High temperature high strength ductile cement paste based on graphite material and its preparation and application

Abstract

The application provides a high-temperature high-strength toughness cement slurry based on graphite material and preparation and application thereof, and the high-temperature high-strength toughness cement slurry based on elastic graphite comprises, in terms of weight parts, 100 parts by weight of high-sulfate-resistant G-grade oil well cement, 2-6 parts by weight of elastic graphite, 2-6 parts by weight of expanded graphite, 20-50 parts by weight of quartz sand, 0-15 parts by weight of super-high-temperature strength anti-decay material, 0.5-2 parts by weight of dispersing agent, 2-4 parts by weight of high-temperature stabilizer, 0.5-4 parts by weight of high-temperature fluid loss additive, 0.2-8 parts by weight of high-temperature retarder, 0.1-1 part by weight of defoaming agent and 40-80 parts by weight of water. The cement slurry is suitable for well cementing operation of high-temperature super-high-temperature wells with a bottom hole temperature of 150-600 DEG C, and the cement stone has high long-term strength and good toughness after hardening into the cement stone under high-temperature super-high-temperature conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-temperature high-strength toughness cement paste based on graphite material and its preparation and application, and belongs to the technical field of oil and gas exploration and development. BACKGROUND

[0002] With the rapid development of China's economy and society, its demand for oil and gas resources continues to grow. In order to ensure national energy security and reduce dependence on foreign oil and gas, it is necessary to increase exploration and development efforts. Among them, deep and ultra-deep oil and gas have great potential and are important replacement resources. Oil and gas reservoirs deeper than 8000m have been proven in Tarim, Junggar, Sichuan, and Qaidam basins. As oil and gas exploration and development continue, the number of deep and ultra-deep wells is gradually increasing, and wellbore temperatures are becoming higher, with bottomhole temperatures reaching over 240℃. At the same time, heavy oil thermal recovery wells and in-situ conversion wells have bottomhole temperatures as high as 600℃. High-temperature and ultra-high-temperature cementing slurry technology is of great significance to ensuring unconventional oil and gas exploration and development in deep and ultra-deep layers.

[0003] To address the problem of long-term strength loss of oil well cement at temperatures above 110℃, the field mainly adds quartz sand to the cement stone to increase the silicon-calcium ratio of the cement stone, thereby ensuring the long-term strength of high-temperature cement stone. Research shows that the long-term strength of sand-added cement stone can remain stable at 110-200℃. However, the long-term strength of sand-added cement stone is low at ultra-high temperatures above 200℃. At the same time, the cement stone is brittle and easily broken under the action of ultra-high temperature, and its toughness needs to be improved. Therefore, developing a high-performance high-temperature high-strength toughness cement paste system is of great importance to improving the quality of ultra-high-temperature oil and gas well cementing and the integrity of the cement sheath.

[0004] The prior art has disclosed many related researches on improving the strength and toughness of high-temperature cement slurry. For example, Chinese patent CN104371678A discloses an expansion toughness cementing slurry and a preparation method thereof. The technology uses rubber powder as a toughening material, but the modification of cement stone toughness by rubber powder under high temperature conditions will fail. Chinese patent CN109679600A discloses a nano material mixed modified ultra-high temperature high performance cementing slurry system and a preparation method thereof. The technology uses coarse and fine silica sand in combination, and combines nano silicon dioxide and nano calcium carbonate to improve the mechanical properties of high-temperature cement stone. The 5-day strength can reach 60 MPa, and the elastic modulus is about 8.5. Long-term strength decay (more than 28 days) occurs above 240 DEG C. Chinese patent CN110484223A discloses an oil well cement slurry system for preventing high-temperature strength decay and a preparation method thereof. The strength enhancer used in the technology is graphene emulsion, and the suspension stabilizer is micron-sized shaped silicon dioxide and 8-12% xanthan gum. The cement slurry has good construction performance at a temperature of 180 DEG C, and the strength is 35 MPa without decay within 14 days. However, the material cost of the technology is high, and it is not suitable for cementing construction under super-high temperature conditions above 200 DEG C. Chinese patent CN110563428A discloses a cementing cement for ultra-high temperature deep well, a preparation method and application thereof. The first anti-strength decay agent used in the technology is silicon powder, and the second anti-strength decay agent is one or more of aluminum oxide, aluminum hydroxide, zinc oxide, zinc hydroxide and strontium chloride. The cement stone strength is 30 MPa without decay at a temperature of 200-240 DEG C. However, the ultra-high temperature strength of the product provided by the technology is still not high enough, and toughness modification is not performed.

[0005] The prior art represented by the above patents has achieved certain effects in the mechanical modification of high-temperature cement, but there are still certain problems in improving the long-term strength of cement stone and the toughness of ultra-high temperature cement stone, which cannot meet the needs of cementing operations under high temperature and super-high temperature conditions such as deep wells, ultra-deep wells and heavy oil thermal recovery wells.

[0006] Therefore, it has become a technical problem to be solved in the field to provide a new type of high-temperature high-strength toughness cement slurry based on graphite material and its preparation and application. SUMMARY

[0007] In order to solve the technical problems of low long-term strength, high brittleness and easy cracking of sand-added cement stone under high temperature and super-high temperature conditions, and the toughness of cement stone under high temperature and super-high temperature conditions, an object of the present application is to provide a high-temperature high-strength toughness cement slurry based on graphite material.

[0008] Another object of the present application is to provide a preparation method of the above-mentioned high-temperature high-strength toughness cement slurry based on graphite material.

[0009] Yet another object of the present application is to provide an application of the high-temperature high-strength flexible cement slurry based on graphite material in the cementing operation of high-temperature ultra-high-temperature wells.

[0010] Yet another object of the present application is to provide a cementing method for high-temperature ultra-high-temperature wells, which uses the high-temperature high-strength flexible cement slurry based on graphite material as described above.

[0011] To achieve the above objects, in one aspect, the present application provides a high-temperature high-strength flexible cement slurry based on graphite material, wherein the high-temperature high-strength flexible cement slurry based on graphite material comprises, by weight:

[0012]

[0013]

[0014] In the present application, the high-sulfate-resistant G-grade oil well cement is a commercially available product, and its main mineral components include dicalcium silicate (2CaO·SiO2), tricalcium silicate (3CaO·SiO2), tricalcium aluminate (3CaO·Al2O3), tetracalcium aluminoferrite (4CaO·Al2O3·Fe2O3), alkaline substances (Na2O and K2O), MgO, and SO3, etc.

[0015] As a specific embodiment of the cement slurry as described above in the present application, the size of the high-sulfate-resistant G-grade oil well cement is 300-400 mesh.

[0016] As a specific embodiment of the cement slurry as described above in the present application, the size of the graphite material, i.e. the elastic graphite and the expanded graphite, is 80-200 mesh.

[0017] As a specific embodiment of the cement slurry as described above in the present application, the elastic graphite has a temperature resistance of 800℃, and a rebound rate of 20-50%.

[0018] As a specific embodiment of the cement slurry as described above in the present application, the expanded graphite will expand under high-temperature conditions above 200℃, with an expansion rate >200 mL / g. In the present application, the elastic graphite and the expanded graphite are commercially available products.

[0019] As a specific embodiment of the cement slurry as described above in the present application, the quartz sand includes a mixture of 100-400 mesh quartz sand and 600-1500 mesh quartz sand.

[0020] In the present application, the mixing ratio of the 100-400 mesh quartz sand and the 600-1500 mesh quartz sand is not specifically required, and the mass ratio can be reasonably adjusted according to the actual operation needs on site, as long as the purpose of the present application can be achieved. For example, in some embodiments of the present application, the mass ratio of the 100-400 mesh quartz sand and the 600-1500 mesh quartz sand is 1:1. In addition, the quartz sand used in the present application is a commercially available product.

[0021] As a specific embodiment of the cement slurry described above in the present application, the ultra-high temperature strength anti-decay material includes a compounded mixture of two or more of metakaolin, kaolin, cyanite and chlorite.

[0022] In the present application, the mixing ratio of any two or more of metakaolin, kaolin, cyanite and chlorite is not specifically required, and the mass ratio can be reasonably adjusted according to the actual operation needs on site, as long as the purpose of the present application can be achieved. For example, in some embodiments of the present application, the mass ratio of any two of metakaolin, kaolin, cyanite and chlorite is 1:1.

[0023] In addition, metakaolin, kaolin, cyanite and chlorite used in the present application are also commercially available products.

[0024] As a specific embodiment of the cement slurry described above in the present application, the fineness of the ultra-high temperature strength anti-decay material is 100-400 mesh.

