Temperature resistant retarder, preparation method and application thereof

Abstract

The present application relates to the technical field of oil and gas well development, and particularly relates to a temperature-resistant retarder, a preparation method and application thereof. The retarder is prepared by reacting hydroxyethylidene diphosphonic acid with allyl glycidyl ether to obtain a phosphorus-containing monomer; the phosphorus-containing monomer is reacted with a functional monomer and sodium hypophosphite to synthesize the temperature-resistant retarder; the functional monomer is a mixture of maleic anhydride and sodium styrene sulfonate. The temperature-resistant retarder can significantly prolong the thickening time of magnesium oxychloride cement in a high-temperature environment of an oil and gas well, effectively control the setting behavior of the cement slurry, improve the operation window, and ensure the safety of downhole operations. The retarder prepared by the present application has excellent adaptability and application prospect in crack reservoir plugging, and provides strong technical support for efficient and safe application of the magnesium oxychloride cement system in oil and gas well drilling engineering.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas well development, and in particular to a temperature-resistant retarder, a preparation method thereof and an application thereof. Background Art

[0002] Loss during oil and gas well drilling is a major challenge for the oil and gas industry, particularly in fractured formations. Traditional plugging materials often struggle to achieve optimal sealing results and can cause reservoir damage, impacting oil and gas production. Magnesium oxychloride cement, a cementitious material with early strength, high temperature resistance, and excellent acid solubility, demonstrates excellent plugging potential in complex formations, particularly fractured reservoirs. Compared to traditional Portland cement, magnesium oxychloride cement is more suitable for reservoir plugging applications requiring rapid sealing with subsequent smooth unblocking.

[0003] However, as the exploration and development of oil and gas resources gradually move towards deeper layers, the underground operating temperature has increased significantly, placing higher demands on the high-temperature resistance and operability time of plugging materials. The rapid setting characteristics of magnesium oxychloride cement will cause its setting speed to be further accelerated in the high-temperature environment of oil and gas wells, and the thickening time is too short, which seriously affects construction safety and greatly limits its wide application in oil and gas well engineering. Currently, the commonly used retarders on the market are mostly developed for silicate cement and magnesium oxysulfate cement. They are difficult to adapt to the special ionic environment and reaction mechanism of magnesium oxychloride cement, resulting in poor retarding effect and low adaptability, and may even cause problems such as abnormal setting or decreased strength. The research and development of heat-resistant retarders specifically suitable for magnesium oxychloride cement is still in its infancy and cannot meet the actual needs of plugging operations in fractured formations in current oil and gas well engineering.

[0004] CN106565911A discloses a method for preparing a retarding carboxylic acid water-reducing agent for magnesium oxychloride cement. However, this agent is primarily designed for use in normal-temperature building material construction applications and lacks validation for the high-temperature, high-salinity environments of oil and gas wells. Its carboxyl-based polymer structure exhibits poor stability and limited functionality in high-temperature, high-salinity environments, failing to meet the comprehensive requirements for retarding performance, structural stability, and engineering operability in high-temperature, complex downhole environments.

[0005] CN111747670B discloses an enhanced magnesium oxysulfate cement retarder, which includes the following components and their weight parts: 0.1 to 3 parts of gluconic acid, 0.1 to 0.5 parts of sodium gluconate, 0.1 to 0.5 parts of malonic acid, and 0.1 to 0.5 parts of succinic acid. It can be used to improve the performance of magnesium oxysulfate cement, increase the strength of magnesium oxysulfate cement, and extend the setting time of magnesium oxysulfate cement. Although the disclosed retarder is suitable for magnesium oxysulfate cement systems under normal temperature conditions, it has significant deficiencies in temperature adaptability, cement system compatibility, retarding mechanism, and adaptability to oil and gas well field construction, and cannot meet the effective regulation of the hydration behavior of magnesium oxychloride cement in a high-temperature, high-salt environment required by the present invention.

