AU2014240187B2 - Ceramic particles and methods for making the same - Google Patents

Abstract

Disclosed is a population of ceramic particles that includes a plurality of individual, free flowing particles, The plurality has a total weight and particle size distribution. The effective width of the distribution is the difference between the distribution's d95 and d5 particle sizes. The distribution's effective width exceeds 100 5 microns and includes three abutting and non-overlapping regions that include a first region, a second region, and a third region. The first region abuts the second region and the second region abuts the third region. The width of the second region is at least 25% of the effective Width. The weight of particles in the second region does not exceed 15% of the plurality of particle's total weight. The weight of particles in the first region and io the third region each exceed the weight of particles in the second region, Methods of making the populations of ceramic particles are also disclosed

Description

CRQSSrRBPiEEHCE TO llLA rED AFPlJC^TIOM

This implicationm·a TivisionaF application derived from Australian Patent Application No: 2:011216058 (PC2TATS2011 /0123957: W0 201 1/100203), claiming priority of UR:Appjication No. 61 /303097, the entire contents of which are, jncorpiUted hv reference herein. Each patent and patent application cited herein is also hereby incorporated by reference in its entirety.

BAUKUROUfeD OF ΊΉΕ INVENTION

Populations of ceramic particles may he used in a wide variety of industrial processes and prodticts including, for example: .abrasive media; as a granular coating for asphalt based rooting shingle; as flliratfon medium for liquids; as a imhstituie for sand in investment easting processes; and as proppants in a downhole drilling operations where the ceramic particles may be referred to as proppants. Proppants made from ceramic particles may be used in deep wells where the pressure exerted ba the ceramic proppant exceeds the crush; resistance of con ventionai proppan ts such as sandand resin coated sand.

Examples of patents and published patent: applications directed to proppants include:/PS 33:76;930; US 4s632,S7b;TlS 7,067,445; US 7,528,096:, US 2006/0177661 and/UST0bS/0W063§.

SLJMMARA

Embodiments of the present invention include populations· of particles baying certain characteristics to improve crush strength, conductivity, and resistance to settling while alsolowering nianufocturing cost for the producer of the ceramic particles: Populationsof ceramic·particles described herein can be created using conventional equipment and raw materials.

One embodiment of the present invention comprises populations of ceramic particles comprising a plurality of individual, free flowing particles. The plurality of particles having a total weight and particle size distribution including d^5 and d* particle si ;ses, Jle. dirtribution has an effective width which is the di ifemned between the distribution's d$s and d> particle sizes,.:The-:di^jrtbnti0n-V:eiTeetive' width exceeds 100 microns and comprises three abitttihg and nwn-dyeriapping^^ regions incinding a hrst region, a second region, and a third region, The first region abuts the second region and the second region abuts the third region, d^he widdi of the second region is at least 23% of the effective width. The weight of particles in the second region does not exceed 13% of the population’s total'weight and the weight of particles in the first region and the third region each exceed the weight of particles in the second region.

Another embodiment of the present invention relates to a process for manuiactnring a population of ceramic particles. The following steps, Providing an initial population of particles having a total weight and particle size distribution. Separating the iratial population of particles into at leastthree portions, identified herein as portion A, portion B and portion C wherein the d«} Of portion A is less than the dss pf portion B which is less than the ds^ of portion C. Combining portion A and portion C thereby creating a final population of particles having a total weight and particle size distribution ineluding d05 add ds particle sizes. The distribution's effective width is the difference between the distribution's dgs and d?particle sizes. The -.distribution's effective width exceeds 100 nucrons and comprises three ahutfing and non-overlapping regions including a first region, a second region, and a third region. The first region abuts the second region·: and the-second region ahutaihe third: region. The widtfeof the fecond region is at least 2:5% of the effective width. The weight Of particles in the: second region does not exceed 15% of the and the weight of particles in the first region and the thirdiregionfeach exeeedithc weigh t of partic les in th e second 'region.

Another emhodimepfrelatesiM process fer manuiaeturing a population of ceramic particles. The process may comprise the followingZteps. Providing a first population Of particles and a second population of1particles whefeiwthe dy> of the first pp|>ul»tt.drt''pd^$''^rt:'ihe dio pf the second population. Combining the first population and the second population thereby cmating a final population having a total weight and particle size dirtrthuiion including d§« and dj particle sizes. The distribution has an effective width which is the difference between the distribution's d«*5 and d$ particle sizes. The distribution's effective width exceeds 100 microns and comprises three ahutfing and hoh-overlaimmg regions including· h first region, a second region, and a third region. The first region abuts the second region and. the second region abuts the third region. The:: width of the second region is at least 25% of the effective width. The weight of particles in the second region does not exceed 15% offbefinal population's total weight and the weight of particles in the first region and the third region each exceed the weight of particles in the second region,

BRIEF DESCRIPTION OF THE DRAWINGS

Fig, 1 is a first graph of weight percent versos: particle diameter;

Fig. 2 is a first process flow chart;

Fig. 3 Is a second graph of weight percent versus particle diameter; and

Fig. 4 is a second process flow "chart..

