Method for preparing high temperature cement for CO2-containing environments and cement slurry thereof

Abstract

The application discloses a kind of preparation method of high-temperature cementing cement for CO2-containing environment and cement slurry, belong to oil and gas development technical field.The high-temperature cementing cement of the application includes the following components by mass fraction: acid high-temperature cementing special high-iron phase cement 60~72 parts;Strength stabilizer 25~40 parts;High-temperature corrosion inhibitor 2~5 parts;Fluid loss additive 3~5 parts;High-temperature retarder 2~4 parts;Suspension stabilizer 1~3 parts;Dispersing agent 0.5~3 parts;Defoaming agent 0.05~0.2 parts.The application adjusts the ratio of C3S and C2S in cement clinker, increases the proportion of C4AF at the same time, improves the brittleness problem of high-temperature cementing cement stone by using the high toughness of C4AF hydration product;And introduce γ-C2S, absorb CO2 gas in the invading cement slurry and convert into CaCO3, improve the resistance to CO2 corrosion.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, and specifically to a high-temperature cementing cement for use in acidic environments containing CO2 and a method for preparing the cement slurry thereon. Background Technology

[0002] During oil and gas resource extraction, acidic gases such as CO2 are often present, posing a severe challenge to the long-term sealing integrity of cement sheaths. For high-temperature cementing operations, on the one hand, the high-temperature and high-pressure environment causes the hydration products of conventional oil well cement to undergo crystal transformation, leading to a significant increase in cement stone porosity and permeability, and a decline in mechanical properties; on the other hand, under high-temperature conditions, downhole CO2 is usually in a supercritical state, possessing extremely strong diffusion and penetration capabilities, and can rapidly invade along the micro-cracks and pores inside the cement stone, triggering a deep carbonation reaction, further exacerbating cement stone dissolution and weight loss and interfacial cementation failure.

[0003] Under the combined effect of the above two factors, cement sheaths are highly susceptible to losing their interlayer sealing capacity, severely impacting the safe lifespan and recovery efficiency of oil and gas wells. Currently, existing high-temperature cementing systems still have significant shortcomings in dealing with the combined effects of high CO2-content acidic environments and high temperatures, failing to simultaneously and effectively suppress strength degradation caused by high temperatures and supercritical CO2 corrosion damage. Therefore, there is an urgent need to develop a high-temperature cement slurry system specifically designed for high-CO2-content acidic gas environments, addressing both the cement base material and additives to improve cementing quality and long-term sealing reliability under acidic high-temperature conditions. Summary of the Invention

[0004] To overcome the defects and shortcomings of existing technologies, this invention develops a method for preparing high-temperature cementing cement and cement slurry for CO2-containing environments. The aim is to solve the technical problem that existing cement slurry systems are prone to strength degradation, increased permeability, and insufficient corrosion resistance under the synergistic effect of high temperature and supercritical CO2, leading to long-term failure of the sealing integrity of the cement sheath.

[0005] Specifically, addressing the issue that the reaction rate of cement minerals in high-temperature cementing environments increases rapidly with the bottom-hole temperature, thereby increasing the difficulty and cost of using cement slurry systems, this invention adjusts the ratio of C3S and C2S in cement clinker while increasing the proportion of C4AF. The high toughness of C4AF hydration products is used to improve the brittleness of high-temperature cementing cement stone. On the other hand, by adjusting the cooling regime and introducing some γ-C2S, CO2 gas intruding into the cement slurry is absorbed and converted into CaCO3, improving the resistance to CO2 corrosion. Thus, the long-term sealing integrity of the cement sheath and construction safety are achieved in high-temperature acidic environments.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a high-temperature cementing cement for use in CO2-containing environments, comprising the following components by weight: 60-72 parts of high-ferrous phase cement for acidic high-temperature cementing; Strength stabilizer 25-40 parts; 2-5 parts of high-temperature corrosion inhibitor; 3-5 parts of water loss reducer; 2-4 parts of high-temperature retarder; 1-3 parts of suspension stabilizer; Dispersant 0.5-3 parts; Defoamer 0.05~0.2 parts.

[0007] The total mass fraction of the acidic high-temperature cement for cementing, high-iron phase cement, strength stabilizer and high-temperature corrosion inhibitor is 100 parts.

[0008] Furthermore, the high-ferrous phase cement for acidic high-temperature cementing is composed of high-ferrous phase cement clinker and dihydrate gypsum mixed at a mass ratio of (94~96):(4~6); the specific surface area of ​​the high-ferrous phase cement for acidic high-temperature cementing is 260~280 m². 2 / kg.

[0009] Furthermore, in the high-iron phase cement clinker: the ratio of C3S to C2S is 0.82~1.10, wherein the crystal forms of C2S include β-C2S and γ-C2S; the C4AF content is ≥18%, the C3A content is ≤3%, and the f-CaO content is ≤1.5%.

