WO2020019070A1 - Cement compositions and methods of making the same - Google Patents

Abstract

The application of nanotechnology in well cementing operations enhances the mechanical properties of the cement. As a result, better zonal isolation and protection of the environment is achieved. Well cementing operations have previously used pre-fabricated nanoparticles in cement slurries. Prefabricated particles, however, have been found to exhibit improper dispersion within a resulting cement sheath, negatively impacting its mechanical properties. The present disclosure is directed to the in situ synthesis the nanoparticles within a cement slurry as it hydrates to form a cured/hardened cement matrix. In situ nanoparticle preparation is a platform technology that enables the preparation of wide variety of nanoparticles, while controlling their size, morphology and result in high dispersion. In addition to mitigating the dispersion problem observed with prefabricated nanoparticles, the in situ approach for nanoparticle synthesis described herein employs inexpensive precursors, reducing the cost of the nanoparticles and an overall well cementing operation significantly.

Description

CEMENT COMPOSITIONS AND METHODS OF MAKING THE SAME

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 62/702,584, filed July 24, 2018, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This present invention relates generally to cement compositions. More particularly, the present invention relates to the in situ formation of nanoparticles during the preparation of cement slurries. More particularly, the present invention relates to the formation of cement matrices having nanoparticles dispersed therein where the cement matrices are formed from cement slurries having nanoparticles formed in situ during the preparation of said cement slurries.

BACKGROUND OF THE DISCLOSURE

[0003] Nanotechnology is the field of researching, synthesizing and using materials at the nanoscale level, i.e., 1-100 nm. Nanoparticles (NPs) can be classified as zero-dimensional (0D; having all its dimensions within the nano-domain), one-dimensional (1D; having two of its dimensions in the nano-domain) and two-dimensional (2D; having only one of its dimensions in the nanodomain). Spherical NPs are examples of 0D NPs, carbon nanotubes (CNTs) are examples of 1D NPs, whereas graphene is an example of 2D NPs. 0D, 1D and 2D nanomaterials have unique properties such as high specific surface area, mechanical strength and high chemical reactivity. These properties make such nanomaterials suitable for various applications including well cementing operations in the oil and gas industry.

[0004] Well cementing is a vital process that requires introducing a cement slurry to the annular space between the wellbore and a casing (steel pipe inserted inside the well after drilling) by pumping the cement slurry down the casing and circulating it up the annulus (the space between the casing and the formation). The cement slurry then sets and hardens to form a cement sheath between the wellbore and the casing. Cementing is one of the most crucial operations as it ensures complete zonal isolation, protection of ground water, and structural integrity of the wellbore. However, the performance of the cement sheath may be affected by several factors such as gas migration, quality of the cement slurry, subsequent drilling and completion activities, high pressure fluid injection and formation movement. These factors may lead to well integrity issues or even wellbore failures, which result in costly remediation operations, production interruptions and environmental issues. Thus, the long-term productivity of a well is highly dependent on the quality and durability of the cement sheath.

[0005] Conventional cement-based materials are usually brittle, have low tensile strength and exhibit bulk shrinkage. Furthermore, the products resulting from cement hydration (C-S- H, i.e., calcium-silicate-hydrate) occupy a smaller volume than the reactants, which induces pore formation within the cement sheath. Many research institutions have been investigating the addition of colloidal particles to the cement mix to improve cement properties and to overcome the previously mentioned shortcomings. These particle additives may influence nucleation and crystallization of the cement material (functional additives) or only fill the pores which form in the cement sheath without interfering with its nucleation or growth (inert additives or fillers).

[0006] The addition of pre-fabricated nanoparticles (NPs) to a cement slurry has been found to enhance its workability and the mechanical properties of the resulting hardened cement. Nanoscale Si0₂ (also referred to as nano-SiO ). for example, has been shown to increase the 3-day compressive strength of high volume fly ash (HVFA) concrete (known to suffer from early compressive strength) by 80% by reducing porosity. Nanoscale AI₂O₃ (also referred to as“nano-Al₂0₃”)has been shown to increase the modulus of elasticity of cement mortar without impacting its compressive strength. Nanoscale Ti0₂ (also referred to as “nano-Ti0₂”) has been shown to increase early-age hydration of Portland cement as well as compressive and flexural strengths. Moreover, nanoscale Ti0₂-containing cement also displays self-cleaning characteristics and higher abrasion resistance than that of nanoscale Si0₂. Nanoscale Zr0₂ (also referred to as“nano-Zr0₂”), through pore filling and bridging, improves compressive strength and the microstructure of the cement while decreasing its permeability and porosity. Nanoscale CaCC>₃ shortens the induction period for tricalcium silicates (C₃S) hydration and improves various mechanical properties such as hardened property, impact resistance, flexural strength, low permeability to liquid water and sound absorption.

[0007] Carbon nanofibers (CNFs) and nanotubes (CNTs) have been found to increase the tensile strength of the cement sheath. Both have also been found to increase the modulus of elasticity and compressive strength. The high interaction between CNTs and cement hydrates enables CNTs to work as a bridge across the cracks/voids, which help with load transfer. CNTs, CNFs and FeoCF NPs have been shown to modify the electrical resistance of concrete, especially under load, and contribute to what is known as self-sensing concrete. Nano-clay composites have demonstrated the ability to increase resistance to chloride penetration, reduce permeability and shrinkage of the cement and increase its mechanical properties. Furthermore, NPs can assist in the process of cement hydration due to their ability to act as nuclei for cement hydrates such as nano-smectite. NP addition has also enabled the incorporation of higher percentage by-products into a cement slurry, without compromising the qualities of the resulting cement sheath. This is very attractive from an environmental point of view, since it entails less reliance on cement and beneficial use of waste products. Other areas of investigation for NP-containing cement have included: low water adsorption, water proofing, antimicrobial activity, high Young’s modulus, blast heat resistance, high flexibility, corrosion resistance, and freeze/thaw resistance.

[0008] All previous research has considered the addition of commercially available pre fabricated NPs, which limits the dispersion of the NPs in a cement slurry and substantially increases the cost of a well cementing operation. NPs can be added to a cement slurry in the form of an aqueous dispersion/slurry or in the form of a solid powder. The performance of the cement sheath is highly dependent on its microstructure which is influenced by the nanomaterials added to the starting cement slurry. Proper dispersion of the nanomaterials in the cement slurry prevents the formation of weak zones inside the cement sheath. Weak zones, which can compromise the integrity of the cement sheath, typically arise from agglomeration of the NPs. For example, AI₂O₃ NPs added to cement mortar at relatively low concentrations have been shown to increase the modulus of elasticity. Nevertheless, aggregation of the AI₂O₃ NPs at higher concentrations significantly decreased the modulus of elasticity of the cement mortar.

[0009] Typically, commercial/pre-fabricated NPs undergo agglomeration in order to reduce their high surface energy. CNFs and CNTs have the tendency to agglomerate because they are highly hydrophobic. Other reasons that may cause agglomeration of such nanomaterials are the existence of attractive forces (for example, van der Waals). Hence, these particles must be split apart prior to their addition to a cement slurry. Accordingly, NP addition involves two major steps, breaking down agglomerates of NPs to yield individual NPs, followed by stabilizing the individual NPs to prevent their re-agglomeration. NP de- agglomeration and stabilization can be accomplished through one or a combination of mechanical, physical and/or chemical methods. Mechanical methods pertain to imparting energy to the slurry by means of, for example, high shear mixing, mechanical stirring, ultrasonication and ball milling. Physical methods include modifying the surface of the NPs by, for example, organic admixtures, surfactants and/or polymers by utilizing electrostatic and/or steric repulsion to prevent re-agglomeration of the NPs. Chemical methods of dispersing and/or preventing the NPs from re- agglomeration include anchoring functional groups onto the surface by means of chemical reactions to enhance the hydrophilicity of the NPS, making them easier to disperse in an aqueous environment. While there are numerous methods to make commercial/prefabricated NPs suitable for use in cement slurries, the application of these methods adds considerable cost, time and labor to a well cementing operation and may require major modifications to the equipment and practices currently in use.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For a more complete understanding of the present invention, including features and advantages, reference is now made to the detailed description of the invention along with the accompanying figures.

[0011] FIG. 1 is a graph illustrating the compressive strength (Megapascals, MPa), measured using an Ultrasonic Cement Analyzer (UCA), over time (hours, h) of cement matrices formed from cement slurries: nano-CaS0₄ slurry prepared by Ml (NRi_,i, A), nano- CaC0₃ slurries prepared by Ml (NP_¾i, B) and M2 (NP_2,2, C), nano-Fe(OH)₃ slurries prepared by Ml (NP_3,I, D), M2 (NP_{3 2}, E) and M3 (NP_{3 3}, F), Class G Portland cement slurry (CS, G), NaCl-containing Class G slurry (CSi H), NaN0₃-containing Class G slurry (CS₂, 1), Fe(N0₃)₃-containing Class G slurry (CS₃, J) and NaOH-containing Class G slurry (CS₄, K) formed in accordance with various aspects of the present disclosure;

[0012] FIG. 2 is a graph illustrating the compressive strength (MPa), as measured using 1) an Ultrasonic Cement Analyzer (UCA) and 2) a Destructive Test, of cement matrices formed from cement slurries: Class G Portland cement (CS), NaCl-containing Class G slurry (CS1), nano-CaSCri slurry prepared by method Ml (NPu). and nano-CaC0₃ slurry prepared by method Ml (NP_¾i) formed in accordance with various aspects of the present disclosure; and [0013] FIG. 3 is a graph illustrating the reproducibility of 3 replicates expressed as +/- 1 standard deviation (dashed curves) from the average of nano-Fe(OH)₃ slurries prepared by Ml (NP_{3 I}, A), M2 (NP_3,¾ B) and M3 (NP_{3 3}, C) and cured at 25°C; compared to Class G slurry (CS, D).

