Preparation method and application of modified resin based on lignite

Abstract

The invention relates to the technical field of drilling fluids, and discloses a preparation method and application of modified resin based on lignite, and the preparation method comprises the following steps: S1, reacting poly (1, 4-butanediol adipate) with hexamethylene diisocyanate under the action of a dibutyltin dilaurate catalyst, after the reaction, continuing to add a chain extender to obtain a chain extender; carrying out chain extension reaction, finally adding glutamic acid, and reacting to obtain a polyurethane solution; and S2, adding the polyurethane solution into the lignite resin, stirring and mixing at 60-65 DEG C for 20-30 minutes, and drying to obtain the lignite-based modified resin. The modified resin based on the lignite prepared by the invention solves the problem that the existing lignite resin product is high in moisture content and water-insoluble substance content, and meanwhile, the modified resin has a good filtrate loss reduction effect.

Description

Technical Field

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

[0002] Lignite resin is commonly used in traditional drilling fluid treatment agents due to its wide availability and low cost, often used to improve filtration performance. However, its limited content of active groups (such as carboxyl and hydroxyl groups) and poor molecular chain regularity make it unsuitable for use in complex drilling environments. Traditional lignite resin typically has a moisture content exceeding 15% and a water-insoluble content as high as 20-30%, failing to meet the requirements of the new standard Q / SHCG 0166-2023 (moisture ≤10%, water-insoluble content ≤15%), severely affecting its dispersibility and stability in drilling fluids. At temperatures above 120℃, lignite resin is prone to thermo-oxidative degradation, losing its ability to control drilling fluid filtration loss, leading to thickened filter cake, a sharp increase in filtration loss, and potentially causing wellbore collapse and stuck pipe. For example, application number 202010614775.3 discloses a drilling fluid filtration reducer, lignite resin, and its preparation method. This product has good filtration reduction effects, but the lignite resin has a high water-insoluble content. In existing technologies, although lignite resins are modified through methods such as sulfonation and hydroxymethylation, the modified products still suffer from limited functionality and cannot meet the current demands for high-performance drilling fluid treatment agents in deep wells, ultra-deep wells, and complex formation drilling operations. Therefore, developing a lignite-based modified resin that combines excellent temperature resistance, salt resistance, and efficient filtration loss reduction has become a key issue that urgently needs to be addressed in the field of drilling fluid technology. 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, aiming to solve the problems of high moisture content and water-insoluble matter content, and poor salt resistance in existing lignite resin products.

[0004] Technical solution

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a modified resin based on lignite, comprising the following steps: S1. Poly(1,4-butanediol adipate) and hexamethylene diisocyanate are reacted under the action of dibutyltin dilaurate catalyst. After the reaction, a chain extender is added to carry out a chain extension reaction. Finally, glutamic acid is added and reacted to obtain a polyurethane solution. S2. Add the polyurethane solution to the lignite resin, stir and mix at 60-65℃ for 20-30 minutes, and dry to obtain the lignite-based modified resin.

[0006] Furthermore, the method for preparing the polyurethane solution is as follows: Add 0.006-0.009 mol of poly(1,4-butanediol adipate) to a reaction flask and vacuum dry at 110-120℃ for 2-3 h. Cool the mixture to 75-80℃ and, under nitrogen atmosphere, add 0.02-0.03 mol of hexamethylene diisocyanate and 0.1-0.12 mmol of dibutyltin dilaurate. React for 1-2 h, then maintain the temperature at 65-70℃ and add 0.01-0.016 mol of chain extender. React for 1-1.5 h, adjust the temperature to 40-45℃, add 0.005-0.006 mol of glutamic acid, and react for 1-3 h. After the reaction is complete, add 65-70 mL of deionized water at room temperature and stir to mix, obtaining a polyurethane solution.

[0007] Further, the chain extender is any one of 2,2-dihydroxymethylbutyric acid, 1,2-propanediol, 1,4-butanediol, and sodium sulfonate intermediate.

[0008] Furthermore, the method for preparing the sodium sulfonate intermediate is as follows: Step 1: Add 3-dimethylamino-1-propanol and malonyl chloride to N,N-dimethylformamide solvent, stir and mix, continue to add triethylamine catalyst, react at 45-50℃ for 1-2 h, after which distill under reduced pressure, wash, and obtain intermediate 1; Step 2: Add intermediate 1,3-chloro-2-hydroxypropanesulfonate sodium to 25-30 mL of 5-6% sodium hydroxide aqueous solution, react at 50-55℃ for 5-7 h, cool, add 0.1 mol / L hydrochloric acid dropwise to adjust the pH to neutral, and evaporate by rotary evaporation to obtain sodium sulfonate intermediate.

