Preparation method of comb-type salt-resistant fracturing drag reducer

Abstract

The invention relates to the technical field of drag reducers, and discloses a preparation method of a comb-type salt-resistant fracturing drag reducer, which comprises the following steps: adding a chitosan-based polymer, modified graphene, polyoxyethylene resin, potassium chloride, acrylamide and water into a stirrer, and stirring to obtain the comb-type salt-resistant fracturing drag reducer. A plurality of side chains in the chitosan-based polymer can generate a steric hindrance effect, and the flow resistance of the fracturing drag reducer in pipelines and cracks is reduced by reducing the viscosity; salt-resistant monomers such as 2-acrylamide-2-methylpropanesulfonic acid are introduced during synthesis of the chitosan-based polymer, so that the fracturing drag reducer can keep stable molecular structure and performance in a high-salinity environment; graphene in the modified graphene has a layered structure and a self-lubricating property, so that the lubricating coefficient can be reduced, and the resistance between the fracturing resistance-reducing liquid and a pipeline as well as between the fracturing resistance-reducing liquid and a crack is reduced; the ester group has a stable chemical mechanism and is not easy to decompose in a high-salt environment, so that the fracturing drag reducer has a certain salt-resistant effect.

Description

Technical Field

[0001] The invention relates to the technical field of drag reducers, in particular to a method for preparing a comb-type salt-resistant fracturing drag reducer. Background Art

[0002] During the oil extraction process, fracturing drag reducers will generate a certain amount of frictional resistance when flowing in pipelines and the bottom layer. In order to increase oil and gas recovery rates and reduce production costs, fracturing drag reducers are needed to reduce viscosity. By reducing the frictional resistance during fluid flow, it is ensured that the fracturing drag reducer can smoothly enter the underground rock formation, thereby increasing the oil and gas recovery rate.

[0003] In some high-salinity environments such as offshore oil fields, there are certain requirements for the salt resistance of fracturing drag reducers, which require fracturing drag reducers to maintain stable performance in high-salinity environments. Therefore, how to increase oil and gas production and reduce mining costs in harsh environments is of great significance. For example, patent CN117551233B discloses a fracturing drag reducer and its preparation method, which has the characteristics of enhanced drag reduction performance and environmental friendliness, but the salt resistance effect needs to be improved. Summary of the invention

[0004] 1. Technical issues to be resolved In view of the deficiencies of the prior art, the present invention provides a method for preparing a comb-shaped salt-resistant fracturing drag reducer, which has good salt resistance and drag reduction properties.

[0005] (II) Technical solution To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a method for preparing a comb-type salt-resistant fracturing drag reducer, comprising the following steps: adding 4-8 parts by weight of a chitosan-based polymer, 5-7 parts by weight of modified graphene, 2-5 parts by weight of a polyoxyethylene resin, 2-4 parts by weight of potassium chloride, 20-40 parts by weight of acrylamide, and 15-25 parts by weight of water into a stirrer, stirring at room temperature for 20-30 minutes, and obtaining a comb-type salt-resistant fracturing drag reducer after stirring.

[0006] Preferably, the preparation method of the chitosan-based polymer is: Step 1, add 3-dimethylamino-1-propanol and itaconic anhydride to N,N-dimethylformamide solvent, stir and disperse, introduce nitrogen protection, react at 60-75°C for 12-16h, and distill under reduced pressure after the reaction, wash to obtain intermediate 1; Step 2, adding 3-7 parts by weight of chitosan to dimethyl sulfoxide solvent to dissolve, heating in a water bath at 70-90° C., adding 4-9 parts by weight of 2,3-epoxypropyltrimethylammonium chloride at constant pressure, reacting for 6-10 hours, washing with anhydrous ethanol after the reaction, drying, dialyzing, and concentrating to obtain quaternized chitosan; Step 3, add 4-8 parts by weight of quaternized chitosan and 5-10 parts by weight of intermediate 1 to N,N-dimethylformamide solvent, stir and mix, continue to add 0.02-0.04 parts by weight of p-toluenesulfonic acid catalyst, react at 90-115° C. for 4-7 hours, wash and dry after completion to obtain intermediate 2; Step 4: Add acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and N,N-dimethylacrylamide to N,N-dimethylformamide solvent, stir to dissolve, introduce nitrogen, heat in a water bath at 15-30°C, continue to add intermediate 2 and azobisisobutyronitrile initiator, stir to react for 16-22h, wash with anhydrous ethanol after the reaction, and dry to obtain a chitosan-based polymer.