[0025] The amount of the ultra-high temperature strength anti-decay material varies according to the bottom hole temperature of the target well. As a specific embodiment of the cement slurry described above in the present application, when the bottom hole temperature is 150-180℃, the amount of the ultra-high temperature strength anti-decay material is 0-5 parts by weight, when the bottom hole temperature is 180-240℃, the amount of the ultra-high temperature strength anti-decay material is 5-10 parts by weight, and when the bottom hole temperature is 240℃ or higher, the amount of the ultra-high temperature strength anti-decay material is 10-15 parts by weight.

[0026] As a specific embodiment of the cement slurry described above in the present application, the high-temperature stabilizer includes a compounded mixture of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol.

[0027] In the present application, the mixing ratio of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol is not specifically required, and the mass ratio can be reasonably adjusted according to the actual operation needs on site, as long as the purpose of the present application can be achieved. In addition, nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol used in the present application are commercially available products.

[0028] As a specific embodiment of the cement slurry described above in the present application, the dispersant comprises a polycarboxylic acid dispersant for oil well cement.

[0029] As a specific embodiment of the cement slurry described above in the present application, the high-temperature fluid loss additive comprises a 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethylacrylamide / itaconic acid / maleic anhydride quaternary polymer.

[0030] In the present application, the 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethylacrylamide / itaconic acid / maleic anhydride quaternary polymer is a quaternary polymer prepared by using 2-acrylamido-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, itaconic acid and maleic anhydride as raw materials by using a conventional polymerization method.

[0031] As a specific embodiment of the cement slurry described above in the present application, the high-temperature retarder comprises a 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethylammonium chloride / acrylamide / acrylic acid quinary polymer.

[0032] In the present application, the 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethylammonium chloride / acrylamide / acrylic acid quinary polymer is a quinary polymer prepared by using 2-acrylamido-2-methylpropanesulfonic acid, itaconic acid, diallyldimethylammonium chloride, acrylamide and acrylic acid as raw materials by using a conventional polymerization method.

[0033] As a specific embodiment of the cement slurry described above in the present application, the defoaming agent comprises a silicone-based or organic ester-based defoaming agent. The polycarboxylic acid dispersant for oil well cement, the silicone-based defoaming agent and the organic ester-based defoaming agent used in the present application are all commercially available products.

[0034] On the other hand, the present application also provides a preparation method of the high-temperature high-strength toughness cement slurry based on graphite material described above, wherein the preparation method comprises:

[0035] (1) uniformly mixing high-sulfate-resistant G-grade oil well cement, elastic graphite, expanded graphite, quartz sand, ultra-high-temperature strength anti-degradation material, dispersant and high-temperature stabilizer to obtain a dry powder mixture;

[0036] (2) mixing a high-temperature fluid loss additive, a high-temperature retarder and a defoaming agent in water to obtain a mixed solution; adding the dry powder mixture into the mixed solution and stirring at a high speed until uniform to obtain the high-temperature high-strength toughness cement slurry based on graphite material.

[0037] As a specific embodiment of the above preparation method of the present application, in step (2), the high-temperature fluid loss additive and the high-temperature retarder are added to the clean water, and then stirred at a low rotation speed of 4000±200 rpm to obtain the mixed solution.

[0038] As a specific embodiment of the above preparation method of the present application, in step (2), the dry powder mixture is added to the obtained mixed solution within 15 seconds.

[0039] As a specific embodiment of the above preparation method of the present application, in step (2), the stirring is performed at a high rotation speed of 12000±500 rpm for 35 seconds.

[0040] In another aspect, the present application also provides the use of the above high-temperature high-strength and toughness cement slurry based on graphite material in cementing operations of high-temperature and ultra-high-temperature wells.

[0041] In still another aspect, the present application also provides a cementing method for high-temperature and ultra-high-temperature wells, wherein the method uses the above high-temperature high-strength and toughness cement slurry based on graphite material.

[0042] As a specific embodiment of the above method of the present application, the bottom hole temperature of the high-temperature and ultra-high-temperature well is 150-600℃.

[0043] As a specific embodiment of the above method of the present application, the high-temperature and ultra-high-temperature well includes a deep well, an ultra-deep well, a shale oil in-situ conversion well, or a heavy oil thermal recovery well.

[0044] The high-temperature high-strength and toughness cement slurry based on graphite material provided by the present application is suitable for cementing operations of high-temperature and ultra-high-temperature wells with a bottom hole temperature of 150-600℃, and can meet the higher requirements for mechanical properties such as cement sheath strength and toughness in cementing operations of high-temperature and ultra-high-temperature wells such as deep wells, ultra-deep wells, and heavy oil thermal recovery wells. After the cement slurry system hardens into cement stone under high-temperature and ultra-high-temperature conditions, the cement stone has high long-term strength and good toughness. In summary, the cement slurry system has good comprehensive performance and important application value for improving the cementing quality of high-temperature and ultra-high-temperature wells such as deep wells, ultra-deep wells, and heavy oil thermal recovery wells.

[0045] Specifically, compared with the prior art, the high-temperature high-strength and toughness cement slurry based on graphite material provided by the present application has the following beneficial effects:

[0046] (1) This invention introduces graphite materials (including elastic graphite and expanded graphite) into cement stone, which has three unique advantages: First, the graphite material has a layered structure. When the cement stone is damaged by external forces, the graphite layers need to overcome interlayer forces to peel off, which consumes energy and is beneficial to improving the mechanical properties of the cement stone. Second, elastic graphite has strong temperature resistance and high resilience. Under high temperature and ultra-high temperature conditions and simultaneously subjected to downhole pressure, it will be highly compressed and can recover after the pressure is released, which is beneficial to improving the mechanical properties of high temperature and ultra-high temperature cement stone. Third, expandable graphite expands during the cement hydration process under high temperature and ultra-high temperature conditions, filling the pores between the high temperature and ultra-high temperature cement hydration products, promoting the formation of a dense high temperature cement stone microstructure. Therefore, the addition of expandable graphite is beneficial to improving the microstructure and pore size distribution of the cement stone, thereby improving the mechanical properties of the cement stone. The above three advantages of graphite materials help to ensure the integrity of the cement sheath under high temperature and high pressure conditions downhole.

[0047] (2) The present invention uses mixed quartz sand. Compared with ordinary quartz sand, the mixed quartz sand has a better effect on improving the strength of high temperature and ultra-high temperature cement stone due to the close packing effect.

[0048] (3) The present invention uses any two of the following as a compound mixture: metakaolinite, kaolinite, kyanite and chlorite as an ultra-high temperature strength anti-degradation material. The aluminum-containing minerals with nano-sized interlayer spacing in these ultra-high temperature strength anti-degradation materials can participate in the secondary hydration reaction of high temperature cement, inhibit the formation of parallel needle-shaped hard calcium silicate (C5S6H), and promote the formation of high temperature stable hydration product calcium silicate, forming a high temperature stable fiber network structure, thereby preventing the degradation of cement stone strength.

[0049] (4) In view of the problem of poor stability of cement slurry under ultra-high temperature conditions, the present invention uses a compound formed by nano alumina, magnesium aluminum silicate and polyvinyl alcohol as ultra-high temperature stabilizer, so that a network structure can be formed inside the cement slurry under ultra-high temperature conditions, increasing the viscosity and particle structure force of the system, thereby improving the stability of ultra-high temperature cement slurry.

[0050] (5) The high-temperature dispersant, high-temperature water loss reducer, and high-temperature retarder used in this invention result in excellent overall performance of the high-temperature cement slurry system. The cement slurry provided by this invention exhibits good stability under high and ultra-high temperature conditions, with a density difference of less than 0.05 g / cm³. 3 Its water loss performance meets the standards, it has good rheological properties, and its thickening time and density are adjustable. Its cementing performance meets the cementing requirements of oil and gas wells.

[0051] (6) The application realizes close packing among high-sulfate-resistant G-grade oil well cement (300-400 mesh) used in the cement slurry system, graphite material (80-200 mesh), quartz sand and super-high-temperature strength anti-decay material through reasonable design of the particle size of the material, and the 28-day cement stone strength of the cement slurry hardened into cement stone under super-high-temperature conditions is greater than 40 MPa, and the long-term decay is more than 60 days, and the mechanical properties of the cement stone are significantly improved.

