Bile ester compounds modified nitrogen-based cellulose acrylamide polymers, their synthesis methods and leak-sealing applications

Abstract

This invention discloses a bile ester-modified nitrogen-based cellulose acrylamide polymer, its synthesis method, and its application in plugging leaks. The method involves placing 15 parts of bile ester-modified nitrogen-based cellulose, 100-120 parts of allyl monomer, 0.5-1 part of crosslinking agent, and 1000 parts of deionized water in a container. The mixture is thoroughly stirred until homogeneous. High-purity nitrogen gas is then introduced into the container, and 0.1-0.5 parts of initiator are injected at 40°C, followed by continuous stirring for 6 hours to obtain the bile ester-modified nitrogen-based cellulose acrylamide polymer. The allyl monomer is acrylamide or 2-acrylamido-2-methylpropanesulfonic acid; the initiator is potassium persulfate, ammonium persulfate, azobisisobutyronitrile, or β-cyclodextrin; and the crosslinking agent is chitosan or polyethylene glycol diacrylate. This polymer exhibits excellent tensile mechanical properties, good salt and temperature resistance, and can be used for plugging leaks in ultra-deep wells at temperatures up to 180°C.

Description

Technical Field

[0001] This invention relates to a bile ester compound-modified nitrogen-based cellulose acrylamide polymer, and also to a method for synthesizing the bile ester compound-modified nitrogen-based cellulose acrylamide polymer and its application in well plugging, belonging to the field of downhole plugging technology in oil and gas fields. Background Technology

[0002] Well leakage is a common and complex situation in drilling operations. Once severe leakage occurs, drilling fluid can rapidly and in large quantities flow into the formation through formation fractures, not only losing drilling fluid and prolonging the drilling cycle, but also causing a drop in well pressure, leading to wellbore instability, inducing formation fluid inrush into the wellbore, and even blowouts. Therefore, it is necessary to design efficient plugging technologies and materials to quickly restore the pressure balance of the wellbore system and ensure the safe and efficient operation of the drilling process. Bridge plug plugging technology, through optimized arrangement and matching of plugging materials, can effectively mitigate or seal porosity, fracture leakage, or void leakage, thereby improving the pressure-bearing capacity of weak formations. Furthermore, this method has advantages such as fast plugging speed, low cost, and simple operation, attracting widespread interest from researchers. Among them, interpenetrating network polymer plugging materials, as effective plugging materials in bridge plug plugging technology, can form stable bonds between polymers with different functions through "forced mutual compatibility," achieving synergistic sealing and bridging to meet the plugging needs of oilfields.

[0003] Traditional interpenetrating polymeric plugging agents are generally composed of polymer blends of two or more cross-linked and interpenetrating polymer networks. The pure organic phase system's temperature resistance, hardness, and other properties cannot meet the requirements of medium- and high-temperature formations. Its plugging effect is often poor in terms of sealing strength, sealing depth, temperature resistance, and salt resistance. Furthermore, organic polymer systems also suffer from poor shear resistance, plugging ability, profile improvement ability, and erosion resistance, resulting in unsatisfactory actual plugging effects. While single inorganic plugging materials possess excellent high-temperature resistance and chemical stability, their insufficient toughness and poor dispersibility in oil-based drilling fluids lead to poor plugging effects. Even though inorganic fiber materials can play a bridging role in the plugging process, the lack of effective chemical bonding between traditional filler materials and fiber bridging materials often prevents the formation of a dense and efficient plug.

[0004] Chinese invention patent CN 111961160B discloses an active polymer for use in high-molecular-weight gel plugging agents, its preparation method, and its application. The active polymer is a polycondensable macromolecular polymer with hydroxymethyl groups (-CH2OH) on its surface. The active polymer is prepared by reverse microemulsion polymerization of hydrophobic monomers and acrylamide monomers in the presence of a functional crosslinking agent, chain extender, initiator, and ethylenediaminetetraacetic acid. However, its temperature resistance only reaches 150℃, and its maximum sealing value for fractures after curing is 3.36 MPa, which still cannot meet the application requirements of ultra-deep wells. Summary of the Invention

[0005] The primary objective of this invention is to overcome the problems existing in the prior art and provide a bile ester compound modified nitrogen-based cellulose-based acrylamide polymer with high cured strength, excellent tensile mechanical properties, good salt and temperature resistance, and can be used for plugging leaks in ultra-deep wells at temperatures up to 180°C.

[0006] To solve the above technical problems, the bile ester compound modified nitrogen-based cellulose acrylamide polymer of the present invention has the following raw material components and weight contents: 15 parts bile ester compound modified nitrogen-based cellulose, 100-120 parts allyl monomer, 0.1-0.5 parts initiator and 0.5-1 parts crosslinking agent.

[0007] As a preferred embodiment of the present invention, the allyl monomer is acrylamide or 2-acrylamido-2-methylpropanesulfonic acid.

[0008] As a preferred embodiment of the present invention, the initiator is potassium persulfate, ammonium persulfate, azobisisobutyronitrile or β-cyclodextrin, and the crosslinking agent is chitosan or polyethylene glycol diacrylate.

[0009] As a preferred embodiment of the present invention, the raw material components and their weight contents are as follows: 15 parts of bile ester compound modified nitrogen-based fiber, 100 parts of allyl monomer, 0.1 parts of initiator and 0.5 parts of crosslinking agent.

[0010] As a preferred embodiment of the present invention, the raw material components and their weight contents are as follows: 15 parts of bile ester compound modified nitrogen-based fiber, 110 parts of allyl monomer, 0.3 parts of initiator and 0.7 parts of crosslinking agent.

[0011] As a preferred embodiment of the present invention, the raw material components and their weight contents are as follows: 15 parts of bile ester compound modified nitrogen-based fiber, 120 parts of allyl monomer, 0.5 parts of initiator and 1 part of crosslinking agent.

