METHODS FOR DETERMINING REACTIVE INDEX FOR E E TX S
COMPONENTS, ASSOCI ATE COMPOSITIONS, AND METHODS OF USE
BACKGROUND
[000 j present invention relates to cementitious components and, more
particularly, in certain embodiments, to methods of determining a reactive index for
cement i io s components,
[0002] In general, well treatments include a wide variety of methods that may be
performed in oi , gas, geo er a and/or water wells, such drilling, completion and
workover methods. he drilling, completion and workover methods may include, but a e not
limited to, drilling, fracturing, acidizing, logging, cementing, gravel packing, perforating and
conformance methods. Many of these wel treatments are designed to enhance and/or
facilitate the recovery of desirable fluids fro a subterranean well. These fl uids may include
hydrocarbons such as oil and/or gas,
[0003] i cementing methods, such as well construction and remedial cementing,
settable compositions ar commonly utilized. As used herein, the term "settable
composition" refers to a composiiion(s) that hydrauSfcaliy sets or otherwise develops
compressive strength. Settable compositions ay be used in primary cementing operations
whereby pipe strings, such as casing and liners, are cemented i well bores, h performing
primary cementing, a settable composition may be pumped into an annuius between a
subterranean formation and the pipe string disposed in the subterranean formation or
between the pipe string and a larger conduit disposed in the subterranean formation. The
settable composition should set in the annuius, thereby forming an annular sheath of
hardened cement {e.g., a cement sheath) that should support and position the pipe string in
the wel bore and bond the exterior surface of the pipe string to the walls of the we l bore or
to the larger conduit. Settable compositions also may be used in remedial cementing
methods, such as the placement of cement plugs, a d in s ueeze cementing for sealing voids
in a pipe string, cement sheath, gravel pack, formation, and the like. Settable compositions
ay aiso be used in surface applications, for example, construction cementing.
[0004] Settable compositions for use in subterranean formations may typically
include a cementitious component which hyclraulicalSy sets, or otherwise hardens, to develop
compressive strength. Examples of cementitious components that can be included in settable
compositions include Portland cement, calcium alummate cement, cement kiln dust, lime
kiln dust, fly ash, slag, pumice, and rice-hull ash, among others. The performance of these
different cementitious components i settable compositions may vary and can even vary for
a particular cementitious component depending, for example, on the particular type or source
I
of the component For example, certain o these r entit ous components may have
undesirable properties that can ake them -unsuitable for use in well treatments. addition,
variation of the performance for the cem ti i us components can lead to ack of
predictability and consistency or the cementitious components when used in treatment
fluids. This lack o predictability consistency may even be apparent for the same
cementiiious component, for example, if sourced from different locations.
SUMMARY
[0005] The present invention relates to cementitious components and, more
particularly, in certain embodiments, to methods of determining a reactive index for
cementitious components.
[0006] An embodiment discloses a method of cementing comprising: providing
settabie composition comprising water and a cementitious component having a determined
reactive index; and allowing the settabie composition to set to form a hardened mass.
[000?] Another embodiment discloses a method of measuring reactivity of a
cementitious component comprising: measuring a parameter of th cementitious component,
the cementitious component having a specific surface area; a d dividing the measured
parameter by the specific surface area of the cementitious component to obtain a reactive
index for the cementitious component.
[0008] Another embodiment discloses settabie composition comprising: water: and
a cementitious component having a calculated reactive index.
[0009] The features and advantages of the. present invention wil be readily apparent
to those skilled in the art. While numerous changes may be made b those skilled in the art,
such changes are within the spirit of the invention.
BRIEF DESCRIPTION OF TOE DRAWINGS
[0 ] These drawings illustrate certain aspects of some of the embodiments of th
present invention, and should not be used to limit or define the invention.
[00 ] F G. 1 is a chart showing measured reactive indexes for various supply
sources of cement kiln dust.
[00 ] FIG. 2 is a chart comparing actual versus predicted compressive strength for
dr blends of cement kiln dust.
[00 ] FIG. 3 is a chart comparing actual versus predicted volume average apparent
viscosity at 5 sec 5 for dry blends of cement kiln dust
[0014] FIG. 4 i a chart comparing actual versus predicted volume average apparent
viscosity at 5 1 sec' for dry blends of cement kiln dust.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0 ] The present invention relates to cementitious components and, more
particularly, in certain embodiments, to methods of determining a reactive index for
cementitious components. By determining the reactive index for cementitious components,
blends of cementitious components may be used in wel treatments, according to particular
embodiments, that can provide more predictable and consistent performance. In addition,
additional embodiments may include using the determined reactive index to provide blends
of cementitious components in which on or more parameters have been optimized,
including compressive strength, Young's Modulus, fluid loss, and/or thickening time, for
example
[00 16] Without being limited b theory, the reactive index of cementitious
component may be referred to a measure of the cementitious component's reactivity as
adjusted for differences i surface area. Example techniques for determining the reactive
index may comprise measuring a parameter of the cementitious component, and then
dividing the measured parameter by the specific surface area of the cementitious component
In some embodiments, the reactive index for a cementitious component may be calculated in
accordance with the following equation:
R MP / SSA
wherein R is the reactive index, MP is the measured parameter of the cementitious
component, ari SSA is the specific surface area of the cementitious component, h general,
specific surface area is a property of a particulate solid and, as used herein, is defined as the
total surface area of the cementitious component divided by the mass of the cementitious
component or the tota surface area divided by the bulk volume of the cementitious
component.
