A thickener for high-temperature fracturing fluid and its preparation method

Abstract

This invention relates to the field of oilfield chemical technology and discloses a thickener for high-temperature fracturing fluid and its preparation method. The invention involves esterifying a quaternary ammonium salt phenolic resin with diphenylacetyl chloride, followed by sulfonation with chlorosulfonic acid, and then preparing a thickener solution to obtain the thickener for high-temperature fracturing fluid. Introducing quaternary ammonium salt cations and a large number of sulfonate anions into the phenolic resin forms a zwitterionic structure, which enhances the association between molecular chains, thereby increasing the viscosity of the solution and providing excellent thickening effect and salt resistance. The introduction of heat-resistant diphenyl structures into the side chains of the phenolic resin in the thickener improves its high-temperature resistance, making it less prone to thermal decomposition and exhibiting excellent high-temperature performance. This makes it well-suited for practical applications in high-temperature, high-salt oil and gas extraction and fracturing fluid systems.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, specifically to a thickener for high-temperature fracturing fluid and its preparation method. Background Technology

[0002] Oilfield fracturing technology involves injecting high-pressure fluid into underground rock formations to create artificial fractures, thereby increasing oil and gas permeability and production. The type of fracturing fluid plays a crucial role in oil and gas extraction. Adding viscosifiers to the fracturing fluid can increase its viscosity and enhance the suspension of proppant, thus improving fracturing effectiveness and oil and gas extraction efficiency. Common viscosifiers include polyacrylamide, guar gum, surfactants, and zwitterionic polymers. While these viscosifiers have good viscosity-increasing properties, they often lack the necessary high-temperature resistance and salt tolerance to meet the demands of fracturing fluid operations in high-temperature, high-salt environments.

[0003] Phenolic resins possess high strength, excellent high-temperature resistance, and good crosslinking properties, making them suitable as oil and gas extraction aids such as fracturing proppant, gel profile control agents, filtration loss reducers, and water shut-off agents. Modifying phenolic resins to expand their practical applications in fracturing and other oil and gas extraction fields is a research hotspot. Patent CN116162216B discloses the use of epoxy resin to modify phenolic resin, preparing a crosslinked network structure epoxy resin-modified phenolic resin polymer for oil fracturing sands, which can meet the sand control requirements of oil wells. The journal *Polymer Materials Science and Engineering* published an article titled "Synthesis and Properties of Novel Water-Soluble Quaternary Ammonium Base-Containing Photosensitive Resin," reporting the reaction of triethylamine hydrochloride with epoxy phenolic resin to obtain a quaternary ammonium base-containing photosensitive resin, which can be applied in the field of water-based solder resists. However, the phenolic resins in the aforementioned patents do not provide thickening effects and cannot be used in fracturing fluid thickening systems. Summary of the Invention

[0004] This invention provides a thickener for high-temperature fracturing fluid and its preparation method, which solves the problems of low thickening effect of phenolic resin and its difficulty in being applied to fracturing fluid thickeners.

[0005] The technical solution of this invention: A method for preparing a thickener for high-temperature fracturing fluid:

[0006] Step (1): Add 100g:(0.2-0.6)mol:(0.012-0.04)mol:(0.2-0.6)mol of quaternary ammonium salt phenolic resin, triethylamine, 4-dimethylaminopyridine, and diphenylacetyl chloride to N,N-dimethylformamide. After stirring and reacting, distill under reduced pressure, wash the product with acetone, and dry to obtain diphenyl quaternary ammonium salt phenolic resin.

[0007] Step (2): Add diphenyl quaternary ammonium salt phenolic resin to dichloromethane, stir, and then add a dichloromethane solution of chlorosulfonic acid dropwise under a nitrogen atmosphere. The ratio of diphenyl quaternary ammonium salt phenolic resin to chlorosulfonic acid is 100g:(1500-2500)g. After stirring and reacting, pour the solution into water, stir, add an aqueous sodium hydroxide solution, and then extract with a saturated sodium chloride solution. After separation, dry the dichloromethane organic layer with anhydrous sodium sulfate, distill under reduced pressure, wash the product with acetone, dry, and add the product to deionized water to prepare a 0.2-0.8% (w / w) thickener solution to obtain a thickener for high-temperature fracturing fluid. The preparation reaction formula is:

[0008] .

