Cross-linking agent for gelation as well as preparation method and application of cross-linking agent

Abstract

The invention discloses a cross-linking agent for gelation as well as a preparation method and application thereof, and relates to the technical field of working solutions for petroleum engineering, the cross-linking agent for gelation comprises the following components in percentage by mass: 10%-30% of multi-benzene-ring-containing long-chain polyboric acid, 5%-10% of polyethylene glycol, 4%-8% of alkali, 10%-25% of auxiliary ligand and the balance of water. The long-chain polyborate with a large steric hindrance structure is used for preparing the organic boron cross-linking agent, and the multi-head organic boron cross-linking agent with a long molecular chain is prepared through complex reaction of polyhydric alcohol, polymeric alcohol and the long-chain polyborate. According to the cross-linking agent which takes long-chain polyboronic acid containing multiple benzene rings as a main chain segment, at least one boron ion is linked on different benzene rings and comprehensively shows a macromolecular and multi-boron ion structure, not only can the concentration of vegetable gum cross-linked with the cross-linking agent be greatly reduced, but also the strength of formed gel is higher due to multi-point cross-linking in space.

Description

Technical Field

[0001] The present invention relates to the technical field of working fluids for petroleum engineering, and in particular to a cross-linking agent for gelation, a preparation method and application thereof. Background Art

[0002] Cross-linking agents are widely used in a variety of fields, including fracturing fluids, acid solutions, profile control and water plugging agents, and temporary plugging and well-killing gels. Commonly used cross-linking agents include soluble borates, zirconium salts, titanium salts, and aluminum salts. The ionized boron ions, zirconium ions, titanium ions, and aluminum ions (commonly referred to as central ions) react with plant gums, polymers, and the like to form a spatial network structure, achieving a surge in liquid viscosity and meeting the performance requirements of various application areas. In order to delay the cross-linking time, polyhydroxy alcohols are usually used as ligands to react with soluble borates, zirconium salts, titanium salts, and aluminum salts to obtain soluble organic borates, organic zirconium salts, organic titanium salts, and organic aluminum salts as organic cross-linking agents. However, the essence of cross-linking is still the cross-linking reaction between the central ions ionized by the cross-linking agent and plant gums, polymers, and the like. Due to the influence of spatial distance, plant gums and polymers must reach a certain concentration before they can cross-link with the central ions ionized by the cross-linking agent. However, higher concentrations of plant gums and polymers not only increase the application cost, but also make the preparation process more complicated (high-molecular substances such as plant gums and polymers are prone to produce "fish eyes" when prepared at high concentrations). In addition, subsequent gel breaking is more difficult, and a large amount of residue is produced after gel breaking, which affects the subsequent oil and gas production process.

[0003] Patent CN202211151698.8 discloses a method for preparing a crosslinker for low-concentration, heat-resistant, and shear-resistant guar gum. The method uses ethylene glycol and n-butanol as ligands, reacts with boric acid to obtain a complex, and then undergoes an acid-base neutralization reaction with m-xylenediamine at high temperature to graft boron ions onto both sides of the m-xylenediamine. Finally, dipentaerythritol and sodium hydroxide are added to react at high temperature to obtain an amino borate crosslinker. Compared to conventional crosslinkers, the boron ions are located on both sides of the amine group of m-xylenediamine, which increases the chain length of the crosslinker, allowing it to crosslink guar gum (a plant gum) at lower concentrations.

[0004] Patent CN202111438161.5 discloses a crosslinker for ultra-low concentration plant-based glue fracturing fluids, its synthesis process, and its application. Deionized water and sodium hydroxide are first mixed and heated for reaction. Borax, glucose, glyoxal, and sorbitol are then added in sequence and heated in a sealed manner. After a certain reaction time, the crosslinker is cooled to obtain the crosslinker. In essence, it is still a conventional organoboron crosslinker, using a variety of polyhydroxy alcohols as ligands. Ultimately, the crosslinking effect is still achieved by the boron ions finally ionized by the borax, and the molecular chain length of the crosslinker is not increased.

[0005] Patent CN201811310367.8 provides a low-concentration hydroxypropyl guar gum fracturing fluid and preparation method, in which the nano-silica organoboron crosslinker is nano-silica with organic boronic acid groups on its surface. The nano-silica is dispersed in a polar organic solvent, a silane coupling agent is added for reflux reaction, and the polar organic solvent is removed to obtain nano-silica with amino groups on its surface; the nano-silica with amino groups on its surface is dispersed in a polar organic solvent, and formaldehyde phenylboronic acid is added for reaction to obtain a dispersion of nano-silica with phenylboronic acid groups on its surface modified with aldimine groups; sodium borohydride is added to the dispersion to generate the nano-silica organoboron crosslinker. The essence of this crosslinker is that phenylboronic acid groups are grafted onto the nano-silica using nano-silica as a carrier, and it appears as a crosslinker with a longer structure.

[0006] The current cross-linking agents have the following problems:

[0007] 1) The chain length of the cross-linking agent suitable for low-concentration plant gum in the prior art is relatively short, so that a higher plant gum concentration is still required during cross-linking;

[0008] 2) The chain length of nano-silica crosslinkers containing phenylboronic acid groups in the prior art has increased to a certain extent. However, since the phenylboronic acid groups are covalently bonded to the nano-silica through amino groups, they do not truly form a long-chain molecule. They are easily broken under high temperature and high shear conditions, resulting in poor high-temperature shear resistance of the crosslinked gel.

[0009] 3) In the prior art, only single-point central ions or double-point central ions on a plane are cross-linked with plant gums, and the cross-linking strength is weak. There is a lack of spatial multi-point central ions and plant gums that are cross-linked to form a spatial network structure. Summary of the Invention

[0010] Based on the problems existing in the background technology, the purpose of the present invention is to provide a cross-linking agent for gelation, a preparation method and application thereof, which uses a long-chain polyboric acid containing multiple benzene rings as the main segment, and has at least one boron ion linked to different benzene rings. The cross-linking agent comprehensively exhibits a macromolecular and polyboron ion structure, which can not only significantly reduce the concentration of the plant gum cross-linked with it, but also has a higher gel strength due to the multi-point cross-linking in space.

