Resin-reinforced gel plugging agent, preparation method and application thereof

Abstract

The application discloses a resin-reinforced gel plugging agent and a preparation method and application thereof. Raw materials in the following mass percentages are cured under an acidic condition at high temperature to obtain the resin-reinforced gel plugging agent. Specifically, the raw materials include 5-15% of a water-soluble resin aqueous solution, 10-30% of a polymer monomer, 1-10% of a rheological modifier, 0.1-1% of a crosslinking agent, 0.01-0.1% of an initiator, and the balance of water. The water-soluble resin in the water-soluble resin aqueous solution is a partially methyl etherified melamine resin. The plugging agent combines the advantages of conventional gels, such as good viscoelasticity and strong self-adaptability, and resin-based polymer materials, such as excellent high-temperature resistance and high strength after curing. The obtained resin-reinforced gel plugging agent has excellent high-temperature resistance, high structural strength and excellent plugging effect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of drilling fluid plugging, and particularly relates to a resin-reinforced gel plugging agent and a preparation method and application thereof. BACKGROUND

[0002] Lost circulation is a phenomenon that a large amount of drilling fluid leaks into the formation during oilfield drilling construction, and is one of the most common drilling engineering problems in fractured complex formations. After the problem of lost circulation occurs in oil and gas drilling and production construction, not only is the drilling time consumed and a large amount of drilling fluid lost, but improper treatment can also cause downhole complex accidents such as well collapse, blowout, and sticking, and even lead to wellbore abandonment, causing significant economic losses. Therefore, efficiently solving the problem of lost circulation is crucial to ensuring downhole safety, improving drilling speed, and saving drilling costs.

[0003] Polymer gel is one of the commonly used and effective plugging materials in oilfield sites. During site construction, a certain amount of gel plugging agent solution is injected into the lost circulation layer, and after curing, the fractures are plugged, playing a role in isolating drilling fluid from formation fluid. The gel plugging agent currently used has achieved good results in treating conventional lost circulation problems, but as oil and gas exploration and development expand to deep layers, high temperature and high pressure become one of the main problems faced by drilling plugging, and higher requirements are put forward for the high-temperature resistance and high-pressure resistance of the gel plugging agent after curing. Among them, the temperature resistance and structural strength of the gel plugging agent after curing 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 a preparation method and application thereof. The gel plugging agent comprises the following raw material components in mass percentage: acrylamide monomer 8-20%, active polymer 0.05-0.5%, organic polymer crosslinking agent 0.1-1.0%, resin toughening agent 3.0-8.0%, rheological control agent 1.0-5.0%, crosslinking regulator 0.01-0.5%, and the balance is water. The gel plugging agent of the invention has certain high-temperature resistance and gel sealing strength, but the high-temperature resistance, gel sealing strength, and plugging effect still need to be further improved.

[0004] Therefore, it is of great significance to develop a gel plugging agent with high-temperature resistance and high strength to solve the problem of lost circulation in high-temperature deep fractured formation. SUMMARY

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

[0006] To achieve the above object, the present application provides the following technical scheme: a resin-strengthened gel plugging agent, raw materials in the following mass percentage are cured under acidic conditions at high temperature to obtain the resin-strengthened gel plugging agent, specifically, the raw materials include water-soluble resin aqueous solution 5%-15%, polymer monomer 10%-30%, rheological modifier 1%-10%, crosslinking agent 0.1%-1%, initiator 0.01%-0.1%, and the rest is water.

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

[0008]

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

[0010] Further, the rheological modifier is hectorite or a combination of hectorite and xanthan gum, and the mass ratio of hectorite and xanthan gum in the combination of hectorite and xanthan gum is 1:0.5-1.5; the hectorite is a nanoscale flaky hectorite with positive charges on the crystal surface and negative charges on the crystal edge, and the weight average molecular weight of the xanthan gum is 2 million-4 million.

[0011] Further, the crosslinking agent is a combination of one of N,N'-methylene bisacrylamide, hexamethylenetetramine and polyethyleneimine and N-methylol acrylamide; the mass ratio of N,N'-methylene bisacrylamide, hexamethylenetetramine or polyethyleneimine to N-methylol acrylamide is 1-3:1.

[0012] Further, the initiator is one or more than two combinations of ammonium persulfate, potassium persulfate and benzoyl peroxide.

[0013] The present application also provides a preparation method of the resin-strengthened gel plugging agent, and the specific steps are as follows:

[0014] S1 add the water-soluble resin aqueous solution into water, stir uniformly to obtain a mixed solution A;

[0015] S2 add the polymer monomer into the mixed solution A, stir uniformly to obtain a mixed solution B;

[0016] S3 add the rheological modifier into the mixed solution B, stir uniformly to obtain a mixed solution C;

[0017] S4 adds the crosslinking agent into the mixed solution C, stirs uniformly, obtains mixed solution D, then adds the initiator, stirs uniformly, under the acid condition, high-temperature solidification, namely the resin reinforced gel plugging agent.

