Thermal insulation material for geothermal well cementing and preparation method thereof

Abstract

The present invention discloses a geothermal well cementing insulation material and a preparation method thereof, belonging to the field of geothermal resource development technology. The geothermal well cementing insulation material comprises, by weight percentage, 55-75% hollow ceramic microspheres, 5-15% waste rock wool board powder, 15-25% protein shale powder, and 5% modified polycarbonate. The hollow ceramic microspheres are prepared from lithium slag, zirconium silicide, molybdenum tailings, rare earth tailings, and sawdust. Based on the principle of synergistic effect, the geothermal well cementing insulation material, which is prepared by mixing the hollow ceramic microspheres, waste rock wool board powder, protein shale powder, and modified polycarbonate in a certain proportion, is environmentally friendly, has low thermal conductivity, good thermal insulation effect, high mechanical strength, high activity performance, good flexibility, and low cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of geothermal resource development, and in particular relates to a thermal insulation material for geothermal well cementing and a preparation method thereof. Background Art

[0002] Geothermal energy is a vast, sustainable, and renewable resource hidden within the Earth. It boasts vast reserves and widespread distribution, and represents a new type of clean energy. The development and utilization of geothermal energy offers significant social and environmental benefits, enormous market potential, and promising development prospects. However, a common challenge in the extraction of geothermal resources is heat loss.

[0003] In order to reduce heat loss, improve the comprehensive utilization rate of geothermal resources and bring higher economic benefits, research is conducted on the thermal insulation technology of geothermal well cementing cement ring. Usually, low thermal conductivity materials are added. However, the addition of low thermal conductivity materials will lead to instability of the cement slurry system and slow strength development, which directly affects the cementing quality and safety. Therefore, it is particularly important to develop an insulation material with low thermal conductivity, good stability, good compatibility and conducive to strength development to reduce heat loss in the wellbore during geothermal extraction. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a thermal insulation material for geothermal well cementing and a preparation method thereof, so as to at least solve some of the above technical problems.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A thermal insulation material for geothermal well cementing, wherein the raw materials of the thermal insulation material for geothermal well cementing include the following components in percentage by weight:

[0007] Hollow ceramic microspheres: 55-75wt.%;

[0008] Waste rock wool board powder: 5-15% wt.%;

[0009] Protein shale powder: 15-25wt.%;

[0010] Modified polycarbonate: 5wt.%;

[0011] The hollow ceramic microbeads are prepared from lithium slag, zirconium silicide, molybdenum tailings, rare earth tailings and sawdust as raw materials.

[0012] The hollow ceramic microbeads of the present invention are lightweight, high in strength, have high volcanic ash activity, and have excellent thermal insulation effects. They bond well with other inorganic cementitious materials and can promote the early hydration and strength development of geothermal cement. The waste rock wool board powder has good thermal insulation properties due to its low thermal conductivity. It can not only form a good three-dimensional network structure with the cement hydration products, but also provide a support for the hollow ceramic microbeads, protein shale powder, and modified polycarbonate. The protein shale is mainly composed of SiO2, which has volcanic ash activity and a large number of microporous structures. After being ground into powder, its volcanic ash activity can be further enhanced. Utilizing the microporous structure and volcanic ash activity, it can not only be used as a filling material to fill the gaps between the hollow ceramic microspheres, waste rock wool boards, cement particles, and hydration products, but can also be used as a thermal insulation material and active material to enhance the performance of the thermal insulation material for cementing. The modified polycarbonate exhibits excellent hydrophilicity and temperature resistance, forming a strong bond with other substrate materials. It interacts with the network structure formed by waste rock wool board powder to achieve toughness and reduce brittleness. Furthermore, it fully utilizes solid waste materials such as lithium slag, molybdenum tailings, rare earth tailings, and waste rock wool board, significantly reducing the environmental impact of solid waste, achieving a green, environmentally friendly, and low-cost approach.

[0013] The hollow ceramic microspheres are prepared by using lithium slag, zirconium silicide, molybdenum tailings, rare earth tailings and sawdust. A large amount of air is contained in the hollow ceramic microspheres, which can reduce the thermal conductivity of the thermal insulation material and improve the thermal insulation performance. At the same time, the hollow ceramic microspheres provide SiO2 and Al2O3 components necessary for ceramics. In addition, the lithium slag, molybdenum tailings and rare earth tailings are the main sources of alkali metal oxides (K2O and Na2O). The rare earth oxides in the rare earth tailings can serve as stabilizers and sintering aids to improve the strength and toughness of the ceramic microspheres. As the firing temperature increases, the dolomite in the molybdenum tailings forms a diopside phase interlaced network structure, which improves the strength of the ceramic microspheres. The zirconium silicide further improves the density and strength of the ceramic microspheres. The sawdust generates a large amount of gas at high temperature, which provides basic conditions for forming a hollow structure.