[0012] As a preferred embodiment of the present invention, the preparation of the bile ester compound modified nitrogen-based fiber includes the following steps in sequence:

[0013] Step S1: Prepare non-metallic doped nitrogen-based fibers;

[0014] Step S2: Modify the non-metallic nitrogen-doped fibers;

[0015] Step S3: Prepare bile ester compounds;

[0016] Step S4: Synthesize nitrogen-based fibers modified with bile ester compounds.

[0017] As a preferred embodiment of the present invention, in step S1: the nitrogen-based fiber is a TiN fiber, and the TiN fiber is heat-treated with NaH2PO4·2H2O in an Ar atmosphere in a tube furnace for 1 hour to obtain P-doped TiN fiber.

[0018] As a preferred embodiment of the present invention, in step S2: the P-doped TiN fiber is added to a dopamine solution, stirred for 12 hours, and then transferred to a hydrothermal reactor for heat treatment to obtain amino-modified P-doped TiN fiber.

[0019] As a preferred embodiment of the present invention, step S3 includes the following sub-steps in sequence:

[0020] Step S3.1: Dissolve 4-methylaniline in anhydrous ethanol;

[0021] Step S3.2: Dissolve p-hydroxybenzaldehyde in anhydrous ethanol;

[0022] Step S3.3: Add the above ethanol solution of p-hydroxybenzaldehyde dropwise to the ethanol solution of 4-methylaniline, and reflux by rotary evaporation for 3 hours to obtain 4-methylbenziferine phenol;

[0023] Step S3.4: Mix N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine evenly, then slowly add them dropwise to adipic acid solution, then add the above-mentioned 4-methylbenzifer base phenol, react at room temperature, evaporate by rotary evaporation, filter out the precipitate, and dry to obtain 4-methylbenzifer base phenylvaleric acid;

[0024] Step S3.5: Dissolve the above-mentioned 4-methylbenziferic acid base phenylvaleric acid in anhydrous ethanol to form solution A;

[0025] Step S3.6: Mix N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine evenly, dissolve them in ethanol, and then add them to the above solution A;

[0026] Step S3.7: After adding cholic acid and stirring, the mixture is repeatedly filtered, then rotary evaporated, filtered, and dried to obtain tris(4-methylbenziferic acid) cholic acid ester.

[0027] As a preferred embodiment of the present invention, step S4 includes the following sub-steps in sequence:

[0028] Step S4.1: Disperse the above-mentioned amino-modified P-doped TiN fibers in an ethanol solution;

[0029] Step S4.2: Add the above tris(4-methylbenziferyl phenylvalerate)cholate and stir at 50°C for 5 hours to obtain NH2-P-TiN fibers modified with tris(4-methylbenziferyl phenylvalerate)cholate.

[0030] As a preferred embodiment of the present invention, in step S1: the nitrogen-based fiber is SiN fiber, and SiN fiber and thiourea are heat-treated in a tube furnace under Ar atmosphere for 1 hour to obtain S-doped SiN fiber.

[0031] In step S2: the S-doped SiN fiber is added to NaOH solution, stirred for 12 hours, and then transferred to a hydrothermal reactor for heat treatment to obtain hydroxyl-modified S-doped SiN fiber;

[0032] Step S3 prepares tris(4-methylbenziferine phenylvaleric acid) cholate;

[0033] Step S4 synthesizes OH-S-SiN fibers modified with tris(4-methylbenziferyl phenylvaleric acid) cholate.

[0034] As a preferred embodiment of the present invention, in step S1: the nitrogen-based fiber is BN fiber, and the BN fiber is heat-treated with NaH2PO4·2H2O in an Ar atmosphere in a tube furnace for 1 hour to obtain P-doped BN fiber;

[0035] In step S2: the P-doped BN fiber is added to a dopamine solution, stirred for 12 hours, and then transferred to a hydrothermal reactor for heat treatment to obtain amino-modified P-doped BN fiber.

[0036] Step S3 prepares tris(4-nitrobenschiff base phenylvaleric acid) cholate;

[0037] Step S4 synthesizes NH2-P-BN fibers modified with tris(4-nitrobenzifero phenylvaleric acid) cholate.

[0038] As a preferred embodiment of the present invention, in step S1: the nitrogen-based fiber is TiN fiber, and the TiN fiber and thiourea are heat-treated in a tube furnace under Ar atmosphere for 1 hour to obtain S-doped TiN fiber;

[0039] In step S2: the S-doped TiN fiber is added to a dopamine solution, stirred for 12 hours, and then transferred to a hydrothermal reactor for heat treatment to obtain amino-modified S-doped TiN fiber.

[0040] Step S3 prepares tris(biphenylschoffine phenylvaleric acid) cholate;

[0041] Step S4 synthesizes NH2-S-TiN fibers modified with tri(biphenylschoff base phenylvaleric acid) cholate.

[0042] As a preferred embodiment of the present invention, in step S1: the nitrogen-based fiber is SiN fiber, and SiN fiber and thiourea are heat-treated in a tube furnace under Ar atmosphere for 1 hour to obtain S-doped SiN fiber.

[0043] In step S2: the S-doped SiN fiber is added to NaOH solution, stirred for 12 hours, and then transferred to a hydrothermal reactor for heat treatment to obtain hydroxyl-modified S-doped SiN fiber;

[0044] Step S3 prepares tris(4-ethylbenzifero phenylvaleric acid) cholate;

[0045] Step S4 synthesizes OH-S-SiN fibers modified with tris(4-ethylbenziferyl phenylvaleric acid) cholate.

[0046] Another objective of this invention is to overcome the problems existing in the prior art and provide a method for synthesizing a bile ester compound modified nitrogen-based cellulose acrylamide polymer. The prepared bile ester compound modified nitrogen-based cellulose acrylamide polymer has high curing strength, excellent tensile mechanical properties, good salt resistance and temperature resistance, and can be used for plugging leakage in ultra-deep wells at a high temperature of 180°C.

