BACKGROUND

[0001] Carbon dioxide (CO2) is the most commonly produced greenhouse gas and a contributor to global climate change. Capturing and reacting CO2 into solid carbonates is one of the most effective methods of reducing the amount of carbon dioxide in the atmosphere with the goal of reducing global climate change.

[0002] Recent efforts have been directed toward curing concrete in a CO2 environment to make use of the cement hydration byproduct Ca(OH)2 to form CaCOs in an effort to react/remove atmospheric CO2. Conventional cement curing processes involve treating a cement composition with steam, optionally in an atmospheric CO2 containing environment. This process is rate limited by the diffusion of CO2 gas penetrating through cement from the outer surface to the center. The major disadvantage of the conventional process is that the process is diffusion limited and therefore, slow. Further, the process in inefficient as only a small percentage of CO2 provided during the curing can be reacted into the curing cement.

SUMMARY

[0003] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

[0004] In one aspect, embodiments disclosed herein relate to a cement emulsion comprising a cement, water, and carbon dioxide. In one or more embodiments, the carbon dioxide is liquid or super critical and dispersed in the cement emulsion composition.

[0005] In another aspect, embodiments disclosed herein relate to a method of producing a cement emulsion composition. Methods include mixing a cement and water to form a hydrated cement composition, and emulsifying the hydrated cement composition with liquid or supercritical CO2. [0006] In another aspect, embodiments disclosed herein relate to articles formed from or comprising the cement emulsion composition.

[0007] In another aspect, embodiments disclosed herein relate to a method of treating a wellbore, comprising mixing a cement and water to form a hydrated cement composition, and emulsifying the hydrated cement composition with liquid or supercritical CO2 and pumping the cement emulsion composition into the wellbore.

[0008] In yet another aspect, embodiments disclosed herein relate to a method of manufacturing an article. Methods include mixing a cement and water to form a hydrated cement composition, and emulsifying the hydrated cement composition with liquid or supercritical CO2 and 3D printing the cement emulsion composition to produce the article. Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

[0009] FIG. 1 is a schematic of conventional steam and carbon dioxide cement curing processes.

[0010] FIG. 2 is a comparison of the compressive strength of steam-cured cement vs steam- and CO2- cured cement.

[0011] FIG. 3 is a diagram of an apparatus for the production of a cement emulsion composition.

DETAILED DESCRIPTION

[0012] Embodiments of the present disclosure generally relate to cement emulsion compositions which are advantageously cured by emulsifying with liquid or supercritical carbon dioxide. Herein, cement emulsion refers to a composition comprising at least a cementious continuous and a liquid or supercritical dispersed phase. The diffusion of gaseous carbon dioxide into a hydrated cement mixture is a slow and inefficient process for curing a cement composition. Dispersing liquid or supercritical carbon dioxide homogeneously throughout a cement emulsion via an emulsifying process and maintaining the composition under sufficient pressure enhances the curing process. Fig. 1 illustrates a general process for the production of a hydrated cement composition from at least a cement and water and subsequently curing the cement compositions. Compositions cured via steam-only require significantly longer cure times. Further, carbon dioxide-reactive additives may be introduced to improve properties of the cured cement, such as the storage modulus or the elasticstorage component of the shear modulus. Cement emulsion compositions according to embodiments of the present disclosure may also be 3D printed or pumped downhole for use in a wellbore.

[0013] Cement Emulsion Composition

[0014] Embodiments disclosed herein relate to a cement emulsion composition comprising a cement, water, and liquid or supercritical carbon dioxide. The cement is not particularly limited and may be a Portland or non-Portland cement. The Portland cement may be, for example, a Class G or Class H cement when used downhole. Examples of suitable non-Portland cements may include but are not limited to high alumina cement, Sorel cement, and geopolymeric cement. In one or more embodiments, the amount of cement may have a lower limit of 20%, 30%, 40%, or 50% and an upper limit of 50%, 60% or 70% by total weight of the composition, where any lower limit may be used in combination with any upper limit.

[0015] The cement is hydrated with water and upon hydration forms calcium hydroxide, Ca(OH)2. The water may comprise salts, metals, organics, or other common impurities. In one or more embodiments, the amount of water may have a lower limit of 15%, 20%, 30%, or 40% and an upper limit of 30%, 40%, 50%, 60%, 70% or 80% by total weight of the composition, where any lower limit may be used in combination with any upper limit.

