High-temperature and high-strength cement slurry retarder and its preparation method

Abstract

This invention relates to the field of cementing retarder technology, specifically a high-temperature, high-strength cement slurry retarder and its preparation method. The former comprises a pentagonal copolymer retarder, sodium borate, and sodium tripolyphosphate. The pentagonal copolymer retarder is composed of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrene sulfonate, vinylpyrrolidone, and phosphate acrylate, and is obtained by adding the pentagonal copolymer retarder, sodium borate, and sodium tripolyphosphate to water, mixing them thoroughly, and then allowing a chelation reaction to occur. Under high temperature and high pressure conditions, this high-temperature, high-strength cement slurry retarder not only significantly prolongs the thickening time of the cement slurry but also maintains good settling stability, solving the problem of poor high-temperature settling stability caused by existing retarders.

Description

Technical Field

[0001] This invention relates to the field of cementing retarder technology, specifically a high-temperature resistant, high-strength cement slurry retarder and its preparation method. Background Technology

[0002] To ensure safe cementing operations in ultra-deep wells at ultra-high temperatures, sufficient high-temperature retarders need to be added to the cement slurry to adjust the thickening time and meet safety requirements. However, ultra-deep well cementing involves long primary cementing sections, large amounts of retarders, and significant temperature differences between the top and bottom of the cement slurry. This can easily lead to excessive retardation at the top of the cement slurry, posing serious safety risks to subsequent operations.

[0003] Retarder is one of the three main agents in cementing slurry. In cementing long, single-stage cementing sections of ultra-deep wells, a key challenge is addressing the large temperature difference (140°C) across a wide temperature range of 90°C to 230°C. High-temperature retarders from foreign oil companies are expensive and cannot be used alone; they must be used in combination with other additives from the same manufacturer, resulting in high capital requirements and long purchase cycles. Most domestic retarders lack resistance to temperatures up to 200°C, degrading and breaking molecular chains at high temperatures, leading to poor high-temperature stability of the cement slurry, poor compatibility with other cement slurry additives, and difficulty in controlling thickening time, resulting in unsatisfactory cementing quality. Therefore, developing a high-strength retarder for cement slurries with high temperature resistance and large temperature differences in long, single-stage cementing sections has become one of the bottlenecks in the development of cementing slurry technology for ultra-deep wells.

[0004] Currently, most retarders used domestically suffer from insufficient high-temperature resistance, with a temperature tolerance not exceeding 200℃. They exhibit strong dispersion under high-temperature conditions and poor compatibility with other admixtures, posing serious safety risks to cementing operations. For example, lignin sulfonate retarders are only suitable for temperatures up to 130℃. Carboxylic acids and their salts, such as widely used tartaric acid, gluconic acid, and glucohepanoate, are only suitable for temperatures up to 150℃, and tartaric acid is prone to over-retardation when the bottom-hole temperature is below 93℃. Commonly used inorganic retarders, such as boric acid or its salts, affect the effectiveness of polyamine and cellulose fluid loss control agents when used in combination, indicating poor compatibility. Polymer retarders, such as 2-acrylamide-2-methylpropanesulfonic acid (AMPS) copolymer retarders, suffer from problems such as excessive dosage, "core-encapsulation" during thickening experiments, and a narrow applicable temperature range.

[0005] Domestic scholars have made certain achievements in the research of polymer high-temperature retarders. For example, Peng Zhigang, Xu Zunjian, Feng Qian and others developed a polymer oil well cement retarder using phosphorus-containing compounds as the main raw materials and hydroxyethyl acrylate, vinyl sulfonate and phosphate acrylate as polymer monomers in a ratio of 4:2:1. Its temperature resistance is greater than 170℃ but does not exceed 200℃. Qi Zhigang and others synthesized a binary copolymer retarder using itaconic acid (IA) and 2-acrylamide-2-methylpropanesulfonic acid (AMPS) as monomers. The suitable operating temperature range is 120℃ to 180℃. Sun Yongcai, Wang Xuguang and others used AMPS as the main structural unit and copolymerized it with two other ethylene monomers to prepare the high-temperature retarder DHTR400. The maximum temperature resistance is 200℃. Further research is needed on the top strength development of cement slurry with large temperature difference.

[0006] To address the problems and defects of conventional retarders and polymer-based high-temperature retarders in terms of high-temperature retardation capacity, high-temperature stability, compatibility, and strength development at the top of long cementing sections, there is an urgent need to develop new polymer-based high-temperature retarders through the optimization, grafting, and modification of synthetic materials. This would improve the working morphology and adsorption capacity of the retarder's functional groups, optimize the retardation effect under high and low temperature conditions, and solve the problems of weak high-temperature resistance and slow strength development at the return surface of cement slurry in long cementing sections of ultra-deep wells. Summary of the Invention

[0007] This invention provides a high-temperature resistant, high-strength cement slurry retarder and its preparation method, overcoming the shortcomings of the prior art and effectively solving the problem that existing retarders easily cause poor high-temperature settling stability of cement slurry.

