SETTABLE COMPOSITIONS COMPRISING OLLAST ITE AND PUMICE
AND METHODS OF USE
BACKGROUND
[000 ] The present invention relates to cementing operations and, more
particularly, in certain embodiments, to settable compositions comprising woilasionite
and pumice and associated methods of use in cementing operations,
[0002] n cementing operations, such as well construction and remedial cementing,
settable compositions are commonly utilized. As used her in the term "settable
composition" refers to a composition that hydrauSieaSiy sets or otherwise develops
compressive strength. Settable compositions may be used in primary cementing operations
whereby p pe strings, such as casing and liners, are cemented in well bores. n a typical
primary cementing operation, a settable composition may be pumped nto an annulus
between the walls of the well bore and the exterior surface of the p pe string disposed therein
or between th pipe string and a larger conduit in the subterranean formation. The settable
composition may set in the annular space, thereby forming an annular sheath of hardened,
substantially impermeable material (e.g., a cement sheath) that ay support and position the
pipe string in the well bore and may bond the exterior surface of the pipe string to the well
bore walls or to larger conduit. Among other things, the cement sheath surrounding the p pe
siring should function to prevent the migration of fluids in the annulus, as well as protecting
the pipe siring from corrosion. Settable compositions als may be used in remedial
cementing methods, such as in the placement of plugs and in squeeze cementing for sealing
voids in a pipe string, cement sheath, gravel pack, subterranean formation, and the like.
[0003] A particular challenge in cementing operations is the development of
satisfactory mechanical properties in a settable composition within a reasonable time period
after placement in the subterranean formation. During the life of a well, the subterranean
cement sheath undergoes numerous strains and stresses as a result of temperature effects,
pressure effects, and impact effects. The ability to withstand these strains and stresses is
directly related to the mechanical properties of the settable composition after setting. The
m chanical properties are often characterized using parameters such as compressive strength,
tensile strength, Young's Modulus, Poissoi s Ratio, elasticity, and the ike. These properties
may be modified by the inclusion of additives.
[0004] One type of settable composition that has been used comprises Portland
cement as th cementitious component. Portland cement s one of the more common
cementitious components used throughout the work! and is usually produced by a process
that comprises sintering a mixture of a predetermined composition and then grinding the
.resulting Portland cement clinker. While Portland cement has been used in well construction
and remedial cementing for a number of years, drawbacks to Portland cement include the
energy requirements to produce Portland cement. These energy requirements greatly
increase the cost of creating Portland cement. Efforts to reduce the cost of settahle
compositions have come in the form of replacing Portland cement with other solid
particulate components.
SUMMARY
[0005] An embodiment discloses a method of cementing. Embodiments of the
method may comprise providing a settable composition that may comprise wollastonite,
pumice, a calcium-ion source, and water, wherein the wollastonite may be present n an
amount in a range of from about 25% to about 75% by combined weight of the wollastonite
and pumice, and. wherein the pumice may present in an amount in a range of from about 25%
to about 75% by combined weight of the wollastonite and pumice. Embodiments of the
method further comprise allowing the settable composition to set.
[0006] Another embodiment discloses a method of ce enting Embodiments of the
method may comprise preparing a base fluid that may comprise water and lime.
Embodiments of the method further may comprise preparing a dr b!ervd thai ma comprise
wollastonite and pumice, wherein the wollastonite may be present in an amount in a range of
from about 25% to about 75% by combined weight of the wollastonite and pumice, wherein
the pumice .may be present in an amount in a range o f from about 25% to about 75% by
combined weight of the wollastonite and pumice. Embodiments of the method further may
comprise combining the base fluid and the dry blend to form a settable composition that is
essentially free of Portland cement. Embodiments of the method further may comprise
introducing the settable composition into a subterranean formation. Embodiments of the
ethod further may comprise allowing the composition to set in the subterranean formation,
[0007] Another embodiment discloses a settable composition that may comprise
wollastonite- pumice, a calcium-ion source, water, wherein the wollastonite may be present
in an amount i a range of from about 25% to about 75 b combined weight of the
wollastonite and pumice, and where in th pumice may be present in an amount i a range of
from about 25% t about 75% by combined weight of the wollastonite and pumice.
