High specific surface area additives as a compressive strength enhancer for polysialate systems

Abstract

Polysialate precursor compositions are presented that are useful for cementing a subterranean well, among other uses. The precursor compositions use high specific surface area additives to boost the compressive strength of polymers made from the precursor compositions. Other precursor compositions presented herein use low calcium aluminosilicate sources to form polysialate systems that can be used in CO2 service without chemical degradation.

Description

HIGH SPECIFIC SURFACE AREA ADDITIVES AS A COMPRESSIVE STRENGTH ENHANCER FOR POLYSIALATE SYSTEMSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims priority benefit of United States Provisional Patent Application Serial No. 63 / 603890 filed November 29, 2023, which is entirely incorporated herein by reference.FIELD

[0002] This application for patent relates to polysialate compositions. More particularly the invention relates to the use of high specific surface area additives in polysialate compositions to enhance compressive strength of the final polymer.BACKGROUND

[0003] Geopolymers are a class of materials that are formed by chemical reaction of various aluminosilicates, oxides, and silicates to form an amorphous three- dimensional framework cement-like structure. Aluminum, silicon, and oxygen atoms combine to form a tetrahedral polysialate in which aluminum and silicon are chemically bonded to shared oxygen atoms. The polysialate is a polymer matrix that can host a number of other species, which may be chemically bonded to the matrix or may be included as separate domains around which the polymer matrix is formed. The term geopolymer was proposed and first used by J. Davidovits. His work is described in Davidovits, J: “Synthesis of New High-Temperature GeoPolymers for Reinforced Plastics / Composites.' Society of Plastics Engineers, IUPAC International Symposium on Macromolecules, Stockholm (1976). Other terms have been used to describe materials synthesized utilizing a similar chemistry, such as alkali-activated cement, geocement, alkali-bonded ceramic, inorganic polymer, hydroceramic. In the following description, the term polysialate will be used.

[0004] Polysialate systems have been investigated for use in several applications, including as concrete systems within the construction industry, as refractory materialsand as encapsulants for hazardous and radioactive waste streams. Such systems are also recognized as being rapid setting and hardening materials. They exhibit superior hardness and chemical stability. The preparation of polysialate systems generally involves mixing a blend of reactive solid materials and activating the polymerization reaction by adding an alkaline solution. Typically, the slurry mixture is then applied and allowed to harden in place. In construction, faster hardening is usually valued.

[0005] In the oil and gas industry, cement-like materials are used to line wells to provide isolation and structural support within the well. Use of cement-like materials in hydrocarbon wells presents unique challenges. The slurry mixture precursor is typically pumped over long distances to the location where the mixture is to set, so the mixture must be pumpable without undue burden on equipment. Additionally, ambient conditions encountered in a typical hydrocarbon well are much more extreme than those encountered in a typical construction application. Further, the large vertical extent of hydrocarbon well applications presents challenges of density, temperature, and pressure not faced in the construction industry. Additionally, materials encountered in subterranean settings, such as presence of high salt content in some formations, presents challenges in application of cement-like materials. Other applications, like plugs, squeeze, and injector wells for water or carbon dioxide, also require a cementitious precursor to be pumped to an application site, so polysialate compositions find broad use where pumping is required.

[0006] Cementitious materials need to have certain compressive strength to meet requirements of various applications. Compressive strength develops in a cementitious polymer as the polymerization reaction proceeds. The final compressive strength is influenced by composition of the precursor mixture, such as alkalinity, concentration of polymerizable species, and reaction conditions. Some uses of polysialate systems are trending toward using lower density precursor mixtures (having lower concentration of solids) with less caustic ingredients. For example, in some cases sodium carbonate is becoming favored as an alkalinity source, rather than sodium hydroxide, which is a generally more hazardous and challenging substance. For example, using sodium hydroxide as an alkalinity sourcefor a polysialation reaction releases large amounts of heat that must be dissipated as the polymer hardens. Use of sodium carbonate as an alkalinity source, however, can cause delayed development of compressive strength, and can ultimately result in lower eventual compressive strength, especially in lower density precursors. Additionally, water extended precursor mixtures (also sometimes referred to as “lightweight slurries”), having high water-to-solids ratio, have lower equivalent circulating densities and are typically deployed to formations having low fracture gradient to avoid circulation loss and / or formation damage. The higher water content, however, can lead to lower reactant concentration, longer curing times, and lower ultimate compressive strength. Further, in many cases, non-reactive materials are used to boost slurry density of the polymerization precursor mixture and / or hardness / compressive strength of the resulting polymer. These non-reactive materials take up solid volume within the reaction mixture, reducing the penetration of polymer within the solid matrix, and beyond a certain point can weaken the resulting polysialate system. Compositions and methods are needed that can boost compressive strength of polysialate systems, especially for lightweight densities and water extended precursors.SUMMARY

[0007] Embodiments described herein provide methods, comprising mixing water with a solid aluminosilicate source, an alkalinity source, and an additive having specific surface area above about 10 m2 / g to form a polymerization precursor mixture; placing the polymerization precursor mixture at a target location in a subterranean well; and hardening the polymerization precursor at the target location.

[0008] Other embodiments described herein provide a method, comprising mixing water with a solid aluminosilicate source having 0-10% by weight calcium oxide and an alkalinity source, wherein the alkalinity source contains no more than about 5.2 mol / L sodium hydroxide and no less than about 4.7 mol / L sodium silicate, to form a polymerization precursor having a solids volume fraction of at least about 30% and a slurry density of at least about 14 pounds per gallon; pumping the polymerizationprecursor to a target location in a subterranean well; and hardening the polymerization precursor at the target location

[0009] Other embodiments described herein provide a dry precursor composition for a polysialate system, comprising an aluminosilicate source; a non-hydroxide activator; and a high specific surface area additive having specific surface area greater than 10 m2 / g.

[0010] Other embodiments described herein provide a pumpable polymerization precursor having a slurry density of at least about 14 pounds per gallon, the polymerization precursor comprising an aluminosilicate source having less than 10% calcium oxide by weight and an alkalinity source having no more than about 5.2 mol / L sodium hydroxide and no less than about 4.7 mol / L sodium silicate..BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figs. 1 -6 are graphs showing compression strength of various polysialates systems according to embodiments described herein.