[0007] Preferably, in step 1, the mass ratio of 3-dimethylamino-1-propanol to itaconic anhydride is 1.2-1.5:1.

[0008] Preferably, in the step 4, the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, intermediate 2, and azobisisobutyronitrile initiator is 1.2-1.4:1:0.7-0.9:1.5-2.3:0.01-0.03.

[0009] Preferably, the preparation method of the modified graphene is: S1. Add 5-10 parts by weight of graphene oxide to 55-90 parts by weight of thionyl chloride, disperse by ultrasonication, and after uniform dispersion, react at 60-75° C., filter after the reaction, wash, and dry to obtain chlorinated graphene; S2. Add chlorinated graphene to the ethanol solvent, stir and disperse, continue to add 1,3-di(dimethylamino)-2-propanol and p-toluenesulfonic acid catalyst, react at 60-90° C. for 8-12 hours, and after completion, wash and dry to obtain intermediate 3; S3. Add 4-8 parts by weight of intermediate 3 and 3-7 parts by weight of 1,3-propane sultone to acetone solvent for dissolution, then dropwise add 2-6% sodium hydroxide solution, react at 70-85° C. for 7-14 hours, concentrate under reduced pressure after the reaction to remove the solvent, and recrystallize the crude product in ethanol to obtain modified graphene.

[0010] Preferably, the reaction time in S1 is 14-20 hours.

[0011] Preferably, the mass ratio of the chlorinated graphene, 1,3-di(dimethylamino)-2-propanol, and p-toluenesulfonic acid catalyst in S2 is 0.4-0.6:1:0.01-0.03.

[0012] 3. Beneficial technical effects The present invention obtains the comb-type salt-resistant fracturing drag reducer by adding chitosan-based polymer, modified graphene, polyoxyethylene resin, potassium chloride, acrylamide and water into a stirrer for stirring.

[0013] The hydroxyl group in 3-dimethylamino-1-propanol reacts with the anhydride in itaconic anhydride to introduce a carbon-carbon double bond to obtain intermediate 1. The amino group in chitosan reacts with the epoxy group in 2,3-epoxypropyltrimethylammonium chloride to open the epoxy ring and introduce a hydroxyl group and a quaternary ammonium salt to obtain quaternary chitosan. The quaternary chitosan undergoes an esterification reaction with intermediate 1 to introduce an ester group to obtain intermediate 2. Intermediate 2 undergoes a polymerization reaction with acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, and N,N-dimethylacrylamide to introduce an amide group and a salt-resistant monomer to obtain a chitosan-based polymer. The acyl chloride group in acyl chloride graphene reacts with the hydroxyl group of 1,3-di(dimethylamino)-2-propanol to introduce a tertiary amine and an ester group to obtain intermediate 3. The tertiary amine in intermediate 3 reacts with 1,3-propane sultone to generate a quaternary ammonium salt group to obtain modified graphene.

[0014] The multiple side chains in the chitosan-based polymer can produce a steric hindrance effect, hindering the molecules from approaching each other, and reducing the flow resistance of the fracturing drag reducer in the pipeline and cracks by reducing the viscosity; the ester group on the side chain is a hydrophobic monomer, which can improve the rheological properties of the fracturing drag reducing fluid and improve the drag reduction efficiency; the amino group in the chitosan molecular structure shields the salt ions from interacting with the charges in the polymer molecular chain to a certain extent, thereby ensuring the stability of the polymer; when synthesizing the chitosan-based polymer, salt-resistant monomers such as 2-acrylamide-2-methylpropane sulfonic acid are introduced to further ensure that the fracturing drag reducer can maintain a stable molecular structure and performance in a high-salinity environment; the graphene in the modified graphene has a layered structure and self-lubricating properties, which can reduce the lubrication coefficient and reduce the resistance between the fracturing drag reducing fluid and the pipeline and cracks; the quaternary ammonium salt group can reduce the surface tension of the liquid, thereby reducing the resistance when the liquid flows, thereby improving the flow effect of the fracturing drag reducer; the ester group has a stable chemical structure and is not easy to decompose in a high-salinity environment, so that the fracturing drag reducer has a certain salt resistance effect. DETAILED DESCRIPTION Example 1

