ACID-SOLUBLE CEMENT COMPOSITIONS COMPRISING CEMENT KILN
OUST AND METHODS OF USE,
BACKGROUND
[0001] The preseni invention relates to cementing operations and, ore particularly,
in certain embodiments, to acid-soluble cement compositions that comprise cement kiln dust
(* C D ) and associated methods of use.
[0002] Cement compositions may be used in a variety of subterranean applications.
For example, in subterranean well construction, a pipe string (e.g., easing, liners, expandable
tubuiars, etc.) may be run into a we l bore 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 annuius between
the walls of the well bore and the exterio surface of the p pe string disposed therein. The
cement composition may set in the annular space, thereby forming an annular sheath of
hardened, substantially impermeable cement (i a cement sheath) that may support and
position the pipe string in the well bore and may bond the exterior surface of the pipe string
to the subterranean formation Among other things, the cement sheath surrounding the pipe
string functions to prevent the migration of fluids in the a u us, as well as protecting the
pipe string r om corrosion. Cement compositions also may be used in remedial cementing
methods for example, to sea cracks o holes in pipe strings or cement sheaths, t seal highly
permeable formation zones or fractures, to place a cement plug, and th like. Cement
compositions also may be used in surface applications, for example, construction cementing
[0003] n some applications, it may be desirable for the cement composition to be
aci soluble. For instance, an acid-soluble cement composition may b desirable in
applications where it is anticipated that the hardened cement will be removed in subsequent
well bore operations. One particular application includes use of an acid-soluble cement
composition to plug permeable zones in a formation that may allo the undesired flow of
fluid into, or from, the we l bore. For example, the permeable atones may result in the loss of
circulation of fluids, such as a drilling fluid or a cement composition, in the well bore or an
undesired influx of gas or water into the well bore. The permeable zones include, for
example, vugs, voids, fractures (natura l or otherwise produced) and the like. Other
applications for acid-s ub e cement compositions include, for example, the formation of
annular plugs and isolation of gravel-packed well bore intervals. Examples of acid-soluble
cement compositions include those comprising Sorei cements and Portland cements.
SUMMARY
[0004] The present invention relates to cementing operations a d, more particularly,
in certain embodiments, to acid-soluble cement compositions that comprise CKD and
associated methods of use,
[0005] An embodiment of the present invention prov ides a method of cementing
comprising: providing an acid-soluble cement composition comprising a kiln dust and
water; allowing the acid-soluble cement composition to set t form an acid-soiubie hardened
mass; and contacting the acid-soluble hardened mass with an acid.
0 6] Another embodiment of the present invention provides a method cementing.
The method of cementing may comprise placing an acid-soluble cement composition in a
subterranean formation. The acid-soluble cement composition ma comprise cement kiln
dust in an amount of 00% by weight of a total amount of ee entit o s components in the
acid-soluble cement composition and water. The method further may comprise allowing the
acid-sokible cement composit ion to set to form an acid-soluble hardened mass. The method
further may comprise contacting the acid-soluble hardened mass with an acid.
[0007] Another embodiment of the present invention provides a method of
cementing. The method may comprise placing an acid-soluble cement composition in a
subterranean formation. The acid-soluble cement composition may comprise ce ent kiln
dus and water, wherein the acid-soiubie cement composition is free of any acid-soluble
tillers. The method further may comprise allowing the acid-soluble cement composition to
set to form an acid-sol e hardened mass. The method further may comprise contacting the
acid-soluble hardened mass with an acid.
[0008] The features and advantages of the present: invention wil be readily apparent
to those skilled in the art. While numerous changes may be made by those skilled in the art,
such changes are within th spirit of the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0009] The present invention relates to cementing operations and, more particularly,
in certain embodiments, to acid-soluble cement compositions that comprise C D a d
associated methods of use There may be several potential advantages to the methods and
compositions of the present invention, only som of which may be alluded to herein. One of
the many potential advantages o f embodiments o f the present invention is tha the inclusion
of the CKD in the acid-soluble cement compositions should reduce the amount of, or
potentially eliminate, a higher cost additive, such as Portland or Sorel cement, resulting in a
more economical cemen composition. Another potential advantage of embodiments of the
present invention is that reduction of the amount of Portland cement should reduce the
carbon footprint of the acid-soluble cement compositions.
[0010] Embodiments of the ae c-so bi cement compositions of the present
invention may comprise CKD. Additional embodiments of the acid-soluble cement
compositions may comprise a hydraulic cement; a component selected from the group
consisting of CKD, a natural poz o an and a combination thereof: and water. In an
embodiment, the hydraulic cement ma comprise Sorel cement. In another embodiment, the
cement compositions may further comprise an acid-soluble filler. in additional
embodiments, the cement compositions may comprise CKD and be tree of any acid-soluble
fillers. n yet another embodiment, the cement compositions may further comprise a source
o f calcium ions (e.g., hydraied lime).. Other optional additives may also be included in
embodiments of the cement compositions of the present invention as desired, including, but
not limited to. .fly ash, s ag cement, metakaolin, shale, zeolite, combinations thereof, and the
like, Additionally, embodiments of the cement compositions of the present invention may be
foamed and/or extended as desired by those of ordinary skill in the art.
[00 i 1] The acid-soluble cement compositions of the present invention should have a
density suitable .for a particular application as desired by those of ordinary skill in the art,
with the benefit of this disclosure in some embodiments, the cement compositions of the
present invention may have a density in the range of from about 8 pounds per gallon ("ppg")
to about 16 ppg. n other embodiments, the cement compositions ma be foamed to a
density in the range of rom about 8 ppg to about 1.3 ppg.
[0012] Embodiments of the acid -soluble cement compositions of the present
invention ma comprise a hydraulic cement A variety of hydraulic cements may be utilized
in accordance with the present invention, including, but not limited to, those comprising
calcium, aluminum, silicon, oxygen, iron, and/o sulfur, which set and harden by reaction
with water. Suitable hydraulic cements include, but are not limited to, Sore cements.
Portland cements, po o lana cements, gypsum cements, high alumina content cements, slag
cements, silica cements, and combinations thereof. In certain embodiments, the hydraulic
cement may comprise a Portland cement. In some embodiments, th Portland cements that
are suited for use in the present invention are classified as Classes A, C, G, and cements
according to American Petroleum institute, AP Specification for Materials and Testing for
Well Cements, API Specification 10, Fifth E , July 1, 1990. n addition, n some
embodiments, cements suitable for use in the present invention may be classified as A T
Type I , 1, o 1 As wi l be discussed in more detail below, acid-soluble fillers can be used
with hydraulic cements {such as Portland cement) thai do harden i to an acid-soluble mass.
