High thermal conductivity slurry composition and method thereof

Abstract

The present invention provides various high thermal conductivity slurry compositions and methods for producing pressurized slurries that form such high thermal conductivity compositions. [Solution] A high thermal conductivity slurry composition is provided. This composition comprises a slurry mixture containing a high thermal conductivity material and an optional dispersant. The high thermal conductivity material is in the form of a plurality of particles having a broad particle size distribution over at least two logarithmic units. The high thermal conductivity material is present in an amount effective enough for the slurry composition to have a thermal conductivity of at least 3 W / m°K when the slurry mixture is compressed or settled at a target location.

Description

Technical Field

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 305,639, filed on Feb. 1, 2022, which is incorporated herein by reference.

[0002] The field of the present invention is compositions and methods for heat transfer in geothermal heat recovery, and more particularly, compositions having high thermal conductivity that can be deployed / installed in ultra-high temperature wells.

Background Art

[0003] The background description includes information useful in understanding the present invention. It is not admitted that any of the information provided herein is prior art, or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0004] All publications and patent applications mentioned in this specification are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. In case the definition or use of a term in an incorporated reference contradicts or conflicts with the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

[0005] Geothermal wells have been used to provide heating and cooling systems that transfer heat between the ground and the earth. In a typical vertical well closed-loop system, two pipes joined by a U-shaped connector at the bottom, forming a continuous casing, are installed vertically in a well drilled into the ground (see U.S. Patent Application No. 2012 / 0247766). This type of system is commonly used for heating and cooling residential and commercial buildings. Here, a conventional grout mixture is clay-based and is pumped into the well to fill the annular space between the casing and the geological formation. As a result, the grout forms a seal to prevent contamination of groundwater and to prevent contamination of the subsurface from the surface. The grout mixture may further contain a thermally conductive material to assist in heat transfer between the working fluid in the casing and the target location, and the working fluid may circulate within the well loop to transfer heat to a heat exchanger on the ground surface.

[0006] In most cases, conventional grout mixtures harden in the presence of heat. However, conventional geothermal wells are shallow below the surface and are effective in providing heating or cooling to locations near the well (e.g., heat exchangers) through heat transfer, whereas geothermal well systems for geothermal power generation require considerable depth (e.g., at least 500 feet) underground and / or proximity to known geothermal hot zones (e.g., tectonic plate boundaries) to reach a suitable target location where the thermal energy required for power generation can be obtained. Such target locations can exhibit extreme temperatures (e.g., 300°C), which leads to premature hardening of conventional grout mixtures, generally failing to provide sufficiently high thermal conductivity, making power generation ineffective or even unfeasible.

[0007] Furthermore, because the grout mixture needs to harden after installation in conventional geothermal wells, the grout mixture typically contains a considerable amount of hardening material (e.g., cement-based material) for hardening. Unfortunately, these hardening materials do not exhibit high thermal conductivity, so even if the grout composition contains some thermally conductive material, a significant portion of the grout composition lacks thermal conductivity at best and acts as an insulator at worst. Consequently, all or almost all grout compositions formed from conventional grout mixtures cannot efficiently conduct the thermal energy necessary for power generation, nor can they maintain workability during construction at extreme temperatures (e.g., 300°C) near the target location for power generation (e.g., geothermal energy source).

[0008] Particulate mixtures that do not contain curable materials have been used for specific underground applications, such as sealing underground pipes (see, for example, U.S. Patents 6,715,543 and 7,258,174). Although these particulate mixtures do not contain curable materials, they lack high thermal conductivity and are generally unsuitable for application at extreme temperatures (e.g., 300°C) near the target location (e.g., geothermal energy source). On the other hand, certain grout mixtures are disclosed in U.S. Patent Application 2021 / 0071063, in which a curable component is combined with thermally conductive materials having multiple particle sizes to form a cured thermally conductive material with low water permeability. However, such mixtures still have relatively low thermal conductivity and are generally unsuitable for heat harvesting, where the extracted heat is used for power generation.

[0009] U.S. Patent Application 2011 / 0232858 teaches a system and method for extracting heat for power generation from high-temperature (e.g., 500°C) geological formations, in which one or more boreholes contain a thermally conductive compression packing material that conducts heat to a piping system at a target location. Here, the compression packing material is graphite formulated as powder or rods. To reduce the occurrence of voids that can act as insulation, the '858 application relies on high-pressure molding. Thus, while multiple and / or extensive carbon-filled conduits can be formed in the geological formation, heat transfer to the working fluid in a tube-in-tube system is typically limited to the end of the system (otherwise the compression pressure would crush the tube-in-tube system), thereby significantly reducing overall heat extraction. Heat extraction can be increased by using multiple graphite-filled channels converging in the tube-in-tube system, but such an increase increases operational complexity and cost.

[0010] Thus, despite the existence of various compositions for geothermal heat transfer known in the art, all or almost all of them suffer from several drawbacks. Therefore, the need for high thermal conductivity compositions and methods for their heat transfer remains. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] U.S. Patent Application No. 2012 / 0247766 [Patent Document 2] U.S. Patent No. 6,715,543 [Patent Document 3] U.S. Patent No. 7,258,174 [Patent Document 4] U.S. Patent Application No. 2021 / 0071063 [Patent Document 5] U.S. Patent Application No. 2011 / 0232858 [Overview of the Initiative] [Problems that the invention aims to solve]

[0012] The subject matter of this invention is directed toward various high thermal conductivity slurry compositions and methods for producing pumpable slurries that form such high thermal conductivity compositions. Advantageously, high thermal conductivity compositions are typically formed from non-cemental slurry mixtures and can be used in enclosure applications in heat extraction wells, particularly in closed-loop geothermal system wells for geothermal power generation. The envisioned high thermal conductivity compositions facilitate installation, advantageously improve heat transfer per unit length of the well from the target location, and maintain structural integrity even after seismic events. This improved heat transfer leads to greater uptake of thermal energy into the working fluid, increasing the profitability of the power generation well.

[0013] In one aspect of the subject matter of the present invention, the inventors envision a high thermal conductivity slurry composition comprising a slurry mixture. The slurry composition contains the high thermal conductivity material in the form of multiple particles having a broad particle size distribution that enables compact settling / compression at the target location, thereby thermally bonding with the formation by a casing and an optional dispersant. In various embodiments, the slurry mixture has a deposition rate of multiple particles that, upon addition of water, allows the particles to be pumped to the target location without substantially settling before reaching the target location.

[0014] The high thermal conductivity material is assumed to be in the form of multiple particles having a broad particle size distribution over at least two-logarithmic units or at least three-logarithmic units. In various embodiments, the broad particle size distribution is 0.1 μm to 5.0 mm. In further embodiments, the high thermal conductivity material is assumed to be present in an amount effective enough for the slurry composition to have a thermal conductivity of at least 3 W / m°K, at least 3 W / m°K, or at least 10 W / m°K when the slurry mixture is compressed or settled at the target position. Among other options, preferred high thermal conductivity materials include graphite powder, flaked graphite, pyrolysis graphite, desulfurized petroleum coke, graphene, fly ash, copper powder, aluminum nitride, and / or silicon carbide. Most typically, the high thermal conductivity material is present in the slurry mixture in an amount of at least 10 mass% or at least 30 mass% of volume. In certain embodiments, the slurry mixture may also contain at least one functional agent, such as plasticizers, surfactants, organic polymers, silica fillers, NaCl or KCl or other inorganic salts, and clay.

[0015] Referring to pumpable slurries, it is preferable that the pumpable slurry contains a high thermal conductivity slurry composition mixed with water. The pumpable slurry typically has a density of 10–30 pounds / gallon and / or a water content of 1–20 gallons / 100 pounds of high thermal conductivity material. As is readily apparent, the pumpable slurry may be produced by combining the high thermal conductivity slurry composition with a large amount of water, mixing the water with the high thermal conductivity slurry composition to form a pumpable slurry. In various embodiments, the amount of water is sufficient to produce a slurry density of 10–30 pounds / gallon. It is further assumed that the pumpable slurry may be supplied to a pump that pumps the pumpable slurry into the well. Most typically, the pumpable slurry is pumped into the well at a rate that allows for at least partial compression or sedimentation of the slurry mixture at the target location.

[0016] Referring to the installation of a high thermal conductivity composition, the installation method typically involves pumping a pumpable slurry to a target location having a target temperature of at least 300°C. The pumpable slurry is preferably delivered into an annular space between the well and a casing located within the well, thereby replacing the fluid in the annular space. In some embodiments, the target location may be at least 3,000 feet underground and / or extend substantially vertically.