[0008] 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 spirit of the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0009] Embodiments of the present invention disclose settable corn-positions
comprising wollastonite, pumice, a calcium-ion source, and water. One of th many
potential advantages of embodiments of the settable compositions is that use of wollastonite
and pumice may provide the settable compositions with adequate compressive strengths for
use in subterranean applications without the need of Portland cement By way of example,
the compressive strength of the settable compositions containing wollastonite and pumice
may be equal to or greater than a settable composition in which the wollastonite and pumic
has been replaced with Portland cement Accordingly, embodiments of the sellable
compositions may be used in a variety of subterranean applications where settable
compositions may be used, including, but not limited to, primary and remedial cementing.
[0010] n some embodiments, the settable compositions may comprise wollastonite.
Wollastonite is generally a calcium inosilicate mineral used in industrial applications, such
as ceramics, friction products, metal making, paint filler, and plastics. Wollastonite may be
mined in a number .of different locations throughout the world and then processed for use in
industrial applications. Wollastonite may be considered a cementitious component as it sets
and hardens in the presence of silica, lime and water. Wollastonite used n embodiments of
the present invention may have a mean particle size in a range of from about 1 microns to
about 200 microns, and, alternatively, from about 5 microns to about 0 -microns. The
wollastonite may be included in embodiments of the settable compositions in an amount
suitable for a particular application. In some embodiments, the wollastonite may be present
in the settable compositions in an amount in a range of from about 25% to about 75% by
combined weight of the wollastonite and pumice. In particular embodiments, the
wollastonite may be present in an amount ranging between any of and/or including any of
about 25%, about 30%, about 40%, about 50%, about 60%, about 0%, or about 75% by
combined weight of the wollastonite and pumice. One of ordinary skill, with the benefit of
this disclosure, should recognize the amount of the wollastonite to include for a chosen
application
[00 ] n some embodiments, the settable compositions may comprise pumice.
Generally, pumice is a volcanic rock that exhibits cementitious properties, in that t may set
and harden i the presence of lime and water. Pumice may be mined in a number of
different locations throughout the world and then processed for use in industrial applications.
.Pumice used in embodiments of the present invention may have a mean particle size in a
range of from about 1 microns to about. 50 microns, and, alternatively, from about 1 microns
to about 20 microns. An example of a suitable pumice is available from Mess Pumice
Products, Inc., a a City, Idaho, under the trade name DS-200 having an average particle
size of less than 20 microns. The pumice may be included in embodiments of the settable
compositions in an amount suitable fo a particular application. In some embodiments, the
pu ic ma be present the settable compositions in a n amount in the range of from about
25% to about 75% by combined weight of the wollastonite and pumice. In some
embodiments, the pumice may be present in an amount ranging between any of and/or
including an of about 25%, about 30%, about 40%, about 50%, about 60%, about 70%, or
about 75% b combined weight of the wollastonite and pumice. One of ordinary skill in the
art, th the benefit of this disclosure, should recognize the appropriate amount of the
pumice to include for a chosen application.
[0 2] n some embodiments, the settable compositions may comprise a calcium-ion
source. Th calcium-ion source may be included in the settable compositions for providing
calcium ions for reaction with the wollastonite and/or pumice, for example. On example of
a suitable calcium-ion source comprises lime. As used herein, the term l me" is intended to
include calcium oxide, calcium hydroxide, or a combination thereof. I some embodiments,
the calcium-ion source may be present in the settable compositions in an amount i the range
of about. 0. 1% to about % by combined weight of the wollastonite and pumice in further
embodiments, the calcium-ion source may be included in an amount in the range of from
about 1% to about 10% by combined weight of the wollastonite and pumice.
