OA17534A

OA17534A - Cement set activators for set-delayed cement compositions and associated methods.

Info

Publication number: OA17534A
Application number: OA1201500356
Authority: OA
Inventors: Thomas J. Pisklak; Kyriacos Agapiou; Pauline A. OTIENO; Ronnie G. Morgan; Peter J. BOUL; Lance E. Brothers
Original assignee: Halliburton Energy Services, Inc.
Priority date: 2013-03-31
Filing date: 2014-03-28
Publication date: 2017-02-10

Abstract

Disclosed herein are cement compositions and methods of using set-delayed cement compositions in subterranean formations. A method of cementing in a subterranean formation, may comprise providing a set-delayed cement composition comprising water, pumice, hydrated lime, and a set retarder, activating the set-delayed cement composition with a cement set activator, wherein the cement set activator comprises at least one activator selected from the group consisting of nanosilica, a polyphosphate, and combinations thereof, introducing the set-delayed cement composition into a subterranean formation, and allowing the set-delayed cement composition to set in the subterranean formation.

Description

CEMENT SET ACTIVATORS FOR SET-DELAYED CEMENT COMPOSITIONS AND ASSOCIATED METHODS

BACKGROUND

The présent invention relates to subterranean cementing operations and, more particularly, in certain embodiments, to set-delayed cernent compositions and methods of using setdelayed cernent compositions in subterranean formations.

Cernent compositions may be used in a variety of subterranean operations. For example, in subterranean well construction, a pipe string (e.g., casing, liners, expandable tubulars, etc.) may be run into a well bore and cemented in place. The process of cementing the pipe string in place is commonly referred to as “primary cementing.” In a typical primary cementing method, a cernent composition may be pumped into an annulus between the walls of the well bore and the exterior surface of the pipe string disposed therein. The cernent composition may set in the annular space, thereby forming an annular sheath of hardened, substantially imperméable cernent (i.e., a cernent sheath) that may support and position the pipe string in the well bore and may bond the exterior surface of the pipe string to the subterranean formation. Among other things, the cernent sheath surrounding the pipe string functions to prevent the migration of fluids in the annulus, as well as protecting the pipe string from corrosion. Cernent compositions also may be used in remédiai cementing methods, for example, to seal cracks or holes in pipe strings or cernent sheaths, to seal highly permeable formation zones or fractures, to place a cernent plug, and the like.

A broad variety of cernent compositions hâve been used in subterranean cementing operations. In some instances, set-delayed cernent compositions hâve been used. Setdelayed cernent compositions are characterized by remaining in a pumpable fluid state for an extended period of time (e.g., at least about 1 day to about 2 weeks or more). When desired for use, the set-delayed cernent compositions should be capable of being activated whereby reasonable compressive strengths are developed. For example, a cernent set activator may be added to a set-delayed cernent composition whereby the composition sets into a hardened mass. Among other things, the set-delayed cernent composition may be suitable for use in well bore applications, for example, where it is desired to préparé the cernent composition in advance. This may allow, for example, the cernent composition to be stored prior to its use. In addition, this may allow, for example, the cernent composition to be prepared at a convenient location and then transported to the job site. Accordingly, capital expenditures may be reduced due to a réduction in the need for on-site bulk storage and mixing equipment. This may be particularly useful for offshore cementing operations where space onboard the vessels may be limited.

While set-delayed cernent compositions hâve been developed heretofore, challenges exist with their successful use in subterranean cementing operations. For example, set-delayed cernent compositions prepared with Portland cernent may hâve undesired gélation issues which can limit their use and effectiveness in cementing operations. Other set-delayed compositions that hâve been developed, for example, those comprising hydrated lime and quartz, may be effective in some operations but may hâve limited use at lower températures as they may not develop sufficient compressive strength when used in subterranean formations having lower bottom hole static températures. In addition, it may be problematic to activate some set-delayed cernent compositions while maintaining acceptable thickening times and compressive strength development.

SUMMARY

An embodiment discloses a method of cementing in a subterranean formation, comprising: providing a set-delayed cernent composition comprising water, pumice, hydrated lime, and a set retarder; activating the set-delayed cernent composition with a cernent set activator, wherein the cernent set activator comprises at least one activator selected from the group consisting of nanosilica, a polyphosphate, and combinations thereof; introducing the set-delayed cernent composition into a subterranean formation; and allowing the setdelayed cernent composition to set in the subterranean formation.

Another embodiment discloses a method for activating a set-delayed cernent composition comprising: providing a set-delayed cernent composition comprising pumice, hydrated lime in an amount of about 10% to about 30% by weight of the pumice, a set retarder in an amount of about 1% to about 5% by weight of the pumice, and water in an amount of about 35% to about 70% by weight of the pumice; storing the set-delayed cernent composition for a period of at least about 1 day; activating the set-delayed cernent composition with a cernent set activator, wherein the cernent set activator comprises a polyphosphate and an additive selected from the group consisting of nanosilica and a monovalent sait; introducing the set-delayed cernent composition into an annulus between a conduit disposed in a well bore and a wall of the well bore or another conduit; and allowing the set-delayed cernent composition to set in the annulus.

Yet another embodiment discloses an activated set-delayed cernent composition comprising: water; pumice; hydrated lime; a set retarder; and a cernent set activator, wherein the cernent set activator comprises at least one activator selected from the group consisting of nanosilica, a polyphosphate, and combinations thereof.

Yet another embodiment discloses a cementing System comprising mixing equipment for mixing an activated set-delayed cernent composition, the activated set-delayed cernent composition comprising water, pumice, hydrated lime, a set retarder, and, a cernent set activator, wherein the cernent set activator comprises at least one activator selected from the group consisting of nanosilica, a polyphosphate, and combinations thereof. The cementing system may further comprise pumping equipment for delivering the set-delayed cernent composition into a well bore.

The features and advantages of the présent invention will be readily apparent to those skilled in the art. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The présent invention relates to subterranean cementing operations and, more particularly, in certain embodiments, to set-delayed cernent compositions and methods of using setdelayed cernent compositions in subterranean formations. In particular embodiments, the présent invention provides improved cernent set activators for activation of set-delayed cernent compositions. Embodiments of the cernent set activators may be used to activate a set-delayed cernent composition while achieving désirable thickening times and compressive strength development.

Embodiments of the set-delayed cernent compositions of the présent invention may generally comprise water, pumice, hydrated lime, and a set retarder. Optionally, the setdelayed cernent compositions may further comprise a dispersant. Advantageously, embodiments of the set-delayed cernent compositions may be capable of remaining in a pumpable fluid state for an extended period of time. For example, the set-delayed cernent compositions may remain in a pumpable fluid state for at least about 1 day or longer. Advantageously, the set-delayed cernent compositions may develop reasonable compressive strengths after activation at relatively low températures.