[0008] One of the technical solutions of the present invention is achieved through the following measures: a high-temperature and high-strength cement slurry retarder, the raw materials of which include a pentagonal copolymer retarder, sodium borate and sodium tripolyphosphate in a mass ratio of 10:(1 to 2):(0.6 to 1.1), the raw materials of the pentagonal copolymer retarder include, by weight, 25 to 35 parts of 2-acrylamido-2-methylpropanesulfonic acid, 20 to 30 parts of acrylic acid, 20 to 30 parts of sodium styrene sulfonate, 5 to 8 parts of vinylpyrrolidone and 7 to 10 parts of phosphate acrylate.

[0009] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions:

[0010] The above-mentioned high-temperature resistant and high-strength cement slurry retarder is obtained by the following method:

[0011] S1, add the required amounts of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone and phosphate acrylate to deionized water and stir until homogeneous to obtain a mixed solution, then adjust the pH of the mixed solution;

[0012] S2, place the mixed solution in a nitrogen atmosphere to isolate it from oxygen, stir the mixed solution until it is completely dissolved, add the required amount of initiator solution dropwise to the mixed solution and heat it to reflux. After the polymerization reaction occurs, a viscous liquid is obtained.

[0013] S3, the viscous liquid is cooled to room temperature, and then purified, dried and pulverized in sequence to obtain a five-component copolymer retarder;

[0014] S4. Add the required amount of pentyl copolymer retarder, sodium borate and sodium tripolyphosphate to deionized water in sequence and mix well to obtain a mixture. Place the mixture in a nitrogen atmosphere and carry out a chelation reaction to obtain a viscous solution. Purify, dry and pulverize the viscous solution again and dissolve it in deionized water to obtain a high-temperature and high-strength cement slurry retarder.

[0015] In step S1 above, the mass concentration of the solute (2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone and phosphate acrylate) in the mixed solution is 12% to 18%.

[0016] In step S1 above, the pH of the mixed solution is adjusted to 4 to 8 using a sodium hydroxide solution with a mass concentration of 8% to 12%.

[0017] In step S2 above, the initiator solution is prepared by mixing ammonium persulfate and potassium bisulfite in a mass ratio of (1 to 1.5):1, and the mass concentration of solute (ammonium persulfate and potassium bisulfite) in the initiator solution is 3% to 5%.

[0018] In step S2 above, the amount of initiator solution added is 12% to 40% of the weight of the solute (2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone and phosphate acrylate) in the mixed solution.

[0019] In step S2 above, the temperature during stirring is 30°C to 50°C, and the polymerization reaction time is 5h to 8h. In step S4, the temperature during the chelation reaction is 45°C to 70°C, and the time is 4h to 6h.

[0020] In step S3 above, the mass concentration of the solute (pentapolymer retarder, sodium borate and sodium tripolyphosphate) in the high-temperature and high-strength cement slurry retarder is 30% to 45%.

[0021] The second technical solution of the present invention is achieved through the following measures: a method for preparing a high-temperature resistant, high-strength cement slurry retarder, which is carried out according to the following method:

[0022] S1, add the required amounts of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone and phosphate acrylate to deionized water and stir until homogeneous to obtain a mixed solution, then adjust the pH of the mixed solution;

[0023] S2, place the mixed solution in a nitrogen atmosphere to isolate it from oxygen, stir the mixed solution until it is completely dissolved, add the required amount of initiator solution dropwise to the mixed solution and heat it to reflux. After the polymerization reaction occurs, a viscous liquid is obtained.

[0024] S3, the viscous liquid is cooled to room temperature, and then purified, dried and pulverized in sequence to obtain a five-component copolymer retarder;

[0025] S4. Add the required amount of pentyl copolymer retarder, sodium borate and sodium tripolyphosphate to deionized water in sequence and mix well to obtain a mixture. Place the mixture in a nitrogen atmosphere and carry out a chelation reaction to obtain a viscous solution. Purify, dry and pulverize the viscous solution again and dissolve it in deionized water to obtain a high-temperature and high-strength cement slurry retarder.

[0026] The high-temperature and high-strength cement slurry retarder of this invention can not only significantly prolong the thickening time of cement slurry under high temperature and high pressure conditions, but also maintain good settling stability of cement slurry, thus solving the problem that existing retarders easily cause poor high-temperature settling stability of cement slurry. Attached Figure Description

[0027] Figure 1 The graph shows the temperature versus thickening time curves of cement slurry prepared using the high-temperature resistant and high-strength cement slurry retarder prepared in Examples 12 to 14 of this invention as raw material.

[0028] Figure 2 The thickening test curve of the high-temperature resistant and high-strength cement slurry retarder prepared in Example 13 of the present invention at 220°C is shown. Detailed Implementation

[0029] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.

