Polymer microspheres for oil-based drilling fluid leak-stopping agent while drilling and preparation method thereof

Abstract

The present application relates to the technical field of plugging agents for oil-based drilling fluids and its preparation method, and is a kind of plugging agent for oil-based drilling fluid with high-strength and high-toughness polymer microspheres and its preparation method, the raw materials of the former include acrylonitrile, dimethyl diallyl ammonium chloride, 2-acrylamido-2-methylpropane sulfonic acid, crosslinking agent, deionized water, white oil, emulsifier and initiator. The plugging agent for oil-based drilling fluid with high-strength and high-toughness polymer microspheres has strong pertinence, can effectively plug various size pores, has high strength, good toughness, and the pressure-bearing capacity is as high as 15MPa; it has good compatibility in oil-based drilling fluid system, stable demulsification voltage, can form high-strength and high-toughness filter cake during drilling, effectively prevent the formation damage problem caused by leakage; significantly improve the reusability of oil-based drilling fluid, reduce the application cost of oil-based drilling fluid, effectively alleviate the great environmental pressure brought by the disposal of waste oil-based drilling fluid as hazardous waste.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of a plugging agent for oil-based drilling fluid and a preparation method thereof, and is a high-strength and high-toughness polymer microsphere drilling plugging agent for oil-based drilling fluid and a preparation method thereof. BACKGROUND

[0002] With the exploitation of oil and gas resources, most of the strata explored have the characteristics of high temperature and high pressure, and the drilling fluid loss problem caused by the reasons such as large strata inclination, strong strata water sensitivity, developed stratification, abnormal ground stress, high strata pressure, complex pressure system, and high bottom hole temperature is becoming more and more serious. The commonly used plugging products in drilling are generally polymer gel, which is most widely used because of its good adaptability in drilling and many types, but this type of product also has problems such as uncontrollable product quality, complicated application program, and low pressure resistance. For example, the ZND special gel developed by Southwest University and the FORM-A series of the third generation of crosslinked bridge plugs developed by M-I Company are water-based materials, which have poor effect in oil-based drilling fluid. Although the bridging plugging material has relatively low cost, simple field construction, and wide raw material sources, the particle size ratio of the bridging plugging material is relatively strict compared with the strata ratio, and the bridging plugging material needs to be used with other materials to achieve a relatively ideal plugging effect. Cement slurry plugging material is widely used because of its high pressure resistance, wide source, and low cost, but this type of plugging material cannot effectively accumulate and top, and can only form a small sand pile at the drilling hole, which has great difficulty in filling. For example, the fiber cement slurry used in the Sumatra Basin oilfield and the publicly disclosed silicate water glass type temperature-resistant material and MTC cement slurry in the international market are often formed with small gaps around the filling body after dehydration, which cannot be effectively plugged, and usually need to be used with bridging plugging materials. This also leads to the fact that the bridging plugging material can be widely used in water-based drilling fluid, but limits its application in oil-based drilling fluid.

[0003] With the increase of the depth of oil and gas drilling, the drilling difficulty increases, the bottom hole pressure and temperature show an increasing trend, and the drilling fluid must have higher strength and toughness. The current plugging agent cannot completely meet the size requirements of high-density high-temperature deep wells. SUMMARY

[0004] The present application provides a high-strength and high-toughness polymer microsphere drilling plugging agent for oil-based drilling fluid and a preparation method thereof, which overcomes the shortcomings of the prior art and effectively solves the problems of poor compatibility and poor strength and toughness of the existing drilling plugging material in oil-based drilling fluid.

[0005] One of the technical solutions of the present application is realized by the following measures: a high-strength and high-toughness polymer microsphere lost circulation control agent for oil-based drilling fluid, raw materials include acrylonitrile 10-15 parts, dimethyl diallyl ammonium chloride 14-21 parts, 2-acrylamido-2-methylpropane sulfonic acid 20-30 parts, crosslinking agent 0.01-0.03 parts, deionized water 20-30 parts, white oil 40-45 parts, emulsifier 4-6 parts, initiator 0.03-0.09 parts.