[0011] The present invention is achieved through the following technical solutions:

[0012] In the first aspect, the present application provides a cross-linking agent for gelation, which comprises the following components, calculated by mass percentage: 10% to 30% of long-chain polyboric acid containing multiple benzene rings, 5% to 10% of polyethylene glycol, 4% to 8% of a base, 10% to 25% of a co-ligand, and the remainder is water.

[0013] The polyethylene glycol is any one of polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600.

[0014] The alkali is any one of sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0015] The auxiliary ligand is any one of sorbitol, glycerol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, diethylene glycol acetal, and triethylene glycol.

[0016] Long-chain polyborates with large steric hindrance structures are used in the preparation of organoboron crosslinkers. Through complexation reactions with polyols and polymeric alcohols, long-chain multi-head organoboron crosslinkers are prepared. The polyborates used are long-chain polyboric acids containing benzene rings. The larger steric hindrance of the benzene rings allows the multi-headed "boric acid" groups to be more stretched, while the intermediate chain segments connecting the multi-headed "boric acids" are longer. This allows the multi-headed organoboron crosslinker to form a macromolecular chain after complexation with polyols and polymeric alcohols. This can significantly reduce the concentration of the thickener being crosslinked, relying on the macromolecular chain multi-headed crosslinker to crosslink with the low-concentration thickener. Using long-chain polyboric acids containing multiple benzene rings as the main chain segment and at least one boron ion attached to different benzene rings, the crosslinker exhibits a comprehensive macromolecular, multi-boron ion structure. This crosslinker can not only significantly reduce the concentration of the plant gum it is crosslinked with, but also, due to the multi-point crosslinking in space, the resulting gel is stronger. At the same time, the introduction of polyethylene glycol into the crosslinker system has a complexing effect with the long-chain polyisocyanate containing benzene rings, which can, to a certain extent, make the crosslinker into a more complex complex with longer chain segments, further reducing the concentration of the plant gum crosslinked with it. In addition, the use of some polyhydroxy alcohols as auxiliary ligands further delays the gelation time.

[0017] Furthermore, the general structural formula of the polyboric acid containing multiple benzene rings is:

[0018]

[0019] Wherein, X includes O or (CH2) z , z is 1 to 3; at least one of m1, m2, m3, m4, and m5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes;

[0020] At least one of n1, n2, n3, n4, and n5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes.

[0021] 4,4'-Oxybis(1,4-phenylene)diboronic acid is preferred.

[0022] Furthermore, the general structural formula of the polyboric acid containing multiple benzene rings is:

[0023]

[0024] Among them, at least one of m1, m2, m3, m4, and m5 is HO—B—OH, where B is connected to the benzene ring, and the others are H or alkanes;

[0025] At least one of n1, n2, n3, n4, and n5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes.

[0026] 4,4'-Biphenyldiboronic acid is preferred.

[0027] Furthermore, the general structural formula of the polyboric acid containing multiple benzene rings is:

[0028]

[0029] Among them, at least one of m1, m2, m3, m4, and m5 is HO—B—OH, where B is connected to the benzene ring, and the others are H or alkanes;

[0030] At least one of n1, n2, n3, n4, and n5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes.

[0031] Dibenzothiophene-4,6-diboric acid and dibenzothiophene-2,8-diboric acid are preferred.

[0032] Furthermore, the general structural formula of the polyboric acid containing multiple benzene rings is:

[0033]

[0034] Among them, at least one of m1, m2, m3, m4, and m5 is HO—B—OH, where B is connected to the benzene ring, and the others are H or alkanes;

[0035] At least one of n1, n2, n3, n4, and n5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes.

[0036] 9,9-Dimethyl-2,7-fluorenediboronic acid is preferred.

[0037] Furthermore, the general structural formula of the polyboric acid containing multiple benzene rings is:

[0038]

[0039] Wherein, X, Y, and Z are O or (CH2) w One of , w is 1-3;

[0040] At least one of m1, m2, m3, m4, and m5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes;

[0041] At least one of n1, n2, n3, n4, and n5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes;

[0042] At least one of R1, R2, R3, R4, and R5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes.

[0043] Furthermore, the polyethylene glycol is at least one of polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600.

[0044] Furthermore, the base is at least one of sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0045] Furthermore, the auxiliary ligand is at least one of sorbitol, glycerol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, diethylene glycol acetal, and triethylene glycol.

[0046] Furthermore, the general structural formula of the polyboric acid containing multiple benzene rings is:

[0047]

[0048] Among them, at least one of m1, m2, m3, m4, and m5 is HO—B—OH, where B is connected to the benzene ring, and the others are H or alkanes;

[0049] At least one of n1, n2, n3, n4, and n5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes;

[0050] At least one of R1, R2, R3, R4, and R5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes.

[0051] Triphenylamine-4,4',4"-triboric acid is preferred.

[0052] In a second aspect, the present application provides a method for preparing a cross-linking agent for gelation, comprising the following steps:

[0053] S1: Add 20%-25% of water to the total amount of the crosslinking agent for gelation into the reactor, and add alkali under stirring according to the formula ratio to dissolve evenly;

[0054] S2: Add long-chain polyboric acid containing multiple benzene rings into the reactor under stirring according to the formula ratio and dissolve evenly;

[0055] S3: Add polyethylene glycol, co-ligand and remaining water to the reactor under stirring according to the formula ratio and dissolve them evenly;

[0056] S4: raising the temperature in the reactor, reacting for 4-6 hours under stirring, stopping the reaction, and cooling to room temperature to obtain the cross-linking agent for gelation.

[0057] Furthermore, the reaction temperature in step S4 is 70°C to 90°C.

[0058] In a third aspect, the present application provides an application of the above-mentioned gelation cross-linking agent or the gelation cross-linking agent prepared by the above-mentioned preparation method, including use in preparing fracturing fluid, acid fluid, profile control and water plugging agent, and temporary plugging and well killing gel.