[0012] Fig. 7 is a graph showing compression strength of comparative polysialate systems.DETAILED DESCRIPTION

[0013] In the following description, numerous details are set forth to provide an understanding of the present disclosure. However, it may be understood by those skilled in the art that the methods of the present disclosure may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

[0014] At the outset, it should be noted that in the development of any such actual embodiment, numerous implementation — specific decisions are made to achieve the developer's specific goals, such as compliance with system related and business related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. In addition, the compositionused / disclosed herein can also comprise some components other than those cited. In the summary of the disclosure and this detailed description, each numerical value should be read once as modified by the term "about" (unless already expressly so modified), and then read again as not so modified unless otherwise indicated in context. The term “about” should be understood as any amount or range within 10% of the recited amount or range (for example, a range from about 1 to about 10 encompasses a range from 0.9 to 11 ). Also, in the summary and this detailed description, it should be understood that a concentration range listed or described as being useful, suitable, or the like, is intended that any concentration within the range, including the end points, is to be considered as having been stated. For example, “a range of from 1 to 10” is to be read as indicating each possible number along the continuum between about 1 and about 10. Furthermore, one or more of the data points in the present examples may be combined together, or may be combined with one of the data points in the specification to create a range, and thus include each possible value or number within this range. Thus, even if specific data points within the range, or even no data points within the range, are explicitly identified or refer to a few specific data points, it is to be understood that inventors appreciate and understand that any data points within the range are to be considered to have been specified, and that inventors possessed knowledge of the entire range and the points within the range.

[0015] Regarding chemical formulas, it should be noted that measurements may not conform precisely to the chemical formulas described herein due to various sources of error that can affect real-world testing. The chemical formulas described herein should therefore be understood as expressing the nominal chemical makeup of compounds, where real-world testing may show close, but not exact, conformity to the formulas.

[0016] As used herein, “embodiments” refers to non-limiting examples disclosed herein, whether claimed or not, which may be employed or present alone or in any combination or permutation with one or more other embodiments. Each embodiment disclosed herein should be regarded both as an added feature to be used with one or more other embodiments, as well as an alternative to be used separately or in lieuof one or more other embodiments. It should be understood that no limitation of the scope of the claimed subject matter is thereby intended, any alterations and further modifications in the illustrated embodiments, and any further applications of the principles of the application as illustrated therein as would normally occur to one skilled in the art to which the disclosure relates are contemplated herein.

[0017] Geopolymer materials, and other alkali activated polysialate systems, are formed by disposing an aluminosilicate source and an alkalinity source, which serves as an activator for the polysialation reaction, in a water mixture having high pH. Examples of aluminosilicate sources that can be used include (but are not limited to) ASTM Class C fly ash, ASTM Class F fly ash, fly ash not classified by ASTM, volcanic ash, volcanic glass, slag, ferrous slag, ferroalloy slag, non ferrous slag, such as copper slag, nickel slag, tin slag, zinc slag, and the like, blast furnace slag, basic oxygen furnace slag, electric arc furnace slag, and ground slags, such as ground blast furnace slag, ground granulated blast furnace slag (GGBS), diatomaceous earths, pumice, and calcined clays, which may be partially or fully calcined clays, aluminum-containing silica fume, natural aluminosilicate, feldspars, which may be dehydrated, andalusite, halloysite, alumina and silica sols, synthetic aluminosilicate glass powder, zeolite, scoria, allophone, bentonite, pumice, red mud, which may be calcined. Other examples of aluminosilicates with similar activity are ashes produced by combustion of some forest or agricultural industry by-products commonly known as biomass ash, or more specifically biomass fly ash, from various sources such as witchgrass ash, walnut shell ash, rice husk ash, and the like. These materials contain a significant proportion of an amorphous aluminosilicate phase, which polymerizes in strong alkaline solutions. The more common aluminosilicates are fly ash and blast furnace slag. Mixtures of two or more aluminosilicate sources may also be used if desired. In addition, alumina and silica may be added separately, for example as a blend of bauxite and silica fume. Other amorphous silica sources can also be used, which may include soda-lime glass dust, borosilicate glass dust, microsilica, fumed silica, precipitated silica, nanosilica, rice husk ash, or a combination thereof. It should be noted that some of the aluminosilicate sources mentioned above, such as GGBS and ASTM Class C fly ash, also contain calcium oxide, so these materials can also be considered alkalinity sources.

[0018] Suitable aluminosilicate sources for purposes here can have widely varying amounts of calcium oxide. In some cases, such aluminosilicate sources have at least 2%, at least 7%, at least 12%, at least 18%, or at least 25% by weight calcium oxide. These aluminosilicate sources become reactive when placed in strongly alkaline environments, typically at pH greater than 10. The aluminosilicate sources described above react under such conditions to form geopolymers and other polysialate materials derived from alkali activated materials. Binder components such as Portland cement, kaolin, bauxite, aluminum oxide, and aluminum hydroxide can also be included. Calcium oxide, however, is not needed in an aluminosilicate source to achieve the increased compressive strength described herein. High specific surface area metakaolin, for example, having a low amount of calcium oxide, or zero calcium oxide, can be used for embodiments herein.

[0019] The alkalinity source may be an alkali metal hydroxide, an alkaline-earth metal hydroxide, or combinations thereof. Alkali metal hydroxides may be sodium or potassium hydroxide. Alkaline-earth metal hydroxides may include calcium or barium hydroxide. The metal hydroxide may be in the form of a solid or an aqueous mixture Also, the alkalinity source in another embodiment can be encapsulated. The alkalinity source, when in solid and / or liquid state, can be trapped in a capsule that will break when subjected to, for example, mechanical stress on the capsule, or coating degradation owing to temperature, chemical exposure or radiation exposure. Also, the alkalinity source, when in solid and / or liquid state, can be trapped in a capsule that will naturally degrade if made from a biodegradable or self-destructive material. Furthermore, the alkalinity source, when in liquid state, may be adsorbed into a porous material and may be released after a certain time or due to a predefined event. The alkalinity source may be present in the composition at a concentration between about 1 M to 10M or between 3M and 6M.

[0020] The alkalinity source can be formed in-situ by adding a non-hydroxide material and a hydroxide to a polymerization precursor mixture to generate an alkalinity source by reaction. The non-hydroxide material is an ionic material that can react with a hydroxide to yield alkali material that can be an alkalinity source. The hydroxide can be an alkaline earth hydroxide, such as calcium hydroxide, while thenon-hydroxide material can be an alkali metal salt, such as sodium carbonate or sodium silicate.

[0021] Formation of a polysialate system may also involve a metal silicate. The metal silicate may be an alkali metal silicate such as sodium silicate, sodium metasilicate or potassium silicate. Silicates of Li, Na, K, Rb, and Cs or their combination can be used. The metal silicate, such as sodium metasilicate, may be present at a concentration between 0.01 kg / L and 0.2 kg / L, or between 0.05 kg / L and 0.1 kg / L. The SiO2 / Na2O molar ratio may be less than or equal to 3.2. The Sit / foO molar ratio may be less than or equal to or less than 3.2. The metal silicate may be present in the composition at a concentration between about 0.1 M and 5M, or between 0.5M and 2M. The metal silicates may be dry blended with the aluminosilicate source. Also, the metal silicate in another embodiment may be encapsulated. In some cases, a metal silicate can function as an alkalinity source, or to supply alkalinity by reaction. As noted above, an alkali metal silicate can react with a hydroxide to form alkaline species in-situ.

