An epoxy resin for sealing oil and gas wells and a method for preparing the same

Abstract

The present application relates to oil and gas well plugging technology field, specifically, it relates to a kind of epoxy resin for oil and gas well plugging and its preparation method, it includes the following raw materials: ion liquid block type epoxy resin, self-cleavage type amine curing agent, phenyl glycidyl ether, composite filler, gamma-glycidyl ether oxygen propyl trimethoxysilane and end carboxyl butyronitrile liquid rubber.In the present application, ion liquid block type epoxy resin enhances the mechanical strength and heat resistance of the cured network by rigid imidazole ring structure, significantly improves the interface compatibility and bonding strength of resin system on humid, high salt well wall;Self-cleavage type amine curing agent remains chemically inert at room temperature, ensures that the resin slurry has a long enough operating window and excellent storage stability during pumping phase;When entering target high temperature layer, capping group rapidly cleaves, releases high-activity polypeptide amine, initiates rapid crosslinking and curing reaction, avoids plugging failure caused by delayed or incomplete curing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas well plugging, in particular to an epoxy resin for oil and gas well plugging and a preparation method thereof. BACKGROUND

[0002] During the exploration and development and subsequent abandonment of oil and gas fields, ensuring the long-term sealing integrity of the wellbore is a core technical link for preventing interlayer channeling, ensuring geological storage safety, and avoiding environmental pollution. Epoxy resin materials are widely regarded as high-performance plugging materials to replace traditional cement due to their excellent bonding strength, excellent mechanical properties, stable chemical inertness, and extremely low permeability. Among them, bisphenol F type epoxy resin has inherent low viscosity characteristics and exhibits good flow and wetting ability in the complex and narrow space downhole, which has significant application potential.

[0003] However, the existing conventional epoxy resin system has insufficient viscosity stability under complex conditions such as high temperature and high salt downhole, and the compatibility and bonding force between the system and the wellbore solid wall interface are prone to decay, resulting in a weak plugging layer and a risk of sealing failure. In view of this, we propose an epoxy resin for oil and gas well plugging and a preparation method thereof. SUMMARY

[0004] The present application aims to provide an epoxy resin for oil and gas well plugging and a preparation method thereof to solve the problem of insufficient viscosity stability of the existing conventional epoxy resin system under complex conditions such as high temperature and high salt downhole, and the compatibility and bonding force between the system and the wellbore solid wall interface are prone to decay, resulting in a weak plugging layer and a risk of sealing failure.

[0005] The present application provides an epoxy resin for oil and gas well plugging, comprising the following raw materials: ionic liquid block type epoxy resin, self-cleavage type amine curing agent, phenyl glycidyl ether, composite filler, gamma-glycidyl ether oxypropyl trimethoxysilane and carboxyl-terminated butyronitrile liquid rubber.

[0006] The ionic liquid block type epoxy resin is prepared by block copolymerization of 1-allyl-3-methylimidazole chloride and bisphenol F type epoxy prepolymer.

[0007] The self-cleavage type amine curing agent is a heat-cleavable latent curing agent prepared by condensing amino acids to form a polypeptide intermediate and end-capping reaction with isocyanate.

[0008] As a preferred, the ionic liquid block type epoxy resin is 90-100 parts by weight, the self-cleavage type amine curing agent is 50-65 parts by weight, the phenyl glycidyl ether is 15-20 parts by weight, the composite filler is 40-60 parts by weight, the gamma-glycidyl ether oxypropyl trimethoxysilane is 1-3 parts by weight, and the carboxyl-terminated butyronitrile liquid rubber is 8-12 parts by weight.

[0009] As preferred, the preparation method of the ion liquid block type epoxy resin is as follows:

[0010] Under nitrogen protection, the bisphenol F type epoxy resin is mixed with 1-allyl-3-methyl imidazole chloride salt, stirred at 300-500 rpm for 20-40 min at 60-80℃; then boron trifluoride ether is added, and reacted at 80-100℃ for 4-6 h to form an epoxy-ion liquid block copolymer; after the reaction is completed, it is cooled to room temperature, and 5-10% of butyl glycidyl ether based on the mass of the copolymer is added to obtain the ion liquid block type epoxy resin.

[0011] As preferred, the molar ratio of the bisphenol F type epoxy resin mixed with 1-allyl-3-methyl imidazole chloride salt is 1:0.2-0.4.

[0012] As preferred, the addition amount of the boron trifluoride ether is 0.5-1.0% based on the mass of the bisphenol F type epoxy resin.

