METHOD OF CEMENTING IN A SUBTERRANEAN FORMATION USING CEMENT COMPOSITION
COMPRISING LIGNITE - BASED GRAFTED COPOLYMERS
BACKGROUND
[000 j Cement compositions may be used in a variety of subterranean operations.
5 For example, in subterranean well construction, a pipe string (e.g., casing, liners, expandable
tub lars etc.) may be run into a well bore and cemented in place. The process of cementing
the pipe string in place is commonly referred to as "primary cementing " n a typical
primary cementing method, a cement composition may be pumped into an annulus between
the walls o f the well bore and the exterior surface of the pipe string disposed therein. The
10 cement composition may set in the annular space, thereby forming an annular sheath of
hardened, substantially impermeable cement (i.e., cement sheath) tha may support and
position the pipe string in the we bore and may bond the exterior surface of the pipe string
to the subterranean formation. Among other things, the cement sheath surrounding the pipe
siring functions to prevent the migration of fluids in the annulus, as well as protecting the
. pipe strin fro corrosion. Cement compositions also may be used n remedial cementing
methods, or example, to sea cracks or holes pipe strings or cement sheaths, to seal highly
permeable formation zones or fractures, to place a cement plug, and the like..
[0002] One problem that may be encountered during the placement of a cement
composition in a well bore is unwanted gas migration from the subterranean formation into
20 and through the cement composition. Gas migration may b caused by the behavior of the
cement composition during a transition phase i which the cement: slurry changes from a true
hydraulic fluid to a highly viscous mass showin some solid characteristics. When first
placed in the annulus, the cement composition acts as a true liquid and thus transmits
hydrostatic pressure. However, during the transition phase, certain events occur that cause
2 5 the cement composition to lose its ability to transmit hydrostatic pressure. One of those
events is the loss of fluid from the slurry to the subterranean formation. Another event is the
development of static gel strength in the slurry. As a result, the pressure exerted on the
formation by the cement composition may fall below the pressure of the ga in the formation
such that the gas may begin to migrate into and through the cement composition. When gas
30 migration begins, th cement composition typically has a ge strength of about. 00 lb 0
ft The gas migration may cause flow channels to form in the cement composition. With
ti me the gel strength of the cement composition Increases to a value sufficient to resist the
pressure exerted by the gas in the formation against the composition. At this point, the
cement composition typically has a gel strength of about 500 b Oit 1. The cement slurry
35 then sets into a solid mass.
[00 3] Unfortunately, the flow channels formed in the cement during .such gas
migration remain in the cement composition o ce it has set Those l ow channels can permit
further migration of gas through the set ce en composition. Thus, the se cement
composition residing in the ann us may be ineffective at maintaining the isolation of the
adjacent subterranean formation. To overcome this problem, attempts have been made to
desig cement composition having shorter transition t me i.e., the period of ti e during
which gas migration into the slurry can occur, which is typically the t e ranging fr o when
the gel strength of the slurr i about 100 lb,/ 00 ft 2 to when it is about 500 ll G ft 3, as
measured using a Multiple Analysis Cement System (MACS* S . available fr o Fann
instrument Company) in accordance with the procedure for determining cement transition
times set forth in API RP - Recommended Practice on Determining the Static Gel
Strength of Ce e t Formulations, dated August 1, 2010. Gas migration control additives
have been developed to provide shorter transition times. One particular additive for
controlling gas migration is a copolymer of sodium 2 aer ta ido 2~methylpropanesulfonate
and N,N-dimetbyIacrylaraide. While this additive can be used to control gas migration, the
highest percent activity it can be effectively used as an aqueous solution is 9% by weight
above which the solution becomes too viscous fo the liquid additive pumps to handle.
Other additives that ma be used may either be too expensive or may provide transition
times that ma be longer than desired.
SUMMARY
[0004] An embodiment of the present invention comprises a method of cementing n
a subterranean formation, comprising; introducing a cement composition comprising cement,
water, and a lignite-based copolymer h to a subterranean formation, wherein the . gnitebased
copolymer comprises a lignite backbone, a first grafted monomer selected from the
group consisting of 2-acrylamido-2-methylpropanesulfonic acid, a salt of 2~acrylarmdo~2~
methylpropanesulfonic acid, and any combination thereof and a second grafted monomer
comprising , -dimethylacrylamide; and allowing the cement composition to set in the
subterranean formation, wherein cement composition has a transition time of less than: or
equal to about 50 minutes.
