High-temperature-resistant oil well cement retarder and preparation method thereof

Abstract

The invention provides a high-temperature-resistant oil well cement retarder and a preparation method thereof, and relates to the technical field of cement retarder materials. The high-temperature-resistant oil well cement retarder is prepared from the following materials in parts by weight: 30 to 40 parts of sulfo-siloxane grafted lignosulfonate, 5 to 10 parts of self-repairing microcapsules, 5 to 8 parts of zinc oxide, 2 to 3 parts of hexagonal boron nitride nanosheets, 1 to 2 parts of pH buffering agent, 2 to 4 parts of polycarboxylic acid water reducing agent and 8 to 12 parts of deionized water. According to the high-temperature-resistant oil well cement retarder disclosed by the invention, the temperature resistance of the high-temperature-resistant oil well cement retarder is improved; the phenomena of bulging, core wrapping and the like in a high-temperature experiment are avoided; the dispersion uniformity of the high-temperature-resistant oil well cement retarder on cement particles is improved, and local premature solidification or excessive retarding in cement paste is prevented; the problem that the strength is reduced due to the fact that retarder components are adsorbed on the surfaces of cement particles to hinder formation and growth of hydration products is solved.

Description

Technical Field

[0001] The invention relates to the technical field of cement retarder materials, and in particular to a high-temperature resistant oil well cement retarder and a preparation method thereof. Background Art

[0002] Cement slurry retarders play a crucial role in oil drilling, completion, and cementing operations. Retarders extend the cement hydration induction period and improve the rheological properties of the cement slurry under high-temperature cementing conditions, enabling the cement slurry to meet downhole pumping time requirements, thereby ensuring the safety and quality of cementing operations. With the continuous increase in drilling depths, the demand for cementing deep and ultra-deep wells is becoming increasingly urgent, placing higher demands on the high-temperature resistance of retarders.

[0003] High-temperature oil well cement retarders are chemical additives that maintain effective retarding properties even in high-temperature environments. They slow the hydration reaction of cement under high-temperature conditions, preventing premature setting of the cement slurry and ensuring good fluidity and stability during pumping. Furthermore, high-temperature retarders must maintain this retarding effect without compromising the subsequent strength development of the cement paste.

[0004] Although a variety of high-temperature-resistant oil well cement retarders are available on the market, their heat resistance still has certain limitations. For example, some traditional organic retarders, such as lignin sulfonates and their derivatives, and hydroxycarboxylic acids (salts), while effective at retarding setting, significantly weaken at high temperatures (e.g., above 150°C), making them unable to meet the requirements of ultra-high-temperature cementing operations. Furthermore, during high-temperature experiments, existing high-temperature-resistant oil well cement retarders are prone to bulging and core encapsulation. This is primarily due to the uneven dispersion of cement particles by the retarder at high temperatures, resulting in localized premature setting or excessive retarding within the cement slurry. While some high-temperature-resistant oil well cement retarders delay the cement hydration reaction, they also adversely affect the subsequent strength development of the cement paste. This is primarily due to certain components in the retarder adsorbing on the surface of cement particles, hindering the formation and growth of cement hydration products and reducing the strength of the cement paste. Based on this, the present invention provides a high-temperature-resistant oil well cement retarder and a method for its preparation. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-temperature resistant oil well cement retarder and a preparation method thereof, thereby improving the temperature resistance of the high-temperature resistant oil well cement retarder; avoiding phenomena such as bulging and core encapsulation in high-temperature experiments; improving the uniformity of the dispersion of the high-temperature resistant oil well cement retarder on cement particles, preventing local premature solidification or excessive retarding in the cement slurry; and avoiding the problem of strength reduction caused by the adsorption of retarder components on the surface of cement particles, which hinders the formation and growth of hydration products.

[0006] On the one hand, the present invention provides a high-temperature resistant oil well cement retarder, comprising the following materials in parts by weight: 30-40 parts of sulfonic acid-siloxane grafted lignin sulfonate, 5-10 parts of self-repairing microcapsules, 5-8 parts of zinc oxide, 2-3 parts of hexagonal boron nitride nanosheets, 1-2 parts of pH buffer, 2-4 parts of polycarboxylate water reducer and 8-12 parts of deionized water.