[0059] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0060] (1) Under extremely low plant gum concentration conditions, the crosslinking agent of the present invention can form a gel with the plant gum, and the minimum concentration of the crosslinkable plant gum is 0.12%;

[0061] (2) Under the condition of 0.15% plant gum concentration, the crosslinking agent of the present invention forms a gel with the plant gum at 70°C and 100°C. -1 The viscosity after shearing for 1 hour under shear rate conditions is ≥50mPa·s;

[0062] (3) Under the condition of 0.25% plant gum concentration, the crosslinking agent of the present invention forms a gel with the plant gum at 120°C and 100 -1 The viscosity after shearing for 1 hour under shear rate conditions is ≥50mPa·s. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the examples. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can also derive other relevant drawings based on these drawings without inventive effort. In the drawings:

[0064] Figure 1 This is the heat and shear resistance curve of 0.15% (w) hydroxypropyl guar gum + 0.25% (v) cross-linking agent in Example 1 of the present invention;

[0065] Figure 2 This is the heat and shear resistance curve of 0.25% (w) hydroxypropyl guar gum + 0.3% (v) cross-linking agent in Example 1 of the present invention;

[0066] Figure 3 This is the heat and shear resistance curve of 0.15% (w) hydroxypropyl guar gum + 0.25% (v) cross-linking agent in Example 4 of the present invention;

[0067] Figure 4This is the heat and shear resistance curve of 0.25% (w) hydroxypropyl guar gum + 0.3% (v) cross-linking agent in Example 4 of the present invention;

[0068] Figure 5 This is the heat and shear resistance curve of 0.15% (w) hydroxypropyl guar gum + 0.25% (v) cross-linking agent in Example 7 of the present invention;

[0069] Figure 6 This is the heat and shear resistance curve of 0.25% (w) hydroxypropyl guar gum + 0.3% (v) cross-linking agent in Example 7 of the present invention;

[0070] Figure 7 This is the heat and shear resistance curve of 0.15% (w) hydroxypropyl guar gum + 0.25% (v) cross-linking agent in Example 10 of the present invention;

[0071] Figure 8 This is the heat and shear resistance curve of 0.25% (w) hydroxypropyl guar gum + 0.3% (v) cross-linking agent in Example 10 of the present invention;

[0072] Figure 9 This is the heat and shear resistance curve of 0.25% (w) hydroxypropyl guar gum + 0.3% (v) cross-linking agent in Comparative Example 8. DETAILED DESCRIPTION

[0073] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0074] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0075] Example 1

[0076] This embodiment provides a cross-linking agent for gelation, the formula of which is: 12% 4,4'-biphenyldiboronic acid, 6% polyethylene glycol 600, 4.5% sodium hydroxide, 12% sorbitol and 65.5% water.

[0077] The preparation method of the cross-linking agent for gelation is as follows:

[0078] S1: Add 200g of water to the reactor, add 45g of sodium hydroxide under stirring at 150rpm, and continue stirring for 10 minutes to dissolve evenly;

[0079] S2: Add 120 g of 4,4'-biphenyldiboronic acid to the above reaction kettle under stirring at 150 rpm and continue stirring for 10 minutes until it is evenly dissolved;

[0080] S3: Under stirring conditions of 150 rpm, 60 g of polyethylene glycol 600, 120 g of sorbitol and the remaining 455 g of water were added to the above reactor in sequence and stirred for 10 minutes until the mixture was evenly dissolved;

[0081] S4: The reactor was heated to 70° C. and stirred at 150 rpm for 4 hours. The reaction was stopped and cooled to room temperature to obtain a cross-linking agent for gelation.

[0082] Example 2

[0083] This embodiment provides a cross-linking agent for gelation, the formula of which is: 28% 4,4'-biphenyldiboronic acid, 9% polyethylene glycol 200, 7.5% potassium hydroxide, 22% triethylene glycol and 33.5% water.

[0084] The preparation method of the cross-linking agent for gelation is as follows:

[0085] S1: Add 250g of water to the reactor, add 75g of potassium hydroxide under stirring at 100rpm, and continue stirring for 10 minutes to dissolve evenly;

[0086] S2: Add 280 g of 4,4'-biphenyldiboronic acid to the above reaction kettle under stirring at 100 rpm and continue stirring for 10 minutes until it is evenly dissolved;

[0087] S3: Under stirring at 100 rpm, 90 g of polyethylene glycol 200, 220 g of triethylene glycol and the remaining 85 g of water were added to the above reaction kettle in sequence and stirred for 10 minutes until the mixture was evenly dissolved.

[0088] S4: The reactor was heated to 90° C. and stirred at 100 rpm for 6 hours. The reaction was stopped and cooled to room temperature to obtain a cross-linking agent for gelation.

[0089] Example 3

[0090] This embodiment provides a cross-linking agent for gelation, the formula of which is: 20% 4,4'-oxybis(1,4-phenylene)diboronic acid, 8% polyethylene glycol 400, 6% sodium carbonate, 18% glycerol and 48% water.

[0091] The preparation method of the cross-linking agent for gelation is as follows:

[0092] S1: Add 250g of water to the reactor, add 60g of sodium carbonate under stirring at 150rpm, and continue stirring for 10 minutes to dissolve evenly;

[0093] S2: Add 200 g of 4,4'-oxybis(1,4-phenylene)diboronic acid to the above reaction kettle under stirring at 150 rpm and continue stirring for 10 minutes until the mixture is evenly dissolved.

[0094] S3: Add 80 g of polyethylene glycol 400, 180 g of glycerol and the remaining 230 g of water to the above reaction kettle under stirring at 150 rpm, and continue stirring for 10 minutes to dissolve evenly;

[0095] S4: The reactor was heated to 85° C. and stirred at 150 rpm for 5 hours. The reaction was stopped and cooled to room temperature to obtain a cross-linking agent for gelation.

[0096] Example 4

[0097] This embodiment provides a cross-linking agent for gelation, the formula of which is: 16% dibenzothiophene-4,6-diboric acid, 3% polyethylene glycol 200, 3% polyethylene glycol 600, 2% sodium hydroxide, 2.5% potassium hydroxide, 12% ethylene glycol, and 61.5% water.