[0006] CN116396049A discloses a high water-resistant magnesium oxychloride cement and its preparation method. Its raw materials are composed of light-burned magnesium oxide, magnesium chloride hexahydrate and retarder. By adjusting the ratio of light-burned magnesium oxide, magnesium chloride hexahydrate and water, only one retarder is used to modify the magnesium oxychloride cement, and the acid radical ions in the retarder are combined with the magnesium chloride to form a hygroscopic cement. 2+ However, this retarder primarily reduces the solubility of the product in water, lacks a comprehensive hydration control mechanism, and lacks validation of its adaptability in high-temperature environments. This makes it difficult to meet the stringent requirements for retarding effect and control of the operating window in plugging operations in high-temperature, fractured reservoirs in oil and gas wells. Summary of the Invention

[0007] To address the above problems, the present invention proposes a temperature-resistant retarder, its preparation method, and application. By constructing a temperature-resistant retarder with synergistic effects of free radical polymerization and polycondensation, the retarder can significantly prolong the thickening time of magnesium oxychloride cement in the high-temperature environment of oil and gas wells, and has stronger engineering adaptability and technological advancement.

[0008] The heat-resistant retarder described in the present invention is prepared by reacting a phosphorus-containing monomer, sodium hypophosphite and a functional monomer; the phosphorus-containing monomer is prepared by reacting hydroxyethylidene diphosphonic acid and allyl glycidyl ether. The functional monomer is a mixture of maleic anhydride and sodium styrene sulfonate. The phosphorus-containing monomer is combined with the functional monomer and synthesized through a "hydrolysis-free radical polymerization-polycondensation synergistic mechanism" under hydrogen peroxide initiation conditions. Specifically, maleic anhydride is hydrolyzed to maleic acid under heating conditions, and the free radicals generated by the triggering can guide it to copolymerize with phosphorus-containing monomers, sodium styrene sulfonate and other functional monomers to form a main chain structure. At the same time, the sodium hypophosphite introduced into the system can undergo a condensation reaction with the maleic acid generated by hydrolysis under the action of hydrogen peroxide, introducing a low-valent phosphorus structure, thereby achieving structural functionalization and improving heat resistance.

[0009] The specific preparation steps of the heat-resistant retarder are:

[0010] (1) Mix hydroxyethylidene diphosphonic acid and deionized water and stir evenly, adjust the pH value of the solution to neutral, and add allyl glycidyl ether and stir evenly to obtain a mixture.

[0011] In this step, hydroxyethylidene diphosphonic acid and deionized water are mixed and stirred to a pH of 7 using a 5mol / L sodium hydroxide solution to avoid the impact of an acidic environment on subsequent reactions. Allyl glycidyl ether is then added and stirred at a speed of 300rpm to 500rpm to form a uniform solution system, providing good basic conditions for subsequent nucleophilic addition reactions. In terms of mass ratio, hydroxyethylidene diphosphonic acid: allyl glycidyl ether=15:8 can both improve the addition reaction conversion rate and reduce side reactions.

[0012] (2) The above mixture was stirred at 80-85°C for 2-2.5 hours, then stirred at 90-95°C for 1-1.5 hours, and cooled to obtain solution I.

[0013] In this step, the mixed solution is first heated to 80-85°C and stirred at this temperature for 2-2.5 hours to allow the addition reaction between hydroxyethylidene diphosphonic acid and allyl glycidyl ether to fully occur. The temperature is then raised to 90-95°C and stirred for 1-1.5 hours to complete the reaction. During the reaction, a cooling reflux device is used to prevent volatilization and loss of the reactants. After the reaction is completed, the solution is allowed to cool naturally to room temperature to obtain Solution I.

[0014] (3) Extract and purify solution I, and dry the extract to constant weight to obtain a phosphorus-containing monomer solid. After pulverization, a phosphorus-containing monomer powder is obtained.

[0015] In this step, an equal volume of diethyl ether is added to the phosphorus-containing monomer solution (I) for extraction. This extraction process is repeated 3-4 times to fully remove unreacted starting materials and other impurities. The organic phase is separated using a separatory funnel, and the remaining material is placed in a vacuum drying oven and dried to constant weight at 50°C to obtain a white phosphorus-containing monomer solid. The solid is ground and passed through a 100-300 mesh sieve to obtain a phosphorus-containing monomer powder.

[0016] (4) Add phosphorus-containing monomer powder, maleic anhydride, sodium hypophosphite and sodium styrene sulfonate to deionized water, stir and dissolve at 60-65°C to obtain solution II.