[0016] The calcium hydroxide formed from hydration of the cement is reacted with carbon dioxide to form calcium carbonate, CaCCE. To maintain the dispersion of the carbon dioxide throughout the composition, the composition is maintained during cure at a pressure and temperature sufficient to ensure the carbon dioxide remains liquid or supercritical. In one or more embodiments, the amount of carbon dioxide may have a lower limit of 1%, 2%, 3%, 5%, 7.5%, 10%, 12.5%, 15%, or 20%, and an upper limit of 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% by total weight of the composition, where any lower limit may be used in combination with any upper limit. [0017] In one or more embodiments, cement emulsion compositions according to the present disclosure may comprise one or more additives. Additives according to the present disclosure may include, but are not limited to crystalline silica, dispersants, retarders, surfactants, fluid loss control compounds, viscosifiers, weighting agents, CO2 reactive compounds, and combinations thereof.

[0018] Crystalline Silica

[0019] In embodiments, the cement emulsion composition may comprise crystalline silica particles for high temperature applications. Crystalline silica may be used when the composition is to be used in temperatures exceeding a lower limit of 110 °C. The size and distribution of the crystal silica particles used may vary widely, and in some embodiments may have an average size ranging from a lower limit of any one of 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 1 pm, 10 pm, 25 pm, and 50 pm, to an upper limit of any one of 800 nm, 1 pm, 2 pm, 5 pm, 10 pm, 25 pm, 50 pm, 75 pm, and 100 pm, where any lower limit may be used in combination with any appropriate upper limit. In one or more embodiments, the amount of crystalline silica may have a lower limit of 5%, 10%, 20%, 30%, or 35% and an upper limit of 40%, 50%, 60%, or 70% by total weight of cement, where any lower limit may be used in combination with any upper limit.

[0020] Dispersants

[0021] In embodiments, the cement emulsion composition may comprise dispersants. Dispersants, or friction reducers, may be used to modify or improve the rheological properties of the cement emulsion composition. Dispersants may be lignosulfonates, melamine-formaldehydes, or poly carboxylates. Examples of suitable dispersants may include but are not limited to poly carboxylate ether, such as Ethacryl G™ manufactured by Coatex, USA; or NC-S-1, SC-8, and SC-9 from Fritz Industries. In one or more embodiments, the amount of dispersants may have a lower limit of 0.1%, 0.5%, 1% or 2% and an upper limit of 3%, 4%, or 5% by total weight of cement, where any lower limit may be used in combination with any upper limit.

[0022] Retarders [0023] In embodiments, the cement emulsion composition may comprise retarders. Retarders may be used to delay the cure, or hardening, of the cement emulsion composition. Retarders may be lignosulfonates, or AMPS-AA (co-polymer of 2- acrylamido-2-methylpropane sulfonic acid and acrylic acid) or AMPS-AA-IA(co- polymer of 2-acrylamido-2-methylpropane sulfonic acid, acrylic acid and itaconic Acid) polymer. Examples of suitable retarders may include but are not limited to FR- 1, FR-2, PCR-3, PCR-4, and SR-I from Fritz Industries. In one or more embodiments, the amount of retarders used may have a lower limit of 0.1%, 0.5%, 1% or 2% and an upper limit of 3%, 4%, or 5% by total weight of cement, where any lower limit may be used in combination with any upper limit.

[0024] Accelerators

[0025] In embodiments, the cement emulsion composition may comprise accelerators. Accelerators may be used to increase the rate of curing, and speed hardening, of the cement emulsion composition. Accelerators may include CaCh and NaCl. In one or more embodiments, the amount of accelerators used may have a lower limit of 0.1%, 0.5%, 1% or 2% and an upper limit of 3%, 4%, or 5% by total weight of cement, where any lower limit may be used in combination with any upper limit.