[0030] The present invention will be further described below with reference to embodiments:

[0031] Example 1: The high-temperature and high-strength cement slurry retarder comprises a pentagonal copolymer retarder, sodium borate, and sodium tripolyphosphate in a mass ratio of 10:(1 to 2):(0.6 to 1.1). The pentagonal copolymer retarder comprises, by weight, 25 to 35 parts of 2-acrylamido-2-methylpropanesulfonic acid, 20 to 30 parts of acrylic acid, 20 to 30 parts of sodium styrene sulfonate, 5 to 8 parts of vinylpyrrolidone, and 7 to 10 parts of phosphate acrylate.

[0032] The high-temperature, high-strength cement slurry retarder of this invention not only significantly prolongs the thickening time of cement slurry under high temperature and high pressure conditions, but also maintains good settling stability. This is mainly due to the introduction of the five-membered heterocyclic lactam compound N-vinylpyrrolidone monomer, which can form stable association structures between and within molecules. This gives the high-temperature, high-strength cement slurry retarder of this invention temperature-sensitive properties, enabling it to better adapt to a wider range of cementing requirements. At lower temperatures, the hydration of polar groups in the molecular chain is stronger than the hydrophobic effect, resulting in water solubility of the pentagonal copolymer retarder. As the temperature rises, the hydration weakens, leading to a decrease in viscosity and a suitable initial consistency. At higher temperatures, the degree of hydration of the molecular chain weakens with increasing temperature, and the association of hydrophobic groups in the molecule is significantly enhanced. Furthermore, due to the high SSS content in the pentagonal copolymer retarder molecule, the strong hydrophilicity of the pentagonal copolymer retarder molecular chain is ensured, allowing the hydrophobic associated phase to remain in a microscopic phase-separated state without sedimentation. This results in an increase in the hydrodynamic volume of the pentagonal copolymer retarder molecule and an increase in solution viscosity, exhibiting good thickening properties. Consequently, the high-temperature and high-strength cement slurry retarder prepared using the pentagonal copolymer retarder prepared in this invention exhibits excellent sedimentation stability under high temperature and high pressure.

[0033] In this invention, the molecular weight of the pentacetic copolymer retarder is between 12,000 and 38,000, and it is easily soluble in water.

[0034] Example 2: As an optimization of the above example, the high-temperature resistant and high-strength cement slurry retarder is obtained by the following method:

[0035] S1, add the required amounts of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone and phosphate acrylate to deionized water and stir until homogeneous to obtain a mixed solution, then adjust the pH of the mixed solution;

[0036] S2, place the mixed solution in a nitrogen atmosphere to isolate it from oxygen, stir the mixed solution until it is completely dissolved, add the required amount of initiator solution dropwise to the mixed solution and heat it to reflux. After the polymerization reaction occurs, a viscous liquid is obtained.

[0037] S3, the viscous liquid is cooled to room temperature, and then purified, dried and pulverized in sequence to obtain a five-component copolymer retarder;

[0038] S4. Add the required amount of pentyl copolymer retarder, sodium borate and sodium tripolyphosphate to deionized water in sequence and mix well to obtain a mixture. Place the mixture in a nitrogen atmosphere and carry out a chelation reaction to obtain a viscous solution. Purify, dry and pulverize the viscous solution again and dissolve it in deionized water to obtain a high-temperature and high-strength cement slurry retarder.

[0039] Example 3: As an optimization of the above example, in step S1, the mass concentration of the solute (2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone and phosphate acrylate) in the mixed solution is 12% to 18%.

[0040] Example 4: As an optimization of the above example, in step S1, the pH of the mixed solution is adjusted to 4 to 8 by using a sodium hydroxide solution with a mass concentration of 8% to 12%.

[0041] Example 5: As an optimization of the above example, in step S2, the initiator solution is prepared by mixing ammonium persulfate and potassium bisulfite in a mass ratio of (1 to 1.5):1, and the mass concentration of solute (ammonium persulfate and potassium bisulfite) in the initiator solution is 3% to 5%.

[0042] In this invention, the initiator solution is a mixture of ammonium persulfate and potassium bisulfite, which maintains good initiation effect at relatively low temperatures, with an effective component conversion rate of 50% to 70%, demonstrating high efficiency. During the polymerization reaction, the initiator should be added as evenly and slowly as possible to prevent violent polymerization that could lead to explosive polymerization of the reactants.

[0043] Example 6: As an optimization of the above example, in step S2, the amount of initiator solution added is 12% to 40% of the weight of the solute (2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone and phosphate acrylate) in the mixed solution.

[0044] Example 7: As an optimization of the above example, in step S2, the temperature during stirring is 30°C to 50°C and the polymerization reaction time is 5h to 8h. In step S4, the temperature during chelation reaction is 45°C to 70°C and the time is 4h to 6h.

[0045] Example 8: As an optimization of the above example, in step S3, the mass concentration of solute (pentapolymer retarder, sodium borate and sodium tripolyphosphate) in the high-temperature and high-strength cement slurry retarder is 30% to 45%.