[0052] In conclusion, the high-temperature high-strength toughness cement slurry based on graphite material provided by the application can be applied to well cementing operation of deep wells, super-deep wells, heavy oil thermal recovery wells and other high-temperature super-high-temperature wells with bottom hole temperature of 150-600℃, and can meet higher requirements for mechanical properties such as cement sheath strength and toughness in the well cementing operation process of deep wells, super-deep wells, heavy oil thermal recovery wells and other high-temperature super-high-temperature wells. In some specific embodiments of the application, the 28-day cement stone strength of the cement slurry hardened into cement stone is greater than 40 MPa, the 7-day cement stone elastic modulus is less than 7 GPa, and the long-term decay is more than 60 days. BRIEF DESCRIPTION OF DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0054] Figure 1 The SEM graph of the high-temperature high-strength toughness cement slurry based on graphite material provided by the application in Embodiment 2 hardened into cement stone. DETAILED DESCRIPTION

[0055] It should be noted that the terms "comprising" and any variation thereof in the specification and claims of the application and the above-mentioned drawings are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0056] The ranges disclosed herein are given out of a lower limit and an upper limit. Each of these limits can be independently one or more. A range given as between a lower limit and an upper limit is inclusive of the lower and upper limits. Ranges are independently combinable, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range is listed as 60-120 and 80-110, it is understood that a range of 60-110 and 80-120 is also contemplated. In addition, if a minimum range value of 1 and 2 is listed and a maximum range value of 3, 4 and 5 is listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0057] In the present application, unless otherwise stated, the numerical range "a-b" represents a shorthand for the full set of real combinations of a to b, wherein a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in the present application, and "0-5" is just a shorthand for these numerical combinations.

[0058] In the present application, unless otherwise stated, all the embodiments and preferred embodiments mentioned in the present application can be combined with each other to form new technical solutions.

[0059] In the present application, unless otherwise stated, all the technical features and preferred features mentioned in the present application can be combined with each other to form new technical solutions.

[0060] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application is further described in detail below in combination with the accompanying tables, drawings and examples. The following described examples are part of the examples of the present application, but not all the examples, and are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the examples in the present application, all other examples obtained by those skilled in the art without making creative efforts are within the scope of protection of the present application. If the specific conditions are not mentioned in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not mentioned by the manufacturer, they are all conventional products that can be purchased on the market.

[0061] Example 1

[0062] The present embodiment provides a high-temperature high-strength ductile cement slurry based on graphite material with a temperature resistance of 150℃, which comprises, by weight:

[0063] 100 parts by weight of high sulfate-resistant G-grade oil well cement (325 mesh), 2 parts by weight of elastic graphite (temperature resistance up to 800℃, resilience rate 20-50%, size 100 mesh), 2 parts by weight of expanded graphite (size 100 mesh), 30 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 5 parts by weight of super-high-temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded in a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol in a mass ratio of 1:2:1), 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive), 1.2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid quinary polymer (high-temperature retarder), 0.1 part by weight of tributyl phosphate (defoaming agent), and 55 parts by weight of water;

[0064] The high-temperature high-strength toughness cement slurry based on graphite material is prepared by a preparation method comprising the following specific steps:

[0065] (1) Take 100 parts by weight of high sulfate-resistant G-grade oil well cement, 2 parts by weight of elastic graphite (temperature resistance up to 800℃, resilience rate 20-50%), 2 parts by weight of expanded graphite (which will expand under high-temperature conditions above 200℃, expansion rate >200 mL / g), 30 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 5 parts by weight of super-high-temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded in a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol in a mass ratio of 1:2:1), and mix the dry powders uniformly to obtain a dry powder mixture;

[0066] (2) Take 55 parts by weight of water, mix 2 parts by weight of high-temperature fluid loss additive, 1.2 parts by weight of high-temperature retarder and 0.1 part by weight of defoaming agent into the water and pour into a stirrer, rotate the stirrer at a low speed (4000±200 rpm), and add the dry powder mixture within 15 seconds, cover the lid of the stirrer, continue to stir at a high speed (12000±500 rpm) for 35 seconds, and the high-temperature high-strength toughness cement slurry based on graphite material is obtained.

[0067] Comparative Example 1-1

[0068] This comparative example provides a cement slurry based on graphite material, which comprises, in parts by weight:

[0069] 100 parts by weight of high sulfate-resistant G-grade oil well cement (325 mesh), 2 parts by weight of elastic graphite (temperature-resistant up to 800°C, springback rate 20-50%, size 100 mesh), 2 parts by weight of expanded graphite (which will expand under high temperature conditions above 200°C, expansion rate >200 mL / g, size 100 mesh), 30 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 5 parts by weight of ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded at a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of stabilizer (warm rubber), 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive), 1.2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid quinary polymer (high-temperature retarder), 0.1 part by weight of tributyl phosphate (defoaming agent), and 55 parts by weight of water;

[0070] The graphite material-based cement slurry is prepared by a preparation method comprising the following specific steps:

[0071] (1) Take 100 parts by weight of high sulfate-resistant G-grade oil well cement, 2 parts by weight of elastic graphite (temperature-resistant up to 800°C, springback rate 20-50%), 2 parts by weight of expanded graphite (which will expand under high temperature conditions above 200°C, expansion rate >200 mL / g), 30 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 5 parts by weight of ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded at a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of stabilizer (warm rubber, which is in a dry powder state), and mix the dry powders uniformly to obtain a dry powder mixture;

[0072] (2) Weigh 55 parts by weight of water, mix 2 parts by weight of high-temperature fluid loss additive, 1.2 parts by weight of high-temperature retarder, and 0.1 part by weight of defoaming agent into the water and pour into a stirrer, rotate the stirrer at a low speed (4000±200 rpm), and add the dry powder mixture within 15 seconds, cover the lid of the stirrer, and continue to stir at a high speed (12000±500 rpm) for 35 seconds to obtain the graphite material-based cement slurry.

[0073] Comparative Example 1-2

[0074] This comparative example provides a graphite material-based cement slurry, which comprises, by weight parts:

[0075] 100 parts by weight of high sulfate-resistant G-grade oil well cement (325 mesh), 2 parts by weight of elastic graphite (temperature-resistant up to 800°C, rebound rate 20-50%, size 100 mesh), 2 parts by weight of expanded graphite (which will expand under high temperature conditions above 200°C, expansion rate > 200 mL / g, size 100 mesh), 30 parts by weight of 200 mesh quartz sand, 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a complex formed by nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol in a mass ratio of 1:2:1), 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive), 1.2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid pentapolymer (high-temperature retarder), 0.1 part by weight of tributyl phosphate (defoaming agent), and 55 parts by weight of water;

[0076] The graphite material-based cement slurry is prepared by a preparation method comprising the following specific steps:

[0077] (1) Take 100 parts by weight of high sulfate-resistant G-grade oil well cement, 2 parts by weight of elastic graphite (temperature-resistant up to 800°C, rebound rate 20-50%), 2 parts by weight of expanded graphite (which will expand under high temperature conditions above 200°C, expansion rate > 200 mL / g), 30 parts by weight of 200 mesh quartz sand, 1 part by weight of polycarboxylic acid dispersant, and 3 parts by weight of high-temperature stabilizer (a complex formed by nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol in a mass ratio of 1:2:1), and mix the dry powders uniformly to obtain a dry powder mixture;

[0078] (2) Weigh 55 parts by weight of water, mix 2 parts by weight of high-temperature fluid loss additive, 1.2 parts by weight of high-temperature retarder, and 0.1 part by weight of defoaming agent into the water and pour into a stirrer, the stirrer rotates at low speed (4000±200 rpm), and the dry powder mixture is added within 15 seconds, the lid of the stirrer is covered, and the stirring is continued at high speed (12000±500 rpm) for 35 seconds, to obtain the graphite material-based cement slurry.

[0079] Comparative Examples 1-3

[0080] This comparative example provides an elastic graphite-based cement slurry, which comprises, by weight parts:

[0081] 100 parts by weight of high sulfate-resistant G-grade oil well cement (325 mesh), 2 parts by weight of elastic graphite (temperature resistant up to 800℃, resilience rate of 20-50%, size of 100 mesh), 30 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio of 1:1), 5 parts by weight of ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded according to a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol according to a mass ratio of 1:2:1), 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive), 1.2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid quinary polymer (high-temperature retarder), 0.1 part by weight of tributyl phosphate (defoaming agent), and 55 parts by weight of water;

[0082] The elastic graphite-based cement slurry is prepared by a preparation method comprising the following specific steps:

[0083] (1) Take 100 parts by weight of high sulfate-resistant G-grade oil well cement, 2 parts by weight of elastic graphite (temperature resistant up to 800℃, resilience rate of 20-50%), 30 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio of 1:1), 5 parts by weight of ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded according to a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, and 3 parts by weight of high-temperature stabilizer (a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol according to a mass ratio of 1:2:1), and uniformly mix the dry powders to obtain a dry powder mixture;

[0084] (2) Take 55 parts by weight of water, mix 2 parts by weight of high-temperature fluid loss additive, 1.2 parts by weight of high-temperature retarder, and 0.1 part by weight of defoaming agent into the water and pour into a stirrer, rotate the stirrer at a low speed (4000±200 revolutions / minute), and add the dry powder mixture within 15 seconds, cover the lid of the stirrer, and continue to stir at a high speed (12000±500 revolutions / minute) for 35 seconds to obtain the elastic graphite-based cement slurry.