[0026] Surfactants

[0027] In embodiments, the cement emulsion composition may comprise surfactants. Surfactants may be used to stabilize the dispersed phase and improve emulsification of the carbon dioxide. Surfactants used may be traditional, CCh-philic, or CCh-reactive molecules. Particularly, CCh-philic surfactants may improve dispersion uniformity. Suitable surfactants may be anionic, cationic, or non-ionic. Examples of suitable surfactants may include but are not limited to sodium dodecyl sulfate (SDS), sodium lauryl sulfate (SLS), sodium lauryl ether sulfate (SLES), alcohol ethoxy sulfate (AES), alpha olefin sulfonate (AOS), sodium oleate, sulphanol, cetyltrimethyl ammonium bromide (CTAB), cetrimide, neopor, microair, cocodi ethanol ami de (CDA), or hydrolyzed protein such as albumin. In one or more embodiments, the amount of surfactants used may have a lower limit of 1%, 2%, 3%, 4%, or 5% and an upper limit of 6%, 7%, 8%, 9%, or 10% by total weight of cement, where any lower limit may be used in combination with any upper limit. [0028] Fluid Loss Control Compounds

[0029] In embodiments, the cement emulsion composition may comprise fluid loss control compounds. Fluid loss control compounds may be used to maintain a suitable liquid/solid ratio in the cement emulsion composition. Examples of suitable fluid loss control compounds may include but are not limited to AMPS-NNDMA (co-polymer of 2-acrylamido-2 -methylpropane sulfonic acid and N,N dimethyl acrylamide) and AMPS-NNDMA-AA(co-polymer of 2-acrylamido-2-methylpropane sulfonic acid, N,N dimethyl acrylamide and acrylic Acid) polymers. In one or more embodiments, the amount of fluid loss control compounds used may have a lower limit of 0.1%, 0.5%, 1% or 2% and an upper limit of 3%, 4%, or 5% by total weight of cement, where any lower limit may be used in combination with any upper limit.

[0030] Viscosifiers

[0031] In embodiments, the cement emulsion composition may comprise viscosifiers. Viscosifiers may be used to increase the viscosity of the cement emulsion composition. Examples of suitable viscosifiers may include but are not limited to hydroxyethyl cellulose (HEC) and diutane. In one or more embodiments, the amount of viscosifiers used may have a lower limit of 0.1%, 0.5%, 1% or 2% and an upper limit of 3%, 4%, or 5% by total weight of cement, where any lower limit may be used in combination with any upper limit.

[0032] Weighting Agents

[0033] In embodiments, the cement emulsion composition may comprise weighting agents. Weighting agents may be high-density materials used for increasing the density of the cement emulsion composition. Examples of suitable weighting agents used may include but are not limited to iron oxide, manganese oxide, barium sulfate and bentonite clays. In one or more embodiments, the amount of weighting agents may have a lower limit of 5%, 10%, 20%, 30%, 40%, or 50% and an upper limit of 50%, 70%, 90%, 110%, 130%, or 150% by total weight of cement, where any lower limit may be used in combination with any upper limit.

[0034] Light Weight Additives [0035] In embodiments, the cement emulsion composition may comprise light weight agents or additives. Light weight additives may be low-density materials used for decreasing the density of the cement emulsion composition. Examples of suitable light weight additives may include but are not limited to 3M™ glass beads having various specific gravity and cenospheres. The light weight additives may have a density ranging from a lower limit of 0.1 g/cm ³ , 0.2 g/cm ³ , or 0.3 g/cm ³ to an upper limit of 0.4 g/cm ³ , 0.5 g/cm ³ , or 0.6 g/cm ³ , where any lower limit may be used in combination with any upper limit. The light weight additives may have a particle size ranging from a lower limit of 10 pm, 20 pm, 30 pm, 40 pm, or 50 pm to an upper limit of 50 pm, 60 pm, 70 pm, 80 pm, 90 pm, or 100 pm where any lower limit may be used in combination with any upper limit. In one or more embodiments, the amount of weighting agents may have a lower limit of 5%, 10%, 20%, 30%, 40%, or 50% and an upper limit of 50%, 70%, 90%, 110%, 130%, or 150% by total weight of cement, where any lower limit may be used in combination with any upper limit.

[0036] CO 2 Reactive Compounds

[0037] In embodiments, the cement emulsion composition may comprise CO2 reactive compounds. CO2 reactive compounds may be either organic or inorganic compounds or materials. Organic materials such as miktoarm star polymers may self-assemble to form micelles in water upon hydration and transform into nanoribbons upon exposure to CO2. The inclusion of such polymers can reinforce the elastic - storage component of the shear modulus of the cement emulsion and aid in CO2 uptake in the cement emulsion. Inorganic compounds reactive with CO2 may also aid in the uptake of CO2 in the cement emulsion. Examples of suitable CO2 reactive compounds may include but are not limited to star-[poly(ethylene glycol)-polystyrene-poly[2-(N,N- diethylamino)ethyl methacrylate]](p-PEG-PS-PDEA), calcium hydroxide (Ca(OH)2), magnesium oxide (MgO), and forsterite (Mg2SiO4). In one or more embodiments, the amount of CO2 reactive compounds used may have a lower limit of 5%, 10%, 20%, or 30% and an upper limit of 40%, 50%, 60%, or 70% by total weight of cement, where any lower limit may be used in combination with any upper limit.

