Resin reinforced gel plugging agent as well as preparation method and application thereof

Abstract

The invention discloses a resin-reinforced gel plugging agent and a preparation method and application thereof.The resin-reinforced gel plugging agent is obtained by conducting high-temperature curing and reaction on the following raw materials in percentage by mass under the acidic condition, specifically, the raw materials comprise 5%-15% of a water-soluble resin aqueous solution, 10%-30% of a polymer monomer, 1%-10% of a rheology regulating agent, 1%-10% of a curing agent, 1%-10% of a curing agent and the balance of water. The plugging agent comprises a water-soluble resin aqueous solution, 0.1%-1% of a cross-linking agent, 0.01%-0.1% of an initiator and the balance of water, and water-soluble resin in the water-soluble resin aqueous solution is melamine resin partially methylated. The plugging agent combines the advantages of good viscoelasticity and strong adaptability of conventional gel and excellent high temperature resistance and high strength after curing of resin high polymer materials; the obtained resin reinforced gel plugging agent has the advantages of excellent high temperature resistance, high structural strength and excellent plugging effect.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling fluid plugging, and in particular to a resin-reinforced gel plugging agent and a preparation method and application thereof. Background Art

[0002] Well leakage is a phenomenon in which a large amount of drilling fluid leaks into the formation during oilfield drilling construction. It is one of the most common drilling engineering problems in fractured complex formations. When a well leakage problem occurs during oil and gas drilling and production construction, it not only wastes drilling time and loses a large amount of drilling fluid, but improper handling may also cause complex underground accidents such as well collapse, blowout, and drill bit sticking, and even cause the wellbore to be scrapped, resulting in significant economic losses. Therefore, efficiently solving the well leakage problem is crucial to ensuring underground safety, increasing drilling speed, and saving drilling costs.

[0003] Polymer gel is one of the commonly used and effective plugging materials in oil fields. During on-site construction, a certain amount of gel plugging agent solution is injected into the leaking layer, and the cracks are sealed after solidification, which plays a role in isolating the drilling fluid from the formation fluid. The gel plugging agent currently used has achieved relatively good results in dealing with conventional well leakage problems. However, with the expansion of oil and gas exploration and development to deeper layers, high temperature and high pressure have become one of the main problems faced by drilling plugging, and higher requirements have been put forward for the high temperature resistance and high pressure sealing performance of the gel plugging agent after solidification. Among them, the temperature resistance and structural strength of the gel plugging agent after solidification are the key to the success of plugging. For example, Chinese patent document CN111961452A discloses a high-temperature resistant, high-strength thixotropic gel plugging agent and its preparation method and application. The gel plugging agent includes the following raw materials in percentage by mass: 8-20% acrylamide monomer, 0.05-0.5% active polymer, 0.1-1.0% organic polymer cross-linking agent, 3.0-8.0% resin toughening agent, 1.0-5.0% rheology control agent, 0.01-0.5% cross-linking regulator, and the balance is water. The gel plugging agent of the invention has certain high temperature resistance and gel plugging strength, but the high temperature resistance, gel plugging strength and plugging effect still need to be further improved.

[0004] Therefore, developing a gel plugging agent that is both high temperature resistant and high strength is of great significance for solving the problem of well leakage in high-temperature deep fractured leakage formations. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a resin-reinforced gel plugging agent and its preparation method and application. The plugging agent of the present invention combines the advantages of conventional gel viscoelasticity and strong adaptability, as well as the advantages of excellent high temperature resistance and high strength after curing of resin-based polymer materials. The obtained resin-reinforced gel plugging agent has excellent high temperature resistance, high structural strength and excellent plugging effect.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a resin-reinforced gel plugging agent, wherein the following raw materials in mass percentage are cured at high temperature under acidic conditions to obtain a resin-reinforced gel plugging agent, specifically, the raw materials include 5%-15% water-soluble resin aqueous solution, 10%-30% polymer monomer, 1%-10% rheology control agent, 0.1%-1% cross-linking agent, 0.01%-0.1% initiator, and the balance is water.

[0007] Furthermore, the water-soluble resin in the water-soluble resin aqueous solution is a partially methylated melamine resin, and the structure is as follows:

[0008]

[0009] Furthermore, the polymer monomer is a combination of two or more of acrylamide, acrylonitrile or 2-acrylamide-2-methylpropane sulfonic acid, and in the combination of acrylamide and 2-acrylamide-2-methylpropane sulfonic acid, the mass ratio of acrylamide to 2-acrylamide-2-methylpropane sulfonic acid is 1-2.5:1.

[0010] Furthermore, the rheology control agent is hectorite or a combination of hectorite and xanthan gum, in which the mass ratio of hectorite to xanthan gum is 1:0.5-1.5; the hectorite is a nano-scale flaky hectorite with a positive charge on the crystal surface and a negative charge on the crystal edge, and the weight average molecular weight of the xanthan gum is 2 million-4 million.

[0011] Furthermore, the crosslinking agent is a combination of one of N,N'-methylenebisacrylamide, hexamethylenetetramine, polyethyleneimine and N-hydroxymethylacrylamide; the mass ratio of N,N'-methylenebisacrylamide, hexamethylenetetramine or polyethyleneimine to the mass ratio of N-hydroxymethylacrylamide is 1-3:1.

[0012] Furthermore, the initiator is one or a combination of two or more of ammonium persulfate, potassium persulfate, and benzoyl peroxide.

[0013] The present invention also provides a method for preparing a resin-reinforced gel plugging agent, the specific steps of which are as follows:

[0014] S1: adding the water-soluble resin aqueous solution into water and stirring evenly to obtain a mixed solution A;

[0015] S2: adding the polymer monomer to the mixed solution A and stirring evenly to obtain a mixed solution B;

[0016] S3: adding the rheology control agent into the mixed solution B and stirring evenly to obtain a mixed solution C;

[0017] S4: adding the cross-linking agent into the mixed solution C, stirring evenly, to obtain a mixed solution D; then adding the initiator, stirring evenly, and curing at high temperature under acidic conditions to obtain a resin-reinforced gel plugging agent.

