A high-toughness and low-density cement slurry system suitable for high-temperature well cementing and its preparation method

Abstract

The present invention discloses a high-toughness and low-density cement slurry system suitable for high-temperature well cementing and a preparation method thereof. The high-toughness and low-density cement slurry system comprises 27-58 wt.% of low heat of hydration cement, 20-40 wt.% of temperature-resistant and slightly expandable lightening material, 10-15 wt.% of molybdenum tailings, 10-15 wt.% of rare earth tailings, 1 wt.% of high-temperature stabilizer and 1-2 wt.% of dispersant by weight percentage. The temperature-resistant and slightly expandable lightening material is formed by mixing hollow microspheres, reinforcing materials, laterite nickel slag and temperature-resistant elastic materials. The present invention solves the problems of performance decline of low-density cement slurry, strength decline of cement stone and insufficient toughness under high-temperature conditions. The provided high-toughness and low-density cement slurry system not only has the characteristics of high temperature resistance, low density, high strength, gas channeling prevention performance and good toughness, but also has good high-temperature slurry stability and filtration loss.

Description

Technical Field

[0001] The present invention belongs to the technical field of the development of cementing materials for oil and gas field development, and particularly relates to a high-toughness and low-density cement slurry system suitable for high-temperature cementing and a preparation method thereof. Background Art

[0002] With the continuous deepening of oil and gas field development towards complex reservoirs, problems such as high temperature and high pressure, easy gas channeling, and long cementing sections with easy leakage have become increasingly prominent. When designing a cement slurry system for cementing in areas with easy leakage and low formation fracture pressure, it is necessary to avoid fracturing the formation and often use low-density cement slurries. However, there are often contradictions between the slurry properties of low-density cement slurries and the reduction of cement slurry density. In addition, with the increasing development of oil and gas resources in high-temperature and high-pressure and easy-leakage well conditions, the high-temperature resistance of the cement slurry needs to be considered while preventing formation fracture. Conventional domestic silicate cement slurry systems will have problems such as high-temperature strength decline, cracking, and poor toughness of the cement stone at high temperatures.

[0003] Chinese Patent CN104263332A discloses a high-temperature-resistant, high-strength, and low-density cement slurry for cementing, which is prepared from the following components, and the weight parts of each component are: 100 parts of low-hydration-heat cement, 15 - 76 parts of a lightening agent, 20 - 40 parts of microsilica, 2 - 10 parts of a fluid loss reducer, 1 - 8 parts of a dispersant, 0 - 5 parts of a retarder, 0 - 1.25 parts of an accelerator, 0 - 5 parts of an anti-gas-channeling agent, 0.2 - 0.8 parts of an antifoaming agent, and 50 - 120 parts of fresh water. The low-hydration-heat cement is a high-sulfur-resistant oil well cement meeting the API standard, and the lightening agent is a high-performance hollow glass microsphere. The temperature range of use of this patent is relatively low.

[0004] Chinese Patent CN110937857A discloses an anti-high-temperature and anti-channeling emulsion elastic and tough cement slurry and a preparation method thereof. The anti-high-temperature and anti-channeling emulsion elastic and tough cement slurry contains the following components in parts by weight: 100 parts of low-hydration-heat cement; 3 - 20 parts of an anti-high-temperature organic anti-channeling emulsion; 3 - 15 parts of an anti-high-temperature inorganic anti-channeling emulsion; 0.5 - 5 parts of an anti-high-temperature toughening material; 20 - 90 parts of a high-temperature strength stabilizing material; 1 - 10 parts of a high-temperature expansive agent; 1 - 12 parts of an anti-high-temperature fluid loss reducer; 0.1 - 10 parts of a high-temperature retarder; 0.5 - 3 parts of an antifoaming agent; 0 - 300 parts of a density adjusting material; and 35 - 200 parts of water.

[0005] The above technologies all have some problems, such as low temperature resistance, high cost, and complex preparation. In view of the above difficulties, it is particularly important to develop a cement slurry system with high temperature resistance, high toughness, and low density. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-toughness and low-density cement slurry system suitable for high-temperature cementing and its preparation method, aiming to solve the problems of performance decline of low-density cement slurry, strength decline of cement stone and insufficient toughness under high-temperature conditions.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A high-toughness and low-density cement slurry system suitable for high-temperature cementing, comprising the following raw materials by weight percentage:

[0009] Low heat of hydration cement: 27 - 58 wt.%;

[0010] Temperature-resistant and slightly expanding lightening material: 20 - 40 wt.%;

[0011] Molybdenum tailings: 10 - 15 wt.%;

[0012] Rare earth tailings: 10 - 15 wt.%;

[0013] High-temperature stabilizer: 1 wt.%;

[0014] Dispersant: 1 - 2 wt.%;

[0015] And additives based on the weight percentage of low heat of hydration cement:

[0016] High-temperature fluid loss reducer: 4 - 8 wt.%;

[0017] High-temperature retarder: 0.5 - 2 wt.%;

[0018] Defoamer: 0.25 wt.%.

