Preparation method and application of a high-temperature-resistant spherical gel plugging agent for oil-based drilling fluids

Abstract

The present application discloses a preparation method and application of a high-temperature-resistant spherical gel plugging agent for oil-based drilling fluids, belonging to the field of drilling fluid treatment agents. The preparation method of the high-temperature-resistant spherical gel plugging agent is as follows: Dissolve emulsifier A and emulsifier B in an oily solvent to obtain an oil phase; Mix and dissolve sodium hydroxide, a water-soluble organic monomer, a high-temperature-resistant monomer, and a crosslinking agent in water to obtain an aqueous phase; Divide the aqueous phase into two parts, and add the larger part of the aqueous phase to the oil phase, and perform shear emulsification to obtain an emulsification reaction mixture; Add a redox system initiator to the emulsification reaction mixture, and carry out heat preservation polymerization; Add the remaining smaller part of the aqueous phase to the emulsion after heat preservation polymerization, and continue heat preservation polymerization to obtain a high-temperature-resistant spherical gel plugging agent with a micron-sized particle size. The high-temperature-resistant spherical gel plugging agent prepared by the present invention has excellent high-temperature resistance and can overcome the problem of poor high-temperature resistance of existing oil-based drilling fluid plugging agents when the formation temperature encountered during drilling is higher than 150 °C.

Description

Technical Field

[0001] The present application belongs to the technical field of drilling fluid treatment agents in petroleum drilling engineering, and relates to a preparation method and application of a high-temperature resistant spherical gel plugging agent for oil-based drilling fluid. Background Art

[0002] With the deepening of oil and gas exploration and development, oil-based drilling fluids are widely used due to their good inhibition, lubricity and many other advantages when drilling in water-sensitive complex formations, shale gas reservoirs, carbonate reservoirs and other formations. However, when drilling in formations with developed bedding and fractures, the consumption of oil-based drilling fluids is large, and well leakage occurs from time to time, causing serious losses. Especially in the application of oil-based drilling fluids in high-temperature formations such as Shunbei, Xinjiang and deep shale gas formations in the southwest, due to the high formation temperature (>150℃), high temperature resistance requirements are required for plugging materials. However, the commonly used plugging materials are often not compatible with oil-based drilling fluids, which affects the rheology and stability of the drilling fluids, and the high temperature resistance is insufficient. They are easily degraded or fail under high temperature conditions, and it is difficult to meet the plugging requirements of high-temperature oil-based drilling fluids.

[0003] In order to improve the plugging performance of plugging materials in oil-based drilling fluids, many scholars have developed some plugging agents for oil-based drilling fluids. For example, patent document CN 111499792 A discloses an amphiphilic nanometer plugging agent for oil-based drilling fluids and its preparation method. The plugging agent has an amphiphilic effect, can reduce downhole friction, increase its shear force, and can withstand temperatures up to 150°C.

[0004] The existing oil-based drilling fluid is equipped with a dedicated high-efficiency drilling plugging agent, which is one of the important technical means to reduce the loss of oil-based drilling fluid. However, the thermal stability of the material itself deteriorates above 150°C, and the effect is reduced. When the formation temperature encountered is higher than 150°C, such as the application temperature of oil-based drilling fluid in Shunbei 5-7 well and Shunbei 4 well in Shunbei work area in Xinjiang, the leakage problem is serious, with an average leakage of 24 to 36m 3 / d; The temperature of the lower combined strata on the southern edge of the Junggar Basin in Xinjiang reaches 170°C, and the plugging performance cannot meet the plugging requirements of oil-based drilling fluids, which can lead to serious leakage of high-temperature oil-based drilling fluids and restrict the smooth progress of drilling projects. Summary of the invention

[0005] In view of this, the problem to be solved by the present invention is to provide a preparation method and application of a high-temperature resistant spherical gel plugging agent for oil-based drilling fluid. The high-temperature resistant spherical gel plugging agent prepared by the present invention has excellent temperature resistance and can overcome the problem of poor temperature resistance of existing oil-based drilling fluid plugging agents when the formation temperature encountered during drilling is higher than 150°C.