[0085] Comparative Examples 1-4

[0086] The present comparative example provides an expanded graphite-based cement slurry, which comprises, in parts by weight:

[0087] 100 parts by weight of high sulfate-resistant G-grade oil well cement (325 mesh), 2 parts by weight of expanded graphite (which will expand under high temperature conditions above 200°C, with an expansion rate >200 mL / g, and a size of 100 mesh), 30 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 5 parts by weight of ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded at a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol at a mass ratio of 1:2:1), 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive), 1.2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethylammonium chloride / acrylamide / acrylic acid quinary polymer (high-temperature retarder), 0.1 part by weight of tributyl phosphate (defoaming agent), and 55 parts by weight of water;

[0088] The expanded graphite-based cement slurry is prepared by a preparation method comprising the following specific steps:

[0089] (1) Take 100 parts by weight of high sulfate-resistant G-grade oil well cement, 2 parts by weight of expanded graphite (which will expand under high temperature conditions above 200°C, with an expansion rate >200 mL / g), 30 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 5 parts by weight of ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded at a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol at a mass ratio of 1:2:1), and mix the dry powders uniformly to obtain a dry powder mixture;

[0090] (2) Take 55 parts by weight of water, mix 2 parts by weight of high-temperature fluid loss additive, 1.2 parts by weight of high-temperature retarder, and 0.1 part by weight of defoaming agent into the water and pour into a stirrer, rotate the stirrer at a low speed (4000±200 rpm), and add the dry powder mixture within 15 seconds, cover the lid of the stirrer, and continue to stir at a high speed (12000±500 rpm) for 35 seconds to obtain the expanded graphite-based cement slurry.

[0091] Comparative Examples 1-5

[0092] The present comparative example provides a cement slurry, which comprises, in parts by weight:

[0093] 100 parts by weight of high sulfate-resistant G-grade oil well cement (325 mesh), 30 parts by weight of 200-mesh quartz sand, 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of stabilizer (tunlun glue, which is in a dry powder state), 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive), 1.2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid pentapolymer (high-temperature retarder), 0.1 part by weight of tributyl phosphate (defoaming agent), and 55 parts by weight of water;

[0094] The cement slurry is prepared by a preparation method comprising the following specific steps:

[0095] (1) Take 100 parts by weight of high sulfate-resistant G-grade oil well cement, 30 parts by weight of 200-mesh quartz sand, 1 part by weight of polycarboxylic acid dispersant, and 3 parts by weight of stabilizer (tunlun glue), and mix the dry powders uniformly to obtain a dry powder mixture;

[0096] (2) Weigh 55 parts by weight of water, mix 2 parts by weight of high-temperature fluid loss additive, 1.2 parts by weight of high-temperature retarder, and 0.1 part by weight of defoaming agent into the water and pour into a stirrer, rotate the stirrer at a low speed (4000±200 rpm), and add the dry powder mixture within 15 seconds, cover the lid of the stirrer, and continue to stir at a high speed (12000±500 rpm) for 35 seconds to obtain the cement slurry.

[0097] Example 2

[0098] This embodiment provides a graphite material-based high-temperature high-strength toughness cement slurry with a temperature resistance of 240°C, which comprises, in parts by weight:

[0099] High sulfate-resistant G-grade oil well cement (325 mesh) 100 parts by weight, elastic graphite 4 parts by weight (temperature resistance up to 800℃, resilience rate 20-50%, size 100 mesh), expanded graphite (which will expand under high temperature conditions above 200℃, expansion rate >200 mL / g, size 100 mesh) 2 parts by weight, 200 mesh and 600 mesh (mass ratio 1:1) mixed quartz sand 40 parts by weight, ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded according to a mass ratio of 1:1) 10 parts by weight, polycarboxylic acid dispersant 1 part by weight, high-temperature stabilizer (a compounded product formed according to a mass ratio of 1:2:1 of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol) 3 parts by weight, 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive) 2 parts by weight, 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethylammonium chloride / acrylamide / acrylic acid pentapolymer (high-temperature retarder) 3.2 parts by weight, tributyl phosphate (defoaming agent) 0.1 parts by weight, and water 57 parts by weight;

[0100] The high-temperature high-strength toughness cement slurry based on graphite material is prepared by a preparation method comprising the following specific steps:

[0101] (1) Take high sulfate-resistant G-grade oil well cement 100 parts by weight, elastic graphite (temperature resistance up to 800℃, resilience rate 20-50%) 4 parts by weight, expanded graphite (which will expand under high temperature conditions above 200℃, expansion rate >200 mL / g) 2 parts by weight, 200 mesh and 600 mesh (mass ratio 1:1) mixed quartz sand 40 parts by weight, ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded according to a mass ratio of 1:1) 10 parts by weight, polycarboxylic acid dispersant 1 part by weight, high-temperature stabilizer (a compounded product formed according to a mass ratio of 1:2:1 of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol) 3 parts by weight, and mix the dry powders uniformly to obtain a dry powder mixture;

[0102] (2) Weigh water 57 parts by weight, mix 2 parts by weight of high-temperature fluid loss additive, 3.2 parts by weight of high-temperature retarder and 0.1 parts by weight of defoaming agent into the water and pour into the stirrer, rotate the stirrer at low speed (4000±200 rpm), and add the dry powder mixture within 15 seconds, cover the lid of the stirrer, continue to stir at high speed (12000±500 rpm) for 35 seconds, and the high-temperature high-strength toughness cement slurry based on graphite material is obtained.

[0103] Comparative Example 2-1

[0104] This comparative example provides a cement slurry based on graphite material, which comprises, in parts by weight:

[0105] High sulfate-resistant G-grade oil well cement (325 mesh) 100 parts by weight, elastic graphite 4 parts by weight (temperature resistance up to 800℃, resilience rate 20-50%, size 100 mesh), expanded graphite (which will expand under high temperature conditions above 200℃, expansion rate >200 mL / g, size 100 mesh) 2 parts by weight, 200 mesh and 600 mesh (mass ratio 1:1) mixed quartz sand 40 parts by weight, ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded according to a mass ratio of 1:1) 10 parts by weight, polycarboxylic acid dispersant 1 part by weight, stabilizer (warm rubber) 3 parts by weight, 2-acrylamido-2-methylpropane sulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive) 2 parts by weight, 2-acrylamido-2-methylpropane sulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid quinary polymer (high-temperature retarder) 3.2 parts by weight, tributyl phosphate (defoaming agent) 0.1 parts by weight, and water 57 parts by weight;

[0106] The graphite material-based cement slurry is prepared by a preparation method comprising the following specific steps:

[0107] (1) Take high sulfate-resistant G-grade oil well cement 100 parts by weight, elastic graphite (temperature resistance up to 800℃, resilience rate 20-50%) 4 parts by weight, expanded graphite (which will expand under high temperature conditions above 200℃, expansion rate >200 mL / g) 2 parts by weight, 200 mesh and 600 mesh (mass ratio 1:1) mixed quartz sand 40 parts by weight, ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded according to a mass ratio of 1:1) 10 parts by weight, polycarboxylic acid dispersant 1 part by weight, stabilizer (warm rubber, which is in a dry powder state) 3 parts by weight, and uniformly mix the dry powders to obtain a dry powder mixture;

[0108] (2) Weigh water 57 parts by weight, mix 2 parts by weight of high-temperature fluid loss additive, 3.2 parts by weight of high-temperature retarder, and 0.1 parts by weight of defoaming agent into the water and pour into a stirrer, rotate the stirrer at a low speed (4000±200 revolutions / minute), and add the dry powder mixture within 15 seconds, cover the lid of the stirrer, and continue to stir at a high speed (12000±500 revolutions / minute) for 35 seconds to obtain the graphite material-based cement slurry.

[0109] Comparative Example 2-2

[0110] This comparative example provides a graphite material-based cement slurry, which comprises, by weight parts:

[0111] 100 parts by weight of high sulfate-resistant G-grade oil well cement (325 mesh), 4 parts by weight of elastic graphite (temperature resistance up to 800°C, resilience rate 20-50%, size 100 mesh), 2 parts by weight of expanded graphite (which will expand under high temperature conditions above 200°C, expansion rate >200 mL / g, size 100 mesh), 40 parts by weight of 200 mesh quartz sand, 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a complex formed by nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol in a mass ratio of 1:2:1), 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive), 3.2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid pentapolymer (high-temperature retarder), 0.1 part by weight of tributyl phosphate (defoaming agent), and 57 parts by weight of water;

[0112] The graphite material-based cement slurry is prepared by a preparation method comprising the following specific steps:

[0113] (1) Take 100 parts by weight of high sulfate-resistant G-grade oil well cement, 4 parts by weight of elastic graphite (temperature resistance up to 800°C, resilience rate 20-50%), 2 parts by weight of expanded graphite (which will expand under high temperature conditions above 200°C, expansion rate >200 mL / g), 40 parts by weight of 200 mesh quartz sand, 1 part by weight of polycarboxylic acid dispersant, and 3 parts by weight of high-temperature stabilizer (a complex formed by nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol in a mass ratio of 1:2:1), and mix the dry powders uniformly to obtain a dry powder mixture;

[0114] (2) Weigh 57 parts by weight of water, mix 2 parts by weight of high-temperature fluid loss additive, 3.2 parts by weight of high-temperature retarder, and 0.1 part by weight of defoaming agent into the water and pour into a stirrer, the stirrer rotates at low speed (4000±200 rpm), and the dry powder mixture is added within 15 seconds, the lid of the stirrer is covered, and the stirring is continued at high speed (12000±500 rpm) for 35 seconds, to obtain the graphite material-based cement slurry.