[0006] The following is a further optimization or / and improvement of one of the above technical solutions of the application:

[0007] The above crosslinking agent uses acrylamide crosslinking agent or divinylbenzene or divinyltetramethyldisiloxane.

[0008] The above white oil uses 3# white oil.

[0009] The above emulsifier uses one or more of Tween 80 (TW-80), sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate and polyvinyl alcohol.

[0010] The above initiator uses one or more of azobisdimethyl isobutyl cyanide, azobisdimethyl isopentyl cyanide, azobisdimethyl isobutyric acid dimethyl ester, potassium persulfate and sodium bisulfite.

[0011] The above high-strength and high-toughness polymer microsphere lost circulation control agent for oil-based drilling fluid is prepared by the following method: first, the required amount of acrylonitrile, dimethyl diallyl ammonium chloride, 2-acrylamido-2-methylpropane sulfonic acid and crosslinking agent are added to the required amount of deionized water and mixed uniformly to obtain the first mixture; second, the pH of the first mixture is adjusted to 7-8, a part of the emulsifier is added and stirred to obtain the second mixture; third, white oil and the remaining emulsifier are added to the second mixture, the solution is stirred uniformly, then sheared and the required amount of initiator is added, inert gas is introduced, the temperature is raised to 40-80℃ under the inert gas atmosphere, and the reaction is carried out for 8-15h to obtain the high-strength and high-toughness polymer microsphere lost circulation control agent for oil-based drilling fluid.

[0012] The second technical solution of the present application is realized by the following measures: the preparation method of the oil-based drilling fluid high-strength and high-toughness polymer microsphere lost circulation control agent in one of the technical solutions, which is carried out according to the following method: first, a required amount of acrylonitrile, dimethyl diallyl ammonium chloride, 2-acrylamido-2-methylpropane sulfonic acid and a crosslinking agent are added to a required amount of deionized water and mixed uniformly to obtain a first mixture; second, the pH of the first mixture is adjusted to 7 to 8, and a part of the emulsifier is added and stirred to obtain a second mixture; third, white oil and the remaining emulsifier are added to the second mixture, the solution is stirred uniformly, then shearing is carried out and a required amount of initiator is added, inert gas is introduced, the temperature is raised to 40 DEG C to 80 DEG C under the inert gas atmosphere, and the reaction is carried out for 8 h to 15 h to obtain the oil-based drilling fluid high-strength and high-toughness polymer microsphere lost circulation control agent.

[0013] The following is a further optimization or / and improvement of the second technical solution of the above application:

[0014] The crosslinking agent described above adopts an acrylamide crosslinking agent or divinyl benzene or divinyl tetramethyl disiloxane.

[0015] The white oil described above adopts 3# white oil.

[0016] The emulsifier described above adopts one or more of Tween 80 (TW-80), sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate and polyvinyl alcohol.

[0017] The initiator described above adopts one or more of azobisdimethyl isobutyl cyanide, azobisdimethyl isopentyl cyanide, dimethyl azobis isobutyrate, potassium persulfate and sodium bisulfite.

[0018] The present application has the following advantages:

[0019] (1) The preparation process is simple, the raw materials come from commonly used polymer raw materials, and the environmental friendliness is excellent, which will not cause damage to the formation;

[0020] (2) The oil-based drilling fluid high-strength and high-toughness polymer microsphere lost circulation control agent has good thermal stability, and still has good plugging capacity at a high temperature of 150 DEG C, the API filtration loss reduction rate is more than 50% under the condition of adding 2%, the oil-based drilling fluid system sealing filtration loss is less than 10 ml under the condition of adding 3%, and the plugging pressure capacity is greater than 8 MPa under the condition of adding 5%, and the change range of rheological parameters is small, which completely meets the requirements of field drilling;

[0021] (3) The oil-based drilling fluid high-strength and high-toughness polymer microsphere lost circulation control agent is oil-soluble microsphere, has good compatibility in the oil-based drilling fluid system, stable demulsification voltage, high strength and good toughness, and can form a high-strength and toughness filter cake in the process of drilling to effectively prevent the formation damage caused by leakage;