[0013] As preferred, the preparation method of the self-cleavage type amine curing agent is as follows:

[0014] L-lysine and L-alanine are taken in a molar ratio of 1:1, dissolved in 10-15 times the volume of dimethylformamide based on the total mass, stirred at 400-600 rpm at room temperature for 30-40 min to completely dissolve; then N,N-dicyclohexyl carbodiimide is added, and after reacting at 0-5℃ for 0.5 h, the temperature is raised to 25-35℃ and the reaction is continued for 6-8 h; after the reaction is completed, the dipeptide intermediate is obtained by filtration;

[0015] The dipeptide intermediate is mixed with hexamethylene diisocyanate, stirred and reacted at 60-70℃ for 2-3 h under nitrogen protection to obtain a capped latent polypeptide amine; after the reaction is completed, the system is removed under reduced pressure, and dried at 50-60℃ under vacuum for 6-8 h to obtain the self-cleavage type amine curing agent.

[0016] As preferred, the addition amount of the N,N-dicyclohexyl carbodiimide is 1.1-1.3 mol equivalents based on the total molar amount of the amino acid.

[0017] As preferred, the molar ratio of the dipeptide intermediate mixed with hexamethylene diisocyanate is 1:1.5-2.0.

[0018] On the other hand, the present application provides a preparation method of an epoxy resin for oil and gas well plugging, for preparing the above-mentioned epoxy resin for oil and gas well plugging, comprising the following steps:

[0019] S1.1, weigh the raw materials as follows: 90-100 parts by weight of ionic liquid block type epoxy resin, 50-65 parts by weight of self-cleavage type amine curing agent, 15-20 parts by weight of phenyl glycidyl ether, 40-60 parts by weight of composite filler, 1-3 parts by weight of gamma-glycidyl ether oxypropyl trimethoxysilane and 8-12 parts by weight of carboxyl-terminated butylnitrile liquid rubber;

[0020] S1.2, mix the ionic liquid block type epoxy resin with the phenyl glycidyl ether, stir at 60℃ for 30min at a speed of 400-500rpm; then add the gamma-glycidyl ether oxypropyl trimethoxysilane, the carboxyl-terminated butylnitrile liquid rubber and the composite filler, continue to stir for 20-30min; after cooling to below 30℃, add the self-cleavage type amine curing agent, uniformly mix, then degas under a vacuum degree of-0.08MPa for 10-15min, and fill to obtain the epoxy resin for oil and gas well plugging.

[0021] Preferably, in S1.2, the composite filler is a composite of nano-silicon dioxide modified by gamma-glycidyl ether oxypropyl trimethoxysilane and quartz powder, with a mass ratio of 1:5.

[0022] Compared with the prior art, the oil and gas well plugging epoxy resin and the preparation method thereof have the following beneficial effects:

[0023] In the oil and gas well plugging epoxy resin and the preparation method thereof, the ionic liquid block type epoxy resin enhances the mechanical strength and heat resistance of the cured network through the rigid imidazole ring structure, significantly improves the interfacial compatibility and bonding strength of the resin system on the humid and high-salt well wall; the self-cleavage type amine curing agent realizes a trigger type curing mechanism: it remains chemically inert at room temperature, ensuring that the resin slurry has a long enough operation window and excellent storage stability during the pumping stage; when entering the target high-temperature layer, the end-capping group rapidly cleaves, releasing a highly active polypeptide amine to initiate a rapid crosslinking and curing reaction, which can accurately convert downhole thermal energy into a curing driving force, avoiding plugging failure caused by delayed or incomplete curing; the two work together to build a plugging system that has excellent construction performance, strong interfacial bonding force, high heat-resistant body and precise trigger curing characteristics. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0025] The application provides an epoxy resin for oil and gas well plugging, which comprises the following raw materials: an ionic liquid block type epoxy resin, a self-cleavage type amine curing agent, a phenyl glycidyl ether, a composite filler, gamma-glycidoxypropyltrimethoxysilane and a carboxyl-terminated butylnitrile liquid rubber.

[0026] The ionic liquid block type epoxy resin is prepared through block copolymerization reaction of 1-allyl-3-methylimidazole chloride and a bisphenol F type epoxy prepolymer.

[0027] The self-cleavage type amine curing agent is a heat-cleavable latent curing agent prepared through condensation of amino acids to generate a polypeptide intermediate and isocyanate end-capping reaction.

[0028] The bisphenol F type epoxy resin (CAS number: 37231-36-0) is purchased from Hubei Shiteng Chemical Technology Co., Ltd.