[0115] Comparative Example 2-3

[0116] This comparative example provides an elastic graphite-based cement slurry, which comprises, by weight parts:

[0117] 100 parts by weight of high sulfate-resistant G-grade oil well cement (325 mesh), 4 parts by weight of elastic graphite (temperature resistance up to 800℃, resilience rate 20-50%), 40 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 10 parts by weight of super-high-temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded in a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol in a mass ratio of 1:2:1), 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive), 3.2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid quinary polymer (high-temperature retarder), 0.1 part by weight of tributyl phosphate (defoaming agent), and 57 parts by weight of water;

[0118] The elastic graphite-based cement slurry is prepared by a preparation method comprising the following specific steps:

[0119] (1) Take 100 parts by weight of high sulfate-resistant G-grade oil well cement, 4 parts by weight of elastic graphite (temperature resistance up to 800℃, resilience rate 20-50%), 40 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 10 parts by weight of super-high-temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded in a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol in a mass ratio of 1:2:1), and mix the dry powders uniformly to obtain a dry powder mixture;

[0120] (2) Weigh 57 parts by weight of water, mix 2 parts by weight of high-temperature fluid loss additive, 3.2 parts by weight of high-temperature retarder, and 0.1 part by weight of defoaming agent into the water and pour into a stirrer, rotate the stirrer at low speed (4000±200 rpm), and add the dry powder mixture within 15 seconds, cover the lid of the stirrer, continue to stir at high speed (12000±500 rpm) for 35 seconds, and the elastic graphite-based cement slurry is obtained.

[0121] Comparative Examples 2-4

[0122] This comparative example provides an expanded graphite-based cement slurry, which comprises, by weight parts:

[0123] 100 parts by weight of high sulfate-resistant G-grade oil well cement (325 mesh), 2 parts by weight of expanded graphite (which will expand under high temperature conditions above 200°C, with an expansion rate >200 mL / g, and a size of 100 mesh), 40 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 10 parts by weight of ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded at a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol at a mass ratio of 1:2:1), 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive), 3.2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid pentapolymer (high-temperature retarder), 0.1 part by weight of tributyl phosphate (defoaming agent), and 57 parts by weight of water;

[0124] The expanded graphite-based cement slurry is prepared by a preparation method comprising the following specific steps:

[0125] (1) Take 100 parts by weight of high sulfate-resistant G-grade oil well cement, 2 parts by weight of expanded graphite (which will expand under high temperature conditions above 200°C, with an expansion rate >200 mL / g), 40 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 10 parts by weight of ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded at a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol at a mass ratio of 1:2:1), and mix the dry powders uniformly to obtain a dry powder mixture;

[0126] (2) Weigh 57 parts by weight of water, mix 2 parts by weight of high-temperature fluid loss additive, 3.2 parts by weight of high-temperature retarder and 0.1 part by weight of defoaming agent into the water and pour into a stirrer, the stirrer rotates at low speed (4000±200 rpm), and the dry powder mixture is added within 15 seconds, the cover of the stirrer is covered, and the stirring is continued at high speed (12000±500 rpm) for 35 seconds, to obtain the expanded graphite-based cement slurry.

[0127] Comparative Examples 2-5

[0128] The comparative example provides a cement slurry, which comprises, in parts by weight:

[0129] 100 parts by weight of high sulfate-resistant G-grade oil well cement (325 mesh), 40 parts by weight of 200-mesh quartz sand, 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of stabilizer (tunlun glue, which is in a dry powder state), 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive), 3.2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid pentapolymer (high-temperature retarder), 0.1 part by weight of tributyl phosphate (defoaming agent), and 57 parts by weight of water;

[0130] The cement slurry is prepared by a preparation method comprising the following specific steps:

[0131] (1) Take 100 parts by weight of high sulfate-resistant G-grade oil well cement, 40 parts by weight of 200-mesh quartz sand, 1 part by weight of polycarboxylic acid dispersant, and 3 parts by weight of stabilizer (tunlun glue), and mix the dry powders uniformly to obtain a dry powder mixture;

[0132] (2) Weigh 57 parts by weight of water, mix 2 parts by weight of high-temperature fluid loss additive, 3.2 parts by weight of high-temperature retarder, and 0.1 part by weight of defoaming agent into the water and pour into a stirrer, rotate the stirrer at a low speed (4000±200 rpm), and add the dry powder mixture within 15 seconds, cover the lid of the stirrer, and continue to stir at a high speed (12000±500 rpm) for 35 seconds to obtain the cement slurry.

[0133] Example 3

[0134] This embodiment provides a graphite material-based high-temperature high-strength toughness cement slurry with a temperature resistance of 600°C, which comprises, in parts by weight:

[0135] 100 parts by weight of high sulfate-resistant G-grade oil well cement (325 mesh), 6 parts by weight of elastic graphite (temperature resistance up to 800℃, resilience rate 20-50%, size 100 mesh), 2 parts by weight of expanded graphite (which will expand under high temperature conditions above 200℃, expansion rate >200 mL / g, size 100 mesh), 50 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 15 parts by weight of ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded in a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a compound formed by nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol in a mass ratio of 1:2:1), 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive), 3.2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid pentapolymer (high-temperature retarder), 0.1 part by weight of tributyl phosphate (defoaming agent), and 57 parts by weight of water;

[0136] The high-temperature high-strength toughness cement slurry based on graphite material is prepared by a preparation method comprising the following specific steps:

[0137] (1) Take 100 parts by weight of high sulfate-resistant G-grade oil well cement, 6 parts by weight of elastic graphite (temperature resistance up to 800℃, resilience rate 20-50%), 2 parts by weight of expanded graphite (which will expand under high temperature conditions above 200℃, expansion rate >200 mL / g), 50 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 15 parts by weight of ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded in a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a compound formed by nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol in a mass ratio of 1:2:1), and mix the dry powders uniformly to obtain a dry powder mixture;

[0138] (2) Weigh 57 parts by weight of water, mix 2 parts by weight of high-temperature fluid loss additive, 3.2 parts by weight of high-temperature retarder and 0.1 part by weight of defoaming agent into the water and pour into the stirrer, rotate the stirrer at low speed (4000±200 rpm), and add the dry powder mixture in 15 seconds, cover the lid of the stirrer, continue to stir at high speed (12000±500 rpm) for 35 seconds, and the high-temperature high-strength toughness cement slurry based on graphite material is obtained.

[0139] Comparative Example 3-1

[0140] This comparative example provides a cement slurry based on graphite material, which comprises, by weight parts:

[0141] High sulfate-resistant G-grade oil well cement (325 mesh) 100 parts by weight, elastic graphite 6 parts by weight (temperature resistance up to 800℃, resilience rate 20-50%, size 100 mesh), expanded graphite (which will expand under high temperature conditions above 200℃, expansion rate >200 mL / g, size 100 mesh) 2 parts by weight, 200 mesh quartz sand 50 parts by weight, polycarboxylic acid dispersant 1 part by weight, high-temperature stabilizer (a complex formed by nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol in a mass ratio of 1:2:1) 3 parts by weight, 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive) 2 parts by weight, 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid pentapolymer (high-temperature retarder) 3.2 parts by weight, tributyl phosphate (defoaming agent) 0.1 parts by weight, and water 57 parts by weight;

[0142] The high-temperature high-strength toughness cement slurry based on graphite material is prepared by a preparation method comprising the following specific steps:

[0143] (1) Take high sulfate-resistant G-grade oil well cement 100 parts by weight, elastic graphite (temperature resistance up to 800℃, resilience rate 20-50%) 6 parts by weight, expanded graphite (which will expand under high temperature conditions above 200℃, expansion rate >200 mL / g) 2 parts by weight, 200 mesh quartz sand 50 parts by weight, polycarboxylic acid dispersant 1 part by weight, high-temperature stabilizer (a complex formed by nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol in a mass ratio of 1:2:1) 3 parts by weight, and mix the dry powders uniformly to obtain a dry powder mixture;

[0144] (2) Weigh water 57 parts by weight, mix 2 parts by weight of high-temperature fluid loss additive, 3.2 parts by weight of high-temperature retarder and 0.1 parts by weight of defoaming agent into the water and pour into the stirrer, rotate the stirrer at low speed (4000±200 rpm), and add the dry powder mixture in 15 seconds, cover the lid of the stirrer, continue to stir at high speed (12000±500 rpm) for 35 seconds, and the high-temperature high-strength toughness cement slurry based on graphite material is obtained.