[0022] (4) The oil-based drilling fluid high-strength and high-toughness polymer microsphere while drilling plugging agent has high targeting, and the size of the microsphere can be adjusted according to the formation aperture;

[0023] (5) The oil-based drilling fluid high-strength and high-toughness polymer microsphere while drilling plugging agent can significantly improve the reusability of the oil-based drilling fluid, reduce the application cost of the oil-based drilling fluid, and effectively alleviate the great environmental pressure brought by the disposal of waste oil-based drilling fluid as hazardous waste. DETAILED DESCRIPTION

[0024] The present application is not limited by the following examples, and the specific implementation can be determined according to the technical solution of the present application and the actual situation. The various chemical reagents and chemical products mentioned in the present application are well-known and commonly used chemical reagents and chemical products in the prior art unless otherwise specified; the percentages in the present application are mass percentages unless otherwise specified; the solutions in the present application are aqueous solutions with water as the solvent unless otherwise specified, for example, a hydrochloric acid solution is an aqueous hydrochloric acid solution.

[0025] The present application will be further described below in conjunction with examples:

[0026] Example 1: The oil-based drilling fluid high-strength and high-toughness polymer microsphere while drilling plugging agent, the raw materials include acrylonitrile 10-15 parts, dimethyl diallyl ammonium chloride 14-21 parts, 2-acrylamido-2-methylpropane sulfonic acid 20-30 parts, crosslinking agent 0.01-0.03 parts, deionized water 20-30 parts, white oil 40-45 parts, emulsifier 4-6 parts, initiator 0.03-0.09 parts, by weight; The following preparation method is used: first, the required amount of acrylonitrile, dimethyl diallyl ammonium chloride, 2-acrylamido-2-methylpropane sulfonic acid, crosslinking agent is added to the required amount of deionized water and mixed uniformly to obtain the first mixture; second, the pH of the first mixture is adjusted to 7-8, a part of the emulsifier is added and stirred to obtain the second mixture; third, the white oil and the remaining emulsifier are added to the second mixture, the solution is stirred uniformly, then sheared and the required amount of initiator is added, inert gas is introduced, the temperature is raised to 40-80 DEG C under the inert gas atmosphere, and the reaction is carried out for 8-15 hours to obtain the oil-based drilling fluid high-strength and high-toughness polymer microsphere while drilling plugging agent.

[0027] Example 2: The oil-based drilling fluid high-strength high-toughness polymer microsphere while drilling plugging agent, the raw materials include acrylonitrile 10 parts or 15 parts, dimethyl diallyl ammonium chloride 14 parts or 21 parts, 2-acrylamide-2-methyl propane sulfonic acid 20 parts or 30 parts, crosslinking agent 0.01 parts or 0.03 parts, deionized water 20 parts or 30 parts, white oil 40 parts or 45 parts, emulsifier 4 parts or 6 parts, initiator 0.03 parts or 0.09 parts by weight; The following preparation method is obtained: first, the required amount of acrylonitrile, dimethyl diallyl ammonium chloride, 2-acrylamide-2-methyl propane sulfonic acid, crosslinking agent is added to the required amount of deionized water and mixed uniformly to obtain the first mixture; second, the pH of the first mixture is adjusted to 7 or 8, a part of the emulsifier is added and stirred to obtain the second mixture; third, the white oil and the remaining emulsifier are added to the second mixture, the solution is stirred uniformly, then sheared and the required amount of initiator is added, inert gas is introduced, the temperature is raised to 40℃ or 80℃ under the inert gas atmosphere, and the reaction is carried out for 8h or 15h to obtain the oil-based drilling fluid high-strength high-toughness polymer microsphere while drilling plugging agent.

[0028] Example 3: As an optimization of the above-mentioned examples, the crosslinking agent is acrylamide crosslinking agent or divinylbenzene or divinyltetramethyldisiloxane.

[0029] The acrylamide crosslinking agent can use N'N methylene bisacrylamide.

[0030] Example 4: As an optimization of the above-mentioned examples, the white oil uses 3# white oil.

