Preparation method of a plugging agent for shale and coal and a water-based drilling fluid

Abstract

The present invention relates to the technical field of drilling fluids, and particularly relates to a preparation method of a plugging agent for shale and coal rock and an aqueous drilling fluid, which are used to solve the problems that the existing plugging agents have poor plugging effects on the micro-cracks of shale and coal rock and poor stability in high-temperature environments; after adding the plugging agent for shale and coal rock to the aqueous drilling fluid, by the synergistic effect of the high-temperature-resistant nano-polymer emulsion and the silane-modified nano-montmorillonite, it can enter the micro-cracks of shale and coal rock and intertwine with each other to jointly construct a three-dimensional plugging network structure, effectively plug the cracks, effectively prevent the invasion of drilling fluid filtrate into the formation, and has excellent high-temperature resistance, so that its structure is stable in high-temperature environments, and it can still maintain good plugging performance under harsh conditions such as high temperature and high pressure and drilling fluid scouring, meet the high-temperature drilling requirements for the exploitation of deep shale gas and coalbed methane, and help improve the safety and efficiency of drilling operations.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling fluids, and specifically relates to a preparation method of a plugging agent for shale and coal rock and a water-based drilling fluid. Background Art

[0002] Drilling fluid is the blood of drilling, and plays roles such as cleaning the bottom of the well, carrying cuttings, balancing formation pressure, and maintaining wellbore stability during drilling operations. A water-based drilling fluid is a drilling liquid based on water, and has irreplaceable environmental protection advantages compared with traditional oil-based drilling fluids, and has gradually become the mainstream liquid in the drilling field.

[0003] With the large-scale development of unconventional oil and gas resources (such as shale gas and coalbed methane), many challenges are faced during the drilling process. Shale and coal rock have unique geological characteristics, with complex pore structures and abundant microfractures. During drilling operations, the filtrate of the water-based drilling fluid is extremely easy to invade the formation through these microfractures, resulting in hydration swelling, dispersion, and collapse of shale and coal rock, and further causing problems such as wellbore instability, seriously affecting drilling efficiency, increasing production costs, and possibly causing permanent damage to the reservoir. However, the existing plugging agents have poor plugging effects on microfractures, cannot effectively prevent filtrate invasion, and have poor stability in high-temperature environments, with a significant decline in plugging performance, affecting the overall performance of the drilling fluid.

[0004] Therefore, developing a preparation method of a plugging agent for shale and coal rock and a water-based drilling fluid that can stably play a role at high temperatures and have high plugging ability for microfractures in shale and coal rock is of great significance for improving the safety and efficiency of drilling operations. Summary of the Invention

[0005] In order to overcome the above technical problems, the purpose of the present invention is to provide a preparation method of a plugging agent for shale and coal rock and a water-based drilling fluid, which solves the problems that the existing plugging agents have poor plugging effects on microfractures in shale and coal rock, cannot effectively prevent filtrate invasion, have poor stability in high-temperature environments, and have a significant decline in plugging performance, affecting the overall performance of the drilling fluid.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A preparation method of a plugging agent for shale and coal rock, comprising the following steps:

[0008] Step 1: Weigh 10 parts of a high-temperature resistant nano-polymer emulsion, 0.5 - 3.5 parts of silane-modified nano-montmorillonite, and 0.5 - 2.0 parts of an emulsifier by weight, and set aside; the emulsifier is one of sodium dodecyl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, and fatty alcohol polyoxyethylene ether;

[0009] Step 2: Stir and mix the high-temperature resistant nano-polymer emulsion, silane-modified nano-montmorillonite, and emulsifier at a temperature of 25 °C and a stirring rate of 12,000 r / min for 60 min to obtain a plugging agent for shale and coal rock;

[0010] Among them, the high-temperature resistant nano-polymer emulsion is prepared by the following steps:

[0011] Step a1: Add 2-methoxy-4-vinylphenol, epichlorohydrin, and tetrabutylammonium bromide into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection and stir and react at a temperature of 25 - 30 °C and a stirring rate of 300 - 400 r / min for 10 - 20 min. Then raise the temperature to 95 - 100 °C and continue to stir and react for 4 - 5 h. After the reaction is completed, distill the reaction product under reduced pressure to remove the unreacted epichlorohydrin, and then cool it to room temperature to obtain Intermediate 1;

[0012] Step a2: Add Intermediate 1, ethylenediamine, and isopropanol into a three-necked flask equipped with a stirrer, a thermometer, a gas pipe, and a reflux condenser. Introduce nitrogen for protection and stir and react at a temperature of 25 - 30 °C and a stirring rate of 300 - 400 r / min for 20 - 30 min. Then adjust the pH to 8 - 9 with sodium hydroxide solution, and then raise the temperature to reflux and continue to stir and react for 20 - 30 h. After the reaction is completed, cool the reaction product to room temperature, and then rotary evaporate to remove the solvent to obtain Intermediate 2;

[0013] Step a3: Add Intermediate 2 and anhydrous methanol into a three-necked flask equipped with a stirrer, a thermometer, and a constant pressure dropping funnel. Stir and react at a temperature of 25 - 30 °C and a stirring rate of 300 - 400 r / min for 20 - 30 min. Then gradually add 1,3-propane sultone solution dropwise while stirring, control the dropping rate at 1 - 2 drops / s. After the dropping is completed, raise the temperature to 65 - 70 °C and continue to stir and react for 30 - 40 h. Then adjust the pH to 8 - 8.5 with sodium hydroxide solution, and then continue to stir and react for 5 - 10 min. After the reaction is completed, cool the reaction product to room temperature, then rotary evaporate to remove the solvent, then add it to anhydrous ether, and then vacuum filter. Rotary evaporate the filtrate to remove the solvent to obtain a diallyl sulfonate monomer;

[0014] Step a4: Add the diallyl sulfonate monomer, N,N-dimethylacrylamide, acrylic acid, sodium dodecyl sulfate, and deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection. Stir and react at a temperature of 25 - 30 °C and a stirring rate of 300 - 400 r / min for 15 - 25 min. Then add ammonium persulfate and continue to stir and react at a temperature of 70 - 75 °C for 6 - 8 h. After the reaction is completed, cool the reaction product to room temperature to obtain a high-temperature-resistant nano-polymer emulsion;

[0015] Among them, the silane-modified nano-montmorillonite is prepared by the following steps:

[0016] Step b1: Add montmorillonite and deionized water into a three-necked flask equipped with a stirrer and a thermometer. Stir and react at a temperature of 25 - 30 °C and a stirring rate of 300 - 400 r / min for 5 - 6 h. Then perform ultrasonic treatment for 20 - 30 min under the condition of an ultrasonic power of 400 - 500 W. Then add octadecyltrimethylammonium bromide and raise the temperature to 55 - 60 °C and continue to stir and react for 4 - 5 h. After the reaction is completed, cool the reaction product to room temperature, then centrifuge. Wash the precipitate with absolute ethanol and distilled water 3 - 5 times respectively. Then place it in a vacuum drying oven and dry at a temperature of 40 - 45 °C for 2 - 3 h to obtain nano-modified montmorillonite;

[0017] Step b2: Add the nano-modified montmorillonite and an ethanol solution into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser connected to a gas pipe. Introduce nitrogen for protection. Stir and react at a temperature of 25 - 30 °C and a stirring rate of 300 - 400 r / min for 20 - 30 min. Then add γ-glycidoxypropyltrimethoxysilane and raise the temperature to 55 - 60 °C and continue to stir and react for 10 - 15 h. After the reaction is completed, cool the reaction product to room temperature, then centrifuge. Wash the precipitate with absolute ethanol 3 - 5 times. Then place it in a vacuum drying oven and dry at a temperature of 80 - 85 °C for 6 - 7 h to obtain silane-modified nano-montmorillonite.