[0145] Comparative Example 3-2

[0146] This comparative example provides a cement slurry based on elastic graphite, which comprises, by weight:

[0147] 100 parts by weight of high sulfate-resistant G-grade oil well cement (325 mesh), 6 parts by weight of elastic graphite (temperature resistance up to 800°C, resilience rate 20-50%, size 100 mesh), 50 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 15 parts by weight of super-high-temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded in a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol in a mass ratio of 1:2:1), 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive), 3.2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid quinary polymer (high-temperature retarder), 0.1 part by weight of tributyl phosphate (defoaming agent), and 57 parts by weight of water;

[0148] The elastic graphite-based cement slurry is prepared by a preparation method comprising the following specific steps:

[0149] (1) Take 100 parts by weight of high sulfate-resistant G-grade oil well cement, 6 parts by weight of elastic graphite (temperature resistance up to 800°C, resilience rate 20-50%), 50 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 15 parts by weight of super-high-temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded in a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, and 3 parts by weight of high-temperature stabilizer (a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol in a mass ratio of 1:2:1), and uniformly mix the dry powders to obtain a dry powder mixture;

[0150] (2) Take 57 parts by weight of water, mix 2 parts by weight of high-temperature fluid loss additive, 3.2 parts by weight of high-temperature retarder, and 0.1 part by weight of defoaming agent into the water and pour into a stirrer, rotate the stirrer at a low speed (4000±200 revolutions / minute), and add the dry powder mixture within 15 seconds, cover the lid of the stirrer, and continue to stir at a high speed (12000±500 revolutions / minute) for 35 seconds to obtain the elastic graphite-based high-temperature high-strength toughness cement slurry.

[0151] Comparative Example 3-3

[0152] This comparative example provides an expanded graphite-based cement slurry, which comprises, by weight parts:

[0153] 100 parts by weight of high sulfate-resistant G-grade oil well cement (325 mesh), 2 parts by weight of expanded graphite (which will expand under high temperature conditions above 200°C, with an expansion rate >200 mL / g, and a size of 100 mesh), 50 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 15 parts by weight of ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded at a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol at a mass ratio of 1:2:1), 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive), 3.2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid quinary polymer (high-temperature retarder), 0.1 part by weight of tributyl phosphate (defoaming agent), and 57 parts by weight of water;

[0154] The cement slurry based on expanded graphite is prepared by a preparation method comprising the following specific steps:

[0155] (1) Take 100 parts by weight of high sulfate-resistant G-grade oil well cement, 2 parts by weight of expanded graphite (which will expand under high temperature conditions above 200°C, with an expansion rate >200 mL / g), 50 parts by weight of mixed quartz sand of 200 mesh and 600 mesh (mass ratio 1:1), 15 parts by weight of ultra-high temperature strength anti-degradation material (100 mesh metakaolin and 100 mesh chlorite compounded at a mass ratio of 1:1), 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of high-temperature stabilizer (a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol at a mass ratio of 1:2:1), and mix the dry powders uniformly to obtain a dry powder mixture;

[0156] (2) Weigh 57 parts by weight of water, mix 2 parts by weight of high-temperature fluid loss additive, 3.2 parts by weight of high-temperature retarder and 0.1 part by weight of defoaming agent into the water and pour into a stirrer, the stirrer rotates at low speed (4000±200 rpm), and the dry powder mixture is added within 15 seconds, the cover of the stirrer is covered, and the stirring is continued at high speed (12000±500 rpm) for 35 seconds, to obtain the cement slurry based on expanded graphite.

[0157] Comparative Examples 3-4

[0158] The present comparative example provides a cement slurry, which comprises, in parts by weight:

[0159] 100 parts by weight of high sulfate-resistant G-grade oil well cement (325 mesh), 50 parts by weight of 200-mesh quartz sand, 1 part by weight of polycarboxylic acid dispersant, 3 parts by weight of stabilizer (tannen glue, in dry powder state), 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethylacrylamide / itaconic acid / maleic anhydride quaternary polymer (high-temperature fluid loss additive), 3.2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethylammonium chloride / acrylamide / acrylic acid quinary polymer (high-temperature retarder), 0.1 part by weight of tributyl phosphate (antifoaming agent), and 57 parts by weight of water;

[0160] The cement slurry is prepared by a preparation method comprising the following specific steps:

[0161] (1) Take 100 parts by weight of high sulfate-resistant G-grade oil well cement, 50 parts by weight of 200-mesh quartz sand, 1 part by weight of polycarboxylic acid dispersant, and 3 parts by weight of stabilizer (tannen glue), and mix the dry powders uniformly to obtain a dry powder mixture;

[0162] (2) Weigh 57 parts by weight of water, mix 2 parts by weight of high-temperature fluid loss additive, 3.2 parts by weight of high-temperature retarder, and 0.1 part by weight of antifoaming agent into the water and pour them into a stirrer, rotate the stirrer at a low speed (4000±200 rpm), and add the dry powder mixture within 15 seconds, cover the lid of the stirrer, and continue to stir at a high speed (12000±500 rpm) for 35 seconds to obtain the cement slurry.

[0163] Test Example 1

[0164] In this test example, the cement slurries provided by Example 1, Comparative Example 1-1, Comparative Example 1-2, Comparative Example 1-3, Comparative Example 1-4, and Comparative Example 1-5 are first cured at 150℃ and 20MPa for 2 days, 7 days, 28 days, and 60 days, and then the compressive strength of the hardened cement stone, the elastic modulus of the cement stone after 7 days, and the stability of the cement slurry are determined according to the test method specified in GB19139-2012. The test results obtained in this Test Example 1 are shown in Table 1 below.

[0165] Table 1 Stability of cement slurry and mechanical properties of cement stone under temperature condition of 150℃

[0166]

[0167] As can be seen from Table 1 above, compared with Example 1, the cement slurry provided by Comparative Example 1-1 does not contain a composite high-temperature stabilizer, but only uses tannen glue as a stabilizer, and the upper and lower density difference of the cement slurry exceeds 0.05 g / cm 3, there is free liquid, and the stability of the cement slurry is poor; while the density difference of the cement slurry provided by the embodiment 1 of the present application is only 0.01 g / cm 3 , there is no free liquid, and the stability of the cement slurry is good, which shows that the composite high-temperature stabilizer used in the embodiment 1 of the present application has a good effect of improving the stability;

[0168] It can also be seen from the above table 1 that, compared with the embodiment 1, the cement slurry provided by the comparative example 1-2 does not use the ultra-high-temperature strength anti-decay material and the compounded quartz sand, and the cement stone obtained after the cement slurry hardens has obvious decay under the condition of 150℃ high temperature with the increase of the age, while the compressive strength of the cement stone obtained after the cement slurry provided by the embodiment 1 of the present application does not decay and continuously increases with the increase of the age, which shows that the ultra-high-temperature strength anti-decay material and the compounded quartz sand used in the embodiment 1 of the present application have obvious anti-decay effect on the strength of the cement stone;

[0169] It can also be seen from the above table 1 that, compared with the embodiment 1, the cement slurry provided by the comparative example 1-3 does not use the expanded graphite, and the strength of the cement stone of each age obtained after the cement slurry hardens is low, which shows that the expanded graphite used in the embodiment 1 of the present application is beneficial to improve the strength of the high-temperature cement stone;

[0170] It can also be seen from the above table 1 that, compared with the embodiment 1, the cement slurry provided by the comparative example 1-4 does not use the elastic graphite, and the elastic modulus of the 7-day cement stone is high, which shows that the elastic graphite used in the embodiment 1 of the present application is beneficial to improve the toughness of the high-temperature cement stone and reduce the elastic modulus of the cement stone;

[0171] It can also be seen from the above table 1 that, compared with the embodiment 1, the cement slurry provided by the comparative example 1-5 does not use the elastic graphite, the expanded graphite, the ultra-high-temperature strength anti-decay material and the compounded quartz sand, and does not contain the composite high-temperature stabilizer, and the mechanical properties of the cement stone obtained after the cement slurry hardens are very poor under the temperature condition of 150℃, and the stability of the cement slurry is poor, which affects the safety and quality of the cementing.

[0172] According to the experimental data in the above table 1 and the comparative analysis as shown above, it can be known that the strength of the cement stone obtained after the cement slurry provided by the embodiment 1 of the present application hardens is greater than 50 MPa, the elastic modulus of the 7-day cement stone is less than 7 GPa, and the long-term decay is more than 60 days. It can be seen that the cement stone obtained after the cement slurry system hardens under the condition of high temperature and ultra-high temperature has high long-term strength and good toughness, i.e. excellent mechanical properties and good stability, which is beneficial to ensure the safety of the cementing construction and improve the quality of the cementing.