[0019] In the high-toughness and low-density cement slurry system suitable for high-temperature cementing of the present invention, the percentage of low heat of hydration cement is 27 - 58 wt.%, for example: 27 wt.%, 28 wt.%, 29 wt.%, 30 wt.%, 31 wt.%, 32 wt.%, 33 wt.%, 34 wt.%, 35 wt.%, 36 wt.%, 37 wt.%, 38 wt.%, 39 wt.%, 40 wt.%, 41 wt.%, 42 wt.%, 43 wt.%, 44 wt.%, 45 wt.%, 46 wt.%, 47 wt.%, 48 wt.%, 49 wt.%, 50 wt.%, 51 wt.%, 52 wt.%, 53 wt.%, 54 wt.%, 55 wt.%, 56 wt.%, 57 wt.%, 58 wt.%.

[0020] In a high-toughness and low-density cement slurry system suitable for high-temperature cementing of the present invention, the percentage of temperature-resistant micro-expansion reducing material is 20-40 wt.%, such as 20 wt.%, 21 wt.%, 22 wt.%, 23 wt.%, 24 wt.%, 25 wt.%, 26 wt.%, 27 wt.%, 28 wt.%, 29 wt.%, 30 wt.%, 31 wt.%, 32 wt.%, 33 wt.%, 34 wt.%, 35 wt.%, 36 wt.%, 37 wt.%, 38 wt.%, 39 wt.%, 40 wt.%.

[0021] In a high-toughness and low-density cement slurry system suitable for high-temperature cementing of the present invention, the percentage of molybdenum tailings is 10-15 wt.%, such as 10 wt.%, 10.5 wt.%, 11 wt.%, 11.5 wt.%, 12 wt.%, 12.5 wt.%, 13 wt.%, 13.5 wt.%, 14 wt.%, 14.5 wt.%, 15 wt.%.

[0022] In a high-toughness and low-density cement slurry system suitable for high-temperature cementing of the present invention, the percentage of the dispersant is 1-2 wt.%, such as 1 wt.%, 1.2 wt.%, 1.4 wt.%, 1.6 wt.%, 1.8 wt.%, 2 wt.%.

[0023] In the admixture of the present invention, based on the weight percentage of the low heat of hydration cement, the dosage of the high-temperature fluid loss reducer is 4-8 wt.%, such as 4 wt.%, 4.5 wt.%, 5 wt.%, 5.5 wt.%, 6 wt.%, 6.5 wt.%, 7 wt.%, 7.5 wt.%, 8 wt.%.

[0024] In the admixture of the present invention, based on the weight percentage of the low heat of hydration cement, the proportion of the high-temperature retarder is 0.5-2 wt.%, such as 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, 1.0 wt.%, 1.1 wt.%, 1.2 wt.%, 1.3 wt.%, 1.4 wt.%, 1.5 wt.%, 1.6 wt.%, 1.7 wt.%, 1.8 wt.%, 1.9 wt.%, 2.0 wt.%.

[0025] In some embodiments of the present invention, a high-toughness and low-density cement slurry system suitable for high-temperature cementing comprises the following raw materials by weight percentage:

[0026] Low heat of hydration cement: 35-55 wt.%;

[0027] Temperature-resistant micro-expansion reducing material: 30-40 wt.%;

[0028] Molybdenum tailings: 10-15 wt.%;

[0029] Rare earth tailings: 10 - 15 wt.%;

[0030] High - temperature stabilizer: 1 wt.%;

[0031] Dispersant: 1 - 2 wt.%;

[0032] And additives based on the weight percentage of low - heat - of - hydration cement:

[0033] High - temperature fluid - loss reducer: 5 - 8 wt.%;

[0034] High - temperature retarder: 0.5 - 2 wt.%;

[0035] Defoamer: 0.25 wt.%;

[0036] Preferably, the temperature - resistant slightly - expanding weight - reducing material is composed of hollow microspheres, reinforcing materials, laterite nickel slag, and temperature - resistant elastic materials in a mass ratio of (5 - 7):(1 - 2):(1 - 2):1.

[0037] Under the action of laterite nickel slag, elastic particles (temperature - resistant elastic materials) and ultrafine particles (reinforcing materials) in the present invention, the high - temperature toughness, gas - channeling prevention property, and compactness of the cement stone are improved.

[0038] Further, the molybdenum tailings have SiO₂ content > 62 wt.%, Al₂O₃ content > 5 wt.%, and its average particle size ≥ 800 mesh.

[0039] Further, the rare earth tailings have SiO₂ content > 55 wt.%, Al₂O₃ content > 14 wt.%, CaF₂ content 0.25 - 0.30 wt.%, and its average particle size ≥ 800 mesh.

[0040] Further, the hollow microspheres are composed of borosilicate hollow glass microspheres and aluminosilicate hollow ceramic microspheres in a mass ratio of (2 - 4):(5 - 9), preferably 3:7; the particle size of the borosilicate hollow glass microspheres is 20 - 80 μm, and the compressive strength is 30 - 90 MPa; the particle size of the aluminosilicate hollow ceramic microspheres is 10 - 200 μm, and the compressive strength ≥ 350 MPa.

