Preparation method and application of modified resin based on lignite

Abstract

The invention discloses a preparation method and application of modified resin based on lignite, and belongs to the technical field of drilling fluid. The preparation method comprises the following steps: adding lignite resin, modified cellulose, modified cardanol and hydrolyzed polyacrylonitrile ammonium salt into deionized water, stirring at 60-80 DEG C for 2-4 hours, drying, and crushing to obtain the lignite-based modified resin. A quaternary ammonium group can be strongly adsorbed on the edge of a clay particle with negative electricity through electrostatic interaction, so that the filtrate loss reduction capability of the modified resin can be improved, stearoyl chloride and a carbon long chain of cardanol can be wound and crosslinked, a hydrophobic association effect is achieved, the salt resistance of the modified resin is enhanced, and a viscosity reduction effect is achieved; the biphenyl structure in the modified cardanol can improve the high-temperature resistance of the modified resin, and carboxyl can be complexed with high-valence metal ions in the drilling fluid, so that the salt resistance of the modified resin is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of drilling fluid technology, and more specifically, relates to a method for preparing and applying a modified resin based on lignite. Background Technology

[0002] As global oil and gas exploration expands into deep wells, ultra-deep wells, and complex geological conditions, extremely high demands are placed on drilling fluid performance. Traditional drilling fluid treatment agents suffer from insufficient temperature resistance and limited functionality, easily threatening drilling safety during complex geological exploration. Reducing filtration loss and viscosity is crucial for ensuring downhole safety and efficiency. While lignite resin, as a natural organic polymer, possesses certain adsorption, film-forming, and temperature resistance properties, its molecular structure lacks stability, making it difficult to meet requirements under high temperature and pressure. Therefore, a modified resin based on lignite is key to solving this problem. For example, Chinese patent application CN120248367A discloses a high-temperature resistant lignite resin and its preparation method. This invention's lignite resin exhibits excellent high-temperature resistance, improving its effectiveness in drilling fluids; however, its salt resistance and viscosity-reducing effects need further improvement. Summary of the Invention

[0003] Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a method for preparing and applying a modified resin based on lignite. The modified resin of this invention not only has the effects of reducing filtration loss and viscosity, but also has good temperature and salt resistance, and can be used in drilling fluids.

[0004] Technical solution To solve the above problems, the technical solution adopted by the present invention is as follows: The present invention discloses a method for preparing a modified resin based on lignite, comprising the following steps: (1) Preparation of modified cellulose; (2) Preparation of modified cashew phenol; (3) Add lignite resin, modified cellulose, modified cashew phenol and hydrolyzed polyacrylonitrile ammonium salt to deionized water, stir at 60-80℃ for 2-4 hours, dry and pulverize to obtain a lignite-based modified resin.

[0005] Furthermore, in step (1), the method for preparing modified cellulose is as follows: Step 1: Add a 40% (w / w) aqueous solution of tetrapropylammonium hydroxide and polyethylene glycol to the reactor and stir and mix them under a water bath at 25-50℃. Then add cellulose and stir continuously at 45-55℃ for 20-40 minutes. Next, slowly add 2,3-epoxypropyltrimethylammonium chloride to the reaction system and continue to keep the reaction at the temperature for 5-8 hours. After the reaction is completed, wash repeatedly with anhydrous ethanol and deionized water and dry to obtain quaternized cellulose. Step 2: Under nitrogen protection, quaternized cellulose and triethylamine are added to N,N-dimethylformamide solvent and stirred at 90-100℃ for 1-2 hours. Then, stearoyl chloride is added dropwise, and the reaction temperature is maintained while stirring for 4-8 hours. After the reaction is completed, the mixture is filtered, washed, and dried to obtain modified cellulose.

[0006] Furthermore, in step one, the ratio of the 40% (w / w) tetrapropylammonium hydroxide aqueous solution, polyethylene glycol, cellulose, and 2,3-epoxypropyltrimethylammonium chloride is 70-80 mL: 15-20 mL: 4.8-5 g: 2.3-2.5 g.

[0007] Furthermore, in step two, the ratio of N,N-dimethylformamide, quaternized cellulose, triethylamine, and stearoyl chloride is 40-50 mL: 2-2.1 g: 0.7-0.9 g: 1-1.2 g.

