OA17387A - Settable compositions comprising wollastonite and pumice and methods of use. - Google Patents

Abstract

Methods and compositions are provided that relate to cementing operations, including a method of cementing that may comprise providing a settable composition that may comprise wollastonite, pumice, a calcium-ion source, and water, 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, 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 may comprise allowing the settable composition to set.

Description

SETTABLE COMPOSITIONS COMPRISING WOLLASTONITE AND PUMICE AND METHODS OF USE

BACKGROUND [0001] The présent invention relates to cementing operations and, more particularly, in certain embodiments, to settable compositions comprising wollastonite and pumice and associated methods of use in cementing operations.

[0002] In cementing operations, such as well construction and remédiai cementing, settable compositions are commonly utilized. As used herein. the term “settable composition” refera to a composition that hydrauücally sets or otherwise develops compressive strength. Settable compositions may be used in primary cementing operations whereby pipe strings, such as casing and liners, are cemenled in well bores. In a typical primary cementing operation, a settable composition may be pumped into an annulus between the walls of the well bore and the exterior surface of the pipe string disposed therein or between the 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 imperméable material (e.g., a cernent sheath) that may support and position the pipe string in the well bore and may bond the exterior surface of the pipe string to the well bore walls or to larger conduit. Among other things, the cernent sheath surrounding the pipe string should function to prevent the migration of fluids in the annulus, as well as protecting the pipe string from corrosion. Settable compositions also may be used in remédiai cementing methods, such as in the placement of plugs and in squeeze cementing for sealing voids in a pipe string, cernent 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 cernent sheath undergoes uumerous strains and stresses as a resuit of température eiTects, pressure eftecis, and impact eflécts. The ability to withstand these strains and stresses is directly related to the mechanical properties of the settable composition after setting. The mechanical properties are often characterized using parameters such as compressive strength, tensile strength, Young’s Moduius, Poisson*» Ratio, elasticity, and the like. These properties may be modifiedby the inclusion of additives.

[0004] One type of settable composition that has been used comprises Portland cernent as the cementitious component. Portland cernent is one of the more common cementitious components used throughout the worid and is usually produced by a process that. comprises sintering a mixture of a predetermined composition and then grinding the resulting Portland cernent clinker. While Portland cernent has been used in well construction and remédiai cementing for a number of years, drawbacks to Portland cernent include the energy requirements to produce Portland cernent. These energy requirements greatly increase the cost of creating Portland cernent. Efforts to reduce the cost of serfable 5 compositions hâve corne in ihe form of replacing Portland cernent with other solid particulate components.

SUMMARY [0005] An embodiment disdoses a method of cemeriting. Embodiments of the method may comprise providing a settable composition that may comprise woliastonite, pumice, a calcium-ion source, and water, wherein the woliastonite may be présent in an amount in a range of from about 25% to about 75% by combined weight of the woliastonite and pumice, and wherein the pumice may présent in an amount in a range of from about 25% to about 75% by combined weight of the woliastonite and pumice. Embodiments of the method further may comprise allowing the settable composition ta set.

[0006] Another embodiment dïscloses a method of cementing. Embodiments of the method may comprise preparing a base fluid thaï may comprise water and lime. Embodiments of the method further may comprise preparing a dry blend that may comprise woliastonite and pumice, wherein the woliastonite may be présent in an amount in a range of from about 25% to about 75% by combined weight of the woliastonite and pumice, wherein the pumice may be présent in an amount in a range of from about 25% to about 75% by combined weight of the woliastonite and pumice. Embodiments of the method further may comprise combining the base fluid and the dry blend to form a settable composition that is essentiaily free of Portland cernent. Embodiments of the method further may comprise mtrodueing the settable composition into a subterranean formation. Embodiments of the method further may comprise allowing the composition to set in the subterranean formation.

[0007] Another embodiment discioses a settable composition that may comprise woliastonite, pumice, a calcium-ion source, water, wherein the woliastonite may be présent in an amount in a range of from about 25% to about. 75% by combined weight of the woliastonite and pumice, and wherein the pumice may be présent in an amount in a range of from about 25% to about 75% by combined weight of the ivollastonite and pumice.