[0031] Example 5: As an optimization of the above-mentioned examples, the emulsifier uses one or more of Tween 80 (TW-80), sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate and polyvinyl alcohol.

[0032] Example 6: As an optimization of the above-mentioned examples, the initiator uses one or more of azobisdimethyl isobutyl cyanide, azobisdiisopropyl cyanide, dimethyl azobis isobutyrate, potassium persulfate and sodium bisulfite.

[0033] Example 7: The oil-based drilling fluid with high-strength and high-toughness polymer microspheres while drilling plugging agent, raw materials include acrylonitrile 100 grams, dimethyl diallyl ammonium chloride 140 grams, 2-acrylamido-2-methylpropane sulfonic acid 200 grams, N'N methylene bisacrylamide 0.2 grams, deionized water 250 grams, 3# white oil 400 grams, TW-80 50 grams, azobisdimethyl isobutyronitrile 0.7 grams; The following preparation method is obtained: first, the required amount of acrylonitrile, dimethyl diallyl ammonium chloride, 2-acrylamido-2-methylpropane sulfonic acid, N'N methylene bisacrylamide is added to the required amount of deionized water and mixed uniformly to obtain the first mixture; second, the pH of the first mixture is adjusted to 7, 30 grams of TW-80 is added and stirred to obtain the second mixture; third, 3# white oil and 20 grams of TW-80 are added to the second mixture, the solution is stirred uniformly, sheared and the required amount of azobisdimethyl isobutyronitrile is added, nitrogen is introduced, the temperature is raised to 60°C under nitrogen atmosphere, and the reaction is carried out for 12 hours to obtain the oil-based drilling fluid with high-strength and high-toughness polymer microspheres while drilling plugging agent.

[0034] Example 8: The oil-based drilling fluid with high-strength and high-toughness polymer microspheres while drilling plugging agent, raw materials include acrylonitrile 150 grams, dimethyl diallyl ammonium chloride 200 grams, 2-acrylamido-2-methylpropane sulfonic acid 250 grams, divinylbenzene 0.3 grams, deionized water 300 grams, 3# white oil 450 grams, sodium dodecyl sulfonate 60 grams, dimethyl azobis isobutyrate 0.9 grams; The following preparation method is obtained: first, the required amount of acrylonitrile, dimethyl diallyl ammonium chloride, 2-acrylamido-2-methylpropane sulfonic acid, divinylbenzene is added to the required amount of deionized water and mixed uniformly to obtain the first mixture; second, the pH of the first mixture is adjusted to 7, 30 grams of sodium dodecyl sulfonate is added and stirred to obtain the second mixture; third, 3# white oil and 30 grams of sodium dodecyl sulfonate are added to the second mixture, the solution is stirred uniformly, sheared and the required amount of dimethyl azobis isobutyrate is added, nitrogen is introduced, the temperature is raised to 70°C under nitrogen atmosphere, and the reaction is carried out for 10 hours to obtain the oil-based drilling fluid with high-strength and high-toughness polymer microspheres while drilling plugging agent.

[0035] Example 9: the oil-based drilling fluid with high-strength and high-toughness polymer microspheres while drilling plugging agent, raw materials include acrylonitrile 120 grams, dimethyl diallyl ammonium chloride 170 grams, 2-acrylamido-2-methylpropane sulfonic acid 260 grams, divinyltetramethyldisiloxane 0.1 grams, deionized water 300 grams, 3# white oil 450 grams, polyvinyl alcohol 60 grams, potassium persulfate and sodium bisulfite 0.9 grams; the following preparation method is obtained: first, the required amount of acrylonitrile, dimethyl diallyl ammonium chloride, 2-acrylamido-2-methylpropane sulfonic acid, divinyltetramethyldisiloxane is added to the required amount of deionized water and mixed uniformly to obtain the first mixture; second, the pH of the first mixture is adjusted to 7, 30 grams of polyvinyl alcohol is added and stirred to obtain the second mixture; third, 3# white oil and the remaining polyvinyl alcohol are added to the second mixture, the solution is stirred uniformly, shearing is carried out, and the required amount of potassium persulfate and sodium bisulfite is added, nitrogen is introduced, the temperature is raised to 80℃ under the nitrogen atmosphere, and reaction is carried out for 8h to obtain the oil-based drilling fluid with high-strength and high-toughness polymer microspheres while drilling plugging agent.

