CEMENT COMPOSITIONS COMPRISING SUB-MICRON ALUMINA AND
ASSOCIATEDMETHODS
BACKGROUND
[0001] The present invention relates to cementing operations. More particularly, in
certain embodiments, the present invention relates to cement compositions and methods of
cementing in a subterranean formation that include sub-micron alumina for accelerating setting.
[0002] In general, well treatments include a wide variety of methods that may be
performed in oil, gas, geothermal and/or water wells, such as drilling, completion and workover
methods. The drilling, completion and workover methods may include, but are not limited to,
drilling, fracturing, acidizing, logging, cementing, gravel packing, perforating and conformance
methods. Many of these well treatments are designed to enhance and/or facilitate the recovery
of desirable fluids from a subterranean well.
[0003] In cementing methods, such as well construction and remedial cementing, well
cement compositions are commonly utilized. For example, in subterranean well construction, a
pipe string (e.g., casing and liners) may be run into a well bore and cemented in place using a
cement composition. The process of cementing the pipe string in place is commonly referred to
as "primary cementing." In a typical primary cementing method, a cement composition may be
pumped into an annulus between the walls of the well bore and the exterior surface of the pipe
string disposed therein. The cement composition sets in the annular space, thereby forming an
annular sheath of hardened, substantially impermeable cement that supports and positions the
pipe string in the well bore and bonds the exterior surface of the pipe string to the subterranean
formation. Among other things, the annular sheath of set cement surrounding the pipe string
functions to prevent the migration of fluids in the annulus, as well as protecting the pipe string
from corrosion. Cement compositions also may be used in remedial cementing methods, such
as squeeze cementing and the placement of cement plugs.
[0004] The hydration of the cement in these cementing methods is a complex process
because several phases may take part in the reaction simultaneously. In order to control the
reaction processes to render the compositions suitable for well cementing, various additives such
as retarders, strength enhancers, and accelerators may be added. However, the operating
conditions for wells are becoming more challenging and demanding, and the search for new
materials continues to meet these challenges. For instance, cement slurries, used in well
cementing often encounter problems of gaining sufficient strength in a reasonable amount of
time for well operations to continue. The costs associated with wait-on-cement ("WOC") play
an important role in well cementing. This problem may be further aggravated if latex is used
with the cement. Furthermore, when latex is present in cement slurries, addition of calcium salts
or other salts to accelerate the setting of cement, for example, at low temperatures, can cause
coagulation of the latex with resultant gelling of the cement slurries. This gelling may result in
premature loss of fluidity of the cement slurry before placement in the desired location in the
well bore. Latex may be used for fluid loss control, to provide resiliency to the set cement,
and/or to reduce the issues associated with gas channeling. Latex-containing cement
compositions, however, may have slower strength development with respect to comparable
cement compositions.
SUMMARY
[0005] The present invention relates to cementing operations. More particularly, in
certain embodiments, the present invention relates to cement compositions and methods of
cementing in a subterranean formation that include sub-micron alumina for accelerating setting.
[0006] According to one aspect of the present invention, there is provided a method of
cementing in a subterranean formation comprising: introducing a cement composition into the
subterranean formation, wherein the cement composition comprises hydraulic cement, submicron
alumina, and water; and allowing the cement composition to set in the subterranean
formation.
[0007] According to another aspect of the present invention, there is provided a method
of cementing in a subterranean formation comprising: preparing a cement composition
comprising hydraulic cement, sub-micron alumina for accelerating setting of the cement
composition, latex, and water, wherein the sub-micron alumina has a particle size of about 150
m to about 950 run, wherein preparing the cement composition comprises providing a colloidal
alumina dispersion comprising the sub-micron alumina in an aqueous base fluid; introducing the
cement composition into a well bore in a space between the subterranean formation and a
conduit disposed in the well bore; and allowing the cement composition to set.
[0008] According to another aspect of the present invention, there is provided a cement
composition comprising hydraulic cement, sub-micron alumina, and water.
[0009] 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 within the scope of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] T e present invention relates to cementing operations. More particularly, in
certain embodiments, the present invention relates to cement compositions and methods of
cementing in a subterranean formation that include sub-micron alumina for accelerating setting.
[001 1] There may be several potential advantages to the methods and compositions of
the present invention, only some of which may be alluded to herein. One of the many
advantages of the present invention is that inclusion of sub-micron alumina in cement
compositions may improve the mechanical properties of the cement composition. By way of
example, inclusion of sub-micron alumina may provide accelerated setting and, thus, accelerated
strength development, particularly in latex-containing cement compositions. While the methods
and compositions of the present invention may be suitable for use in a wide variety of cementing
operations, they may be particularly suitable for use in latex-containing cement compositions in
low temperature wells, such as those having a bottomhole circulating temperature of about 40°F
to about 180°F and, alternatively, of about 40°F to about 125°F.
[0012] An embodiment of the cement compositions of the present invention comprises
hydraulic cement, sub-micron alumina, and water. In certain embodiments, the cement
compositions may further comprise latex. Those of ordinary skill in the art will appreciate that
the example 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
about 4 pounds per gallon ("lb/gal") to about 20 lb/gal. In certain embodiments, the cement
compositions may have a density in the range of about 8 lb/gal to about 17 lb/gal. Embodiments
of the cement compositions may be foamed or unfoamed or may comprise other means to
reduce their densities, such as hollow microspheres, low-density elastic beads, or other densityreducing
additives known in the art. Those of ordinary skill in the art, with the benefit of this
disclosure, will recognize the appropriate density for a particular application.
