A modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent, its preparation method and application

Abstract

This invention provides a modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent, its preparation method, and its application. The sand-fixing agent comprises the following raw materials by mass percentage: 30-50% modified epoxy phenolic resin, 2-5% temperature-responsive curing agent, 3-5% emulsifier, 5-10% emulsification aid, 0.0005-0.002% high-efficiency demulsifier, and the balance being water. The modified epoxy phenolic resin is obtained by modifying phenolic resin with epoxy resin and a modifier. This sand-fixing agent uses modified epoxy phenolic resin as the cementing phase, combined with a temperature-responsive curing agent and multifunctional additives, to form a stable O / W type microemulsion system. It is suitable for vertical wells, horizontal wells, and secondary sand control scenarios in loose sandstone reservoirs, has a wide applicable temperature range, and solves the contradiction between the compressive strength and permeability of the sand column after cementation in traditional resin sand-fixing agents. It improves the stability of the sand-fixing working fluid and reduces the on-site construction risks of resin-based sand-fixing working fluids.

Description

Technical Field

[0001] This invention relates to a modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent, its preparation method and application, belonging to the field of oilfield chemical technology. Background Technology

[0002] Sand production in oilfields is a common core extraction problem in loose sandstone reservoirs, heterogeneous reservoirs, and long-term developed reservoirs. It not only directly affects the production capacity and development efficiency of oil wells, but also increases operating costs and safety risks, and is one of the key factors restricting the efficient development of oilfields.

[0003] To address the sand production problem in oilfields, three major technical systems have been established: mechanical sand stabilization, chemical sand stabilization, and composite sand stabilization. Among these, chemical sand stabilization agents offer a simpler construction process, lower equipment requirements, and compatibility with existing oilfield operating systems, demonstrating significant advantages over the "high investment and high complexity" of mechanical and composite sand stabilization. In chemical sand stabilization, resin-based sand stabilizing agents have gained widespread use due to their high compatibility, good bonding strength, and simple construction process. Epoxy resin and phenolic resin are the two most commonly used resins; however, using either alone cannot achieve optimal results, and they are generally used in combination to meet higher requirements.

[0004] Currently, the compounding of epoxy resin and phenolic resin is generally done through simple physical blending. However, simple physical blending of epoxy resin and phenolic resin results in insufficient compatibility, leading to phase separation at high temperatures, which in turn causes the solidified body to weaken and become brittle. Epoxy-phenolic resin, due to its combination of the high adhesiveness of epoxy resin and the high-temperature resistance of phenolic resin, has become the preferred cementing material for sand-producing formations. For example, Chinese patent document CN116162216A provides a method for preparing epoxy-modified phenolic resin for oil fracturing sands. This method uses epoxy resin to modify phenolic resin, preparing a cross-linked network polymer structure, which increases the mechanical strength of the phenolic resin. By introducing long flexible ether chains, it acquires excellent mechanical properties, increases the tensile strength of the phenolic resin, and enhances its toughness. However, in this patent, the resin solution is mainly composed of modified resin, with the addition of a small amount of curing agent and coupling agent. The overall system is oil-soluble, and its viscosity is easily affected by temperature and shear rate, which may lead to difficulties in injection or uniform spreading in low-permeability formations, resulting in uneven sand-fixing effects. Chinese patent document CN110684517A provides a self-polymerizing, consolidating, pressure-resistant, permeable, and temperature-resistant sand-preventing agent, which includes the following components: a resin compound system, a coupling agent, an organic solvent, an emulsifier, a filler, and a curing agent. The mass percentage of each component is as follows: resin compound system 30-40%; organic solvent 40-50%; coupling agent 5-7%; filler 5-8%; curing agent 4-5% and emulsifier 5-8%. The sum of the mass percentages of each component is 100%. The resin compound system is composed of epoxy resin E-44, epoxy resin E-51, phenolic resin F-51, and polyvinylpyrrolidone K30.