[0017] The proposed method further includes a step of removing the replaced fluid through a return space located within the casing. The return space located within the casing may be surrounded by a secondary conduit located within the casing, and a second annular space may be formed between the casing and the secondary conduit. Therefore, in the step of removing the replaced fluid through the return space, a second fluid moving from the second annular space to the return space may be used.

[0018] The proposed method may further include the step of allowing a pumpable slurry to settle or compress in at least a portion of the annular space, thereby forming a high thermal conductivity composition within the well. The high thermal conductivity composition is intended to exchange heat with at least a portion of the casing and at least a portion of the surrounding geological formation. For this purpose, the pumpable slurry is allowed to be pumped to a predetermined location and, after pumping, undergo at least partial compression (by passive settling or active compression) at the target location.

[0019] In certain embodiments, the geological formation is assumed to include a number of cracks filled at least partially with a highly thermally conductive material, where the highly thermally conductive material within the cracks exchanges heat with a compressed highly thermally conductive composition within the well. Among other options, suitable highly thermally conductive materials within the cracks include graphite powder, flaked graphite, pyrolytic graphite, desulfurized petroleum coke, graphene, fly ash, copper powder, aluminum nitride, and silicon carbide.

[0020] Various objects, features, aspects, and advantages of the subject matter of the present invention will become more apparent from the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings in which like numerals represent like components.

Brief Description of the Drawings

[0021] [Figure 1] FIG. 1 is a schematic view showing an embodiment of a geothermal well including a shaft during installation of a pumpable slurry. [Figure 2] FIG. 2 is a schematic view showing an embodiment of the geothermal well of FIG. 1 after compression or sedimentation of at least a part of the pumpable slurry. [Figure 3] FIG. 3 is a schematic view showing an embodiment of the shaft and casing of FIG. 1 disposed in a geothermal well. [Figure 4] FIG. 4 is a schematic view showing another embodiment of the shaft and casing of FIG. 1 disposed in a geothermal well. [Figure 5] FIG. 5 is a schematic view showing still another embodiment of the shaft and casing of FIG. 1 disposed in a geothermal well.

Modes for Carrying Out the Invention

[0022] The inventors have discovered various compositions for high thermal conductivity slurries and methods for producing pumpable slurries, including the same, as well as methods for installing high thermal conductivity compositions, including the same. Advantageously, the high thermal conductivity slurry compositions are pumpable and formed from slurry mixtures that can be used for encasement applications in heat extraction wells, such as closed-loop geothermal system wells, and possess thermal conductivity suitable for power generation. Furthermore, the proposed compositions do not require hardening materials (e.g., cement-based materials), resulting in improved workability of the pumpable slurry, increased thermal efficiency of the high thermal conductivity composition, and increased power generation from the power generation well. Therefore, it should be understood that, in at least some embodiments, the proposed compositions do not exhibit hardening or curing due to hydration of cement-based materials. As a result, the proposed compositions remain deformable or movable without crack formation and / or loss of contact with the well or casing.

[0023] In the most typical embodiment of the subject matter of the present invention, the slurry mixture of a high thermal conductivity slurry composition comprises a high thermal conductivity material and an optional dispersant, wherein the high thermal conductivity material is in the form of multiple particles having a broad particle size distribution over at least 2-logarithmic units, at least 2.5-logarithmic units, or at least 3-logarithmic units. In this context, it should be understood that the broad particle size distribution of the high thermal conductivity material stabilizes the form or structure of the high thermal conductivity composition during compression or sedimentation of the slurry mixture without the use of a curable material (e.g., a cement-based material), thereby reducing the permeability of liquid through the high thermal conductivity composition compared to a composition containing particles with a narrow particle size distribution. As used herein, the terms “compression” and / or “settling” mean that a compressed or settled slurry mixture is movable in the presence of a considerable force (e.g., an earthquake) while (a) experiencing a decrease in water content of at least 1 mass%, 2 mass%, 3 mass%, 4 mass%, 5 mass%, 10 mass%, 20 mass%, 30 mass%, 40 mass%, 60 mass%, 70 mass%, 80 mass%, or 90 mass%, compared to the slurry mixture before compression or settling; (b) experiencing an increase in density of at least 1 mass%, 2 mass%, 3 mass%, 4 mass%, 5 mass%, 10 mass%, 15 mass%, 20 mass%, 30 mass%, 40 mass%, 50 mass%, 60 mass%, 70 mass%, 80 mass%, 90 mass%, 100 mass%, or more compared to the slurry mixture before compression or settling; or (c) experiencing both (a) a decrease in water content and (b) an increase in density. Furthermore, it should be noted that in one embodiment, the envisioned slurry composition may settle over time without requiring an active compression process, while in other embodiments, the slurry composition may be actively compressed (for example, by increasing the pressure at the target location).

[0024] The particle size distribution in a slurry mixture of high thermal conductivity materials can be represented by the concept of sorting. The concept of sorting may be a qualitative measure of the degree or range of variation in different particle sizes in a mixture of unconsolidated materials (e.g., the high thermal conductivity materials in the slurry mixture). A poorly sorted mixture of unconsolidated materials may contain a wide spectrum of particle sizes, such as particles in the particle size range of gravel, sand, silt, and clay. In comparison, a moderately sorted mixture of unconsolidated materials may contain a spectrum of small particle sizes, such as medium-grained or fine-grained sand, while a very well sorted lump may contain only one relatively homogeneous particle size, such as coarse silt. From the above viewpoint, a slurry mixture may contain a poorly sorted mixture of high thermal conductivity materials, which, when the slurry mixture is compressed or settled, exhibits a decrease in the permeability of the liquid through the high thermal conductivity composition compared to a composition containing particles with at least a moderately sorted mixture of unconsolidated materials. In various embodiments, the high thermal conductivity material can have an average particle size of 0.1 μm to 5.0 mm.

[0025] After compression or sedimentation of the slurry mixture, the high thermal conductivity material of the high thermal conductivity composition is expected to settle or be filled together in such a manner that the movement of fluid through the high thermal conductivity composition is minimized by the broad particle size distribution of the high thermal conductivity material. In various embodiments, the high thermal conductivity composition has a permeability of 1 darcy or less, 0.1 darcy or less, 0.01 darcy or less, 0.001 darcy or less, or 0.0001 darcy or less, according to ASTM D4630-19. According to ASTM D4630-19, 1 darcy is defined as a permeability of 1 cm in cross-sectional area at a pressure difference of 1 atm per cm length (1 atm / 1 cm). 2 Flow velocity per 1 cm 3 / s (1cm 3 / s / 1cm 2 ), corresponds to a fluid with a viscosity of 1 cp flowing through a porous medium. In that sense, this index should be considered a surrogate index of inter-particle contact (a smaller Darcy number indicates greater inter-particle contact), and by extension, it should be understood to represent the thermal conductivity between particles.

[0026] Regarding the particle size distribution of high thermal conductivity material particles, it is generally assumed that such a distribution is effective in forming a fluid seal in the annular space between the well and the casing of the heat harvester within the well. Typical particle size distributions are described in U.S. Patent Nos. 6,715,543 and 7,528,174, which are incorporated herein by reference. Therefore, it is generally preferable that the particles have an average particle size of 0.1 μm to 5 mm, and that at least 90% of the total particles have an average particle size that falls within a particle size range of at least two orders of magnitude, at least three orders of magnitude, or at least four orders of magnitude. For example, preferred average particle size ranges are 0.1 mm to 10 mm, or 50 μm to 5 mm, or 5 μm to 5 mm, or 1 μm to 1 mm, or 10 μm to 5 mm. Furthermore, the particle size distribution is such that at least 20% by mass, or at least 25% by mass, or at least 30% by mass, or at least 35% by mass, or at least 40% by mass of all particles fall within the lower 20%, lower 25%, or lower 35% of the particle size range, while at least 10% by mass, or at least 15% by mass, or at least 20% by mass, or at least 25%, or at least 30% by mass of all particles fall within the upper 15%, upper 20%, or upper 25% of the particle size range of all particles.

[0027] Therefore, by weight, the majority of particles (at least 51%, or at least 60%, or at least 70%, or at least 75%) are in the millimeter to sub-millimeter (but greater than or equal to 50 μm) particle size range, while the remainder of the particles are in the less than 50 μm particle size range. For example, about 80 percent of the total particle mass has average particle sizes of 0.5–1 mm, 0.25–0.5 mm, 0.125–0.25 mm, and 0.0625–0.125 mm, and about 20 percent of the total particle mass has average particle sizes in the 5–65 μm range, with about 50% of those being in the approximately 5 μm particle size range. From a different perspective, the particle size distribution is such that at least 45% by mass of all particles, or at least 50% by mass, or at least 55% by mass, or at least 60% by mass, have a 20 / 40 mesh size; at least 10% by mass of all particles, or at least 15% by mass, or at least 20% by mass, or at least 25% by mass, or at least 30% by mass, have a 100 mesh size; at least 7% by mass of all particles, or at least 10% by mass, or at least 12% by mass, or at least 15% by mass, or at least 20% by mass, have a 200 mesh size; and at least 2% by mass of all particles, or at least 3% by mass, or at least 4% by mass, or at least 5% by mass, or at least 7% by mass, have an average particle size of less than 25 μm.