[0018] Further, in S1, the stirring rate is 600 rpm-1000 rpm, and the stirring time is 10 min-30 min;

[0019] In S2, the stirring rate is 200 rpm-400 rpm, and the stirring time is 10 min-30 min;

[0020] In S3, the stirring rate is 200 rpm-400 rpm, and the stirring time is 2 min-10 min;

[0021] In S4, the stirring rate is 200 rpm-400 rpm, and the stirring time is 2 min-10 min.

[0022] Furthermore, in S4, the curing temperature is 120° C.-180° C., and the curing time is 10 h-24 h.

[0023] The present invention also provides the use of the above-mentioned resin-reinforced gel plugging agent or the resin-reinforced gel plugging agent prepared by the above-mentioned preparation method as a plugging agent for malignant leakage in fractured formations. The specific steps of the application are: injecting a first displacement fluid, a resin-reinforced gel plugging agent and a second displacement fluid into the fractured formation in sequence, wherein the amount of the first displacement fluid is 40%-80% of the total volume of the resin-reinforced gel plugging agent; the amount of the second displacement fluid is 20%-60% of the total volume of the resin-reinforced gel plugging agent; the first displacement fluid and the second displacement fluid are polymer solutions with an apparent viscosity ≥500mPa·s.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects:

[0025] The present invention provides a resin-reinforced gel plugging agent, which comprises a water-soluble resin, a polymer monomer, a cross-linking agent, a rheology control agent and an initiator. The polymer monomer can undergo a free radical polymerization reaction under the action of the initiator, and dehydrate and condense under the action of the cross-linking agent to form a first polymer gel network structure; the terminal ether bonds in the water-soluble resin are cured at high temperature under acidic conditions, undergo a hydrolysis reaction, and generate active hydroxyl groups. At the same time, the tertiary amine groups connected to the hydroxymethyl groups are decomposed to obtain secondary amine groups and formaldehyde. Finally, the active secondary amine groups can undergo a polycondensation and cross-linking reaction with the hydroxyl groups or ether bonds to generate stable methylene bridge groups to form a second resin network structure. The formation process is as follows:

[0026]

[0027] At the same time, the hydroxyl groups generated by the hydrolysis of the water-soluble resin of the present invention can also cross-link the polymer chains into a network, forming a third resin-reinforced gel network structure. Under the effect of the triple network structure, the temperature resistance and structural strength of the cured gel plugging agent are greatly improved.

[0028] Further, the rheology control agent of the present invention adopts hectorite, which can form a reversible "card house" structure through electrostatic attraction in an aqueous solution, which is manifested as an increase in the viscosity of the gel solution on a macro scale. Under weak stress conditions, the uncured gel system can be prevented from being diluted by underground fluids; the most preferred rheology control agent also includes xanthan gum, which can form a super-bonded ribbon-shaped spiral copolymer in an aqueous solution, forming a fragile mesh structure similar to glue, which can support the morphology of solid particles, droplets and bubbles, and shows a strong emulsification stabilization effect and high suspension ability. Through the "shear thinning and standing thickening" characteristics of hectorite and xanthan gum, the gel plugging agent before curing is not easy to be diluted and can be fully cured to play a role. Changing the type of rheology control agent, especially reducing the proportion of hectorite in the rheology control agent mixed with xanthan gum and hectorite, the performance of the obtained plugging agent is poor.

[0029] Furthermore, the preparation method of the resin-reinforced gel plugging agent of the present invention is simple and easy to operate, and has good dilution resistance. After the gel solution is prepared according to a certain proportion at the drilling site, it can be injected into the formation according to the method provided by the present invention. It has the advantages of easy injection, high gel strength, and excellent temperature resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Structural diagram of conventional polymer gel and the resin-reinforced gel of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0032] The invention provides a resin-reinforced gel plugging agent. The resin-reinforced gel plugging agent comprises the following raw materials in percentage by mass: 5% to 15% of a water-soluble resin aqueous solution, 10% to 30% of a polymer monomer, 1% to 10% of a rheology control agent, 0.1% to 1% of a cross-linking agent, 0.01% to 0.1% of an initiator, and the balance is water. The raw materials are cured at high temperature under acidic conditions to obtain the resin-reinforced gel plugging agent.

[0033] According to the preferred embodiment of the present invention, the resin-reinforced gel plugging agent comprises the following raw materials in percentage by mass: 5% to 10% water-soluble resin aqueous solution, 10% to 20% polymer monomer, 2% to 8% rheology control agent, 0.2% to 0.8% cross-linking agent, 0.01% to 0.05% initiator, and the balance is water;

[0034] Further preferably, the resin-reinforced gel plugging agent comprises the following raw materials in percentage by mass: 10% water-soluble resin aqueous solution, 15% polymer monomer, 5% rheology control agent, 0.6% cross-linking agent, 0.02% initiator, and the balance is water.

[0035] According to the preferred embodiment of the present invention, the concentration of the water-soluble resin aqueous solution is 30-50 wt %. The water-soluble resin used in the present invention is a partially methylated melamine resin, and its structural formula is shown in formula (I):

[0036]

[0037] According to the present invention, the polymer monomer is preferably a combination of two or more of acrylamide, acrylonitrile or 2-acrylamido-2-methylpropane sulfonic acid; further preferably, the polymer monomer is a combination of acrylamide and 2-acrylamido-2-methylpropane sulfonic acid, wherein the mass ratio of acrylamide to 2-acrylamido-2-methylpropane sulfonic acid is 1-2.5:1, more preferably 2:1.

[0038] Preferably according to the present invention, the rheology control agent is laponite, or a combination of laponite and xanthan gum; further preferably, the rheology control agent is a combination of laponite and xanthan gum, wherein the mass ratio of laponite to xanthan gum is 1:0.5-1.5, further preferably 1:1.

[0039] According to the present invention, the hectorite is a nano-scale flaky hectorite with positive charges on the crystal surface and negative charges on the crystal edge, in a disc shape, with an average diameter of 15-40nm and an average thickness of 0.5-1.5nm; the weight average molecular weight of xanthan gum is 2-4 million.

