CA2921428A1 - Mitigation of contamination effects in set-delayed cement compositions comprising pumice and hydrated lime - Google Patents

Abstract

Methods and compositions for cementing are disclosed. Embodiments include a method of cementing comprising: providing a set-delayed cement composition comprising water, pumice, hydrated lime, a primary set retarder, a secondary set retarder; activating the set-delayed cement composition to produce an activated cement composition; introducing the activated cement composition into a subterranean formation; and allowing the activated cement composition to set in the subterranean formation.

Description

2 PCT/US2014/054799 MITIGATION ()F CONTAMINATIM EFFECTS IN SET-DELAYED -CEMENT
COMPOSITIONS COMPRISING PUMWE AND HYDRATED LIME
BACKGROUND
[0(I01j Cement compositions may be used .in a variety of subterranean operations.
For example, in subterranean well construction, a pipe string (e.g., casing, liners, expandable tubularsõ etc.) may be run into a wellbore and cemented in place. The process of cementing the pipe string in place is commonly referred to as "primary cementing." In a typical primary ceinenting mthod, a cement composition may be pumped into an annulus between the walls of the wellbore and the exterior surface of the pipe string disposed therein. The cement composition may set in the annular space, thereby !brining an annular sheath of hardened, substantially impermeable tetTleRt (i.e., a cement sheath) that may support and posit* the pipe string in the wellbore and bond the exterior surface -of the pipe string to the subterranean formation. -Among other things, the cement sheath surrotmding the pipe string functions to prevent the migration of fluids in the annulns and to protect the pipe string from corrosion. Cement compositions also may be used in remedial cementing methods to, for example, seal cracks or- holes in pipe strings or cement sheaths, seal highly permeable formation zones or fractures, place cement plugsõ and the like.
100021 .A broad variety of cement compositions have been used in subterranean cementing operations. in some instances, set-delayed cement compositions have been used.
Set-delayed cement compositions are characterized by their ability to remain in a. pumpable fluid state fir at least about one day (e.g., about 7 days, about 2 weeks, about 2 years or more) at room temperature (i.e., about SWF) in quiescent storage. When desired tbr use, the set-delayed cement compositions may be capable of activation whereby reasonable compressive strengths may be developed. For example,. a cement set activator may be added to a set-delayed cement composition whereby the composition sets into a hardened mass.
Among other things, the set-delayed cement composition may be suitable -for use in wellbore applications, ibr example, where it is desired to prepare the cement composition in advance.
This may allow for the cement composition to be stored prior to its use. In addition, this may allow for the cement composition to be prepared at a convenient location betbre -being

3(1 transported to the job site. .Accordingly, capital and operational expenditures may be reduced due to a reduction in the need for on-site bulk storage and -mixing equipment.
Advantageously, this may be particularly useful for offshore cementing operations where space onboard the vessels may be limited.
[0003] While set-delayed cement compositions have been developed before, challenges exist with their successful use in subterranean cementing operations. For example, set-delayed cement compositions prepared with Portland cement may have undesired gelation issues which may limit their use and effectiveness in cementing operations. Other set-delayed compositions that have been developed, for example, those comprising hydrated lime and quartz, may have limited use at lower temperatures as they may not develop sufficient compressive strength when Eised in subterranean formations having lower bottom hole static temperatures.
[0004I The large-scale manufactum of set-delayed cement compositions may present additional challenges. Large batch mixers or transport trucks used during the manufitcturina process of' the set-delayed cement compositions may contaminate the set-delayed cement compositions with residual cementitious matter front previous manutacturing operations.
The cementitious contaminants may reduce the effectiveness of the tandem or aetivators used with the set-delayed cernent compositions. The cent ntitious contaminants may even render du.; se-delayed cement compositions unusable. Thorough cleaning of the mixers before transitioning to a new cement composition may be expensive and decrease manufacturing efficiency% Furthermore the use of cleaning agents (e.g., silica sand) may be inetTeetiVe 10005] These drawings illustrate certain aspeets of sonie of the embodiments of the present method, and should not be uSed to limit or define the method.
[0006] 'Fla illustrates a system :kir preparation an delivery of a set-delayed cement composition to a wellbom in accordance with- Certain embodiments.
10007] :FIG. 2A illustrates surtlice equipment that may be used in placement of a set-de14ed canon eottipoition in a wellbore inAi.t:ixIttlatk:e with certain ertibodiments.
[0008] Fla 2B illustrates placement of a set-delayed cement compsition into a wellbore annulus in accordance with certain embodiments:

DESCRIPTION OF PREFERRED EMBODIMENTS
100091 The present ernh(xliments relate to subterranean cementing operations and, more particularly, in certain embodiments, to set -delayed Cement compositions and inethods fusing set-delayed cement compositions in subterranean formations.
[00101 Embodiments of the set-delayed'cement compositions may generally comprise water, pumice, hydrated lime, and a primary set retarder. Optionally, the set-delayed cement compositions may further comprise a. dispersant.
Advantageously, embodithents of the set-delayed cement compositions tm remain in a pumpable fluid state for an extended period of time. For example, the set-delayed cement compositions may remain in a pumpable fluid state for at least about 1 day or longer (e.g., about 2 years or long,er). Advantageously,. the Set-delayed cement compositiOns may develop reasonable compressive strengths after activation at relatively low temperatures. While the set-delayed cement composition's May be Suitable for a number of subterranean cementing operations, they :may be particularly suitable for use in subterranean formations having relatively low bottont hole static temperatures, eg., temperatures less titan about 200F or ranging from about 100`17 to about 200T. In alternative embodiments, the set-delayed -cement cOmpesitions may be Used in subterranean lOrmations having bottom hole static temperatures up to 450T- or higher.
100111 The water use.d in embodiments of -04.7 set-delayed cement compositions :may be from any source provided that it does not contain an excess of compounds that may undesirably affect other components in the set-delayed cement compositions..
For example, a set-delayed cement composition may comprise fresh water or sah water. Salt water generally may include one or more. dissolved salts therein and may be saturated or unsaturated as desired frir a- particular application. Seawater or brines may be suitable for use in embodiments. I:nether, the water may be pftsent in an amount sufficient to form a pumpable 8Iurry. In certain embodiments, the Watet may be present in the set-delayed cement compositions in an amount in the range of from about 33% to :about 200%
by weight of the pumice. In certain etnbodiments, the water may be present in the set-delayed cethent compositions in an amount in the range of from about 35% to about 70% by weight of the pumice. OW of ordinary skill in the art with the ix,nefit of this disclosure will recognize the appropriate amount of water to use for a chosen application.
[00121 Embodiments (tithe set-delayed cement compositions may comprise 'pumice.
Generally, pamiee is a volcanic rock that ctm exhibit cementitiOus properties in that it May set and harden in the presence of hydrated lime and water. The pumice may be ground or um...!round. Generally, the pumice may have any particle size distribution as desired for a