[0029] 1-allyl-3-methylimidazole chloride (CAS number: 65039-10-3, purity 96%), L-lysine (CAS number: 56-87-1, purity BR, 99%), L-alanine (CAS number: 56-41-7, purity BR, 99%), N,N-dicyclohexyl carbodiimide (CAS number: 538-75-0, purity AR, 99%), and gamma-glycidoxypropyltrimethoxysilane (CAS number: 2530-83-8, purity BR, 98%) are all purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0030] Boron trifluoride diethyl ether (CAS number: 109-63-7, purity 99%) and carboxyl-terminated butylnitrile liquid rubber (CAS number: 25265-19-4, purity 99%) are purchased from Hubei Chengfeng Chemical Co., Ltd.

[0031] Butyl glycidyl ether (CAS number: 2426-08-6, purity 99%) and phenyl glycidyl ether (CAS number: 122-60-1, purity 99%) are both purchased from Changzhou Hongyu Chemical Co., Ltd.

[0032] Hexamethylene diisocyanate (CAS number: 822-06-0, purity greater than or equal to 99%) is purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.

[0033] The composite filler is a composite of nano-silicon dioxide modified by gamma-glycidoxypropyltrimethoxysilane and quartz powder, and the mass ratio is 1:5.

[0034] The preparation method of the composite filler is as follows: 5% of γ-glycidyloxypropyltrimethoxysilane based on the mass of nanosilica is added to ethanol, stirred at room temperature for 30 min, and the pH is adjusted to 4 with acetic acid to obtain a hydrolysis solution; nanosilica is added to the hydrolysis solution, ultrasonicated for 10-15 min, and stirred at 40-60°C for 60 min to obtain a modified nanosilica suspension; quartz powder is added to the modified nanosilica suspension and mixed uniformly; then the wet solid is collected by filtration, washed with ethanol twice to remove unreacted free silane and solvent residues, and the wet solid is oven dried at 110°C for 8-12 h to obtain the composite filler.

[0035] Example 1: A preparation method of an epoxy resin for oil and gas well plugging, comprising the following steps:

[0036] S1.1, weigh the following raw materials: 90 parts by weight of ionic liquid block type epoxy resin, 50 parts by weight of self-cleavage type amine curing agent, 15 parts by weight of phenyl glycidyl ether, 40 parts by weight of composite filler, 1 part by weight of γ-glycidyloxypropyltrimethoxysilane, and 8 parts by weight of carboxyl-terminated butylnitrile liquid rubber;

[0037] S1.2, mix the ionic liquid block type epoxy resin with the phenyl glycidyl ether, stir at 60°C at a speed of 400 rpm for 30 min; then add the γ-glycidyloxypropyltrimethoxysilane, carboxyl-terminated butylnitrile liquid rubber, and composite filler, continue to stir for 30 min; after cooling to below 30°C, add the self-cleavage type amine curing agent, uniformly mix, then degas under a vacuum of-0.08 MPa for 15 min, and fill to obtain the epoxy resin for oil and gas well plugging.

[0038] The preparation method of the ionic liquid block type epoxy resin is as follows:

[0039] Under nitrogen protection, the bisphenol F type epoxy resin is mixed with 1-allyl-3-methylimidazole chloride salt at a molar ratio of 1:0.2, stirred at 60°C at a speed of 300 rpm for 40 min; then 0.5% of boron trifluoride ether based on the mass of the bisphenol F type epoxy resin is added, and reacted at 80°C for 6 h to form an epoxy-ionic liquid block copolymer; after the reaction is completed, the temperature is cooled to room temperature, 5% of butyl glycidyl ether based on the mass of the copolymer is added, and the ionic liquid block type epoxy resin is obtained.

[0040] The preparation method of the self-cleavage type amine curing agent is as follows:

[0041] L-lysine and L-alanine were dissolved in 10 times the total mass of dimethylformamide at a molar ratio of 1:1, and stirred at room temperature at a speed of 400 rpm for 30 min to completely dissolve them; then 1.1 mol equivalents of N,N-dicyclohexyl carbodiimide were added, and the reaction was carried out at 0-5°C for 0.5 h, and then the temperature was raised to 30°C and the reaction was continued for 6 h; after the reaction was completed, the dipeptide intermediate was obtained by filtration;

[0042] The dipeptide intermediate was mixed with hexamethylene diisocyanate at a molar ratio of 1:1.5, and stirred at 60°C under nitrogen protection for 3 h to obtain a capped latent polypeptide amine; after the reaction was completed, the system was removed under reduced pressure, and dried at 60°C under vacuum for 8 h to obtain a self-cleavage type amine curing agent.