[0098] The preparation method of the cross-linking agent for gelation is as follows:

[0099] S1: Add 220g of water to the reactor, add 20g of sodium hydroxide and 25g of potassium hydroxide in sequence under stirring at 150rpm, and continue stirring for 10 minutes to dissolve evenly;

[0100] S2: Add 160 g of dibenzothiophene-4,6-diboric acid to the above reaction kettle under stirring at 150 rpm and continue stirring for 10 minutes until it is evenly dissolved;

[0101] S3: Under stirring at 150 rpm, 30 g of polyethylene glycol 200, 30 g of polyethylene glycol 600, 120 g of ethylene glycol and the remaining 395 g of water were added to the above reaction kettle in sequence and stirred for 10 minutes until the mixture was evenly dissolved.

[0102] S4: The reactor was heated to 75° C., stirred at 150 rpm for 4.5 hours, the reaction was stopped, and the mixture was cooled to room temperature to obtain a cross-linking agent for gelation.

[0103] Example 5

[0104] This embodiment provides a cross-linking agent for gelation, the formula of which is: 28% dibenzothiophene-4,6-diboric acid, 9% polyethylene glycol 400, 3.5% potassium hydroxide, 4% sodium carbonate, 22% 1,2-propylene glycol, and 33.5% water.

[0105] The preparation method of the cross-linking agent for gelation is as follows:

[0106] S1: Add 250g of water to the reactor, add 35g of potassium hydroxide and 40g of sodium carbonate in sequence under stirring at 150rpm, and continue stirring for 10 minutes to dissolve evenly;

[0107] S2: Add 280 g of dibenzothiophene-4,6-diboric acid to the above reaction kettle under stirring at 150 rpm and continue stirring for 10 minutes until it is evenly dissolved;

[0108] S3: Under stirring conditions of 150 rpm, 90 g of polyethylene glycol 400, 220 g of 1,2-propylene glycol and the remaining 85 g of water were added to the above reactor in sequence, and stirring was continued for 10 minutes to dissolve evenly;

[0109] S4: The reactor was heated to 85° C. and reacted for 5.5 hours under a stirring condition of 150 rpm. The reaction was stopped and cooled to room temperature to obtain a cross-linking agent for gelation.

[0110] Example 6

[0111] This embodiment provides a cross-linking agent for gelation, whose formula is: 20% dibenzothiophene-2,8-diboric acid, 3% polyethylene glycol 200, 3% polyethylene glycol 400, 2% polyethylene glycol 600, 3% sodium hydroxide, 3% sodium carbonate, 9% 1,4-butanediol, 9% 1,2-propylene glycol, and 48% water.

[0112] The preparation method of the cross-linking agent for gelation is as follows:

[0113] S1: Add 230g of water to the reactor, add 30g of sodium hydroxide and 30g of sodium carbonate in sequence under stirring at 120rpm, and continue stirring for 10 minutes to dissolve evenly;

[0114] S2: Add 200 g of dibenzothiophene-2,8-diboric acid to the above reaction kettle under stirring at 120 rpm and continue stirring for 10 minutes until it is evenly dissolved;

[0115] S3: Under stirring conditions of 120 rpm, 30 g of polyethylene glycol 200, 30 g of polyethylene glycol 400, 20 g of polyethylene glycol 600, 90 g of 1,4-butanediol, 90 g of 1,2-propylene glycol and the remaining 250 g of water were added to the above reactor in sequence, and stirring was continued for 10 minutes to dissolve evenly;

[0116] S4: The reactor was heated to 80° C. and reacted for 5.5 hours under a stirring condition of 120 rpm. The reaction was stopped and cooled to room temperature to obtain a cross-linking agent for gelation.

[0117] Example 7

[0118] This embodiment provides a cross-linking agent for gelation, the formula of which is: 12% 9,9-dimethyl-2,7-fluorenediboric acid, 6% polyethylene glycol 600, 5% sodium hydroxide, 15% diethylene glycol acetal, and 62% water.

[0119] The preparation method of the cross-linking agent for gelation is as follows:

[0120] S1: Add 250g of water to the reactor, add 50g of sodium hydroxide under stirring at 150rpm, and continue stirring for 10 minutes to dissolve evenly;

[0121] S2: Add 120 g of 9,9-dimethyl-2,7-fluorenediboric acid to the above reaction kettle under stirring at 150 rpm and continue stirring for 10 minutes until the mixture is evenly dissolved.

[0122] S3: Under stirring conditions of 150 rpm, 60 g of polyethylene glycol 600, 150 g of diethylene glycol acetal and the remaining 370 g of water were added to the above reactor in sequence, and stirring was continued for 10 minutes to dissolve evenly;

[0123] S4: The reactor was heated to 75° C. and stirred at 150 rpm for 5 hours. The reaction was stopped and the mixture was cooled to room temperature to obtain a cross-linking agent for gelation.

[0124] Example 8

[0125] This embodiment provides a cross-linking agent for gelation, the formula of which is: 30% 9,9-dimethyl-2,7-fluorenediboric acid, 8% polyethylene glycol 200, 8% sodium carbonate, 25% triethylene glycol, and 29% water.

[0126] The preparation method of the cross-linking agent for gelation is as follows:

[0127] S1: Add 230g of water to the reactor, add 80g of sodium carbonate under stirring at 100rpm, and continue stirring for 10 minutes to dissolve evenly;

[0128] S2: Add 300 g of 9,9-dimethyl-2,7-fluorenediboric acid to the above reaction kettle under stirring at 100 rpm and continue stirring for 10 minutes until it is evenly dissolved;

[0129] S3: Under stirring conditions of 100 rpm, 80 g of polyethylene glycol 200, 250 g of triethylene glycol and the remaining 60 g of water were added to the above reaction kettle in sequence, and stirring was continued for 10 minutes to dissolve evenly;

[0130] S4: The reactor was heated to 70° C. and stirred at 100 rpm for 5 hours. The reaction was stopped and cooled to room temperature to obtain a cross-linking agent for gelation.

[0131] Example 9

[0132] This embodiment provides a cross-linking agent for gelation, the formula of which is: 25% 9,9-dimethyl-2,7-fluorenediboric acid, 10% polyethylene glycol 400, 5% potassium hydroxide, 13% sorbitol, and 47% water.