[0013] some embodiments, the settable compositions may further comprise
hydraulic cement, A variety o f hydraulic cements may be utilized in accordance with the
present invention, including, but not limited to, those comprising calcium, aluminum, silicon,
oxygen, iron, and/or sulfur, which set and harden by reaction with water. Suitable hydraulic
cements inc lude, but are not limited to, Portland cements pozzolanic cements, gypsum
cements, high alumina content cements, silica cements, and an combination thereof n
certain embodiments, the hydraulic cement may comprise a Portland cement. Portland
cements that ma be suited for us in example embodiments may be classified as Class A, C,
H and G cements according to American Petroleum Institute, AP Specification for Mater ls
and Testing for Well Cements, I Specification 10, Fifth Ed., Jul 1, 1 90. in addition, in
some embodiments, hydraulic cements suitable for use in the present invention may be
classified as ASTM Type , II, or ill.
0014] Where present, the hydraulic cement generally may be included i the
settable compositions in an amount sufficient to provide the desired compressive strength,
density, and/or cost. In some embodiments the hydraulic cement may be present the settable
compositions in an amount in the range of from about 0.1% to about 50% by combined
weight of the wollastonite and pu ice. For example, the hydraulic cement may be present in
an amount ranging between any of and/or including any of about 0.1%, about .1%, about 5%,
about 10%, about 20%, about 30%, about 40%, or about 50% by combined weight of the
wollastonite and pumice. In some embodiments, the hydraulic cement may be included i a
amou t that does not exceed about 1%, does not exceed about 5% bwo , does not exceed
about %, does not exceed about 20%, does not exceed about 30%, does not exceed about
40%, or does not exceed about 50% by combined weight of the wollastonite and pumice.
[0 5] n some embodiments, the settabie compositions may be essentially free of
any additional een entit o is components, such as t e hydraulic cement described herein (e.g.,
contains less than about % by combined weight of the wollastonite. and pumice). In
particular embodiments, the settabie compositions may be essentially f e of, or even free of,
Portland cement in some embodiments, the settabie compositions may comprise additional
cemen titious components, such as the hydraul ic cement, i an amount less than about 1% by
combined weight of the wollastonite and pumice and, alternatively, less than about 0. 1% by
combined weight of the wollastoni te and pumice.
[0 ] In so e embodiments, the settabie compositions may further comprise a
dispersant. Where present, the dispersant should act, among other things, to control the
rheoiogy of the settabie composition. While a variety of dispersants known to those skilled in
the art may be used in accordance with the present invention, examples of suitable
dispersants include naphthalene sulfonic aci condensate with formaldehyde; acetone,
formaldehyde, and sulfite condensate; e amme sulfonate condensed with formaldehyde;
an combination thereof. Where used, the dispersant should be present n embodiments of
the settabie compositions in an amount sufficient to prevent geiation of the settabie
composition and/or improve rheoiogica! properties. In some embodiments, the dispersant
may be present in the settabie compositions in an amount in the range of from about 0.1% to
about 5% by combined weight of the wollastonite and pumice.
[0 1 ] The water used in embodiments of the settabie compositions of the present
invention may include, for example, fresh water, saltwater (e.g., water containing one or more
salts dissolved therein), brine (e.g., saturated saltwater produced from subterranean
formations), seawater. or any combination thereof Generally, the water may be from any
source, provided, for example, that i does not contain an excess o compounds that may
undesirably affect other components in the settabie composition, n some embodiments, the
water may be included in an amount sufficient to form a pumpable slurry, in some
embodiments, the water may be included in the settabie compositions in an amount in a
range o .from about 40% to about 200% by combined weight of the wollastonite and
pumice. In some embodiments, the water may be included in an amount i a range of from
about 40% to about . 0% by combined weight of th l!astonite and pumice
[00 ] Other additives suitable for use in subterranean cementing operations may
also be added to embodiments of the se ah compositions, in accordance with embodiments
of the present invention. Examples of such additives include, but are no limited to, strengthretrogression
additives, set accelerators, set retarders, weighting agents, lightweight
additives, gas-generating additives, mechanical property enhancing additives, lost-circulation
materials, uid-S ss eont S additives, foaming additives, thixotropic additives, and any
combination thereof. Specific examples of these, and other, additives include crystalline
silica, amorphous silica, fumed silica, salts, fibers, hydr ta e clays, calcined shale, vitrified
shale, microspheres, fly ash, diatomaeeous earth, metaka in ground periire, rice husk ash,
natural poz o an, eolite, cement ki n dust, resins, any combination thereof, and the like. A
person having ordinary ski ll 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.
