A water-based drilling fluid viscosity reducer and water-based drilling fluid system and a method for preparing the same

Abstract

The application discloses a water-based drilling fluid viscosity reducer, a water-based drilling fluid system and a preparation method thereof, S1, acrylic acid and vinyl sulfonic acid are added into a container containing water in a mass ratio of (1-2):1, and tannic acid is added into the container in a mass ratio of (acrylic acid and vinyl sulfonic acid):tannic acid = (7-9):1; the monomer mass concentration is 10%-25%; S2, the three monomers in the container are stirred until they are uniformly mixed; S3, an initiator is added into the container in an amount of 2%-6% of the total weight of the three monomers, and the container is sealed after the addition is completed; S4, inert gas is introduced into the container, and constant-temperature reaction is carried out after air in the container is fully removed; S5, after the constant-temperature reaction is completed, stirring and cooling are carried out until room temperature is reached, and a polymer solution is obtained; and S6, the polymer solution is centrifuged and dried, and finally, solid powder of the viscosity reducer is obtained. The viscosity reducer obtained can resist high temperature and high density, and can meet the drilling requirements under high temperature and high density.

Description

Technical Field

[0001] This invention belongs to the field of drilling engineering and relates to a water-based drilling fluid viscosity reducer and a water-based drilling fluid system and its preparation method. Background Technology

[0002] High-temperature resistance is one of the technical challenges of water-based drilling fluids. Increased temperature causes clay particles and inferior soil in barite to disperse at high temperatures, leading to thickening of the drilling fluid. Under high temperatures, the thermal motion of clay mineral flaky particles intensifies, enhancing the ability of water molecules to penetrate the clay crystal layer, increasing the concentration of clay particles in the drilling fluid, thus increasing viscosity and reducing fluidity. Adding viscosity reducers to the drilling fluid allows them to preferentially adsorb onto the edges of clay particles with low charge, increasing the zeta potential, increasing the hydration film thickness, preventing edge-to-edge and edge-to-face connections of clay particles, and preventing the formation of a network structure, thus acting as a diluent. Viscosity reducers also adsorb onto the surface of drill cuttings, inhibiting hydration swelling and dispersion, which helps reduce viscosity and shear stress, and improves drilling fluid fluidity. As the exploration and development of Xinjiang oilfield gradually moves towards ultra-deep formations of 9,000 meters, the bottom-hole temperature reaches as high as 200℃ and the density reaches more than 2.5g / cm3. Under high temperature and high pressure conditions, it is difficult to control the rheology of drilling fluid, and viscosity reducers are needed to regulate the rheology of drilling fluid and improve its fluidity.

[0003] However, conventional viscosity reducers are not strong enough to withstand high temperatures. Under high temperature and high density conditions, the increased viscosity of drilling fluid makes it difficult for the working fluid in the wellbore to meet the requirements for safe drilling. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a water-based drilling fluid viscosity reducer and a water-based drilling fluid system and its preparation method, which can obtain a viscosity reducer resistant to high temperature and high density to meet the drilling requirements under high temperature and high density conditions.

[0005] To achieve the above objectives, the present invention employs the following technical solution: A method for preparing a water-based drilling fluid viscosity reducer includes the following steps: S1, add acrylic acid and vinyl sulfonic acid to a container filled with water at a molar ratio of (1-2):1, and then add tannic acid to the container at a mass ratio of (acrylic acid and vinyl sulfonic acid): tannic acid = (7-9):1, with a monomer mass concentration of 10%-25%; S2, stir the three monomers in the container until they are evenly mixed; S3, add 2%-6% of the total weight of the three monomers as initiator to the container, and seal the container after the addition is complete; S4. Inert gas is introduced into the container to fully remove the air inside the container. Then, the temperature is raised to 60-75℃ and the reaction is carried out at a constant temperature for 7-9 hours. S5. After the isothermal reaction is completed, the product in the container is stirred and cooled to room temperature to obtain a polymer solution. S6, the polymer solution is centrifuged and dried to finally obtain a solid powder of viscosity reducer.