[0013] Embodiments of the cement compositions of the present invention comprise a
hydraulic cement. Any of a variety of hydraulic 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. Such hydraulic cements, include,
but are not limited to, Portland cements, pozzolana cements, gypsum cements, high-aluminacontent
cements, slag cements, silica/lime cements and combinations thereof. In certain
embodiments, the hydraulic cement may comprise a Portland cement. The Portland cements
that may be suited for use in embodiments of the present invention are classified as Class A, C,
G and H cements according to American Petroleum Institute, Recommended Practice for
Testing Well Cements, API Specification 10B-2 (ISO 10426-2), First edition, July 2005. In
addition, in some embodiments, cements suitable for use in the present invention may include
cements classified as ASTM Type I, II, or III. Belite cements also may be suitable for use in
embodiments of the present invention. Belite cements typically contain belite (dicalcium
silicate, C2S) as the sole or primary calcium silicate. For example, belite cement may comprise
belite in an amount of at least about 50% by weight of calcium silicates. By way of further
example, a belite cement may comprise belite in an amount of at least about 80% by weight of
calcium silicates and, alternatively, in an amount of at least about 95% by weight of calcium
silicates. However, due to their slower rate of strength development, belite cements may not be
suitable for certain applications, such as in latex-containing cement compositions.
[0014] Embodiments of the cement compositions of the present invention further
comprise sub-micron alumina. As used herein, sub-micron alumina is defined as alumina
having any one of the structural features or dimensions, for example, length, width, thickness, or
diameter, of greater than about 100 nanometers ("nm") and less than about 1 micron or, in a
preferred range, of greater than about 150 nm to about 950 nm. For example, the sub-micron
alumina may have a particle size in the range of about 200 nm to about 800 nm and,
alternatively, in the range of about 400 nm to about 500 nm. In contrast to sub-micron alumina,
it should be understood that nano-alumina has a particle size of less than about 100 nm. Submicron
alumina, however, may be more useful than nano-alumina due, for example, to its low
cost as compared with nano-materials. It should be noted that the sub-micron alumina may be
used in combination with differently sized particles of alumina, in accordance with present
embodiments. For example, alumina with particle sizes greater than about 1 micron and/or less
than about 100 nm may be included in a cement composition in accordance with present
embodiments.
[0015] As used herein, "particle size" refers to volume surface mean diameter ("Ds")
which is related to the specific surface area. Volume surface mean diameter may be defined by
the following formula: Ds = 6/ ( sAwpp) where F = Sphericity; Aw= Specific surface area and
pp = Particle density. It should be understood that the particle size of the su mic on alumina
may vary based on the measurement technique, sample. preparation, and .sample conditions (e.g.,
temperature, concentration, etc.). One technique for measuring particle size of the sub-micron
alumina at room temperature (approx. 80°F) includes dispersing the particle in a suitable solvent
(such as chloroform, dichloroethane, acetone, methanol, ethanol, water, etc.) by sonification and
proper dilution. A dispersing agent may be used to deagglomerate the particles, if needed. The
diluted, dispersed solution may then be placed on a carbon-coated copper grid with 300 mesh
size by using a micropipette. It may then be dried and examined by Transmission electron
microscopy (TEM). The particle size distribution may be obtained with high accuracy using an
appropriate computation technique. By way of example, TEM image processing may use
image-processing software such as Image-Pro® Plus software from Media Cybernetics to
determine the particle size. Another example technique involves use of calibrated drawing tools
in Digital Micrograph software followed by statistical analysis of the data with Kaleida-Graph
software to determine the particle size.
[0016] Different types of sub-micron alumina may be used in accordance with
embodiments of the present invention. For example, the sub-micron alumina may be provided
as a colloidal alumina dispersion that comprises sub-micron alumina particles suspended in base
fluid such as water. Embodiments of the present invention also may include sub-micron
alumina in a dry, free-flowing state. Alternatively, discrete particles of the sub-micron alumina
may be agglomerated to form a cohesive mass. The agglomerated sub-micron alumina may then
be included in the cement composition in embodiments of the present invention. It should be
understood that the agglomerated sub-micron alumina generally should disperse into discrete
particles of sub-micron alumina after mixing with the cement composition, either immediately
after a delay period. Alternately, a suitable dispersant, for example an anionic acrylate polymer
or suitable surfactants, capable of dispersing agglomerated alumina into discrete particles of
sub-micron alumina may be added to mix water, followed by solid alumina or a dispersion in a
base fluid, and finally solid cement blend. Alternately, solid alumina powder may be coated with
a dispersing compound capable of dispersing agglomerated alumina into discrete particles of
sub-micron alumina and used as a solid additive to cement blend or to mix water.
[0017] Sub-micron alumina differs from larger-sized particulate materials (e.g., largersized
particulate alumina) particular that may be included cement compositions due to its high
surface to volume ratio. The area of the interface between the cement matrix and the submicron
alumina is typically an order of magnitude greater than that in compositions containing
larger-sized composite materials. Due to their high surface energy, the sub-micron alumina may
exhibit improved properties as compared to larger-sized materials.