[0009] Furthermore, in step (1), the temperature of the stirring reaction is 20-30℃, and the reaction time is 18-24h.

[0010] Furthermore, in step (2), the temperature of the stirring reaction is 0-5℃, and the reaction time is 12-24h.

[0011] Furthermore, in step (2), an aqueous solution of sodium hydroxide is added to adjust the pH to 7-9.

[0012] Furthermore, the preparation method of quaternary ammonium salt phenolic resin includes the following steps: adding triethylamine hydrochloride and epoxy phenolic resin in a ratio of (0.15-0.4) mol:100g to water, heating to 75-80℃, stirring for 5-8 hours, distilling under reduced pressure, adding toluene, azeotropically removing water, removing toluene again under reduced pressure, washing the product with saturated sodium chloride solution, drying, adding the product to deionized water to prepare a tackifier solution, and obtaining quaternary ammonium salt phenolic resin. The preparation reaction formula is:

[0013] .

[0014] (III) Beneficial technical effects: This invention utilizes the esterification reaction of quaternary ammonium salt phenolic resin with diphenylacetyl chloride, and the introduced diphenyl structure then undergoes a sulfonation reaction with chlorosulfonic acid to introduce a large number of sulfonate groups into the side chain of the phenolic resin. The solution is then formulated as a thickener to obtain a thickener for high-temperature fracturing fluid.

[0015] This invention introduces quaternary ammonium salt cations and a large number of sulfonate anions into phenolic resin to form a zwitterionic structure, which can improve the association between molecular chains, thereby increasing the viscosity of the solution and having a good thickening effect.

[0016] The phenolic resin in the tackifier of this invention contains zwitterionic structures of quaternary ammonium salt and sulfonate, exhibiting unique anti-polyelectrolyte solution behavior. It disrupts the internal salt bonds of the polymer zwitterionic bonds, enhances the association between polymer molecules, and can maintain good apparent viscosity and tackifying effect in salt solutions, with excellent salt resistance.

[0017] The phenolic resin side chain of the tackifier of this invention introduces a heat-resistant diphenyl structure, which is beneficial to improving the high-temperature resistance of the tackifier, making it less prone to thermal decomposition. Furthermore, the diphenyl structure facilitates sulfonation with chlorosulfonic acid, which can reduce the sulfonation reaction of the benzene ring in the phenolic resin main chain, maintain the good structural stability of the phenolic resin main chain, reduce the influence of sulfonate groups in the main chain on the heat resistance of the phenolic resin, and give the tackifier excellent high-temperature resistance. It has good practical applications in high-temperature and high-salinity oil and gas extraction and fracturing fluid systems. Detailed Implementation

[0018] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with specific embodiments.

[0019] The epoxy phenolic resin grade Nanya 704 described below is from Shenzhen Huiya New Materials Technology Co., Ltd.

[0020] Example 1

[0021] (1) Add 22 mmol of triethylamine hydrochloride and 10 g of epoxy phenolic resin to 80 mL of water, heat to 75 °C, stir and react for 8 h, add toluene after vacuum distillation, remove water by azeotropic distillation, remove toluene by vacuum distillation, wash the product with saturated sodium chloride solution and dry to obtain quaternary ammonium salt phenolic resin.

[0022] (2) Add 15g of quaternary ammonium salt phenolic resin, 50mmol of triethylamine, 3.3mmol of 4-dimethylaminopyridine and 50mmol of diphenylacetyl chloride to 100mL of N,N-dimethylformamide. Stir the reaction at 20℃ for 24h, distill under reduced pressure, wash the product with acetone and dry to obtain diphenyl quaternary ammonium salt phenolic resin.