[00 ] n general, cementitious components are particulate solids that hydraulic-ally
set, or otherwise harden, to develo compressive strength in the presence of water. Nonlimiting
examples of cementitious components tha may e suitable for use in embodiments
of the. present invention include Portland cements, calcium aluminate, gypsum, pozzolanic
materials, and kiln dust. Mixtures of one or more different cementitious components may
also be used. In so e embodiments, the cementitious component may be combined with
lime.
[0018] In some embodiments, the cementitious component may comprise Portland
cement. Portland cement is a commonly used cementitious component that hydrau!ica!ly
reacts with water to develop compressive strength. Examples of suitable Portland cements
may include those classified as Classes A, C, G and H cements according to American
Petroleum institute, API Specification for Materials and Testing f r Well Cements, API
Specification 10, Fifth Edition, July 1, 1990. n addition, Portland cements suitable for use
in embodiments of ihe prese invention also include those classified as ASTM Type i,
I/ , . III, IV, or V, In some embodiments, blends of cementitious components containing
Portland cement may be used,
00 ] In some embodiments, the cementitious component may comprise a calcium
aluminate. Calcium aluminate may hydraulically react with water t develop compressive
strength. Calcium a um naie may be included in cements commonly referred to as calcium
aluminate cements or high alumina content cements. Calc m aluminate cements may be
prepared in a manufacturing process that includes mixing a calcium bearing material (e.g.,
limestone) a d an aluminum-bearing materia! (e.g., bauxite},
[0020 In some embodiments, the cementitious component may comprise gypsum.
Gypsum is a material that sets in the presence of water to develop compressive strength.
Gypsum may be included in cements commonly referred to as g p sum cements. For use in
cements, gypsum may, in some instances, be burned at extremely high temperatures and then
ground, n particular embodiments, gypsum may be added to Portland cement.
[002 In some embodiments, the cementitious component may comprise a
pozzolanic material. Po zo anie materials that may be suitable for use include a wide variety
of natural or artificial materials that exhibit cementitious properties in th presence of
calcium hydroxide. Examples of suitable po z lanic material that may be suitable for use in
embodiments of the present invention include natural a d artificial pozzoians, such as fly
ash, silica fume, slag, burned shale, burned clay, metakaolin, pumice, diatornaceous earth,
volcanic ash, opaline shale, tuff, and burned organic materials, such as agricultural waste
ash, municipal waste ash (e,g., municipal solid waste ash), waste-water treatment waste ash,
animal waste ash, non-human-non-animal industrial waste ash, and combinations thereof.
Specific examples of agricultural waste ash include, for example, rice husk ash, wood (e.g.,
sawdust, bark, twigs, branches, other waste wood) ash, tree leave ash, corn cob ash, cane
(e.g., sugar cane) ash, bagasse ash, grain (e.g., amaranth, barley, corn flaxseed millet, oat,
j lnoa, rye, wheat etc.) and related by-product(s) (e.g., husks, hulls, etc.) ash, orchard ash,
vine trimming ash, grass (e.g., orai Tifton, native shiba, etc.) ash, straw ash, ground nut
shell ash, legume (e.g., soybean) ash, and combinations thereof.
[0022] in some embodiments, the cementitious component may comprise kiln
dust. One example of a kiln dust includes cement kiln dust. Cement kiln dust, as that terra: is
used herein, refers to a partially calcined ki n feed which is removed fr om the gas stream and
collected, for example, in a dust collector during the manufacture of cem nt The cement
k ln dust generally may exhibit cementitious properties, in thai i may se t and harden in the
presence of water. Usually, large quantities of cement kiln dust ar collected in the
production of cement thai are commonly disposed of as waste. Disposal of the cement kiln
dust can add undesirable costs to the manufacture of the cement, as well as the
environmental concerns associated with its disposal. The chemical analysis o f the cement
kiln dust from various cement manufactures varies depending o a number of factors,
including the particular kil feed, the efficiencies of the cement production operation, and
the associated dust collection systems. Cement kin dust generally may comprise variety of
oxides, suc as Si<¾, A ¾ , Fe 0 , CaO, gO SO.?, and K 0 . Another example of a
kiln dust includes li e kiln dust. Lim ki n dust, as that term is used herein, refers to a
product generated in the manufacture of lime. The ime kiln dust may be collected, for
example, by dust control systems in the calcination of ime stone,
[0023] n some embodiments, one or more parameters of the cementitious
component may be measured and then used in determining the reactive index. The
parameters may include a number of different parameters that may be measured using
standard laboratory testing techniques for sellable composition comprising a cementitious
component a d water. Additional components may also be included in the sellable
compositions, for example, to vary one or more properties of the treatment fluid. Parameters
of the eenientitious component, or settable composition contained therein, that may be
measured include, for example, compressive strength. Young's Modulus, fluid loss,
thickening time, rheological values (e.g., volume average apparent viscosity, plastic
viscosity, yield point etc.) and/or free water.