[0046] In this invention, the design concept of the pentaneous copolymer retarder is to appropriately increase the molecular chain length and molecular side chain stiffness to enhance the thermal stability of the main chain, while improving the side chain stiffness and maintaining a relative balance between high-temperature shear dilution and thickening.

[0047] In the five-component copolymer retarder, the main chain is based on 2-acrylamido-2-methylpropanesulfonic acid, a monomer with sulfonic acid functional groups. At the same time, sodium styrene sulfonate monomer, a functional group monomer that enhances the rigidity and steric hindrance of the molecular chain, is introduced into the main chain to enhance the ability to resist high temperature and prevent sedimentation. Acrylic acid monomer with strong adsorption carboxylic acid group is also introduced to enhance the adsorption of cement particles under high temperature conditions and ensure the high temperature retarding effect.

[0048] The main chain is grafted with N-vinylpyrrolidone monomers, a five-membered heterocyclic lactam compound, forming a stable associated structure with temperature-sensitive capabilities. At lower temperatures, the molecular chains aggregate, preventing the retarder molecules from unwinding and significantly weakening their adsorption capacity for cement particles, thus promoting cement particle hydration. At higher temperatures, the molecular side chains unwind, significantly enhancing the adsorption of cement particles and effectively delaying thickening time, thereby reducing the temperature sensitivity of the high-temperature resistant, high-strength cement slurry retarder of this invention.

[0049] Introducing acrylate phosphate monomers at the other end of the main chain enhances the rigidity of both the main chain and side chains, improving the temperature resistance range. The ester groups hydrolyze slowly at high temperatures, participating in chelation to generate new chelate groups, which then perform adsorption on the surface of cement particles, further inhibiting cement hydration. This increases the temperature resistance range of the pentagonal copolymer retarder and reduces temperature sensitivity. Ultimately, this results in a pentagonal copolymer retarder with high-temperature resistance and salt tolerance, making it widely applicable.

[0050] Example 9:

[0051] This high-temperature resistant, high-strength cement slurry retarder comprises a five-component copolymer retarder, sodium borate, and sodium tripolyphosphate in a mass ratio of 10:1:0.7. The five-component copolymer retarder, by weight, includes 25 parts of 2-acrylamido-2-methylpropanesulfonic acid, 20 parts of acrylic acid, 20 parts of sodium styrene sulfonate, 5 parts of vinylpyrrolidone, and 7 parts of phosphate acrylate, and is obtained according to the following method:

[0052] S1, add the required amounts of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone, and phosphate acrylate to deionized water and stir until homogeneous to obtain a mixed solution. Adjust the pH of the mixed solution to 6 using an 8% sodium hydroxide solution. The mass concentration of the solutes (2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone, and phosphate acrylate) in the mixed solution is 12%.

[0053] S2, the mixed solution is placed in a nitrogen atmosphere to isolate it from oxygen, and then stirred at 30°C until completely dissolved. The required amount of initiator solution is then added dropwise to the mixed solution, and the mixture is heated and refluxed. After 5 hours of polymerization, a viscous liquid is obtained. The initiator solution is a mixture of ammonium persulfate and potassium bisulfite in a mass ratio of 1:1. The mass concentration of the solute (ammonium persulfate and potassium bisulfite) in the initiator solution is 3%, and the amount of initiator solution added is 20% of the weight of the solute (2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone, and phosphate acrylate) in the mixed solution.

[0054] S3, the viscous liquid is cooled to room temperature, and then purified, dried and pulverized in sequence to obtain a five-component copolymer retarder;

[0055] S4. Add the required amount of pentyl copolymer retarder, sodium borate and sodium tripolyphosphate to deionized water in sequence and mix well to obtain a mixture. Place the mixture in a nitrogen atmosphere and carry out a chelation reaction at 60°C for 5 hours to obtain a viscous solution. Purify, dry and pulverize the viscous solution again and dissolve it in deionized water to obtain a 40% (w / w) retarder for high-temperature and high-strength cement slurry.

[0056] Example 10:

[0057] This high-temperature resistant, high-strength cement slurry retarder comprises a five-component copolymer retarder (mass ratio 10:2:1.0), sodium borate, and sodium tripolyphosphate. The five-component copolymer retarder, by weight, includes 35 parts 2-acrylamido-2-methylpropanesulfonic acid, 30 parts acrylic acid, 30 parts sodium styrene sulfonate, 8 parts vinylpyrrolidone, and 10 parts phosphate acrylate, and is obtained according to the following method:

[0058] S1, add the required amounts of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone, and phosphate acrylate to deionized water and stir until homogeneous to obtain a mixed solution. Adjust the pH of the mixed solution to 6 using a 12% sodium hydroxide solution. The mass concentration of the solutes (2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone, and phosphate acrylate) in the mixed solution is 18%.