[0022] Materials having high specific surface area can be added to polysialate precursor mixtures to promote polymerization and development of compressive strength, especially in low density precursor mixtures, such as precursor mixtures having slurry density no more than about 19 ppg, for example up to 18.5 ppg, for example less than about 16 ppg or less than about 15 ppg or less than about 12 ppg, and / or mixtures using less active alkaline materials as alkalinity sources. The improvement of compressive strength in polysialate systems is, in many cases, pronounced in systems made from precursor mixtures having low slurry densities. Reactive materials having high specific surface area can also be especially useful in polymer formulations that include a high volume fraction of non-reactive solids. Use of reactive high specific surface area additives can promote formation and strengthening of the polymer matrix between the non-reactive particles.

[0023] The high specific surface area additives described herein can be polymerizers, polymerizing in a polysialation reaction, or non-polymerizers, not polymerizing in such reaction. The non-polymerizers are generally used in combination with polymerizers. Such high-surface area additives can promotepolymerization of aluminum-silicon-oxygen reactants so that less severe alkaline materials and / or lower solids content can be used in polymerization precursor compositions. These high specific surface area additives also generally help with boosting compressive strength in the resulting polysialate system, especially early in curing, where polymerization precursors having low solid volume fraction and low slurry density are used to promote pumpability and target a certain equivalent circulating density. These high specific surface area additives also generally help with boosting compressive strength in polysialate systems that feature high volume fraction of non-reactive solids, strengthening the comparatively sparse polysialate matrix to avoid failures. Pumpable polymerization precursor mixtures generally have viscosity less than about 300 cP at ambient conditions, and inclusion of the high specific surface area additives described herein promotes early gelation in low solid volume fraction and low slurry density polymerization precursors.

[0024] Pumpable poilymerization precursor mixtures are generally most useful where the precursor must be deployed to an inaccessible location before setting begins. The most common application for such precursors is in the oil and gas industry, where the precursor must be pumped into a well to create a cement sheath within the well. Use of the high specific surface area additives described herein enhances development of compressive strength, both ultimate compressive strength and early compressive strength, of polysialate systems used for well cementing. Fast development of early compressive strength is useful in such applications to allow subsequent activities to proceed upon realization of a desired compressive strength in the developing polymer system.

[0025] Polymerizable high specific surface area additives that can boost compressive strength include silica fume, metakaolin, diatomaceous earth, and waste or recycled glass pozzolan powders. Polymerizable, high specific surface area additives that can boost compressive strength can include other silica or aluminum containing materials that polymerize in a polysialation reaction. Sieved aluminosilicate materials such as sieved type F or type C fly ash, sieved ground granulated blastfurnace slag, other sieved slags, or sieved volcanic ash can be used. Such materials can be obtained by wet or dry sieveing of alkali activatedaluminosilicate materials having D90 diameter less than 10 pm, for example less than 5 pm.

[0026] Non-polymerizing, high specific surface area additives that can boost compressive strength of a polysialate system, when combined with polymerizing high specific surface area additives, include glass bubbles, barite particles, hematite particles, and inert gas bubbles (such as in polymers made from foamed or partially foamed precursors). Polymerizable high specific surface area additives generally promote polymerization by providing high contact area between solids containing reactants and reaction solution containing alkalinity sources and water. High contact area with water accelerates dissolution of reactive species from the solids while high contact with activators directly promotes reactivity. It is believed that nonpolymerizing, high specific surface area additives can promote polymerization, in some cases, by creating a high-energy, high-mobility zone, with very high areal extent, near the phase boundary for large area of enhanced reactivity. Additionally, some non-polymerizing, high specific surface additives have considerable compression strength on their own. By occupying space within the polymer, space that might otherwise have gone unoccupied, it is believed that the strength of such additives can boost the compression strength of the polymer system. Mixtures of different high specific surface area materials, including mixtures of different polymerizable high specific surface area materials, mixtures of different non- polymerizable high specific surface area materials, and mixture of polymerizable and non-polymerizable high specific surface area materials can be used.

[0027] The high specific surface area additives herein generally lead to higher compressive strength polysialate systems made from precursors using low intensity activators such as sodium carbonate and hydrated lime. The enhancement of compressive strength is generally more pronounced in low density precursor mixtures, such as polymerization precursor mixtures having slurry density no more than about 18.5 pounds per gallon (ppg), for example having density less than about 16 (ppg or about 15 ppg.

[0028] The high specific surface area additives herein generally have higher surface area than the aluminosilicate source used in a particular precursorcomposition. Thus, an additive will have “high” surface area if the surface area of the additive is greater than a surface area of the aluminosilicate material used for a particular precursor mixture. These high specific surface area additives can be used with any of the aluminosilicate sources described herein to similar effect. High specific surface area additives are those solids whose specific surface area is larger than about 10 m2 / g, such as larger than about 20 m2 / g, for example larger than about 30 m2 / g, larger than about 50 m2 / g, larger than about 100 m2 / g, larger than about 125 m2 / g, larger than about 150 m2 / g, and potentially up to about 200 m2 / g. Solids used as high specific surface area additives in subterranean zonal isolation applications typically have specific surface area of 1 - 5 m2 / g. In some cases, the high specific surface area additive has a specific surface area that is at least 50% greater than a specific surface area of an aluminosilicate source, or all aluminosilicate sources, in the polymerization precursor mixture. The specific surface area of a solid material, as described herein, is the total area of the solid material that is exposed for contact with molecules of a fluid (gas or liquid) divided by the mass of the solid material. In the polysialation context, the specific surface area of a polymerization precursor ingredient is particularly relevant as the area for contact with molecules of the reactive liquid fraction of the precursor mixture.

[0029] Multiple methods to determine a specific surface area can be used, such as liquid chemical adsorption through Langmuir sorption, for example using Anton- Paar analyzers, gas adsorption using Brunauer-Emmett-Teller (BET) analyzers (using, for example, analytical methods that conform to ISO 9277-2022, entitled “Determination of the specific surface area of solids by gas adsorption - BET method”), gas permeability, gas porosity, particle size analysis using analyzers such as the Malvern MasterSizer 2000 or 3000 model, and / or Blaine fineness measurement. Any or all such methods can provide measurement of specific surface area of a solid, or data that can be used to determine specific surface area. Specific surface areas of polymerization precursor additives, obtained using such methods, that are in the ranges expressed above increase the compressive strength of a polysialate system. For many applications, determination of specific surface area using liquid chemical adsorption can be most directly applicable to polysialateprecursors since contact with a liquid reaction phase is what promotes polymerization in such mixtures.