[0006] Preferably, in S1, the vinyl sulfonic acid is 2-acrylamido-2-methylpropanesulfonic acid or sodium styrene sulfonate.

[0007] Preferably, the specific process of S2 is as follows: stir the monomer in the container at room temperature for 5 minutes until it is evenly mixed.

[0008] Preferably, in S3, the initiator is cerium ammonium nitrate and potassium persulfate, with cerium ammonium nitrate and potassium persulfate having the same weight.

[0009] Preferably, in step S3, before adding the initiator, the pH of the solution in the container is adjusted to 5 using sodium hydroxide.

[0010] Preferably, in S6, the centrifugation process is as follows: dialysis purification is performed using an MD3500 dialysis bag.

[0011] Preferably, in S6, the drying temperature is 60-80℃.

[0012] A water-based drilling fluid viscosity reducer is prepared using the method described above.

[0013] A water-based drilling fluid system comprising: 100 parts water, 1-2 parts sodium bentonite, 0.5-2.5 parts the above-mentioned viscosity reducer, 1-3 parts magnesium aluminum silicate, 1-5 parts lignite resin, 1-6 parts hydrolyzed sodium polyacrylonitrile, 2-8 parts shale inhibitor Soltex, 1-5 parts white oil, 0.5-1 part Span 80, 2-5 parts ultrafine calcium carbonate, 0.5-1 part sodium sulfite, and 750-780 parts barite.

[0014] A method for preparing a water-based drilling fluid system involves sequentially adding 1-2 parts of sodium bentonite, 0.5-2.5 parts of the above-mentioned viscosity reducer, 1-3 parts of magnesium aluminum silicate, 1-5 parts of lignite resin, 1-6 parts of hydrolyzed sodium polyacrylonitrile, 2-8 parts of shale inhibitor Soltex, 1-5 parts of white oil, 0.5-1 part of Span 80, 2-5 parts of ultrafine calcium carbonate, 0.5-1 part of sodium sulfite, and 750-780 parts of barite to 100 parts of water. After each addition, the mixture is stirred for 5-10 minutes until homogeneous, at a stirring speed of 10,000-12,000 rpm.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The viscosity reducer of this invention can effectively adsorb and disperse clay particles in water-based drilling fluids, thereby effectively reducing the internal friction of high-density drilling fluid systems and achieving a good dispersion and viscosity reduction effect. Secondly, this invention has a low molecular weight, and tannic acid, as a monomer, has high steric hindrance, stable structure, and good high-temperature resistance. Attached Figure Description

[0016] Figure 1 The acrylic acid is the structural unit of the present invention; Figure 2 The structural unit of 2-acrylamido-2-methylpropanesulfonic acid of the present invention; Figure 3 The structural unit of sodium styrene sulfonate in this invention; Figure 4 The structural unit of tannic acid in this invention; Detailed Implementation The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0017] It should be noted that the terms “front,” “back,” “left,” “right,” “up,” and “down” used in the following description refer to the directions shown in the attached diagram, while the terms “inside” and “outside” refer to the directions toward or away from the geometric center of a specific component, respectively.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0019] The chemical composition of the water-based drilling fluid viscosity reducer described in this invention is a copolymer of acrylic acid, vinyl sulfonic acid and tannic acid, with a molecular weight of approximately 10,000.

[0020] The structural units of acrylic acid, vinyl sulfonic acid, and tannic acid are as follows: Figure 1-4 As shown.

[0021] Vinyl sulfonic acid is 2-acrylamido-2-methylpropanesulfonic acid or sodium styrene sulfonate.

[0022] The preparation method of the water-based drilling fluid viscosity reducer of the present invention includes the following steps: a. Add acrylic acid, vinyl sulfonic acid, and tannic acid to a three-necked flask containing distilled water in a certain proportion. The total mass concentration of the monomers is 10%-25%. Add a water bath heating and stirring device.