[0036] Example 10: the oil-based drilling fluid with high-strength and high-toughness polymer microspheres while drilling plugging agent, raw materials include acrylonitrile 100 grams, dimethyl diallyl ammonium chloride 150 grams, 2-acrylamido-2-methylpropane sulfonic acid 200 grams, N'N methylene bisacrylamide 0.2 grams, deionized water 250 grams, 3# white oil 400 grams, Tween 80 50 grams, azobis isopropyl cyano 0.5 grams; the following preparation method is obtained: first, the required amount of acrylonitrile, dimethyl diallyl ammonium chloride, 2-acrylamido-2-methylpropane sulfonic acid, N'N methylene bisacrylamide is added to the required amount of deionized water and mixed uniformly to obtain the first mixture; second, the pH of the first mixture is adjusted to 8, 25 grams of Tween 80 is added and stirred to obtain the second mixture; third, 3# white oil and the remaining Tween 80 are added to the second mixture, the solution is stirred uniformly, shearing is carried out, and the required amount of azobis isopropyl cyano is added, nitrogen is introduced, the temperature is raised to 60℃ under the nitrogen atmosphere, and reaction is carried out for 12h to obtain the oil-based drilling fluid with high-strength and high-toughness polymer microspheres while drilling plugging agent.

[0037] The present application adopts the method of inverse emulsion polymerization to form a three-dimensional network polymer under the action of a high-efficiency crosslinking agent, using cationic monomers quaternary ammonium salt (dimethyl diallyl ammonium chloride) and sulfonate groups (2-acrylamido-2-methylpropane sulfonic acid) with high charge density.

[0038] The application provides a polymer gel microsphere for oil-based drilling fluid, which has high strength, good toughness, adjustable size and strong pertinence, namely, a high-strength and high-toughness polymer microsphere for oil-based drilling fluid lost circulation material while drilling, forms an excellent mud cake on a well wall, solves the leakage problem in the drilling process, and improves the reusability of the oil-based drilling fluid.

[0039] The application is described below with the following application examples.

[0040] Application Example 1

[0041] The preparation method of the oil-based drilling fluid of the application example comprises the following steps.

[0042] (1) 340 mL of 3# white oil is taken, 3wt% of a main emulsifier (tall oil fatty acid amide), 3wt% of an auxiliary emulsifier (tall oil fatty acid amide) and 1.5wt% of a wetting agent (lecithin) are added, and high-speed stirring is performed for 20 min; then 2.5wt% of an organic clay, 1.5wt% of calcium oxide are added, and high-speed stirring is performed for 20 min; then 60 mL of a calcium chloride aqueous solution with a concentration of 30wt% is added, and high-speed stirring is performed for 20 min; then 3wt% of a filtration loss reducer is added, and stirring is continued for 20 min, so that 400 mL of a base oil-based drilling fluid is obtained;

[0043] (2) 3wt% of the high-strength and high-toughness polymer microsphere for oil-based drilling fluid lost circulation material while drilling (hereinafter referred to as a lost circulation material) of Example 7 is added to the base oil-based drilling fluid, high-speed stirring is performed for 20 min, and then the mixture is transferred into an aging tank, and an oil-based drilling fluid is obtained by aging at 150℃ for 16 h.

[0044] Comparative Example 1

[0045] The oil-based drilling fluid is different from the oil-based drilling fluid of Application Example 1 only in that the lost circulation material of Example 7 is not added.

[0046] Experimental Example 1

[0047] The oil-based drilling fluids provided by Application Example 1 and Comparative Example 1 are respectively evaluated for plugging effect by using a high-temperature and high-pressure filtration instrument (GGS42-2).

[0048] A sand disc with a size of 5 μm, 20 μm or 40 μm is used to simulate a leakage layer, and the cumulative leakage amount (mL) of the oil-based drilling fluids provided by Application Example 1 and Comparative Example 1 under different pressure differentials (MPa) is respectively investigated, and the data results are shown in Table 1.