[0005] Another embodiment of the present invention comprises a method of
cementing in a subterranean formation, comprising; introducing a cement composition
comprising cement, water, and a lignite-based copolymer into a well bore having a bottom
hole circulating temperature of less than or equal to about 100 F wherein the lignite-based
copolymer comprises: a backbone in an amount of about 20% to about 40% by weight of the
lignite-based copolymer, the backbone comprising ca stici ed lignite; and grafted pendant
ro i an amount of about 60% to about 80% b weight of the lignite-based copolymer,
the grafted pendant groups comprising sodium 2-acrylamido-2-met ylpro anes lfonate a d
-dimediylacrylaraide in a molar ratio of sodium 2-acrylamtdo-2-methylpropanesulfonate
and dimethy acry a ide. of about 0/90 to about 60/40; and allowing the cement
composition to set. in the subterranean formation, wherein the cement composition has a
trans io t e of ess tha or equal to about 30 minutes,
[0006] Yet another embodiment of the preset invention comprises a cement
composition comprising: cement; water; and a lignite-based copolymer comprising lignite
backbone, first grafted monomer selected from the group consisting of 2-acr am do-2-
methyipropanesuifonic acid, a salt o 2~acrytamido-2-methylpropanesul ionic acid, and any
combination thereof, and second grafted monomer comprising N,N-dimethyi ry! mide,
wherein the cement composition has a transition time at 60°F and 6,300 psi of less than or
equal to about 0 minutes.
[0007] The features and advantages of the present invention will be readily apparent
to those skilled in the art, While numerous changes may be made by those skilled in the art,
such changes are withi the spirit of the invention.
BRIEF DESCRIPTION OF TOE DRAWINGS
[0008] These drawings illustrate certa aspects of so e of the embodiments of the
present invention, should not be used to limit or define the invention.
[0009] F G. is a plot of static gel strength for a comparative cement composition.
[0 ] F G. 2 is a plot of static gel strength for a cement composition in accordance
with embodiments of the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[00 11] The present invention relates to subterranean cementing operations and, ore
particularly in certain embodiments, to cement compositions comprising a lignite-based
copolymer and methods of use. Advantageously, the lignite-based copolymer may o
to shorten the transition time of a cement composition, which i defmed herein as the period
of time after the composition is placed into a well bore during which the pressure exerted o
the subterranean formation by the cement composition s less than the pressure of the gas n
the formation such that gas migration into the composition can occur. The transition time is
typically the time ranging from when the gel strength of the composition is about 0 .100
V* to when it s about 500 lb/100 t For example, a cement composition comprising the
lignite-based copolymer may have a transition time of less than about 50 minutes and,
alternatively, less than about 60 minutes. Even further, the lignite-based copolymer may
also function to reduce fluid os from a cement composition. I addition, the lignite-based
copolymer may provide improved wait-on-cement times the time for the cement
composition to achieve a compressive strength of 500 ps — s compared to the inclusion of
other additives for reducing transition time that may have a secondary effect of retarding
compressive strength development.
[0012] Embodiments of the cement compositions may comprise a lignite-based
copolymer that comprises a lignite backbone and grafted pendants groups that comprise 2-
a ryian do-2-met y!propanesuifo nic acid and N,N-dimeiliy!aerySaniide ("DMA")- Salts o
2-acrylamido-2-methy1propanes«lfonic acid, such as sodium 2-acr m do-2-
methylpropanesulfbnate, may also be used. The term "AMPS' as used herein includes 2-
acrylarnido-2-methy!propanesulfonic acid, as well as salt thereo The term 'lignite" as used
herein includes a variet of lo rank coals, including oxidized lignite (e.g., leonardite), mine
lignin, brown coal or slack. Those of ordinary skill in th art will appreciate that the lignite
may be treated with a caustic (e.g., potassium hydroxide, sodium ydros ide, or ammonium
hydroxide) to sol iSi e the lignite in water. By way of example, treatment of the lignite
with a caustic solution generally ma dissolve or disperse a portion of the lignite into
solution. Such solution may then be concentrated to increase the lignite solution or may be
sed directly in the polymerization.