[0133] The preparation method of the cross-linking agent for gelation is as follows:

[0134] S1: Add 200g of water to the reactor, add 50g of potassium hydroxide under stirring at 120rpm, and continue stirring for 10 minutes to dissolve evenly;

[0135] S2: Add 250 g of 9,9-dimethyl-2,7-fluorenediboric acid to the above reaction kettle under stirring at 120 rpm and continue stirring for 10 minutes until the mixture is evenly dissolved.

[0136] S3: Under stirring conditions of 120 rpm, 100 g of polyethylene glycol 400, 130 g of sorbitol and the remaining 270 g of water were added to the above reaction kettle in sequence, and stirring was continued for 10 minutes to dissolve evenly;

[0137] S4: The reactor was heated to 85° C. and stirred at 120 rpm for 5 hours. The reaction was stopped and the mixture was cooled to room temperature to obtain a cross-linking agent for gelation.

[0138] Example 10

[0139] This embodiment provides a cross-linking agent for gelation, the formula of which is: 12% triphenylamine-4,4',4"-triboric acid, 4% polyethylene glycol 200, 2% polyethylene glycol 400, 3% sodium hydroxide, 3% sodium carbonate, 10% sorbitol, 12% diethylene glycol ether, and 54% water.

[0140] The preparation method of the cross-linking agent for gelation is as follows:

[0141] S1: Add 240g of water to the reactor, add 30g of sodium hydroxide and 30g of sodium carbonate in sequence under stirring at 100rpm, and continue stirring for 10 minutes to dissolve evenly;

[0142] S2: Add 120 g of triphenylamine-4,4',4"-triboric acid to the above reaction kettle under stirring at 100 rpm and continue stirring for 10 minutes until the mixture is evenly dissolved.

[0143] S3: Under stirring conditions of 100 rpm, 40 g of polyethylene glycol 200, 20 g of polyethylene glycol 400, 100 g of sorbitol, 120 g of diethylene glycol acetal and the remaining 300 g of water were added to the above reactor in sequence, and stirring was continued for 10 minutes to dissolve evenly;

[0144] S4: The reactor was heated to 88° C. and stirred at 100 rpm for 4 hours. The reaction was stopped and cooled to room temperature to obtain a cross-linking agent for gelation.

[0145] Example 11

[0146] This embodiment provides a cross-linking agent for gelation, the formula of which is: 24% triphenylamine-4,4',4"-triboric acid, 7% polyethylene glycol 400, 6% sodium carbonate, 10% ethylene glycol, 8% glycerol and 45% water.

[0147] The preparation method of the cross-linking agent for gelation is as follows:

[0148] S1: Add 230g of water to the reactor, add 60g of sodium carbonate under stirring at 120rpm, and continue stirring for 10 minutes to dissolve evenly;

[0149] S2: Add 240 g of triphenylamine-4,4',4"-triboric acid to the above reaction kettle under stirring at 120 rpm and continue stirring for 10 minutes until it is evenly dissolved;

[0150] S3: Under stirring conditions of 120 rpm, 70 g of polyethylene glycol 400, 100 g of ethylene glycol, 80 g of glycerol and the remaining 220 g of water were added to the above reactor in sequence and stirred for 10 minutes until uniformly dissolved;

[0151] S4: The reactor was heated to 82° C. and stirred at 120 rpm for 6 hours. The reaction was stopped and the mixture was cooled to room temperature to obtain a cross-linking agent for gelation.

[0152] Example 12

[0153] This embodiment provides a gelling crosslinking agent having a formula of: 15% 4,4'-oxybis(1,4-phenylene)diboronic acid, 15% triphenylamine-4,4',4"-triboric acid, 7% polyethylene glycol 600, 8% potassium hydroxide, 22% diethylene glycol acetal, and 33% water.

[0154] Preparation method of the cross-linking agent for gelation:

[0155] S1: Add 250g of water to the reactor, add 80g of potassium hydroxide under stirring at 150rpm, and continue stirring for 10 minutes to dissolve evenly;

[0156] S2: Under stirring conditions of 150 rpm, 150 g of 4,4'-oxybis(1,4-phenylene)diboric acid and 150 g of triphenylamine-4,4',4"-triboric acid were added to the above reaction kettle in sequence, and stirring was continued for 10 minutes until they were evenly dissolved;

[0157] S3: Under stirring conditions of 150 rpm, 70 g of polyethylene glycol 600, 220 g of diethylene glycol acetal and the remaining 80 g of water were added to the above reactor in sequence, and stirring was continued for 10 minutes to dissolve evenly;

[0158] S4: The reactor was heated to 90° C. and stirred at 150 rpm for 6 hours. The reaction was stopped and the mixture was cooled to room temperature to obtain a cross-linking agent for gelation.

[0159] Comparative Example 1

[0160] This comparative example provides a cross-linking agent for gelation, the formula of which is: 20% borax, 25% sorbitol, 8% sodium carbonate and 47% water.

[0161] The preparation method of the cross-linking agent for gelation is as follows:

[0162] S1: Add 250g of water to the reactor, add 80g of sodium carbonate under stirring at 100rpm, and continue stirring for 10 minutes to dissolve evenly;

[0163] S2: Under stirring conditions of 100 rpm, 200 g of borax was added to the above reactor in sequence and stirred for 10 minutes until it was evenly dissolved;

[0164] S3: Under stirring conditions of 100 rpm, 250 g of sorbitol and the remaining 220 g of water were added to the above reactor in sequence, and stirring was continued for 10 minutes to dissolve evenly;

[0165] S4: The reactor was heated to 80° C. and stirred at 100 rpm for 5 hours. The reaction was stopped and the mixture was cooled to room temperature to obtain a cross-linking agent for gelation.

[0166] Comparative Example 2

[0167] This comparative example provides a gelling crosslinking agent. The formula of this crosslinking agent, as compared to Example 1, differs in that 4,4'-biphenyldiboronic acid is replaced with borax, while the rest of the formula remains unchanged. The specific formula is: 12% borax, 6% polyethylene glycol 600, 4.5% sodium hydroxide, 12% sorbitol, and 65.5% water.