[0019] Strength-retrogression additives may be included in embodiments of the
settable composition to, for example, prevent the retrogression of strength after the lettable
composition has been allowed to develop compressive strength when the settable
composition is exposed to high temperatures. These additives ma allow the settable
compositions to form as intended, preventing cracks and premature failure of the
cementitious composition. Examples of suitable strength-retrogression additives may
include, but are not limited to, amorphous silica, coarse grain crystalline silica, fine grain
Crystalline silica, or a combination thereof.
[0020] Set accelerators may be included in embodiments of the settable
compositions to, for example, increase the rate of setting reactions. Control of setting time
may a!!ow for the ability to adjust to we!! bore conditions or customize set times for
individual jobs. Examples of suitable set accelerators may include, bu are not limited to,
aluminum sulfate, alums, calcium chloride* calcium sulfate, gypsum-hemihydrate,. sodium
aiuminate, sodium carbonate, sodium chloride, sodium silicate, sodium sulfate, ferric
chloride, or a combination thereof.
[0021] Set retarders may be included in embodiments of the settable compositions
to, for example, increase the thickening time of the settable compositions. Examples of
suitable set retarders include, but ar not limited to, ammonium, alkali metals, alkaline earth
metals, borax, metal salts of calcium Ugnosulfonate, earboxy methyl hydroxyethyl cellulose,
suifoalkylated gnis s, hydroxycarboxy acids, copolymers of -acryla. ido- -met yipropa e
sulfonic acid salt and acrylic acid or maleic acid, saturated salt or a combination thereof.
One example of a suitable lfo lky! ed lignin comprises a suSfomethyiated Isgnin.
[0022] W ighti g agents may be included in embodiments of the settable
compositions to, for example, increase the density of the settable compositions. Examples of
suitable weighting agents include, but hot limited to, ground barium sulfate, barite, hematite,
calc m carbonate, siderite, llmenite, magnesium oxide, sand, sa t, or a combination thereof.
[0023] Lightweight additives may be included in embodiments of the settab le
compositions to, for example, decrease the density of th settable compositions. Examples
of suitable lightweight additives include, but are not limited to. bentonite, coal, diatomaceous
earth, expanded periite, fly ash, gilsonite, hollow microspheres, low-density elastic beads,
nitrogen, poz oian bento te sodium silicate, combinations thereof or other lightweight
additives known in the art,
[0024] Gas-generating additives ay be included in embodiments of the settable
compositions to release gas at a predetermined time, which may be beneficial to prevent gas
migration from the formation through the settable composition before t hardens, te
generated gas ay combine with or inhibit the permeation of the settable composition by
formation gas. Examples of suitable gas-generating additives include, but are not limited to,
metal particles (e.g., aluminum powder) that react with an alkal in solution to generate a gas
[0025] Mechanical-property-enhancing additives may be included n embodiments
of the settable compositions to, for example, ensure adequate compressive strength and longterm
structural integrity. These properties can be affected by the strains, stresses,
temperature, pressure, and impact effects from a subterranean environment. Examples of
mechanical property enhancing additives include but are not limited to, carbon fibers, glass
fibers, metal fibers, mineral fibers, silica fibers, polymeric elastomers, and latexes.
[0026] Lost-circulation materials may be included in embodiments of the settable
compositions to, for example, help prevent the loss of fluid circulation nto the subterranean
formation. Examples of lost-circulation materials include but are not limited to, cedar bark,
shredded cane stalks, mineral fiber, mica flakes, cellophane, calcium carbonate, ground
rubber, polymeric materials, pieces of plastic, grounded marble, wood, nut hulls, formica,
corncobs, and cotton hulls.
