A CO2 corrosion-resistant thermal insulation material for cementing and its preparation method

Abstract

The present invention discloses a CO2 corrosion-resistant thermal insulation material for cementing and its preparation method, addressing the problems of existing cementing cement being susceptible to acid corrosion, resulting in low heat recovery and utilization efficiency and severe heat loss. The CO2 corrosion-resistant thermal insulation material for cementing comprises 40-65 wt.% of an insulating matrix, 5-10 wt.% of aluminum titanate, 15-25 wt.% of sodium monofluorophosphate, and 15-25 wt.% of potassium aminotri(methylenephosphonate). The insulating matrix is obtained by mixing hollow ceramic microspheres, waste rock wool board powder, opal rock powder, and modified polycarbonate. The present invention not only improves the high-temperature stability, early strength, toughness, and CO2 corrosion resistance of the cementing system, but also reduces fluid loss, lowers the thermal conductivity of the cementing stone while meeting construction performance requirements, and improves the thermal insulation capacity of the cement stone, effectively reducing heat loss during geothermal resource extraction and improving geothermal resource utilization.

Description

Technical Field

[0001] The present invention belongs to the technical field of geothermal resource development, and in particular relates to a CO2 corrosion-resistant thermal insulation material for cementing and a preparation method thereof. Background Art

[0002] Geothermal energy, as a green, environmentally friendly, low-carbon, and highly efficient renewable resource, has garnered widespread attention. Currently, the two most commonly used heat extraction media for geothermal resource extraction are water and CO2. Water, when used as a heat extraction medium, undergoes physical and chemical reactions with rock minerals in the formation, destabilizing the reservoir and reducing the purity of the working fluid. Furthermore, dissolved minerals in water can cause scaling in the wellbore, surface equipment, and various pipelines, shortening equipment lifespan. Furthermore, low working fluid recovery is a challenge. Supercritical CO2, when used for geothermal resource extraction, offers several properties superior to water, improving heat extraction efficiency and increasing economic benefits, making it of great significance for hot dry rock development. However, when using supercritical CO2, the cement sheath is subject to acidic corrosion, leading to degradation of the cement stone. To address this issue, it is necessary to improve the corrosion resistance of the cement sheath. Furthermore, during geothermal resource extraction, the wellhead water temperature is significantly lower than the reservoir temperature. To improve wellhead water temperature and geothermal resource utilization efficiency, cement slurries with low thermal conductivity and good thermal insulation can be used for cementing operations.

[0003] In summary, in order to improve heat extraction and utilization efficiency, reduce heat loss, avoid resource waste, and increase economic benefits, it is particularly important to develop a CO2 corrosion-resistant insulation material for cementing. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a CO2 corrosion-resistant thermal insulation material for cementing cement 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 CO2 corrosion-resistant thermal insulation material for cementing, comprising the following raw materials in percentage by weight:

[0007] Thermal insulation matrix: 40-65wt.%;

[0008] Aluminum titanate: 5-10wt.%;

[0009] Sodium monofluorophosphate: 15-25wt.%

[0010] Potassium aminotrimethylenephosphonate: 15-25wt.%;

[0011] The heat-insulating matrix is obtained by mixing hollow ceramic microspheres, waste rock wool board powder, opal powder and modified polycarbonate in a weight ratio of (11-15):(1-3):(3-5):(1-2).

[0012] In some embodiments of the present invention, the CO2 corrosion-resistant thermal insulation material for cementing cement is composed of the following raw materials in percentage by weight:

[0013] Thermal insulation matrix: 50-65wt.%;

[0014] Aluminum titanate: 8-10wt.%;

[0015] Sodium monofluorophosphate: 20-25wt.%

[0016] Potassium aminotrimethylenephosphonate: 15-20wt.%;

[0017] Preferably, the thermal insulation matrix is obtained by mixing hollow ceramic microspheres, waste rock wool board powder, opal powder and modified polycarbonate in a weight ratio of (11-12):(1-2):(3-4):1.

[0018] Furthermore, the aluminum titanate is in powder form, and its particle size is ≥800 mesh.

[0019] Furthermore, the sodium monofluorophosphate is in powder form, has a particle size greater than 325 mesh, and a purity greater than 99 wt.%.

