Oil-soluble organic aluminum high-temperature cross-linking agent, preparation method and application

Abstract

The invention discloses an oil-soluble organic aluminum high-temperature cross-linking agent as well as a preparation method and application thereof, and belongs to the technical field of oil field cross-linking agents. The preparation method comprises the following steps: (1) adding an aluminum trichloride solution into a three-mouth reaction bottle provided with a condensation reflux device, adding long-chain carboxylate under full stirring, and carrying out a water bath heating reaction to obtain a reaction product; washing the reaction product with water for three times, drying to constant weight by using phosphorus pentoxide, purifying by using anhydrous acetone, and drying to obtain an intermediate product; and (2) adding the intermediate product and oxalic acid into a three-neck flask provided with a condensation reflux device, mixing by using ethanol as a solvent, adding a catalyst, carrying out water bath heating reaction, carrying out reduced pressure distillation to obtain ethanol after the reaction is finished, and adding white oil for dissolving to obtain the oil-soluble organic aluminum high-temperature cross-linking agent. The cross-linking agent can achieve the goals of high-temperature slow release and advanced on-line mixing, the construction process is greatly simplified, and the construction convenience is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of oil field crosslinking agents, and in particular relates to an oil-soluble organic aluminum high-temperature crosslinking agent, a preparation method and application thereof. Background Art

[0002] Fracturing fluid is the entire liquid squeezed into the formation during the fracturing construction of petroleum production. It plays the role of transmitting pressure, pressing the formation, forming new cracks, propping or expanding the original cracks in the formation, and carrying proppants into the cracks. Therefore, in the fracturing process, choosing a suitable fracturing fluid system is crucial to increasing the production of a single well and reducing its damage to the reservoir.

[0003] A cross-linking agent is an additive that can undergo cross-linking reactions with thickener macromolecules through coordination bonds or chemical bonds. Its main function is to improve the fracture-forming ability, sand-carrying performance, and temperature and shear resistance of the fracturing fluid system.

[0004] Chinese patent CN 112375555A discloses a method for preparing an organic aluminum crosslinking agent that can be crosslinked with a W / O inverse emulsion drag reducer, comprising the following steps: (1) dissolving organic aluminum in water in a reaction kettle, stirring until completely dissolved, and preparing a mixed solution I, wherein the first organic aluminum mass fraction of the mixed solution I is 6-7%, and the second organic aluminum mass fraction of the mixed solution I is 1-2%; (2) heating the mixed solution I in step (1) to 50-90°C, and adding an organic complex ligand to the mixed solution I while stirring to obtain a mixed solution II, wherein the mass fraction of the organic matter as the complex ligand in the mixed solution II is 5-6%; (3) isothermally reacting the mixed solution II in step (2) at 50-90°C for 3-5h, and then cooling to room temperature to obtain a light yellow uniform transparent clear liquid, which is the organic aluminum crosslinking agent. The invention can realize the online mixing of the glue liquid, reduce the difficulty of fracturing transformation of shale oil and gas reservoirs, and improve the transformation efficiency.

[0005] Chinese patent CN 108456513A discloses an organic aluminum crosslinking agent for fracturing fluid, a preparation method and an application thereof. The crosslinking agent comprises: each component by weight, 100 parts by weight of distilled water; 7-25 parts by weight of aluminum chloride; 12-25 parts by weight of polyacid / polyacid salt; 5-15 parts by weight of organic amine; 85-125 parts by weight of polyol. The organic aluminum crosslinking agent prepared by the invention has a simple preparation method and low raw material cost. The organic aluminum crosslinking agent can crosslink polyacrylamide or partially hydrolyzed polyacrylamide polymers under neutral conditions, and does not need to add a pH adjuster to adjust the pH value of the polymer solution, forming a fracturing fluid with excellent performance, which can meet the fracturing construction of 60-120°C formations and has broad application prospects.