[0040] Preferably according to the present invention, the crosslinking agent is a combination of one of N,N'-methylenebisacrylamide, hexamethylenetetramine, polyethyleneimine and N-hydroxymethylacrylamide; the ratio of the mass of N,N'-methylenebisacrylamide, hexamethylenetetramine or polyethyleneimine to the mass of N-hydroxymethylacrylamide is 1-3:1, and more preferably 2:1.

[0041] More preferably, the crosslinking agent is a combination of N-methylol acrylamide and N,N'-methylene bis acrylamide, wherein the mass ratio of N-methylol acrylamide to N,N'-methylene bis acrylamide is 1-3:1, more preferably 2:1.

[0042] Preferably according to the present invention, the initiator is one or a combination of two or more of ammonium persulfate, potassium persulfate, and benzoyl peroxide; further preferably, the initiator is benzoyl peroxide.

[0043] According to the present invention, the method for preparing the above-mentioned resin-reinforced gel plugging agent comprises the steps of:

[0044] (1) adding a water-soluble resin aqueous solution into water and stirring uniformly to obtain a mixed solution A;

[0045] (2) adding the polymer monomer to the mixed solution A and stirring evenly to obtain a mixed solution B;

[0046] (3) adding the rheology control agent to the mixed solution B and stirring evenly to obtain a mixed solution C;

[0047] (4) adding a crosslinking agent to the mixed solution C and stirring evenly to obtain a mixed solution D; then adding an initiator, stirring evenly, and curing at high temperature to obtain a resin-reinforced gel plugging agent, as shown in FIG. Figure 1 As shown, compared with conventional polymer gel, the resin-reinforced gel plugging agent has a denser three-dimensional network structure, which effectively improves its temperature resistance and structural strength.

[0048] Preferably according to the present invention, the stirring rate in step (1) is 600-1000 rpm, more preferably 600-800 rpm; the stirring time is 10-30 min, more preferably 10-20 min.

[0049] Preferably according to the present invention, the stirring rate in step (2) is 200-400 rpm, more preferably 200-300 rpm; the stirring time is 10-30 min, more preferably 10-20 min.

[0050] Preferably according to the present invention, the stirring rate in step (3) is 200-400 rpm, more preferably 200-300 rpm; the stirring time is 2-10 min, more preferably 2-5 min.

[0051] According to the present invention, preferably, the stirring rate in step (4) is 200-400 rpm, preferably 200-300 rpm; the stirring time is 2-10 min, more preferably 2-5 min.

[0052] The curing temperature of the resin-reinforced gel plugging agent of the present invention is 120-180° C., preferably 130-160° C.; the curing time is 10-24 hours, preferably 10-16 hours; more preferably, the curing temperature is 150° C.; the curing time is 12 hours.

[0053] According to the present invention, the resin-enhanced gel plugging agent is used as a plugging agent for treating malignant leakage in fractured formations, wherein the specific application steps are: injecting a first displacement fluid, a resin-enhanced gel plugging agent and a second displacement fluid into the fractured formation in sequence.

[0054] Preferably according to the present invention, the first displacement fluid and the second displacement fluid are both high-viscosity polymer solutions; further preferably, the high-viscosity polymer solution can be a non-ionic polyacrylamide aqueous solution with an apparent viscosity ≥500mPa·s, preferably a non-ionic polyacrylamide aqueous solution of 600-800mPa·s, wherein, in the present invention, the apparent viscosity is an indicator used to evaluate the fluidity of the polymer solution.

[0055] Preferably according to the present invention, based on the total volume of the resin-reinforced gel plugging agent, the amount of the first displacement fluid is 40-80% of the total volume of the gel plugging agent, more preferably 40-60%, and the amount of the second displacement fluid is 20-60% of the total volume of the gel plugging agent, more preferably 20-40%.

[0056] In the present invention, the first displacement fluid plays the role of driving away the drilling fluid and formation water in the leakage channel, thereby preventing the resin-reinforced gel plugging agent mixture from being diluted by the drilling fluid and formation water; the second displacement fluid plays the role of completely displacing the resin-reinforced gel plugging agent mixture into the leakage channel, thereby preventing the resin-reinforced gel plugging agent mixture from solidifying in the wellbore due to the inability to completely enter the cracks, and also preventing the drilling fluid in the wellbore from diluting the resin-reinforced gel plugging agent mixture.

[0057] The concentration of the water-soluble resin aqueous solution used in the embodiment is 40 wt %. The water-soluble resin is a partially methylated melamine resin, and its structural formula is shown in formula (I).

[0058] The hectorite used in the embodiment is a nano-scale flaky hectorite with positive charge on the crystal surface and negative charge on the crystal edge, which is approximately disc-shaped, with an average diameter of 25 nm and an average thickness of 0.92 nm; the weight average molecular weight of the xanthan gum used is 3 million.

[0059] Example 1

[0060] A resin-reinforced gel plugging agent A1 comprises the following raw materials in percentage by mass: 10% of a water-soluble resin aqueous solution, 15% of a polymer monomer, 5% of a rheology control agent, 0.6% of a cross-linking agent, 0.02% of an initiator, and the remainder being water, wherein the total content of each component is 100%.

[0061] Wherein, the polymer monomer is a combination of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid, and the mass ratio of acrylamide to 2-acrylamido-2-methylpropanesulfonic acid is 2:1;

[0062] The rheology control agent is a combination of hectorite and xanthan gum, and the mass ratio of hectorite to xanthan gum is 1:1;

[0063] The cross-linking agents are N-hydroxymethyl acrylamide and N,N'-methylenebisacrylamide, and the mass ratio of N-hydroxymethyl acrylamide to N,N'-methylenebisacrylamide is 2:1;

[0064] The initiator is benzoyl peroxide.

[0065] The preparation method of the above-mentioned resin-reinforced gel plugging agent comprises the following steps:

[0066] (1) adding the water-soluble resin aqueous solution into deionized water, stirring at a stirring rate of 700 rpm for 15 min until the mixture is uniformly mixed, to obtain a mixed solution A;

[0067] (2) adding the polymer monomer to the mixed solution A, stirring at a low speed of 250 rpm for 15 min until the monomer is uniformly dispersed, to obtain a mixed solution B;

[0068] (3) adding the rheology control agent to the mixed solution B, stirring at a low speed of 250 rpm for 3 min until the mixture is evenly dispersed, to obtain a mixed solution C;

[0069] (4) Add the crosslinking agent to the mixed solution C, stir at a low speed for 3 min at a stirring rate of 250 rpm until it is evenly dispersed, to obtain a mixed solution D; then add the initiator, stir at a low speed for 3 min at a stirring rate of 250 rpm until it is evenly dispersed, and cure at 150° C. for 12 h under acidic conditions to obtain the resin-reinforced gel plugging agent A1.