[0008] Furthermore, in step (2), the method for preparing modified cashew phenol is as follows: S1: Under nitrogen protection, cashew phenol and 3-chloropropylamine were added to N,N-dimethylformamide solvent and mixed evenly. Then anhydrous potassium carbonate was added and reacted at 60-80℃ for 8-12 hours. After the reaction was completed, the mixture was cooled to room temperature, dried by vacuum distillation, and purified to obtain intermediate 1. S2: Add intermediate 1,3,3',4,4'-biphenyltetracarboxylic acid dianhydride to N,N-dimethylformamide solvent, stir and react at 100-110℃ for 16-20h. After the reaction is completed, filter, wash and dry, and purify to obtain modified cashew phenol.

[0009] Furthermore, the ratio of N,N-dimethylformamide, cashew phenol, 3-chloropropylamine, and anhydrous potassium carbonate in S1 is 45-55 mL: 3-3.1 g: 1.4-1.5 g: 2.2-2.3 g.

[0010] Furthermore, the ratio of N,N-dimethylformamide and intermediate 1,3,3',4,4'-biphenyltetracarboxylic acid dianhydride in S2 is 40-60 mL: 2.8-2.9 g: 2.2-2.3 g.

[0011] Further, in step (3), the weight parts of each component are: 40-50 parts of deionized water, 30-35 parts of lignite resin, 3-5 parts of modified cellulose, 2-4 parts of modified cashew phenol, and 4-6 parts of hydrolyzed polyacrylonitrile ammonium salt.

[0012] Furthermore, the application in drilling fluids.

[0013] Beneficial technical effects Quaternized cellulose is obtained by quaternizing cellulose to introduce quaternary ammonium salt groups. These groups can be strongly adsorbed onto the edges of negatively charged clay particles through electrostatic interactions, which helps the modified resin form a dense, low-permeability filter cake on the well wall, improving its filtration loss reduction capacity. Subsequent reaction with stearoyl chloride introduces hydrophobic long chains. Stearoyl chloride and the long carbon chains of cashew phenol can undergo entanglement and cross-linking, playing a hydrophobic association role. This allows the associated structure to be maintained even in high-salt environments, preserving the viscosity reduction and filtration loss reduction effects, and enhancing the salt resistance of the modified resin. This effect can also break down... The clay spatial network structure plays a role in reducing viscosity. Cashew phenol first reacts with 3-chloropropylamine to obtain intermediate 1, and then reacts with 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to generate modified cashew phenol with a rigid biphenyl skeleton and terminal carboxyl groups. The biphenyl structure has high thermal stability and is not prone to twisting or curling at high temperatures, which can improve the high temperature resistance of the modified resin. The carboxyl groups can complex with high-valence metal ions in drilling fluid, eliminating the flocculation and destructive effects of these ions on clay slurry and enhancing the salt resistance of the modified resin. Attached Figure Description

[0014] Figure 1 This is the synthetic reaction formula for modified cashew phenol. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] To better understand the above technical solutions, the following will provide a detailed description of the technical solutions in conjunction with the accompanying drawings and specific embodiments.

[0017] The reagents used in the following specific embodiments are of analytical grade. Additionally: Polyethylene glycol: Polyethylene glycol 6000, purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd.; Cellulose: powder, particle size 90um, purchased from Aladdin Reagent Co., Ltd. Lignite resin: Production batch number 20240236-01, purchased from Xinxiang Xinlei Oilfield Additives Co., Ltd.