[0006] Currently, most thickeners used are heterochain polymers. However, due to the increase in formation depth in oil and gas wells, the temperature in the oil and gas wells increases, and heterochain polymers do not perform well under high temperature conditions. The carbon main chain of polyacrylamide has the advantage of high temperature resistance and is cheap, but it is undeniable that its powder configuration is not easy, which leads to complicated construction conditions of existing fracturing fluids.

[0007] Therefore, it is necessary to develop an oil-soluble organic aluminum high-temperature cross-linking agent that is easy to construct, a preparation method and an application. Summary of the invention

[0008] In order to solve the shortcomings of existing fracturing fluids, such as inconvenient storage and complicated construction methods, and to enhance the high temperature resistance of fracturing fluids, the oil phase of the polymer emulsion is utilized.

[0009] The purpose of the present invention is to provide an oil-soluble organic aluminum high-temperature crosslinking agent, a preparation method and an application. The crosslinking agent can be added to the water-in-oil polyacrylamide emulsion in advance. Since the crosslinking agent has a long carbon chain and is easy to dissolve in the oil phase, the oil phase of the emulsion is utilized. Under low temperature or room temperature conditions, since the polyacrylamide and the crosslinking agent are stored in separate phases, premature contact between the crosslinking center and the amide group in the polyacrylamide emulsion is avoided, and the mixture can be mixed in advance and prepared online. When the mixed emulsion breaks the emulsion after encountering high temperature conditions, the crosslinking agent molecules themselves decompose, and the hydrophilic group oxalate increases its water solubility, which promotes the release of the crosslinking agent in the oil phase to the water phase. The crosslinking center crosslinks with the polyacrylamide in the water phase, so that the position of the crosslinking agent is transferred, and the goals of high-temperature sustained release of the crosslinking agent and early online mixing are achieved, which greatly simplifies the construction process and improves the convenience of construction.

[0010] In order to achieve the above object, the present invention adopts the following technical solution:

[0011] An oil-soluble organic aluminum high temperature crosslinking agent, the structural formula of the crosslinking agent is as follows:

[0012]

[0013] The preparation method of the oil-soluble organic aluminum high-temperature cross-linking agent comprises the following steps:

[0014] (1) adding aluminum chloride solution to a three-necked reaction flask equipped with a condensing reflux device, adding a long-chain carboxylate under sufficient stirring, and heating the reaction in a water bath to obtain a reaction product; washing the reaction product with water three times, drying it with phosphorus pentoxide to a constant weight, and then purifying it with anhydrous acetone and drying it to obtain an intermediate product;

[0015] (2) The intermediate product and oxalic acid are added to a three-necked flask equipped with a condensing reflux device, mixed with ethanol as a solvent, a catalyst is added, and the reaction is heated in a water bath. After the reaction is completed, the ethanol is distilled off under reduced pressure, and white oil is added to dissolve, thereby obtaining an oil-soluble organic aluminum high-temperature crosslinking agent.

[0016] As a preferred embodiment of the present invention, the concentration of aluminum chloride is 1.2-1.6wt%;

[0017] As a preferred embodiment of the present invention, the molar ratio of the long-chain carboxylate to aluminum chloride is 1:

[0018] (2.5-3.5).

[0019] As a preferred embodiment of the present invention, the carbon chain number of the long-chain carboxylate is 12-18.

[0020] As a preferred embodiment of the present invention, the reaction time of step (1) is 3.5-4.5 h, and the reaction temperature is 65-75°C.

[0021] As a preferred embodiment of the present invention, the drying temperature after purification in step (1) is 95-105°C.

[0022] As a preferred embodiment of the present invention, the molar ratio of oxalic acid to the intermediate product in step (2) is (1-1.5):1.

[0023] As a preferred embodiment of the present invention, the ratio of the mass of ethanol described in step (2) to the total mass of oxalic acid and the intermediate product is (1-1.2):1.