[0014] FIG. 4 is a graph illustrating the reproducibility of 3 replicates expressed as +/- 1 standard deviation (dashed curves) from the average of nano-Fe(OH)₃ slurries prepared by Ml (NP_3,I, A), M2 (NP₃ 2, B) and M3 (NP_{3 3}, C) and cured at 80°C; compared to Class G slurry (CS, D).

[0015] FIG. 5 is a graph illustrating the compressive strength (MPa), measured using an Ultrasonic Cement Analyzer (UCA), over time (h) of cement matrices formed from cement slurries: nano-Fe(OH)₃ slurries prepared by Ml (NP_3J. A), M2 (NP_{3 2}. B) and M3 (NP_{3 3}, C), Class G slurry (CS, D), commercial nano-Si0₂-containing Class G slurry (NP₄, E), commercial nano-Fe₂0₃-containing Class G slurry (NP₅. F) formed in accordance with various aspects of the present disclosure;

[0016] FIG. 6 is a graph illustrating sedimentation type III experiments for different in situ NPs prepared using Ml, and commercial NPs used in this study at 25°C with specific beaker dimensions (600 ml, OD: 88 mm, height: 122 mm): CaS0₄ (NPi), CaC0₃ (NP₂), Fe(OH)₃ (NP₃), Si0₂ (NP₄) and commercial Fe₂0₃ (NP5);

[0017] FIG. 7 is a graph illustrating the compressive strength (MPa), measured using an Ultrasonic Cement Analyzer (UCA), over time (h) of cement matrices formed from cement slurries: nano-CaC0₃ slurry prepared by Ml (NP_¾i, A), nano-Fe(OH)₃ slurry prepared by M3 (NP_{3 3}, B), nano-CaC0₃ slurry prepared by Ml including 0.7% BWOC dispersant (NP_2.i+CFR 12. C), nano-Fe(OH)₃ slurry prepared by M3 including 0.7% BWOC dispersant (NP_{3 3}+CFRl2, D), Class G slurry (CS, E) and Class G slurry including 0.7% BWOC dispersant (CS+CFR12, F);

[0018] FIG. 8 is a graph illustrating the compressive strength (MPa), measured using an Ultrasonic Cement Analyzer (UCA), over time (h) of cement matrices formed from cement slurries: a slurry with 0.225% nano-Fe(OH)₃ prepared by Ml (NP₃ . A), a slurry with 0.550% nano-Fe(OH)₃ prepared by Ml (NP₃ . B), a slurry with 1.000% nano-Fe(OH)₃ prepared by Ml (NP_3,I, C), and a Class G slurry (CS, D);

[0019] FIG. 9 is a graph illustrating the compressive strength (MPa), measured using an Ultrasonic Cement Analyzer (UCA), over time (h) of cement matrices formed from cement slurries: a slurry with 0.225% nano-Fe(OH)₃ prepared by M2 (NP_{3 2}. A), a slurry with 0.550% nano-Fe(OH)₃ prepared by M2 (NP_{3 2}. B), a slurry with 1.000% nano-Fe(OH)₃ prepared by M2 (NP_{3 2}, C), and a Class G slurry (CS, D);

[0020] FIG. 10 is a graph illustrating the compressive strength (MPa), measured using an Ultrasonic Cement Analyzer (UCA), over time (h) of cement matrices formed from cement slurries: a slurry with 0.225% nano-Fe(OH)₃ prepared by M3 (NP_{3 3}, A), a slurry with 0.550% nano-Fe(OH)₃ prepared by M3 (NP_{3 3}, B), a slurry with 1.000% nano-Fe(OH)₃ prepared by M3 (NP_{3 3}, C), and a Class G slurry (CS, D);

[0021] FIG. 11 shows, for a cement matrix formed from CS slurry, an energy dispersive X- ray (EDX) image with bright regions indicative of aluminum (top left), an EDX image with bright regions indicative of iron (top right) and a scanning electron microscopy (SEM) image (bottom);

[0022] FIG. 12 shows, for a cement matrix formed from NP₃,_I slurry, an EDX image with bright regions indicative of aluminum (top left), an EDX image with bright regions indicative of iron (top right) and an SEM image (bottom);

[0023] FIG. 13 shows, for a cement matrix formed from NP₃,₂ slurry, an EDX image with bright regions indicative of aluminum (top left), an EDX image with bright regions indicative of iron (top right) and an SEM image (bottom);

[0024] FIG. 14 is a graph comparing the porosity of cured cement matrices formed from a Class G slurry (CS), a nano-Fe(OH)₃ slurry prepared by Ml (NP_3,I), a nano-Fe(OH)₃ slurry prepared by M2 (NP_{3 2}) and a nano-Fe(OH)₃ slurry prepared by M3 (NP_{3 3});

[0025] FIG. 15 is a graph comparing the permeability of cured cement matrices formed from a Class G slurry (CS), a nano-Fe(OH)₃ slurry prepared by Ml (NP_3,I) and a nano- Fe(OH)₃ slurry prepared by M2 (NP_{3 2}) and a nano-Fe(OH)₃ slurry prepared by M3 (NP_{3 3});

[0026] FIG. 16 is a graph illustrating triaxial compressive stress test results for a cement matrix formed from a Class G slurry (CS);

[0027] FIG. 17 is a graph illustrating triaxial compressive stress test results for a cement matrix formed from a nano-Fe(OH)₃ slurry prepared by Ml (NP_3,I); and

[0028] FIG. 18 is a graph illustrating triaxial compressive stress test results for a cement matrix formed from a nano-Fe(OH)₃ slurry prepared by M2 (NP_{3 2}). DET AILED DESCRIPTION

[0029] While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts which can be employed in a wide variety of specific contexts. The specific embodiment discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.

[0030] To facilitate the understanding of this invention, and for the avoidance of doubt in construing the claims herein, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. The terminology used to describe specific embodiments of the invention does not delimit the invention, except as outlined in the claims.

[0031] Terms such as“a,”“an,” and“the” are not intended to refer to a singular entity unless explicitly so defined, but include the general class of which a specific example may be used for illustration. The use of the terms“a” or“an” when used in conjunction with “comprising” in the claims and/or the specification may mean“one” but may also be consistent with“one or more,”“at least one,” and/or“one or more than one.”

[0032] The use of the term“or” in the claims is used to mean“and/or” unless explicitly indicated to refer to alternatives as mutually exclusive. Thus, unless otherwise stated, the term“or” in a group of alternatives means“any one or combination of’ the members of the group. Further, unless explicitly indicated to refer to alternatives as mutually exclusive, the phrase“A, B, and/or C” means embodiments having element A alone, element B alone, element C alone, or any combination of A, B, and C taken together.

[0033] Similarly, for the avoidance of doubt and unless otherwise explicitly indicated to refer to alternatives as mutually exclusive, the phrase“at least one of’ when combined with a list of items, means a single item from the list or any combination of items in the list. For example, and unless otherwise defined, the phrase“at least one of A, B and C,” means“at least one from the group A, B, C, or any combination of A, B and C.” Thus, unless otherwise defined, the phrase requires one or more, and not necessarily not all, of the listed items.

[0034] The terms “comprising” (and any form thereof such as “comprise” and “comprises”),“having” (and any form thereof such as“have” and“has”),“including” (and any form thereof such as“includes” and“include”) or“containing” (and any form thereof such as“contains” and“contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0035] The term“effective” as used in the specification and claims, means adequate to provide or accomplish a desired, expected, or intended result.

[0036] The terms“about” or“approximately” are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the terms are defined to be within 10%, within 5%, within 1%, and in certain aspects within 0.5%.

[0037] In accordance with various aspects of the present disclosure, the properties of cement, concrete and binders are enhanced through the in situ preparation of nanoparticles (NPs). While NP-based cements have been widely studied as discussed generally above, the in situ preparation of NPs during the formation of cement slurries has not been considered in the art. The inventors of the present application have found that in situ preparation of NPs solves at least two major problems associated with industry scale applications of NPs in cement slurries. First, the NPs are prepared from their water-soluble precursors, reducing the cost for cement slurry preparation. Second, the NPs are forced to nucleate and/or grow within the NP-based cement slurry, providing the optimum size allowed by a given slurry as well as ultimate dispersion into the slurry granted by the mobility of the precursors. As used herein, the term “cement slurry” is defined as a semiliquid mixture having cement particles suspended in water. The relative amounts of cement powder and water used to form a cement slurry is not particularly limiting and can be changed depending on various factors such as application (such as well cementing, road paving, building of vertical and/or weight bearing structures, etc.) and/or environmental considerations (such as temperature, pressure, surrounding atmospheric composition, presence of contaminants, etc.). In some instances, the slurry can be relatively thin (that is, have a relatively low viscosity). In some instances, the slurry can be in the form of a thick paste or mortar. As used herein, the term“cement matrix” means a hardened or cured cement formed from a cement slurry.