[0005] However, current epoxy phenolic resin microemulsion-based sand-fixing agents have significant drawbacks: First, it is difficult to balance the stability and demulsification response of the microemulsion; stable microemulsions are difficult to demulsify, while unstable microemulsions have short shelf lives, failing to meet the needs of on-site construction. Second, most curing agents are single-response, unable to adapt to a wide temperature range, and cause significant damage to formation permeability after curing. Therefore, there is an urgent need to develop a microemulsion-based sand-fixing agent with high compressive strength, good permeability, and high stability. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent, its preparation method, and its application. The sand-fixing agent of this invention uses modified epoxy phenolic resin as the cementing phase, combined with a temperature-responsive curing agent and multifunctional additives, to form a stable O / W microemulsion system. It can be used in a temperature range of 45-110℃, exhibits high compressive strength of the solidified body, high permeability retention, and long-term stability of the working fluid. This solves the contradiction between the compressive strength and permeability of the sand column after cementation in traditional resin sand-fixing agents, improves the stability of the sand-fixing working fluid, and reduces the on-site construction risks of resin-based sand-fixing working fluids. It is suitable for vertical wells, horizontal wells, and secondary sand control scenarios in loose sandstone reservoirs.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A modified epoxy-phenolic resin composite metastable microemulsion sand-fixing agent comprises the following raw materials in weight percentages: 30-50% modified epoxy-phenolic resin, 2-5% temperature-responsive curing agent, 3-5% emulsifier, 5-10% emulsification aid, 0.0005-0.002% high-efficiency demulsifier, and the balance being water; wherein the modified epoxy-phenolic resin is obtained by modifying phenolic resin with epoxy resin and modifier.

[0009] According to the present invention, the epoxy resin is preferably a bisphenol A type epoxy resin, more preferably an E20 epoxy resin, an E51 epoxy resin or an E44 epoxy resin, and more preferably an E44 epoxy resin.

[0010] According to a preferred embodiment of the present invention, the phenolic resin is a type 2123 phenolic resin, a type 2127 phenolic resin, or a type 2130 phenolic resin, and more preferably a type 2127 phenolic resin.

[0011] According to a preferred embodiment of the present invention, the mass ratio of the epoxy resin to the phenolic resin is 1-5:10, and more preferably 3:10.

[0012] According to a preferred embodiment of the present invention, the modifier is 4-aminophenol, 4-aminocatechol, p-aminosalicylic acid, 2-chloro-4-aminophenol, or 2-methyl-4-aminophenol, more preferably 4-aminophenol, 4-aminocatechol, or p-aminosalicylic acid, and even more preferably 4-aminocatechol or p-aminosalicylic acid; the mass ratio of the modifier to the phenolic resin is 1:5-20, more preferably 1:10.

[0013] According to a preferred embodiment of the present invention, the modified epoxy phenolic resin is prepared by the following method:

[0014] Phenolic resin and epoxy resin are mixed and etherified under the catalysis of an acidic catalyst; then modifiers and polymerization inhibitors are added and reacted, followed by post-treatment to obtain modified epoxy phenolic resin.

[0015] More preferably, the catalyst is p-toluenesulfonic acid or oxalic acid, more preferably p-toluenesulfonic acid; the mass of the acidic catalyst is 0.2-1% of the mass of the phenolic resin.

[0016] More preferably, the temperature of the etherification reaction is 80-120℃, more preferably 90-100℃; the time of the etherification reaction is 2-6h, more preferably 3-4h; this step etherifies the epoxy group of the epoxy resin with the hydroxymethyl group of the phenolic resin.

[0017] More preferably, the polymerization inhibitor is hydroquinone, and the mass of the polymerization inhibitor is 0.002-0.01% of the mass of the phenolic resin;

[0018] More preferably, the reaction temperature after adding the modifier and polymerization inhibitor is 60-90℃, more preferably 70-80℃; the reaction time is 1-4h, more preferably 2-3h.