[0007] Furthermore, the preparation method of the sulfonic acid-siloxane grafted lignin sulfonate includes: mixing sodium lignin sulfonate with 2-acrylamido-2-methylpropanesulfonic acid, hexamethyldisiloxane and ethanol, adding an initiator azobisisobutyronitrile, reacting in a microwave reactor at a power of 700-800W and a temperature of 70-80°C for 4-5 hours, and washing the reaction product with ethanol and vacuum drying to obtain the product.

[0008] Furthermore, the weight ratio of the sodium lignin sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, hexamethyldisiloxane, ethanol, and azobisisobutyronitrile is 1: (0.4-0.6): (0.2-0.4): (3-4): (0.003-0.005).

[0009] Furthermore, the preparation method of the self-healing microcapsules includes: mixing sodium silicate and potassium dihydrogen phosphate, adding deionized water and stirring until completely dissolved to obtain a core material solution; dissolving polyethylene glycol and Span-80 in deionized water, heating to 55-65°C to form a homogeneous solution; slowly dripping the core material solution into the homogeneous solution while stirring at 4600-5000 rpm to form a water-in-water emulsion, adding glutaraldehyde to the emulsion, cross-linking and curing at 35-45°C for 2-3 hours, centrifuging, washing, and drying to obtain the microcapsules.

[0010] Furthermore, the core material solution is prepared at a stirring speed of 250-350 rpm, a stirring time of 30-40 min, and a water bath temperature of 45-55° C.; wherein the amount ratio of sodium silicate, potassium dihydrogen phosphate, and deionized water is (5-6) g: (3-4) g: (24-30) mL.

[0011] Furthermore, the dosage ratio of polyethylene glycol, Span-80 and deionized water in the homogeneous solution is (6-8) g: (1-2) g: (60-80) mL.

[0012] Furthermore, the weight ratio of the sodium silicate, polyethylene glycol, Span-80 and glutaraldehyde is (25-30): (30-40): (5-10): (2-5).

[0013] Furthermore, the pH buffer is a Tris-HCl buffer solution.

[0014] On the other hand, the present invention also provides a method for preparing a high-temperature resistant oil well cement retarder, which comprises the following steps: adding sulfonic acid-siloxane grafted lignin sulfonate to deionized water and stirring at 45-55°C and 250-350 rpm for 30-40 minutes; sequentially adding hexagonal boron nitride nanosheets, zinc oxide, self-healing microcapsules, and a pH buffer, mixing using a high-speed shear emulsifier, adding a polycarboxylate water reducer and mixing, spray drying, controlling the moisture content of the powder to be less than 1%, and passing through a 200-mesh sieve to obtain the retarder.

[0015] Furthermore, the rotation speed of the high-speed shear emulsification is 10000-12000 rpm, and the time is 30-40 min; the inlet temperature of the spray drying is 170-180°C, and the outlet temperature is 70-80°C.

[0016] The beneficial effects of the present invention are: This invention restructures the molecular structure by introducing sulfonic acid and siloxane groups onto the lignin sulfonate backbone, creating a synergistic system of steric hindrance and electrostatic repulsion, significantly improving high-temperature adsorption stability. The grafted sulfonic acid groups in the sulfonic acid-siloxane graft copolymer form a double-layer structure on the cement particle surface through electrostatic repulsion, while the hydrophobic segments of the siloxane groups (-Si-O-Si-) maintain conformational stability even at high temperatures. The synergistic effect of the charge repulsion of the sulfonic acid groups and the steric hindrance of the siloxane segments effectively reduce the tendency of cement particles to flocculate and promote uniform dispersion of the cement slurry system.