[0013] Where present, the hydraulic cement generally may be included in the acidsoluble
cement compositions in an amount sufficient to provide the desired compressive
strength, density, and/or cost, lit accordance with embodiments, at least a portion o f the
hydraulic cement and potentially eve all of the hydraulic cement may be replaced with
C D and/or a natural pozzofan. n an embodiment, at a least a portion o f the hydraulic
cement i replaced with C D and/or a natural pozzolan. in some embodiments, the
hydraulic cement may be present in th cement compositions of the present invention in an
amount in the range of 0% to about 99% b weight o f cementitious components. As used
herein, the term by weight o f cementitious components" refers to the concentration o f the
particular component by weight o f total amount o f cementitious components included in
the cement composition, Cementitious components include those components or
combinations o f components o f the cement compositions that hydraulic-ally set, or otherwise
harden, to develop compressive strength, including, for example. Sore! cement, Portland
cement, CKD, fl ash, pumice, slag, lime, shale, and the like. For example, the cementitious
components may comprise the hydraulic cement and any additional cementitious
components that may be present in the acid-soluble cement composition. The hydraulic
cement may b present, in certain embodiments, in a . amount of about 5%, about 0%,
about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about
50%, about 55%, about 60%, about 65%, about 0%, about 75%, about 80%, about 90%, or
about 95%, n an embodiment, the hydraulic cement may be present in a amount in the
range o f 0% to about 95% by weight of cementitious components, in another embodiment,
the hydraulic cement may be present in an amount in the range o f about 20% to about 95%
b y weight o f cementitious components. n yet another embodiment, the hydraulic cement
may be present in an amount in the range o f about 50% to about 90% by weight o f
cementitious components. One o f ordinary skill in the a , with the benefit of this disclosure,
will recognize the appropriate amount of the hydraulic cement to include for a chosen
application
[00 4] An example of a suitable hydraulic cement comprises a Sorel cement Sorel
cements typically include magnesia-based cement systems formed from a mixture of
magnesium oxide and magnesium chloride. However, as used herein, the term "Sorel
cement" is intended to encompass any of a variety of metal oxides and soluble salts which
together form a hydraulic cement, n the presence of water, the metal oxide and the soluble
salt forming the Sorel ceme t should solidify into an acid-soluble mass. Embodiments of the
Sorel cements should rapidly develop a desirable compressive strength, in accordance with
embodiments, at least a portion of the Sorel cement may be replaced with C D and/or a
natural po so an. n a embodiment, at a least portion o f the soluble salt is replaced with
CKD and/or a natural po o an.
[ 0 In an embodiment, the Sorel cement comprises a metal oxide. In one
particular embodiment, the Sorel cement comprises an alkaline earth metal oxide, such as
mag esium oxide. A suitable metal oxide is THERMATE LT additive, available from
Halliburton Energy Services, inc. The metal oxide present in the Sorel cement should have
an activity level sufficient to provide the desired reactivity. For example, the higher the
activity level of the metal oxide, the fester the reaction of th metal oxide with the other
components of the Sorel cement to -form the hardened mass. The activity level of the metal
oxide may vary based on a number of factors. For example, the particle size differential of
the metal oxide particles may affect the activity level. A smaller particle size differential may
result in a higher activity level due, inter alia, to a greater surface area. Another factor that
may affect the activity level of the metal oxide is a sintering process. By varying the heat
applied during, and time of. the sintering process, metal oxide with varying activity levels
may be provided. Metal oxide that has not been treated by a sintering process may have a
very high activity level, and thus it may be highly reactive in the Sorel cements. n an
embodiment, a relatively more reactive metal oxide may be desired, such as where it may be
desired to have a cement composition with a relatively short set time, for example, whet)
desired to rapidly sea off a permeable zone. n an alternative embodiment, a relatively less
reactive metal oxide may be desired, for example, where a delay may be desired between
mixing the cement composition and the formation of a hardened mass.
[0 ] A wide variety of soluble salts are suitable for use in the Sorel cement,
including metal chlorides. .In one embodiment, the Sorel cement comprises an alkaline earth
metal chloride, such as magnesium chloride. An example of a suitable magnesium chloride
is C-TEK additive, available .from Halliburton Energy Services, Inc. I an alternative
embodiment, the Sore! cement comprises magnesium sulfate or ammonium mono or dibasic
phosphate.
[0 7] In an embodiment, the Sore! cement ma comprise the metal oxide and the
soluble salt in a metal-oxide-to-soluble-salt ratio of about 3:1 to about 1:3. in another
embodiment, the metai-oxide-to-aoiuble-sait ratio may range from about 2:1 to about \ :2. n
yet another embodiment, the meial~oxide~io~soluble~saIt ratio may range from about .5 1 to
about : 1.5 One of ordinary skill in the art will recognize the appropriate ratio of the metal
oxide and soluble salt to include for a particular application.
[001 ] Embodiments of the acid-soluble cement compositions generally may
comprise CKD, which is a material generated in the manufacture of cement CKD, as that
term is used herein, refers to a partially calcined kiln feed which is removed from the gas
stream a d collected, for example, in a dust collector during the manufacture of cement.
Usually, large quantities of CKD are collected i the production of cement that are
commonly disposed of as waste. Disposal of the CKD as waste can add undesirable costs to
the manufacture of the cement, as well as the environmental concerns associated with its
disposal. The chemical analysis of CKD fro various cement manufactures varies
depending on a umber of factors, including th particular kiln feed, the efficiencies of the
cement production operation, the associated dus collection systems. CKD generally
may comprise variety of oxides, such as SiO A O3, , Ca.0, gO S 3, a . and
0 . The term "CKD" Is used herein to mean cement kiln dust made as described above
and equivalent forms of cement k iln dust made in other ways,
f00l9| The CKD generally may exhibit cementitious properties, in that it may set
and harden i n the presence of water. I accordance with embodiments of the present
invention, the CKD may be used, among other things, to replace higher cost cementitious
components, such as Portland cement and/or Sore! cement, resulting in more economical
cement compositions n addition, substitution of the CKD for the Portland and/or Sore
cement should result in a cement composition w th a reduced carbon footprint.
[0020] The CKD may be included in the acid-soluble cement compositions in an
amount sufficient to provide the desired compressive strength, density, cost reduction, and/or
reduced carbon footprint. In some embodiments, the CKD may be present in the cement
compositions of the present invention in a amount in the range of from about % to 100%
by weight of cementitious components. For example, the CKD may be present in an amount
of about 5%, about %, about % , about 20%, about 25%, about 30%, about 35%, about
40% about 45%, about 50%, about 55%, about 60%, about 05%, about 70%, about 75%,
about 80%, about 90%, or about 95%. h one embodiment;, the CKD may be present an
amount in the range of from about 5% to about 99% by weight of ee entit o s components.
n another embodiment, th KD may be present in an amount in the range of from about
5% to about 80% by weight of eementitious components, in yet another embodiment, the
CKD may he present in an amount in the range of from about 50% to about 80% by weight
of eementitious components. One of ordinary skill i th art, with the benefit of this
disclosure, will recognize the appropriate amount of CKD to include or a chosen
application.