[0019] More preferably, the post-processing step is as follows: cooling the reaction system to 40-50℃, adding a pH adjuster to adjust the pH of the system to 7-8, neutralizing the residual acidic catalyst, thereby obtaining the modified epoxy phenolic resin; the pH adjuster is a sodium carbonate aqueous solution with a concentration of 5-10wt%.

[0020] According to a preferred embodiment of the present invention, the temperature-responsive curing agent is an anhydride cyclodextrin inclusion complex.

[0021] According to a preferred embodiment of the present invention, the acid anhydride is maleic anhydride and / or phthalic anhydride, more preferably a composition of maleic anhydride and phthalic anhydride, wherein the mass ratio of maleic anhydride to phthalic anhydride in the composition is 1:1.

[0022] According to a preferred embodiment of the present invention, the cyclodextrin is α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin, and more preferably β-cyclodextrin.

[0023] According to a preferred embodiment of the present invention, the mass ratio of acid anhydride to cyclodextrin in the temperature-responsive curing agent is 1:1.

[0024] According to a preferred embodiment of the present invention, the temperature-responsive curing agent is prepared by the following method: cyclodextrin is dissolved in deionized water at 60-80°C to form a saturated solution, then acid anhydride is added, and the mixture is stirred and reacted at 50-60°C for 2-4 hours. After naturally cooling to room temperature, the mixture is filtered, and the filtered solid is dried at 40-60°C to constant weight to obtain the temperature-responsive curing agent.

[0025] According to a preferred embodiment of the present invention, the emulsifier is one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and polysorbate; preferably, the fatty alcohol polyoxyethylene ether is AEO-9 or AEO-10, the alkylphenol polyoxyethylene ether is NP-9 or NP-10, and the polysorbate is Tween 60 or Tween 80; more preferably, the emulsifier is one or two of AEO-10, NP-10, and Tween 80, more preferably a mixture of AEO-10 ​​and NP-10, wherein the mass ratio of AEO-10 ​​to NP-10 in the mixture is 1:2.

[0026] According to a preferred embodiment of the present invention, the emulsifying agent is n-propanol, isopropanol, n-butanol, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, propylene glycol methyl ether, or dipropylene glycol dimethyl ether; more preferably, it is one or more of isopropanol, n-butanol, and ethylene glycol monobutyl ether; more preferably, it is a mixture of n-butanol and ethylene glycol monobutyl ether, wherein the mass ratio of n-butanol to ethylene glycol monobutyl ether in the mixture is 2:1.

[0027] According to a preferred embodiment of the present invention, the high-efficiency demulsifier is a polyol polyether oilfield demulsifier SP-169.

[0028] According to the present invention, the preparation method of the above-mentioned modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent includes the following steps:

[0029] Under stirring conditions, water, modified epoxy phenolic resin, temperature-responsive curing agent, emulsifier, emulsifying aid, and high-efficiency demulsifier are mixed and stirred for 1-2 hours until homogeneous and transparent to obtain a modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent.

[0030] According to the present invention, the above-mentioned modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent is used for sand fixation in sandstone reservoirs; the specific application method is as follows:

[0031] (1) Inject pre-fluid to clean the formation;

[0032] (2) Inject the modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent;

[0033] (3) Guan Jinghou Ning.

[0034] According to the present invention, the injection volume and injection method of the pre-treatment fluid and the modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent can be determined according to the methods commonly used in the art.

[0035] The technical features and beneficial effects of this invention are as follows:

[0036] 1. This invention modifies the surface of phenolic resin with epoxy resin and a specific modifier to construct a composite interface structure of "epoxy flexible segments - phenolic rigid skeleton". This retains the core advantages of phenolic resin, such as high temperature resistance and high bonding strength, while the epoxy groups of epoxy resin and the hydroxymethyl groups of phenolic resin undergo a cross-linking reaction to fill the pores and defects on the surface of phenolic resin, reducing brittleness after curing. At the same time, the modifier embeds specific functional groups into the resin network to form a special modified resin. The hydrophilicity of the phenolic resin surface is improved after modification, and the binding force with the hydroxyl groups on the surface of sand particles is enhanced, effectively solving the problems of easy cracking and weak interfacial bonding of traditional phenolic resin sand fixing agents.