[0028] Furthermore, since high thermal conductivity compositions are substantially free of curable materials (e.g., cement-based materials) in most embodiments, it should be recognized that they remain mobile and / or deformable in the presence of considerable forces (e.g., earthquakes, thermal expansion and / or contraction of the casing of a heat extraction device embedded in the high thermal conductivity material) to minimize damage to the geothermal well containing the high thermal conductivity composition. Such deformability is particularly beneficial when geological stresses or temperature fluctuations in the heat extraction structure would otherwise cause cracks in the cured or hardened material. Indeed, the mobility and / or deformability of the high thermal conductivity composition ensures continuous contact between the high thermal conductivity composition and the heat extraction structure encased in the high thermal conductivity composition. Moreover, the workability of the slurry mixture of the high thermal conductivity slurry composition is improved, making it possible to place the slurry composition in the well even under extreme temperature conditions (e.g., at least 300°C) resulting from the substantially absence of certain curable materials (e.g., cement-based materials) in the slurry mixture. Furthermore, it should be recognized that, due to the relatively broad particle size distribution, voids formed by larger particles are easily filled by smaller particles, resulting in a significant improvement in thermal conductivity.

[0029] The inventors further assume that the high thermal conductivity material is present in an amount effective for the slurry composition to have when the slurry mixture is compressed or settled at the target location, with thermal conductivity of at least 1 W / m°K, at least 4 W / m°K, at least 10 W / m°K, at least 15 W / m°K, at least 20 W / m°K, at least 25 W / m°K, at least 35 W / m°K, and at least 40 W / m°K. Without being bound by theory, it is assumed that the compression or settling (to the extent thereof) of the slurry mixture due to the broad particle size distribution of the high thermal conductivity material results in an improvement in thermal conductivity for the high thermal conductivity composition compared to a composition containing particles with a narrow particle size distribution. Thus, conversely, any given volume of settled or compressed high thermal conductivity material has 15% or less, 10% or less, 8% or less, 6% or less, 5% or less, 4% or less, 3% or less, and 2% or less of the given volume as void.

[0030] As is already understood, high thermal conductivity materials result in improved thermal conductivity of high thermal conductivity compositions formed from slurry mixtures, and are therefore used to provide geothermal well loops with the ability to extract heat more efficiently during operation compared to all, or almost all, known grout compositions. Suitable high thermal conductivity materials include, but are not limited to, graphite, sand, quartz silica, carbon nanotubes, graphene, boron nitride, brass, brass alloys, chromium-nickel steel, carbon steel, stainless steel, transition metals (e.g., copper, cadmium, cobalt, gold, silver, iridium, iron, molybdenum, nickel, platinum, zinc, etc.), transition metal alloys (e.g., copper alloys, cadmium alloys, cobalt alloys, gold alloys, silver alloys, iridium alloys, iron alloys, molybdenum alloys, nickel alloys, platinum alloys, zinc alloys, etc.), post-transition metals (e.g., lead, tin, etc.), post-transition metal alloys (e.g., lead alloys, tin alloys, etc.), alkaline earth metal alloys (e.g., beryllium alloys, magnesium alloys, etc.), or combinations thereof. In certain embodiments, the high thermal conductivity material is a carbon allotrope, and particularly assumed allotropes include graphite powder, exfoliated graphite, flake graphite, pyrolysis graphite, desulfurized petroleum coke, graphene, fly ash, copper powder, aluminum nitride, silicon carbide, and combinations thereof.

[0031] In some embodiments, a high thermal conductivity material can be present in the slurry mixture of a high thermal conductivity slurry composition in an amount sufficient to provide the desired thermal conductivity to the high thermal conductivity slurry of a geothermal well. The high thermal conductivity material can be present in the slurry mixture in an amount of at least 5% by mass, or 10% by mass, or 20% by mass, or 25% by mass, or 30% by mass, or 35% by mass, or 40% by mass, or 45% by mass, or 50% by mass, or 55% by mass, or 60% by mass, or 65% by mass, or 70% by mass, or 75% by mass, or 75% by mass, or 80% by mass, or 85% by mass, or even more, based on the total mass of the slurry mixture. Alternatively, the high thermal conductivity material may be present in the slurry mixture in amounts of 80% by mass or less, 70% by mass, 60% by mass, 50% by mass, 45% by mass, 40% by mass, 35% by mass, 20% by mass, 15% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the high thermal conductivity material may be present in the slurry mixture in amounts of about 50 to about 80% by mass, about 55% to about 85% by mass, or about 60% to about 90% by mass, based on the total mass of the slurry mixture.

[0032] Therefore, in some embodiments, the high thermal conductivity composition formed from a slurry mixture of a high thermal conductivity slurry composition containing a high thermal conductivity material has at least 0.5 British heat units (BTU / hr·ft·°F) per hour per 1 degree Fahrenheit temperature, at least 0.57 BTU / hr·ft·°F (1 W / m°K), at least 1.73 BTU / hr·ft·°F (3 W / m°K), at least 2.0 BTU / hr·ft·°F, at least 2.31 BTU / hr·ft·°F (4 W / m°K), at least 4.0 BTU / hr·ft·°F, and at least 5.78 BTU U / hr·ft·°F (10W / m°K), at least 6.0 BTU / hr·ft·°F, at least 8.0 BTU / hr·ft·°F, at least 10 BTU / hr·ft·°F, at least 12 BTU / hr·ft·°F, at least 14 BTU / hr·ft·°F, at least 16 BTU / hr·ft·°F, at least 20 BTU / hr·ft·°F, at least 20 BTU / hr·ft·°F, at least 25 BTU / hr·ft·°F, at least 30 BTU / hr·ft·°F, or at least 40 BTU / hr·ft·°F, or even higher. Alternatively, a high thermal conductivity composition formed from a slurry mixture containing a high thermal conductivity material has a thermal conductivity of 30 BTU / hr·ft·°F or less, 25 BTU / hr·ft·°F or less, 20 BTU / hr·ft·°F or less, 18 BTU / hr·ft·°F or less, 16 BTU / hr·ft·°F or less, 14 BTU / hr·ft·°F or less, 12 BTU / hr·ft·°F or less, or 10 BTU / hr·ft·°F or less.

[0033] If the envisioned composition contains a dispersant, the dispersant may be present in the slurry mixture of the high thermal conductivity slurry composition and is envisioned to act as a thinner or degumming agent to improve the workability of the high thermal conductivity slurry composition. In some embodiments, dispersants include, but are not limited to, acid derivatives, salts of acid derivatives, phosphates, sodium carbonate, polymers or monomeric sodium silicate complexes (e.g., sodium metasilicate, water glass, etc.), lignite compounds, and low molecular weight polymers, soaps, surfactants, sulfonates, or combinations thereof.

[0034] Acid derivatives that can be used as dispersants in slurry mixtures include, but are not limited to, derivatives of tannic acid, derivatives of citric acid (e.g., citrate), derivatives of humic acid, derivatives of phosphoric acid, disodium hydrogen phosphate, trisodium phosphate, dihydrogen phosphate, quebracho, derivatives of quebracho, sulfomethylated quebracho, derivatives of sulfomethylated quebracho, alkylated quebracho, derivatives of alkylated quebracho, naphthalene sulfonic acid condensed with formaldehyde, and any combination thereof. Salts of these acid derivatives may also be suitable as dispersants (e.g., sodium salts of acid derivatives), including, but are not limited to, sodium humate, sodium phosphate, sodium citrate, sodium tannate, and any combination thereof. Phosphates suitable for use as dispersants include, but are not limited to, sodium polyphosphate, tetrasodium polyphosphate, sodium tripolyphosphate, sodium hexametaphosphate, sodium acid pyrophosphate, sodium metaphosphate, sodium hexametaphosphate, and any combination thereof. Suitable lignite compounds include, but are not limited to, lignosulfonates, alkali salts of lignosulfonic acid (e.g., alkaline earth metals such as sodium, potassium, or calcium), lignosulfonates of acrylic acid, caustic lignite, caustic leonardite, iron lignosulfonate, chromium lignosulfonate, iron-chromium lignosulfonate, lignosulfonic acid transition metals (e.g., zirconium lignosulfonate, titanium lignosulfonate, etc.), sulfoalkylated lignite, or combinations thereof.