DETAILED DESCRIPTION

As used herein^ the phrase ‘^KspuMon.:of eerdthio -|i^cies?*'is:^ed:<as:a.gefteral·:: description of a plurality of ihdivfidftal, Roe Rowing ceramic paitielcs; Tefiiis such as proppant abrasive grains and roofing: granules describe populations of ceramic particles that'are' intended lor use in Specific applications. ^•t^edhet^^The'terprs'^proppanrM'^i^ppaijts’bnpy'^R^iin^ohangei^Jy to identify alarge "quantity of cerauilc particles that ane typically Pltxe&amp;'wifiTa ira<dui»ig. fluid and then forcefully inserted ihtp a well bore. The particles, which may have an average diameter between 200 microns: and 2.4 nim, become lodged in fissures crated in the: geological:formation by the fracturing fluid, After the fracturing fluid has been withdrawn, theipafticles remain to the fissures. As fluids located near the well bore drain through the fissures, into the well and are then pumped to the surface of the well, the inci i \ id ual,particles prop open the passageways through the fissures thereby allowing additional fluids to fill the well. Use of proppants may improye die economic periormanee of the well.by enabling the capture of more fluid than would be possible if proppants were not used: on the same well. in order to manufacture largesuch as proppams, commereial manufacturers of nuuMnade proppants may use large rotating pan style mixers to mix dry ingredients with wet ingredients and then form a large quantity of manually deformable spherically shaped particles that may be referred to as greenware. Thdigfeenwarej prior to any further processing such as sorting or heating, may be referred :: to herein: as the on ginal, pppu 1 ation of parities,

With regard to the dry ingredients used to make the greenware, suitable starting materials ioelude oxides such as alnhildufu oxides, silicon oxides, magnesium oxides and mixtmestbereol Other exemplary: startmgtmaterials include:clays (whicbare: predominately hydrated alurhiuah such as kaolin, diasppre clay, hurley clay, and flint elay, hauxitie clays, natuml or synthetic bauxites, altunino-silicmes, rnagaesium silicatesi mixtures thereof and the like. Various sintering aids, such as bentonite clay, iron oxide, horon, boron carbide, aluminum dihoride, boron nitride, boron phosphide, other boron compounds, or fluxes, such as sodium carbonate, lithium carbonate, feldspar, manganese oxide, ritania, and sodium silicaieSrhay he added in amounts up to about ten weight percent to aid sintering, if desired, a binder may be added to me mixture to improve particle formation and to increase the strength of the greenware, Generally the binder is added at ahpid Qd> percent by weight based on the weight of the Oxides.: Suitable binder materials:include starch, resin or wax, calcium carbonate, or a combination thereof The: dry ingredients::;riiay be ground by ball milling or: other amnion processes. Prior to grinding, the dry: jpgred tents may be dried to improve the ease of grinding.

In one embodiment, the dry ingredients may be combined with a /wet ingredient, suchM water,:ohd.mixed m an intensive mixer having a rotatable contaihment vessel: provided: with: a rptor table and a rotatable i mpacti ng impeller, such as ah Eirieh mixer. The.mtorimbiefdrvpsu^rot.atesltd'mi opposite direction to the impacting Impeller. The: impaetmgdmpoUer may be in. theMrrn of a disk/Withrods or bars attached to the dlsk and aligned generally parallel with: the,impeller’ s axis Of rotation. Sufflcieiit water is heeded to cause essentially spherical particles of the mixture to form. After such particles have : formed, Additional ceramic· powder may bemadded and the mixer0¾ be further operated: to cause accretion of the addedmaterial tofthe particles being Ibrmdd. The resulting: greenware Is then dried, usually in a dryer at between about 1OCAC and about 301FC, to moisture content of less than about Id weight percent