[0070] Example 2

[0071] A resin-reinforced gel plugging agent A2 comprises the following raw materials in percentage by mass: 5% of a water-soluble resin aqueous solution, 10% of a polymer monomer, 5% of a rheology control agent, 0.6% of a cross-linking agent, 0.02% of an initiator, and the remainder being water, wherein the total content of each component is 100%.

[0072] Wherein, the polymer monomer is a combination of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, and the mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid is 1:1;

[0073] The rheology control agent is a combination of hectorite and xanthan gum, and the mass ratio of hectorite to xanthan gum is 1:0.5;

[0074] The cross-linking agent is a combination of N-hydroxymethyl acrylamide and N,N'-methylenebisacrylamide, and the mass ratio of N-hydroxymethyl acrylamide to N,N'-methylenebisacrylamide is 2:1;

[0075] The initiator is benzoyl peroxide.

[0076] The preparation method of the above-mentioned resin-reinforced gel plugging agent comprises the following steps:

[0077] (1) adding the water-soluble resin aqueous solution into deionized water, stirring at a stirring rate of 600 rpm for 30 min until the mixture is uniformly mixed, to obtain a mixed solution A;

[0078] (2) adding the polymer monomer to the mixed solution A, stirring at a low speed of 200 rpm for 30 min until the monomer is uniformly dispersed, to obtain a mixed solution B;

[0079] (3) adding the rheology control agent to the mixed solution B, stirring at a low speed of 200 rpm for 10 min until the mixture is uniformly dispersed, to obtain a mixed solution C;

[0080] (4) Add the crosslinking agent to the mixed solution C, stir at a low speed for 10 min at a stirring rate of 200 rpm until it is evenly dispersed, and obtain a mixed solution D; then add the initiator, stir at a low speed for 10 min at a stirring rate of 200 rpm until it is evenly dispersed, and cure at 120° C. for 24 h under acidic conditions to obtain a resin-reinforced gel plugging agent A2.

[0081] Example 3

[0082] A resin-reinforced gel plugging agent A3 comprises the following raw materials in percentage by mass: 15% of a water-soluble resin aqueous solution, 24% of a polymer monomer, 8% of a rheology control agent, 0.8% of a cross-linking agent, 0.02% of an initiator, and the remainder being water, wherein the total content of each component is 100%.

[0083] Wherein, the polymer monomer is a combination of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, and the mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid is 2.5:1;

[0084] The rheology control agent is a combination of hectorite and xanthan gum, and the mass ratio of hectorite to xanthan gum is 1:1.5;

[0085] The cross-linking agent is a combination of N-hydroxymethyl acrylamide and N,N'-methylenebisacrylamide, and the mass ratio of N-hydroxymethyl acrylamide to N,N'-methylenebisacrylamide is 2:1;

[0086] The initiator is benzoyl peroxide.

[0087] The preparation method of the above-mentioned resin-reinforced gel plugging agent comprises the following steps:

[0088] (1) adding the water-soluble resin aqueous solution into deionized water, stirring at a stirring rate of 800 rpm for 15 min until the mixture is uniformly mixed, to obtain a mixed solution A;

[0089] (2) adding the polymer monomer to the mixed solution A, stirring at a low speed of 300 rpm for 20 min until the monomer is uniformly dispersed, to obtain a mixed solution B;

[0090] (3) adding the rheology control agent to the mixed solution B, stirring at a low speed of 300 rpm for 5 min until the mixture is evenly dispersed, to obtain a mixed solution C;

[0091] (4) Add the crosslinking agent to the mixed solution C, stir at a low speed for 5 minutes at a stirring rate of 300 rpm until it is evenly dispersed, and obtain a mixed solution D; then add the initiator, stir at a low speed for 5 minutes at a stirring rate of 300 rpm until it is evenly dispersed, and cure at 130° C. for 16 hours under acidic conditions to obtain a resin-reinforced gel plugging agent A3.

[0092] Example 4

[0093] A resin-reinforced gel plugging agent A4 comprises the following raw materials in percentage by mass: 8% of a water-soluble resin aqueous solution, 20% of a polymer monomer, 1% of a rheology control agent, 0.2% of a cross-linking agent, 0.02% of an initiator, and the remainder being water, wherein the total content of each component is 100%.

[0094] Wherein, the polymer monomer is a combination of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, and the mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid is 2:1;

[0095] The rheology control agent is a combination of hectorite and xanthan gum, and the mass ratio of hectorite to xanthan gum is 1:1;

[0096] The cross-linking agent is a combination of N-hydroxymethyl acrylamide and N,N'-methylenebisacrylamide, and the mass ratio of N-hydroxymethyl acrylamide to N,N'-methylenebisacrylamide is 1:1;

[0097] The initiator is benzoyl peroxide.

[0098] The preparation method of the above-mentioned resin-reinforced gel plugging agent comprises the following steps:

[0099] (1) adding the water-soluble resin aqueous solution into deionized water, stirring at a stirring rate of 1000 rpm for 10 min until the mixture is uniformly mixed, to obtain a mixed solution A;

[0100] (2) adding the polymer monomer to the mixed solution A, stirring at a low speed of 400 rpm for 10 min until the monomer is uniformly dispersed, to obtain a mixed solution B;

[0101] (3) adding the rheology control agent to the mixed solution B, stirring at a low speed of 400 rpm for 2 min until the mixture is evenly dispersed, to obtain a mixed solution C;

[0102] (4) Add the crosslinking agent to the mixed solution C, stir at a low speed for 2 min at a stirring rate of 400 rpm until it is evenly dispersed, and obtain a mixed solution D; then add the initiator, stir at a low speed for 2 min at a stirring rate of 400 rpm until it is evenly dispersed, and cure at 140° C. for 18 h under acidic conditions to obtain a resin-reinforced gel plugging agent A4.