[0047] To solve the above technical problems, the present invention provides a method for synthesizing a cholesteric ester-modified nitrogen-based cellulose acrylamide polymer, comprising the following steps: placing 15 parts of cholesteric ester-modified nitrogen-based cellulose, 100-120 parts of allyl monomer, 0.5-1 parts of crosslinking agent, and 1000 parts of deionized water in a container; mixing the solution thoroughly and uniformly by vigorous stirring; then introducing high-purity nitrogen gas into the container for 30 minutes; adjusting the reaction temperature to 40°C; injecting 0.1-0.5 parts of initiator; and stirring continuously for 6 hours to obtain the cholesteric ester-modified nitrogen-based cellulose acrylamide polymer; wherein the allyl monomer is acrylamide or 2-acrylamido-2-methylpropanesulfonic acid, the initiator is potassium persulfate, ammonium persulfate, azobisisobutyronitrile, or β-cyclodextrin, and the crosslinking agent is chitosan or polyethylene glycol diacrylate.

[0048] Another objective of this invention is to overcome the problems existing in the prior art and provide a plugging application of bile ester compound modified nitrogen-based cellulose-based acrylamide polymer for plugging leaks in ultra-deep wells at a high temperature of 180°C downhole.

[0049] To solve the above technical problems, this invention applies bile ester compound-modified nitrogen-based cellulose-based acrylamide polymer to plugging cement slurry.

[0050] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. Non-metallic element-doped nitrogen-based fiber materials, including boron nitride, titanium nitride, silicon nitride, etc., are prepared by simple and easy electrospinning and high-temperature annealing processes. The nitrogen-based fiber materials are modified with hydroxyl and amino functional groups. The nitrogen-based fiber materials with functional group modification are modified by liquid crystal arm molecules containing rigid conjugated systems such as double bonds or triple bonds. The inorganic fiber is encapsulated by the interaction of hydrogen bonds and other interactions. Finally, an acrylamide polymer supported by an inorganic fiber skeleton is obtained, and an organic / inorganic hybrid material is constructed.

[0051] 2. Improve the loose structure between the matrix of the bridging and sealing material, enhance the interaction between the bridging material and the filler material, and improve the temperature resistance, shear resistance, pressure resistance and other properties of traditional organic polymer sealing materials.

[0052] 3. The provided organic / inorganic hybrid materials, with their unique network structure and synergistic effect, endow the plugging agent with new physicochemical properties, opening up new avenues for the design of plugging agents with excellent plugging performance, high strength, salt and alkali resistance, high sealing rate, excellent shear resistance, high strength, low price, and high temperature resistance.

[0053] 4. To construct stable chemical bonds between organic and inorganic materials, the organic polymer is oriented and assembled through the induction of groups on the surface of inorganic fibers, and a tight interfacial contact is established between the two. This approach combines the advantages of both organic and inorganic plugging materials while avoiding their disadvantages when used alone. It designs and synthesizes interpenetrating network particulate plugging agents that are resistant to high temperatures of 180℃, have high pressure resistance, high strength, and low cost, and provides targeted plugging materials for fractured and cavernous reservoirs.

[0054] 5. The bile ester compound modified nitrogen-based cellulose acrylamide polymer prepared by this invention has excellent properties such as high temperature resistance, high strength, tight sealing performance, excellent plugging performance, high strength and salt and alkali resistance, high plugging rate, organic / non-polar hybrid structure, excellent shear resistance, and can maintain high storage modulus and loss modulus even after aging under high temperature conditions. It can fundamentally meet the pressure-bearing plugging requirements of high-permeability and fractured leakage formations. Attached Figure Description

[0055] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The drawings are provided for reference and illustration only and are not intended to limit the present invention.

[0056] Figure 1 The synthesis process of the bile ester compound in Example 1;

[0057] Figure 2 This refers to the process of modifying nitrogen-based fibers with bile acid ester compounds in Example 1;

[0058] Figure 3The polymerization process of the bile ester compound-modified nitrogen-based cellulose-based acrylamide polymer in Example 7;

[0059] Figure 4 The image shows the TG-DSC spectrum of the sample from Example 6. Detailed Implementation

[0060] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0062] The present invention will be further described in detail below with reference to embodiments, but the embodiments are not intended to limit the technical solutions of the present invention. Any person skilled in the art can refer to the content of the present invention and appropriately change the raw materials, process conditions, and other aspects to achieve other corresponding objectives within the scope of the technology disclosed in the present invention. Such changes do not depart from the content of the present invention, and all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of the present invention.

[0063] To better explain the present invention, the main contents of the present invention are further illustrated below with reference to specific laboratory embodiments, but the contents of the present invention are not limited to the following embodiments.

[0064] Example 1

[0065] The preparation of the bile ester compound-modified nitrogen-based fiber in this invention includes the following steps:

[0066] Step S1: Preparation of P-doped TiN fibers:

[0067] Using tetrabutyl titanate as the titanium source and acetic acid and anhydrous ethanol as solvents, polyvinylpyrrolidone (PVP) was added after stirring to increase the viscosity of the spinning solution. The mixed solution was stirred evenly to obtain the precursor spinning solution. Then, TiO2 fiber precursor was prepared by uniaxial electrospinning. TiO2 fiber precursor was reduced and nitrided at 900℃ for 2h in an ammonia atmosphere to obtain TiN fiber. TiN fiber was then heat-treated with NaH2PO4·2H2O in an Ar atmosphere at 550℃ for 1h in a tube furnace to obtain P-doped TiN fiber, i.e., P-TiN.

[0068] Step S2: Amine-modified P-doped TiN fibers

[0069] Dopamine was dissolved in deionized water to obtain a 2M solution. P-doped TiN fibers were added to the solution and stirred for 12 hours. The solution was then transferred to a hydrothermal reactor and heat-treated at 140°C for 2 hours to obtain amino-modified P-doped TiN fibers, namely NH2-P-TiN.