[0059] S2, the mixed solution is placed in a nitrogen atmosphere to isolate it from oxygen, and then stirred at 35°C until completely dissolved. The required amount of initiator solution is then added dropwise to the mixed solution, and the mixture is heated and refluxed. After polymerization for 5 hours, a viscous liquid is obtained. The initiator solution is a mixture of ammonium persulfate and potassium bisulfite in a mass ratio of 1.5:1. The mass concentration of the solute (ammonium persulfate and potassium bisulfite) in the initiator solution is 5%, and the amount of initiator solution added is 24% of the weight of the solute (2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone, and phosphate acrylate) in the mixed solution.

[0060] S3, the viscous liquid is cooled to room temperature, and then purified, dried and pulverized in sequence to obtain a five-component copolymer retarder;

[0061] S4. Add the required amount of pentyl copolymer retarder, sodium borate and sodium tripolyphosphate to deionized water in sequence and mix well to obtain a mixture. Place the mixture in a nitrogen atmosphere and carry out a chelation reaction at 70°C for 4 hours to obtain a viscous solution. Purify, dry and pulverize the viscous solution again and dissolve it in deionized water to obtain a 40% (w / w) retarder for high-temperature and high-strength cement slurry.

[0062] Example 11:

[0063] This high-temperature resistant, high-strength cement slurry retarder comprises a five-component copolymer retarder (mass ratio 10:1.5:0.7), sodium borate, and sodium tripolyphosphate. The five-component copolymer retarder, by weight, includes 30 parts 2-acrylamido-2-methylpropanesulfonic acid, 25 parts acrylic acid, 25 parts sodium styrene sulfonate, 7 parts vinylpyrrolidone, and 8 parts phosphate acrylate, and is obtained according to the following method:

[0064] S1, add the required amounts of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone, and phosphate acrylate to deionized water and stir until homogeneous to obtain a mixed solution. Adjust the pH of the mixed solution to 5.5 using a 10% sodium hydroxide solution. The mass concentration of the solutes (2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone, and phosphate acrylate) in the mixed solution is 16%.

[0065] S2, the mixed solution is placed in a nitrogen atmosphere to isolate it from oxygen, and then stirred at 40°C until completely dissolved. The required amount of initiator solution is then added dropwise to the mixed solution, and the mixture is heated and refluxed. After 7 hours of polymerization, a viscous liquid is obtained. The initiator solution is a mixture of ammonium persulfate and potassium bisulfite in a mass ratio of 1.2:1. The mass concentration of the solute (ammonium persulfate and potassium bisulfite) in the initiator solution is 4%, and the amount of initiator solution added is 20% of the weight of the solute (2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone, and phosphate acrylate) in the mixed solution.

[0066] S3, the viscous liquid is cooled to room temperature, and then purified, dried and pulverized in sequence to obtain a five-component copolymer retarder;

[0067] S4. Add the required amount of pentyl copolymer retarder, sodium borate and sodium tripolyphosphate to deionized water in sequence and mix well to obtain a mixture. Place the mixture in a nitrogen atmosphere and carry out a chelation reaction at 65°C for 4 hours to obtain a viscous solution. Purify, dry and pulverize the viscous solution again and dissolve it in deionized water to obtain a 40% (w / w) retarder for high-temperature and high-strength cement slurry.

[0068] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0069] First, the high-temperature and high-strength cement slurry retarder of this invention breaks through the limitations of traditional polymer retarders in terms of the type and quantity of copolymer monomers. It is obtained by mixing a preferred five-component copolymer retarder with an inorganic high-temperature resistant retarder (inorganic salt sodium borate) at a certain proportion at room temperature and then adding a chelating agent sodium tripolyphosphate for chelation reaction. It combines the advantages of polymer retarders and inorganic salt retarders, avoids the disadvantages of using them alone, and organically combines the advantages of single temperature resistance and wide temperature application range with the promotion of early strength of the high surface with large temperature difference. It not only meets the high temperature resistance technical requirements of ultra-deep well cementing, but also solves the problem of difficulty in exerting early strength of the high surface with large temperature difference.

[0070] Secondly, the molecular design of the high-temperature and high-strength cement slurry retarder of this invention incorporates a five-component copolymer retarder. In the molecular structure design of the five-component copolymer retarder, the main chain is composed of sulfonic acid functional groups (2-acrylamido-2-methylpropanesulfonic acid), which improves the molecular chain stiffness and enhances the stability and salt resistance of the main chain. The introduction of ethylene monomers with carboxylic acid groups (sodium styrene sulfonate) further enhances the adsorption capacity on the cement surface, preventing cement particle hydration and achieving a retarding effect. The introduction of carboxylic acid groups (acrylic acid) also enhances the adsorption capacity on the cement surface, preventing cement particle hydration and achieving a retarding effect. 2+ Chelation, delaying Ca 2+The concentration reaches supersaturation, enhancing the high-temperature resistance and better meeting the high-temperature requirements. The introduction of a five-membered heterocyclic lactam compound (N-vinylpyrrolidone) grafted onto the side chain improves the side chain stiffness and makes the molecular structure more stable, preventing molecular chain breakage at high temperatures and further enhancing the high-temperature resistance of the polymer structure. This invention uses a five-membered copolymer retarder with good retarding effect and strong high-temperature resistance as raw material to prepare a high-performance, high-strength, high-temperature resistant cement slurry retarder, solving the problem of rapid high-temperature hydration of cement slurry.