[0023] Specifically, acrylic acid and vinyl sulfonic acid are added to a three-necked flask containing distilled water at a molar ratio of (1-2):1. Then, tannic acid is added to the container at a mass ratio of (acrylic acid and vinyl sulfonic acid): tannic acid = (7-9):1.

[0024] b. Stir the three monomers from a at room temperature for 10 minutes until they are thoroughly mixed; c. Add sodium hydroxide to b to adjust the pH of the solution in the container to 5, then add a certain proportion of initiator. After the addition is complete, seal the container and add a nitrogen gas purging device.

[0025] The initiator is 2%-6% of the total weight of the three monomers. The initiators are cerium ammonium nitrate and potassium persulfate, with equal weights of cerium ammonium nitrate and potassium persulfate.

[0026] d. Pour nitrogen gas into the three-necked flask to completely remove the air inside the flask, then slowly heat the water bath to 60-75℃ and maintain the temperature for 7-9 hours.

[0027] e. Stop heating and stirring, and cool the product from step d to room temperature to obtain a polymer solution. Centrifuge and dry the solution to obtain a solid powder of the viscosity reducer.

[0028] The water-based drilling fluid system described in this invention has the following formulation: 100 parts water + 1-2 parts sodium bentonite + 0.5-2.5 parts viscosity reducer + 1-3 parts magnesium aluminum silicate + 1-5 parts lignite resin + 1-6 parts hydrolyzed sodium polyacrylonitrile + 2-8 parts shale inhibitor Soltex + 1-5 parts white oil + 0.5-1 part Span 80 + 2-5 parts ultrafine calcium carbonate + 0.5-1 part sodium sulfite + 750-780 parts barite (density approximately 2.2 g / cm3).

[0029] The system is prepared as follows: 1-2 parts of sodium bentonite, 0.5-2.5 parts of viscosity reducer, 1-3 parts of magnesium aluminum silicate, 1-5 parts of lignite resin, 1-6 parts of hydrolyzed sodium polyacrylonitrile, 2-8 parts of shale inhibitor Soltex, 1-5 parts of white oil, 0.5-1 part of Span 80, 2-5 parts of ultrafine calcium carbonate, 0.5-1 part of sodium sulfite, and 750-780 parts of barite are added sequentially to 100 parts of water. After each addition, the mixture is stirred for 5-10 minutes with a high-speed mixer until homogeneous, at a stirring speed of 10000-12000 rpm.

[0030] Example 1 (Optimal): The preparation process of the viscosity reducer is as follows: a. Add acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid in a molar ratio of 1:1 to a three-necked flask containing distilled water. Then add tannic acid in a mass ratio of (acrylic acid + 2-acrylamido-2-methylpropanesulfonic acid):(tannic acid) = 9:1. Add a water bath heating and stirring device. The monomer mass concentration is 20%. b. Stir the monomer from a at room temperature for 5 minutes until it is thoroughly mixed; c. Add sodium hydroxide to b and adjust the pH to 5. Then add 1% of the total weight of the three monomers of cerium ammonium nitrate and 1% of the total weight of the three monomers of potassium persulfate. After the addition is complete, seal the container and add a nitrogen purging device. d. Pour nitrogen gas into the three-necked flask to completely remove the air inside the flask, then slowly heat the water bath to 75°C and react at a constant temperature for 8 hours; e. Stop heating and stirring, and cool the product from step d to room temperature. Use an MD3500 dialysis bag for dialysis purification, and then dry at 70°C to obtain a solid viscosity reducer.

[0031] The preparation process for the high-temperature, high-density drilling fluid system is as follows: The system formulation is as follows: 100 parts water + 1-2 parts sodium bentonite + 0.5-2.5 parts viscosity reducer + 1-3 parts magnesium aluminum silicate + 0.5-1 part filtration loss reducer DSP-1 + 1-5 parts lignite resin + 1-6 parts hydrolyzed sodium polyacrylonitrile + 2-8 parts shale inhibitor Soltex + 1-5 parts white oil + 0.5-1 part Span 80 + 2-5 parts ultrafine calcium carbonate + 0.5-1 part sodium sulfite + 840-880 parts barite (density 2.3 g / cm³). 3 about).