[0037] 2. This invention uses an anhydride cyclodextrin inclusion complex as a temperature-responsive curing agent. The cavity structure of cyclodextrin encapsulates the anhydride molecules. At room temperature, the curing agent cannot be released to cure the resin. When the formation temperature is reached, the inclusion structure of cyclodextrin disintegrates, the anhydride is released and cross-links with the resin to cure, allowing for precise control of the curing timing.

[0038] 3. The sand-fixing agent of the present invention contains specific emulsifiers and emulsification aids, which work synergistically with other components to make the resulting sand-fixing agent emulsion uniform and stable. At the same time, under the formation temperature, the directional adsorption characteristics of the microemulsion particles in the sand-fixing agent of the present invention can destroy the stable structure of the microemulsion, realize oil-water separation, and the cementing phase forms a "flexible cross-linking-rigid support" composite consolidation layer on the surface of sand particles under the continuous action of the temperature-responsive curing agent, which has high consolidation strength, good anti-dilution properties, low formation damage and wide temperature range adaptability.

[0039] 4. The sand-fixing agent of the present invention can be used in a temperature range of 45-110℃, with a solidified body compressive strength ≥8MPa, and a 70% diluted working fluid solidified body compressive strength ≥7MPa, a permeability retention rate ≥60%, and long-term stability. It is suitable for vertical wells, horizontal wells, and secondary sand control scenarios in loose sandstone reservoirs. It solves the contradiction between the compressive strength and permeability of the sand column after cementation by traditional resin sand-fixing agents, improves the stability of the sand-fixing working fluid, and reduces the on-site construction risks of resin-based sand-fixing working fluids.

[0040] 5. The sand-fixing agent prepared by this invention has the advantages of uniform and stable working fluid, moderate curing speed, high sand-fixing strength, and good permeability retention. It is also simple to construct, safe and stable, and suitable for widespread promotion. Detailed Implementation

[0041] To make the technical solutions of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described. It should be noted that the following embodiments are only used to better understand the technical solutions of the present invention, and should not be construed as limiting the present invention.

[0042] Example 1

[0043] A modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent comprises the following raw materials by mass percentage: 40% modified epoxy phenolic resin, 5% temperature-responsive curing agent, 3% emulsifier, 5% emulsification aid, 0.001% high-efficiency demulsifier, and the balance being water.

[0044] The modified epoxy phenolic resin is obtained by modifying phenolic resin with epoxy resin and a modifier. The epoxy resin is E44 epoxy resin, the phenolic resin is type 2127 phenolic resin, and the modifier is para-aminosalicylic acid. The mass ratio of epoxy resin to phenolic resin is 3:10, and the mass ratio of modifier to phenolic resin is 1:10. The modified epoxy phenolic resin is prepared by the following method: phenolic resin and epoxy resin are mixed and etherified at 100°C for 3 hours under the catalysis of acidic catalyst p-toluenesulfonic acid (0.5% of the phenolic resin mass). The temperature is then lowered to 80°C, and the modifier and polymerization inhibitor hydroquinone are added. The reaction is carried out at 80°C for 2 hours (0.005% of the phenolic resin mass). After the reaction is complete, the reaction system is cooled to 45°C, and a 5wt% sodium carbonate aqueous solution is added to adjust the pH to 7 to neutralize the residual acidic catalyst, thus obtaining the modified epoxy phenolic resin.