[0103] Example 5

[0104] A resin-reinforced gel plugging agent A5 comprises the following raw materials in percentage by mass: 12% of a water-soluble resin aqueous solution, 30% of a polymer monomer, 5% of a rheology control agent, 0.1% of a cross-linking agent, 0.02% of an initiator, and the remainder being water, wherein the total content of each component is 100%.

[0105] Wherein, the polymer monomer is a combination of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, and the mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid is 2:1;

[0106] The rheology control agent is a combination of hectorite and xanthan gum, and the mass ratio of hectorite to xanthan gum is 1:1;

[0107] The cross-linking agent is a combination of N-hydroxymethyl acrylamide and N,N'-methylenebisacrylamide, and the mass ratio of N-hydroxymethyl acrylamide to N,N'-methylenebisacrylamide is 3:1;

[0108] The initiator is ammonium persulfate.

[0109] The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that in Example 1, and the resin-reinforced gel plugging agent A5 is obtained by curing at 150° C. for 12 hours under acidic conditions.

[0110] Example 6

[0111] A resin-reinforced gel plugging agent A6 comprises the following raw materials in percentage by mass: 10% of a water-soluble resin aqueous solution, 15% of a polymer monomer, 2% of a rheology control agent, 0.6% of a cross-linking agent, 0.1% of an initiator, and the remainder being water, wherein the total content of each component is 100%.

[0112] Wherein, the polymer monomer is a combination of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, and the mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid is 2:1;

[0113] The rheology control agent is a combination of hectorite and xanthan gum, and the mass ratio of hectorite to xanthan gum is 1:1;

[0114] The cross-linking agent is a combination of N-hydroxymethyl acrylamide and N,N'-methylenebisacrylamide, and the mass ratio of N-hydroxymethyl acrylamide to N,N'-methylenebisacrylamide is 2:1;

[0115] The initiator is potassium persulfate.

[0116] The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that in Example 1, and the resin-reinforced gel plugging agent A6 is obtained by curing at 150° C. for 12 hours under acidic conditions.

[0117] Example 7

[0118] A resin-reinforced gel plugging agent A7 comprises the following raw materials in percentage by mass: 10% of a water-soluble resin aqueous solution, 15% of a polymer monomer, 10% of a rheology control agent, 0.6% of a cross-linking agent, 0.01% of an initiator, and the remainder being water, wherein the total content of each component is 100%.

[0119] Wherein, the polymer monomer is a combination of acrylamide and acrylonitrile, and the mass ratio of acrylamide to acrylonitrile is 2:1;

[0120] The rheology control agent is a combination of hectorite and xanthan gum, and the mass ratio of hectorite to xanthan gum is 1:1;

[0121] The cross-linking agent is a combination of N-hydroxymethyl acrylamide and N,N'-methylenebisacrylamide, and the mass ratio of N-hydroxymethyl acrylamide to N,N'-methylenebisacrylamide is 2:1;

[0122] The initiators are benzoyl peroxide and ammonium persulfate.

[0123] The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that in Example 1, and the resin-reinforced gel plugging agent A7 is obtained by curing at 150° C. for 12 hours under acidic conditions.

[0124] Example 8

[0125] A resin-reinforced gel plugging agent A8 comprises the following raw materials in percentage by mass: 10% of a water-soluble resin aqueous solution, 15% of a polymer monomer, 5% of a rheology control agent, 0.6% of a cross-linking agent, 0.02% of an initiator, and the remainder being water, wherein the total content of each component is 100%.

[0126] Wherein, the polymer monomer is a combination of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, and the mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid is 2:1;

[0127] The rheology control agent is hectorite;

[0128] The cross-linking agent is a combination of N-hydroxymethyl acrylamide and N,N'-methylenebisacrylamide, and the mass ratio of N-hydroxymethyl acrylamide to N,N'-methylenebisacrylamide is 2:1;

[0129] The initiators are benzoyl peroxide, ammonium persulfate, and potassium persulfate.

[0130] The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that in Example 1, and the resin-reinforced gel plugging agent A8 is obtained by curing at 160° C. for 12 hours under acidic conditions.

[0131] Example 9

[0132] A resin-reinforced gel plugging agent A9 comprises the following raw materials in percentage by mass: 10% of a water-soluble resin aqueous solution, 15% of a polymer monomer, 5% of a rheology control agent, 0.6% of a cross-linking agent, 0.05% of an initiator, and the remainder being water, wherein the total content of each component is 100%.

[0133] Wherein, the polymer monomer is a combination of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, and the mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid is 2:1;

[0134] The rheology control agent is a combination of hectorite and xanthan gum, and the mass ratio of hectorite to xanthan gum is 1:1;

[0135] The crosslinking agent is a combination of N-hydroxymethyl acrylamide and hexamethylenetetramine, and the mass ratio of N-hydroxymethyl acrylamide to hexamethylenetetramine is 2:1;

[0136] The initiator is benzoyl peroxide.

[0137] The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that in Example 1, and the resin-reinforced gel plugging agent A9 is obtained by curing at 180° C. for 10 h under acidic conditions.

[0138] Comparative Example 1

[0139] A resin-reinforced gel plugging agent B1 is as in Example 1, except that the amount of the water-soluble resin aqueous solution is 20%, and the other conditions are the same as in Example 1.

[0140] The amount of water-soluble resin used in this comparative example is too high. The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that in Example 1, and the resin-reinforced gel plugging agent B1 is obtained.

[0141] Comparative Example 2

[0142] A resin-reinforced gel plugging agent B2 is as in Example 1, except that the amount of polymer monomer used is 5%, and other conditions are the same as in Example 1.

[0143] In this comparative example, the amount of polymer monomer used is too small. The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that of Example 1, and resin-reinforced gel plugging agent B2 is obtained.

[0144] Comparative Example 3

[0145] A resin-reinforced gel plugging agent B3 is as in Example 1, except that the mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid in the polymer monomer is 0.5:1, and other conditions are the same as in Example 1.

[0146] In this comparative example, the proportion of acrylamide in the polymer monomer is too low. The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that of Example 1, and a resin-reinforced gel plugging agent B3 is obtained.