In conventional processes the distribution of particle^i'amet^rsiproduced by tile agglomeratof is so wide that the^s^ibtttid^itteiu^es particles5that/aie-.0.yers:ke^.asd'' particles th^me aodorsi/cd as well as paiticlissihm 4>p^pnaf^iy:'|i:5^:fpfi^e in:'a well bore, tk^laaiei^'fenciioBi-as a proppanibeeause they are difficult to place in the geological formation. The undersized proppanis may be top small to ftmction as a prpppmt because they tepd to fill the voids betyipen other appropriately sized proppant part icles and thereby reduce the conductivity of a Enid through die proppant pack, CktnsequeUtj^, propprpt rnanufacturers typically remove the oversized and nndersized particles viable proppant that has acceptable conductivity and resistance to crashing. However, as the width of the particle size distribution is decreased byeliminating the oyemized apd undersized particles, the parrieles reraammg in the distribution tend to form a nronornodal distribution with ,|b^!^:'lpPdacttvity::Ujian the original population but Crashing may increase beyond an acceptable level. The oversized and undersized particles are removed by allowing the particles to How through a series of screens. Each screen contains a plurality of rmifbnnly ^aped and sized bples that allow particles smaller than the:screen/s hole opening to riow through the screen and prevents particles larger/than the: |creeh’s:hole opening from passingfheretlu-ough. As explained above, if the proppant manukmipring process cannot Control the diameter of the individual proppant particles as closely as desired^ the Screening process may need -to divert and then of the original pfpppant population which are either too large or too ::sma!L IP soHm:eommercial operations:,: up to 311 weight percent of the proppan ts are removed during: the screening process and then returned to the: beginning of the, proppant: rhahhileturrag' process where they can be recovered/,' Proppant manullcttuingprocesses that yield less: than 70 weight percent usabie product on a single pass therethrough are known. %hi!e the:recycled material may be recoverable thereby avoiding a significant economic lossdft'material cost, the labor involved in nianutaeturing and recovering 30 weight percent of the greenware is an economic burden which Ultimately increases the Cost of producing the proppan t.

Hie dried and screened greenware may then be hePed/hl aiuriikeii'ta^ elevated temperature, such as 10007C or higher, thereby sintering and/or bondihgfhe agglomerated pains of dry ingredients toone another and iboning porous, crush resistant proppant particles. Suitable sintering temperatures are generally about 1200*G arid cou ld be as high as 15Q0°C.

As will be explained below, one embodiment of a psjeess of tins indention reduces the cost of producing the proppant by separating ah initial Quantity of partly into at least three portionSj which are identifled herein as portion A, portion Bypordon C> and then combining portion A with portion C thereby creating a final proppant population. Portion B may be sold as a separate product witho pi further processing. The savings in labor costs 'associated with substantially improving the yield of the manufacturing process may sign i ft c antly i rapro v e (lie economic performance of the proppant manufecturitig proeess.

Proppants may be eharacterixed using one or more physical characteristics "including^particlesize distribution, : As used herein, particle size distribution is determined using a CAMlSIZER*' optical particle size analyzer wMoktSmanufkitpisiky Retsch Techno lo gy in Germany. The particle size analyzer provides A graph of particle sizerdistribatidh which may:indicate:numerous particle size metrics, such as djo, which is used to wb i ch is iess than 50 percent of the particles5 diameters and greater than 50 percent of the particles' diameters. Similarly,, $5 tdeuhfes the particle diameter Which isless thah 95 percentof the particles:‘ diameters and greater than 5 .-percent'of the particles- diameters. For any distribution, similar val ues can he calculated for Other particle· StzlB.'hii^tjics such asd;0, dAw^and d*

Another important physical describe proppahts is conductivity which may be generally described as a measure of the resistance the prripphht ezerts on a fluid as the fluid moves thrOn gh the proppant. Conductivity is debrn^pdmslng-tkepi^pdiapl described in ISf) 13003-5.

Yet aiio^efimpot^fohmdt^stimma/proppani’A^tHfy to withstand crushing; Cmsh resistance is a term commonly used to denote the strength of a proppant and may be determined using ISO 13303-2, A stmhg proppanf generates a lower Weight percent crushed proppant than a weak proppant -at ttsesame closure stress. For example, under the same test conditions, a proppant that has a2: Weight percent crushed proppant is considered to be a strong proppant and is preferiodto a Whak prdppant that has a 10 weight percent crushed proppant.

Men proppahts are used in drilling operations;, fee-particles are mixed with,a fluid which is then forcefully pumped downhole, As the fluid and the particles entrained therein: are pumped into the well, some of the particles tend to settle at a taster rate: t han .pth-er of particles, The depth of the well may impact the degree of separati» with shallow (i.e. less than 2000 meters) experiencing less separation than deep wells fue, greater than 4000 meters) i f the same nuxtureiof fracturing fluid and proppant are used in each well This phenomenon may be refeTi^;;|Q::^^i'·^. the ‘‘proppant settling prph|etn,! which is a widely redoghi zed and persi stent prohlem fe the companies that use proppants as part of their process to fracture geological formations. The proppant Settling problem may lead to small particles accumulating in one loeauoa within the fracture zone while the large particles accumulate in a second location within the fracture zone, The uncontrolled seiitlhgpf particles within the fracture zone may decrease the effectiveness of the proppant and thereby decrease the economic performance:;of the: well The inventors of this invention recogui zed that this problem could be; substantially reduced or eliminated by coordinating the selection of the proppants’ physical characteristics, such as particle gi^tdiSttibutionsr^nd' sprite gravity, and chemical compositions so that; most of the part ides sett! e at approximately the same rate, Mixing: a first proppant popidmioni having a first average particle size and specific gravity with:a: second proppant population having; a different average particle size and specific girivity so thatail of the particles in the final population1 of particles settle at; approximately the same rate nray suhstahtiahyTCSpIve the proppant settling: problem.