[0015] (1) Add 3-dimethylamino-1-propanol and itaconic anhydride to N,N-dimethylformamide solvent, wherein the mass ratio of 3-dimethylamino-1-propanol to itaconic anhydride is 1.2:1, stir and disperse, introduce nitrogen protection, react at 60°C for 12 hours, and distill under reduced pressure after the reaction, wash, and obtain intermediate 1; (2) adding 3 parts by weight of chitosan to dimethyl sulfoxide solvent to dissolve it, heating it in a water bath at 70° C., adding 4 parts by weight of 2,3-epoxypropyltrimethylammonium chloride at constant pressure, reacting it for 6 hours, washing it with anhydrous ethanol after the reaction, drying it, dialyzing it, and concentrating it to obtain quaternized chitosan; (3) Add 4 parts by weight of quaternized chitosan and 5 parts by weight of intermediate 1 to N,N-dimethylformamide solvent, stir and mix, continue to add 0.02 parts by weight of p-toluenesulfonic acid catalyst, react at 90° C. for 4 hours, wash and dry after reaction, to obtain intermediate 2; (4) Add acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, and N,N-dimethylacrylamide to N,N-dimethylformamide solvent, stir to dissolve, introduce nitrogen, heat in a water bath at 15°C, and continue to add intermediate 2 and azobisisobutyronitrile initiator, wherein the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, intermediate 2, and azobisisobutyronitrile initiator is 1.2:1:0.7:1.5:0.01, stir to react for 16 hours, wash with anhydrous ethanol after the reaction, and dry to obtain a chitosan-based polymer; (5) adding 5 parts by weight of graphene oxide to 55 parts by weight of thionyl chloride, dispersing by ultrasonication, reacting at 60° C. for 14 h after uniform dispersion, filtering after the reaction, washing, and drying to obtain chlorinated graphene; (6) Adding chlorinated graphene to ethanol solvent, stirring and dispersing, and continuing to add 1,3-di(dimethylamino)-2-propanol and p-toluenesulfonic acid catalyst, wherein the mass ratio of chlorinated graphene, 1,3-di(dimethylamino)-2-propanol, and p-toluenesulfonic acid catalyst is 0.4:1:0.01, reacting at 60°C for 8h, and after completion, washing and drying to obtain intermediate 3; (7) adding 4 parts by weight of intermediate 3 and 3 parts by weight of 1,3-propane sultone to an acetone solvent for dissolution, then dropping a 2% sodium hydroxide solution, reacting at 70° C. for 7 h, and concentrating under reduced pressure to remove the solvent after the reaction. The crude product was recrystallized in ethanol to obtain modified graphene; (8) 4 parts by weight of chitosan-based polymer, 5 parts by weight of modified graphene, 2 parts by weight of polyethylene oxide resin, 2 parts by weight of potassium chloride, 20 parts by weight of acrylamide, and 15 parts by weight of water were added into a stirrer and stirred at room temperature for 20 minutes to obtain a comb-type salt-resistant fracturing drag reducer. Example 2