[0017] This invention utilizes a water-in-water (W / W) emulsion template method to construct pH / temperature-responsive microcapsules, enabling precise controlled release of silicate repair fluid and self-repair of microcracks. The core material solution (sodium silicate / potassium dihydrogen phosphate) forms an oil-droplet-like dispersed phase under the action of a Span-80 emulsifier. Polyethylene glycol (PEG), a temperature-sensitive shell material, forms a three-dimensional network structure under glutaraldehyde crosslinking. When microcracks appear within the cement, the core material released upon rupture of the microcapsules reacts with cement hydration products to form a dense repair layer, suppressing thermal expansion cracking of the cement paste at high temperatures. The chemical bonding between the repair layer and the cement matrix avoids the strength loss associated with overadsorption of traditional retarders.

[0018] In the preparation of microcapsules, PEG is used as a wall material component, inhibiting microcapsule aggregation through steric hindrance. In a cement slurry system, the hydroxyl groups of PEG form hydrogen bonds with the surface of cement particles, reducing interparticle friction and improving flow properties. The lubricating effect of PEG promotes uniform adsorption of the grafted product on the cement particle surface, further enhancing dispersibility. The emulsifying function of PEG ensures stable dispersion of the microcapsules, preventing uneven repair capacity caused by localized aggregation.

[0019] The hexagonal boron nitride (h-BN) nanosheets in this invention possess excellent thermal conductivity, rapidly conducting heat within the cement paste and reducing localized high-temperature stress. Their layered structure creates a "nano-ballooning" effect within the cement paste, reducing inter-particle friction. The h-BN thermal network effectively suppresses the volume expansion of the cement paste at high temperatures, preventing bulging. The lubricating effect of h-BN synergizes with PEG to significantly reduce the yield stress of the cement paste, improving workability.

[0020] This invention utilizes the synergistic effects of sulfonic acid-siloxane grafted lignin sulfonate, self-healing microcapsules, h-BN nanosheets, and a pH buffer to create a four-in-one "adsorption-controlled release-repair-buffering" system, achieving both enhanced high-temperature resistance and durability. The sulfonic acid-siloxane grafted lignin sulfonate forms a protective layer on the surface of cement particles through electrostatic adsorption, while the h-BN nanosheets embed themselves in the hydration products to form a "nano-fence" structure. These two synergistic effects reduce the porosity of the cement paste, improving its compressive strength and high-temperature resistance. DETAILED DESCRIPTION

[0021] The following is a clear and complete description of the technical solution of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0022] It should be noted that the polyethylene glycol in the present invention is polyethylene glycol-6000, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; hexagonal boron nitride nanosheets are purchased from Shanghai MCC New Materials Co., Ltd.; Tris-HCl buffer solution, item number: T2194, is purchased from Merck; polycarboxylate water reducer, purchased from Shanghai Kaiyin Chemical, brand RHEOPLUS412; polyvinyl alcohol, CAS number: 9002-89-5, product number: 363065, is purchased from Merck; the remaining raw materials are commercially available.

[0023] Example 1 This embodiment provides a high-temperature resistant oil well cement retarder, comprising the following materials in parts by weight: 35 parts of sulfonic acid-siloxane grafted lignin sulfonate, 7 parts of self-healing microcapsules, 6 parts of zinc oxide, 2.5 parts of hexagonal boron nitride nanosheets, 1.5 parts of pH buffer, 3 parts of polycarboxylate water reducer and 10 parts of deionized water.

[0024] The preparation method of the sulfonic acid-siloxane grafted lignin sulfonate comprises: mixing sodium lignin sulfonate with 2-acrylamido-2-methylpropanesulfonic acid, hexamethyldisiloxane and ethanol, adding an initiator azobisisobutyronitrile, reacting for 4.5 hours in a microwave reactor at a power of 750W and a temperature of 75°C, washing the reaction product with ethanol and vacuum drying at 60°C to obtain the product; the weight ratio of sodium lignin sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, hexamethyldisiloxane, ethanol and azobisisobutyronitrile is 1:0.5:0.3:3.5:0.004.