[0017] In this step, deionized water is added to a container equipped with a heating, stirring, and cooling reflux system. Then, phosphorus-containing monomer powder, maleic anhydride, sodium hypophosphite, and sodium styrene sulfonate are added in that order. The mass ratio of phosphorus-containing monomer: maleic anhydride: sodium hypophosphite: sodium styrene sulfonate is (3-4):3:2:(1-2). The system temperature is controlled at 60-65°C and stirred at 300-500 rpm until all solids are completely dissolved, forming a uniform, transparent solution II. A temperature of 60°C accelerates monomer dissolution and prevents self-polymerization before polymerization.

[0018] (5) Add hydrogen peroxide dropwise to solution II and control the temperature to 110-115°C. Stir and react for 3-3.5 hours. After the reaction is complete, cool naturally to obtain a temperature-resistant retarder.

[0019] In this step, hydrogen peroxide is added in an amount equal to 20%-25% of the total mass of the phosphorus-containing monomer and functional monomer, and is slowly dripped into Solution II at a rate of 0.5-1 drop / second. During the dripping process, the reaction system temperature is gradually raised to 110-115°C and stirred at this temperature for 3-3.5 hours. Hydrogen peroxide acts as an initiator, decomposing at high temperatures to produce free radicals, which trigger free radical polymerization between the monomers, producing the target heat-resistant retarder. After the reaction is completed, the reaction liquid is allowed to cool naturally to room temperature, yielding a yellow, transparent liquid, which is the heat-resistant retarder for magnesium oxychloride cement. Careful control of temperature and dripping during this step is crucial. Below 110°C, the initiator decomposition rate is slow, polymerization is incomplete, the product molecular weight is low, and the retarding effect is poor. Above 115°C, the free radical concentration is too high, which can lead to rapid polymer chain termination and a broadened molecular weight distribution. Furthermore, high temperatures may decompose the sodium styrene sulfonate monomer, affecting heat resistance. Slowly adding hydrogen peroxide can avoid excessive local concentration of hydrogen peroxide and prevent violent polymerization of the reaction (violent heat release leading to system out of control). Keep warm for 3-3.5 hours to ensure sufficient free radical polymerization. If the time is too short, the monomer conversion rate will be insufficient and the content of effective ingredients in the retarder will be low; if the time is too long, the polymer may cross-link or degrade, affecting performance.

[0020] In the present invention, the heat-resistant retarder prepared is copolymerized with functional monomers such as sodium hypophosphite and maleic anhydride, sodium styrene sulfonate to form a multifunctional polymer structure, thereby achieving a retarding effect from the molecular structure and enhancing the heat resistance of the retarder. Among them, the multiple phosphate groups in the phosphorus-containing monomer have good chelating and adsorption capabilities, and can coordinate with the magnesium ions in magnesium oxychloride cement, effectively inhibiting the generation rate of cement hydration products and delaying the thickening time of cement slurry; at the same time, the structure can also maintain strong stability under high temperature conditions to prevent high-temperature decomposition and failure. The carboxyl structure introduced by maleic anhydride during the polymerization process has strong polarity and can associate with the hydroxyl groups on the surface of cement particles through hydrogen bonds, constructing a continuous and dense hydration barrier film on the surface of the particles, slowing down the diffusion rate of water molecules into the interior of the cement particles, thereby reducing the hydration reaction rate of the cement. As a monomer containing sulfonic acid groups, sodium styrene sulfonate provides a strong polar group in the polymer. Its steric hindrance and ionic effects can significantly delay the nucleation and growth process on the surface of cement particles, playing a synergistic retarding role. In addition, sodium hypophosphite introduces phosphate groups into the polymer molecular chain. These groups work synergistically with the phosphate groups of phosphorus-containing monomers to form stable complexes with magnesium ions in cement in a multi-point chelation manner, increasing the number of active sites in the system that can chelate magnesium ions and further enhancing the complexing ability for magnesium ions. The retarder constructed by the synergistic construction of the above multifunctional monomers can more effectively delay the cement hydration reaction, significantly prolong the thickening time of magnesium oxychloride cement, and provide a more sufficient construction operation window for high-temperature operations in oil and gas wells.