The water used in embodiments of the set-delayed cernent compositions of the présent invention 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 cernent compositions. For example, a set-delayed cernent composition may comprise fresh water or sait water. Sait water generally may include one or more dissolved salts therein and may be saturated or unsaturated as desired for a particular application. Seawater or brines may be suitable for use in embodiments of the présent invention. Further, the water may be présent in an amount sufficient to form a pumpable slurry. In certain embodiments, the water may be présent in the set-delayed cernent composition in an amount in the range of from about 33% to about 200% by weight of the pumice. In certain embodiments, the water may be présent in the set-delayed cernent compositions in an amount in the range of from about 35% to about 70% by weight of the pumice. One of ordinary skill in the art with the benefit of this disclosure will recognize the appropriate amount of water for a chosen application.

Embodiments of the set-delayed cernent compositions may comprise pumice. Generally, pumice is a volcanic rock that can exhibit cementitious properties, in that it may set and harden in the presence of hydrated lime and water. The pumice may also be ground, for example. Generally, the pumice may hâve any particle size distribution as desired for a particular application. In certain embodiments, the pumice may hâve a mean particle size in a range of from about 1 micron to about 200 microns. The mean particle size corresponds to d50 values as measured by particle size analyzers such as those manufactured by Malvern Instruments, Worcestershire, United Kingdom. In spécifie embodiments, the pumice may hâve a mean particle size in a range of from about 1 micron to about 200 micron, from about 5 microns to about 100 microns, or from about 10 micron to about 50 microns. In one particular embodiment, the pumice may hâve a mean particle size of less than about 15 microns. An example of a suitable pumice is available from Hess Pumice Products, Inc., Malad, Idaho, as DS-325 lightweight aggregate, having a particle size of less than about 15 microns. It should be appreciated that particle sizes too small may hâve mixability problems while particle sizes too large may not be effectively suspended in the compositions. One of ordinary skill in the art, with the benefit of this disclosure, should be able to select a particle size for the pumice suitable for use for a chosen application.

Embodiments of the set-delayed cernent compositions may comprise hydrated lime. As used herein, the term “hydrated lime” will be understood to mean calcium hydroxide. The hydrated lime may be included in embodiments of the set-delayed cernent compositions, for example, to form a hydraulic composition with the pumice. For example, the hydrated lime may be included in a pumice-to-hydrated-lime weight ratio of about 10:1 to about 1:1 or a ratio of about 3:1 to about 5:1. Where présent, the hydrated lime may be included in the setdelayed cernent compositions in an amount in the range of from about 10% to about 100% by weight of the pumice, for example. In some embodiments, the hydrated lime may be présent in an amount ranging between any of and/or including any of about 10%, about 20%, about 40%, about 60%, about 80%, or about 100% by weight of the pumice. In some embodiments, the cementitious components présent in the set-delayed cernent composition may consist essentially of the pumice and the hydrated lime. For example, the cementitious components may primarily comprise the pumice and the hydrated lime without any additional components (e.g., Portland cernent, fly ash, slag cernent) that hydraulically set in the presence of water. One of ordinary skill in the art, with the benefit of this disclosure, will recognize the appropriate amount of the hydrated lime to include for a chosen application.

Embodiments of the set-delayed cernent compositions may comprise a set retarder. A broad variety of set retarders may be suitable for use in the set-delayed cernent compositions useful in the présent invention. For example, the set retarder may comprise a phosphates, a phosphonic acid, phosphonic acid dérivatives, phosphonates, lignosulfonates, salts, organic acids, carboxymethylated hydroxyethylated celluloses, synthetic co- or ter-polymers comprising sulfonate and carboxylic acid groups, borate compounds, dérivatives thereof, or mixtures thereof. In certain embodiments, the set retarders used in the set-delayed cernent compositions useful in the présent invention are phosphonic acid dérivatives, such as methylene phosphonic acid dérivatives as described in U.S. Pat. No. 4,676,832, the disclosure of which is incorporated herein by reference. Examples of suitable set retarders include, among others, methylene phosphonates such as Micro Matrix® cernent retarder (MMCR) available from Halliburton Energy Services, Inc., of Duncan, Oklahoma, as), Dequest® 2006 additive, and Dequest® 2066 additive. Dequest® 2006 additive, and Dequest® 2066 additive are both available from Thermphos, North America / Italmatch Chemicals. Dequest® 2066 additive is a pH neutralized diethylenetriaminepentamethylenephosphonate. Dequest® 2006 additive is nitrilotrismethylenetriphosphonate. Dequest® 2066 additive may be the stronger of the two Dequest® additives in certain Systems. In some embodiments, methylene phosphonates and/or methylene phosphonic acid dérivatives may be used to retard the pumice-containing compositions disclosed herein for extended periods of time. One of the many advantages of the embodiments of the présent invention is that these stronger cernent retarders may be successfully used with the cernent set activators discussed later. Generally, the set retarder may be présent in the set-delayed cernent composition used in the présent invention in an amount sufficient to delay the setting for a desired time. In some embodiments, the set retarder may be présent in the set-delayed cernent compositions in an amount in the range of from about 0.01 % to about 10% by weight of the pumice. In spécifie embodiments, the set retarder may be présent in an amount ranging between any of and/or including any of about 0.01%, about 0.1%, about 1%, about 2%, about 4%, about 6%, about 8%, or about 10% by weight of the pumice. One of ordinary skill in the art, with the benefit of this disclosure, will recognize the appropriate amount of the set retarder to include for a chosen application.

As previously mentioned, embodiments of the set-delayed cernent compositions may optionally comprise a dispersant. Examples of suitable dispersants include, without limitation, sulfonated-formaldehyde-based dispersants and polycarboxylated ether dispersants. One example of a suitable sulfonated-formaldehyde-based dispersant that may be suitable is a sulfonated acetone formaldéhyde condensate, available from Halliburton Energy Services, Inc., as CFR™-3 dispersant. Examples of suitable polycarboxylated ether dispersants include Liquiment® 514L and 5581F dispersants (available from BASF Corporation, Houston, Texas) and Coatex dispersants (available from Coatex Inc.). While a variety of dispersants may be used in accordance with embodiments of the présent invention, polycarboxylated ether dispersants may be particularly suitable for use in some embodiments. Without being limited by theory, it is believed that polycarboxylated ether dispersants may synergistically interact with other components of the set-delayed cernent composition. For example, it is believed that the polycarboxylated ether dispersants may react with certain set retarders (e.g., phosphonic acid dérivatives) resulting in formation of a gel that suspends the pumice and hydrated lime in the composition for an extended period of time.

In some embodiments, the dispersant may be included in the set-delayed cernent compositions in an amount in the range of from about 0.01% to about 5% by weight of the pumice. In spécifie embodiments, the dispersant may be présent in an amount ranging between any of and/or including any of about 0.01%, about 0.1%, about 0.5%, about 1%, about 2%, about 3%, about 4%, or about 5% by weight of the pumice. One of ordinary skill in the art, with the benefit of this disclosure, will recognize the appropriate amount of the dispersant to include for a chosen application.