[0018] Further, in S1, the stirring rate is 600 revolutions / minute-1000 revolutions / minute, and the stirring time is 10min-30min.

[0019] In S2, the stirring rate is 200 revolutions / minute-400 revolutions / minute, and the stirring time is 10min-30min.

[0020] In S3, the stirring rate is 200 revolutions / minute-400 revolutions / minute, and the stirring time is 2min-10min.

[0021] In S4, the stirring rate is all 200 revolutions / minute-400 revolutions / minute, and the stirring time is all 2min-10min.

[0022] Further, in S4, the solidification temperature is 120 DEG C-180 DEG C, and the solidification time is 10h-24h.

[0023] The application also provides the application of the resin reinforced gel plugging agent or the resin reinforced gel plugging agent prepared by the preparation method as a plugging agent for the vicious leakage of fractured formation, and the specific steps are as follows: sequentially injecting a first displacement fluid, the resin reinforced gel plugging agent and a second displacement fluid in the fractured formation, 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, and the first displacement fluid and the second displacement fluid are polymer solutions with apparent viscosity ≥500mPa·s.

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

[0025] The resin reinforced gel plugging agent provided by the application comprises a water-soluble resin, a polymer monomer, a crosslinking agent, a rheological modifier and an initiator, the polymer monomer can occur free radical polymerization under the action of the initiator and dehydrates and condenses to form a first heavy polymer gel network structure under the action of the crosslinking agent, the end group ether bond in the water-soluble resin occurs hydrolysis under the acid condition and high-temperature solidification, generates active hydroxyl, at the same time, the tertiary amine group connected with the hydroxymethyl decomposes to obtain a secondary amine group and formaldehyde, finally, the active secondary amine group can occur polycondensation crosslinking reaction with the hydroxyl or the ether bond, generates a stable methylene bridge group, forms a second heavy resin network structure, and the forming process is as follows:

[0026]

[0027] Meanwhile, the hydroxyl groups generated by hydrolysis of the water-soluble resin of the present application can also crosslink the polymer chains into a network, forming a third reinforced gel network structure. Under the action of the triple network structure, the temperature resistance and structural strength of the cured gel plugging agent are greatly improved.

[0028] Further, the rheological modifier of the present application adopts hectorite, which can form a reversible "card house" structure in an aqueous solution through electrostatic attraction, and macroscopically, the viscosity of the gel solution increases, which can prevent the uncured gel system from being diluted by underground fluid under weak stress conditions; the optimal rheological modifier also includes xanthan gum, which can form an ultrabonding belt-shaped spiral copolymer in an aqueous solution, forming a fragile gel-like network structure that can support the morphology of solid particles, liquid droplets and bubbles, showing strong emulsification stability and high suspension capacity; through the "shear thinning and standing thickening" characteristics of hectorite and xanthan gum, the gel plugging agent before curing is not easily diluted, so as to fully cure and play a role. Changing the type of rheological modifier, especially reducing the proportion of hectorite in the rheological modifier mixed with xanthan gum, the prepared plugging agent has poor performance.

[0029] Further, the preparation method of the resin-reinforced gel plugging agent of the present application is simple and easy to operate, has good anti-dilution property, and can be prepared according to a certain proportion on the drilling site, then injected into the formation according to the method provided by the present application, and has the advantages of easy injection, high gel strength, excellent temperature resistance and the like. BRIEF DESCRIPTION OF DRAWINGS

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

[0031] The present application will be further described below in combination with the drawings and specific embodiments.

[0032] The present application provides a resin-reinforced gel plugging agent, which comprises the following raw materials in mass percentage: 5-15% of water-soluble resin aqueous solution, 10-30% of polymer monomer, 1-10% of rheological modifier, 0.1-1% of crosslinking agent, 0.01-0.1% of initiator, and the balance of water; the above raw materials are cured under acidic conditions at high temperature to obtain the resin-reinforced gel plugging agent.

[0033] According to the present application, the resin-reinforced gel plugging agent comprises the following raw materials in mass percentage: 5-10% of water-soluble resin aqueous solution, 10-20% of polymer monomer, 2-8% of rheological modifier, 0.2-0.8% of crosslinking agent, and 0.01-0.05% of initiator, and the balance of water.

[0034] Further preferably, the resin-reinforced gel plugging agent comprises the following raw materials in mass percentage: 10% of water-soluble resin aqueous solution, 15% of polymer monomer, 5% of rheological modifier, 0.6% of crosslinking agent, 0.02% of initiator, and the rest of water.

[0035] According to the present application, preferably, the concentration of the water-soluble resin aqueous solution is 30-50 wt%, and the water-soluble resin used in the present application is a partially methylated melamine resin, the structural formula of which is shown as formula (I)

[0036]

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

[0038] According to the present application, preferably, the rheological modifier is hectorite, or a combination of hectorite and xanthan gum; further preferably, the rheological modifier is a combination of hectorite and xanthan gum, wherein the mass ratio of hectorite to xanthan gum is 1:0.5-1.5, further preferably 1:1.