[0021] The retarder obtained by the present invention can be applied to a plugging agent for drilling, and can be used in combination with magnesium oxychloride cement to achieve safe and stable plugging.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The heat-resistant retarder described in the present invention can significantly prolong the thickening time of magnesium oxychloride cement under high-temperature conditions in oil and gas wells, effectively regulating the setting behavior of cement slurry, extending the construction operation window, and ensuring downhole operation safety. Furthermore, it has excellent heat resistance and system compatibility, effectively improving the workability and stability of cement slurry and enhancing the sealing effect. It is suitable for plugging leaks in fractured reservoirs of oil and gas wells and has broad application prospects. Furthermore, the preparation method is safe and efficient. Compared to commercially available finished phosphorus-containing monomers, the phosphorus-containing monomers prepared in the present invention are more affordable and the raw materials are readily available. This method has promising prospects for industrial production and promotion, and is expected to effectively solve the problem of well leakage in fractured reservoirs of oil and gas wells and promote the development of oil and gas extraction technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Infrared spectrum analysis of the prepared phosphorus-containing monomer;

[0025] Figure 2 Infrared spectrum analysis of the prepared heat-resistant retarder;

[0026] Figure 3 This is the thickening curve of magnesium oxychloride cement slurry containing temperature-resistant retarder. DETAILED DESCRIPTION

[0027] To make the technical advantages of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0028] Comparative Example 1

[0029] Only citric acid was used as a retarder.

[0030] Comparative Example 2

[0031] Only borax was used as a retarder.

[0032] Comparative Example 3

[0033] Only IA-AMPS polymer was used as retarder.

[0034] Comparative Example 4

[0035] The preparation method of the retarder omitting the phosphorus-containing monomer comprises the following specific steps:

[0036] (1) Add 200g of deionized water to a container equipped with a heating, stirring, and cooling reflux device, followed by 15g of maleic anhydride, 10g of sodium hypophosphite, and 5g of sodium styrene sulfonate. Maintain the system temperature at 60°C and stir at 300 rpm until all solids are completely dissolved, forming a homogeneous, transparent solution.

[0037] (2) Place 7.5 g of hydrogen peroxide in a constant pressure dropping funnel and slowly drip it into the above solution at a rate of 0.5 drops / second. Control the temperature to 115 °C and stir the mixture for 3 h. After the reaction is complete, cool it naturally to obtain retarder R-0.

[0038] Example 1

[0039] The preparation method of the heat-resistant retarder comprises the following specific steps:

[0040] (1) Mix 15 g of hydroxyethylidene diphosphonic acid and 37.9 g of water and stir until uniform. Pour the mixture into a container equipped with a heating and stirring device and a cooling and reflux device. Adjust the pH value of the solution to 7 with 5 mol / L sodium hydroxide solution. Add 8 g of allyl glycidyl ether and stir until uniform.

[0041] (2) The mixture was stirred at 80°C for 2 h and at 95°C for 1 h, and then cooled to obtain solution I.

[0042] (3) Solution I was extracted and purified three times with ether, and the extract was dried at 50°C to a constant weight to obtain a phosphorus-containing monomer solid. After pulverization, the solid was passed through a 100-mesh sieve to obtain a phosphorus-containing monomer powder.

[0043] A portion of the phosphorus-containing monomer powder was scanned by Fourier infrared spectroscopy to obtain Figure 1 The results show that the phosphorus-containing monomer was successfully synthesized. Specifically, from the infrared spectrum of the product, it can be seen that 3330 cm -1 is the stretching vibration of OH; 2386 cm -1 This is the absorption peak of carbon dioxide in the air. It is also possible that there is no absorption peak here, which is caused by adjusting the baseline; 1645 cm -1 is the stretching vibration of C=C; 1565 cm -1 is the bending vibration of OH; 1457, 1416 cm -1 is the in-plane bending vibration of CH; 1200 cm -1 The left and right sides are the stretching vibrations of PO; 1111cm -1 It is the symmetric and asymmetric stretching of CO; 1065 cm -1 is the stretching vibration peak of P=O; 980, 918 cm -1 is the out-of-plane bending of CH; 550 cm -1 is the bending vibration of PO, which shows that the target phosphorus-containing monomer was successfully synthesized.

[0044] (4) Add 200 g of deionized water to a container equipped with a heating, stirring, and cooling reflux system. Then, add 20 g of the prepared phosphorus-containing monomer powder, 15 g of maleic anhydride, 10 g of sodium hypophosphite, and 5 g of sodium styrene sulfonate. Maintain the system temperature at 60°C and stir at 300 rpm until all solids are completely dissolved, forming a homogeneous, transparent solution II.