Other additives suitable for use in subterranean cementing operations also may be included in embodiments of the set-delayed cernent compositions. Examples of such additives include, but are not limited to, weighting agents, lightweight additives, gas-generating additives, mechanical-property-enhancing additives, lost-circulation materials, filtrationcontrol additives, fluid-loss-control additives, defoaming agents, foaming agents, thixotropic additives, and combinations thereof. In embodiments, one or more of these additives may be added to the set-delayed cernent composition after storing but prior to placement of the set-delayed cernent composition into a subterranean formation. A person having ordinary skill in the art, with the benefit of this disclosure, should readily be able to détermine the type and amount of additive useful for a particular application and desired resuit.

Those of ordinary skill in the art will appreciate that embodiments ofthe set-delayed cernent compositions of the présent invention generally should hâve a density suitable for a particular application. By way of example, the set-delayed cernent compositions may hâve a density in the range of from about 4 pounds per gallon (“Ib/gal”) to about 20 Ib/gal. In certain embodiments, the set-delayed cernent compositions may hâve a density in the range of from about 8 Ib/gal to about 17 Ib/gal. Embodiments of the set-delayed cernent compositions may be foamed or unfoamed or may comprise other means to reduce their densifies, such as hollow microspheres, low-density elastic beads, or other density-reducing additives known in the art. In embodiments, the density may be reduced after storing the composition, but prior to placement in a subterranean formation. Those of ordinary skill in the art, with the benefit of this disclosure, will recognize the appropriate density for a particular application.

As previously mentioned, the set-delayed cernent compositions may hâve a delayed set in that they remain in a pumpable fluid state for an extended period of time. For example, the set-delayed cernent compositions may remain in a pumpable fluid state for a period of time from about 1 day to about 7 days or more. In some embodiments, the set-delayed cernent compositions may remain in a pumpable 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 on a high température high-pressure consistometer at room température (e.g., about 80°F) in accordance with the procedure for determining cernent thickening times set forth in API RP Practice 10B-2, Recommended Practice for Testing Well Cements, First Edition, July 2005. As set forth in Example 4 below, an example composition was prepared that comprised pumice, 20% hydrated lime, 1.4% dispersant (Liquiment® 514L), 1.26% set retarder (Micro Matrix® cernent retarder), and 62% water (ail % by weight of pumice). After 45 days of storage at ambient conditions, the example composition was mixed with 6% calcium chloride by weight of the pumice. At 140°F, the example composition had a thickening time (time to 70 Bc) of 2 hours and 36 minutes and developed 50 psi compressive strength in 9 hours and 6 minutes as measured on an Ultrasonic Cernent Analyzer (“UCA”), available from Fann Instrument Company, Houston, TX, while maintained at 3000 psi. After 48 hours, the sample was crushed and had a compressive strength of 2,240 psi.

When desired for use, embodiments of the set-delayed cernent compositions may be activated (e.g., by combination with a cernent set activator) to thereby set into a hardened mass. The term “cernent set activator” or “activator”, as used herein, refers to an additive that activâtes a set-delayed or heavily retarded cernent composition and may also accelerate the setting of the set-delayed or heavily retarded cernent. By way of example, embodiments of the set-delayed cernent compositions may be activated to set to form a hardened mass in a time period in the range of from about 2 hours to about 12 hours. For example, embodiments of the set-delayed cernent compositions may set to form a hardened mass in a time period ranging between any of and/or including any of about 2 days, about 4 days, about 6 days, about 8 days, about 10 days, or about 12 days.

In some embodiments, the set-delayed cernent compositions may set to hâve a désirable compressive strength after activation. Compressive strength is generally the capacity of a material or structure to withstand axially directed pushing forces. The compressive strength may be measured at a specified time after the set-delayed cernent composition has been activated and the résultant composition is maintained under specified température and pressure conditions. Compressive strength can be measured by either a destructive method or non-destructive method. The destructive method physically tests the strength of treatment fluid samples at various points in time by crushing the samples in a compression-testing machine. The compressive strength is calculated from the failure load divided by the crosssectional area resisting the load and is reported in units of pound-force per square inch (psi). Non-destructive methods typically may employ an Ultrasonic Cernent Analyzer (“UCA”), available from Fann Instrument Company, Houston, TX. Compressive strengths may be determined in accordance with API RP 10B-2, Recommended Practice for Testing Well Cements, First Edition, July 2005.

By way of example, the set-delayed cernent composition, may develop a 24-hour compressive strength in the range of from about 50 psi to about 5000 psi, alternatively, from about 100 psi to about 4500 psi, or alternatively from about 500 psi to about 4000 psi. In some embodiments, the set-delayed cernent composition 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. In some embodiments, the compressive strength values may be determined using a UCA at température ranging from 100°F to 200°F while maintained at 3000 psi.

In some embodiments, the set-delayed cernent composition may hâve a désirable thickening time after activation. Thickening time typically refers to the time a fluid, such as a cernent composition, remains in a fluid state capable of being pumped. A number of different laboratory techniques may be used to measure thickening time to give an indication of the amount of time a treatment fluid will remain pumpable in a well. An example technique for determining whether a treatment fluid is in a pumpable fluid state may use a hightemperature high-pressure consistometer at specified pressure and température conditions, in accordance with the procedure for determining cernent thickening times set forth in the afore-mentioned API RP Practice 10B-2. The thickening time may be the time for the treatment fluid to reach 70 Bearden units of consistency (“Bc”) and may be reported in time to reach 70 Bc. In some embodiments, the set-delayed cernent compositions may hâve a thickening time of greater than about 1 hour, alternatively, greater than about 2 hours, alternatively greater than about 5 hours at 3,000 psi and températures in a range of from about 50°F to about 400°F, alternatively, in a range of from about 80°F to about 250°F, and alternatively at a température of about 140°F.

Embodiments of the présent invention may include addition of a cernent set activator to the set-delayed cernent compositions. Examples of suitable cernent set activators include, but are not limited to, calcium chloride, triethanolamine, sodium silicate, zinc formate, calcium acetate, sodium hydroxide, sodium sulfate, and combinations thereof. An additional example of a suitable cernent set activator includes nanosilica. Yet another example of a suitable cernent activator includes a polyphosphate. It has been found that the combination of the nanosilica and the polyphosphate may be used to activate embodiments of the set-delayed cernent compositions. Additionally, the combination of the polyphosphate and a monovalent sait has proven to be a particularly effective cernent set activator in accordance with embodiments of the présent invention. Advantageously, set-delayed cernent compositions activated with the nanosilica, a polyphosphate, the combination of a nanosilica and a polyphosphate, or the combination of a polyphosphate and a monovalent sait may hâve acceptable thickening times and/or compressive strength development. Moreover the activators or combinations of activators of the preceding sentence may exhibit better results, as compared to other activators such as calcium chloride, in compositions comprising heavily retarded cernent compositions such as compositions using methylene phosphonates and/or methylene phosphonic acid dérivatives as discussed above.