[0018] Example 1 This embodiment provides a modified resin based on lignite, the preparation method of which specifically includes the following steps: (1) Add 70 mL of 40% tetrapropylammonium hydroxide aqueous solution and 15 mL of polyethylene glycol to the reactor and stir and mix them under a water bath at 25°C. Then add 4.8 g of cellulose and stir continuously at 45°C for 20 min. Then slowly add 2.3 g of 2,3-epoxypropyltrimethylammonium chloride to the reaction system and continue to keep the reaction at the temperature for 5 h. After the reaction is completed, wash repeatedly with anhydrous ethanol and deionized water and dry to obtain quaternized cellulose. (2) Under nitrogen protection, 2g of quaternized cellulose and 0.7g of triethylamine were added to 40mL of N,N-dimethylformamide solvent. The mixture was stirred at 90℃ for 1h, and then 1g of stearoyl chloride was added dropwise. The reaction temperature was maintained and the mixture was stirred for 4h. After the reaction was completed, the mixture was filtered, washed and dried to obtain modified cellulose. (3) Under nitrogen protection, 3g of cashew phenol and 1.4g of 3-chloropropylamine were added to 45mL of N,N-dimethylformamide solvent and mixed evenly. Then 2.2g of anhydrous potassium carbonate was added and the mixture was reacted at 60℃ for 8h. After the reaction was completed, the mixture was cooled to room temperature, distilled under reduced pressure, dried and purified to obtain intermediate 1. (4) Add 2.8 g of intermediate 1 and 2.2 g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to 40 mL of N,N-dimethylformamide solvent. Stir the mixture at 100 °C for 16 h. After the reaction is complete, filter, wash and dry, and purify to obtain modified cashew phenol, as shown below. Figure 1 As shown; (5) Add 30 parts by weight of lignite resin, 3 parts by weight of modified cellulose, 2 parts by weight of modified cashew phenol and 4 parts by weight of hydrolyzed polyacrylonitrile ammonium salt to 40 parts by weight of deionized water, stir at 60°C for 2 hours, dry and pulverize to obtain a lignite-based modified resin.

[0019] Example 2

[0020] This embodiment provides a modified resin based on lignite, the preparation method of which specifically includes the following steps: (1) Add 80 mL of 40% tetrapropylammonium hydroxide aqueous solution and 20 mL of polyethylene glycol to the reactor and stir and mix them under a water bath at 50°C. Then add 5 g of cellulose and stir continuously at 55°C for 40 min. Then slowly add 2.5 g of 2,3-epoxypropyltrimethylammonium chloride to the reaction system and continue to keep the reaction at the temperature for 8 h. After the reaction is completed, wash repeatedly with anhydrous ethanol and deionized water and dry to obtain quaternized cellulose. (2) Under nitrogen protection, 2.1 g of quaternized cellulose and 0.9 g of triethylamine were added to 50 mL of N,N-dimethylformamide solvent and stirred at 100 °C for 2 h. Then, 1.2 g of stearoyl chloride was added dropwise and the reaction temperature was maintained while stirring for 8 h. After the reaction was completed, the mixture was filtered, washed and dried to obtain modified cellulose. (3) Under nitrogen protection, 3.1 g of cashew phenol and 1.5 g of 3-chloropropylamine were added to 55 mL of N,N-dimethylformamide solvent and mixed evenly. Then 2.3 g of anhydrous potassium carbonate was added and the mixture was reacted at 80 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature, distilled under reduced pressure, dried and purified to obtain intermediate 1. (4) Add 2.9 g of intermediate 1 and 2.3 g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to 60 mL of N,N-dimethylformamide solvent, stir and react at 110 °C for 20 h. After the reaction is completed, filter, wash and dry, and purify to obtain modified cashew phenol. (5) Add 35 parts by weight of lignite resin, 5 parts by weight of modified cellulose, 4 parts by weight of modified cashew phenol and 6 parts by weight of hydrolyzed polyacrylonitrile ammonium salt to 50 parts by weight of deionized water, stir at 80°C for 4 hours, dry and pulverize to obtain a lignite-based modified resin.