[0008] The features and advantages of the présent 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 présent invention disclose settable compositions comprising wollastonite, pumice, a calcium-ion source, and water. One of the many potential advantages of embodiments of the settable compositions is that use of wollastonite and pumice may provide the settable compositions with adéquate compressive strengths for use in subterranean applications without the need of Portland cernent. 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 pumice has been replaced with Portland cernent. Accordingly, embodiments of the settable compositions may be used in a variety of subterranean applications where settable compositions may be used, including, but not limited to, primary and remédiai cementing.

[0010] In some embodiments, the settable compositions may comprise wollastonite. Wollastonite is generally a calcium inosilicate minerai used in industrial applications, such as ceramics, friction products, métal 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 sels and hardens in the presence of silica, lime and water. Wollastonite used in embodiments of the présent invention may hâve a mean particle size in a range of from about l microns to about 200 microns, and, altematively, from about 5 microns to about lOO 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 présent 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 présent in an amount ranging between any of and/or including any of about 25%, about 30%, about 40%, about 50%, about 60%, about 70%, or about 75% by combined weight of the wollastonite and pumice. One of ordinary skill, with the benefît of this disclosure, should recognize the amount of the wollastonite to include for a chosen application.

[0011] In some embodiments, the settable compositions may comprise pumice. Generally, pumice is a voleanic rock that exhibits cementitious properties, in that it may set and harden in the presence of lime and water. Pumice may Lie mined in a number of different locations throughout the world and then processed for use in industrial applications. Pumice used in embodiments of the présent invention may hâve a mean particle size in a range of from about 1 microns to about 50 microns, and, altematively, from about 1 microns to about 20 microns. An example of a suitable pumice is available from Mess Pumice

Products, Inc., Malad 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 settabie compositions in an amount suitable for a particular application. In some embodiments, the pumice may be présent the settabie compositions in an 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 présent in an amount ranging between any of and/or including any of about 25%, about 30%, about 40%, about 50%, about 60%, about 70%, or about 75% by combined weight of the wollastonite and pumice. One of ordinary skill in the art, with the benelît of this disclosure, should recognize the appropriate amount of the pumice to include for a chosen application.

[0012] ln some embodiments, the settabie compositions may comprise a calcium-ion source. The calcium-ion source may be included in the settabie compositions for providing calcium ions for reaction with the wollastonite and/or pumice, for example. One example of a suitable calcium-ion source comprises lime. As used herein, the term “lime” is intended to include calcium oxide, calcium hydroxide, or a combination thereof. In some embodiments, the calcium-ion source may be présent in the settabie compositions in an amount in the range of about 0.1% to about 15% 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 iirom about 1% to about 10% by combined weight of the wollastonite and pumice.

[0013] In some embodiments, the settabie compositions may further comprise hydraulic cernent A variely of hydraulic cements may be utilized in accordance with the présent invention, including, but not limited to, those comprising calcium, alumlnum, silicon, oxygen, iron, and/or sulfur, which set and hardèn by reaction with water. Suitable hydraulic cements include, but are not limited to, Portland cements, pozzolanic cements, gypsum cements, high alumina content cements, silica cements, and any combination thereof. In certain embodiments, the hydraulic cernent may comprise a Portland cernent. Portland cements that may be suited for use in example embodiments may be classified as Class A, C, I l and G cements according to American Petroleum Instituts, API Spécification for Materials and Testing for Well Cements, API Spécification 10, Fifth Ed., Jul. 1, 1990. In addition, in some embodiments, hydraulic cements suitable for use in the présent invention may be classified as ASTM Type I, II, or III.

[0014] Where présent, the hydraulic cernent generally may be included in the settabie compositions in an amount sufficient to provide the desired compressive strength, density, and/or cost. In some embodiments, the hydraulic cernent may be présent the settabie compositions in an amount in the range of from aboui 0.1% to about 50% by combined weight of the wollastonîte and pumice. For example, the hydraulic cernent may be présent in an amount ranging between any of and/or încluding any of about 0.1%, about l%, about 5%, about 10%, about 20%, about 30%, about. 40%, or about 50% by combined weight of the wollastonîte and pumice. In some embodiments, the hydraulic cernent may be included in an amount that does not exceed about I %, does not exceed about 5% bwoc, does not exceed about 10%, does not exceed about 20%, cloes not exceed about 30%, does not exceed about 40%, or does not exceed about 50% by combined weight of the wollastonîte and pumice.