[0024] Compressive strength is generally the capacity of a material or structure to
withstand axially directed pushing forces. The compressive strength of the cementitious
component may be measured at a specified time after the cementitious component has been
mixed with water and t e resultant treatment fluid is maintained under specified temperature
and pressure conditions. For example, co ress ve strength can be measured a a t me in the
range of about 24 to about 4 hours after the fluid is mixed and the fluid is maintained at a
temperature of 1?0 and atmospheric pressure. Compressive strength can be measured by
either a destructive method or non-destructive method. The destructive method physically
tests the strength of treatment fluid samples at various points i time by crushing the samples
in a compression-testing machine. The compressive strength is calculated fr om the failure
load divided y the cross-sectional area resisting the load and is reported in units of poundforce
per square inch (psl). Non-destructive methods typically may employ an Ultrasonic
Cement Analyzer "OCA ), available from Fann Instrument Company, Houston, TX.
Compressive strengths may be determined i accordance with AP RP 0B-2, Recommended.
Practice for Testing ei Cements, First Edition, July 2005.
[0025] Young's/modulus also referred to as the modulus of elasticity is a measure of
the relationship of an applied stress to d e resultant strain in general a highly deformable
(plastic) material will exhibit a lower modulus when the confined stress is increased. Thus,
the Young's modulus is an elastic constant that demonstrates the ability of the tested material
to withstand applied loads. A number of different laboratory techniques may be used to
measure the Young's modulus of a treatment fluid comprising a eementitious component
after the treatment fluid has been allowed to set for a period of time at speci fied temperature
and pressure conditions.
[0026] Fluid loss typically refers to loss of a fluid such as a treatment fluid into a
subterranean formation. A number of different laboratory techniques may be used to
measure fluid loss of a treatment fluid to give an indication of the behavior of the treatment
fluid in a well, Fluid loss may be measured using a static fluid-loss test, with either a static
or st red fluid-loss ceil, in accordance with the afore-mentioned API RP Practice B 2.
[0027] Thickening time typically refers to the time a fluid, such as a treatment fluid,
comprising the eementitious component, remains in a fluid state capable of being pumped.
A number of different laboratory techniques may be used to measure thickening time to give
an indication of the amount of time a treatment fluid will remain pumpabie in a wel An
example technique for determining whether a treatment fluid is in a pumpabie fluid state may
use a high-temperature high-pressure consistometer at specified pressure and temperature
conditions, in accordance with the procedure for determining cement thickening times set
forth in the afore-mentioned API RP Practice 10 2. The thickening time may be the time
for the treatment fluid to reach 70 Searden units of consistency ("8e") and may be reported
i time to reach 70 Be
[0028] Rheological values of a fluid may be determined to characterize the fluid's
rheoiogical behavior. Rheological values that ma be determined include volume average
apparent viscosity, yield point and plastic viscosity, among others. Plastic viscosity is
typically a measure of the resistance of a fluid to fl ow in some embodiments, the yield
point may be parameter of the Bingham plastic model, the yield point being the slope of
the shear stress/shear rate line above the yield point. Yield point is typically a measure of the
point at which a material can no longer deform elastically. n some embodiments, th yield
point may be a parameter of the Bingham plastic model, the yield point being the yield stress
extrapolated t a shear rate of zero. A number of different laboratory techniques may be
used to measure theological values of a treatment fluid to give an indication of the behavior
of the treatment fluid in a well. e logicaSvalues may be determined in accordance with
the procedure set forth AP P Practice -2.
[0029 Free water typically refers to any water in a fluid that i n excess to what is
required to fully hydrate the components of the fluid. Free water can be undesired as it may
physically .separate from a cement composition as it sets. Free water may also be referred to
as free fl uid A number of different laboratory techniques may be used to measure free water
of a treatment fluid to give an indication of the behavior of the treatment fluid in a well. F ee
water may be determined in accordance with the procedure set forth in API RP Practice . OB-
2.
[0030] As previously mentioned, the reactivity of cementitious components may
vary between different types of cementitious components or eve between different sources
for a particular type of eemeniitious component. Fo example, the reactivity of Portland
cement and another cementitious component, such as a pozzolanic material, may b
different By way of further example, the reactivity of a cementitious component may vary
between different sources for the cementitious component In some embodiments, the
reactive index of the cementitious component vary between two or more different
sources by a factor of at least about 2 . For example, the reactive index of the cementitious
component between different sources may vary b an amount between any of and/or
including any of about 2: , about : , about 50: J about J00: 1, about 250: , about 500: 1, or
about 00 1. Because the .reactivity varies between different cementitious components and
even between different sources for a cementitious component, the performance different
cementitious components may be unpredictable and may also lead to a lack of consistency
for the cementitious components when used in treatment fluids such as settahle
compositions, n some instances, the performance of a particular cementitious component
may have undesirable properties, which may make it unsuitable for use For example, a
cementitious component from a particular source may have properties making it undesirable
or use.
[003 ] n some embodiments, a blend of two or more different cementitious
components may be used to provide a blended cementitious component tha may have
properties suitable for use in a particular application. This may be particularly useful for
example, where one of the cementitious components in the blend may have properties
making t unsuitable for particular applications. For example, a cementitious component
such as cement kiln dust from a first source may be blended with cementitious component
such as cement kiln dus from a second source n some embodiments, one or both of the
cementitious components ay have reactivities that are unsuitable for a particular
application. For example, th e a ctivities of a cementitious component may be
individually too slow or too fast for a particular application. The blends of the cementitious
component from the two fferen sources may form a blended cementitious component
having compressive strength properties that are suitable for the application in some
embodiments, the relative proportions (e.g., weight fractions) of each cementitious
component i the blended cementitious component may then e adjusted to adjust the
compressive strength properties of the blended cementitious -component.