[0035] Examples of suitable low molecular weight polymers include polyacrylates, alkali salts of polyacrylic acid, poly(sulfonated styrene-co-maleic anhydride), poly(acrylic acid-co-vinyl sulfonic acid), alkali salts of polymethacrylate, polyacrylamide-2-acrylamide-2-methylpropanesulfonic acid, sodium salts of polyacrylamide-2-acrylamide-2-methylpropanesulfonic acid, polymers produced from condensed naphthalene sulfonate sulfonated polymers, polymers of unsaturated dicarboxylic acids, polymers of monoethylenically unsaturated monocarboxylic acids, and polymers of ethylenically unsaturated monomers and polyaldehydes. Examples include, but are not limited to, graft polymers of cheylene glycol, allyloxybenzenesulfonate polymers, alkylated polymer salts of allyloxybenzenesulfonic acid, terpolymers and lignosulfonates of tetrahydrophthalic acid, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid, graft copolymers and lignosulfonates of tetrahydrophthalic acid, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid, and organosilicon polymers. As used herein, the term "low molecular weight polymer" means a polymer with a molecular weight of less than 1,000,000.

[0036] Suitable soaps that can be used as dispersants include sodium stearate, potassium stearate, ammonium stearate, sodium aurate, potassium aurate, sodium myristate, potassium myristate, sodium ricinoleate, potassium ricinoleate, sodium palmitate, potassium palmitate, calcium caprylate, sodium caprylate, potassium caprylate, 4,7,10,13,16,19-docosahexaenoic acid, 4,7,10,13,16-docosapentaenoic acid, and 5,8,11,14,17-eico Sapentaenoic acid, 5,8,11,14-eicosatetraenoic acid, 5,8,11-eicosatrienoic acid, 6,9,12,15-octadecatetraenoic acid, 7,10,13,16,19-docosapentaenoic acid, 7,10,13,16-docosatetraenoic acid, 8,11,14,17-eicosatetraenoic acid, 8,11,14-eicosatrienoic acid, behenic acid, capric acid, caprylic acid, cis-11-docosenoic acid, cis-11-eicosenoic acid, cis-11-octadecenoic acid, cis-15-tetracosenoic acid, cis-4-decenoic acid, cis-4-dodecenoic acid, cis -4-tetradecenoic acid, cis-5-lauroyl acid, cis-5-tetradecenoic acid, cis-6-octadecenoic acid, cis-9-decenoic acid, cis-9-dodecenoic acid, cis-9-eicosenoic acid, cis-9-hexadecenoic acid, cis-9-tetradecenoic acid, cis-tetracosenoic acid, caprylic acid, decenoic acid, dihydroxystearic acid, docosadienoic acid, docosahexaenoic acid, docosapentaenoic acid, dotriacontanoic acid, eicosadienoic acid, eicosanoic acid, eicosapentaenoic acid, eicosatetraenoic acid, eicosatrienoic acid, eicosenoic acid, erucic acid, heptadeca Examples include, but are not limited to, tetracosanoic acid, heptadecenoic acid, hexacosanoic acid, hexadecadienoic acid, hexadecenoic acid, lauric acid, linoleic acid, linolenic acid, myristic acid, nonadecanoic acid, nonanoic acid, octacosanoic acid, octadecatetetraenoic acid, octadecatetrienoic acid, oleic acid, palmitic acid, pentadecanoic acid, pentadecenoic acid, pentatricriacontanoic acid, ricinoleic acid, stearic acid, tetracosanoic acid, tetradecenoic acid, tetratricriacontanoic acid, triacontanoic acid, tridecanoic acid, tritricriacontanoic acid, or combinations thereof.

[0037] Suitable sulfonates for use as dispersants include, but are not limited to, melamine sulfonate condensed with formaldehyde, sulfonated styrene-maleic anhydride copolymer, sulfonated vinyltoluene-maleic anhydride copolymer, sodium naphthalene sulfonate condensed with formaldehyde, sulfonated acetone condensed with formaldehyde, acrylic acid interpolymers, allyloxybenzene sulfonates, allyl sulfonates, or combinations thereof.

[0038] In some embodiments, the dispersant may be present in the slurry mixture of the high thermal conductivity slurry composition in an amount sufficient to impart the desired viscosity to the slurry mixture. The dispersant may be present in the slurry mixture in an amount of at least 0.1% by mass, 0.5% by mass, 1% by mass, 2% by mass, 3% by mass, 4% by mass, 5% by mass, 6% by mass, 7% by mass, 8% by mass, 9% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the dispersant may be present in the slurry mixture in an amount of 20% by mass or less, 19% by mass, 18% by mass, 17% by mass, 16% by mass, 15% by mass, 14% by mass, 13% by mass, 12% by mass, 11% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the dispersant may be present in the slurry mixture in an amount of about 1 to about 20% by mass, about 5% to about 15% by mass, or about 7% to about 13% by mass, based on the total mass of the slurry mixture.

[0039] The slurry mixture of the high thermal conductivity slurry composition may further contain at least one functional agent. The functional agent can be used to modify the rheological properties of the slurry mixture or to improve the mixability of the slurry mixture in response to various stimuli such as temperature, pressure, contact with other materials, or combinations thereof. The functional agent may be selected from the group consisting of plasticizers, surfactants, organic polymers, silica fillers, NaCl, KCl or other inorganic salts, clay, and combinations thereof.

[0040] Plasticizers may be present in the slurry mixture of a high thermal conductivity slurry composition to improve workability for easier installation. In various embodiments, the term “plasticizer” refers to a substance that improves the fluidity of the slurry mixture, thereby improving its workability, or that allows the slurry mixture to be manufactured with a small amount of water while maintaining comparable workability. Suitable plasticizers include, but are not limited to, polycarboxylic acid ether plasticizers, phthalate plasticizers, terephthalate plasticizers, sulfonamide plasticizers, benzoate plasticizers, phosphate plasticizers, or combinations thereof.

[0041] In some embodiments, a plasticizer may be present in the slurry mixture of a high thermal conductivity slurry composition in an amount sufficient to impart the desired workability to the slurry mixture. The plasticizer may be present in the slurry mixture in an amount of at least 1% by mass, 2% by mass, 3% by mass, 4% by mass, 5% by mass, 6% by mass, 7% by mass, 8% by mass, 9% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the plasticizer may be present in the slurry mixture in an amount of 20% by mass or less, 19% by mass, 18% by mass, 17% by mass, 16% by mass, 15% by mass, 14% by mass, 13% by mass, 12% by mass, 11% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the plasticizer may be present in the slurry mixture in an amount of about 1 to about 20% by mass, about 5% to about 15% by mass, or about 7% to about 13% by mass, based on the total mass of the slurry mixture.

[0042] Surfactants may be present in the slurry mixture of a high thermal conductivity slurry composition to improve the surface properties of the slurry mixture. Suitable surfactants include, but are not limited to, nonionic surfactants, anionic surfactants, cationic surfactants, zwitterionic surfactants, or combinations thereof.

[0043] Suitable nonionic surfactants include alkoxylates (e.g., alkoxylated nonylphenol condensates such as poly(oxy-1,2-ethanediyl) and alpha-(4-nonylphenyl)-omega-hydroxy-branched), alkylphenols, ethoxylated alkylamines, ethoxylated oleates, tall oils, ethoxylated fatty acids, alkyl polyglycosides, sorbitan esters, methyl glucoside esters, amine ethoxylates, diamine ethoxylates, polyglycerol esters, alkyl ethoxylates, polypropoxylated and / or polyethoxylated alcohols, linear alcohol alkoxylates, dodecylbenzene sulfonate derivatives, Examples include, but are not limited to, linear nonylphenols, dioxanes, ethylene oxides, polyethylene glycols, ethoxylated castor oil, polyoxyethylene nonylphenol ethers, tetraethylene glycol dodecyl ethers, ethylene oxides, decylamine oxides, dodecylamine oxides, alkylamine oxides, ethoxylated amides, alkoxylated fatty acids, alkoxylated alcohols (e.g., lauryl alcohol ethoxylate, ethoxylated nonylphenol), ethoxylated fatty amines, ethoxylated alkylamines (e.g., cocoalkylamine ethoxylate), any derivatives thereof, and any combination thereof. As used herein, the term “derivative” means any compound produced from one of the compounds, for example, by replacing one atom in the listed compounds with another atom or group of atoms, or by rearranging two or more atoms in the compounds.