[0043] Example 2: Compared with Example 1, the difference is that the molar ratio of bisphenol F type epoxy resin mixed with 1-allyl-3-methyl imidazole chloride salt is 1:0.3.

[0044] Example 3: Compared with Example 1, the difference is that the molar ratio of bisphenol F type epoxy resin mixed with 1-allyl-3-methyl imidazole chloride salt is 1:0.4.

[0045] Viscosity determination: Place an appropriate amount of prepared resin sample in a constant temperature sample cup, control the temperature (such as 25°C or 60°C); select an appropriate speed (such as 50 rpm or 100 rpm), and record the viscosity value after the reading is stable.

[0046] Determination of glass transition temperature (Tg): Take 5-10 mg of completely cured resin sample and place it in a DSC sample pan; scan at a certain heating rate (usually 10°C / min) under a nitrogen atmosphere, and the scanning range is from room temperature to a sufficiently high temperature (such as 250°C); on the obtained heat flow-temperature curve, the temperature corresponding to the midpoint of the curve step change is the glass transition temperature.

[0047] Adhesion strength determination: Prepare standard steel test pieces (such as 40Cr steel), and perform sandblasting and cleaning treatment on the bonding surface; mix the resin with the curing agent system, and uniformly coat it on the overlapping surface of the two test pieces to form a bonding layer with a specified thickness and area; completely cure under specified conditions; compare the test pieces after being immersed in simulated well conditions of salt water (such as 3.5% NaCl solution) at high temperature (such as 90°C) for 7 days with those under dry conditions; fix the test pieces on the testing machine, and perform tensile shear testing at a constant rate until failure, and record the maximum load; adhesion strength = maximum load / bonding area.

[0048] Table 1 Performance data of ionic liquid block type epoxy resin

[0049] Viscosity (25°C) Tg after curing Dry adhesion strength Wet adhesion strength Wet strength retention rate Example 1 1650 mPa-s 108℃ 18.5 MPa 14.2 MPa 76.8% Example 2 2400 mPa-s 121℃ 19.8 MPa 17.5 MPa 88.4% Example 3 3380 mPa-s 115℃ 20.1 MPa 16.9 MPa 84.1%

[0050] As the molar ratio increased from 1:0.2 to 1:0.4, the viscosity of the resin increased significantly from 1,650 mPa·s to 3,380 mPa·s; this is because the ionic liquid segment itself has strong polarity and large intermolecular force, and the increase in its embedding density directly leads to the increase in the bulk viscosity of the resin.

[0051] Example 2 (molar ratio 1:0.3) exhibited the highest glass transition temperature (121℃) and excellent dry-state bonding strength; this indicates that at this ratio, the ionic liquid segment effectively enhances the rigidity of the resin matrix and improves the interfacial adhesion, while not negatively affecting the overall crosslinking density of the epoxy network, reaching an optimal balance point.

[0052] The wet-state bonding strength is a key indicator of downhole plugging performance; Example 2 also exhibited the highest wet-state bonding strength (17.5 MPa) and wet-state strength retention rate (88.4%); this proves that the amount of ionic liquid segment introduced can most effectively resist the intrusion of water molecules and inhibit the decay of interfacial adhesion.

[0053] When the ratio is further increased to Example 3 (molar ratio 1:0.4), although the dry-state bonding strength still increases slightly due to the physical interaction between the ionic liquid segment and the matrix, both the Tg and the wet-state bonding strength decrease; this is because too high a content of ionic liquid begins to destroy the structural integrity and uniformity of the epoxy curing network, introduces too many flexible segments, and forms a too-thick hydrophilic layer at the interface, which is not conducive to long-term wet-heat stability.

[0054] Example 4: A method for preparing an epoxy resin for oil and gas well plugging, comprising the following steps:

[0055] S1.1, weigh the following raw materials: 100 parts by weight of ionic liquid block type epoxy resin, 65 parts by weight of self-cleavage type amine curing agent, 20 parts by weight of phenyl glycidyl ether, 60 parts by weight of composite filler, 3 parts by weight of γ-glycidyl ether oxypropyl trimethoxysilane, and 12 parts by weight of carboxyl-terminated butylnitrile liquid rubber;

[0056] S1.2, mix the ionic liquid block type epoxy resin with the phenyl glycidyl ether, stir at 60℃ and a speed of 400 rpm for 30 min; then add the γ-glycidyl ether oxypropyl trimethoxysilane, the carboxyl-terminated butylnitrile liquid rubber, and the composite filler, and continue stirring for 30 min; after cooling to below 30℃, add the self-cleavage type amine curing agent, mix uniformly, then degas under a vacuum of -0.08 MPa for 15 min, and fill to obtain the epoxy resin for oil and gas well plugging.