[0021] While the preceding description describes CKD, the present invention is
broad enough to encompass the use of other part ially calcined kiln feeds that may be present
in embodiments of the cement compositions of the present invention in an amount in a range
of form about 1% to abou 0% by weight of eementitious components. For example,
embodimen ts of the acid-soluble cement compositions may comprise lime kiln dust, which is
a materia! that is generated during the manufacture of lime. The term "lime kiln dust"
typically refers to partially calcined kiln feed which can be removed from the gas stream
and collected, for example, in a dust collector during the manufacture of lime. The chemical
analysis of lime kiln dust from various Hme manufactures varies depending on a number of
factors, including the particular limestone or dolon iii limestone feed, the type of kiln, the
ode of operation of the kiln, the efficiencies of the lime production operation, and the
associated dust collection systems. Lime kiln dust generally may comprise varying amounts
of free Hme and free magnesium, lime stone, and/or doiomitic limestone and a variety of
oxides, such as S A 1 0 CaO, gO, SO,, a Q, and . and other
components, such as chlorides.
[0022] Embodiments of the acid-soluble cement compositions may further comprise
a natural pozzoian. Natural po o an are generally present on the Earth's surface and set
and harden in the presence of hydrated lime and water. Examples of natura po o ans
include pumieite, diatomaceous earth, volcanic ash, opaline shale, tuff, and combinations
thereof. Generally, pumieite is volcanic rock thai exhibits eementitious properties, in that
it may set and harden in the presence of a source of calcium ions and water. Hydrated lime
may b used in combination with the pumieite, for example, to provide sufficient calcium
tons for the pumieite to set The natural pozzoian may be used, among other things, to
replace higher cost eementitious components, such as Portland or Sorei cement, in
embodiments of the sealant compositions, resulting in mor economical sealant
compositions. n addition, substitution of the. natural pozzoian for the Portland cement
and/or Sore cement should result in a cement composition with a reduced carbon footprint.
[0023 ] Where present, the natural pozzolan may be included in an sufficient
to provide the desired compressive strength, density, cost reduction and/or reduced carbon
footprint fo r a particular application. n some embodiments, the natural pozzo!an be
present in the acid-soluble cement compositions of the present invention in an amount in the
range of from about % to about 100% by weight o f eementitious components. For
example, the natural pozzolan may be present in an amount of about 5%, about 10%, about
15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%,
about 55%, about 60%, about 6 %, about 70% about 75%, about 80%, about 90% or about
95%, h one embodiment, the natural po olan may be present in an amount in the range of
from about 5% to abou 99% by weight o eementitious components, In another
embodiment, the natural po olan may be present in an amount i the range of from about
5% to about 80% by weight of eementitious components, in yet another embodiment, the
natural pozzolan may be present in an amount in the range of from about % to about 50%
b weight of eementitious components, in ye another embodiment, the natural pozzolan
may be present in an amount in the range of from about 25% to about 50% by weight of
eementitious components. One of ordinary skill n the art, wi t the benefit of this disclosure,
will recognize the appropriate amount of the natural pozzolan to include for a chosen
application.
[0024] The water that may be used in embodiments of the cement compositions ay
Include, for example, freshwater, saltwater (e.g., water containing one or more salts
dissolved therein), brine (e.g., saturated saltwater produced from subterranean formations),
seawater, or combinations thereof, Generally, the water ay be from any source, provided
that the wafer does not contain an excess o compounds that may undesirably affect other
components in the cement composition. In some embodimen ts, the water may be included in
an amount sufficient to form a pumpabie slurry. In some embodiments, the water may be
included in the cement compositions of the present invention in an amount in the range o
about 40% to about 200% by weight of eementitious components. In some embodiments,
the water may be included in an amount in the .range o f about 40% to about 0% by weight
of eementitious components. One of ordinary skill in the art, with the benefit of this
disclosure, wi l recognize the appropriate amount of water to include for chosen
application,
[0025 Embodiments of the cement compositions ay further comprise a source of
calcium ions, such as lime. In certain embodiments, the source of calcium ons may includ
hydrated lime. The source of calcium ions may be included in embodiments of th cement
compositions, for example to, fo r a hydraulic composition with other components of the
cement compositions, such as the pumice, fly ash, slag, and/or shale. Where present, the
ime may be included in the cement compositions i an amount sufficient for a particular
application, i some embodiments, the ime may be present in an a ou t in the range o
f o about 1% to about 40% b weight of eementitious components. For example, the li e
may be present n an amount of about 5%, about 10%, about 1.5%, about 20%, about 25%,
about 30%, or about 35%, In one embodiment, the lime may be present in an amount in the
range of from about 5% to about 20% by weight o eementitious components. One of
ordinary skill in the art, with the benefit of this disclosure, w l recognize the appropriate
amount of the lime to include for a chosen application.
[0026] Embodiments o f the acid-soluble cement compositions may further comprise
an acid-soluble filler. The acid-soluble filler may be used, for example, in compositions that
comprise Portland cement with the acid-soluble filler providing an acid-solubie component
so that the compositions ca b dissolved and removed. In an embodiment, the acid-soluble
filler is present i a cement composition comprising a Sore! cement. Examples of suitable
acid-soluble filler materials that are non-reactive with other components in the compositions,
including without limitation dolomite, magnesium carbonate, calcium carbonate, and zin
carbonate. Where used, the acid-soluble filler may be present in the acid-soluble cement
composition n a amount o f from about 0 1% to about 300% by weight of the eementitious
component. n an embodiment, the acid-soluble filler is present in an amount of from about
50% to about 400% by weight of the eementitious component in an embodiment, the acidsoluble
filler is present in an amount of f om about 0% to about 300% b weight of the
eementitious component, in. alternative embodiments, the acid-soluble cement compositions
may be free of the acid-soluble .filler in that the acid-solubie cement compositions comprises
the acid-solubie filler in a amount of about 0% by weight of the eementitious component.