Embodiments of the présent invention may include a cernent set activator comprising nanosilica. As used herein, the term “nanosilica” refers to silica having a particle size of less than or equal to about 100 nanometers (“nm”). The size of the nanosilica may be measured using any suitable technique. It should be understood that the measured size of the nanosilica may vary based on measurement technique, sample préparation, and sample conditions such as température, concentration, etc. One technique for measuring particle size of the nanosilica is Transmission Electron Microscope (TEM) observation. An example of a suitable commercially available technique based on laser diffraction technique may use a Zetasizer Nano ZS supplied by Malvern Instruments, Worcerstershire, UK. In some embodiments, the nanosilica may comprise colloïdal nanosilica. The nanosilica may also be stabilized using any suitable technique. In some embodiments, the nanosilica may be stabilized with a métal oxide, such as lithium oxide, sodium oxide, potassium oxide, and/or a combination thereof. Additionally the nanosilica may be stabilized with an amine and/or a métal oxide as mentioned above. Embodiments of the nanosilicas hâve an additional advantage in that they hâve been known to fill in pore space in cements which can resuit in superior mechanical properties in the cernent after the cernent has set.

Embodiments of the présent invention may include a cernent set activator comprising a combination of a monovalent sait and a polyphosphate. The monovalent sait and the polyphosphate may be combined prior to addition to the set-delayed cernent composition or may be separately added to the set-delayed cernent composition. The monovalent sait used may be any sait that dissociâtes to form a monovalent cation, such as sodium and potassium salts. Spécifie examples of suitable monovalent salts include potassium sulfate, calcium chloride, and sodium sulfate. A variety of different polyphosphates may be used in combination with the monovalent sait for activation of the set-delayed cernent compositions, including polymeric metaphosphate salts, phosphate salts, and combinations thereof, for example. Spécifie examples of polymeric metaphosphate salts that may be used include sodium hexametaphosphate, sodium trimetaphosphate, sodium tetrametaphosphate, sodium pentametaphosphate, sodium heptametaphosphate, sodium octametaphosphate, and combinations thereof. A spécifie example of a suitable cernent set activator comprises a combination of sodium sulfate and sodium hexametaphosphate. Interestingly, sodium hexametaphosphate is also known in the art to be a strong retarder of Portland cements. Because of the unique chemistry of polyphosphates, polyphosphates may be used as a cernent set activator for embodiments of the set-delayed cernent compositions disclosed herein. The ratio of the monovalent sait to the polyphosphate may range, for example, from about 2:1 to about 1:25 or from about 1:1 to about 1:10. Embodiments of the cernent set activator may comprise the monovalent sait and the polyphosphate sait in a ratio (monovalent sait to polyphosphate) ranging between any of and/or including any of about 5:1,2:1, about 1:1, about 1:2, about 1:5, about 1:10, about 1:20, or about 1:25.

In some embodiments, the combination of the monovalent sait and the polyphosphate may be provided as a liquid additive that may be used for activation of a set-delayed cernent composition. The liquid additive may comprise water, the monovalent sait, the polyphosphate and a dispersant. Examples of suitable dispersants include, without limitation, sulfonated-formaldehyde-based dispersants and polycarboxylated ether dispersants. One example of a suitable sulfonated-formaldehyde-based dispersant is a sulfonated acetone formaldéhyde condensate, available from Halliburton Energy Services, Inc., as CFR™-3 dispersant. One example of a suitable polycarboxylated ether dispersant is Liquiment® 514L or 5581F dispersants, available from BASF Corporation, Houston, Texas. The dispersant may be included in the liquid additive in an amount from about 0.2% to 8% about by weight of the liquid additive. The water may be included in the liquid additive in an amount from about 90% to about 99.9% by weight of the liquid additive. The combination of the monovalent sait and the polyphosphate may range from about 0.1% to about 2.5% by weight of the liquid additive.

Without being limited by theory, a description of a mechanism for activation of a lime and pozzolan set-delayed cernent composition using a set-delayed cernent activator comprising a combination of sodium sulfate and sodium hexametaphosphate is provided. It is believed that the sodium sulfate produces sodium hydroxide upon reaction with the lime. This reaction causes a resulting rise in the pH of the slurry and consequently an increase in the rate of dissolution of silicon dioxide. Cernent hydration rate has a direct relationship with the proportion of free silicates and/or aluminosilicates. Sodium hexametaphosphate chelates and increases the dissolution rate of calcium hydroxide. The combination of sodium sulfate and sodium hexametaphosphate créâtes a synergy in various compositions of set-delayed cernent compositions that provides better results than the singular use of either cernent set activator.

The cernent set activator should be added to embodiments of the set-delayed cernent composition in an amount sufficient to activate the extended settable composition to set into a hardened mass. In certain embodiments, the cernent set activator may be added to the set-delayed cernent composition in an amount in the range of about 0.1% to about 20% by weight of the pumice. In spécifie embodiments, the cernent set activator may be présent in an amount ranging between any of and/or including any of about 0.1%, 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 recognize the appropriate amount of the cernent set activator to include for a chosen application.

As will be appreciated by those of ordinary skill in the art, embodiments of the set-delayed cernent compositions of the présent invention may be used in a variety of subterranean operations, including primary and remédiai cementing. In some embodiments, a set-delayed cernent composition may be provided that comprises water, pumice, hydrated lime, a set 10 retarder, and optionally a dispersant. The set-delayed cernent composition may be introduced into a subterranean formation and allowed to set therein. As used herein, introducing the set-delayed cernent composition into a subterranean formation includes introduction into any portion of the subterranean formation, including, without limitation, into a well bore drilled into the subterranean formation, into a near well bore région surrounding the well bore, or into both. Embodiments of the présent invention may further include activation of the set-delayed cernent composition. The activation of the set-delayed cernent composition may comprise, for example, addition of a cernent set activator to the setdelayed cernent composition. The cernent set activator may be added to the set-delayed cernent composition prior to introduction into the subterranean formation.

In some embodiments, a set-delayed cernent composition may be provided that comprises water, pumice, hydrated lime, a set retarder, and optionally a dispersant. The set-delayed cernent composition may be stored, for example, in a vessel or other suitable container. The set-delayed cernent composition may be permitted to remain in storage for a desired time period. For example, the set-delayed cernent composition may remain in storage for a time period of about 1 day or longer. For example, the set-delayed cernent composition may remain in storage for a time period of about 1 day, 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 some embodiments, the set-delayed cernent composition may remain in storage for a time period in a range of from about 1 day to about 7 days or longer. Thereafter, the set-delayed cernent composition may be activated, for example, by addition of a cernent set activator, introduced into a subterranean formation, and allowed to set therein.

In primary cementing embodiments, for example, embodiments of the set-delayed cernent composition may be activated and introduced into a space between a conduit (e.g., pipe strings, liners) located in the well bore and a wall of the well bore (or another conduit), the well bore penetrating the subterranean formation. The set-delayed cernent composition may be allowed to set to form an annular sheath of hardened cernent in the space between the conduit and the well bore wall (or the other conduit). Among other things, the set cernent composition may form a barrier, preventing the migration of fluids in the well bore. The set cernent composition also may, for example, support the conduit in the well bore.