[0023] (3) Add 10g of diphenyl quaternary ammonium salt phenolic resin to 40mL of dichloromethane, stir, and then add 250mL of dichloromethane solution containing 180g of chlorosulfonic acid dropwise under a nitrogen atmosphere. Stir and react at 0℃ for 18h. Pour the solution into 300mL of water, stir for 12h, add 25% sodium hydroxide aqueous solution to adjust the pH of the solution to 9, and then extract with saturated sodium chloride solution. After separation, dry the dichloromethane organic layer with anhydrous sodium sulfate, distill under reduced pressure, wash the product with acetone, dry, add the product to deionized water, and prepare a 0.2% thickener solution to obtain a thickener for high-temperature fracturing fluid.

[0024] Example 2

[0025] (1) Add 15 mmol of triethylamine hydrochloride and 10 g of epoxy phenolic resin to 80 mL of water, heat to 80 °C, stir and react for 5 h, add toluene after vacuum distillation, remove water by azeotropic distillation, remove toluene by vacuum distillation, wash the product with saturated sodium chloride solution and dry to obtain quaternary ammonium salt phenolic resin.

[0026] (2) Add 15g of quaternary ammonium salt phenolic resin, 30mmol of triethylamine, 1.8mmol of 4-dimethylaminopyridine and 30mmol of diphenylacetyl chloride to 100mL of N,N-dimethylformamide. Stir the reaction at 25℃ for 18h, distill under reduced pressure, wash the product with acetone and dry to obtain diphenyl quaternary ammonium salt phenolic resin.

[0027] (3) Add 10g of diphenyl quaternary ammonium salt phenolic resin to 40mL of dichloromethane, stir, and then add 200mL of dichloromethane solution containing 150g of chlorosulfonic acid dropwise under a nitrogen atmosphere. Stir and react at 5℃ for 12h. Pour the solution into 300mL of water, stir for 18h, add 20% sodium hydroxide aqueous solution to adjust the pH of the solution to 8, and then extract with saturated sodium chloride solution. After separation, dry the dichloromethane organic layer with anhydrous sodium sulfate, distill under reduced pressure, wash the product with acetone, dry, add the product to deionized water, and prepare a 0.4% thickener solution to obtain a thickener for high-temperature fracturing fluid.

[0028] Example 3

[0029] (1) Add 40 mmol of triethylamine hydrochloride and 10 g of epoxy phenolic resin to 130 mL of water, heat to 80 °C, stir and react for 6 h, add toluene after vacuum distillation, remove water by azeotropic distillation, remove toluene by vacuum distillation, wash the product with saturated sodium chloride solution, and dry to obtain quaternary ammonium salt phenolic resin.

[0030] (2) Add 15g of quaternary ammonium salt phenolic resin, 90mmol of triethylamine, 6mmol of 4-dimethylaminopyridine, and 90mmol of diphenylacetyl chloride to 120mL of N,N-dimethylformamide. Stir the reaction at 30℃ for 18h, distill under reduced pressure, wash the product with acetone, and dry to obtain diphenyl quaternary ammonium salt phenolic resin.

[0031] (3) Add 10g of diphenyl quaternary ammonium salt phenolic resin to 50mL of dichloromethane, stir, and then add 400mL of dichloromethane solution containing 250g of chlorosulfonic acid dropwise under a nitrogen atmosphere. Stir and react at 0℃ for 24h. Pour the solution into 400mL of water, stir for 12h, add 20% sodium hydroxide aqueous solution to adjust the pH of the solution to 9, and then extract with saturated sodium chloride solution. After separation, dry the dichloromethane organic layer with anhydrous sodium sulfate, distill under reduced pressure, wash the product with acetone, dry, add the product to deionized water, and prepare a 0.6% thickener solution to obtain a thickener for high-temperature fracturing fluid.