One of ordinary ski in the ait, with the benefit of this disclosure, wi l recognize the
appropriate amount of the acid-soluble filler to include for a chosen appl ication,
[0027] Embodiments o f the acid-soluble cement compositions ma further comprise
f y ash, A variety of fl ashes may be suitable, including fly ash classified as Class C and
Class P fly ash according to American Petroleum institute, A P . Specification for Materials
and Testing for Well Cements, A P Specification , Fifth Ed , July 1, 90. Class C fly ash.
comprises both silica and lime s thai, when mixed with water, it should set to form a
hardened mass. Class V fly ash generally does no contain sufficient lime, so an additional
source of calcium ions is required for the Class F fly ash to form a hydraulic co position h
some embodiments, lime may be mixe with Class F fl ash in an amount in the range of
about 0.1% to about. 25% by weight o t.be fl ash. some instances, the me may be
hydrated lime. Suitable examples of fly ash include, but are no limited to., POZMiX* A
cement additive, commercially available -from Halliburton Energy Services, Inc., Duncan,
Oklahoma.
[0028] Where present, the fly ash generally may be included in the acid-soluble
cement compositions in an amount sufficient to provide the desired compressive strength,
density, and/or cost. In some embodiments, the fly ash may be present i the cement
compositions of the present invention in an amount in the range of about 5% to about 75%
by weight of cemeniitious components. n some embodiments, the fly ash may be present in
an amount in the range of about % to about 60% by weight of eementitious components.
One of ordinary skill in the art, with the benefit of this disclosure, will recognize the
appropriate amount of the fly ash to include for a chosen application.
[0029] Embodiments o f the acid-soluble cement compositions ma further comprise
a slag cement. n some embod ents a slag cement that may be suitable for use may
comprise slag. Slag generally does not contain sufficient basic materia! so s!ag cement may
further comprise a base to produce a hydraulic composition that may react with water to set
to form a hardened mass. Examples of suitable sources of bases include, but are not limited
to, sodium hydroxide, sodium bicarbonate, sodium carbonate, lime, and combinations
thereof.
[0030] Where present, the slag cement generally may be included in the acid-soluble
cement compositions in an amount sufficient to provide the desired compressive strength,
density, and/or cost in some embodiments, the slag cement may be present in the cement
compositions of the present invention i a amount i the range of about 0.1% to about 99%
b weight of cemeniitious co ponents n some embodiments, the slag cement may be
present in an amount in the range of about 5% to about 5% by weight of eementitious
components. One of ordinary skill in the art. with the benefit of this disclosure will
recognize the appropriate amount of the slag cement to include for a chosen application.
[0031 ] Embodiments of the acid-soluble cement compositions may further comprise
metakaolin. Generally, metakaolin is a white pozxolan that may be prepared by heating
kaolin clay, or example, to temperatures in the range o f about 600 C to about C. i
some embodiments, the metakaolin may be present in th cement compositions of the
present invention i an amount in the range of about 5% t about 95% by weight of
eementitious components, in some embodiments, th metakaolin may be present in an
amount in the range of about % to about 50% by weight of eementitious components. One
o f ordinary skill in the art, with the benefit of this disclosure, will recognize the appropriate
amount o .be metakaolin to include for a chosen application.
[0032] Embodiments of the acid-soluble cement compositions may further comprise
shale. Among other things, shale included in the cement compositions may react with excess
ime to form a suitable cementing material, for example, calcium silicate hydrate A variety
of shales may be suitable, including those comprising silicon, aluminum, calcium, and/or
magnesium. An example of a suitable shale comprises vitri fied shale. Suitable examples of
vitrified shale include, but are not limited to, P ESS R SEAL FINE LCM material and
PRESSUR-SEAE COARSE LCM material, which are commercially available from Ϊ CI
Energy Services, I c ., Houston, Texas. Generally, the shale may have any particle size
distribution as desired for a particular application. I certain embodiments, the shale may
have a particle size distribution in the range o about 37 micrometers to about 4,750
micrometers.
[0033] Where present, th shale may be included in the acid-soluble cement
compositions of th present invention in an amount sufficient to provide the desired
compress e strength, density, and/or cost h so e embodiments, the shale may be present
in the cement compositions of the present invention n an amount in the range o f about 5% to
about 75% by weight of cementitious components i some embodiments, the shale may be
present in an amount in the range of about % to about. 35% by weight of cementitious
components. One of ordinary skill in the art, with the benefit of this disclosure, wi l
recognize the appropriate amount of the shale to include for a chosen application.
[0034] Embodiments of the acid-soluble cement compositions ma further comprise
zeolite. Zeolites generally are porous ahimino-silicate minerals that may be either a natural
or synthetic material. Synthetic zeolites are based on the same type of structural cel as
natural zeolites, and may comprise alununosi!icate hydrates. As used herein, the term
"zeolite" refers to a l natural and synthetic forms o f zeolite. Examples o f suitable zeolites
are described in more detail in U.S. Patent No. 7,445,669, An example of a suitable source
o f zeolite is available from the C2C Zeolite Corporation o Calgary, Canada. In so e
embodiments, the zeolite may be present in the cement compositions of the present invention
n an amount in the range o f about 5% to about 65% by weight of cementitious components.
In certain embodiments, the zeolite may be present in an amount in the range of about %
to about 40% by weight of cementitious components. One of ordinary skill in the art, with
the benefit of th s disclosure, wi l recognize the appropriate amount of the zeolite to include
for a chosen application.
[0035] Embodiments of the acid-soluble cement compositions may further comprise
a set-retarding additive. As used herein, the term "set-retarding additive" refers to an
additive thai retards the setting of the acid-soluble cement compositions of the present
invention. Examples of suitable set-retarding additives include,, bui are not limited to,
ammonium, alkali metals, alkaline earth metals, etal salts of su!fba!ky Sated lignins, organic
acids (e.g., Irydroxyearhoxy acids), copolymers that comprise acrylic acid or maleic acid, and
combinations thereof. One example of a suitable sulfoalkylaied gnin comprises a
sulfomethylated lignin. Suitable set-retarding additives are disclosed in more detail in
United States Patent No, Re, 31,190, the entire disclosure of which is incorporated herein
b reference. Suitable set-retarding additives are commercially available from Halliburton
Energy Services, nc. under the trademarks R 4, R -5, -?, , HR*-
25, fiR^-601, SCR™- 100, and SCR™-50(> retarders. Generally, where used, the setretarding
additive a b included in the cement compositions of the present in vention in a
amount sufficient to provide the desired set retardation, in some embodiments, the setretarding
additive may be present n the cement compositions of the present invention an
amount in the range of about 0.1% to about 5% by weigh t of cementitious componen ts. One
of ordinary skill in the art, with the benefit of this disclosure, wil recognize the appropriate
amount of the set-retarding additive to include for a chosen application.