[0147] Comparative Example 4

[0148] A resin-reinforced gel plugging agent B4 is as in Example 1, except that the amount of the rheology control agent is 15%, and the other conditions are the same as in Example 1.

[0149] The dosage of the rheology control agent in this comparative example is too high. The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that in Example 1, and the resin-reinforced gel plugging agent B4 is obtained.

[0150] Comparative Example 5

[0151] A resin-reinforced gel plugging agent B5 is as in Example 1, except that the mass ratio of hectorite to xanthan gum in the rheology control agent is 1:2, and other conditions are the same as in Example 1.

[0152] In this comparative example, the proportion of hectorite in the rheology control agent is too low. The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that in Example 1, and a resin-reinforced gel plugging agent B5 is obtained.

[0153] Comparative Example 6

[0154] A resin-reinforced gel plugging agent B6 is as in Example 1, except that the amount of the cross-linking agent is 1.5%, and the other conditions are the same as in Example 1.

[0155] The amount of cross-linking agent used in this comparative example is too high. The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that in Example 1, and resin-reinforced gel plugging agent B6 is obtained.

[0156] Comparative Example 7

[0157] A resin-reinforced gel plugging agent B7 is as in Example 1, except that the mass ratio of N-hydroxymethyl acrylamide to N,N'-methylenebisacrylamide in the cross-linking agent is 0.5:1, and other conditions are the same as in Example 1.

[0158] In this comparative example, the proportion of N-hydroxymethyl acrylamide in the cross-linking agent is relatively small. The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that of Example 1, and a resin-reinforced gel plugging agent B7 is obtained.

[0159] Comparative Example 8

[0160] A resin-reinforced gel plugging agent B8 is as in Example 1, except that the amount of initiator used is 0.3%, and other conditions are the same as in Example 1.

[0161] The dosage of the initiator in this comparative example is too high. The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that in Example 1, and the resin-reinforced gel plugging agent B8 is obtained.

[0162] Comparative Example 9

[0163] A gel plugging agent B9 is as in Example 1, except that no water-soluble resin aqueous solution is added, and other conditions are the same as in Example 1.

[0164] The preparation method of the above gel plugging agent is the same as that in Example 1, and gel plugging agent B9 is obtained.

[0165] Comparative Example 10

[0166] A resin-reinforced gel plugging agent B10 is as in Example 1, except that the mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid in the polymer monomer is 4:1, and other conditions are the same as in Example 1.

[0167] In this comparative example, the proportion of acrylamide in the polymer monomer is too high. The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that of Example 1, and a resin-reinforced gel plugging agent B10 is obtained.

[0168] Comparative Example 11

[0169] A resin-reinforced gel plugging agent B11 is as in Example 1, except that the cross-linking agent is divinylbenzene, and other conditions are the same as in Example 1.

[0170] The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that in Example 1, and a resin-reinforced gel plugging agent B11 is obtained.

[0171] Comparative Example 12

[0172] A resin-reinforced gel plugging agent B12 is as in Example 1, except that the rheology control agent is sodium alginate, and other conditions are the same as in Example 1.

[0173] The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that in Example 1, and a resin-reinforced gel plugging agent B12 is obtained.

[0174] Comparative Example 13

[0175] A resin-reinforced gel plugging agent B13 is as in Example 1, except that the rheology control agent is polyvinyl alcohol, and other conditions are the same as in Example 1.

[0176] The preparation method of the above-mentioned resin-reinforced gel plugging agent is the same as that in Example 1, and a resin-reinforced gel plugging agent B13 is obtained.

[0177] Test example

[0178] The gel plugging agents obtained in Examples 1-9 and Comparative Examples 1-13 were subjected to mechanical property tests and high-temperature plugging effect tests.

[0179] Mechanical properties test of gel plugging agent after curing: A universal electronic tensile testing machine was used to test the tensile mechanical properties of the resin-reinforced gel plugging agent after gelation. Among them, the greater the gel fracture stress, the higher the tensile strength of the resin-reinforced gel after curing, and vice versa, the lower the tensile resistance. Specifically, the gelation condition of the gel plugging agent is: the gel plugging agent is cured at 150°C for 12 hours to obtain a gel. The test condition of the universal electronic tensile testing machine is a tensile rate of 1 mm / s, and the results are shown in Table 1.

[0180] The plugging effect of gel plugging agent: A high temperature and high pressure plugging test device is used to test the plugging effect of curable gel plugging agent on cracks. The device mainly includes a constant temperature box, a constant flow pump, a core holder, and a high-pressure manifold. A cylindrical steel fracture core model with a length of 10 cm and a crack width of 3 mm is used to simulate the leaking formation. Specific test method: place the steel fracture core model in the core holder and apply annular pressure to 5MPa; use a constant flow pump to inject clean water into the core holder to saturate it, and heat the temperature inside the constant temperature box to 150°C; place the prepared resin-enhanced gel plugging agent in an intermediate container; inject the first displacement fluid (700mPa·s non-ionic polyacrylamide aqueous solution, the injection amount is 50% of the volume of the gel plugging agent), gel plugging agent (the injection amount is 100% of the volume of the entire fracture space) and the second displacement fluid (700mPa·s non-ionic polyacrylamide aqueous solution, the injection amount is 30% of the volume of the gel plugging agent) into the core holder in sequence; seal both ends of the core holder and let it stand for 12 hours to allow the plugging agent to solidify; use a constant flow pump to inject drilling fluid for pressurization, record the pressure at the inlet end of the fracture model in real time, and take the highest pressure when the drilling fluid leaks from the outlet end of the fracture model as the highest plugging pressure of the gel on the fracture. The drilling fluid base slurry was continuously injected into the fracture model, and the pressure value when linear leakage occurred at the outlet of the fracture model was recorded, i.e., the plugging failure pressure, as an indicator for evaluating the plugging performance of the gel plugging agent after plugging failure. The test temperature was 150°C, and the results are shown in Table 1.