[0018] It is now recognized that the sub-micron alumina utilized with present
embodiments, may have an impact on certain physical characteristics of the cement
compositions. For example, relative to cement compositions that do not contain sub-micron
alumina, inclusion of sub-micron alumina may provide for more rapid strength development as
well as accelerated setting. More particularly, inclusion of a colloidal sub-micron alumina
dispersion in a cement slurry in an amount of about 0.2 gallons per 94-pound sack of cement
("gps") may increase the strengths from about 20% to about 65% after twenty-four hours
compared to an identical slurry without sub-micron alumina, in accordance with embodiments
of the present invention. In addition, inclusion of a colloidal sub-micron alumina dispersion in a
latex-containing composition in an amount of 0.05 gps to about 0.2 gps may increase strength by
at least about 85% after forty-eight hours with potentially up to 2.5 times higher strength after
forty-eight hours. The colloidal alumina dispersion may contain, for example, about 10% to
about 30% dispersed sub-micron alumina phase (e.g., 400 nm to 500 nm) by weight.
[001 ] Accordingly, a cement composition in accordance with present embodiments
may comprise a sufficient amount of the sub-micron alumina to provide the desired
characteristics (e.g., strength development) for the cement composition. In some embodiments,
the sub-micron alumina may be present in the cement composition in an amount in the range of
about 0.1% to about 10% by weight of the cement on a dry basis ("bwoc") (e.g., about 0.5%,
about 1%, about 2%, about 4%, about 6%, about 8%, etc.). More particularly, the sub-micron
alumina may be present in embodiments of the cement composition in an amount in the range of
about 0.5% to about 5% bwoc.
[0020] The water used in embodiments of the cement compositions of the present
invention may be freshwater or saltwater (e.g., water containing one or more salts dissolved
therein, seawater, brines, saturated saltwater, etc.). In general, the water may be present in an
amount sufficient to form a pumpable slurry. In certain embodiments, the water may be present
in the cement compositions in an amount in the range of about 33% to about 200% bwoc. n
certain embodiments, the water may be present in an amount in the range of about 35% to about
70% bwoc.
[0021] Moreover, embodiments of the cement compositions of the present invention also
may comprise latex. As will be understood by those skilled in the art, the latex may comprise
any of a variety of rubber materials that are commercially available in latex form, either as
aqueous emulsions or dry powders. Suitable rubber materials include natural rubber (e.g., cis-
1,4-polyisoprene), modified natural rubber, synthetic rubber, and combinations thereof.
Synthetic rubber of various types may be utilized, including ethylene-propylene rubbers,
styrene-butadiene rubbers, nitrile rubbers, nitrile butadiene rubbers, butyl rubber, neoprene
rubber, polybutadiene rubbers, acrylonitrile-styrene-butadiene rubber, polyisoprene rubber, and
AMPS-styrene-butadiene rubber, combinations thereof. As used herein, the term "AMPS"
refers to 2-acrylamido-2-methylpropanesulfonic acid and salts thereof. In certain embodiments,
the synthetic rubber may comprise AMPS in an amount ranging from about 7.5% to about 10%,
styrene in an amount ranging from about 30% to about 70% and butadiene in an amount ranging
from about 30% to about 70%. Examples of suitable AMPS-styrene-butadiene rubbers are
described in more detail in U.S. Patent Nos. 6,488,764 and 6,184,287, the entire disclosures of
which are incorporated herein by reference. Those of ordinary skill in the art will appreciate
that other types of synthetic rubbers are also encompassed within the present invention.
[0022] In certain embodiments, the latex comprises an aqueous emulsion that comprises
styrene-butadiene rubber. As will be appreciated, the aqueous phase of the emulsion comprises
an aqueous colloidal dispersion of the styrene-butadiene copolymer. Moreover, in addition to
the dispersed styrene-butadiene copolymer, the emulsion may comprise water in the range of
about 40% to about 70% by weight of the emulsion and small quantities of an emulsifier,
polymerization catalysts, chain modifying agents, and the like. As will be appreciated, styrenebutadiene
latex is often produced as a terpolymer emulsion that may include a third monomer to
assist in stabilizing the emulsion. Non-ionic groups which exhibit steric effects and which
contain long ethoxylate or hydrocarbon tails also may be present.
[0023] In accordance with embodiments of the present invention, the weight ratio of the
styrene to the butadiene in the latex may be in the range of about 10:90 to about 90: 10. In some
embodiments, the weight ratio of the styrene to the butadiene in the emulsion may be in the
range of about 20:80 to about 80:20. An example of a suitable styrene-butadiene latex has a
styrene-to-butadiene weight ratio of about 25:75 and comprises water in an amount of about
50% by weight of the emulsion. Such a styrene-butadiene latex is available from Halliburton
Energy Services, Inc., Duncan, Okla., under the name Latex 2000™ cement additive. Another
example of a suitable styrene-butadiene latex has a styrene-to-butadiene weight ratio of about
30:70.
[0024] Where used, the latex may be provided in the cement compositions of the present
invention in an amount sufficient for the desired application. In some embodiments, the latex
may be included in the cement compositions in an amount in the range of about 2% to about
45% bwoc. In some embodiments, the latex may be included in the cement compositions in an
amount in the range of about 5% to about 27% bwoc.