[0010] Furthermore, the high-iron phase cement clinker is prepared by calcining a mixture of limestone, sandstone, iron powder, red mud, and fly ash in a mass ratio of (76~79):(4~13):(6~9):(0~5):(2~10), as follows: Limestone, sandstone, iron powder, red mud, and fly ash are mixed in a certain mass ratio to obtain a mixed raw meal. The mixed raw meal is ground together to a fineness of ≤10% on a 0.08 mm square hole sieve and ≤1.5% on a 0.2 mm square hole sieve. 10% of the mass of water is added to the ground mixed raw meal, and after being mixed evenly, it is pressed into a corrugated test cake and dried at 105℃ to constant weight. The dried corrugated test cake was heated to 840~860℃ and held for 20 min; then the temperature was raised to 1360~1420℃ and calcined for 40~60 min; after calcination, it was first rapidly cooled to 600~700℃, then slowly cooled to 420~500℃, and finally rapidly cooled to room temperature to obtain high-iron phase cement clinker.

[0011] Heating to 840~860℃ and holding for 20 minutes is the method to maximize the decomposition rate of calcium carbonate.

[0012] Furthermore, the preparation of high-ferrous phase cement for acidic high-temperature cementing is as follows: High-iron phase cement clinker is crushed to a maximum particle size of ≤8 mm; Weigh the crushed high-ferrous phase cement clinker and dihydrate gypsum according to the mass ratio, and grind them together until the final particle size is 260~280 μm. 2 / kg, thus obtaining acidic high-temperature cement for cementing with high ferrous phase.

[0013] Furthermore, the specific surface area of ​​gypsum dihydrate is 280 m². 2 / kg.

[0014] Furthermore, the strength stabilizer is composed of construction sand, high-purity quartz sand and porcelain powder mixed in a mass ratio of (10~60):(10~60):(10~60); Yellow sand contains >90% SiO2 and >5% Al2O3; high-purity quartz sand contains >99% SiO2; ceramic powder contains >65% SiO2, >20% Al2O3, and has a water absorption rate of <0.5%. The yellow sand is composed of two particle size distributions: 200 mesh and 325 mesh, and the mass ratio of 200 mesh yellow sand to 325 mesh yellow sand is (50~85):(15~50); The high-purity quartz sand is composed of two particle size distributions: 200 mesh and 800 mesh, and the mass ratio of 200 mesh high-purity quartz sand to 800 mesh high-purity quartz sand is (70~85):(15~30). The porcelain powder consists of two particle size distributions: 180 mesh and 260 mesh, with a mass ratio of 7:3 between 180 mesh and 260 mesh porcelain powder.

[0015] Furthermore, the high-temperature corrosion resist is composed of lightly calcined magnesium oxide, heavily calcined magnesium oxide, and dead-burned magnesium oxide mixed in a mass ratio of (0~1):(1~10):(90~100); The light-burned magnesia consists of two particle size distributions: 200 mesh and 400 mesh, with a mass ratio of 200 mesh light-burned magnesia to 400 mesh light-burned magnesia of 7:3. The recalcined magnesia consists of two particle size distributions: 200 mesh and 325 mesh, with a mass ratio of 200 mesh recalcined magnesia to 325 mesh recalcined magnesia of 5:5. The particle size of the dead-burned magnesium oxide is 170 mesh.

[0016] Furthermore, the water loss reducing agent is an AMPS-amide-carboxylic acid polymer; the high-temperature retarder is one or more of gluconate, sulfonate or tartrate; the suspension stabilizer is one or more of AM-AMPS-NVP polymer and microsilica; the dispersant is a formaldehyde-acetone condensate; and the defoamer is tributyl phosphate.

[0017] A second aspect of the present invention provides a method for preparing the cement slurry of the above-mentioned high-temperature cementing cement, comprising: Weigh out the mixing water according to a water-cement ratio of 0.40 to 0.70 and set it aside. The water-cement ratio is the mass ratio of the mixing water to the acidic high-temperature cementing special high-iron phase cement. Weigh each component according to its mass percentage and mix them thoroughly to obtain a mixture; Pour the mixture into the weighed mixing water within 15 seconds and stir at 4000 rpm. After the mixture has been completely poured in, continue stirring at 12000 rpm for 35 seconds to obtain cement slurry.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. High temperatures strongly promote the hydration of cement minerals. The hydration activity of cement minerals is no longer the primary factor affecting the early compressive strength of cement stone; however, different types of cement minerals still exhibit different hydration rates under high-temperature conditions. In existing conventional cementing systems, γ-C2S is usually absent or present in very small amounts (<1%). This is because during cement production, rapid cooling processes are used to obtain C3S and C2S (mainly β-C2S) that are metastable at room temperature, thus ensuring the hydration activity of the cement. γ-C2S, due to its extremely low hydration activity and the volume expansion accompanying the transformation from β-C2S to γ-C2S, easily leads to clinker pulverization. Therefore, it is considered a harmful mineral and deliberately suppressed in conventional cement production.