[0014] In some embodiments of the present invention, a thermal insulation material for geothermal well cementing is provided, wherein the raw materials of the thermal insulation material for geothermal well cementing include the following components in percentage by weight:

[0015] Hollow ceramic microspheres: 60-75wt.%;

[0016] Waste rock wool board powder: 8-12% wt.%;

[0017] Protein shale powder: 18-22wt.%;

[0018] Modified polycarbonate: 5wt.%;

[0019] The hollow ceramic microbeads are prepared from lithium slag, zirconium silicide, molybdenum tailings, rare earth tailings and sawdust as raw materials.

[0020] Furthermore, the hollow ceramic microspheres have a particle size of 5 to 40 μm and a thermal conductivity of 0.09 to 0.11 W / (m·K).

[0021] Furthermore, the lithium slag is mainly composed of quartz phase, andalusite, corundum, and a small amount of glass phase, kaolinite and lithium carbonate; the SiO2 content in the lithium slag is greater than 60wt.%, the Al2O3 content is greater than 20wt.%, the Na2O content is 0.2-0.8wt.%, and the K2O content is 0.1-4wt.%.

[0022] Furthermore, the purity of the zirconium silicide is greater than 99.9 wt.%.

[0023] Furthermore, the molybdenum tailings are mainly composed of diopside, albite and dolomite; the SiO2 content in the molybdenum tailings is greater than 52wt.%, and the Al2O3 content is greater than 14wt.%.

[0024] Furthermore, the main chemical components (SiO2, Fe2O3, Al2O3 and CaO, etc.) in the rare earth tailings account for more than 82wt.%, the SiO2 content in the rare earth tailings is more than 55wt.%, the Al2O3 content is more than 14wt.%, and the CaF2 content is 0.25-0.30wt.%.

[0025] Furthermore, the sawdust is formed by crushing dry sawdust, and its average particle size is less than 20 meshes.

[0026] The present invention also provides a method for preparing a thermal insulation material for geothermal well cementing, comprising: weighing hollow ceramic microspheres, waste rock wool board powder, protein shale powder, and modified polycarbonate, and mixing them to obtain the thermal insulation material for geothermal well cementing; preferably, pneumatic homogenization is used to mix the raw materials. Preferably, pneumatic homogenization is used to mix the raw materials.

[0027] Furthermore, the preparation method of the hollow ceramic microspheres includes:

[0028] Step A, drying and calcining the lithium slag at high temperature to obtain activated lithium slag;

[0029] Step B, weighing activated lithium slag, zirconium silicide, molybdenum tailings and rare earth tailings in a mass ratio of (60-74):(13-15):(10-20):(1-5), wet ball milling and drying to form a mixture A;

[0030] Step C, weighing a mixture A and sawdust in a mass ratio of (90-95):(5-10), uniformly mixing them to form a mixture B, using a flame spray gun to spray the mixture B, and cooling and solidifying to obtain a sprayed product;

[0031] Step D, collecting the sprayed product and vacuum drying it to obtain the hollow ceramic microspheres;

[0032] Preferably, in step A, the drying is carried out in an oven at a drying temperature of 50 to 70° C. and a baking time of 7 to 8 hours; the calcination temperature is 680 to 700° C. and a calcination time of 1 to 1.5 hours;

[0033] Preferably, in step B, wet ball milling is performed using anhydrous ethanol as the liquid medium, the liquid-to-solid ratio is 2:1, the ball milling speed is 30 r / min, and the time is 1.5 to 2 h; and drying is performed in an oven at a drying temperature of 50 to 70° C. and a time of 1.5 to 2 h.

[0034] Preferably, in step C, the powder feeding gas of the mixture B is oxygen, the powder feeding speed is 15 g / s, the gas introduced into the flame spray gun is oxygen-acetylene, the oxygen pressure is 0.5-0.7 MPa, the acetylene pressure is 0.12-0.15 MPa, the jet flame temperature is 2500-2600° C., and the quenching distance is 450-500 mm; distilled water is used as the cooling medium, and the melt sprayed product is sprayed into the distilled water for rapid cooling and solidification;

[0035] Preferably, in step D, a vacuum drying oven is used for drying, the vacuum degree of vacuum drying is 0.05-0.08 MPa, the drying temperature is 70-85° C., and the drying time is 6-7 h.