[0168] The preparation method of the cross-linking agent for gelation is as follows:

[0169] S1: Add 200g of water to the reactor, add 45g of sodium hydroxide under stirring at 150rpm, and continue stirring for 10 minutes to dissolve evenly;

[0170] S2: Add 120 g of borax to the above reactor under stirring at 150 rpm and continue stirring for 10 minutes until it is evenly dissolved;

[0171] S3: Under stirring conditions of 150 rpm, 60 g of polyethylene glycol 600, 120 g of sorbitol and the remaining 455 g of water were added to the above reactor in sequence and stirred for 10 minutes until the mixture was evenly dissolved;

[0172] S4: The reactor was heated to 70° C. and reacted for 4 hours under a stirring condition of 150 rpm. The reaction was stopped and cooled to room temperature to obtain a cross-linking agent for gelation.

[0173] Comparative Example 3

[0174] This comparative example provides a gelling crosslinking agent. The formula is the same as that of Example 5, except that dibenzothiophene-4,6-diboric acid is replaced with borax. The remaining ingredients remain unchanged. The specific formula is: 28% borax, 9% polyethylene glycol 400, 3.5% potassium hydroxide, 4% sodium carbonate, 22% 1,2-propylene glycol, and 33.5% water.

[0175] The preparation method of the cross-linking agent for gelation is as follows:

[0176] S1: Add 250g of water to the reactor, add 35g of potassium hydroxide and 40g of sodium carbonate in sequence under stirring at 150rpm, and continue stirring for 10 minutes to dissolve evenly;

[0177] S2: Add 280 g of borax to the above reactor under stirring at 150 rpm and continue stirring for 10 minutes until it is evenly dissolved;

[0178] S3: Under stirring conditions of 150 rpm, 90 g of polyethylene glycol 400, 220 g of 1,2-propylene glycol and the remaining 85 g of water were added to the above reactor in sequence, and stirring was continued for 10 minutes to dissolve evenly;

[0179] S4: The reactor was heated to 85° C. and reacted for 5.5 hours under a stirring condition of 150 rpm. The reaction was stopped and cooled to room temperature to obtain a cross-linking agent for gelation.

[0180] Comparative Example 4

[0181] This comparative example provides a gelling crosslinking agent. The formula of this crosslinking agent is similar to that of Example 9, except that 9,9-dimethyl-2,7-fluorenediboric acid is replaced with borax. The remaining ingredients remain unchanged. The specific formula is: 25% borax, 10% polyethylene glycol 400, 5% potassium hydroxide, 13% sorbitol, and 47% water.

[0182] The preparation method of the cross-linking agent for gelation is as follows:

[0183] S1: Add 200g of water to the reactor, add 50g of potassium hydroxide under stirring at 120rpm, and continue stirring for 10 minutes to dissolve evenly;

[0184] S2: Add 250 g of borax to the above reactor under stirring at 120 rpm and continue stirring for 10 minutes until it is evenly dissolved;

[0185] S3: Under stirring conditions of 120 rpm, 100 g of polyethylene glycol 400, 130 g of sorbitol and the remaining 270 g of water were added to the above reaction kettle in sequence, and stirring was continued for 10 minutes to dissolve evenly;

[0186] S4: The reactor was heated to 85° C. and stirred at 120 rpm for 5 hours. The reaction was stopped and the mixture was cooled to room temperature to obtain a cross-linking agent for gelation.

[0187] Comparative Example 5

[0188] This comparative example provides a gelling crosslinking agent. The formula thereof is different from that of Example 11, except that triphenylamine-4,4',4"-triboric acid is replaced with borax, while the rest of the formula remains unchanged. The specific formula is: 24% borax, 7% polyethylene glycol 400, 6% sodium carbonate, 10% ethylene glycol, 8% glycerol, and 45% water.

[0189] The preparation method of the cross-linking agent for gelation is as follows:

[0190] S1: Add 230g of water to the reactor, add 60g of sodium carbonate under stirring at 120rpm, and continue stirring for 10 minutes to dissolve evenly;

[0191] S2: Add 240 g of borax to the above reactor under stirring at 120 rpm and continue stirring for 10 minutes until it is evenly dissolved;

[0192] S3: Under stirring conditions of 120 rpm, 70 g of polyethylene glycol 400, 100 g of ethylene glycol, 80 g of glycerol and the remaining 220 g of water were added to the above reactor in sequence and stirred for 10 minutes until uniformly dissolved;

[0193] S4: The reactor was heated to 82° C. and stirred at 120 rpm for 6 hours. The reaction was stopped and the mixture was cooled to room temperature to obtain a cross-linking agent for gelation.

[0194] Comparative Example 6

[0195] This comparative example provides a gelling crosslinking agent. The formula thereof is different from that of Example 12, except that triphenylamine-4,4',4"-triboric acid is replaced with borax, while the rest of the formula remains unchanged. The specific formula is: 15% 4,4'-oxybis(1,4-phenylene)diboric acid, 15% borax, 7% polyethylene glycol 600, 8% potassium hydroxide, 22% diethylene glycol acetal, and 33% water.

[0196] The preparation method of the cross-linking agent for gelation is as follows:

[0197] S1: Add 250g of water to the reactor, add 80g of potassium hydroxide under stirring at 150rpm, and continue stirring for 10 minutes to dissolve evenly;

[0198] S2: Under stirring conditions of 150 rpm, 150 g of 4,4'-oxybis(1,4-phenylene)diboric acid and 150 g of borax were added to the above reaction kettle in sequence, and stirring was continued for 10 minutes until the mixture was evenly dissolved;

[0199] S3: Under stirring conditions of 150 rpm, 70 g of polyethylene glycol 600, 220 g of diethylene glycol acetal and the remaining 80 g of water were added to the above reaction kettle in sequence, and stirring was continued for 10 minutes to dissolve and mix;

[0200] S4: The reactor was heated to 90° C. and stirred at 150 rpm for 6 hours. The reaction was stopped and cooled to room temperature to obtain a cross-linking agent for gelation.

[0201] Comparative Example 7

[0202] This comparative example provides a gelling crosslinker. The formula differs from Example 2 in that polyethylene glycol 200 is removed and replaced by water. The remaining formula remains unchanged. The specific formula is: 28% 4,4'-biphenyldiboronic acid, 7.5% potassium hydroxide, 22% triethylene glycol, and 42.5% water.