4 paaicular application. In certain embodiments, the pumice may have a mean particle size in a range of from about 1 micron to about 200 microns. 'I' he mean particle size corresponds to d50 values as measured by particle size analyzers such as those manufactured by Malvern instruments, Worcestershire., United Kingdom in specific embodiments, the pumice may have a mean particle size in a range of from about 1 micron to about 200 microns, isrom about 5 microns to about 100- microns, or :from about 10 -microns to about 50 microns. In one particular enthodiment, the pumice may have a mean particle sin of less than about 15 microns. An example of a suitable pumice is IDS7:.325 lightweight aggregate, available from Has Putnice PrOducts, inc., Malad, Idaho. 1)5-325 aggregate has a particle size of less than about 15 microns. It. should be appreciated that particle sizes to small may have mixability probleins while particle sizes too large may nOt he effectively suspended in the compositions. One of ordinary skill in the art, with the benefit of this disclosure, should be -able to select a puruiee with a particle size suitable for a chosen application, [00131 Embodiments of the set-delayed cement compositions may comprise hydrated lime. As used herein, the term "hydrated lune will be understood to Mall calcium hydroxide. in some etribodiments, the hydrated lime may be provided as quicklime (calcium oxide) which hydrates When mixed with water to form the hydrated lime. The hydrated lime may be included in embOdiments Of the set-delayed cement compositions, for exatnple, to limn a hydraulic composition with the pumice. For example, the hydrated. lime may be included in a putnice-to-hydrated-lime weight ratio of about 10:1 to about 1:1 or 3:1 to about

5:1, Where present, the hydrated lime may be included in the set-delayed cement compositions in an amount in the range of from about; 10% to about 1(X)% by weitilit of the pumice. Ibr example. In SOIlle eMbOdiMenN, the hydrated lime may he present in an amount ranging between any of andlor including any of about 10%, about 20%, about zIOVN about 60%, about 80%, or about 100% by weight of the pumice, in some ethbodiments, the eethentitiouS components, present in the set-delayed cement composition may consist essentially oldie pumice and the hydrated lime. For example., the cementitious components may primarily comprise the pumice HO the hydrated lime without, any additional components (e.g., Portland cement, 'fly asb, slag cement) that hydraulically set in the presence: Of Water. Otte of ordinary skill in the art, with the benefit of this diselostire, will recognize the appropriate amount of hydrated lime to include for a chosen application, [0014) Embodiments of the set-delayed cement compositions may comprise a primary set retarder: A broad variety of primary set retarders may be suitable, for use in the set-dolayed cement compositions. For example, the primary set retarders may comprise phosphonic acids, such as ethylenediamine tetra(Methylene phosphonie acid), diethylenetriamine penta(thethylene Phosphonic acid), etc.; phosphonic acid derivatives;
lignosulfonates, suCh as sodium 4,,nosultbnate, calcium lignosulfonate, etc.;
salts such as stannous sulfate, lead acetate, monobasic calcium Phosphate: organic acids such as citric acid, tartaric acid, etc:, cellulOse derivkives such as hydroxyl ethyl cellulose MEC) and earboxymethyl hydroxyeth,y1 cellulose (CMHEC); synthetic co- r.a- ter-polymers comprising suifonate and carboxylic acid groups such as su1fonate4unctiona1ized acrylamide-acrylic acid co-polymers; borate e.ompounds such as alkali borates, Sodium metaborate, sodium tetraborate, potassium pentabOnte; derivatives thereof or mixtures thereof.
One example of a suitable commercial primary set retarder is Micro Matrix'''. cement retarder, available frOm Halliburton Energy Services, Inc., Houston, Texas. Generally, the primary :set retarder may be present in the set7delayed cement coMpositions in an amount sufficient to delay seAting for a desired time. :In some embodiments, the primary set retarder may be present in the set-delayed cement compositions in an amount in the range of from about. 0,01% to about 10%
by weight of the pumice. in specific embodiments, the primary set rcAarder may be present in AO amount ranging between any of 'and/or including, any of about f>01%., about 0.1%, about 1%õ about 2%, about 4%, about 6%, about 8%, or about 10% by weight of the pumice.
(Mc of ordinary skill in the art, with the benefit of this disclosure, will recognize the appropriate amount of primary set retarder to include for a chosen application.
[0015] As discussed above, an issue with the manufacture of set-delayed centent corripositions is the potential for cementitions Contamination at the bulk plant or during transport. Cementitious contamination, as defined herein, refers to the ,contamination of a set-delayed cement composition ..Vith tiny material that is not an intended component of the set-delayed ce.ment composition; said material being unintentionally added, directly or indirectly, to the se-delayed cement composition; %viterein said material is cementitious iti and of itself, becomes cementitious upon the unintended contact with the set-delayed cement composition, andlor promotes or induces early setting, gelling. Or any other type of :cementitious reaction in the set-delayed cement composition. Typically.
cementitious contamination may be mitigated. by cleaning the bulk plant machinery or the transport trucks.
However, this procedure may be costly andfor ineffective. Supplementing the set-delayed cement coMpesitions with additional cement retarders may be A low cost and more effective alternative to the typical cementitious contamination cleanup methods.
AdvantageoWy, the use of multiple retarders may provide superior mechanical properties as compared to using a higher coneentration of a single retarder. For example, using a high concentration of a single retarder may cause the set-delayed cement composition slurry to thicken. This thickening effect may cause field handling And pumpability issues.