[0036] The preparation method of the waste rock wool board powder is as follows: after drying the waste rock wool board or rock wool board waste, the waste rock wool board or rock wool board waste is coarsely crushed by a crusher and then ground by an ultrafine grinder to obtain the waste rock wool board powder;

[0037] Preferably, the average particle size of the waste rock wool board powder is ≥325 mesh;

[0038] The preparation method of the protein shale powder comprises: placing the protein shale in an oven for drying, and then placing the protein shale in an ultrafine grinding mill for grinding to obtain the protein shale powder;

[0039] Preferably, the protein shale powder has an average particle size of ≥1200 mesh and a SiO2 content of ≥90%;

[0040] The preparation method of the modified polycarbonate comprises: melt-blending waste rock wool board powder and polycarbonate in a mass ratio of 1:9, granulating, cooling, crushing, and then performing low-temperature plasma modification to form the modified polycarbonate;

[0041] Preferably, the average particle size of the modified polycarbonate is ≥325 mesh.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. Based on the principle of synergistic enhancement, the geothermal well cementing insulation material prepared by mixing hollow ceramic microspheres, waste rock wool board powder, protein shale powder and modified polycarbonate in a certain proportion has the characteristics of being green and environmentally friendly, having low thermal conductivity, good thermal insulation effect, high mechanical strength, high activity performance, good flexibility and low cost.

[0044] 2. The thermal insulation material for geothermal well cementing of the present invention is added to cementing gelling materials to improve the stability of the system, reduce the filtration loss, and improve the early strength and toughness of geothermal well cementing cement. While meeting the construction performance requirements, it can reduce the thermal conductivity of cement stone, improve the thermal insulation capacity of cement stone, effectively reduce the heat loss during geothermal resource exploitation, and improve the utilization rate of geothermal resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The scanning electron microscope spectrum of the hollow ceramic microspheres of the present invention is shown in FIG. DETAILED DESCRIPTION

[0046] In order to make those skilled in the art better understand the present invention, the following will be combined with the accompanying drawings in the embodiments of the present invention. Figure 1 The technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0047] The hollow ceramic microbeads in the embodiment of the present invention have a particle size of 5 to 40 μm and a thermal conductivity of 0.09 to 0.11 W / (m·K).

[0048] The lithium slag in the embodiment of the present invention is mainly composed of quartz phase, andalusite, corundum, and a small amount of glass phase, kaolinite and lithium carbonate; wherein the SiO2 content is greater than 60wt.%, the Al2O3 content is greater than 20wt.%, the Na2O content is 0.2-0.8wt.%, and the K2O content is 0.1-4wt.%.

[0049] The purity of zirconium silicide in the embodiment of the present invention is greater than 99.9 wt.%.

[0050] The molybdenum tailings in the embodiment of the present invention are mainly composed of diopside, albite and dolomite, wherein the SiO2 content is greater than 52wt.%, and the Al2O3 content is greater than 14wt.%.

[0051] The main chemical components (SiO2, Fe2O3, Al2O3 and CaO, etc.) in the rare earth tailings in the embodiment of the present invention account for more than 82wt.%, of which the SiO2 content is more than 55wt.%, the Al2O3 content is more than 14wt.%, and the CaF2 content is 0.25~0.30wt.%.

[0052] Example 1

[0053] As a preferred embodiment of the present invention, the specific composition of a thermal insulation material for geothermal well cementing disclosed in this embodiment is shown in Table 1. The preparation method thereof is as follows: hollow ceramic microspheres, waste rock wool board powder, protein shale powder, and modified polycarbonate are weighed in proportion, and the raw materials are mixed by pneumatic homogenization to obtain thermal insulation material #1 for geothermal well cementing.

[0054] Table 1

[0055] Components Weight percentage (wt.%) Hollow ceramic microspheres 55 Waste rock wool board powder 15 Protein shale powder 25 Modified polycarbonate 5

[0056] In this embodiment, the hollow ceramic microspheres are prepared by flame spraying using lithium slag, zirconium silicide, molybdenum tailings, rare earth tailings and sawdust as raw materials, specifically:

[0057] Step A, drying the lithium slag in an oven at 60° C. for 8 h, and then calcining the slag in a muffle furnace at 700° C. for 1.5 h to obtain activated lithium slag;

[0058] Step B, placing activated lithium slag, zirconium silicide, molybdenum tailings, and rare earth tailings in a wet ball mill at a mass ratio of 60:15:20:5 and grinding for 1 hour, using anhydrous ethanol as the liquid medium, a ball milling liquid-to-solid ratio of 2:1, a ball milling speed of 30 r / min, and a ball milling time of 2 hours; and drying in an oven at 60° C. for 2 hours to form a mixture A;

[0059] Step C, mixing mixture A and sawdust in a mass ratio of 95:5 to form mixture B, using a flame spray gun to spray the mixture B, and spraying the sprayed product into distilled water as a cooling medium for rapid cooling and solidification; wherein the powder feeding gas of mixture B is oxygen and the powder feeding rate is 15g / s; the gas introduced into the flame spray gun is oxygen-acetylene, the oxygen pressure is 0.6MPa, the acetylene pressure is 0.12MPa, the spray flame temperature is 2600°C, and the quenching distance is 500mm;

[0060] Step D: Collect the melt-sprayed product and dry it in a vacuum at 80° C. and 0.07 MPa for 6 h to obtain the hollow ceramic microspheres.