[0027] Fiiiid-loss-cootroi additives may be included in embodiments of the settable
compositions to, for example, decrease the volume of fluid that is lost to the subterranean
formation. Properties of the settable compositions may be significantly influenced by their
water content. The loss of fluid ca subject the settable compositions to degradation or
complete failure of design properties. Examples of suitable fluid-loss-eontrol additives
include, but not limited to, certain polymers, such as hydroxyethyl cellulose,
arb rne hy ydroxy t y cellulose, copolymers f 2-¾cry mid -2- n t ylpr pane u fo .ti
acid and acry!amide or , -dimet y ry a ide and graft copolymers comprising a
backbone of ignin or .lignite and pendant groups comprising at least member selected
from the group consisting of 2-acrykmido-2-mei;hyIpropanesuifonic acid, acryk i i le and
, - i methy acryίam e,
[0028] Foaming additives may be included in embodiments of he settable
compositions to, for example, facilitate foaming and/or stabilize the resultant foam formed
therewith. Examples o f suitable foaming additives include, but are not limited to: mixtures
of an ammonium salt of an alkyl ether sulfate, a cocoamidopropyl betaine surfactant, a
cocoamidopropyl diraethylamine oxide surfactant sodium chloride, and water; mixtures of
an am oni u sa t of a n alkyl ether sulfate surfactant, a cocoamidopropyl hydroxysuitaine
surfactant, a cocoamidopropyl dimet ylar m oxide surfactant, sodiu chloride, and water;
hydrolyzed keratin; mixtures of an ethoxylated alcohol ether sulfate surfactant, an alkyl or
alkene amidopropyl betaine surfactant and an alkyl or a!kene diraethyiamine oxide
surfactant; aqueous solutions o an a!pha-o!efiaic sulfonate surfactant and a betaine
surfactant; and combinations thereof,
[0029] Defoammg additives may b included in embodiments of the sellable
compositions to, for example, reduce tendency fo r the sellable composition to .foam during
mixing and pumping o f the settable compositions. Examples of suitable defoaming additives
include, but a e not limited to, po!yoi silicone compounds. Suitable defoaming additives are
available from Halliburton Energy Services, Inc., under the product name *'D-A "
del earners,
003 0 Thixotropie additives may be included in embodiments of the settable
compositions to, for example, provide a settable composition that can be pu pab e as a thin
or lo viscosity fluid, but when allowed to remain quiescent attains a relativel high
viscosity. Among othe things, thixotropie additives may be used to help control free water,
create -rapid- e lation a the slurry sets, combat lost circulation, prevent "fallback" in annular
column, and minimize gas migration. Examples of suitable thixotropie additives include, but
are no limited to, gypsum, water soluble carboxyalkyl, hydroxyalkyl, mixed carboxyalkyS
hydroxyalkyl either of cellulose, polyvalent metal salts, zirconium xy io de with
hydroxyethyScellulose, or a co binat n thereof.
[00 Those of ordinary skill in the art will appreciate that embodiments o the
settable compositions generally should have a density suitable for a particular application.
By way .of example, embodiments f the settable compositions may have a density o f about
4 pounds per gallon fib/gal'') to about I? lb/gal. n certain embodiments, the settable
compositions may have a density of about 8 lb/gal to about . lb. gal. Embodiments of the
settable compositions may be foamed or unfoamed or ay comprise other means to reduce
their densities, such as lightweight additives. n addition, embodiments of the settable
composition m comprise weightings age ts or other means to increase their densities.
Those of ordinary skill in the art, with the benefit of this disclosure, will recognize the
appropriate density for a particular application,
[0032] The components of the settable composition may e combined in any order
desired o form a settable composition that ca n be placed nto a subterranean formation. In
addition, the components of the settable compositions may be combined using any mixing
device compatible with the composition, including a bulk mixer, for example. n some
embodiments, the settable compositions may be prepared b combining the wollastonite and
pumice with water. Other additives may be combined with the water before it is added to the
wollastonite. For example, a base fluid may be prepared tha comprises a cement dispersant,
a calcium-ion source, and water, wherein the base fluid s then combined with the
wollastontte. In some embodiments, the wollastontte and pumice may be dry blended prior
t their combination with the water. n some embodiments, the calcium-ion source may be
dry blended with the wollas nite and pumice. Other suitable techniques may be used for
preparation of the setting compositions as will be appreciated by those of ordinary skill in the
art in accordance with embodiments of the present invention.