[0024] As a preferred embodiment of the present invention, the catalyst in step (2) is concentrated sulfuric acid; the mass of the concentrated sulfuric acid is 0.3-0.4 times the mass of oxalic acid.

[0025] As a preferred solution of the present invention, the reaction time is 4.5-5.5h and the reaction temperature is 75-85°C.

[0026] As a preferred embodiment of the present invention, the ratio of the mass of the white oil to the total mass of oxalic acid and the intermediate product is (1-1.2):1.

[0027] The oil-soluble organic aluminum high-temperature cross-linking agent is used in an oilfield fracturing fluid system.

[0028] The application is as follows: adding the oil-soluble organic aluminum high-temperature crosslinking agent to a polyacrylamide emulsion to obtain a mixed solution, and directly injecting the mixed solution into an oil well; when the mixed emulsion breaks under high temperature conditions, oxalate increases its water solubility, and the crosslinking agent in the oil phase is gradually released to crosslink with the polyacrylamide in the water phase, thereby shifting the position of the crosslinking agent to play a crosslinking role and perform fracturing.

[0029] As a preferred embodiment of the present invention, the volume ratio of the polyacrylamide emulsion to the cross-linking agent in the mixed emulsion is 100:(1.5-2).

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] When existing traditional polyacrylamide is used in oil and gas fields, the liquid preparation vehicle needs to enter the site in advance to prepare the liquid. The thickener is fully swelled in the liquid storage tank. The fracturing vehicle enters the site and then recirculates the liquid in the storage tank to prevent problems caused by uneven liquid during the fracturing process. The construction cycle is long and the liquid preparation intensity is high, which can no longer meet the needs of large-scale fracturing of shale wells.

[0032] In view of the utilization of the oil phase in the water-in-oil emulsion, the present invention provides a crosslinking agent, which is added to the water-in-oil polyacrylamide emulsion in advance. Since the crosslinking agent has a long carbon chain and is easy to dissolve in the oil phase, the oil phase of the emulsion is utilized. Under low temperature or room temperature conditions, since the polyacrylamide and the crosslinking agent are stored in separate phases, the two do not crosslink and can be mixed in advance and prepared online. When the mixed emulsion breaks after encountering high temperature conditions, oxalate increases its water solubility, and the crosslinking agent in the oil phase is gradually released to crosslink with the polyacrylamide in the water phase, thereby shifting the position of the crosslinking agent, achieving the goals of high temperature sustained release of the crosslinking agent, online mixing in advance, and phase storage of the crosslinking center and the crosslinked group. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the preparation process of the cross-linking agent;

[0034] Figure 2 This is a graph showing the temperature resistance of the thickener prepared in Example 3;

[0035] Figure 3 This is a diagram showing the shear resistance of the thickener prepared in Example 3. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Basic Example: An Oil-soluble Organic Aluminum High-Temperature Crosslinking Agent

[0038] The main component structural formula of the cross-linking agent is as follows:

[0039]

[0040] The specific preparation process is achieved through the following reactions:

[0041]

[0042] The preparation method of the oil-soluble organic aluminum high-temperature cross-linking agent comprises the following steps:

[0043] (1) adding aluminum chloride solution to a three-necked reaction flask equipped with a condensing reflux device, adding a long-chain carboxylate under sufficient stirring, and heating the reaction in a water bath to obtain a reaction product; washing the reaction product with water three times, drying it with phosphorus pentoxide to a constant weight, and then purifying it with anhydrous acetone and drying it to obtain an intermediate product;

[0044] The use concentration of the aluminum chloride is 1.5%;

[0045] The carbon chain number of the long-chain carboxylate is 12-18; the molar ratio of the long-chain carboxylate to aluminum chloride is 1:(2.5-3.5);

[0046] The reaction time is 3.5-4.5h, and the reaction temperature is 65-75℃;

[0047] The drying temperature after purification is 95-105°C.