[0061] In this embodiment, the waste rock wool board powder is prepared by drying the waste rock wool boards or rock wool board waste, crushing them with a crusher, and then grinding them with an ultrafine grinder to obtain the waste rock wool board powder.

[0062] In this embodiment, the preparation method of the protein shale powder is: placing the protein shale in an oven to dry, and then placing it in an ultrafine grinder to grind it to obtain the protein shale powder.

[0063] In this embodiment, the preparation method of the modified polycarbonate is as follows: waste rock wool board powder and polycarbonate are melt-blended in a mass ratio of 1:9, granulated, cooled, crushed, and then modified by low-temperature plasma to form modified polycarbonate.

[0064] Example 2

[0065] As a preferred embodiment of the present invention, the specific composition of a thermal insulation material for geothermal well cementing disclosed in this embodiment is shown in Table 2. The preparation method thereof is as follows: hollow ceramic microspheres, waste rock wool board powder, protein shale powder, and modified polycarbonate are weighed in proportion, and the raw materials are mixed by pneumatic homogenization to obtain thermal insulation material #2 for geothermal well cementing.

[0066] Table 2

[0067] Components Weight percentage (wt.%) Hollow ceramic microspheres 65 Waste rock wool board powder 10 Protein shale powder 20 Modified polycarbonate 5

[0068] In this embodiment, the hollow ceramic microspheres are prepared by flame spraying using lithium slag, zirconium silicide, molybdenum tailings, rare earth tailings and sawdust as raw materials, specifically:

[0069] Step A, drying the lithium slag in an oven at 60° C. for 8 h, and then calcining the slag in a muffle furnace at 700° C. for 1.5 h to obtain activated lithium slag;

[0070] Step B, placing activated lithium slag, zirconium silicide, molybdenum tailings, and rare earth tailings in a wet ball mill at a mass ratio of 70:14:13:3 and grinding for 1 hour, using anhydrous ethanol as the liquid medium, a ball milling liquid-to-solid ratio of 2:1, a ball milling speed of 30 r / min, and a ball milling time of 2 hours; and drying in an oven at 60° C. for 2 hours to form a mixture A;

[0071] Step C, mixing mixture A and sawdust in a mass ratio of 90:10 to form mixture B, using a flame spray gun to spray the mixture B, and spraying the sprayed product into distilled water as a cooling medium for rapid cooling and solidification; wherein the powder feeding gas of mixture B is oxygen, and the powder feeding rate is 15g / s; the gas introduced into the flame spray gun is oxygen-acetylene, the oxygen pressure is 0.6MPa, the acetylene pressure is 0.12MPa, the spray flame temperature is 2600°C, and the quenching distance is 500mm;

[0072] Step D: Collect the melt-sprayed product and dry it in a vacuum at 80° C. and 0.07 MPa for 6 h to obtain the hollow ceramic microspheres.

[0073] In this embodiment, the waste rock wool board powder is prepared by drying the waste rock wool boards or rock wool board waste, crushing them with a crusher, and then grinding them with an ultrafine grinder to obtain the waste rock wool board powder.

[0074] In this embodiment, the preparation method of the protein shale powder is: placing the protein shale in an oven to dry, and then placing it in an ultrafine grinder to grind it to obtain the protein shale powder.

[0075] In this embodiment, the preparation method of the modified polycarbonate is as follows: waste rock wool board powder and polycarbonate are melt-blended in a mass ratio of 1:9, granulated, cooled, crushed, and then modified by low-temperature plasma to form modified polycarbonate.

[0076] Example 3

[0077] As a preferred embodiment of the present invention, the specific composition of a thermal insulation material for geothermal well cementing disclosed in this embodiment is shown in Table 3. The preparation method thereof is as follows: hollow ceramic microspheres, waste rock wool board powder, protein shale powder, and modified polycarbonate are weighed in proportion, and the raw materials are mixed using pneumatic homogenization to produce thermal insulation material #3 for geothermal well cementing.

