Preparation method of polymer coating agent for drilling fluid

Abstract

The invention relates to the technical field of oil-gas field development, and discloses a preparation method of a polymer coating agent for drilling fluid. Acrylamide, acrylic acid, adamantane modified quaternary phosphonium salt modified pyridyl benzoxazine and silane imidazoline quaternary ammonium salt are polymerized and then dried, and the polymer coating agent for the drilling fluid is obtained. Due to the benzoxazine, benzene ring and adamantane structures, the rigidity and stability of the polymer coating agent at high temperature are improved; hydrophilic cation ends in the quaternary phosphonium salt and the quaternary ammonium salt are adsorbed on the surface of the shale, and hydrophobic ends cover the surface of the shale, so that contact infiltration of water molecules is inhibited, and the coating inhibition property is improved; a silicon-oxygen bond is not easy to break at high temperature, so that the high-temperature resistance of the coating agent is improved; silane reacts with silicon-oxygen bonds on the surface of the shale to be grafted on the surface of the shale, so that the coating inhibition effect is enhanced; the pyridine group and the imidazoline group increase adsorption points of the polymer coating agent, multi-point adsorption is carried out on drilling cuttings and well walls, coating is formed, and the coating inhibition effect is further enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, in particular to a method for preparing a polymer coating agent for drilling fluid. Background Art

[0002] Coating agent is an additive for drilling fluid, mainly used to wrap drill cuttings, inhibit formation slurrying and improve the performance of drilling fluid. With the continuous increase in drilling depth during oil and gas resource exploration, the complexity of the formation encountered has increased, and mud shale formations that are easily hydrated are often encountered. In order to ensure the smooth progress of drilling, the inhibitory property of drilling fluid is particularly important. Coating agent, also known as coating inhibitor, is a type of shale inhibitor. It mainly plays two roles. One is to inhibit the dispersion of drill cuttings to prevent excessive dispersion of drill cuttings from causing changes in the rheology of the drilling fluid system and maintaining the stability of the drilling fluid; the second is the stabilizing effect on the well wall, which mainly refers to preventing collapse caused by hydration due to long-term contact between the well wall and the drilling fluid. At present, the commonly used drilling fluid coating agents have good application effects under certain conditions, but they generally have the disadvantage of poor temperature resistance, and the temperature resistance generally does not exceed 150°C. With the development of deep wells and ultra-deep wells, the high temperature environment downhole has put forward higher requirements on the temperature resistance of drilling fluids, especially the serious hydration of drill cuttings and clay under high temperature. If the drilling fluid inhibition is insufficient, the coating agent cannot produce effective coating, which is very likely to cause viscosity surge, drill bit mud packing, drill bit stuck and other problems, seriously affecting the drilling efficiency. A natural polymer coating agent IND30 developed in the document "A Natural Polymer Coating Agent for Drilling Fluid" is modified and grafted by natural polymers, which reduces the preparation cost of the coating agent, is easy to biodegrade, and is beneficial to environmental protection, but its coating inhibition effect at high temperature needs to be improved. Summary of the invention

[0003] 1. Technical issues to be resolved

[0004] In view of the shortcomings of the prior art, the present invention provides a method for preparing a polymer coating agent for drilling fluid. The polymer coating agent for drilling fluid prepared by the present invention has a good coating inhibition effect at high temperature.

[0005] (II) Technical solution

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing a polymer coating agent for drilling fluid, the method for preparing a polymer coating agent for drilling fluid comprising the following steps:

[0007] (1) adding 11-15 g of 3-chlorophenol, 10-14 g of 2-alkenyl-4-aminopyridine, and 20-30 g of polyformaldehyde to a toluene solvent, stirring and mixing, heating to a reaction temperature, reacting for 4-8 hours, and filtering, washing, and drying after the reaction to obtain a pyridylbenzoxazine;

[0008] (2) adding 7-10 g of pyridylbenzoxazine to N,N-dimethylformamide solvent, stirring to dissolve, heating to 88-92° C., and dropwise adding 10-12 g of 4-(diphenylphosphino)aniline thereto. After the dropwise addition is complete, reflux and react at a constant temperature for 8-12 h. After the reaction is complete, cooling and distilling under reduced pressure to obtain quaternary phosphonium salt-modified pyridylbenzoxazine;