[0048] (2) adding the intermediate product and oxalic acid into a three-necked flask equipped with a condensing reflux device, mixing with ethanol as a solvent, adding a catalyst, heating in a water bath for reaction, and distilling off the ethanol under reduced pressure after the reaction, adding white oil for dissolution, and obtaining an oil-soluble organic aluminum high-temperature crosslinking agent;

[0049] The molar ratio of oxalic acid to the intermediate product is (1-1.5):1;

[0050] The ratio of the mass of the ethanol to the total mass of the oxalic acid and the intermediate product is (1-1.2):1;

[0051] The catalyst is concentrated sulfuric acid, and the mass of the concentrated sulfuric acid is 0.3-0.4 times the mass of oxalic acid;

[0052] The reaction time is 4.5-5.5h, and the reaction temperature is 75-85°C;

[0053] The ratio of the mass of the white oil to the total mass of oxalic acid and the intermediate product is (1-1.2):1.

[0054] The obtained oil-soluble organic aluminum high-temperature crosslinking agent is added into the polyacrylamide emulsion to obtain a single-component thickener containing the crosslinking agent; the volume ratio of the polyacrylamide emulsion to the crosslinking agent is 100:(1.5-2.0).

[0055] The principle is that aluminum chloride undergoes a replacement reaction with long-chain carboxylates to generate intermediate products, which further undergo an esterification reaction with oxalic acid to wrap and protect the cross-linking center Al. Since the cross-linking agent has a long carbon chain that is easy to dissolve in the oil phase, the oil phase of the emulsion is utilized. Since polyacrylamide and the cross-linking agent are stored in separate phases, the two do not cross-link and can be mixed in advance and prepared online. When the mixed emulsion breaks down after encountering high temperature conditions, oxalate increases its water solubility, and the cross-linking agent in the oil phase is gradually released to cross-link with the polyacrylamide in the water phase, thereby shifting the position of the cross-linking agent, achieving the goals of separate phase storage of the cross-linking center and the cross-linked group, temperature-controlled phase transition of the cross-linking agent, high-temperature sustained release, and advance online mixing.

[0056] The present invention will be further described below with reference to specific embodiments and accompanying drawings:

[0057] Example 1

[0058] 120 g of aluminum chloride solution with a mass concentration of 1.5% was added to a three-necked reaction flask equipped with a condensation reflux device, and 50.06 g of a long-chain carboxylate (carbon chain number 12) solution with a mass concentration of 2% was slowly added under sufficient stirring, and the mixture was heated to 70° C. in a water bath for 4 hours. After washing with water 3 times, the mixture was dried to constant weight at 100° C. in the presence of phosphorus pentoxide, and then purified with anhydrous acetone to obtain 2.8 g of an intermediate product; the obtained intermediate product and 1.6 g of oxalic acid were mixed in a three-necked flask equipped with a condensation reflux device using 5 g of ethanol as a solvent, 0.48 g of concentrated sulfuric acid was added as a catalyst, and the mixture was heated to 80° C. in a water bath for 5 hours. After the reaction was completed, the ethanol was distilled off under reduced pressure, and 5 g of white oil was added for dissolution to obtain an oil-soluble organic aluminum high-temperature crosslinking agent.

[0059] 1.5 mL of the cross-linking agent was added into 100 mL of polyacrylamide emulsion to obtain a single-dose thickener containing the cross-linking agent.