In remédiai cementing embodiments, a set-delayed cernent composition may be used, for example, in squeeze-cementing operations or in the placement of cernent plugs. By way of example, the set-delayed composition may be activated and placed in a well bore to plug an opening, such as a void or crack, in the formation, in a gravel pack, in the conduit, in the cernent sheath, and/or a microannulus between the cernent sheath and the conduit.

The exemplary set-delayed cernent compositions disclosed herein may directly or indirectly affect one or more components or pièces of equipment associated with the préparation, 11 delivery, recapture, recycling, reuse, and/or disposai of the disclosed set-delayed cernent compositions. For example, the disclosed set-delayed cernent 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, and/or recondition the exemplary setdelayed cernent compositions. The disclosed set-delayed cernent compositions may also directly or indirectly affect any transport or delivery equipment used to convey the setdelayed cernent compositions to a well site or downhole such as, for example, any transport vessels, conduits, pipelines, trucks, tubulars, and/or pipes used to compositionally move the set-delayed cernent compositions from one location to another, any pumps, compressors, or motors (e.g., topside or downhole) used to drive the set-delayed cernent compositions into motion, any valves or related joints used to regulate the pressure or flow rate of the setdelayed cernent compositions, and any sensors (i.e., pressure and température), gauges, and/or combinations thereof, and the like. The disclosed set-delayed cernent compositions may also directly or indirectly affect the various downhole equipment and tools that may corne into contact with the set-delayed cernent compositions such as, but 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, cernent pumps, surface-mounted motors and/or pumps, centralizers, turbolizers, scratchers, floats (e.g., shoes, collars, valves, etc.), logging tools and related telemetry equipment, 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., electrohydraulic wet connect, dry connect, inductive coupler, etc.), control lines (e.g., electrical, fïber optic, hydraulic, etc.), surveillance lines, drill bits and reamers, sensors or distributed sensors, downhole heat exchangers, valves and corresponding actuation devices, tool seals, packers, cernent plugs, bridge plugs, and other wellbore isolation devices, or components, and the like.

To facilitate a better understanding of the présent invention, the following examples of certain aspects of some embodiments are given. In no way should the following examples be read to limit, or define, the entire scope of the invention.

EXAMPLE 1

The following sériés of tests was performed to evaluate the force résistance properties of comparative cernent compositions comprising pumice and hydrated lime. Three different comparative sample settable compositions, designated Samples 1-3, were prepared using pumice (DS-325 lightweight aggregate), hydrated lime, Liquiment® 514L dispersant, and water, as indicated in the table below. After préparation, the samples were placed in an UCA 12 and cured at 140°F and 3,000 psi for 24 hours. The cured cernent was then removed from the UCA and crushed to yield the compressive strength values provided in Table 1 below.

TABLE 1

Compressive Strength Tests

Sample		1	2	3
Density	Ib/gal	14.3	14.3	14.3
Pumice:Lime Wt Ratio		3:1	4:1	5:1
Pumice	g	400	400	500
Lime	g	134	103	100
Dispersant	g	12	4	13
Water	g	196	187	220
24-Hr Crush Strength	psi	2,240	1900	1960

Example 1 thus indicates that cernent compositions that comprise pumice and lime in a weight ratio ranging from 3:1 to 5:1 may develop compressive strengths suitable for particular applications.

EXAMPLE 2

A sample set-delayed cernent composition, designated Sample 4, having a density of 13.3 10 Ib/gal was prepared that comprised 500 grams of pumice (DS-325 lightweight aggregate),

100 grams of hydrated lime, 13 grams of Liquiment® 514L dispersant, 24 grams of Micro Matrix® cernent retarder, and 300 grams of water. The rheological properties of the sample were measured after storing at room température and pressure for periods of 1 day and 6 days. After préparation, the rheological properties of the sample were determined at room température (e.g., about 80°F) using a Model 35A Fann Viscometer and a No. 2 spring, in accordance with the procedure set forth in API RP Practice 10B-2, Recommended Practice for Testing Well Cements. The results of this test are set forth in the table below.

TABLE 2

Viscosity Tests

Age of Sample (days)	Fann Readings	Yield Point (lb/100ft²⁾	Plastic Viscosity (centipois e)
600	300	200	100	6	3
1	560	322	244	170	4 6	3 8	84	238
6	498	310	228	136	2 4	2 0	122	188

Example 2 thus indicates that set-delayed cernent compositions that comprise pumice, hydrated lime, a dispersant, a set retarder, and water can remain fluid after 6 days.

EXAMPLE 3

A sample set-delayed cernent composition, designated Sample 5, having a density of 13.4 Ib/gal was prepared that comprised 500 grams of pumice (DS-325 lightweight aggregate), 100 grams of hydrated lime, 7 grams of Liquiment® 514L dispersant, 6.3 grams of Micro

Matrix® cernent retarder, and 304 grams of water. The rheological properties of the sample 10 were measured after storing at room température and pressure for période of from 1 day to days. The rheological properties were measured at room température (e.g., about 80°F) using a Model 35A Fann Viscometer and a No. 2 spring, in accordance with the procedure set forth in API RP Practice 10B-2, Recommended Practice for Testing Well Cements. The results of this test are set forth in the table below.

Table 3

Viscosity Tests

Age of Sample (Days)	Fann Readings
300	200	100	6	3
1	462	300	130	12	8
2	458	282	122	6	4
5	420	260	106	3	2

8	446	270	110	4	1
12	420	252	100	3	2
19	426	248	94	2	1

After 7 days, calcium chloride in the amount indicated in Table 4 below was added to a separately prepared sample of the same formulation as above. The sample was then placed in an UCA and the initial setting time, which is the time for the composition to reach a compressive strength of 50 psi while maintained at 3,000 psi was determined in accordance with API RP Practice 10B-2, Recommended Practice for Testing Well Cements. The initial setting time of the sample was also determined without addition of the calcium chloride. The samples with and without the calcium chloride were heated to a température of 140°F in 30 minutes and then maintained at that température throughout the test.

TABLE 4

Compressive Strength Tests

Age of Sample (Days)	Test Température (°F)	CaCI₂(% by wt of Pumice & Lime)	Initial Setting Time (hr:min)
7	140	0	no set after 4 days
7	140	10	5:11

Example 3 thus indicates that the set-delayed cernent compositions that comprise pumice, hydrated lime, a dispersant, a set retarder, and water will not set for a period of at least 19 days at ambient température and over 4 days at 140°F. Example 3 further indicates that sample set-delayed cernent compositions may be activated at a desired time by addition of a suitable activator.

EXAMPLE 4

A sample set-delayed cernent composition, designated Sample 6, having a density of 13.4 Ib/gal was prepared that comprised pumice (DS-325 lightweight aggregate), 20% hydrated lime, 1.4% Liquiment® 514L dispersant, 1.26% Micro Matrix® cernent retarder, and 62% of water (ail by weight of pumice, referred to in the table below as “% bwop”). After 45 days in storage at ambient conditions, the sample was mixed with 6% calcium chloride. At 140°F, the sample had a thickening time (time to 70 Bc) of 2 hours and 36 minutes and an initial setting time (time to 50 psi) of 9 hours and 6 minutes as measured using an UCA while maintained at 3000 psi. After 48 hours, the sample was crushed with a mechanical press which gave a compressive strength of 2,240 psi. The thickening time and initial setting time were both determined in accordance with API RP Practice 10B-2, Recommended Practice for Testing Well Cements. The results of this test are set forth in the table below.