[0018] As a further scheme of the present invention: The dosage ratio of the 2-methoxy-4-vinylphenol, epichlorohydrin, and tetrabutylammonium bromide in step a1 is 10 g: 40 - 50 g: 1.2 - 1.8 g.

[0019] As a further scheme of the present invention: The dosage ratio of the intermediate 1, ethylenediamine, and isopropanol in step a2 is 10 mmol: 21 - 23 mmol: 60 - 70 mL.

[0020] As a further scheme of the present invention: The mass fraction of the sodium hydroxide solution in step a2 is 15 - 25%.

[0021] As a further solution of the present invention: the dosage ratio of the intermediate 2, anhydrous methanol and 1,3 - propane sultone solution in step a3 is 10 mmol: 40 - 50 mL: 35 - 40 mL.

[0022] As a further solution of the present invention: the 1,3 - propane sultone solution in step a3 is a solution formed by dissolving 1,3 - propane sultone in anhydrous methanol according to a ratio of 10 mmol: 15 mL; the mass fraction of the sodium hydroxide solution is 15 - 25%.

[0023] As a further solution of the present invention: the dosage ratio of the dienyl sulfonate monomer, N,N - dimethylacrylamide, acrylic acid, sodium dodecyl sulfate, deionized water and ammonium persulfate in step a4 is 8 - 10 g: 3 - 4 g: 2 - 3 g: 0.6 - 1.0 g: 70 - 80 mL: 0.1 - 0.3 g.

[0024] As a further solution of the present invention: the dosage ratio of the montmorillonite, deionized water and octadecyltrimethylammonium bromide in step b1 is 2 g: 70 - 80 mL: 0.1 - 0.2 g.

[0025] As a further solution of the present invention: the dosage ratio of the nano - modified montmorillonite, ethanol solution and γ - glycidoxypropyltrimethoxysilane in step b2 is 1 g: 50 - 60 mL: 1.5 - 5.5 mL.

[0026] As a further solution of the present invention: the volume fraction of the ethanol solution in step b2 is 85 - 90%.

[0027] As a further solution of the present invention: an aqueous drilling fluid comprises the following raw materials:

[0028] Base slurry, PAC - LV viscosifier, JHJS - 150 filtration reducer, JNJS - 220 high - temperature resistant filtration reducer, JXA - 1 inhibitor, plugging agent for shale and coal rock, sodium hydroxide, quicklime, RH - 220 lubricant, potassium chloride, barite powder and fresh water.

[0029] As a further solution of the present invention: the preparation method of the aqueous drilling fluid comprises the following steps:

[0030] Step 1: Prepare the base slurry: Weigh 93.64 g of clear water, 6 g of raw ore soil, and 0.36 g of anhydrous sodium carbonate according to the dosage ratio of clear water, raw ore soil, and anhydrous sodium carbonate. Then add anhydrous sodium carbonate to the clear water and stir and mix for 30 min at a temperature of 25°C and a stirring rate of 1000 r / min. After that, add the raw ore soil and continue to stir and react for 30 min. Then let it stand for 24 h to obtain the base slurry;

[0031] Step 2: Prepare the drilling fluid:

[0032] Step S21: Add 120 g of the base slurry to 233 mL of clear water and stir and mix for 5 min at a temperature of 25°C and a stirring rate of 12000 r / min to obtain a mixed slurry;

[0033] Step S22: Add 0.6 g of PAC-LV thickener to the mixed slurry and stir and mix for 5 min at a temperature of 25°C and a stirring rate of 4000 r / min. Then add 6 g of JHJS-150 filtration reducer and continue to stir and mix for 5 min. Then add 3 g of JNJS-220 high-temperature resistant filtration reducer and continue to stir and mix for 5 min. Then add 1 g of JXA-1 inhibitor and continue to stir and mix for 5 min. Then add 1 g of plugging agent for shale and coal rock and continue to stir and mix for 5 min. Then add 0.2 g of sodium hydroxide and 7 g of potassium chloride and continue to stir and mix for 5 min. Then add 0.5 g of quicklime and continue to stir and mix for 5 min. Then add 3.5 g of RH-220 lubricant and continue to stir and mix for 5 min. Then add barite powder to increase the density to 1.8 g / cm 3 , and then stir and mix for 20 min at a temperature of 25°C and a stirring rate of 12000 r / min to obtain the drilling fluid.

[0034] Advantages of the present invention:

[0035] A preparation method of a plugging agent for shale and coal and a water-based drilling fluid of the present invention, by mixing a base slurry, a PAC-LV viscosifier, a JHJS-150 filtration reducer, a JNJS-220 high-temperature-resistant filtration reducer, a JXA-1 inhibitor, a plugging agent for shale and coal, sodium hydroxide, quicklime, an RH-220 lubricant, potassium chloride, barite powder and clear water, a water-based drilling fluid is obtained; this water-based drilling fluid uses water as the continuous phase. Compared with oil-based drilling fluids, it is more environmentally friendly and has a lower cost, meeting the requirements of green mining and economic benefits. After adding a plugging agent for shale and coal to it, through the synergistic effect of a high-temperature-resistant nano-polymer emulsion and silane-modified nano-montmorillonite, it can enter the micro-fractures of shale and coal and intertwine with each other to jointly construct a three-dimensional plugging network structure, effectively plug the fractures, effectively prevent the invasion of drilling fluid filtrate into the formation, and has excellent high-temperature resistance, making its structure stable in high-temperature environments, so that it can still maintain good plugging performance under harsh conditions such as high temperature and high pressure and drilling fluid scouring, meeting the high-temperature drilling requirements for the exploitation of deep shale gas and coalbed methane, and helping to improve the safety and efficiency of drilling operations.

[0036] In the process of preparing the plugging agent for shale and coal, a high-temperature-resistant nano-polymer emulsion was first prepared. First, 2-methoxy-4-vinylphenol and epichlorohydrin were reacted. The hydroxyl group on 2-methoxy-4-vinylphenol underwent a ring-opening reaction with epichlorohydrin, thereby introducing a chlorine atom to obtain intermediate 1. Then, intermediate 1 and ethylenediamine were reacted. The chlorine atom on intermediate 1 and the amino group on ethylenediamine reacted to introduce the -NH- bond and form two alkenyl groups simultaneously to obtain intermediate 2. Then, using intermediate 2 and 1,3-propane sultone, the -NH- on intermediate 2 underwent a ring-opening reaction with 1,3-propane sultone, thereby forming a sodium sulfonate group to obtain a diene-based sulfonate monomer. Finally, the diene-based sulfonate monomer, N,N-dimethylacrylamide, and acrylic acid were polymerized to form a polymer to obtain a high-temperature-resistant nano-polymer emulsion; the molecular structure of this high-temperature-resistant nano-polymer emulsion contains a large number of benzene rings and sodium sulfonate groups, endowing it with high-temperature stability, and using the two alkenyl groups on the diene-based sulfonate monomer to enhance the cross-linking degree of the polymer. The presence of sodium sulfonate groups and carboxylic acid groups enhances the electrostatic adsorption of polymer microspheres. Therefore, after adding the high-temperature-resistant nano-polymer emulsion to the drilling fluid, it can easily enter the micro-fractures of shale and coal, and through physical adsorption and chemical reactions of active groups with the fracture surface, tightly adhere to the fracture wall, and at the same time accumulate and fill in the fractures to form an effective blockage, preventing further invasion of drilling fluid filtrate into the formation, thereby playing a role in plugging micro-fractures.