[0078] Table 3

[0079] Components Weight percentage (wt.%) Hollow ceramic microspheres 75 Waste rock wool board powder 5 Protein shale powder 15 Modified polycarbonate 5

[0080] In this embodiment, the hollow ceramic microspheres are prepared by flame spraying using lithium slag, zirconium silicide, molybdenum tailings, rare earth tailings and sawdust as raw materials, specifically:

[0081] Step A, drying the lithium slag in an oven at 60° C. for 8 h, and then calcining the slag in a muffle furnace at 700° C. for 1.5 h to obtain activated lithium slag;

[0082] Step B, activated lithium slag, zirconium silicide, molybdenum tailings, and rare earth tailings are placed in a wet ball mill in a mass ratio of 74:13:10:3 and ground for 1 hour, the liquid medium is anhydrous ethanol, the ball milling liquid-to-solid ratio is 2:1, the ball milling speed is 30 r / min, and the ball milling time is 2 hours; after ball milling, the mixture is dried in an oven at 60°C for 2 hours to form a mixture A; Step C, the mixture A and sawdust are mixed in a mass ratio of 92:8 to form a mixture B, the mixture B is sprayed with a flame spray gun, and the sprayed product is sprayed into distilled water as a cooling medium for rapid cooling and solidification; wherein the powder feeding gas of the mixture B is oxygen and the powder feeding speed is 15 g / s; the gas introduced into the flame spray gun is oxygen-acetylene, the oxygen pressure is 0.6 MPa, the acetylene pressure is 0.12 MPa, the spray flame temperature is 2600°C, and the quenching distance is 500 mm;

[0083] Step D: Collect the melt-sprayed product and dry it in a vacuum at 80° C. and 0.07 MPa for 6 h to obtain the hollow ceramic microspheres.

[0084] In this embodiment, the waste rock wool board powder is prepared by drying the waste rock wool boards or rock wool board waste, crushing them with a crusher, and then grinding them with an ultrafine grinder to obtain the waste rock wool board powder.

[0085] In this embodiment, the preparation method of the protein shale powder is: placing the protein shale in an oven to dry, and then placing it in an ultrafine grinder to grind it to obtain the protein shale powder.

[0086] In this embodiment, the preparation method of the modified polycarbonate is as follows: waste rock wool board powder and polycarbonate are melt-blended in a mass ratio of 1:9, granulated, cooled, crushed, and then modified by low-temperature plasma to form modified polycarbonate.

[0087] Example 4

[0088] As a preferred embodiment of the present invention, the specific composition of a thermal insulation material for geothermal well cementing disclosed in this embodiment is shown in Table 4. The preparation method thereof is as follows: hollow ceramic microspheres, waste rock wool board powder, protein shale powder, and modified polycarbonate are weighed in proportion, and the raw materials are mixed by pneumatic homogenization to obtain thermal insulation material #4 for geothermal well cementing.

[0089] Table 4

[0090] Components Weight percentage (wt.%) Hollow ceramic microspheres 60 Waste rock wool board powder 15 Protein shale powder 20 Modified polycarbonate 5

[0091] In this embodiment, the hollow ceramic microspheres are prepared by flame spraying using lithium slag, zirconium silicide, molybdenum tailings, rare earth tailings and sawdust as raw materials, specifically:

[0092] Step A, drying the lithium slag in an oven at 60° C. for 8 h, and then calcining the slag in a muffle furnace at 700° C. for 1.5 h to obtain activated lithium slag;

[0093] Step B, activated lithium slag, zirconium silicide, molybdenum tailings, and rare earth tailings are placed in a wet ball mill at a mass ratio of 65:15:15:5 and ground for 1 hour, the liquid medium is anhydrous ethanol, the ball milling liquid-to-solid ratio is 2:1, the ball milling speed is 30 r / min, and the ball milling time is 2 hours; after ball milling, the mixture is dried in an oven at 60°C for 2 hours to form a mixture A; Step C, the mixture A and sawdust are mixed at a mass ratio of 94:6 to form a mixture B, the mixture B is sprayed with a flame spray gun, and the sprayed product is sprayed into distilled water as a cooling medium for rapid cooling and solidification; wherein the powder feeding gas of the mixture B is oxygen and the powder feeding speed is 15 g / s; the gas introduced into the flame spray gun is oxygen-acetylene, the oxygen pressure is 0.6 MPa, the acetylene pressure is 0.12 MPa, the spray flame temperature is 2600°C, and the quenching distance is 500 mm;

[0094] Step D: Collect the melt-sprayed product and dry it in a vacuum at 80° C. and 0.07 MPa for 6 h to obtain the hollow ceramic microspheres.