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

[0040] According to the present application, preferably, the crosslinking agent is a combination of one of N,N'-methylenebisacrylamide, hexamethylenetetramine and polyethyleneimine, and N-methylol acrylamide; the mass ratio of N,N'-methylenebisacrylamide, hexamethylenetetramine or polyethyleneimine to N-methylol acrylamide is 1-3:1, further preferably 2:1.

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

[0042] According to the present application, preferably, the initiator is one or more of ammonium persulfate, potassium persulfate and benzoyl peroxide; further preferably, the initiator is benzoyl peroxide.

[0043] According to the present application, the preparation method of the resin-reinforced gel plugging agent described above comprises the following steps:

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

[0045] (2) adding polymer monomer into mixed solution A, stirring uniformly to obtain mixed solution B;

[0046] (3) adding rheological modifier into mixed solution B, stirring uniformly to obtain mixed solution C;

[0047] (4) adding crosslinking agent into mixed solution C, stirring uniformly to obtain mixed solution D; then adding initiator, stirring uniformly, high-temperature curing, which is resin-strengthened gel plugging agent, as shown in the following formula, compared with conventional polymer gel, the resin-strengthened gel plugging agent has a more compact three-dimensional network structure, so that the temperature resistance and structural strength are effectively improved. Figure 1

[0048] According to the application, preferably, the stirring rate in step (1) is 600-1000 rpm, and further preferably 600-800 rpm; the stirring time is 10-30 min, and further preferably 10-20 min.

[0049] According to the application, preferably, the stirring rate in step (2) is 200-400 rpm, and further preferably 200-300 rpm; the stirring time is 10-30 min, and further preferably 10-20 min.

[0050] According to the application, preferably, the stirring rate in step (3) is 200-400 rpm, and further preferably 200-300 rpm; the stirring time is 2-10 min, and further preferably 2-5 min.

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

[0052] The resin-strengthened gel plugging agent of the application has a curing temperature of 120-180℃, preferably 130-160℃; a curing time of 10-24 h, preferably 10-16 h; and further preferably, the curing temperature is 150℃, and the curing time is 12 h.

[0053] According to the application, the resin-strengthened gel plugging agent is applied to crack formation and malignant leakage, as a plugging agent.

[0054] ​According to the present application, preferably, 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 ≥ 500 mPa·s, preferably 600-800 mPa·s, wherein in the present application, the apparent viscosity is an index used to evaluate the flowability of a polymer solution.

[0055] According to the present application, preferably, the amount of the first displacement fluid is 40-80% of the total volume of the resin-reinforced gel plugging agent, further preferably 40-60%, and the amount of the second displacement fluid is 20-60% of the total volume of the resin-reinforced gel plugging agent, further preferably 20-40%.

[0056] In the present application, the first displacement fluid plays a role in driving away the drilling fluid and the formation water in the lost circulation channel, thereby preventing the resin-reinforced gel plugging agent mixture from being diluted by the drilling fluid and the formation water; the second displacement fluid plays a role in completely displacing the resin-reinforced gel plugging agent mixture into the lost circulation channel, thereby preventing the resin-reinforced gel plugging agent mixture from solidifying in the wellbore due to incomplete entry into the fracture, 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 examples is 40 wt%, and the water-soluble resin is a partially methylated melamine resin, the structural formula of which is shown as formula (I).

[0058] The lithium smectite used in the examples is a nanoscale flaky lithium smectite with positive charges on the crystal surface and negative charges on the crystal edges, in the form of an approximate disc, 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, comprising the following raw materials in mass percentage: the amount of water-soluble resin aqueous solution is 10%, the amount of polymer monomer is 15%, the amount of rheological modifier is 5%, the amount of crosslinking agent is 0.6%, the amount of initiator is 0.02%, and the balance is water, and the total content of each component is 100%.

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

[0062] The rheological modifier is a combination of lithium smectite and xanthan gum, and the mass ratio of lithium smectite to xanthan gum is 1:1;

[0063] The crosslinking agent is N-hydroxymethyl acrylamide and N,N'-methylene bisacrylamide, and the mass ratio of N-hydroxymethyl acrylamide and N,N'-methylene bisacrylamide is 2:1;

[0064] The initiator is benzoyl peroxide.

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

[0066] (1) The water-soluble resin aqueous solution is added to deionized water, and high-speed stirring is performed at a stirring rate of 700 rpm for 15 min until it is uniformly mixed to obtain a mixed solution A;

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

[0068] (3) The rheological modifier is added to the mixed solution B, and low-speed stirring is performed at a stirring rate of 250 rpm for 3 min until it is uniformly dispersed to obtain a mixed solution C;

[0069] (4) The crosslinking agent is added to the mixed solution C, and low-speed stirring is performed at a stirring rate of 250 rpm for 3 min until it is uniformly dispersed to obtain a mixed solution D; then the initiator is added, and low-speed stirring is performed at a stirring rate of 250 rpm for 3 min until it is uniformly dispersed, and then it is cured at 150°C under acidic conditions for 12 h 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 the following mass percentages: the water-soluble resin aqueous solution is used in an amount of 5%, the polymer monomer is used in an amount of 10%, the rheological modifier is used in an amount of 5%, the crosslinking agent is used in an amount of 0.6%, the initiator is used in an amount of 0.02%, and the balance is water, and the total content of the components is 100%.