[0025] Embodiments of the cement compositions of the present invention also may
comprise a latex stabilizer. Among other things, the latex stabilizer may be included in
embodiments of the cement compositions for preventing the cement compositions from
prematurely coagulating. Suitable latex stabilizers may include a surfactant or combination of
surfactants for preventing the premature inversion of the latex emulsion. Examples of suitable
latex stabilizers include, but are not limited to, surfactant molecules containing ethoxylated alkyl
sulfonates and sulfates. Additional examples of suitable latex stabilizing surfactants which are
suitable for this purpose may have the formula R-Ph-0(OCH 2CH2)mOH where R contains an
alkyl group of from about 5 to about 30 carbon atoms, Ph contains a phenyl group, and m is an
integer having value between 5 to 50. An example of a surfactant of this formula is ethoxylated
nonylphenyl containing in the range of about 20 to about 30 moles of ethylene oxide. Another
example of a suitable surfactant is a salt having the formula Ri(R 20 ) S0 3X where i contains
an alkyl group having 5 to 20 carbon atoms, R2 contains the group -CH2- CH2-, n is an integer
having value in between 10 to 40, and X is any suitable cation. An example of surfactant of
this formula is the sodium salt of a sulfonated compound derived by reacting a C1 -15 alcohol
with about 15 moles of ethylene oxide having the formula H(CH2 ) 12- 5(CH2CH20 )15S0 a.
Specific examples of suitable latex stabilizers include Stabilizer 434B™ latex stabilizer,
Stabilizer 434C™ latex stabilizer, and Stabilizer 434D™ latex stabilizer, which are available from
Halliburton Energy Services, Inc. While embodiments of the present invention encompass a
wide variety of different latex stabilizers and amounts thereof that may be included in the
cement compositions of the present invention depending on the particular latex used and other
factors, the latex stabilizer may be included in embodiments of the cement compositions in an
amount in the range of about 0% to about 30% by weight of the aqueous latex in the cement
composition and, alternatively, about 10% to about 20% by weight.
[0026] Other additives suitable for use in subterranean cementing operations also may be
added to embodiments of the cement compositions, in accordance with embodiments of the
present invention. Examples of such additives include, but are not limited to, strengthretrogression
additives, set accelerators, set retarders, 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, nano-particles, and combinations thereof. By way of example, the
cement composition may be a foamed cement composition further comprising a foaming agent
and a gas. 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, diatomaceous earth, metakaolin, rice husk ash, natural pozzolan, zeolite, cement
kiln dust, lime, elastomers, resins, nano-clays (e.g., naturally occurring, organically modified),
nano-silica, nano-zinc oxide, nano-boron, nano-iron oxide, nano-zirconium oxide, nanomagnesium
oxide, nano-barite, 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 for a particular application and desired result.
[0027] An example of a cement composition of the present invention comprises Portland
cement, colloidal alumina dispersions in an aqueous base fluid in an amount of about 0.05 gps to
about 0.2 gps, and water. The colloidal alumina dispersions may comprise sub-micron alumina
in an amount of about 10% to about 30% by weight of the dispersions. Embodiments of the
example cement composition further may comprise an aqueous latex, such as styrene-butadiene
latex or AMPS-styrene-butadiene latex. Additional additives may include a defoaming agent
(such as D-AIR 3000L™ defoamer), a cement set retarder (such as HR-6L retarder), and a
cement dispersant (such as CFR-3L dispersant).
[0028] Another example of a cement composition of the present invention comprises
Portland cement, colloidal alumina dispersions in an aqueous base fluid in an amount of about
0.05 gps to about 0.2 gps, styrene-butadiene latex in an amount of about 1.5 gps, and water. The
colloidal alumina dispersions may comprise sub-micron alumina in an amount of about 10% to
about 30% by weight of the dispersions. Embodiments of the example cement composition
further may comprise an aqueous latex, such as styrene-butadiene latex or AMPS-styrenebutadiene
latex. Additional additives may include a defoaming agent (such as D-AIR 3000L™
defoamer), a latex stabilizer (such as Stabilizer 434D™ latex stabilizer), a cement set retarder
(such as HR-6L retarder), and a cement dispersant (such as CFR-3L dispersant).
[0029] As will be appreciated by those of ordinary skill in the art, embodiments of the
cement compositions of the present invention may be used in a variety of subterranean
applications, including primary and remedial cementing. Embodiments of the cement
compositions may be introduced into a subterranean formation and allowed to set therein.
Embodiments of the cement compositions may comprise, for . example, cement, sub-micron
alumina, and water. Embodiments of the cement compositions further may comprise latex in
certain applications.
[0030] In primary cementing embodiments, for example, a cement composition may be
introduced into a space between a subterranean formation and a conduit (e.g., pipe string)
located in the subterranean formation. The cement composition may be allowed to set to form a
hardened mass in the space between the subterranean formation and the conduit. Among other
things, the set cement composition may form a barrier, preventing the migration of fluids in the
well bore. The set cement composition also may, for example, support the conduit in the well
bore.