[0044] Suitable anionic surfactants include alpha-sulfo fatty acid methyl ester salts. Examples of compounds include, but are not limited to, sodium sulfates, hydrolyzed keratin, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, alkyl ether sulfates, sodium 4-(1'heptylnonyl)benzenesulfonate, sodium dioctyl sulfosuccinate, sodium octylbenzenesulfonate, sodium hexadecyl sulfate, sodium laureth sulfate, quaternary ammonium compounds (e.g., trimethylcocoammonium chloride, trimethyltallowammonium chloride, dimethyldicocoammonium chloride, etc.), cetylpyridinium chloride, alkyl ester sulfonates, alkyl ether sulfonates, alkyl ether sulfates, alkali metal alkyl sulfates, alkyl sulfonates, alkylaryl sulfonates, sulfosuccinates, alkyl disulfonates, alkylaryl disulfonates, alkyl disulfates, alcohol polypropoxylated sulfates, alcohol polyethoxylated sulfates, any derivatives thereof, and any combination thereof.

[0045] Suitable zwitterionic surfactants include, but are not limited to, alkylamine oxides, alkyl betaines, alkylamidopropyl betaines, alkyl sulfobetaines, alkyl sultaines, dihydroxyalkyl glycinates, alkyl amphoacetates, phospholipids, alkylaminopropionic acids, alkyliminomonopropionic acids, alkyliminodipropionic acids, dipalmitoyl phosphatidylcholine, amine oxides, betaines, modified betaines, alkylamidobetaines (e.g., cocoamidopropyl betaine), and any combination thereof.

[0046] Examples of surfactants that may exhibit viscoelastic properties include, but are not limited to, sulfosuccinates, taurates, amine oxides (e.g., amidoamine oxides), ethoxylated amides, alkoxylated fatty acids, alkoxylated alcohols, ethoxylated fatty amines, ethoxylated alkylamines, betaines, modified betaines, alkylamide betaines, quaternary ammonium compounds, alkyl sulfates, alkyl ether sulfates, alkyl sulfonates, ethoxylated esters, ethoxylated glycoside esters, alcohol ethers, any derivatives thereof, and any combination thereof.

[0047] In some embodiments, the surfactant may be present in the slurry mixture of a high thermal conductivity slurry composition in an amount sufficient to impart the desired surface properties to the slurry mixture. The surfactant may be present in the slurry mixture in an amount of at least 1% by mass, 2% by mass, 3% by mass, 4% by mass, 5% by mass, 6% by mass, 7% by mass, 8% by mass, 9% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the surfactant may be present in the slurry mixture in an amount of 20% by mass or less, 19% by mass, 18% by mass, 17% by mass, 16% by mass, 15% by mass, 14% by mass, 13% by mass, 12% by mass, 11% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the surfactant may be present in the slurry mixture in an amount of about 1 to about 20% by mass, about 5% to about 15% by mass, or about 7% to about 13% by mass, based on the total mass of the slurry mixture.

[0048] Organic polymers may be present in the slurry mixture of a high thermal conductivity slurry composition to improve the properties of the slurry mixture. Suitable organic polymers include, but are not limited to, natural compounds, synthetic compounds, or combinations thereof. Non-limited examples of suitable natural compounds include cold water soluble polysaccharides and polysaccharide ethers, such as polysaccharides, cellulose ethers, starch ethers (amylose and / or amylopectin and / or derivatives thereof), guar ethers, dextrins, or combinations thereof. Non-limited examples of suitable synthetic compounds include protective colloids, such as one or more polyvinylpyrrolidone and / or polyvinyl acetate, polyvinyl alcohol, melamine formaldehyde sulfonate, naphthalene formaldehyde sulfonate, propylene oxide and ethylene oxide block copolymers, styrene-maleic acid and / or vinyl ether-maleic acid copolymers.

[0049] In some embodiments, the organic polymer may be present in the slurry mixture of a high thermal conductivity slurry composition in an amount sufficient to impart the desired properties of the slurry mixture. The organic polymer may be present in the slurry mixture in an amount of at least 1% by mass, 2% by mass, 3% by mass, 4% by mass, 5% by mass, 6% by mass, 7% by mass, 8% by mass, 9% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the organic polymer may be present in the slurry mixture in an amount of 20% by mass or less, 19% by mass, 18% by mass, 17% by mass, 16% by mass, 15% by mass, 14% by mass, 13% by mass, 12% by mass, 11% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the organic polymer may be present in the slurry mixture in an amount of about 1 to about 20% by mass, about 5% to about 15% by mass, or about 7% to about 13% by mass, based on the total mass of the slurry mixture.

[0050] If desired, silica packing materials may be present in the slurry mixture of a high thermal conductivity slurry composition to improve the properties of the slurry mixture. Suitable silica packing materials may be pyrogenic silica or precipitated finely-divided silica. The silica packing materials may have particle sizes of about 50 to 10,000 angstroms, about 50 to about 400 angstroms, or about 100 to about 300 angstroms. The silica packing materials may be present in the slurry mixture in an amount of at least 1% by mass, 2% by mass, 3% by mass, 4% by mass, 5% by mass, 6% by mass, 7% by mass, 8% by mass, 9% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the silica filler may be present in the slurry mixture in amounts of 20% by mass or less, 19% by mass, 18% by mass, 17% by mass, 16% by mass, 15% by mass, 14% by mass, 13% by mass, 12% by mass, 11% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the silica filler may be present in the slurry mixture in amounts of about 1 to about 20% by mass, about 5% to about 15% by mass, or about 7% to about 13% by mass, based on the total mass of the slurry mixture.

[0051] Inorganic salts may be present in the slurry mixture of a high thermal conductivity slurry composition to improve the miscibility of the slurry mixture. Suitable inorganic salts include, but are not limited to, NaCl and KCl. Inorganic salts may be present in the slurry mixture in an amount of at least 1% by mass, 2% by mass, 3% by mass, 4% by mass, 5% by mass, 6% by mass, 7% by mass, 8% by mass, 9% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, inorganic salts may be present in the slurry mixture in an amount of 20% by mass or less, 19% by mass, 18% by mass, 17% by mass, 16% by mass, 15% by mass, 14% by mass, 13% by mass, 12% by mass, 11% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, inorganic salts may be present in the slurry mixture in an amount of about 1 to about 20% by mass, about 5% to about 15% by mass, or about 7% to about 13% by mass, based on the total mass of the slurry mixture.

[0052] Clay may be present in the slurry mixture of a high thermal conductivity slurry composition to modify the fluidity of the slurry mixture. Suitable clays include smectite clays, palygorskite-sepiolite phyllosilicate clays, kaolinite-serpentine clays, nontronite, bentonite, hectorite, attapulgite, fluorinated mica, montmorillonite, bydelite, saponite, sepiolite, kaolinite, illite, those with cation exchanges, or combinations thereof.

[0053] Among the suitable smectite clays, including nontronite, montmorillonite, saponite, hectorite, and beederite, other smectite clays suitable for use as aqueous swelling clays of this disclosure include, but are not limited to, ariettite, ferrosaponite, souconite, stevensite, sinefoadite, volconcoreite, jahontobite, and any combination thereof. Suitable phyllosilicic clays of the parigorskite-sepiolite group include, but are not limited to, ataprugite, tupersauchiite, windhokite, yofortierite, falcondite, ferrisepiolite, looflinite, and any combination thereof. Suitable water-swellable clays of the kaolinite-serpentine group include, but are not limited to, kaolinite, green allite, flypontite, halloysite, dickite, lizardite, manandonite, nacrite, clonstettite, clinochrysotile, chrysotile, nepite, ozinite, webskiite, pecorite, orthochrysotile, parachrysotile, calliopilite, brindleyite, bertierine, amesite, antigorite, bomite, and any combination thereof.

[0054] In some embodiments, clay may be present in the slurry mixture of a high thermal conductivity slurry composition in an amount sufficient to impart a desired amount of properties to the slurry mixture. The clay may be present in the slurry mixture in an amount of at least 1% by mass, 2% by mass, 3% by mass, 4% by mass, 5% by mass, 6% by mass, 7% by mass, 8% by mass, 9% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the clay may be present in the slurry mixture in an amount of 20% by mass or less, 19% by mass, 18% by mass, 17% by mass, 16% by mass, 15% by mass, 14% by mass, 13% by mass, 12% by mass, 11% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the clay may be present in the slurry mixture in an amount of about 1 to about 20% by mass, about 5% to about 15% by mass, or about 7% to about 13% by mass, based on the total mass of the slurry mixture.

[0055] The slurry mixture of the high thermal conductivity slurry composition may contain various additives such as insulating materials, retarders, aggregates, or combinations thereof. The additives modify the thermodynamic properties of the slurry mixture or the resulting high thermal conductivity composition, or further modify the rheological properties of the slurry mixture.