[0015] In some embodiments, the settable compositions may be essentially free of any additional cementitious components, such as the hydraulic cernent described herein (e.g,, contains less than about 1% by combined weight of the wollastonîte and pumice). In particular embodiments, the settable compositions may be essentially free of, or even free of, Portiand cernent. In some embodiments, the settable compositions may comprise additional cementitious components, such as the hydraulic cernent, in an amount less than about 1% by combined weight of the wollastonîte and pumice and, altematively, less than about 0.1% by combined weight of the wollastonîte and pumice.

[0016] In some embodiments, the settable compositions may further comprise a dispersant. Where présent, the dispersant should act, among other things, to control the rheology of the settable composition. While a variety of dispersants known to those skilled in the art may be used in accordance with the présent invention, examples of suitable dispersants include naphthalene sulfonic acid condensate with formaldéhyde; acetone, formaldéhyde, and sulfite condensate; melamine sulfonate condensed with fonnaldehyde; any combination thereof. Where used, the dispersant should be présent in embodiments of the settable compositions in an amount sufficient to prevent gélation of the settable composition and/or împrove rheological properties. In some embodiments, the dispersant may be présent in the settable compositions in an amount in the range of from about 0,1% to about 5% by combined weight of the wollastonîte and pumice.

[0017] The water used in embodiments of thé settable compositions of the présent invention may include, for example, freshwater, saltwater (e.g., water containîng 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, lor example, that it does not contain an excess of compounds that may undesirably affect other components in the settable composition. In some embodiments, the water may be included in an amount sufficient to form a pumpable slurry. In sonie embodiments, the water may be included in the settable compositions in an amount in a range of from about 40% to about 200% by combined weight of the wollastonîte and pumiee. In some embodiments, the water may be included in an amount in a range of from about 40% to about 150% by combined weigbl ofthe wollastonité and pumiee.

[00181 Other additives suitable for use in subterranean cementing operations may also be added to embodiments of the settable compositions, in accordance with embodiments 5 of the présent invention. Examples of such additives include, but are not limited to, strengthretrogression additives, sei accelerators, set retarders, weighting agents, lightweight additives, gas-generating additives, mechanical property enhancing additives, lost-circulation materials, fluid-ioss-control additives, foaming additives, tbixotropic additives, and any combination thereof. Spécifie examples of these, and other, additives include crystalline 10 silica, amorphous silica, fumed silica, salts, libers, hydratable clays, calcined shale, vitrified shale, microspheres, fly ash, diatoraaceous earth, metakaolin, ground perlite, rice husk ash, naturel pozzolan, zeolite, cernent kiln dust, resins, any combination thereof and the like. A pèrson having ordinary skill in the art, with the bénefit of this disclosure, will readily be able to détermine the type and amount of additive useful for a particular application and desired 15 resuit.

[0019] Strength-retrogression additives may be included in embodiments of the settable composition to, for example, prevent the rétrogression of strength after the settable composition has been allowed to develop compressive strength when the settable composition is exposed to high températures. These additives may allow the settable 20 compositions to form as intended, preventing cracks and prématuré failure of the cementitious composition. Examples of suitable strengih-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 25 compositions to, for example, increase the rate of setting reactions. Control of setting time may allow for the ability to adjust io well bore conditions or customize set times for individual jobs. Examples of suitable set accelerators may include, but are not limited to, aluminum sulfate, alunis, calcium chloride, calcium sulfate, gypsum-hemihydrate, sodium alummaie, sodium carbonate, sodium chloride, sodium silicate, sodium sulfate, ferrie 30 chloride, or a combination thereof.