[0057] The method for preparing the ionic liquid block type epoxy resin is as follows:

[0058] The bisphenol F type epoxy resin is mixed with 1-allyl-3-methyl imidazole chloride in a molar ratio of 1:0.3 under nitrogen protection, and stirred at 80℃ at a speed of 500 rpm for 20 min; then 1.0% of the mass of the bisphenol F type epoxy resin of boron trifluoride ether is added, and reacted at 100℃ for 4h to generate an epoxy-ion liquid block copolymer; after the reaction is completed, it is cooled to room temperature, and 10% of the mass of the copolymer of butyl glycidyl ether is added to obtain an ion liquid block type epoxy resin.

[0059] The preparation method of the self-cleavage type amine curing agent is as follows:

[0060] L-lysine and L-alanine are taken in a molar ratio of 1:1, dissolved in 15 times the volume of dimethylformamide based on the total mass, and stirred at a speed of 600 rpm at room temperature for 30 min to completely dissolve; then 1.2 mol equivalents of N,N-dicyclohexyl carbodiimide based on the total molar amount of amino acids are added, and after reaction at 0-5℃ for 0.5h, the temperature is raised to 35℃ and the reaction is continued for 6h; after the reaction is completed, a dipeptide intermediate is obtained by filtration;

[0061] The dipeptide intermediate is mixed with hexamethylene diisocyanate in a molar ratio of 1:1.8 under nitrogen protection and stirred at 70℃ for 2h to obtain a capped latent polypeptide amine; after the reaction is completed, the system is removed under reduced pressure and dried at 60℃ under vacuum for 6h to obtain a self-cleavage type amine curing agent.

[0062] Example 5: Compared with Example 4, the difference is that the amount of N,N-dicyclohexyl carbodiimide added is 1.1 mol equivalents based on the total molar amount of amino acids.

[0063] Example 6: Compared with Example 4, the difference is that the amount of N,N-dicyclohexyl carbodiimide added is 1.3 mol equivalents based on the total molar amount of amino acids.

[0064] Example 7: Compared with Example 4, the difference is that the molar ratio of the dipeptide intermediate mixed with hexamethylene diisocyanate is 1:1.5.

[0065] Example 8: Compared with Example 4, the difference is that the molar ratio of the dipeptide intermediate mixed with hexamethylene diisocyanate is 1:2.0.

[0066] Determination of curing exothermic profile: Take 5-10 mg of the mixture (epoxy resin and self-immolative amine curing agent mixed at low temperature, such as -10°C) and place it in a DSC sample pan. Scan the sample from room temperature to 250°C or higher under a nitrogen atmosphere at a certain heating rate (such as 10°C / min) and analyze the resulting heat flow-temperature curve: the initial exothermic peak onset temperature represents the temperature at which the self-immolative curing begins; the peak top temperature represents the temperature at which the maximum reaction rate occurs.

[0067] Determination of gel time: Place the mixture of resin and curing agent on the measuring instrument hot cell or hot plate which has been preheated to a certain temperature (such as 90°C, 120°C, 150°C); start the instrument and let the probe oscillate in the sample in a certain way periodically; record the time from the start of heating to the point at which the resin viscosity increases to the point at which it can block the probe oscillation or pull up, i.e. the gel time at that temperature.

[0068] Determination of final curing degree: Test the total reaction enthalpy ΔH total of the uncured mixture by DSC residual ; cure another sample under the set curing conditions (such as 90°C / 2h + 120°C / 2h); re-scan the cured sample by DSC and measure its residual reaction enthalpy ΔH total ; the curing degree (%) = [(ΔH total - ΔH residual ) / ΔH total ] x 100%.

[0069] Table 2 Performance data of self-immolative amine curing agents

[0070] Initial decomposition temperature DSC peak temperature Gelation time at 120°C Final degree of cure Example 4 94℃ 138℃ 24.5 min 98.2% Example 5 91℃ 145℃ 28.1 min 95.5% Example 6 95℃ 137℃ 23.8 min 98.5% Example 7 92℃ 135℃ 26.3 min 97.8% Example 8 97℃ 142℃ 22.0 min 96.0%

[0071] As can be seen from Comparative Examples 4, 5 and 6, the initial cleavage temperature of Example 5 (1.1 equivalent) is slightly lower, and the curing degree is significantly lower (95.5%), which indicates that the condensation reaction is not complete, and the product contains impurities that are not completely capped or by-products with irregular structures, resulting in slightly poor latency and defects in the final crosslinked network.