[0037] In the process of preparing the plugging agent for shale and coal rock, a silane-modified nano-montmorillonite was also prepared. First, ultrasonic treatment was used to exfoliate the montmorillonite, reducing the particle size while producing a nano-modified montmorillonite with a layered structure. Then, γ-glycidoxypropyltrimethoxysilane was used to treat the nano-modified montmorillonite. The siloxane on γ-glycidoxypropyltrimethoxysilane hydrolyzed to form silanol, which could effectively graft onto the surface of the nano-modified montmorillonite, and a large number of epoxy groups were introduced at the same time, obtaining the silane-modified nano-montmorillonite. After modification, the silane-modified nano-montmorillonite not only changed the surface properties of the montmorillonite, making it change from hydrophilic to partially lipophilic, reducing its interaction with water and inhibiting the hydration swelling of the montmorillonite, but also the organosilicon groups formed a certain steric hindrance on its surface, enhancing the structural stability of the montmorillonite. After entering the micro-crack surface of shale and coal rock, it can be oriented on the crack surface to form a dense and flexible plugging film, which can effectively block the penetration of drilling fluid filtrate. At the same time, the epoxy groups and organosilicon groups are connected to the crack surface in the form of chemical bonds, enhancing the adhesion between the montmorillonite and the crack surface, making the plugging film more firm and not easily washed away by the filtrate, further improving the plugging effect. Detailed implementation mode

[0038] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0039] Example 1:

[0040] This example is a preparation method of an aqueous drilling fluid, including the following steps:

[0041] Step S1: Add 10 g of 2-methoxy-4-vinylphenol, 40 g of epichlorohydrin, and 1.2 g of tetrabutylammonium bromide into a three-necked flask equipped with a stirrer, a thermometer, and a gas guide tube, introduce nitrogen protection, stir and react for 10 min under the conditions of a temperature of 25 °C and a stirring rate of 300 r / min, then continue to stir and react for 4 h under the condition of heating to 95 °C. After the reaction, the reaction product is subjected to vacuum distillation to remove the unreacted epichlorohydrin, and then cooled to room temperature to obtain intermediate 1;

[0042] Step S2: Add 10 mmol of intermediate 1, 21 mmol of ethylenediamine, and 60 mL of isopropanol into a three-necked flask equipped with a stirrer, a thermometer, a gas pipe, and a reflux condenser. Introduce nitrogen for protection. Stir and react for 20 min under the conditions of a temperature of 25°C and a stirring rate of 300 r / min. Then adjust the pH to 8 with a 15% sodium hydroxide solution. Then raise the temperature to reflux and continue stirring and reacting for 20 h. After the reaction is completed, cool the reaction product to room temperature. Then rotate the evaporator to remove the solvent to obtain intermediate 2;

[0043] Step S3: Add 10 mmol of intermediate 2 and 40 mL of anhydrous methanol into a three-necked flask equipped with a stirrer, a thermometer, and a constant-pressure dropping funnel. Stir and react for 20 min under the conditions of a temperature of 25°C and a stirring rate of 300 r / min. Then, while stirring, gradually add dropwise a 1,3-propanesultone solution formed by dissolving 35 mL of 1,3-propanesultone in 15 mL of anhydrous methanol according to 10 mmol:15 mL. Control the dropping rate to be 1 drop / s. After the dropping is completed, raise the temperature to 65°C and continue stirring and reacting for 30 h. Then adjust the pH to 8 with a 15% sodium hydroxide solution. Then continue stirring and reacting for 5 min. After the reaction is completed, cool the reaction product to room temperature. Then rotate the evaporator to remove the solvent. Then add it to anhydrous ether. Then perform vacuum filtration. Rotate the evaporator to remove the solvent from the filtrate to obtain the diallyl sulfonate monomer;

[0044] Step S4: Add 8 g of the diallyl sulfonate monomer, 3 g of N,N-dimethylacrylamide, 2 g of acrylic acid, 0.6 g of sodium dodecyl sulfate, and 70 mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection. Stir and react for 15 min under the conditions of a temperature of 25°C and a stirring rate of 300 r / min. Then add 0.1 g of ammonium persulfate and raise the temperature to 70°C and continue stirring and reacting for 6 h. After the reaction is completed, cool the reaction product to room temperature to obtain the high-temperature-resistant nano-polymer emulsion;

[0045] Step S5: Add 2 g of montmorillonite and 70 mL of deionized water into a three-necked flask equipped with a stirrer and a thermometer. Stir and react for 5 h under the conditions of a temperature of 25°C and a stirring rate of 300 r / min. Then perform ultrasonic treatment for 20 min under the condition of an ultrasonic power of 400 W. Then add 0.1 g of octadecyltrimethylammonium bromide and raise the temperature to 55°C and continue stirring and reacting for 4 h. After the reaction is completed, cool the reaction product to room temperature. Then centrifuge, wash the precipitate with anhydrous ethanol and distilled water three times in sequence. Then place it in a vacuum drying oven and dry it at a temperature of 40°C for 2 h to obtain the nano-modified montmorillonite;

[0046] Step S6: Add 1 g of nano-modified montmorillonite and 50 mL of ethanol solution with a volume fraction of 85% into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser with a gas guide tube. Protect with nitrogen. Stir and react for 20 min under the conditions of a temperature of 25 °C and a stirring rate of 300 r / min. Then add 1.5 mL of γ-glycidoxypropyltrimethoxysilane and continue to stir and react for 10 h under the condition of heating to 55 °C. After the reaction is completed, cool the reaction product to room temperature, then centrifuge, wash the precipitate with absolute ethanol three times, and then place it in a vacuum drying oven and dry for 6 h at a temperature of 80 °C to obtain silane-modified nano-montmorillonite;

[0047] Step S7: Weigh 10 parts of high-temperature-resistant nano-polymer emulsion, 0.5 part of silane-modified nano-montmorillonite, and 0.5 part of emulsifier by weight and set aside; the emulsifier is sodium dodecyl sulfate;

[0048] Step S8: Stir and mix the high-temperature-resistant nano-polymer emulsion, silane-modified nano-montmorillonite, and emulsifier at a temperature of 25 °C and a stirring rate of 12000 r / min for 60 min to obtain a plugging agent for shale and coal rock;

[0049] Step S9. Prepare the base slurry: Weigh clear water, raw ore soil, and anhydrous sodium carbonate according to the dosage ratio of 93.64 g: 6 g: 0.36 g. Then add anhydrous sodium carbonate to the clear water and stir and mix for 30 min under the conditions of a temperature of 25 °C and a stirring rate of 1000 r / min. Then add the raw ore soil and continue to stir and react for 30 min. Then let it stand for 24 h to obtain the base slurry;

[0050] Step S10. Prepare the drilling fluid: Add 120 g of the base slurry to 233 mL of clear water and stir and mix for 5 min under the conditions of a temperature of 25 °C and a stirring rate of 12000 r / min to obtain a mixed slurry; add 0.6 g of PAC-LV thickener to the mixed slurry and stir and mix for 5 min under the conditions of a temperature of 25 °C and a stirring rate of 4000 r / min. Then add 6 g of JHJS-150 filtration reducer and continue to stir and mix for 5 min. Then add 3 g of JNJS-220 high-temperature-resistant filtration reducer and continue to stir and mix for 5 min. Then add 1 g of JXA-1 inhibitor and continue to stir and mix for 5 min. Then add 1 g of the plugging agent for shale and coal rock and continue to stir and mix for 5 min. Then add 0.2 g of sodium hydroxide and 7 g of potassium chloride and continue to stir and mix for 5 min. Then add 0.5 g of quicklime and continue to stir and mix for 5 min. Then add 3.5 g of RH-220 lubricant and continue to stir and mix for 5 min. Then add barite powder to increase the density to 1.8 g / cm 3, and then stirred and mixed for 20 min under the conditions of a temperature of 25 °C and a stirring rate of 12,000 r / min to obtain a drilling fluid.

