34 may be attached to the casing 30. for example,
to centralize
the easing 30 in the wellborn 22 prior to and during the cementing operation.
1006011 With continued reference to FIG. 28, the set-delayed cement
composition 14
may be pumped down the interior of the casing 30. 'fhe set-delayed cement
composition 14
may be allowed to flow down the interior of the casing :10 through the easing
shoe 42 at the
bottom of the easing 30 and up around the casing 30 into the wellborn annulus
32. The set-
delayed 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 easing 30 in
the wellbore
22. While not illustrated, Other techniques may also be utilized for
introduction of the set-
delayed cement composition 14. By way of example, reverse circulation
techniques may be
used that. include introducing the set-delayed cement composition 14 into the
subterranean
formation 20 by way of the wellbore annulus 32 instead of through the casing
30.
[0061,1 As it is introduced, the set-delayed cement composition 14 may
displace
other fluids 36, such as drilling fluids andior spacer fluids that may be
present in the interior
23
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of the casing 30 and/or the wellbore annulus 32. At least a portion of the
displaced fluids 36
may exit the wet-11)6re 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 Fla 2A. Referring again
to FIG. 213, a
bottom plug 44 may be introduced into the wellbore 22 ahead of the set-delayed
cement
composition 14, for example, to septirate the set-delayed cement composition
14 from the
fluids 36 that may be inside the casing 30 prior to cementing. Alter the
bottom plug 44
readies the landing collar 46, a diaphragm or other suitable device should
rupture to allow
the set-delayed cement composition 14 through the bottom plug 44. In FIG. 213,
the bottom
plug 44 is shown on the landing collar 46. In the illustrated embodiment, a
top plug 48 may
he introduced into the .wellbore 22 behind the set-delayed cement composition
14. The top
plug 48 may separate the set-delayed cement composition 14 from a displacement
sfluid 50
and also push the set-delayed cement composition 14 through the bottom plug
44.
[00621 The exemplary set-delayed 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 set-
delayed cement compositions. For example, the disclosed set-delayed 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 set-delayed cement compositions. The disclosed set-delayed cement
compositions
may also directly or indirectly affect any transport or delivery equipment
used to convey the
set-delayed 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 set-delayed cement compositions from one location to another, any
pumps,
compressors, or motors (e.g., topside or downhole) used to drive the set-
delayed cement
compositions into motion, any valves or related joints used to regulate the
pressure or flow
rate of the set-delayed cement compositions, and any sensors (i.e., pressure
and temperature),
gauges, and/or combinations thereof, and the like. The disclosed set-delayed
cement
compositions may also directly or indirectly affect the various downhole
equipment and
tools that may come into contact with the set-delayed cement compositions such
as, but not
limited to, wellbore casing, welthore liner, completion string, insert
strings, drill string,
coiled tubing, slickline, wirehne, drill pipe, drill collars, mud motors,
downhole motors
and/or pumps, cement pumps, surface-mounted Motors and/or pumps, centralizers,
turbolizers, scratchers, floats (c.gõ shoes, collars, valves, etc.), logging
tools and related
telemetry equipment, actuators (e.g., electromechanical devices,
hydromeclumical devices,
24
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etc.). sliding sleeves, production sleeves, plugs, screens, filters, flow
control devices (e.g.,.
inflow control devices, autonomous inflow control devices, outflow control
devites, etc.),
couplings (es., 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.
EXAMPLES
[0063] To tacilitate a better understanding of the present 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
embocliments.
Example 1
[0064] A two part set-delayed cement composition was prepared which comprised
the following component slurries:
Table I
Slurry A Compositional Makeup Slurry 13 Compositional Makeup
Component Weight. (g) Component Weight (g)
Water 175.0 Water 350.0
'Pumice 500.0 ' Hydrated Lime 350.0
Silica Additive 100.0 Weighting Agent 70.0
¨Weighting Agent 30.0 Dispersant 2,0 -----\
rDispersant :3.5
[00651 Slurry A was prepared in a Waring' blender by first adding water to the
:
blender followed by a dispersant, Liquiment t? - 5581F dispersant. The
dispersant was allowed
to fully disperse, then the pumice, silica (Silicalite cement additive), and a
weight additive
(MicroMaxr FP weight additive) were added. After all of the components were
added,
Slurry A was blended at a speed of 6000 rpm for 40 seconds to fully homogenize
the sample.