[0072] Examples 4 (1.2 equivalent) and 6 (1.3 equivalent) both exhibit high curing degrees (>98%) and sharp curing exothermic peaks, indicating that 1.2 equivalents is sufficient to ensure the generation of high-purity dipeptide intermediates.

[0073] As can be seen from Comparative Examples 4, 7 and 8, as the molar ratio increases from 1:1.5 to 1:2.0, the initial cleavage temperature gradually increases (from 92°C to 97°C), and the gel time significantly shortens (from 26.3 min to 22.0 min); this indicates that a higher capping rate produces a more stable chemical structure that requires higher energy (temperature) to cleave, thereby improving latency.

[0074] Example 8 (1:2.0) showed the best latency but a decrease in the degree of cure (96.0%); this indicates that an excess of HDI can cause partial functional groups to be over-shielded or form structures that are difficult to cleave, hindering the complete progress of the curing reaction and thus impairing the network integrity of the final material.

[0075] Example 9: A method for preparing an epoxy resin for oil and gas well plugging, comprising the following steps:

[0076] S1.1. Take the following raw materials by weight: 95 parts by weight of ionic liquid block type epoxy resin, 60 parts by weight of self-cleavage type amine curing agent, 18 parts by weight of phenyl glycidyl ether, 50 parts by weight of composite filler, 2 parts by weight of γ-glycidyl ether oxypropyl trimethoxysilane, and 10 parts by weight of carboxyl-terminated butylnitrile liquid rubber;

[0077] S1.2. Mix the ionic liquid block type epoxy resin with the phenyl glycidyl ether, stir at 60°C at a speed of 400 rpm for 30 min; then add the γ-glycidyl ether oxypropyl trimethoxysilane, the carboxyl-terminated butylnitrile liquid rubber, and the composite filler, continue to stir for 30 min; after cooling to below 30°C, add the self-cleavage type amine curing agent, uniformly mix, then degas under a vacuum of -0.08 MPa for 15 min, and fill to obtain the epoxy resin for oil and gas well plugging.

[0078] The method for preparing the ionic liquid block type epoxy resin is as follows:

[0079] Under nitrogen protection, mix the bisphenol F type epoxy resin with 1-allyl-3-methylimidazole chloride salt at a molar ratio of 1:0.3, stir at 60°C at a speed of 400 rpm for 30 min; then add 0.6% of boron trifluoride ether based on the mass of the bisphenol F type epoxy resin, react at 90°C for 5 h to form an epoxy-ionic liquid block copolymer; after the reaction is completed, cool to room temperature, add 8% of butyl glycidyl ether based on the mass of the copolymer to obtain the ionic liquid block type epoxy resin.

[0080] The method for preparing the self-cleavage type amine curing agent is as follows:

[0081] Take L-lysine and L-alanine at a molar ratio of 1:1, dissolve them in 12 times the volume of dimethylformamide based on the total mass, stir at a speed of 500 rpm at room temperature for 30 min to completely dissolve them; then add 1.2 mol equivalents of N,N-dicyclohexyl carbodiimide based on the total molar amount of the amino acids, react at 0-5°C for 0.5 h, then warm up to 30°C and continue to react for 6 h; after the reaction is completed, filter to obtain the dipeptide intermediate;

[0082] The dipeptide intermediate was mixed with hexamethylene diisocyanate at a molar ratio of 1:1.8, and stirred at 60°C under nitrogen protection for 3h to obtain a capped latent polypeptide amine. After the reaction, the system was removed under reduced pressure, and dried at 60°C under vacuum for 6h to obtain a self-cleavage amine curing agent.

[0083] Example 10: Compared with Example 9, the difference is that the ion liquid block type epoxy resin is 90 parts by weight.

[0084] Example 11: Compared with Example 9, the difference is that the ion liquid block type epoxy resin is 100 parts by weight.

[0085] Example 12: Compared with Example 9, the difference is that the self-cleavage amine curing agent is 50 parts by weight.

[0086] Example 13: Compared with Example 9, the difference is that the self-cleavage amine curing agent is 65 parts by weight.