[0030] In one method, specific surface area (“SSA”) can be measured by gravimetrically measuring mass of ethylene glycol monoethyl ether (EGME) onto a finely divided sample. This method (“the EGME method”), known in the arts of geotechnical and soil sciences for measuring specific surface area of soils, clays, and other finely divided materials is well-established and is considered reliable and robust. The EGME method is suitable for determining the SSA of materials that have significant internal structures, such as fly ashes, GGBS, metakaolin, fumed silica, rice husk ash, bentonite, Portland cement, and other polysialation raw materials.

[0031] In the EGME method, a dessicator is used to expose a sample to EGME. An oil-free vacuum pump is attached to the dessicator. The dessicator has an enclosure with a sample support and a lid. A source of EGME is placed in the bottom of the dessicator below the sample support.

[0032] The source of EGME is prepared by drying 200 g of anhydrous calcium chloride in a 200°C over for at least 16 hours in an evaporation dish. After drying, the dish containing the dry calcium chloride is removed from the oven and 20 mL of EGME is thoroughly mixed into the calcium chloride while still hot. The evaporation dish with the calcium chloride / EGME mixture is placed in the bottom of the dessicator, below the sample support, and the lid of the dessicator is attached to seal the dessicator. The dessicator remains closed unless test samples are being added or removed to minimize exposure to the environment.

[0033] To prepare a sample, the sample material is placed in a bottle equipped with an air-tight screw thread. The bottle is placed in an oven and the sample is dried at 105°C for at least 16 hours. The sample bottle is then removed from the oven, sealed, and allowed to cool. One gram of the dried sample is placed in a weighing dish, preferably aluminum, that is at least 73 mm in diameter. Mass of the weighting dish alone (mdish), and mass of the weighing dish with sample (minitiai) are measured. Mass of the sample is msampie = minitiai - mdish. Three grams of EGME is slowly added to the weighing dish while swirling to mix. No mixing object is introduced to themixture. The mixture is mixed until it uniformly covers the bottom of the weighing dish.

[0034] The weighing dish with the mixed sample is then placed on the sample support in the dessicator, and the dessicator is then sealed using the lid. A vacuum is slowly drawn within the dessicator to avoid disturbing the sample, to a pressure of 0.010 bar or lower and the dessicator is left to equilibrate. Time to achieve equilibrium depends on the sample being tested. For very high surface area materials, equilibration time could be many days. For materials with SSA less than about 15 m2 / g, equilibration time can be 18-24 hours. After equilibrium is reached, vacuum is slowly released and the mass of the weighing dish with sample is measured (mtinai). All mass measurements in this method are performed using an analytical grade laboratory balance having precision of at least 0.0001 g. Equilibrium can be assessed by testing multiple samples of the same material, where minimal change in rrifinai, for example difference in rrifinai between otherwise identical samples that is less than 0.0005 g, indicates the materials equilibrated successfully.

[0035] Mass of EGME adsorbed onto the sample is calculated as= mtinai - , initial. SSA is then computed using the following equation:

[0036] In general, the adjuvant effect of high specific surface area additives is exhibited only for additives having substantial amorphous morphology. It is found that the additives need at least moderate amorphous content, such as at least 50% amorphous content, for example at least 90% or 98% amorphous content, to provide a substantial improvement in compressive strength of a polysialate system. Reduction of amorphous content below about 50% rapidly reduces the improvement in compressive strength exhibited by the additive. Likewise, reduction of specific surface area below a threshold that depends on the amorphous content of the additive, also rapidly reduces the improvement in compressive strength exhibited by the additive.

[0037] Thickening time of the polymerization precursor mixture formed by adding water to the materials described herein can be influenced by adding retarders andaccelerators. Several retarders may delay the setting and hardening of polysialate systems. Retarders such as sodium pentaborate decahydrate, borax, sucrose, boric acid, lignosulphonates, sodium glucoheptonate, tartaric acid, citric acid, or phosphorus containing compounds such as phosphoric acid, salts thereof, or mixtures thereof can be added to the polymerization precursor particulate mixture in amounts of 0.01 to 5 part per hundred by weight of the total particulate precursor mixture. The amount of retardation of the polymerization reaction, and the setting of the polymerization precursor, depends on the type of raw materials used for the slurry and the type and relative quantity of retarder used. Adding too much retarder reagent to a polymerization precursor can cause the precursor to remain unhardened by interfering with the polymerization reaction so the polymer does not set. In other embodiments a retarder solution can be added to the carrier fluid or to the polymerization precursor, or both. By this means, the same precursor could be pumped into different sections of a well and setting time of the precursor in the different sections can be controlled through addition of a different amount of the retarder solution.

[0038] Accelerators can also be added to the polymerization precursor particulate mixture in amounts up to about 0.01 -10, such as 1 -5, parts per hundred weight of the total particulate precursor mixture. The amount of acceleration of the polymerization reaction, and the setting of the slurry, depends on the type of raw materials used for the polymerization precursor and the type and relative quantity of accelerating reagent used. Adding too much accelerator to a polymerization precursor can cause the precursor to thicken too quickly making it difficult to deploy the precursor to target locations downhole. It should be noted that the retarders and accelerants described herein can be included as particulate materials in the polymerization precursor composition, or such reagents can be added to water before the water is added to a precursor composition described herein.

[0039] Precursor mixtures for use in well lining applications typically have a slurry density range from 0.84 g / cm3(7 Ibm / gal) to 2.87 g / cm3(24 Ibm / gal), such as 1.32 g / cm3(11 Ibm / gal) to 2.4 g / cm3(20 Ibm / gal) or 1 .32 g / cm3(11 Ibm / gal) to 2.16 g / cm3(18 Ibm / gal), for example 1.36 g / cm3(11.3 Ibm / gal) to 1.92 g / cm3(16 Ibm / gal). Theslurry density can be influenced by quantity of water added and / or by adding density modifiers. Water typically makes up from about 20% by weight to about 60% by weight of a polysialate precursor mixture. The methods of boosting compressive strength described herein are especially useful for precursor mixtures having slurry density no more than about 18.5 Ibm / gal (ppg, 2.22 g / cm3), for example mixtures having slurry density less than about 16 ppg (1 .92 g / cm3) or less than about 15 ppg (1 .8 g / cm3) or less than about 12 ppg (1 .44 g / cm3). These methods can be especially useful for precursor mixtures having slurry density of about 14-16 ppg.