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

[0073] The rheological modifier is a combination of hectorite and xanthan gum, and the mass ratio of hectorite and xanthan gum is 1:0.5;

[0074] The crosslinking agent is a combination of N-hydroxymethyl acrylamide and N,N'-methylene bisacrylamide, and the mass ratio of N-hydroxymethyl acrylamide and N,N'-methylene bisacrylamide is 2:1;

[0075] The initiator is benzoyl peroxide.

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

[0077] (1) The water-soluble resin aqueous solution is added to deionized water, and high-speed stirring is performed at a stirring rate of 600 rpm for 30 min until it is uniformly mixed to obtain a mixed solution A;

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

[0079] (3) The rheological modifier is added to the mixed solution B, and low-speed stirring is performed at a stirring rate of 200 rpm for 10 min until it is uniformly dispersed to obtain a mixed solution C;

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

[0081] Example 3

[0082] A resin-reinforced gel plugging agent A3 comprises the following raw materials in mass percentage: the amount of the water-soluble resin aqueous solution is 15%, the amount of the polymer monomer is 24%, the amount of the rheological modifier is 8%, the amount of the crosslinking agent is 0.8%, the amount of the initiator is 0.02%, and the balance is water, and the total content of each component is 100%.

[0083] 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 2.5:1;

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

[0085] The crosslinking agent is a combination of N-methylol acrylamide and N,N'-methylene bisacrylamide, and the mass ratio of N-methylol acrylamide to N,N'-methylene bisacrylamide is 2:1;

[0086] The initiator is benzoyl peroxide.

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

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

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

[0090] (3) adding the rheological modifier into the mixed solution B, stirring at a stirring speed of 300 rpm for 5 min to obtain a mixed solution C;

[0091] (4) adding the crosslinking agent into the mixed solution C, stirring at a stirring speed of 300 rpm for 5 min to obtain a mixed solution D; then adding the initiator, stirring at a stirring speed of 300 rpm for 5 min to disperse uniformly, and curing at 130°C for 16 h under acidic conditions to obtain the resin-strengthened gel plugging agent A3.

[0092] Example 4

[0093] A resin-strengthened gel plugging agent A4 includes the following raw materials in the following mass percentages: the water-soluble resin solution is used in an amount of 8%, the polymer monomer is used in an amount of 20%, the rheological modifier is used in an amount of 1%, the crosslinking agent is used in an amount of 0.2%, the initiator is used in an amount of 0.02%, and the balance is water, and the total content of each component is 100%.

[0094] 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;

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

[0096] The crosslinking agent is a combination of N-methylol acrylamide and N,N'-methylene bisacrylamide, and the mass ratio of N-methylol acrylamide to N,N'-methylene bisacrylamide is 1:1;

[0097] The initiator is benzoyl peroxide.

[0098] The preparation method of the resin-strengthened gel plugging agent includes the following steps:

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

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

[0101] (3) Add the rheological modifier into the mixed solution B, and stir at a stirring speed of 400 rpm for 2 min until it is uniformly dispersed to obtain a mixed solution C;

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

[0103] Example 5

[0104] A resin-strengthening gel plugging agent A5 includes the following raw materials in the following mass percentages: the amount of water-soluble resin aqueous solution is 12%, the amount of polymer monomer is 30%, the amount of rheological modifier is 5%, the amount of crosslinking agent is 0.1%, the amount of initiator is 0.02%, and the balance is water, and the total content of each component is 100%.

[0105] 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;

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

[0107] The crosslinking agent is a combination of N-methylol acrylamide and N,N'-methylene bisacrylamide, and the mass ratio of N-methylol acrylamide to N,N'-methylene bisacrylamide is 3:1;

[0108] The initiator is ammonium persulfate.

[0109] The preparation method of the resin-strengthening gel plugging agent is as shown in Example 1, and the resin-strengthening gel plugging agent A5 is obtained by curing at 150℃ for 12 h under acidic conditions.

[0110] Example 6

[0111] A resin-strengthening gel plugging agent A6 includes the following raw materials in the following mass percentages: the amount of water-soluble resin aqueous solution is 10%, the amount of polymer monomer is 15%, the amount of rheological modifier is 2%, the amount of crosslinking agent is 0.6%, the amount of initiator is 0.1%, and the balance is water, and the total content of each component is 100%.

[0112] 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.

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

[0114] The crosslinking agent is a combination of N-methylol acrylamide and N,N'-methylenebisacrylamide, and the mass ratio of N-methylol acrylamide to N,N'-methylenebisacrylamide is 2:1.

[0115] The initiator is potassium persulfate.