[0038] In accordance with various aspects of the present disclosure, in situ nanoparticle preparation can be accomplished by first dissolving nanoparticle precursors in an amount of water to be added to a dry cement powder to make a cement slurry. In some instances, as discussed herein, nanoparticles will be prepared from two precursors. In other instances, one or more than two nanoparticle precursors can be used. Each precursor can be dissolved in a certain volume of water. The volumes of water, each containing a single precursor dissolved therein, can then be combined and mixed. Then, dry cement powder can be added to the combined mixture, which, depending upon the reaction rate of the two NP precursors, may contain freshly precipitated NPs therein. A sufficient amount of dry cement is added to result in a cement slurry upon mixing/blending.

[0039] In another approach, starting amounts of dry cement powder and water are each split into a number of equal portions, established by weight and/or volume. A plurality of NP precursor-cement slurries is then prepared by dissolving a distinct nanoparticle precursor in each water portion followed by the addition of a corresponding portion of dry cement powder. The plurality of NP precursor-cement slurries is then combined and the distinct NP precursors, now in a single slurry, react to form NPs. In this approach, the number of equal portions into which the dry cement and the water are split will equal the number of nanoparticle precursors used. For example, if two NP precursors are used for the in situ preparation of nanoparticles, the dry cement powder and water will be split into two equal portions. When two precursors (“precursor A” and“precursor B”) are used, each nanoparticle precursor is then added to a corresponding portion of water to form a precursor solution A and a precursor solution B. Then, a portion of dry cement powder is added to each precursor solution to form a NP precursor-cement slurry A and a NP precursor-cement slurry B. Then, the NP precursor-cement slurry A and the NP precursor-cement slurry B are then mixed together and the nanoparticles (“AB”) are formed in situ in the combined slurry.

[0040] In yet another approach, starting amounts of dry cement powder and water are each split into a number of unequal portions, established by weight and/or volume. For example, when the water is split into two portions, the ratio of the two portions can range from about 5:95 to about 49:51. Similarly, when the dry cement powder is split into two portions, the ratio of the two portions can range from about 5:95 to about 49:51. A plurality of NP precursor-cement slurries are then prepared by dissolving a distinct nanoparticle precursor in each water portion followed by the addition of a corresponding portion of dry cement powder. The plurality of NP precursor-cement slurries is then combined and the distinct NP precursors, now in a single slurry, react to form NPs. In this approach, the number of unequal portions into which the dry cement and the water are split will equal the number of nanoparticle precursors used. For example, if two NP precursors are used for the in situ preparation of nanoparticles, the dry cement powder and water will be split into two unequal portions. When two precursors (“precursor A” and“precursor B”) are used, each nanoparticle precursor is then added to a corresponding portion of water to form a precursor solution A and a precursor solution B. Then, a portion of dry cement powder is added to each precursor solution to form a NP precursor-cement slurry A and a NP precursor-cement slurry B. Then, the NP precursor-cement slurry A and the NP precursor-cement slurry B are then mixed together and the nanoparticles (“AB”) are formed in situ in the combined slurry.

[0041] In yet another approach, NP solid precursors are mixed into a dry cement powder to form a NP precursors-cement powder. The NP precursors-cement powder is then mixed in an appropriate amount of water to form a NP precursors-cement slurry. The NP precursors- cement slurry is subjected to continued mixing/blending to convert the NP precursors into NPs and form a NP-cement slurry.

[0042] In yet another approach, NP solid precursors and dry cement powder are mixed into water in sequential steps. For example, when two precursors (“precursor A” and“precursor B”) are used, precursor A can first be mixed in the water to form a precursor A solution. To the precursor A solution, an amount of dry cement powder can be added and mixed to form a precursor A-cement slurry. Precursor B can then be mixed into the precursor A-cement slurry to form an initial precursor A/B-cement slurry. Then, another amount of dry cement powder can be added to and mixed with the initial precursor A/B-cement slurry to form a final precursor A/B-cement slurry. NPs formed in accordance with various aspects of the present disclosure can have diameters ranging from about 1 nanometer (nm) to about 6 micrometers (pm).

[0043] The difference between the five approaches of NP preparation is the nucleation step. While the first approach allows for nucleation to take place within the aqueous solution prior to mixing the cement powder, the second through fifth approaches ensure that both nucleation and growth occur within a cement slurry. In the second through fifth approaches, however, the rate of nucleation and growth within a cement slurry may vary. A comparison between the approaches allows evaluation of the role of NP nucleation versus growth. In addition, the use of different approaches to prepare NPs of different types provides alternative routes in case of a failure.

[0044] Regardless of approach, in some instances, the amount of each precursor in each volume of water will be stoichiometric. For example, if Fe(OH)₃ nanoparticles are to be produced, a first NP precursor can have 1 molar equivalent of Fe³⁺ ions and a second NP precursor can have 3 molar equivalents of OH ions. Also, for example, if CaC0₃ nanoparticles are to be produced, a first NP precursor can have 1 molar equivalent of Ca²⁺ and a second NP precursor can have 1 molar equivalent of C0₃ ² ions. In other instances, one of the precursors can be in excess relative to the other precursor. [0045] In some instances, an amount of dry cement powder will be added such that the cement slurry has a water to cement powder ratio ranging from about 0.1: 1 to about 1 : 1 by weight, alternatively from about 0.2: 1 to about 0.8: 1, alternatively from about 0.3: 1 to about 0.6: 1, alternatively from about 0.3: 1 to about 0.5: 1, and alternatively from about 0.4: 1 to about 0.5: 1.

[0046] In some instances, the cement slurry can be formed such that it has a NP precursors to cement powder ratio ranging from about 0.01 :99.91 to about 20:80 by weight, alternatively from about 0.05:99.95 to about 15:85, alternatively from about 0.1 :99.9 to about 10:90, alternatively from about 0.15:99.85 to about 5:95, alternatively from about 0.2:99.8 to about 2.5:97.5, alternatively from about 0.35:99.65 to about 1.25:98.75, alternatively from about 0.4:99.6 to about 1 :99, alternatively from about 0.45:99.55 to about 0.8:99.2, alternatively from about 0.5:99.5 to about 0.8:99.2, and alternatively from about 0.55:99.45 to about 0.75:99.25 by weight. In some instances, the cement slurry can be formed such that it has a NP to cement powder ratio ranging from about 0.01 :99.91 to about 20:80, alternatively from about 0.05:99.95 to about 15:85, alternatively from about 0.1 :99.9 to about 10:90, alternatively from about 0.15:99.85 to about 5:95, alternatively from about 0.2:99.8 to about 2.5:97.5, alternatively from about 0.35:99.65 to about 1.25:98.75, alternatively from about 0.4:99.6 to about 1 :99, alternatively from about 0.45:99.55 to about 0.8:99.2, alternatively from about 0.5:99.5 to about 0.8:99.2, and alternatively from about 0.55:99.45 to about 0.75:99.25.

[0047] In accordance with varying aspects of the present disclosure, NPs can be formed in situ by a double displacement reaction scheme as follows:

where AY (s) is the resulting NP. The AX and BY compositions are not particularly limiting. The only requirement of the AX and BY compositions are that they be soluble in water and, upon reacting form an insoluble nanoparticle AY. Nanoparticles which can be formed in situ via a double displacement reaction include, but are not limited to, Ag₂C0₃, Ag₂S0₄, Ag₂Cr₂0₇, Ag₃P0₄, Ag₂S, AgBr, AgCl, Agl, Al₂0₃, Al(OH)₃, Al₂(Cr₂0₇)₃, AlP0₄, BaC0₃, BaCr0₄, BaF₂, BaS0₄, CaF, CaS0₄, CaC0₃, CaC₂0₄, Ca₃(P0₄)₂, CaCr₂0₇, Cr(OH)₃, Cr₂(S0₄)₃, CrP0₄, Cu(OH)₂, Cu₃(P0₄)₂, CuC0₃, CuCr₂0₇, Fe(OH)₂, Fe(OH)₃, Fe₂(Cr₂0₇)₃, Fe₃(P0₄)₂, FeC0₃, FeCr₂0₇, FeP0₄, FeS, MgF₂, Mg(OH)₂, MgC0₃, Mg₃(P0₄)₂, MgCr₂0₇, Mn(OH)₂, MnC0₃, Mn₃(P0₄)₂, MnS, MnS0₃, MnSi0₃, Ni(OH)₂, NiC0₃, Ni₃(P0₄)₂, NiS, N1SO3, NiSiOs, SrC0₃, SrS0₄, SrCr0₄, SrCr₂0₇, Zn(OH)₂, ZnC0₃, Zn₃(P0₄)₂, ZnS, and ZnCr₂0₇. As may be appreciated, the choice of AX and BY compositions, and amounts of each to be used in cement slurries may be guided by general solubility rules for ionic compounds and solubility product constants. In addition to the above, numerous other insoluble NPs containing metals such as lead, mercury, cadmium, cobalt, palladium, platinum, gold, molybdenum, tungsten, bismuth, indium, actinides, zirconium, tungsten, actinides and lanthanides may be prepared using double displacement reactions, if desirable. Generally, AX water soluble metal-containing salt, where A is the metal and BY is water soluble compound containing an anionic Y species which when ionically bound to the metal A to form AY, while the anion X and cation B react to form a water soluble compound BX.