[0095] In this embodiment, the waste rock wool board powder is prepared by drying the waste rock wool boards or rock wool board waste, crushing them with a crusher, and then grinding them with an ultrafine grinder to obtain the waste rock wool board powder.

[0096] In this embodiment, the preparation method of the protein shale powder is: placing the protein shale in an oven to dry, and then placing it in an ultrafine grinder to grind it to obtain the protein shale powder.

[0097] In this embodiment, the preparation method of the modified polycarbonate is as follows: waste rock wool board powder and polycarbonate are melt-blended in a mass ratio of 1:9, granulated, cooled, crushed, and then modified by low-temperature plasma to form modified polycarbonate.

[0098] Example 5

[0099] As a preferred embodiment of the present invention, the specific composition of a thermal insulation material for geothermal well cementing disclosed in this embodiment is shown in Table 5. The preparation method thereof is as follows: hollow ceramic microspheres, waste rock wool board powder, protein shale powder, and modified polycarbonate are weighed in proportion, and the raw materials are mixed by pneumatic homogenization to obtain thermal insulation material #5 for geothermal well cementing.

[0100] Table 5

[0101] Components Weight percentage (wt.%) Hollow ceramic microspheres 70 Waste rock wool board powder 12 Protein shale powder 13 Modified polycarbonate 5

[0102] In this embodiment, the hollow ceramic microspheres are prepared by flame spraying using lithium slag, zirconium silicide, molybdenum tailings, rare earth tailings and sawdust as raw materials, specifically:

[0103] Step A, drying the lithium slag in an oven at 60° C. for 8 h, and then calcining the slag in a muffle furnace at 700° C. for 1.5 h to obtain activated lithium slag;

[0104] Step B, placing activated lithium slag, zirconium silicide, molybdenum tailings, and rare earth tailings in a wet ball mill at a mass ratio of 68:15:15:2 and grinding for 1 hour, using anhydrous ethanol as the liquid medium, a ball milling liquid-to-solid ratio of 2:1, a ball milling speed of 30 r / min, and a ball milling time of 2 hours; and drying in an oven at 60° C. for 2 hours to form a mixture A;

[0105] Step C, mixing mixture A and sawdust in a mass ratio of 93:7 to form mixture B, using a flame spray gun to spray the mixture B, and spraying the sprayed product into distilled water as a cooling medium for rapid cooling and solidification; wherein the powder feeding gas of mixture B is oxygen and the powder feeding rate is 15g / s; the gas introduced into the flame spray gun is oxygen-acetylene, the oxygen pressure is 0.6MPa, the acetylene pressure is 0.12MPa, the spray flame temperature is 2600°C, and the quenching distance is 500mm;

[0106] Step D: Collect the melt-sprayed product and dry it in a vacuum at 80° C. and 0.07 MPa for 6 h to obtain the hollow ceramic microspheres.

[0107] In this embodiment, the waste rock wool board powder is prepared by drying the waste rock wool boards or rock wool board waste, crushing them with a crusher, and then grinding them with an ultrafine grinder to obtain the waste rock wool board powder.

[0108] In this embodiment, the preparation method of the protein shale powder is: placing the protein shale in an oven to dry, and then placing it in an ultrafine grinder to grind it to obtain the protein shale powder.

[0109] In this embodiment, the preparation method of the modified polycarbonate is as follows: waste rock wool board powder and polycarbonate are melt-blended in a mass ratio of 1:9, granulated, cooled, crushed, and then modified by low-temperature plasma to form modified polycarbonate.

[0110] Test example

[0111] The geothermal well cementing insulation materials #1 to #5 prepared in Examples 1 to 5 were all used to prepare cement slurries in accordance with GB / T19139. The formula was: 80% G-grade oil well cement + 20% insulation material (by mass ratio), and 0.5% high-temperature retarder and 2% high-temperature fluid loss additive based on 100% G-grade oil well cement and insulation material, with a water-cement ratio of 0.5, to obtain cementing slurry systems #1 to #5, respectively.

[0112] Cement slurry was prepared according to GB / T19139 standard with the following formula: 100% G-grade oil well cement + 0.5% high temperature retarder + 2% high temperature fluid loss additive (by mass ratio) and a water-cement ratio of 0.5 to obtain a comparative cementing slurry system.

[0113] The above-mentioned G-grade oil well cement is provided by Jiahua Special Cement Co., Ltd., and the high-temperature retarder and high-temperature fluid loss additive are provided by Sichuan Xuran Hongchen New Materials Co., Ltd. The high-temperature retarder is an AMPS polymer; the high-temperature fluid loss additive is a 2-acrylamido-2-methylpropanesulfonic acid polymer.