The inventors of tins invention have also recognized that coordinating the selection of a first proppant population hbylhg:A;icftoWn'particle-she·;and speeific;gravhy with a second proppant popniatidn: havipg.o knpWn particle size and/or speci fic: gravity that is different feom the first proppant population’s particle side and specific gravity can he used to intentionally create a spectrum of settling rates which can be used to gauss a beneficial and controllable difference: in the rates at which the particles settle. For example* small particles having: a high spec if! Cigrayity can bemad© to settle much more partiel^ that have a low .specific1 gravity. If desired, the differeneein Settling cap. be accentuated so that most pf fhe small particles enter the fractures in the geological formation and travel as; for as possibleanto the fissures be fore the larger particles can reach the opening, of the "fissure. Selectively inserting the smaller particles and then the larger particles may be desirable because U can lead to the prevention of particle back flow which is the undesired removal of panicles from Fissures as the fracturing fluid is removed.

Shown in Fig. 1 is graph of weight percent versus diameter tor a population of eeraniie particles of one embodiment of this invention. The effective width of die distribution, see arrow 28, is defined herein as these^:· arrow 3¾ rind particle size effs see arrow 32. As previously described^ the particle size distribution's d$ and di** may be determined using an optical particle size analyzer.

Within the effective width there axe at least three abutting and non-overlapping regions including first region 34, second region 36: and third region 38. The first region abuts the second region and the second region abuts the third region. Ilie weight of particles; in the first region and the weight of panicles in the third region each exceed the weight of particles in the second region. In Fig. 1, the weight of particles in the fdgisns is 40 percent of the pdpulatidu’s total weight and theweight^oFparticlesin the second region is 10 percent With regard to the mean particlesfe also r^ as the dstj, the dgo of the first region is inherenfly less than the dsyoTdie second region which is; inherently less than the dss ofthe thirdregiom Furthermore, the width of the second region, which is defined as^cStlfi^Ciehe^eenpai^ciisize-dwi^ see ariow 40, and dniiu, see arrow 42, is approximately 25% of the width of elective width 28 .

With regard to the weight percentages of the first, secondand third regions, a population of ceramic particles of this invention may region that are individually between 5 and 85 weight percent ofthe popuiafiorrs total weight provided the total ofthe Iksfti^^urdngp^is does not exceed 00%. The second region does not exceed 15 weight percent ofthe population’s total weight, in some emhoditnehtSj the second region may account for no more than Iff Weight percent, 5 weight percent or even 0 weight percent of the population'^ total weight. Weight percentages of the first or third regions between 5 and 85, such as IS, 35,40.0,63.5 and 75 7 are also fogsible. Similarly, weight percentages of the second region between 0 and IS, such as 3,0,6,2, 0,5 and 12J are feasible.

The boundaries of the fimf second and third regions shown in Fig, I are defined for use herein as follows. The fifot region extends from the populations dj to the second regiofos dm.»··· The third region extends from the second region's dm3S to the population’s <Ι?5· The second region exists 'between'.the"first region; anil third-region thereby occupying the region between the dmi,, and tire : tlmso Tor a particular pop ulailpn, of ceramic pattieies, the fcri abet the are the particle si^es that cooperatively debne a region which shnuiianeousiytpt oeeupies at ieast 25 % ofthe diatrihution^ width between its d« and civs paiticie sizes; (2) the weight percent of dm particles in the first region and third region each exceed die weight: percent of particles in the seeondiregion; and (3) the weight percent of particles in the second region does not exceed I S weight percept: of the. population's total weight· The boundaries of the second: region (?.c. the particle sizes corresponding: to the d^y and the:d^:) may be deteopipod by using a particle size ^aly^^dcier^tedhe particle di ameters in the population of particles anti then using sieves to determine the weight percent of partieies between selected particle diameters^