[0049] As shown in Table 1, for the three sand table simulation experiments, under the condition of continuous pressurization at 150℃, the loss of application example 1 is less than that of comparative example 1, in the 20μm sand table simulation experiment, application example 1 reduces the filtration loss by 33.3% compared with comparative example 1, and finally in the 40μm sand table simulation experiment, comparative example 1 is all lost when pressurized to 13MPa, while the addition of 3wt% of the plugging material of application example 1 significantly reduces the loss and does not all lose. It shows that the oil-based drilling fluid prepared by the oil-based drilling fluid high-strength and high-toughness polymer microsphere drilling plugging agent of the application can bear pressure of more than 10MPa in the three sand tables, and is suitable for different pore formations. The oil-based drilling fluid high-strength and high-toughness polymer microsphere drilling plugging agent can be applied to different pore formations, and the pressure bearing capacity can reach 15MPa.

[0050] Application Example 2

[0051] The preparation method of the oil-based drilling fluid of the application example includes the following steps:

[0052] (1) Take 340mL of 3# white oil, add 3wt% of main emulsifier (tall oil fatty acid amide), 3wt% of auxiliary emulsifier (tall oil fatty acid amide) and 1.5wt% of wetting agent (lecithin), and stir at high speed for 20min; then add 2.5wt% of organic clay, 1.5wt% of calcium oxide, and stir at high speed for 20min; then add 60mL of 30wt% calcium chloride aqueous solution, and stir at high speed for 20min; then add 3wt% of filtration reducer, and continue to stir for 20min, to obtain 400mL of base oil-based drilling fluid;

[0053] (2) Add 3wt% of the plugging material of example 8 to the base oil-based drilling fluid, stir at high speed for 20min, then add 400g of barite, continue to stir for 30min, and transfer into two aging tanks, respectively at 80℃ and 150℃ for 16h to obtain the oil-based drilling fluid.

[0054] Comparative Example 2

[0055] The difference between the oil-based drilling fluid and the oil-based drilling fluid of application example 2 is only that the plugging material of example 8 is not added.

[0056] Comparative Example 3

[0057] The difference between the oil-based drilling fluid and the oil-based drilling fluid provided by application example 2 is only that the plugging material added is not the plugging material provided by example 8, but 3% of 600 mesh calcium carbonate.

[0058] Experimental Example 2

[0059] The oil-based drilling fluids provided by application example 2 and comparative example 2 were respectively evaluated for closed loss effect using a high temperature and high pressure filtration instrument (GGS41-A):

[0060] Using 100g of quartz sand to simulate the leakage layer, the cumulative leakage amount (mL) of the oil-based drilling fluid provided by application example 2, comparative example 2 at different temperatures (℃) was investigated, and the data results are shown in Table 2. It should be noted that 20-40 mesh of analytical pure quartz sand was used.

[0061] As can be seen from Table 2, the plugging material of example 8 can significantly reduce the closed filtration loss of the oil-based drilling fluid at different temperatures, and the closed filtration loss of the oil-based drilling fluid system of application example 2 is less than 10ml.

[0062] Experimental example 3

[0063] The oil-based drilling fluid provided by application example 2, comparative example 2 and comparative example 3 was respectively evaluated for closed leakage effect using a high temperature and high pressure filtration instrument (GGS41-A).

[0064] Using 100g of mixed quartz sand to simulate the leakage layer, the cumulative leakage amount (mL) of the oil-based drilling fluid provided by application example 2, comparative example 2 and comparative example 3 at different temperatures (℃) was investigated, and the data results are shown in Table 3. It should be noted that 20-40 mesh of mixed quartz sand was used.

[0065] As can be seen from Table 3, the cumulative leakage amount of the oil-based drilling fluid of application example 2 at 80℃ and 120℃ is significantly lower than that of comparative example 2 and comparative example 3.