001 3 ] Th lignite-based copolymer may contain a sufficient amount of the lignite
backbone to provide a desirable decrease in the transition time n some embodiments, the
lignite-based copolymer may comprise the lignite backbone i an amount in a range of ro
about 5% to about 95% by weight of the copolymer. n alternative embodiments, the lignite
backbone may be present in a range of from about 0% to about 50% by weight and
alternatively rom about 20% to about 40% by weight n particular embodiments, the
lignite backbone may be present in an amount ranging between any of and/or including any
o f about 5%, about %, about 20% about 30%, about 40%, about 50%, about 60%, about
70%, about 80%, about 90%, or about 95% by weight. One of ordinary skill n the art, w t
the benefit of this disclosure, will recognize the appropriate amount of the lignite backbone
to inc de for a chos application.
00 14 As previously mentioned, the lignite-backbone ay be grafted with pendant
groups that include AMPS and DMA. In some embodiments, the AMPS and the DMA may
be present in the pendant groups in a random nature. By way of example, each of the
pendant groups may comprise one or more of AMPS and DMA in a random nature.
Generally, the lignite-based copolymer may contain a sufficient amount of the pendant
groups to provide desirable decrease in the transition time. n some embodiments, the
lignite-based copolymer may comprise the pendant groups n an amount in a range of from
about 5% to about 95% by weight of the copolymer. alternative embodiments, the
pendant groups may be present in a range of from about 50% to about 90% by weight and
alternatively from about 60% to about 80% b weight, In particular embodiments, the
pendant groups may be present in a n amount ranging between any of and/or including any of
about 5%, about 10%, about 20%, about 30%, -about 40%, about 50%, about 60%, about
0%, about 80%, about 90%, or about 95% by weight. One of ordinary skill in the art, with
the benefit of this disclosure, wil recognize the. appropriate amount of the pendants groups
to include for a chosen application.
[0 5] n some embodiments, the pendant groups ay comprise AMPS and DMA.
The AMPS and DMA may present in an AMPS-to-DMA molar ratio in a range of from
about 0/100 to about 0/0. In alternative embodiments, the AMPS-DMA molar ratio may
be from about 0/100 to abou 50/50 and, alternatively, from about 10/90 to about 60/40 n
particular embodiments, the AMPS -to-DMA molar ratio may between any of and/or include
any o f about 0/ 0, about /90 about 20/80. about 25/75, about 33/67, about 40/60, about
50/50, about 60/40, about 67/33, about 75/25, about 80/20, about 90/ , or about 00/0. One
of ordinary skill in the art, with the benefit of this disclosure, wil l recognize the appropriate
AMPS-DMA molar ratio to use for a chosen application. h some embodiments, the pendant
group may further comprise one or more co-monomers. Where present, the co-monomers
may be included in an amount equal to o less than about 10% by weight of the pendants
groups and alternatively equal to or less than about 5% by weight. alternative
embodiments, the pendant groups may be essentially free of any additional co-monomers, in
that the pendants groups comprise the AMPS and the DMA in an amount greater than or
equal to about 99 9% by weight. n some embodiments, the pendant groups may consist of
the AMPS and the DMA.
[0016] some embodiments, the lignite-based copolymer may be provided in an
aqueous solution. The aqueous solution may comprise the lignite-based copolymer in an
amoun of equal t or less than about 30% by weight of the aqueous solution. in some
embodiments, the aqueous solution may comprise the lignite-based polymer in an amount in
a range of from about 5% to about 30% by weight and, alternatively, from about 10% to
about 25% by weight. In one particular embodiment, the aqueous solution may comprise the
lignite-based polymer in an amount of about 25% by weight. One of ordinary skill in the art,
with the benefit of this disclosure, will recognize the appropriate amount of the lignite-based
copolymer to include in the aqueous solution for a chosen application.