[0056] If desired or necessary, an insulating material may be present in the slurry mixture of the high thermal conductivity slurry composition to modify the thermal conductivity of the resulting high thermal conductivity composition. This is counterproductive to the high thermal conductivity material, but is also desirable for some geothermal wells near the surface to minimize heat transfer to the outside of the well. Suitable insulating materials may be solid particles having low thermal conductivity. Specific examples of insulating materials suitable for use in slurry mixtures include, but are not limited to, glass (e.g., glass spheres), diatomaceous earth, vermiculite, calcium silicate, polyurethane, polyurethane foam, perlite, glass fibers, rock wool, mineral fibers, cellulose, and any combination thereof.

[0057] In some embodiments, the thermal insulation material may be present in the slurry mixture of a high thermal conductivity slurry composition in an amount effective in providing the slurry mixture with a desired amount of thermal insulation. The thermal insulation material may be present in the slurry mixture in an amount of at least 1% by mass, 2% by mass, 3% by mass, 4% by mass, 5% by mass, 6% by mass, 7% by mass, 8% by mass, 9% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the thermal insulation material may be present in the slurry mixture in an amount of 20% by mass or less, 19% by mass, 18% by mass, 17% by mass, 16% by mass, 15% by mass, 14% by mass, 13% by mass, 12% by mass, 11% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the thermal insulation material may be present in the slurry mixture in an amount of about 1 to about 20% by mass, about 5% to about 15% by mass, or about 7% to about 13% by mass, based on the total mass of the slurry mixture.

[0058] In some embodiments, the salts containing cations and anions include, but are not limited to, at least one of the following as cations: lithium, potassium, sodium, hydronium, ammonium, calcium, magnesium, quaternary amines, magnesium, calcium, strontium, barium, titanium, cesium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, aluminum, zirconium, and any combination thereof; and, as anions, at least one of the following as cations: chloride, bromide, nitrate ion, iodide, hydroxide, nitrite ion, hexafluoroantimonate ion, hexafluoroarsenate ion, hexafluorophosphate ion, propionate ion, lactate ion, tartrate ion, phosphate ion, phosphonium, borate ion, silicate ion, sulfate ion, acetate ion, aluminate ion, chromate ion, dichromate ion, permanganate ion, chlorate ion and perchlorate ion, formate ion, or any combination thereof.

[0059] In other embodiments, the retarder may include a cationic oligomer or polymer. Such suitable cationic oligomers or polymers include, but are not limited to, at least one monomer comprising imines, alkyleneimines, ethyleneimines, propyleneimines, amines, ethyleneamines, organic amines, quaternary amines, acrylamides, methacrylamides, putrescine, cadaverine, spermidine, spermine, diethylenetriamine, tetramethylenediamine, triethylenetetramine, tetraethylenepentamine, diallyldimethylammonium chloride, (2-methacryloyloxyethyl)trimethylammonium chloride, vinylpyrrolidone, derivatives thereof, salts thereof, or combinations thereof.

[0060] Silicates suitable for use as retarders may be any type suitable for the aforementioned use, including silicates, oligomeric silicates, polymeric silicates, etc. Examples of suitable silicates include, but are not limited to, alkaline earth metal silicates, alkaline earth metal silicates, and any combination thereof, such as sodium silicate, calcium silicate, potassium silicate, sodium metasilicate, calcium metasilicate, and potassium metasilicate.

[0061] In some embodiments, the retarder may be present in the slurry mixture of the high thermal conductivity slurry composition in an amount sufficient to impart a desired amount of swelling reduction to one or more components of the slurry mixture. The retarder may be present in the slurry mixture in an amount of at least 1% by mass, 2% by mass, 3% by mass, 4% by mass, 5% by mass, 6% by mass, 7% by mass, 8% by mass, 9% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the retarder may be present in the slurry mixture in an amount of 20% by mass or less, 19% by mass, 18% by mass, 17% by mass, 16% by mass, 15% by mass, 14% by mass, 13% by mass, 12% by mass, 11% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the retarder may be present in the slurry mixture in an amount of about 1 to about 20% by mass, about 5% to about 15% by mass, or about 7% to about 13% by mass, based on the total mass of the slurry mixture.

[0062] Aggregates may be present in the slurry mixture of the high thermal conductivity slurry composition as a filler. Non-limiting examples of suitable aggregates include sand or quartz sand, as described in U.S. Patents 6,715,543 and 7,258,174, which are incorporated herein by reference in their entirety. In various embodiments, the aggregate may be in the form of multiple particles having a broad particle size distribution over at least 2-logarithmic units, at least 2.5-logarithmic units, or at least 3-logarithmic units. In some embodiments, the broad particle size distribution of the aggregate, when combined with a high thermal conductivity material, imparts further integrity to the form or structure of the high thermal conductivity composition during compression or sedimentation of the slurry mixture without the use of a hardening material (e.g., a cement-based material), thereby reducing the permeability of liquid through the high thermal conductivity composition compared to compositions containing particles with a narrow particle size distribution.

[0063] In certain embodiments, the aggregate is quartz sand. The aggregate may have an average particle size of 0.1 μm to 5.0 mm. The aggregate may be present in the slurry mixture in an amount of at least 1% by mass, 2% by mass, 3% by mass, 4% by mass, 5% by mass, 6% by mass, 7% by mass, 8% by mass, 9% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the aggregate may be present in the slurry mixture in an amount of 20% by mass or less, 19% by mass, 18% by mass, 17% by mass, 16% by mass, 15% by mass, 14% by mass, 13% by mass, 12% by mass, 11% by mass, or 10% by mass, based on the total mass of the slurry mixture. Alternatively, the aggregate may be present in the slurry mixture in an amount of about 1% to about 20% by mass, about 5% to about 15% by mass, or about 7% to about 13% by mass, based on the total mass of the slurry mixture.

[0064] A method for producing a pumpable slurry is also provided. This method involves combining a high thermal conductivity slurry composition with a large amount of water. This method further involves mixing the water with the high thermal conductivity slurry composition to form a pumpable slurry. Any method or process can be used for mixing, including a static mixer, a rotary mixer, or a recirculating jet mixer. The slurry mixture of the high thermal conductivity slurry composition has a viscosity that, upon addition of water, allows the slurry mixture to be pumped to a target position having a target temperature. In certain embodiments, the slurry mixture has a particle deposition rate that, upon addition of water, allows the mixture to be pumped to the target position without the particles substantially settling before reaching the target position.

[0065] In various embodiments, the amount of water is sufficient to produce a slurry density of about 10 to about 30 pounds / gallon, about 12 to about 25 pounds / gallon, or about 14 to about 16 pounds / gallon. Alternatively, the amount of water is sufficient to produce a slurry density of at least 10 pounds / gallon, at least 12 pounds / gallon, at least 14 pounds / gallon, at least 16 pounds / gallon, at least 18 pounds / gallon, at least 20 pounds / gallon, at least 22 pounds / gallon, at least 24 pounds / gallon, at least 26 pounds / gallon, or 28 pounds / gallon. Alternatively, the amount of water is sufficient to produce a slurry density of 30 pounds / gallon or less, 28 pounds / gallon or less, 26 pounds / gallon or less, 24 pounds / gallon or less, 22 pounds / gallon or less, 20 pounds / gallon or less, 18 pounds / gallon or less, 16 pounds / gallon or less, 14 pounds / gallon, or 12 pounds / gallon.

[0066] The pressurized slurry may have a water content of 1 to 50 gallons / 100 pounds of high thermal conductivity material, 1 to 40 gallons / 100 pounds of high thermal conductivity material, 1 to 30 gallons / 100 pounds of high thermal conductivity material, 1 to 20 gallons / 100 pounds of high thermal conductivity material, or 10 to 20 gallons / 100 pounds of high thermal conductivity material. Alternatively, the pressurized slurry may have a water content of at least 1 gallon / 100 pounds of high thermal conductivity material, at least 5 gallons / 100 pounds of high thermal conductivity material, or at least 10 gallons / 100 pounds of high thermal conductivity material. Alternatively, the pressurized slurry may have a water content of 50 gallons / 100 pounds or less of high thermal conductivity material, 40 gallons / 100 pounds or less of high thermal conductivity material, or 30 gallons / 100 pounds or less of high thermal conductivity material.

[0067] Figures 1 and 2 are schematic diagrams showing embodiments of a geothermal well 10, including the well 12 during the installation of a pumpable slurry 14A (Figure 1) and the well 12 after at least a portion of the pumpable slurry 14A has been compressed or settled to form a high thermal conductivity composition 14B (Figure 2). The geothermal well 10 further includes a casing 16 positioned within the well 12 such that an annular space 18 is formed between the well 12 and the casing 16. The pumpable slurry 14A is pumped through the annular space 18 of the well 12 (Figure 1) or located within it (Figure 2). The geothermal well 10 is formed in a geological formation 20. During at least a portion of the compression or settling, the pumpable slurry 14A forms a high thermal conductivity composition 14B. In this context, it should be understood that the high thermal conductivity composition 14B in Figure 2 exchanges heat with at least a portion of the casing 16 and at least a portion of the formation 20 surrounding the well 12 via the high thermal conductivity material 24 within the crack 22. As described above, the high thermal conductivity material is in the form of multiple particles (which may have a broad particle size distribution) within the well and crack, thereby substantially improving thermal contact between the casing 16 and the high-temperature formation at the target location, while maintaining mobility to minimize damage in the presence of considerable forces (e.g., earthquakes, thermal expansion, and thermal contraction).