[0048] While NPs can be formed using a double displacement reaction scheme, the present invention is not limited thereto. In some instances, NPs containing a single metal such as iron, nickel, copper, silver, gold, titanium and aluminum, can be formed by reacting a corresponding water soluble metal-containing salt with a suitable reducing agent. In some instances, metal oxide nanoparticles can be fabricated in situ from a water-soluble metal- containing salt, a base and/or an oxidizing agent. In some instances, metal or metalloid oxide nanoparticles can be fabricated in situ, from a water-soluble metal-containing salt and either an acid or a base, via a hydrolysis and condensation reaction mechanism. Metal/metalloid oxide nanoparticles which can be formed in situ in accordance with various aspects of the present disclosure include, but are not limited to, Al₂0₃, Si0₂, Sc₂0₃, Ti0₂, V₂Os, Cr₂0₃, MnO, Mn0₂, MgO, iron oxides with their various crystal structures (e.g., FeO, Fe₂0₃, Fe₃0₄), CuO, Cu₂0, ZnO, Zr0₂, SnO, Sn0₂, Sb₂0₃, Bi₂0₃, and W0₃.

[0049] In some instances, the water used to form a cement slurry is freshwater. In some instances, the water used to form a cement slurry is purified water. In some instances, the water used to form a cement slurry is de-ionized water. In some instances, the water used to form a cement slurry is seawater. In some instances, the water used to form a cement slurry is brine. In some instances, the water used to form a cement slurry is brackish water.

[0050] In some instances, a NP dispersion aid can be added to enhance the dispersion of the NPs within the cement slurry. In some instances, the dispersion aid can be added to the water prior to addition of the NP precursors. In some instances, the dispersion aid can be added to the water at the same time as addition of the NP precursors. In some instances, the dispersion aid can be added to the water after addition of the NP precursors and prior to addition of the dry cement powder. In some instances, the dispersion aid can be added to the water after addition of the NP precursors and at the same time as addition of the dry cement powder. In some instances, the dispersion aid can be added to the water after addition of the NP precursors and after addition of the dry cement powder. In some instances, the dispersion aid can be added as the NPs are forming. In some instances, the dispersion aid can be added after the NPs are formed. In some instances, the dispersion aid can be a component of the dry cement powder. In some instances, cement slurries according to the present disclosure can have between about 0.01 and about 5.0 % by weight of cement (BWOC) of the dispersion aid. In other instances, cement slurries according to the present disclosure can have between about 0.05 and about 4.5 % BWOC, alternatively between about 0.1 and about 4 % BWOC, alternatively between about 0.2 and about 3 % BWOC, alternatively between about 0.3 and about 2 % BWOC, alternatively between about 0.4 and about 1 % BWOC, alternatively between about 0.5 and about 0.9 % BWOC, alternatively between about 0.6 and about 0.8 % BWOC, and alternatively about 0.7 % BWOC of the dispersion aid.

[0051] The NP dispersion aid can have any structure which reduces agglomeration of the NPs and aids in dispersing the NPs within the water and/or cement slurry. In some instances, aNP dispersion aid can have the following general structure:

X-Y-Z

where X is an NP binding group; Z is hydrophilic functional group; and Y is a linking group. In general X can be any polar functional group capable of coordinating to the surface of a NP such as, for example, a carboxylic acid, an alcohol, an amine, a thiol, a phosphine, and a phosphine oxide. X can be any polar functional group that is hydrophilic, providing compatibility with the water phase of the cement slurry. Like X, Z can be a functional group such as for example, a carboxylic acid, an alcohol, an amine, a thiol, a phosphine, and a phosphine oxide. The linking group Y is not particularly limiting. In some instances, the Y group can be a linear or branched, saturated or unsaturated, carbon chain having between 2 and 24 carbons. In some instances, the linking group Y can be a linear or branched, saturated or unsaturated, mono- or polyester carbon chain having between 2 and 24 carbons and at least one oxygen. In some instances, the linking group Y can be a linear or branched, saturated or unsaturated, mono- or polyamine carbon chain having between 2 and 24 carbons and between at least one nitrogen. In some instances, the linking group Y can be a linear or branched, saturated or unsaturated, mono- or polysulfide carbon chain having between 2 and 24 carbons and between at least one sulfur.

[0052] In some instances, the dispersion aid can have the following general structure: X-Y

where X is an NP binding group and Y is a hydrophilic polymer, copolymer, terpolymer, or block copolymer. In general X can be any polar functional group capable of coordinating to the surface of a NP such as, for example, a carboxylic acid, an alcohol, an amine, a thiol, a phosphine, and a phosphine oxide. In general, Y can be a hydrophilic polymer such as, for example, a polyethylene glycol (PEG), a polyethylene oxide (PEO), a poly(acrylic acid), a poly(methacrylic acid), a poly(2-ethyl acrylic acid) (PEAAc), a poly(2-propylacrylic acid), a polyKYY-diethylaminoethyl methacrylate) (PDEAEMA), a polyvinyl pyrrolidone (PVP), a polyacrylamide, a poly (vinyl alcohol) (PVOH), a poly carboxylic acid, a polycarboxylate salt, a polycarboxylate ether and a polysaccharide. In some instances, the dispersion aid can be provided by CFR-12 (Trican Well Service Ltd., Calgary, Alberta, Canada). CFR-12 is a blend comprising about 15 wt% of a polycarboxylate ether (the active dispersion aid), 30 to less than 60 wt% of diatomaceous earth, 10 to less than 30 wt% aluminum oxide, 3 to less than 7 wt% boric acid, 3 to less than 7 wt% calcium oxide and 1 to less than 5 wt% ferric oxide)

[0053] Nanoparticles formed in accordance with various aspects of the present disclosure can be used in the preparation of cement slurries using, for example, a dry cement powder manufactured according to the specifications of the American Society for Testing and Materials (an“ASTM cement”), dry cement powder manufactured to the specifications of the American Petroleum Institute (an“API cement”), a concrete (cement plus fine and course aggregates of sand, crushed stones, gravel and so on), gypsum (calcium sulfate dihydrate), fly ash, silica flour, silica fume, metakaolin, a microcement and any combination thereof. In some instances, additional compositions such as bentonite, calcium carbonate, glass (for example, glass spheres), ceramics (for example, ceramic spheres), a salt (for example, NaCl, CaCl . KC1), barite, hematite, and any combination thereof, can be added to cement slurries formed in accordance with various aspect of the present disclosure.

[0054] In some instances, nanoparticles formed in accordance with various aspects of the present disclosure can be used in the preparation of cement slurries having an ASTM Type I (general purpose) portland cement, which characteristically has a fairly high tricalcium silicate (cement notation: C₃S) content for good early strength development, for the construction of, for example, buildings, bridges, pavements, precast units, and other similar structures. In other instances, nanoparticles formed in accordance with various aspects of the present disclosure can be used in the preparation of cement slurries having an ASTM Type II (moderate sulfate resistance) portland cement, which characteristically has a low tricalcium aluminate (<8%; cement notation: C₃A) content, for the construction of structures which will be exposed to soil or water containing sulfate ions. In other instances, nanoparticles formed in accordance with various aspects of the present disclosure can be used in the preparation of cement slurries having an ASTM Type III (high early strength) portland cement, for use in, for example rapid construction projects and cold weather concreting. In other instances, nanoparticles formed in accordance with various aspects of the present disclosure can be used in the preparation of cement slurries having an ASTM Type IV (low heat of hydration, i.e., slow reacting) portland cement, which characteristically has a low C₃S (<50%) and C₃A content, for the construction of massive structures such as dams. In other instances, nanoparticles formed in accordance with various aspects of the present disclosure can be used in the preparation of cement slurries having an ASTM Type V (high sulfate resistance) portland cement, which characteristically has a very low C₃A (<5%) content, for the construction of structures which will be exposed to high levels of sulfate ions. In other instances, nanoparticles formed in accordance with various aspects of the present disclosure can be used in the preparation of cement slurries having an ASTM White portland cement, which characteristically has no tetracalcium aluminoferrite (cement notation: C₄AF) and low MgO content for the construction of decorative structures or items.