[0036] Optionally, other additional additives may be added to the acid-soluble
cement compositions of the present invention as deemed appropriate by one skilled in the art,
with the benefit of this disclosure. Examples of such additives include, but are not limited
to, strength-retrogression additives, set accelerators, weighting agents, lightweight additives,
gas-generating additives, rneeiianical-property-enhancing additives, lost-circulation
materials, filtration-control additives, dispersants, fluid- ioss-control additives, defoaming
agents, foaming agents, oi swe a le particles, water-swe.llab.le particles, thixotropie
additi ves, and combinations thereof. Specific examples of these, and other, additi ves include
crystalline silica, amorphous s ica, fumed silica, salts, fibers, ydratab e clays,
microspheres, rice hus ash, elastomers, elastomerie particles, resins, latex, combinations
thereof, and the like. A person having ordinary skill in the art, with the benefit of this
disclosure, will readily be able to determine the type and amount of additive useful fo a
particular application and desired result.
[0037] 'The components of the acid-soluble cement compositions ma e combined
any order desired to form an acid-soluble cement composition that can b placed into a
subterranean formation. in addition, the components of the acid-soluble cement
compositions may be combined using any mixing device compatible with the composition,
including a bulk mixer, for example, in some embodiments, a dry blend may first be formed
by dry blending dry components comprising, for example, C .D and/or hydraulic cement.
The dry blend ay then be combined with water to .form the acid-soluble cement
composition. Other suitable techniques may be used for preparation of the a id-s
cement compositions as will be appreciated by those of ordinary skill in the art i accordance
with embodiments of the present invention.
[0038] As will be appreciated by those of ordinary skill in the art. the acid-soluble
cement compositions of the present invention may be used in subterranean operations n
accordance with embodiments of the present invention. Without limitation, the cement
composition may be used to seal off one or more subterranean zones from a well bore; to
plug a void or crack in a conduit disposed in the well bore; t plug a voi or crack in a
cement sheath disposed in the well bore; to p ug an opening between the cement sheath and
the conduit; to prevent the loss of fluid from the well bore into loss circulation zones such as
a void, vug, or fracture; to form an annular plug; to isolate a gravel packed interval of the
well bore; or combinaiions thereof. In an embodiment, the acid-soluble cement composition
may be used to form a acid-soluble barrier (e.g., a plug, a seal, etc.) n a subterranean
formation. For example, the acid-soluble cement composition ay be introduced into a
well-bore annu u and allowed to set to form an acld-solub!e cement sheath
[0039] An example of a method of the present invention comprises placing an acidsoluble
cement composition in & subterranean formation, and allowing the acid-soluble
cement composition to set in the formation is intended to be understood that the phrase
"placing a acid-soluble cement composition in the subterranean formation" encompasses
placement of the eement composition in the well bore and or placement of the cement
composition in rock surrounding the well bore with the well bore penetrating the
subterranean formation, among others. The cement composition should form an acid-soluble
hardened as In the subterranean formation. The acid-soluble hardened ass can be left n
the subterranean formation permanently or can be removed. Removal of the hardened mass
may be desired so that the subterranean formation can be utilized in subsequent hydrocarbon
production n accordance with embodiments of the present invention. In an embodiment,
removal of the hardened mass includes contacting the hardened mass with an aqueous acid
composition to at least partially dissolve the hardened mass. n some embodiments, the
hardened mass may be completed removed n other embodiments, the hardened mass may
be partially removed. For example, the aqueous acid composition may contact the hardened
mass to form through openings in th hardened mass to place the subterranean formation in
communication with the interior of a pipe string, for example. The aqueous acid
composition may include, for example, from about 7.5% to about 28% hydrochloric acid by
weight of the composition. n an embodiment, the aqueous acid composition includes
hydrochloric acid in a amount of about 5% by weight.
[0040] Another example of a method of the -present invention comprises placing an
acid-soluble cement composition in a well-bore annu (e.g., an at us between a pipe
str i g disposed in a well bore and a wall of the wel bore); and allowing the acid soluble
cement composition to set. For example, the acid-soluble cement composition may set in the
well-bore annu u to form an acid-soluble cement sheath. The acid-soluble cement sheath
ca be left n the subterranean formation permanently or can be removed- Removal of the
hardened mass may b desired so that the subterranean formation can be utilized i
subsequent hydrocarbon production n accordance with embodiments of the present
invention, in an embodiment, removal of the hardened mass includes contacting the
hardened mass with an aqueous acid composition to at least partially dissolve the hardened
mass. For example, the aqueous acid composition may contact the hardened mass to form
through openings in the hardened mass to place the subterranean formation in
communication with the interior of a pipe string, for example. som embodiment, the
aqueous acid composition may be placed into the well bor and allowed to contact the
hardened mass through one or more openings in the pipe string.
[00 ] To facilitate a better understanding of the present invention, 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 scope of the invention.
EXAMPLE 1
[0042] A series of acid-soluble cement compositions was prepared at room
temperature and subjected to crush strength and solubility testing. Each of the samples
contained sufficient water to provide the density provided in the table below and. comprised
various quantities of Class H Portland cement, o cim C , and/or calcium carbonate, as
indicated in the table below.
[0043] Solubility Testing: For the solubility testing, each sample was poured into a
2-inch cube and allowed to cure in a water bath at °F for either 48 hours (Samples -5) or
72 hour (Samples 6- ). After curing, the sample cubes are placed in an 0 water bath
for at least 30 minutes and then weighed to determine an initial weight. Each sample cube
was then submerged in 2,000 milliliters of a 15% by weight hydrochloric acid solution in a
3,00 milliliter beaker. The sample cube was supported n the acid solution above a
magnetic stir bar. The magnetic stir bar was rotated to create a sltsht vortex on the surface of
the acid solution. After 30 minutes, the sample cube was removed from th ac d solution
an weighed to determine a final weight. The acid solubility of each composition was
calculated by the following formula:
Acid Solubility ~ (initial Weight - Final Weight) Initial Weight x 00
0044 Crush Strength 'Testing: For the crush strength testing, each sample was
poured into a 2-inch cube, allowed to cure in a water bath at 0*F for 48 hours (Samples I-
5) or 72 hours (Samples 6-10), and then crushed. The crush strengths were determined using
a Tinius Olson tester in accordance with AP Specification 0 .
[0045] The results of the tests are se forth in the table below. l t the following table,
percent by weight is based on the weight of the cement and the CKD in the samples.
TABLE 1
Crush Strength Tests:
Cement, CK , and CaC
[0046] Example thus indicates that acid-soluble cement compositions containing
from 25% to 100% CKD by weight, from 0% to 75% Portland ce e t by weight, and from
100% to 300% calcium carbonate by weight may have properties suitable for use n acidsoluble
operations.
EXAMPLE 2
[0047] An additional series of acid-soluble cement compositions was prepared and
subjected to thickening time, force resistance, and rheologiea.1 tests. Each of the samples
contained sufficient water to provide the density provided in the table below and comprised
various quantities of Class Portland cement, Holcim CKD, calcium carbonate, a isp rsa
(CF "-3 cement friction reducer), and/or a set-retarding additive, a indicated in th table
below, i the following tables, percent b y weight is based o the weight of the cement and
the K n the samples.