[0020] Furthermore, the potassium aminotri(methylenephosphonate) is a crystalline powder with a particle size greater than 160 mesh and a purity greater than 98 wt.%.

[0021] Furthermore, the hollow ceramic microspheres are prepared by flame spraying using lithium slag, zirconium silicide, molybdenum tailings, rare earth tailings and sawdust as raw materials; preferably, the hollow ceramic microspheres have a particle size of 10 to 30 μm and a thermal conductivity of 0.09 to 0.11 W / (m·K).

[0022] 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.

[0023] The lithium slag 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.%.

[0024] The effective substance content of the zirconium silicide is greater than 99.9 wt.%

[0025] The molybdenum tailings are mainly composed of diopside, albite and dolomite, wherein the SiO2 content is greater than 52wt.%, and the Al2O3 content is greater than 14wt.%.

[0026] The main chemical components (SiO2, Fe2O3, Al2O3 and CaO, etc.) in the rare earth tailings account for more than 82%, 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.%.

[0027] The sawdust is formed by crushing dry sawdust, and its average particle size is less than 20 meshes.

[0028] 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, greatly improving the strength and toughness of the ceramic microspheres. As the firing temperature increases, the dolomite in the molybdenum tailings forms a diopside interlaced network structure, thereby improving 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, providing basic conditions for forming a hollow structure.

[0029] The preparation method of the hollow ceramic microspheres comprises:

[0030] Step A, drying and calcining the lithium slag at high temperature to obtain activated lithium slag;

[0031] 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; preferably, the mass ratio of activated lithium slag, zirconium silicide, molybdenum tailings and rare earth tailings is 70:15:10:5;

[0032] 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; preferably, the mass ratio of the mixture A to the sawdust is 90:10;

[0033] Step D: collecting the sprayed product and vacuum drying it to obtain the hollow ceramic microspheres.

[0034] The present invention adopts a flame spraying method to form hollow ceramic microspheres, which has a simple process flow, convenient equipment operation and low energy consumption.

[0035] Preferably, in step A, the drying is carried out in an oven at a baking 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;

[0036] Preferably, in step B, wet ball milling is performed, wherein the liquid medium is anhydrous ethanol, 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 the drying is performed in an oven at a baking temperature of 50 to 70° C. and a time of 1.5 to 2 h;

[0037] 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;

[0038] 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 baking temperature is 70-85° C., and the drying time is 6-7 h.

[0039] Furthermore, the waste rock wool board powder is obtained by drying, crushing and grinding the waste rock wool board or rock wool board waste, and its average particle size is ≥325 mesh.

[0040] Furthermore, the protein shale powder is obtained by drying and grinding the protein shale, and has an average particle size of ≥1200 meshes and a SiO2 content of ≥90wt.%.

[0041] Furthermore, the modified polycarbonate is formed by melt blending, granulating, cooling, crushing, and then low-temperature plasma modification of waste rock wool board powder and polycarbonate in a mass ratio of (1-2): (9-10), preferably 1:9, with an average particle size of ≥325 mesh;

[0042] The present invention also provides a method for preparing the above-mentioned CO2 corrosion-resistant thermal insulation material for cementing cement, comprising the following steps: weighing an insulation matrix, aluminum titanate powder, sodium monofluorophosphate and potassium aminotri(methylenephosphonate), and fully mixing them to obtain the CO2 corrosion-resistant thermal insulation material for cementing cement.

[0043] Preferably, a powder mixer is used to mix the thermal insulation matrix, aluminum titanate powder, sodium monofluorophosphate and potassium aminotri(methylene)phosphonate for 5 to 10 minutes.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention combines the inorganic material sodium monofluorophosphate and the organic material potassium aminotrimethylphosphonate to synergistically enhance the CO2 corrosion resistance. The sodium monofluorophosphate reacts with the cement hydration product calcium hydroxide to form apatite, which coats the surface of the remaining hydration products to form a dense protective layer to prevent further CO2 intrusion; the potassium aminotrimethylphosphonate aqueous solution is weakly acidic and can react with the calcium hydroxide in the cement hydration product to form apatite. 2+Chelation forms complexes, reduces the easily carbonized substances in the hydration products, inhibits and interferes with the formation and growth of calcium carbonate, and thus improves CO2 corrosion resistance; aluminum titanate has good heat resistance, and its microstructure has crystalline phases and pores, which give it low thermal conductivity and corrosion resistance. On the one hand, it can enhance temperature resistance, and on the other hand, it cooperates with the thermal insulation matrix to enhance thermal insulation performance.