[0032] The tw or more cementitious components in the blended cementitious
component may include, for example, two or more different types of cementitious
components such as Portland cement and cement kiln dust. Alternatively, the two or more
cementitious components in the blended cementitious component may include, for example,
a cementitious component from two or more different sources. For example, a first
cementitious component may comprise cement kiln dust from a . first source, and the second
cementitious component may comprise cement kiln dust from a second source. It should be
understood that embodiments are not limited to only two different sources, but may include a .
cementitious component, such as cement kiln dust, from three, four, five, or even more
different sources- The two or more different sources for the cementitious component may
inciude different manufactures, different cement manufacturing plants, and the like. A
cementitious component, such as cement kiln dust which is a byproduct from the cement
manufacturing plant, may have a number of different sources available throughout the world.
For example, different sources for cement kiln dust may inciude different man fa turii g
plants throughout the world at which cement kiln dust can be generated.
[0033] The two or mor cementitious components may be blended to form the
blended cementitious component, for example, prior to combination with water and/or other
components of the treatment fluid. In particular embodiments, the two or more cementitious
components may be dry blended to form a dry blend comprising the two or more
cementitious components. The dry blend may then be combined with water and/or other
components, in any order, t form the treatment fluid. However, the use of the term "blend"
is not intended to imply that the two or more cementitious components have been dry
blended prior to combination with water. For example, the blend of two or more
cementitious components ma not be combined until after one, or even both, of the
cementitious components has already been blended with water.
[0034] n some embodiments, the reactive index may be used to optimize the
blended cementitious component, wherein the blended cementitious component comprises
two or more cementitious components. For example, the reactive index may be used to
optimize one or more parameters of the blended cementitious component, including
compressive strength. Young's Modulus, fluid ioss, and/or thickening time. Optimizing the
blended cementitious component may include determining the reactive index for each of the
cementitious components in the blended cemeiiiitious component. The reactive indexes for
the cementitious components may then be used to predict the performance of the blended
cemeiiiitious component. The ratio of each cementitious component may be adjusted to
optimize the performance of the blended cementitious compo ent The performance of the
blended cementitious component may be optimized with the performance of the blended
cementitious component est ated using the following equation:
Wherein is the estimated parameter for the blended cementitious component, is the
individual cementitious component om the set of cementitious components ! to n, n is an
integer, j is the reactive index for cementitious component i, SSA* is the specific surface
area for cementitious component i, ί is the mas fraction of the cementitious component ,
and wherein is a number from ί to 10. The set of cementitious components may include 2
or more different cementitious components. The two or more different cementitious
component may be different types of cementitious components, such as Portland cement and
slag, or may be from different sources, such as cement kiln dust from a first source and
cement kil dust fro a second source in some embodiments, may be 1. In alternative
embodiments, n may be 7/3.
[0035] .In some embodiments, the mean particle size of the cementitious component
may be altered from its original particle size. The reactive index may then be measured for
the altered cementitious component. The altered cementitious component may be included
in a blended cementitious component in accordance with present embodiments, the mean
particle size of the cementitious co pone t can e altered usi g an suitable technique,
including, without limitation, grinding or separating to provide a materia! having an altered
particle size. Separating the cementitious component ma include sieving or an other
suitable technique for separating the cementitious component to provide a mean particle size
that ha been altered from its original size. For example, sieving ma be used to produce
cementitious component having an increased or reduced mean particle size as desired for a
particular application. By way of further example, grinding may be used to decrease the
mean particle size of the cementitious component. Combinations of grinding and separating
may be used in some embodiments. The term "ground" or "grinding" as used herein means
i i
using a grinder (e.g., ba l mill, rod mill, etc.) to reduce the particle size of the specified
components). An example of a suitable grinder s an 8000 Mixer/Mill* ball mill, available
from SPEX Sample Prep In so e embodiments, the cementitious component may be
grou d for a time period in a range of from about 30 minutes to about hour.
[0036] The mea particle size of the cementitious component can be altered to any
size suitable for use n cementing operations. n some embodiments, the mean particle size
of the ememi iou component may be altered from ts original particle size to have a mean
particle size a range of about ! micron to about 350 microns. The mean particle size
corresponds to dSO values as measured by particle size analyzers such as those manufactured
by Malvern instruments, Worcestershire, United Kingdom
[0037] In so e embodiments, the mean particle size of the cementitious component
may b increased from its original size. For example, the mean particle size of the
cementitious component may be at least 5% greater than ts original size. In someembodiments,
at least a portion of the cementitious component may be increased to a size
that is in a range o from about 5% to about 500% greater than its original size. n some
embodiments, the mean particle size ay be increased to a size ranging between a y of
and/or including any of about. 5%, about 10%, about 20%, about 30%, about 40%, about
50%, about 60%ab t 70% about about 90%, about 0%, about 200%, about 300%,
about 400%, or about 500% greater than its original size.