[0021] Set retarders may be included in embodiments of the settable compositions to, for examplc, increase the thickening time of the settable compositions. Examples of suitable set retarders include, but are not limited to, ammonium, alkali mêlais, alkaline earth metals, borax, métal salts of calcium lignosulfonate, carboxymefhyl hydroxyethyl cellulose, 35 suifoalkylated lignins, hydroxycarboxy acids, ccpolymers of 2-a.crytamido-2-meîhylpropane (X sulfonic acid sait and acrylic acid or maleic acid, saturated sali, or a combination thereof, One exemple of a suitable sulfoalkylated lignin comprises a sulfomethylated lignin.

[0022] Weightmg agents may be included in embodiments of the settable compositions to, for example, increase the density of the settable compositions. Examples of 5 suitable weighting agents include, but not limited to, ground barium sulfate, barite, hématite, calcium carbonate, siderite, Ihnenite, magnésium oxide, sand, sait, or a combination thereof.

[0023] Lighiweight additives may be included in embodiments of the settable compositions to, for example, decrease the density of the settable compositions. Exemples of suitable lightweight additives include, but are not limited to, bentonite, coal, diatomaceous 10 earth, expanded perlite, fly ash, gilsonite, hollow raicrospheres, low-density elastic beads, nitrogen, pozzolan-bentonite, sodium silicate, combinations thereof, or other lightweight additives known in the art.

[0024] Gas-generating additives may be included in embodiments of the settable compositions to release gas at a predetermined time, which may be bénéficiai to prevent gas 15 migration from the formation through the settable composition before it hardens. The generated gas may combine with or inhibit the perméation of the settable composition by formation gas. Examples of suitable gas-generating additives include, but are not limited to, métal particles (e.g., aluminum powder) that reaci with an alkaline solution to generate a gas.

[0025] Mechanical-property-enhancing additives may be included in embodiments 20 of the settable compositions to, for example, ensure adéquate compressive strength and iongterm structural integrity. These properties can be affocted by the strains, stresses, température, pressure, and impact eft'ects from a subterranean environment. Examples of mechanical property cnhancing additives include, but. are not limited to, carbon fibers, glass fibers, métal fibers, minerai 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 into the subterranean formation. Examples of lost-circulation materials include but are not limited to, eedar bark, shredded cane stalks, minerai fiber, mica flakes, cellophane, calcium carbonate, ground rubber, polymeric materials, pièces of plastic, grounded marble, wood, nut hulls, formica, 30 corncobs, and cotton hulls.

[0027] Fluid-loss-control 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 setiable compositions may be significanUy influeneed by their water content. The loss of fluid can subject the settable compositions to dégradation or 35 complété failure of design properties. Examples of suitable fluid-loss-control additives

include, but not limited to, certain polymers, such as hydroxyethyl cellulose» earboxymethylhjtoro.xyethyl cellulose, copoiymers oi'2-acryiamido-2-ïncthylpropanesuIfonic acid .and acrylamide or Ν,Ν-dimethyIacrylamide, and graït copolymers comprising a backbone of lignin or lignite and pendant groups comprising at least one member selected 5 foâ the group consisting of 2-acrylamido-2-meihylpn>panesulfonic acid, aerylomtrile, and Ν,Ν-dimethylacrylamide, [0028] Foaming additives may be included in embodiments of the settable compositions to, for example, faeilitate foaming and/or stabilise the résultant foam formed theréwith. Examples of suitable foaming additives include, but are not limited to: mixtures 10 of an ammonium sait of an alkyl ether sulfate, a cocoamidopropyl betaine surfactant, a cocoamidopropyl dimethylamine oxide surfactant, sodium chloride, and water; mixtures of an ammonium sait of an alkyl ether sulfate surfactant, a cocoamidopropyl hydroxysultaine surfactant, a cocoamidopropyl dimethylamine oxide surfactant, sodium chloride, and water; hydrolyzed keratin; mixtures of an ethoxylated alcohol ether sulfate surfactant, an alkyl or 15 alkene amidopropyl betaine surfactant, and an alkyl or alkene dimethylamine oxide surfactant; aqueous solutions of an alpha-oleflnic sulfonate surfactant and a betaine surfactant; and combinations thereof.