[0051] Example 2:

[0052] This example is a preparation method of an aqueous drilling fluid, which includes the following steps:

[0053] Step S1: Add 10 g of 2-methoxy-4-vinylphenol, 45 g of epichlorohydrin, and 1.5 g of tetrabutylammonium bromide into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection, and stir and react for 15 min under the conditions of a temperature of 28 °C and a stirring rate of 350 r / min. Then, continue to stir and react for 4.5 h under the condition of heating to 98 °C. After the reaction is completed, distill the reaction product under reduced pressure to remove the unreacted epichlorohydrin, and then cool it to room temperature to obtain Intermediate 1;

[0054] Step S2: Add 10 mmol of Intermediate 1, 22 mmol of ethylenediamine, and 65 mL of isopropanol into a three-necked flask equipped with a stirrer, a thermometer, a gas pipe, and a reflux condenser. Introduce nitrogen for protection, and stir and react for 25 min under the conditions of a temperature of 28 °C and a stirring rate of 350 r / min. Then, adjust the pH to 8.5 with a 20% sodium hydroxide solution by mass fraction, and then continue to stir and react for 25 h under the condition of heating to reflux. After the reaction is completed, cool the reaction product to room temperature, and then remove the solvent by rotary evaporation to obtain Intermediate 2;

[0055] Step S3: Add 10 mmol of Intermediate 2 and 45 mL of anhydrous methanol into a three-necked flask equipped with a stirrer, a thermometer, and a constant-pressure dropping funnel. Stir and react for 25 min under the conditions of a temperature of 28 °C and a stirring rate of 350 r / min. Then, while stirring, gradually add dropwise a 1,3-propane sultone solution formed by dissolving 38 mL of 1,3-propane sultone in 15 mL of anhydrous methanol according to 10 mmol:15 mL, control the dropping rate to be 1 drop / s. After the dropping is completed, continue to stir and react for 35 h under the condition of heating to 68 °C. Then, adjust the pH to 8 with a 20% sodium hydroxide solution by mass fraction, and then continue to stir and react for 8 min. After the reaction is completed, cool the reaction product to room temperature, then remove the solvent by rotary evaporation, then add it to anhydrous ether, and then perform vacuum filtration. Rotate and evaporate the filtrate to remove the solvent to obtain a diallyl sulfonate monomer;

[0056] Step S4: Add 9 g of diallyl sulfonate monomer, 3.5 g of N,N-dimethylacrylamide, 2.5 g of acrylic acid, 0.8 g of sodium dodecyl sulfate, and 75 mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection. Stir and react for 20 min at a temperature of 28 °C and a stirring rate of 350 r / min. Then add 0.2 g of ammonium persulfate and continue to stir and react for 7 h under the condition of heating to 72 °C. After the reaction is completed, cool the reaction product to room temperature to obtain a high-temperature-resistant nano-polymer emulsion;

[0057] Step S5: Add 2 g of montmorillonite and 75 mL of deionized water into a three-necked flask equipped with a stirrer and a thermometer. Stir and react for 5.5 h at a temperature of 28 °C and a stirring rate of 350 r / min. Then perform ultrasonic treatment for 25 min under the condition of an ultrasonic power of 450 W. Then add 0.15 g of octadecyltrimethylammonium bromide and stir and react for 4.5 h under the condition of heating to 58 °C. After the reaction is completed, cool the reaction product to room temperature, then centrifuge, wash the precipitate with absolute ethanol and distilled water 4 times successively, and then place it in a vacuum drying oven and dry it for 2.5 h at a temperature of 42 °C to obtain nano-modified montmorillonite;

[0058] Step S6: Add 1 g of nano-modified montmorillonite and 55 mL of an ethanol solution with a volume fraction of 88% into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser of a gas pipe. Introduce nitrogen for protection. Stir and react for 25 min at a temperature of 28 °C and a stirring rate of 350 r / min. Then add 3.5 mL of γ-glycidoxypropyltrimethoxysilane and continue to stir and react for 12 h under the condition of heating to 58 °C. After the reaction is completed, cool the reaction product to room temperature, then centrifuge, wash the precipitate with absolute ethanol 4 times, and then place it in a vacuum drying oven and dry it for 6.5 h at a temperature of 82 °C to obtain silane-modified nano-montmorillonite;

[0059] Step S7: Weigh 10 parts of the high-temperature-resistant nano-polymer emulsion, 2 parts of the silane-modified nano-montmorillonite, and 1.2 parts of the emulsifier by weight for standby; the emulsifier is sodium lauryl polyoxyethylene ether sulfate;

[0060] Step S8: Stir and mix the high-temperature-resistant nano-polymer emulsion, the silane-modified nano-montmorillonite, and the emulsifier for 60 min at a temperature of 25 °C and a stirring rate of 12000 r / min to obtain a plugging agent for shale and coal rock;

[0061] Step S9: Prepare the base slurry: Weigh 93.64 g of clear water, 6 g of raw ore soil, and 0.36 g of anhydrous sodium carbonate according to the dosage ratio of clear water, raw ore soil, and anhydrous sodium carbonate. Then add anhydrous sodium carbonate to the clear water and stir and mix for 30 min at a temperature of 25°C and a stirring rate of 1000 r / min. Then add the raw ore soil and continue to stir and react for 30 min. Then let it stand for 24 h to obtain the base slurry;

[0062] Step S10: Prepare the drilling fluid: Add 120 g of the base slurry to 233 mL of clear water and stir and mix for 5 min at a temperature of 25°C and a stirring rate of 12000 r / min to obtain a mixed slurry; Add 0.6 g of PAC-LV thickener to the mixed slurry and stir and mix for 5 min at a temperature of 25°C and a stirring rate of 4000 r / min. Then add 6 g of JHJS-150 filtration reducer and continue to stir and mix for 5 min. Then add 3 g of JNJS-220 high-temperature resistant filtration reducer and continue to stir and mix for 5 min. Then add 1 g of JXA-1 inhibitor and continue to stir and mix for 5 min. Then add 1 g of plugging agent for shale and coal rock and continue to stir and mix for 5 min. Then add 0.2 g of sodium hydroxide and 7 g of potassium chloride and continue to stir and mix for 5 min. Then add 0.5 g of quicklime and continue to stir and mix for 5 min. Then add 3.5 g of RH-220 lubricant and continue to stir and mix for 5 min. Then add barite powder to increase the density to 1.8 g / cm 3 , and then stir and mix for 20 min at a temperature of 25°C and a stirring rate of 12000 r / min to obtain the drilling fluid.