[0031] In remedial cementing embodiments, a cement composition may be used, for
example, in squeeze-cementing operations or in the placement of cement plugs. By way of
example, the cement composition may be placed in a well bore to plug a void or crack in the
conduit or the cement sheath or a microannulus between the cement sheath and the conduit.
[0032] To facilitate a better understanding of the present technique, the following
examples of some specific embodiments are given. In no way should the following examples be
read to limit, or to define, the scope of the invention.
EXAMPLE 1
[0033] This example was performed to analyze the effect of including sub-micron
alumina in a cement composition. For this example, six different slurries were prepared. The
cement compositions were then tested to determine their rate of strength development and
thickening times. As set forth below, the respective test results for the six different slurries
demonstrate that inclusion of sub-micron alumina in the slurry provides faster early strength
development and shortened thickening times.
[0034] Slurries 1-6 each included Portland Class H cement, 0.05 gps of a defoamer (DAIR
3000L™ available from Halliburton Energy Services, Inc.), and sufficient water to provide
the density listed in the table below. Slurries 2, 4, and 6 also included a colloidal alumina
dispersion in an amount of 0.2 gps. The colloidal alumina dispersion was supplied by Bee
Chems, India and contained sub-micron alumina (400 nm to 500 nm) in an aqueous base fluid in
an amount of about 20% by weight.
[0035] After the six slurries were prepared, tests were performed to determine various
physical characteristics associated with inclusion of the sub-micron alumina in each of the
slurries. One of these tests was performed to determine the rate of strength development for
each of the slurries. An ultrasonic cement analyzer ("UCA") available from FANN Instrument
Company, USA (Controller Model 304) was used to determine the compressive strength rate as
a function of time. The rate of strength development was calculated as the slope of the initial
linear part (starting from the onset of the strength development) of the compressive strength
versus time graph. Additionally, the UCA was also used to determine the compressive strength
of the slurries after twenty-four hours and the time for the slurries to develop a compressive
strength of 500 psi. The thickening time associated with each slurry was determined by
performing a thickening-time test at 125°F in accordance with API Recommended Practice 10B-
2. The thickening time for each slurry was defined as time required for the respective slurry to
reach a consistency of 70 Bearden units (Be) at 125°F.
[0036] The results of these tests are provided in the table below.
TABLE 1. Effect of Sub-Micron Alumina on Development of High-Early
Strength and Thickening Times in Latex-Containing Slurries
Gelling behavior was observed for this density.
[0037] Table 1 illustrates the development of high-early strength for slurries containing
sub-micron alumina. In particular, as compared to slurries without sub-micron alumina, the
compressive strength obtained in twenty-four hours increased dramatically for the slurries
containing sub-micron alumina with the increase in compressive strength from 20% to 65%,
depending on, for example, slurry density. Moreover, the time required for the development of
500 psi was considerably shorter as compared to the slurries without sub-micron alumina.
Moreover, the thickening times in Table 1 also indicate that slurries containing sub-micron
alumina should also have shorter thickening times, and yet of sufficient duration to meet
placement requirements, suggesting that sub-micron alumina may act as a set accelerator, in
addition to acting as a strength enhancer and as an additive for increasing rates of strength
development.
EXAMPLE 2
[0038] This example was performed to compare sub-micron alumina with a
conventional cement set accelerator (Econolite™ additive). For this example, four different
slurries were prepared. The cement compositions were then tested to determine their rate of
strength development and thickening times. As set forth below, the respective test results for the
four different slurries demonstrate that inclusion of sub-micron alumina in the slurry provides
comparable results to the Econolite ™additive at a reduced quantity.
[0039] Slurries 7-10 each included Portland Class H cement, 0.05 gps of a defoamer CDAIR
3000L™ available from Halliburton Energy Services, Inc.), and sufficient water to provide
the density listed in the table below. Slurry 8 also included Econolite™ additive, available from
Halliburton Energy Services, Inc. Slurries 9-10 also included a colloidal alumina dispersion
supplied by Bee Chems, India. The colloidal alumina dispersion contained sub-micron alumina
(400 nm to 500 nm) in an aqueous base fluid in an amount of about 20% by weight.
[0040] After the four slurries were prepared, tests were performed to compare various
physical characteristics of each of the slurries. One of these tests was performed to determine
the rate of strength development for each of the slurries. A UCA was used to determine the
compressive strength rate as a function of time. The rate of strength development was
calculated as the slope of the initial linear part (starting from the onset of the strength
development) of the Compressive strength versus Time graph. Additionally, the UCA was used
to determine the compressive strength of the slurries after twenty-four hours and the time for the
slurries to develop a compressive strength of 500 psi. The thickening time associated with each
cement slurry was determined by performing a thickening-time test at 125°F in accordance with
API Recommended Practice 1OB-2. The thickening time for each slurry was defined as the time
required for the respective slurry to reach a consistency of 70 Be at 125°F.
[0041] The results of these tests are provided in the table below.
TABLE 2. Comparison of Sub-Micron Alumina
With a Conventional Cement Set Accelerator
The thickening time for Slurry 7 could not be measured precisely.
The % solids in Slurry 9 was equivalent to the Econolite in Slurry 8.
[0042] Table 2 illustrates that sub-micron alumina provides better strength development
rates and reasonable thickening times when compared with a conventional cement set
accelerator. More particularly, at the same slurry density, a lower quantity of sub-micron
alumina provided equivalent results to that of the Econolite™ additive.