[0016] (1) Add 3-dimethylamino-1-propanol and itaconic anhydride to N,N-dimethylformamide solvent, wherein the mass ratio of 3-dimethylamino-1-propanol to itaconic anhydride is 1.3:1, stir and disperse, introduce nitrogen protection, react at 64°C for 13 hours, and distill under reduced pressure after the reaction, wash, and obtain intermediate 1; (2) adding 4 parts by weight of chitosan to dimethyl sulfoxide solvent to dissolve it, heating it in a water bath at 72° C., adding 5 parts by weight of 2,3-epoxypropyltrimethylammonium chloride at constant pressure, reacting it for 7 hours, washing it with anhydrous ethanol after the reaction, drying it, dialyzing it, and concentrating it to obtain quaternized chitosan; (3) Add 5 parts by weight of quaternized chitosan and 6 parts by weight of intermediate 1 to N,N-dimethylformamide solvent, stir and mix, continue to add 0.02 parts by weight of p-toluenesulfonic acid catalyst, react at 95° C. for 5 h, wash and dry after reaction, to obtain intermediate 2; (4) Add acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, and N,N-dimethylacrylamide to N,N-dimethylformamide solvent, stir to dissolve, introduce nitrogen, heat in a water bath at 18°C, and continue to add intermediate 2 and azobisisobutyronitrile initiator, wherein the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, intermediate 2, and azobisisobutyronitrile initiator is 1.2:1:0.7:1.7:0.01, stir to react for 17 hours, wash with anhydrous ethanol after the reaction, and dry to obtain a chitosan-based polymer; (5) adding 6 parts by weight of graphene oxide to 60 parts by weight of thionyl chloride, dispersing by ultrasonication, reacting at 64° C. for 15 h after being uniformly dispersed, filtering, washing, and drying after the reaction to obtain graphene chloride; (6) Adding chlorinated graphene to ethanol solvent, stirring and dispersing, and continuing to add 1,3-di(dimethylamino)-2-propanol and p-toluenesulfonic acid catalyst, wherein the mass ratio of chlorinated graphene, 1,3-di(dimethylamino)-2-propanol, and p-toluenesulfonic acid catalyst is 0.5:1:0.01, reacting at 70°C for 9h, and after completion, washing and drying to obtain intermediate 3; (7) adding 6 parts by weight of the intermediate 3 and 4 parts by weight of 1,3-propane sultone to an acetone solvent for dissolution, then dropping a 3% sodium hydroxide solution, reacting at 72° C. for 9 h, and concentrating under reduced pressure to remove the solvent after the reaction. The crude product was recrystallized in ethanol to obtain modified graphene; (8) 5 parts by weight of chitosan-based polymer, 6 parts by weight of modified graphene, 3 parts by weight of polyethylene oxide resin, 2 parts by weight of potassium chloride, 25 parts by weight of acrylamide, and 18 parts by weight of water were added into a stirrer and stirred at room temperature for 22 minutes to obtain a comb-type salt-resistant fracturing drag reducer. Example 3

[0017] (1) Add 3-dimethylamino-1-propanol and itaconic anhydride to N,N-dimethylformamide solvent, wherein the mass ratio of 3-dimethylamino-1-propanol to itaconic anhydride is 1.3:1, stir and disperse, introduce nitrogen protection, react at 65°C for 14 hours, and distill under reduced pressure after the reaction, wash, and obtain intermediate 1; (2) adding 5 parts by weight of chitosan to dimethyl sulfoxide solvent to dissolve it, heating it in a water bath at 80° C., adding 7 parts by weight of 2,3-epoxypropyltrimethylammonium chloride at constant pressure, reacting it for 8 hours, washing it with anhydrous ethanol after the reaction, drying it, dialyzing it, and concentrating it to obtain quaternized chitosan; (3) Add 6 parts by weight of quaternized chitosan and 7 parts by weight of intermediate 1 to N,N-dimethylformamide solvent, stir and mix, continue to add 0.03 parts by weight of p-toluenesulfonic acid catalyst, react at 105° C. for 5 h, wash and dry after reaction, to obtain intermediate 2; (4) Add acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, and N,N-dimethylacrylamide to N,N-dimethylformamide solvent, stir to dissolve, introduce nitrogen, heat in a water bath at 22°C, and continue to add intermediate 2 and azobisisobutyronitrile initiator, wherein the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, intermediate 2, and azobisisobutyronitrile initiator is 1.3:1:0.8:1.9:0.02, stir to react for 19 hours, wash with anhydrous ethanol after the reaction, and dry to obtain a chitosan-based polymer; (5) adding 7 parts by weight of graphene oxide to 75 parts by weight of thionyl chloride, dispersing by ultrasonication, reacting at 78° C. for 17 h after being uniformly dispersed, filtering by suction after the reaction, washing, and drying to obtain graphene chloride; (6) Adding chlorinated graphene to ethanol solvent, stirring and dispersing, and continuing to add 1,3-di(dimethylamino)-2-propanol and p-toluenesulfonic acid catalyst, wherein the mass ratio of chlorinated graphene, 1,3-di(dimethylamino)-2-propanol, and p-toluenesulfonic acid catalyst is 0.5:1:0.02, reacting at 75°C for 10 hours, and after completion, washing and drying to obtain intermediate 3; (7) adding 6 parts by weight of the intermediate 3 and 5 parts by weight of 1,3-propane sultone to an acetone solvent for dissolution, then dropping a 4% sodium hydroxide solution, reacting at 77° C. for 10 h, and concentrating under reduced pressure to remove the solvent after the reaction. The crude product was recrystallized in ethanol to obtain modified graphene; (8) Add 6 parts by weight of chitosan-based polymer, 6 parts by weight of modified graphene, 3 parts by weight of polyethylene oxide resin, 3 parts by weight of potassium chloride, 30 parts by weight of acrylamide, and 20 parts by weight of water into a stirrer and stir at room temperature for 25 minutes to obtain a comb-type salt-resistant fracturing drag reducer. Example 4

