Graft modified cellulose filtrate reducer and preparation method thereof

Abstract

The invention relates to the technical field of oilfield chemistry, and discloses a graft modified cellulose filtrate reducer and a preparation method thereof.The preparation method comprises the following steps that modified hydroxyethyl cellulose, 2-acrylamide-2-methyl propane sulfonic acid, dimethyl diallyl ammonium chloride, alkenylated cardanol and N, N '-methylene bisacrylamide are added into deionized water, stirring is conducted, and a mixture is obtained; the preparation method comprises the following steps: adding cellulose into a reaction kettle, stirring for 10-15 minutes at the temperature of 40-60 DEG C at the speed of 300-400 rpm, dropwise adding ammonium persulfate and sodium hydrogen sulfite into a system, and continuously reacting for 4-6 hours to obtain the grafted modified cellulose filtrate reducer. The filtrate reducer disclosed by the invention has good high temperature resistance and salt resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil field chemistry, in particular to a grafted modified cellulose fluid loss additive and a preparation method thereof. BACKGROUND

[0002] In the process of oil and gas drilling, the filtration loss control of drilling fluid directly affects the wellbore stability and operation safety. With the development of deep and ultra-deep oil and gas exploration, complex high-temperature and high-salt formations have higher requirements for the performance of drilling fluid. As a key treatment agent, the fluid loss additive needs to maintain stable performance in high-temperature and high-salt environments, reduce the invasion of filtrate into the formation, and form a high-quality mud cake to ensure wellbore stability. The traditional fluid loss additive has insufficient temperature resistance, which easily leads to a sharp increase in filtration loss, and the salt resistance cannot meet the needs of complex formations such as deep sea and salt-gypsum layers. Therefore, how to avoid this phenomenon is the key to solving the problem. Patent No. CN120025795B discloses a fluid loss additive for oil-based drilling fluid. The fluid loss additive has the characteristics of wide raw material sources, good compatibility with oil-based drilling fluid, easy industrial production, and controllable environmental pollution problems. However, the salt resistance and high-temperature resistance need to be improved. SUMMARY

[0003] (I) Technical problems to be solved In view of the deficiencies of the prior art, the present application provides a grafted modified cellulose fluid loss additive and a preparation method thereof. The fluid loss additive has good high-temperature resistance and salt resistance.

[0004] (II) Technical solutions To achieve the above-mentioned purpose, the present application provides the following technical solutions: a grafted modified cellulose fluid loss additive, characterized in that it comprises the following components by weight: 28-32 parts by weight of modified hydroxyethyl cellulose, 4-6 parts by weight of 2-acrylamide-2-methyl propane sulfonic acid, 2-4 parts by weight of dimethyl diallyl ammonium chloride, 3-5 parts by weight of alkenylized cashew phenol, 0.3-0.5 parts by weight of ammonium persulfate, 0.3-0.4 parts by weight of sodium bisulfite, 0.08-0.1 parts by weight of N,N'-methylene bisacrylamide, and 50-55 parts by weight of deionized water.

[0005] Further, the preparation method of the modified hydroxyethyl cellulose is as follows: under the protection of nitrogen gas, hydroxyethyl cellulose and acryloyl chloride are added to a tetrahydrofuran solvent, stirred and mixed, then triethylamine is added, and reacted at room temperature for 4-6 hours. After the reaction is completed, the reaction liquid is added to anhydrous ether at a speed of 1-2 drops per second under stirring, white precipitate is separated out, the precipitate is collected by suction filtration, washed with anhydrous ethanol for 2-3 times, and dried at 40-50°C until constant weight to obtain the modified hydroxyethyl cellulose.

[0006] Further, the preparation method of the modified hydroxyethyl cellulose has the following ratio of tetrahydrofuran, hydroxyethyl cellulose, acryloyl chloride, triethylamine, and anhydrous ether: 15-20 mL: 2.75-2.78 g: 2.32-2.36 g: 0.04-0.05 g: 130-150 mL.