[0032] The system preparation method is as follows: add the treatment agents to the water in the above order, and stir with a high-speed mixer for 5-10 minutes until uniform after each addition, with a stirring speed of 10000-12000 rpm.

[0033] Example 2: The preparation process of the viscosity reducer is as follows: a. Add acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid in a molar ratio of 1:1 to a three-necked flask containing distilled water. Then add tannic acid in a mass ratio of (acrylic acid + 2-acrylamido-2-methylpropanesulfonic acid):(tannic acid) = 7:1. Add a water bath heating and stirring device. The monomer mass concentration is 20%. b. Stir the monomer from a at room temperature for 5 minutes until it is thoroughly mixed; c. Add sodium hydroxide to b and adjust the pH to 5. Then add 1% of the total weight of the three monomers of cerium ammonium nitrate and 1% of the total weight of the three monomers of potassium persulfate. After the addition is complete, seal the container and add a nitrogen purging device. d. Pour nitrogen gas into the three-necked flask to completely remove the air inside the flask, then slowly heat the water bath to 75°C and react at a constant temperature for 8 hours; e. Stop heating and stirring, and cool the product from step d to room temperature. Use an MD3500 dialysis bag for dialysis purification, and then dry at 70°C to obtain a solid viscosity reducer.

[0034] The preparation process for the high-temperature, high-density drilling fluid system is as follows: The system formulation is as follows: 100 parts water + 1-2 parts sodium bentonite + 0.5-2.5 parts viscosity reducer + 1-3 parts magnesium aluminum silicate + 0.5-1 part filtration loss reducer DSP-1 + 1-5 parts lignite resin + 1-6 parts hydrolyzed sodium polyacrylonitrile + 2-8 parts shale inhibitor Soltex + 1-5 parts white oil + 0.5-1 part Span 80 + 2-5 parts ultrafine calcium carbonate + 0.5-1 part sodium sulfite + 840-880 parts barite (density 2.3 g / cm³). 3 about).

[0035] The system preparation method is as follows: add the treatment agents to the water in the above order, and stir with a high-speed mixer for 5-10 minutes until uniform after each addition, with a stirring speed of 10000-12000 rpm.

[0036] Example 3: The preparation process of the viscosity reducer is as follows: a. Add acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid to a three-necked flask containing distilled water at a molar ratio of 2:1. Then add tannic acid at a mass ratio of (acrylic acid + 2-acrylamido-2-methylpropanesulfonic acid):(tannic acid) = 7:1. Add a water bath heating and stirring device. The monomer mass concentration is 15%. b. Stir the monomer from a at room temperature for 5 minutes until it is thoroughly mixed; c. Add sodium hydroxide to b and adjust the pH to 5. Then add 3% of the total weight of the three monomers of cerium ammonium nitrate and 3% of the total weight of the three monomers of potassium persulfate. After the addition is complete, seal the container and add a nitrogen purging device. d. Pour nitrogen gas into the three-necked flask to completely remove the air inside the flask, then slowly heat the water bath to 60°C and react at a constant temperature for 7 hours; e. Stop heating and stirring, and cool the product from step d to room temperature. Use an MD3500 dialysis bag for dialysis purification, and then dry at 70°C to obtain a solid viscosity reducer.

[0037] The preparation process for the high-temperature, high-density drilling fluid system is as follows: The system formulation is as follows: 100 parts water + 1-2 parts sodium bentonite + 0.5-2.5 parts viscosity reducer + 1-3 parts magnesium aluminum silicate + 0.5-1 part filtration loss reducer DSP-1 + 1-5 parts lignite resin + 1-6 parts hydrolyzed sodium polyacrylonitrile + 2-8 parts shale inhibitor Soltex + 1-5 parts white oil + 0.5-1 part Span 80 + 2-5 parts ultrafine calcium carbonate + 0.5-1 part sodium sulfite + 840-880 parts barite (density 2.3 g / cm³). 3 about).