[0116] The preparation method of the resin-reinforced gel plugging agent is as shown in Embodiment 1, and the resin-reinforced gel plugging agent A6 is obtained by curing at 150°C for 12h under an acidic condition.

[0117] Embodiment 7

[0118] A resin-reinforced gel plugging agent A7 includes the following raw materials in the following mass percentages: the amount of water-soluble resin aqueous solution is 10%, the amount of polymer monomer is 15%, the amount of rheology modifier is 10%, the amount of crosslinking agent is 0.6%, the amount of initiator is 0.01%, and the balance is water, and the sum of the content of each component is 100%.

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

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

[0121] The crosslinking agent is a combination of N-methylol acrylamide and N,N'-methylenebisacrylamide, and the mass ratio of N-methylol acrylamide to N,N'-methylenebisacrylamide is 2:1.

[0122] The initiator is a combination of benzoyl peroxide and ammonium persulfate.

[0123] The preparation method of the resin-reinforced gel plugging agent is as shown in Embodiment 1, and the resin-reinforced gel plugging agent A7 is obtained by curing at 150°C for 12h under an acidic condition.

[0124] Embodiment 8

[0125] A resin-reinforced gel plugging agent A8 comprises the following raw materials in mass percentage: 10% of water-soluble resin aqueous solution, 15% of polymer monomer, 5% of rheological modifier, 0.6% of crosslinking agent, 0.02% of initiator, and the balance of water, and the total content of the components is 100%.

[0126] 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.

[0127] The rheological modifier is hectorite.

[0128] The crosslinking agent is a combination of N-methylol acrylamide and N,N'-methylenebisacrylamide, and the mass ratio of N-methylol acrylamide to N,N'-methylenebisacrylamide is 2:1.

[0129] The initiator is benzoyl peroxide, ammonium persulfate, or potassium persulfate.

[0130] The resin-reinforced gel plugging agent A8 is prepared according to the method of Example 1, and is cured at 160°C for 12h under acidic conditions.

[0131] Example 9

[0132] A resin-reinforced gel plugging agent A9 comprises the following raw materials in mass percentage: 10% of water-soluble resin aqueous solution, 15% of polymer monomer, 5% of rheological modifier, 0.6% of crosslinking agent, 0.05% of initiator, and the balance of water, and the total content of the components is 100%.

[0133] 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.

[0134] The rheological modifier 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-methylol acrylamide and hexamethylenetetramine, and the mass ratio of N-methylol acrylamide to hexamethylenetetramine is 2:1.

[0136] The initiator is benzoyl peroxide.

[0137] The resin-reinforced gel plugging agent A9 is prepared according to the method of Example 1, and is cured at 180°C for 10h under acidic conditions.

[0138] Comparative Example 1

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

[0140] The amount of the water-soluble resin in this comparative example was too high. A resin-reinforced gel plugging agent B1 was prepared according to the method of Example 1.

[0141] Comparative Example 2

[0142] A resin-reinforced gel plugging agent B2 was prepared according to the method of Example 1, except that the amount of the polymer monomer was 5%, and other conditions were the same as in Example 1.

[0143] The amount of the polymer monomer in this comparative example was too low. A resin-reinforced gel plugging agent B2 was prepared according to the method of Example 1.

[0144] Comparative Example 3

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

[0146] The proportion of acrylamide in the polymer monomer in this comparative example was too low. A resin-reinforced gel plugging agent B3 was prepared according to the method of Example 1.

[0147] Comparative Example 4

[0148] A resin-reinforced gel plugging agent B4 was prepared according to the method of Example 1, except that the amount of the rheology modifier was 15%, and other conditions were the same as in Example 1.

[0149] The amount of the rheology modifier in this comparative example was too high. A resin-reinforced gel plugging agent B4 was prepared according to the method of Example 1.

[0150] Comparative Example 5

[0151] A resin-reinforced gel plugging agent B5 was prepared according to the method of Example 1, except that the mass ratio of hectorite to xanthan gum in the rheology modifier was 1:2, and other conditions were the same as in Example 1.

[0152] The proportion of hectorite in the rheology modifier in this comparative example was too low. A resin-reinforced gel plugging agent B5 was prepared according to the method of Example 1.

[0153] Comparative Example 6

[0154] A resin-reinforced gel plugging agent B6 was prepared according to the method of Example 1, except that the amount of crosslinking agent was 1.5%, and other conditions were the same as in Example 1.

[0155] The amount of crosslinking agent in this comparative example was too high. The resin-reinforced gel plugging agent B6 was prepared according to the method of Example 1.

[0156] Comparative Example 7

[0157] A resin-reinforced gel plugging agent B7 was prepared according to the method of Example 1, except that the mass ratio of N-methylol acrylamide to N,N'-methylenebisacrylamide in the crosslinking agent was 0.5:1, and other conditions were the same as in Example 1.

[0158] The proportion of N-methylol acrylamide in the crosslinking agent in this comparative example was too small. The resin-reinforced gel plugging agent B7 was prepared according to the method of Example 1.