[0007] Further, the preparation method of the alkenylated cardanol is as follows: Step one: adding cardanol, 2,2-di(bromomethyl)-1,3-propanediol, and sodium hydroxide into acetone solvent, stirring uniformly, then continuing to add sodium hydroxide, and continuing to react for 3-5 h; after the reaction is completed, cooling to room temperature, standing to separate layers, washing the upper acetone layer with deionized water for 5-8 min, standing to separate layers, and then discharging the lower water phase; repeating the washing for 2-3 times, adding anhydrous magnesium sulfate into the washed acetone solution to adsorb residual water, stirring for 30-35 min, removing the drying agent by filtration, transferring the filtrate to a rotary evaporator, and distilling the crude product under reduced pressure at 40-45℃ to obtain the intermediate 1; Step two: adding the intermediate 1 and acrylic acid into toluene solvent under inert gas protection, stirring and mixing, then adding p-toluenesulfonic acid catalyst, continuing to react for 6-8 h, cooling to room temperature after the reaction is completed, transferring to a separatory funnel, washing with a 5% sodium chloride solution for 2-3 times, washing with deionized water until neutral, drying the organic phase with anhydrous magnesium sulfate for 10-12 h, filtering and removing toluene by rotary evaporation, purifying the crude product by silica gel column chromatography, collecting the target fraction, and vacuum drying after rotary evaporation to obtain the alkenylated cardanol.

[0008] Further, the ratio of acetone, cardanol, 2,2-di(bromomethyl)-1,3-propanediol, and sodium hydroxide in step one is 20-22 mL: 3.32-3.36 g: 5.24-5.28 g: 0.9-1.1 g.

[0009] Further, the reaction temperature in step one is 65-75℃.

[0010] Further, the ratio of toluene, intermediate 1, acrylic acid, and p-toluenesulfonic acid in step two is 35-40 mL: 5.63-5.66 g: 2.56-2.58 g: 0.06-0.07 g.

[0011] Further, the reaction temperature in step two is 110-120℃.

[0012] Further, the preparation method of the grafted modified cellulose fluid loss additive is as follows: adding modified hydroxyethyl cellulose, 2-acrylamide-2-methyl propane sulfonic acid, dimethyldiallylammonium chloride, alkenylized cardanol, N,N'-methylene bisacrylamide into deionized water, stirring at 300-400 rpm for 10-15 min at 40-60 DEG C, then adding ammonium persulfate and sodium bisulfite dropwise into the system, and continuing to react for 4-6 h to obtain the grafted modified cellulose fluid loss additive.

[0013] (Three) beneficial technical effects The present application introduces sulfonic acid groups by grafting 2-acrylamide-2-methyl propane sulfonic acid on cellulose, and the sulfonic acid groups can still be ionized in a high salt environment, thus maintaining the molecular chain stretching, so that the fluid loss additive is more stable in seawater drilling fluid, and the salt resistance of the fluid loss additive can be effectively improved. The thermal stability of the sulfonic acid group is better than that of the carboxyl group, and the cellulose molecular chain is not easily broken at high temperature, so that the high temperature resistance of the fluid loss additive is improved. The quaternary ammonium salt groups are introduced into the cellulose by grafting dimethyldiallylammonium chloride, and the stability of the quaternary ammonium salt is better than that of the cellulose in a high salt environment due to the electric property of the quaternary ammonium salt not being affected by high valence ions, so that the salt resistance of the fluid loss additive can be improved. The alkenyl group is introduced into the cardanol, which can make the cardanol graft copolymerize with cellulose like other monomers, and on the other hand, the hydrophobic long chain of the cardanol itself can reduce the penetration of water molecules and delay the hydrolytic degradation of the polymer at high temperature, and the introduction of the alkenyl group can form a more stable hydrophobic layer to delay the thermal degradation of the fluid loss additive, so that the high temperature resistance of the fluid loss additive is improved. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is the synthesis reaction formula of the alkenylized cardanol. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application is described clearly and completely, obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present application.

[0016] In order to better understand the above technical scheme, the above technical scheme will be described in detail in combination with the drawings of the specification and specific embodiments.