[0017] Embodiments of the cement compositions of the present invention may
comprise a cement. Any of a variety of cements suitable for use in subterranean cementing
operations may be used in accordance with embodiments of the present invention. Suitable
examples include hydraulic cements that comprise calcium, aluminum, silicon, oxygen
and/or sulfur which set and harden by reaction with water. Suitable hydraulic cements
include, but are not limited to, Portland cements, poz o na cements, gypsum cements, high
alumina content cements, slag cements, silica cements, and combinations thereof. certain
embodiments, the hydraulic cement may comprise a Portland cement, including Portiand
cements classified as Classes A, C, and cements according to American Petroleum
institute, API Specification for Materials a i Testing for Well Cements, API Specification
10, Fifth Edition, July , 1990. in addition, Portland cements suitable for use in
embodiments the present invention may also include those classified as ASTM Type 1. II, III.
IV. or V.
[0 1 ] Embodiments of the cement compositions may comprise water. The water
may be fresh water or sail water. Salt water generally may include one or more dissolved
salts therein and ay be saturated or unsaturated as desired for particular application
Seawater or brines may be suitable for use in embodiments of the present invention. Further,
the water ay be present in an amount sufficient to form a pumpahle slurry. In some
embodiments, the water ay be included in the settab!e compositions of the present
invention in an amount in the range of fro about 30% to about 200% by weight of the
cement. or example, the water may b present in an amount ranging between any of and/or
including any of about 30%, about 40%, about 50%, about 75%, about 100%, about 25%,
about 50%, about 75%, or about 200 b weight of the cement. In specific embodiments,
the water may e included in an amount in the range of from about 40% to about 150% by
weight of the cement. One of ordinary skill in the art, with the benefit of this disclosure, will
recog iz the appropriate a ount of water to include for a chosen application
[0019] Other additives suitable for use in subterranean cementing operations also
may be added to embodiments of the cement compositions. Examples of such additives
include, but are not limited to, strength-retrogression additives, set accelerators, weighting
agents, lightweight additives, gas-generating additives, mechanical property enhancing
additives, lost-circulation materials, filtration-control additives, dispersants, fluid loss control
additives, defoaming agents, foaming agents, thixotropic additives, and combinations
thereof. Specific examples of these, and other, additives include crystalline silica,
amorphous silica, fumed silica, salts, fibers, hydratable clays, calcined shale, vitrified shale,
microspheres, fly ash, slag, diafo a eous earth, metakaolin, rice husk ash, natural pozzolan,
zeolite, cement kiln dust, ime, elastomers, resins, latex, combinations thereof, and the ike
A person having ordinary skill in the art, with the benefit of this disclosure, wil l readily be
able to determine the type and amount of additive useful for a particular application and
desired result
[0020] Those of ordinary skil in the art wi l appreciate that the cement compositions
generally should have a density suitable for a particular application. By way of example, the
cement composition may have a density in the range of from about 4 pounds per gallon
('ib/gal") to about 20 lb/gal. In certain embodiments, the cement compositions may have
density in the range of from about 8 lb/gal to about 7 lb/gal Embodiments of the cement
compositions may be foamed or nfoamed 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. For example, the cement compositions may be foamed with a gas
to reduce its density and further comprise a foaming agent. Those of ordinary skill in the art,
with the benefit of this disclosure, will recognize the appropriate density for a particular
application.
[00 As previously mentioned, the cement compositions may have a transition
time that has been shortened in accordance with embodiments of the present invention. n
some embodiments, a method of reducing a transition time of a cement composition may
comprise including a lignite-based copolymer in the cement composition. Due to the
presence of the lignite-based copolymer for example, the transition times of the cement
compositions may be less than or equal to about minutes, n alternative embodiments,
the cement compositions may have transitions times iess than or equal: to about 60 minutes,
alternatively less than or equal to about 60 minutes, alternatively less than or equal to about
50 minutes, alternatively less than or equal to about 40 minutes, alternatively less than or
equal to about 30 minutes, alternatively less than or equal to about 20 minutes, or
alternatively less tha or equal to about . minutes. As a result, a cemen composition may
be pumped to its desired location i a welt bore, e.g., the annuSus, and allowed to set without
being concerned tha gas migration could compromise its abil ity to seal an area of the well
bore. That is, there is insufficient time for the gas to migrate into and through the cement
composition and form flow channels therein. The lignite-based copolymer thus ay function
as a gas migration control additive in the cement compositions.