[0025] The preparation method of the self-healing microcapsules includes: stirring 27g of sodium silicate and 17g of potassium dihydrogen phosphate at 50°C and 300rpm for 35min, adding 135mL of deionized water and stirring until completely dissolved to obtain a core material solution; dissolving 35g of polyethylene glycol and 7g of Span-80 in 350mL of deionized water, heating to 60°C to form a homogeneous solution; slowly dripping the core material solution into the homogeneous solution under stirring at 4800rpm to form a water-in-water emulsion, adding 3.5g of glutaraldehyde to the emulsion, cross-linking and curing at 40°C for 2.5h, centrifuging, washing with deionized water, and drying at 60°C for 24h to obtain the product.

[0026] The preparation method of this high-temperature resistant oil well cement retarder comprises the following steps: adding sulfonic acid-siloxane grafted lignin sulfonate to deionized water and stirring at 50°C and 300 rpm for 35 minutes; sequentially adding hexagonal boron nitride nanosheets, zinc oxide, self-healing microcapsules, and Tris-HCl buffer solution; mixing for 35 minutes using a high-speed shear emulsifier at a speed of 11,000 rpm; adding a polycarboxylate water reducer and further mixing; and spray drying. The spray drying inlet temperature is 175°C, the outlet temperature is 75°C, and the moisture content of the powder is controlled to be 0.8wt%. The powder is then passed through a 200-mesh sieve to obtain the obtained product.

[0027] Example 2 This embodiment provides a high-temperature resistant oil well cement retarder, comprising the following materials in parts by weight: 30 parts of sulfonic acid-siloxane grafted lignin sulfonate, 5 parts of self-healing microcapsules, 5 parts of zinc oxide, 2 parts of hexagonal boron nitride nanosheets, 1 part of pH buffer, 2 parts of polycarboxylate water reducer and 8 parts of deionized water.

[0028] The preparation method of the sulfonic acid-siloxane grafted lignin sulfonate includes: mixing sodium lignin sulfonate with 2-acrylamido-2-methylpropanesulfonic acid, hexamethyldisiloxane and ethanol, adding an initiator azobisisobutyronitrile, reacting in a microwave reactor at a power of 700 W and a temperature of 70° C. for 4 hours, washing the reaction product with ethanol, and vacuum drying at 60° C. to obtain the obtained product; the weight ratio of sodium lignin sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, hexamethyldisiloxane, ethanol, and azobisisobutyronitrile is 1:0.4:0.2:3:0.003.

[0029] The preparation method of the self-healing microcapsules includes: stirring 25g of sodium silicate and 15g of potassium dihydrogen phosphate at 45°C and 250rpm for 30min, adding 120mL of deionized water and stirring until completely dissolved to obtain a core material solution; dissolving 30g of polyethylene glycol and 5g of Span-80 in 300mL of deionized water, heating to 55°C to form a homogeneous solution; slowly dripping the core material solution into the homogeneous solution under stirring at 4600rpm to form a water-in-water emulsion, adding 2g of glutaraldehyde to the emulsion, cross-linking and curing at 35°C for 2h, centrifuging, washing with deionized water, and drying at 60°C for 24h to obtain the product.

[0030] The preparation method of this high-temperature resistant oil well cement retarder comprises the following steps: adding sulfonic acid-siloxane grafted lignin sulfonate to deionized water and stirring at 45°C and 250 rpm for 30 minutes; sequentially adding hexagonal boron nitride nanosheets, zinc oxide, self-healing microcapsules, and Tris-HCl buffer solution; mixing for 30 minutes using a high-speed shear emulsifier at a speed of 10,000 rpm; adding a polycarboxylate water reducer and further mixing; and spray drying. The spray drying inlet temperature is 170°C, the outlet temperature is 70°C, and the moisture content of the powder is controlled to be 0.8wt%. The powder is then passed through a 200-mesh sieve to obtain the retarder.

[0031] Example 3 This embodiment provides a high-temperature resistant oil well cement retarder, comprising the following materials in parts by weight: 40 parts of sulfonic acid-siloxane grafted lignin sulfonate, 10 parts of self-healing microcapsules, 8 parts of zinc oxide, 3 parts of hexagonal boron nitride nanosheets, 2 parts of pH buffer, 4 parts of polycarboxylate water reducer and 12 parts of deionized water.