[0032] Example 4

[0033] (1) Add 30 mmol of triethylamine hydrochloride and 10 g of epoxy phenolic resin to 100 mL of water, heat to 75 °C, stir and react for 8 h, add toluene after vacuum distillation, remove water by azeotropic distillation, remove toluene by vacuum distillation, wash the product with saturated sodium chloride solution, dry, and obtain quaternary ammonium salt phenolic resin.

[0034] (2) Add 15g of quaternary ammonium salt phenolic resin, 70mmol of triethylamine, 4.6mmol of 4-dimethylaminopyridine and 70mmol of diphenylacetyl chloride to 120mL of N,N-dimethylformamide. Stir the reaction at 25℃ for 24h, distill under reduced pressure, wash the product with acetone and dry to obtain diphenyl quaternary ammonium salt phenolic resin.

[0035] (3) Add 10g of diphenyl quaternary ammonium salt phenolic resin to 50mL of dichloromethane, stir, and then add 300mL of dichloromethane solution containing 110g of chlorosulfonic acid dropwise under a nitrogen atmosphere. Stir and react at 5℃ for 18h. Pour the solution into 350mL of water, stir for 18h, add 30% sodium hydroxide aqueous solution to adjust the pH of the solution to 9, and then extract with saturated sodium chloride solution. After separation, dry the dichloromethane organic layer with anhydrous sodium sulfate, distill under reduced pressure, wash the product with acetone, dry, add the product to deionized water, and prepare a 0.8% thickener solution to obtain a thickener for high-temperature fracturing fluid.

[0036] Comparative Example 1: Quaternary ammonium salt phenolic resin (prepared according to the method of Example 1) was added to deionized water to prepare a 0.2% (w / w) thickener solution to obtain a thickener for fracturing fluid.

[0037] Comparative Example 2: Diphenyl quaternary ammonium salt phenolic resin (prepared according to the method of Example 1) was added to deionized water to prepare a 0.2% (w / w) thickener solution to obtain a thickener for fracturing fluid.

[0038] Comparative Example 3

[0039] (1) Add 15g of quaternary ammonium salt phenolic resin (prepared according to the method of Example 1), 50mmol of triethylamine, 3.3mmol of 4-dimethylaminopyridine and 50mmol of benzoyl chloride to 100mL of N,N-dimethylformamide, stir and react at 20℃ for 24h, distill under reduced pressure, wash the product with acetone and dry to obtain phenyl quaternary ammonium salt phenolic resin.

[0040] (2) Add 10g of phenyl quaternary ammonium salt phenolic resin to 40mL of dichloromethane, stir, and then add 250mL of dichloromethane solution containing 180g of chlorosulfonic acid dropwise under a nitrogen atmosphere. Stir the reaction at 0℃ for 18h, pour the solution into 300mL of water, stir for 12h, add 25% sodium hydroxide aqueous solution to adjust the pH of the solution to 9, then extract with saturated sodium chloride solution, dry the dichloromethane organic layer with anhydrous sodium sulfate after separation, distill under reduced pressure, wash the product with acetone, dry, add the product to deionized water, and prepare a 0.2% thickener solution to obtain a thickener for fracturing fluid.

[0041] The fracturing fluid was sheared at 25°C for 3 minutes with a solution of thickener, and the initial apparent viscosity was measured using a viscometer.

[0042] Potassium chloride was added to the solution of the fracturing fluid thickener, and the mass fraction of potassium chloride was controlled at 2%. The solution was sheared at 25°C for 3 minutes, and the apparent viscosity was measured by a viscometer.

[0043] The fracturing fluid viscosity modifier solution was heat-treated at 150°C for 72 hours in a reactor, cooled to room temperature, and sheared at 25°C for 3 minutes before the apparent viscosity was tested. The test results are shown in Table 1.