[0033] Embodiments of the settable compositions may be used in a variety of
subterranean applications, including primary and remedial cementing, among others.
Embodiments may include providing a settable composition and allowing the settable
composition to set. Embodiments of the settable compositions may comprise, for example,
wollastonite, pumice, a calcium-ion source, and water. As used herein, introducing the
settable composition i to a subterranean formation includes introduction into any portion of
the subterranean formation, including, without limitation into a well bore drilled into the
subterranean formation, into a near well bore region surrounding the well bore, or i to both.
[0034] primary-cementing embodiments, for example, a settable composition may
be introduced into a well-bore annulus; and allowed to set in the well-bore annulus to form a
harde ed ass The well-bore annulus ay include, for example, an annular space between
a conduit (e.g., pipe string, liner, etc.) and a wall of a well bore or between the conduit and a
larger conduit in th well bore. Generally, ir most instances, the hardened mass should x
the conduit in the well bore.
[0035] In remedial-cementing embodiments, a seitable composition may be used, for
example, in sqaeexe-cementing operations or in the placement of plugs. By way of example,
the seitable composition may be placed in a well bore to plug a void or crack in the
formation, in a gravel pack, n the conduit, in the cement sheath, and/or a microa nu s
between the cement sheath a d the conduit in another embodiment, the settable
composition may be placed into well or to form a plug in the well bore with the plug, for
example, sealing the well bore.
EXAMPLES
[0036] To facilitate a better understanding of the present invention, the following
0 examples of certain aspects of some embodiments are given . n no wa should the following
examples be read to limit, or define, the entire scope of the invention.
Example
[0037] The following series of tests was performed to evaluate the mechanical
properties of settable compositions comprising wollastonite and pumice. Six different
settable compositions, labeled Samples .1-6, were prepared using the indicated amounts of
water, wollastonite, pumice, lime, and a cement dispersant. The amounts of these
components in each sample are indicated in the table below with by wf * indicating the
percent of the componen t by combined weight of the wollastonite and pumice and gallon per
sack ( ga /sk ) indicating the gallons of the respective component per 94-pound sack of the
0 wollastonite and pumice. The dispersani used was CF .- cement friction reducer, from
Halliburton Energy Services, Inc., Duncan, Oklahoma.
[0038] Alter preparation, the settable compositions were allowed to cure for 48
hours in a x metal cylinder that was placed in a water bath at 0 F to form set cement
cylinders immediately after removal from the water bath, destructive compressive strengths
5 were determined using a mechanical press in accordance with AP P 10 -2 The results of
this test are set forth in the table below.
Table I
1!
[0039] Based on the results of these tests, sellable compositions comprising
wo!lastomte and pumice can develop acceptable compressive strengths. For example, in
Sample 1. a compressive strength of 9 psi was obtained by including 30% bwoc
wollastonite and 70% bwoc c . n Sample 2, a compressive strength if 550 psi was
acquired by including 40% bwoc wollastonite and 60% bwoc pumice.
2
[0040] The following series of tests was performed to evaluate the fluid loss o
settable compositions comprising wollastonite and pumice. Four different sellable
compositions, designated Samples 7- 0, were prepared using the indicated amounts of water
wollastonite, pumice, lime, a cement dispersant, a cement retarder, and a f luid-loss-comrol
add ive. The amounts of these components n each sample are indicated in the table below
with % by wt' indicating the amount of the component by combined weight of the
wollastonite and pumice and gallon per sack "ga /sk ) indicating the gallons of the
respective component per 94-pound sack of the wollastonite and pumice. The cement
dispersant was €FR ~3 cement dispersant. from Halliburton Energy Services, nc. The
cement retarder was H 5 cement retarder from Halliburton Energy Services, nc. The
fluid-loss-control additive was Halad ' -344 from Halliburton Energy Services, Inc.