[0032] The preparation method of the sulfonic acid-siloxane grafted lignin sulfonate comprises: mixing sodium lignin sulfonate with 2-acrylamido-2-methylpropanesulfonic acid, hexamethyldisiloxane and ethanol, adding an initiator azobisisobutyronitrile, reacting for 5 hours in a microwave reactor at a power of 800 W and a temperature of 80° C., washing the reaction product with ethanol and vacuum drying at 60° C. to obtain the product; the weight ratio of sodium lignin sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, hexamethyldisiloxane, ethanol and azobisisobutyronitrile is 1:0.6:0.4:4:0.005.

[0033] The preparation method of the self-healing microcapsules includes: stirring 30g of sodium silicate and 20g of potassium dihydrogen phosphate at 55°C and 350rpm for 40min, adding 150mL of deionized water and stirring until completely dissolved to obtain a core material solution; dissolving 40g of polyethylene glycol and 10g of Span-80 in 400mL of deionized water, heating to 65°C to form a homogeneous solution; slowly dripping the core material solution into the homogeneous solution under stirring at 5000rpm to form a water-in-water emulsion, adding 5g of glutaraldehyde to the emulsion, cross-linking and curing at 45°C for 3h, centrifuging, washing with deionized water, and drying at 60°C for 24h to obtain the product.

[0034] The preparation method of this high-temperature resistant oil well cement retarder comprises the following steps: adding sulfonic acid-siloxane grafted lignin sulfonate to deionized water and stirring at 55°C and 350 rpm for 40 minutes; sequentially adding hexagonal boron nitride nanosheets, zinc oxide, self-healing microcapsules, and Tris-HCl buffer solution; mixing for 40 minutes using a high-speed shear emulsifier at a speed of 12,000 rpm; adding a polycarboxylate water reducer and further mixing; and spray drying. The spray drying inlet temperature is 180°C, the outlet temperature is 80°C, and the moisture content of the powder is controlled to be 0.8wt%. The powder is then passed through a 200-mesh sieve to obtain the obtained product.

[0035] Example 4 This embodiment provides a high-temperature resistant oil well cement retarder, comprising the following materials in parts by weight: 30 parts of sulfonic acid-siloxane grafted lignin sulfonate, 10 parts of self-healing microcapsules, 5 parts of zinc oxide, 3 parts of hexagonal boron nitride nanosheets, 1 part of pH buffer, 4 parts of polycarboxylate water reducer and 8 parts of deionized water.

[0036] The preparation method of the sulfonic acid-siloxane grafted lignin sulfonate comprises: mixing sodium lignin sulfonate with 2-acrylamido-2-methylpropanesulfonic acid, hexamethyldisiloxane and ethanol, adding an initiator azobisisobutyronitrile, reacting for 5 hours in a microwave reactor at a power of 800 W and a temperature of 70° C., washing the reaction product with ethanol and vacuum drying at 60° C. to obtain the product; the weight ratio of sodium lignin sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, hexamethyldisiloxane, ethanol and azobisisobutyronitrile is 1:0.4:0.4:3:0.003.

[0037] The preparation method of the self-healing microcapsules includes: stirring 25g of sodium silicate and 20g of potassium dihydrogen phosphate at 45°C and 350rpm for 30min, adding 150mL of deionized water and stirring until completely dissolved to obtain a core material solution; dissolving 30g of polyethylene glycol and 10g of Span-80 in 300mL of deionized water, heating to 65°C to form a homogeneous solution; slowly dripping the core material solution into the homogeneous solution under stirring at 4600rpm to form a water-in-water emulsion, adding 5g of glutaraldehyde to the emulsion, cross-linking and curing at 35°C for 3h, centrifuging, washing with deionized water, and drying at 60°C for 24h to obtain the product.