[0071] Third, the high-temperature and high-strength cement slurry retarder of the present invention adopts a free radical aqueous solution polymerization process, and the initiator is an inorganic peroxide, specifically a mixed solution of ammonium persulfate and potassium bisulfite in a certain proportion, which makes the conversion rate of the synthesized high-temperature and high-strength cement slurry retarder of the present invention high and the operation process simple and easy.

[0072] Fourth, to address the problem of high-temperature dispersibility in existing high-temperature retarders, this invention introduces a five-membered heterocyclic lactam compound (N-vinylpyrrolidone) into the molecular chain. This increases the rigidity of the molecular chain, causing partial self-polymerization and partial formation of a viscous gel-like substance, increasing the consistency of the cement slurry, improving its high-temperature dispersibility, and mitigating the "bulging" and "core-encapsulation" phenomena in cement slurry under high-temperature conditions. Simultaneously, by replacing some monocarboxyl-containing monomers with monocarboxyl-containing monomers and introducing acrylic acid, the high-temperature dispersibility of the high-temperature resistant, high-strength cement slurry retarder of this invention is further reduced, solving the problem of high-temperature cement slurry sedimentation.

[0073] Fifth, the retarder for high-temperature and high-strength cement slurry of this invention has a suitable molecular weight, is easy to dissolve in water, has a good linear relationship, and is not sensitive to dosage or temperature, making it more operable for on-site operations.

[0074] Sixth, the high-temperature and high-strength cement slurry retarder of this invention contains a small amount of inorganic salt retarder, which undergoes a complexation reaction with calcium ions in the cement slurry under medium and low temperature conditions, effectively delaying and inhibiting the hydration process of cement, ensuring a retarding effect at medium and low temperatures. For normal cementing operations, it ensures that there is no temperature inversion phenomenon in the thickening experiment, that is, there will be no phenomenon of long thickening time at high temperature and short thickening time at low temperature, thus providing a guarantee for safe cementing operations.

[0075] Seventh, the five-component polymer retarder obtained by polymerization and purification in this invention is then chelated again with sodium borate and chelating agent sodium tripolyphosphate in an oxygen-free nitrogen atmosphere at 45°C to 70°C, and purified again. This process avoids the misalignment of retarding functional groups, reduces impurities, and increases the effective components of the high-temperature retarder.

[0076] Example 12:

[0077] This high-temperature resistant, high-strength cement slurry retarder is obtained by the following method:

[0078] S1. Add an appropriate amount of deionized water to a four-necked flask reaction apparatus equipped with a reflux condenser, thermometer, and stirrer, and fix it in a constant temperature water bath. Weigh out 25 parts of 2-acrylamido-2-methylpropanesulfonic acid, 20 parts of acrylic acid, 35 parts of sodium styrene sulfonate, 8 parts of N-vinylpyrrolidone, and 12 parts of phosphate acrylate, and place them in the four-necked flask reaction apparatus. Stir evenly to obtain a mixed solution with a total solute mass concentration of 18%. Add an 8% sodium hydroxide solution to adjust the pH of the mixed solution to 5.

[0079] S2, adjust the temperature of the constant temperature water bath to 45℃, introduce inert nitrogen gas into the four-necked flask reaction apparatus to remove oxygen from the apparatus, stir at a low speed of 600 rpm to completely dissolve the mixed solution, then add the initiator solution dropwise to the apparatus and heat to reflux. After reacting at a constant temperature for 6 hours, a viscous liquid is obtained; wherein, the initiator solution is a mixed aqueous solution of ammonium persulfate and potassium bisulfite in a mass ratio of 1.2:1, the mass concentration of solute (ammonium persulfate and potassium bisulfite) in the initiator solution is 3%, and the amount of initiator solution added is 20% of the weight of solute (2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone and phosphate acrylate) in the mixed solution;

[0080] S3, the viscous liquid is cooled to room temperature, purified, dried and pulverized to obtain a five-component copolymer retarder;

[0081] S4. The pentyl copolymer retarder, sodium borate and sodium tripolyphosphate are mixed evenly in a mass ratio of 10:1.5:0.7 and dissolved in deionized water to obtain a high-temperature and high-strength cement slurry retarder with a mass concentration of 40%.