[0045] The temperature-responsive curing agent is an anhydride cyclodextrin inclusion complex, wherein the anhydride is a combination of maleic anhydride and phthalic anhydride, with a mass ratio of maleic anhydride to phthalic anhydride of 1:1; the cyclodextrin is β-cyclodextrin; and the mass ratio of anhydride to cyclodextrin is 1:1. The temperature-responsive curing agent is prepared by the following method: cyclodextrin is dissolved in deionized water at 70°C to form a saturated solution, the anhydride is added, the temperature is lowered to 55°C, the mixture is stirred at 55°C for 3 hours, and after natural cooling to room temperature, it is filtered. The filtered solid is dried at 50°C to constant weight to obtain the temperature-responsive curing agent.

[0046] The emulsifier is a mixture of AEO-10 ​​and NP-10, with a mass ratio of AEO-10 ​​to NP-10 of 1:2.

[0047] The emulsifying aid is a mixture of n-butanol and ethylene glycol monobutyl ether, wherein the mass ratio of n-butanol to ethylene glycol monobutyl ether in the mixture is 2:1;

[0048] The high-efficiency demulsifier is SP-169 type demulsifier for oil fields.

[0049] The preparation method of the above-mentioned modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent includes the following steps:

[0050] Under stirring conditions, water, modified epoxy phenolic resin, temperature-responsive curing agent, emulsifier, emulsifying aid, and high-efficiency demulsifier are mixed and stirred for 2 hours until homogeneous and transparent to obtain a modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent.

[0051] Example 2

[0052] A modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent comprises the following raw materials in the following mass percentages: 40% modified epoxy phenolic resin, 4% temperature-responsive curing agent, 3% emulsifier, 5% emulsification aid, 0.001% high-efficiency demulsifier, and the balance being water; the composition of the remaining raw materials and the preparation method are the same as in Example 1.

[0053] Example 3

[0054] A modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent comprises the following raw materials in the following mass percentages: 50% modified epoxy phenolic resin, 3% temperature-responsive curing agent, 5% emulsifier, 8% emulsification aid, 0.001% high-efficiency demulsifier, and the balance being water; the composition of the remaining raw materials and the preparation method are the same as in Example 1.

[0055] Example 4

[0056] A modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent comprises the following raw materials in the following mass percentages: 50% modified epoxy phenolic resin, 2% temperature-responsive curing agent, 5% emulsifier, 8% emulsification aid, 0.001% high-efficiency demulsifier, and the balance being water; the composition of the remaining raw materials and the preparation method are the same as in Example 1.

[0057] Example 5

[0058] A modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent is described in Example 4, except that the modifier is 4-aminocatechol.

[0059] Example 6

[0060] A modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent is described in Example 4, except that the acid anhydride is maleic anhydride.

[0061] Example 7

[0062] A modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent is described in Example 4, except that the emulsifying aid is n-butanol.

[0063] Comparative Example 1

[0064] A modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent is described in Example 4, except that no modifier is added.

[0065] Comparative Example 2

[0066] A modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent is described in Example 4, except that phenolic resin is used instead of modified epoxy phenolic resin.

[0067] Comparative Example 3

[0068] A modified epoxy phenolic resin composite metastable microemulsion type sand-fixing agent is described in Example 4, except that cyclodextrin is not added to the temperature-responsive curing agent.

[0069] Comparative Example 4

[0070] A modified epoxy phenolic resin composite metastable microemulsion type sand-fixing agent is described in Example 4, except that acid anhydride is not added to the temperature-responsive curing agent.

[0071] Comparative Example 5

[0072] A modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent is described in Example 4, except that no emulsifying aids are added.

[0073] Experimental Example 1

[0074] The following performance tests were conducted on the sand-fixing agents prepared in the examples and comparative examples:

[0075] Take 20g of sand-fixing agent and put it into a 50mL transparent plastic tube with a cap. Place it in a constant temperature water bath at different temperatures and observe. Record the time when the liquid becomes completely opaque. Record this as the initial setting time.