Shown in Tig. 2 is a flow chart of a process that may be used to produce an embodiment of a population of ceramic particles of this invention. Step 5fi represents providing an initial quantity of particles that have a total weight and particle size distribution. The initial quantity may have a mpnomodal or multimodal particle size disirihution and may be produced using raw materials and conventional equipment, such as spray dryers, high intensity shear mixers and pan agglomeratop which are known to those skilled in the art of manufacturing proppaht. In. step 52, the initial quantity:#? particles is separated into portion A, portion B and portion C which are identified in Tig, 2 by part numbers 54, 56 and 58, respectively. The dso of portion A is less thap the of portion B which is less than the d.w of portion C. Separating the initial, quantity into three portions may be done using an air .classification system, a cyclonic· separator or a screening mechanism. Step 60 represents combining portion A wii|iportion C to create,a final population of ceramic particles 62 that does not include portion B, Tito particles in :portion B may be sold without further screening or other modification: thereby avoiding 'ithe "costs associated wi th recovering 25 percent or more of the partieies: ifom the initiat quantity of ceramic particles.

Fig, 3 discloses a hypothetical particle size distribution^^ particles that could he maniitoctured by the process disclosed inFig, 2 wherein, after the: initial quantity of particl.es was divided into a portion A, portion: B and portion C, portions A and € were combined thereby creating the final populatioh of ceramic particles haying the particle size distribution disclosed in Fig. 3. The final population of ceramic partieies has a total weight and. a particle; size distribution iHcludihg-d<*f ;and. d$ particle sizes, The distribution’s effective width, which is ;the difference bcfweenthe distribution^·#^ and ds particle si/es, exceeds 100 microns and comprises three abutting and noipovetiapping regions including first region 34 which abuts second region 36 win ch ate 38. The - Width off he second region is: at least 25% of the effective width and the weight of particles in the second region does not exceed 15% of the final population’s total weight. Furthermore, the weight of particles in the first region and die third region each exceed the Weight of particles in the second region. -psnulbcturmg an embodiment of the applicant's invention will he described with Merenee to Fig, 4 wherein step ^represents prevising a '&amp;&amp;: pdantitv of pdrtictes having a d» particle size. Step 82 represents providing a second quantity of particles having a particle size distribution having a dj o parfieie size. The first selected so that the ^ of the first quantity is less than the dp :pfthe second quahtity, In step 84, the first and second quantities are then mixed to create a final population of ceramic particles. The final popniafion has a particle size diatnbdtififijlipludiai^ds and fiss particle sizes. Tit#. distnbufioB-ias-^.eflfecti've width which is the difference between the do^and dy particle sizes. Theeffeefive width exceeds 100 microns and comprises three abutting and rum-overlapping regions including a ..first·'.regionwhich..ahuts^secpndifegion Which, in turn, abuts a third region. The Weight of particles In the first region:; andfhe third region each exceed the weight of particles in the second ;fegidp:, The width of the seeoru] region’s particle size distribution is at least 25% of the width pf the final population’s efiectfV&amp;'^i^bv

With regard , ip the process disclosed in Fig,4,;the;first quantity of partfcles has an average specific gravity andpaffieie size distribution. The second quantity of particles has an average specific gravity and particle sizeldistfibution. In some embodiments, the average specific gravity of the particles in the second quantity may be:gfleastfOff;less than .the average specific gravity of the particles ib the; first quantity, Ifdesired, the average specific: gravity of fiigpartiefes in the second Quantity may be 15%,:;20% dr even. 25% .less than the average specific gravity of the particles in the first :quantity . By coordinating the : selection o f the particle size distributions and av erage specific gravi ties, the first quantity: of particles: pah be made to settlelat approximately fire same rate as the second qiiantiiy of particles, Ini-some- embodiments, controlling the average specific gravity of ilie second quantity 1© weight percent less than the average specific gravity o f the first quantity of particles will substantially mitigate or prevent undesirable partic ie settling,

If' as .In th#: process' OisclOiSed in Fig, 4: two different populations of particles are combined to matittiacfctre an. embodiment :of a:poptil:ailon of ceramic patticl.es of this invemion» then both the physical (i.e. specific gravity and particle size distribution) and chemical compositions) characteristicsofthe first «aid second quantities may be independently selected to create a final population. For example, in one embodiment a population of ceramic particles of tlris invention may baye a particle size distribution which has first region 34, second region 36 shown in Fig. 3, In tins embodiment there are no particles in the second region. The particles in first region 34 may be chemicallyidentical to particles Altcmatiyejy, the particles in the first region may have a firat chemical composition and the particles in the third region may have a second chemical composition Which t| chemically distinct ftom the first chemical composition. As used herein, two chemical compositions arc considered to be ‘‘chemically distincf if: (l) the cotnpositions do not contain at least one chemical compound in common; or (2) if the compositions do contain at least one compound in common then there is at least a 10 weight percent difference, based on the total weight of the composition, 'between the amount of the compound in the first composition and. the amount .of the compound i?r the second : composition. An x-ray : fluorescent ,(XR.F). analytical apparatus may be used to determine the quantities of compounds such as AlrCb and Si O?. For example, in a first em bodiment, if the entire population o f particles in the population of ceramic· particles is madetirorn bauxite which has: a first chemical composition that includes at least $$). weight percent AbOs* then tlicchemical epnipositipnS: of the: regions are not chemically distinct. In a second embodiment, if the particles in the first region are made from .bauxite and the particles in the third region have a chemical composition that includes less than I weight percent AbOi and at least 50 weight percent Si€h,then the compositions ofthefirst and thStl·'are'bh^nsMt:l.y distinct. In the second embodiment, the particles in the third region may include sand. In a third embodiment if the particles in the first regionare made from bauxite and thereby have 60 weight percent or more Af>Oj while the particles in the third region are made from day that includes less than $0 weight percent AbCh then the compositions of the .first, and third regions are eheroleally:'distinct