[0040] Density modifiers can include density increasing particles and density lowering particles. Low-density particles may be added to the precursor particulate mixture to achieve lower slurry densities for a given amount of water added, or heavy particles may be added to achieve higher slurry densities. The lightweight or low- density particles may have densities lower than 2 g / cm3, or lower than 1 .3 g / cm3. Examples include hollow glass or ceramic microspheres (cenospheres), plastic particles such as polypropylene beads, rubber particles, uintaite (sold as GILSONITE™), vitrified shale, petroleum coke or coal or combinations thereof. The lightweight particles may be present in the compositions at concentrations between about 0.06 kg / L and 0.6 kg / L (20 Ib / bbl and 200 Ib / bbl). The particle size range of the low-density particles may be between about 38 pm and 3350 pm (6 mesh and 400 mesh). The heavy particles typically may have densities exceeding 2 g / cm3, or more than 3 g / cm3. Examples include hematite, barite, ilmenite, silica (e.g. crystalline silica sand), crushed granite and also manganese tetroxide commercially available under the trade names of MicroMax™ and MicroMax FF™.

[0041] Other additives that can be used in polymerization precursors herein include anti-foam agents, defoamers, silica, fluid-loss control additives, viscosifiers, dispersants, expanding agents, anti-settling additives or combinations thereof. Selection of the type and amount of additive largely depends on the nature and composition of the set composition, and those of ordinary skill in the art will understand how to select a suitable type and amount of additive for compositions herein.

[0042] The fluid-loss control agent may comprise a latex. The latex may be an alkali-swellable latex. The latex may be present in the polymerization precursor compositions at a concentration between 0.02 L / L and 0.3 L / L or between 0.05 L / L and 0.15 L / L.

[0043] Viscosifiers may comprise diutan gum having a molecular weight higher than about 1 x 106. The diutan gum may be present in the polymerization precursor mixture at a concentration between 0.14 g / L and 1.4 g / L (0.05 Ibm / bbl and 0.5 Ibm / bbl). In some cases, viscosifiers are present in the dry alkali activated precursor at a concentration of 0.1-5% by weight of the total dry precursor. Other viscosifiers may comprise a polysaccharide material, which may be a biopolymer. Suitable polysaccharide biopolymers can include welan gum, a polyanionic cellulose (PAC), a carboxymethylcellulose (CMC), and combinations thereof. One or more polysaccharide materials, which may be biopolymers, may be present in the polymerization precursor mixture at a concentration between 0.14 g / L and 1.4 g / L (0.05 Ibm / bbl and 0.5 Ibm / bbl). The molecular weight of the polysaccharide material, which may be a biopolymer, may be between 100,000 and 1 ,000,000.

[0044] Carboxylic acids including gluconic acid and soluble salts thereof, glucoheptonic acid and soluble salts thereof, tartaric acid and soluble salts thereof, citric acid and soluble salts thereof, glycolic acid and soluble salts thereof, lactic acid and soluble salts thereof, formic acid and soluble salts thereof, acetic acid and soluble salts thereof, proprionic acid and soluble salts thereof, oxalic acid and soluble salts thereof, malonic acid and soluble salts thereof, succinic acid and soluble salts thereof, adipic acid and soluble salts thereof, malic acid and soluble salts thereof, nicotinic acid and soluble salts thereof, benzoic acid and soluble salts thereof, and ethylenediamine tetraacetic acid (EDTA) and soluble salts thereof may be included in the compositions described herein as retarders or dispersants or both. Phosphoric acids may be present for the same purpose. Salts of these acids may also be employed. These materials may be present in the polymerization precursor compositions at concentrations between 0.5 g / L and 10 g / L, or between 1 g / L and 5 g L.

[0045] Expanding agents may comprise calcium sulphate hemihydrate, metal oxides such as MgO or combinations thereof. The expanding agents may be present in the polymerization precursor compositions at concentrations between 0.01 kg / L and 0.2 kg / L of slurry, or between 0.05 and 0.1 kg / L.

[0046] The water added to form the polymerization precursor can be activator-free water or part of an activator solution. In some cases, additional activator may be included with the water to make an incremental activator solution, which used alone without any other activators would be non-activating, that is added to the precursor mixture to make the final polymerization precursor, and / or added to an intermediate mixture. For example, an alkali activated precursor mixture containing a solid activator may be mixed with a solution of an activator in water to form a polymerization precursor having a target total amount of activator. In such cases, the solution can be a non-activating solution of alkali metal hydroxide MOH, alkaline earth metal oxide or hydroxide such as Ca(OH)2, Sr(OH)2, Mg(OH)2, Ba(OH)2, an alkali metal salt selected from the group consisting of M2CO3, M2SO4, M3PO4, M2C2O4, M2xSiyC>2y+x where x is 1 , 2, or 3 and y is 1 or 2, MF, M2SiFe, MIO3, M2MOO4, where M is Li, Na, K, Rb, or Cs, or a combination thereof, that adds an incremental amount of activator to the activator present in the precursor particulate mixture prior to blending with the solution. Because the alkali activated precursor mixture contains solid activator, the added activator solution can contain an amount of activator that alone would be insufficient to set the polymerization precursor, and thus would be non-activating, but when combined with the components released by reaction of the solid activator with water, results in desired setting. In some embodiments, a first water volume, free of activator, can be added, and a second water volume comprising a non-activating water material that contains some activator can be added separately, in any order.Examples

[0047] A number of polysialate systems were made using precursor mixtures with various aluminosilicate sources, densities, and high specific surface area additives. Two polysialate systems were also made as comparative examples. The additives used had properties set forth below in Table 1.Table 1In some of the polymer systems, Alccofine 1203 was used as a high specific surface area additive.

[0048] Fig. 1 is a graph 100 showing compressive strength of polysialate systems made from precursor mixtures incorporating various high specific surface area additives. Compressive strength is plotted against the right vertical axis and specific surface area of the high specific surface area additives is plotted against the left vertical axis. Along the x-axis is a description of components of each precursor mixture. For each mixture, the component shown along the x-axis of the graph 100 was mixed with fly ash Type-C and water, with soda ash and lime as activators, to form a polymerization precursor composition. Each polymerization precursor composition had a slurry density of 13.2 ppg, and all used the same type and concentration of activator. At 102, a control specimen using only fly ash Type-C as the sole reactant, is shown. Additionally, for each component along the x-axis, a “shoulder” of the bar shows the specific surface area of the high specific surface area additives used in the precursor. The specific surface area of each additives is also shown in Table 1 , above. For example, at 104, a central bar 104a shows the compressive strength of the polymer system resulting from hardening the polymerization precursor mixture, and a shoulder 104b shows the specific surface area of the high specific surface area additive used in the precursor. The high specific surface area additive used at 104 is metakaolin. At 106, Alccofine 1203 is used as the high specific surface area additive. At 108, a first silica fume is used as the high specific surface area additive. At 110, a second silica fume is used as the high specific surface area additive. At 112, diatomaceous earth is used as the highspecific surface area additive. In each case using a high specific surface area additives, the amount of high specific surface area additives used was 5 wt% of the total polymerization precursor mixture. Each polymerization precursor mixture was cured for 72 hours at 170°F and atmospheric pressure.