[0045] (5) Place 12.5 g of hydrogen peroxide in a constant pressure dropping funnel and slowly drip it into solution II at a rate of 0.5 drops / second. Control the temperature to 115°C and stir the mixture for 3 hours. After the reaction is complete, cool naturally to obtain the temperature-resistant retarder R-1.

[0046] A portion of R-1 was scanned by Fourier infrared spectroscopy to obtain Figure 2 The results show that the target polymer was successfully synthesized. Specifically, from the infrared spectrum of the product, it can be seen that 3448.06 cm -1 The -OH stretching vibration is at 2409.41 cm -1 PH stretching vibration at 1713.55 cm -1 It is the characteristic absorption of C=O; 1593.20 cm -1assigned to the benzene ring skeleton (C=C) vibration of sodium styrene sulfonate; 1407.4 cm -1 assigned to the bending vibration of C-H; 1185.05 cm -1 assigned to the sulfonic acid group S=O stretching vibration of sodium styrene sulfonate structure; 1043.54 cm -1 assigned to the P=O bond and possible ether bond (C-O-C) of the phosphorus-containing monomer; 899.61 cm -1 assigned to the phosphoric acid structure (such as P-O-H) in the phosphorus-containing monomer; in addition, 1000 cm -1 the following peaks such as 541.56 cm -1 are the bending vibrations of C-C and C-O bonds in the polymer backbone, and the overall spectral characteristics are consistent with the structural functional group vibration rules of maleic anhydride, sodium styrene sulfonate, phosphorus-containing monomer and sodium hypophosphite, verifying the composition of the polymer product.

[0047] Example 2

[0048] The preparation method of the temperature-resistant retarder is specifically as follows:

[0049] (1) 15 g of hydroxyethylidene diphosphonic acid and 37.9 g of water were uniformly mixed and stirred, and then poured into a container with heating stirring and cooling reflux device, a 5 mol / L sodium hydroxide solution was used to adjust the pH value of the solution to 7, and 8 g of allyl glycidyl ether was uniformly stirred and added.

[0050] (2) The mixture was stirred at 80°C for 2 h and at 95°C for 1 h, and then cooled to obtain solution I.

[0051] (3) Solution I was purified by extraction with ether for 3 times, the extract was dried at 50°C to constant weight to obtain a phosphorus-containing monomer solid, which was crushed and sieved through a 100 mesh sieve to obtain a phosphorus-containing monomer powder.

[0052] (4) 200 g of deionized water was added to a container with heating stirring and cooling reflux device, and then 15 g of the prepared phosphorus-containing monomer powder, 15 g of maleic anhydride, 10 g of sodium hypophosphite and 10 g of sodium styrene sulfonate were sequentially added. The temperature of the system was controlled at 60°C, and the stirring was performed at a speed of 300 rpm until all the solids were completely dissolved to form a uniform transparent solution II.

[0053] (5) 12.5 g of hydrogen peroxide was placed in a constant pressure dropping funnel, and slowly dropped into solution II at a speed of 0.5 drop / s, and the temperature was controlled at 115°C, and the stirring reaction was performed for 3 h. After the reaction was completed, the temperature was naturally cooled to obtain the temperature-resistant retarder R-2.

[0054] Example 3

[0055] The preparation method of the temperature-resistant retarder is specifically as follows:

[0056] (1) Mix 15 g of hydroxyethylidene diphosphonic acid and 37.9 g of water and stir until uniform. Pour the mixture into a container equipped with a heating and stirring device and a cooling and reflux device. Adjust the pH value of the solution to 7 with 5 mol / L sodium hydroxide solution. Add 8 g of allyl glycidyl ether and stir until uniform.

[0057] (2) The mixture was stirred at 80°C for 2 h and at 95°C for 1 h, and then cooled to obtain solution I.

[0058] (3) Solution I was extracted and purified three times with ether, and the extract was dried at 50°C to a constant weight to obtain a phosphorus-containing monomer solid. After pulverization, the solid was passed through a 100-mesh sieve to obtain a phosphorus-containing monomer powder.

[0059] (4) Add 200 g of deionized water to a container equipped with a heating, stirring, and cooling reflux system. Then, add 20 g of the prepared phosphorus-containing monomer powder, 15 g of maleic anhydride, 10 g of sodium hypophosphite, and 5 g of sodium styrene sulfonate. Maintain the system temperature at 60°C and stir at 300 rpm until all solids are completely dissolved, forming a homogeneous, transparent solution II.