[0018] (1) Add 3-dimethylamino-1-propanol and itaconic anhydride to N,N-dimethylformamide solvent, wherein the mass ratio of 3-dimethylamino-1-propanol to itaconic anhydride is 1.4:1, stir and disperse, introduce nitrogen protection, react at 70°C for 15 hours, and distill under reduced pressure after the reaction, wash, and obtain intermediate 1; (2) adding 7 parts by weight of chitosan to dimethyl sulfoxide solvent to dissolve it, heating it in a water bath at 88° C., adding 8 parts by weight of 2,3-epoxypropyltrimethylammonium chloride at constant pressure, reacting it for 8 hours, washing it with anhydrous ethanol after the reaction, drying it, dialyzing it, and concentrating it to obtain quaternized chitosan; (3) Add 7 parts by weight of quaternized chitosan and 8 parts by weight of intermediate 1 to N,N-dimethylformamide solvent, stir and mix, continue to add 0.04 parts by weight of p-toluenesulfonic acid catalyst, react at 110° C. for 6 hours, wash and dry after reaction, to obtain intermediate 2; (4) Add acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, and N,N-dimethylacrylamide to N,N-dimethylformamide solvent, stir to dissolve, introduce nitrogen, heat in a water bath at 27°C, and continue to add intermediate 2 and azobisisobutyronitrile initiator, wherein the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, intermediate 2, and azobisisobutyronitrile initiator is 1.3:1:0.8:2.1:0.03, stir to react for 20 hours, wash with anhydrous ethanol after the reaction, and dry to obtain a chitosan-based polymer; (5) adding 8 parts by weight of graphene oxide to 80 parts by weight of thionyl chloride, dispersing by ultrasonication, reacting at 70° C. for 18 h after uniform dispersion, filtering, washing, and drying after the reaction to obtain graphene chloride; (6) Adding chlorinated graphene to ethanol solvent, stirring and dispersing, and continuing to add 1,3-di(dimethylamino)-2-propanol and p-toluenesulfonic acid catalyst, wherein the mass ratio of chlorinated graphene, 1,3-di(dimethylamino)-2-propanol, and p-toluenesulfonic acid catalyst is 0.6:1:0.03, reacting at 80°C for 10 hours, and after completion, washing and drying to obtain intermediate 3; (7) adding 7 parts by weight of the intermediate 3 and 6 parts by weight of 1,3-propane sultone to an acetone solvent for dissolution, then dropping a 5% sodium hydroxide solution, reacting at 83° C. for 10 h, and concentrating under reduced pressure to remove the solvent after the reaction. The crude product was recrystallized in ethanol to obtain modified graphene; (8) 7 parts by weight of chitosan-based polymer, 6 parts by weight of modified graphene, 4 parts by weight of polyethylene oxide resin, 3 parts by weight of potassium chloride, 35 parts by weight of acrylamide, and 22 parts by weight of water were added into a stirrer and stirred at room temperature for 27 minutes to obtain a comb-type salt-resistant fracturing drag reducer. Example 5