[0038] The system preparation method is as follows: add the treatment agents to the water in the above order, and stir with a high-speed mixer for 5-10 minutes until uniform after each addition, with a stirring speed of 10000-12000 rpm.

[0039] Example 4: The preparation process of the viscosity reducer is as follows: a. Add acrylic acid and sodium styrene sulfonate in a molar ratio of 1:1 to a three-necked flask containing distilled water, then add tannic acid in a mass ratio of (acrylic acid + sodium styrene sulfonate):(tannic acid) = 9:1. Add a water bath heating and stirring device. The monomer mass concentration is 25%. b. Stir the monomer from a at room temperature for 5 minutes until it is thoroughly mixed; c. Add sodium hydroxide to b and adjust the pH to 5. Then add 3% of the total weight of the three monomers of cerium ammonium nitrate and 3% of the total weight of the three monomers of potassium persulfate. After the addition is complete, seal the container and add a nitrogen purging device. d. Pour nitrogen gas into the three-necked flask to completely remove the air inside the flask, then slowly heat the water bath to 75°C and react at a constant temperature for 8 hours; e. Stop heating and stirring, and cool the product from step d to room temperature. Use an MD3500 dialysis bag for dialysis purification, and then dry at 70°C to obtain a solid viscosity reducer.

[0040] The preparation process for the high-temperature, high-density drilling fluid system is as follows: The system formulation is as follows: 100 parts water + 1-2 parts sodium bentonite + 0.5-2.5 parts viscosity reducer + 1-3 parts magnesium aluminum silicate + 0.5-1 part filtration loss reducer DSP-1 + 1-5 parts lignite resin + 1-6 parts hydrolyzed sodium polyacrylonitrile + 2-8 parts shale inhibitor Soltex + 1-5 parts white oil + 0.5-1 part Span 80 + 2-5 parts ultrafine calcium carbonate + 0.5-1 part sodium sulfite + 840-880 parts barite (density 2.3 g / cm³). 3 about).

[0041] The system preparation method is as follows: add the treatment agents to the water in the above order, and stir with a high-speed mixer for 5-10 minutes until uniform after each addition, with a stirring speed of 10000-12000 rpm.

[0042] Example 5: The preparation process of the viscosity reducer is as follows: a. Add acrylic acid and sodium styrene sulfonate in a molar ratio of 2:1 to a three-necked flask containing distilled water. Then add tannic acid in a mass ratio of (acrylic acid + sodium styrene sulfonate):(tannic acid) = 9:1. Add a water bath heating and stirring device. The monomer mass concentration is 10%. b. Stir the monomer from a at room temperature for 5 minutes until it is thoroughly mixed; c. Add sodium hydroxide to b and adjust the pH to 5. Then add 1% of the total weight of the three monomers of cerium ammonium nitrate and 1% of the total weight of the three monomers of potassium persulfate. After the addition is complete, seal the container and add a nitrogen purging device. d. Pour nitrogen gas into the three-necked flask to completely remove the air inside the flask, then slowly heat the water bath to 70°C and react at a constant temperature for 9 hours; e. Stop heating and stirring, and cool the product from step d to room temperature. Use an MD3500 dialysis bag for dialysis purification, and then dry at 70°C to obtain a solid viscosity reducer.

[0043] The preparation process for the high-temperature, high-density drilling fluid system is as follows: The system formulation is as follows: 100 parts water + 1-2 parts sodium bentonite + 0.5-2.5 parts viscosity reducer + 1-3 parts magnesium aluminum silicate + 0.5-1 part filtration loss reducer DSP-1 + 1-5 parts lignite resin + 1-6 parts hydrolyzed sodium polyacrylonitrile + 2-8 parts shale inhibitor Soltex + 1-5 parts white oil + 0.5-1 part Span 80 + 2-5 parts ultrafine calcium carbonate + 0.5-1 part sodium sulfite + 840-880 parts barite (density 2.3 g / cm³). 3 about).