[0041] The hollow microspheres of the present invention are mixed with borosilicate hollow glass microspheres and aluminosilicate hollow ceramic microspheres. On the one hand, the borosilicate hollow glass microspheres and aluminosilicate hollow ceramic microspheres have small densities, which are 0.4 - 0.6 g / cm 3 、0.3 - 0.5 g / cm 3, it can be used as a lightweight material to reduce the material density; on the second hand, according to the difference in their compressive strengths, by adjusting the mixing ratio of the two, it can adapt to different pressure environments, reduce the cracking of microbeads caused by high temperature and high pressure, improve the material stability and control costs; on the third hand, according to the different particle sizes of the two, through the method of particle gradation matching, the density of the material can be improved, and then the lightweight effect and pressure-bearing capacity of the material can be improved.

[0042] Furthermore, the reinforcing material is composed of pseudo-boehmite, nano-boehmite and protein shale powder mixed in a mass ratio of (2-3):(2-3):5, and the preferred ratio is 2:3:5; the purity of the pseudo-boehmite > 90wt.%, and the average particle size is 5-10μm; the nano-boehmite is in powder form, its purity > 98wt.%, and the crystal particle size is 10-15nm; the particle size of the protein shale powder ≥ 1200 mesh, and the main component of the protein shale powder is amorphous active silica, and the SiO2 content ≥ 90wt.%.

[0043] Through the combined action of crystalline silica and amorphous silica (protein shale), crystalline hydrated alumina (nano-boehmite) and gel hydrated alumina (pseudo-boehmite), the present invention can not only increase the temperature resistance of the cement stone, but also promote the early hydration process of the cement; and its nano and ultra-fine materials have a large specific surface area, which can be used as nucleation sites during the hydration process to accelerate the hydration rate of the cementitious material. Pseudo-boehmite and nano-boehmite participate in the cement hydration reaction to increase the aluminum element content in the hydration products; the protein shale powder participates in the cement hydration reaction to increase the silicon element content; under the synergistic effect of each component, the calcium-silicon ratio (Ca / Si) is reduced, promoting the formation of C-A-S-H products with better temperature resistance, and then improving the high-temperature strength stability of the cement slurry system.

[0044] Furthermore, the temperature-resistant elastic material is composed of waste ceramic powder, polycarbonate and polyphenylene sulfide in a mass ratio of (0.5-1.5):(0.5-3):(5-9), and is prepared by melt blending through blending, granulation, cooling, pulverization, and then modified by low-temperature plasma; the particle size of the waste ceramic powder ≥ 800 mesh, and the main chemical components of the waste ceramic powder are SiO2 and Al2O3, the SiO2 content ≥ 75wt.%, and the Al2O3 content ≥ 15wt.%; preferably, the mass ratio of the waste ceramic powder, polycarbonate and polyphenylene sulfide is 1:2:7.

[0045] Furthermore, the particle size of the laterite nickel slag ≥ 325 mesh, and the main chemical components of the laterite nickel slag are SiO2, Al2O3, CaO and MgO, where the SiO2 content ≥ 50wt.%, and the MgO content ≥ 20wt.%.

[0046] The main components of laterite nickel slag are SiO2 and MgO. While synergistically improving the temperature resistance of materials with reinforcing materials, it can also participate in the cement hydration reaction to form Mg(OH)2 crystals, resulting in micro-expansion, effectively compensating for the shrinkage of the cement slurry for well cementing in high-temperature and high-pressure environments, and improving the cementing quality to prevent gas channeling. The temperature-resistant elastic material mixes waste ceramic powder, polycarbonate, and polyphenylene sulfide by melt blending, which also improves the toughness, strength, and roughness of the elastic material. On the one hand, polyphenylene sulfide has poor toughness, and its toughness can be effectively improved by adding polycarbonate with strong toughness and good compatibility with it for modification. On the other hand, the main components of waste ceramic powder are SiO2 and Al2O3, and it has a small particle size; it can play a role in heterogeneous nucleation during the crystallization of polyphenylene sulfide, while improving the strength and surface roughness of polyphenylene sulfide, and can improve the cementing strength with cement hydration products.

[0047] Preferably, the high-temperature stabilizer is a clay mineral;

[0048] The dispersant is an aldehyde-ketone condensate;

[0049] The high-temperature fluid loss reducer is a 2-acrylamido-2-methylpropanesulfonic acid polymer;

[0050] The high-temperature retarder is an AMPS polymer;

[0051] The defoamer is tributyl phosphate.

[0052] The present invention also provides a preparation method for a high-toughness and low-density cement slurry system suitable for high-temperature well cementing, which is applied to the high-temperature-resistant micro-expansion toughening and weight-reducing material for well cementing, including:

[0053] Step 1: Uniformly mix low heat of hydration cement, temperature-resistant micro-expansion weight-reducing material, molybdenum tailings, rare earth tailings, high-temperature stabilizer, and dispersant in various proportions to obtain dry materials;

[0054] Step 2: Uniformly mix the high-temperature fluid loss reducer, high-temperature retarder, and defoamer in various proportions with water to obtain liquid materials;

[0055] Step 3: Uniformly mix the dry materials and liquid materials according to the GB / T19139 standard to obtain the high-toughness and low-density cement slurry system suitable for high-temperature well cementing.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] 1. The high-toughness and low-density cement slurry system applicable to high-temperature cementing of the present invention not only has the characteristics of high temperature resistance, low density, high strength, gas channeling prevention performance and good toughness, but also has good high-temperature slurry stability and filtration loss. By adding temperature-resistant micro-expansion reducing materials, the present invention improves the high temperature resistance, lightness, high strength, micro-expansion and toughness of the cement slurry.