With regard tothe packing of proppant particles when they are inserted in a fissure in a geological formation, the: distribution of die proppant particles' diameters may impact the: physical amngemeni of the packed particles which could impaetthe pronjiaiu's crush strength and conduct hi ty. Consider, for example, a proppant pack that includes a mixture of three different size proppant particles having average diameters of Eh, D; and Dn respectively, wherein the aihallest diameter particles have an average diameter equal to D*, fiierm^ium--<iame^:;p^rticlds have an average diameter equal to Da arid the iargesi particles have an average·dianieter equal to 13$, Within die pack, the largest diameter particles may frequently ablit one another thereby forming an essentially coMihuotls matrix that defines numerous passageway s there: between. The medium ske pUftioles and smallest size particles may: he; selected fofoadily fill: the passageways between the .largest particles. Because the largest diameter particles form a matrix through the pack, the crash resistance of the largest particies essentially determines: theeixish resistance of the proppant pack. Wi thin the same pack, the smallest and rhediutn^diameter partibles may have little impact on the proppant: pack’s crush resistance because they fit Within the voids created by the matrix '.but, M the saipe time, the small and medium size particles May reduce the conductivity of the proppant pack by fit ling ihe voids between the large partieies thereby blocking the passageways through which a fluid could flow. In contrasty a distribution of proppant particles inaysbe seiedted so. thatThe smallest and/or medium diameter partieles are too large to fit within the^i^.creat^.%'th^:iarge' partieies thereby forcing many of larger particles aw'n^:'fr&amp;m.0he'm^^erihh.d[rred.uctng the .number of contact points between the large particles. This disruption to the packing pattern of the large particles may be facilitated by selecting a population of partieles wherein the ratio Of theparticle's dsfoss exceeds 0.22. Populations of particles that have a dsxfe ratio gmamr thmi 0i30 or even 0.35 are feasible. Populations of particles that have a diesis ratio greater tliau 0,22 may be advantageous for two reasons. : First,., the disrupted packing pattern may create many more points of contact between the largest particles and the smaller partieles thereby distributing the force apphed frj the pack Over a broader area which results in improved resistance to crushing. Second, the passageways defined by the largest particles are forced open by the medium and smallest diameter particles thereby foeiliMing the flow of a fluid through the proppant pack. Incertain endrodiments, a pty^pant of this invention may contain a unique distribution of partM© sizes that colieoipfely^pitwideresistance to ci^^h^::re$i^anceld^tUi%daring the fracturing process and conductivity of fluid throogh the proppant These desirable performance characteristics are believed to be due at least in part to the particles’ ability to pek in a disrupted packing pattern.

EXAMPLES

To illustrate an embodiment of a population of ceramic particles of this invention, the inventors manuiactuted a population of proppants as follows. The Starting raw materials ineludedt 4(X1 kg of Arkansas 5αηχί1β*Λν^ώ^8ά·'%«βηι:ρΓ^^1^'·ρρ«η4·4ο,8»'· average particle size of about ίό microns; 7 kg of a commercially avaiialde com starch binder; and 113 kg (25f) lbs.) of water added to a rotating Eiricb mixer which is a well known agglomeraior. The raw materials Slledi the chaniber Of the mixer approximately two-thirds fell. Rotation of the table aid impeller were codtmiid;^::^pm^^ately' 1.5 minutes until particles of a suitable size were formed. Approximately 1 Oh kg of additional bauxite was slow ly added thereby coating the previously fonp^ltaitidl^.wi^'. a layer of inaterfal. : Rotation of the table and impeller were continued for:approximately 4 nhuntes thereby resulting m the formation of spherical particles which may be referred to : herein::as greenware. The particles were then dried in a dryerafSOCEC until the moisture content of the particles was less th an: 1091 To: achi eve the desired densi ty and strength, dieidried particles were then heated to I40(ft€ for approximately one hour. The resulting: particles had a sphericity of about 0.9, as detefipined using the Rfumbeirt and Sloss chart.