[0070] Step S3: Preparation of bile ester compounds

[0071] Step S3.1: Weigh 8g of 4-methylaniline into a 200ml round-bottom flask and add 50ml of anhydrous ethanol to dissolve it;

[0072] Step S3.2: Dissolve 10g of p-hydroxybenzaldehyde in 10ml of anhydrous ethanol in a 50ml beaker.

[0073] Step S3.3: Slowly add the ethanol solution of p-hydroxybenzaldehyde to the ethanol solution of 4-methylaniline, and reflux at 80°C for 3 hours to obtain 4-methylbenzifer base phenol (intermediate 1);

[0074] Step S3.4: Weigh 5g of adipic acid into a 100mL round-bottom flask and dissolve it in 10mL of ethanol. Weigh 5g of N,N'-dicyclohexylcarbodiimide and 0.2g of 4-dimethylaminopyridine into a 50mL beaker and mix them thoroughly. Slowly add the mixture dropwise to the adipic acid solution above, then add 5g of the 4-methylbenzifer base phenol obtained above. React at room temperature for 36h, evaporate by rotary evaporation, filter out the precipitate, and dry to obtain 4-methylbenzifer base phenylvaleric acid (intermediate 2).

[0075] Step S3.5: Take 1g of the 4-methylbenziferine phenylvaleric acid obtained above by drying and put it into a 100mL round-bottom flask, add ethanol to dissolve it, and form solution A;

[0076] Step S3.6: Weigh 0.7g of N,N'-dicyclohexylcarbodiimide and 0.02g of 4-dimethylaminopyridine into a 100mL beaker, dissolve them in ethanol, and then add them to the above solution A.

[0077] Step S3.7: Add 0.51g of cholic acid and stir at 30℃ for 36h. Then, after repeated filtration, rotary evaporation, filtration, and drying, the final product, tris(4-methylbenziferyl phenylvaleric acid)cholate, is obtained. It is a three-armed liquid crystal macromolecule, abbreviated as cholate compound. The above synthesis process is as follows: Figure 1 As shown.

[0078] Step S4: Preparation of nitrogen-based fibers modified with bile ester compounds

[0079] Step S4.1: Disperse 5g of NH2-P-TiN obtained in step S2 in an ethanol solution;

[0080] Step S4.2: Add 1g of tris(4-methylbenziferyl phenylvaleric acid)cholate obtained in step S3, and stir at 50℃ for 5h to obtain NH2-P-TiN fiber modified with tris(4-methylbenziferyl phenylvaleric acid)cholate, named Sample 1. The above modification process is as follows: Figure 2 As shown.

[0081] Example 2

[0082] The remaining methods and steps not described in this embodiment are the same as those in Embodiment 1, except that:

[0083] In step S1: the titanium source material is changed to tetrabutyl silicate as the silicon source, and the corresponding nitrogen-based fiber is SiN fiber. The SiN fiber and thiourea are heat-treated in an Ar atmosphere in a tube furnace for 1 hour to obtain S-doped SiN fiber.

[0084] In step S2: Dopamine is replaced with NaOH, S-doped SiN fibers are added to NaOH solution, stirred for 12 hours, and then transferred to a hydrothermal reactor for heat treatment to obtain hydroxyl-modified S-doped SiN fibers, i.e., OH-S-SiN.

[0085] Step S3 still prepares tris(4-methylbenziferyl phenylvaleric acid) cholate;

[0086] Step S4: Disperse the hydroxyl-modified S-doped SiN fibers in an ethanol solution, add tris(4-methylbenziferyl phenylvalerate)cholate, and stir at 50°C for 5 hours to obtain OH-S-SiN fibers modified with tris(4-methylbenziferyl phenylvalerate)cholate, named Sample 2.

[0087] Example 3

[0088] The remaining methods and steps not described in this embodiment are the same as those in Embodiment 1, except that:

[0089] In step S1: the titanium source material is changed to tributyl borate as the boron source, and the corresponding nitrogen-based fiber is BN fiber. The BN fiber is heat-treated with NaH2PO4·2H2O in an Ar atmosphere in a tube furnace for 1 hour to obtain P-doped BN fiber.

[0090] In step S2: P-doped BN fibers are added to a dopamine solution, stirred for 12 hours, and then transferred to a hydrothermal reactor for heat treatment to obtain amino-modified P-doped BN fibers, namely NH2-P-BN.

[0091] In step S3, 4-methylaniline is replaced with 4-nitroaniline to prepare tris(4-nitrobenschiff base phenylvaleric acid) cholate.

[0092] In step S4, amino-modified P-doped BN fibers are dispersed in an ethanol solution, and tris(4-nitrobenzirphine phenylvalerate)cholate is added. The mixture is stirred at 50°C for 5 hours to obtain NH2-P-BN fibers modified with tris(4-nitrobenzirphine phenylvalerate)cholate, which are named Sample 3.

[0093] Example 4

[0094] The remaining methods and steps not described in this embodiment are the same as those in Embodiment 1, except that:

[0095] In step S1: the nitrogen-based fiber is still TiN fiber, the phosphorus doping source (NaH2PO4·2H2O) is changed to thiourea doping, and the TiN fiber and thiourea are heat-treated in a tube furnace under Ar atmosphere for 1 hour to obtain S-doped TiN fiber.

[0096] In step S2: S-doped TiN fibers are added to a dopamine solution, stirred for 12 hours, and then transferred to a hydrothermal reactor for heat treatment to obtain amino-modified S-doped TiN fibers, namely NH2-S-TiN.

[0097] In step S3, 4-methylaniline is replaced with benzidine to prepare tris(biphenyl Schiff base phenylvaleric acid) cholate.

[0098] In step S4, the amino-modified S-doped TiN fibers were dispersed in an ethanol solution, and tris(biphenyl Schiff base phenylvaleric acid)cholate was added. The mixture was stirred at 50°C for 5 hours to obtain tris(biphenyl Schiff base phenylvaleric acid)cholate-modified NH2-S-TiN fibers, which were named Sample 4.