[0009] (3) adding 5-8 g of quaternary phosphonium salt-modified pyridylbenzoxazine, 11-15 g of 1-adamantyl methacrylate, and 0.03-0.07 g of sodium ethoxide catalyst to tetrahydrofuran solvent, stirring and mixing, reacting at 30-35° C. for 2-4 h, filtering, washing, and drying after the reaction to obtain adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine;

[0010] (4) Add 6-8 g of succinic acid, 11-15 g of diethylenetriamine, and 42-45 g of a water-carrying agent to a reactor, stir and mix, react at 160-170° C. for 5-7 h, then heat to 190-200° C. and continue to react for 3-4 h until no water is carried out. After the reaction is completed, remove toluene by rotary evaporation to obtain an imidazoline intermediate;

[0011] (5) adding the imidazoline intermediate to an anhydrous ethanol solvent, stirring to dissolve, then adding ethylene (chloromethyl) dimethoxysilane thereto, heating to 48-60° C. to react for 10-14 hours, after the reaction is completed, removing the anhydrous ethanol by rotary evaporation, recrystallizing in an ethanol-acetone mixed solution under an ice bath, and vacuum drying to obtain a silane imidazoline quaternary ammonium salt;

[0012] (6) 8-12 g of acrylamide, 2-4 g of acrylic acid, 3-6 g of adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine, and 4-8 g of silane imidazoline quaternary ammonium salt are added to deionized water, stirred at 200-400 rpm for 20-40 min to fully dissolve them, and then 0.05-0.09 g of initiator is added thereto, nitrogen is introduced for 30-40 min to deoxygenate, the temperature is raised to the reaction temperature, and the reaction is carried out for 3-6 h. After the reaction is completed, vacuum drying is performed to obtain a polymer coating agent for drilling fluid.

[0013] Preferably, the reaction temperature in step (1) is 95-105°C.

[0014] Preferably, the dripping time of 4-(diphenylphosphino)aniline in step (2) is controlled within 30-50 min.

[0015] Preferably, the water-carrying agent in step (4) is toluene.

[0016] Preferably, in step (5), the mass ratio of the imidazoline intermediate to vinyl (chloromethyl) dimethoxysilane is 1:1.2-1.8.

[0017] Preferably, the mass ratio of ethanol to acetone in the ethanol-acetone mixed solution in step (5) is 1:1.05-1.1.

[0018] Preferably, the initiator in step (6) is azobisisoheptanonitrile.

[0019] Preferably, the reaction temperature in step (6) is 50-70°C.

[0020] (III) Beneficial technical effects

[0021] The invention obtains a polymer coating agent for drilling fluid by polymerizing acrylamide, acrylic acid, adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine and silane imidazoline quaternary ammonium salt under an initiator and then drying.

[0022] 3-Chlorophenol, 2-alkenyl-4-aminopyridine and polyformaldehyde undergo Mannich condensation reaction to obtain pyridylbenzoxazine, chlorine in pyridylbenzoxazine and 4-(diphenylphosphino)aniline undergo quaternization reaction to obtain quaternary phosphonium salt-modified pyridylbenzoxazine and introduce amino group, amino group in quaternary phosphonium salt-modified pyridylbenzoxazine and 1-adamantyl methacrylate undergo Michael addition reaction to obtain adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine. Succinic acid and diethylenetriamine undergo amidation reaction and cyclization reaction to obtain imidazoline intermediate, and imidazoline intermediate and ethylene (chloromethyl) dimethoxysilane undergo quaternization reaction to obtain silane imidazoline quaternary ammonium salt.