[0019] This invention optimizes the clinker cooling process by employing a segmented cooling technique of "rapid cooling → slow cooling → rapid cooling," successfully introducing an appropriate amount of γ-C2S into cement clinker. This γ-C2S exhibits a stronger chemical absorption capacity for CO2, enabling it to adsorb and convert CO2 that intrudes into the cement sheath during cementing into stable CaCO3. This, in turn, endows the cement stone with active resistance to CO2 corrosion, significantly improving the long-term sealing integrity of the cement sheath in acidic environments.

[0020] This invention achieves precise control of the rate and temperature range of each cooling stage: a first rapid cooling (e.g., ≥30℃ / min to 600~700℃) ensures that C3S generated at high temperature does not decompose into C2S, preserving its hydration activity; subsequently, slow cooling (e.g., 5~15℃ / min to 400℃) induces a partial crystal transformation of β-C2S to generate γ-C2S; finally, rapid cooling again (e.g., ≥30℃ / min to room temperature) inhibits the complete conversion of β-C2S to γ-C2S, retaining some β-C2S to ensure the basic hydration activity of cement. This segmented cooling process achieves a balance between preserving C3S activity and controlling the generation of γ-C2S.

[0021] 2. This invention improves the intrinsic toughness of cement stone by increasing the C4AF content in cement clinker (≥18%) and utilizing the high-toughness iron-phase hydration products generated by C4AF hydration. This avoids the problems of poor interfacial compatibility and stress concentration points between conventional exogenous toughening materials (such as polymer fibers, latex, etc.) and the cement matrix. Simultaneously, the increased iron-phase content lowers the temperature of the liquid phase during cement raw meal calcination, which helps reduce clinker calcination temperature, fuel consumption, and CO2 emissions, resulting in significant energy-saving and carbon-reducing benefits.

[0022] 3. This invention achieves precise control of the cement hydration process by adjusting the ratio of C3S to C2S in cement clinker to 0.82~1.10. This leverages the characteristics of C3S (rapid hydration rate and high early strength) and C2S (slow hydration rate, high later strength and low heat of hydration) to achieve the same result. Under high-temperature curing conditions, a reasonable hydration rate matching promotes the uniform distribution and dense packing of hydration products, optimizes the microporous structure of the cement stone, reduces the number of harmful macropores, and thus promotes the continuous and stable increase of the compressive strength of the cement stone. Simultaneously, this invention controls the specific surface area of ​​the high-ferrous phase cement for acidic high-temperature cementing to be 260~280 m². 2 / The appropriate fineness (kg) ensures the full utilization of cement hydration activity while avoiding the problems of increased water demand and excessive adsorption of admixtures caused by excessively fine particles, thus ensuring that the cement paste system has good workability and mechanical properties.

[0023] 4. This invention utilizes a rational blend of lightly calcined, heavily calcined, and dead-calcined magnesium oxide, leveraging their significant differences in hydration activity to form chemical protection against CO2 at different service stages of cement stone: lightly calcined magnesium oxide (high activity) rapidly forms a protective film in the early stages; heavily calcined magnesium oxide (medium activity) maintains alkalinity through continuous reaction in the middle stages; and dead-calcined magnesium oxide (extremely low activity) continuously absorbs CO2 and undergoes micro-expansion self-repair during long-term service. These three components work synergistically to reduce the corrosive damage of CO2 to the mechanical properties of cement stone. Furthermore, the high-temperature corrosion inhibitor and strength stabilizer, through elemental synergy, promote the stable development of high-temperature strength in cement stone. Specifically, the silicon element in the strength stabilizer induces the transformation of hydration products into a high-temperature stable phase by reducing the calcium-silicon ratio of the system; aluminum ions partially replace silicon in the hydration products, increasing the steric hindrance for crystal transformation. Simultaneously, magnesium ions in the high-temperature corrosion inhibitor dissolve into the crystal structure of the hydration products, further increasing the difficulty of crystallization transformation. The steric hindrance of silicon, aluminum, and magnesium at the microscale significantly inhibits the unfavorable crystal transformation of hydration products at high temperatures, thereby synergistically promoting the stable development of cement stone strength. Simultaneously, the increased iron phase (C4AF) content lowers the temperature of the liquid phase during cement raw meal calcination, which helps reduce clinker calcination temperature, fuel consumption, and CO2 emissions, resulting in significant energy-saving and carbon-reducing benefits. Detailed Implementation

[0024] In this invention, C3S represents tricalcium silicate (3CaO·SiO2), C2S represents dicalcium silicate (2CaO·SiO2), C3A represents tricalcium aluminate (3CaO·Al2O3), C4AF represents tetracalcium aluminoferrite (4CaO·Al2O3·Fe2O3), and f-CaO represents free calcium oxide.

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0026] In this embodiment of the invention, the specific surface area of ​​gypsum dihydrate is 280 m². 2 / kg.

[0027] Yellow sand contains >90% SiO2 and >5% Al2O3; high-purity quartz sand contains >99% SiO2; ceramic powder contains >65% SiO2, >20% Al2O3, and has a water absorption rate of <0.5%.

[0028] The porcelain powder consists of two particle size distributions: 180 mesh and 260 mesh, with a mass ratio of 7:3 between 180 mesh and 260 mesh porcelain powder.