6 [00161 Embodiments of the set-delayed cement compositions may additionally comprise one or more secondary set retarders in addition to the primary set retarder. 'The secondary set retarders may be .used to mitigate the effect of cementitious contaminants residual :manufacturing contaminants) on the set-delayed cement compositions.
Cementitious contaminants, as defined herein,- referS to any material that is not an intended component of the set-delayed cement. composition; said material being unintentionally added, directly or indirectly, to the set-delayed cement composition;. wherein said material is cemerititious in and of itself, becomes cementitious upon the unintended contact with the setclelayed cement composition, and/or promotes or induces early setting, gelling, Or any other type of cementitious reaction in the set-delayed cement composition. Without limitation, examples of ccmentitious contaminants include the nnintended addition of 'hydraulic cements such as Portland cement, calcium illuminate cement, etc.; pozzolanic material such as fly ash, etc.;
slag; cement kiln dust; plasters such as gypsum plasters, lime, plasterS, cernent plaster, etc.;
materials that promote or induce cemernitious reactions; and any combination thereof Cementitious contarninants may have an adverse effect on the properties of the set-delayed cement compositions. Embodiments of the Set-delayed cement compositions comprising secondary set retarders -may also comprise cementhious contaminants that were Unintentionally added to the set-delayed -ccirient composition.
[00171 A broad variety of secondary set retarders :may be suitable for use in the set, delayed cement compositions. The secondary set retarder May be chemically different from the primary set. retarder; alternatively the secondary set retarder niay be chemically similar to the primary .set retarder. For example, the seeondary set retarders may comprise phosphonic acids, such as ethylenediamine tetTa(inethylene phosphonic diethylenetriarnine penta(tnethylene phosphonic acid), etc.; phosphonic acid derivatives;
lignosulfonates, such as sodium lignostilfonate, calcium lignosulfonate, etc.; salts such as stannous sulfate, lead acetate, monobasic 'caleium phosphate; organic acids such as citric add, tartaric acid, ete;
cellulose derivatives .such :as hydroxyl ethyl cellulose (iEC) and carboxymethyl hydroxyethyl celltilose (CMHEC); synthetic en- or ter-polymersõ comprising sulfonate and carboxylic acid groups such as .sulfonate-ftinctionalized acrylamide-acrOic acid co-polymers; boratt.,, compounds Such as :alkali borates, sodium metaborate, sodium tetraborate, potassium pentaborate; derivatives thereof or mixtures thereof One example of a suitable commercial secondary set retarder is 'Micro Matrie cement retarder, available from lialliburton Energy Services, Inc., Houston, Texas. Generally, the secondary set retarder may be present in the set-delayed cement compositions in an amount sufficient to delay setting for a desired time. In some embodiments, the secondary set retarder may be present

7 the set-delayed cement compoons in an amount in the !love of from about 0.01%
to about 10% by weight of the punkt. In specific embodiments, the secondary set retarder may be present in an amount ranging between any of and/or including any of about 0.01%, about abott 1%, t.tbottt 2%, about 4%, about tS(.'/=i,, about 8%, or about 18% by weight of the pumice. One of ordinary skill in the art, with the benefit of this disclosure, will recognize the appropriate amount of secondary set retarder to include for a chosen application.
100181 As previously mentioned, embodiments of the set-delayed cement compositions may optionally coinprise a dispersant. EXamples of suitable dispersants include, without limitation, -sulfonated-lbrinaldehyde7based dispersants.
(e.g., sultbnated acetone fonnaidehyde condensate), exaMples of which may include :Mud* 19 Available from Geo Specialty Chemicals, Ambler, Pennsylvania. Other suitable dispersants may be polycarboxylated ether dispersants such as Ligktimete 5581F and Liquimene 5141, available from BASF Corporation Houston, Texas; or Ethacryl G available fim Coatex, Genay, France. An additional exaMple of a suitable commercially available dispersant is Rrst-3 dispersant, available from Halliburton Energy Services, Inc, Houston,.
Texm. Of particular importance in regards to the examples that fbilow, is that the 13quimete 514, diSpersaiit eOmpriSes 36% by Weight of the polycarboxylated ether hi water.
While a variev of dispersants may be used in accordance with embodiments, polyearboxylated ether dispersants May be particularly suitable for use in some. ernbodiinents.
Without .being;
limited by theory, .it is believed that polycarboxylated ether dispersants may synergistically interact with Other components Of the set-delayed cement composition. For example, it. is believed that the polycarboxylated ether dispersants may-react with certain set retarders (e.g., phosphonic acid deri.vatives) tesulting in formation of a gel that suspends the pumice and hydrated lime in the composition for an extended period of time.
[00191 in some embodinients, the dispersant may be included in the set-delayed cement compositions in an amount in the range of from about 0,01% to about 5%
by weight of the pumice. In specific embodiments, the dispersant may be present in an amount ranging between any of andfor including- any of about 0,01%, a.bout 0.1%, about 0,5%, about 1%, about 2%, about 3%, about 4%, or about 5% by weight of the pumice. With the benefit of this disclosure, one of ordinary skill in the art will recognize the appropriate amount of dispersant to include for a chosen: application.
[00201 Other additives suitable ibr use in subterranean eeMentin operations also .may be included in embodiments of the setrdelaye,d cement compositions.
Examples of such ,additives include, but are not limited to: weighting agents. Ilithtweight additives, gas-