[0019] (1) Add 3-dimethylamino-1-propanol and itaconic anhydride to N,N-dimethylformamide solvent, wherein the mass ratio of 3-dimethylamino-1-propanol to itaconic anhydride is 1.5:1, stir and disperse, introduce nitrogen protection, react at 75°C for 16 hours, and distill under reduced pressure after the reaction, wash, and obtain intermediate 1; (2) adding 7 parts by weight of chitosan to dimethyl sulfoxide solvent to dissolve it, heating it in a water bath at 90° C., adding 9 parts by weight of 2,3-epoxypropyltrimethylammonium chloride at constant pressure, reacting it for 10 hours, washing it with anhydrous ethanol after the reaction, drying it, dialyzing it, and concentrating it to obtain quaternized chitosan; (3) Add 8 parts by weight of quaternized chitosan and 10 parts by weight of intermediate 1 to N,N-dimethylformamide solvent, stir and mix, continue to add 0.04 parts by weight of p-toluenesulfonic acid catalyst, react at 115° C. for 7 hours, wash and dry after reaction, to obtain intermediate 2; (4) Add acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, and N,N-dimethylacrylamide to N,N-dimethylformamide solvent, stir to dissolve, introduce nitrogen, heat in a water bath at 30°C, and continue to add intermediate 2 and azobisisobutyronitrile initiator, wherein the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, intermediate 2, and azobisisobutyronitrile initiator is 1.4:1:0.9:2.3:0.03, stir to react for 22 hours, wash with anhydrous ethanol after the reaction, and dry to obtain a chitosan-based polymer; (5) adding 10 parts by weight of graphene oxide to 90 parts by weight of thionyl chloride, dispersing by ultrasonication, reacting at 75° C. for 20 h after being uniformly dispersed, filtering, washing, and drying after the reaction to obtain graphene chloride; (6) Adding chlorinated graphene to ethanol solvent, stirring and dispersing, and continuing to add 1,3-di(dimethylamino)-2-propanol and p-toluenesulfonic acid catalyst, wherein the mass ratio of chlorinated graphene, 1,3-di(dimethylamino)-2-propanol, and p-toluenesulfonic acid catalyst is 0.6:1:0.03, reacting at 90°C for 12h, and after completion, washing and drying to obtain intermediate 3; (7) adding 8 parts by weight of the intermediate 3 and 7 parts by weight of 1,3-propane sultone to an acetone solvent for dissolution, then dropping a 6% sodium hydroxide solution, reacting at 85° C. for 14 h, and concentrating under reduced pressure to remove the solvent after the reaction. The crude product was recrystallized in ethanol to obtain modified graphene; (8) 8 parts by weight of chitosan-based polymer, 7 parts by weight of modified graphene, 5 parts by weight of polyethylene oxide resin, 4 parts by weight of potassium chloride, 40 parts by weight of acrylamide, and 25 parts by weight of water were added into a stirrer and stirred at room temperature for 30 minutes to obtain a comb-type salt-resistant fracturing drag reducer.

[0020] Comparative Example 1 4 parts by weight of chitosan-based polymer, 5 parts by weight of polyethylene oxide resin, 4 parts by weight of potassium chloride, 40 parts by weight of acrylamide and 25 parts by weight of water were added into a stirrer and stirred at room temperature for 20 minutes to obtain a comb-type salt-resistant fracturing drag reducer.

[0021] Comparative Example 2 5 parts by weight of modified graphene, 5 parts by weight of polyethylene oxide resin, 4 parts by weight of potassium chloride, 40 parts by weight of acrylamide and 25 parts by weight of water were added into a stirrer and stirred at room temperature for 20 minutes to obtain a comb-type salt-resistant fracturing drag reducer.

[0022] Add 10 4 The fracturing drag reducer was added to the high-mineralization brine with a drag reduction rate of 1000 mg / L, and the test results are shown in Table 1. The calcium ion concentration in the high-mineralization brine is 1000 mg / L, the magnesium ion solubility is 200 mg / L, the sodium ion solubility is 3200 mg / L, and the chloride ion concentration is 5600 mg / L; the shear rate is 170 s -1 , shear time is 30min, temperature is 25℃; drag reduction rate η=1-△P / P0, P0 is the water pressure drop before adding fracturing fluid drag reducer, unit is Pa; △P is the water pressure drop after adding fracturing fluid drag reducer, unit is Pa.