[0159] Comparative Example 8

[0160] A resin-reinforced gel plugging agent B8 was prepared according to the method of Example 1, except that the amount of initiator was 0.3%, and other conditions were the same as in Example 1.

[0161] The amount of initiator in this comparative example was too high. The resin-reinforced gel plugging agent B8 was prepared according to the method of Example 1.

[0162] Comparative Example 9

[0163] A gel plugging agent B9 was prepared according to the method of Example 1, except that no water-soluble resin aqueous solution was added, and other conditions were the same as in Example 1.

[0164] The gel plugging agent B9 was prepared according to the method of Example 1.

[0165] Comparative Example 10

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

[0167] The proportion of acrylamide in the polymer monomer in this comparative example was too high. The resin-reinforced gel plugging agent B10 was prepared according to the method of Example 1.

[0168] Comparative Example 11

[0169] A resin-reinforced gel plugging agent B11 was prepared according to the method of Example 1, except that the crosslinking agent was divinylbenzene, and other conditions were the same as in Example 1.

[0170] The method for preparing the resin-reinforced gel plugging agent was according to Example 1, to obtain the resin-reinforced gel plugging agent B11.

[0171] Comparative Example 12

[0172] A resin-reinforced gel plugging agent B12 was prepared according to the method of Example 1, except that the rheology modifier was sodium alginate, and other conditions were the same as in Example 1.

[0173] The method for preparing the resin-reinforced gel plugging agent was according to Example 1, to obtain the resin-reinforced gel plugging agent B12.

[0174] Comparative Example 13

[0175] A resin-reinforced gel plugging agent B13 was prepared according to the method of Example 1, except that the rheology modifier was polyvinyl alcohol, and other conditions were the same as in Example 1.

[0176] The method for preparing the resin-reinforced gel plugging agent was according to Example 1, to obtain the resin-reinforced gel plugging agent B13.

[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 property test of the cured gel plugging agent: the tensile mechanical property of the resin-reinforced gel plugging agent after gelation was tested using a universal electronic tensile testing machine. The greater the gel fracture stress, the higher the tensile strength of the resin-reinforced gel after curing, and vice versa. Specifically, the gelation conditions of the gel plugging agent were: the gel plugging agent was cured at 150°C for 12h to obtain a gel. The test conditions of the universal electronic tensile testing machine were a tensile rate of 1mm / s, and the results are shown in Table 1.

[0180] Plugging effect of the gel lost-circulation material: The plugging effect of the solidifiable gel lost-circulation material on the fracture is tested by using a high-temperature and high-pressure lost-circulation testing device, which mainly comprises a thermostat 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 fracture width of 3 mm is used to simulate the lost-circulation formation. The specific testing method is as follows: the steel fracture core model is placed in the core holder and the ring pressure is added to 5 MPa; the constant-flow pump is used to inject clean water into the core holder to saturate it, and the temperature inside the thermostat box is heated to 150°C; the prepared resin-strengthened gel lost-circulation material is placed in the intermediate container; the first displacement fluid (700 mPa·s non-ionic polyacrylamide aqueous solution, the injection amount is 50% of the volume of the gel lost-circulation material), the gel lost-circulation material (the injection amount is 100% of the volume of the entire fracture space), and the second displacement fluid (700 mPa·s non-ionic polyacrylamide aqueous solution, the injection amount is 30% of the volume of the gel lost-circulation material) are sequentially injected into the core holder; the both ends of the core holder are sealed, and the lost-circulation material is cured for 12 h; the constant-flow pump is used to inject the drilling fluid for pressurization, and the inlet pressure of the fracture model is recorded in real time. The highest pressure when the drilling fluid leaks from the outlet end of the fracture model is taken as the highest plugging pressure of the gel to the fracture. The drilling fluid base slurry is continuously injected into the fracture model, and the pressure value when linear leakage occurs at the outlet end of the fracture model is recorded as the plugging failure pressure, which is used as an index for evaluating the plugging performance of the gel lost-circulation material after plugging failure. The testing temperature is 150°C, and the results are shown in Table 1.

[0181] Table 1 Mechanical mechanical properties and high-temperature fracture plugging effect test data of the cured gel lost-circulation material

[0182]