[0076] After the sand-fixing agent and engineering sand (40-100 mesh) are mixed evenly at a weight ratio of 20:50, the mixture is placed in a glass tube with an inner diameter of 25 mm and compacted. The mixture is then kept at a certain temperature for 72 hours to solidify and prepare a cemented rock core sample. Its compressive strength and gas permeability are then tested.

[0077] The test results of different embodiments and comparative indicators are shown in Table 1.

[0078] Table 1 Indicator Test Results

[0079]

[0080] As can be seen from Table 1, the sand-fixing agents obtained by different technical solutions provided in the embodiments of the present invention all have good indoor evaluation effects at various temperatures. Comparative Example 1, lacking a modifier, experienced a significant decrease in the compressive strength of its cemented core. This was because, despite the etherification reaction, the compatibility between epoxy resin and phenolic resin remained poor, leading to phase separation at high temperatures and resulting in strength degradation and brittle failure of the solidified body. Comparative Example 2, using phenolic resin instead of modified epoxy phenolic resin, also experienced a significant decrease in the compressive strength of its cemented core. This was because pure phenolic resin cement is brittle and has weak bonding with the sand grain surface. Comparative Example 3, lacking cyclodextrin in its temperature-responsive curing agent, resulted in a short initial setting time, failing to meet construction requirements. This was because the acid anhydride catalyzed too quickly under temperature conditions. Comparative Example 4, lacking acid anhydride in its temperature-responsive curing agent, failed to solidify. Comparative Example 5, lacking emulsifying aids, resulted in the working fluid separating and becoming unusable. This was because modified epoxy phenolic resin can only form a metastable microemulsion under the combined action of emulsifiers and emulsifying aids.

[0081] Experimental Example 2

[0082] Field application cases

[0083] The sand-fixing agent from the above embodiments shall be applied as follows:

[0084] (1) Inject pre-fluid to clean the formation;

[0085] (2) Inject the modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent;

[0086] (3) Guan Jinghou Ning.

[0087] The on-site construction effects of different implementation methods are shown in Table 2.

[0088] Table 2. Effects of the modified epoxy phenolic resin composite metastable microemulsion sand-fixing agents in Examples 1-4

[0089]

[0090] The modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent provided in Examples 1-4 has shown good results in field application, as follows: (1) After sand-fixing measures, no sand was found in the wellhead samples, and the daily production of liquid / oil was stable; (2) With sand-fixing measures combined with pre-cleaning of the formation, the production capacity of the oil well was not affected, and the daily production of liquid / oil increased significantly; (3) The modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent is suitable for different well types of directional and horizontal wells in sandstone reservoirs in oilfields, with a high success rate and low construction risk.

Claims

1. A modified epoxy-phenolic resin composite metastable microemulsion sand-fixing agent, characterized in that, The raw materials include the following percentages by weight: 30-50% modified epoxy phenolic resin, 2-5% temperature-responsive curing agent, 3-5% emulsifier, 5-10% emulsifying aid, 0.0005-0.002% high-efficiency demulsifier, and the balance being water; the modified epoxy phenolic resin is obtained by modifying phenolic resin with epoxy resin and modifier.

2. The modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent according to claim 1, characterized in that, The epoxy resin is a bisphenol A type epoxy resin, preferably an E20 epoxy resin, an E51 epoxy resin, or an E44 epoxy resin, more preferably an E44 epoxy resin; the phenolic resin is a 2123 type phenolic resin, a 2127 type phenolic resin, or a 2130 type phenolic resin, preferably a 2127 type phenolic resin; the mass ratio of the epoxy resin to the phenolic resin is 1-5:10, preferably 3:

10.

3. The modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent according to claim 1, characterized in that, The modifier is 4-aminophenol, 4-aminocatechol, p-aminosalicylic acid, 2-chloro-4-aminophenol, or 2-methyl-4-aminophenol, preferably 4-aminophenol, 4-aminocatechol, or p-aminosalicylic acid, more preferably 4-aminocatechol or p-aminosalicylic acid; the mass ratio of the modifier to the phenolic resin is 1:5-20, preferably 1:

10.