[0009] Further, in step one, the ratio of N,N-dimethylformamide solvent, 3-dimethylamino-1-propanol, malonyl chloride, and triethylamine catalyst is 50-60 mL: 1-2 mmol: 0.5-1 mmol: 0.01-0.02 mmol.

[0010] Furthermore, in step two, the mass ratio of intermediate 1 to sodium 3-chloro-2-hydroxypropanesulfonate is 1.2-1.4 mmol: 2.4-2.8 mmol.

[0011] Furthermore, in S2, the mass ratio of polyurethane solution to lignite resin is 10-15g: 35-40g.

[0012] Furthermore, the application in drilling fluids.

[0013] (Three beneficial technical effects) By encapsulating lignite resin with hydrophobic segments of polyurethane solution (such as butylene adipate), the moisture content is reduced, meeting the Q / SHCG 0166-2023 standard (≤10%). The polyurethane molecular chains and lignite resin molecules form a stable composite structure through physical encapsulation and chemical adsorption, which can encapsulate large molecular impurities in lignite resin that are originally difficult to dissolve within the composite system. At the same time, the hydrophilic groups (carboxyl groups, sodium sulfonate groups) introduced by the chain extender and the terminal carboxyl groups of glutamic acid end capping can improve the dispersion and solubility of the modified resin in water, reduce the content of water-insoluble matter, and meet the new standard's requirements for product purity.

[0014] The flexible structure of polyurethane segments complements the rigid framework of lignite resin, enabling the construction of an "elastic plugging network" in drilling fluid. This network is uniformly adsorbed onto the surface of bentonite particles, reducing interparticle porosity and forming a thin, dense filter cake. Simultaneously, end-capping the polyurethane with glutamic acid introduces carboxyl groups that can form coordination bonds with metal ions in the drilling fluid, further enhancing the filter cake's bonding strength and reducing filtration loss. This is far superior to traditional lignite resin, effectively reducing drilling fluid leakage into the formation and exhibiting good salt resistance. Attached Figure Description

[0015] Figure 1 This is the infrared spectrum of polyurethane in the polyurethane solution of Example 4. Detailed Implementation

[0016] 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.

[0017] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific embodiments.

[0018] Lignite resin, purchased from Xinxiang Xinlei Oilfield Additives Co., Ltd., production batch number: 20240236-01.

[0019] Poly(1,4-butanediol adipate) diol (Mn=2000).

[0020] Example 1

[0021] A method for preparing a modified resin based on lignite includes the following steps: S1. Add 0.006 mol of poly(1,4-butanediol adipate) to the reaction flask, dry under vacuum at 110 °C for 2 h, cool to 75 °C, and under nitrogen atmosphere, add 0.02 mol of hexamethylene diisocyanate and 0.1 mmol of dibutyltin dilaurate, react for 1 h, then maintain the temperature at 65 °C, add 0.01 mol of chain extender, react for 1 h, adjust the temperature to 40 °C, add 0.005 mol of glutamic acid, react for 1 h, and after the reaction is complete, add 65 mL of deionized water at room temperature, stir and mix to obtain a polyurethane solution; S2. Add 10g of polyurethane solution to 35g of lignite resin, stir and mix at 60℃ for 20min, and dry to obtain lignite-based modified resin.

[0022] Furthermore, the chain extender is 2,2-dihydroxymethylbutyric acid.

[0023] The preparation method of the sodium sulfonate intermediate is as follows: Step 1: Add 1 mmol of 3-dimethylamino-1-propanol and 0.5 mmol of malonyl chloride to 50 mL of N,N-dimethylformamide solvent, stir and mix, then add 0.01 mmol of triethylamine catalyst, react at 45 °C for 1 h, and after the reaction is completed, distill under reduced pressure and wash to obtain intermediate 1; Step 2: Add 1.2 mmol of intermediate 1 and 2.4 mmol of sodium 3-chloro-2-hydroxypropanesulfonate to 25 mL of 5% sodium hydroxide aqueous solution. React at 50 °C for 5 h. Cool, add 0.1 mol / L hydrochloric acid to adjust the pH to neutral, and evaporate by rotary evaporation to obtain sodium sulfonate intermediate.