[0022] While the lignite-based copolymers may be effective at shortening transition
times in a variety of cementing applications, they may be particularly effective in wells
having lower bottom static temperatures ("BUST"), By way of example, the lignite-based
copolymers may suitable for use wells drilled through shallow water flow zones where
low BHST's may be applicable h some embodiments, the lignite-based copolymers may be
used in wells drilled in deep water (e.g., greater than or equal to 5,000 feet). n so e
embodiments, the lignite-based copolymers may be used in a well bore having a BHST of
less than or equa to about 100 , alternatively less than or equal to about 70 , and
alternatively less tha or equal to about 60 . some embodiments, the .ignite-based
copolymers may be used in a well bore having a BHST in a range o from about 50° to
about !Q0 should be understood that the lignite-based copolymers may also be used in
well bores having BHST's outside these particular temperatures.
[0023] As will be appreciated by those of ordinary skill in the art, embodi ts of
the cement compositions of the present invention may be used in variety of subterranean
operations, including primary a d remedial cementing.. In some embodiments, a cement
composition may be provided that comprises water, cement, and a lignite-based copolymer.
The lignite-based copolymer may comprise a gnite backbone and grafted pendant groups
comprising AMPS and DMA. one particular embodiment, lignite based copolymer may
comprise the lignite backbone in an amount of about 30% by weight and the grafted pendant
groups in an amount of about 70% by weight with the grafted pendant groups having an
AMPS-to-DMA molar ratio n a range of from abou 10/90 to about 60/40. The cement
composition may be introduced into a subterranean formation and allowed to set therein. As
used herein, introducing the cement composition int a subterranean formation includes
introduction into any portion of the subterranean formation, including, without limitation,
into a well bore drilled into the subterranean formation, into a near we l bore region
surrounding the wel bore, or into both.
[0024] n primary cementing embodiments, for example, embodiments of the
cement composition may be introduced into a well bore annuls, such between a wall of a
well bore and a conduit (e.g., pipe strings, liners) located in the well bore, the well bo e
penetrating the subterranean formation. The cement composition may be allowed to set to
form an annular sheath of hardened cement n the well bore annulus. Among other things,
the se cement composition may form a barrier, preve ti g the igratio of fluids in the wel
bore. The set cement composition also may, or example, support the conduit i the well
bore.
[0025] In remedial cementing embodiments, cement composition may be used, for
example, in squeeze-cementing operations or in the placement of cement plugs. By way of
example, the composition may be placed in a we l bore to plug an opening, such as a vo d or
c.rac in the formation, in a gravel pack, in the conduit, in the cement sheath, and/or a
microannulus between the cement sheath and the conduit.
EXAMPLES
[0026] To facilitate better understanding of the present invention, the following
examples of certain aspects of so e embodiments are given. n no way should the following
examples be read to limit, or define, the entire scope of the invention.
Polymer Synthesis
[0027] Lignite-based polymers wer synthesized such that the final polymer
concentration in aqueous solution was 25 weight percent (wi ) while maintaining a
polymer/lignite weight ratio of 70/30 The AMPS/DMA molar ratio was varied, as indicated
in Table below. The polymerization of the 50:50 molar ratio comprised charging a 250
milliliter round bottom fl ask with 20 grams of lignite (Super-Lig from BASF Corporation)
followed by addition of 16 1 37 grams of deionized water. Next, a small a ount of sodium
hydroxide was added (approximately .48 grams) to caustieize the lignite, making it water
soluble. A small amount of sodium formate ( 1 37 grams) was added to keep the molecular
weight low enough to have a product that can be pumped in the field. Next, the solution was
charged with 65.28 grams of sodium 2 a ry amido-2 et ylpr panesuffonate (AMPS 2403
monomer, 50 wt % aqueous solution from Lubrkol Corporation) and 14.08 grams of DMA
(from Sign a-Al lri h Co. LLC). Finally, the initiator system was added (2.58 grants o
triethanolamine and 7 35 grams of a 0 w/v % sodium pers iate solution). The round
bottom flask was then sealed with a .rubber septa and purged with nitrogen. Th solution was
allowed to react for approximately I to 2 hours. The resulting grafted polymer solutions
were then utilized for the following examples.