[0038] The preparation method of this high-temperature resistant oil well cement retarder comprises the following steps: adding sulfonic acid-siloxane grafted lignin sulfonate to deionized water and stirring at 45°C and 350 rpm for 30 minutes; sequentially adding hexagonal boron nitride nanosheets, zinc oxide, self-healing microcapsules, and Tris-HCl buffer solution; mixing for 30 minutes using a high-speed shear emulsifier at a speed of 12,000 rpm; adding a polycarboxylate water reducer and further mixing; and spray drying. The spray drying inlet temperature is 180°C, the outlet temperature is 70°C, and the moisture content of the powder is controlled to be 0.8wt%. The powder is then passed through a 200-mesh sieve to obtain the obtained product.

[0039] Comparative Example 1 In Comparative Example 1, lignin sulfonate was used to replace the sulfonic acid-siloxane grafted lignin sulfonate of Example 1. The rest of the steps were the same as those of Example 1.

[0040] Comparative Example 2 In Comparative Example 2, no sulfonic acid-siloxane grafted lignin sulfonate was added, and the rest was the same as in Example 1, and the preparation steps were the same as in Example 1.

[0041] Comparative Example 3 In Comparative Example 3, polyethylene glycol was replaced by polyvinyl alcohol, and the rest was the same as in Example 1, and the preparation steps were the same as in Example 1.

[0042] Comparative Example 4 In Comparative Example 4, no self-repairing microcapsules were added, and the rest was the same as in Example 1, and the preparation steps were the same as in Example 1.

[0043] Comparative Example 5 In Comparative Example 5, the hexagonal boron nitride nanosheets are replaced with graphene, and the rest are the same as in Example 1, and the preparation steps are the same as in Example 1.

[0044] Comparative Example 6 In Comparative Example 6, citric acid-triethanolamine was replaced with phosphate buffered saline solution, product number P4474, purchased from Merck, and the rest was the same as in Example 1, and the preparation steps were the same as in Example 1.

[0045] Test Example: The following tests were performed on the retarders prepared in Examples 1-4 and Comparative Examples 1-8: The thickening time and compressive strength at 200°C were measured with reference to SY / T 5504.1-2013 “Evaluation methods for oil well cement admixtures Part 1: Retarder”; High temperature resistance: Test the retarder's retarding effect at 180°C. If the thickening curve is normal and no abnormal phenomena such as bulging and core formation occur, increase the test temperature to 190°C and continue testing until the retarder fails. Record the temperature before the retarder fails as the highest temperature, and test the compressive strength of the cement at this temperature. The results are shown in Table 1 below.

[0046] Table 1: Performance Test Thickening time (min) Compressive strength (MPa) Maximum temperature resistance (℃) Compressive strength at the highest temperature (MPa) Example 1 365 35.7 280 33.4 Example 2 358 35.2 280 32.8 Example 3 351 34.8 280 32.2 Example 4 344 34.5 270 31.8 Comparative Example 1 278 28.6 230 24.1 Comparative Example 2 154 22.4 180 18.7 Comparative Example 3 305 30.2 250 26.5 Comparative Example 4 318 27.9 260 23.8 Comparative Example 5 291 29.1 240 25.3 Comparative Example 6 332 31.5 250 28.6 Combined with the above content, it can be seen that the thickening time of Comparative Example 1 is reduced by 24%, and the temperature resistance is reduced by 50°C, which proves that the sulfonic acid-siloxane grafting significantly enhances the high-temperature adsorption stability of lignin sulfonate, and its steric hindrance effect delays the cement hydration reaction. Comparative Example 3 shows that the temperature-sensitive properties of polyethylene glycol are crucial for the controlled release of microcapsules, while the rigid shell material of polyvinyl alcohol causes the release rate of the repair fluid to be too fast. The high-temperature compressive strength of Comparative Example 4 decreased by 29%, and obvious cracks appeared after hot rolling at 180°C, indicating that the silicate repair fluid of the microcapsule fills the microcracks through capillary action, thereby improving long-term durability. The temperature resistance of Comparative Example 5 is reduced by 40°C, and the layered structure of hexagonal boron nitride nanosheets can selectively adsorb Ca 2+ , inhibiting the abnormal growth of ettringite crystals, while graphene is prone to agglomeration due to π-π stacking.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A high temperature resistant oil well cement retarder, characterized in that: The invention comprises the following materials in parts by weight: 30-40 parts of sulfonic acid group-siloxane grafted lignin sulfonate, 5-10 parts of self-repairing microcapsules, 5-8 parts of zinc oxide, 2-3 parts of hexagonal boron nitride nanosheets, 1-2 parts of pH buffer, 2-4 parts of polycarboxylate water reducer and 8-12 parts of deionized water.