[0181] Table 1 Mechanical properties of gel plugging agent after curing and test data of high temperature crack plugging effect

[0182]

[0183] It can be seen from the data in Table 1 that the maximum tensile fracture stress of the resin-reinforced gel of Example 1 of the present invention after curing is 354 KPa, indicating that the resin-reinforced gel of the present invention has high structural strength and excellent mechanical properties, and the maximum pressure bearing capacity is 7.62 MPa, indicating that the gel plugging agent of the present invention has excellent high-temperature pressure-bearing and sealing capabilities; the maximum tensile fracture stress of the resin-reinforced gel of Example 2 of the present invention after curing is 267 KPa, indicating that the resin-reinforced gel of the present invention has high structural strength and excellent mechanical properties, and the maximum pressure bearing capacity is 6.32 MPa, indicating that the gel plugging agent of the present invention has excellent high-temperature pressure-bearing and sealing capabilities; The maximum tensile fracture stress of the resin-reinforced gel after curing is 284 KPa, indicating that the resin-reinforced gel of the present invention has high structural strength and excellent mechanical properties. The maximum pressure bearing capacity is 6.68 MPa, indicating that the gel plugging agent of the present invention has excellent high-temperature pressure-bearing and sealing capabilities; the maximum tensile fracture stress of the resin-reinforced gel of Example 4 of the present invention after curing is 291 KPa, indicating that the resin-reinforced gel of the present invention has high structural strength and excellent mechanical properties. The maximum pressure bearing capacity is 6.71 MPa, indicating that the gel plugging agent of the present invention has excellent high-temperature pressure-bearing and sealing capabilities; the maximum tensile fracture stress of the resin-reinforced gel of Example 5 of the present invention after curing is The maximum tensile stress at break of the resin-reinforced gel of Example 6 after curing is 232 KPa, indicating that the resin-reinforced gel of the present invention has a high structural strength and excellent mechanical properties, and the maximum bearing capacity is 5.36 MPa, indicating that the gel plugging agent of the present invention has excellent high-temperature pressure-bearing and plugging capabilities; the test data results of Examples 2-6 are compared with those of Example 1, and the water-soluble resin aqueous solution, polymer monomer, rheology control agent, cross-linking agent, When the amount of the initiator is not within the optimal concentration range, the mechanical properties after curing and the crack plugging effect at high temperature are slightly reduced, but still maintained at a high level; the maximum tensile fracture stress of the resin-reinforced gel of Example 7 of the present invention after curing is 253 KPa, indicating that the resin-reinforced gel of the present invention has high structural strength and excellent mechanical properties, and the maximum pressure bearing capacity is 6.07 MPa, indicating that the gel plugging agent of the present invention has excellent high-temperature pressure-bearing plugging ability; the maximum tensile fracture stress of the resin-reinforced gel of Example 8 of the present invention after curing is 302 KPa, indicating that the resin-reinforced gel of the present invention has high structural strength and excellent mechanical properties, and the maximum pressure bearing capacity is 6.83MPa, indicating that the gel plugging agent of the present invention has excellent high-temperature pressure-bearing plugging ability; the maximum tensile fracture stress of the resin-reinforced gel of Example 9 of the present invention after curing is 231KPa, indicating that the resin-reinforced gel of the present invention has high structural strength and excellent mechanical properties, and the maximum pressure-bearing capacity is 5.29MPa, indicating that the gel plugging agent of the present invention has excellent high-temperature pressure-bearing plugging ability; the test data results of Examples 7-9 are compared with those of Example 1, and it can be obtained that when the types of polymer monomers, rheology control agents, and cross-linking agents are not the optimal solutions, the mechanical properties after curing and the crack plugging effect at high temperature are slightly reduced, but still maintained at a high level. .

[0184] Since comparative example 1-13 does not adopt the technical solution of the present invention, the maximum tensile fracture stress is lower than that of embodiment 1-9, and the pressure bearing capacity and the pressure value when the plugging fails are also lower than those of embodiment 1-9. Specifically, in comparative example 1, due to the addition of excessive water-soluble resin, at this time, in addition to a small part of the resin that can be cross-linked with the gel network, more resin will self-solidify at high temperature, but due to the steric hindrance effect of the gel network, the resin is not easy to solidify, and the partially solidified resin structure is also very loose, and the performance of the obtained plugging agent is poor; since comparative example 9 does not add water-soluble resin, the system lacks a three-dimensional network reinforced by resin, so the mechanical properties and pressure-bearing plugging capacity of the material are greatly reduced. In Comparative Example 2, due to the small amount of polymer monomer added, the structure formed is relatively loose due to the steric hindrance effect of the gel network; in Comparative Example 3, due to the low proportion of acrylamide in the polymer monomer, the too little acrylamide can only cross-link with part of the resin, and the three-dimensional network structure formed by the cross-linking will produce steric hindrance to the curing of the resin itself, resulting in performance degradation; in Comparative Example 10, due to the high proportion of acrylamide in the polymer monomer, the number of polyacrylamide segments that are not fully cross-linked in the system after curing increases, the looseness of the three-dimensional network structure increases, the mechanical properties of the material after curing decreases, and the pressure-bearing and sealing capacity decreases. In Comparative Example 4, adding an excessive amount of rheology control agent will lock the moisture in the system, resulting in insufficient crosslinking of the polymer monomer and the water-soluble resin, and the fluidity of the system before curing becomes poor, making it difficult to fill the crack space and easily generating pores, resulting in reduced pressure bearing capacity; in Comparative Example 5, due to the low proportion of lithium soap in the rheology control agent, the free-flowing moisture in the system increases, the density of the formed gel network decreases, resulting in a decrease in the maximum tensile fracture stress of the material, and at the same time, the anti-pollution property of the system before curing becomes poor, and it is easy to be invaded by other liquids in the crack space, resulting in poor filling effect after curing and reduced pressure bearing capacity; in Comparative Example 12, due to the use of sodium alginate as the rheology control agent, lithium soap cannot form a "card house" in the aqueous solution "-like network structure, the density of the gel network formed after curing is reduced, resulting in a decrease in the maximum tensile fracture stress of the material. At the same time, the thickening effect is significantly reduced compared with that of lithium soapstone at the same dosage, resulting in the system being easily contaminated by other fluids before curing, the filling effect is worse after curing, and the pressure bearing capacity is reduced; Comparative Example 13 uses polyvinyl alcohol as a rheology control agent, and the viscosity of its aqueous solution will increase with time, which will increase the difficulty of on-site construction. At the same time, since it contains a large amount of hydroxyl groups, it can form hydrogen bonds at low temperatures to play a rheology control role, but it is easy to dehydrate and etherify at high temperatures (150°C), thereby losing solubility, which in turn affects the strength of the gel structure after curing, and the pressure-bearing and sealing capacity is also significantly reduced.In Comparative Example 6, due to the excessive amount of cross-linking agent used, the cross-linking between the polymer monomer is tighter, resulting in only a small part of the water-soluble resin being cross-linked on the gel network, and the remaining resin being free in the three-dimensional network structure of the gel, and the mechanical properties and pressure-bearing capacity of the material after curing are greatly reduced; in Comparative Example 7, due to the small proportion of N-hydroxymethyl acrylamide in the cross-linking agent, the active hydroxyl groups that can dehydrate and condense with a large number of amino groups in the polymer monomer are reduced, the three-dimensional network structure formed is not dense enough, and the material performance is reduced macroscopically; in Comparative Example 11, due to other types of cross-linking agents, active hydroxyl sites that can be cross-linked cannot be provided, so the three-dimensional network structure formed is not dense enough, the mechanical properties of the material are reduced, and the pressure-bearing and sealing capacity are reduced; in Comparative Example 8, due to the excessive amount of initiator added, implosion will occur, resulting in increased pores in the material, and the mechanical properties and pressure-bearing and sealing capacity are greatly reduced.