[0029] The light-burned magnesia consists of two particle size distributions: 200 mesh and 400 mesh, with a mass ratio of 200 mesh light-burned magnesia to 400 mesh light-burned magnesia of 7:3. The recalcined magnesia consists of two particle size distributions: 200 mesh and 325 mesh, with a mass ratio of 200 mesh recalcined magnesia to 325 mesh recalcined magnesia of 5:5. The particle size of the dead-burned magnesium oxide is 170 mesh.

[0030] In this embodiment of the invention, the water loss reducing agent is an AMPS-amide-carboxylic acid polymer; the dispersant is a formaldehyde-acetone condensate; and the defoamer is tributyl phosphate.

[0031] In this embodiment of the invention, the cooling rate for the two rapid cooling cycles is ≥30℃ / min, and the cooling rate for the slow cooling cycle is 5~15℃ / min.

[0032] Example 1, as a preferred embodiment of the present invention, discloses a high-temperature cementing cement, the specific composition of which is shown in Table 1.

[0033] Table 1. Composition of High-Temperature Cement in Example 1

[0034] In this embodiment, the high-ferrous phase cement for acidic high-temperature cementing is composed of high-ferrous phase cement clinker and dihydrate gypsum mixed at a mass ratio of 96:4; the specific surface area of ​​the high-ferrous phase cement for acidic high-temperature cementing is 280 m². 2 / kg.

[0035] In high-iron phase cement clinker, the ratio of C3S to C2S is 0.83, with β-C2S content of 19.48%, γ-C2S content of 10.24%, C4AF content of 18.3%, C3A content of 1.3%, and f-CaO content of 0.7%.

[0036] High-iron phase cement clinker is prepared by calcining a mixture of limestone, sandstone, iron powder, red mud, and fly ash, as follows: Limestone, sandstone, iron powder, red mud, and fly ash were mixed in a mass ratio of 77.5:7.5:8:3.5:3.5 to obtain a mixed raw meal. The mixed raw meal was ground together to a fineness of 10% residue on a 0.08 mm square hole sieve and 1.5% residue on a 0.2 mm square hole sieve. Water of 10% by mass was added to the ground mixed raw meal, and after being mixed evenly, it was pressed into corrugated test cakes and dried at 105℃ to constant weight. The dried corrugated test cake was heated to 840℃ and held for 20 min; then the temperature was raised to 1360℃ and calcined for 60 min; after calcination, it was first rapidly cooled to 650℃, then slowly cooled to 450℃, and finally rapidly cooled to room temperature to obtain high-iron phase cement clinker.

[0037] The preparation of high-ferrous phase cement for acidic high-temperature cementing is as follows: Jaw crusher is used to crush high-iron phase cement clinker to a maximum particle size of ≤8 mm. Crushed high-ferrous phase cement clinker and dihydrate gypsum were weighed at a mass ratio of 96:4 and ground together in a ball mill until the final particle size was 280 μm. 2 / kg, thus obtaining acidic high-temperature cement for cementing with high ferrous phase.

[0038] The strength stabilizer is made by mixing construction yellow sand, high-purity quartz sand and porcelain powder in a mass ratio of 30:45:25; wherein the mass ratio of 200 mesh yellow sand to 325 mesh yellow sand is 50:50, and the mass ratio of 200 mesh high-purity quartz sand to 800 mesh high-purity quartz sand is 85:15.

[0039] The high-temperature corrosion inhibitor is a mixture of lightly calcined magnesium oxide, heavily calcined magnesium oxide, and dead-calcined magnesium oxide in a mass ratio of 0.3:4.7:95.

[0040] The high-temperature retarder is a mixture of gluconate and tartrate in a 1:1 mass ratio, and the suspension stabilizer is an AM-AMPS-NVP polymer.

[0041] Example 2, as a preferred embodiment of the present invention, discloses a high-temperature cementing cement, the specific composition of which is shown in Table 2.

[0042] Table 2. Composition of High-Temperature Cement in Example 2

[0043] In this embodiment, the high-ferrous phase cement for acidic high-temperature cementing is composed of high-ferrous phase cement clinker and dihydrate gypsum mixed at a mass ratio of 95:5; the specific surface area of ​​the high-ferrous phase cement for acidic high-temperature cementing is 260 m². 2 / kg.

[0044] In high-iron phase cement clinker: the ratio of C3S to C2S is 1.00, of which β-C2S content is 18.12%, γ-C2S content is 9.33%, C4AF content is 18.2%, C3A content is 2.12%, and f-CaO content is 1.33%.

[0045] High-iron phase cement clinker is prepared by calcining a mixture of limestone, sandstone, iron powder, and fly ash, as follows: Limestone, sandstone, iron powder, and fly ash were mixed in a mass ratio of 77.5:10.5:4:8 to obtain a mixed raw meal. The mixed raw meal was ground together to a fineness of 10% residue on a 0.08 mm square hole sieve and 1.5% residue on a 0.2 mm square hole sieve. 10% water by mass was added to the ground mixed raw meal, and after being mixed evenly, it was pressed into corrugated test cakes and dried at 105℃ to constant weight. The dried corrugated test cake was heated to 850℃ and held for 20 min; then the temperature was raised to 1400℃ and calcined for 40 min; after calcination, it was first rapidly cooled to 600℃, then slowly cooled to 500℃, and finally rapidly cooled to room temperature to obtain high-iron phase cement clinker.