[0021] Example 3

[0022] This embodiment provides a modified resin based on lignite, the preparation method of which specifically includes the following steps: (1) Add 75 mL of 40% tetrapropylammonium hydroxide aqueous solution and 18 mL of polyethylene glycol to the reactor and stir and mix them under a water bath at 35°C. Then add 4.9 g of cellulose and stir continuously at 50°C for 30 min. Then slowly add 2.4 g of 2,3-epoxypropyltrimethylammonium chloride to the reaction system and continue to keep the reaction at the temperature for 6 h. After the reaction is completed, wash repeatedly with anhydrous ethanol and deionized water and dry to obtain quaternized cellulose. (2) Under nitrogen protection, 2.05 g of quaternized cellulose and 0.8 g of triethylamine were added to 45 mL of N,N-dimethylformamide solvent. The mixture was stirred at 95 °C for 1.5 h. Then, 1.1 g of stearoyl chloride was added dropwise. The reaction temperature was maintained and the mixture was stirred for 6 h. After the reaction was completed, the mixture was filtered, washed and dried to obtain modified cellulose. (3) Under nitrogen protection, 3.05 g of cashew phenol and 1.45 g of 3-chloropropylamine were added to 50 mL of N,N-dimethylformamide solvent and mixed evenly. Then 2.25 g of anhydrous potassium carbonate was added and the mixture was reacted at 70 °C for 10 h. After the reaction was completed, the mixture was cooled to room temperature, distilled under reduced pressure, dried and purified to obtain intermediate 1. (4) Add 2.85 g of intermediate 1 and 2.25 g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to 50 mL of N,N-dimethylformamide solvent, stir and react at 105 °C for 18 h. After the reaction is completed, filter, wash and dry, purify to obtain modified cashew phenol. (5) Add 33 parts by weight of lignite resin, 4 parts by weight of modified cellulose, 3 parts by weight of modified cashew phenol and 5 parts by weight of hydrolyzed polyacrylonitrile ammonium salt to 45 parts by weight of deionized water, stir at 70°C for 3 hours, dry and pulverize to obtain a lignite-based modified resin.

[0023] Example 4

[0024] This embodiment provides a modified resin based on lignite, the preparation method of which specifically includes the following steps: (1) Add 72 mL of 40% tetrapropylammonium hydroxide aqueous solution and 16 mL of polyethylene glycol to the reactor and stir and mix them under a 30°C water bath. Then add 4.85 g of cellulose and stir continuously at 48°C for 25 min. Then slowly add 2.35 g of 2,3-epoxypropyltrimethylammonium chloride to the reaction system and continue to keep the reaction at the temperature for 6 h. After the reaction is completed, wash repeatedly with anhydrous ethanol and deionized water and dry to obtain quaternized cellulose. (2) Under nitrogen protection, 2.02 g of quaternized cellulose and 0.75 g of triethylamine were added to 42 mL of N,N-dimethylformamide solvent. The mixture was stirred at 92 °C for 1 h. Then, 1.05 g of stearoyl chloride was added dropwise. The reaction temperature was maintained and the mixture was stirred for 5 h. After the reaction was completed, the mixture was filtered, washed and dried to obtain modified cellulose. (3) Under nitrogen protection, 3.02 g of cashew phenol and 1.42 g of 3-chloropropylamine were added to 48 mL of N,N-dimethylformamide solvent and mixed evenly. Then 2.22 g of anhydrous potassium carbonate was added and the mixture was reacted at 65 °C for 9 h. After the reaction was completed, the mixture was cooled to room temperature, distilled under reduced pressure, dried and purified to obtain intermediate 1. (4) Add 2.82 g of intermediate 1 and 2.22 g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to 45 mL of N,N-dimethylformamide solvent, stir at 102 °C for 17 h, filter, wash and dry, and purify to obtain modified cashew phenol; (5) Add 32 parts by weight of lignite resin, 3 parts by weight of modified cellulose, 2 parts by weight of modified cashew phenol and 5 parts by weight of hydrolyzed polyacrylonitrile ammonium salt to 42 parts by weight of deionized water, stir at 65°C for 2 hours, dry and pulverize to obtain a lignite-based modified resin.