8 generating additives, .111.0diailkal-prpperty-enbancinu additives, lost,,circulation materials, fatration-control additives, thiid-loss-cotitrol additives, detbaming agents, foamina- agents, thixotropic additives, and combinations- thereof. In embodiments, one or more of these additives may he added to the set-delayed cement C913113pSitii./T1 after storing but prior to placement of the set-delayed cement composition into a subterranean formation.
With the benefit of this disclosure, a person having ordinary skill in the art Will be able to determine the type and amount ladditive useful for a particular :application and desired result, [0021] Those of ordinary Skill in the art will appreciate that embodiments of the set-delayed cement: coMpoSitions generally shotild have a density suitable for a particular application. By way of example, the set-delayed cement compositions_may have a. density in the range of from about 4 .pounds per gallonõ ("Ibigal") to about 20 'lb/gal.
In certain embodiments,. the set-delayed cement compositions may have a density in the range of from about 8 Ibigal to about 17 lb/gat Entbodiments,of the set-delayed cement coMpositions may be foamed or tin:foamed or may comprise other means to reduce their densities, such as hollow microspheres, low-density elastic beads, or other density-reducing additives known in the att. In embodiments, the density may be twiticed after storing the eonmosition, but prior to placement in a subterranean formation. Those of ordinary skill in the art, with the benefit of this discloSure, will recognize the tippropriate density for a particular application, [(10221 As previously mentioned, the set-delayed cement compositions may have a delayed set in that they remain in a pumpable fluid state for at least one day (e.g., at least about I day, about 2 weeks, about 2 years or more) at room temperature in quiescent storage.
For :example, the set-delayed cement compositions May remain in a pumpable fluid state tbr _a period of titne from about 1 day to about. 7 days or more. In some embodiments, the set-delayed cement compositions may remain in a pumpabie fluid state for at least about 1 day, about 7 days, about 10 days, about 20 days, about 30 days, about 40 days, about 50 days, about 60 days, or longer. A fluid is considered to be in a pumpable fluid state where the fluid has a consistency of less than 70 Bearden units of consistency ("BC), as measured using a pressurized consistometer in accordance with the procedure for determining 'cement thickening times Set forth in API RP Practice I013-2, Recotnmended Practice 16r Thstitig Well Cements, First Edition, July :2005.
[0023] When desired. for use, embodiments of the set-delayed cement compositions may be activated (e.g., by combination with an activator) to set: into a hardened mass. By way of example, embodiments of the set-delayed cement compositions may be activated to tbrm a hardened mass in a time period in the range of from _about 1 hour to about 12 hours.
For example, embodiments of the set-delayed cement compositions may set to form a