8 In so e embodiments, the mean particle size of the cementitious component
may be reduced fr om its original size. For example, the mean particle size may be reduced
in an amount sufficient to increase the compressive strength of the cementitious component
n some embodiments, the cementitious component may have a mean particle size that is at
ieast 5% less than its original size. some embodiments, at least portion of the
cementitious component may be reduced to have a mean particle size in a range of from
about 5% to about 95% of its original size. For example, the mean particle size may b
reduced to a size ranging between any o and/or including any of about 5%, about %,
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% of its original size. By wa of example, the reduced particle size cementitious
component may have a mean particle size o less than about 15 micro ns in some
embodiments, the reduced particle size cementitious component may have a mean particle
size of less than about microns, less than about 5 microns, less than about 4 microns, less
than about 3 microns, less than about 2 microns, or less than about I micron. In specific
embodiments, the reduced particle size cementitious component ma have a mean particle
size in a range of from about 0.1 microns to about 15 microns, from about 0. 1 microns to
about microns, or from about 1 micron to about microns. One of ordinary skill n the
art, with the benefit of this disclosure, should be able to select a particie size for the
cementitious component suitable for a particular application.
[0039] n some embodiments, the mean particle size of the cement ki ln dust may be
reduced in n amount sufficient to provide a increase i compressive strength for the
sellable composition. For example, the mean particle e may be reduced to provide an
increase in compressive strength of at least about 5%, about 25%, about 50%, about 75%, or
about 100%.
[0040] n accordance with present embodiments, the cementitious components may
be included in treatment fluids that can be used in a variety of operations that may be
performed in subterranean formations. The cementitious component ay have reactive
index calculated according to disclosed embodiments. n some embodiments, a blended
cementitious component may be used. In some embodiments, the reactive index may b
used in determining the cementitious components in a . particular blended cementitious
component. As referred to herein, the term "treatment fluid" will be understood to mean any
fluid that may be used n a subterranean application in conjunction with a desired function
a d/or for a desired purpose. The term "treatment fluid" is not intended to imply any
particular action by the fluid. Treatment fluids often are used in, e.g., well drilling,
completion, and stimulation operations. Examples of such treatment fluids include drilling
fluids, well cleanup fluids, worfcover fluids, conformance fluids, gravel pack fluids, acidizing
fluids, fracturing fluids, cement compositions, spacer fluids, and the like,
[0 4 1] While embodiments of the compositions and methods may be used in a
variety of applications, they may be particularly useful for subterranean well completion and
remedial operations such as primary cementing of casings and liners in well bores. They
also ma b useful for surface cementing operations, including construction cementing
operations. Accordingly, embodiments of the present invention disclose se ta le
compositions comprising a cementitious component and water.
[0042 The cementitious component may be included in embodiments of the settable
compositions in a n amount suitable for particular application Sn som embodiments, the
cementitious. component may comprise cement kiln dust. The cement kiln dust may be
present i an amount in a range of from about 0.0 % to 0% by weight of the cementitious
component ( woc") For example, the cement k ln dust may b present in a amount
ranging between any of and/or including any of about 0.01%, about 5%, about 10%, about
20%, about. 30%, 40%, about 50%, about 60%, about 70%, about 80%, about 90%, or about
00 . The cementitious component may be free or essentially free (for example, no ore
than 1 by weight of the cementitious component) of any additional cementitious
components other than the cementitious component n some embodiments, the cementitious
component may be essentially free of Portland cement. One of ordinary skill in the art with
the benefit of this d s !osure should be able to determine an appropriate amount of the
cementitious component to include for a particular application
0043 The water used in embodiments of the setiable compositions of the present
invention may include, for example, freshwater, saltwater (e.g., water containing one or mo e
salts dissolved therein), brine (e.g., saturated saltwater produced from subterranean
formations), seawater, or any combination thereof. Generally, th water may be from any
source, provided, for example, that it does not contain an excess of compounds that may
undesirably af eet other components i the setiable composition. In some embodiments, the
wate may be included n an amount sufficient to form a p mpable slurry n some
embodiments, the water may be included in the setiable compositions of the present
inven tion in an amount in a range of fro about 40% to about 200% b oc For example, the
water may be present in an amount ranging between any of and/or including an o about
50%, about 75%, about 100%, about 25%, about 0%, or about 175% b weight of the
cement n specific embodiments, the water a be included in an amou t in the range of
iroro about 40% to about 150% bwoc. One of ordinary skill in the art, with the benefit of
this disclosure, will recognize the appropriate amount of water to include for a chosen
application.
[0044] Other additives suitable for us in subterranean cementing operations may
also be added to embodiments of the setiable compositions, in accordance with embodiments
of the present invention. Examples of such additives include, but are not limited to, f idloss-
control additive, set retarder, strength-retrogression additives, set accelerators,
weighting agents, lightweight additives, gas-generating additives, mecharacal-propertyenhaneing
additives, lost-circulation materials, filtration-control additives, foaming
additives, thixotropic additives, and any combination thereof. Specific examples of these,
and other, additives include crystalline silica, amorphous silica, turned silica, salts, fibers,
hydratable clays, calcined shale, vitrified shale, microspheres, hollo glas spheres, fly ash,
diatomaceous earth, metakaolin, ground perlite, rice husk ash, natural po o an, zeolite,
cement kiln dust, resins, any combination 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
[0 45] Those of ordinary skill in th art will appreciate that embodiments of the
settabie compositions generally should have a density suitable for a particular application.