[0058] 2. The present invention uses laterite nickel ore slag, waste ceramic tile powder, molybdenum tailings and rare earth tailings as raw materials, greatly reducing the environmental protection pressure brought by solid waste. The materials are green and environmentally friendly and have low costs. At the same time, protein shale powder, molybdenum tailings and rare earth tailings, as alternative materials for silica sand, greatly reduce the costs. Detailed implementation manners

[0059] In order to enable those skilled in the art to better understand the solution 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 embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope protected by the present invention.

[0060] In the following embodiments, the low heat of hydration cement is provided by Jiahua Special Cement Co., Ltd., the high temperature retarder and the high temperature fluid loss reducer are both provided by Sichuan Xuran Hongchen New Materials Co., Ltd., and the high temperature stabilizer is a clay mineral. The high temperature retarder is an AMPS polymer; the high temperature fluid loss reducer is a 2-acrylamido-2-methylpropanesulfonic acid polymer; the dispersant is an aldehyde-ketone condensate; unless otherwise specified in the embodiments, all are in weight percentages.

[0061] In the molybdenum tailings used in the embodiments of the present invention, the SiO2 content > 62 wt.%, the Al2O3 content > 5 wt.%, and the average particle size ≥ 800 mesh.

[0062] In the rare earth tailings used in the embodiments of the present invention, the SiO2 content > 55 wt.%, the Al2O3 content > 14 wt.%, the CaF2 content is 0.25 - 0.30 wt.%, and the average particle size ≥ 800 mesh.

[0063] In the embodiments of the present invention, the particle size of the borosilicate hollow glass microspheres is 20 - 80 μm, and the compressive strength is 30 - 90 MPa;

[0064] In the embodiments of the present invention, the particle size of the aluminosilicate hollow ceramic microspheres is 10 - 200 μm, and the compressive strength ≥ 350 MPa.

[0065] In the embodiments of the present invention, the nano-boehmite used is in powder form, with a purity > 98 wt.% and a crystal particle size of 10 - 15 nm;

[0066] In the embodiments of the present invention, the particle size of the protein shale powder used is ≥ 1200 mesh, and the main component of the protein shale powder is amorphous active silica, with the SiO2 content ≥ 90 wt.%.

[0067] In the embodiments of the present invention, the particle size of the waste ceramic tile powder used is ≥ 800 mesh, and the main chemical components of the waste ceramic tile powder are SiO2 and Al2O3, with the SiO2 content ≥ 75 wt.% and the Al2O3 content ≥ 15 wt.%;

[0068] In the embodiments of the present invention, the particle size of the laterite nickel slag used is ≥ 325 mesh, and the main chemical components of the laterite nickel slag are SiO2, Al2O3, CaO and MgO, among which the SiO2 content ≥ 50 wt.% and the MgO content ≥ 20 wt.%.

[0069] Example 1

[0070] As a preferred embodiment of the present invention, a high-toughness and low-density cement slurry system suitable for high-temperature well cementing disclosed in this embodiment is composed as shown in Table 1, and additives based on the weight percentage of low heat of hydration cement (taking low heat of hydration cement as 100 wt.%): 8 wt.% high-temperature fluid loss reducer, 0.5 wt.% high-temperature retarder and 0.25 wt.% defoamer.

[0071] Table 1

[0072] Component Weight ratio (wt.%) Low heat of hydration cement 27 Temperature-resistant slightly expanding lightening material 40 Molybdenum tailings 15 Rare earth tailings 15 High-temperature stabilizer 1 Dispersant 2

[0073] In this embodiment, the temperature-resistant micro-expansion lightening material is composed of hollow microspheres, reinforcing materials, laterite nickel slag and temperature-resistant elastic materials mixed in a mass ratio of 5:2:2:1.

[0074] In this embodiment, the hollow microspheres are composed of borosilicate hollow glass microspheres and aluminosilicate hollow ceramic microspheres mixed in a mass ratio of 3:7.

[0075] In this embodiment, the reinforcing material is composed of pseudo-boehmite, nano-boehmite and protein shale powder mixed in a mass ratio of 2:3:5.

[0076] In this embodiment, the temperature-resistant elastic material is composed of waste ceramic tile powder, polycarbonate and polyphenylene sulfide in a mass ratio of 1:2:7, and after being melt-blended, blended, granulated, cooled, pulverized, and then modified by low-temperature plasma.

[0077] In this embodiment, according to the above raw materials and additives in the preparation method (where the addition amount of water is determined by the water-cement ratio of 0.6), cement slurry is prepared according to the GB / T19139 standard to form a high-toughness and low-density cement slurry system 1#.