[0046] The present invention utilizes a thermally insulating matrix, primarily composed of SiO2 and Al2O3, which, when added to cement, significantly reduces the calcium-to-silicon ratio (Ca / Si). This reduction in the Ca / Si ratio not only ensures the high-temperature strength of the cement paste and improves its heat resistance, but also reduces the formation of alkaline hydration products, inhibiting the formation of calcium carbonate. This, in turn, synergistically enhances the corrosion resistance of the cement paste with potassium aminotrimethylphosphonate and sodium monofluorophosphate.

[0047] The CO2 corrosion-resistant thermal insulation material for cementing cement of the present invention, which is mixed in a certain proportion under the synergistic effect of various components, can not only improve the high-temperature stability, early strength, toughness and CO2 corrosion resistance of the cementing cement system; but also reduce the filtration loss, reduce the thermal conductivity of the cementing cement stone while meeting the construction performance requirements, improve the thermal insulation capacity of the cement stone, effectively reduce the heat loss in the process of geothermal resource exploitation, and improve the utilization rate of geothermal resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The weight loss curves of the cementing slurry systems 1# to 5# of the present invention and the comparative cementing slurry system after 28 days of corrosion are shown. DETAILED DESCRIPTION

[0049] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0050] 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).

[0051] 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.%.

[0052] The effective substance content of zirconium silicide in the embodiment of the present invention is greater than 99.9 wt.%.

[0053] 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.%.

[0054] 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.%.

[0055] The hollow ceramic microspheres of the embodiment of the present invention are prepared by a flame spraying method using lithium slag, zirconium silicide, molybdenum tailings, rare earth tailings and sawdust as raw materials, specifically:

[0056] 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;

[0057] 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;

[0058] 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;

[0059] 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.

[0060] The preparation method of the waste rock wool board powder in the embodiment of the present invention is: after the waste rock wool board or rock wool board waste is dried, it is coarsely crushed by a crusher and then ground by an ultrafine grinder to obtain the waste rock wool board powder.

[0061] The preparation method of the protein shale powder in the embodiment of the present invention is: placing the protein shale in an oven for drying, and then placing it in an ultrafine grinding mill to grind it to obtain the protein shale powder.

[0062] The preparation method of the modified polycarbonate in the embodiment of the present invention 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 the modified polycarbonate.

[0063] Example 1

[0064] As a preferred embodiment of the present invention, the specific composition of a CO2 corrosion-resistant thermal insulation material for cementing disclosed in this embodiment is shown in Table 1.

[0065] Table 1

[0066] Components Weight percentage (wt.%) Insulation matrix 40 Aluminum titanate powder 10 Sodium monofluorophosphate 25 Potassium aminotrimethylphosphonate 25

[0067] In this embodiment, the thermal insulation matrix is obtained by mixing hollow ceramic microspheres, waste rock wool board powder, opal powder and modified polycarbonate in a weight ratio of 11:3:5:1.

[0068] In this embodiment, the insulation matrix, aluminum titanate powder, sodium monofluorophosphate, and aminotri(methylenephosphonic acid) potassium in a weight percentage of 40:10:25:25 were placed in a powder mixer and fully mixed for 5 minutes to obtain a CO2 corrosion-resistant insulation material 1# for cementing cement.

[0069] Example 2

[0070] As a preferred embodiment of the present invention, the specific composition of a CO2 corrosion-resistant thermal insulation material for cementing cement disclosed in this embodiment is shown in Table 2.

[0071] Table 2

[0072]

[0073]

[0074] In this embodiment, the thermal insulation matrix is obtained by mixing hollow ceramic microspheres, waste rock wool board powder, opal powder and modified polycarbonate in a weight ratio of 11:3:5:1.

[0075] In this embodiment, the insulation matrix, aluminum titanate powder, sodium monofluorophosphate, and potassium aminotri(methylenephosphonate) in a weight percentage of 52:8:20:20 were placed in a powder mixer and fully mixed for 5 minutes to obtain CO2 corrosion-resistant insulation material 2# for cementing cement.