[0029] Defoaming additives may be included in embodiments of the settable compositions to, for exemple, reduce tendency for the settable composition to foam during 20 mixing and pumpihg of the settable compositions. Examples of suitable defoaming additives include, but are not limited to, polyol silicone compounds. Suitable defoaming additives are avai labié from Halliburton Energy Services, Inc., under the product name “D-A1R™” defbamers.

[0030] Thixotropic additives may be included in embodiments of the settable 25 compositions to, for example, provide a settable composition that can be pumpable as a thin or low viscosity fluid, but when allowed to remain quiescent attains a relatively high viscosity. Among other things, thixotropic additives may be used to help control free water, create rapid gélation as the slurry sets, combat lost circulation, prevent “fallback” in annular column, and minimize gas migration. Examples of suitable thixotropic additives include, but 30 are not limited to, gypsum, water soluble carboxyalkyl, hydroxyalkyl, mixed carboxyalkyl hydroxyalkyl either of cellulose, polyvalent métal salts, zirconium oxyehloride with hydroxyethvl cellulose, or a combination thereof [0031] Those of ordinary skill in the art will appreciaie that embodiments of the settable compositions generally should hâve a density suitable for a particular application.

By way of example, embodiments of the settable compositions may hâve a density of about /xf pounds per galion (“Ib/gal”) to about 17 lb/gal. In certain embodiments, the settabie compositions may hâve a density ofabout 8 Ib/gal io about 17 Ib/gal. Embodiments ofthe settabie compositions may be foamed or unfoamed or may comprise other means to reduce their densifies, such as lighiweight additives. In addition, embodiments of the settabie composition may comprise weightings agents or other means to increase their densifies. Those of ordinary skîll in the art, with the benefît of this disclosure, wiil recognize the appropriais density for a particular application.

[0032] The components of the settabie composition may be combined in any order desired to form a settabie composition that can be placed into a subterranean formation, In addition, 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, the settabie compositions may be prepared by combining the woliastonite and pumice with water. Other additives may be combined with the water before it is added to the woliastonite. For example, a base fluid may be prepared that comprises a cernent dispersant, a calcium-ion source, and water, wherein the base fluid is then combined with tire woliastonite. In some embodiments, the woliastonite and pumice may be drv blended prior to their combination with lhe water. In some embodiments, the calcium-ion source may be dry blended with the woliastonite and pumice. Other suitable techniques may be used for préparation of the setting compositions as will be appreciated by those of ordinary sklli in the art in accordance with embodiments ofthe présent invention.

[00331 Embodiments of the settabie compositions may be used in a variety of subterranean applications, including primary and remédiai cementing, among others, Embodiments may ineiude providing a settabie composition and allowing the settabie composition to set. Embodiments of the settabie compositions may comprise, for example, woliastonite, pumice, a calcium-ion source, and water. As used herein, introducing the settabie composition into 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 région surrounding the weli bore, or into both.

[0034] In primary-cementing embodiments, for example, a settabie composition may be introduced into a well-bore annulus; and allowed to set in the well-bore annulus to form a hardened mass. The well-bore annulus mav include, for example, an annulai' 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 the well bore. Generally, in most instances, the hardened mass shoukl fix the conduit in the well bore.

[0035] In remedial-cementingembodiments. a settable composition may be used, for example, in squeeze-cementing operations or in the placement of plugs. By way of example, the seltable composition may be placed in a well bore to plug a voîd or crack in the formation, in a grave! pack, in the conduit, in the cernent sheath, andfor a microannulus 5 between the cernent sheath and the conduit, In another embodiment, the settable composition may be placed into a well bore 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 présent invention, the following 10 examples of certain aspects of some embodiments are given. In no wav should the following examples be read to tirait, or define, the entire scope of the invention.

Example l [0037] The following séries of tests was performed to evaluate the mechanical properties of settable compositions comprising wollastonite and pumice. Six different 15 settable compositions, labeled Samples 1-6, were prepared using the indicated amounts of water, wollastonite, pumice, lime, and a cernent dispersant. The amounts of these components in each sample are indicated in the table below with “% by wt’’ indicating the percent of the component by combined weight of the wollastonite and pumice and gallon per sack (“gal/sk”) indicating the gallons of the respective component per 94-pound sack of the 20 wollastonite and pumice. The dispersant used was CFR.-3™ cernent friction reducer, from I lalliburton Energy Services, Inc,, Duncan, Oklahoma.