By way o f example, embodimenls o f the sellable compositions may have a density of about
4 pounds per gallon b/gal' to about 20 lb/gal certain embodiments, the settabie
compositions may have a density o f about lb/gal to about 1? lb/gal. Embodiments of the
settabie compositions may be foamed or unfoamed or ay comprise other means to reduce
their densities, such as hollow microspheres, low-density elastic beads, or other densityr
ducin additives known in the art. addition, the settabie composition ay comprise
weighting agents or other means to increase their densities. Those of ordinary skill in the art,
with the benefit of this disclosure, wi l recognize the appropriate density for a particular
application.
[0046] n some embodiments, the settabie compositions may have thickening time
of greater than about hour, alternatively, greater than about 2 hours, alternat ely greater
than about 5 hours at 3,000 psi and temperatures i a range of from about 50*F to about
400°F alternatively, i a range of from about 80 F to about 2 5 F and alternatively at a
temperature of about 0 F. n some embodiments, the settabie composition may have a 24-
hour compressive strength n a range o f from about 0 psi to about ,00 0 psi and,
alternatively, from about 350 psi about 3,000 psi at atmospheric pressure and temperatures in
range of from about 50 to about 4 00* alternatively, n a range of from about 0 ,F to
about 250°P, and alternatively at a temperature of about 0 F.
[0047] The components of the settabie composition may be combined i any order
desired to fo rm a settabie composition that can be placed i to a subterranean fo rmati on n
adds io , the components of the settabie 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 the cementitious component or mixture- of
cementitious components. The dry blend may the be combined with water to form the
settabie composition. Other suitable techniques may be used for preparation of the settabie
compositions as will be appreciated by those of ordinary skil in the art in accordance with
embodiments of the present invention.
[0048] A wil be appreciated by those of ordinary skill in the art, embodiments of
the cement compositions of the present invention may be use in a variety of cementing
operations, including surface and subterranean operations, such as primary and remedial
cementing. In some embodiments, a cement composition may be provided tha comprises a
cementitious component and water, and allowed set, n certain embodiments, the cement
composition may be introduced into a subterranean formation and allowed to set therein.
used herein, introducing the cement composition into a subterranean formation includes
introduction into any portion of the subterranean formation, including, without limitation,
into a we l bore drilled into the subterranean formation into a near well bore region
surrounding the well bore, or to both.
[0049] n primary-cementing embodiments, for example, embodiments may
comprise providi a cement composition, introducing the cement composition into wellbore
annulus; and allowing the cement composition to set n the annulus to form a hardened
mass, The well-bore annulus ay include, for example, an annular space between a conduit
(e.g., pipe string, liner, etc.) and a wall of wel bore or between the conduit and a larger
conduit in the well bore. Generally, in most instances, the hardened ass should fix the
conduit in the well bore.
[0050] n remedial-cementing embodiments, a cement composition ay be used, for
example, i 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 an opening, such as a
void or crack in the formation, in a gravel pack, in the conduit, in the cement sheath, and/or a
snicroa undus between the cement sheath and the conduit or formation. An example of such
a method may comprise placing the cement composition into the void, and allowing the
cement composition to set in the void.
[005 ] While the preceding description is directed to the use of the cementitious
component in cementing methods, it should be understood that embodiments of the present
technique also encompasses the use of the cementitious component in any of a variety of
different subterranean treatments. he cementitious component may have a reactive judex
determined according t disclosed embodiments. in so e embodiments, a blended
cementitious component may e used. In some embodiments, the reactive index may be
use in determining the amount of cementitious components that are in a particular blended
cementitious component. An example method may include a subterranean treatment method
that comprises providing a treatment fluid comprising the cementitious component and
introducing the treatment fluid into a subterranean formation. For example, a drilling fluid
may comprise the cementitious component, wherein the drilling fluid may be circulated
downwardly through a drill pipe and drill bit and then upwardly through the we l bore to the
surface. The drilling fluid used may be any number of fluids (gaseous or liquid) and
mixtures of fluids an solids {such as solid suspensions, mixtures, and emulsions).
[0052] in some embodiments, a spacer fluid ay comprise the cementitious
component, which ay have a determined reactive inde according to disclosed
embodiments. Spacer fluids may be used, for example, in the displacement of fluids from
well bore I a embodiment, the fluid displaced by the spacer fluid comprises a dri li g
fluid. By way of example, the spacer fluid ay be used to displace the drilling fluid from
the well bore. The drilling fluid may include, for example, any number of fluids, such as
solid suspensions, mixtures, and emulsions. Additional steps in embodiments of the method
may comprise introducing a pipe string into the well bore, introducing a cement composition
into the well bore with the spacer fluid separating the cement composition and the first fluid.
n an embodiment* the cement composition may be allowed to set in the well bore. The
cement composition may include, for example, cement and water. n some embodiments, at
least a portion of the spacer fluid may be left in the well bore, the spacer fluid in the well
bore setting to form a hardened mass.