[0185] From the above, it can be seen that the resin-reinforced gel plugging agent prepared in the embodiment of the present invention has a high structural strength, thus having excellent tensile mechanical properties. At the same time, the gel plugging agent prepared in the present invention has a high maximum crack plugging pressure at 150°C after curing, indicating that the gel plugging agent of the present invention has excellent high-temperature pressure-bearing plugging ability. The above data show that the gel plugging agent of the present invention has the advantages of high temperature resistance and high strength, and has important research value in solving the problem of well leakage in high-temperature deep fracture leakage formations.

[0186] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A resin-reinforced gel plugging agent, characterized in that: The following raw materials in mass percentage are cured at high temperature under acidic conditions to obtain a resin-reinforced gel plugging agent, specifically, 5%-15% water-soluble resin aqueous solution, 10%-30% polymer monomer, 1%-10% rheology control agent, 0.1%-1% cross-linking agent, 0.01%-0.1% initiator, and the balance is water, and the water-soluble resin in the water-soluble resin aqueous solution is a partially methylated melamine resin.

2. A resin-reinforced gel plugging agent according to claim 1, characterized in that: The partially methylated melamine resin has the following structure:

3. A resin-reinforced gel plugging agent according to claim 1, characterized in that: The polymer monomer is a combination of two or more of acrylamide, acrylonitrile or 2-acrylamide-2-methylpropane sulfonic acid. In the combination of acrylamide and 2-acrylamide-2-methylpropane sulfonic acid, the mass ratio of acrylamide to 2-acrylamide-2-methylpropane sulfonic acid is 1-2.5:

1.

4. A resin-reinforced gel plugging agent according to claim 1, characterized in that: The rheology control agent is hectorite or a combination of hectorite and xanthan gum, wherein the mass ratio of hectorite to xanthan gum is 1:0.5-1.5; the hectorite is a nano-scale flaky hectorite with positive charge on the crystal surface and negative charge on the crystal edge, and the weight average molecular weight of the xanthan gum is 2 million-4 million.

5. The resin-enhanced gel plugging agent according to claim 1, characterized in that: The crosslinking agent is a combination of one of N,N'-methylenebisacrylamide, hexamethylenetetramine, polyethyleneimine and N-hydroxymethylacrylamide; the mass ratio of N,N'-methylenebisacrylamide, hexamethylenetetramine or polyethyleneimine to the mass ratio of N-hydroxymethylacrylamide is 1-3:

1.

6. The resin-reinforced gel plugging agent according to claim 1, characterized in that: The initiator is one or a combination of two or more of ammonium persulfate, potassium persulfate and benzoyl peroxide.

7. The method for preparing a resin-reinforced gel plugging agent according to claims 1 to 6, characterized in that: The specific steps are as follows: S1: adding the water-soluble resin aqueous solution into water and stirring evenly to obtain a mixed solution A; S2: adding the polymer monomer to the mixed solution A and stirring evenly to obtain a mixed solution B; S3: adding the rheology control agent into the mixed solution B and stirring evenly to obtain a mixed solution C; S4: adding the cross-linking agent into the mixed solution C, stirring evenly, to obtain a mixed solution D; then adding the initiator, stirring evenly, and curing at high temperature under acidic conditions to obtain a resin-reinforced gel plugging agent.

8. The method for preparing a resin-reinforced gel plugging agent according to claim 7, characterized in that: In S1, the stirring rate is 600 rpm-1000 rpm, and the stirring time is 10 min-30 min; In S2, the stirring rate is 200 rpm-400 rpm, and the stirring time is 10 min-30 min; In S3, the stirring rate is 200 rpm-400 rpm, and the stirring time is 2 min-10 min; In S4, the stirring rate is 200 rpm-400 rpm, and the stirring time is 2 min-10 min.

9. The method for preparing a resin-reinforced gel plugging agent according to claim 7, characterized in that: In S4, the curing temperature is 120°C-180°C, and the curing time is 10h-24h.

10. Use of the resin-reinforced gel plugging agent according to any one of claims 1 to 6 or the resin-reinforced gel plugging agent prepared by the preparation method according to any one of claims 7 to 9 as a plugging agent for malignant leakage in fractured formations, characterized in that: The specific application steps are: injecting a first displacement fluid, a resin-reinforced gel plugging agent and a second displacement fluid into the fractured formation in sequence, wherein the amount of the first displacement fluid is 40%-80% of the total volume of the resin-reinforced gel plugging agent; the amount of the second displacement fluid is 20%-60% of the total volume of the resin-reinforced gel plugging agent; the first displacement fluid and the second displacement fluid are polymer solutions with an apparent viscosity ≥500mPa·s.

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