[0023] The benzoxazine in the adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine is composed of a benzene ring and a pyridine ring connected by an oxazine ring. The number of benzene rings is further increased by introducing the quaternary phosphonium salt. The rigid structure of the adamantane and the benzene ring improves the rigidity and stability of the polymer coating agent at high temperatures. When in contact with mudstone, the hydrophilic cationic ends contained in the quaternary phosphonium salt and the quaternary ammonium salt can be adsorbed on the mudstone surface by electrostatic attraction, and the hydrophobic ends cannot extend into the water and will cover the mudstone surface, which can reduce the hydrophilicity of the mudstone surface, effectively inhibit the contact penetration of water molecules, and improve The coating inhibition of the coating agent is improved; the bond energy of the silicon-oxygen bond in the silane imidazoline quaternary ammonium salt is relatively high and is not easy to break at high temperatures, thereby improving the high temperature resistance of the coating agent; the organosilane can be grafted onto the surface of the shale by reacting with the silicon-oxygen bonds on the surface of the shale, and the organic end covers the surface of the shale, thereby enhancing the coating inhibition effect; the adsorption points of the polymer coating agent are increased by introducing pyridine groups and imidazoline groups, and the formed polymer macromolecules extend long chains and are adsorbed at multiple points on drill cuttings, clay particles or well walls to form a coating, thereby reducing or preventing contact with moisture, thereby further enhancing the coating inhibition effect. DETAILED DESCRIPTION

[0024] Example 1

[0025] (1) adding 11 g of 3-chlorophenol, 10 g of 2-alkenyl-4-aminopyridine, and 20 g of polyformaldehyde to a toluene solvent, stirring and mixing, heating to 95° C. for reaction for 4 h, filtering, washing, and drying after the reaction to obtain pyridylbenzoxazine;

[0026] (2) adding 7 g of pyridylbenzoxazine to N,N-dimethylformamide solvent, stirring to dissolve, heating to 88° C., and dripping 10 g of 4-(diphenylphosphino)aniline thereinto, the dripping time being controlled within 30 min. After the dripping is completed, reflux and react at a constant temperature for 8 h. After the reaction is completed, cooling and distilling under reduced pressure to obtain quaternary phosphonium salt-modified pyridylbenzoxazine;

[0027] (3) adding 5 g of quaternary phosphonium salt-modified pyridylbenzoxazine, 11 g of 1-adamantyl methacrylate, and 0.03 g of sodium ethoxide catalyst to tetrahydrofuran solvent, stirring and mixing, reacting at 30° C. for 2 h, filtering, washing, and drying after the reaction to obtain adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine;

[0028] (4) Add 6 g of succinic acid, 11 g of diethylenetriamine, and 42 g of toluene water-carrying agent to the reactor, stir and mix, react at 160° C. for 5 h, then heat to 190° C. and continue to react for 3 h until no water is carried out. After the reaction is completed, remove toluene by rotary evaporation to obtain an imidazoline intermediate;

[0029] (5) adding an imidazoline intermediate to an anhydrous ethanol solvent, stirring to dissolve, and then adding ethylene (chloromethyl) dimethoxysilane thereto, wherein the mass ratio of the imidazoline intermediate to ethylene (chloromethyl) dimethoxysilane is 1:1.2, heating to 48° C. to react for 10 hours, and after the reaction is completed, removing the anhydrous ethanol by rotary evaporation, and recrystallizing in an ethanol-acetone mixed solution under an ice bath, wherein the mass ratio of ethanol to acetone is 1:1.05, and vacuum drying to obtain a silane imidazoline quaternary ammonium salt;

[0030] (6) 8 g of acrylamide, 2 g of acrylic acid, 3 g of adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine, and 4 g of silane imidazoline quaternary ammonium salt were added to deionized water, stirred at 200 rpm for 20 min to fully dissolve them, and then 0.05 g of azobisisoheptanenitrile initiator was added thereto. Nitrogen was introduced for 30 min to deoxygenate, and the temperature was raised to 50° C. for reaction for 3 h. After the reaction was completed, vacuum drying was performed to obtain a polymer coating agent for drilling fluid.