EXAMPLE 3
[0043] This example was performed to compare sub-micron alumina with another
conventional cement set accelerator (calcium chloride). For this example, three different
slurries were prepared. The cement compositions were then tested to determine their rate of
strength development and thickening times. As set forth below, the respective test results for the
three different slurries demonstrate that inclusion of sub-micron alumina in the slurry provides
comparable results to the calcium chloride at a lower quantity.
[0044] Slurries 11-13 each included Portland Class H cement, 0.05 gps of a defoamer
(D-AIR 3000L™ available from Halliburton Energy Services, Inc.), and sufficient water to
provide the density listed in the table below. Slurry 12 also included calcium chloride. Slurries
13 also included a colloidal alumina dispersion in an amount of 0.2 gps. The colloidal alumina
dispersion was supplied by Bee Chems, India and contained sub-micron alumina (400 nm to 500
nm) in an aqueous base fluid in an amount of about 20% by weight.
[0045] After the three slurries were prepared, tests were performed to compare various
physical characteristics of each of the slurries. One of these tests was performed to determine
the rate of strength development for each of the slurries. A UCA was used to determine the
compressive strength rate as a function of time. The rate of strength development was
calculated as the slope of the initial linear part (starting from the onset of the strength
development) of the Compressive strength versus Time graph. Additionally, the UCA was also
used to determine the compressive strength of the slurries after twenty-four hours and the time
for the slurries to develop a compressive strength of 500 psi. The thickening time associated
with each cement slurry was determined by performing a thickening-time test at 125°F in
accordance with API Recommended Practice 10B-2. The thickening time for each slurry was
defined as the time required for the respective slurry to reach a consistency of 70 Be at 125°F.
[0046] The results of these tests are provided in the table below.
TABLE 3. Comparison of Sub-Micron Alumina
With a Conventional Cement Set Accelerator
At 16.4 lb/gal some gelling was noticed, regardless of the cement set accelerator.
[0047] Table 3 illustrates that sub-micron alumina provides comparable strength
development rates and reasonable thickening times when compared with a conventional cement
set accelerator. More particularly, at the same slurry density, a lower quantity of sub-micron
alumina provided equivalent results to that of calcium chloride.
EXAMPLE 4
[0048] This example was performed to analyze the effect of including sub-micron
alumina in latex-containing cement compositions. For this example, four different slurries were
prepared. The cement compositions were then tested to determine their rate of strength
development and thickening times. As set forth below, the respective test results for the four
different slurries demonstrate that inclusion of sub-micron alumina in the slurry provides higher
early strengths and faster strength development rates with reasonable thickening times.
[0049] Slurries 14-17 each contained Portland Class H cement, latex in an amount of 1.5
gps, and a colloidal alumina dispersion in an amount ranging from 0 gps to 0.2 gps. Sufficient
water was included in the slurries to provide a density of 16.4 lb/gal. Additional additives
present in each slurry were D-AIR 3000L™ defoamer in an amount of 0.05 gps, Stabilizer
434D™ latex stabilizer in an amount of 0.2 gps, HR®-6L cement set retarder in an amount of
0.05 gps, and CFR-3L™ dispersant in an amount of 0.143 gps. The latex included in the slurries
was Latex 2000™ cement additive having a particle size ranging from 150 n to 200 nm. The
colloidal alumina dispersion was supplied by Bee Chems, India and contained sub-micron
alumina (400 nm to 500 nm) in an aqueous base fluid in an amount of about 20% by weight.
[0050] After the four slurries were prepared, tests were performed to compare various
physical characteristics of each of the slurries. One of these tests was performed to determine
the rate of strength development for each of the slurries. A UCA was used to determine the
compressive strength rate as a function of time. The rate of strength development was
calculated as the slope of the initial linear part (starting from the onset of the strength
development) of the Compressive strength versus Time graph. Additionally, the UCA was also
used to determine the compressive strength of the slurries after twenty-four and forty-eight
hours. The thickening time associated with each cement slurry was determined by performing a
thickening-time test in accordance with API Recommended Practice 10B-2. The thickening time
for each slurry was based on the respective slurry reaching a consistency of 70 Be at 80°F.
[0051] The results of these tests are provided in the table below.
TABLE 4. Effect of Sub-Micron Alumina Loading on Strength Development and
Thickening Times on Slurries Containing Latex
[0052] Table 4 illustrates that there were significant increases in twenty-four hour and
forty-eight hour compressive strength values as the concentration of sub-micron alumina was
increased from 0 gps to 0.2 gps. As compared to the neat latex slurry, the forty-eight hour
compressive strength increased almost 2.5 times by addition of 0.2 gps of sub-micron alumina.
It should be noted that the test temperature was 80°F. At 0.2 gps of sub-micron alumina, the
slurry had a reasonable thickening time of 6 hours and 56 minutes. The neat latex slurry at this
temperature took more than 28 hours to reach 70 Be. The results indicate that sub-micron
alumina when added to latex-containing cement slurries acts as a set accelerator, a strength
enhancer and provides for increased rates of strength development at low temperatures.