[0183] As can be seen from the data in Table 1, the maximum tensile fracture stress of the resin-strengthened gel of Example 1 of the present application after curing is 354 KPa, indicating that the resin-strengthened gel of the present application 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 application has excellent high-temperature pressure-bearing plugging capacity; the maximum tensile fracture stress of the resin-strengthened gel of Example 2 of the present application after curing is 267 KPa, indicating that the resin-strengthened gel of the present application 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 application has excellent high-temperature pressure-bearing plugging capacity; the maximum tensile fracture stress of the resin-strengthened gel of Example 3 of the present application after curing is 284 KPa, indicating that the resin-strengthened gel of the present application has high structural strength and excellent mechanical properties, and the maximum pressure-bearing capacity is 6.68 MPa, indicating that the gel plugging agent of the present application has excellent high-temperature pressure-bearing plugging capacity; the maximum tensile fracture stress of the resin-strengthened gel of Example 4 of the present application after curing is 291 KPa, indicating that the resin-strengthened gel of the present application has high structural strength and excellent mechanical properties, and the maximum pressure-bearing capacity is 6.71 MPa, indicating that the gel plugging agent of the present application has excellent high-temperature pressure-bearing plugging capacity; the maximum tensile fracture stress of the resin-strengthened gel of Example 5 of the present application after curing is 244 KPa, indicating that the resin-strengthened gel of the present application has high structural strength and excellent mechanical properties, and the maximum pressure-bearing capacity is 5.84 MPa, indicating that the gel plugging agent of the present application has excellent high-temperature pressure-bearing plugging capacity; the maximum tensile fracture stress of the resin-strengthened gel of Example 6 of the present application after curing is 232 KPa, indicating that the resin-strengthened gel of the present application has high structural strength and excellent mechanical properties, and the maximum pressure-bearing capacity is 5.36 MPa, indicating that the gel plugging agent of the present application has excellent high-temperature pressure-bearing plugging capacity; the test data of Examples 2-6 compared with Example 1 show that when the amounts of the water-soluble resin aqueous solution, the polymer monomer, the rheological modifier, the crosslinking agent and the initiator are not within the optimal concentration range, the mechanical properties after curing and the crack plugging effect at high temperature are slightly reduced, but still remain at a high level; the maximum tensile fracture stress of the resin-strengthened gel of Example 7 of the present application after curing is 253 KPa, indicating that the resin-strengthened gel of the present application 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 application has excellent high-temperature pressure-bearing plugging capacity; the maximum tensile fracture stress of the resin-strengthened gel of Example 8 of the present application after curing is 302 KPa, indicating that the resin-strengthened gel of the present application has high structural strength and excellent mechanical properties, and the maximum pressure-bearing capacity is 6.83MPa, which shows that the gel plugging agent of the present application has excellent high-temperature pressure-bearing plugging capacity; the maximum tensile fracture stress of the resin-strengthened gel after curing in Example 9 is 231KPa, which shows that the resin-strengthened gel of the present application has high structural strength and excellent mechanical properties, and the maximum pressure-bearing capacity is 5.29MPa, which shows that the gel plugging agent of the present application has excellent high-temperature pressure-bearing plugging capacity; the test data results of Examples 7-9 compared with Example 1 show that when the types of polymer monomers, rheological control agents and crosslinking agents are not the optimal scheme, the mechanical properties after curing and the crack plugging effect at high temperature are slightly reduced, but still remain at a high level.

[0184] Comparative Example 1-13 does not adopt the technical scheme of the present application, so the maximum tensile fracture stress is lower than that of Example 1-9, the pressure capacity and the pressure value at plugging failure are also lower than those of Example 1-9. Specifically, Comparative Example 1 adds an excessive amount of water-soluble resin, at this time, except for a small part of the resin which can be crosslinked with the gel network, more resin will be cured at high temperature, but due to the steric hindrance effect of the gel network, the resin is not easy to cure, and the structure of the partially cured resin is also very loose, so the performance of the obtained plugging agent is poor; Comparative Example 9 does not add water-soluble resin, so the system lacks the three-dimensional network reinforced by the resin, and the mechanical properties and pressure plugging capacity of the material are greatly reduced. Comparative Example 2 adds too little amount of polymer monomer, and due to the steric hindrance effect of the gel network, the formed structure is relatively loose; Comparative Example 3 has too low proportion of acrylamide in the polymer monomer, and too little acrylamide can only be crosslinked with part of the resin, and the three-dimensional network structure formed by crosslinking will also produce steric hindrance to the curing of the resin itself, resulting in performance decline; Comparative Example 10 has too high proportion of acrylamide in the polymer monomer, and the increase of the polyacrylamide segment which is not fully crosslinked in the system after curing increases the looseness of the three-dimensional network structure, and the mechanical properties of the material after curing are reduced, and the pressure plugging capacity is reduced. In Comparative Example 4, an excessive amount of rheological modifier is added, which will lock the water in the system, resulting in insufficient crosslinking of the polymer monomer and the water-soluble resin, and poor flowability of the system before curing, which is not easy to fill the crack space and is easy to produce air holes, resulting in reduced pressure capacity; Comparative Example 5 has too low proportion of hectorite in the rheological modifier, and the increase of free-flowing water in the system reduces the compactness of the formed gel network, resulting in reduced maximum tensile fracture stress of the material, and the anti-pollution property of the system before curing is poor, and other liquids are easy to enter the crack space, resulting in poor filling effect after curing and reduced pressure capacity; Comparative Example 12 selects sodium alginate as the rheological modifier, which cannot form the "card house" network structure of hectorite in aqueous solution, and the compactness of the formed gel network after curing is reduced, resulting in reduced maximum tensile fracture stress of the material, and the thickening effect is obviously reduced compared with hectorite at the same amount, resulting in easy pollution of the system before curing by other fluids, poor filling effect after curing, and reduced pressure capacity; Comparative Example 13 selects polyvinyl alcohol as the rheological modifier, and the viscosity of its aqueous solution will increase with time, which will increase the difficulty of on-site construction, and at the same time, due to the presence of a large number of hydroxyl groups, hydrogen bonds can be formed at low temperature to play a rheological control role, but at high temperature (150℃), dehydration etherification is easy to occur, thereby losing solubility, and further affecting the strength of the gel structure after curing, and the pressure plugging capacity is also obviously reduced.Comparative Example 6: due to the excessive amount of crosslinking agent, the crosslinking between the polymer monomer is more closely, so that only a small amount of water-soluble resin can be crosslinked on the gel network, the rest of the resin is 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; Comparative Example 7: due to the small proportion of N-methylol acrylamide in the crosslinking agent, the active hydroxyl group that can dehydrate and condense with a large number of amino groups in the polymer monomer is less, and the three-dimensional network structure formed is not dense enough, and the material performance is macroscopically reduced; Comparative Example 11: due to other types of crosslinking agents, which cannot provide active hydroxyl sites that can be crosslinked, the three-dimensional network structure formed is not dense enough, and the mechanical properties and pressure bearing and plugging capacity of the material are reduced; Comparative Example 8: due to the excessive amount of initiator, which can cause explosive polymerization, resulting in an increase in the number of pores in the material, and the mechanical properties and pressure bearing and plugging capacity are greatly reduced.