[0055] In some instances, nanoparticles formed in accordance with various aspects of the present disclosure can be used in the preparation of cement slurries having an API class A portland cement (53% C₃S, 24% dicalcium silicate (C₂S), > 8+% C₃A, 8% C₄AF; Wagner Fineness of 1,500-1,900 cm²/g). In other instances, nanoparticles formed in accordance with various aspects of the present disclosure can be used in the preparation of cement slurries having API class B portland cement (47% C₃S, 32% C₂S, < 5% C₃A, 12% C₄AF; Wagner Fineness of 1,500-1,900 cm²/g). In other instances, nanoparticles formed in accordance with various aspects of the present disclosure can be used in the preparation of cement slurries having API class C portland cement (58% C₃S, 16% C₂S, 8% C₃A, 8% C₄AF; Wagner Fineness of 2,000-2,800 cm²/g). In other instances, nanoparticles formed in accordance with various aspects of the present disclosure can be used in the preparation of cement slurries having API class G or H portland cement (50% C₃S, 30% C₂S, 5% C₃A, 12% C₄AF; Wagner Fineness of 1,400-1,700 cm²/g).

[0056] In well cementing applications, the mixing and blending of the cement slurry can performed according to American Petroleum Institute (API) specifications. In accordance with various aspects of the present disclosure, blending and mixing of the NP precursors, NPs and dry cement powder, and/or NP precursors and dry cement powder can be accomplished in any suitable manner. In some instances, mixing can be accomplished manually. In other instances, mixing can be accomplished with use of an apparatus such as a blender, a twin shaft mixer, a vertical axis mixer, a drum mixer, an in-transit mixer, a portable concrete mixer, and a self-loading mixer. During mixing, the precursors react to form nanoparticles. In some instances, mixing and blending can take place under ambient pressure and temperature. In some instances, mixing and blending can be performed at an elevated temperature. In some instances, mixing and blending can be performed at a temperature below ambient temperature and above the freezing point of water.

[0057] Following the cement slurry preparation, the slurry is conditioned (i.e. subjected to pressure and temperature) to simulate downhole conditions using a conditioning cell that provides continuous mixing and heats up the slurry to the required temperature (25 - 90)°C. Then, a series of tests is run on each sample to study the compressive strength, tensile strength, thickening time, fluid loss, rheology, free water, permeability and porosity as the cement slurry cures or hardens to form a resulting cement matrix.

[0058] In some instances, cement matrices formed in accordance with various aspects of the present disclosure can have anywhere from about 0.05 to about 5 wt% of nanoparticles by weight of cement (BWOC). As used herein, BWOC is determined relative to the amount of dry cement powder used to make a corresponding cement slurry. In other instances, cement matrices formed in accordance with various aspects of the present disclosure can have anywhere from about 0.1 to about 4 wt%, alternatively from about 0.15 to about 3 wt%, alternatively from about 0.2 to about 2 wt%, alternatively from about 0.225 to about 1.75 wt%, alternatively from about 0.25 to about 1.5 wt%, alternatively from about 0.4 to about 1.4 wt%, alternatively from about 0.5 to about 1.3 wt%, alternatively from about 0.5 to about 1.2 wt%, alternatively from about 0.5 to about 1 wt% of nanoparticles BWOC. In some instances, as shown in the examples below, the preparation of cement slurries resulting in cement matrices with about 0.66 wt% of NPs has been found particularly effective from an efficiency and raw materials input perspective.

EXAMPLES

[0059] The following examples are included for the sake of completeness of disclosure and to illustrate the methods of making the compositions and composites of the present invention as well as to present certain characteristics of the compositions. In no way are these examples intended to limit the scope or teaching of this disclosure.

General procedure

[0060] Portland cement (mainly Class G) powder was used in the examples below to prepare the cement slurries as it is the most commonly employed in the oil and gas industry. Water-soluble salts, as shown in Table 1, were used as precursors to form the NPs as well as simulate the side products from the NP precipitation reactions (Rl) to (R4). These NPs included CaS0₄ (NPi), CaC0₃ (NP₂) and Fe(OH)₃ (NP₃). All reactions were assumed to proceed to completion.

CaCl_{2 (aq)} + Na₂S0_{4 (aq)} · CaS0_{4 (S)} + 2NaCl _(aq) (Rl)

CaCl_{2 (aq)} + Na₂C0_{3 (aq)} ^ CaC0_{3 (S)} + 2NaCl _(aq) (R2)

Fe(N0₃)_{3 (aq)} + NaOH _(aq) *· Fe(OH)_{3 (s)} + 3NaN0_{3 (aq)} (R3)

FeCl_{3 (aq)} + 3NaOH _(aq) *· Fe(OH)_{3 (s)} + 3NaCl _(aq) (R4)

[0061] The NPs were prepared in situ using 3 different methods (Ml to M3) and, hence were labeled with two indexes. For example, NP_¾i refers to CaC0₃ NPs prepared by Ml. In addition to a control sample that shows Class G cement (CS), other control samples capturing the side products or precursors per NP preparation reactions Rl to R4 were labeled as CSi to CS₄, as shown in Table 3. Cement slurries incorporating commercial nano-Si0₂ (average particle size ~ 7 nm) and nano-Fe₂0₃ (average particle size < 50 nm) were also used in order to provide a comparison with the in situ prepared NPs. The commercial Si0₂ and Fe₂0₃ NPs were labeled as NP₄ and NP₅. respectively. Trican dispersant CFR-12 was added to some slurries to investigate the role of NP dispersion within the slurry.

Table 1.

In-situ preparation ofNPs [0062] The NP impregnated-cement slurries were prepared using three methods.

[0063] In a first method (Ml), the volume of the water to be added to the cement (i.e. 350 ml) was divided into two equal portions. The first NP precursor was dissolved in the first water portion to form a first NP precursor aqueous solution and the second NP precursor was dissolved in the second water portion to form a second NP precursor aqueous solution. The amounts of first and second NP precursors were stoichiometric. After that, the first and second NP precursor aqueous solutions were mixed together in a blender for 10 - 20 seconds (s). The dry cement was then added to the freshly precipitated NPs and mixing commenced for another 96 s.

[0064] In a second method (M2), the cement and the water to be added to it were split into two equal masses. A first NP precursor was added to a first water portion to form a first NP aqueous solution, the first amount of dry cement powder was then added to the first NP precursor aqueous solution and mixed for about 28 seconds (s) to form a first NP precursor cement slurry. Separately, a second NP precursor was added to a second water portion to form a second NP aqueous solution, the second amount of dry cement powder was then added to the second NP precursor aqueous solution and mixed for about 28 seconds (s) to form a second NP precursor cement slurry. Then, the first and second NP precursor cement slurries were mixed together for 56 s using a blender to form a NP-containing cement slurry upon reaction of the NP precursors. The amounts of first and second NP precursors were stoichiometric.

[0065] In a third method (M3), stoichiometric amounts of first and second NP precursor salts were added directly to an amount of dry cement powder, followed by thoroughly mixing with a rod to ensure proper distribution of the first and second NP precursor salts within the dry cement powder to form a dry blend. Then, the dry blend was mixed with the water in a blender for 120 s to form a NP-containing cement slurry upon reaction of the NP precursors.

[0066] Another method (M4) involved mixing a first NP precursor aqueous solution with a first half of dry cement powder and mixing for 20 s. Then, adding a second NP precursor aqueous solution to the slurry and continue mixing for another 20 s, followed by the addition of the second half of the dry cement. The resultant slurry (now containing first and second NP precursors) was then mixed for 80 s.

[0067] The typically employed water to cement ratio of 0.44 wt.% was maintained in all slurries (M. Tabatabaei, A. D. Taleghani, and N. Alem, “Economic Nano-Additive to Improve Cement Sealing Capability,” in SPE Western Regional Meeting, 2019, pp. 23-26). The mixing and blending of the cement slurries was performed according to API specifications (API RP 10B-2: Clause 5.3.4). Following cement slurry preparation, the slurry was conditioned for 20 min using a conditioning cell that provided continuous mixing at 25°C.

[0068] Similar to the slurries containing in situ prepared NPs, all other cement slurries in this work were prepared according to API specifications (API RP 10B-2: Clause 5.3.4) using a water to cement ratio of 0.44 wt.%. Class G slurry (CS) was prepared by directly mixing the dry cement with water in a blender for 120 s. Commercial NP slurries (NP₄ & NP₅) were prepared by mixing the commercial NPs with the water in a blender for 10 - 15 s before cement addition. The mixing was then continued after adding the cement for another 96 s. The other control sample slurries (CS₁ CS₂, CS₃ and CS₄) were prepared similar to CS with the exception of dissolving the salts in the water before mixing it with the cement. Slurries containing CFR-12 involved the addition of CFR-12 to the dry cement instead of water. All slurries were then conditioned through continuous mixing at 25°C for 20 min.

Testing protocols

[0069] The evolution of the compressive strength over time was measured using an ultrasonic cement analyzer (UCA). A destructive test was also used to provide another measurement for compressive strength. In the destructive test, cement cubes were casted and cured for 48 h at 1500 psia and 25°C before being crushed using a digital compressive strength tester.