The entire:population of particles exitingfhe drying oven: but prior to flowing through the furnace is defined herein as the parent population of particles. After heat freattnent: in a furnace at 140()--(), the parent population of particles was screened by directing the particles to flow through a,first commercial screening device which contained, in a linear arrangement, a 14.: mesh screen and then a 50 mesh screen . The; first screening device mmdved particles that dither (a) did; not flow through the 14 mesh screen or fb) did. flow theACiimesh screen., thereby leaving a population of proppants that were small enough to: flow through a 14 mesh screen and too large to flow through a 50 mesh screen. This population of pariicles i§ dfefihed herein as the initial population of particles and is designated Lot 1 in Table 1. I.ot I .$^,ma4e:::lp..^w through a second process which included a commercial sct&amp;ning device that contained a 20 mesh screen and a 35mesh screen. The second screening dteviep diverted and captured the particles into three separate portions. Portion A contained 14 mesh screen in the first screening devaee hip were too large to flow through the 20 mesh screen. Thepartieles in portion B were small enough to flow and too large to flow through the 35 mesh screen and are designated l ot 2 in Table 1.

The particles in portion C were small enough in flow throughthe 35 mesh screen bin too large to flow through the SB mesh semen in the first screening device. Thepartieles in portion A and portion (;' \vere recombined ihereby creating the final proppant population which is designated Lot 3 in Table 1. The partieles in portion B were permanently separated fiorn the final proppant population.

Shown below in Table 1 are ilm peAinenf charaeteristics 0if Oaeh proppant. All numerical values, except for percentages, are in microns.

Table 1

! Effective Width is the difference between the distribution’? d.^and d>. ~ Gap Size is the width of the second region which is the difference between the distribution's T,.. and 4,..,,. ' Gup % is the Gap Size divided by die l·! fective Width. 4 Amount is the weight of particles in each region divided by the weight afpaftieles in the hnal population.

The data clear ly detnonstrates that the populati on of particles of this invention, as represented fey Lot 3,met the ibilowing criteria. First, the population’s effective width exceeded 1Q0 microns. Second, the width of the second repoeTi.e.the Gap %) was at least 25% of the Effective Width. Third, the weight percent of particles in the second region was less than 15% ofthe final .population’s weight, Fourth, the weight percent of particles in the fet region anti the third region each esceetted the weight percent o tpariicics in the second region.

To illustratethe advantage obtained by an embodiment of a proppant of this invention, the crush resistance o f the initial popul ation, final population and proppant i n portion Brwete measured at pressures ofh&amp;JfMPa t iiiiiOO psih H1T4 MPa f 15,()00 psi) and 1 -37:9 MPa 12(),000 psi) using the procedure described in ISO 13603-2. Each of the crush resistance values in Table 2 represents an average of three sampies: The crush resistance values are expressed as a weight percent of thepainple’s starting weight. Thedower the number, the better the resistance to crushing.

Table 2

Thedata in Table 2 demonstrates that for an embodiment of:a proppant of this invention die final proppant population: (fe. Lot T) had a crush resistance whiehisboth (a): approximately eciuivaknt to tile crush resistance of the initial proppant population fie. Lot 1} and (h) lower and dierefbre better than the crush resistance of the proppant in portion B (fe. Lot 2} which were removed and avaiiahle as a separate product In sharp contrast to emtveitiionai pmppant : manufacturing processes wherein only the proppants in portion B were eommercialiy valuable and the proppants in portions A and G wem recycled, the proppants in portions A and <3of this invention were combined to create a final proppant with a crush resistance better than the proppants in parti on B. The abil tty to avo id the costs inherent in reeyeling largo percentages of the initial proppant population may provide a distinct economle advantage to; the proppant manufacturer.

The: above dpscripiiop:'&amp;:ponsidere$ ol particular embodiments only. Modifications of the inyeptipn- will .peepr ipfhose ohdled in the art and to those who make or use the inyention. There lore,, it Is understood that theombodi rn en is, shown in: the drawings and described above are merely for illustrative purposes and are not: intended tpjimit the: scope of the invention,.which is defmed by the ilpllowing eiaiois as mterpreted according to the prine Iples, of patent law, 'inc 1 udhig the Ifeeirine of Ep uiy alen ts. A reference herein to a patent document or other matter which is given as prior art lS'::iu>t::tak^::aS'as::^miS5ion'::tSiat'that document or prior art was part of common general knowledge at the priority date of any of the claims.