[0044] Table 1 Apparent viscosity test of thickeners for fracturing fluids

[0045]

[0046] Compared with Comparative Examples 1-3, the initial apparent viscosity of the fracturing fluid thickeners in Examples 1-4 reached 181.4-331.9 mPa·s. This is mainly because the introduction of quaternary ammonium salt cations and a large number of sulfonate anions into the phenolic resin forms an amphoteric structure, which can improve the association between molecular chains, thereby increasing the viscosity of the solution and having a good thickening effect. Furthermore, it still has a high apparent viscosity in potassium chloride solution and excellent salt resistance. This is mainly because the amphoteric structure of the quaternary ammonium salt and sulfonate contained in the sample has a unique anti-polyelectrolyte solution behavior, which breaks the internal salt bond of the polymer amphoteric ions and enhances the association between polymer molecules. It can maintain good apparent viscosity and thickening effect in salt solutions. Simultaneously, after high-temperature heat treatment, the fracturing fluid thickener also has a high apparent viscosity. This is mainly due to the introduction of heat-resistant diphenyl structures into the side chains of phenolic resin, which helps improve the high-temperature resistance of the thickener, making it less prone to thermal decomposition. Furthermore, the diphenyl structure facilitates sulfonation with chlorosulfonic acid, reducing the sulfonation reaction of the benzene rings in the phenolic resin main chain. This maintains good structural stability of the phenolic resin main chain and reduces the impact of sulfonate groups in the main chain on the heat resistance of the phenolic resin.

[0047] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a thickener for high-temperature fracturing fluid, characterized in that, The preparation method includes the following steps: Step (1): Add quaternary ammonium salt phenolic resin, triethylamine, 4-dimethylaminopyridine, and diphenylacetyl chloride to N,N-dimethylformamide, stir and react, then distill under reduced pressure, wash the product, and dry to obtain diphenyl quaternary ammonium salt phenolic resin. Step (2): Add diphenyl quaternary ammonium salt phenolic resin to dichloromethane, stir, and then add dichloromethane solution of chlorosulfonic acid dropwise under nitrogen atmosphere. After stirring and reacting, pour the solution into water, stir, add sodium hydroxide aqueous solution, extract and separate, wash the product, dry, add the product to deionized water, prepare a thickener solution, and obtain a thickener for high-temperature fracturing fluid. The preparation method of the quaternary ammonium salt phenolic resin includes the following steps: adding triethylamine hydrochloride and epoxy phenolic resin to water, heating to 75-80℃, stirring and reacting for 5-8 hours, distilling under reduced pressure and adding toluene, azeotropically removing water, washing the product, and drying to obtain the quaternary ammonium salt phenolic resin.

2. The method for preparing the thickener for high-temperature fracturing fluid according to claim 1, characterized in that, In step (1), the ratio of quaternary ammonium salt phenolic resin, triethylamine, 4-dimethylaminopyridine, and diphenylacetyl chloride is 100g:(0.2-0.6)mol:(0.012-0.04)mol:(0.2-0.6)mol.

3. The method for preparing the thickener for high-temperature fracturing fluid according to claim 1, characterized in that, The temperature of the stirring reaction in step (1) is 20-30℃, and the reaction time is 18-24h.

4. The method for preparing the thickener for high-temperature fracturing fluid according to claim 1, characterized in that, In step (2), the ratio of diphenyl quaternary ammonium salt phenolic resin to chlorosulfonic acid is 100g: (1500-2500)g.

5. The method for preparing the thickener for high-temperature fracturing fluid according to claim 1, characterized in that, The temperature of the stirring reaction in step (2) is 0-5℃, and the reaction time is 12-24h.

6. The method for preparing the thickener for high-temperature fracturing fluid according to claim 1, characterized in that, In step (2), sodium hydroxide aqueous solution is added to adjust the pH to 7-9.

7. The method for preparing the thickener for high-temperature fracturing fluid according to claim 2, characterized in that, The mass fraction of the thickener solution in (2) is 0.2-0.8%.

8. The method for preparing the thickener for high-temperature fracturing fluid according to claim 1, characterized in that, The ratio of triethylamine hydrochloride to epoxy phenolic resin is (0.15-0.4) mol: 100g.

9. A thickener for high-temperature fracturing fluid prepared by any one of claims 1-8.

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