[0025] Example 5

[0026] This embodiment provides a modified resin based on lignite, the preparation method of which specifically includes the following steps: (1) Add 78 mL of 40% tetrapropylammonium hydroxide aqueous solution and 18 mL of polyethylene glycol to the reactor and stir and mix them under a water bath at 40°C. Then add 4.95 g of cellulose and stir continuously at 52°C for 35 min. Then slowly add 2.45 g of 2,3-epoxypropyltrimethylammonium chloride to the reaction system and continue to keep the reaction at the temperature for 7 h. After the reaction is completed, wash repeatedly with anhydrous ethanol and deionized water and dry to obtain quaternized cellulose. (2) Under nitrogen protection, 2.08 g of quaternized cellulose and 0.85 g of triethylamine were added to 48 mL of N,N-dimethylformamide solvent. The mixture was stirred at 98 °C for 2 h. Then, 1.15 g of stearoyl chloride was added dropwise. The reaction temperature was maintained and the mixture was stirred for 7 h. After the reaction was completed, the mixture was filtered, washed and dried to obtain modified cellulose. (3) Under nitrogen protection, 3.08 g of cashew phenol and 1.48 g of 3-chloropropylamine were added to 52 mL of N,N-dimethylformamide solvent and mixed evenly. Then 2.28 g of anhydrous potassium carbonate was added and the mixture was reacted at 75 °C for 11 h. After the reaction was completed, the mixture was cooled to room temperature, distilled under reduced pressure, dried and purified to obtain intermediate 1. (4) Add 2.88 g of intermediate 1 and 2.28 g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to 55 mL of N,N-dimethylformamide solvent, stir at 108 °C for 19 h, filter, wash and dry, purify to obtain modified cashew phenol; (5) Add 34 parts by weight of lignite resin, 4 parts by weight of modified cellulose, 4 parts by weight of modified cashew phenol and 5 parts by weight of hydrolyzed polyacrylonitrile ammonium salt to 48 parts by weight of deionized water, stir at 75°C for 4 hours, dry and pulverize to obtain a lignite-based modified resin.

[0027] Comparative Example 1 The main difference between Comparative Example 1 and Example 5 is that quaternized cellulose is used instead of modified cellulose.

[0028] Comparative Example 2 The main difference between Comparative Example 2 and Example 5 is that intermediate 1 is used instead of modified cashew phenol.

[0029] Performance testing The lignite-based modified resins prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to performance tests.

[0030] (1) High temperature resistance test: Preparation of test samples: Preparation of base slurry: In a sample cup containing 350 mL of distilled water, add 0.80 g (weighed to 0.01 g) of anhydrous sodium carbonate and 2.50 g (weighed to 0.01 g) of bentonite for drilling fluid test slurry preparation, stir at high speed for 20 min, interrupting at least twice to scrape off the sample adhering to the cup wall, and cure in a sealed environment at 25℃±1℃ for 24 h to obtain the base slurry.

[0031] Preparation of high-temperature resistant sample slurry: Take 350 mL of base slurry and add 17.50 g (weighed to 0.01 g) of lignite-based modified resin prepared in Examples 1-5 and Comparative Examples 1-2. Stir at high speed for 20 min, interrupting twice during the process to scrape off the sample adhering to the cup wall. Then add 52.50 g (weighed to 0.01 g) of sodium chloride and stir at high speed for 10 min. Add 2 mL of 20% sodium hydroxide solution to adjust the pH to obtain the sample slurry.

[0032] Test method: Transfer the slurry into a high-temperature tank and heat-roll it at 180℃, 190℃, and 200℃ for 16 hours respectively. Remove the high-temperature tank, cool it to room temperature, open it, pour it into a mixing cup, and stir at high speed for 5 minutes.

[0033] Based on the apparent viscosity and filtration loss test methods in GB / T16783.1-2014 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 1: Water-based Drilling Fluids", the apparent viscosity of the slurry at 24℃±3℃ and the filtration loss at high temperature and high pressure (150℃ / 3450kPa) were tested.

[0034] The test results are shown in Table 1.

[0035] Table 1: High Temperature Resistance Test

[0036] As can be seen from Table 1, the lignite-based modified resin drilling fluid slurry prepared in Examples 1-5 can maintain a low filtration loss under high temperature conditions and has good high temperature resistance.

[0037] (2) Salt tolerance test: Preparation of test samples: Preparation of base slurry: In a sample cup containing 350 mL of distilled water, add 0.80 g (weighed to 0.01 g) of anhydrous sodium carbonate and 2.50 g (weighed to 0.01 g) of bentonite for drilling fluid test slurry preparation, stir at high speed for 20 min, interrupting at least twice to scrape off the sample adhering to the cup wall, and cure in a sealed environment at 25℃±1℃ for 24 h to obtain the base slurry.

[0038] Preparation of freshwater test slurry: Take 350 mL of base slurry and add 10.50 g (weighed to 0.01 g) of lignite-based modified resin prepared in Examples 1-5 and Comparative Examples 1-2. Stir at high speed for 20 min, interrupting at least twice to scrape off the sample adhering to the cup wall. Transfer the slurry to a high-temperature tank and heat-roll at 180°C for 16 h. Remove the high-temperature tank, cool to room temperature, open it, pour the slurry into a stirring cup, and stir at high speed for 5 min to prepare the freshwater sample slurry.