[0068] The geothermal well 10 may be connected to a circulation pump (not shown) above ground above the formation 20. In a preferred embodiment, the formation 20 includes a number of cracks 22, which are filled at least partially with a high thermal conductivity material 24. In this context, it should be noted that the high thermal conductivity material 24 in the cracks 22 exchanges heat with the high thermal conductivity composition 14B in the well 12, and is typically composed of the same material. Among other suitable materials, the high thermal conductivity material 24 in the cracks 22 may be graphite powder, flaked graphite, pyrolytic graphite, desulfurized petroleum coke, graphene, fly ash, copper powder, aluminum nitride, silicon carbide, and any reasonable combination thereof. It will also be understood that, as shown in Figure 1, when a pumpable slurry 14A is sent through the annular space 18 of the well 12, the high thermal conductivity material 24 is obtained from the pumpable slurry 14A. From a different perspective, the pumpable slurry 14A within the annular space 18 contains the same material as the high thermal conductivity material 24 within the crack 22. In certain embodiments, a secondary conduit 26 defining a return space 28 is located within the casing 16. In such a configuration, a second annular space 30 is formed between the casing 16 and the secondary conduit 26. As is readily apparent, the casing with the inner secondary conduit forms a closed-loop working fluid conduit through which the working fluid circulates during operation.

[0069] In some embodiments, the installation of the slurry composition is preferably (but not required) carried out in reverse circulation, as shown in Figure 1 (and this is described, for example, in PROCEEDINGS, Thirty-Fifth Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, February 1-3, 2010, which is incorporated herein by reference). For example, as shown in Figure 1, slurry 14A is supplied through the annular space 18 to the annular space and crack 22 (typically the terminal portion of the well) at the target location, and at least a portion of the slurry exits upward from the target location through the inner return conduit 26 (typically through a valve or other fluid control structure, but not shown). It should be noted that by installing in this manner, the slurry in the crack and the annular space at the target location are continuous, and thus a continuous path for heat transfer is provided.

[0070] It should be further understood that the inner return conduit 26 forms a fluid path 28 for the high-temperature working fluid when the power generation system is in operation. The space between the casing 16 and the inner return conduit 26 forms a fluid path 30 that transports the working fluid to a target position when the power generation system is in operation. It should be noted that the fluid path 30 can therefore be used to "wash away" any slurry remaining in the inner return conduit 26, as shown in Figure 2. Direction of the working fluid from the fluid path 30 to 28 can be done via valves or other fluid control structures (e.g., using stinger valves and flapper valves at the end of the tube-in-tube conduit, not shown).

[0071] Figures 3–5 are schematic diagrams showing embodiments of a casing 16 installed in a geothermal well 10, where the orientation of the well is not perpendicular (offset relative to normal). The casing 16 can be positioned in any manner known in the art of geothermal wells. In one embodiment, the casing 16 is positioned in the center of the well 12 (Figure 3). In another embodiment, the casing 16 is partially offset within the well 12 (Figure 4). In yet another embodiment, the casing 16 is fully offset within the well 12 (Figure 5). Advantageously, and as shown in Figures 3–5, regardless of the position of the casing 16, the casing 16 remains at least partially encased in the high thermal conductivity composition 14B. With respect to the remaining numbers in Figures 3–5, the same numbers refer to the same components already identified in Figures 1–2.

[0072] In certain embodiments, the target position extends substantially vertically. As used herein, the term “substantially” means that the target position extends toward the center of the Earth, but may be offset from the center by 15 degrees or less, 10 degrees or less, 5 degrees or less, or 1 degree or less. It should be understood that the geothermal well 10 may have multiple target positions, and therefore may have both a substantially vertical target position and a target position extending in a direction of at least 30 degrees.

[0073] In view of the above, the inventors envision various methods for installing the high thermal conductivity composition 14B in a well 12. For example, this method may include the step of pumping a pumpable slurry 14A to a target location in the well 12 having a target temperature of at least 200°C, at least 300°C, at least 350°C, at least 400°C, at least 450°C, or at least 500°C. The target location may be at least 500 feet, at least 600 feet, at least 700 feet, at least 800 feet, at least 900 feet, at least 1,000 feet, at least 1,250 feet, at least 1,500 feet, at least 1,750 feet, at least 2,000 feet, at least 2,500 feet, at least 3,000 feet, at least 4,000 feet, or at least 5,000 feet underground. In these embodiments and other embodiments, the pumpable slurry 14A is delivered to the annular space 18 between the well 12 and the casing 16 located within the well 12, thereby replacing the fluid in the annular space 18. Most typically, the target site is a dry, hot rock formation, which in most cases has low or almost no permeability (e.g., intrusive igneous or metamorphic rock).

[0074] In various embodiments, the pumpable slurry 14A requires agitation (e.g., using a static mixer, rotary mixer, or recirculation jet mixer) before being pumped into the well 12. For example, a batch mixer can continuously agitate the pumpable slurry 14A before pumping it into the well 12, maintaining fluidity and suspension. The pumpable slurry 14A may then be supplied to a pump that pumps it into the well 12. In various embodiments, the pumpable slurry 14A is delivered to an annular space 18 between the well 12 and a casing 16 located in the well 12, thereby replacing the fluid in the annular space 18.

[0075] The proposed method may also include a further step of removing the replaced fluid through a return space 28 located within the casing 16. The fluid can be removed using any method or apparatus known in the art for removing fluid. In various embodiments, the replaced fluid is removed through the return space 28 using a secondary fluid moving from the second annular space 30 to the return space 28. In further embodiments, the proposed method also includes a step of allowing a pumpable slurry 14A to settle or compress in at least a portion of the annular space 18 and the crack 22, thereby forming a high thermal conductivity composition 14B in the well 12. The pumpable slurry 14A is pumped to a predetermined position, and after pumping, at least a portion of the pumpable slurry 14A is compressed at the target position to form high thermal conductivity compositions 14B and 24 in the well 12 and the crack 22, respectively.

[0076] Referring further to Figure 2, during power generation operation of the geothermal well 10, the working fluid moves through a second annular space 30 within a closed-loop working fluid conduit (partially formed by the casing 16 and internal conduit 26) and returns to the surface through a return space 28. However, it should be understood that the flow of the working fluid may also be in the reverse direction. As the working fluid moves through the second annular space 30, geothermal heat from the target location, conducted by the high thermal conductivity composition 14B and the high thermal conductivity material 24 in the crack 22, is transferred to the working fluid, thereby increasing the temperature of the working fluid. The working fluid then moves toward the surface through the return space 28. A heat exchanger and a turbine generator (neither shown) are installed in close proximity to the geothermal well 10 and can utilize the temperature of the working fluid to generate electrical energy. [Examples]

[0077] Tables 1-6 describe exemplary high thermal conductivity slurry compositions suitable for use herein. However, it should be understood that these compositions are provided merely to illustrate specific aspects of the subject matter of the invention and are not intended to limit the scope of the subject matter of the invention.

[0078] Table 1

[0079] Table 2

[0080] Table 3

[0081] Table 4

[0082] Table 5

[0083] Table 6

[0084] In further conceivable embodiments, particularly when the slurry is placed at a relatively high temperature (e.g., at least 250°C, or at least 275°C, or at least 300°C, or at least 325°C, or at least 350°C), and / or when the slurry is surrounded by dry (and possibly porous) rock, the inventors believe that at least partial dewatering of the heat transfer slurry system may reduce its thermal conductivity. To mitigate this risk after the placement of the non-cemental slurry, the inventors envision continuously or intermittently injecting water under pressure from the surface into the annular space between the casing of the closed-loop circuit and the larger casing or well in which the casing is placed. Alternatively, the water may be supplied to the target location via one or more dedicated conduits extending into or into the compressed or settled non-cemental high-thermal-conductivity composition. Depending on the porosity of the settled or compressed slurry, such replenishment of water lost to the surrounding formation or evaporation can maintain or improve the thermal conductivity of the settled or compressed slurry without further intervention, thus helping to maintain the peak thermal efficiency of such a system. Alternatively, or further, if the porosity (or water permeability) of the settled or compressed slurry is very low, it is conceivable that the slurry composition can be adjusted so that the permeability increases or decreases as needed to achieve the required flow rate of water from the surface to the depths. As is readily understood, such adjustments depend on the expected rate of water loss, the porosity of the surrounding formation, temperature, etc., and those skilled in the art can easily adjust the permeability according to quantitative protocols, such as those found in ASTM D4630-19, for example.