With reference to the use of the word(s) “comprise'1 or “comprises” or “comprising” in the foregoing description and/or in the following claims, unless the context requires otherwise, those words are used on the basis and dear understanding that they are ίο be interpreted inclusively, rather than exclusively, and that each of those words is to be so interpreted in construing the foregoing description and/or the following claims.

Claims (11)

1. CLAIMS WSat: is claiiSed is; 1.. : . flpopulation ofceramic particles, comprising: a. g.pittrality of indiyidual, free''fld^iiti;:CCfamic particles, said plurality of particles haying a total weight and par dele siye distribution including d^and. dspaillcfe; sffes; t>, said distribution lias an effective width which is the difference between the distribution's d# and: ds particle sizes, said distribution's effective width; exceeds 100 microns and comprises three abutting and non-overlapping regions including a first, region, a second region, and a third region wherein the first region abuts the second' region and the second regi on abuts the third region; and wherein the wid th of said second regidh is at lea#: 25% of the effective width; c, wherein the Weight of parti cles in sai d second regi on does not exceed i S% of the plurality .of particle's' total weight, and the weight of particles in said first region: and said third region: each exceed the weight of particles in said ^second region; and: d. wherein said population of paiticles have an avernge diameter betvveen 22t3 microns and 2,4 nun.
2. 2. The population of e i aim 1 wherei n the ratio of dod® exceeds(L22.
3. 3, The population of claim 1 wherein the r$tio:df%:dte exceeds ¢630. 4; The population of any one of claims 1 to 3 wherein the width of said second region is at least 30% of the effective width.
4. 5.. The population of any one of claims 1.: to 4 wherein the weight of the particles in said firsfregioh exceeds at least 5 percent of the plurality of particles'total weight. 6:, The population of claim 5 wherein the weight of the partieies in said first region exceeds at least 15 percept of thepitirali ty of particles' total weight. λ The population of'any one of claims 1. to bWherein liie weight of the particles in said third region exceeds at least 5 percent of the plurality Ofiparticles’ total weight. $. The population of claim 7 wherein the weight of the particles in said third region exceeds at least 15 pereentpf iheplufality of particles' total .weight,;
5. 9. The population; of claim 8 \yberein the weight of the particles in said third region exceeds at least 40 percent of the plarahty of particlesf total weight;
6. 10. The population of claim 9 -wherein the weightof the particles in said second region does not exceed It) percent of the plurality ofip^iclp’s-ipiat^i^ii
7. 31. The population of any one of chums I to 10 wherein the Weight of'the particles in said second regiondoes not exceed 10 percent of theplurality of particlels total weight. 12. lire population of any one of claims I to 10 wherein the weight of the particles in said second region does not exceed 5.percent of the plurality o f particle's total weight
8. 12, A process, for numuiacturing a popu lation of ceramic particles, composing the steps: of: a. providing a first quantity of particles and a second quantity of particles, wherein the d^i Ot the first quantity is legsthan the dof the second quantity and the difference between the average specific gravity of the particles in the first quantity and the average specific gravity of the particles in the second quantity is atleast 15% of the first quanfity’s average specific, gmvity, and h. combining the first quantity and the second quantity thereby creating a final population of ceramic particles having a total weight and particle size distribution including daj and d> particle sixes, said distribution has an elective width which is the difference between the distribution's dfe and ds particle sixes/said distflbutioifs effective width exceeds lOOrnierorts and comprises three abutting and nop* Overlapping regions including q first aatfc&amp;iufd region wherein the first region abuts the second region and die second region abets the third regioii; wherein: the.width of said second region is at 1 east :35 %cjf the effective1 Width* ,pnd>vvherein the weight of panicles in said second region 'does not exceed 15% of said final population of ceramic particles' total weight arid the w eight; of -Region-and said third region each exceed the weight of particles in said: second1 region,
9. 14, The process of claim 1"3 wherein the particles in the first quantity have ait average specific gravity, the particles in the second quantity have an average specifie/gravity and the difference between the first quantity's average specific gravity and the second quantity's average specific gravity is at least 10% of the first quantity's average specific gravity. 151 The process of claim 13 w herein said particles in said first quantity have a first chemical composition, said particles in saidseeond quantity have a second chemical composition, and the chemical compositionsareclminieailydistinctfinm each other.
10. 16. The process of claim 15 wherein at least one of said chemical conipositions compfiscs at least ·50'weight percent. SiOT
11. 17 . The process of claim 15 wherein only one of said chemical compositions comprises at least T:0''Weightiperceui'SiC)2.. iSi The process of claim 17 wherein said at least: one of said chenueat: compositions comprising at least 50 Weight percent SiO.> comprises sand, ID.: The process ofeiaim l'i''wher©lai6niy'0ne.'0FMd.chemicalcompositions comprises at leasf TO:1we i girt percent 44*03 -