[0173] Test example 2

[0174] The cement paste provided by Example 2, Comparative Example 2-1, Comparative Example 2-2, Comparative Example 2-3, Comparative Example 2-4 and Comparative Example 2-5 is cured at 240℃ and 20MPa for 2 days, 7 days, 28 days and 60 days, and then the compressive strength of the hardened cement stone, the elastic modulus of the cement stone after 7 days and the stability of the cement paste are determined according to the test method specified in GB19139-2012. The test results obtained in Test Example 2 are shown in Table 2 below.

[0175] Table 2 Stability of the cement paste and mechanical properties of the cement stone under high temperature conditions of 240℃

[0176]

[0177] As can be seen from Table 2 above, compared with Example 2, the cement paste provided by Comparative Example 2-1 does not contain a composite high-temperature stabilizer, but only uses warm glue as a stabilizer. The difference between the upper and lower densities of the cement paste reaches 0.10g / cm 3 , there is free liquid, and the cement paste settles seriously. The difference between the upper and lower densities of the cement paste provided by Example 2 of the present application is only 0.03g / cm 3 , there is no free liquid, and the stability of the cement paste is good, indicating that the composite high-temperature stabilizer used in Example 2 of the present application has a good effect of improving stability;

[0178] As can be seen from Table 2 above, compared with Example 2, the cement paste provided by Comparative Example 2-2 does not use an ultrahigh-temperature strength anti-decay material and compounded quartz sand. With the increase of the age, the cement stone under the condition of 240℃ high temperature decays obviously, and only less than 20MPa is left. With the increase of the age, the compressive strength of the cement stone obtained after the cement paste provided by Example 2 of the present application is hardened does not decay and continues to increase, indicating that the ultrahigh-temperature strength anti-decay material and the compounded quartz sand used in Example 2 of the present application have a significant effect of resisting the decay of the cement stone strength;

[0179] As can be seen from Table 2 above, compared with Example 2, the cement paste provided by Comparative Example 2-3 does not use expanded graphite. The strength of the cement stone of each age obtained after the cement paste is hardened is low, indicating that the expanded graphite used in Example 2 of the present application expands under ultrahigh temperature conditions, which can improve the microstructure and pore size distribution of the cement stone, and the SEM image of the cement stone is shown in Figure 1 , thereby being beneficial to improving the strength of the high-temperature cement stone;

[0180] As can be seen from Table 2 above, compared with Example 2, the cement paste provided by Comparative Example 2-4 does not use elastic graphite, and the elastic modulus of the 7-day cement stone is high, indicating that the elastic graphite used in Example 2 of the present application is beneficial to improving the toughness of the high-temperature cement stone and reducing the elastic modulus of the cement stone;

[0181] It can also be seen from the above Table 2 that, compared with Example 2, the cement slurry provided by Comparative Examples 2-5 does not use elastic graphite, expanded graphite, ultra-high temperature strength anti-decay material and compound quartz sand, and does not contain a composite high-temperature stabilizer, and the mechanical properties of the cement stone obtained after the cement slurry is hardened under a high temperature condition of 240℃ are very poor, and the stability of the cement slurry is poor, which affects the safety and quality of well cementing, while the cement stone obtained after the cement slurry provided by Example 2 of the present application is hardened (7 days) has a strength of more than 50 MPa under a high temperature condition of 240℃, and has good stability, which is beneficial to guarantee the safety of well cementing construction and improve the quality of well cementing.

[0182] According to the experimental data in the above Table 2 and the comparative analysis as shown above, it can be seen that the cement stone obtained after the cement slurry provided by Example 2 of the present application is hardened has a strength of more than 45 MPa, a 7-day cement stone elastic modulus of less than 7 GPa, and a long-term non-decay of more than 60 days. It can be seen that the cement slurry system is hardened into a cement stone under high-temperature and ultra-high-temperature conditions, and the cement stone has high long-term strength and does not decay, good toughness, i.e., excellent mechanical properties and good stability, which is beneficial to guarantee the safety of well cementing construction and improve the quality of well cementing.

[0183] Test Example 3

[0184] In this test example, the cement slurry provided by Example 3, Comparative Example 3-1, Comparative Example 3-2, Comparative Example 3-3 and Comparative Example 3-4 is cured at a high temperature condition of 600℃ for 2 days, 7 days, 28 days and 60 days, and then the compressive strength of the hardened cement stone and the elastic modulus of the 7-day cement stone are measured according to the test method specified in GB19139-2012. Since the high temperature condition of 600℃ is mainly used for underground gasification, thickening thermal recovery wells, etc., which is low-temperature condition well cementing, high-temperature production, the mechanical properties of the cement stone under this condition are mainly considered, and therefore the stability of the cement slurry is not investigated in this test example. The test results obtained in this Test Example 3 are shown in Table 3 below.

[0185] Table 3 Mechanical properties of cement stone under a high temperature condition of 600℃

[0186]

[0187] As can be seen from the above Table 3, compared with Example 3, the cement slurry provided by Comparative Example 3-1 does not use the ultra-high temperature strength anti-decay material and the compounded quartz sand, and the cement stone under the condition of 600℃ high temperature obviously decays with the increase of the age, and only less than 10MPa is left, while the compressive strength of the cement stone obtained after the cement slurry provided by the present application of Example 3 is hardened does not decay and continuously increases with the increase of the age, which shows that, in the cement slurry provided by the present application of Example 3, due to the addition of the ultra-high temperature strength anti-decay material, the aluminum-containing mineral with nanometer-sized interlayer spacing in the ultra-high temperature strength anti-decay material participates in the secondary hydration reaction of the high-temperature cement, inhibits the generation of parallel needle-shaped xonotlite (C5S6H), and promotes the generation of high-temperature stable hydration product tobermorite, forming a high-temperature stability fiber network structure, thereby preventing the strength decay of the cement stone, so that the long-term strength of the cement stone obtained after the cement slurry provided by Example 3 is hardened can still be maintained at a high level under the condition of 600℃ high temperature; this also shows that the ultra-high temperature strength anti-decay material and the compounded quartz sand used in the present application of Example 3 have obvious anti-decay effect on the strength of the cement stone;

[0188] As can be seen from the above Table 3, compared with Example 3, the cement slurry provided by Comparative Example 3-2 does not use the expanded graphite, and the strength of the cement stone of each age after the cement slurry is hardened is low, which shows that the expanded graphite used in the present application of Example 3 can expand under the condition of 600℃ ultra-high temperature, and can improve the microstructure and pore size distribution of the cement stone, thereby being beneficial to improving the strength of the high-temperature cement stone;

[0189] As can be seen from the above Table 3, compared with Example 3, the cement slurry provided by Comparative Example 3-3 does not use the elastic graphite, and the elastic modulus of the 7-day cement stone is high, which shows that the elastic graphite used in the present application of Example 3 is beneficial to improving the toughness of the high-temperature cement stone and reducing the elastic modulus of the cement stone;

[0190] As can be seen from the above Table 3, compared with Example 3, the cement slurry provided by Comparative Example 3-4 does not use the elastic graphite, the expanded graphite, the ultra-high temperature strength anti-decay material and the compounded quartz sand, and does not contain the composite high-temperature stabilizer, and under the condition of 600℃ ultra-high temperature, the mechanical properties of the cement stone are very poor, the microstructure is loose, and the sealing integrity of the cement sheath cannot be guaranteed, while the strength of the cement stone obtained after the cement slurry provided by the present application of Example 3 is hardened (28 days) can still exceed 40MPa under the condition of 600℃ ultra-high temperature, which is beneficial to improving the sealing integrity of the cement sheath.

[0191] According to the experimental data in the above Table 3 and the comparative analysis as shown above, it can be seen that the strength of the cement stone provided by the cement slurry of the embodiment 3 of the present application after hardening (28 days) into the cement stone is still greater than 40 MPa, the elastic modulus of the 7-day cement stone is lower than 7 GPa, and the long-term does not decline for more than 60 days. It can be seen that after the cement slurry system provided by the embodiment of the present application is hardened into the cement stone under the high temperature and ultra-high temperature conditions, the long-term strength of the cement stone is high and does not decline, the toughness is good, that is, the mechanical properties are excellent, and the stability is good, which is beneficial to guarantee the safety construction of well cementing and improve the quality of well cementing.