[0048] The samples were prepared at room temperature with thickening t me tests
conducted at 0 F on a portion of each composition n accordance with API Specification
10. The crush strength of Sample 12 was determined by pouring the sample into a 2-inch
cube, allowing t to cure in a water bath at 0 F for 72 hours, and then crushing the cured
cube. The crush strength was determined using a Tinius Olson tester in accordance with API
Specification 0 . The results of the thickening time and force resistance tests are provided in
the table below.
TABLE 2
Thickening Time Tests:
Cement, CK D a d CaCG 3
[0049] For the rheologieal tests, additional portions of the acid-soluble cement
compositions were conditioned in an atmospheric consistometer to the test temperature.
After conditioning, the rheology of the compositions was determined using a Fann Mode! 35
viscometer at the temperature indicated in the table below using a bob sleeve and spring
# 1 in accordance with the procedure set forth in API Specification . The results of the
rheologieal tests are set forth in the table below n the following table, percent by weight is
based on the weight of the cement and the CKD n the samples.
TABLE 3
h ! icai Tests:
[0050] Example 2 thus indicates that acid-soluble cement c pos ti containing
from 25% to 50% C .D by weight, f om 50% to 75% Portland cement by weight, and 00%
calc m carbonate by weight ay have properties suitable for use in acid-soluble operations.
EXAMPLE 3
[00 ] An additional acid-soluble cement composition was prepared to determine
force resistance properties of compositions comprising pumicite. The composition contained
sufficient water to provide the density provided in the table be!ow and comprised Class
Portland cement, 200-mesh pumicite, calcium carbonate, a set-retarding additive ( R 5
r tart r), and hydrated lime, as indicated in the table below. For the acid solubility testing,
the composition was poured into a 2-inch cube and cured at 180 for 24 hours. The acid
solubility of the composition was then determined by submerging the cured cube in a 5%
by weight hydrochloric acid solution in accordance with the procedure described above in
Example . For the crush strength testing, the composition was poured into a 2-inch cube,
allowed to cure in a water bath for 24 hours at 1 O' , and the crushed. The 24-hour crush
strength was determined using a Tinius Olson tester in accordance with AP Specification
10. The results of the tests are set forth i n the table below. n the following table, percent by
weight is based on the weight of the cement and the C D in th samples.
TABLE 4
Crush Strength Tests:
Ce e t, Ptimieite, a d C CO
[0052] Example 3 thus indicates that acid-soluble cement corn-positions containing
Portland cement, puniicite, and calcium carbonate may have properties suitable for use in
acid-soluble operations.
EXAMPLE 4
[0053] A additional serie of acid-soluble ce e t compositions was prepared at
room iemperatore to determine force resistance properties of compositions comprising Sore!
cement .g. f a mixture o f magnesium chloride an magnesium oxide), C .0 and/or
pumicite. Each of the samples contained water, magnesium chloride (C-TEK), magnesium
oxide (T R ATE .' LT additive), Ho!cim CKD* 200-mesh pumicite, and/or hydrated
lime, as indicated in the table below. The crush strength of the compositions was determined
b pouring each composition into a 2-inch cube, allowing the cube to cure in -a water ba h a t
140°F for either 24 or 48 hours, and then crushing the cured cube, The crush strengths were
determined using a T us Olson tester in accordance with API Specification . The results
of the tests ar set forth n the table below.
TABLE 5
t SSttrreennggtthh T. ests:
Sore! Cement, CKD, and/or Pumicite
[0054] Example 4 thus indicates tha acid-soluble cement compositions containing
Sore! cement, cement kiln dust, .and/or pumicite may have properties -suitable o r use i acidsoluble
operations.
EXAMPLE 5
[ 55] An additional series of acid-soluble cement compositions was prepared at
room temperature to determine force resistance properties o f lightweight compositions
comprising Sorel ceme t .g., a mixture of magnesium chloride and magnesium oxide) and
CKD. Each of the samples contained water, magnesium chloride (C T additive),
magnesium oxide (T ER A E LT additive), Holcim CKD, a set-retarding additive (RTE
. inhibitor), and glass bubbles ( G 2000 glass bies}, as indicated in the tabic below,
he crush strength of the compositions was determined by pouring each composition into a 2-
inch cube, allowing the cube to cure in a water bath at 40 F for 24 hours, and then crushing
the cured cube. The crash strengths were determined using a Tinkts Olson tester in
accordance with AP Specification 0 . The results of the tests are set forth in the table
below.
TABLE 6
Crush Strength Tests:
Sorel Ceme and CKD
[0056] Example 5 t us indicates that acid-soluble cement compositions having a
lightweight and containing Sorel cement and cement kiln dust may have properties suitable
for use i acid-soluble operations.
EXAMPLE 6
[0057] A additional series of acid-soluble cement compositions was prepared at
room temperature and subjected to thickening time tests at 140°F i accordance with AP
Specification 10. Each of the samples contained water, magnesium chloride (C-TEK
additive), magnesium oxide (THERMATE ' L additive), Holcim CKD, and a retarder (RTE
inhibitor) as indicated the table below. The results of the tests are set forth in the
table below.
TABLE 7
Thickening Time Tests:
Sor Cement a d € $
[0058] Example thus indicates that acid-soiuble cement compositions containing
Sore cement and cement kiln d st may have properties suitable for use in acid-soiuble
operations.
EXAMPL 7
[0059] An additional acid-soluble cement composition was prepared at room.
temperature and subjected to crush strength and solubility testing. This sample was prepared
to test the Solubility of an acid-soluble cement composition comprising CKD and tree of any
acid-soiuble fillers. The sample comprised olc CKD (25% bwob), Texas Lehigh Class
Portland cement (.25% bwob), fly ash (P Z IX A cement additive, 25% bwob),
bentoiiite (2,5% bwob), a set-retarding additive ( fc -800 retarder, 0 4% bwob), a f uid- o scontrol
additive (HALAD *-447. 0.25% bwob), a fr ee-water- on ro additive (WG EXP
tree- ater control agent, 0,2% bwob), and fresh water ( 6.2 gal/s ) The abbreviation %
bwob" indicates the percent of the component by weight of a cement blend comprising the
CKD, Portland cement, and fly ash The abbreviation "gal/sk" indicates gallon per 89.5-
pound sack of the cement blend. The sample had a density of pounds per gallon.
[0060] Crush Strength Testing: For the crush strength testing, a portion of the
sample was poured into a 2-inch cube and allowed to cure in a water bath at 140 F for 7
days. Alter curing, the sample cubes were placed in an 80°F water bath tor at least 30
minutes and then crushed. The crush strengths were determined using a Tin s Olson tester
i accordance with API Specification 10. The determined crush strength was 2,200 psi.