[0006] The present invention provides a method for preparing a high temperature resistant spherical gel plugging agent for oil-based drilling fluid, comprising the following steps:

[0007] S1. Dissolve emulsifier A and emulsifier B in an oily solvent to obtain an oil phase; emulsifier A is selected from sorbitan fatty acid esters; emulsifier B is selected from polyoxyethylene ethers;

[0008] Mix and dissolve sodium hydroxide, a water-soluble organic monomer, a temperature-resistant monomer, and a crosslinking agent in water to obtain an aqueous phase; the water-soluble organic monomer is one or more of acrylic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid; the temperature-resistant monomer is one or more of N,N-dimethylacrylamide, N-vinylpyrrolidone, and 2-methyl-2-propenenitrile; the crosslinking agent is one or more of N,N-methylenebisacrylamide, ethylene glycol diacrylate, and 1,3-butanediol diacrylate;

[0009] S2. Divide the aqueous phase into two parts, add the larger part of the aqueous phase to the oil phase, and perform shear emulsification to obtain an emulsification reaction mixture; add a redox system initiator to the emulsification reaction mixture and carry out heat preservation polymerization;

[0010] S3. Add the remaining smaller part of the aqueous phase to the emulsion after heat preservation polymerization, and continue heat preservation polymerization to obtain a micron-sized high-temperature-resistant spherical gel plugging agent.

[0011] When the formation temperature encountered during drilling is higher than 150 °C, the existing oil-based drilling fluid plugging agent has poor temperature resistance, resulting in serious leakage of high-temperature oil-based drilling fluid. Based on this, the main purpose of the present invention is to provide a preparation method of a high-temperature-resistant spherical gel plugging agent for oil-based drilling fluid.

[0012] The specific embodiments of the present invention are achieved through the following technical solutions:

[0013] The first step: Add emulsifier A to an oily solvent such as white oil, heat up to 50 - 60 °C to completely dissolve it, and then add emulsifier B and stir until dissolved to obtain an oil phase.

[0014] The second step: Dissolve sodium hydroxide in a certain amount of water to prepare an aqueous sodium hydroxide solution, cool it to room temperature, and slowly add the water-soluble organic monomer, the temperature-resistant monomer, and the water-soluble crosslinking agent under stirring, and stir until completely dissolved and uniform to obtain an aqueous phase.

[0015] The third step: Divide the obtained aqueous phase into two parts, add one part (60% - 80%) to the obtained oil phase, emulsify with a shear emulsifier for 7 - 15 min to obtain an emulsification reaction mixture; preferably, nitrogen is introduced into the emulsification reaction mixture for 10 - 30 min, keep the temperature constant at 35 - 50 °C, add the oxidant and reductant of the initiation system, stir for 3 - 6 min, and carry out heat preservation polymerization at 60 - 70 °C for 0.5 - 1 h;

[0016] Step 4: Add the remaining other aqueous phase (20% - 40%) into the emulsion after heat preservation polymerization, preferably stir for 3 - 6 min, and carry out heat preservation polymerization at 60 - 70 °C for 2 - 4 h to obtain the high-temperature-resistant spherical gel plugging agent for oil-based drilling fluids.

[0017] In the present invention, the above-mentioned emulsifier A is selected from sorbitan fatty acid esters, preferably one of sorbitan fatty acid esters and sorbitan monostearate.

[0018] The above-mentioned emulsifier B is selected from polyoxyethylene ethers, preferably one or more of polyoxyethylene sorbitan ether stearate, polyoxyethylene sorbitan monooleate, and polyoxyethylene octylphenol ether-10, more preferably polyoxyethylene octylphenol ether-10. The mass ratio of emulsifier A to emulsifier B can be (1.0 - 3.0):(0.5 - 1.0), preferably (1.5 - 3.0):(0.5 - 1.0), and preferably stir and dissolve in white oil to prepare the oil phase.