[0031] Example 2

[0032] (1) adding 15 g of 3-chlorophenol, 14 g of 2-alkenyl-4-aminopyridine, and 30 g of polyformaldehyde to a toluene solvent, stirring and mixing, heating to 105° C. and reacting for 8 h. After the reaction is completed, filtering, washing, and drying to obtain pyridylbenzoxazine;

[0033] (2) adding 10 g of pyridylbenzoxazine to N,N-dimethylformamide solvent, stirring to dissolve, heating to 92° C., and dripping 12 g of 4-(diphenylphosphino)aniline thereinto, the dripping time being controlled within 50 min. After the dripping is completed, reflux and react at a constant temperature for 12 h. After the reaction is completed, cooling and distilling under reduced pressure to obtain quaternary phosphonium salt-modified pyridylbenzoxazine;

[0034] (3) adding 8 g of quaternary phosphonium salt-modified pyridylbenzoxazine, 15 g of 1-adamantyl methacrylate, and 0.07 g of sodium ethoxide catalyst to tetrahydrofuran solvent, stirring and mixing, reacting at 35° C. for 4 h, filtering, washing, and drying after the reaction to obtain adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine;

[0035] (4) Add 8 g of succinic acid, 15 g of diethylenetriamine, and 45 g of toluene water-carrying agent to the reactor, stir and mix, react at 170° C. for 7 h, then heat to 200° C. and continue to react for 4 h until no water is carried out. After the reaction is completed, remove toluene by rotary evaporation to obtain an imidazoline intermediate;

[0036] (5) adding an imidazoline intermediate to an anhydrous ethanol solvent, stirring to dissolve, and then adding ethylene (chloromethyl) dimethoxysilane thereto, wherein the mass ratio of the imidazoline intermediate to ethylene (chloromethyl) dimethoxysilane is 1:1.8, heating to 60° C. to react for 14 hours, and after the reaction is completed, removing anhydrous ethanol by rotary evaporation, and recrystallizing in an ethanol-acetone mixed solution under an ice bath, wherein the mass ratio of ethanol to acetone is 1:1.1, and vacuum drying to obtain a silane imidazoline quaternary ammonium salt;

[0037] (6) 12 g of acrylamide, 4 g of acrylic acid, 6 g of adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine, and 8 g of silane imidazoline quaternary ammonium salt were added to deionized water, stirred at 400 rpm for 40 min to fully dissolve them, and then 0.09 g of azobisisoheptanenitrile initiator was added thereto. Nitrogen was introduced for 40 min to deoxygenate, and the temperature was raised to 70° C. for reaction for 6 h. After the reaction was completed, vacuum drying was performed to obtain a polymer coating agent for drilling fluid.

[0038] Example 3

[0039] (1) Add 13 g of 3-chlorophenol, 12 g of 2-alkenyl-4-aminopyridine, and 25 g of polyformaldehyde to a toluene solvent, stir and mix, heat to 100° C., react for 6 h, and after the reaction is completed, filter, wash, and dry to obtain pyridylbenzoxazine;

[0040] (2) adding 8.5 g of pyridylbenzoxazine to N,N-dimethylformamide solvent, stirring to dissolve, heating to 90° C., and dripping 11 g of 4-(diphenylphosphino)aniline thereinto, the dripping time being controlled within 40 min. After the dripping is completed, reflux and react at a constant temperature for 10 h. After the reaction is completed, cooling and distilling under reduced pressure to obtain quaternary phosphonium salt-modified pyridylbenzoxazine;

[0041] (3) adding 6.5 g of quaternary phosphonium salt-modified pyridylbenzoxazine, 13 g of 1-adamantyl methacrylate, and 0.05 g of sodium ethoxide catalyst to tetrahydrofuran solvent, stirring and mixing, reacting at 32° C. for 3 h, and filtering, washing, and drying after the reaction to obtain adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine;

[0042] (4) Add 7 g of succinic acid, 13 g of diethylenetriamine, and 43.5 g of toluene water-carrying agent to the reactor, stir and mix, react at 165 ° C for 6 h, then heat to 195 ° C and continue to react for 3.5 h until no water is carried out. After the reaction is completed, remove toluene by rotary evaporation to obtain an imidazoline intermediate;