[0061] Solubility Testing: For the solubility testing, portion of the sample was
poured nto a 2-inch cube and allowed to cure n a water bath at 40 F for 4 hours. After
curing, the sample cubes were placed in an 80°F water bath for at least 30 minutes and then
weighed to determine an initial weight. Each sample cube was then submerged in 2,000
milliliters of 5% by weight hydrochloric acid solution in a 3,000 milliliter beaker at
ambient conditions. The sample cube was supported n the acid solution above a magnetic
77
stir bar. The mag e c stir bar was rotated to create a slight vortex on the surface of the acid
solution. At specified intervals, the sample cube was removed from the acid solution a d
weighed to determine a interval weight. Weight loss of the cube was determined b
subtracting the interval weight from the initial weight. The sample cube was returned
to the acid solution. The acid solubility of each composition was calculated by the following
formula;
Acid Solubility - Weight Loss / initial Weight c !00
After 2 hours, the testing was completed. The results of the solubility testing are set forth in
the table below.
TABLE 8
Acid-Solubility Tests:
25% , 50% Cement, and 25% Fly Ash i 15% CL
[0062] The solubility testing was repeated using a 7.5% by weight hydrochloric acid
solution. The results of this test are set forth below.
TABLE 9
Acid So uM i y Tests:
25% CKD, 50 Cement, a d 25% Fly Ash in 7,5% C
[0063] Example 7 thus indicates that acid-soluble cement compositions containing
CKD and free of an additional acid-soluble filler may have solubility properties suitable for
use in acid-soluble operations.
EXAMPLE 8
[0064 An additional acid-soiubie cement composition was prepared at ro o
temperature and subjected to crush strength and solubility testing. This sample was prepared
to further test the solubility of an acid-soluble cement composition comprising CKD and free
of any acid-soluble fillers. The sample comprised ole CKD (100% bwob), calcium
chloride (3% bwob). and fresh water (6 67 ga /s The abbreviation " bwob" indicates the
percent of the component by weight of a cement blend consisting of the CKD. 'The sample
had a density of 13 pounds per gallon.
[0065] Crush Strength Testing: For the crush strength testing, a portion of the
sample was poured into a 2-inch x . 4-inch cylinder and allowed to cure n water bath at
17{ F for 24 hours. After curing, the sample cubes were placed n an 0 F water bath for at
least. 30 minutes and then crushed. The crush strengths were determined using a T ius
Olson tester i accordance with API Specification 0 . The determined crush strength was
345 psi.
[0066] Solubility Testing: For the solubility testing, portion of the sample was
poured into a 2-inch x 4-inch cylinder and allowed to cure n a water bath at !40°F for 24
hours. After curing, the sample cylinders were placed in an 0 F water bath for at least 30
minutes and the weighed to determine an initial weight. Each sample cylinder was the
submerged i 2.000 milliliters of a 7,5% by weight hydrochloric acid solution at 40¾ in a
3,000 milliliter beaker. The sample cylinder was supported in the acid solution above a
magnetic stir bar. The magnetic stir bar was rotated to create a slight vortex on the surface
of i acid solution The sample cylinder was observed, and the time for complete
dissolution of the sample cylinder wa recorded f not completely dissolved, the sample
cylinder was removed f om the acid solution after 2 hours and weighed to determine a final
weight. The acid solubility was. then was calculated by the following formula:
Acid Solubility (Initial Weight - Final Weight) / initial Weight x 0
The solubility testing was repeated using a 7.5% by weight hydrochloric acid solution and a
15% by weight hydrochloric acid solution. The results of the solubility testing are set forth
in the table below.
TABLE
Acid-Solubility Tests: 100% K
[0067] Example 8 thus indicates that acid-soluble cement compositions containing
CKD and ree of an additional acid-soluble filler may have solubility properties suitable lor
use in a d-soJubSe operations,
[0068] It should be understood that the compositions and methods are described n
terms of "comprising," "containing," or "including" various components or steps, the
compositions and methods can also "consist essentially of * or "consist the various
components and steps. Moreover, the indefinite articles "a" or "an," as used in the claims,
are defined herein to mean one or ore than one of Che element that it introduces.
0069] For the sake of brevity, only certain ranges ar explicitly disclosed herein.
However, ranges from any Sower Strait may be combined with any upper limit to recite a
range not explicitly recited, as we as, ranges from any lower limit may be combined with
any oilier lower limit to recite a range ot explicitly recited, in the same way, ranges from
any upper limit may e 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.
equi va ent! '- "from approximately a to b., equivalent!)', "from approximately a-b")
disclosed herein is to be understood to set forth every number and range encompassed within
the broader range of va es even if not explicitly recited. Thus, every point or individual
value ma serve as t own lower or upper li it combined with any other point o individual
value or any other lower or upper limit, to recite a range not explicitly recited.
[0070] Therefore, the present invention is we l adapted to attain the ends and
advantages mentioned as well as those that are inherent therein. The particular embodiments
disclosed above are illustrative only, as the present invention may be modified and practiced
h different but equivalent manners apparent to those skilled in the art having the benefit of
the teachings herein. Although individual embodiments are discussed, the invention covers
all combinations of all those 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. t is therefore evident that the particular illustrative
embodiments disclosed above may be altered or modified and all such variations are
considered within the scope an spirit of the present invention. If there is any conflict in the
usages of a word or term in this specification and one or raore paterst(s or other documents
that may be incorporated herein by reference, the definitions that are consistent with this
specification should be adopted.
Wha s clai e s :
1. A method of cementing comprising;
providing an acid-soluble cement composition comprising kiln dust and
water;
allowing the acid-soluble cement composition to set to form an acid-soluble
hardened mass; and
contacting the acid-soluble hardened mass with an acid.
2. A method according to claim I wherein the acid-soluble cement composition
has a density of about 8 pounds per gallon to about pounds per gallon.
3. A method according to claim .1 or claim 2 wherein the acid-soluble cement
composition further comprises a hydraulic cement selected from the group consisting of a
Portland cement, a poz lana cement, a gypsum cement, a high alumina content cement, a
slag cement, a silica cement, and any combination thereof.
4. A method according to any preceding claim wherein the kil dust comprises
cement kiln dust
5. A method according to any preceding claim wherein the kiln dust comprises
lime kiln dust.
6. A method according to a y preceding claim wherein the kiln dust is present
in an amount in a range of ro m about 1% to 100% by weight of a total amount of
cementitious components present in the acid-soluble cement composition.
. A method according to an one of claims 1, 2 or 4-6 wherein the kiln dust is
present in an amount of about 00%by weight o f a total amount of cementitious components
present in the acid-soluble cement composition.