[0046] The preparation of high-ferrous phase cement for acidic high-temperature cementing is as follows: Jaw crusher is used to crush high-iron phase cement clinker to a maximum particle size of ≤8 mm. Crushed high-ferrous phase cement clinker and dihydrate gypsum were weighed at a mass ratio of 95:5 and ground together in a ball mill until the final particle size was 260 μm. 2 / kg, thus obtaining acidic high-temperature cement for cementing with high ferrous phase.

[0047] The strength stabilizer is made by mixing construction yellow sand, high-purity quartz sand and porcelain powder in a mass ratio of 14:56:30; wherein the mass ratio of 200 mesh yellow sand to 325 mesh yellow sand is 72:28, and the mass ratio of 200 mesh high-purity quartz sand to 800 mesh high-purity quartz sand is 80:20.

[0048] The high-temperature corrosion inhibitor is a mixture of lightly calcined magnesium oxide, heavily calcined magnesium oxide, and dead-calcined magnesium oxide in a mass ratio of 0.8:4:95.2.

[0049] The high-temperature retarder is tartrate, and the suspension stabilizer is microsilica.

[0050] Example 3, as a preferred embodiment of the present invention, discloses a high-temperature cementing cement, the specific composition of which is shown in Table 3.

[0051] Table 3. Composition of High-Temperature Cement in Example 3

[0052] In this embodiment, the high-ferrous phase cement for acidic high-temperature cementing is composed of high-ferrous phase cement clinker and dihydrate gypsum mixed at a mass ratio of 94.5:5.5; the specific surface area of ​​the high-ferrous phase cement for acidic high-temperature cementing is 260 m². 2 / kg.

[0053] In the high-iron phase cement clinker: the ratio of C3S to C2S is 0.96, of which the content of β-C2S is 17.41%, the content of γ-C2S is 11.35%, the content of C4AF is 18.1%, the content of C3A is 0.94%, and the content of f-CaO is 0.82%.

[0054] High-iron phase cement clinker is prepared by calcining a mixture of limestone, sandstone, iron powder, and fly ash, as follows: Limestone, sandstone, iron powder, and fly ash were mixed in a mass ratio of 78.5:8:7.5:6 to obtain a mixed raw meal. The mixed raw meal was ground together to a fineness of 10% residue on a 0.08 mm square hole sieve and 1.5% residue on a 0.2 mm square hole sieve. Water of 10% by mass was added to the ground mixed raw meal, and after being mixed evenly, it was pressed into corrugated test cakes and dried at 105℃ to constant weight. The dried corrugated test cake was heated to 850℃ and held for 20 min; then the temperature was raised to 1380℃ and calcined for 45 min; after calcination, it was first rapidly cooled to 620℃, then slowly cooled to 500℃, and finally rapidly cooled to room temperature to obtain high-iron phase cement clinker.

[0055] The preparation of high-ferrous phase cement for acidic high-temperature cementing is as follows: Jaw crusher is used to crush high-iron phase cement clinker to a maximum particle size of ≤8 mm. Crushed high-ferrous phase cement clinker and dihydrate gypsum were weighed at a mass ratio of 94.5:5.5 and ground together in a ball mill until the final particle size was 260 μm. 2 / kg, thus obtaining acidic high-temperature cement for cementing with high ferrous phase.

[0056] The strength stabilizer is made by mixing construction yellow sand, high-purity quartz sand and porcelain powder in a mass ratio of 35:25:40; wherein the mass ratio of 200 mesh yellow sand to 325 mesh yellow sand is 85:15, and the mass ratio of 200 mesh high-purity quartz sand to 800 mesh high-purity quartz sand is 85:15.

[0057] The high-temperature corrosion inhibitor is a mixture of lightly calcined magnesium oxide, heavily calcined magnesium oxide, and dead-burned magnesium oxide in a mass ratio of 1:5.6:94.4.

[0058] The high-temperature retarder is a mixture of gluconate and sulfonate in a mass ratio of 2:8, and the suspension stabilizer is a mixture of AM-AMPS-NVP polymer and microsilica in a mass ratio of 4:6.

[0059] Example 4, as a preferred embodiment of the present invention, discloses a high-temperature cementing cement, the specific composition of which is shown in Table 4.

[0060] Table 4. Composition of High-Temperature Cement in Example 4

[0061] In this embodiment, the high-ferrous phase cement for acidic high-temperature cementing is composed of high-ferrous phase cement clinker and dihydrate gypsum mixed at a mass ratio of 96:4; the specific surface area of ​​the high-ferrous phase cement for acidic high-temperature cementing is 270 m². 2 / kg.