[0060] (5) Place 10 g of hydrogen peroxide in a constant pressure dropping funnel and slowly drip it into solution II at a rate of 0.5 drops / second. Control the temperature to 115 °C and stir the mixture for 3 h. After the reaction is complete, cool naturally to obtain the temperature-resistant retarder R-3.

[0061] Example 4

[0062] The preparation method of the heat-resistant retarder comprises the following specific steps:

[0063] (1) Mix 15 g of hydroxyethylidene diphosphonic acid and 37.9 g of water and stir until uniform. Pour the mixture into a container equipped with a heating and stirring device and a cooling and reflux device. Adjust the pH value of the solution to 7 with 5 mol / L sodium hydroxide solution. Add 8 g of allyl glycidyl ether and stir until uniform.

[0064] (2) The mixture was stirred at 80°C for 2 h and at 95°C for 1 h, and then cooled to obtain solution I.

[0065] (3) Solution I was extracted and purified three times with ether, and the extract was dried at 50°C to a constant weight to obtain a phosphorus-containing monomer solid. After pulverization, the solid was passed through a 100-mesh sieve to obtain a phosphorus-containing monomer powder.

[0066] (4) Add 200 g of deionized water to a container equipped with a heating, stirring, and cooling reflux system. Then, add 20 g of the prepared phosphorus-containing monomer powder, 15 g of maleic anhydride, 10 g of sodium hypophosphite, and 5 g of sodium styrene sulfonate. Maintain the system temperature at 60°C and stir at 300 rpm until all solids are completely dissolved, forming a homogeneous, transparent solution II.

[0067] (5) Place 12.5 g of hydrogen peroxide in a constant pressure dropping funnel and slowly drip it into solution II at a rate of 0.5 drops / second. Control the temperature to 110°C and stir the mixture for 3 hours. After the reaction is complete, cool naturally to obtain the temperature-resistant retarder R-4.

[0068] Example 5

[0069] The preparation method of the heat-resistant retarder comprises the following specific steps:

[0070] (1) Mix 15 g of hydroxyethylidene diphosphonic acid and 37.9 g of water and stir until uniform. Pour the mixture into a container equipped with a heating and stirring device and a cooling and reflux device. Adjust the pH value of the solution to 7 with 5 mol / L sodium hydroxide solution. Add 8 g of allyl glycidyl ether and stir until uniform.

[0071] (2) The mixture was stirred at 85°C for 2.5 h and at 90°C for 1.5 h, and then cooled to obtain solution I.

[0072] (3) Solution I was extracted and purified three times with ether, and the extract was dried at 50°C to a constant weight to obtain a phosphorus-containing monomer solid. After pulverization, the solid was passed through a 300-mesh sieve to obtain a phosphorus-containing monomer powder.

[0073] (4) Add 200 g of deionized water to a container equipped with a heating, stirring, and cooling reflux system. Then, add 15 g of the prepared phosphorus-containing monomer powder, 15 g of maleic anhydride, 10 g of sodium hypophosphite, and 5 g of sodium styrene sulfonate. Maintain the system temperature at 65°C and stir at 500 rpm until all solids are completely dissolved, forming a homogeneous, transparent solution II.

[0074] (5) Place 9 g of hydrogen peroxide in a constant pressure dropping funnel and slowly drip it into solution II at a rate of 1 drop / second. Control the temperature to 115 °C and stir the mixture for 3.5 h. After the reaction is complete, cool naturally to obtain the temperature-resistant retarder R-5.

[0075] Example 6

[0076] The preparation method of the heat-resistant retarder comprises the following specific steps:

[0077] (1) Mix 15 g of hydroxyethylidene diphosphonic acid and 37.9 g of water and stir until uniform. Pour the mixture into a container equipped with a heating and stirring device and a cooling and reflux device. Adjust the pH value of the solution to 7 with 5 mol / L sodium hydroxide solution. Add 8 g of allyl glycidyl ether and stir until uniform.

[0078] (2) The mixture was stirred at 80°C for 2.5 h and at 90°C for 1 h, and then cooled to obtain solution I.

[0079] (3) Solution I was extracted and purified three times with ether, and the extract was dried at 50°C to a constant weight to obtain a phosphorus-containing monomer solid. After pulverization, the solid was passed through a 200-mesh sieve to obtain a phosphorus-containing monomer powder.