[0017] Embodiment 1 (1) Under nitrogen gas protection, 2.75 g of hydroxyethyl cellulose, 2.32 g of acryloyl chloride were added into 15 mL of tetrahydrofuran solvent, stirred and mixed, then 0.04 g of triethylamine was added, and reacted at room temperature for 4 h. After the reaction was completed, the reaction solution was added into 130 mL of anhydrous ether at a rate of 1 drop per second under stirring, and a white precipitate was separated out. The precipitate was collected by suction filtration, washed with anhydrous ethanol for 2 times, and dried at 40°C to constant weight to obtain modified hydroxyethyl cellulose; (2) 3.32 g of cardanol, 5.24 g of 2,2-bis(bromomethyl)-1,3-propanediol were added into 20 mL of acetone solvent, stirred and mixed, then 0.9 g of sodium hydroxide was further added, and reacted at 65°C for 3 h. After the reaction was completed, it was cooled to room temperature, and separated into layers by standing. The upper acetone layer was washed with deionized water for 5 min by shaking, and separated into layers by standing. The lower aqueous phase was discharged. The acetone solution after washing was added with anhydrous magnesium sulfate to adsorb residual water, stirred for 30 min, and filtered to remove the drying agent. The filtrate was transferred to a rotary evaporator, and distilled under reduced pressure at 40°C to obtain a crude product. The crude product was placed in a vacuum drying oven, and dried at 40°C to constant weight to obtain intermediate 1. (3) Under nitrogen gas protection, 5.63 g of intermediate 1, 2.56 g of acrylic acid were added into 35 mL of toluene solvent, stirred and mixed, then 0.06 g of p-toluenesulfonic acid catalyst was added, and reacted at 110°C for 6 h. After the reaction was completed, it was cooled to room temperature, and transferred to a separatory funnel. The organic phase was washed with 5% sodium chloride solution for 2 times, and then with deionized water until neutral. The organic phase was dried with anhydrous magnesium sulfate for 10 h, filtered, and rotary evaporated to remove toluene. The crude product was purified by silica gel column chromatography, the target fraction was collected, rotary evaporated, and vacuum dried to obtain alkenylated cardanol, as shown in Figure 1 . (4) 28 parts by weight of modified hydroxyethyl cellulose, 4 parts by weight of 2-acrylamide-2-methylpropane sulfonic acid, 2 parts by weight of dimethyldiallylammonium chloride, 3 parts by weight of alkenylated cardanol, and 0.08 parts by weight of N,N'-methylenebisacrylamide were added into deionized water, stirred at 300 rpm for 10 min at 40°C, then 0.3 parts by weight of ammonium persulfate and 0.3 parts by weight of sodium bisulfite were added dropwise into the system, and reacted for 4 h to obtain a grafted modified cellulose fluid loss additive.

[0018] Example 2 (1) Under the protection of nitrogen gas, 2.78 g of hydroxyethyl cellulose, 2.36 g of acryloyl chloride were added to 20 mL of tetrahydrofuran solvent, stirred and mixed, then 0.05 g of triethylamine was added, and the reaction was carried out at room temperature for 6 h. After the reaction was completed, the reaction solution was added to 150 mL of anhydrous ether at a rate of 2 drops per second under stirring, and white precipitate was separated by stirring. The precipitate was collected by suction filtration, washed with anhydrous ethanol for 3 times, and dried at 50°C until the weight was constant to obtain modified hydroxyethyl cellulose; (2) 3.36 g of cardanol, 5.28 g of 2,2-bis(bromomethyl)-1,3-propanediol were added to 22 mL of acetone solvent, stirred and mixed, then 1.1 g of sodium hydroxide was further added, and the reaction was continued at 75°C for 5 h. After the reaction was completed, it was cooled to room temperature, and then separated into layers by standing. The upper acetone layer was washed with deionized water for 8 min by shaking, and then separated into layers by standing. The lower aqueous phase was removed. The acetone solution after washing was added with anhydrous magnesium sulfate to adsorb residual water, stirred for 35 min, and then filtered to remove the drying agent. The filtrate was transferred to a rotary evaporator, and distilled at 45°C under reduced pressure to obtain a crude product. The crude product was placed in a vacuum drying oven and dried at 50°C until the weight was constant to obtain intermediate 1. (3) Under the protection of nitrogen gas, 5.66 g of intermediate 1, 2.58 g of acrylic acid were added to 40 mL of toluene solvent, stirred and mixed, then 0.07 g of p-toluenesulfonic acid catalyst was added, and the reaction was continued at 120°C for 8 h. After the reaction was completed, it was cooled to room temperature, and then transferred to a separatory funnel. The organic phase was washed with 5% sodium chloride solution for 3 times, and then washed with deionized water until neutral. The organic phase was dried with anhydrous magnesium sulfate for 12 h, filtered, and then the toluene was removed by rotary evaporation. The crude product was purified by silica gel column chromatography, the target fraction was collected, and then dried in vacuum after rotary evaporation to obtain alkenylated cardanol; (4) 32 parts by weight of modified hydroxyethyl cellulose, 6 parts by weight of 2-acrylamide-2-methylpropane sulfonic acid, 4 parts by weight of dimethyldiallylammonium chloride, 5 parts by weight of alkenylated cardanol, and 0.1 part by weight of N,N'-methylenebisacrylamide were added to deionized water, and stirred at 60°C at 400 rpm for 15 min. Then, 0.5 part by weight of ammonium persulfate and 0.4 part by weight of sodium bisulfite were added dropwise to the system, and the reaction was continued for 6 h to obtain a grafted modified cellulose fluid loss additive.