[0049] The data shown in Fig. 1 demonstrate that, in each case, the high specific surface area additive boosted the compressive strength of the resulting polymer system. No particular correlation is shown between the specific surface area of the additive and the eventual compressive strength developed by the polymer system. Each additive, however, does result in an increase in the compressive strength.

[0050] Fig. 2 is a graph 200 that is organized in a way similar to the graph 100, with high specific surface area additives shown on the x-axis, compressive strength plotted against the right vertical axis, and specific surface area of the high specific surface area additives plotted against the left vertical axis. The aluminosilicate source, in this case, is a mixture of fly ash Type-C and recycled glass pozzolan material. In each case, the recycled glass pozzolan material is 15 wt% of the polymerization precursor mixture. As in the graph 100, at 202, the properties of a polymer system made from a control mixture using no high specific surface area additive is shown. At 204, 206, and 208, the properties of polymer systems made from mixtures using high specific surface area additives are shown. In each case, 5 wt% of the precursor mixture was high specific surface area additives. At 204, the high specific surface area additive is VCAS Ultra 200. At 206, the high specific surface area additive is VCAS 160. At 208, the high specific surface area additive is ACAS glass pozzolan.

[0051] The data of Fig. 2 show that the additive having higher specific surface area, namely the glass pozzolan, increased the compressive strength of the resulting polymer system. While the two additives having negligible surface area, VCAS Ultra 200 and VCAS 160, had little beneficial effect on resulting compressive strength, the glass pozzolan boosted compressive strength of the polymer system by about 38%.

[0052] Fig. 3 is a graph 300 showing compressive strength of polymer systems made from polymerization precursor mixtures incorporating Silica Fume-1 , set forth in Table 1 above, as the high specific surface area additive. Percent, by weight ofblend, of the additive is plotted along the horizontal axis, and compressive strength along the left vertical axis. The polymerization precursor mixtures used all had slurry densities of 15.2 ppg, GGBS as aluminosilicate source, and sodium silicate as activator. The stacked bars show curing for 8 hours and 24 hours. The compressive strength developed in each case is printed in the stacked bars.

[0053] At 302, the stacked bar shows compressive strength development of a polymerization precursor mixture having no high specific surface area additive as a control result. At 304, the stacked bar shows compressive strength development of the polymerization precursor mixture used for the polymer system of 302, along with 5%, by weight of blend, Silica Fume-1 added to the polymerization precursor mixture as a high specific surface area additive. At 304, the stacked bar shows a similar polymer system made from a precursor having 10%, by weight of blend, Silica Fume- 1. Each polymerization precursor mixture had a slurry density of 15.2 ppg and was cured at 111 °F and atmospheric pressure. Each stacked bar of the graph 300 has a first bar 306 that shows compressive strength after 8 hours of curing and a second bar 308 that shows compressive strength after 24 hours of curing.

[0054] The data of Fig. 3 show that, in each case, longer curing developed higher compressive strength. The data of Fig. 3 also show that including more of the high specific surface area additive, in this case Silica Fume-1 , in the polymerization precursor mixture resulted in higher compressive strength after 8 hours of curing and after 24 hours of curing, at least up to 10% by weight of blend in the precursor m ixture. However, the benefit of increasing the amount of high specific surface area additive from 5% to 10% was much less than the benefit of adding 5% additive to a precursor with no additive. The data of Fig. 3 thus show that use of a high specific surface area material in a polymerization precursor mixture can speed initial growth of compressive strength, as evidenced by the higher compressive strength exhibited by the mixtures containing Silica Fume-1 after only 8 hours of curing. Thus, as shown in Fig. 3, short-term growth in compressive strength, as well as final compressive strength, are both boosted by use of a high specific surface area additive in an alkali activatedprecursor mixture. Additionally, the data of Fig. 3 exhibit a trend of rapidly diminishing incremental effect of adding more high specific surface area additive,indicating that most of the effect is realized up to the first 5%, by weight of blend, of additive.

[0055] Fig. 4 is a graph 400 showing effect on compressive strength of a polymerization precursor mixture using GGBS as an aluminosilicate source and soda ash as activator, if Silica Fume-1 is added to the precursor. The graph 400 has two bars, a first bar 402 and a second bar 404. Each bar plots compressive strength of a polymer system along the y-axis. The first bar 402 plots the compressive strength of a polymer system made from a precursor mixture comprising GGBS and soda ash, with no high specific surface area additive. The second bar 404 plots the compressive strength of a polymer system made from the same precursor but including 5%, by weight of blend, Silica Fume-1 . Each polymerization precursor mixture had a slurry density of 15.2 ppg and was cured at 167°F and 1 ,500 psi pressure for 24 hours.

[0056] The data of Fig 4 show that use of a high specific surface area additive in a polymerization precursor mixture based on GGBS and soda ash, cured at high pressure, also results in a polymer system having improved compressive strength. In this case, the improvement observed was slightly above 28%.

[0057] Fig. 5 is a graph 500 showing data similar to that of Fig. 4, for polymer systems made from alkali activated polymerization precursors having lower slurry density and using sodium hydroxide and sodium silicate as activators. Rather than 15.2 ppg, which was the slurry density of the precursor mixtures used for Fig. 4, the precursor mixtures used for Fig. 5 had slurry density of 11.7 ppg. The only other difference in Fig. 5 is the use of less high specific surface area additive. As in Fig. 4, at 502 a first bar plots compressive strength of a GGBS polymer system made from a precursor having no high specific surface area additive and slurry density of 11 .2. At 504 a second bar plots compressive strength of the same precursor having 3%, by weight of blend, Silica Fume-1 as high specific surface area additive. In this case, despite having significantly less Silica Fume-1 than was used in Fig. 4, compressive strength improvement of the polymer system was nearly 83%.

[0058] The data in Fig. 5 thus show that, for lightweight (low density) polymerization precursor mixtures, the effect of adding a high specific surface areaadditive on compressive strength of the polymer system is directionally larger than for higher weight (density) precursor mixtures. The data in Fig. 5 also show that the effect can be observed using different aluminosilicate sources and different activators.