[0099] Example 5

[0100] The remaining methods and steps not described in this embodiment are the same as those in Embodiment 1, except that:

[0101] In step S1: the titanium source material is changed to tetrabutyl silicate as the silicon source, and the corresponding nitrogen-based fiber is SiN fiber. The phosphorus doping source (NaH2PO4·2H2O) is changed to thiourea doping. The SiN fiber and thiourea are heat-treated in an Ar atmosphere in a tube furnace for 1 hour to obtain S-doped SiN fiber.

[0102] In step S2: Dopamine is replaced with NaOH, S-doped SiN fibers are added to NaOH solution, stirred for 12 hours, and then transferred to a hydrothermal reactor for heat treatment to obtain hydroxyl-modified S-doped SiN fibers.

[0103] In step S3: 4-methylaniline is replaced with 4-ethylaniline to prepare tris(4-ethylbenzifero phenylvaleric acid) cholate.

[0104] In step S4, the hydroxyl-modified S-doped SiN fibers are dispersed in an ethanol solution, and tris(4-ethylbenzifer phenylvalerate)cholate is added. The mixture is stirred at 50°C for 5 hours to obtain OH-S-SiN fibers modified with tris(4-ethylbenzifer phenylvalerate)cholate, which are named Sample 5.

[0105] Example 6

[0106] 15 parts of tris(4-methylbenziferyl phenylvaleric acid)cholate-modified NH2-P-TiN fiber, 100 parts of acrylamide, 0.5 parts of chitosan (CTS) crosslinking agent, and 1000 parts of deionized water were placed in a container. The mixture was thoroughly stirred until homogeneous. Then, high-purity nitrogen gas was introduced into the container and continuously purged for 30 minutes. The reaction temperature was adjusted to 40℃. After adding 0.1 parts of potassium persulfate initiator, the mixture was stirred continuously for 6 hours to obtain a tris(4-methylbenziferyl phenylvaleric acid)cholate-modified NH2-P-TiN fiber-based acrylamide polymer, named Sample 6. The polymerization process is as follows: Figure 3 As shown.

[0107] Example 7

[0108] 15 parts of tris(4-methylbenziferyl phenylvalerate)cholate-modified OH-S-SiN fiber, 110 parts of 2-acrylamido-2-methylpropanesulfonic acid, 0.6 parts of polyethylene glycol diacrylate crosslinking agent, and 1000 parts of deionized water were placed in a container. The mixture was thoroughly mixed by vigorous stirring. Then, high-purity nitrogen gas was introduced into the container and continuously purged for 30 minutes. The reaction temperature was adjusted to 40℃. After injecting 0.3 parts of ammonium persulfate initiator, the mixture was stirred continuously for 6 hours to obtain a tris(4-methylbenziferyl phenylvalerate)cholate-modified OH-S-SiN fiber-based acrylamide polymer, named Sample 7.

[0109] Example 8

[0110] 15 parts of tris(4-nitrobenzyl phenylvalerate)cholate-modified NH2-P-BN fiber, 120 parts of acrylamide, 1 part of chitosan crosslinking agent, and 1000 parts of deionized water were placed in a container. The mixture was thoroughly mixed by vigorous stirring. Then, high-purity nitrogen gas was introduced into the container and continuously purged for 30 minutes. The reaction temperature was adjusted to 40℃. After injecting 0.1 parts of β-cyclodextrin initiator, the mixture was stirred continuously for 6 hours to obtain a tris(4-nitrobenzyl phenylvalerate)cholate-modified NH2-P-BN fiber-based acrylamide polymer, named Sample 8.

[0111] Example 9

[0112] 15 parts of tris(biphenylschoff base phenylvalerate)cholate-modified NH2-S-TiN fiber, 110 parts of acrylamide, 0.7 parts of polyethylene glycol diacrylate crosslinking agent, and 1000 parts of deionized water were placed in a container. The mixture was thoroughly mixed by vigorous stirring. Then, high-purity nitrogen gas was introduced into the container and continuously purged for 30 minutes. The reaction temperature was adjusted to 40℃. After injecting 0.5 parts of azobisisobutyronitrile initiator, the mixture was stirred continuously for 6 hours to obtain a tris(biphenylschoff base phenylvalerate)cholate-modified NH2-S-TiN fiber-based acrylamide polymer, named Sample 9.

[0113] Example 10

[0114] 15 parts of tris(4-ethylbenziferyl phenylvalerate)cholate-modified OH-S-SiN fiber, 120 parts of 2-acrylamido-2-methylpropanesulfonic acid, 1 part of polyethylene glycol diacrylate crosslinking agent, and 1000 parts of deionized water were placed in a container. The mixture was thoroughly mixed by vigorous stirring. Then, high-purity nitrogen gas was introduced into the container and continuously purged for 30 min. The reaction temperature was adjusted to 40℃. After injecting 0.3 parts of β-cyclodextrin initiator, the mixture was stirred continuously for 6 h to obtain a tris(4-ethylbenziferyl phenylvalerate)cholate-modified OH-S-SiN fiber-based acrylamide polymer, named Sample 10.

[0115] I. Thermal stability tests were conducted on the polymer of Example 6. Thermogravimetric analysis (TGA) is a commonly used method for determining the thermal stability of polymers. Generally, the higher the polymer's decomposition temperature, the higher its stability and the better its heat resistance. The results are as follows: Figure 4 The thermal properties of the polymers shown remain largely consistent. The maximum weight loss occurs at 400℃, where the CH bonds break due to the high temperature. However, the polymers show almost no weight loss before 300℃, indicating that they can be used in ultra-deep wells.