[0023] Table 1: Drag reduction effect test

[0024] It can be seen from Table 1 that Examples 1-5 of the present invention have better drag reduction performance than Comparative Examples 1-2 under the same environment, and can maintain a good drag reduction rate even in a high-salt environment, and have good salt resistance.

[0025] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a comb-shaped salt-resistant fracturing drag reducer, characterized in that: The following steps are involved: 4-8 parts by weight of chitosan-based polymer, 5-7 parts by weight of modified graphene, 2-5 parts by weight of polyethylene oxide resin, 2-4 parts by weight of potassium chloride, 20-40 parts by weight of acrylamide, and 15-25 parts by weight of water are added into a stirrer and stirred at room temperature for 20-30 minutes to obtain a comb-type salt-resistant fracturing drag reducer.

2. The method for preparing the comb-shaped salt-resistant fracturing drag reducer according to claim 1, characterized in that: The preparation method of the chitosan-based polymer is: Step 1, add 3-dimethylamino-1-propanol and itaconic anhydride to N,N-dimethylformamide solvent, stir and disperse, introduce nitrogen protection, react at 60-75°C for 12-16h, and distill under reduced pressure after the reaction, wash to obtain intermediate 1; Step 2, adding 3-7 parts by weight of chitosan to dimethyl sulfoxide solvent to dissolve, heating in a water bath at 70-90° C., adding 4-9 parts by weight of 2,3-epoxypropyltrimethylammonium chloride at constant pressure, reacting for 6-10 hours, washing with anhydrous ethanol after the reaction, drying, dialyzing, and concentrating to obtain quaternized chitosan; Step 3, add 4-8 parts by weight of quaternized chitosan and 5-10 parts by weight of intermediate 1 to N,N-dimethylformamide solvent, stir and mix, continue to add 0.02-0.04 parts by weight of p-toluenesulfonic acid catalyst, react at 90-115° C. for 4-7 hours, wash and dry after completion to obtain intermediate 2; Step 4: Add acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and N,N-dimethylacrylamide to N,N-dimethylformamide solvent, stir to dissolve, introduce nitrogen, heat in a water bath at 15-30°C, continue to add intermediate 2 and azobisisobutyronitrile initiator, stir to react for 16-22h, wash with anhydrous ethanol after the reaction, and dry to obtain a chitosan-based polymer.

3. The method for preparing the comb-type salt-resistant fracturing drag reducer according to claim 2, characterized in that: In the step 1, the mass ratio of 3-dimethylamino-1-propanol to itaconic anhydride is 1.2-1.5:

1.

4. The method for preparing the comb-shaped salt-resistant fracturing drag reducer according to claim 2, characterized in that: In the step 4, the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, intermediate 2, and azobisisobutyronitrile initiator is 1.2-1.4:1:0.7-0.9:1.5-2.3:0.01-0.

03.

5. The method for preparing the comb-shaped salt-resistant fracturing drag reducer according to claim 1, characterized in that: The preparation method of the modified graphene is: S1. Add 5-10 parts by weight of graphene oxide to 55-90 parts by weight of thionyl chloride, disperse by ultrasonication, and after uniform dispersion, react at 60-75° C., filter after the reaction, wash, and dry to obtain chlorinated graphene; S2. Add chlorinated graphene to the ethanol solvent, stir and disperse, continue to add 1,3-di(dimethylamino)-2-propanol and p-toluenesulfonic acid catalyst, react at 60-90° C. for 8-12 hours, and after completion, wash and dry to obtain intermediate 3; S3. Add 4-8 parts by weight of intermediate 3 and 3-7 parts by weight of 1,3-propane sultone to acetone solvent for dissolution, then dropwise add 2-6% sodium hydroxide solution, react at 70-85° C. for 7-14 hours, concentrate under reduced pressure after the reaction to remove the solvent, and recrystallize the crude product in ethanol to obtain modified graphene.

6. The method for preparing the comb-type salt-resistant fracturing drag reducer according to claim 5, characterized in that: The reaction time in S1 is 14-20h.

7. The method for preparing the comb-shaped salt-resistant fracturing drag reducer according to claim 5, characterized in that: The mass ratio of the chlorinated graphene, 1,3-di(dimethylamino)-2-propanol and p-toluenesulfonic acid catalyst in S2 is 0.4-0.6:1:0.01-0.03.

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