[0059] Fig. 6 is a graph 600 showing the effect of Silica Fume-1 as a high specific surface area additive in a different polymer system. Like the other graphs, the graph 600 plots compressive strength of various polymer systems on the left vertical axis. All the polymer systems of Fig. 6 were made from polymerization precursor mixtures using GGBS as an aluminosilicate source and a mixture of sodium hydroxide and sodium silicate as activator. All the polymerization precursor mixtures of Fig. 6 had slurry density of 11 .7 ppg. All the polymer systems of Fig. 6 resulted from curing at 110°F and atmospheric pressure.

[0060] There are two groups of bars in the graph 600, a first group of bars 610 plots compressive strength of polymer systems made from a precursor mixture that was cured for 24 hours, and a second group of bars 620 plots compressive strength of polymer systems made from a precursor mixture that was cured for 144 hours. Each group of bars 610 and 620 has a first bar that plots compressive strength of a polymer system made from a precursor mixture that used no high specific surface are additive and a second bar that plots compressive strength of a polymer system made from a precursor mixture that used 3%, by weight of blend, Silica Fume-1 as a high specific surface area additive. Thus, the first group of bars 610 has a first bar 612 showing compressive strength using no additive and a second bar 614 showing compressive strength using 3%, by weight of blend, Silica Fume-1. Likewise, the second group of bars 620 has a first bar 622 showing compressive strength using no additive and a second bar 624 showing compressive strength using 3%, by weight of blend, Silica Fume-1.

[0061] The data of Fig. 6 show a number of trends. First, use of a small amount of Silica Fume-1 boosted compressive strength of all the polymer systems, consistent with the results shown in Fig. 3. Second, the improvement in compressive strength was larger after short-term curing of 24 hours than after ultimate curing, also consistent with the results shown in Fig. 3. Third, comparing the results in Fig. 6 tothose in Fig. 5, it can be seen that the effect of high specific surface area additives on compressive strength is quite reproduceable.

[0062] Higher density polymerization precursor mixtures can be formulated to include high specific surface area materials to boost compressive strength of the resulting polymer system. Table 2 shows two precursor formulations, each using Tg- bin fly ash as an aluminosilicate and 50% NaOH solution as alkalinity source. The second formulation replaces about one-third of the aluminosilicate with MetaMax metakaolin obtained from BASF Corp. Each precursor formulation had slurry density of 18.5 ppg and solid volume fraction of about 55%. The specific formulations, and curing results, are shown in the table.Table 2

[0063] The data of Table 2 show that merely substituting high specific surface area metakaolin for a portion of Tg bin-3 aluminosilicate, with all other components and parameters being essentially equal, increases 24 hr and 48 hr crush strength substantially using an 18.5 ppg polymerization precursor mixture.

[0064] Fig. 7 is a graph 700 showing the effect of using crystalline additives in alkali activated polymerization precursor mixtures. The crystalline additives, in this case, were crystalline silicas. Results from using two such additives are demonstrated in Fig. 7, and properties of the two crystalline additives are set forth in Table 1. The data of Fig. 7 show that highly crystalline materials, seemingly regardless of specific surface area, do not boost compressive strength of a polymer system. The data of Table 1 suggest that the highly crystalline nature of these two additives dramatically reduces, or eliminates, any reactivity benefit even for a crystalline material having relatively elevated specific surface area of 11 .28 m2 / g.

[0065] As described herein, polysialate polymer systems are attractive for uses in well cementing and other subterranean applications. In some embodiments, the well may be used for carbon capture, utilization, and storage (CCUS) and / or for recovery and use of geothermal energy. Geothermal energy is a promising source of renewable energy that captures energy from heat generated or stored within the earth. For example, geothermal energy may be used to perform climate control (e.g., heating, cooling) for structures (e.g., buildings) using heat pumps and / or to generate electricity (e.g., by heating water to generate steam and drive a turbine with the steam). The wells described herein may be used to circulate a working fluid that exchanges heat within the earth formation through which the wellbore extends. The working fluid may be circulated to the surface where a surface heat exchanger is used to transfer thermal energy to another fluid used to generate electricity and / or for climate control. After the thermal energy is transferred from the working fluid in the surface heat exchanger, the working fluid is circulated back to the earth formation to continue the cycle.

[0066] CCUS facilitates the capture, use, and / or storage of carbon (e.g., carbon dioxide), which has a goal of achieving carbon neutrality and / or net zero carbonemissions (NZE). Carbon capture may include the capture of carbon dioxide from large point sources, such as power plants, refineries, cement plants, other industrial processing plants, or other industrial facilities that use fossil fuels, biomass fuels, or other fuels that generate carbon dioxide. The captured carbon dioxide may be converted into valuable products such as, for example, ethanol, sustainable aviation fuel, chemicals, mineral aggregates, and / or other products. Alternatively, the carbon dioxide may be stored in geologic formations, such as in depleted hydrocarbon reservoirs. The carbon dioxide may be introduced into the earth formation through a wellbore, such as the wellbores described herein. In the earth formation, the carbon in the carbon dioxide may be dispersed in an aqueous phase and stored as carbon dioxide, may be stored in mineral form (e.g., as a carbonate, such as calcium carbonate, magnesium carbonate, iron(ll) carbonate), or as another form of carbon.

[0067] Use of polysialate systems made from aluminosilicate materials having substantial amounts of calcium in CO2-rich applications can result in reactions between the CO2 and calcium in the polysialate system. In such cases, aluminosilicate materials having low amounts of calcium, or zero calcium, typically as calcium oxide, can be used to reduce such interactions. Metakaolin is an aluminosilicate material that has zero, or low, calcium content, (typically about 1 -5% calcium oxide depending on the material), so its chemical makeup can be very attractive in some cases for polysialate systems to be used as barrier materials in CO2 storage applications, but metakaolin is difficult to use for pumpable alkali activated precursor mixtures because adding enough metakaolin to develop suitable compressive strength often makes the polymerization precursor so viscous as to be unpumpable. Addition of substances to make the precursor pumpable, in turn, reduces reactivity of the precursor to such an extent that the precursor often fails to develop any compressive strength.

[0068] It has been found that metakaolin-based polymerization precursors that have low or zero calcium can be made pumpable, and can develop suitable early compressive strength, where strong activators are used. In these cases, it has been found that using an activator comprising A) a 50% NaOH solution and B) a 38% sodium silicate solution, where a mass ratio of A to B is less than about 1.0, forexample about 0.30 or lower, yields suitable results. In such cases, precursors having no more than about 5.2 mol / L NaOH and no less than about 4.7 mol / L of sodium silicate generally offer advantageous performance. The parameters above are expressed as “about” because concentrations very near but outside these ranges are not quite as good, but properties rapidly deteriorate much outside the ranges above. Data is presented below showing compressive strength development in pumpable polymerization precursors based on metakaolin as the aluminosilicate source, where the polymerization precursor have slurry density up to about 16 ppg, but such methods are believed to be effective for slurry densities up to about 19 ppg.