[0116] II. Viscosity and curing strength tests were conducted on the polymers of Examples 6 to 10, and the results are shown in Table 1:

[0117] Table 1. Effect of crosslinking agent on viscosity and strength

[0118]

[0119] As shown in Table 1, the crosslinking agent increases with increasing amount, and the crosslinking agent enables the linear polymer molecules to crosslink with each other to form a spatial network structure through the bridging effect of covalent or ionic bonds. However, the continuous increase in the amount of crosslinking agent will lead to over-crosslinking of the entire gel system, which will eventually reduce the strength of the entire system. The crosslinking agents in Examples 6 to 10 are within a suitable ratio range.

[0120] III. Mechanical properties and crack sealing effect tests were conducted on the polymers from Examples 6 to 10: A steel crack model with a length of 10 cm and a crack width of 3.0 mm was used to simulate the leakage channel. Specific test method: 500 mL of polymer was poured into the leakage-sealing device's water-loss cylinder; a movable piston was placed on top, and the cylinder cap was tightened to seal it; after curing for 8 hours, drilling fluid was injected using a high-displacement horizontal flow pump to pressurize the system, and the pressure at the inlet end of the crack model was recorded in real time. The highest pressure at which the drilling fluid leaked from the outlet end of the crack model was taken as the highest sealing pressure of the polymer on the crack. The experimental temperature was 180℃, and the results are shown in Table 2.

[0121] Table 2 Test data on the mechanical properties and crack sealing effect of the polymer after curing

[0122]

[0123]

[0124] As shown in Table 2, the maximum tensile fracture stress of the polymer after curing is 216.4 kPa (higher than the system requirement: tensile fracture stress not less than 100 kPa for a 3 mm crack), and the highest sealing pressure for cracks after curing is 16.3 MPa (higher than the system requirement: sealing pressure not less than 8 MPa for a 3 mm crack). This indicates that the polymers prepared in Examples 6 to 10 have excellent tensile mechanical properties and excellent crack sealing effect after curing.

[0125] IV. The demulsification voltage of the polymers from Examples 6 to 10 before and after high-temperature aging at 180°C was tested, and the results are shown in Table 3:

[0126] Table 3. Demulsification voltage test data of polymers before and after high-temperature aging at 180℃.

[0127] Demulsification voltage (V) before aging Demulsification voltage (V) after aging Sample 6 612 563.4 Sample 7 632 588.6 Sample 8 696 624.3 Sample 9 671 617.5 Sample 10 665 611.5

[0128] As can be seen from Table 3, the demulsification voltage decreased after aging because the polymer viscosity increased during the aging process, and the imine bonds connecting some fibers and the polymer network were destroyed, resulting in a decrease in the overall polymer demulsification voltage. The decrease was less than 15% of the system requirement.

[0129] V. Antifouling performance tests were conducted on the polymers from Examples 6 to 10.

[0130] During drilling, the environment inside the wellbore is often harsh due to the different properties of the fluids inside the formation, or the presence of working fluids from previous drilling, acid fracturing, and other construction processes. This can have a significant impact on the polymer system. This section mainly evaluates the anti-fouling properties of the polymers obtained in Examples 6 to 10.

[0131] Prepare a 20% sodium chloride solution, a 20% calcium chloride solution, a 10% dilute hydrochloric acid solution, a 10% sodium hydroxide solution, an oil-based drilling fluid, a water-based drilling fluid, and crude oil. Add the polymers from Examples 6 to 10 to the prepared mixed solutions at a mass fraction of 10%. Observe the consolidation time and consolidation status. The consolidation time is shown in Table 4.

[0132] Table 4. Consolidation time (h) for different pollution sources

[0133]

[0134] Table 4 records the effects of different pollution sources on the consolidation time. Although the consolidation time of sodium chloride solution, calcium chloride solution, sodium hydroxide solution, oil-based drilling fluid, and water-based drilling fluid with crude oil was prolonged, it was still within the expected range of 4-6 hours, indicating that the polymers of Examples 6 to 10 have good salt resistance.

[0135] This invention uses hydroxyl and amino-modified non-metallic elements to dope nitrogen-based fibers. Then, ligands such as 4-methylaniline react with p-hydroxybenzaldehyde to prepare phenolic compounds containing Schiff base liquid crystal units. Cholic acid is combined with the phenolic compounds containing Schiff base liquid crystal units to prepare cholate-modified nitrogen-based fibers. Furthermore, during the free radical polymerization of acrylamide monomer under the action of an initiator, nonpolar hydrogen bonds are formed between the modified fibers and amide functional groups, constructing an interpenetrating network polymer system. Tris(4-ethylbenziff base phenylvaleric acid) cholate modification effectively allows nitrogen-based fibers to penetrate the three-dimensional resin network in the form of imine bonds. The addition of modified fibers forms a cross-linked network of nitrogen-based fibers in the middle of the acrylamide polymer network, improving the strength, salt resistance, and temperature resistance of the final product.

[0136] The above description is merely a preferred embodiment of the present invention, showing and describing the basic principles, main features, and advantages of the present invention. It is not intended to limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. In addition to the above embodiments, the present invention may have other implementations without departing from the spirit and scope of the invention. Various changes and modifications to the present invention are possible, and all technical solutions formed by equivalent substitutions or equivalent transformations fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents. Technical features not described in the present invention can be implemented by or using existing technology, and will not be elaborated here.

Claims

1. A cholic acid ester compound-modified nitrogen-based fiber-based acrylamide polymer, characterized by, The raw material components and weight contents are as follows: 15 parts of cholic acid ester compound modified nitrogen-based fiber, 100-120 parts of allyl monomer, 0.1-0.5 parts of initiator and 0.5-1 parts of crosslinking agent; the allyl monomer is acrylamide or 2-acrylamido-2-methylpropane sulfonic acid, the initiator is potassium persulfate, ammonium persulfate, azobisisobutyronitrile or β-cyclodextrin, and the crosslinking agent is chitosan or polyethylene glycol diacrylate; The preparation of the cholic acid ester compound modified nitrogen-based fiber comprises the following steps in sequence: Step S1, preparing a non-metal doped nitrogen-based fiber; Step S2, modifying the non-metal doped nitrogen-based fiber with a hydroxyl group or an amino group; Step S3, preparing a phenolic compound containing a Schiff base liquid crystal unit by reacting 4-methylaniline, 4-nitroaniline, diphenylamine or 4-ethylaniline with p-hydroxybenzaldehyde, respectively, and combining cholic acid with the phenolic compound containing a Schiff base liquid crystal unit to prepare a cholic acid ester compound; Step S4, synthesizing a nitrogen-based fiber modified by the cholic acid ester compound.