[0024] Example 2

[0025] A method for preparing a modified resin based on lignite includes the following steps: S1. Add 0.009 mol of poly(1,4-butanediol adipate) to the reaction flask, dry under vacuum at 120°C for 3 h, cool to 80°C, and under nitrogen atmosphere, add 0.03 mol of hexamethylene diisocyanate and 0.12 mmol of dibutyltin dilaurate, react for 2 h, then maintain the temperature at 70°C and add 0.016 mol of chain extender, react for 1.5 h, adjust the temperature to 45°C, add 0.006 mol of glutamic acid, react for 3 h, and after the reaction is complete, add 70 mL of deionized water at room temperature, stir and mix to obtain a polyurethane solution; S2. Add 15g of polyurethane solution to 40g of lignite resin, stir and mix at 65℃ for 30min, and dry to obtain lignite-based modified resin.

[0026] The chain extender is 1,2-propanediol.

[0027] The preparation method of the sodium sulfonate intermediate is as follows: Step 1: Add 2 mmol of 3-dimethylamino-1-propanol and 1 mmol of malonyl chloride to 60 mL of N,N-dimethylformamide solvent, stir and mix, then add 0.02 mmol of triethylamine catalyst, react at 50 °C for 2 h, and after the reaction is completed, distill under reduced pressure and wash to obtain intermediate 1. Step 2: Add 1.4 mmol of intermediate 1 and 2.8 mmol of sodium 3-chloro-2-hydroxypropanesulfonate to 30 mL of a 6% sodium hydroxide aqueous solution. React at 55 °C for 7 h. After cooling, add 0.1 mol / L hydrochloric acid dropwise to adjust the pH to neutral. Then, evaporate by rotary evaporation to obtain the sodium sulfonate intermediate.

[0028] Example 3

[0029] A method for preparing a modified resin based on lignite includes the following steps: S1. Add 0.0075 mol of poly(1,4-butanediol adipate) to the reaction flask, dry under vacuum at 115 °C for 2 h, cool to 78 °C, and under nitrogen atmosphere, add 0.025 mol of hexamethylene diisocyanate and 0.11 mmol of dibutyltin dilaurate, react for 2 h, then maintain the temperature at 68 °C and add 0.013 mol of chain extender, react for 1.2 h, adjust the temperature to 43 °C, add 0.0055 mol of glutamic acid, react for 2 h, and after the reaction is complete, add 68 mL of deionized water at room temperature, stir and mix to obtain a polyurethane solution; S2. Add 12g of polyurethane solution to 38g of lignite resin, stir and mix at 63℃ for 25min, and dry to obtain lignite-based modified resin.

[0030] The chain extender is 1,4-butanediol.

[0031] The preparation method of the sodium sulfonate intermediate is as follows: Step 1: Add 1.5 mmol of 3-dimethylamino-1-propanol and 0.75 mmol of malonyl chloride to 55 mL of N,N-dimethylformamide solvent, stir and mix, then add 0.015 mmol of triethylamine catalyst, react at 47 °C for 1.5 h, and after the reaction is completed, distill under reduced pressure and wash to obtain intermediate 1; Step 2: Add 1.3 mmol of intermediate 1 and 2.6 mmol of sodium 3-chloro-2-hydroxypropanesulfonate to 27 mL of a 5.5% sodium hydroxide aqueous solution. React at 53 °C for 6 h. After cooling, adjust the pH to neutral by adding 0.1 mol / L hydrochloric acid dropwise. Then, evaporate by rotary evaporation to obtain the sodium sulfonate intermediate.

[0032] Example 4

[0033] A method for preparing a modified resin based on lignite includes the following steps: S1. Add 0.006 mol of poly(1,4-butanediol adipate) to a reaction flask, dry under vacuum at 110°C for 2 h, cool to 75°C, and under nitrogen atmosphere, add 0.02 mol of hexamethylene diisocyanate and 0.1 mmol of dibutyltin dilaurate, react for 1 h, then maintain the temperature at 65°C, add 0.01 mol of chain extender, react for 1 h, adjust the temperature to 40°C, add 0.005 mol of glutamic acid, react for 1 h, and after completion, add 65 mL of deionized water at room temperature, stir and mix to obtain a polyurethane solution; according to Figure 1 The infrared spectrum of polyurethane shows that at 1247 cm⁻¹... -1 An absorption peak appears at 1730 cm⁻¹ for the S=O group in the sulfonic acid group. -1 An absorption peak for urethane (CO-NH) appears at 2964 cm⁻¹. -1 An absorption peak for methyl (-CH3) or methylene (-CH2-) appears at 3354 cm⁻¹. -1 An absorption peak of -NH appears at this point; S2. Add 15g of polyurethane solution to 40g of lignite resin, stir and mix at 65℃ for 30min, and dry to obtain lignite-based modified resin.