[0082] In Example 12 of this invention, the weight-average molecular weight of the pentagonal copolymer retarder is 28,000. Its molecular structure backbone is composed of three monomers: 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and sodium styrene sulfonate. N-vinylpyrrolidone monomer and acrylate phosphate monomer are grafted onto both ends of the backbone, respectively.

[0083] Example 13:

[0084] The difference from Example 12 of the present invention is that in step S1, the material ratio is changed to "weigh 30 parts of 2-acrylamido-2-methylpropanesulfonic acid, 25 parts of acrylic acid, 30 parts of sodium styrene sulfonate, 10 parts of N-vinylpyrrolidone, and 7 parts of phosphate acrylate", and the remaining steps are the same as in Example 12.

[0085] In Example 13 of this invention, the weight-average molecular weight of the pentagonal copolymer retarder is 36,000. Its molecular structure backbone consists of four monomers: 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, and phosphate acrylate, with N-vinylpyrrolidone monomer grafted onto the acrylic acid side chain.

[0086] Example 14:

[0087] The difference from Example 12 of the present invention is that in step S1, the material ratio is changed to "22 parts 2-acrylamido-2-methylpropanesulfonic acid, 16 parts acrylic acid, 20 parts sodium styrene sulfonate, 19 parts N-vinylpyrrolidone, 23 parts phosphate acrylate", and the remaining steps are the same as in Example 12.

[0088] In Example 14 of this invention, the weight-average molecular weight of the pentagonal copolymer retarder is 15,000. Its molecular structure consists of five monomers: 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, phosphate acrylate, and N-vinylpyrrolidone.

[0089] Example 15: Cement slurries were prepared using the high-temperature resistant and high-strength cement slurry retarder prepared in Examples 12 to 14 of the present invention as one of the raw materials. These cement slurries were denoted as cement slurries A, B, and C, respectively. The thickening time of each cement slurry was tested under the conditions of a temperature of 150°C to 220°C, a pressure of 180 MPa, and a heating time of 110 min.

[0090] Various cement slurry formulations:

[0091] Cement slurry A: 100 parts Shawan G-grade cement + 40 parts quartz sand + 1.5 parts dispersant + 8 parts microsilica + 6 parts water loss reducer + 4 parts high-temperature resistant and high-strength cement slurry retarder obtained in Example 12 of this invention + 52 parts water.

[0092] Cement slurry B: 100 parts Shawan G-grade cement + 40 parts quartz sand + 1.5 parts dispersant + 8 parts microsilica + 6 parts water loss reducer + 6 parts high-temperature resistant and high-strength cement slurry retarder obtained in Example 13 of this invention + 50 parts water.

[0093] Cement slurry C: 100 parts Shawan G-grade cement + 40 parts quartz sand + 1.5 parts dispersant + 8 parts microsilica + 6 parts water loss reducer + 8 parts high-temperature resistant and high-strength cement slurry retarder obtained in Example 14 of this invention + 48 parts water.

[0094] The test results for the thickening time of each cement paste, such as Figure 1 As shown, from Figure 1It can be seen that the higher the temperature, the shorter the thickening time of each cement slurry; the lower the temperature, the longer the thickening time of each cement slurry, meeting the requirement of 220℃ resistance to cyclic temperature. Furthermore, when the temperature difference is 10℃, the thickening time change is less than 40%, indicating that the cement slurry obtained using the high-temperature resistant, high-strength cement slurry retarder of this invention as a raw material does not exhibit temperature sensitivity.

[0095] Example 16: Cement slurry B was prepared using the high-temperature resistant, high-strength cement slurry retarder prepared in Example 13 of this invention as one of the raw materials. The formula is shown in Example 15. Cement slurry B was cured for 24 hours at different bottom-hole static temperatures (pressure 21 MPa, temperature 200℃ to 230℃) to obtain cement stone. The compressive strength of the cement stone was tested. Test conditions: cycle coefficient was 0.9, and the thickening time of cement slurry B was controlled between 320 and 350 min. At the same time, the compressive strength of the cement stone after 48 hours and 72 hours was tested at top temperatures of 90℃, 100℃, and 110℃.

[0096] The test results are shown in Table 1. The cement stone exhibits rapid strength development and high compressive strength under different bottom-hole static temperatures above 200℃. Under conditions with a large temperature difference of over 140℃, the early strength of the cement stone at the return surface is well developed, with a minimum compressive strength of 7.9 MPa at 48h and a compressive strength greater than 14 MPa at 72h, which can well meet the technical requirements of cementing with large temperature differences in a single long cementing section of ultra-deep wells.

[0097] Example 17: Cement slurry B was prepared using the high-temperature and high-strength cement slurry retarder prepared in Example 13 of the present invention as one of the raw materials. The formula is shown in Example 15. Cement slurry B was subjected to a thickening time test under high temperature and high pressure (temperature is 220°C, pressure is 180MPa).