[0043] (5) adding an imidazoline intermediate to an anhydrous ethanol solvent, stirring to dissolve, and then adding ethylene (chloromethyl) dimethoxysilane thereto, wherein the mass ratio of the imidazoline intermediate to ethylene (chloromethyl) dimethoxysilane is 1:1.5, heating to 54° C. to react for 12 hours, and after the reaction is completed, removing anhydrous ethanol by rotary evaporation, and recrystallizing in an ethanol-acetone mixed solution under an ice bath, wherein the mass ratio of ethanol to acetone is 1:1.08, and vacuum drying to obtain a silane imidazoline quaternary ammonium salt;

[0044] (6) 10 g of acrylamide, 3 g of acrylic acid, 4.5 g of adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine, and 6 g of silane imidazoline quaternary ammonium salt were added to deionized water, stirred at 300 rpm for 30 min to fully dissolve them, and then 0.07 g of azobisisoheptanenitrile initiator was added thereto. Nitrogen was introduced for 35 min to deoxygenate, and the temperature was raised to 60° C. to react for 4.5 h. After the reaction was completed, vacuum drying was performed to obtain a polymer coating agent for drilling fluid.

[0045] Example 4

[0046] (1) adding 11 g of 3-chlorophenol, 10 g of 2-alkenyl-4-aminopyridine, and 20 g of polyformaldehyde to a toluene solvent, stirring and mixing, heating to 95° C. for reaction for 4 h, filtering, washing, and drying after the reaction to obtain pyridylbenzoxazine;

[0047] (2) adding 7 g of pyridylbenzoxazine to N,N-dimethylformamide solvent, stirring to dissolve, heating to 88° C., and dripping 10 g of 4-(diphenylphosphino)aniline thereinto, the dripping time being controlled within 30 min. After the dripping is completed, reflux and react at a constant temperature for 8 h. After the reaction is completed, cooling and distilling under reduced pressure to obtain quaternary phosphonium salt-modified pyridylbenzoxazine;

[0048] (3) adding 8 g of quaternary phosphonium salt-modified pyridylbenzoxazine, 15 g of 1-adamantyl methacrylate, and 0.07 g of sodium ethoxide catalyst to tetrahydrofuran solvent, stirring and mixing, reacting at 35° C. for 4 h, filtering, washing, and drying after the reaction to obtain adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine;

[0049] (4) Add 8 g of succinic acid, 15 g of diethylenetriamine, and 45 g of toluene water-carrying agent to the reactor, stir and mix, react at 170° C. for 7 h, then heat to 200° C. and continue to react for 4 h until no water is carried out. After the reaction is completed, remove toluene by rotary evaporation to obtain an imidazoline intermediate;

[0050] (5) adding an imidazoline intermediate to an anhydrous ethanol solvent, stirring to dissolve, and then adding ethylene (chloromethyl) dimethoxysilane thereto, wherein the mass ratio of the imidazoline intermediate to ethylene (chloromethyl) dimethoxysilane is 1:1.5, heating to 54° C. to react for 12 hours, and after the reaction is completed, removing anhydrous ethanol by rotary evaporation, and recrystallizing in an ethanol-acetone mixed solution under an ice bath, wherein the mass ratio of ethanol to acetone is 1:1.08, and vacuum drying to obtain a silane imidazoline quaternary ammonium salt;

[0051] (6) 10 g of acrylamide, 3 g of acrylic acid, 4.5 g of adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine, and 6 g of silane imidazoline quaternary ammonium salt were added to deionized water, stirred at 300 rpm for 30 min to fully dissolve them, and then 0.07 g of azobisisoheptanenitrile initiator was added thereto. Nitrogen was introduced for 35 min to deoxygenate, and the temperature was raised to 60° C. to react for 4.5 h. After the reaction was completed, vacuum drying was performed to obtain a polymer coating agent for drilling fluid.