2. The high temperature resistant oil well cement retarder according to claim 1, characterized in that: The preparation method of the sulfonic acid-siloxane grafted lignin sulfonate comprises: mixing sodium lignin sulfonate with 2-acrylamido-2-methylpropanesulfonic acid, hexamethyldisiloxane and ethanol, adding an initiator azobisisobutyronitrile, reacting in a microwave reactor at a power of 700-800W and a temperature of 70-80°C for 4-5 hours, and washing the reaction product with ethanol and vacuum drying to obtain the product.

3. A high temperature resistant oil well cement retarder according to claim 2, characterized in that: The weight ratio of the sodium lignin sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, hexamethyldisiloxane, ethanol and azobisisobutyronitrile is 1: (0.4-0.6): (0.2-0.4): (3-4): (0.003-0.005).

4. The high temperature resistant oil well cement retarder according to claim 1, characterized in that: The preparation method of the self-healing microcapsules includes: mixing sodium silicate and potassium dihydrogen phosphate, adding deionized water and stirring until completely dissolved to obtain a core material solution; dissolving polyethylene glycol and Span-80 in deionized water, heating to 55-65°C to form a homogeneous solution; slowly dripping the core material solution into the homogeneous solution while stirring at 4600-5000 rpm to form a water-in-water emulsion; adding glutaraldehyde to the emulsion, cross-linking and curing at 35-45°C for 2-3 hours, centrifuging, washing, and drying to obtain the self-healing microcapsules.

5. A high temperature resistant oil well cement retarder according to claim 4, characterized in that: The core material solution is prepared by stirring at a speed of 250-350 rpm, for a time of 30-40 minutes, and in a water bath at a temperature of 45-55° C.; wherein the amount ratio of sodium silicate, potassium dihydrogen phosphate, and deionized water is (5-6) g: (3-4) g: (24-30) mL.

6. The high temperature resistant oil well cement retarder according to claim 4, characterized in that: The dosage ratio of polyethylene glycol, Span-80 and deionized water in the homogeneous solution is (6-8) g: (1-2) g: (60-80) mL.

7. The high temperature resistant oil well cement retarder according to claim 4, characterized in that: The weight ratio of the sodium silicate, polyethylene glycol, Span-80 and glutaraldehyde is (25-30): (30-40): (5-10): (2-5).

8. The high temperature resistant oil well cement retarder according to claim 1, characterized in that: The pH buffer is a Tris-HCl buffer solution.

9. A method for preparing a high temperature resistant oil well cement retarder according to any one of claims 1 to 8, characterized in that the steps include: The sulfonic acid-siloxane grafted lignin sulfonate is added to deionized water and stirred at 45-55° C. and 250-350 rpm for 30-40 minutes; hexagonal boron nitride nanosheets, zinc oxide, self-healing microcapsules, and pH buffer are added in sequence, mixed using a high-speed shear emulsifier, and a polycarboxylate water reducer is added and mixed, followed by spray drying to control the moisture content of the powder to be less than 1%; and the powder is passed through a 200-mesh sieve to obtain the product.

10. The method for preparing a high temperature resistant oil well cement retarder according to claim 9, characterized in that: The rotation speed of the high-speed shear emulsification is 10000-12000 rpm, and the time is 30-40 min; the inlet temperature of the spray drying is 170-180°C, and the outlet temperature is 70-80°C.