[0038] In one or more embodiments, upon combination of the appropriate components detailed above, the composition may be mixed with liquid or supercritical carbon dioxide via an emulsifying process to form a cement emulsion composition. The cement emulsion composition may have a density of 30 to 60 kg/m ³ .

[0039] In one or more embodiments, the cement emulsion composition may be maintained at a temperature and pressure sufficient to maintain the carbon dioxide in a liquid or supercritical state to form a cured cement composition. Cured cement compositions according to the present disclosure may have a compressive strength of at least 23 MPa after 8 hours, and of at least 37 MPa after 3 days. Cured cement compositions according to the present disclosure may have a density of 6 to 22 ppg.

[0040] Method of Producing a Cement Emulsion Composition

[0041] Embodiments according to the present disclosure relate to a method of producing a cement emulsion composition. Generally, the cement and dry additives are dry blended to form a dry blend. The liquid additives are mixed with the water. The dry blend is mixed with the water to form a hydrated cement composition. Referring to Fig. 3, the dry blend may be provided in a cementing unit 1. To the cementing unit may be added the liquid components to form the hydrated cement composition. The super critical carbon dioxide may be provided by a supercritical carbon dioxide unit 2. The hydrated cement composition and the supercritical carbon dioxide are each flowed to an emulsion generator 3 and mixed. Mixing may be performed with a high speed (greater than 1000 RPM) mechanical blender that works under pressure. The hydrated cement composition is emulsified with compressed CO2 in the emulsion generator 3 to achieve the desired cement emulsion composition density.

[0042] Method o f Treating a Wellbore

[0043] Embodiments according to the present disclosure relate to a method of treating a wellbore with a cement emulsion composition. A cement emulsion composition is produced according to the method detailed above. Once the desired cement emulsion density is achieved, the cement emulsion composition is pumped downhole into a wellbore. The cement emulsion composition is maintained at a temperature and pressure sufficient to maintain the carbon dioxide in a liquid or supercritical state until the cement emulsion composition is cured.

[0044] Article [0045] Embodiments according to the present disclosure relate to articles comprising the cement emulsion composition. Articles may be formed entirely or partly of the cement emulsion composition and allowed to cure to form a desired article. Examples may include, but are not limited to bricks, concrete structures, and specially designed patterns for surface or downhole use.

[0046] Method of Producing an Article

[0047] Embodiments according to the present disclosure relate to a method of producing an article. In one or more embodiments the cement emulsion composition is produced according to embodiments of the present disclosure. The cement emulsion composition may be provided in a 3D printing apparatus to be 3D printed. A high- pressure 3D printer, in which CO2 gas/liquid is emulsified under pressure using a highspeed mechanical blender before entering into the 3D printing tip may be used. The cement emulsion composition may be extruded from the 3D printing apparatus into an ambient atmosphere. According to one or more embodiments, the cement emulsion composition may be 3D printed under sufficient temperature and pressure to maintain the carbon dioxide in a liquid or supercritical state. In both the ambient and pressurized embodiments, the presence of water may assist in the kinetics of the lime-carbonation reaction. Water may be included with the carbon dioxide to improve the curing reaction.

[0048] EXAMPLES

[0049] Example 1

[0050] A cement emulsion composition was prepared according to embodiments of the present disclosure comprising:

Cement - 700 g

Water - 308 g

Suspending aid - 1.5 g

Foaming agent - 7 g

Liquid CO ₂ - 132.3 g

The cement emulsion composition was cured at 180 °F and 3000 psi for 3 days.

The cured cement composition exhibited a compressive strength of 4300 psi. [0051] Comparative Example 1

[0052] A cement emulsion composition was prepared according to Example 1 using the following amounts, except the composition was steam cured.

Cement - 700 g

Water - 308 g

Suspending aid - 1.5 g

The steam-cured cement composition was cured at 180 °F and 3000 psi for 3 days.

The steam-cured cement composition exhibited a compressive strength of 3300 psi.

[0053] Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.