[0038] After préparation, the settable compositions were allowed to cure for 48 hours in a 2” x 4” métal cylinder that was placed in a water bath at 180°F to form set cernent cylinders. Immediately after lemoval from the water bath, destructive compressive strengths 25 were detemtined using a mechanical press in accordance with API RP IOB-2. The results of this test are set forte in the table below.

Table 1

Samples	Ingrédients	Temp o p	48hr C'omp. Streneth PSÎ
Density Ib/gal	Water gal/sk	Wollastonite % by wt	Pumice | %by ! wt i	Lime % by wi	Cernent Dispersant % by wt
1	14.2	5.59	30	70 1	5	0.5	180	519
2	14.2	5.85	40	.	5	0.5	180	550
3	14.2	6.11	50	50 1	5	0.5	180	452
4	14.2	6.14	50	50 1	5	0	180	234
5	14.2	6.35	50	50 I	10	0	180	272
6	14.2	6.79	75	25 1	5	0	180	170

[0039] Based on the results of these tests, settable compositions comprising wollastonite and pumice can develop acceptable compressive strengths. For example, in Sample 1, a compressive strength of 519 psi was obtained by including 30% bwoc wollastonite and 70% bwoc pumice. In Sample 2, a compressive strength if 550 psi was 5 acquired by including 40% bwoc wollastonite and 60% bwoc pumice.

Example 2 [0040] The following sériés of tests was performed to evaîuate the fluid loss of settable compositions comprising wollastonite and pumice. Four different settable compositions, desîgnated Samples 7-10, were prepared using the indicated amounts of water, 10 wollastonite, pumice, lime, a cernent dispersant, a cernent retarder, and a fluid-loss-control additive. The amounts of these components in 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 (“gal/sk”) indicating the gallons of the respective component per 94-pound sack of the wollastonite and pumice. The cernent 15 dispersant was CFR^:S-3 cernent dispersant from Halliburton Energy Services, Inc. The cernent retarder was HR'M cernent retarder from Halliburton Energy Services, Inc. The fluid-loss-control additive was Halad™-344 from Halliburton Energy Services, Inc.

After préparation, the sample settable compositions werepoured into a pre-heated cell with a 325-mesh screen and a fluid-loss test was performed for 30 minutes at 1,000 psi and 180°F 20 in accordance with API RP 10B-2. The results of this test are set forth in the table below.

Table 2

Sample	Ingrédients	ΛΡΙ Fluid Loss* cc/30 min
Density Ib/gal	Water gal/sk	Wollastonite % by wt	Pumice % by wt	Lime %by wt	Cernent Dispersant % by wt	Cernent Retarder % by wt	FluidLoss- Control Additive % by wt
7	14.2	5.83	40	60	5 ΐ	0.5	0.5	0.25	87.8
8	14.2	5.81	40	60	5 | 0.5 i 0.5	0.5	152.4
9	13.8	6.58	40	60	5	0.5	0.5	0.5	127
to	14.2	5.80	40	60	s	0.5	0.5	0.75	117.1

’Calculated API Fluid Loss [0041] As illustrated, settable compositions comprising wollastonite and pumice may hâve acceptable fluid-loss control For example. ?\P1 fluid loss of less than or equal to

117 cc/30 min were obtained for Samples 7 and 10.

Example 3 [0042] The following sériés of tests was performed to evaluate the thickening time of settable compositions comprising wollastonite and pumice. Three different settable compositions, labeled Samples 11-13, were prepared using the Indicated amounts of water, wollastonite, pumice, lime, a cernent dispersant, and a cernent sel retarder. The amounts of these components in each sample are indicated in the table below with “bv wt” indicating the amount ofthe comportent by combined weight ofthe wollastonite and pumice and gallon per sack Cgai/sk”) indicating the gallons of the respective component per 94-pound sack of the wollastonite and pumice. The settable compositions had a density of 14.2 Ib/gal. The cernent dispersant was CFR*-3 cernent dispersant from Flalliburton Energy Services, Inc. The cernent set retarder used was HR*-5 retarder, from Halliburton Energy Services, Inc., Duncan, Oklahoma. After préparation, the thickening times, which is the time required for the compositions to reach 70 Bearden units of consistency, were determined at 180°F in accordance with API RP 10B-2.