[0019] The present invention mainly formulates the aqueous phase with water-soluble organic monomers, heat-resistant monomers, and cross-linking agents; wherein the water-soluble organic monomers are two or three mixtures of acrylic acid (AA), acrylamide (AM), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

[0020] Moreover, the heat-resistant monomers in the present invention are one or more of N,N-dimethylacrylamide (DMAA), N-vinylpyrrolidone (NVP, molecular formula is C6H9NO), and 2-methyl-2-propenenitrile.

[0021] The present invention also uses a water-soluble cross-linking agent, specifically one or more of N,N-methylenebisacrylamide, ethylene glycol diacrylate, and 1,3-butanediol diacrylate. Preferably, a water-soluble cross-linking agent is used, more preferably N,N-methylenebisacrylamide, which is beneficial to improving the heat resistance of the product, etc. The addition amount of the cross-linking agent can be 0.1% - 0.6% of the total mass of the monomers, and more preferably the addition amount of the cross-linking agent is 0.1% - 0.3% of the total mass of the monomers. The pH value of the aqueous phase can be adjusted to 8 - 10 with sodium hydroxide in the present invention.

[0022] After obtaining the oil phase and the aqueous phase respectively, in the examples of the present invention, the aqueous phase is first divided into two parts, and the larger part of the aqueous phase is added to the oil phase, and shear emulsification is carried out to obtain an emulsification reaction mixture (forming a uniformly dispersed suspension system); specifically, the mass ratio of the larger part of the aqueous phase is 60% - 80%, and the other aqueous phase is 20% - 40%.

[0023] Preferably, after the obtained emulsion reaction mixture is deoxygenated by passing nitrogen, a redox initiator system is added for heat preservation polymerization. The redox initiator system is a redox initiation system, which consists of an oxidant and a reductant. The oxidant is preferably ammonium persulfate or potassium persulfate, and the reductant is preferably sodium bisulfite, ferrous sulfate, sodium sulfite or sodium metabisulfite; the addition amount of the initiator ranges from 0.4% to 1.0% of the total mass of the monomers. The temperature of the heat preservation polymerization is preferably 60-70 °C; the time is 0.5-1 h.

[0024] After that, in the embodiment of the present invention, the remaining less aqueous phase is added to the emulsion after heat preservation polymerization, stirred evenly, and heat preservation polymerization is continued to obtain the spherical gel plugging agent product. The temperature of the heat preservation polymerization is preferably 60-70 °C; the time is 2-4 h.

[0025] In the embodiment of the present invention, the structural general formula of the high-temperature resistant spherical gel plugging agent for oil-based drilling fluid can be:

[0026]

[0027] Among them, R1 represents one or several mixtures of -COONa and -CONH2, R2 represents one or several mixtures of -CONHC(2CH3)CH2SO3Na, C6H8ON, -C5H9ON, and -CH2CHCH3CN, and R3 represents -CONHCH2NHCO-, -CONCH3CH2-, -CONCH2CH2CH2CH2-; the molar ratio of each structural unit m:n:p:o:q=(0.001-0.01):(0-0.2):(0-0.1):(0-0.1):(0-0.1).

[0028] The present invention also provides the application of the high-temperature resistant spherical gel plugging agent obtained by the preparation method as described above in the preparation of oil-based drilling fluid. The present invention has no special restrictions on the oil-based mud used, and conventional compositions can be used. Specifically, the addition amount of the high-temperature resistant spherical gel plugging agent can be 1%-5%. In the embodiment of the present invention, the prepared oil-based drilling fluid is used for high-temperature formations above 150 °C.

[0029] In the embodiment of the present invention, a spherical gel plugging agent with nano-micron particle size is prepared by the method of inverse emulsion seed polymerization. This spherical gel has an interpenetrating network structure, which improves the temperature resistance of the structure; at the same time, specific temperature-resistant monomers are introduced to improve the temperature resistance of the gel. The temperature resistance of this plugging agent can reach 180 °C.