[0098] The test results are as follows Figure 2 As shown, by Figure 2 It can be seen that the high-temperature resistant and high-strength cement slurry retarder of the present invention has strong high-temperature resistance and a flat and stable thickening curve, indicating that the high-temperature resistant and high-strength cement slurry retarder of the present invention does not exhibit high-temperature shear dilution phenomenon under high-temperature conditions, has good high-temperature stability, and does not exhibit "bulging" or "core-encasing" phenomena. The thickening time is 420 min, which meets the technical requirements for cementing of ultra-deep wells.

[0099] In summary, the high-temperature and high-strength cement slurry retarder of the present invention can not only significantly prolong the thickening time of cement slurry under high temperature and high pressure conditions, but also maintain good settling stability of cement slurry, thus solving the problem that existing retarders easily cause poor high-temperature settling stability of cement slurry.

[0100] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

[0101]

Claims

1. A retarder for high-temperature and high-strength cement slurry, characterized in that... The raw materials include a pentagonal copolymer retarder, sodium borate, and sodium tripolyphosphate in a mass ratio of 10:1 to 2:0.6 to 1.

1. The pentagonal copolymer retarder comprises, by weight, 25 to 35 parts of 2-acrylamido-2-methylpropanesulfonic acid, 20 to 30 parts of acrylic acid, 20 to 30 parts of sodium styrene sulfonate, 5 to 8 parts of vinylpyrrolidone, and 7 to 10 parts of phosphate acrylate. The high-temperature resistant, high-strength cement slurry retarder is obtained by the following method: S1, add the required amounts of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone and phosphate acrylate to deionized water and stir until homogeneous to obtain a mixed solution, then adjust the pH of the mixed solution; S2, place the mixed solution in a nitrogen atmosphere to isolate it from oxygen, stir the mixed solution until it is completely dissolved, add the required amount of initiator solution dropwise to the mixed solution and heat it to reflux. After the polymerization reaction occurs, a viscous liquid is obtained. S3, the viscous liquid is cooled to room temperature, and then purified, dried and pulverized in sequence to obtain a five-component copolymer retarder; S4. Add the required amount of pentyl copolymer retarder, sodium borate and sodium tripolyphosphate to deionized water in sequence and mix well to obtain a mixture. Place the mixture in a nitrogen atmosphere and carry out a chelation reaction to obtain a viscous solution. Purify, dry and pulverize the viscous solution again and dissolve it in deionized water to obtain a high-temperature and high-strength cement slurry retarder.

2. The high-temperature resistant, high-strength cement slurry retarder according to claim 1, characterized in that... In step S1, the mass concentration of the solute in the mixed solution is 12% to 18%.

3. The high-temperature resistant, high-strength cement slurry retarder according to claim 1 or 2, characterized in that... In step S1, the pH of the mixed solution is adjusted to 4 to 8 using a sodium hydroxide solution with a mass concentration of 8% to 12%.

4. The high-temperature resistant, high-strength cement slurry retarder according to claim 1 or 2, characterized in that... In step S2, the initiator solution is prepared by mixing ammonium persulfate and potassium bisulfite in a mass ratio of 1 to 1.5:1, and the mass concentration of the solute in the initiator solution is 3% to 5%.

5. The high-temperature resistant, high-strength cement slurry retarder according to claim 1 or 2, characterized in that... In step S2, the amount of initiator solution added is 12% to 40% of the weight of the solute in the mixed solution.

6. The high-temperature resistant, high-strength cement slurry retarder according to claim 1 or 2, characterized in that... In step S2, the temperature during stirring is 30°C to 50°C, and the polymerization reaction time is 5h to 8h. In step S4, the temperature during the chelation reaction is 45°C to 70°C, and the time is 4h to 6h.

7. The high-temperature resistant, high-strength cement slurry retarder according to claim 1 or 2, characterized in that... The mass concentration of solute in the retarder for high-temperature and high-strength cement slurry is 30% to 45%.

8. A method for preparing a high-temperature resistant, high-strength cement slurry retarder according to any one of claims 1 to 7, characterized in that... Perform the following steps: S1, add the required amounts of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, sodium styrene sulfonate, vinylpyrrolidone and phosphate acrylate to deionized water and stir until homogeneous to obtain a mixed solution, then adjust the pH of the mixed solution; S2, place the mixed solution in a nitrogen atmosphere to isolate it from oxygen, stir the mixed solution until it is completely dissolved, add the required amount of initiator solution dropwise to the mixed solution and heat it to reflux. After the polymerization reaction occurs, a viscous liquid is obtained. S3, the viscous liquid is cooled to room temperature, and then purified, dried and pulverized in sequence to obtain a five-component copolymer retarder; S4. Add the required amount of pentyl copolymer retarder, sodium borate and sodium tripolyphosphate to deionized water in sequence and mix well to obtain a mixture. Place the mixture in a nitrogen atmosphere and carry out a chelation reaction to obtain a viscous solution. Purify, dry and pulverize the viscous solution again and dissolve it in deionized water to obtain a high-temperature and high-strength cement slurry retarder.

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