TABLE 5

Age of Sampl e (Days)	Test Température (°F)	Calcium Chloride (% bwop)	Thickening Time to 70 Bc (hr:min)	Initial Setting Time (hr:min)	48 Hr Crush Strength (psi)
45	140	6	2:36	9:36	2,240

Example 4 thus indicates that the set-delayed cernent compositions that comprise pumice, hydrated lime, a dispersant, a set retarder, and water will not set for a period of at least 45 days at ambient température. Example 4 further indicates that sample set-delayed cernent compositions may be activated at a desired time by addition of a suitable activator.

EXAMPLE 5

This example was performed to evaluate the ability of sodium hydroxide and sodium sulfate to activate a set-delayed cernent composition that comprised pumice (DS-325 lightweight aggregate), hydrated lime, Liquiment® 514L dispersant, Micro Matrix® cernent retarder, and water. Four sample set-delayed cernent compositions, designated Samples 7-10, were prepared having concentrations of components as indicated in the table below. The samples were monitored via an UCA. After the samples were placed in the UCA, the pressure was increased to 3,000 psi, and the température was increased to 100°F over a 15-minute time period and held for the duration of the test. A portion of the slurry was retained and poured into a plastic cylinder to monitor the slurry behavior at room température and pressure. These procedures were repeated for ail samples.

Sample 7 was monitored for 72 hours over which time no strength was developed and the slurry was still pourable when removed from the UCA. The portion kept at room température and pressure was likewise still pourable after 72 hours.

Sample 8 was prepared using the same slurry design as Sample 7 except that sodium hydroxide was added as an activator. The sodium hydroxide was added in solid form directly to the mixing jar that contained the prepared sample. As can be seen from Table 6, Sample

8, reached 50 psi of compressive strength at 16 hours and 36 minutes. The strength continued to build, reaching a maximum of 1,300 psi, when the test was stopped at 72 hours. The cured cernent was removed from the UCA and crushed with a mechanical press which gave a compressive strength of 969 psi. The portion kept at room température and 5 pressure was crushed after 7 days resulting in a compressive strength of 143 psi.

Sample 9 was prepared using the same slurry design as Sample 8 except that sodium sulfate was added as an activator. The sodium sulfate was added in solid form directly to the mixing jar that contained the prepared slurry. Sample 9 reached 50 psi of compressive strength at 67 hours and 29 minutes. The strength continued to build, slowly, reaching a 10 maximum of 78 psi, when the test was stopped at 72 hours. The cured cernent was removed from the UCA and crushed with a mechanical press which gave a compressive strength of 68.9 psi. The portion kept at room température and pressure was still too soft to be crushed after 7 days.

Sample 10 was prepared using the same slurry design as Sample 8 except that equal 15 amounts of sodium hydroxide and sodium sulfate were added as an activator. The sodium hydroxide and sodium sulfate were added in solid form directly to the mixing jar that contained the prepared slurry. Sample 10 reached 50 psi of compressive strength at 22 hours and 40 minutes. The strength continued to build, reaching a maximum of 900 psi, when the test was stopped at 72 hours. The cured cernent was removed from the UCA and 20 crushed with a mechanical press which gave a compressive strength of 786 psi. The portion kept at room température and pressure was crushed after 7 days resulting in a compressive strength of 47.9 psi.

The results of these tests are set forth in the table below. The abbreviation “% bwop” refers to the percent of the component by weight of the pumice. The abbreviation “gal/sk” refers to 25 gallons of the component per 46-pound sack of the pumice. The abbreviation “RTP” refers to room température and pressure.

TABLE 6

Sample		7	8	9	10
Density	Ib/gal	13.38	13.38	13.38	13.38
Water	% bwop	61.97	63.60	64.62	64.11
Pumice	% bwop	100	100	100	100

Hydrated Lime	% bwop	20	20	20	20
Dispersant	gal/sk	0.07	0.07	0.07	0.07
Set Retarder	% bwop	0.06	0.06	0.06	0.06
Sodium Hydroxide	% bwop	—	4	—	2
Sodium Sulfate	% bwop	—	—	4	2
UCA
Temp/Press	F/Psi	100/3000	100/3000	100/3000	100/3000
Initial Set (50 psi)	hr:min	>78	16:36	67:29	22:40
Final Set (100 psi)	hr:min	—	21:08	—	32:44
24 Hr Comp. Strength	psi	—	138.74	-	59.60
48 Hr Comp. Strength	psi	—	711.35	—	331.48
72 Hr Comp. Strength	psi	—	1300	78	900
72 Hr Crush Strength (UCA)	psi	—	969	68.90	786
7-Day Crush Strength (RTP)	psi	—	143.20	0.00	47.90

Example 5 thus indicates that sodium hydroxide, sodium sulfate, and combinations of the two can activate the set-delayed cernent compositions, but to varying degrees. The testing showed that both sodium hydroxide and combinations of sodium hydroxide with sodium 5 sulfate activated the cernent compositions to an acceptable level. When compared to the non-activated composition, sodium sulfate activated the cernent compositions, but much less so than the sodium hydroxide or combination of sodium hydroxide and sodium sulfate.

EXAMPLE 6

This example was performed to evaluate the effect of sodium sulfate and sodium hexametaphospate on the setting time of a set-delayed cernent composition having a density of 13.5 Ib/gal that comprised pumice (DS-325 lightweight aggregate), hydrated lime, 5 Liquiment® 5581F dispersant, Micro Matrix® cernent retarder, and water. Micro Matrix® cernent retarder (MMCR) is a phosphonate cernent retarder. Four sample set-delayed cernent compositions, designated Samples 11-14, were prepared having concentrations of components as indicated in the table below, based on the percentage of the component by weight of the pumice (% bwop). The samples were cast in 2”x4” cylinders and cured for 24 10 hours in a water bath. One set of samples (samples 11, 12, and 13) were cured at 100 °F and another set of samples (samples 14, 15, and 16) were cured at 110 °F. Uniaxial compression tests we performed on ail samples after the 24 hour period.

Samples 11 and 14 were activated using sodium hexametaphosphate. Samples 12 and 15 were activated using a combination of sodium hexametaphosphate and sodium sulfate.

Samples 13 and 16 were activated with calcium chloride. The additive was added directly to the mixing jar that contained the prepared sample. As can be seen from Table 7, samples containing the combination of sodium sulfate and sodium hexametaphosphate achieved higher 24-hour compressive strengths than those samples set at the same température with only sodium sulfate. This increase in strength observed when sodium sulfate is added, 20 highlights the synergy between sodium sulfate and sodium hexametaphosphate in activating the setting of the extended life cernent slurry. Furthermore, when calcium chloride was used to activate the cernent there was no compressive strength observed either at 100 °F or 110 °F. The cernent did not set in either case. This highlights the activating power of sodium hexametaphosphate and the sodium hexametaphosphate and sodium sulfate combination 25 with regards to calcium chloride.