Table 3

			Ingrédients			1
Sample s	Densit y Ib/gal	Wate r gal/s ~k	Wollastonit e % by wt	Pumie e % by wt	Lim e % by wt	Cernent Dispersan t % by wt	Cernent 1 Retarde ; r ï %by | wt i	îhickenin g Time hr:min
11	14.2	5.83	40	60	5	0.5	0.5 I	12:00-
12	14.2	5.84	40	60	5	0.5	0.25 1	6:23
13	14.2	5.84	40	60	5	0.5	0-1 1	2.42

[0043] As illustrated, settable compositions comprising wollastonite and pumice may hâve acceptable thickening times. For example, thickening times from over 12 hours to just under 2.5 hours were seen in Samples 11 and 13, respectively.

Example 4 [0044] The following sériés of tests was performed to further evaluate the compressive strength of settable compositions comprising wollastonite and pumice. A single settable composition, labeled Sample 14, was prepared using the indicated amounts of water, wollastonite, pumice, lime, a cernent dispersant, and a cernent set retarder. The amounts of these components in each sample are indicated in the table below with “% by wt” indicating the amount of the component by combined weight ofthe wollastonite and pumice and gallon per sack (“gai/sk”) indicating the gallons of the respective component per 94-pound sack of the cementitious component. The settable composition had a density of 14.2 Ib/gal. The

cernent set retarder used was HR*-5 retarder, from Halliburton Energy Services, Inc., Duiïcan, Oklahoma.

[00451 After préparation, the 24-hour and 48-hour compressive slrengths were determined for the sample settable composition using an Ultrasonic Cernent Analyzcr 5 (“UCA”), available from Fann Instrument Company, Houston, TX. In the UCA, the sample cernent 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 API RP IOB-2.

Table 4

Satnple	| Ingrédients	UCA 24-Honr Comp. Strength PSI	UCA 48-Hour Comp. Strength PSI	48-Hour Comp. (Crash) Strength PSI
1 Density 1 Water	Wollastoiiîte % by wt	Pumice % by wt	Lime % by wt	Cernent Dispersant % by wt	Cernent Retarder % by wt
Ib/gal	| gal/sk ? ?
14	| 14.2	I 5.84	40	60	5	0.5	0.25	832	900	568

[0046] Accordingly, Table 4 mdicates thaï acceptable compressive slrengths may be obtained for settable compositions comprising woftastonite and pumiee. For example, a compressive strength of 900 PSI was obtained at 48 hours in Sample 14.

[0047] It shouîd be understood that the compositions and methods arc described in 15 terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of’ the various components and steps. Moreover, the indefinhe articles “a” or “an,” as used in the claims, are defîned herein to mean one or more than one of the element that it introduces.

[0048] For the sake of brevity, only certain ranges are explieitiy disclosed herein. 20 However, ranges from any lower limit may be combined with any upper limit to récité a range not explieitiy recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explieitiy recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explieitiy recited. Additionally, whenever a numerical range with a lower limit and an upper limit is 25 disclosed, any number and any inclnded range falling within the range are specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equîvalently, “from approximately a to b,” or, equîvalently, “from approximately a-b”) disclosed herein is to be understood to sei forth every number and range encompassed within the broader range of values even if not explieitiy recited. Thus, every point or individual 30 value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit to recite a range not explieitiy recited.

[0049] Therefore, the présent invention is well adapted to attain the ends and advantages mentioned as well as those that are inhérent therein. The particular embodiments disclosed above are illustrative only, as the présent invention may be modified and praciiced in different but équivalent manners apparent to those skilled in the art having the benefît of 5 the teachings herein. Ahhough îndividual embodiments are discussed, the invention covers ail combinations of ail those embodiments, Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the daims below. Also, the terms in the daims hâve their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentée. It is therefore évident that the particular illustrative 10 embodiments disclosed above may be allered or modified and ail such variations are considered within the scope and spirit of the présent invention. If there is any conflict in the usages of a word or term in ihis spécification and one or more patent(s) or other documents that may be incorporated herein by reference, the définitions that are consistent with this spécification should be adopted.