[0044] The system preparation method is as follows: add the treatment agents to the water in the above order, and stir with a high-speed mixer for 5-10 minutes until uniform after each addition, with a stirring speed of 10000-12000 rpm.

[0045] Example 6: The preparation process of the viscosity reducer is as follows: a. Add acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid in a molar ratio of 1:1 to a three-necked flask containing distilled water. Then add tannic acid in a mass ratio of (acrylic acid + 2-acrylamido-2-methylpropanesulfonic acid):(tannic acid) = 9:1. Add a water bath heating and stirring device. The monomer mass concentration is 20%. b. Stir the monomer from a at room temperature for 5 minutes until it is thoroughly mixed; c. Add sodium hydroxide to b and adjust the pH to 5. Then add 2% of the total weight of the three monomers of cerium ammonium nitrate and 2% of the total weight of the three monomers of potassium persulfate. After the addition is complete, seal the container and add a nitrogen purging device. d. Pour nitrogen gas into the three-necked flask to completely remove the air inside the flask, then slowly heat the water bath to 60°C and react at a constant temperature for 8 hours; e. Stop heating and stirring, and cool the product from step d to room temperature. Use an MD3500 dialysis bag for dialysis purification, and then dry at 70°C to obtain a solid viscosity reducer.

[0046] The preparation process for the high-temperature, high-density drilling fluid system is as follows: The system formulation is as follows: 100 parts water + 1-2 parts sodium bentonite + 0.5-2.5 parts viscosity reducer + 1-3 parts magnesium aluminum silicate + 0.5-1 part filtration loss reducer DSP-1 + 1-5 parts lignite resin + 1-6 parts hydrolyzed sodium polyacrylonitrile + 2-8 parts shale inhibitor Soltex + 1-5 parts white oil + 0.5-1 part Span 80 + 2-5 parts ultrafine calcium carbonate + 0.5-1 part sodium sulfite + 840-880 parts barite (density 2.3 g / cm³). 3 about).

[0047] The system preparation method is as follows: add the treatment agents to the water in the above order, and stir with a high-speed mixer for 5-10 minutes until uniform after each addition, with a stirring speed of 10000-12000 rpm.

[0048] Comparative Example 1: The tannic acid monomer was removed, while other conditions remained consistent with Example 1 for comparison. The preparation process of the viscosity reducer was as follows: a. Add acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid in a molar ratio of 1:1 to a three-necked flask containing distilled water, and add a water bath heating and stirring device. The monomer mass concentration is 20%. b. Stir the monomer from a at room temperature for 5 minutes until it is thoroughly mixed; c. Add sodium hydroxide to b and adjust the pH to 5, then add potassium persulfate at 1% of the total weight of the two monomers. After the addition is complete, seal the container and add a nitrogen purging device. d. Pour nitrogen gas into the three-necked flask to completely remove the air inside the flask, then slowly heat the water bath to 75°C and react at a constant temperature for 8 hours; e. Stop heating and stirring, and cool the product from step d to room temperature. Use an MD3500 dialysis bag for dialysis purification, and then dry at 70°C to obtain a solid viscosity reducer.

[0049] The preparation process for the high-temperature, high-density drilling fluid system is as follows: The system formulation is as follows: 100 parts water + 1-2 parts sodium bentonite + 0.5-2.5 parts viscosity reducer + 1-3 parts magnesium aluminum silicate + 0.5-1 part filtration loss reducer DSP-1 + 1-5 parts lignite resin + 1-6 parts hydrolyzed sodium polyacrylonitrile + 2-8 parts shale inhibitor Soltex + 1-5 parts white oil + 0.5-1 part Span 80 + 2-5 parts ultrafine calcium carbonate + 0.5-1 part sodium sulfite + 840-880 parts barite (density 2.3 g / cm³). 3 about).