[0085] Therefore, in at least some embodiments, the non-cemental high thermal conductivity composition has water permeability that allows water to penetrate at least 50%, or at least 60%, or at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90% of the compressed or settled non-cemental high thermal conductivity composition. As a result, the potential loss of thermal conductivity after at least one year, or at least three years, or at least five years, or at least seven years, or at least ten years (compared to the thermal conductivity immediately after installation) is less than 30%, or less than 25%, or less than 20%, or less than 15%, or less than 10%, or even lower.

[0086] In some embodiments, numerical values ​​representing properties such as the amount and concentration of components, reaction conditions, etc., used to describe and claim specific embodiments of the present invention should be understood to be modified in some cases by the term “about”. As used herein, the terms “about” and “approximately” mean, when referring to a specified measurable value (parameter, quantity, temporal duration, etc.), to the extent appropriate for performing in the disclosed embodiments, to include the specified value and variations from the specified value, for example, variations of ±10%, ±5%, ±1%, or ±0.1% or less of the specified value. Thus, the values ​​themselves that the modifiers “about” or “approximately” refer to are also specifically disclosed. The description of value ranges herein is intended to serve merely as abbreviations for individually referring to each individual value that falls within the range. Unless otherwise stated herein, each individual value is incorporated herein as it is individually described herein.

[0087] All methods described herein may be performed in any suitable order unless otherwise specifically indicated herein or unless it is clearly inconsistent with the context. Any examples or exemplary language (e.g., "e.g.") provided herein with respect to specific embodiments are intended solely to better illustrate the invention and do not limit the scope of the other claimed invention. Nothing in this specification should be construed as indicating a non-claimed element essential to the practice of the invention.

[0088] As used herein and throughout the following claims, the meanings of “a,” “an,” and “the” include multiple references unless otherwise clearly indicated by the context. Also, as used herein, the meaning of “in” includes “in” and “on” unless otherwise clearly indicated by the context. As used herein, and unless otherwise indicated by the context, the term “coupled to” is intended to include both direct coupling (two elements being coupled to each other in contact) and indirect coupling (at least one additional element being placed between the two elements). Thus, the terms “coupled to” and “coupled with” are used synonymously.

[0089] It will be apparent to those skilled in the art that many modifications are possible beyond those already described without departing from the inventive concept as set forth herein. Therefore, the subject matter of the present invention is not limited beyond the appended claims. Furthermore, in the interpretation of both this specification and the claims, all terms should be interpreted as broadly as possible in accordance with the context. In particular, the terms “comprises” and “comprising” should be interpreted in a non-exclusive manner as referring to an element, component, or process, indicating that the mentioned element, component, or process may exist, be utilized, or be combined with other elements, components, or processes not explicitly mentioned. Where the specification or claims refer to at least one selected from the group consisting of A, B, C..., and N, the sentence should be interpreted as requiring only one element from that group, and not A+N, B+N, etc.

Claims

1. A high thermal conductivity slurry composition, A slurry mixture comprising a high thermal conductivity material and an optional dispersant, The aforementioned high thermal conductivity material is in the form of multiple particles having a broad particle size distribution, The broad particle size distribution extends at least two logarithmic units, The high thermal conductivity material is present in an amount effective enough to cause the slurry composition to have a thermal conductivity of at least 3 W / m°K when the slurry mixture is compressed or settled at the target position. Slurry composition.

2. The composition according to claim 1, wherein the slurry mixture further comprises at least one functional agent.

3. The composition according to claim 2, wherein the functional agent is selected from the group consisting of plasticizers, surfactants, organic polymers, silica fillers, NaCl or KCl or other inorganic salts, and clay.

4. The composition according to claim 1, wherein the broad particle size distribution extends over at least three logarithmic units.

5. The composition according to claim 1, wherein the broad particle size distribution is 0.1 μm to 5.0 mm.

6. The composition according to any one of claims 1 to 5, wherein the high thermal conductivity material is selected from the group consisting of graphite powder, flake graphite, pyrolysis graphite, desulfurized petroleum coke, graphene, fly ash, copper powder, aluminum nitride, and silicon carbide.

7. The composition according to claim 1, wherein the high thermal conductivity material is present in the slurry mixture in an amount of at least 10% by mass.

8. The composition according to claim 1, wherein the high thermal conductivity material is present in the slurry mixture in an amount of at least 30% by mass.

9. The composition according to claim 1, wherein the high thermal conductivity material is present in an amount effective enough to cause the slurry mixture to have a thermal conductivity of at least 4 W / m°K when compressed or settled at the installation site.

10. The composition according to claim 1, wherein the high thermal conductivity material is present in an amount effective enough to cause the slurry mixture to have a thermal conductivity of at least 15 W / m°K when compressed or settled at the installation site.

11. The composition according to claim 1, wherein the slurry mixture has a deposition rate of the plurality of particles that, upon addition of water, enables the particles to be pumped to the target position without substantially settling before reaching the target position.

12. A pumpable slurry, comprising a high thermal conductivity slurry composition according to any one of claims 1 to 11, mixed with water.

13. A pumpable slurry according to claim 12, having a density of 10 to 30 pounds / gallon.

14. A pumpable slurry according to claim 12 or 13, wherein the water content is 1 to 20 gallons / 100 pounds of high thermal conductivity material.

15. A method for producing a slurry that can be pumped, A step of combining the high thermal conductivity slurry composition according to claims 1 to 11 with a large amount of water, and A step of mixing the water and the high thermal conductivity slurry composition to form the slurry, wherein the amount of water is sufficient to produce a slurry density of 10 to 30 pounds / gallon, A manufacturing method that includes this.

16. The method according to any one of claims 15, further comprising the step of supplying the pumpable slurry to a pump for pumping into a well.

17. The method according to claim 16, wherein the step of pumping the slurry into the well is performed at a rate that allows at least partial compression or sedimentation of the slurry mixture at the target location.

18. A method for installing a high thermal conductivity composition into a well, A step of pumping a pumpable slurry according to any one of claims 12 to 14 to a target location having a target temperature of at least 200°C, wherein the pumpable slurry is sent to an annular space between the well and a casing located inside the well, thereby replacing the fluid in the annular space. The steps include removing the replaced fluid through a return space located within the casing, and A step of compressing the pumpable slurry in at least a portion of the annular space to form the high thermal conductivity composition in the well, wherein the high thermal conductivity composition exchanges heat with at least a portion of the casing and at least a portion of the geological formation surrounding the well, the pumpable slurry is pumped to a predetermined location, and after pumping, at least partial compression or sedimentation of the slurry occurs at the target location. Methods that include...

19. The method according to claim 18, wherein the target location is at least 3,000 feet underground.

20. The method according to claim 18, wherein the target position extends substantially vertically.

21. The method according to claim 18, wherein the return space located within the casing is sealed within a secondary conduit located within the casing, and a second annular space is formed between the casing and the secondary conduit.

22. The method according to claim 21, wherein the step of removing the substituted fluid through the return space uses a second fluid moving from the second annular space to the return space.

23. The method according to any one of claims 18 to 22, wherein the geological formation comprises a plurality of cracks at least partially filled with a high thermal conductivity material, and the high thermal conductivity material in the cracks exchanges heat with the compressed high thermal conductivity composition in the well.

24. The method according to claim 23, wherein the high thermal conductivity material in the crack is selected from the group consisting of graphite powder, flake graphite, pyrolysis graphite, desulfurized petroleum coke, graphene, fly ash, copper powder, aluminum nitride, and silicon carbide.

25. The method according to claim 18, further comprising the step of pumping water to the slurry that has been compressed or settled at a target location, at least partially, after the slurry has been compressed or settled, in order to maintain or increase the thermal conductivity of the slurry that has been compressed or settled at the target location.

26. A method for reducing the loss of heat conduction in a non-cemental, high-thermal-conductivity composition in a borehole, A step of supplying water in situ to the non-cemental high thermal conductivity composition, wherein the non-cemental high thermal conductivity composition is compressed or settles at the target position, and the amount of water supplied is sufficient to reduce the loss of heat conduction of the non-cemental high thermal conductivity composition compared to when the non-cemental high thermal conductivity composition was installed. Methods that include...

27. The method according to claim 26, wherein the water is supplied through an annular space between the casing of the closed-loop circuit and the well wall or well casing.

28. The method according to claim 26, wherein the non-cemental high thermal conductivity composition has permeability to water that allows water to penetrate at least 75% of the compressed or settled non-cemental high thermal conductivity composition.

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