[0030] In the embodiment of the present invention, this plugging agent is a water-in-oil gel, which has good compatibility with oil-based drilling fluid and does not change the rheological properties of oil-based drilling fluid; D 50The particle size distribution is 0.5 - 10 μm, which can participate in the formation of mud cake, improve the quality of mud cake, and reduce the high-temperature high-pressure filtration loss. This material mainly solves the problems of easily caving and leaking formations in the drilling of deep wells and ultra-deep wells, and high-temperature bedding fracture-developed formations with relatively high bottom-hole temperatures (>150°C). It can effectively reduce the loss of oil-based drilling fluid, prevent well leakage, improve the wellbore stability ability, reduce downhole complications of oil-based drilling fluid, and reduce the comprehensive cost of drilling fluid. This material does not need to be dried and granulated and can be directly used for the plugging of oil-based drilling fluid, which is convenient to use and easy to promote. Detailed implementation manners

[0031] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0032] To further understand the present application, the preparation method and application of a high-temperature-resistant spherical gel plugging agent for oil-based drilling fluid provided by the present application will be specifically described below in conjunction with embodiments.

[0033] Example 1:

[0034] Add 8 g of AMPS (2-acrylamide-2-methylpropanesulfonic acid) to 50 g of water, adjust the pH value to 8 - 10 with sodium hydroxide, then add 12.5 g of AM, 1 g of DMAA, and 0.0645 g of N,N'-methylenebisacrylamide. After fully dissolving, form a uniform aqueous solution. Add 5.25 g of sorbitan fatty acid ester and 1.75 g of polyoxyethylene octylphenol ether-10 to 70 g of white oil. After complete dissolution, continuously stir and emulsify in an emulsifier. Add 80% of the above aqueous solution to the obtained oil phase and emulsify for 10 min to form a uniformly dispersed suspension system. Pass nitrogen into the emulsification reaction mixture for 20 min, heat in a 45°C water bath, and add a 5 mL aqueous solution containing 0.15 g of ammonium persulfate and a 5 mL aqueous solution containing 0.15 g of sodium bisulfite under stirring. After reacting at 60°C for 0.7 h, add the remaining aqueous solution to the reacted emulsion, stir evenly, and keep warm at 60°C for 4 h to obtain the high-temperature-resistant spherical gel plugging agent for oil-based drilling fluid;

[0035] Its main structural formula is:

[0036]

[0037] Example 2:

[0038] Add 5 g of AMPS to 50 g of water, adjust the pH value to 8 - 10 with sodium hydroxide, then add 17.5 g of AM, 1 g of NVP, and 0.12 g of N,N - methylenebisacrylamide. After complete dissolution, a homogeneous aqueous solution is formed; add 5.25 g of sorbitan fatty acid ester and 1.75 g of polyoxyethylene octylphenol ether - 10 to 70 g of white oil. After complete dissolution, continuously stir and emulsify in an emulsifier. Add 80% of the above - mentioned aqueous solution to the obtained oil phase, emulsify for 10 min to form a uniformly dispersed suspension system; pass nitrogen into the emulsification reaction mixture for 20 min, heat in a 45°C water bath, and add a 5 - mL aqueous solution containing 0.15 g of ammonium persulfate and a 5 - mL aqueous solution containing 0.15 g of sodium bisulfite under stirring. After reacting at 65°C for 0.5 h, add the remaining aqueous solution to the reacted emulsion, stir evenly, and keep it warm at 65°C for 4 h to obtain the high - temperature - resistant spherical gel plugging agent for oil - based drilling fluids;

[0039] Its main structural formula is:

[0040]

[0041] Example 3:

[0042] Add 7 g of AMPS to 50 g of water, adjust the pH value to 8 - 10 with sodium hydroxide, then add 13 g of AM, 1 g of NVP, 1 g of DMAA, and 0.12 g of N,N - methylenebisacrylamide. After complete dissolution, a homogeneous aqueous solution is formed; add 5.25 g of sorbitan fatty acid ester and 1.75 g of polyoxyethylene octylphenol ether - 10 to 70 g of white oil. After complete dissolution, continuously stir and emulsify in an emulsifier. Add 80% of the above - mentioned aqueous solution to the obtained oil phase, emulsify for 10 min to form a uniformly dispersed suspension system; pass nitrogen into the emulsification reaction mixture for 20 min, heat in a 45°C water bath, and add a 5 - mL aqueous solution containing 0.20 g of ammonium persulfate and a 5 - mL aqueous solution containing 0.20 g of sodium bisulfite under stirring. After reacting at 70°C for 0.5 h, add the remaining aqueous solution to the reacted emulsion, stir evenly, and keep it warm at 65°C for 4 h to obtain the high - temperature - resistant spherical gel plugging agent for oil - based drilling fluids;

[0043] Its main structural formula is:

[0044]

[0045] Comparative Example 1

[0046] Add 5 g of AMPS to 50 g of water, adjust the pH value to 8 - 10 with sodium hydroxide, then add 17.5 g of AM, 1 g of DMAA, and 0.11 g of N,N - methylenebisacrylamide. After complete dissolution, a uniformly dispersed aqueous solution is formed; add 5.25 g of sorbitan fatty acid ester and 1.75 g of polyoxyethylene octylphenol ether - 10 to 70 g of white oil. After complete dissolution, continuously stir and emulsify in an emulsifier. Add the above - mentioned aqueous solution to the oil phase and emulsify for 15 min to form a uniformly dispersed suspension system; heat the above - mentioned system in a 40 °C water bath, and add a 5 mL aqueous solution of 0.16 g of ammonium persulfate and a 5 mL aqueous solution of 0.16 g of sodium bisulfite under stirring. The reaction is completed within 1 h, and keep it at 65 °C for 4 h to obtain the high - temperature - resistant spherical gel plugging agent for oil - based drilling fluids;

[0047] Its main structural formula is:

[0048]

[0049] Comparative Example 2

[0050] Add 4 g of AA to 50 g of water, adjust the pH value to 8 - 10 with sodium hydroxide, then add 16 g of AM and 0.10 g of N,N - methylenebisacrylamide. After complete dissolution, a uniformly dispersed aqueous solution is formed; add 5.25 g of sorbitan fatty acid ester and 1.75 g of polyoxyethylene octylphenol ether - 10 to 70 g of white oil. After complete dissolution, continuously stir and emulsify in an emulsifier. Add 80% of the above - mentioned aqueous solution to the obtained oil phase and emulsify for 10 min to form a uniformly dispersed suspension system; pass nitrogen into the emulsification reaction mixture for 20 min, heat it in a 45 °C water bath, and add a 5 mL aqueous solution containing 0.10 g of ammonium persulfate and a 5 mL aqueous solution containing 0.10 g of sodium bisulfite under stirring. After reacting at 70 °C for 0.5 h, add the remaining aqueous solution to the reacted emulsion, stir evenly, and keep it at 65 °C for 4 h to obtain the high - temperature - resistant spherical gel plugging agent for oil - based drilling fluids;

[0051] Its main structural formula is:

[0052]

[0053] Evaluate the products prepared in the examples of the present invention, and the results are as follows:

[0054] (1) Particle size analysis

[0055] Measure the high - temperature - resistant spherical gel plugging agent obtained in the examples using a laser particle size analyzer. As shown in Table 1, the particle size of the lost - circulation - control agent for oil - based drilling fluids obtained in the present invention is in the micron range and can be used to plug micro - fissures and pores.