[0087] Gel time determination: The mixture of resin and curing agent is placed on the determination instrument hot tank or hot plate which has been preheated to a certain temperature (such as 90°C or 120°C, simulating different downhole temperatures); start the instrument, and let the probe or small paddle swing in the sample in a certain way; record the time from the start of heating to the viscosity of the resin increases to a continuous filament can be formed when the probe is blocked or pulled up, which is the gel time at that temperature.

[0088] Compressive strength determination: The completely cured epoxy resin sample is processed into a standard size test block (such as a cube with a side length of 50mm or a cylinder with a diameter of 50mm and a length of 100mm); the test block is placed in the center of the pressure disc of the testing machine, and the pressure is applied at a constant loading rate (for example, 1-5mm / min) until the test block breaks; record the pressure-displacement curve and read the maximum load value; compressive strength (MPa) = maximum load (N) / initial bearing area of the test block (mm 2） .

[0089] Table 3 Performance data of epoxy resin for oil and gas well plugging

[0090] Viscosity (60°C) Gelation time at 120°C Compressive strength Example 9 2850 mPa-s 25.5 min 89.5 MPa Example 10 2600 mPa-s 24.8 min 85.2 MPa Example 11 3100 mPa-s 26.1 min 88.1 MPa Example 12 2750 mPa-s 32.0 min 78.3 MPa Example 13 2950 mPa-s 19.5 min 86.9 MPa

[0091] As can be seen from Comparative Examples 9, 10 and 11, the resin dosage increases from 90 parts to 100 parts, and the viscosity of the system increases from 2,600mPa·s to 3,100mPa·s; this is because the ion liquid block type epoxy resin itself is the main contributor to the viscosity of the system.

[0092] The resin dosage change has a relatively mild effect on the gel time and compressive strength; Example 9 (95 parts) exhibits the highest compressive strength (89.5 MPa), indicating that at this ratio, the best stoichiometric balance with 60 parts of the curing agent is achieved, forming the highest crosslinking density and the most perfect network structure.

[0093] As can be seen from Comparative Examples 9, 12, and 13, the curing agent dosage has a very significant effect on the reaction speed (gel time); when the dosage is increased from 50 parts to 65 parts, the gel time is sharply shortened from 32.0 minutes to 19.5 minutes; this is because more curing agent can release more active amines after thermal cracking, greatly accelerating the crosslinking reaction.

[0094] The curing agent of Example 12 (50 parts) is significantly insufficient, resulting in defects in the crosslinking network, and thus the lowest compressive strength (78.3 MPa).

[0095] Example 13 (65 parts) has a high crosslinking density and fast gel, but the strength is slightly lower than that of Example 9, which is due to the non-uniformity of the network structure or the increase in brittleness caused by the excess curing agent.

[0096] After the above determination, Example 9 is selected as the optimal example;

[0097] Comparative Example 1: Compared with Example 9, the difference is that no ionic liquid block type epoxy resin is added, and a bisphenol F epoxy resin is directly used.

[0098] Comparative Example 2: Compared with Example 9, the difference is that a dicyandiamide curing agent is used instead of a self-cracking amine curing agent.

[0099] Table 4 Performance data of epoxy resins for oil and gas well plugging

[0100] Viscosity (60°C) Gelation time at 120°C Compressive strength Example 9 2850 mPa-s 25.5 min 89.5 MPa Comparative Example 1 2250 mPa-s 24.8 min 72.4 MPa Comparative Example 2 2900 mPa-s > 120 min 51.3 MPa

[0101] Comparative Example 1 uses a bisphenol F epoxy resin, although the viscosity and gel time change little, but the compressive strength decreases by nearly 20%; this strongly proves that the introduction of the ionic liquid block is not a simple physical mixing, it significantly enhances the bulk strength of the resin matrix and the interfacial bonding force with the filler through chemical bonding, thus bringing a qualitative leap in mechanical properties.

[0102] Comparative Example 2 uses dicyandiamide as a curing agent; dicyandiamide is a high-latency curing agent, and its curing initiation temperature is usually higher than 150°C; under the test temperature of 120°C simulating downhole conditions, dicyandiamide is difficult to effectively decompose and initiate a curing reaction, and shows extremely long gel time (more than 2 hours still not completely gelled), and the final cured product has very poor strength (51.3 MPa) due to extremely low reaction degree, and completely cannot meet the plugging requirement; this proves from the negative side that the self-cleavage amine curing agent of the present application has unique advantages in triggering curing in a medium-high temperature (such as 90-120°C) downhole environment.