[0034] The chain extender is a sodium sulfonate intermediate.

[0035] The preparation method of the sodium sulfonate intermediate is as follows: Step 1: Add 2 mmol of 3-dimethylamino-1-propanol and 1 mmol of malonyl chloride to 60 mL of N,N-dimethylformamide solvent, stir and mix, then add 0.02 mmol of triethylamine catalyst, react at 50 °C for 2 h, and after the reaction is completed, distill under reduced pressure and wash to obtain intermediate 1. Step 2: Add 1.3 mmol of intermediate 1 and 2.6 mmol of sodium 3-chloro-2-hydroxypropanesulfonate to 27 mL of a 5.5% sodium hydroxide aqueous solution. React at 53 °C for 6 h. After cooling, adjust the pH to neutral by adding 0.1 mol / L hydrochloric acid dropwise. Then, evaporate by rotary evaporation to obtain the sodium sulfonate intermediate.

[0036] Comparative Example 1 The difference between this comparative example and Example 4 is that no sodium sulfonate intermediate was added.

[0037] Comparative Example 2 The difference between this comparative example and Example 4 is that no polyurethane solution was added.

[0038] The modified resins based on lignite prepared in the examples and comparative examples were evaluated for performance according to standard Q / SHCG0166-2023 "Lignite Resins for Drilling Fluid Filtration Reduction". The results are shown in Table 1.

[0039] The evaluation of the product's filtration loss reduction performance in drilling fluid was conducted in both fresh water and brine slurries. After aging at 180℃ for 16 hours, the high-pressure filtration loss was measured using a Type 42 high-temperature and high-pressure fluid loss analyzer, according to Q / SHCG0166-2023 "Filtration Loss Reducing Agents for Drilling Fluids - Lignite Resin Type". The composition of the two evaluation systems is shown below: Base slurry formulation: Add 0.79 (±0.05) g of anhydrous sodium carbonate and 22.5 (±0.5) g of bentonite for drilling fluid test slurry preparation to a sample cup containing 350 mL of distilled water, 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℃ for 24 h.

[0040] Freshwater slurry formulation: Add 10.5g of the sample of this invention to 350mL of base slurry, and stir at high speed for 20min, interrupting twice during the process to scrape off the sample adhering to the cup wall. Transfer the above slurry to a high-temperature tank and heat-roll at 180℃ for 16h.

[0041] Saltwater slurry formulation: Take 350 ml of base slurry and add 17.5 g of the sample of this invention. Stir at high speed for 20 min, interrupting twice during the process to scrape off the sample adhering to the cup wall. Then add 52.5 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.

[0042] Table 1: Performance Testing Implementing projects Water-insoluble matter (%) Moisture (%) Freshwater slurry, high temperature and high pressure filtration loss (mL) Brine slurry, high temperature and high pressure filtration loss (mL) Example 1 7.8 8.2 16.3 22.8 Example 2 8.5 8.3 17.1 24.3 Example 3 8.3 8.5 17.5 23.1 Example 4 7.4 8.0 15.4 21.7 Comparative Example 1 10.6 11.3 20.1 28.4 Comparative Example 2 15.7 14.5 25.7 31.1 As shown in Table 1, the lignite-based modified resin prepared in this invention exhibits good salt and temperature resistance, while also possessing low water insolubility. The polyurethane molecular chain (containing the hydrophobic segment of butylene adipate) locks in the free water in the lignite resin through physical encapsulation and efficiently removes it during the drying process. The carboxyl groups introduced by the chain extender (such as 2,2-dimethylolbutyric acid and sodium sulfonate intermediates) and the hydrophilic groups of sodium sulfonate, combined with the terminal carboxyl groups capped with glutamic acid, significantly improve the dispersibility and solubility of the lignite resin in water, transforming previously difficult-to-dissolve large molecular impurities (such as undegraded lignin) into dispersible components.