[0039] Preparation of sodium chloride contaminated slurry: Take 350 mL of base slurry and add 17.50 g (weighed to 0.01 g) of lignite-based modified resin prepared in Examples 1-5 and Comparative Examples 1-2. Stir at high speed for 20 min, interrupting twice to scrape off the sample adhering to the cup wall. Then add 52.50 g (weighed to 0.01 g) of sodium chloride and stir at high speed for 10 min. Add 2 mL of 20% sodium hydroxide solution to adjust the pH. Transfer the above slurry to a high-temperature tank and heat-roll at 180°C for 16 h. Remove the high-temperature tank, cool to room temperature, open it, pour into a stirring cup, and stir at high speed for 5 min to prepare sodium chloride contaminated slurry.

[0040] Test method: Based on the apparent viscosity and filtration loss test methods in GB / T16783.1-2014 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 1: Water-based Drilling Fluids", the apparent viscosity and high-temperature and high-pressure (150℃ / 3450kPa) filtration loss of fresh water sample slurry and sodium chloride contaminated slurry were tested at 24℃±3℃.

[0041] The test results are shown in Table 2.

[0042] Table 2: Salt Tolerance Test As can be seen from Table 2, the lignite-based modified resin drilling fluid slurry prepared in Examples 1-5 can maintain a low filtration loss under high salt conditions and has good salt resistance.

[0043] (3) Viscosity reduction performance test: Preparation of test samples: Preparation of freshwater-based slurry: Add 400mL of tap water to a cup, add 2g of anhydrous sodium carbonate and dissolve it completely, then slowly add 40g of bentonite, stir at high speed for 2 hours, and then let it stand in a sealed environment at 25℃ for hydration, and set aside for later use.

[0044] Preparation of high-salt-content freshwater-based slurry: Add 400mL of tap water to a cup, add 2g of anhydrous sodium carbonate, 2g of sodium chloride and 4g of calcium chloride and dissolve them completely. Then slowly add 40g of bentonite, stir at high speed for 2 hours, and then let it stand in a sealed environment at 25℃ for hydration.

[0045] Preparation of test samples: Take 400 mL of the two base slurries mentioned above, add 2 g of the lignite-based modified resins prepared in Examples 1-5 and Comparative Examples 1-2 to the two base slurries respectively, stir for 20 min, and the corresponding test samples are obtained.

[0046] Test method: Rheological parameters: The parameters were determined according to the standard SY / T5621-93 "Evaluation Procedure for Viscosity Reducers for Water-based Drilling Fluids" at a test temperature of 25℃. The apparent viscosity and plastic viscosity of the samples were calculated.

[0047] Viscosity reduction rate: The viscosity reduction rate was tested using a six-speed rotational viscometer and after high-temperature aging of the drilling fluid. The viscosity reduction rate test formula is as follows: Viscosity reduction rate (%) = [(AV0-AV1) / AV0]×100%, where AV0 is the reading of the base slurry without lignite-based modified resin treatment under the six-speed rotational viscometer, and AV1 is the reading of the base slurry with lignite-based modified resin treatment under the six-speed rotational viscometer.

[0048] The test results are shown in Table 3.

[0049] Table 3: Viscosity Reduction Performance Test As can be seen from Table 3, the addition of the lignite-based modified resin drilling fluid slurry prepared in Examples 1-5 can reduce the apparent viscosity of the drilling fluid after aging, and has good viscosity-reducing performance.

[0050] The comparison shows that Comparative Example 1, lacking the hydrophobic long chain of stearoyl chloride, cannot entangle and crosslink with the long chain of modified cashew phenol. This weakens the hydrophobic association under high temperature and high salt conditions, resulting in poor dismantling of the original strong spatial network structure between clay particles. Consequently, the stability of the system decreases, and the high temperature resistance, salt resistance, and viscosity reduction effects are all reduced compared to the examples. Comparative Example 2 uses intermediate 1 instead of modified cashew phenol. It lacks both the rigid biphenyl skeleton of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to resist molecular chain curling at high temperatures and the terminal carboxyl group. This causes the flexible molecular chains to easily curl up at high temperatures, failing to effectively open the spatial structure between clay particles and dismantle its structure. Furthermore, it cannot form complexes with calcium ions, sodium ions, etc., resulting in a significant decrease in high temperature resistance, salt resistance, and viscosity reduction effects compared to the examples.