9 hardened 'mass in a time period ranging betett any of andfor including any of about I day, about 2 days, about 4 days, about 0 days, about 8 days, aboat 10 days, or about 12 days.
[00241 In some embodiments, the, set-delayed cement compositions may set to have a desirable compressive strength after activation. Compressive strength is generally the capacity of a material or structure to withstand axially directed palling forces. The compressive strength may be measured at a specified time: after the set-delayed cement i01.11pOiti011 has been aCtivated and the resultant composition is maintained undt.1 :specified temperature and pressure conditions. Compressive strength can be measured by either destruetive or non-destructive Methods. The destructive method physically tests the strength of treatment fluid samples at various points in time by crushing the samples in ,a compression-testing machine. The compressive strength is calculated: from the failure load divided by the cross-sectional area resisting the load and is reported in units of pound4orce per square inch (psi). Non --destructive methods May employ a UCATm ultrasonic cement analyzer, available, front Fann Instrument Company, Houston, TX. Compressive strength values May be determined in accordance with API RP 10B-2, Recommended Practice fiir Tesling Vel1 aments, First Edition, July 2005.
1I0025'1 By way of example, the set-delayed cement-compositions -may develop a hour compressive strength in the range of from about 50 psi to: abentt 5000 psi, -alternatively, from about 100 psi to about 4500 psi, or alternatively from about 500 psi to about 4000 psi, In seine embodiments:, the set-delayed cement compositions may develop A.
compressive strength in 24 hours Of at least about 50 psi, at least about: 100 psi, at least :about 500 psi, or more hi some embodimentsõ the compressive Strength values may be determitk..d using destructive or iron-destructive methods at a temperature ranging from 100"F to 2001.-7 [00261 Embodiments may include the addition of a cement set activator to the set-delayed cement compositions. Examples of suitable cement set activators include, but are not limited to: amines such as triethanolamine, diethanotamine; silicates such as sodium.
silicate; zinc forinate., calcium acetate; .Groups lA .and 11A hydroxides such as sodium hydroxide, magnesium hydmide, and calcium hydroxide; monovalent salts such as sodium chloride; divalent salts such as calcium chloride,: nanosilica (i.e., silica having a particle Size of less than or equal to about MO nanometers); polyphosphates; and combinations thereof. In some embodiments, a combination of the polyphosphate and a monovalent salt may be used for activation. The monovalent salt may be any salt that dissociates to form a .monovalent cation, such As SOdit1111 OM potassium salts. Specific examples of suitable monovalent salts include potassium sulfate, and sodium sulfate. A variety of different polyphosphates may be used in combination with the monovalent salt Ibr activation of the set-delayed cement compositions, including polymeric metaphosphate salts, phosphate salts, and combinations thereof: Specific examples of pOlyrrierie metaphosphate salts that Ttlay be used include sodium hexametaphosphate, sodium trimetaphosphate, sodium tetrametaphosphate, sodium pnt etaphophatr. xiiuin heptametaphOsphate, sodium octametaphosphate, and .combinations thereof A specific example of a. suitable cement set activator comprises :a combination of sodium sulfate and :sodium hexametaphosphate. In particular embodiments, the activator May be provided and added to the set-delayed cement Composition as a liquid additive, for exa.mple., a liquid additive comprising a monovalent salt, a polyphosphate, and optionally a dispersant.
[00271 Tile Ceraellt set activator Should be added to embodiments of the set-delayed cement compositions in amounts sufficient to induce the set-delayed cement compositions to set into a. hardened mass. In certain embodiments, the cement .set activator may be added to a se-delayed centent composition in an amo-unt in the range of about 1% to about 20% by weight of the pumice, in specific embodiments, the cement set activator may be present in an amount ranging between any of andfor including any of about 1%, about 5%, about 10%, about 15%, or about 20% by weight of the pumice, one of ordinary skill in the art, with the benefit of this disclosure, will K.-cognize the appropriate amount of cement set activator to include for a chosen application.
[00281 :As will be appreciated by those of ordinary skill in the art, embodiments of the set-delayed cement conipositions may be used in a variety of subterranean operations, including primary, and remedial cementing. In some embodiments, a set-delayed cement composition may be provided that comprises water, pumice, hydrated lime, a set retarder, .and optionally a dispersant. The set-delayed cement composition may be introduced into a subterranean. formation and allowed to set therein. As used herein, introducing the set-delayed cement composition into a subterranean formation includes:
introduction into any portion of the subterranean formation, including-, without limitation, into a wellbore drilled into the subterranean formation, into a near wellbore region surrounding the wellbore, or into both. Embodiments may further include activation of the set-delayed cement composition.
The activation of the set-delayed cement composition may cornprise, for exaMple, =the addition of a cement set activator to the set-delayed cement composition.
[00291 In some embodiments, a set-delayed cement composition may be provided that comprises water, pumice, hydrated lime, a set retarder, and optionally a dispersant. The set-delayed cement coMpositiori may be gored, for example, in a vessel of other Suitable container. The set-delayed cement composition may be permitted to remain. in storage foe a desired time period. For example, the set-delayed cement tomposition may remain in 'storage for a time period of about 1 day or 'longer. For example, the set-delayed cement composition may remain in storage frit- a time period of (*Out 1 clay, about 2 days, about 5 days, about 7 days, about 10 days, about 20 'days, about 30 days, about 40 days, about 50 days, about 60 days, or longer. :In simile embodiments, the se-delayed cement composition may remain in storage for a time periOd ìn a rang;... of t7rom about l day to about 7 days or longer. Thereafter, the set,delayed cement- composition may be activated, for example, by addition of a cement set activator, introduced into a subterranean formation, and allowed to Set therein:
[003.01 In pritnary cementing embodiments, for example, .embodiments of the set-delayed cement compoSition may be: introduced into an annular space between a conduit located in a etlhon. and the walls of a wellbore and oi a larger conduit in the xvellbore), Wherein the wellbore penetrates the subterranean formation. The set-delayed cement composition may be allowed to, set in the annular space to form an annular sheath of hardened cement, 'The set-dehryed cement composition may form a barrier that prevents the migration of fluids in the wellbore. The set-delayed cement composition may also, for example', support the conduit in the wellbore.
[00311 in remedial cementing embodiments, a. set-delayed cement composition may be used, for example, in squeeze-(_ementing operations or in the placement of cement plum.
'By way of example, the set-delayed composition may be placed in a wellbore to plug an 20. 'opening. (e.g., a void or crack) in the formation, in a gravel pack, M
the conduit, in the cement sheath, andlor between the cement sheath and the conduit (e.g., a mieroannulus).
[00321 An example embodiment comprises a method of cementing comprising:
providing, a Set-delayed cement composition comprising water, pumice, hydrated litne, a primary set retarder, and a secondary set retarder; activating the set-delayed cement composition to produce ,an aetiVated cement composition; introducing the activated cement composition into a subterranean tbrmation; and allowing the activated cement composition to set in the subterranean formation.
1100311 :An example embodiment comprises a :method of mitigating contamination in the manufacture of a set-delayed eel-nem composition, the method comprising:
providing a dry-blend cement composition comprising pumice and hydrated lime; and preparing a set-delayed cement composition comprising water,' the dry-blend cement composition, a primary set retarder, arid a swortdary set retarder, [00341 An example embodiment comprises a set-delayed cement composition comprising; water; pumice; hydrated Hine; a primary set retarder;: and a Secondary set :retarder; wherein the set-delayed cement composition further comprises a cementitious contaminant; and whetein the set-delayed cement composition will remain in a pumpable fluid State frit a time period of at least abOut I day at toOm temperatthe in quiescent storage.
[0035] An example embodiment etnnprises a set-delayed cement system comprising:
a set-delayed cernent composition comprising water, pumice, hydrated lime, a primary set retarder, and a secondary set retarder; wherein the set-delayed ceinent composition -additionally comprises a cementitious contaminant; an activator for activating the set delayed cetnent composition; mixing e,quipment fOr mixing the set-delayed cetnem composition and the activator to form an activated cement composition; and pumping equipmentibr delivering the activated centerit eomposition into a wellbore.
[0036] Referring now to FIG, 1, preparation ola set-delayed cement composition in accordance with example embodiments will now be described. FIG. 1 illustrates a system 2 for preparation of a set-delayed cement composition and delivery to a µ,vellbore in accordance with certain embodiments. As shown, the set-delayed cement composition may be mixed in mixing equipme.nt 4, suCh as a jet mixer, re-circ.ulating mixer, or a batch mixer, for example, and then pumped via pumping equipment 6 to the \Venom. _In some embodiments, the mixing, equipment 4 and the pumping equipment 6 :may he disposed on one or More cement trucks as will be apparmt to those of ordinary skill in the art. in some.
embodiments, a jet mixer may be used,: tbr example, to continuously -mix the limesettable material with the water as it is being pumped to the wellbore.
[0037] An example technique tbr placing a set-delayed cenient composition into a subterranean formation will now be described with reference to FIGS, 2A and 2B. 'FIG. 2A
illustrates surface equipment 10 that .may be used in placement of a set-delayed cement coMposition in accordance with certain embodiments. It should be noted that while FIG. 2A
generally dep.icts a land-based operation, those skilled in the art will readily recognize that the principles described herein are equally applicable to subsea operations that employ floating or sea-based platforms and rigs, without .departing from the scope of the disclosure.
As -illustrated by FICi..2A, the surface Nuipmerit 10 may include a cementing -unit 12, which .may include one or more cement trucks. The cementing unit 12 may include mixing equipment 4 and pun-Ong equipment 6 (e.g.., FIG. 1) as will be apparent to those of ordinary Skill in the art. The cementing unit 12 may pump a set-delayed cement composition 14 through a feed pipe 16 and to a cementing head 18 whieb conveys the set-delayed cement composition 14 downhole.
[0038] Turning no.s,,v to FIG. 23, the setAtIayed cement cornposition 14 may be placed into a Subterranean formation 20 in accordance with example emboditnents. As illustrated, a wellbore 22 may be drilled into the subterranean formation 20.
While wellbore 22 is shown extending generally vertically into the subterranean formation 20, the principles described herein are also applicable to wellbores that extend at an angle thmugh the.
subterranean formation 20, such as horizontal and slanted wellbores. As illustrated, the wellbore 22 COmmises walls 24 in the illustrated embodiment, a suriace casing 26 has been inserted into the wellbore 22. The surface casing NS may be cemented to the walls 24 of the wellbore 22 by cement sheath 28. in the illustrated embodiment, one or more additional conduits (e.g., intermediate casing, production casing, liners, etc.), shown here as casing 30 may also be disposed in the wellbore 22. As illustrated, there is a wellbore annulus 32 tbmed between the casing 30 and the walls 24 of the welIbore 22 andfor the surface casing 26. One or more centralizers 34 may be attached to the casing 30, for example, to centralize the casing 30 in the wellbore 22 prior to and during the cementing, operation.
[0039] With continued reference to F1G. 2B, the set-delayed cement compositions 14 may be pumped down the interior of the casing 30..I.he setAelayed cement composition 14 may be allowed to flow down the interior of the casing 30 through the easing shoe 42 at the bottom of the casing 30 and up around the casing 30 into the wellbore annulus 32. The set-delayed cement composition 14 may be allowed to set in the wellbore annulus 32, for example, to ibrm a cement sheath that supports and positions the casing 30 in the wellbore 22. While not illustrated, other techniques may also be utilized for introduction of the set-delayed cement composition 14. By way of example, reverse circulation techniques may he used that include introducing the set.-delayed cement composition 14 into the subterranean lomation 20 by way of the wellbore annulus 32 instead of through the casing 30.
[00401 As it is introduced, the set-delayed cement composition .14 may displace other fluids 36, such as drilling fluids andfor spacer fluids that may be present in the interior of the casing 30 and/or the wellbore annulus 32. At least a portion of the displaced fluids 36 may exit the wellbore annulus 32 via a flow line 38 and be deposited, for example, in one or more retention pits 40 (e.g, a mud pit)õ as shown on FIG. 2A. Referring again to FIG. 2B, a bottom plug 44 may be introduced into the wellbore 22 ahead of the set-delayed cement composition 14, for example, to separate the set-delayed cement composition 14 from the fluids 36 that may be inside the easing 30 prior to cementing. After the bottom plug 44 reaches the landing collar 46, a diaphragm or other suitable device. rupture to allow the set-delayed cement composition 14 through the bottom pl.ug 44. :In FIG. 2B, the bottom plug 44 is shown on the landing collar 46. In the illustrated embodiment, a top plug 48 may be introduced into the wellbore 22 behind the set-delayed cement composition 14.
The top plug 48 may separate the set-delayed cement composition 14 from a displacement fluid 50 and also push the set-delayed cement composition 14 through the bottom ping 44.