[0076] Example 3

[0077] As a preferred embodiment of the present invention, the specific composition of a CO2 corrosion-resistant thermal insulation material for cementing disclosed in this embodiment is shown in Table 3.

[0078] Table 3

[0079] Components Weight percentage (wt.%) Insulation matrix 65 Aluminum titanate powder 5 Sodium monofluorophosphate 15 Potassium aminotrimethylphosphonate 15

[0080] In this embodiment, the thermal insulation matrix is obtained by mixing hollow ceramic microspheres, waste rock wool board powder, opal powder and modified polycarbonate in a weight ratio of 11:3:5:1.

[0081] In this embodiment, the insulation matrix, aluminum titanate powder, sodium monofluorophosphate, and potassium aminotri(methylenephosphonate) in a weight percentage of 65:5:15:15 were placed in a powder mixer and fully mixed for 5 minutes to obtain CO2 corrosion-resistant insulation material 3# for cementing cement.

[0082] Example 4

[0083] As a preferred embodiment of the present invention, the specific composition of a CO2 corrosion-resistant thermal insulation material for cementing cement disclosed in this embodiment is shown in Table 4.

[0084] Table 4

[0085]

[0086]

[0087] In this embodiment, the thermal insulation matrix is obtained by mixing hollow ceramic microspheres, waste rock wool board powder, opal powder and modified polycarbonate in a weight ratio of 13:2:4:1.

[0088] In this embodiment, the insulation matrix, aluminum titanate powder, sodium monofluorophosphate, and potassium aminotri(methylenephosphonate) in a weight percentage of 52:8:20:20 were placed in a powder mixer and fully mixed for 5 minutes to obtain CO2 corrosion-resistant insulation material 4# for cementing cement.

[0089] Example 5

[0090] As a preferred embodiment of the present invention, the specific composition of a CO2 corrosion-resistant thermal insulation material for cementing cement disclosed in this embodiment is shown in Table 5.

[0091] Table 5

[0092] Components Weight percentage (wt.%) Insulation matrix 52 Aluminum titanate powder 8 Sodium monofluorophosphate 20 Potassium aminotrimethylphosphonate 20

[0093] In this embodiment, the thermal insulation matrix is obtained by mixing hollow ceramic microspheres, waste rock wool board powder, opal powder and modified polycarbonate in a weight ratio of 15:1:3:1.

[0094] In this embodiment, the insulation matrix, aluminum titanate powder, sodium monofluorophosphate, and potassium aminotri(methylenephosphonate) in a weight percentage of 52:8:20:20 were placed in a powder mixer and fully mixed for 5 minutes to obtain CO2 corrosion-resistant insulation material 5# for cementing cement.

[0095] Comparative Example 1

[0096] Compared to Example 1, this comparative example does not contain sodium monofluorophosphate. Specifically, the raw material composition, by mass, is: thermal insulation matrix: aluminum titanate powder: potassium aminotri(methylenephosphonate) in a ratio of 40:10:25. All other conditions remain the same. The material produced in this comparative example is designated D1#.

[0097] Comparative Example 2

[0098] This comparative example, compared to Example 1, does not contain potassium aminotris(methylenephosphonate). Specifically, the raw material composition, by mass, is: thermal insulation substrate: aluminum titanate powder: potassium aminotris(methylenephosphonate) at a ratio of 40:10:25. All other conditions remain the same. The material produced in this comparative example is designated D2#.

[0099] Test example

[0100] Cement slurries were prepared using CO2 corrosion-resistant insulation materials 1# to 5# for cementing cement prepared in Examples 1 to 5, and materials D1# to D2# prepared in the comparative example, in accordance with GB / T19139. The formula was: 80% G-grade oil well cement + 20% CO2 corrosion-resistant insulation material for cementing cement (mass ratio), and 1% high-temperature retarder and 2.5% high-temperature fluid loss additive, based on 100% of G-grade oil well cement and CO2 corrosion-resistant insulation material for cementing cement, with a water-cement ratio of 0.5, to obtain cementing slurry systems 1# to 5# and D1# to D2#, respectively.