Slurry B was prepared in the same manner as Slurry A. The calculated density
of Slurry A
was 13.33 pounds per gallon (ppg) and Slurry B was 12.75 ppg
[00661 Immediately after preparation (designated Day 0) and periodically
thereafter,
the theological properties of the samples were determined using a Model 35A
Fann
Viscometer and a No. 2 spring with a Farm Yield Stress Adapter (FYSA), in
accordance with
. ,
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the procedure set forth in API RP- Practice 1013-2., Recommended Prodiee fin.
Testing Well
Cements. Dispersant. was added as needed to .maintain adequate viscosity
values. % bwoP
refers to "percent by weight of the pumice," and .% bwont. refers to "percent
by weight. of
hydrated lime."
Table 2.
Slurry A itheofogical Profile
FY.SA Readings Additional
'
Dispersant 1
3 6 100 200 300 31) 6D
(% bwoP)
t
Day 0 48 49 71 87.5 103 48 47 ¨
¨ ¨
Da!?' 3 15 27.5 42 58.5 73 21 23 0.01
!
Day 7 25.5 26.5 47.5 67.5 89 17 14 --
!
... _________________________________________________________________________
Day 40 4_5 8 56 99 143 1 1 0.10
'
Table 3
Slurry IA kheological Profile
I
MA Readings Additional
Dispersant .
3 6 100. 200 300 3D 61)
M.bwolt0
,
:
Day 0 25 /7 41 57 78 10 10 ....
,
. ,
Day 3.. 215 23 80,5 145 214 12 12 -- ,
'
.
Day-7 22 26 80,5 149.5 .220 12 .12 _
. ___________________________________ .
Day 40 3 3,5 16 .:.,. -?,-.
.1 30.5 1 1
0.02
............. ,.
[00671 To form the set:table combined slurry, 129.4 grams Of Slurry B was -
added to
500.0 grams of-Slurry A. This was performed by adding Slurry A to a Waring'
blender set to
4000 rpm and slowly pouring in Slurry El to term Slurry A13 with a final
slurry composition
of:
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Table 4
Slurry AB Compositional Makeup
. .
Component % buOP
Water 95.0
Pumice 100.0
Silica Additive 20.0
'Hydrated Lime 20.0
¨ Weight Additive ¨ 10.0
Dispersant 0.80
[0068] The calculated density of Slurry AB was 13,23 ppg. A portion of Slurry
AB
was accelerated with 10% bwoP CaC.12 by mixing 200.0 grams of Slurry A.B with
21.92
grams of 43% CaC12 solution. This Sample is shown in table -5 as accelerated.
Immediately
after preparation, the theology of the sample was measured using a Model 35A
Fann
Viscometer and a No. 2 spring with a Fan Yield Stress Adapter (FYSA), in
accordance with
the procedure set forth in API RP Practice 1013-2, Recommended Practice fOr
Testing Well
Cements.
Table 5
Slurry AB Rheological Profile
FYSA Readings
3 6 100 200 300 3D 6D
Unaccelerated 2 2 15 36 59 1 1
Accelerated 1 2 12 I 28 50 1
[00691 .After mixing the two component slurries to activate the set-delayed
cement
composition, the combined slurry was cured in a 2" by 4" plastic cylinder that
was placed in
a water bath at between about 90 F to about 150c F to form set cylinders. Then
the
destructive compressive strength (C.S.) was measured using a mechanical press
in
accordance with API RP Practice 1013-2, Recommended Practice )(Or Testing Well
Cements.
The results of this test are set tbrth in Table 6 below. The reported
compressive strengths are
an average for two cylinders of each sample_ Compressive strength measurements
were
taken at 24 hours,
100701 For comparison, a non-two part set-delayed slurry was prepared by
combining 350 grams water, 500 grams pumice, 100 grams hydrated lime, 20 grams
Micromax4 weight additive, 6,25 grams Micro Matrix cement retarder, and 3.5
grams
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Liquimene 5581F dispersant, This slurry (-NCI) was aged 35 days prior- to use,
activated
with 10% bwoP CaCl2sOlution. and cured in the water baths at the same time as-
Slurry AB.
Table 6
(ompressive Strength Tests
Slurry Temp.-( Fl Time .(firs) C.S. (psi)
AB 900 24 92
AB (accelerated) 90,0 24 .105
NCI 90.0 24 Fluid*
AB 100.0 24 98
_
AB (accelerated) 100.0 24 165
_
NCI 100.0 24 .Fluid*
AB 120.0 24 1718
NCI 120.0 24 Gel**
AB 140.0 24 2240
NCI 140.0 431
AB 150.0 24 2479
NC1 150.0 802
Slurry remained unset and tlowable
" Slurry was gelled and not I.-towable
[00711 As Example I shows, slurry AB is more active at lower temperatures than
NCI. Without being limited by theory, this effect may be due to the tack of
cement retarders
in 81.urry AB and/or the inclusion of a Silica additive.