TABLE 7

Sample		11	12	13	14	15	16
Set Température	°F	100	100	100	110	110	110
Density	Ib/gal	13.1	13.2	13.2	13.1	13.2	13.2
Water	% bwop	70	70	70	70	70	70
Pumice	% bwop	100	100	100	100	100	100
Hydrated Lime	% bwop	20	20	20	20	20	20

Dispersant	% bwop	1.2	1.2	1.2	1.2	1.2	1.2
Set Retarder (MMCR)	% bwop	1.3	1.3	1.3	1.3	1.3	1.3
Sodium Hexametaphosphate	% bwop	2	2	—	2	2	—
Sodium Sulfate	% bwop	—	2	—	-	2	—
Calcium Chloride	% bwop	—	—	2	—	—	2
24 hr. Comp. Strength	psi	0	70	0	205	360	0

Example 6 thus indicates that sodium hexametaphosphate, sodium sulfate, and combinations of the two can activate the set-delayed cernent compositions, but to varying degrees. The testing showed that the combination of sodium sulfate and sodium hexametaphosphate activated the cernent compositions under conditions were calcium 5 chloride would not effectively activate the cernent to set.

EXAMPLE 7

This example was performed to further evaluate the ability of sodium sulfate and sodium hexametaphospate to activate a set-delayed cernent composition having a density of 13.5 Ib/gal that comprised pumice (DS-325 lightweight aggregate), hydrated lime, Liquiment® 10 5581F dispersant, Micro Matrix® cernent retarder, and water. Micro Matrix® cernent retarder (MMCR) is a phosphonate cernent retarder. Five sample set-delayed cernent compositions, designated Samples 17-21, were prepared having concentrations of components as indicated in the table below. The thickening times of the samples were both determined in accordance with API RP Practice 10B-2, Recommended Practice for Testing Well Cements. 15 The results of this test are set forth in the table below.

Samples 17, 19, and 20 were activated using a combination of sodium hexametaphosphate and sodium sulfate as a liquid additive. The liquid additive was added directly to the mixing jar that contained the prepared sample. The liquid additive comprised sodium hexmetaphosphate (10 g), sodium sulfate (10 g), Liquiment® 5581F dispersant (2.5 g), and 20 water (50 g). Samples 18 and 21 were activated with calcium chloride. As can be seen from

Table 8, Sample 17 reached 100 Bc after 5.5 hours whereas Sample 18 (with calcium chloride did not set after 100 hours). Samples 19 and 20 were set at 140 °F. These samples had compositions with 2.6 and 5.2% MMCR (% bwop), respectively. They were activated with the sodium sulfate and sodium hexametaphosphate and they gave thickening times of 25 1 hour and 5.5 hours, respectively. The thickening times of the activated samples was determined at 140°F in accordance with API RP Practice 10B-2, Recommended Practice for

Testing Well Cements. The results of this test are set forth in the table below.

TABLE 8

Sample		17	18	19	20
Density	Ib/gal	13.2	13.2	13.2	13.1
Température	°F	100	100	140	140
Water	% bwop	70	70	70	70
Pumice	% bwop	100	100	100	100
Hydrated Lime	% bwop	20	20	20	20
Dispersant	% bwop	1.2	1.2	1.2	1.2
Set Retarder	% bwop	1.3	1.3	2.6	5.2
Sodium Hexametaphosphate	% bwop	2	—	2	2
Sodium Sulfate	% bwop	2	—	2	2
Calcium Chloride	% bwop	—	2	—	—
Thickening Time to 100 Bc (hr:min)		5.5 hours	> 100 hours	1 hour	5.5 hours

Example 17, 19, and 20 thus indicate that sodium hexametaphosphate, sodium sulfate, and 5 combinations of the two can activate the set-delayed cernent compositions where activation with calcium chloride is inadéquate for a phosphonate set retarder such as MMCR was used.

EXAMPLE 8

This example was performed to evaluate the ability of nanosilica to activate set-delayed cernent compositions composition having a density of 13.5 Ib/gal that comprised pumice (DS-325 lightweight aggregate), 20% hydrated lime in an amount of, 1.2% Liquiment® 5581F dispersant, 1.3% Micro Matrix® cernent retarder, and 60% water (ail by weight of pumice).

Samples 21-26 were activated with nanosilica stabilized with lithium oxide. The nanosilica stabilized with lithium oxide was a colloïdal nanosilica that was approximately 20% active. Samples 21-26 were stabilized with nanosilica stabilized with lithium oxide (LSS-35 from Nissan Chemical), referred to in the table below as Nanosilica A. The nanosilica stabilized with lithium oxide was a colloïdal nanosilica that was approximately 20% active. The nanosilica was added directly to the mixing jar containing the prepared sample for each sample. After activation, the thickening times were measured at various températures after the addition of varying amounts of lithium stabilized activators. The thickening time was determined in accordance with API RP Practice 10B-2, Recommended Practice for Testing 10 Well Cements. The results of this test are set forth in the table below.

TABLE 9

Sample	Test Temp. °F	Activator	Thickening Time to 70 Bc (hr:min)	Thickening Time to 100 Bc (hr:min)
Type	% bwop
21	73	Nanosilica A	10	<00:30	<00:30
22	80	Nanosilica A	8	00:35	00:35
23	80	Nanosilica A	7	04:00	04:30
24	80	Nanosilica A	5.5	04:40	06:00
25	80	Nanosilica A	4	14:00	22:00
26	110	Nanosilica A	6.9	00:25	00:35

Example 8 thus indicates that decreasing the amount of the nanosilica stabilized with lithium oxide added to the slurry leads to increased thickening times.

EXAMPLE 9

This Example describes an additional combination of activators with a synergetic effect similar to the effect described in Samples 17, 19, and 20. Sample set-delayed cernent compositions, designated Samples 27-30, with densities as shown in Table 10, were prepared comprising pumice (DS-325 lightweight aggregate), 20% hydrated lime, 1.2 % Liquiment® 5581F dispersant, 2.6% Micro Matrix® cernent retarder, and 76% of water (ail by weight of pumice). Samples 21-24 ail demonstrate synergies between dissimilar activators. Sample 27 uses the activator combination of sodium sulfate and sodium hexametaphosphate (as in Samples 17, 19, and 20). At a set température of 140 °F, the 24hour compressive strength of the sample was determined to be 800 psi. LSS-75 is used in sample 28 as a synergetic component to sodium hexametaphosphate (replacing sodium sulfate’s rôle in sample 27). If LSS-75 was added in place of sodium sulfate, the compressive strength is even higher, at 950 psi. LSS-75 is referred to in the table below as Nanosilica B and is a nanosilica stabilized by lithium oxide sold by Nissan Chemical Ltd. The Sample 29 uses a different nanosilica additive supplied by Nissan Chemical. This additive is SNOWTEX-PS-M, referred to in the table below as Nanosilica C. The 24-hour compressive strength of the cernent cured in sample 24 cured at 140 °F is 962 psi. Sample 30 illustrâtes the use of nanosilica as a synergetic additive to sodium hexametaphosphate at lower température (110°F).