[0070] Cyclic axial testing was conducted to determine the effect of compression cycles on the elastic properties of the cement sample. A cylindrical sample (1 inch in diameter and 2 inches long) was prepared, cured for 2 days at 80°C and submerged in oil under 2.5 MPa of pressure in a triaxial rock testing machine. The sample was compressed until a certain strain value (0.2%) was reached and then the load was decreased so the sample could return to its original shape. Ten compression cycles were applied after which the sample was compressed until it failed. The peak in the compressive stress after these compression cycles was compared to the peak without any compression cycles to assess the impact of subsequent pressure cycles on the durability of the cement sheath.

[0071] Porosity and permeability test samples were prepared by pouring the cement slurry into a cylindrical mold and leaving it to cure for 2 days at 80°C. Then, porosity was calculated by making bulk and skeletal density measurements using a gas pycnometer, whereas permeability was determined by pulse decay method using helium.

[0072] NP characterization within the cement matrix was accomplished using scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX). In addition, sedimentation experiments were carried out to provide details on particle settling following their preparation using Ml. The precursor solutions were mixed together in a blender for 30 s to form the NPs before pouring them into a beaker (600 ml, OD: 88 mm, height: 122 mm) to observe the movement of the interface over time, per sedimentation type III protocol (S. Verma, B. Prasad, and I. M. Mishra, “Pretreatment of petrochemical wastewater by coagulation and flocculation and the sludge characteristics,” J. Hazard. Mater., vol. 178, no. 1-3, pp. 1055-1064, 2010).

Results Compressive Strength

[0073] FIG. 1 is a graphical display of the evolution of cement compressive strength over time for nano-CaS0₄ slurry prepared by Ml (NRi_,i, A in FIG. 1), nano-CaC0₃ slurries prepared by Ml (NP_¾i, B in FIG. 1) and M2 (NP_{2 2}, C in FIG. 1), nano-Fe(OH)₃ slurries prepared by Ml (NP_3,I, D in FIG. 1), M2 (NP_{3 2}, E in FIG. 1) and M3 (NP_{3 3}, F in FIG. 1), Class G slurry (CS, G in FIG. 1), NaCl-containing Class G slurry (CSi, H in FIG. 1), NaN0₃- containing Class G slurry (CS₂, I in FIG. 1), Fe(N0₃)₃-containing Class G slurry (CS₃, J in FIG. 1) and NaOH-containing Class G slurry (CS₄, K in FIG. 1).

[0074] As shown in FIG. 1, the nano-CaS0₄ slurry prepared by Ml (NPu) showed overall higher compressive strength than the Class G slurry (CS). However, a slurry containing the same amount of NaCl side product from Rl (CSi in Table 1) displayed an even higher value of compressive strength than exhibited by NRi_,i. Therefore, the use NPu appears ineffective. A similar trend similar to NRi_,i is observed with nano-CaC0₃ slurries prepared using Ml (NP_2,I) and M2 (NP₂₂). This also indicates that the increase in the compressive strength for in situ prepared nano-CaC0₃ slurries was mainly due to the NaCl side product.

[0075] At this stage, the destructive test was carried out in order to ensure the reliability of the UCA measurements. Three replicates of cubes belonging to samples CS, CSi, NPu and NP₂.I were crushed using the digital compressive strength tester. The results reported in FIG. 2 after 48 h of curing time show that UCA provides a more conservative estimation of the compressive strength, since higher values of compressive strength were obtained using the destructive test. Nevertheless, the same trend in compressive strength with respect to the different samples was still captured by the destructive test.

[0076] FIG. 1 also provides data for nano-Fe(OH)₃ prepared by the three different methods (NP₃4, NP_3,2 and NP_{3 3}). These samples exhibit an increased compressive strength compared to class G control sample (CS) by 70 to 80% in the first 24 h. Control samples CS₂ and CSi could not achieve the compressive strength values obtained by NP₃₂ to NP_{3 3}. Even though Fe(N0₃)₃-containing class G slurry (CS₃) showed significant increase in compressive strength (around 44% increase in 6 days), the development of the compressive strength was much slower than that of the NP₃ slurries. The high 6-day compressive strength of CS₃ slurry could result from the conversion of Fe(N0₃)₃ precursor to Fe(OH)₃ with hydroxide ions appearing from the cement hydration reaction. Reproducibility of the results obtained by NP_{3 I} (A in FIGS. 3-4), NP_{3 2} (B in FIGS. 3-4) and NP_{3 3} (C in FIGS. 3-4) at 25°C and 80°C are shown in FIGS. 3 and 4, respectively, for three replicates and compared to Class G slurry (CS, D in FIGS. 3-4).

[0077] FIG. 5 is a graphical display of the evolution of compressive strength over time for nano-Fe(OH)₃ slurries prepared by Ml (NP_{3 I}, A in FIG. 5), M2 (NP_{3 2}, B in FIG. 5) and M3 (NP_{3 3}, C in FIG. 5), Class G slurry (CS, D in FIG. 5), commercial nano-Si0₂-containing Class G slurry (NP₄, E in FIG. 5) and commercial nano-Fe₂0₃-containing Class G slurry (NP₅, F in FIG. 5). As can be seen, in situ prepared Fe(OH)₃ NPs (NP_3,I, NP_{3 2} & NP_{3 3}) outperformed slurries of commercially available NPs.

[0078] As previously discussed, high dispersion of NPs in cement slurries is crucial for suitable performance in various applications (M. Husein, “Preparation of nanoscale organosols and hydrosols via the phase transfer route,” J Nanoparticle Res., vol. 19, no. 12, p. 405, 2017). In order to investigate the role of dispersion of the NPs, sedimentation type III experiments were conducted to investigate the speed at which various NPs employed in this study aggregate and settle from a hydrosol. FIG. 6 is a graphical display of sedimentation type III experiments for different in situ prepared (using Ml) and commercial NPs used in this study at 25°C with specific beaker dimensions (600 ml, OD: 88 mm, height: 122 mm). The results in FIG. 6 show that the aggregation and settling of CaS0₄ (NPi), CaC0₃ (NP₂) and commercial Fe₂0₃ (NP₅) particles were fast, whereas Fe(OH)₃ (NP₃) and Si0₂ (NP₄) particles remained stable in the hydrosol. Without being bound to theory, this could be one of the reasons behind the exceptional performance of the in situ prepared Fe(OH)₃ nanoparticles compared with the in situ prepared CaS0₄ and CaC0₃ nanoparticles. [0079] In order to further investigate the role of the state of NP dispersion on cement strengthening, 0.7 wt% (based on dry cement) of a Trican dispersant (CFR-12) was added to one of the CaC0₃ slurries (NR_¾i), and one of the Fe(OH)₃ slurries (NP_{3 3}) at 25°C. Another control sample containing class G cement and 0.7% by weight of cement (BWOC) CFR-12 was introduced to capture the impact of CFR-12 on the compressive strength of the cement. FIG. 7 is a graphical display of the evolution of compressive strength over time for nano- CaC0₃ slurry prepared by Ml (NR_¾i, A in FIG. 7), nano-Fe(OH)₃ slurry prepared by M3 (NP₃ , B in FIG. 7), nano-CaC0₃ slurry prepared by Ml including 0.7% BWOC dispersant (NP_{2 i}+CFRl2, C in FIG. 7), nano-Fe(OH)₃ slurry prepared by M3 including 0.7% BWOC dispersant (NP_{3 3}+CFRl2, D in FIG. 7), Class G slurry (CS, E in FIG. 7) and Class G slurry including 0.7% BWOC dispersant (CS+CFR12, F in FIG. 7). As can be seen in FIG. 7, while NP,_., slurry exhibited only an 8% increase in the compressive strength (after 7 days), the NP_¾i slurry with dispersant displayed a significant 40% increase in compressive strength compared with NP_¾i without dispersant. Moreover, the slurry containing NP_¾i and CFR-12 achieved similar compressive strength to the that of NP_{3 3} and CFR-12. The increase in compressive strength can only be attributed to the dispersion state of CaC0₃ NPs, especially since the addition of CFR-12 alone did not lead to the same degree of enhancement in the compressive strength, as evident from FIG. 7. Thus, it can be inferred that if the in situ prepared particles tend to aggregate fast, effective dispersion may enhance their performance, whereas if the particles are already well dispersed little improvement in compressive strength can be achieved.

[0080] The effect of NP content on the compressive strength of the cement matrices formed from corresponding slurries was examined for the in situ preparation of nano- Fe(OH)₃ using methods Ml, M2 and M3. Cement matrices having NP weight percentages of 0.270%, 0.660% and 1.200% BWOC for each method was evaluated. FIG. 8 shows the compressive strength of cement matrices formed from nano-Fe(OH)₃ slurries prepared using Ml and having 0.270% (A), 0.660% (B) and 1.200% (C) BWOC nano-Fe(OH)₃; FIG. 8 also shows the compressive strength of a cement matrix formed from Class G slurry (CS, D) for reference. FIG. 9 shows the compressive strength of cement matrices formed from nano- Fe(OH)₃ slurries prepared using M2 and having 0.270% (A), 0.660% (B) and 1.200% (C) BWOC nano-Fe(OH)₃; FIG. 9 also shows the compressive strength of a cement matrix formed from Class G slurry (CS, D) for reference. FIG. 10 shows the compressive strength of cement matrices formed from nano-Fe(OH)₃ slurries prepared using M3 and having 0.270% (A), 0.660% (B) and 1.200% (C) BWOC nano-Fe(OH)₃; FIG. 10 also shows the compressive strength of a cement matrix formed from Class G slurry (CS, D) for reference. FIGS. 8-10 confirm that, among the different contents tested in this study, 0.660% BWOC of NPs presents a good balance between the cost of NPs and product quality, regardless of in situ synthetic protocol.