[0043] Comparative Examples 1 and 2, lacking the core process steps of this invention (Comparative Example 1 lacks the sodium sulfonate intermediate, and Comparative Example 2 lacks the polyurethane solution), both exhibited significantly deteriorated performance. In Comparative Example 1, the absence of the sodium sulfonate intermediate resulted in insufficient hydrophilic groups (sodium sulfonate), decreased dispersion and solubility of the lignite resin, ineffective dispersion of insoluble impurities, and increased water-insoluble matter. Simultaneously, salt resistance was lost, and Na⁺ in the brine system damaged the filter cake structure, leading to a sharp increase in filtration loss, and excessive moisture due to decreased polyurethane encapsulation efficiency. Comparative Example 2, completely lacking polyurethane solution (only unmodified lignite resin), showed reduced performance. Without polyurethane solution, there was neither hydrophobic encapsulation to reduce moisture nor hydrophilic groups to improve solubility, retaining the original defects of the lignite resin (high moisture content and high insoluble matter). Furthermore, the absence of the polyurethane-lignite interpenetrating network made the molecular chains prone to degradation at 180°C, resulting in a loose filter cake structure and complete loss of filtration loss reduction and temperature and salt resistance, failing to meet the requirements for drilling fluid use.

[0044] 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. Unless otherwise specified, 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.

[0045] 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.

[0046] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments.

Claims

1. A method for preparing a modified resin based on lignite, characterized in that, Includes the following steps: S1. Poly(1,4-butanediol adipate) and hexamethylene diisocyanate are reacted under the action of dibutyltin dilaurate catalyst. After the reaction, a chain extender is added to carry out a chain extension reaction. Finally, glutamic acid is added and reacted to obtain a polyurethane solution. S2. Add the polyurethane solution to the lignite resin, stir and mix at 60-65℃ for 20-30 minutes, and dry to obtain the lignite-based modified resin.

2. The method for preparing the lignite-based modified resin according to claim 1, characterized in that, The polyurethane solution is prepared by: Add 0.006-0.009 mol of poly(1,4-butanediol adipate) to a reaction flask and vacuum dry at 110-120℃ for 2-3 h. Cool the mixture to 75-80℃ and, under nitrogen atmosphere, add 0.02-0.03 mol of hexamethylene diisocyanate and 0.1-0.12 mmol of dibutyltin dilaurate. React for 1-2 h, then maintain the temperature at 65-70℃ and add 0.01-0.016 mol of chain extender. React for 1-1.5 h, adjust the temperature to 40-45℃, add 0.005-0.006 mol of glutamic acid, and react for 1-3 h. After the reaction is complete, add 65-70 mL of deionized water at room temperature and stir to mix, obtaining a polyurethane solution.

3. The method for preparing the lignite-based modified resin according to claim 2, characterized in that, The chain extender is any one of 2,2-dihydroxymethylbutyric acid, 1,2-propanediol, 1,4-butanediol, and sodium sulfonate intermediate.

4. The method for preparing the lignite-based modified resin according to claim 3, characterized in that, The preparation method of the sodium sulfonate intermediate is as follows: Step 1: Add 3-dimethylamino-1-propanol and malonyl chloride to N,N-dimethylformamide solvent, stir and mix, continue to add triethylamine catalyst, react at 45-50℃ for 1-2 h, after which distill under reduced pressure, wash, and obtain intermediate 1; Step 2: Add intermediate 1,3-chloro-2-hydroxypropanesulfonate sodium to the sodium hydroxide aqueous solution, react at 50-55℃ for 5-7 hours, cool, add hydrochloric acid dropwise to adjust the pH, and evaporate by rotary evaporation to obtain sodium sulfonate intermediate.

5. The method for preparing the lignite-based modified resin according to claim 4, characterized in that, In step one, the ratio of N,N-dimethylformamide solvent, 3-dimethylamino-1-propanol, malonyl chloride, and triethylamine catalyst is 50-60 mL: 1-2 mmol: 0.5-1 mmol: 0.01-0.02 mmol.

6. The method for preparing the lignite-based modified resin according to claim 4, characterized in that, In step two, the mass ratio of intermediate 1 to sodium 3-chloro-2-hydroxypropanesulfonate is 1.2-1.4 mmol: 2.4-2.8 mmol.

7. The method for preparing the lignite-based modified resin according to claim 1, characterized in that, In step S2, the mass ratio of polyurethane solution to lignite resin is 10-15g: 35-40g.

8. An application of a lignite-based modified resin as described in any one of claims 1-7, characterized in that, Its application in drilling fluids.

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