[0203] The preparation method of the cross-linking agent for gelation is as follows:

[0204] S1: Add 250g of water to the reactor, add 75g of potassium hydroxide under stirring at 100rpm, and continue stirring for 10 minutes to dissolve evenly;

[0205] S2: Add 280 g of 4,4'-biphenyldiboronic acid to the above reaction kettle under stirring at 100 rpm and continue stirring for 10 minutes until it is evenly dissolved;

[0206] S3: Under stirring conditions of 100 rpm, 220 g of triethylene glycol and the remaining 175 g of water were added to the above reactor in sequence, and stirring was continued for 10 minutes to dissolve evenly;

[0207] S4: The reactor was heated to 90° C. and stirred at 100 rpm for 6 hours. The reaction was stopped and the mixture was cooled to room temperature to obtain a cross-linking agent for gelation.

[0208] Comparative Example 8

[0209] This comparative example provides a gelling crosslinker. The formula differs from that of Example 4 in that polyethylene glycol 200 and polyethylene glycol 600 are removed and replaced by water. The remaining formula remains unchanged. The specific formula is: 16% dibenzothiophene-4,6-diboric acid, 2% sodium hydroxide, 2.5% potassium hydroxide, 12% ethylene glycol, and 67.5% water.

[0210] The preparation method of the cross-linking agent for gelation is as follows:

[0211] S1: Add 220g of water to the reactor, add 20g of sodium hydroxide and 25g of potassium hydroxide in sequence under stirring at 150rpm, and continue stirring for 10 minutes to dissolve evenly;

[0212] S2: Add 160 g of dibenzothiophene-4,6-diboric acid to the above reaction kettle under stirring at 150 rpm and continue stirring for 10 minutes until it is evenly dissolved;

[0213] S3: Under stirring conditions of 150 rpm, 120 g of ethylene glycol and the remaining 455 g of water were added to the above reactor in sequence, and stirring was continued for 10 minutes to dissolve evenly;

[0214] S4: The reactor was heated to 75° C. and stirred at 150 rpm for 4.5 hours. The reaction was stopped and the mixture was cooled to room temperature to obtain a cross-linking agent for gelation.

[0215] Comparative Example 9

[0216] This comparative example provides a gelling crosslinker. The formula is the same as that of Example 8, except that polyethylene glycol 200 is removed and replaced by water. The remaining formula remains unchanged. The specific formula is: 30% 9,9-dimethyl-2,7-fluorenediboric acid, 8% sodium carbonate, 25% triethylene glycol, and 37% water.

[0217] The preparation method of the cross-linking agent for gelation is as follows:

[0218] S1: Add 230g of water to the reactor, add 80g of sodium carbonate under stirring at 100rpm, and continue stirring for 10 minutes to dissolve evenly;

[0219] S2: Add 300 g of 9,9-dimethyl-2,7-fluorenediboric acid to the above reaction kettle under stirring at 100 rpm and continue stirring for 10 minutes until it is evenly dissolved;

[0220] S3: Under stirring conditions of 100 rpm, 250 g of triethylene glycol and the remaining 140 g of water were added to the above reactor in sequence, and stirring was continued for 10 minutes to dissolve evenly;

[0221] S4: The reactor was heated to 70° C. and reacted for 5 hours under a stirring condition of 100 rpm. The reaction was stopped and cooled to room temperature to obtain a cross-linking agent for gelation.

[0222] Performance testing

[0223] 1. The gelling properties of the cross-linking agents prepared in the above examples and comparative examples were tested.

[0224] The test method is as follows: 1000ml of tap water is added to varying amounts of hydroxypropyl guar gum at a stirring rate of 300rpm. Stirring is continued for 10 minutes, and the fracturing fluid base fluid is allowed to stand for 4 hours to obtain the base fluid. 100ml of the prepared base fluid is then taken into a beaker and various amounts of cross-linking agent are added. The gelling process is observed under manual stirring, and the gelling strength is evaluated by stirring with a glass rod, tipping the beaker, and hanging the beaker with the glass rod. The test results are shown in Table 1. Note: If the water forms a gel when stirred with a glass rod, it is considered to have gelled. If it not only gels but also sticks out when the beaker is tilted after gelling, this indicates good gelling. If it not only gels, sticks out, and can be hung with a glass rod, this indicates excellent gelling.

[0225] Table 1

[0226]

[0227]

[0228] 2. The cross-linking agents prepared in the above examples and comparative examples were subjected to temperature and shear resistance tests.

[0229] The test method is: take a small amount of gel and use a rheometer to test the heat and shear resistance. The test conditions are: shear rate 170s -1 , observe its viscosity after shearing for 1 hour at different temperatures.

[0230] Example 1 is a long-chain polyboric acid containing multiple benzene rings in the second general structural formula of polyboric acid containing multiple benzene rings, Example 4 is a long-chain polyboric acid containing multiple benzene rings in the third general structural formula of polyboric acid containing multiple benzene rings, Example 7 is a long-chain polyboric acid containing multiple benzene rings in the fourth general structural formula of polyboric acid containing multiple benzene rings, and Example 10 is a long-chain polyboric acid containing multiple benzene rings in the sixth general structural formula of polyboric acid containing multiple benzene rings. Each of the long-chain polyboric acids containing multiple benzene rings in the general structural formula selects an embodiment to carry out the heat resistance and shear resistance test, and the test results are as follows: Figures 1 to 8 As shown; of all comparative examples, only comparative examples 7, 8, and 9 can form gels at a hydroxypropyl guar gum concentration of 0.12% to 0.25%. Comparative examples 7, 8, and 9 all contain long-chain polyboric acid containing multiple benzene rings, and none of them contain polyvinyl alcohol. Comparative example 8 is selected for the heat and shear resistance test (compared with Example 4, comparative example 8 only lacks polyvinyl alcohol). The test results are shown as follows: Figure 9 shown.