[0114] The engineering properties of cement slurries #1 to #5 and a comparative cement slurry system were tested at 120°C according to the GB / T19139 oil well cement test method. The results are shown in Table 6.

[0115] Table 6

[0116]

[0117] The experimental data in Table 6 show that the cementing slurry systems #1-#5 prepared in Examples 1-5 exhibited water loss less than or equal to 35 ml, while their fluidity and free liquid content met construction requirements. The slurries exhibited excellent stability, controllable thickening times, and excellent engineering performance, significantly outperforming the comparative cementing slurry systems without the addition of the geothermal well cementing insulation material. The geothermal well cementing insulation material of the present invention exhibits excellent compatibility with admixtures, a controllable thickening time, improved slurry stability, reduced water loss, and reduced free liquid content, making it suitable for the preparation of existing cementing slurry systems.

[0118] The cementing slurry systems #1 to #5 and the comparative cementing slurry system were cured at 150°C and then tested for performance. Compressive strength was tested using a NYSQ-2017 pressure testing machine; the elastic modulus of the cement paste was measured using a triaxial stress testing machine; and the thermal conductivity of the cement paste was tested using a DRE-2C thermal conductivity tester using the transient plane heat source method. The test results are shown in Table 7.

[0119] Table 7

[0120]

[0121] The experimental data in Table 7 show that the cementing slurry systems #1 to #5 prepared in Examples 1 to 5 all exhibited 24-hour compressive strengths exceeding 12 MPa, demonstrating rapid strength development. These systems also improved the heat resistance of the cement paste, ensuring that its strength persisted even under high-temperature conditions. Their 48-hour elastic modulus was less than 7 GPa, effectively increasing its toughness. Furthermore, their thermal conductivity was significantly lower than that of a control cementing slurry system without the addition of geothermal well cementing insulation. These test results demonstrate that the geothermal well cementing insulation prepared in accordance with the present invention exhibits low thermal conductivity, excellent toughness and stability, promotes early strength development and heat resistance of cement, and exhibits excellent compatibility with admixtures.

[0122] In summary, the technical solution of the present invention can effectively improve the early strength, toughness and thermal insulation performance of cementing cement.

[0123] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention and are intended to illustrate the technical solutions of the present invention, rather than limiting them, and certainly not limiting the patent scope of the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features therein may be replaced by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention. In other words, any changes or refinements made to the main design concept and spirit of the present invention that have no substantive significance, provided that the technical problems they solve are still consistent with those of the present invention, should be included in the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields should also be included in the patent protection scope of the present invention.

Claims

1. A thermal insulation material for geothermal well cementing, characterized in that: The raw materials of the thermal insulation material for geothermal well cementing include the following components in percentage by weight: Hollow ceramic microspheres: 55~75wt.%; Waste rock wool board powder: 5~15%wt.%; Protein shale powder: 15~25wt.%; Modified polycarbonate: 5wt.%; The hollow ceramic microspheres are prepared using lithium slag, zirconium silicide, molybdenum tailings, rare earth tailings and sawdust as raw materials; The preparation method of the modified polycarbonate comprises the following steps: melt-blending waste rock wool board powder and polycarbonate in a mass ratio of 1:9, subjecting them to blending, granulation, cooling, and crushing, and then subjecting them to low-temperature plasma modification to form the modified polycarbonate.

2. The thermal insulation material for geothermal well cementing according to claim 1, characterized in that: The raw materials of the thermal insulation material for geothermal well cementing include the following components in percentage by weight: Hollow ceramic microspheres: 60~75wt.%; Waste rock wool board powder: 8~12%wt.%; Protein shale powder: 18~22wt.%; Modified polycarbonate: 5wt.%; The hollow ceramic microbeads are prepared from lithium slag, zirconium silicide, molybdenum tailings, rare earth tailings and sawdust as raw materials.

3. The thermal insulation material for geothermal well cementing according to claim 1 or 2, characterized in that: The hollow ceramic microspheres have a particle size of 5 to 40 μm and a thermal conductivity of 0.09 to 0.11 W / (m·K).

4. The thermal insulation material for geothermal well cementing according to claim 1 or 2, characterized in that: The SiO2 content in the lithium slag is >60wt.%, Al2O3 content is >20wt.%, Na2O content is 0.2~0.8wt.%, and K2O content is 0.1~4wt.%.

5. The thermal insulation material for geothermal well cementing according to claim 1 or 2, characterized in that: The purity of the zirconium silicide is greater than 99.9 wt.%.