[0062] In the high-iron phase cement clinker, the ratio of C3S to C2S is 0.88, with β-C2S content of 16.26%, γ-C2S content of 12.35%, C4AF content of 19.14%, C3A content of 1.48%, and f-CaO content of 0.82%.

[0063] High-iron phase cement clinker is prepared by calcining a mixture of limestone, sandstone, iron powder, red mud, and fly ash, as follows: Limestone, sandstone, iron powder, red mud, and fly ash were mixed in a mass ratio of 76.5:8.5:7:3.5:4.5 to obtain a mixed raw meal. The mixed raw meal was ground together to a fineness of 10% residue on a 0.08 mm square hole sieve and 1.5% residue on a 0.2 mm square hole sieve. Water of 10% by mass was added to the ground mixed raw meal, and after being mixed evenly, it was pressed into corrugated test cakes and dried at 105℃ to constant weight. The dried corrugated test cake was heated to 850℃ and held for 20 min; then the temperature was raised to 1370℃ and calcined for 55 min; after calcination, it was first rapidly cooled to 600℃, then slowly cooled to 420℃, and finally rapidly cooled to room temperature to obtain high-iron phase cement clinker.

[0064] The preparation of high-ferrous phase cement for acidic high-temperature cementing is as follows: Jaw crusher is used to crush high-iron phase cement clinker to a maximum particle size of ≤8 mm. Crushed high-ferrous phase cement clinker and dihydrate gypsum were weighed at a mass ratio of 96:4 and ground together in a ball mill until the final particle size was 270 μm. 2 / kg, thus obtaining acidic high-temperature cement for cementing with high ferrous phase.

[0065] The strength stabilizer is made by mixing construction yellow sand, high-purity quartz sand and porcelain powder in a mass ratio of 60:20:20; wherein the mass ratio of 200 mesh yellow sand to 325 mesh yellow sand is 55:45, and the mass ratio of 200 mesh high-purity quartz sand to 800 mesh high-purity quartz sand is 75:25.

[0066] The high-temperature corrosion inhibitor is composed of lightly calcined magnesium oxide, heavily calcined magnesium oxide, and dead-calcined magnesium oxide mixed in a mass ratio of 0.6:9:90.4.

[0067] The high-temperature retarder is gluconate, and the suspension stabilizer is microsilica.

[0068] Example 5, as a preferred embodiment of the present invention, discloses a high-temperature cementing cement, the specific composition of which is shown in Table 5.

[0069] Table 5. Composition of High-Temperature Cement in Example 5

[0070] In this embodiment, the high-ferrous phase cement for acidic high-temperature cementing is composed of high-ferrous phase cement clinker and dihydrate gypsum mixed at a mass ratio of 94:6; the specific surface area of ​​the high-ferrous phase cement for acidic high-temperature cementing is 280 m². 2 / kg.

[0071] In high-iron phase cement clinker, the ratio of C3S to C2S is 1.10, with β-C2S content of 14.32%, γ-C2S content of 10.36%, C4AF content of 18.43%, C3A content of 2.14%, and f-CaO content of 1.33%.

[0072] High-iron phase cement clinker is prepared by calcining a mixture of limestone, sandstone, iron powder, red mud, and fly ash, as follows: Limestone, sandstone, iron powder, red mud, and fly ash were mixed in a mass ratio of 77:12.5:7:0.8:2.7 to obtain a mixed raw meal. The mixed raw meal was ground together to a fineness of 10% residue on a 0.08 mm square hole sieve and 1.5% residue on a 0.2 mm square hole sieve. Water of 10% by mass was added to the ground mixed raw meal, and after being mixed evenly, it was pressed into corrugated test cakes and dried at 105℃ to constant weight. The dried corrugated test cake was heated to 840℃ and held for 20 min; then the temperature was raised to 1390℃ and calcined for 45 min; after calcination, it was first rapidly cooled to 700℃, then slowly cooled to 430℃, and finally rapidly cooled to room temperature to obtain high-iron phase cement clinker.

[0073] The preparation of high-ferrous phase cement for acidic high-temperature cementing is as follows: Jaw crusher is used to crush high-iron phase cement clinker to a maximum particle size of ≤8 mm. Crushed high-ferrous phase cement clinker and dihydrate gypsum were weighed at a mass ratio of 94:6 and ground together in a ball mill until the final particle size was 280 μm. 2 / kg, thus obtaining acidic high-temperature cement for cementing with high ferrous phase.

[0074] The strength stabilizer is made by mixing construction yellow sand, high-purity quartz sand and porcelain powder in a mass ratio of 20:60:20; wherein the mass ratio of 200 mesh yellow sand to 325 mesh yellow sand is 50:50, and the mass ratio of 200 mesh high-purity quartz sand to 800 mesh high-purity quartz sand is 85:15.

[0075] The high-temperature corrosion inhibitor is composed of lightly calcined magnesium oxide, heavily calcined magnesium oxide and dead-burned magnesium oxide in a mass ratio of 0.5:8.3:91.2.