[0041] The exemplary set-delayed cement compositions disclosed herein may directly or indirectly affect one or mote components or pieces of equipment associated with the preparation, delivery, =recapture, recycling, reuse, and/or disposal of the disclosed set-delayed cement compositions. For example, the disclosed set-delayed cement compositions may directly or indirectly affect one or more mixers, related mixing equipment, mud pits, storage facilities or units, composition separators, heat exchangers, sensors, gauges, pumps, compressors, and the like used generate, store, monitor, regulate, andfor recondition the exemplary set-delayed cement compositions. The disclosed set-delayed cement compositions may also directly or indirectly afitct any transport or delivery equipment used to convey the set-delayed cement compositions to a well site or downhole such as, for example, any transport vessels, conduits, pipelines, trucks, tubular, arid or pipes used to compositionally move the set-delayed cement compositions from one location to another, any pumps, compressors, or motors (e.g., topside or downhole) used to drive the set-delayed cement compositions into motion, any valves or related joints used to regulate the pressure or flow rate of the set-delayed cement compositions, and any sensors pressure and temperature), gauges, and/or combinations thereof, and the like. The disclosed set-delayed cement compositions may also directly or indirectly alTect the -various downhole equipment and tools that may come into contact with the set-delayed cement compositions such as, hut not limited to, wellbore casing, wellbore liner, completion string, insert strings, drill string, coiled tubing, slickline, wireline, drill pipe, drill collars, mud motors, downhole motors and/or pumps, cement pumps, surface-mounted motors andlor pumpsõ centralizers, turbolizers, scratchers, floats (e.g., shoes, collars, valves, etc.), logging tools and related telemetry equipmentõ actuators (e.g., electromechanical devices, hydromechanical devices, etc), sliding sleeves, production sleeves, plugs, screens, .filters, flow control devices (e.g., inflow control devices, autonomous inflow control devices, outflow control devices, etc.), couplings (e.g., electro-hydraulic wet connect, dry connect, inductive coupler, etc.), control lines electricalõ fiber optic, hydraulic, etc.), surveillance lines, drill bits and reamers, sensors or distributed sensors, downhole heat exchanaers, valves and corresponding actuation devices, tool seals, packers, cement plugs, bridge plugs, and other wellbore isolation devices, or components, and the like.
EXAMPLES
[0042.1 To facilitate a better understanding of the present embodiments, the following c.txamples of certain aSpects of some embodiments are given, in no way should the following exatnples be read to limit, or define, the entire scope of the embodiments.

Exalt*pie [0043.1 TiNtAvt-tilOW4and Out.mds Of pumice and hydrated lime fOr use in a set-delayed cement coMposition- were dry blended at a bulk Own faCility. Samples of the dry blend cement composition were collected for use. Using the collected dry blend cement composition, six experimental set-delayed samples were prepared. 'fhe experimental samples differed only in that each contained A unique secondary set retarder. Two additional laboratory set-delayed samples were prepared using pumice and hydrated lime that were not dry blended in the trial. The two laboratory samples did not contain a secondary retarder;
however, one of the laboratory samples was intentionally contarninated with Class li Portland cement, The experimental and laboratory Samples additionally comprised water, weight additive (ground hausmannite ore), a primary retarder (phosphonic acid 'derivative), and a polycarboxylated ether dispersant lite compositional makeup of the eight samples is displayed in Table 1 below. While not indicated in Table I, it is believed that the six experimental samples were contaminated with Portland cement or other eementitious 15. contaminants at the bulk plant facility.
Table 1 Sample Composftions % By weight Laboratory Laboratory Experimental of Pumice 'Sample 1 (g) Sample 2 (g) Samples (g) Pumice 100 133.3 133.3 113.3 Lime 20 16.7 26.7 26.7 Water 1 65 80.0 80.0 80.0 Weighting Additive 2.0 2.7 Primary Retarder 0.06 galisk 1.7 1.7 1.7 Dispersant: 0.60 0.8 0.8 0.8 Class 11.
Portland Cement 5.0 6.67 00441 As discussed..in the preceding paragrilph, the six experimental SEITITICS each comprised A unique .secondary set .retarder. The secondary set retarder was present in an amount of 0,5% by weiAt of the pumice, ATI eight of the samples were placed in sealed containers and allowed to age 'for 2A hours before observation. The six retarders used. for the experimental Samples comprised zinc oxide, a copolymer of 2-acrylamido-2-methylpropane sulfonic acid and acrylic acid, a lignosultbnate retarder, tartaric acid, potassium pentaborate, and citric kid. The results of each OTTIbination are listed in Table 2 below.
Table 2 Sample Regal&
:Sample Secondary Retarder Observation Laboratory Sample I None Still floWable =
Laboratory Sample 2 None Gelled overnight Experimental Sample 1 Zinc Oxide -Gelled overnight Experimental Sample 2 Copolymer Gelled OVerilight Experimental Sample 3 Liimosulfonate Still flowable Experimental Sample 4 Tartaric Acid Partially gelled overnight Experimental Sample 5 Potassium Pentaborate Still flowable Experimental Sample:, 6 Citric Acid Cielled immediately [0045] The results indicate that the set-delayed samples adversely reacted to the inclusion of 'Portland Class H cement. In particular, Laboratory Sample 2 that included the Portland Class /4 cement gelled while Laboratory Sample 1 without any added Portland cement was still flowable. As seen from the experimental -smnplesõ the addition of a secondary set retarder May be used to counteract the cetnentitious contaminants from the