Results Product characterization

[0081] SEM along with EDX were used to study the morphology of CS, NP₃ and NP_3.2 cured samples. FIG. 11 shows, for a cement matrix formed from CS slurry, an EDX image with bright regions indicative of aluminum (top left), an EDX image with bright regions indicative of iron (top right) and an SEM image (bottom). FIG. 12 shows, for a cement matrix formed from NP₃,_I slurry, an EDX image with bright regions indicative of aluminum (top left), an EDX image with bright regions indicative of iron (top right) and an SEM image (bottom). FIG. 13 shows, for a cement matrix formed from NP_3.2 slurry, an EDX image with bright regions indicative of aluminum (top left), an EDX image with bright regions indicative of iron (top right) and an SEM image (bottom). From the EDX results, it can be noticed that there is a correlation between the content of iron and aluminum in the nano-Fe(OH)₃ samples (NP₃,_I and NP₃,₂). Such a correlation is not as strong in class G control sample (CS), where native iron exists. SEM was used to investigate the morphology of the samples in areas of overlap between iron and aluminum. As shown in the SEM images, the length of the aluminosilicate crystals in CS is larger than their length in the samples containing NP₃ and NP₃ 2. Traces of iron NPs with an average size between 30 - 50 nm were observed to be attached to those crystals. Thus, these NPs could be the reason behind the inhibition of cement crystal growth causing the cement matrix to be more compact, hence the increase in compressive strength.

Results Porosity and Permeability

[0082] Porosity and permeability measurements were conducted for NP_3,I, NP_3.2. NP_{3 3} and CS cured samples. FIG. 14 is a graph displaying the porosity (%) of CS, NP_3,I, NP_{3 2}, NP_{3 3}, respectively, from left to right. FIG. 15 is a graph displaying the permeability (mD) of CS, NP_3,I, NPs; . NP_{3 3}, respectively, from left to right. The Fe(OH)₃ NPs prepared in situ via Ml (NP_3,i) exhibited porosity and permeability values 5% and 52% lower than the CS sample, respectively. The Fe(OH)₃ NPs prepared in situ via M2 (NP_{3 2}) exhibited porosity and permeability values 7% and 10% lower than the CS sample, respectively. The Fe(OH)₃ NPs prepared in situ via M3 (NP_{3 3}) exhibited porosity and permeability values 48% and 93% lower than the CS sample, respectively.

Results Cyclic compressive stress resistance

[0083] Triaxial compressive stress testing was conducted on three cement matrices. The first matrix was formed from a nano-Fe(OH)₃ cement slurry formed according to Ml (NP₃4). The second matrix was formed from a nano-Fe(OH)₃ cement slurry formed according to M2 (NP_{3 2}). The third matrix was prepared from a class G cement slurry (CS). FIG. 16 shows CS suffered fatigue after 10 compression cycles (B) which caused it to fail before reaching its original maximum strain (A). As shown in FIG. 17, unlike the CS cement matrix, the NP₃ cement matrix resisted the cyclical compression (10 cycles, B) and maintained its original peak strain (A). Also as shown in FIG. 18, unlike the CS cement matrix, the NP_3.2 cement matrix resisted the cyclical compression (10 cycles, B) and maintained its original peak strain (A). Thus, it can be concluded that the in situ prepared Fe(OH)₃ NPs enhanced the durability of the resulting cement matrix and increased resistance to fatigue.

[0084] Results Experimental observations

[0085] This disclosure teaches various methods for the large-scale synthesis and application of NPs in cement slurries for strengthening resultant cured cement matrices. The cost of NPs and their state of dispersion have been addressed by in situ preparation of the particles from their inexpensive water-soluble precursors. The effect of in situ prepared NPs on compressive strength, cyclical compressive stress, porosity and permeability was studied. While not limiting the scope of the invention in any way, the in situ preparation of Fe(OH)₃ NPs in cement slurries was found particularly effective. Slurries containing in situ Fe(OH)₃ NPs exhibited significant enhancement in compressive strength regardless of the synthesis method. Those slurries also showed higher resistance to cyclic compressive stress and reductions in porosity and permeability. The effectiveness of Fe(OH)₃ based slurries can be attributed to the slower kinetics of growth/aggregation of the Fe(OH)₃ particles which allowed the Fe(OH)₃ NPs to remain suspended and well dispersed within the slurry without any dispersing agents. In situ prepared Fe(OH)₃ NPs also affect the cement structure by hindering the growth of long cement crystals making the cement matrix more compact as well as through acting as a filler reducing porosity and permeability while providing support preventing the collapse of pore throats. [0086] Successful implementation of the techniques presented presents an opportunity for reliable cement sheath for better zonal isolation (i.e. better protection of ground water), less cement requirement (hence, reduced cost and GHG footprint associated with cement manufacturing) as well as less load on earth associated with the mass of cement used.

[0087] Although the above results demonstrate the applicability of in situ prepared NPs to class G cement, the methods of in situ preparation of NPs described herein are applicable to all other classes and types of cementing compositions previously identified.

[0088] STATEMENTS OF THE DISCLOSURE

[0089] Statement 1: A composition of matter, the composition comprising a cement powder; a first nanoparticle precursor; and a second nanoparticle precursor.

[0090] Statement 2: A composition according to Statement 1, further comprising water.

[0091] Statement 3: A composition according to Statement 2, wherein the water is any one of freshwater, purified water, de-ionized water, seawater, brine, and brackish water.

[0092] Statement 4: A composition according to Statement 2 or 3, wherein the composition has a water to cement powder ratio ranging from about 0.1 : 1 to about 1 : 1 by weight.

[0093] Statement 5: A composition according to any one of Statements 1-4, further comprising a dispersion aid.

[0094] Statement 6: A composition according to any one of Statements 1-5, wherein the composition has a nanoparticle precursors to cement powder ratio ranging from about 0.01:99.91 to about 20:80 by weight.

[0095] Statement 7: A multi-component system for making a cement slurry, the system comprising a first aqueous solution comprising a first water soluble nanoparticle precursor; a second aqueous solution comprising a second water soluble nanoparticle precursor; and a cement powder.

[0096] Statement 8: A system according to Statement 7, wherein one or both of the first aqueous solution and the second aqueous solution further comprises a dispersion aid.

[0097] Statement 9: A system according to Statement 7 or 8, wherein the cement powder comprises a dispersion aid.

[0098] Statement 10: A system according to any one of Statements 7-9, wherein the system has a water to cement powder ratio ranging from about 0.1 : 1 to about 1 : 1 by weight. [0099] Statement 11 : A system according to any one of Statements 7-10, wherein the system has a nanoparticle precursors to cement powder ratio ranging from about 0.01 :99.91 to about 20:80 by weight.

[00100] Statement 12: A multi-component system for making a cement slurry, the system comprising an aqueous solution comprising a first water soluble nanoparticle precursor and a second water soluble nanoparticle precursor; and a cement powder.

[00101] Statement 13: A system according to Statement 12, wherein the aqueous solution further comprises a dispersion aid.

[00102] Statement 14: A system according to Statement 12 or 13, wherein the powder comprises a dispersion aid.

[00103] Statement 15: A system according to any one of Statements 12-14, wherein the system has a water to cement powder ratio ranging from about 0.1 : 1 to about 1 : 1 by weight.

[00104] Statement 16: A system according to any one of Statements 12-15, wherein the system has a nanoparticle precursors to cement powder ratio ranging from about 0.01 :99.91 to about 20:80 by weight.

[00105] Statement 17: A multi-component system for making a cement matrix, the system comprising: a first cement slurry comprising a first cement powder, a first nanoparticle precursor, and water; and a second cement slurry comprising a second cement powder, a second nanoparticle precursor, and water.

[00106] Statement 18: A system according to Statement 17, further comprising a dispersion aid in one or both of the first cement slurry and the second cement slurry.

[00107] Statement 19: A system according to Statement 17 or 18, wherein one or both of the first cement slurry and the second cement slurry has a water to cement powder ratio ranging from about 0.1 : 1 to about 1 : 1 by weight.

[00108] Statement 20: A system according to any one of Statements 17-19, wherein one or both of the first cement slurry and the second cement slurry has a nanoparticle precursors to cement powder ratio ranging from about 0.01 :99.91 to about 20:80 by weight.

[00109] Statement 21 : A method of making a cement slurry, the method comprising adding a cement powder, a first nanoparticle precursor and a second nanoparticle precursor to water; and mixing the cement powder, the first nanoparticle precursor and the second nanoparticle precursor in the water to form a cement slurry. [00110] Statement 22: A method according to Statement 21, wherein the water is any one of freshwater, purified water, de-ionized water, seawater, brine, and brackish water.