[0078] Example 2

[0079] As a preferred embodiment of the present invention, a high-toughness and low-density cement slurry system suitable for high-temperature cementing disclosed in this embodiment has the composition shown in Table 2, and additives based on the weight percentage of low heat of hydration cement (taking low heat of hydration cement as 100 wt. %): 6 wt. % high-temperature fluid loss reducer, 1 wt. % high-temperature retarder, and 0.25 wt. % defoamer.

[0080] Table 2

[0081] Component Weight ratio (wt.%) Low heat of hydration cement 43.5 Temperature-resistant slightly expanding lightening material 30 Molybdenum tailings 12 Rare earth tailings 12 High-temperature stabilizer 1 Dispersant 1.5

[0082] In this embodiment, the temperature-resistant micro-expansion lightweight material is composed of hollow microspheres, reinforcing materials, laterite nickel ore slag, and temperature-resistant elastic materials in a mass ratio of 5:2:2:1.

[0083] In this embodiment, the hollow microspheres are composed of borosilicate hollow glass microspheres and aluminosilicate hollow ceramic microspheres in a mass ratio of 3:7.

[0084] In this embodiment, the reinforcing material is composed of pseudo-boehmite, nano-boehmite, and protein shale powder in a mass ratio of 2:3:5.

[0085] In this embodiment, the temperature-resistant elastic material is composed of waste tile powder, polycarbonate, and polyphenylene sulfide in a mass ratio of 1:2:7, and is modified by low-temperature plasma after being blended, granulated, cooled, pulverized by means of melt blending.

[0086] In this embodiment, according to the above raw materials and additives in the preparation method (where the addition amount of water is determined by the water-cement ratio of 0.6), cement slurry is prepared according to the GB / T19139 standard to form the high-toughness and low-density cement slurry system 2#.

[0087] Example 3

[0088] As a preferred embodiment of the present invention, a high-toughness and low-density cement slurry system suitable for high-temperature cementing disclosed in this embodiment has the composition shown in Table 3, and additives based on the weight percentage of low heat of hydration cement (taking low heat of hydration cement as 100 wt. %): 4 wt. % high-temperature fluid loss reducer, 2 wt. % high-temperature retarder, and 0.25 wt. % defoamer.

[0089] Table 3

[0090] Component Weight ratio (wt.%) Low heat of hydration cement 58 Temperature-resistant slightly expanding lightening material 20 Molybdenum tailings 10 Rare earth tailings 10 High-temperature stabilizer 1 Dispersant 1

[0091] In this embodiment, the temperature-resistant slightly expandable weighting material is formed by mixing hollow microspheres, reinforcing materials, laterite nickel slag, and temperature-resistant elastic materials in a mass ratio of 5:2:2:1.

[0092] In this embodiment, the hollow microspheres are formed by mixing borosilicate hollow glass microspheres and aluminosilicate hollow ceramic microspheres in a mass ratio of 3:7.

[0093] In this embodiment, the reinforcing materials are formed by mixing pseudo-boehmite, nano-boehmite, and protein shale powder in a mass ratio of 2:3:5.

[0094] In this embodiment, the temperature-resistant elastic materials are formed by mixing waste tile powder, polycarbonate, and polyphenylene sulfide in a mass ratio of 1:2:7, and are modified by low-temperature plasma after being blended, granulated, cooled, pulverized by means of melt blending.

[0095] In this embodiment, according to the above raw materials and admixtures in the preparation method (where the addition amount of water is determined by the water-cement ratio of 0.6), cement slurry is prepared according to the GB / T19139 standard to form a high-toughness low-density cement slurry system No. 3.

[0096] Example 4

[0097] As a preferred embodiment of the present invention, a high-toughness low-density cement slurry system suitable for high-temperature well cementing disclosed in this embodiment is composed as shown in Table 4, and admixtures in terms of the weight percentage of low heat of hydration cement (taking low heat of hydration cement as 100 wt. %): 6 wt. % high-temperature fluid loss reducer, 1 wt. % high-temperature retarder, and 0.25 wt. % defoamer.

[0098] Table 4

[0099] Component Weight ratio (wt.%) Low heat of hydration cement 43.5 Temperature-resistant slightly expanding lightening material 30 Molybdenum tailings 12 Rare earth tailings 12 High-temperature stabilizer 1 Dispersant 1.5

[0100] In this embodiment, the temperature-resistant slightly expandable weighting material is formed by mixing hollow microspheres, reinforcing materials, laterite nickel slag, and temperature-resistant elastic materials in a mass ratio of 6:1:2:1.

[0101] In this embodiment, the hollow microspheres are formed by mixing borosilicate hollow glass microspheres and aluminosilicate hollow ceramic microspheres in a mass ratio of 3:7.

[0102] In this embodiment, the reinforcing materials are formed by mixing pseudo-boehmite, nano-boehmite, and protein shale powder in a mass ratio of 2:3:5.

[0103] In this embodiment, the temperature-resistant elastic material is prepared by melt blending waste ceramic powder, polycarbonate, and polyphenylene sulfide in a mass ratio of 1:2:7, followed by blending, granulation, cooling, pulverization, and then low-temperature plasma modification.