8. A method according to any one of claims 1, 2 or 4-7 wherein the acid-soluble
cement composition is ree of any additional cementitious components other than the kiln
dust.
9. A method according to any preceding claim wherein the acid-soluble cement
composition is free of an acid soluble filler.
10. A method according to any preceding claim wherein the acid-soluble cement
composition is free of an acid-soluble filler selected from the group consisting of dolomite,
magnesium carbonate, calcium carbonate, zinc carbonate, and any combination thereof.
. A method according to any one of claims 1-6, , or . wherein the acidsoluble
cement composition further comprises an additive selected from the group consisting
of a fly ash. a slag cement, metakaolin, shale, zeolite, crystalline silica, amorphous silica.
filmed silica, salt, fiber, h dra ab e clay, microsphere, rice usk ash, an elastomer, a
elastomerie particle, a resin, a latex, and any combination thereof,
, A method according to any preceding claim wherein the acid-soluble cement
composition further comprises an additive selected from the group consisting of a setretarding
additive, a strength-retrogression additive, a set accelerator, a weighting agent a
lightweight additive, a gas-generating addilive, mechanical-property-enhancing additive, a
lost-circulation material, a filtration-control additive, a dispersant, a fluid- loss-control
additive, a defoaming agent, a foaming agent, an oi!-swe!iable particle, water-swe ab e
panicle, a thixotropic additive, and any combination thereof
A method according to any preceding claim wherein contacting the a ic -
soluble hardened mass with an acid comprises contacting the acid-soluble hardened mass
with an aqueous acid composition, wherein the aqueous acid composition comprises
hydrochloric acid present n the aqueous acid composition in an amount of about 7 5% to
about 28% by weight of the aqueous acid composition.
4 A method according to any preceding claim further comprising; placing the
acid-soluble cement composition into a subterranean formation.
15. A method according to claim 4 wherein th acid-soluble cement
composition is allowed to set n a well-bore annulus in th subterranean formation, wherein
the acid contacts the acid-soluble hardened mass through one or more openings in a pipe
string disposed in the subterranean formation.
. A method of cementing comprising;
placing an acid-soluble cement composition in a subterranean formation, the
acid-soluble cement composition comprising:
cement kiln dust in an amount of 00% b weight of a total amount
of cementitious components in the acid-soluble cement composition; and
water;
allowing the acid-soluble cement composition to set to form an acid-soluble
hardened mass; and
contacting the acid-soluble hardened mass with an acid.
A method .according to claim 16 wherein the acid-soluble cement
composition is free of an acid-soluble filler.
. A method according to claim or cla im wherein the acid-soluble cement
composition is free of an acid-soluble filler selected from th group consisting of dolomite,
magnesium carbonate, calcium carbonate, zinc carbonate, and any combination thereof.
19. A met od according to any one of claims 16-18 wherein the acid-soluble
cement composition further comprises an additive selected from the group consisting of a
set-retarding additive, a strength-retrogression additive, a set accelerator, a weighting agent
a lightweight additive, a gas-generating additive, a mechanica!-property-enhaneing additive,
a lost-circulation material, a filtration-control additive, a dispersant, a fluid-loss-control
additive, a defoaming agent, a foaming agent, an oi -swe ab c particle, a vvaier-swellable
particle, a tfoixotropic additive, and any combination thereof.
20. A metho according to any one of claims 6- 9 wherein contacting the a id
soluhle hardened mass w t an acid comprises contacting the acid-soluble hardened mass
with an aqueous a i composition, wherein the aqueous acid composition comprises
hydrochloric acid present in the aqueous acid composition in an amount of about 7.5% to
about 28% by weight of the aqueous acid composition.
. A method according to any one of claims 16-20 wherein the placing the acidsoluble
composition comprises placing the acid-soluble composition in a well-bore annul us
between a pipe string disposed in the subterranean formation and a wall of a well bore.
22. A method according to any one of claims - wherein the acid-soluble
cement composition is allowed to set in a . well-bore annulus in the subterranean formation,
wherein the acid contacts the acid-soluble hardened mass through one or more openings in a
pipe string disposed in the subterranean formation,
23. A method of cementing comprising:
placing an acid-soluble cement composition in a subterranean formation, the
acid-soluble cement compos ion comprising ceme t ki n dust and water, wherein the acidsoluble
cement composition is free of any acid-soluble fillers;
allowing the acid-soluble cement composition to set to form an acid-soluble
hardened mass; and
contacting the acid-soluble hardened mass with an acid.
24. A method according to claim 23 wherein the acid-soluble cement
composition further comprises a hydraulic cement selected from the group consisting of a
Portland cement, a poz olan cement, a gypsum cement, a high alumin content cement, a
slag cement, a silica cement, and any combination thereof,
25. A method according to claim 23 or claim 24 wherein the cement kiln d ust is
present n an amount n a range of from about % to 100% by weight of a total amount of
eemeniitious components present in the acid-soluble cement composition,
26 A method according to an one of claims 23-25 wherein the cement kil dust
is present in an amount of about 0% by weight of a total amount of cementitious
components present in the ac - o ub e cement composition.
27. A method according to any one of claims 23-26 wherein the acid-soluble
cement composition is free of any additional cementitious components other than the cement
ln dust.
28. A method according to an one of claims 23-25 wherein the acid-soluble
cement composition farther comprises an additive selected from the group consisting of a fly
ash, a s ag cement, eta a l n shale, zeolite, crystalline silica, amorphous silica, famed
silica, salt, fiber, hydratable clay, microsphere, rice husk ash, an elastomer, an eiastomeric
particle, a resin, a latex, and any combination thereof
29 A method according to any one of claims 23-28 wherein the -acid-soluble
cement composition further comprises an additive selected front the group consisting of a
set-retarding additive, a strength-retrogression additive, a set accelerator, a weighting agent,
a lightweight additive, a gas-generating additive, a mechanical-property-enhaneing additive,
a lost-circulation material, a filtration-control additive, a dispersanL a fluid-loss-eontrol
addiisve, a defoaming agent, a foaming agent, an oil-sweliabie particle, a water-swel Sable
particle, a th xotrop c additive, and a y combination thereof
30. A method according to any one of claims 23-29 wherein contacting the acidsoluble
hardened mass with an acid comprises contacting the acid-soluble hardened mass
with an aqueous acid composition, wherein the aqueous acid composition comprises
hydrochloric ac d present in the aqueous acid composition in an amount of about 7.5% to
about 28% by weight of the aqueous acid composition.
31. A method according to any one of claims 23-30 wherein the acid-soluble
cement composition is allowed to set In a well-bore a annulus in the subterranean formation,
wherein the acid contacts the acid-soluble hardened mass through one or more openings in a
pipe strin disposed in the subterranean formation.