After preparation the sample settable compositions were poured into pre-heated cell with a
325-mesh screen and a fluid-loss test was performed for 30 minutes a .1,000 ps and 1 0 F
n accordance with AP RP 10B-2. The results of this test are set forth in the table below.
Table 2
'Calculated API luid Loss
[0041 ] As illustrated, settable compositions comprising wollastonite and pumice
may have acceptable fluid-loss control For example, API fluid loss of ess than or equal to
ec/30 mm were obtained for Samples 7 and .
Example 3
[0042] The following series of tests was performed to evaluate the thickening time
of settable compositions comprising wollastonite and pumice. Three different setiahle
compositions, labeled Samples - 3 were prepared using the indicated amounts of water,
wollastonite, pumice, li e, a cement dispersa and a cement set retarder. The amounts o
these components in each sample are indicated in the table below with "by wt" indicating th
amount of the component by combined weight of the o iasionite and pumice and gallon per
sack ga /s "} indicating the gallons of the respective component per 94-pound sack of the
wollastonite and pumice. The settable compositions had a density o !4.2 lb/gal. The cement
dispersant was C ¾-3 cement dispersant from Halliburton Energy Services, Inc. The
cement set retarder used was H * 5 retarder. fro Halliburton Energy Services, Inc.,
Duncan, Oklahoma After preparation, the thickening times, which is the time required for
the compositions to reach 70 Bearden units of consistency, were determined at F in
accordance with API B-2.
Table 3
[0043] As illustrated, settable compositions comprising wollastonite and pumice
may have acceptable thickening times. For example, thickening times from over hours to
just under 2.5 hours were seen n Samples and , respectively.
Example 4
[0044] The following series of tests was performed to further evaluate the
compressive strength of settable compositions comprising wo astoni e and pumice. A single
settable composition, labeled Sample 14, was prepared using the indicated amounts of water,
wollastonite, pumice, lime, a cement dispersant, and a cement set retarder. The amounts o
these components in each sample are indicated h the table below with *% by wt'* indicating
the amount of the component by combined weight of the woliasionite and pumice and gallon
per sac ( ga /sk ) indicating the gallons of the respective component per 94-pound sack of
the ceme t tio s component. The settable composition had a density of 1 .2 lb gal. The
cement set retarder used was R 5 retarder, from Halliburton Energy Services, Inc.,
Duncan , O aho
[0045] After preparation, the 24-hour and 48-hour compressive strengths were
determined for the sample settable composition using an Ultrasonic Cement Analyzer
("UCA"), available fro Fann Instrument Company, Houston, TX. in the CA, the sample
cement compositions were cured at 180 F while maintained at 3000 psi After removal from
the UCA, the destructive compressive strength of the sample was determined using a
mechanical press in accordance with AP P 2 .
Table 4
[0046] Accordingly, Table 4 indicates that acceptable compressive strengths .may be
obtained for settable compositions comprising woUaston.te and pumice. For example, a
compressive strength of 900 PS was obtained at 48 hours in Sample 14.
[0047] t should be understood that the compositions a d 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 * the various
components an steps. Moreover, the indefinite articles *a" or " , as used in the claims,
are defined herein to mean on or more than one of the element that it introduces.
[0048] 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 not explicitly recited, as well as, ranges from any ower limit may be combined with
any other lower limit to recite a range not explicitly recited, in th same way, ranges from
any upper limit may be combined with any other upper limit to recite a range not explicitly
recited. Additionally, whenever a numerical range with a lower limit and an upper l it is
disclosed, any number and any included range tailing within the range are specifically
disclosed. n particular, every range of value (of the form, "from about a to about b, or,
equivalent y, "from approximately a to b or, equivalentty, "from approximately a-b")
disclosed herein is to be understood to set forth every number and range encompassed within
the broader range of values even if not explicitly recited. Thus, every point or individual
value may serve as its ow lower or upper limit combined with any other point or individual
value or an other lower or upper limit, to recite a range not explicitly recited.
[ 49] 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 i ed and practiced
in different but equivalent manners apparent to those skilled in the art having the benefit of
the teachings herein. Although individual embodiments are discussed, the invention covers
all combinations of ail those embodiments. Furthermore no limitations are intended to th
details o f construction or design herein shown, other than as des r ed in the claims below.
Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly
and clearly defined by the patentee. It is therefore evident that the particular illustrative
embodiments disclosed above ma be altered or modified and a i 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 patent(s) o other documents
that may be incorporated herein by reference, the definitions that are consistent with this
specification should e adopted.

What is claimed is:
1. A method of cementing comprising:
providing a settable composition comprising:
woStastonite:
pumice;
a calcium-ion source; and
water
wherein the wollastoniie k present in an amount in a range of from
about 25% to about 75% by combined weight of the wollastonite and pumice; and
wherein the pumice Is present in an amount in a range of from about
25% to about 75% by combined weight of the wo.Uaston.ite and pumice; and
allowing the settable composition to set.
2 . The method of claim 1, wherein the settable composition has a density in a .
range of from about pounds per gallon to about 20 pounds per gallon.
3. The method of claim , wherein the water is present in an amount i a range
of from about 40% to about 200% by combined weight of the wollastonite and pumice.
4. The method of clai wherein the calcium-ion source compri ses lime.
5. The method of claim , wherein the calcium-ion source is present in an
amount in a range of from abou 0.1% to about 25% by combined weight of the wollastonite
and pumice,
6. The method of claim 1, wherein the settable composition further comprises
a additive selected from th group consisting of a dispersant, a strength-retrogression
additive, a set accelerator, a set retarder, a weighting agent, a lightweight additive, a gasgenerating
additive, a mechanical property enhancing additive, a lost-circulation material, a
filtration-control additive, a fluid oss control additive, a foaming additive, a defoa.mi g
additive, a thixotropic additive, and any combination thereof.
7. The method of claim 1, wherein the settable composition further comprises
a n additive selected from the group consisting of crystal e silica, amorphous silica, fumed
silica, salts, fibers, hydratable clays, calcined shale, vitrified shale, microspheres, fly ash,
diatomaceoas earth, m ta a l n groun per!ite, rice husk ash, natural po z lan ¾e
cement kiln dust, resins, any co bi ation thereof.
8. The method of claim , wherein the settable composition s essentially free of
an additional cementitious materials,
9 . The method of claim wherein the seitable composition is free of Portland
ce en
10. The method of claim 1 wherein the settable composition is introduced i to a
subterranean formation.
. The method of claim 1 , wherein the seitable composition is allowed to se n
a well-bore ann ! .
12. The method of clai 1 , wherein the settable composition is used i primary
cementing.
The method of clai , wherein the settable composition is used in remedial
cementing.
. A method of cementing comprising:
preparing a base fluid comprising water an lime;
preparing a dry blend comprising woilastonite and pumice, wherein the
woilastonite is present in an amount n a range o from about 25% to about 75% by
combined weight of the woilastonite and pumice, wherein the pumice is present n an
amount in a range of from about 25% to about 75% by combined weight of the wo asto ite
and pumice;
combining the base fluid and the dry blend to form a setiabie composition
that s essentially free of Portland cement;
introducing the settable composition into a subterranean formation; and
allowing the composition to set in the subterranean formation.
15 The method of claim 14, wherein the lime is present in the settable
composition in an amount in a range of from about 0.1% to about 25% by combined weight
of the woilastonite and pumice
16. The method of a m 14, wherein the settable composition is free of Portland
cement
7. The method of clai 14 wherein the settable composition is allowed to set in
a wel -bore ann h s.
. The method of claim 4 , wherein the settable composition is used i primary
cementing.
. The method of claim 14, wherein the settable composition is used in remedial
cemeutine.
20. A settable composition comprising;
woilastonite;
pumice;
a calcium-ion source; a d
water;
wherein he wolfastoniie is present in an amount n a range of from about
25% to about 75% by combined weight of the o aston e and pumice; and
wherein the p c is present in an amount n a range of fro about 25% to
about 75% by combined weight of the woHastonite and pumice,
21 . The settable composition of claim 20 further comprising one or m re of the
features defined in any one of claims 2-9,