[0052] Example 5

[0053] (1) adding 15 g of 3-chlorophenol, 14 g of 2-alkenyl-4-aminopyridine, and 30 g of polyformaldehyde to a toluene solvent, stirring and mixing, heating to 105° C. and reacting for 8 h. After the reaction is completed, filtering, washing, and drying to obtain pyridylbenzoxazine;

[0054] (2) adding 10 g of pyridylbenzoxazine to N,N-dimethylformamide solvent, stirring to dissolve, heating to 92° C., and dripping 12 g of 4-(diphenylphosphino)aniline thereinto, the dripping time being controlled within 50 min. After the dripping is completed, reflux and react at a constant temperature for 12 h. After the reaction is completed, cooling and distilling under reduced pressure to obtain quaternary phosphonium salt-modified pyridylbenzoxazine;

[0055] (3) adding 6.5 g of quaternary phosphonium salt-modified pyridylbenzoxazine, 13 g of 1-adamantyl methacrylate, and 0.05 g of sodium ethoxide catalyst to tetrahydrofuran solvent, stirring and mixing, reacting at 32° C. for 3 h, and filtering, washing, and drying after the reaction to obtain adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine;

[0056] (4) Add 7 g of succinic acid, 13 g of diethylenetriamine, and 43.5 g of toluene water-carrying agent to the reactor, stir and mix, react at 165 ° C for 6 h, then heat to 195 ° C and continue to react for 3.5 h until no water is carried out. After the reaction is completed, remove toluene by rotary evaporation to obtain an imidazoline intermediate;

[0057] (5) adding an imidazoline intermediate to an anhydrous ethanol solvent, stirring to dissolve, and then adding ethylene (chloromethyl) dimethoxysilane thereto, wherein the mass ratio of the imidazoline intermediate to ethylene (chloromethyl) dimethoxysilane is 1:1.2, heating to 48° C. to react for 10 hours, and after the reaction is completed, removing the anhydrous ethanol by rotary evaporation, and recrystallizing in an ethanol-acetone mixed solution under an ice bath, wherein the mass ratio of ethanol to acetone is 1:1.05, and vacuum drying to obtain a silane imidazoline quaternary ammonium salt;

[0058] (6) 8 g of acrylamide, 2 g of acrylic acid, 3 g of adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine, and 4 g of silane imidazoline quaternary ammonium salt were added to deionized water, stirred at 200 rpm for 20 min to fully dissolve them, and then 0.05 g of azobisisoheptanenitrile initiator was added thereto. Nitrogen was introduced for 30 min to deoxygenate, and the temperature was raised to 50° C. for reaction for 3 h. After the reaction was completed, vacuum drying was performed to obtain a polymer coating agent for drilling fluid.

[0059] Comparative Example 1

[0060] The difference between this comparative example and Example 5 is that no adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine is added in step (6).

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 5 is that no silane imidazoline quaternary ammonium salt is added in step (6).

[0063] Add 1 g of anhydrous sodium carbonate to 400 mL of distilled water, add 16.0 g of bentonite while stirring, continue stirring for 15 min, and seal and cure at 25° C. for 24 h to obtain a 4% bentonite-based slurry.

[0064] Take 350mL of the prepared bentonite-based slurry, add 0.4% of the drilling fluid polymer coating agent, stir at 8000rpm for 20min to fully dissolve it, then place it in an aging tank, age it at 220℃ for 16h, cool it to room temperature, stir it at 8000rpm for 5min, and use a six-speed viscometer to measure its apparent viscosity, plastic viscosity and dynamic shear force. The test results are shown in Table 1.

[0065] Table 1: Rheological properties tested.

[0066]

[0067] Prepare a 0.4% drilling fluid polymer coating solution with distilled water, place 20g shale cuttings (8-10 mesh) in an aging tank, add 350mL of drilling fluid polymer coating solution, and then place the aging tank in a roller heating furnace at different temperatures for 16 hours. After cooling, pour out the solution and cuttings, pass through a 40-mesh sieve, and place the cuttings left on the sieve in a 105°C oven to constant weight. Calculate the rolling recovery rate by the ratio of the obtained cuttings mass to the initial cuttings mass. The test results are shown in Table 2.

[0068] Table 2: Rolling recovery test.