4. The modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent according to claim 1, characterized in that, The modified epoxy phenolic resin was prepared according to the following method: Phenolic resin and epoxy resin are mixed and etherified under the catalysis of an acidic catalyst; then modifiers and polymerization inhibitors are added and reacted, followed by post-treatment to obtain modified epoxy phenolic resin. The catalyst is p-toluenesulfonic acid or oxalic acid, more preferably p-toluenesulfonic acid; the mass of the acidic catalyst is 0.2-1% of the mass of the phenolic resin. The etherification reaction is carried out at a temperature of 80-120℃, preferably 90-100℃; the etherification reaction is carried out for a time of 2-6 hours, preferably 3-4 hours. The polymerization inhibitor is hydroquinone, and the mass of the polymerization inhibitor is 0.002-0.01% of the mass of the phenolic resin. The reaction temperature after adding the modifier and polymerization inhibitor is 60-90℃, preferably 70-80℃; the reaction time is 1-4h, preferably 2-3h. The post-processing step is as follows: the reaction system is cooled to 40-50℃, a pH adjuster is added to adjust the pH of the system to 7-8, and the residual acidic catalyst is neutralized to obtain the modified epoxy phenolic resin; the pH adjuster is a sodium carbonate aqueous solution with a concentration of 5-10wt%.

5. The modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent according to claim 1, characterized in that, The temperature-responsive curing agent is an anhydride cyclodextrin inclusion complex; the anhydride is maleic anhydride and / or phthalic anhydride, preferably a combination of maleic anhydride and phthalic anhydride, wherein the mass ratio of maleic anhydride to phthalic anhydride in the composition is 1:1; the cyclodextrin is α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin, more preferably β-cyclodextrin; the mass ratio of anhydride to cyclodextrin in the temperature-responsive curing agent is 1:

1.

6. The modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent according to claim 5, characterized in that, The temperature-responsive curing agent is prepared by the following method: cyclodextrin is dissolved in deionized water at 60-80℃ to form a saturated solution, then acid anhydride is added, and the mixture is stirred at 50-60℃ for 2-4 hours. After naturally cooling to room temperature, the mixture is filtered, and the filtered solid is dried at 40-60℃ to constant weight to obtain the temperature-responsive curing agent.

7. The modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent according to claim 1, characterized in that, The emulsifier is one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and polysorbate; preferably, the fatty alcohol polyoxyethylene ether is AEO-9 or AEO-10, the alkylphenol polyoxyethylene ether is NP-9 or NP-10, and the polysorbate is Tween 60 or Tween 80; more preferably, the emulsifier is one or two of AEO-10, NP-10, and Tween 80, more preferably a mixture of AEO-10 ​​and NP-10, wherein the mass ratio of AEO-10 ​​to NP-10 in the mixture is 1:

2.

8. The modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent according to claim 1, characterized in that, The emulsifying agent is n-propanol, isopropanol, n-butanol, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, propylene glycol methyl ether, or dipropylene glycol dimethyl ether, preferably one or more of isopropanol, n-butanol, and ethylene glycol monobutyl ether; more preferably a mixture of n-butanol and ethylene glycol monobutyl ether, wherein the mass ratio of n-butanol to ethylene glycol monobutyl ether in the mixture is 2:1; The high-efficiency demulsifier is SP-169 type demulsifier for oilfields, which is a polyol polyether.

9. A method for preparing the modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent according to any one of claims 1-8, characterized in that, The steps include the following: Under stirring conditions, water, modified epoxy phenolic resin, temperature-responsive curing agent, emulsifier, emulsifying aid, and high-efficiency demulsifier are mixed and stirred for 1-2 hours until homogeneous and transparent to obtain a modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent.

10. The application of the modified epoxy phenolic resin composite metastable microemulsion sand-fixing agent according to any one of claims 1-8, characterized in that, Used for sand fixation in sandstone reservoirs.

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