[0101] Cement slurry was prepared according to GB / T19139 standard, with the following formula: 100% G-grade oil well cement, 1% high-temperature retarder and 2.5% high-temperature fluid loss additive (by mass ratio) based on 100% of G-grade oil well cement, and a water-cement ratio of 0.5 to obtain a comparative cementing slurry system.

[0102] 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.

[0103] According to the GB / T19139 oil well cement test method, cementing slurry systems 1#~5# and D1#~D2# were tested at 150℃ to compare the cement slurry engineering performance of the cementing slurry systems. The results are shown in Table 6.

[0104] Table 6

[0105]

[0106]

[0107] The experimental data in Table 6 show that the cementing slurry systems 1#-5# prepared in Examples 1-5 all exhibited water loss less than 50 ml, fluidity and free liquid content that met construction requirements, excellent slurry stability, controllable thickening time, and excellent engineering performance. These performance characteristics far outperformed those of the comparative cementing slurry system without the addition of the CO2 corrosion-resistant thermal insulation material for cementing cement. The CO2 corrosion-resistant thermal insulation material for cementing cement of the present invention exhibits excellent compatibility with admixtures, a controllable thickening time, and is suitable for the preparation of existing cementing slurry systems.

[0108] Cement pastes from the aforementioned cementing slurry systems 1#-5#, D1#-D2#, and a comparative cementing slurry system were placed in a high-temperature, high-pressure corrosion reactor in a high-temperature, high-pressure, vapor-containing supercritical CO₂ environment. The curing temperature was 150°C, the CO₂ pressure was 5 MPa, the total pressure was 10 MPa, and the partial pressure of N₂ was 28 days. Compressive strength was tested using a NYSQ-2017 pressure testing machine. Permeability measurements were also conducted for each slurry sample according to the SY / T6466-2000 standard, "Evaluation Method for High-Temperature Performance of Oil Well Cement." 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.

[0109] Table 7

[0110]

[0111]

[0112] According to the experimental data in Table 7, after a certain corrosion age, the comparative cementing slurry system without the addition of the CO2 corrosion-resistant thermal insulation material for cementing cement had low compressive strength and showed signs of decline, while the cementing slurry systems 1# to 5# configured in Examples 1 to 5 had high compressive strength and did not show any decline, with a slight increase in compressive strength. This indicates that the CO2 corrosion-resistant thermal insulation material for cementing cement of the present invention can improve the temperature resistance of cement stone. At the same time, the permeability of the comparative cementing slurry system increased significantly, while the permeability of cementing slurry systems 1# to 5# increased slightly, but overall was much lower than that of the comparative cementing slurry system, indicating that the CO2 corrosion-resistant thermal insulation material for cementing cement of the present invention can form a protective layer on the surface of the hydration product, increase the density of the cement matrix, protect the cement stone from CO2 corrosion, and have excellent corrosion resistance. Analysis of the data of cementing slurry systems D1# and D2# shows that the compressive strength is reduced when sodium monofluorophosphate or potassium aminotrimethylphosphonate is added alone, the permeability is increased, and the thermal conductivity remains essentially unchanged. The results show that the synergistic effect of sodium monofluorophosphate and potassium aminotrimethylphosphonate helps to enhance the corrosion resistance of the present invention. In addition, the thermal conductivity of cementing slurry systems 1# to 5# is much lower than that of the comparative cementing slurry system, indicating that the CO2 corrosion-resistant thermal insulation material for cementing cement of the present invention has the characteristics of low thermal conductivity and good thermal insulation effect.

[0113] The cement pastes from the aforementioned cementing slurry systems 1# to 5# and the comparative cementing slurry system were placed in a high-temperature, high-pressure corrosion reactor. The cement pastes were exposed to a high-temperature, high-pressure, and vapor-containing supercritical CO2 environment. The curing temperature was 150°C, the CO2 pressure was 5 MPa, the total pressure was 10 MPa, and the N2 partial pressure was 28 days. The cured products of each cementing slurry system were subjected to thermogravimetric analysis. Figure 1 shown.