[0104] In this embodiment, according to the preparation method, the above raw materials and additives (where the water addition amount is determined by a water-cement ratio of 0.6) are used to prepare cement slurry in accordance with the GB / T 19139 standard, forming a high-toughness and low-density cement slurry system 4#.

[0105] Example 5

[0106] As a preferred embodiment of the present invention, a high-toughness and low-density cement slurry system suitable for high-temperature well cementing disclosed in this embodiment is composed as shown in Table 5, and additives based on the weight percentage of low heat of hydration cement (taking low heat of hydration cement as 100 wt.%) are: 6 wt.% high-temperature fluid loss reducer, 1 wt.% high-temperature retarder, and 0.25 wt.% defoamer.

[0107] Table 5

[0108] Component Weight ratio (wt.%) Low heat of hydration cement 43.5 Temperature-resistant slightly expanding lightening material 30 Molybdenum tailings 12 Rare earth tailings 12 High-temperature stabilizer 1 Dispersant 1.5

[0109] In this embodiment, the temperature-resistant micro-expansion lightening material is composed of hollow microspheres, reinforcing materials, laterite nickel slag, and temperature-resistant elastic materials mixed in a mass ratio of 7:1:1:1.

[0110] In this embodiment, the hollow microspheres are composed of borosilicate hollow glass microspheres and aluminum silicate hollow ceramic microspheres mixed in a mass ratio of 3:7.

[0111] In this embodiment, the reinforcing material is composed of pseudo-boehmite, nano-boehmite, and protein shale powder mixed in a mass ratio of 2:3:5.

[0112] In this embodiment, the temperature-resistant elastic material is prepared by melt blending waste ceramic powder, polycarbonate, and polyphenylene sulfide in a mass ratio of 1:2:7, followed by blending, granulation, cooling, pulverization, and then low-temperature plasma modification.

[0113] In this embodiment, according to the preparation method, the above raw materials and additives (where the water addition amount is determined by a water-cement ratio of 0.6) are used to prepare cement slurry in accordance with the GB / T 19139 standard, forming a high-toughness and low-density cement slurry system 5#.

[0114] Example 6

[0115] As a preferred embodiment of the present invention, a high-toughness and low-density cement slurry system suitable for high-temperature cementing disclosed in this embodiment has a composition as shown in Table 6, and additives based on the weight percentage of low heat of hydration cement (taking low heat of hydration cement as 100 wt. %): 6 wt. % high-temperature fluid loss reducer, 1 wt. % high-temperature retarder, and 0.25 wt. % defoamer.

[0116] Table 6

[0117] Component Weight ratio (wt.%) Low heat of hydration cement 43.5 Temperature-resistant slightly expanding lightening material 30 Molybdenum tailings 12 Rare earth tailings 12 High-temperature stabilizer 1 Dispersant 1.5

[0118] In this embodiment, the temperature-resistant micro-expansion lightweight material is composed of hollow microspheres, reinforcing materials, laterite nickel slag, and temperature-resistant elastic materials mixed in a mass ratio of 5:2:2:1.

[0119] In this embodiment, the hollow microspheres are composed of borosilicate hollow glass microspheres and aluminosilicate hollow ceramic microspheres mixed in a mass ratio of 3:7.

[0120] In this embodiment, the reinforcing material is composed of pseudo-boehmite, nano-boehmite, and protein shale powder mixed in a mass ratio of 2:3:5.

[0121] In this embodiment, the temperature-resistant elastic material is composed of waste tile powder, polycarbonate, and polyphenylene sulfide in a mass ratio of 1:2:7, and after being melt-blended, subjected to blending, granulation, cooling, and pulverization, it is then modified by low-temperature plasma.

[0122] In this embodiment, according to the above raw materials and additives in the preparation method (where the addition amount of water is determined by a water-cement ratio of 0.7), cement slurry is prepared according to the GB / T19139 standard to form the high-toughness and low-density cement slurry system No. 6.

[0123] Example 7

[0124] As a preferred embodiment of the present invention, a high-toughness and low-density cement slurry system suitable for high-temperature cementing disclosed in this embodiment has a composition as shown in Table 7, and additives based on the weight percentage of low heat of hydration cement (taking low heat of hydration cement as 100 wt. %): 6 wt. % high-temperature fluid loss reducer, 1 wt. % high-temperature retarder, and 0.25 wt. % defoamer.

[0125] Table 7

[0126] Component Weight ratio (wt.%) Low heat of hydration cement 43.5 Temperature-resistant slightly expanding lightening material 30 Molybdenum tailings 12 Rare earth tailings 12 High-temperature stabilizer 1 Dispersant 1.5

[0127] In this embodiment, the temperature-resistant micro-expansion lightweight material is composed of hollow microspheres, reinforcing materials, laterite nickel slag, and temperature-resistant elastic materials mixed in a mass ratio of 5:2:2:1.

[0128] In this embodiment, the hollow microspheres are formed by mixing borosilicate hollow glass microspheres and aluminosilicate hollow ceramic microspheres in a mass ratio of 3:7.

[0129] In this embodiment, the reinforcing material is formed by mixing pseudo-boehmite, nano-boehmite and protein shale powder in a mass ratio of 2:3:5.