Example 2
00721 In the previous examples the porzolan and lime slurries were mixed to
give a
hydrated lime content of 20.0% bwoP. The next example illustrates how it may
he advantageous
to mix the two parts in different ratios to produce slurries with varying lime
content. In this
example, 258.8 grams of Slurry 13 was mixed with 500,0 exams of Slurry A to
give a lime
15content of 40% bwoP:
Table .7
Slurry AB Compositional Makeup
Component bwor
Water- 1 15,0
28
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Pumice I 00.0
Silica Additive 20.0
= =
=
Hydrated Lime 40,0
Weighting Agent 14,0
'Dispersant 0.93'
[00731 After mixing, this sample was cured in a water bath at 90 V for 24
hours
then crushed to obtain a compressive strength of 150 psi. The Strength of this
sample was
about 33% greater than the sample with only 20% lime content (105 psi).
Example 3
00741 A two part set-delayed cement composition was prepared which comprised
the following component slurries:
Table 8
Slurry C Compositional Makeup Slurry D Compositional Makeup
Component Weight (g) Component Weight (g)
Water 325.0 Water 350.0
Pumice 500.0 Hydrated Lime 350,0
Weighting Agent 30.0 Weighting Agent 70.0
Dispersant 3.5 Dispersant2.0
[00751 Slurry C was prepared in a Warine blender by first adding water to the
blender followed by a dispersant, Liquimentv 5581F dispersant. The dispersant
was allowed
to hilly disperse, then the pumice and a weight additive (MicroMax''''' PI
weight additive)
w-ere added, After all of the components were added, Slurry C was blended at a
speed of
6000 rpm for 40 seconds to fully homogenize the sample. Slurry was prepared in
the same
manner as Slurry C. The calculated density of Slurry C was 13.24 pounds per
gallon (ppg)
and Slurry 13 was 12.75 ppg.
100761 immediately after preparation (designated Day 0) and periodically
thereafter,
the theological properties of the samples were determined using a Model 35A
Fann
Viscometer and a No. 2 spring with a Farm Yield Stress Adapter (FYSA), in
accordance with
the procedure set forth in API RP Practice 10B-2, Recommended Practice fitt.
Testing Well
Cements. Dispersant was added as needed to maintain adequate viscosity values.
Table 9
Slurry C ftheological Profile
29
. .
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WO 2015/035388 PCT/US2014/054794
FY$A R.eadings .
Additional
,
Dispersant
3 6 100 200 300 3.1) 61)
(% bwom =
Day 0 3 4 , -83.5 167 251 0.5 0,5 --
I
,
Day 3 14.5 16.5 1 46 75 104 7 8
. ,
Day 7 5 8 I 81 154.5 274 1 2
0,01
i. 1
:
Day 40 1 4 6.5 56.5 106 154 1.5 1.5 0.02
.
:
Table 10
Slurry D Itheologieal Profile
FYSA Readings.
Additional
Dispersant
,
3 6 100 200 300 3D 61) e/i)
bwollt.)-
, __________________________________________________________________________
Day 0 75 /7 41 57 78 10 10 ¨
_________________ ______I _____
Day 3 2L5 23 80.5 145 214 12 12 --
Day 7 11 26 80.5 149.5 220 12 17 --
Day 40 3 3.5 16 13 30.5 7 7 0.02
[0077] To form the settable combined slurry, .129.4 grams of Slurry D was
added to
500,0 grams of Slurry C. This was perfbrmed by adding Slurry C to a Waring
blender set to
4000 rpm and slowly pouring in Slurry D to -form Slurry CD with- a final
slurry composition
of:
Table 11
Slurry CD Compositional Makeup
Component 14i bwoP
___________________________________________ ,
Water 85.0
Pumice 100.0
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Hydrated Lime 20.0
Weighting Agent 10.0
Dispersant 0.80
100781 The calculated density of Slurry CD was 13.13 ppg. A pottion of Slum,
CD
was accelerated with tO% bwoP CaCl2 by mixing 2000 grams of Slurry CD with
21_51
grams of 43% CaC12 solution. This sample is shown in table 11 as accelerated.