[0019] Example 3 (1) Under nitrogen gas protection, 2.77 g of hydroxyethyl cellulose, 2.34 g of acryloyl chloride were added to 18 mL of tetrahydrofuran solvent, stirred and mixed, then 0.04 g of triethylamine was added, and reacted at room temperature for 5 h. After the reaction was completed, the reaction solution was added to 140 mL of anhydrous ether at a rate of 1 drop per second under stirring, and white precipitate was separated by stirring. The precipitate was collected by suction filtration, washed with anhydrous ethanol twice, and dried at 45°C until the weight was constant to obtain modified hydroxyethyl cellulose; (2) 3.34 g of cardanol, 5.26 g of 2,2-bis(bromomethyl)-1,3-propanediol were added to 21 mL of acetone solvent, stirred and mixed, then 1 g of sodium hydroxide was further added, and reacted at 70°C for 4 h. After the reaction was completed, it was cooled to room temperature, and after standing and layering, the upper acetone layer was washed with deionized water for 7 min, and after standing and layering, the lower aqueous phase was discharged. The acetone solution after washing was added with anhydrous magnesium sulfate to adsorb residual moisture, stirred for 33 min, filtered to remove the drying agent, and the filtrate was transferred to a rotary evaporator and distilled at 42°C under reduced pressure to obtain a crude product. The crude product was placed in a vacuum drying oven and dried at 45°C until the weight was constant to obtain intermediate 1; (3) Under nitrogen gas protection, 5.64 g of intermediate 1, 2.57 g of acrylic acid were added to 38 mL of toluene solvent, stirred and mixed, then 0.06 g of p-toluenesulfonic acid catalyst was added, and reacted at 115°C for 7 h. After the reaction was completed, it was cooled to room temperature, transferred to a separatory funnel, washed with 5% sodium chloride solution twice, and then washed with deionized water until neutral. The organic phase was dried with anhydrous magnesium sulfate for 11 h, filtered, and the toluene was removed by rotary evaporation. The crude product was purified by silica gel column chromatography, the target fraction was collected, and after rotary evaporation, it was vacuum dried to obtain alkenylated cardanol; (4) 30 parts by weight of modified hydroxyethyl cellulose, 5 parts by weight of 2-acrylamide-2-methylpropane sulfonic acid, 3 parts by weight of dimethyldiallylammonium chloride, 4 parts by weight of alkenylated cardanol, and 0.09 parts by weight of N,N'-methylenebisacrylamide were added to deionized water, stirred at 350 rpm at 50°C for 12 min, then 0.4 parts by weight of ammonium persulfate and 0.3 parts by weight of sodium bisulfite were added dropwise to the system, and reacted for 5 h to obtain a grafted modified cellulose fluid loss additive.