Example
[0028] The following series of tests was performed to eva ate the use of a lignitebased
copolymer as a gas migration control addiiive for cement cornposttions. Seven sample
cement compositions, designated Samples 1-7, were prepared that included a lignite-based
copolymer. The lignite-based copolymer use in each sample was prepared as described
above. Each of the sample cement compositions comprised 600 grams of LaFarge Joppa
Class H Cement, 189.8 grams of sea water, 12 grams of potassium chloride, 0,4 grams of
EZ-FL ) blending additive (available from Halliburton Energy Services, Inc.), 29.4 grams
of an inorganic cement set accelerator, and ,8 grams of the grafted polymer solution (25 wt
% aqueous solution of the lignite-based copolymer).
[0029] The transition time fo each sample cement composition to change from
having a static ge strength of 1.00 100 ft 2 to having a static gel strength of 500 lb/100 r
was determined using the following procedure. Further, the t e required to reach a static
gel strength of 00 b/ !00 r (referred to as gel time) of each sample cement
composition was a so determined. The static gel strengths were determined at 60¾F and
6,300 pounds per square inch psi ) The static gel strength development tests were
performed using a MACS* II analyzer. This analyzer measures the shear resistance of a
sample cement composition under downhole temperature and pressure while the sample
remains essentially static. The test was conducted b mixin the sample and placing it into
the analyzer. The initial temperature was 80°F and 500 psi. Th sample was then stirred and
cooled to the test conditions. After 42 minutes the sample reached 6 F and 6.300 psi. The
stirring wa continued for 90 more minutes, and the sample was then allowed to remain
essentially static. The stirring paddle is rotated at a rate of about 0 . 1 degrees per minute
while the shear .resistance on the paddle is measured. The shear resistance is correlated to
the static gel strength (units are lb/ 1 0 f ). Per the above procedure, the zero gel time is the
time the sample takes to reach 1 0 lb/100 f n e stirring is stopped,
[0030] Fluid loss tests were also performed on each sample cement composition at
room temperature and 000 p s i differential pressure in accordance with AP Recommended
Practice -2 . Each sample cement composition was conditioned at 0 F for 20 minutes
followed by performing the fluid oss tests with the cells at room temperature.
[00 ] The results for the gel strength development and fluid loss tests are provided
i the table below. The zero gel time and transition for Sample 7 having an AMPS-DMA.
molar ratio of 100/0 were not determined.
i
TABLE
[0032] Example 1 thus indicates that the lignite-based copolymer may function to
shorten transition times. Decreasing the amount of AMPS as compared to the amount of
DMA in the copolymer generally provided shorter transition m - For example, transitions
times of less than 30 minutes were obtained for sample cement compositions 2-4 having an
AMPS-to~DMA molar ratio o f from 25/75 to 50/50. Further, Example i also indicates that
the lignite-based copolymer may provide desirable levels of fluid loss control.
Example 2
[0033] Two additional sample cement compositions, designated Samples 8 and 9,
were prepared to compare a lignite-based copolymer to another graft ed copolymer. Each of
the sample cement compositions comprised 600 grams of a arge Joppa Class Cement,
89.8 grams of sea water, 2 grams of potassium chloride, 0.4 grams of EZ-FLO"" blending
additive (available from Halliburton Energy Services, Inc.), 29.4 grams of an inorganic
cement set accelerator, and 4. grams of Zoneseal* 2000 foaming additive (available fro
Halliburton Energy Sen-ices. Inc.).
[0034] Sample 8 was a comparative composition tha further comprised a ad*
3 additive (available from Halliburton Energy Services, Inc.) an amount of 1 .8
grams Ha ad 413L additive is a grafted polymer solution t at is 25% active and comprises
a lignite backbone grafted with AMPS, DMA, and aerylonitrile.
[0035] Sample 9 further comprised the grafted polymer solution in an amount of
.8 grams. The graft ed polymer solution was prepared as described above and comprised a
lignite-based copo mer comprised a lignite backbone (30% by weight) and grafted pendants
groups (70% by weight) having an AMPS-to-DMA molar ratio of 50/50.
[0036] After preparation, static gel strength development tests were performed for
each sample using a MACS*"' analyzer as described above for Example . A plot of static
gei strength development as a function of ti e was made for each sample. FIG. 1 show
static gei strength development for Sample 8. Sample 8 had a transition time of
approximately 40 minutes. F G 2 shows static ge strength development for Sample 9.