[0056] Table 1 Particle size D of the products in the examples50

[0057] Serial number <![CDATA[Particle size D 50 , μm]]> Example 1 2.86 Example 2 2.38 Example 3 2.24

[0058] (2) Compatibility with oil-based drilling fluids

[0059] The oil-based drilling fluid obtained by reacting the examples and comparative examples was added with a high-temperature-resistant spherical gel plugging agent into the oil-based mud (oil-based drilling fluid + 3% of the product by volume of the oil-based drilling fluid). After aging at 180 °C in a high-temperature roller furnace for 16 h, the rheology of the drilling fluid was measured with a six-speed rotational viscometer at 65 °C. The results are shown in Table 2. As can be seen from Table 2, when the product of the present invention is added to the oil-based drilling fluid, the rheological properties of the system change little after high-temperature aging; the high-temperature and high-pressure filtration loss decreases with the increase of the product dosage, from 13 mL to 5.6 mL. However, the compatibility of Comparative Examples 1 and 2 with the oil-based drilling fluid is poor, and the high-temperature and high-pressure filtration loss is poor. This shows that the high-temperature-resistant spherical gel plugging agent has good compatibility with the oil-based drilling fluid and has good filtration loss reduction and plugging performance.

[0060] Table 2 Evaluation of the compatibility between the product dosage of the examples and the drilling fluid

[0061] High-temperature resistant spherical gel plugging agent / % AV / mPa.s PV / mPa.s YP / mPa.s Gel / (Pa / Pa) <![CDATA[FL HTHP / mL]]> Base slurry 44.0 37 7.0 2.5 / 3.0 13 Base slurry + 3% product of Example 1 43.5 37 6.5 2.5 / 3.0 5.8 Base slurry + 3% product of Example 2 42.0 36 6.0 2.5 / 3.0 5.6 Base slurry + 3% product of Example 3 43.0 37 6.0 2.5 / 3.0 6.2 Base slurry + 3% product of Comparative Example 1 58.0 42.0 16.0 5.0 / 15.0 12 Base slurry + 3% product of Comparative Example 2 76.0 54.0 22 7.0 / 21.0 23

[0062] Note: 8:2 diesel: 20% calcium chloride aqueous solution + 4% emulsifier + 2% calcium oxide + 3% organophilic clay + 2% filtration loss reducer + 320 g barite (density 1.8 g / cm 3 ).

[0063] (3) Temperature resistance

[0064] To investigate the temperature resistance of the high-temperature-resistant spherical gel plugging agent, the high-temperature-resistant spherical gel plugging agent was placed in the oil-based drilling fluid and rolled and aged at 180 °C for 48 h. The performance of the high-temperature-resistant spherical gel plugging agent and the leakage amount measured with a 20-40 mesh sand bed were used to represent the plugging ability, and the plugging effect of the high-temperature-resistant spherical gel plugging agent was further evaluated. The results are shown in Table 3. The results show that the high-temperature-resistant spherical gel plugging agent has good compatibility with the oil-based drilling fluid within 48 h; the reduction rate of the high-temperature and high-pressure filtration loss after adding the high-temperature-resistant spherical gel plugging agent reaches 50%, and the filtration loss maintains a decrease within 48 h. The products of the comparative examples have poor performance in terms of compatibility, high-temperature and high-pressure filtration loss, and plugging performance, indicating that the temperature resistance cannot reach 180 °C. The results show that the high-temperature-resistant spherical gel plugging agent still maintains good performance at 180 °C / 48 h, meeting the temperature resistance requirement of 180 °C for the spherical gel.

[0065] Table 3 Temperature resistance of the product of the examples at 180 °C

[0066]

[0067]

[0068] Note: 8:2 diesel: 20% calcium chloride aqueous solution + 4% emulsifier + 2% calcium oxide + 3% organoclay + 2% filtration loss reducer + 500 g barite (density 1.8 g / cm 3 ).

[0069] It can be seen from the experimental results that the plugging agent has a good plugging effect. Therefore, the characteristics of this product include: the temperature resistance reaches 180 °C, it has good compatibility with oil-based drilling fluids, has the functions of reducing filtration loss and preventing leakage, and can be used for plugging high-temperature formations.