[0063] Example 3:

[0064] This example is a preparation method of a water-based drilling fluid, including the following steps:

[0065] Step S1: Add 10 g of 2-methoxy-4-vinylphenol, 50 g of epichlorohydrin, and 1.8 g of tetrabutylammonium bromide to a three-necked flask equipped with a stirrer, a thermometer, and a gas guide tube. Introduce nitrogen protection and stir and react for 20 min at a temperature of 30°C and a stirring rate of 400 r / min. Then raise the temperature to 100°C and continue to stir and react for 5 h. After the reaction is completed, distill off the unreacted epichlorohydrin under reduced pressure for the reaction product, and then cool to room temperature to obtain Intermediate 1;

[0066] Step S2: Add 10 mmol of intermediate 1, 23 mmol of ethylenediamine, and 70 mL of isopropanol into a three-necked flask equipped with a stirrer, a thermometer, a gas pipe, and a reflux condenser. Introduce nitrogen for protection. Stir and react for 30 min under the conditions of a temperature of 30 °C and a stirring rate of 400 r / min. Then adjust the pH to 9 with a 25% sodium hydroxide solution. Then raise the temperature to reflux and continue stirring and reacting for 30 h. After the reaction is completed, cool the reaction product to room temperature. Then rotate and evaporate to remove the solvent to obtain intermediate 2;

[0067] Step S3: Add 10 mmol of intermediate 2 and 50 mL of anhydrous methanol into a three-necked flask equipped with a stirrer, a thermometer, and a constant-pressure dropping funnel. Stir and react for 30 min under the conditions of a temperature of 30 °C and a stirring rate of 400 r / min. Then, while stirring, gradually add dropwise a 1,3-propanesultone solution formed by dissolving 40 mL of 1,3-propanesultone in 15 mL of anhydrous methanol according to 10 mmol:15 mL. Control the dropping rate at 2 drops / s. After the dropping is completed, raise the temperature to 70 °C and continue stirring and reacting for 40 h. Then adjust the pH to 8.5 with a 25% sodium hydroxide solution. Then continue stirring and reacting for 10 min. After the reaction is completed, cool the reaction product to room temperature. Then rotate and evaporate to remove the solvent. Then add it into anhydrous ether. Then perform vacuum filtration. Rotate and evaporate the filtrate to remove the solvent to obtain the diallyl sulfonate monomer;

[0068] Step S4: Add 10 g of the diallyl sulfonate monomer, 4 g of N,N-dimethylacrylamide, 3 g of acrylic acid, 1.0 g of sodium dodecyl sulfate, and 80 mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection. Stir and react for 25 min under the conditions of a temperature of 30 °C and a stirring rate of 400 r / min. Then add 0.3 g of ammonium persulfate and raise the temperature to 75 °C and continue stirring and reacting for 8 h. After the reaction is completed, cool the reaction product to room temperature to obtain the high-temperature-resistant nano polymer emulsion;

[0069] Step S5: Add 2 g of montmorillonite and 80 mL of deionized water into a three-necked flask equipped with a stirrer and a thermometer. Stir and react for 6 h under the conditions of a temperature of 30 °C and a stirring rate of 400 r / min. Then perform ultrasonic treatment for 30 min under the condition of an ultrasonic power of 500 W. Then add 0.2 g of octadecyltrimethylammonium bromide and raise the temperature to 60 °C and continue stirring and reacting for 5 h. After the reaction is completed, cool the reaction product to room temperature. Then centrifuge. Wash the precipitate with anhydrous ethanol and distilled water 5 times in sequence. Then place it in a vacuum drying oven and dry it at a temperature of 45 °C for 3 h to obtain the nano-modified montmorillonite;

[0070] Step S6: Add 1 g of nano-modified montmorillonite and 60 mL of ethanol solution with a volume fraction of 90% into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser with a gas guide tube. Protect with nitrogen. Stir and react for 30 min at a temperature of 30 °C and a stirring rate of 400 r / min. Then add 5.5 mL of γ-glycidoxypropyltrimethoxysilane and continue to stir and react for 15 h under the condition of heating to 60 °C. After the reaction is completed, cool the reaction product to room temperature, then centrifuge. Wash the precipitate 5 times with anhydrous ethanol, and then place it in a vacuum drying oven and dry for 7 h at a temperature of 85 °C to obtain silane-modified nano-montmorillonite;

[0071] Step S7: Weigh 10 parts of high-temperature-resistant nano-polymer emulsion, 3.5 parts of silane-modified nano-montmorillonite, and 2.0 parts of emulsifier by weight and set aside; the emulsifier is fatty alcohol polyoxyethylene ether;

[0072] Step S8: Stir and mix the high-temperature-resistant nano-polymer emulsion, silane-modified nano-montmorillonite, and emulsifier at a temperature of 25 °C and a stirring rate of 12000 r / min for 60 min to obtain a plugging agent for shale and coal rock;

[0073] Step S9: Prepare the base slurry: Weigh clear water, raw ore soil, and anhydrous sodium carbonate according to the dosage ratio of 93.64 g: 6 g: 0.36 g. Then add anhydrous sodium carbonate to the clear water and stir and mix for 30 min at a temperature of 25 °C and a stirring rate of 1000 r / min. Then add the raw ore soil and continue to stir and react for 30 min. Then let it stand for 24 h to obtain the base slurry;

[0074] Step S10: Prepare the drilling fluid: Add 120 g of the base slurry to 233 mL of clear water and stir and mix for 5 min at a temperature of 25 °C and a stirring rate of 12000 r / min to obtain a mixed slurry; Add 0.6 g of PAC-LV thickener to the mixed slurry and stir and mix for 5 min at a temperature of 25 °C and a stirring rate of 4000 r / min. Then add 6 g of JHJS-150 filtration reducer and continue to stir and mix for 5 min. Then add 3 g of JNJS-220 high-temperature-resistant filtration reducer and continue to stir and mix for 5 min. Then add 1 g of JXA-1 inhibitor and continue to stir and mix for 5 min. Then add 1 g of the plugging agent for shale and coal rock and continue to stir and mix for 5 min. Then add 0.2 g of sodium hydroxide and 7 g of potassium chloride and continue to stir and mix for 5 min. Then add 0.5 g of quicklime and continue to stir and mix for 5 min. Then add 3.5 g of RH-220 lubricant and continue to stir and mix for 5 min. Then add barite powder to increase the density to 1.8 g / cm 3, and then stirred and mixed for 20 min under the conditions of a temperature of 25 °C and a stirring rate of 12,000 r / min to obtain a drilling fluid.

[0075] Comparative Example 1:

[0076] This comparative example is a preparation method of an aqueous drilling fluid, including the following steps:

[0077] Step S1: Add 4 g of N,N-dimethylacrylamide, 3 g of acrylic acid, 1.0 g of sodium dodecyl sulfate, and 80 mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a gas guide tube, introduce nitrogen protection, and stir and react for 25 min under the conditions of a temperature of 30 °C and a stirring rate of 400 r / min. Then add 0.3 g of ammonium persulfate and continue to stir and react for 8 h under the condition of heating to 75 °C. After the reaction is completed, cool the reaction product to room temperature to obtain a nano-polymer emulsion;

[0078] Step S2: Prepare the base slurry: Weigh 93.64 g of clear water, 6 g of raw ore soil, and 0.36 g of anhydrous sodium carbonate according to the dosage ratio of clear water, raw ore soil, and anhydrous sodium carbonate. Then add anhydrous sodium carbonate into the clear water and stir and mix for 30 min under the conditions of a temperature of 25 °C and a stirring rate of 1000 r / min. Then add the raw ore soil and continue to stir and react for 30 min. Then let it stand for 24 h to obtain the base slurry;

[0079] Step S3: Prepare the drilling fluid: Add 120 g of the base slurry into 233 mL of clear water and stir and mix for 5 min under the conditions of a temperature of 25 °C and a stirring rate of 12,000 r / min to obtain a mixed slurry; Add 0.6 g of PAC-LV thickening agent into the mixed slurry and stir and mix for 5 min under the conditions of a temperature of 25 °C and a stirring rate of 4000 r / min. Then add 6 g of JHJS-150 filtration reducer and continue to stir and mix for 5 min. Then add 3 g of JNJS-220 high-temperature resistant filtration reducer and continue to stir and mix for 5 min. Then add 1 g of JXA-1 inhibitor and continue to stir and mix for 5 min. Then add 1 g of the nano-polymer emulsion and continue to stir and mix for 5 min. Then add 0.2 g of sodium hydroxide and 7 g of potassium chloride and continue to stir and mix for 5 min. Then add 0.5 g of quicklime and continue to stir and mix for 5 min. Then add 3.5 g of RH-220 lubricant and continue to stir and mix for 5 min. Then add barite powder to increase the density to 1.8 g / cm 3 , and then stirred and mixed for 20 min under the conditions of a temperature of 25 °C and a stirring rate of 12,000 r / min to obtain a drilling fluid.