[0103] The above shows and describes the basic principles, main features and advantages of the present application. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only preferred examples of the present application, and are not intended to limit the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. An epoxy resin for sealing oil and gas wells, characterized in that, The oil and gas well sealing epoxy resin comprises the following raw materials: 90-100 parts by weight of ion liquid block type epoxy resin, 50-65 parts by weight of self-cleavage type amine curing agent, 15-20 parts by weight of phenyl glycidyl ether, 40-60 parts by weight of composite filler, 1-3 parts by weight of gamma-glycidyl ether oxypropyl trimethoxysilane and 8-12 parts by weight of carboxyl-terminated butyronitrile liquid rubber; The ion liquid block type epoxy resin is prepared by block copolymerization of 1-allyl-3-methyl imidazole chloride and bisphenol F type epoxy resin. The self-cleavage type amine curing agent is a heat-cleavable latent curing agent prepared by condensation of amino acids to generate a polypeptide intermediate and isocyanate end-capping reaction. The preparation method of the ion liquid block type epoxy resin is as follows: Under nitrogen protection, the bisphenol F type epoxy resin is mixed with 1-allyl-3-methyl imidazole chloride, the molar ratio of the bisphenol F type epoxy resin to 1-allyl-3-methyl imidazole chloride is 1:0.2-0.4, stirring at a speed of 300-500 rpm at 60-80℃ for 20-40 min; then, boron trifluoride ether is added, and the reaction is carried out at 80-100℃ for 4-6 h to generate an epoxy-ion liquid block copolymer; after the reaction is completed, the system is cooled to room temperature, 5-10% of butyl glycidyl ether based on the mass of the copolymer is added, and the ion liquid block type epoxy resin is obtained; The preparation method of the self-cleavage type amine curing agent is as follows: L-lysine and L-alanine are taken in a molar ratio of 1:1, dissolved in 10-15 times the volume of dimethylformamide based on the total mass, and stirred at a speed of 400-600 rpm at room temperature for 30-40 min to completely dissolve them; then, N,N-dicyclohexyl carbodiimide is added, the amount of N,N-dicyclohexyl carbodiimide added is 1.1-1.3 mol equivalents based on the total molar amount of amino acids, the reaction is carried out at 0-5℃ for 0.5 h, and then the temperature is raised to 25-35℃ for continuous reaction for 6-8 h; after the reaction is completed, the dipeptide intermediate is obtained by filtration; The dipeptide intermediate is mixed with hexamethylene diisocyanate, the molar ratio of the dipeptide intermediate to hexamethylene diisocyanate is 1:1.5-2.0, the reaction is carried out under nitrogen protection at 60-70℃ for 2-3 h to obtain a capped latent polypeptide amine; after the reaction is completed, the system is removed under reduced pressure, and vacuum drying is carried out at 50-60℃ for 6-8 h to obtain the self-cleavage type amine curing agent.

2. The epoxy resin for use in plugging oil and gas wells according to claim 1, characterized in that, The amount of boron trifluoride ether added is 0.5-1.0% based on the mass of the bisphenol F type epoxy resin.

3. A method for producing an epoxy resin for sealing oil and gas wells, for producing an epoxy resin for sealing oil and gas wells as claimed in any one of claims 1 to 2, characterized in that, The preparation method of the oil and gas well sealing epoxy resin is as follows: S1.1, the following raw materials are weighed: 90-100 parts by weight of ion liquid block type epoxy resin, 50-65 parts by weight of self-cleavage type amine curing agent, 15-20 parts by weight of phenyl glycidyl ether, 40-60 parts by weight of composite filler, 1-3 parts by weight of gamma-glycidyl ether oxypropyl trimethoxysilane and 8-12 parts by weight of carboxyl-terminated butyronitrile liquid rubber; S1.2, the ion liquid block type epoxy resin is mixed with phenyl glycidyl ether, stirred at 60℃ for 30min at a speed of 400-500rpm; then γ-glycidoxypropyltrimethoxysilane, carboxyl-terminated butylnitrile liquid rubber and composite filler are added, and stirring is continued for 20-30min; after cooling to below 30℃, self-cleavage type amine curing agent is added, uniformly mixed, defoamed under a vacuum degree of-0.08MPa for 10-15min, and then filled to obtain the epoxy resin for oil and gas well plugging.

4. The method for preparing epoxy resin for oil and gas well plugging according to claim 3, characterized in that, In the S1.2, the composite filler is a composite of nano-silicon dioxide modified by γ-glycidoxypropyltrimethoxysilane and quartz powder, and the mass ratio is 1:5.