[0080] (4) Add 200 g of deionized water to a container equipped with a heating, stirring, and cooling reflux system. Then, add 20 g of the prepared phosphorus-containing monomer powder, 15 g of maleic anhydride, 10 g of sodium hypophosphite, and 10 g of sodium styrene sulfonate. Maintain the system temperature at 60°C and stir at 400 rpm until all solids are completely dissolved, forming a homogeneous, transparent solution II.

[0081] (5) Place 13.7 g of hydrogen peroxide in a constant pressure dropping funnel and slowly drip it into solution II at a rate of 1 drop / second. Control the temperature to 110°C and stir the mixture for 3.5 hours. After the reaction is complete, cool naturally to obtain the temperature-resistant retarder R-6.

[0082] Test Example 1

[0083] The application effects of the retarder provided in Comparative Examples 1-4 and the temperature-resistant retarder prepared in Examples 1-6 in magnesium oxychloride cement were tested using Test Example 1. The specific operation is as follows:

[0084] Cement-based slurries were prepared according to the preparation method of oil well cement slurries as described in GB / T 19139-2012: 335 parts of light-burned magnesia, 243 parts of magnesium chloride hexahydrate, 173 parts of water, and 6.5 parts of a thixotropic agent. 13.4 parts of the retarder provided in Comparative Example 1 were added to the cement-based slurry to prepare cement slurry C1; 16.75 parts of the retarder provided in Comparative Example 2 were added to the cement-based slurry to prepare cement slurry C2; 5 parts of the retarder provided in Comparative Example 3 were added to the cement-based slurry to prepare cement slurry C3; and 10 parts of the heat-resistant retarders prepared in Comparative Example 4 and Examples 1-6 were added to the cement-based slurries to prepare cement slurries C4-C10.

[0085] The thickening time of cement slurry was tested to characterize the effect of the retarder. The cement-based slurry and cement slurries C1-C10 were tested using a thickener at 90°C. The measurement results are shown in Table 1.

[0086] Table 1 Thickening time of magnesium oxychloride cement slurry containing retarder at 90℃

[0087] .

[0088] As can be seen from the data in Table 1, although the retarder provided in Comparative Examples 1-3 can extend the thickening time of magnesium oxychloride cement slurry to a certain extent, the increase is extremely limited. It only extends the thickening time of the cement slurry from 10 minutes of the base slurry to 18-22 minutes. Compared with the safe construction time required for actual pumping operation, such an increase is far from enough. This fully demonstrates that traditional retarders are difficult to effectively inhibit the hydration reaction rate in the magnesium oxychloride cement system, and the retarding effect is very small, which cannot meet the strict requirements of engineering construction for the control of setting time. The retarder provided in Comparative Example 4 has a retarding effect slightly higher than that of Comparative Examples 1-3, but it is still far below the requirements for the thickening time of cement slurry in actual engineering. This is because the lack of chelating effect of phosphorus-containing monomers means that the magnesium ions in the hydration process of magnesium oxychloride cement cannot be effectively complexed, and the hydration reaction still proceeds at a relatively fast speed, resulting in a shorter thickening time of the cement slurry. It can be seen that phosphorus-containing monomers are the core components that give heat-resistant retarders high-efficiency retarding properties. Their absence will lead to a significant degradation of the retarder's performance in the high-temperature environment of oil and gas wells, making it difficult to meet application requirements in complex engineering scenarios.

[0089] The heat-resistant retarder prepared by the embodiment of the present invention shows significant advantages. When the addition amount is 10 parts, the thickening time of cement slurry C5-C10 is greatly extended to 212-250min, which is more than 20 times higher than that of the base slurry, and can meet the pumping time requirements in complex construction environments. At the same time, the initial consistency of the cement slurry is stably maintained at 16-17Bc, which meets the requirements of construction operations for fluidity and avoids construction obstructions due to excessive viscosity. It can be seen that the heat-resistant retarder can not only efficiently regulate the hydration process of magnesium oxychloride cement and achieve a long-term retarding effect, but also ensure the construction performance of the slurry, and has technical advantages and practical value in the application of magnesium oxychloride cement engineering.