10. bulk plant. By way of example, the experimental samples with the lignosulfbnate and the potassium pentaborate retarders did not gel overnight.
Example 2 [00461 Three liter-sized samples of set-delayed eetnent compositions were prepared using the same components and proportions as Example 1, however, the samples additionally cornpriSed A secondary liignosallonate retarder the saine retarder used in Experimental Sample 3 fi7om Example 1) and/or were intentionally contaminated with Class 14 Portland cement The compositional makeup of the three samples is displayed in Table 3 below, Sample Compositions ) By W eight of Pumice Sample (g) Sample 2 (g) Sample 3 (g) Pumice 1:00 1000.0 1000:0 1000,0 Lime 20 200.0 200.0 200.0 Water: 65 650,0 650.0 650.0 =
, Weighting Agent 2.0 20.0 20.0 20.0 Prirnary Retarder 0.06 galfsk 12.5 11.5 12.5 Dispersant 0.60 6.0 6:0 6.0 Class .FI l'ortland Cement 2.5 0,0 25.0 25.0 Secondary Retarder 0.50 5,0 5.0 0.0 [00471 The volumetric average viscosity was plotted at 100 rpm for each sample over a 21 day span. A Model 35A Fann ViScometer and a No, 2 spring with a Fun Yield Stress Adapter were used to measure the volumetric average viscosity in accordance with the procedure Set forth in API RP Practice 108-2, Recotint1entied Preletiee lin' raging frell Cements. The results of this test are shown in Table 4 below.
Table 4 Volume Average Viscosity of the $amples 51uffy Age ()ays) '0 1 5 12 16 1921 Sample Sample VAV
1417 1560 2015 2457 2743 949 1313 rpm Sample 3 1.749 not .measurable [00481 Liquimene 55811 dispersant was added to Sample 2 on day 19 in an amount of 0.1% by weight of the putnice. Example 2 indicates that the inclusion of a secondary retarder such as a lignosulfonate retarder may be used to counteract the effects of Portland cement in set-delayed cement compositions.
Example 3 [00491 The same set-delayed cement composition of Sample 2 in Example 2 was scaled tip from 3 liters to 15 gallons and also to 35 barrels, The volumetric average viscosity w each sample size. was plotted at 100 rpm over a 21 day span. The results of this test are 111.gs-A in Table 5 Wow.
Table 5 Viscosity Tests 1 titer 15 Gallon 35 hhl SlurryVAV Slurryrry Slurry (4..1 Age V x V N
:tii , ,,....õ. VAV @ Age Age 100 rprn 100 rpm = 10(> rpth (Days) (Days) (Days) ___________________________________________________________________ , 0 l 1417 0 559 0 9'75 , . 1 1560 = 1 897 . 1 , 1508 , 12 2457 5 13113 3 1566.5 16 2743 6 1154.5 4 1677 , 19 949 7 1202.5 , 5 1859 , 2860 7 1950 10 377 . 8 2210

11 988 9 1976 27 , 598 11 1898 .
32 1703 13 202$

16 1.456 17 1989 .

1989 , , 5 [00501 Example 3 thus indicates that the inclusion of .a secondary retarder such as a lignosulfonate retarder may be used to counteraet the effects of Portland cement in set-delayed cernent compositiOns on a larger scale.
1:00511 It should he understood .that the compositions and methods are described. in terms of "co.mprising," "containingõ" or "including" various components or steps, the 10 compositions and methods can also "consist essentially of' or "consist of' the various l 9 components and -steps. Nloreover, the indefinite articles "a" or "an," as used in the claims, are defined herein to mean One or more than one of the element that it introduces.
[00521 For the sake of brevity, only certain ranges are explicitly disclosed herein.
l-lowever, ranges from any lower limit may be conibined with any upper limit to recite a range not explicitly recited, as well as, names from any lower liMit May be combined with any other lower limit to recite a range not explicitly -recited, in the same way, ranges from any upper limit May be combined with any other upper Unlit to recite a. range not explicitly recited. Additionally, whenever a numerical range with a lower limit and an upper :limit- is disclosed, any number and any included range falling 'within the range are Specifically disclosed. In particular, every range of values (of the form, "from about a to about b," or, equivalently, "from approximately a to b," or, equivalently, "from approximately a-b") disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values even if not explicitly recited, Thos, every point or individual value may serve as its own lower or npper limit conibined With any other point or individual value or any other lower or upper limit, to recite:a range not explicitly recited.
[0053) Therefore, the embodiments are well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above,, are illtistrative only, and they :may be modified and practiced in different but equivalent manners appamin to those skilled in the art having the benefit of the teachings herein. Although individual embodiments are discussed, the invention covers all combinations of all those embodiments. Furthennore, no limitations are intended to the details of construction or design herein ShOWn, other than as described in the claims below.
AIso, 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 may be altered or modified and all such variations are anisidered within the scope. and Spirit of the present invention. If there is any conflict in the usages of a word or term in this specification and one or more patent(S) or other documents that may be incorporated herein by reference, the definitions that are consistent with this specifiCation should be adopted.