[0080] Comparative Example 2:

[0081] This comparative example is a preparation method of an aqueous drilling fluid, including the following steps:

[0082] Step S1: Add 10 g of 2-methoxy-4-vinylphenol, 50 g of epichlorohydrin, and 1.8 g of tetrabutylammonium bromide into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection, stir and react for 20 min under the conditions of a temperature of 30 °C and a stirring rate of 400 r / min. Then, continue to stir and react for 5 h under the condition of raising the temperature to 100 °C. After the reaction is completed, distill the reaction product under reduced pressure to remove the unreacted epichlorohydrin, and then cool it to room temperature to obtain Intermediate 1;

[0083] Step S2: Add 10 mmol of Intermediate 1, 23 mmol of ethylenediamine, and 70 mL of isopropanol into a three-necked flask equipped with a stirrer, a thermometer, a gas pipe, and a reflux condenser. Introduce nitrogen for protection, stir and react for 30 min under the conditions of a temperature of 30 °C and a stirring rate of 400 r / min. Then, adjust the pH to 9 with a 25% sodium hydroxide solution, and then continue to stir and react for 30 h under the condition of raising the temperature to reflux. After the reaction is completed, cool the reaction product to room temperature, and then remove the solvent by rotary evaporation to obtain Intermediate 2;

[0084] Step S3: Add 10 mmol of Intermediate 2 and 50 mL of anhydrous methanol into a three-necked flask equipped with a stirrer, a thermometer, and a constant-pressure dropping funnel. Stir and react for 30 min under the conditions of a temperature of 30 °C and a stirring rate of 400 r / min. Then, while stirring, gradually dropwise add a 1,3-propane sultone solution formed by dissolving 40 mL of 1,3-propane sultone in 15 mL of anhydrous methanol according to 10 mmol:15 mL, control the dropping rate at 2 drops / s. After the dropping is completed, continue to stir and react for 40 h under the condition of raising the temperature to 70 °C. Then, adjust the pH to 8.5 with a 25% sodium hydroxide solution, and then continue to stir and react for 10 min. After the reaction is completed, cool the reaction product to room temperature, then remove the solvent by rotary evaporation, then add it to anhydrous ether, and then perform vacuum filtration. Rotate and evaporate the filtrate to remove the solvent to obtain a diallyl sulfonate monomer;

[0085] Step S4: Add 10 g of the diallyl sulfonate monomer, 4 g of N,N-dimethylacrylamide, 3 g of acrylic acid, 1.0 g of sodium dodecyl sulfate, and 80 mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection, stir and react for 25 min under the conditions of a temperature of 30 °C and a stirring rate of 400 r / min. Then, add 0.3 g of ammonium persulfate and continue to stir and react for 8 h under the condition of raising the temperature to 75 °C. After the reaction is completed, cool the reaction product to room temperature to obtain a high-temperature-resistant nano polymer emulsion;

[0086] Step S5: Prepare the base slurry: Weigh 93.64 g of clear water, 6 g of raw ore soil, and 0.36 g of anhydrous sodium carbonate according to the dosage ratio of clear water, raw ore soil, and anhydrous sodium carbonate. Then add anhydrous sodium carbonate to the clear water, and stir and mix for 30 min under the conditions of a temperature of 25°C and a stirring rate of 1000 r / min. Then add the raw ore soil and continue to stir and react for 30 min. After that, let it stand for 24 h to obtain the base slurry;

[0087] Step S6: Prepare the drilling fluid: Add 120 g of the base slurry to 233 mL of clear water, and stir and mix for 5 min under the conditions of a temperature of 25°C and a stirring rate of 12000 r / min to obtain a mixed slurry; Add 0.6 g of PAC-LV thickening agent to the mixed slurry, and stir and mix for 5 min under the conditions of a temperature of 25°C and a stirring rate of 4000 r / min. Then add 6 g of JHJS-150 filtration reducer and continue to stir and mix for 5 min. Then add 3 g of JNJS-220 high-temperature resistant filtration reducer and continue to stir and mix for 5 min. Then add 1 g of JXA-1 inhibitor and continue to stir and mix for 5 min. Then add 1 g of high-temperature resistant nano-polymer emulsion and continue to stir and mix for 5 min. Then add 0.2 g of sodium hydroxide and 7 g of potassium chloride and continue to stir and mix for 5 min. Then add 0.5 g of quicklime and continue to stir and mix for 5 min. Then add 3.5 g of RH-220 lubricant and continue to stir and mix for 5 min. Then add barite powder to increase the density to 1.8 g / cm 3 , and then stir and mix for 20 min under the conditions of a temperature of 25°C and a stirring rate of 12000 r / min to obtain the drilling fluid.

[0088] Comparative Example 3:

[0089] This comparative example is a preparation method of a water-based drilling fluid, including the following steps:

[0090] Step S1: Add 2 g of montmorillonite and 80 mL of deionized water to a three-necked flask equipped with a stirrer and a thermometer, stir and react for 6 h under the conditions of a temperature of 30°C and a stirring rate of 400 r / min. Then carry out ultrasonic treatment for 30 min under the condition of an ultrasonic power of 500 W. Then add 0.2 g of octadecyltrimethylammonium bromide and raise the temperature to 60°C and stir and react for 5 h. After the reaction is completed, cool the reaction product to room temperature, and then centrifuge. Wash the precipitate with absolute ethanol and distilled water 5 times in sequence, and then place it in a vacuum drying oven and dry it at a temperature of 45°C for 3 h to obtain nano-modified montmorillonite;

[0091] Step S2: Add 1 g of nano-modified montmorillonite and 60 mL of ethanol solution with a volume fraction of 90% into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser with a gas guide tube. Protect with nitrogen. Stir and react for 30 min under the conditions of a temperature of 30 °C and a stirring rate of 400 r / min. Then add 5.5 mL of γ-glycidoxypropyltrimethoxysilane and continue to stir and react for 15 h under the condition of heating to 60 °C. After the reaction is completed, cool the reaction product to room temperature, then centrifuge, wash the precipitate with anhydrous ethanol 5 times, and then place it in a vacuum drying oven and dry for 7 h at a temperature of 85 °C to obtain silane-modified nano-montmorillonite;

[0092] Step S3: Prepare the base slurry: Weigh 93.64 g of clear water, 6 g of raw ore soil, and 0.36 g of anhydrous sodium carbonate according to the dosage ratio of clear water, raw ore soil, and anhydrous sodium carbonate of 93.64 g: 6 g: 0.36 g. Then add anhydrous sodium carbonate to the clear water and stir and mix for 30 min under the conditions of a temperature of 25 °C and a stirring rate of 1000 r / min. Then add the raw ore soil and continue to stir and react for 30 min, and then let it stand for 24 h to obtain the base slurry;