[0090] Test Example 2

[0091] The thickening time of the heat-resistant retarder prepared in Example 1 under high temperature and high pressure was tested using Test Example 2. The specific operation is as follows:

[0092] According to the preparation method of oil well cement slurry in GB / T 19139-2012, a cement base slurry was prepared: 335 parts of light-burned magnesia, 243 parts of magnesium chloride hexahydrate, 173 parts of water, and 6.5 parts of a thixotropic agent. 16.75 parts of the heat-resistant retarder prepared in Example 1 were added to the cement base slurry to prepare cement slurry C9. The thickening time of cement slurry C9 was tested at 120°C and 30 MPa using a pressurized thickener. The test results are as follows: Figure 3 shown.

[0093] Depend on Figure 3Under these conditions, the cement slurry thickened in 127 minutes. While this is significantly shorter than the 250 minutes achieved at 90°C, it still offers a relatively long operating time, essentially meeting the requirements for construction in complex formations such as deep and high-temperature wells. This result demonstrates that the heat-resistant retarder prepared by this invention not only performs well under moderate temperatures but also maintains a good retarding effect under high-temperature and high-pressure conditions, demonstrating strong thermal stability and system adaptability.

[0094] In summary, the retarder prepared by the method for preparing a heat-resistant magnesium oxychloride cement retarder provided in the embodiments of the present invention exhibits excellent retarding effect and environmental adaptability. This technical solution not only achieves long-term regulation of the thickening time of magnesium oxychloride cement slurry exceeding 4 hours at 90°C, but also maintains stable retarding performance in a high-temperature environment of 120°C. This effectively resolves the technical contradiction between "high-temperature accelerated hydration" and "pumping requirements" in leak plugging operations in fractured formations in oil and gas wells, fully demonstrating the innovative breakthrough and industrial application potential of this invention in the field of magnesium oxychloride cement retarder technology.

Claims

1. A method for preparing a heat-resistant retarder, characterized in that: Hydroxyethylidene diphosphonic acid is reacted with allyl glycidyl ether to prepare a phosphorus-containing monomer; the phosphorus-containing monomer is reacted with a functional monomer and sodium hypophosphite to synthesize a heat-resistant retarder; the functional monomer is a mixture of maleic anhydride and sodium styrene sulfonate; The specific preparation steps are: (1) Mix hydroxyethylidene diphosphonic acid and deionized water and stir them evenly, adjust the pH value of the solution to neutral, and add allyl glycidyl ether and stir them evenly to obtain a mixture; (2) Stirring the above mixture at 80-85°C for 2-2.5 hours, then at 90-95°C for 1-1.5 hours, and cooling to obtain solution I; (3) extracting and purifying solution I, drying the extract to a constant weight, and pulverizing the extract to obtain phosphorus-containing monomer powder; (4) Add phosphorus-containing monomer powder, maleic anhydride, sodium hypophosphite, and sodium styrene sulfonate to deionized water, and stir and dissolve at 60-65°C to obtain solution II; (5) Add hydrogen peroxide dropwise to solution II and control the temperature to 110-115°C. Stir and react for 3-3.5 hours. After the reaction is complete, cool naturally to obtain a temperature-resistant retarder. In step (1), the mass ratio of hydroxyethylidene diphosphonic acid to allyl glycidyl ether is 15:8; In step (4), the mass ratio of phosphorus-containing monomer: maleic anhydride: sodium hypophosphite: sodium styrene sulfonate is (3-4):3:2:(1-2).

2. The method for preparing a heat-resistant retarder according to claim 1, wherein In step (1), the pH value is adjusted using a sodium hydroxide solution with a concentration of 5 mol / L.

3. The method for preparing a heat-resistant retarder according to claim 1, wherein In step (3), ether extraction and purification are performed; the drying temperature of the extract does not exceed 50°C.

4. The method for preparing a heat-resistant retarder according to claim 1, wherein In step (5), the amount of hydrogen peroxide added is 20%-25% of the total mass of the phosphorus-containing monomer, sodium hypophosphite and functional monomer.

5. The method for preparing a heat-resistant retarder according to claim 1, wherein: The stirring speed is in the range of 300 rpm ~ 500 rpm.

6. Heat-resistant retarder, characterized in that: The method is prepared according to any one of claims 1 to 5.

7. Use of the heat-resistant retarder according to claim 6 in drilling plugging, characterized in that: It is mixed with magnesium oxychloride cement slurry and applied to fractured reservoirs.

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