Claims (19)

1. What is claimed is:

   1. A method of cementing comprising: providing a settable composition comprising: wollastonite;

   pumice;

   a calcium-ion source; and water;

   wherein the wollastonite is présent 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 présent in an amount in a range offrôm about 25% to about 75% by combined weight of the wollastonite and pumice; and allowing the settable composition to set.
2. 2. The method of claim l, wherein the settable composition has a density in a range of from about 12 pounds per gallon to about 20 pounds per gallon.
3. 3. The method of claim I, wherein the water is présent in an amount in a range of from about 40% to about 200% by combined weight of the wollastonite and pumice.
4. 4. The method of claim 1, wherein the calci um-ion -source comprises lime.
5. 5. The method of claim l, wherein the calcium-ion source is présent in an amount in a range of from about 0.1% to about 25% by combined weight of the wollastonite and pumice.
6. 6. The method of claim 1, wherein the settable composition further comprises an additive selected from the group consisting of a dispersant, a strength-retrogression additive, a set accelerator, a set retarder, a weighting agent, a lightweighi additive, a gasgenerating additive, a mechanical property enhancing additive, a lost-circulation material, a filiration-control additive, a fluid Ioss control additive, a foaming additive, a defbaming additive, a thixotropic additive, and any combination thereof.
7. 7. The method of daim 1, wherein the settable composition further comprises an additive selected from the group consisting of crystalline silica, amorpbous silica, fumed silica, salts, fibers, hydratable days, calcined shale, vitrified shale, micraspheres, fl y ash, diatomaceous earth, metakaolin, ground perlite, rice husk ash, naturel pozzolan, zeolite, cernent kiln dust, resins, any combination thereof.
8. 8. The method of claim 1, wherein the settable composition is essentially free of any additional cementitious materials.
9. 9. The method of claim l, wherein the settable composition is free of Portland cernent.

   K). The method of daim 1, wherein the settable composition is introduced into a subterranean formation.

   5 11. The method of daim 10. wherein the settable composition is allowed to set in a well-bore annulus.
10. 12. The method of daim 10, wherein the settable composition is used in primary cementing.
11. 13. The method of claim 10. wherein the settable composition is used in remédiai 10 cementing.
12. 14. A method of cementing comprising:

    preparing a base fluid comprising water and lime:

    preparing a dry blend comprising wollastoniie and pumice, wherein the wollastonite is présent in an amount in a range of from about 25% to about 75% by 15 combined weight of the wollastonite and pumice, wherein the pumice is présent in an amount in a range of from about 25% to about 75% by combined weight of the wollastonite and pumice;

    combining the base fiuid and the dry blend to form a settable composition that is essentially free of Portland cernent;

    20 introducing the settable composition into a subterranean formation; and allowing the composition to sel in the subterranean formation.
13. 15. The method of daim 14, wherein the lime is présent in the settable composition in an amount in a range of from about 0.1% to about 25% by combined weight of the wollastonite and pumice.

    25
14. 16. The method of daim 14, wherein the settable composition is free of Portland cernent.
15. 17. The method of daim 14, wherein the settable composition is allowed to set in a well-bore annulus.
16. 18. The method of claim 14, wherein the settable composition is used in primary 30 cementing.
17. 19. The method of claim 14, wherein the settable composition is used in remédiai cementing.
18. 20. A settable composition comprising:

    wollastonite;

    pumice;

    a calcium-ion source; and water;

    wherein the woUastonite is présent in an amount in a range of from about

    5 25% to about 75% by combined weight of the woUastonite and pumice; and wherein the pumice is présent in an amount in a range of front about 25% to about 75% by combined weight of the woUastonite and pumice.
19. 21. The seltable composition of claim 20 further comprising one or more of the features defined in any one of claims 2-9.