[0192] It can be seen that, compared with the prior art, the high-temperature high-strength toughness cement slurry based on the graphite material provided by the embodiment of the present application has the following beneficial effects:

[0193] (1) The graphite material (including elastic graphite and expandable graphite) is introduced into the cement stone in the embodiment of the present application, which has three unique advantages: first, the graphite material has a lamellar structure inside, when the cement stone is damaged by external force, the graphite lamellar peeling needs to overcome the interlayer force to consume energy, which is beneficial to improve the mechanical properties of the cement stone; second, the elastic graphite material has strong temperature resistance and high resilience, under the high temperature and ultra-high temperature and under the downhole pressure conditions, it will be highly compressed, and after losing the pressure, it can recover, which is beneficial to improve the mechanical properties of the high-temperature and ultra-high temperature cement stone; third, the expandable graphite material will expand during the cement hydration process under the high temperature and ultra-high temperature conditions, fill the pores between the high-temperature and ultra-high temperature cement hydration products, and promote the formation of a dense high-temperature cement stone microstructure, so the addition of the expandable graphite is beneficial to improve the microstructure and pore size distribution of the cement stone, thereby improving the mechanical properties of the cement stone. The above three advantages of the graphite material help to guarantee the integrity of the cement sheath under the high temperature and high pressure environment in the well.

[0194] (2) The mixed quartz sand is used in the embodiment of the present application, compared with the ordinary quartz sand, due to the close packing effect of the mixed quartz sand, the effect of improving the strength of the high-temperature and ultra-high temperature cement stone is better.

[0195] (3) The embodiment of the present application uses a complex mixture of any two of metakaolin, kaolin, cyanite and chlorite as an ultra-high temperature strength anti-declining material, the nanometer-sized aluminum-containing mineral crystal interlayer spacing in the ultra-high temperature strength anti-declining material can participate in the secondary hydration reaction of high-temperature cement, inhibit the generation of parallel needle-shaped calcium silicate hydrate (C5S6H), and promote the generation of high-temperature stable hydration product tobermorite, form an anti-high-temperature stable fiber network structure, thereby preventing the strength decline of the cement stone.

[0196] (4) For the problem of poor stability of cement slurry under ultra-high temperature conditions, the compound formed by nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol is used as an ultra-high temperature stabilizer in the embodiment of the application, so that a network structure can be formed in the cement slurry under ultra-high temperature conditions, the system viscosity and particle structure force are increased, and thus the stability of the ultra-high temperature cement slurry for well cementing can be improved.

[0197] (5) The high-temperature dispersant, high-temperature fluid loss agent and high-temperature retarder used in the embodiment of the application can make the comprehensive performance of the high-temperature cement slurry system good. The cement slurry provided by the application has good stability under high temperature and ultra-high temperature conditions, the upper and lower density difference is less than 0.05 g / cm 3 , the fluid loss performance meets the standard, the rheological property is good, the thickening time and density are adjustable, and the well cementing construction performance meets the demand of oil and gas well cementing.

[0198] (6) The particle size of the material is reasonably designed in the embodiment of the application, so that the high-sulfate-resistant G-grade oil well cement, elastic graphite, quartz sand and ultra-high temperature strength anti-decay material used in the cement slurry system can be tightly packed. After the cement slurry is hardened into cement stone under ultra-high temperature conditions, the 28-day cement stone strength is greater than 40 MPa, and the long-term decay is more than 60 days, and the mechanical properties of the cement stone are significantly improved.

[0199] In summary, the high-temperature high-strength toughness cement slurry based on graphite material provided by the embodiment of the application can be applied to well cementing operations of deep wells, ultra-deep wells, heavy oil thermal recovery wells and other high-temperature ultra-high temperature wells with bottom hole temperatures of 150-600 DEG C, and can meet the higher requirements for mechanical properties such as cement sheath strength and toughness during well cementing operations of deep wells, ultra-deep wells, heavy oil thermal recovery wells and other high-temperature ultra-high temperature wells. In some specific embodiments of the application, after the cement slurry is hardened into cement stone, the 28-day cement stone strength is greater than 40 MPa, the 7-day cement stone elastic modulus is less than 7 GPa, and the long-term decay is more than 60 days.

[0200] The above is only a specific embodiment of the application, which cannot limit the scope of the application, so the replacement of equivalent components or equivalent changes and modifications made within the scope of the patent protection range of the application should still belong to the scope covered by the patent. In addition, the technical features in the application can be freely combined with each other, between technical features, between technical features and technical inventions, and between technical inventions.

Claims

1. A high temperature high strength ductile cement paste based on graphite material, characterized in that, The high-temperature high-strength toughness cement paste based on graphite material comprises, by weight: High-sulfate-resistant G-grade oil well cement 100 parts by weight; Elastic graphite 2-6 parts by weight; Expanded graphite 2-6 parts by weight; Quartz sand 20-50 parts by weight; Ultra-high-temperature strength anti-degradation material 5-15 parts by weight; Dispersing agent 0.5-2 parts by weight; High-temperature stabilizer 2-4 parts by weight; High-temperature fluid loss additive 0.5-4 parts by weight; High-temperature retarder 0.2-8 parts by weight; Defoaming agent 0.1-1 part by weight; Water 40-80 parts by weight; The ultra-high-temperature strength anti-degradation material comprises a compounded mixture of two or more of metakaolin, kaolin, kyanite and chlorite; The high-temperature stabilizer comprises a compounded product of nano-aluminum oxide, magnesium aluminum silicate and polyvinyl alcohol; The quartz sand comprises a mixed product of 100-400 mesh quartz sand and 600-1500 mesh quartz sand; The elastic graphite has a temperature resistance of 800℃ and a rebound rate of 20-50%; The expanded graphite expands at a temperature above 200℃, with an expansion rate of >200 mL / g.

2. The cement paste according to claim 1, characterized in that, The fineness of the ultra-high-temperature strength anti-degradation material is 100-400 mesh.

3. The cement paste according to claim 1, characterized in that, When the bottom hole temperature is 150-180℃, the amount of the ultra-high-temperature strength anti-degradation material is 5 parts by weight; when the bottom hole temperature is 180-240℃, the amount of the ultra-high-temperature strength anti-degradation material is 5-10 parts by weight; and when the bottom hole temperature is above 240℃, the amount of the ultra-high-temperature strength anti-degradation material is 10-15 parts by weight.

4. The cement slurry of claim 1, wherein, The dispersing agent comprises a polycarboxylic acid dispersing agent for oil well cement.

5. The cement paste of claim 1, wherein, The high-temperature fluid loss additive comprises a 2-acrylamido-2-methylpropanesulfonic acid / N,N-dimethyl acrylamide / itaconic acid / maleic anhydride quaternary polymer, which is a quaternary polymer prepared by using 2-acrylamido-2-methylpropanesulfonic acid, N,N-dimethyl acrylamide, itaconic acid and maleic anhydride as raw materials by using a conventional polymerization method.

6. The cement slurry of claim 1, wherein, The high-temperature retarder comprises a 2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / diallyldimethyl ammonium chloride / acrylamide / acrylic acid quinary polymer, which is a quinary polymer prepared by using 2-acrylamido-2-methylpropanesulfonic acid, itaconic acid, diallyldimethyl ammonium chloride, acrylamide and acrylic acid as raw materials by using a conventional polymerization method.

7. The cement paste of claim 1, wherein, The defoaming agent comprises an organic silicon or organic ester defoaming agent.

8. Process for the preparation of a high temperature high strength ductile cement paste based on graphite material according to any one of claims 1 to 7, characterized in that, The preparation method comprises: (1) mixing the high-sulfate-resistant G-grade oil well cement, the elastic graphite, the expanded graphite, the quartz sand, the ultra-high-temperature strength anti-degradation material, the dispersing agent and the high-temperature stabilizer uniformly to obtain a dry powder mixture; (2) adding high-temperature fluid loss additive, high-temperature retarder and defoaming agent into clean water to obtain a mixed solution; adding the dry powder mixture into the mixed solution and stirring at a high speed until the dry powder mixture is uniformly dispersed to obtain the high-temperature high-strength and high-toughness cement slurry based on graphite material.

9. The production method according to claim 8, characterized by, In step (2), the high-temperature fluid loss additive, high-temperature retarder and defoaming agent are added into clean water and stirred at a low speed of 4000±200 rpm to obtain a mixed solution; In step (2), the dry powder mixture is added into the obtained mixed solution within 15 seconds; In step (2), the dry powder mixture is stirred at a high speed of 12000±500 rpm for 35 seconds.

10. Use of the high-temperature high-strength and high-toughness cement slurry based on graphite material according to any one of claims 1-7 in cementing operations of high-temperature and ultra-high-temperature wells.

11. A high temperature ultra-high temperature well cementing method, characterized in that, The method uses the high-temperature high-strength and high-toughness cement slurry based on graphite material according to any one of claims 1-7.

12. The method of claim 11, wherein, The high-temperature and ultra-high-temperature well has a bottom hole temperature of 150-600℃.

13. The method according to claim 11 or 12, characterized in that, The high-temperature and ultra-high-temperature well includes a deep well, an ultra-deep well, a shale oil in-situ conversion well or a heavy oil thermal recovery well.

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