[0051] It should be noted that, in this document, 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 a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0052] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0053] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing a modified resin based on lignite, characterized in that, It comprises the following steps: (1) preparation of modified cellulose; (2) preparation of modified cardanol; (3) adding lignite resin, modified cellulose, modified cardanol and hydrolyzed polyacrylonitrile ammonium salt into deionized water, stirring at 60-80℃ for 2-4h, drying, crushing to obtain a modified lignite resin.

2. The method for preparing the modified lignite-based resin according to claim 1, characterized by, In the step (1), the preparation method of the modified cellulose is: Step one: adding 40% mass fraction of tetrapropyl ammonium hydroxide aqueous solution, polyethylene glycol into the reactor, stirring and mixing under the condition of 25-50℃ water bath, then adding cellulose, continuously stirring at 45-55℃ for 20-40min, then slowly adding 2,3-epoxypropyl trimethyl ammonium chloride into the reaction system, continuing to keep warm for 5-8h, after the reaction is completed, repeatedly washing with anhydrous ethanol and deionized water, drying to obtain quaternary ammonium cellulose; Step two: under the protection of nitrogen gas, adding quaternary ammonium cellulose, triethylamine into N,N-dimethylformamide solvent, stirring at 90-100℃ for 1-2h, then adding stearoyl chloride dropwise, keeping the reaction temperature and stirring for 4-8h, after the reaction is completed, filtering, washing and drying to obtain modified cellulose.

3. The method for preparing modified lignite-based resin according to claim 2, characterized in that, The amount ratio of 40% mass fraction of tetrapropyl ammonium hydroxide aqueous solution, polyethylene glycol, cellulose and 2,3-epoxypropyl trimethyl ammonium chloride in the step one is 70-80mL:15-20mL:4.8-5g:2.3-2.5g.

4. The method for preparing the modified lignite-based resin according to claim 2, characterized by, The amount ratio of N,N-dimethylformamide, quaternary ammonium cellulose, triethylamine and stearoyl chloride in the step two is 40-50mL:2-2.1g:0.7-0.9g:1-1.2g.

5. The method for preparing the lignite-based modified resin according to claim 1, characterized in that, In the step (2), the preparation method of the modified cardanol is: S1: under the protection of nitrogen gas, adding cardanol, 3-chloropropylamine into N,N-dimethylformamide solvent, mixing uniformly, then adding anhydrous potassium carbonate, reacting at 60-80℃ for 8-12h, after the reaction is completed, cooling to room temperature, reducing pressure distillation, drying, purifying to obtain intermediate 1; S2: adding intermediate 1, 3,3',4,4'-biphenyl tetracarboxylic dianhydride into N,N-dimethylformamide solvent, stirring and reacting at 100-110℃ for 16-20h, after the reaction is completed, filtering, washing and drying, purifying to obtain modified cardanol.

6. The method for preparing the lignite-based modified resin according to claim 5, characterized in that, The amount ratio of N,N-dimethylformamide, cardanol, 3-chloropropylamine and anhydrous potassium carbonate in the S1 is 45-55mL:3-3.1g:1.4-1.5g:2.2-2.3g.

7. The method for preparing the lignite-based modified resin according to claim 5, characterized in that, The amount ratio of N,N-dimethylformamide, intermediate 1 and 3,3',4,4'-biphenyl tetracarboxylic dianhydride in the S2 is 40-60mL:2.8-2.9g:2.2-2.3g.

8. The method for preparing the lignite-based modified resin according to claim 1, characterized in that, In the step (3), the weight parts of each component are as follows: deionized water 40-50 parts, lignite resin 30-35 parts, modified cellulose 3-5 parts, modified cardanol 2-4 parts, hydrolyzed polyacrylonitrile ammonium salt 4-6 parts.

9. Use of the modified lignite-based resin according to any one of claims 1 to 8, characterized in that, The application in drilling fluid.

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