Claims (26)

What is claimed is:

1. A. method of cementing comprising;
providing a set-delayed cement composition comprising water, pumice, hydrated lime, a primary set retarder, and a secondary set retarder;
activating the set-delayed cement composition to produce an activated cement composition;
introducing the activated cement composition into a subterranean formation;
and allowing the activated cement composition to set in the subterranean formation.

2. A method according to claim 1 wherein the primary set retarder and the secondary set retarder are each selected from the group consisting of a phosphonic acid, a phosphonic acid derivative, a lignosulfonate, a salt, an organic acid, a carboxymethylated hydroxyethylated cellulose, a synthetic o- or ter-polymer comprising sulfonate and carboxylic acid groups, a borate compound, and any combination thereof.

3. A method according to claim 1 or 2 wherein the set-delayed cement composition further comprises a dispersant.

4. A method according to claim 3 wherein the dispersant comprises at least one dispersant selected from the group consisting of a sulfonated-formaldehyde-based dispersant, polycarboxylated ether dispersant, and any combination thereof.

5. A method according to any of claims 1 to 4 wherein the primary set retarder comprises a phosphonic acid derivative, wherein the secondary set retarder comprises a lignosulfonate retarder, and wherein the set-delayed cement composition further comprises a polycarboxylated ether dispersant.

6. A method according to any of Claims 1 to 5 wherein the primary set retarder and the secondary set retarder are individually present in the set-delayed cement composition in an amount in the range of about 0.01% to about 10% by weight of the pumice.

7. A method according to any of claims 1 to 6 wherein the set-delayed cement composition is contaminated through contact with a cementitious contaminant, wherein the cementitious contaminant is present in an amount of about 5% by weight of the pumice or less, and wherein the cementitious contaminant comprises at least one contaminant selected from the group consisting of a hydraulic cement, a pozzolanic material, slag, cement kiln dust, gypsum plasters, lime plasters, cement plasters, and any combination thereof.

8. A method according to claim 7 wherein the contaminant is unintentionally added to the set-delayed cement composition during blending, transport, or a combination thereof.

9. A method according to any of claims 1 to 8 wherein the activated cement composition is used in a primary-cementing method.

10. A method according to any of claims 1 to 9 wherein the activated cement composition is allowed to harden and form a cement sheath in a well-bore annulus between a conduit in the subterranean formation and a well-bore wall or between the conduit and a larger conduit in the subterranean formation.

11. A method. according to any of claims 1 to 10 wherein the set-delayed cement composition remains in a pumpable fluid state for a time period of at least about 7 days prior to the step of activating the set-delayed cement composition.

12. A method. according to any of claims 1 to 11 further comprising pumping the activated cement composition through a feed pipe and into a wellbore that is penetrating the subterranean formation.

13. A method of mitigating contamination in the manufacture of a set-delayed cement composition, the method comprising:
providing a dry-blend cement composition comprising pumice and hydrated lime; and preparing a set-delayed cement composition comprising water, the dry-blend cement composition, a primary set retarder, and a secondary set retarder.

14. A method according to claim 13 further comprising activating the set-delayed cement composition to produce an activated cement composition and introducing the activated cement composition into a subterranean formation.

15. A method according to claim 13 or 14 further comprising storing the set-delayed cement. composition for a period of about 7 days or longer.

16. A method according to any of claims 13 to 15 wherein the primary set retarder and the secondary set retarder are individually selected from the group consisting of a phosphonic acid, a phosphonic acid derivative, a lignosulfonate, a salt, an organic acid, a carboxymethylated hydroxyethylated cellulose, a synthetic co- or ter-polymer comprising sulfonate and carboxylic acid groups, a borate compound, and any combination thereof.

17. A method according to any of claims 13 to 16 wherein the set-delayed cement composition further comprises a dispersant.

18. A method according to any of claims 13 to 17 wherein the dispersant comprises, at least one dispersant selected from the group consisting of a sulfonated-formaldehyde-based dispersant, a polycarboxylated ether dispersant, and any combination thereof.

19. A. method according to any of claims 13 to 18 wherein the primary set retarder comprises a phosphonic acid derivative, wherein the secondary set retarder comprises a lignosulfonate retarder, and wherein the set-delayed cement composition further comprises a polycarboxylated ether dispersant.

20. A method according to any of claims 13 te 19 wherein the set-delayed cement composition is contaminated through contact with a cementitious contaminant, wherein the cementitious contaminant is present in an amount of about 5% by weight of the pumice or less, and wherein the cementitious contaminant comprises at least one contaminant selected from the group consisting of a hydraulic cement, a pozzolanic material, slag, cement kiln dust, gypsum piasters, lime plasters, cement plasters, and any combination thereof:

21. A method according to any of claims 13 to 20 wherein the contaminant is unintentionally -added to the set-delayed cement composition during blending, transport, or a combination thereof.

22. A Set-delayed cement composition coinprising:
water;
pumice;
hydrated lime;
a primary set retarder; and a secondary set retarder;
wherein the set-delayed cement composition further comprises a cetnentitious contaminant; and wherein the set-delayed cement composition will ntmain in a pumpable fluid state for a time period of at least about 1 day at room ternperature in quiescent storage,

23. A setkielayed cement composition according to claim 22 comprising one or more of the features defined in any one of claims 2 to 7.

24. A set-delayed cement system comprising:
a set-delayed cement composition comprisine water, pumice, hydrated lime, a printary set retarder, and a secondary set retarder; wherein the set-delayed cement composition additionally comprises a cementitious contaminant;
an activator for activating the set-delayed cement composition;

mixing equipment for mixing the set-delayed cement composition and the activator to form an activated cement composition; and pumping equipment for delivering the activated cement composition into a wellbore,

25. A system according to claim 24 wherein the set-delayed cement:
composition further comprises a dispersant.

26. A system according to claim 24 or 25 wherein the primary set retarder comprises a phosphonic acid derivative, wherein the secondary set retarder comprises a lignosulfonate retarder, and wherein the set-delayed cement composition further comprises a polycarboxylated ether dispersant.