[0130] In this embodiment, the temperature-resistant elastic material is formed by mixing waste ceramic tile powder, polycarbonate and polyphenylene sulfide in a mass ratio of 1:2:7, and after being blended, granulated, cooled and pulverized by melt blending, it is then modified by low-temperature plasma.

[0131] In this embodiment, according to the above raw materials and admixtures of the preparation method (where the addition amount of water is determined by a water-cement ratio of 0.8), cement slurry is prepared according to the GB / T19139 standard to form a high-toughness and low-density cement slurry system 7#.

[0132] Comparative Example 1

[0133] 58 wt.% of G-class high-temperature resistant oil well cement, 30 wt.% of silica sand, 10 wt.% of cenospheres, 1 wt.% of high-temperature stabilizer, and 1 wt.% of dispersant are uniformly mixed by weight percentage to obtain a powder material. 6 wt.% of high-temperature fluid loss reducer, 1 wt.% of high-temperature retarder, and 0.25 wt.% of defoamer based on the percentage of G-class high-temperature resistant oil well cement are mixed with water to obtain a mixed liquid (where the addition amount of water is determined by a water-cement ratio of 0.6); the powder material and the mixed liquid are used to prepare cement slurry according to the GB / T19139 standard to form a comparative cement slurry system for well cementing.

[0134] Referring to the test method for oil well cement of GB / T19139, 150°C experimental tests are carried out on the engineering properties of the high-toughness and low-density cement slurry systems 1# - 7# and the comparative cement slurry system for well cementing. The results are shown in Table 8.

[0135] Table 8

[0136] [[ID=!25]]

[0137] According to the experimental data in Table 8, it can be concluded that the slurry density of the high-toughness and low-density cement slurry systems of Examples 1 - 7 is much smaller than that of the comparative cement slurry system for well cementing in Comparative Example 1. The cement slurry density of the high-toughness and low-density cement slurry systems of Examples 1 - 7 is adjustable and each high-temperature engineering property is good. The fluid loss is < 40 ml, and the SPN value for gas channeling prevention is < 1.5, having good gas channeling prevention performance and being able to achieve effective sealing; and the thickening time of its cement slurry system is adjustable and the adaptability of the admixtures is good, which is beneficial to improving the construction safety of high-temperature well cementing operations.

[0138] Pour the cement slurry samples obtained from the high-toughness and low-density cement slurry systems 1# to 7# and the comparative cementing cement slurry system into a copper mold for molding, and then place them in a high-temperature curing kettle for curing. The curing temperature is 180°C, and the curing periods are 2d, 7d, and 28d. Use a NYSQ-2017 pressure testing machine to test the compressive strength; take cores from the cured cement stones, and then conduct triaxial mechanical property tests; the mechanical test standard for cement stones is based on GB / T50266-2013 "Standard for Engineering Rock Mass Test Methods", and the equipment used in the experiment is an RTR-1000 type triaxial rock mechanics tester. The test results are shown in the following table (see Table 9).

[0139] Table 9

[0140]

[0141] As can be seen from the data in Table 9, after curing for a certain age, for the high-toughness and low-density cement slurry systems of Examples 1 to 7, the 2d compressive strength > 20 MPa, and the early strength develops relatively fast; the compressive strength does not show a decline phenomenon under high-temperature environment, and the 28d compressive strength > 30 MPa, meeting the requirements for the compressive strength of cement stones under high-temperature environment; while for Comparative Example 1, there is a phenomenon of 28d strength decline. Therefore, the high-toughness and low-density cement slurry system applicable to high-temperature cementing described in the present invention has good high-temperature resistance, does not show a strength decline phenomenon, and can promote the development of the early strength of cement stones. From the elastic modulus data, it can be seen that for the high-toughness and low-density cement slurry systems of Examples 1 to 7, the elastic modulus at 28d < 6 GPa, which significantly improves the toughness of the cementing cement compared with Comparative Example 1, can meet the performance requirements of the cement slurry for high-temperature cementing projects, and can effectively solve the problem of insufficient toughness of cement stones under high-temperature environment.

[0142] Finally, it should be noted that: the above embodiments are only relatively preferred embodiments of the present invention to illustrate the technical solutions of the present invention, rather than limiting it, and certainly not limiting the patent scope of the present invention; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention; that is to say, any meaningless modifications or polishings made on the main design idea and spirit of the present invention, as long as the technical problems solved are still the same as those of the present invention, should be included in the protection scope of the present invention; in addition, directly or indirectly applying the technical solutions of the present invention to other related technical fields shall also be included in the patent protection scope of the present invention by the same token.