EXAMPLES
[0053] T facilitate a better understanding of th present invention, the following
examples of certain aspects of so e embodiments are given. In no way should the following
examples be read to limit, or define, the entire scope of the invention.
1
[0 54] The react e indexes for compressive strength for thirty-three different
samples of cement kiln dust, designated Samples A through GO, were determined and are
provided in F G. . The C D samples are each from a different supply source, The reactive
indexes for thirty-three CKD samples were determined by dividing the determined 24-hour
compressive strength for a settable composition by the specific surface area of the CKD
sample. The specific surface area or each CKD sample was determined by dividing the total
surface area of the particular CKD sample by the sample mass. The surface area was
determined using a Malvern particle size analyzer. The 24-hour compressive strength tor
each CKD sample was determined by first preparing a settable composition that comprised
the CKD sample in an amount of 100% bwoc and water in an amount sufficient to provide a
density of about lb gal. After preparation, the settable composition was allowed to cure
for 24 hours in a 2" x . 4" metal cylinder tha was placed in a water bath at 70 F to form set
cement cylinders. Immediately after removal from the water bath, destructive compressive
strengths were determined using a mechanical press in accordance with API RP 108-2.
Example 2
0055] Blended ceme itio s components were prepared that comprised mixtures of
the CKD samples from Example ί , as indicated in the table below. The determined reactive
indexes for the CKD samples were then used in the following equation to predict the
performance of each blended cementitious componen t
i == ¾ A ¾ A + ){S$A X¾
Wherein the estimated compressive strength for th blended ement it
component, ¾ is the reactive index for compressive strength for CKD Sample and was
, is 1, SSAj . i the specific suriace area for CKD Sample Z and was 232, ¾ is the mass
fraction of CKD Sample Z, . is the reactive index for compressive strength for CK
Sample F and was 105, SS. is the specific surface area for CKD Sample P and was 2.33,
is the mass fraction of CKD Sample F, R is the reactive index for compressive strength for
CKD Sample E and was 107, SSA is the specific surface area for CKD Sample E and was
3.6, and ¾ is the mass fraction of CKD Sample .
[0056] The estimated compressive strength values for the blended cementiiious
components were then compared with the actual 24-hour compressive strength values for the
blended cementiiious components. The 24-hour compressive strength for each blended
cementitious component was determined by first preparing a sellable composition that
comprised th blended eemeotitious component in an amount of 0% bwoe and water in an
amount sufficient to provide a density of ί 3 lb/gal. A cement dispersant (CFR-3™ cement
friction reducer, from Halliburton Energy Services, inc.) in an amount of from 0.5% bwoe to
.0% bwoe was added to some of the samples and should not impact determined
compressive strength values. After preparation, the sellable composition was allowed to cure
for 24 hours n a 2" 4" metal cylinder tha wa placed i water bath at 40°F to form set
cement cylinders. Immediately after removal from the water bath, destructive compressive
strengths were determined using a mechanical press in accordance with API P 0B-2.
[0057] A chart of the actual compressive strength values versus the estimated
compressive strength values is provided on FIG. 2 As shown on FIG. 2, the charted values
have an R value of 0.952 and a slope of 0.9253. The estimated and actual compressive
strength values for the blended cementiiious components are also provided in Table 1below.
Table
3
[ 058] The reactive indexes for volume average apparent viscosity at 5 . .1 see ' and
5 " were determined for CKD Samples Z F, an E from Example are provided in
Table 2 below. The reactive indexes for these samples were determined by dividing the
determined volume average apparent viscosity for a se tab composition by the specific
surface area o the CKD sample. The specific surface area for each CKD sample was
determined by dividing the total surface are of the particular CKD sample b the sample
mass. The surface area was determined using a Malvern particle size analyzer. The 24-hour
volume average apparent viscosity ("VAV") for each CKD sample was determined by first
preparing a sellable composition that comprised the CK sample in a amount of 100%
bwoc and water in an amount sufficient to provide density of about lb/gal. The volume
average apparent viscosities were measured at 5 1 Isec and 1 se " in accordance with
[0059] Next, blended cementitious components were prepared that comprised
mixtures of CKD samples Z, , E, as indicated in the table below. The determined reactive
indexes at 5 11 se and 5 1 se "' for the CKD samples were then used in the following
equation to predict the performance of each blended cementitious component.
VAV te = (Rlz}(SSAz){fz) ( if}(SSA fr }m + (RI XSSAK) f )
Wherein , is the estimated volume average apparent viscosity for the blended
eetne iti u is the reactive index for volume average apparent viscosity for
CKD Sample Z, SSA* is the specific surface are for CKD Sample Z ¾. is the mass fraction
of CKD Sample Z , m is 7/3, ¾ s the reactive i de for volume average apparent viscosity
for CKD Sample F, SSA is the specific surface area for CKD Sample F is the mass
fraction of CKD Sample F, is the reactive x for volume average apparent viscosity
for CKD Sample E S A is the specific surface area for CKD Sample E, and ¾ is the mass
f action of CKD Sample E.