EXAMPLE 5
[0053] This example was performed to analyze the effect of temperature variation on the
rate of strength development for slurries containing latex and sub-micron alumina. For this
example, three different slurries were prepared. The cement compositions were then tested to
determine their rate of strength development and thickening times. As set forth below, the
respective test results for the three different slurries demonstrate that sub-micron alumina can be
used as an accelerator for latex-containing cement slurries at low temperatures.
[0054] Slurries 18-20 each contained Portland Class H cement, latex in an amount of 1.5
gps, and a colloidal alumina dispersion in an amount of about 0.2 gps. Sufficient water was
included in the slurries to provide a density of 16.4 lb/gal. Additional additives present in each
slurry were D-AIR 3000L™ defoamer in an amount of 0.05 gps, Stabilizer 434D™ latex
stabilizer in an amount of 0.2 gps, HR®-6L cement set retarder in an amount of 0.05 gps, and
CFR-3L™ dispersant in an amount of 0.143 gps. The latex included in the slurries was Latex
2000™ cement additive having a particle size ranging from 150 nm to 200 nm. The colloidal
alumina dispersion was supplied by Bee Chems, India and contained sub-micron alumina (400
nm to 500 nm) in an aqueous base fluid in an amount of about 20% by weight.
[0055] After the three slurries were prepared, tests were performed to determine various
physical characteristics associated with varying the temperature on slurries containing latex and
sub-micron alumina. One of these tests was performed to determine the rate of strength
development for each of the slurries. A UCA was used to determine the compressive strength
rate as a function of time. The rate of strength development was calculated as the slope of the
initial linear part (starting from the onset of the strength development) of the Compressive
strength versus Time graph. Additionally, the UCA was also used to determine the compressive
strength of the slurries after twenty-four, forty-eight hours, seventy-two hours. The forty-eight
and seventy-two hour compressive strength values were not determined for Slurry 20 because it
had higher strength at twenty-four hours. The seventy-two hour compressive strength value was
not determined for Slurry 19 because it had higher strength at forth-eight hours. The thickening
time associated with each cement slurry was determined by performing a thickening-time test in
accordance with API Recommended Practice 10B-2. The thickening time for each slurry was
based on the respective slurry reaching a consistency of 70 Be at 80°F.
[0056] The results of these tests are provided in the table below.
TABLE 5. Effect of Temperature on Strength Development for Slurries
Containing Latex and Sub-Micron Alumina
[0057] Table 5 illustrates that sub-micron alumina may be a suitable set accelerator at
low temperatures for latex-containing slurries. Even at a low temperature of 40°F, a
compressive strength of 1014 psi was obtained in seventy-two hours for Slurry 18. The rate of
strength development increased as the temperature increased from 40°F to 120°F. Thickening
times decreased as the temperature was increased.
EXAMPLE 6
[0058] This example was performed to compare the performance of sub-micron alumina
with nano-silica and sub-micron calcium carbonate. For this example, four different slurries
were prepared. The cement compositions were then tested to determine their rate of strength
development and thickening times. As set forth below, the respective test results for the four
different slurries demonstrate that inclusion of sub-micron alumina in the slurry provides higher
compressive strength with reasonable thickening times.
[0059] Slurries 21-24 each included Portland Class H cement, latex in an amount of 1.5
gps, and sufficient water to provide a density of 16.4 lb/gal. Additional additives present in each
slurry were D-AIR 3000L™ defoamer in an amount of 0.05 gps, Stabilizer 434D™ latex
stabilizer in an amount of 0.2 gps, HR®-6L cement set retarder in an amount of 0.05 gps, and
CFR-3L™ dispersant in an amount of 0.143 gps. Slurry 22 also included a colloidal nano-silica
dispersion (0.2 gps) supplied by Bee Chems, India, under the trade name CemSyn LP (6 nm).
The colloidal nano-silica dispersion contained nano-silica (6 nm) in an amount of about 15% by
weight. Slurry 23 also included a colloidal calcium carbonate dispersion (0.3 gps) supplied by
Revertex-KA Latex (India) Private Limited. The colloidal calcium carbonate dispersion
contained sub-micron calcium carbonate (200 nm to 800 nm) in an amount of 75.5% by weight.
Slurry 24 also included a colloidal alumina dispersion (0.2 gps) supplied by Bee Chems, India.
The colloidal alumina dispersion contained sub-micron alumina (400 nm to 500 nm) in an
aqueous base fluid in an amount of about 20% by weight.
[0060] After the four slurries were prepared, tests were performed to compare various
physical characteristics of each of the slurries. A UCA was used to determine the compressive
strength rate as a function of time. The rate of strength development was calculated as the slope
of the initial linear part (starting from the onset of the strength development) of the Compressive
strength versus Time graph. Additionally, the UCA was also used to determine the compressive
strength of the slurries after forty-eight hours. The thickening time associated with each cement
slurry was determined by performing a thickening-time test in accordance with API
Recommended Practice 10B-2. The thickening time for each slurry was based on the respective
slurry reaching a consistency of 70 Be at 125°F.
[0061] The results of these tests are provided in the table below.
TABLE 6. Comparison of Sub-Micron Alumina With Nano-Silica
and Sub-Micron CaCC>3 for Latex-Containing Slurries
This comparison was performed using a loading of the nano-silica, sub-micron calcium
carbonate, or sub-micron alumina that was found to be best for slurry performance.