2. The cholic acid ester compound-modified nitrogen-based acrylamide polymer according to claim 1, characterized by, The raw material components and weight contents are as follows: 15 parts of cholic acid ester compound modified nitrogen-based fiber, 100 parts of allyl monomer, 0.1 parts of initiator and 0.5 parts of crosslinking agent.

3. The cholic acid ester compound-modified nitrogen-based acrylamide polymer according to claim 1, wherein The raw material components and weight contents are as follows: 15 parts of cholic acid ester compound modified nitrogen-based fiber, 100 parts of allyl monomer, 0.1 parts of initiator and 0.5 parts of crosslinking agent.

4. The cholic acid ester compound-modified nitrogen-based acrylamide polymer according to claim 1, wherein The raw material components and weight contents are as follows: 15 parts of cholic acid ester compound modified nitrogen-based fiber, 100 parts of allyl monomer, 0.1 parts of initiator and 0.5 parts of crosslinking agent.

5. The cholic acid ester compound-modified nitrogen-based acrylamide polymer according to claim 1, wherein In the step S1, the nitrogen-based fiber is a TiN fiber, and the TiN fiber is heat-treated with NaH2PO4·2H2O in a tube furnace under Ar atmosphere for 1 h to obtain a P-doped TiN fiber.

6. The cholic acid ester compound-modified nitrogen-based acrylamide polymer according to claim 5, wherein In the step S2, the P-doped TiN fiber is added into a dopamine solution, stirred for 12 h, and then transferred into an autoclave for heat treatment to obtain an amino-modified P-doped TiN fiber.

7. The cholic acid ester compound-modified nitrogen-based acrylamide polymer according to claim 6, wherein The step S3 comprises the following sub-steps in sequence: Step S3.1, dissolving 4-methylaniline in anhydrous ethanol; Step S3.2, dissolving p-hydroxybenzaldehyde in anhydrous ethanol; Step S3.3, adding the above ethanol solution of p-hydroxybenzaldehyde dropwise into the ethanol solution of 4-methylaniline, and refluxing for 3 h by rotary evaporation to obtain 4-methylphenyl Schiff base phenol; Step S3.4, uniformly mixing N,N'-dicyclohexyl carbodiimide and 4-dimethylamino pyridine, slowly adding them into adipic acid solution, then adding the above 4-methylphenyl Schiff base phenol, and reacting at room temperature, followed by rotary evaporation, filtration and drying to obtain 4-methylphenyl Schiff base phenyl valeric acid; Step S3.5, dissolving the above 4-methylphenyl Schiff base phenyl valeric acid in anhydrous ethanol to form an A solution; Step S3.6, uniformly mixing N,N'-dicyclohexyl carbodiimide and 4-dimethylamino pyridine, dissolving them in ethanol, and then adding the above A solution; Step S3.7, adding cholic acid after stirring, and then repeatedly filtering, rotary evaporation, filtering and drying to obtain tris(4-methylphenyl Schiff base phenyl valeric acid) cholic acid ester.

8. The cholic acid ester compound-modified nitrogen-based acrylamide polymer according to claim 7, wherein The step S4 comprises the following sub-steps in sequence: Step S4.1, dispersing the above-mentioned amino-modified P-doped TiN fiber in an ethanol solution; Step S4.2, adding the above-mentioned tris(4-methylphenylsulfonamide) cholic acid ester, stirring at 50°C for 5h, to obtain tris(4-methylphenylsulfonamide) cholic acid ester-modified NH2-P-TiN fiber.

9. The cholic acid ester compound-modified nitrogen-based fiber-based acrylamide polymer according to claim 1, wherein, in the step S1, the nitrogen-based fiber is SiN fiber, and the SiN fiber is heat-treated with thiourea in a tube furnace under Ar atmosphere for 1h to obtain S-doped SiN fiber; in the step S2, the S-doped SiN fiber is added into NaOH solution, stirred for 12h, and transferred to an autoclave for heat treatment to obtain hydroxyl-modified S-doped SiN fiber; in the step S3, tris(4-methylphenylsulfonamide) cholic acid ester is prepared; and in the step S4, tris(4-methylphenylsulfonamide) cholic acid ester-modified OH-S-SiN fiber is synthesized.

9. The cholic acid ester compound-modified nitrogen-based fiber-based acrylamide polymer according to claim 1, wherein, in the step S1, the nitrogen-based fiber is SiN fiber, and the SiN fiber is heat-treated with thiourea in a tube furnace under Ar atmosphere for 1h to obtain S-doped SiN fiber; in the step S2, the S-doped SiN fiber is added into NaOH solution, stirred for 12h, and transferred to an autoclave for heat treatment to obtain hydroxyl-modified S-doped SiN fiber; in the step S3, tris(4-methylphenylsulfonamide) cholic acid ester is prepared; and in the step S4, tris(4-methylphenylsulfonamide) cholic acid ester-modified OH-S-SiN fiber is synthesized.

10. The cholic acid ester compound-modified nitrogen-based fiber-based acrylamide polymer according to claim 1, wherein, in the step S1, the nitrogen-based fiber is BN fiber, and the BN fiber is heat-treated with NaH2PO4•2H2O in a tube furnace under Ar atmosphere for 1h to obtain P-doped BN fiber; in the step S2, the P-doped BN fiber is added into dopamine solution, stirred for 12h, and transferred to an autoclave for heat treatment to obtain amino-modified P-doped BN fiber; in the step S3, tris(4-nitrophenylsulfonamide) cholic acid ester is prepared; and in the step S4, tris(4-nitrophenylsulfonamide) cholic acid ester-modified NH2-P-BN fiber is synthesized.