[0050] The system preparation method is as follows: add the treatment agents to the water in the above order, and stir with a high-speed mixer for 5-10 minutes until uniform after each addition, with a stirring speed of 10000-12000 rpm.

[0051] Comparative Example 2: The tannic acid monomer was removed, while other conditions remained consistent with Example 3 for comparison. The preparation process of the viscosity reducer was as follows: a. Acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid are added to a three-necked flask containing distilled water at a molar ratio of 2:1. A water bath heating and stirring device is added. The monomer mass concentration is 20%. b. Stir the monomer from a at room temperature for 5 minutes until it is thoroughly mixed; c. Add sodium hydroxide to b and adjust the pH to 5, then add potassium persulfate at 3% of the total weight of the two monomers. After the addition is complete, seal the container and add a nitrogen purging device. d. Pour nitrogen gas into the three-necked flask to completely remove the air inside the flask, then slowly heat the water bath to 60°C and react at a constant temperature for 8 hours; e. Stop heating and stirring, and cool the product from step d to room temperature. Use an MD3500 dialysis bag for dialysis purification, and then dry at 70°C to obtain a solid viscosity reducer.

[0052] The preparation process for the high-temperature, high-density drilling fluid system is as follows: The system formulation is as follows: 100 parts water + 1-2 parts sodium bentonite + 0.5-2.5 parts viscosity reducer + 1-3 parts magnesium aluminum silicate + 0.5-1 part filtration loss reducer DSP-1 + 1-5 parts lignite resin + 1-6 parts hydrolyzed sodium polyacrylonitrile + 2-8 parts shale inhibitor Soltex + 1-5 parts white oil + 0.5-1 part Span 80 + 2-5 parts ultrafine calcium carbonate + 0.5-1 part sodium sulfite + 840-880 parts barite (density 2.3 g / cm³). 3 about).

[0053] The system preparation method is as follows: add the treatment agents to the water in the above order, and stir with a high-speed mixer for 5-10 minutes until uniform after each addition, with a stirring speed of 10000-12000 rpm.

[0054] Example Performance Evaluation Method 1. Appearance of viscosity reducer in the example The appearance of the viscosity reducer was observed with the naked eye under natural light conditions, as shown in Table 1.

[0055] Table 1 Appearance of viscosity reducers

[0056] 2. Performance evaluation of viscosity reducer examples The viscosity-reducing performance of this viscosity reducer was evaluated in bentonite-based slurry, wherein the bentonite-based slurry formulation was: water + 7% bentonite + 10% evaluation soil.

[0057] Take 300 mL of bentonite-based slurry, add 1.0% (effective content calculated based on concentration) of the example product, and stir at high speed for 10 min at 3000 r / min using a mixer. Measure the drilling fluid-based slurry's viscosity using a six-speed viscometer. 100 6. 3.

[0058] The specific measurement method is as follows: Pour the drilling fluid to be tested into a viscosity measuring cup, and read the viscosity values ​​sequentially using a six-speed viscometer at room temperature (25±5℃). 100 6. 3.

[0059] The evaluation results are shown in Table 2: Table 2 Performance evaluation of viscosity reducers in high-concentration bentonite-based slurries

[0060] 3. Performance evaluation of the high-temperature, high-density drilling fluid system example The viscosity-reducing performance of this viscosity reducer was evaluated in a high-density drilling fluid system, wherein the high-density drilling fluid formulation was as follows: 100 parts water + 1 part sodium bentonite + 1 part viscosity reducer + 1 part magnesium aluminum silicate + 0.8 parts filtration loss reducer DSP-1 + 3 parts lignite resin + 2 parts hydrolyzed sodium polyacrylonitrile + 5 parts shale inhibitor Soltex + 3 parts white oil + 0.5 parts Span 80 + 4 parts ultrafine calcium carbonate + 0.5 parts sodium sulfite + 860 parts barite (density 2.3 g / cm³) 3 ).