[00111] Statement 23: A method according to Statement 21 or 22, wherein the cement powder comprises a dispersion aid.

[00112] Statement 24: A method according to any one of Statements 21-23, further comprising adding a dispersion aid to the water.

[00113] Statement 25: A method according to any one of Statements 21-24, wherein adding the cement powder, the first nanoparticle precursor and the second nanoparticle precursor to water comprises adding the first nanoparticle precursor to a first amount of water to form a first nanoparticle precursor-containing aqueous solution; adding the second nanoparticle precursor to a second amount of water to form a second nanoparticle precursor-containing aqueous solution; combining the first nanoparticle precursor-containing aqueous solution and the second nanoparticle precursor-containing aqueous solution; and adding a cement powder to the combined first and second nanoparticle precursor-containing aqueous solutions.

[00114] Statement 26: A method according to any one of Statements 21-24, wherein adding the cement powder, the first nanoparticle precursor and the second nanoparticle precursor to water comprises adding the first nanoparticle precursor to a first amount of water to form a first nanoparticle precursor-containing aqueous solution; adding a first amount of the cement powder to the first nanoparticle precursor-containing aqueous solution to form a first nanoparticle precursor-containing cement slurry; adding the second nanoparticle precursor to a second amount of water to form a second nanoparticle precursor-containing aqueous solution; adding a second amount of the cement powder to the second nanoparticle precursor- containing aqueous solution to form a second nanoparticle precursor-containing cement slurry; and combining the first nanoparticle precursor-containing cement slurry and the second nanoparticle precursor-containing cement slurry.

[00115] Statement 27: A method according to Statement 26, wherein the first amount of water and the second amount of water are the same amount.

[00116] Statement 28: A method according to Statement 26 or 27, wherein a ratio of the first amount of water to the second amount of water ranges from about 5:95 to about 49:51.

[00117] Statement 29: A method according to any one of Statements 26-28, wherein the first amount of the cement powder and the second amount of the cement powder are the same amount. [00118] Statement 30: A method according to any one of Statements 26-29, wherein a ratio of the first amount of the cement powder to the second amount of the cement powder ranges from about 5:95 to about 49:51.

[00119] Statement 31: A method according to any one of Statements 21-24, wherein adding the cement powder, the first nanoparticle precursor and the second nanoparticle precursor to water comprises mixing the cement powder, the first nanoparticle precursor and the second nanoparticle precursor to form a nanoparticle precursors-cement powder mixture; and adding the nanoparticle precursors-cement powder mixture to the water.

[00120] Statement 32: method according to any one of Statements 21-24, wherein adding the cement powder, the first nanoparticle precursor and the second nanoparticle precursor to water comprises adding a first nanoparticle precursor to water to form a first nanoparticle precursor-containing aqueous solution; adding a first amount of the cement powder to the first nanoparticle precursor-containing aqueous solution to form a first nanoparticle precursor-containing cement slurry; and adding a second nanoparticle precursor to the first nanoparticle precursor-containing cement slurry to form a nanoparticle precursors-containing cement slurry.

[00121] Statement 33: A method according to Statement 32, further comprising adding a second amount of the cement powder to the nanoparticle precursors-containing cement slurry.

[00122] All publications, patents and patent applications cited herein are hereby incorporated by reference as if set forth in their entirety herein. While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass such modifications and enhancements.

Claims

CLAIMS What is claimed is:

1. A composition of matter, the composition comprising:

a cement powder;

a first nanoparticle precursor; and

a second nanoparticle precursor.

2. The composition of claim 1, further comprising water.

3. The composition of claim 2, wherein the water is any one of freshwater, purified water, de ionized water, seawater, brine, and brackish water.

4. The composition of claim 2, wherein the composition has a water to cement powder ratio ranging from about 0.1 : 1 to about 1 : 1 by weight.

5. The composition of claim 1, further comprising a dispersion aid.

6. The composition of claim 1, wherein the composition has a nanoparticle precursors to cement powder ratio ranging from about 0.01 :99.91 to about 20:80 by weight.

7. A multi-component system for making a cement slurry, the system comprising:

a first aqueous solution comprising a first water soluble nanoparticle precursor; a second aqueous solution comprising a second water soluble nanoparticle precursor; and

a cement powder.

8. The system of claim 7, wherein

one or both of the first aqueous solution and the second aqueous solution further comprises a dispersion aid; or

the cement powder comprises a dispersion aid.

9. The system of claim 7, wherein the system has a water to cement powder ratio ranging from about 0.1 : 1 to about 1 : 1 by weight.

10. The composition of claim 7, wherein the system has a nanoparticle precursors to cement powder ratio ranging from about 0.01 :99.91 to about 20:80 by weight.

11. A multi-component system for making a cement slurry, the system comprising:

an aqueous solution comprising a first water soluble nanoparticle precursor and a second water soluble nanoparticle precursor; and

a cement powder.

12. The system of claim 11, further comprising a dispersion aid in the aqueous solution or the cement powder.

13. The system of claim 11, wherein the system has a water to cement powder ratio ranging from about 0.1 : 1 to about 1 : 1 by weight.

14. The composition of claim 11, wherein the system has a nanoparticle precursors to cement powder ratio ranging from about 0.01 :99.91 to about 20:80 by weight.

15. A multi-component system for making a cement matrix, the system comprising:

a first cement slurry comprising:

a first cement powder;

a first nanoparticle precursor; and

water; and

a second cement slurry comprising:

a second cement powder;

a second nanoparticle precursor; and

water.

16. The system of claim 15, further comprising a dispersion aid in one or both of the first cement slurry and the second cement slurry.

17. The system of claim 15, wherein one or both of the first cement slurry and the second cement slurry has a water to cement powder ratio ranging from about 0.1: 1 to about 1 : 1 by weight.

18. The composition of claim 15, wherein one or both of the first cement slurry and the second cement slurry has a nanoparticle precursors to cement powder ratio ranging from about 0.01:99.91 to about 20:80 by weight.

19. A method of making a cement slurry, the method comprising:

adding a cement powder, a first nanoparticle precursor and a second nanoparticle precursor to water; and

mixing the cement powder, the first nanoparticle precursor and the second nanoparticle precursor in the water to form a cement slurry.

20. The method of claim 19, wherein the water is any one of freshwater, purified water, de ionized water, seawater, brine, and brackish water.

21. The method of claim 19, further comprising adding a dispersion aid to the water.

22. The method of claim 19, wherein adding the cement powder, the first nanoparticle precursor and the second nanoparticle precursor to water comprises:

adding the first nanoparticle precursor to a first amount of water to form a first nanoparticle precursor-containing aqueous solution;

adding the second nanoparticle precursor to a second amount of water to form a second nanoparticle precursor-containing aqueous solution;

combining the first nanoparticle precursor-containing aqueous solution and the second nanoparticle precursor-containing aqueous solution; and

adding a cement powder to the combined first and second nanoparticle precursor- containing aqueous solutions.

23. The method of claim 19, wherein adding the cement powder, the first nanoparticle precursor and the second nanoparticle precursor to water comprises:

adding the first nanoparticle precursor to a first amount of water to form a first nanoparticle precursor-containing aqueous solution;

adding a first amount of the cement powder to the first nanoparticle precursor- containing aqueous solution to form a first nanoparticle precursor-containing cement slurry; adding the second nanoparticle precursor to a second amount of water to form a second nanoparticle precursor-containing aqueous solution;

adding a second amount of the cement powder to the second nanoparticle precursor- containing aqueous solution to form a second nanoparticle precursor-containing cement slurry; and

combining the first nanoparticle precursor-containing cement slurry and the second nanoparticle precursor-containing cement slurry.

24. The method of claim 23, wherein the first amount of water and the second amount of water are the same amount.

25. The method of claim 23, wherein a ratio of the first amount of water to the second amount of water ranges from about 5:95 to about 49:51.

26. The method of claim 23, wherein the first amount of the cement powder and the second amount of the cement powder are the same amount.

27. The method of claim 23, wherein a ratio of the first amount of the cement powder to the second amount of the cement powder ranges from about 5:95 to about 49:51.

28. The method of claim 19, wherein adding the cement powder, the first nanoparticle precursor and the second nanoparticle precursor to water comprises:

mixing the cement powder, the first nanoparticle precursor and the second nanoparticle precursor to form a nanoparticle precursors-cement powder mixture; and

adding the nanoparticle precursors-cement powder mixture to the water.

29. The method of claim 19, wherein adding the cement powder, the first nanoparticle precursor and the second nanoparticle precursor to water comprises:

adding a first nanoparticle precursor to water to form a first nanoparticle precursor- containing aqueous solution;

adding a first amount of the cement powder to the first nanoparticle precursor- containing aqueous solution to form a first nanoparticle precursor-containing cement slurry; and adding a second nanoparticle precursor to the first nanoparticle precursor-containing cement slurry to form a nanoparticle precursors-containing cement slurry.

30. The method of claim 29, further comprising:

adding a second amount of the cement powder to the nanoparticle precursors- containing cement slurry.