[0070] The product of the present invention is prepared by inverse emulsion seed polymerization through an interpenetrating network structure method to improve the temperature resistance of the gel. The product has good compatibility with oil-based drilling fluids and does not change the rheological properties of oil-based drilling fluids; D 50 The particle size distribution is 0.5 - 10 μm, which can participate in the formation of the mud cake, improve the quality of the mud cake, and reduce the high-temperature high-pressure filtration loss. This product solves the problems of easily caving and leaking formations in the drilling of deep wells and ultra-deep wells, and high-temperature bedding fracture-developed formations with a relatively high bottom-hole temperature (>150 °C). It can effectively reduce the loss of oil-based drilling fluids, prevent well leakage, improve the wellbore stability, reduce downhole complications of oil-based drilling fluids, and reduce the comprehensive cost of drilling fluids.

[0071] The above are only the preferred embodiments of the present invention. It should be noted that for those skilled in the art of this technology, without departing from the technical principle of the present invention, various modifications to these embodiments can be made, and these modifications should also be regarded as the scope protected by the present invention.

Claims

1. A preparation method of a high-temperature-resistant spherical gel plugging agent for oil-based drilling fluids, characterized in that, It includes the following steps: S1. Dissolve emulsifier A and emulsifier B in an oily solvent to obtain an oil phase; emulsifier A is one of sorbitan fatty acid ester and sorbitan monostearate; emulsifier B is one or more of polyoxyethylene sorbitan ether stearate, polyoxyethylene sorbitan monooleate, and polyoxyethylene octylphenol ether-10; Dissolve sodium hydroxide, a water-soluble organic monomer, a temperature-resistant monomer, and a crosslinking agent in water to obtain a water phase; the water-soluble organic monomer is one or more of acrylic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid; the temperature-resistant monomer is one or more of N,N-dimethylacrylamide, N-vinylpyrrolidone, and 2-methyl-2-propenenitrile; the crosslinking agent is one or more of N,N-methylenebisacrylamide, ethylene glycol diacrylate, and 1,3-butanediol diacrylate; S2. Divide the water phase into two parts, namely the first water phase and the second water phase. Add the first water phase to the oil phase, shear and emulsify to obtain an emulsification reaction mixture; add a redox system initiator to the emulsification reaction mixture and carry out heat preservation polymerization; S3. Add the second water phase to the emulsion after heat preservation polymerization, continue heat preservation polymerization to obtain a micron-sized high-temperature-resistant spherical gel plugging agent; the mass of the first water phase is greater than that of the second water phase; The high-temperature resistant spherical gel plugging agent is a water-in-oil gel, D 50 The particle size distribution is 0.5~10 μm.

2. The preparation method according to claim 1, characterized in that, In the redox system initiator in step S2, the oxidant is ammonium persulfate or potassium persulfate, and the reductant is sodium bisulfite, ferrous sulfate, sodium sulfite, or sodium metabisulfite.

3. The preparation method according to claim 1, characterized in that, The temperature of the heat preservation polymerization in steps S2 and S3 is independently 60-70°C; the time of the heat preservation polymerization in step S2 is 0.5-1 h.

4. The preparation method according to claim 3, characterized in that, In step S2, the mass ratio of the first water phase is 60%-80%; the time of the heat preservation polymerization in step S3 is 2-4 h.

5. The preparation method according to any one of claims 1-4, characterized in that, The mass ratio of emulsifier A and B is (1.0-3.0):(0.5-1.0); the addition amount of the crosslinking agent is 0.1%-0.6% of the total mass of the monomers; the addition amount of the initiator is 0.4%-1.0% of the total mass of the monomers; adjust the pH value range of the water phase to 8-10.

6. Application of the high-temperature-resistant spherical gel plugging agent obtained by the preparation method according to any one of claims 1-5 in the preparation of oil-based drilling fluids.

7. The application according to claim 6, characterized in that, The prepared oil-based drilling fluid is used for high-temperature formations above 150°C.

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