Sa ple a transition time of approximately 10 minutes.
[0037] It should be understood that the compositions and methods ar described
terms of "comprising;' "conta ng, or nc!uding various components or steps, the
compositions and methods can also "consist essentially of * or "consist of the various
components and steps. Moreover, the indefinite articles "a' ' or "an," as used in the claims,
are defined herein to mean one or .more than one of the element that it introduces
[0038] For the sake of brevity, only certain ranges are explicitly disclosed herein.
However, ranges from an lower limit may be combined with any upper limit to recite a
range ot explicitly recited as well as, range from any lower limit may be combined with
any other lower limit to recite a range not explicitly recited, n the same way, ranges from
any upper limit ay be combined with any other upper limit to recite a range not explicitly
recited. Additionally, whenever numerical range with a lower mit and an upper limit is
disclosed, any number an any included range falling within the range are specifically
disclosed, particular, every range of values (of the form, "from about a to abou b, or,
equivalent y, "from approximately to b, or, equivalent!}', "from approximately a-b")
disclosed herein is to be understood to set forth every number and range encompassed within
the broader range of values even not explicitly recited. Thus, every point or individual
value may serve as its ow 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.
[0039] Therefore, the present invention is 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, as the present invention may be modified and practiced
n different but equivalent manners apparent to those skilled n the art having the benefit o
the teachings herein, Although individual embodiments are discussed, the invention covers
all combinations of all those embodiments. Furthermore, no .limitations are intended to th
details of construction or design herein show n, other than as described in the claims below.
A so, 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 the present invention f there is any conflict n the
usages of a word or term in this specification and one or more patent(s) or other documents
that may be incorporated herein by reference, the definitions that are consistent with this
specification should be adopted.
What is claimed is:
. A method of cementing i a subterranean formation comprisi ng:
introducing a cement composition comprising cement water, and a lignitebased
copolymer into a subterranean formation wherein the lignite-based copolymer
comprises a lignite backbone, a first grafted monomer selected from th group consisting of
2-acrytaraido-2-methylpropaoesultbnic acid, a salt of 2-acrylamido-2-met hylpix>panesulfonic
ac d, and combinations thereof, and a seco d grafted monomer comprising N,Ndimethy!
aerylarmde; and
allowing the cement composition to set in the subterranean formation,
wherein cemen composition has a transition time of less than or equa to about 0 minutes.
2. The method of claim wherein the cement composition has a transition time
of less tha or equal to about 30 minutes.
3. The method of claim 1 wherein the introducing the cement composition
comprises introducing the cement composition into a well bore having a bottom ho e static
temperature of less than or equal to about 0° .
4. The method of claim wherein the allowing the cement composition to set
comprises allowing the cement composition to set in a well bore annu!us.
5. The method of claim wherein the first grafted monomer comprises the salt
of 2~acrylamido~2~methyipropanesul ionic, the salt comprising a sodium salt.
6. The method of claim I wherein the lignite backbone is present in an amount
of about % to about 50% by weight of the lignite-based copolymer.
7 The method of claim 1 wherein the lignite-based copolymer comprises
pendant groups comprising the first grafted monomer and the second grafted monomer, the
pendant groups present in an amount of about 50% to about 90% by weight of the lignitebased
copolymer.
8 . The method of claim wherein the pendants groups are essentially free of
any additional co-monomers.
9. The method of claim 1 wherein a ratio of the .first grafted monomer to the
second grafted monomer is from about 10/90 to about 60/40
t) . The method of claim 1 wherein the cement comprises at least one hydraulic
cement selected from the group consisting of a Portland cement, a po o ana cement, a
gypsum cement, a high alumina content cement, a slag cement, a silica cement, and any
combination thereof.
1. The method of claim I wherein the cement composition further comprises an
additive selected from the group consisting of a strength-retrogression additive, a set
accelerator, a weighting agent, a lightweight additive, a gas-generating additive, a
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, a
thixotropic additive, and any combination thereof.
12. The method of claim ί wherein the cement composition further comprises an
additive selected from the group consisting of crystalline silica, amorphous silica, fumed
silica, a salt, a fiber, hydratable clay, calcined shale, vitrified shale, a microsphere, fly ash,
slag * diaiomaceous earth, metakaolin, r ce hus ash, natural po oSan, zeolite, cement ki ln
dust, lime, an elastomer, a resin, latex, and a y combination thereof.