6. The thermal insulation material for geothermal well cementing according to claim 1 or 2, characterized in that: The SiO2 content in the molybdenum tailings is greater than 52 wt.%, and the Al2O3 content is greater than 14 wt.%.

7. The thermal insulation material for geothermal well cementing according to claim 1 or 2, characterized in that: The main chemical components in the rare earth tailings account for more than 82wt.%, of which SiO2 content is more than 55wt.%, Al2O3 content is more than 14wt.%, and CaF2 content is 0.25~0.30wt.%.

8. The thermal insulation material for geothermal well cementing according to claim 1 or 2, characterized in that: The sawdust is formed by crushing dry sawdust, and its average particle size is less than 20 meshes.

9. The method for preparing a thermal insulation material for geothermal well cementing according to any one of claims 1 to 8, characterized in that: include: Weighing hollow ceramic microbeads, waste rock wool board powder, protein shale powder and modified polycarbonate, and mixing them to obtain the thermal insulation material for geothermal well cementing; Pneumatic homogenization is used to mix the raw materials.

10. The method for preparing a thermal insulation material for geothermal well cementing according to claim 9, characterized in that: The preparation method of the hollow ceramic microspheres comprises: Step A, drying and calcining the lithium slag at high temperature to obtain activated lithium slag; Step B, weighing activated lithium slag, zirconium silicide, molybdenum tailings and rare earth tailings in a mass ratio of (60-74):(13-15):(10-20):(1-5), wet ball milling and drying to form a mixture A; Step C, weighing a mixture A and sawdust in a mass ratio of (90-95):(5-10), uniformly mixing them to form a mixture B, using a flame spray gun to spray the mixture B, and cooling and solidifying to obtain a sprayed product; Step D, collecting the sprayed product and vacuum drying it to obtain the hollow ceramic microspheres; The preparation method of the waste rock wool board powder is as follows: after drying the waste rock wool board or rock wool board waste, the waste rock wool board or rock wool board waste is crushed by a crusher and then ground by an ultrafine grinder to obtain the waste rock wool board powder; The preparation method of the protein shale powder comprises: placing the protein shale in an oven for drying, and then placing the protein shale in an ultrafine grinding mill for grinding to obtain the protein shale powder; The preparation method of the modified polycarbonate comprises the following steps: melt-blending waste rock wool board powder and polycarbonate in a mass ratio of 1:9, subjecting them to blending, granulation, cooling, and crushing, and then subjecting them to low-temperature plasma modification to form the modified polycarbonate.

11. The method for preparing a thermal insulation material for geothermal well cementing according to claim 10, characterized in that: In step A, drying is performed in an oven at a drying temperature of 50-70° C. and a baking time of 7-8 hours; and calcination is performed at a calcination temperature of 680-700° C. and a calcination time of 1-1.5 hours.

12. The method for preparing a thermal insulation material for geothermal well cementing according to claim 10, characterized in that: In step B, wet ball milling is performed using anhydrous ethanol as the liquid medium, a liquid-to-solid ratio of 2:1, a ball milling speed of 30 r / min, and a time of 1.5 to 2 h; and drying is performed in an oven at a drying temperature of 50 to 70° C. and a time of 1.5 to 2 h.

13. The method for preparing a thermal insulation material for geothermal well cementing according to claim 10, characterized in that: In step C, the powder feeding gas for mixture B is oxygen, the powder feeding rate is 15 g / s, the gas introduced into the flame spray gun is oxygen-acetylene, the oxygen pressure is 0.5~0.7 MPa, the acetylene pressure is 0.12~0.15 MPa, the jet flame temperature is 2500~2600°C, and the quenching distance is 450~500 mm; distilled water is used as the cooling medium, and the melt-sprayed product is sprayed into distilled water for rapid cooling and solidification.

14. The method for preparing a thermal insulation material for geothermal well cementing according to claim 10, characterized in that: In step D, a vacuum drying oven is used for drying, the vacuum degree of vacuum drying is 0.05-0.08 MPa, the drying temperature is 70-85° C., and the drying time is 6-7 h.

15. The method for preparing a thermal insulation material for geothermal well cementing according to claim 10, characterized in that: In the method for preparing waste rock wool board powder, the average particle size of the waste rock wool board powder is ≥325 meshes.

16. The method for preparing a thermal insulation material for geothermal well cementing according to claim 10, characterized in that: In the preparation method of the protein shale powder, the average particle size of the protein shale powder is ≥1200 meshes and the SiO2 content is ≥90%.

17. The method for preparing a thermal insulation material for geothermal well cementing according to claim 10, characterized in that: In the preparation method of the modified polycarbonate, the average particle size of the modified polycarbonate is ≥325 meshes.

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