[0069] Polymerization precursors according to the description above were made, poured to ensure pumpability, and then allowed to set. Comparative formulations were also made and allowed to set. The formulations of the precursors, and setting results, are shown in Table 3.Table 3

[0070] Formulations 1 -6 were observed to be pourable and resulted in set hardened polymer systems having at least adequate strength upon setting. Formulations C1 -C3 were pourable and were observed to polymerize, but the polymerized material exhibited severe expansion resulting in sample fracturing. These data show that polysialate systems can be made from pourable (therefore pumpable) polymerization precursors using only metakaolin as aluminosilicate source with proper activators and correct activator concentration. The data above also show that such systems can use additives for density control. It is believed that other additives, such as hematite and manganese tetraoxide, can also be used for density control, and that the other additives described herein for controlling other properties, such as reactivity, flexibility, and the like, can also be used in such systems.

[0071] Thus, metakaolin, an aluminosilicate material having low or zero calcium content, can be used as a high surface area additive in some cases, and in other cases as the primary (or sole) aluminosilicate source for making polysialates. For example, as demonstrated above, a pumpable polymerization precursor can comprise an aluminosilicate source and an alkalinity source, where the aluminosilicate source is metakaolin and the alkalinity source is a water solution of sodium hydroxide and sodium silicate having no more than about 5.2 mol / L sodium hydroxide and no less than about 4.7 mol / L sodium silicate. In such cases, the activator has a mass ratio of NaOH to NaSiCh that is less than about 1.3. These systems can use density modifiers, and provided solids volume fraction is appropriately controlled, can be pumpable. These system can use density modifiers, and any of the additives described above to control other properties of the polymerization precursor and / or the polymer system. Using calcium-free materials provides polysialate systems that can be used in CO2 environments without degradation from the CO2.

[0072] The preceding description has been presented with reference to present embodiments. Persons skilled in the art and technology to which this disclosure pertains will appreciate that alterations and changes in the described structures and methods of operation can be practiced without meaningfully departing from theprinciple, and scope of this present disclosure. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.

Claims

CLAIMSWe claim:

1. A method, comprising: mixing water with a solid aluminosilicate source, an alkalinity source, and a high specific surface area additive having specific surface area above about 10 m2 / g to form a polymerization precursor; placing the polymerization precursor at a target location in a subterranean well; and hardening the polymerization precursor at the target location.

2. The method of claim 1 , wherein the additive polymerizes in an alkali activated polymerization reaction.

3. The method of claim 1 , further comprising adding a retarder, an accelerator, a density modifier, an anti-foam agent, a defoamer, silica, a fluid-loss control additive, a viscosifier, a dispersant, an expanding agent, an anti-settling additive, or a combination thereof to the polymerization precursor mixture.

4. The method of claim 1 , wherein the solid aluminosilicate source is selected from the group consisting of ASTM Class C fly ash, ASTM Class F fly ash, fly ash not classified by ASTM, volcanic ash, volcanic glass, slag, ferrous slag, ferroalloy slag, non ferrous slag, blast furnace slag, basic oxygen furnace slag, electric arc furnace slag, ground slag, diatomaceous earths, pumice, calcined clays, aluminum- containing silica fume, natural aluminosilicate, feldspar, andalusite, halloysite, alumina and silica sols, synthetic aluminosilicate glass powder, zeolite, scoria, allophone, bentonite, pumice, red mud, soda-lime glass dust, borosilicate glass dust, microsilica, fumed silica, precipitated silica, nanosilica, rice husk ash, other biomass ash, and combinations thereof.

5. The method of claim 1 , wherein the high specific surface area material is selected from the group consisting of amorphous silica, metakaolin, diatomaceous earth, pumice, rice husk ash, recycled glass pozzolan, sieved aluminosilicates, and combinations thereof.

6. A method, comprising: mixing water with a solid aluminosilicate source having 0-10% by weight calcium oxide and an alkalinity source, wherein the alkalinity source contains no more than about 5.2 mol / L sodium hydroxide and no less than about 4.7 mol / L sodium silicate, to form a polymerization precursor ; pumping the polymerization precursor to a target location in a subterranean well; and hardening the polymerization precursor at the target location.

7. The method of claim 6, further comprising adding a retarder, an accelerator, a density modifier, an anti-foam agent, a defoamer, silica, a fluid-loss control additive, a viscosifier, a dispersant, an expanding agent, an anti-settling additive, or a combination thereof to the polymerization precursor mixture.

8. A dry precursor composition for a polysialate system, comprising: an aluminosilicate source; an alkalinity source; and a high specific surface area additive having specific surface area greater than 10 m2 / g.

9. The dry precursor composition of claim 8, wherein the additive polymerizes in an alkali activated polymerization reaction.

10. The dry precursor composition of claim 8, further comprising a retarder, an accelerator, a density modifier, an anti-foam agent, a defoamer, silica, a fluid-loss control additive, a viscosifier, a dispersant, an expanding agent, an anti-settling additive, or a combination thereof.11 . The dry precursor composition of claim 8, wherein the aluminosilicate source is selected from the group consisting of ASTM Class C fly ash, ASTM Class F fly ash, fly ash not classified by ASTM, volcanic ash, volcanic glass, slag, ferrous slag, ferroalloy slag, non ferrous slag, blast furnace slag, basic oxygen furnace slag, electric arc furnace slag, ground slag, diatomaceous earths, pumice, calcined clays, aluminum-containing silica fume, natural aluminosilicate, feldspar, andalusite,halloysite, alumina and silica sols, synthetic aluminosilicate glass powder, zeolite, scoria, allophone, bentonite, pumice, red mud, soda-lime glass dust, borosilicate glass dust, microsilica, fumed silica, precipitated silica, nanosilica, rice husk ash, other biomass ash, and combinations thereof.

12. The dry precursor composition of claim 8, wherein the high specific surface area material is selected from the group consisting of amorphous silica, metakaolin, diatomaceous earth, pumice, rice husk ash, sieved aluminosilicates, recycled glass pozzolan, and combinations thereof.

13. A pumpable polymerization precursor having a slurry density of at least about 14 pounds per gallon, the polymerization precursor comprising an aluminosilicate source having less than 10% calcium oxide by weight and an alkalinity source having no more than about 5.2 mol / L sodium hydroxide and no less than about 4.7 mol / L sodium silicate.

14. The pumpable polymerization precursor of claim 13, wherein the aluminosilicate source consists of metakaolin, type F fly ash, or a combination thereof.

15. The pumpable polymerization precursor of claim 13, further comprising a density modifier.

16. The method of any of claims 1 -7, or the pumpable polymerization precursor of any of claims 13-15, wherein the polymerization precursor has a slurry density of about 14-16 ppg.

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