[0076] The high-temperature retarder is a mixture of sulfonate and tartrate in a mass ratio of 3:7, and the suspension stabilizer is microsilica.

[0077] Comparative Example 1: Weigh the materials according to the formula in Table 6.

[0078] In this comparative example, the G-grade cement is commercially available API G-grade oil well cement; the quartz sand is 200 mesh single particle size; the high-temperature retarder is gluconate; the water loss reducer is AMPS-amide-carboxylic acid polymer; the dispersant is formaldehyde-acetone condensate; the suspension stabilizer is AM-AMPS-NVP polymer; and the defoamer is tributyl phosphate.

[0079] Table 6. Cement composition of Comparative Example 1

[0080] Comparative Example 2 (without strength stabilizer): Weigh the materials according to the formula in Table 7.

[0081] The difference between this comparative example and Example 5 is that no strength stabilizer is added, while the other components are the same as in Example 5.

[0082] Table 7. Cement composition of Comparative Example 2

[0083] Comparative Example 3 (without high-temperature corrosion inhibitor): Weigh the materials according to the formula in Table 8.

[0084] The difference between this comparative example and Example 5 is that no high-temperature corrosion inhibitor is added, while the other components are the same as in Example 5.

[0085] Table 8. Cement composition of Comparative Example 3

[0086] The cementitious materials from Examples 1-5 and Comparative Examples 1-3 were used to prepare cement slurry with a water-cement ratio of 0.44. The engineering performance of the above cement slurry system was tested according to GB / T19139, and the test results are shown in Table 9. The prepared cement slurry was then injected into a mold and placed in a high-temperature, high-pressure curing autoclave. It was cured for 3 days at 200℃ and 20.7 MPa. After the cement slurry was fully hydrated and hardened to form cement stone, a portion of the sample was taken out for mechanical property testing (recorded as 3 days before corrosion). The remaining cement stone was transferred to a high-temperature, high-pressure corrosion reactor and cured for 7 days and 28 days at 200℃, CO2 partial pressure of 5 MPa, and N2 partial pressure of 5 MPa, respectively. Mechanical property tests were then performed after curing (recorded as 7 days after corrosion and 28 days after corrosion), and the results are shown in Table 9.

[0087] Table 9 Engineering Properties of Cement Grout

[0088] As shown in Table 9, the API water loss of Examples 1-5 was 37.6-49.2 mL / 30 min, all lower than that of Comparative Example 1 (55.4 mL / 30 min), indicating that the cement slurry system of the present invention has excellent water loss reduction performance. Regarding density difference, the density difference of all examples was ≤0.04 g / cm³. 3 The flowability of the slurry was comparable to that of Comparative Examples 1-3, indicating good slurry stability. Regarding flowability, the flowability of Examples 1-5 was 22.8-23.8 cm, meeting the requirements for on-site construction. As for thickening time, the thickening time of Examples 1-5 was 328-388 min, significantly longer than Comparative Example 1 (189 min), and could be adjusted within a controllable range according to the formula, indicating that the present invention can effectively extend the thickening time and ensure the construction safety of high-temperature deep well cementing.

[0089] Table 10 Mechanical properties of cement stone

[0090] Note: - indicates that no test is required.

[0091] As shown in Table 10, the compressive strength of Examples 1-5 was 41.56-44.32 MPa 3 days before corrosion, increasing to 45.24-47.55 MPa after 7 days of CO2 corrosion, and further increasing to 46.12-48.33 MPa after 28 days of corrosion, with a strength retention rate of 106%-114%, demonstrating continuous strength growth. The tensile strength was 4.00-4.56 MPa, and the elastic modulus was 8.29-9.56 GPa, indicating that the cement stone has good toughness and deformation coordination ability.

[0092] Comparative Example 1 (Grade G cement + quartz sand): The compressive strength was 38.36 MPa 3 days before corrosion, but dropped to 31.23 MPa after 28 days of corrosion, with a strength retention rate of only 81.4%, showing significant strength degradation. Comparative Example 2 (without strength stabilizer): The compressive strength was only 11.20 MPa 3 days before corrosion, failing to form effective strength. Comparative Example 3 (without high-temperature corrosion inhibitor): The compressive strength was 42.84 MPa 3 days before corrosion, but dropped to 41.17 MPa after 28 days of corrosion, with a strength retention rate of 96.1%, lower than Examples 1-5.

[0093] The above results show that Examples 1-5 of the present invention have excellent compressive strength retention, high tensile strength and low elastic modulus under high temperature and acidic environment, and their comprehensive mechanical properties are significantly better than those of the comparative examples.

[0094] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A high-temperature cementing cement for use in CO2-containing environments, characterized in that, Includes the following components by mass: 60-72 parts of high-ferrous phase cement for acidic high-temperature cementing; Strength stabilizer 25-40 parts; 2-5 parts of high-temperature corrosion inhibitor; 3-5 parts of water loss reducer; 2-4 parts of high-temperature retarder; 1-3 parts of suspension stabilizer; Dispersant 0.5-3 parts; Defoamer 0.05~0.2 parts.