[0069]

[0070]

[0071] It can be seen from Table 1 and Table 2 that, compared with Comparative Examples 1-2, the polymer coating agent for drilling fluid in Examples 1-5 of the present invention still has a better coating inhibition effect after high-temperature aging.

[0072] 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 polymer coating agent for drilling fluid, characterized in that: The method for preparing the polymer coating agent for drilling fluid comprises the following steps: (1) adding 11-15 g of 3-chlorophenol, 10-14 g of 2-alkenyl-4-aminopyridine, and 20-30 g of polyformaldehyde to a toluene solvent, stirring and mixing, heating to a reaction temperature, reacting for 4-8 hours, and filtering, washing, and drying after the reaction to obtain a pyridylbenzoxazine; (2) adding 7-10 g of pyridylbenzoxazine to N,N-dimethylformamide solvent, stirring to dissolve, heating to 88-92° C., and dropwise adding 10-12 g of 4-(diphenylphosphino)aniline thereto. After the dropwise addition is complete, reflux and react at a constant temperature for 8-12 h. After the reaction is complete, cooling and distilling under reduced pressure to obtain quaternary phosphonium salt-modified pyridylbenzoxazine; (3) adding 5-8 g of quaternary phosphonium salt-modified pyridylbenzoxazine, 11-15 g of 1-adamantyl methacrylate, and 0.03-0.07 g of sodium ethoxide catalyst to tetrahydrofuran solvent, stirring and mixing, reacting at 30-35° C. for 2-4 h, filtering, washing, and drying after the reaction to obtain adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine; (4) Add 6-8 g of succinic acid, 11-15 g of diethylenetriamine, and 42-45 g of a water-carrying agent to a reactor, stir and mix, react at 160-170° C. for 5-7 h, then heat to 190-200° C. and continue to react for 3-4 h until no water is carried out. After the reaction is completed, remove toluene by rotary evaporation to obtain an imidazoline intermediate; (5) adding the imidazoline intermediate to an anhydrous ethanol solvent, stirring to dissolve, then adding ethylene (chloromethyl) dimethoxysilane thereto, heating to 48-60° C. to react for 10-14 hours, after the reaction is completed, removing the anhydrous ethanol by rotary evaporation, recrystallizing in an ethanol-acetone mixed solution under an ice bath, and vacuum drying to obtain a silane imidazoline quaternary ammonium salt; (6) 8-12 g of acrylamide, 2-4 g of acrylic acid, 3-6 g of adamantane-modified quaternary phosphonium salt-modified pyridylbenzoxazine, and 4-8 g of silane imidazoline quaternary ammonium salt are added to deionized water, stirred at 200-400 rpm for 20-40 min to fully dissolve them, and then 0.05-0.09 g of initiator is added thereto, nitrogen is introduced for 30-40 min to deoxygenate, the temperature is raised to the reaction temperature, and the reaction is carried out for 3-6 h. After the reaction is completed, vacuum drying is performed to obtain a polymer coating agent for drilling fluid.

2. The polymer coating agent for drilling fluid according to claim 1, characterized in that: The reaction temperature in step (1) is 95-105°C.

3. The polymer coating agent for drilling fluid according to claim 1, characterized in that: The dripping time of 4-(diphenylphosphino)aniline in the step (2) is controlled within 30-50 min.

4. The polymer coating agent for drilling fluid according to claim 1, characterized in that: In the step (4), the water-carrying agent is toluene.

5. The polymer coating agent for drilling fluid according to claim 1, characterized in that: In the step (5), the mass ratio of the imidazoline intermediate to ethylene (chloromethyl) dimethoxysilane is 1:1.2-1.

8.

6. The polymer coating agent for drilling fluid according to claim 1, characterized in that: In the step (5), the mass ratio of ethanol to acetone in the ethanol-acetone mixed solution is 1:1.05-1.

1.

7. The polymer coating agent for drilling fluid according to claim 1, characterized in that: In the step (6), the initiator is azobisisoheptanonitrile.

8. The polymer coating agent for drilling fluid according to claim 1, characterized in that: The reaction temperature in step (6) is 50-70°C.

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