[0093] Step S4: Prepare the drilling fluid: Add 120 g of the base slurry to 233 mL of clear water and stir and mix for 5 min under the conditions of a temperature of 25 °C and a stirring rate of 12000 r / min to obtain a mixed slurry; Add 0.6 g of PAC-LV thickening agent to the mixed slurry and stir and mix for 5 min under the conditions of a temperature of 25 °C and a stirring rate of 4000 r / min. Then add 6 g of JHJS-150 filtration reducer and continue to stir and mix for 5 min. Then add 3 g of JNJS-220 high-temperature resistant filtration reducer and continue to stir and mix for 5 min. Then add 1 g of JXA-1 inhibitor and continue to stir and mix for 5 min. Then add 1 g of silane-modified nano-montmorillonite and continue to stir and mix for 5 min. Then add 0.2 g of sodium hydroxide and 7 g of potassium chloride and continue to stir and mix for 5 min. Then add 0.5 g of quicklime and continue to stir and mix for 5 min. Then add 3.5 g of RH-220 lubricant and continue to stir and mix for 5 min. Then add barite powder to increase the density to 1.8 g / cm 3 , and then stir and mix for 20 min under the conditions of a temperature of 25 °C and a stirring rate of 12000 r / min to obtain the drilling fluid.

[0094] Comparative Example 4:

[0095] This comparative example is a preparation method of an aqueous drilling fluid, including the following steps:

[0096] Step S1: Add 4 g of N,N-dimethylacrylamide, 3 g of acrylic acid, 1.0 g of sodium dodecyl sulfate, and 80 mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection. Stir and react for 25 min at a temperature of 30 °C and a stirring rate of 400 r / min. Then add 0.3 g of ammonium persulfate and continue to stir and react for 8 h under the condition of heating to 75 °C. After the reaction is completed, cool the reaction product to room temperature to obtain a nano-polymer emulsion;

[0097] Step S2: Add 2 g of montmorillonite and 80 mL of deionized water into a three-necked flask equipped with a stirrer and a thermometer. Stir and react for 6 h at a temperature of 30 °C and a stirring rate of 400 r / min. Then perform ultrasonic treatment for 30 min under the condition of an ultrasonic power of 500 W. Then add 0.2 g of octadecyltrimethylammonium bromide and stir and react for 5 h under the condition of heating to 60 °C. After the reaction is completed, cool the reaction product to room temperature, then centrifuge. Wash the precipitate with absolute ethanol and distilled water 5 times in sequence, and then place it in a vacuum drying oven and dry it for 3 h at a temperature of 45 °C to obtain nano-modified montmorillonite;

[0098] Step S3: Weigh 10 parts of nano-polymer emulsion, 3.5 parts of nano-modified montmorillonite, and 2.0 parts of emulsifier by weight and set aside; the emulsifier is fatty alcohol polyoxyethylene ether;

[0099] Step S4: Stir and mix the nano-polymer emulsion, nano-modified montmorillonite, and emulsifier at a temperature of 25 °C and a stirring rate of 12000 r / min for 60 min to obtain a plugging agent for shale and coal rock;

[0100] Step S5: Prepare the base slurry: Weigh clear water, raw ore soil, and anhydrous sodium carbonate according to the dosage ratio of 93.64 g: 6 g: 0.36 g. Then add anhydrous sodium carbonate into the clear water and stir and mix for 30 min at a temperature of 25 °C and a stirring rate of 1000 r / min. Then add the raw ore soil and continue to stir and react for 30 min. Then let it stand for 24 h to obtain the base slurry;

[0101] Step S6: Prepare drilling fluid: Add 120 g of base slurry to 233 mL of clear water, and stir and mix for 5 min under the conditions of a temperature of 25 °C and a stirring rate of 12,000 r / min to obtain a mixed slurry; add 0.6 g of PAC-LV thickener to the mixed slurry, and stir and mix for 5 min under the conditions of a temperature of 25 °C and a stirring rate of 4,000 r / min. Then add 6 g of JHJS-150 filtration reducer and continue to stir and mix for 5 min. Then add 3 g of JNJS-220 high-temperature resistant filtration reducer and continue to stir and mix for 5 min. Then add 1 g of JXA-1 inhibitor and continue to stir and mix for 5 min. Then add 1 g of plugging agent for shale and coal and continue to stir and mix for 5 min. Then add 0.2 g of sodium hydroxide and 7 g of potassium chloride and continue to stir and mix for 5 min. Then add 0.5 g of quicklime and continue to stir and mix for 5 min. Then add 3.5 g of RH-220 lubricant and continue to stir and mix for 5 min. Then add barite powder to increase the density to 1.8 g / cm 3 , and then stir and mix for 20 min under the conditions of a temperature of 25 °C and a stirring rate of 12,000 r / min to obtain the drilling fluid.

[0102] Comparative Example 5:

[0103] The preparation method of a water-based drilling fluid in this comparative example includes the following steps:

[0104] Step S1: Prepare base slurry: Weigh 93.64 g of clear water, 6 g of raw ore soil, and 0.36 g of anhydrous sodium carbonate according to the dosage ratio of clear water, raw ore soil, and anhydrous sodium carbonate. Then add anhydrous sodium carbonate to the clear water, and stir and mix for 30 min under the conditions of a temperature of 25 °C and a stirring rate of 1,000 r / min. Then add the raw ore soil and continue to stir and react for 30 min. Then let it stand for 24 h to obtain the base slurry;

[0105] Step S2: Prepare drilling fluid: Add 120 g of base slurry to 233 mL of clear water, and stir and mix for 5 min under the conditions of a temperature of 25 °C and a stirring rate of 12,000 r / min to obtain a mixed slurry; add 0.6 g of PAC-LV thickener to the mixed slurry, and stir and mix for 5 min under the conditions of a temperature of 25 °C and a stirring rate of 4,000 r / min. Then add 6 g of JHJS-150 filtration reducer and continue to stir and mix for 5 min. Then add 3 g of JNJS-220 high-temperature resistant filtration reducer and continue to stir and mix for 5 min. Then add 1 g of JXA-1 inhibitor and continue to stir and mix for 5 min. Then add 0.2 g of sodium hydroxide and 7 g of potassium chloride and continue to stir and mix for 5 min. Then add 0.5 g of quicklime and continue to stir and mix for 5 min. Then add 3.5 g of RH-220 lubricant and continue to stir and mix for 5 min. Then add barite powder to increase the density to 1.8 g / cm3 , and then stirred and mixed for 20 min under the conditions of a temperature of 25°C and a stirring rate of 12,000 r / min to obtain a drilling fluid.

[0106] The performances of the water-based drilling fluids of Examples 1-3 and Comparative Examples 1-5 were tested, and the test results are shown in the following table:

[0107]

[0108] Referring to the data in the above table, based on the comparison between Examples 1-3 and Comparative Examples 1-5, it can be known that the water-based drilling fluid of the present invention has excellent plugging performance, and its rheological properties change little after high-temperature thermal rolling aging, indicating its excellent high-temperature resistance, the cuttings rolling recovery rate is greater than 95%, and it has excellent inhibition performance.

[0109] Among them, the evaluation method of rheological properties is: at 50°C, the apparent viscosity and plastic viscosity before and after 16 h of high-temperature thermal rolling aging at 150°C were measured.