[0060] The estimated volume average apparent viscosities at 5 ! se 1 and 5 sec
for the blended cernentttious components were then compared with the actual volume
average apparent viscosities at 5 sec and 5 1 sec' for the blended cementitious
components. The volume average apparent viscosities for each blended cementHious
component was determined by first preparing a settabie composition that comprised the
blended cementitious component in an amount of 00% bwoc and water in an amount
sufficient to provide a density of 12 lb/ga After preparation, the volume average apparent
viscosities at. sec and see" were determined in accordance with AP RP B-2
[0061] Charts of the actual volume average viscosity values versus the estimated
volume average viscosity values are provided on FIGS. 3 and 4. As shown on FIG. 3, the
charted values at 5 se ' have an value of 0.9894 and a slope of 0.9975. As shown on
F G. 4, the charted values at 5 1 ' have an value of 0.9931 and a slope of 0.9814. The
estimated and actual volume average viscosity values for the blended cementitious
components are also provided in Table 2 below.
Table 3
[0062] i should be understood that the compositions and methods are described in
terms of "comprising/' "containing," or 'including" various components or steps, the
compositions and methods can a so "consist essentially of or "consist of * the various
components and steps. Moreover, the indefinite articles * or ' a , as used in the claims,
are defi ned herein io mean o or more than one of the element that t introduces.
[0063] For the sake of brevity, only certain ranges are explicitly disclosed herein.
However, ranges from any lower limit may be combined with any upper limit to recite a
range no explicitly recited, as well as, ranges from any lower limit may be combined with
any other lower limit io recite a range not explicitly recited, in the same way, ranges from
any upper limit may be combined wit any other upper limit to recite a range not explicitly
recited. Additionally, whenever a numerical range with a leaver limit and an upper limit is
disclosed, any number and any included range falling within the range ar specifically
disclosed, n particular, ever range of values (of the form, "from about a to about h," or,
equivalently, "from approximately a to b " or, equivatentty, " fro approximately a-b")
disclosed herein is to be understood to set forth every number and range encompassed within
the broader range of values even if not explicitly recited. Thus, every point or individual
value may serve as its own lower or upper limit combined with any other point o individual
value or any other lower or upper limit, to recite a range not explicitly recited.
[0064] Therefore, the present invention is well adapted to attain the ends and
advantages mentioned as wel 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 teachinss 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 and spirit of the present invention, f there is any conflict in the
usages of a word or term in this specification and one or more patentfs) or other documents
that may be incorporated herein by reference, th definitions that are consistent with this
specification should be adopted.

What is claimed is:
. A method of cementing comprising:
providing a settable composition comprising water and a cementitious
component having a . determined reactive index; and
a owing the settable composi tion to set to form a hardened ass
2. The method of claim I wherein the sellable composition has a density in a
range of about 4 pounds per gallon to about 20 pounds pe gallon.
3. The method of claim 1 wherein the water s present in an amount sufficient to
form a pumpable slurry.
4 . The method of claim 1 wherein the cementitious component comprises at
least one component selected fro the group consisting of Portland cement, calcium
aiuminate, gypsum, a po olanic material, kiln dust, and any combination thereof
5. The method of claim 1 wherein the settable composition further comprises a
second cementitious component, wherein the cementitious component and the second
cementitious component have different reactive indexes.
6. The method of claim 5 wherein the cementitious component and the second
cementitious component have .reactive indexes that vary by a factor of at least about 2:1.
7. The method of claim 5 wherein the cementitious component and the second
cementitious component have reactive indexes that vary by a factor of at least about 100:1
8. The method of claim 1 wherein particle size of the cementitious component
has been adjusted to adjust the determined reactive index
9 The method of claim 1 wherein particle of the cementitious component
has been reduced by way of grinding to adjust the determined reactive index.
10 The method of claim wherein the determined reactive index is a measured
parameter of the cementitious component divided by the specific surface area of the
cementitious component.
The method of claim 10 wherein the measured parameter is compressive
strength. Young's modulus, fluid loss, thickening time, a rheological value, free water, or
any combination thereof
The method of claim .1 wherein the settable com os ion comprises a blended
cementitious component, the blended cementitious component comprising the cementitious
component.
3 The method of clai 1.2 further comprising estimating performance of the
settable composition using the following equation
wherein is an estimated parameter for the blended cementitious componenl, is the
individual cementitious component from a set of ceraentitious components 1 to n, n is an
integer, s the reactive index for cementitious component SSA, is the specific surface
area for cementitious component i, f is th mass fraction of the cementitious component i,
and rn is a value fr f to !0.
The method of claim 1 further comprising placing th sellable composition
into a subterranean formation penetrated by a wel bore
. The method of claim 4 wherein settabie composition is used primary
cementing in the well bore,
. The method of clai 14 wherein the settabie composition is used remedial
cementing in the well bore.
. A method of measuring reactivity of a cementitious component comprising:
measuring a parameter of the cemeniiiious component, the cementitious
component having a specific surface area; and
dividing the measured parameter by the specific surface area of the
cementitious component to obtain a reactive index for the cementitious component
18. The method of claim 17 further comprising preparing a settabie composition
comprising the cementitious component, and using the reactive index to adj ust an amount of
the cementitious component i the settabie composition.
9 . The method of claim 17 wherein the measured parameter is compressive
strength, Young's modulus, fluid loss, thickening time, a theological value, free water, or
any combination thereof
20. A settabie composition comprising:
water; and
a cementitious component having a calculated reactive index.
2 1. The settabie composition of claim 20 further comprising one or more of the
features defined n an ne of claims 1-12.