[0114] The study found that the corrosion product of cement is calcium carbonate, and the decomposition temperature range of calcium carbonate is 600-770℃. Thermogravimetric analysis is used to measure the weight loss of cement stone in this temperature range to characterize the corrosion of cement stone under given conditions. The greater the weight loss of the sample in the above range, the more susceptible the sample is to corrosion, and vice versa. Figure 1 The weight loss curves for cementing slurry and cementing slurries 1 to 5 after 28 days of corrosion are compared. Thermogravimetric testing of the samples was performed on a thermal analysis instrument manufactured by Mettle Toledo, Inc., at a heating rate of 10°C / min under nitrogen atmosphere.

[0115] pass Figure 1The experimental results show that within the temperature range of 600-770°C, the weight loss TG (%) of cementing slurries 1#-5# are all less than that of the control cementing slurry, that is, the corrosion resistance of cementing slurries 1#-5# is much greater than that of the control cementing slurry, indicating that the CO2 corrosion-resistant thermal insulation material for cementing cement of the present invention has excellent corrosion resistance.

[0116] In summary, the adoption of the technical solution of the present invention can effectively improve the corrosion resistance and thermal insulation performance of cementing cement.

[0117] 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 CO2 corrosion resistant thermal insulation material for cementing, characterized in that: It is composed of the following raw materials in percentage by weight: Thermal insulation matrix: 40~65wt.%; Aluminum titanate: 5~10wt.%; Sodium monofluorophosphate: 15~25 wt.% Potassium aminotrimethylenephosphonate: 15~25wt.%; The heat-insulating matrix is obtained by mixing hollow ceramic microspheres, waste rock wool board powder, protein shale powder and modified polycarbonate in a weight ratio of (11-15):(1-3):(3-5):(1-2).

2. The CO2 corrosion resistant thermal insulation material for cementing according to claim 1, characterized in that: It is composed of the following raw materials in percentage by weight: Thermal insulation matrix: 50~65wt.%; Aluminum titanate: 8~10wt.%; Sodium monofluorophosphate: 20~25 wt.% Potassium aminotrimethylenephosphonate: 15~20wt.%; The heat-insulating matrix is obtained by mixing hollow ceramic microspheres, waste rock wool board powder, protein shale powder and modified polycarbonate in a weight ratio of (11-12):(1-2):(3-4):

1.

3. A CO2 corrosion resistant thermal insulation material for cementing according to claim 1 or 2, characterized in that: The aluminum titanate is in powder form, and its particle size is ≥800 mesh.

4. A CO2 corrosion resistant thermal insulation material for cementing according to claim 1 or 2, characterized in that: The sodium monofluorophosphate is in powder form, and its particle size is greater than 325 meshes.

5. A CO2 corrosion resistant thermal insulation material for cementing according to claim 1 or 2, characterized in that: The potassium aminotri(methylenephosphonate) is a crystalline powder with a particle size greater than 160 meshes.

6. A CO2 corrosion resistant thermal insulation material for cementing according to claim 1 or 2, characterized in that: The hollow ceramic microbeads are prepared using lithium slag, zirconium silicide, molybdenum tailings, rare earth tailings and sawdust as raw materials through a flame spraying method. The hollow ceramic microbeads have a particle size of 10-30 μm and a thermal conductivity of 0.09-0.11 W / (m·K).

7. A CO2 corrosion resistant thermal insulation material for cementing according to claim 1 or 2, characterized in that: The waste rock wool board powder is obtained by drying, crushing and grinding the waste rock wool boards or rock wool board waste, and the average particle size thereof is ≥325 meshes.

8. The CO2 corrosion resistant thermal insulation material for cementing according to claim 1 or 2, characterized in that: The protein shale powder is obtained by drying and grinding the protein shale, and has an average particle size of ≥1200 meshes and a SiO2 content of ≥90 wt.%.

9. A CO2 corrosion resistant thermal insulation material for cementing according to claim 1 or 2, characterized in that: The modified polycarbonate is formed by melt blending waste rock wool board powder and polycarbonate in a mass ratio of (1-2):(9-10), followed by blending, granulation, cooling, crushing, and then low-temperature plasma modification. The average particle size is ≥325 mesh.

10. The method for preparing a CO2 corrosion resistant thermal insulation material for cementing according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: weighing a heat-insulating matrix, aluminum titanate powder, sodium monofluorophosphate and potassium aminotri(methylene phosphonate), and fully mixing them to obtain the CO2 corrosion-resistant heat-insulating material for cementing cement.

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