[0110] Among them, the evaluation method of plugging performance is: using a filter membrane with a pore size of 220 nm to test the high-temperature and high-pressure (180°C / 3.5 MPa) filtration loss of the water-based drilling fluid after 16 h of high-temperature thermal rolling aging at 180°C;

[0111] Among them, the evaluation method of inhibition performance is: the shale recovery rate is 10 g each of dry shale and coal rock cuttings with a size of 6-10 mesh. After mixing evenly, they were respectively immersed in 350 mL of deionized water, the water-based drilling fluids of Examples 1-3 and Comparative Examples 1-5. After 16 h of high-temperature aging at 150°C, the aged cuttings were filtered through a 40-mesh sieve and dehydrated in a vacuum drying oven at 110°C for 4 h. The dried cuttings were weighed, and the cuttings recovery rate was calculated (cuttings recovery rate = remaining cuttings mass / initial cuttings mass × 100%) to evaluate the inhibition performance of the shale and coal rock cutting fluids.

[0112] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0113] The above content is only an example and illustration of the present invention. Those skilled in the art of this technology make various modifications or supplements to the described specific embodiments or use similar methods to replace them. As long as they do not deviate from the invention or exceed the scope defined by this application, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a plugging agent for shale and coal rock, characterized in that: The following steps are involved: Step 1: Weigh 10 parts of high temperature resistant nano polymer emulsion, 0.5-3.5 parts of silane modified nano montmorillonite and 0.5-2.0 parts of emulsifier according to weight, and set aside; the emulsifier is one of sodium lauryl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate and fatty alcohol polyoxyethylene ether; Step 2: stirring and mixing the high temperature resistant nano polymer emulsion, silane modified nano montmorillonite and emulsifier at a temperature of 25° C. and a stirring rate of 12000 r / min for 60 minutes to obtain a plugging agent for shale and coal rock; Wherein, the high temperature resistant nano polymer emulsion is prepared by the following steps: Step a1: 2-methoxy-4-vinylphenol, epichlorohydrin and tetrabutylammonium bromide are stirred for reaction, and after the reaction is completed, the reaction product is distilled under reduced pressure to obtain intermediate 1; Step a2: stirring the intermediate 1, ethylenediamine and isopropanol for reaction, then adjusting the pH with a sodium hydroxide solution, and then continuing the stirring reaction. After the reaction is completed, the reaction product is cooled and then rotary evaporated to obtain the intermediate 2; Step a3: Stir the intermediate 2 and anhydrous methanol for reaction, then add 1,3-propane sultone solution dropwise while stirring, continue stirring the reaction after the dropwise addition is completed, then adjust the pH with sodium hydroxide solution, then continue stirring the reaction, after the reaction is completed, cool the reaction product, then rotary evaporate, then add it to anhydrous ether, then vacuum filter, and rotary evaporate the filtrate to obtain a diene sulfonate monomer; Step a4: stirring the diene sulfonate monomer, N,N-dimethylacrylamide, acrylic acid, sodium dodecyl sulfate and deionized water for reaction, then adding ammonium persulfate and continuing the stirring reaction, and cooling the reaction product after the reaction is completed to obtain a high temperature resistant nano polymer emulsion; Wherein, the silane-modified nano-montmorillonite is prepared by the following steps: Step b1: stirring montmorillonite and deionized water for reaction, then ultrasonic treatment, then adding octadecyltrimethylammonium bromide for reaction, cooling the reaction product after the reaction, then centrifuging, washing and drying the precipitate to obtain nano-modified montmorillonite; Step b2: stirring the nano-modified montmorillonite and ethanol solution to react, then adding γ-glycidyloxypropyltrimethoxysilane and continuing to stir the reaction, cooling the reaction product after the reaction is completed, then centrifuging, washing and drying the precipitate to obtain silane-modified nano-montmorillonite.

2. The method for preparing a plugging agent for shale and coal rock according to claim 1, characterized in that: The usage ratio of the 2-methoxy-4-vinylphenol, epichlorohydrin and tetrabutylammonium bromide in step a1 is 10g:40-50g:1.2-1.8g.

3. The method for preparing a plugging agent for shale and coal rock according to claim 1, characterized in that: The usage ratio of the intermediate 1, ethylenediamine and isopropanol in step a2 is 10mmol:21-23mmol:60-70mL; the mass fraction of the sodium hydroxide solution is 15-25%.

4. The method for preparing a plugging agent for shale and coal rock according to claim 1, characterized in that: The amount ratio of the intermediate 2, anhydrous methanol and 1,3-propane sultone solution in step a3 is 10mmol:40-50mL:35-40mL; the 1,3-propane sultone solution is a solution formed by dissolving 1,3-propane sultone in anhydrous methanol at a ratio of 10mmol:15mL; the mass fraction of the sodium hydroxide solution is 15-25%.

5. The method for preparing a plugging agent for shale and coal rock according to claim 1, characterized in that: The usage ratio of the diene sulfonate monomer, N,N-dimethylacrylamide, acrylic acid, sodium dodecyl sulfate, deionized water and ammonium persulfate in step a4 is 8-10g:3-4g:2-3g:0.6-1.0g:70-80mL:0.1-0.3g.

6. The method for preparing a plugging agent for shale and coal rock according to claim 1, characterized in that: The usage ratio of the montmorillonite, deionized water and octadecyltrimethylammonium bromide in step b1 is 2g:70-80mL:0.1-0.2g.

7. The method for preparing a plugging agent for shale and coal rock according to claim 1, characterized in that: The usage ratio of the nano-modified montmorillonite, ethanol solution and γ-glycidyloxypropyltrimethoxysilane in step b2 is 1 g: 50-60 mL: 1.5-5.5 mL; the volume fraction of the ethanol solution is 85-90%.

8. A water-based drilling fluid, characterized in that: Including the following ingredients: Base slurry, PAC-LV viscosity enhancer, JHJS-150 fluid loss reducer, JNJS-220 high temperature resistant fluid loss reducer, JXA-1 inhibitor, shale and coal rock plugging agent prepared by the preparation method according to any one of claims 1 to 7, sodium hydroxide, quicklime, RH-220 lubricant, potassium chloride, barite powder and clean water.

9. A method for preparing a water-based drilling fluid as claimed in claim 8, characterized in that: The following steps are involved: Step 1, prepare base slurry: weigh clean water, raw ore soil and anhydrous sodium carbonate according to the ratio of clean water, raw ore soil and anhydrous sodium carbonate of 93.64g:6g:0.36g, then add anhydrous sodium carbonate to clean water, and stir and mix for 30 minutes at a temperature of 25°C and a stirring rate of 1000r / min, then add raw ore soil and continue stirring and reacting for 30 minutes, and then let it stand for 24 hours to obtain base slurry; Step 2: Prepare drilling fluid: Step S21: adding 120 g of the base slurry into 233 mL of clean water, and stirring and mixing for 5 min at a temperature of 25° C. and a stirring rate of 12000 r / min to obtain a mixed slurry; Step S22: Add 0.6g PAC-LV viscosity enhancer to the mixed slurry, and stir and mix for 5 minutes at a temperature of 25°C and a stirring rate of 4000r / min, then add 6g JHJS-150 fluid loss reducer and continue to stir and mix for 5 minutes, then add 3g JNJS-220 high temperature resistant fluid loss reducer and continue to stir and mix for 5 minutes, then add 1g JXA-1 inhibitor and continue to stir and mix for 5 minutes, then add 1g shale and coal rock plugging agent and continue to stir and mix for 5 minutes, then add 0.2g sodium hydroxide and 7g potassium chloride and continue to stir and mix for 5 minutes, then add 0.5g quicklime and continue to stir and mix for 5 minutes, then add 3.5g RH-220 lubricant and continue to stir and mix for 5 minutes, then add barite powder to increase the density to 1.8g / cm 3 , and then stirred and mixed for 20 minutes at a temperature of 25°C and a stirring rate of 12000 r / min to obtain drilling fluid.

Images