[0020] Example 4 (1) Under nitrogen gas protection, 2.76 g of hydroxyethyl cellulose, 2.33 g of acryloyl chloride were added to 17 mL of tetrahydrofuran solvent, stirred and mixed, then 0.04 g of triethylamine was added, and reacted at room temperature for 4 h. After the reaction was completed, the reaction solution was added to 135 mL of anhydrous ether at a rate of 1 drop per second under stirring, and white precipitate was separated by stirring. The precipitate was collected by suction filtration, washed with anhydrous ethanol 3 times, and dried at 42°C until the weight was constant to obtain modified hydroxyethyl cellulose; (2) 3.33 g of cardanol, 5.25 g of 2,2-bis(bromomethyl)-1,3-propanediol were added to 21 mL of acetone solvent, stirred and mixed, then 0.9 g of sodium hydroxide was further added, and reacted at 68°C for 4 h. After the reaction was completed, it was cooled to room temperature, and after standing and layering, the upper acetone layer was washed with deionized water for 6 min, and after standing and layering, the lower aqueous phase was discharged. The acetone solution after washing was added with anhydrous magnesium sulfate to adsorb residual moisture, stirred for 32 min, filtered to remove the drying agent, and the filtrate was transferred to a rotary evaporator and distilled at 40°C under reduced pressure to obtain a crude product. The crude product was placed in a vacuum drying oven and dried at 45°C until the weight was constant to obtain intermediate 1; (3) Under nitrogen gas protection, 5.64 g of intermediate 1, 2.56 g of acrylic acid were added to 36 mL of toluene solvent, stirred and mixed, then 0.06 g of p-toluenesulfonic acid catalyst was added, and reacted at 112°C for 6 h. After the reaction was completed, it was cooled to room temperature, transferred to a separatory funnel, washed with 5% sodium chloride solution twice, and then washed with deionized water until neutral. The organic phase was dried with anhydrous magnesium sulfate for 11 h, filtered, and the toluene was removed by rotary evaporation. The crude product was purified by silica gel column chromatography, the target fraction was collected, and after rotary evaporation, it was vacuum dried to obtain alkenylated cardanol; (4) 29 parts by weight of modified hydroxyethyl cellulose, 4 parts by weight of 2-acrylamide-2-methylpropane sulfonic acid, 3 parts by weight of dimethyldiallylammonium chloride, 3 parts by weight of alkenylated cardanol, and 0.08 parts by weight of N,N'-methylenebisacrylamide were added to deionized water, stirred at 45°C at 350 rpm for 12 min, then 0.3 parts by weight of ammonium persulfate and 0.3 parts by weight of sodium bisulfite were added dropwise to the system, and reacted for 5 h to obtain a grafted modified cellulose fluid loss additive.

[0021] Example 5 (1) Under the protection of nitrogen gas, 2.77 g of hydroxyethyl cellulose, 2.35 g of acryloyl chloride were added into 19 mL of tetrahydrofuran solvent, stirred and mixed, then 0.05 g of triethylamine was added, and the reaction was carried out at room temperature for 5 h. After the reaction was completed, the reaction solution was added into 145 mL of anhydrous ether at a rate of 2 drops per second under stirring, and white precipitate was separated out. The precipitate was collected by suction filtration, washed with anhydrous ethanol for 3 times, and dried at 48°C until the weight was constant to obtain modified hydroxyethyl cellulose; (2) 3.35 g of cardanol, 5.27 g of 2,2-bis(bromomethyl)-1,3-propanediol were added into 22 mL of acetone solvent, stirred and mixed, then 1.1 g of sodium hydroxide was further added, and the reaction was carried out at 72°C for 5 h. After the reaction was completed, the temperature was cooled to room temperature, and the mixture was allowed to stand to separate into layers. The upper acetone layer was washed with deionized water for 7 min, allowed to stand to separate into layers, and the lower aqueous phase was discharged. The acetone solution after washing was added with anhydrous magnesium sulfate to adsorb residual water, stirred for 35 min, filtered to remove the drying agent, and the filtrate was transferred into a rotary evaporator. The crude product was obtained by distillation at 45°C under reduced pressure, and the crude product was placed in a vacuum drying oven and dried at 48°C until the weight was constant to obtain intermediate 1; (3) Under the protection of nitrogen gas, 5.66 g of intermediate 1, 2.57 g of acrylic acid were added into 38 mL of toluene solvent, stirred and mixed, then 0.07 g of p-toluenesulfonic acid catalyst was added, and the reaction was carried out at 118°C for 8 h. After the reaction was completed, the temperature was cooled to room temperature, and the mixture was transferred into a separatory funnel. The organic phase was washed with 5% sodium chloride solution for 3 times, then washed with deionized water until neutral. The organic phase was dried with anhydrous magnesium sulfate for 12 h, filtered, and the toluene was removed by rotary evaporation. The crude product was purified by silica gel column chromatography, the target fraction was collected, and the product was dried in vacuum after rotary evaporation to obtain alkenylated cardanol; (4) 31 parts by weight of modified hydroxyethyl cellulose, 6 parts by weight of 2-acrylamide-2-methylpropane sulfonic acid, 4 parts by weight of dimethyldiallylammonium chloride, 4 parts by weight of alkenylated cardanol, and 0.1 part by weight of N,N'-methylenebisacrylamide were added into deionized water, stirred at 380 rpm for 15 min at 55°C, then 0.5 part by weight of ammonium persulfate and 0.4 part by weight of sodium bisulfite were added dropwise, and the reaction was carried out for 5 h to obtain the grafted modified cellulose fluid loss additive.