[0062] Accordingly, Table 6 illustrates that sub-micron alumina provides higher
strengths and faster set acceleration times when compared with nano-sized silica and sub-micron
calcium carbonate, especially at 80°F.
[0063] 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 in different
but equivalent manners apparent to those skilled in the art having the benefit of the teachings
herein. Furthermore, no limitations are intended to the details of construction or design herein
shown, other than as described in the claims below. 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 of the present invention. While compositions and methods are
described in terms of "comprising," "containing," or "including" various components or steps,
the compositions and methods can also "consist essentially of or "consist of the various
components and steps. Whenever a numerical range with a lower limit and an upper limit is
disclosed, any number and any included range falling within the. range is specifically disclosed.
In particular, every range of values (of the form, "from about a to about b," or, equivalently,
"from approximately a to b," or, equivalently, "from approximately a-b") disclosed herein is to
be understood to set forth every number and range encompassed within the broader range of
values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise
explicitly and clearly defined by the patentee.
CLAIMS
1. A method of cementing in a subterranean formation: introducing a cement composition
into the subterranean formation, wherein the cement composition comprises hydraulic cement,
sub-micron alumina, and water; and allowing the cement composition to set in the subterranean
formation.
2. A method according to claim 1, wherein the hydraulic cement comprises at least one
hydraulic cement selected from the group consisting of a Portland cement, a pozzolana cement,
a gypsum cement, a high-alumina-content cement, a slag cement, a silica/lime cement, and any
combination thereof.
3. A method according to claim 1 or 2, wherein the cement composition comprises belite in
an amount from 0.1 % to about 50% by weight of calcium silicates in the cement composition.
4. A method according to claim 1, 2 or 3, wherein the cement composition comprises a
colloidal alumina dispersion comprising sub-micron alumina suspended in a base fluid.
5. A method according to any preceding claim, comprising providing the sub-micron
alumina in a dry, free-flowing form.
6. A method according to any preceding claim, wherein the sub-micron alumina has a
particle size in the range of about 150 n to about 950 nm.
7. A method according to any preceding claim, wherein the sub-micron alumina is present
in the cement composition in an amount in the range of about 0.1% to about 10% by weight of
the hydraulic cement on a dry basis.
8. A method according to any preceding claim, wherein the cement composition further
comprises a latex.
9. A method according to claim 8, wherein the latex comprises at least one rubber material
selected from the group an ethylene-propylene rubber, a styrene-butadiene rubber, a nitrile
rubber, a nitrile butadiene rubber, a butyl rubber, a neoprene rubber, a polybutadiene rubber, an
acrylonitrile-styrene-butadiene rubber, a polyisoprene rubber, and any combination thereof.
10. A method according to any preceding claim, wherein introducing the cement
composition into the subterranean formation comprises introducing the cement composition into
a well bore in a space between the subterranean formation and a conduit disposed in the well
bore.
11. A method according to any preceding claim, wherein introducing the cement
composition into the subterranean formation comprises introducing the cement composition into
a well bore having a bottomhole circulating temperature of about 40°F to about 180°F.
12. A method according to claim 1, wherein the cement composition comprises hydraulic
cement, sub-micron alumina, latex, and water, wherein the sub-micron alumina has a particle
size of about 150 nm to about 950 urn, wherein the cement composition is prepared by providing
a colloidal alumina dispersion comprising the sub-micron alumina in an aqueous base fluid; and
the method comprises introducing the cement composition into a well bore in a space between
the subterranean formation and a conduit disposed in the well bore; and allowing the cement
composition to set.
13. A method according to clam 12, wherein the latex comprises a styrene-butadiene latex.
14. A method according to claim 12 or 13, wherein the sub-micron alumina is present in the
cement composition in an amount in the range of about 0.1% to about 10% by weight of the
hydraulic cement on a dry basis, and wherein the sub-micron alumina has a particle size of about
400 nm to about 500 nm.
15. A method according to any preceding claim, wherein the cement composition further
comprises at least one additive selected from the group consisting of a latex stabilizer, a
strength-retrogression additive, a set accelerator, a set retarder, a weighting agent, a lightweight
additive, a gas-generating additive, a mechanical property exihancing additive, a lost-circulation
material, a filtration-control additive, a fluid loss control additive, a dispersant, a defoaming
agent, a foaming agent, a thixotropic additive, nano-particles, and any combination thereof.
16. A method according to any preceding claim, wherein the cement composition further
comprises at least one additive selected from the group consisting of a gas, crystalline silica,
amorphous silica, fumed silica, a salt, a fiber, a hydratable clay, calcined shale, vitrified shale, a
microsphere, fly ash, slag, diatomaceous earth, metakaolin, rice husk ash, natural pozzolan,
zeolite, cement kiln dust, lime, an elastomer, a resin, nano-silica, nano-clay, nano-silica, nanozinc
oxide, nano-boron, nano-iron oxide, nano-zirconium oxide, nano-magnesium oxide, nanobarite,
and any combination thereof.
17. A method according to claim 12 or any claim dependent on claim 12, wherein the well
bore has a bottom hole circulating temperature of about 40°F to about 180°F.
18. A cement composition comprising: hydraulic cement, sub-micron alumina, and water.