TABLE 10

Sample		27	28	29	30
Density	Ib/gal	12.89	12.71	12.85	12.71
Température	°F	140	140	140	110
Water	% bwop	76	76	76	76
Pumice	% bwop	100	100	100	100
Hydrated Lime	% bwop	20	20	20	20
Dispersant	% bwop	1.2	1.2	1.2	1.2
Set Retarder	% bwop	2.6	2.6	2.6	2.6
Sodium Hexametaphosphate	% bwop	1.9	2	1.8	1.8

Sodium Sulfate	% bwop	1.8		5.4	—
Nanosilica B	% bwop	—	5.3	—	5.4
Nanosilica C	% bwop	—	—	5.8	—
24-hour Compressive Strength	psi	800	948	962	208

EXAMPLE 10

This example describes the use of different phosphonate retarders and their effects on the 24-hour compressive strength of the activated cernent compositions. Dequest® 2006 and Dequest® 2066 additives are in the same phosphonate family of retarders as MMCR.

Samples 31 and 32 are described in Table 11. Sample 31 is the sample with Dequest® 2066 additive, whereas Sample 32 is that with Dequest® 2066 addtivie. They hâve 24-hour compressive strengths of 452 and 514. This example demonstrates the utility of the combination of sodium hexametaphosphate and sodium sulfate as an activator with other retarders of the phosphonate type.

TABLE 11

Sample	31	32
Density	Ib/gal	13.29	13.23
Température	°F	140	140
Water	% bwop	62	62
Pumice	% bwop	100	100
Hydrated Lime	% bwop	20	20
Dispersant	% bwop	7	7
Phosphonate Set Retarder: Dequest® 2066 Additive	% bwop	0.64	__
Phosphonate Set Retarder: Dequest® 2006	% bwop	—	1.3

Additive
Sodium Hexametaphosphate	% bwop	1.9	2
Sodium Sulfate	% bwop	1.8	—
24-hour Compressive Strength	psi	452	514

It should be understood that the compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of’ or “consist of’ the various components and steps. Moreover, 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.

For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any 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 limit 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. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

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

Claims

What is claimed is:

1. A method of cementing in a subterranean formation, comprising:

providing a set-delayed cernent composition comprising water, pumice, hydrated lime, and a set retarder;

activating the set-delayed cernent composition with a cernent set activator, wherein the cernent set activator comprises at least one activator selected from the group consisting of nanosilica, a polyphosphate, and combinations thereof;

introducing the set-delayed cernent composition into a subterranean formation; and allowing the set-delayed cernent composition to set in the subterranean formation.
2. The method of claim 1 wherein the cernent set activator is added to the setdelayed cernent composition in an amount of about 0.1% to about 20% by weight of the setdelayed cernent composition.
3. The method of claim 1 wherein the cernent set activator comprises the combination of a monovalent sait and the polyphosphate.
4. The method of claim 3 wherein the polyphosphate comprises sodium hexametaphosphate.
5. The method of claim 3 wherein the monovalent sait comprises sodium sulfate.
6. The method of claim 3 wherein the ratio of the monovalent sait to the polyphosphate is from about 2:1 to about 1:25.
7. The method of claim 1 wherein the set retarder comprises at least one retarder selected from the group consisting of a phosphate, a phosphonate, a phosphonic acid, a phosphonic acid dérivative, a lignosulfonate, a sait, an organic acid, a carboxymethylated hydroxyethylated cellulose, a synthetic co- or ter-polymer comprising sulfonate and carboxylic acid groups, a borate compound, and any mixture thereof.
8. The method of claim 1 wherein the set-delayed cernent composition further comprises a dispersant.
9. The method of claim 1 wherein the cernent set activator comprises nanosilica and wherein the nanosilica has been stabilized by at least one nanosilica stabilizer selected from the group consisting of: sodium oxide, potassium oxide, lithium oxide, an amine, and any combination thereof.
10. The method of claim 1 wherein the set-delayed cernent composition remains in a pumpable fluid state for a time period of at least about 7 days prior to the activating.
11. The method of claim 1 wherein the set-delayed cernent composition is introduced into a well bore penetrating the subterranean formation, the well bore having a bottom-hole static température of less than about 200°F.
12. The method of claim 1 wherein the set-delayed cernent composition is introduced into an annulus between a conduit disposed in a well bore and a wall of the well bore or another conduit.
13. The method of claim 1 wherein the set retarder comprises at least one retarder selected from the group consisting of a methylene phosphonic acid dérivative and a methylene phosphonate, and wherein the set-delayed cernent composition further comprises a polycarboxylated ether dispersant.
14. A method for activating a set-delayed cernent composition comprising:

providing a set-delayed cernent composition comprising pumice, hydrated lime in an amount of about 10% to about 30% by weight of the pumice, a set retarder in an amount of about 1% to about 5% by weight of the pumice, and water in an amount of about 35% to about 70% by weight of the pumice;

storing the set-delayed cernent composition for a period of at least about 1 day; activating the set-delayed cernent composition with a cernent set activator, wherein the cernent set activator comprises a polyphosphate and an additive selected from the group consisting of nanosilica and a monovalent sait;

introducing the set-delayed cernent composition into an annulus between a conduit disposed in a well bore and a wall of the well bore or another conduit; and allowing the set-delayed cernent composition to set in the annulus.
15. The method of claim 14, wherein the cernent set activator is added in an amount of about 0.1% to about 20% by weight of the set-delayed cernent composition.
16. The method of claim 14 wherein the cernent set activator comprises a combination of the polyphosphate and the monovalent sait, wherein the polyphosphate comprises sodium hexametaphosphate, and wherein the monovalent sait comprises sodium sulfate.
17. The method of claim 14 wherein the cernent set activator comprises a combination of the polyphosphate and the nanosilica, wherein the polyphosphate comprises sodium hexametaphosphate, and wherein nanosilica has been stabilized by at least one nanosilica stabilizer selected from the group consisting of: sodium oxide, potassium oxide, lithium oxide, an amine, and any combination thereof.
18. An activated set-delayed cernent composition comprising:

water;

pumice;

hydrated lime;

a set retarder; and a cernent set activator, wherein the cernent set activator comprises at least one activator selected from the group consisting of nanosilica, a polyphosphate, and combinations thereof.
19. The composition of claim 18 wherein the cernent set activator comprises a combination of a monovalent sait and the polyphosphate.
20. A cementing System comprising:

mixing equipment for mixing an activated set-delayed cernent

5 composition, the activated set-delayed cernent composition comprising water, pumice, hydrated lime, a set retarder; and, a cernent set activator, wherein the cernent set activator comprises at least one activator selected from the group consisting of nanosilica, a polyphosphate, and combinations thereof; and pumping equipment for delivering the set-delayed cernent composition into a well bore.