[0022] Comparative Example 1 The difference between this comparative example and Example 5 is that 2-acrylamide-2-methylpropane sulfonic acid was not added.

[0023] Comparative Example 2 The difference between this comparative example and Example 5 is that dimethyldiallylammonium chloride was not added.

[0024] Comparative Example 3 The comparative example is different from example 5 in that no alkenylated cardanol is added.

[0025] Performance test: The filtrate reducers prepared in examples 1-5 and comparative examples 1-3 are subjected to performance test.

[0026] The test is performed on water-based oil wells according to GB / T29170-2012 standard to determine the filtrate reduction performance, rheological property and salt resistance of the filtrate reducers. The specific experimental steps are as follows: (1) High temperature resistance test: the filtrate reducers are added to the drilling fluid in an amount of 1%, 1.5% and 3% of the total mass of the drilling fluid, respectively. The drilling fluid formulation is as follows: filtrate reducer + 0.2% NaOH + saturated NaCl + 3.0% bentonite + barite powder + distilled water (the barite powder is added to control the density of the drilling fluid at 1.8-1.9 g / cm 3 ). The prepared drilling fluid is placed in a high temperature roller heating furnace and heated at 200℃ for 16h. After the heating, the system is naturally cooled to room temperature. The rheological property parameters and the high temperature and high pressure filtrate reduction performance of the system are determined according to GB / T29170-2012 standard. The test temperature is 200℃ and the test pressure is 3.5MPa. The test results are shown in Table 1.

[0027] Table 1: High temperature resistance test

[0028] As shown in Table 1, the filtrate reducers prepared in examples 1-5 have good high temperature resistance.

[0029] (2) Salt resistance test: the filtrate reducers are added to the drilling fluid in an amount of 1.5% of the total mass of the drilling fluid at 25℃. The drilling fluid formulation is as follows: filtrate reducer + 0.2% NaOH + 4% NaCl + 3.0% bentonite + barite powder + distilled water (the barite powder is added to control the density of the drilling fluid at 1.8-1.9 g / cm 3 ) and filtrate reducer + 0.2% NaOH + saturated NaCl + 3.0% bentonite + barite powder + distilled water (the barite powder is added to control the density of the drilling fluid at 1.8-1.9 g / cm 3 ). The filtrate reduction performance of the filtrate reducers in the above two drilling fluid systems is determined according to GB / T29170-2012 standard. The test results are shown in Table 2.

[0030] Table 2: Salt resistance test

[0031] As can be seen from Table 2, the fluid loss additives prepared in Examples 1-5 have good salt tolerance.

[0032] It can be seen that, in Comparative Example 1, the salt resistance and charge stability of the molecular chain of the copolymer are reduced due to the lack of sulfonic acid groups, the molecular chain is curled and cannot effectively stretch to play a space barrier role, resulting in a decrease in the high-temperature resistance and salt tolerance; in Comparative Example 2, the electrostatic binding capacity of the polymer to clay particles is weakened due to the lack of positively charged quaternary ammonium salt groups, the blocking capacity of the mud cake is reduced, and the electrostatic repulsion between the molecular chains is weakened, resulting in a significant decrease in the high-temperature resistance and salt tolerance; and in Comparative Example 3, the long-chain hydrophobic group of the alkenyl cardanol is absent, so the polymer mainly relies on chemical bonds at high temperatures, the chain segment thermal motion is intensified, and degradation and curling are more likely to occur, so the high-temperature resistance and salt tolerance of Comparative Example 3 are significantly reduced.

[0033] It should be noted that in this document, the terms "comprising", "containing" or any other variant thereof are intended to cover non-exclusive inclusion, so that processes, methods, articles or devices that include a series of elements not only include those elements, but also include other elements not explicitly listed, or include elements inherent to such processes, methods, articles or devices. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of other identical elements in the process, method, article or device that includes the element.

[0034] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

[0035] Those skilled in the art should understand that the above only describes several specific embodiments of the present application, but not all embodiments.