[0231] From the experimental results, the examples all contain polyphenyl ring long chain polyboric acid and polyvinyl alcohol. Under the condition of 0.15% plant gum concentration, the crosslinking agent of the examples forms a gel with the plant gum at 70℃ and 100℃. -1 The viscosity after shearing for 1 hour under the shear rate condition is ≥50mPa·s; under the condition of 0.25% plant gum concentration, the crosslinking agent in the embodiment forms a gel with the plant gum at 120℃ and 100℃. -1 The viscosity after shearing for 1 hour under shear rate conditions is ≥50mPa·s.

[0232] Comparative Example 8 contains polyboric acid containing polyphenyl rings but does not contain polyvinyl alcohol, and exhibits certain shear resistance, indicating that the cross-linking agent containing polyboric acid containing polyphenyl rings has a certain cross-linking effect at a lower plant gum concentration (under the same conditions, the cross-linking agent without polyboric acid containing polyphenyl rings does not form a gel, see Comparative Examples 1 to 6 in Table 1). This is mainly because the benzene ring of the polyboric acid has a large steric hindrance effect, which makes the multi-headed "boric acid" group more stretched, and the intermediate segment connecting the multi-headed "boric acid" is longer, thereby making the polyboric acid group more elastic. The polyboron cross-linking agent that forms macromolecular chain after its complexation with polyol and polyol can significantly reduce the thickening agent concentration of cross-linking, relies on macromolecular chain polyboron cross-linking agent and low concentration thickening agent cross-linking;Meanwhile, with long-chain polyboric acid containing polyphenyl rings as main segment, at least one boron ion is linked on different benzene rings, and the cross-linking agent of macromolecule and polyboron ion structure is comprehensively shown, not only can significantly reduce the plant glue concentration cross-linked with it, and due to the multi-point cross-linking in space, the gel strength formed is higher, and shear resistance is enhanced. However, due to the absence of polyvinyl alcohol, the shear resistance of comparative example 8 is not as good as the embodiment containing polyvinyl alcohol. This is because polyethylene glycol is introduced into the cross-linking agent system, and has complexation with long-chain polyboric acid containing polyphenyl rings itself, and cross-linking agent can be made to become the complex compound of more complicated and longer segment to a certain extent, further reduces the plant glue concentration cross-linked with it, so that the shear resistance of gel can be further enhanced.

[0233] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A cross-linking agent for gelation, characterized in that The invention comprises the following components by mass percentage: 10% to 30% of long-chain polyboric acid containing multiple benzene rings, 5% to 10% of polyethylene glycol, 4% to 8% of a base, 10% to 25% of an auxiliary ligand, and the balance being water.

2. A gelation cross-linking agent according to claim 1, characterized in that: The general structural formula of the polyboric acid containing multiple benzene rings is: Wherein, X includes O or (CH2) z , z is 1 to 3; at least one of m1, m2, m3, m4, and m5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes; At least one of n1, n2, n3, n4, and n5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes.

3. A gelation cross-linking agent according to claim 1, characterized in that: The general structural formula of the polyboric acid containing multiple benzene rings and long chains is: Among them, at least one of m1, m2, m3, m4, and m5 is HO—B—OH, where B is connected to the benzene ring, and the others are H or alkanes; At least one of n1, n2, n3, n4, and n5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes.

4. A gelation cross-linking agent according to claim 1, characterized in that: The general structural formula of the polyboric acid containing multiple benzene rings is: Among them, at least one of m1, m2, m3, m4, and m5 is HO—B—OH, where B is connected to the benzene ring, and the others are H or alkanes; At least one of n1, n2, n3, n4, and n5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes.

5. The cross-linking agent for gelation according to claim 1, characterized in that: The general structural formula of the polyboric acid containing multiple benzene rings is: Among them, at least one of m1, m2, m3, m4, and m5 is HO—B—OH, where B is connected to the benzene ring, and the others are H or alkanes; At least one of n1, n2, n3, n4, and n5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes.

6. The cross-linking agent for gelation according to claim 1, characterized in that: The general structural formula of the polyboric acid containing multiple benzene rings is: Wherein, X, Y, and Z are O or (CH2) w One of , w is 1-3; At least one of m1, m2, m3, m4, and m5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes; At least one of n1, n2, n3, n4, and n5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes; At least one of R1, R2, R3, R4, and R5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes.

7. The cross-linking agent for gelation according to claim 1, characterized in that: The general structural formula of the polyboric acid containing multiple benzene rings is: Among them, at least one of m1, m2, m3, m4, and m5 is HO—B—OH, where B is connected to the benzene ring, and the others are H or alkanes; At least one of n1, n2, n3, n4, and n5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes; At least one of R1, R2, R3, R4, and R5 is HO—B—OH, where B is connected to the benzene ring, and the rest are H or alkanes.

8. The cross-linking agent for gelation according to any one of claims 1 to 7, characterized in that: The polyethylene glycol is at least one of polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600.

9. The cross-linking agent for gelation according to any one of claims 1 to 7, characterized in that: The alkali is at least one of sodium hydroxide, potassium hydroxide and sodium carbonate.

10. The cross-linking agent for gelation according to any one of claims 1 to 7, characterized in that: The auxiliary ligand is at least one of sorbitol, glycerol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, diethylene glycol acetal, and triethylene glycol.

11. A method for preparing the cross-linking agent for gelation according to any one of claims 1 to 10, characterized in that: The following steps are involved: S1: Add 20% to 25% of the total amount of the crosslinking agent for gelation into the reactor, add alkali according to the formula ratio under stirring conditions, and dissolve evenly; S2: Add long-chain polyboric acid containing multiple benzene rings into the reactor under stirring according to the formula ratio and dissolve evenly; S3: Add polyethylene glycol, co-ligand and remaining water to the reactor under stirring according to the formula ratio and dissolve them evenly; S4: raising the temperature in the reactor, reacting for 4 to 6 hours under stirring, stopping the reaction, and cooling to room temperature to obtain the cross-linking agent for gelation.

12. The method for preparing a cross-linking agent for gelation according to claim 11, characterized in that: The reaction temperature in step S4 is 70°C to 90°C.

13. Use of the cross-linking agent for gelation according to any one of claims 1 to 10 or the cross-linking agent for gelation prepared by the preparation method according to claim 11 or 12, characterized in that: Including those used for preparing fracturing fluid, acid fluid, profile control and water plugging agent, and temporary plugging and well killing gel.

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