[0061] The apparent viscosity (AV), plastic viscosity (PV), and dynamic shear force (YP) of a high-temperature, high-density drilling fluid system were determined using a six-speed viscometer. 6. 3. The temperature resistance of the drilling fluid system was evaluated using a roller heating furnace.

[0062] The specific method is as follows: Pour the drilling fluid to be tested into a viscosity measuring cup, and read the viscosity sequentially using a six-speed viscometer at room temperature (25±5℃). 600 300 6. 3.

[0063] AV is calculated using the following formula:

[0064] PV is calculated using the following formula:

[0065] The dynamic shear force (YP) is calculated using the following formula:

[0066] After testing, the drilling fluid was placed in a roller heating furnace and aged at 240°C for 16 hours. After removal and cooling to room temperature, AV, PV, YP, and other parameters were measured. 6. 3.

[0067] The evaluation results are shown in Table 3: Table 3 Performance of high-temperature, high-density drilling fluid system examples

[0068] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0069] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this teaching should not be determined by reference to the above description, but rather by reference to the foregoing claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed inventive subject matter.

Claims

1. A water-based drilling fluid system, characterized in that, The water-based drilling fluid system includes: 100 parts water, 1-2 parts sodium bentonite, 0.5-2.5 parts viscosity reducer, 1-3 parts magnesium aluminum silicate, 1-5 parts lignite resin, 1-6 parts hydrolyzed sodium polyacrylonitrile, 2-8 parts shale inhibitor Soltex, 1-5 parts white oil, 0.5-1 part Span 80, 2-5 parts ultrafine calcium carbonate, 0.5-1 part sodium sulfite, and 750-780 parts barite. The preparation method of viscosity reducers includes the following steps: S1, add acrylic acid and vinyl sulfonic acid to a container filled with water at a molar ratio of (1-2):1, and then add tannic acid to the container at a mass ratio of (acrylic acid and vinyl sulfonic acid): tannic acid = (7-9):1, with a monomer mass concentration of 10%-25%; Vinyl sulfonic acid is 2-acrylamido-2-methylpropanesulfonic acid or sodium styrene sulfonate; S2, stir the three monomers in the container until they are evenly mixed; S3, add 2%-6% of the total weight of the three monomers as initiator to the container, and seal the container after the addition is complete; The initiators used are cerium ammonium nitrate and potassium persulfate, with equal weights of cerium ammonium nitrate and potassium persulfate; S4. Inert gas is introduced into the container to completely remove the air in the container, and then the temperature is raised to 60-75℃ and kept at a constant temperature for 7-9 hours. S5. After the isothermal reaction is completed, the product in the container is stirred and cooled to room temperature to obtain a polymer solution. S6, the polymer solution is centrifuged and dried to finally obtain a solid powder of viscosity reducer.

2. The water-based drilling fluid system according to claim 1, characterized in that, The specific process for S2 is as follows: Stir the monomer in the container at room temperature for 5 minutes until it is evenly mixed.

3. The water-based drilling fluid system according to claim 1, characterized in that, In S3, before adding the initiator, the pH of the solution in the container is adjusted to 5 using sodium hydroxide.

4. The water-based drilling fluid system according to claim 1, characterized in that, In S6, the drying temperature is 60-80℃.

5. A method for preparing the water-based drilling fluid system according to claim 1, characterized in that, Add 1-2 parts sodium bentonite, 0.5-2.5 parts viscosity reducer, 1-3 parts magnesium aluminum silicate, 1-5 parts lignite resin, 1-6 parts hydrolyzed sodium polyacrylonitrile, 2-8 parts shale inhibitor Soltex, 1-5 parts white oil, 0.5-1 part Span 80, 2-5 parts ultrafine calcium carbonate, 0.5-1 part sodium sulfite, and 750-780 parts barite to 100 parts water in sequence. Stir for 5-10 minutes after each addition until homogeneous, at a stirring speed of 10000-12000 rpm.

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