Claims

1. A graft-modified cellulose fluid loss additive characterized in that, The weight components include 28-32 parts by weight of modified hydroxyethyl cellulose, 4-6 parts by weight of 2-acrylamide-2-methyl propane sulfonic acid, 2-4 parts by weight of dimethyl diallyl ammonium chloride, 3-5 parts by weight of alkenylized cardanol, 0.3-0.5 parts by weight of ammonium persulfate, 0.3-0.4 parts by weight of sodium bisulfite, 0.08-0.1 parts by weight of N, N'-methylene bisacrylamide, 50-55 parts by weight of deionized water; The preparation method of the modified hydroxyethyl cellulose is as follows: under the protection of nitrogen gas, hydroxyethyl cellulose and acryloyl chloride are added to a tetrahydrofuran solvent, and stirred and mixed, then triethylamine is added, and the reaction is carried out at room temperature for 4-6 hours; after the reaction is completed, the reaction liquid is added to anhydrous ether at a speed of 1-2 drops per second under stirring, and white precipitate is separated out, which is collected by suction filtration, washed with anhydrous ethanol for 2-3 times, and dried at 40-50 DEG C until constant weight to obtain the modified hydroxyethyl cellulose; The preparation method of the alkenylized cardanol is as follows: Step one: cardanol and 2,2-bis(bromomethyl)-1,3-propanediol are added to an acetone solvent, stirred and mixed, then sodium hydroxide is continuously added, and the reaction is continuously carried out for 3-5 hours; after the reaction is completed, the reaction system is cooled to room temperature, and the upper acetone layer is washed with deionized water for 5-8 minutes, and then the lower water phase is separated out after standing and layering; the washing process is repeated for 2-3 times, anhydrous magnesium sulfate is added to the washed acetone solution to adsorb residual water, stirred for 30-35 minutes, and then filtered to remove the drying agent; the filtrate is transferred to a rotary evaporator, and distilled at 40-45 DEG C under reduced pressure to obtain a crude product; the crude product is placed in a vacuum drying oven, and dried at 40-50 DEG C until constant weight to obtain an intermediate 1; Step two: under the protection of inert gas, the intermediate 1 and acrylic acid are added to a toluene solvent, stirred and mixed, then p-toluenesulfonic acid catalyst is added, and the reaction is continuously carried out for 6-8 hours; after the reaction is completed, the reaction system is cooled to room temperature, and then transferred to a separatory funnel, washed with a 5% sodium chloride solution for 2-3 times, and then washed with deionized water until neutral; the organic phase is dried with anhydrous magnesium sulfate for 10-12 hours, filtered, and then rotary evaporated to remove toluene; the crude product is purified by silica gel column chromatography, and the target fraction is collected, rotary evaporated, and then vacuum dried to obtain the alkenylized cardanol.

2. The graft-modified cellulose fluid loss additive of claim 1, wherein, In the preparation method of the modified hydroxyethyl cellulose, the amount ratio of tetrahydrofuran, hydroxyethyl cellulose, acryloyl chloride, triethylamine, and anhydrous ether is 15-20 mL:2.75-2.78 g:2.32-2.36 g:0.04-0.05 g:130-150 mL.

3. The graft-modified cellulose fluid loss additive of claim 1, wherein, In step one, the amount ratio of acetone, cardanol, 2,2-bis(bromomethyl)-1,3-propanediol, and sodium hydroxide is 20-22 mL:3.32-3.36 g:5.24-5.28 g:0.9-1.1 g.

4. The graft-modified cellulose fluid loss additive of claim 1, wherein, In step one, the reaction temperature is 65-75 DEG C.

5. The graft-modified cellulose fluid loss additive of claim 1, wherein, In step two, the amount ratio of toluene, intermediate 1, acrylic acid, and p-toluenesulfonic acid is 35-40 mL:5.63-5.66 g:2.56-2.58 g:0.06-0.07 g.

6. The graft-modified cellulose fluid loss additive of claim 1, wherein, The reaction temperature in the second step is 110-120 DEG C.

7. A graft-modified cellulose fluid loss additive according to any one of claims 1 to 6, characterized in that, The preparation method of the grafted modified cellulose filtrate reducer is as follows: adding modified hydroxyethyl cellulose, 2-acrylamide-2-methyl propane sulfonic acid, dimethyl diallyl ammonium chloride, alkenylized cardanol and N,N'-methylene bisacrylamide into deionized water, stirring at 300-400 rpm for 10-15 min at 40-60 DEG C, then adding ammonium persulfate and sodium bisulfite dropwisely into the system, and continuing to react for 4-6 h to obtain the grafted modified cellulose filtrate reducer.

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