[0066] As can be seen from the above experimental examples, the oil-based drilling fluid with high-strength and high-toughness polymer microspheres while drilling plugging agent has strong pertinence and can effectively plug various size pores, has high strength, good toughness, and a pressure bearing capacity of up to 15MPa. The oil-based drilling fluid prepared by using the oil-based drilling fluid with high-strength and high-toughness polymer microspheres while drilling plugging agent has good evaluation effect in the field mud, has good rheological property after long-term high-temperature aging, improves the demulsification voltage, is environmentally friendly, can improve the utilization rate of oil-based drilling fluid, reduces the construction cost, and provides effective and reliable technical support for the field drilling fluid construction.

[0067] The above technical features constitute an embodiment of the present application, which has strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the needs of different situations.

[0068]

Claims

1. A high-strength, high-toughness polymer microsphere plugging agent for oil-based drilling fluids, characterized in that... The raw materials, by weight, include 10 to 15 parts acrylonitrile, 14 to 21 parts dimethyl diallyl ammonium chloride, 20 to 30 parts 2-acrylamido-2-methylpropanesulfonic acid, 0.01 to 0.03 parts crosslinking agent, 20 to 30 parts deionized water, 40 to 45 parts white oil, 4 to 6 parts emulsifier, and 0.03 to 0.09 parts initiator; the crosslinking agent is an acrylamide-based crosslinking agent, or divinylbenzene or divinyltetramethyldisiloxane; The following method is used to obtain the first mixture: First, add the required amount of acrylonitrile, dimethyl diallyl ammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid, and crosslinking agent to the required amount of deionized water and mix evenly to obtain the first mixture; Second, adjust the pH of the first mixture to 7 to 8, add a portion of emulsifier and stir to obtain the second mixture; Third, add white oil and the remaining emulsifier to the second mixture, stir the solution evenly, shear it and add the required amount of initiator, introduce inert gas, and under an inert gas atmosphere, heat to 40℃ to 80℃ and react for 8 to 15 hours to obtain a high-strength and high-toughness polymer microsphere plugging agent for oil-based drilling fluid.

2. The high-strength, high-toughness polymer microsphere plugging agent for oil-based drilling fluid according to claim 1, characterized in that... The white oil used is No. 3 white oil.

3. The high-strength, high-toughness polymer microsphere plugging agent for oil-based drilling fluid according to claim 1 or 2, characterized in that... The emulsifier is one or more of Tween 80, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, and polyvinyl alcohol.

4. The high-strength, high-toughness polymer microsphere plugging agent for oil-based drilling fluid according to claim 1 or 2, characterized in that... The initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, potassium persulfate, and sodium bisulfite.

5. The high-strength, high-toughness polymer microsphere plugging agent for oil-based drilling fluid according to claim 3, characterized in that... The initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, potassium persulfate, and sodium bisulfite.

6. A method for preparing a high-strength, high-toughness polymer microsphere plugging agent for oil-based drilling fluid according to any one of claims 2 to 5, characterized in that, The raw materials, by weight, include 10 to 15 parts acrylonitrile, 14 to 21 parts dimethyl diallyl ammonium chloride, 20 to 30 parts 2-acrylamido-2-methylpropanesulfonic acid, 0.01 to 0.03 parts crosslinking agent, 20 to 30 parts deionized water, 40 to 45 parts white oil, 4 to 6 parts emulsifier, and 0.03 to 0.09 parts initiator; the crosslinking agent is an acrylamide-based crosslinking agent, or divinylbenzene or divinyltetramethyldisiloxane; The process is as follows: First, add the required amount of acrylonitrile, dimethyl diallyl ammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid, and crosslinking agent to the required amount of deionized water and mix thoroughly to obtain the first mixture; Second, adjust the pH of the first mixture to 7 to 8, add a portion of emulsifier and stir to obtain the second mixture; Third, add white oil and the remaining emulsifier to the second mixture, stir the solution thoroughly, shear it, add the required amount of initiator, introduce inert gas, and under an inert gas atmosphere, heat to 40°C to 80°C and react for 8 to 15 hours to obtain a high-strength and high-toughness polymer microsphere plugging agent for oil-based drilling fluid.

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