13 The ethod of claim 1 wherein the cement composition has a density in a
range of from about S pounds per gallon to about pounds per gallon.
4. The method of claim 1 further comprising providing an aqueous solution
comprising the first grafted monomer and the second grafted monomer,
15. The method of claim 14 wherein the aqueous solution comprises the first
grafted monomer and the second grafted monomer in art amount in a range of from about
1 % to about 25% by weight of the aqueous solution
. A method of cementing in a . subterranean formation comprising:
introducing a cement composition comprising cement, water, and a lignitebased
copolymer into a well bore having a bottom hole circulating temperature of less than
or equal to about 00°F, wherein the lignite-based copolymer comprises:
a backbone in an amount of about 20% to abou 40% by weight of
the lignite-based copolymer, th backbone comprising causticized lignite; and
grafted pe dan groups in an amount of about 60% to abou 80% by
weight of the lignite-based copolymer, the grafted pendant groups comprising sodium 2-
aerylamido-2~methylpropanesul.fonate and -d methyiacry amide in a molar ratio of
sodium 2-acrylamido-2-fnetlrylpropanesu fonate and N,N-din ethylacryla ide of about
10/90 to about 60/40; and
allowing the cement composition to set in the subterranean formation,
wherein the cement composition has a transition time o less than or equal to about 30
minutes.
. The method of claim . wherein the we!! bore has a bottom hole static
temperature of less than or equal to about 7Q¾F.
. The method of claim wherein the allowing the cement composition to set
comprises allowing the cement composition t set in well bore annuius.
19. The method of claim 16 wherein the backbone is present in an amount of
about 30% by weight of the lignite-based copolymer, wherein the grafted pendant groups are
present in an amount of about 70% b weight of the lignite-based copolymer, and wherein
the molar ratio of the sodium 2-acrylam»do-2-raethy1propanesuIfonate and
dimethylacrylamide is about 50/50,
20. The method of claim 1.6 wherein the pendants groups are essentially free of
any additional co-monomers
1. The method of claim wherein the cement comprises a least one hydraulic
cement selected from the group consisting of a Portland cement, a po ola a cement, a
m cement, high alumina content cement a slag cement, a silica cement, and any
combination thereof.
22. The method of claim 1 wherein the cement composition further comprises
an additive selected from the group consisting of a strength-retrogression additive, a set
accelerator, a wei ht n agen a lightweight additive, a gas-generating additive, a
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, a
thixotropie additive, and any combination thereof.
23. The method of claim 1 wherein the cement composition further comprises
an additive selected from the group consisting of crystalline silica, amorphous silica, fumed
silica, a salt, a fiber, hydratable day, calcined shale, vitrified shale, a .microsphere, f y ash,
slag, diatoma-ceous earth, metakaolin, rice husk ash, natural pozzolan, zeolite, cement kiln
dust, H e a elastomer, a resin, latex, and a y combination thereof.
24. The method of claim wherein the cement composition has a density in a
range of from about 8 pounds per gallon to about 1? pounds per gallon,
25. The method of c laim iurther comprising providing an aqueous solution
comprising the first grafted monomer and the second grafted monomer.
26. The method of claim 25 wherein the aqueous solution comprises the first
grafted monomer and the second grafted monomer i a n amount in a range of fro about
. % to about 25% by weight of the aqueous solution.
2 . A cement composition comprising:
cement;
water; and
a lignite-based copolymer comprising a lignite backbone, a first grafted
monomer selected from the group consisting of 2-acrylamido-2-methylpropanesulfonic acid,
a salt of 2-ae.rylamido-2-methylpropanesiiSfonic acid, and combinations thereof, and second
grafted monomer comprising N,N-dimethylacrylamide,
wherein the cemeni composition has a transition time at 6 F and 6300 psi
of less than or equal to about 150 minutes.
28. The cement composition of claim 27 wherein the first grafted monomer
comprises the salt of 2-acrylamido-2-methyIpropanesulfbnk !. the salt comprising a sodium
salt.
29. The cement composition of claim 2? wherein the lignite backbone is present
in an amount of about 10% to about 50% by weight of the copolymer.