Immediately
after Preparation, the theology of the sample was measured using a Model 35A
Farm
Viscometer and a No. 2 spring with a Fann Yield Stress Adapter (FYSA), in
accordance with
the procedure Set forth in API RP Practice 10B-2, Recommended Pro ice fir MO*
Well
Cements,
Table 12
Slurry CD ltheological Profile
FYSA Readings
3 6 100 200 I 300 3D 6D
Unaccelerated Slurry was pourable hut very thick
AcceleMted 7.5 8 ii L 14 41.5 3 3
[00791 After mixing the two component slurries to activate the set-delayed
cement
eoMposition, the coMbined slurry was cured in a 2" by 4" plastic cylinder that
was placed in
a water bath at 190 F to form set cylinders. Then the destructive compressive
strength (C.S.)
was measured using 4 mechanical press in accordance with API RP Practice 1013-
2,
Recommended practice for Testing Well Cements, The results of this test are
set Ruth in
Table 12 below. The reported compressive strengths are an average for two
cylinders of each
sample. The samples and controls were cured at 1. atmosphere, between about
90' I' to about
J50' F; compressive strength measurements were taken at 24 or 48 hours.
[00801 For comparison, a non-two part set-delayed shirty was prepared by
combining 350 grams water, 500 grams pumice, 100 grams hydrated lime, 20 grams
Micromait weight additive, 6,25 grams Micro Matrix, cement retarder, and 3,5
grams
Uquimentr 5581F dispersant.. This slurry (NCI) was aged 35 days prior to use,
activated
with 10% hwoP C1C12 solution, and cured in the water baths at the same time as
Slurry AB.
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Table 13
Compressive Strength Tests
Slurry Temp, ( F) Time (hrs) C.S. (psi)
CD 90.0 48 98
CD (activated) 90.0- 48 128
'NCI 90.0 48 Fluid*
CD 100,0 48 105
CD (activated) 100.0 48 216
NCI 100.0 48
120.0 24 78
.NCI 120.0 24 Gel"
CD 140.0 24 566
NC--r 24 431
CD 150.0 24 710
NCI 150.0 24 802
* Slurry remained unset and flowable
** Slurry was gelled and not flowable
Example 4
[0081] A two part set-delayed cement composition was prepared which comprised
the following component slurries:
Table 14
Slurry .E Compositional Makeup Slurry P Compositional Makeup
Component Weight (g) =ME Weight (g)
111=11111Mall 11111011.11113111
Pumice 600.0 111=13111111.1
Dispersant 4.5 Dispersant 0.7
[0082] Slurry E was prepared in a Warine blender by first adding water to the
blender .followed by a dispersant, Liquitnee 5581F dispersant. The dispersant
was allowed
to fully disperse, then the pumice was-addiA Alter all of the components were
added, Slurry
E was blended at a speed of 6000 rpm for 40 seconds to fully homogenize the
sample. Slurry
F was prepared in the same manner as Slurry E. 'the calculated density of
Slurry E was 13,4
pounds per gallon (ppg) and Slurry F was 12.4 ppg. Slurry E and -Slurry F were
then stored
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for 48 hours. After 48 hours neither slurry contained free water. However,
Slurry F was
slightly gelled. and required mixing to make it flowable.
[00831 At 48 hours, 778.7 grams of Slurry E was added to 175.4 grains of
Slurry F.
TIth was performed by adding Slurry E to a Waring!. blender set to 4000- rpm
and slowly
pouring in Slurry F to form Slurry EP, When they were mixed a gel formed and
LO gram of
dispersant (Liquimere 5581F dispersant) was added to make the mixture
flowable.
Table 15
Compositional Mix of Slurry FE
Mix Amount
Wt. (g) Vol. (ml.,) Density (ppg)
Slurry F. 778.7 484.2 13.4
Slurry F 175,4 118.1 12.4
[00841 The calculated density of the final slurry was 13.2 ppe. 15.0 grams Of
C9C1-2
powder (2.5% bwoN4-11.,) was added to the final slurry before placing it in a
consistometa.
The thickening time was measured as 5:38 hours at 140'F and 3000 psi. The
thickening time
was measured using a high-temperature high-pressure consistometer in
.accordance with the
procedure for determining cement thickening times set forth in API RI'
Practice I 013-2,
Recommended Pracfice /Or Testing Well Cements, First Edition, 'July 2005.
100851 It 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 or or "consist of' the
various
components and steps. Moreover, the indefinite articles "a" or "an," us used
in the claims,
are defined herein to mean one or more than one of the element that it
introduces.
[00861 For the sake of brevity, only certain ranges are explicitly disclosed
herein.
However, ranges from any lower limit may be combined with any upper limit to
mite 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 mite 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 !idling 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-b")
disclosed herein is to be understood to set forth every number and range
encompassed within
the broader range of values oven if not explicitly recited. Thus, every point
or individual
33
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.
[0087] 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 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, the
disclosure
covers all combinations of all of the embodiments. 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 referred to herein, the definitions
that are
consistent with this specification should be adopted.
34
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