10. The cholic acid ester compound-modified nitrogen-based fiber-based acrylamide polymer according to claim 1, wherein, in the step S1, the nitrogen-based fiber is BN fiber, and the BN fiber is heat-treated with NaH2PO4•2H2O in a tube furnace under Ar atmosphere for 1h to obtain P-doped BN fiber; in the step S2, the P-doped BN fiber is added into dopamine solution, stirred for 12h, and transferred to an autoclave for heat treatment to obtain amino-modified P-doped BN fiber; in the step S3, tris(4-nitrophenylsulfonamide) cholic acid ester is prepared; and in the step S4, tris(4-nitrophenylsulfonamide) cholic acid ester-modified NH2-P-BN fiber is synthesized.

11. The cholic acid ester compound-modified nitrogen-based fiber-based acrylamide polymer according to claim 1, wherein, in the step S1, the nitrogen-based fiber is TiN fiber, and the TiN fiber is heat-treated with thiourea in a tube furnace under Ar atmosphere for 1h to obtain S-doped TiN fiber; in the step S2, the S-doped TiN fiber is added into dopamine solution, stirred for 12h, and transferred to an autoclave for heat treatment to obtain amino-modified S-doped TiN fiber; in the step S3, tris(biphenylsulfonamide) cholic acid ester is prepared; and in the step S4, tris(biphenylsulfonamide) cholic acid ester-modified NH2-S-TiN fiber is synthesized.

11. The cholic acid ester compound-modified nitrogen-based fiber-based acrylamide polymer according to claim 1, wherein, in the step S1, the nitrogen-based fiber is TiN fiber, and the TiN fiber is heat-treated with thiourea in a tube furnace under Ar atmosphere for 1h to obtain S-doped TiN fiber; in the step S2, the S-doped TiN fiber is added into dopamine solution, stirred for 12h, and transferred to an autoclave for heat treatment to obtain amino-modified S-doped TiN fiber; in the step S3, tris(biphenylsulfonamide) cholic acid ester is prepared; and in the step S4, tris(biphenylsulfonamide) cholic acid ester-modified NH2-S-TiN fiber is synthesized.

12. The cholic acid ester compound-modified nitrogen-based fiber-based acrylamide polymer according to claim 1, wherein, in the step S1, the nitrogen-based fiber is SiN fiber, and the SiN fiber is heat-treated with thiourea in a tube furnace under Ar atmosphere for 1h to obtain S-doped SiN fiber; in the step S2, the S-doped SiN fiber is added into NaOH solution, stirred for 12h, and transferred to an autoclave for heat treatment to obtain hydroxyl-modified S-doped SiN fiber; in the step S3, tris(4-ethylphenylsulfonamide) cholic acid ester is prepared; and in the step S4, tris(4-ethylphenylsulfonamide) cholic acid ester-modified OH-S-SiN fiber is synthesized.

12. The cholic acid ester compound-modified nitrogen-based fiber-based acrylamide polymer according to claim 1, wherein, in the step S1, the nitrogen-based fiber is SiN fiber, and the SiN fiber is heat-treated with thiourea in a tube furnace under Ar atmosphere for 1h to obtain S-doped SiN fiber; in the step S2, the S-doped SiN fiber is added into NaOH solution, stirred for 12h, and transferred to an autoclave for heat treatment to obtain hydroxyl-modified S-doped SiN fiber; in the step S3, tris(4-ethylphenylsulfonamide) cholic acid ester is prepared; and in the step S4, tris(4-ethylphenylsulfonamide) cholic acid ester-modified OH-S-SiN fiber is synthesized. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The step S4 synthesizes the OH-S-SiN fiber modified by tris (4-ethylphenylsulfoxide benzylvaleric acid) cholic acid ester.

13. A method for synthesizing a nitrogen-based cellulose-based acrylamide polymer modified with a cholate ester compound, characterized in that, The step comprises the following steps: placing 15 parts of the cholic acid ester compound modified nitrogen-based fiber, 100-120 parts of an allyl monomer, 0.5-1 part of a crosslinking agent, and 1000 parts of deionized water in a container, mixing the mixed solution uniformly by strong stirring, then introducing high-purity nitrogen into the container, continuously aerating for 30 min, adjusting the reaction temperature to 40℃, injecting 0.1-0.5 parts of an initiator, and continuously stirring for 6 h to obtain a cholic acid ester compound modified nitrogen-based fiber-based acrylamide polymer; the allyl monomer is acrylamide or 2-acrylamido-2-methylpropanesulfonic acid, the initiator is potassium persulfate, ammonium persulfate, azobisisobutyronitrile, or β-cyclodextrin, and the crosslinking agent is chitosan or polyethylene glycol diacrylate; The preparation of the cholic acid ester compound modified nitrogen-based fiber comprises the following steps in sequence: Step S1, preparing a non-metal doped nitrogen-based fiber; Step S2, modifying the non-metal doped nitrogen-based fiber with a hydroxyl group or an amino group; Step S3, preparing a phenolic compound containing a Schiff base liquid crystal unit by reacting 4-methylaniline, 4-nitroaniline, diphenylamine, or 4-ethyl aniline with p-hydroxybenzaldehyde, and combining cholic acid with the phenolic compound containing the Schiff base liquid crystal unit to prepare a cholic acid ester compound; Step S4, synthesizing the cholic acid ester compound modified nitrogen-based fiber.

14. A plugging application of a cholic acid ester compound modified nitrogen-based fiber-based acrylamide polymer, characterized by: The cholic acid ester compound modified nitrogen-based fiber-based acrylamide polymer as claimed in any one of claims 1 to 12 is applied in a lost circulation cement slurry.

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