[0185] As can be seen from the above, the resin reinforced gel plugging agent prepared in the embodiments of the present application has high structural strength, thereby having excellent tensile mechanical properties, and the gel plugging agent prepared in the present application has high maximum sealing pressure at 150℃ after curing, which indicates that the gel plugging agent of the present application has excellent high-temperature pressure bearing and plugging capacity. The above data shows that the gel plugging agent of the present application has the advantages of high temperature resistance and high strength, and has important research value in solving the wellbore leakage problem of high-temperature deep fracture formation.

[0186] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

Claims

1. A resin-reinforced gel sealant, characterized in that, The following raw materials by mass percentage are cured at high temperature under acidic conditions to obtain a resin-reinforced gel sealant: 5%-15% water-soluble resin aqueous solution, 10%-30% polymer monomer, 1%-10% rheology modifier, 0.1%-1% crosslinking agent, 0.01%-0.1% initiator, and the balance being water. The water-soluble resin in the water-soluble resin aqueous solution is a partially methylated melamine resin. The polymer monomers are a combination of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid in a mass ratio of 1-2.5:1; The rheology modifier is a combination of lithium saponite and xanthan gum in a mass ratio of 1:0.5-1.

5. The lithium saponite is a nanoscale sheet-like lithium saponite with a positive charge on the crystal surface and a negative charge on the crystal edge. The weight-average molecular weight of xanthan gum is 2 million to 4 million. The crosslinking agent is a combination of N-hydroxymethylacrylamide and N,N'-methylenebisacrylamide in a mass ratio of 1:1, 2:1, or 3:

1.

2. The resin-reinforced gel sealant according to claim 1, characterized in that, The partially methylated melamine resin has the following structure: 。 3. The resin-reinforced gel sealant 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.

4. A method for preparing a resin-reinforced gel sealing agent according to any one of claims 1 to 3, characterized in that, The specific steps are as follows: S1 Add the water-soluble resin aqueous solution to water and stir until homogeneous to obtain mixture A; S2 Add the polymer monomer to mixture A and stir until homogeneous to obtain mixture B; S3 adds the rheology modifier to mixture B and stirs it evenly to obtain mixture C; S4 adds the crosslinking agent to mixture C and stirs it evenly to obtain mixture D; then adds the initiator, stirs it evenly, and cures it at high temperature under acidic conditions to obtain the resin-reinforced gel sealant.

5. The preparation method of the resin-reinforced gel sealing agent according to claim 4, characterized in that, In S1, the stirring speed is 600 rpm - 1000 rpm, and the stirring time is 10 min - 30 min; In S2, the stirring speed is 200 rpm - 400 rpm, and the stirring time is 10 min - 30 min; In S3, the stirring speed is 200 rpm - 400 rpm, and the stirring time is 2 min - 10 min; In S4, the stirring speed is 200 rpm to 400 rpm, and the stirring time is 2 min to 10 min.

6. The method for preparing a resin-reinforced gel sealing agent according to claim 4, characterized in that, In S4, the curing temperature is 120℃-180℃, and the curing time is 10 h-24 h.

7. The application of the resin-reinforced gel plugging agent according to any one of claims 1 to 3 or the resin-reinforced gel plugging agent prepared by the preparation method according to any one of claims 4 to 6 as a plugging agent for severe leakage in fractured formations, characterized in that, The specific steps of the application are as follows: inject the first displacement fluid, the resin-reinforced gel plugging agent, and the second displacement fluid sequentially into the fractured formation. 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 ≥500 mPa·s.

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