Claims

1. A high-toughness, low-density cement slurry system suitable for high-temperature cementing, characterized in that: The present invention comprises the following raw materials in percentage by weight: Low hydration heat cement: 27~58wt.%; Heat-resistant micro-expansion reducing material: 20~40wt.%; Molybdenum tailings: 10 ~15 wt.%; Rare earth tailings: 10 ~15 wt.%; High temperature stabilizer: 1wt.%; Dispersant: 1~2wt.%; And admixtures expressed as a percentage by weight of low heat of hydration cement: High temperature fluid loss additive: 4~8wt.%; High temperature retarder: 0.5~2wt.%; Defoaming agent: 0.25wt.%; The heat-resistant micro-expansion reduction material is made by mixing hollow microspheres, reinforcing material, laterite nickel slag and heat-resistant elastic material; The reinforcing material is prepared by mixing pseudo-boehmite, nano-boehmite and protein shale powder in a mass ratio of (2-3): (2-3):5; The heat-resistant elastic material is prepared by melt blending, granulating, cooling, and crushing waste tile powder, polycarbonate, and polyphenylene sulfide in a mass ratio of (0.5-1.5):(0.5-3):(5-9), and then subjected to low-temperature plasma modification.

2. The high-toughness, low-density cement slurry system suitable for high-temperature cementing according to claim 1, characterized in that: The present invention comprises the following raw materials in percentage by weight: Low hydration heat cement: 35~55wt.%; Heat-resistant micro-expansion reducing material: 30~40wt.%; Molybdenum tailings: 10 ~15 wt.%; Rare earth tailings: 10 ~15 wt.%; High temperature stabilizer: 1wt.%; Dispersant: 1~2wt.%; And admixtures expressed as a percentage by weight of low heat of hydration cement: High temperature fluid loss additive: 5~8wt.%; High temperature retarder: 0.5~2wt.%; Defoaming agent: 0.25wt.%; The heat-resistant micro-expansion reduction material is prepared by mixing hollow microspheres, a reinforcing material, laterite nickel slag and a heat-resistant elastic material in a mass ratio of (5-7):(1-2):(1-2):

1.

3. A high-toughness, low-density cement slurry system suitable for high-temperature cementing according to claim 1 or 2, characterized in that: The molybdenum tailings have a SiO2 content greater than 62 wt.%, an Al2O3 content greater than 5 wt.%, and an average particle size greater than or equal to 800 meshes.

4. A high-toughness, low-density cement slurry system suitable for high-temperature cementing according to claim 1 or 2, characterized in that: The rare earth tailings have a SiO2 content greater than 55wt.%, an Al2O3 content greater than 14wt.%, and a CaF2 content of 0.25-0.30wt.%, and an average particle size greater than or equal to 800 meshes.

5. The high-toughness, low-density cement slurry system suitable for high-temperature cementing according to claim 1 or 2, characterized in that: The hollow microspheres are formed by mixing borosilicate hollow glass microspheres and aluminum silicate hollow ceramic microspheres in a mass ratio of (2-4):(5-9); the borosilicate hollow glass microspheres have a particle size of 20-80 μm and a compressive strength of 30-90 MPa; the aluminum silicate hollow ceramic microspheres have a particle size of 10-200 μm and a compressive strength of ≥350 MPa.

6. The high-toughness, low-density cement slurry system suitable for high-temperature cementing according to claim 5, characterized in that: The hollow microspheres are formed by mixing borosilicate hollow glass microspheres and aluminum silicate hollow ceramic microspheres in a mass ratio of 3:

7.

7. A high-toughness, low-density cement slurry system suitable for high-temperature cementing according to claim 1 or 2, characterized in that: The purity of the pseudo-boehmite is greater than 90wt.%, and the average particle size is 5-10μm; the nano-boehmite is in powder form, with a purity greater than 98wt.%, and a crystal particle size of 10-15nm; the particle size of the protein shale powder is ≥1200 mesh, and the SiO2 content is ≥90wt.%.

8. The high-toughness, low-density cement slurry system suitable for high-temperature cementing according to claim 1 or 2, characterized in that: The reinforcing material is formed by mixing pseudo-boehmite, nano-boehmite and protein shale powder in a mass ratio of 2:3:

5.

9. A high-toughness, low-density cement slurry system suitable for high-temperature cementing according to claim 1 or 2, characterized in that: The waste tile powder of the temperature-resistant elastic material has a particle size of ≥800 mesh, a SiO2 content of ≥75wt.%, and an Al2O3 content of ≥15wt.%.

10. A high-toughness, low-density cement slurry system suitable for high-temperature cementing according to claim 1 or 2, characterized in that: The mass ratio of waste tile powder, polycarbonate and polyphenylene sulfide is 1:2:

7.

11. A high-toughness, low-density cement slurry system suitable for high-temperature cementing according to claim 1 or 2, characterized in that: The laterite nickel slag has a particle size of ≥325 meshes, a SiO2 content of ≥50 wt.%, and a MgO content of ≥20 wt.%.

12. The method for preparing a high-toughness, low-density cement slurry system suitable for high-temperature cementing according to any one of claims 1 to 11, characterized in that: The following steps are involved: Step 1, uniformly mixing low-hydration hot cement, temperature-resistant micro-expansion reducing material, molybdenum tailings, rare earth tailings, high-temperature stabilizer and dispersant in various proportions to obtain dry material; Step 2: uniformly mix the high-temperature fluid loss additive, high-temperature retarder and defoamer in various proportions with water to obtain a liquid material; Step 3: Evenly mix the dry material and the liquid material to obtain the high-toughness, low-density cement slurry system suitable for high-temperature cementing.

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