2. The high-temperature cementing cement according to claim 1, characterized in that, The high-ferrous phase cement for acidic high-temperature cementing is composed of high-ferrous phase cement clinker and dihydrate gypsum mixed at a mass ratio of (94~96):(4~6); the specific surface area of ​​the high-ferrous phase cement for acidic high-temperature cementing is 260~280 m². 2 / kg.

3. The high-temperature cementing cement according to claim 2, characterized in that, In high-iron phase cement clinker: the ratio of C3S to C2S is 0.82~1.10, and the crystal forms of C2S include β-C2S and γ-C2S; the C4AF content is ≥18%, the C3A content is ≤3%, and the f-CaO content is ≤1.5%.

4. The high-temperature cementing cement according to claim 2, characterized in that, High-iron phase cement clinker is prepared by calcining limestone, sandstone, iron powder, red mud and fly ash in a mass ratio of (76~79):(4~13):(6~9):(0~5):(2~10), as follows: Limestone, sandstone, iron powder, red mud, and fly ash are mixed in a certain mass ratio to obtain a mixed raw meal. The mixed raw meal is ground together to a fineness of ≤10% on a 0.08 mm square hole sieve and ≤1.5% on a 0.2 mm square hole sieve. 10% of the mass of water is added to the ground mixed raw meal, and after being mixed evenly, it is pressed into a corrugated test cake and dried at 105℃ to constant weight. The dried corrugated test cake was heated to 840~860℃ and held for 20 min; then the temperature was raised to 1360~1420℃ and calcined for 40~60 min; after calcination, it was first rapidly cooled to 600~700℃, then slowly cooled to 420~500℃, and finally rapidly cooled to room temperature to obtain high-iron phase cement clinker.

5. The high-temperature cementing cement according to claim 2, characterized in that, The preparation of high-ferrous phase cement for acidic high-temperature cementing is as follows: High-iron phase cement clinker is crushed to a maximum particle size of ≤8 mm; Weigh the crushed high-ferrous phase cement clinker and dihydrate gypsum according to the mass ratio, and grind them together until the final particle size is 260~280 μm. 2 / kg, thus obtaining acidic high-temperature cement for cementing with high ferrous phase.

6. The high-temperature cementing cement according to claim 2, characterized in that, The specific surface area of ​​gypsum dihydrate is 280 m². 2 / kg.

7. The high-temperature cementing cement according to claim 1, characterized in that, The strength stabilizer is made by mixing construction sand, high-purity quartz sand and ceramic powder in a mass ratio of (10~60):(10~60):(10~60); Yellow sand contains >90% SiO2 and >5% Al2O3; high-purity quartz sand contains >99% SiO2; ceramic powder contains >65% SiO2, >20% Al2O3, and has a water absorption rate of <0.5%. The yellow sand is composed of two particle size distributions: 200 mesh and 325 mesh, and the mass ratio of 200 mesh yellow sand to 325 mesh yellow sand is (50~85):(15~50); The high-purity quartz sand is composed of two particle size distributions: 200 mesh and 800 mesh, and the mass ratio of 200 mesh high-purity quartz sand to 800 mesh high-purity quartz sand is (70~85):(15~30). The porcelain powder consists of two particle size distributions: 180 mesh and 260 mesh, with a mass ratio of 7:3 between 180 mesh and 260 mesh porcelain powder.

8. The high-temperature cementing cement according to claim 1, characterized in that, The high-temperature corrosion inhibitor is composed of lightly calcined magnesium oxide, heavily calcined magnesium oxide and dead-burned magnesium oxide in a mass ratio of (0~1):(1~10):(90~100); The light-burned magnesia consists of two particle size distributions: 200 mesh and 400 mesh, with a mass ratio of 200 mesh light-burned magnesia to 400 mesh light-burned magnesia of 7:

3. The recalcined magnesia consists of two particle size distributions: 200 mesh and 325 mesh, with a mass ratio of 200 mesh recalcined magnesia to 325 mesh recalcined magnesia of 5:

5. The particle size of the dead-burned magnesium oxide is 170 mesh.

9. The high-temperature cementing cement according to claim 1, characterized in that, The water loss reducing agent is an AMPS-amide-carboxylic acid polymer; the high-temperature retarder is one or more of gluconate, sulfonate or tartrate; the suspension stabilizer is one or more of AM-AMPS-NVP polymer and microsilica; the dispersant is a formaldehyde-acetone condensate; and the defoamer is tributyl phosphate.

10. A method for preparing cement slurry for high-temperature cementing as described in any one of claims 1 to 9, characterized in that, include: Weigh out the mixing water according to a water-cement ratio of 0.40 to 0.70 and set it aside. The water-cement ratio is the mass ratio of the mixing water to the acidic high-temperature cementing special high-iron phase cement. Weigh each component according to its mass percentage and mix them thoroughly to obtain a mixture; Pour the mixture into the weighed mixing water within 15 seconds and stir at 4000 rpm. After the mixture has been completely poured in, continue stirring at 12000 rpm for 35 seconds to obtain cement slurry.

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