[0060] Example 2

[0061] 120 g of aluminum chloride solution with a mass concentration of 1.5% was added to a three-necked reaction flask equipped with a condensation reflux device, and 56.39 g of a long-chain carboxylate (carbon chain number 14) solution with a mass concentration of 2% was added under sufficient stirring, and the mixture was heated to 70° C. in a water bath for 4 hours. After washing with water 3 times, the mixture was dried to constant weight at 100° C. in the presence of phosphorus pentoxide, and then purified with anhydrous acetone to obtain 2.9 g of an intermediate product; the obtained intermediate product was mixed with 1.53 g of oxalic acid in a three-necked flask equipped with a condensation reflux device using 5 g of ethanol as a solvent, 0.46 g of concentrated sulfuric acid was added as a catalyst, and the mixture was heated to 80° C. in a water bath for 5 hours. After the reaction was completed, the ethanol was distilled off under reduced pressure, and 5 g of white oil was added for dissolution to obtain an oil-soluble organic aluminum high-temperature crosslinking agent.

[0062] 1.8 mL of the cross-linking agent was added into 100 mL of polyacrylamide emulsion to obtain a single-dose thickener containing the cross-linking agent.

[0063] Example 3

[0064] 120 g of aluminum chloride solution with a mass concentration of 1.5% was added to a three-necked reaction flask equipped with a condensation reflux device, and 63.61 g of a long-chain carboxylate (carbon chain number 16) solution with a mass concentration of 2% was added under sufficient stirring, and the mixture was heated to 70° C. in a water bath for 4 hours. After washing with water 3 times, the mixture was dried to constant weight at 100° C. in the presence of phosphorus pentoxide, and then purified with anhydrous acetone to obtain 3.1 g of an intermediate product; the obtained intermediate product was mixed with 1.51 g of oxalic acid in a three-necked flask equipped with a condensation reflux device using 5 g of ethanol as a solvent, 5.98 g of concentrated sulfuric acid was added as a catalyst, and the mixture was heated to 80° C. in a water bath for 5 hours. After the reaction was completed, the ethanol was distilled off under reduced pressure, and 5 g of white oil was added for dissolution to obtain an oil-soluble organic aluminum high-temperature crosslinking agent.

[0065] 2.0 mL of the cross-linking agent was added into 100 mL of polyacrylamide emulsion to obtain a single-dose thickener containing the cross-linking agent.

[0066] Example 4

[0067] 120 g of aluminum chloride solution with a mass concentration of 1.5% was added to a three-necked reaction flask equipped with a condensation reflux device, and 50.06 g of a long-chain carboxylate (carbon chain number 12) solution with a mass concentration of 2% was added under sufficient stirring, and the mixture was heated to 75° C. in a water bath for 4 hours, and then dried to constant weight at 95° C. in the presence of phosphorus pentoxide after washing 3 times, and then purified with anhydrous acetone to obtain 2.8 g of an intermediate product; the obtained intermediate product and 1.6 g of oxalic acid were mixed in a three-necked flask equipped with a condensation reflux device using 5 g of ethanol as a solvent, 0.48 g of concentrated sulfuric acid was added as a catalyst, and the mixture was heated to 80° C. in a water bath for 5 hours. After the reaction was completed, the ethanol was distilled off under reduced pressure, and 5 g of white oil was added for dissolution to obtain an oil-soluble organic aluminum high-temperature crosslinking agent.

[0068] 1.6 mL of the cross-linking agent was added to 100 mL of polyacrylamide emulsion to obtain a single-dose thickener containing the cross-linking agent.

[0069] Example 5

[0070] 120 g of aluminum chloride solution with a mass concentration of 1.5% was added to a three-necked reaction flask equipped with a condensation reflux device, and 69.02 g of a long-chain carboxylate (carbon chain number 18) solution with a mass concentration of 2% was added under sufficient stirring, and the mixture was heated to 70° C. in a water bath for 4 hours. After washing with water 3 times, the mixture was dried to constant weight at 100° C. in the presence of phosphorus pentoxide, and then purified with anhydrous acetone to obtain 3.2 g of an intermediate product; the obtained intermediate product was mixed with 1.45 g of oxalic acid in a three-necked flask equipped with a condensation reflux device using 5 g of ethanol as a solvent, 0.44 g of concentrated sulfuric acid was added as a catalyst, and the mixture was heated to 80° C. in a water bath for 5 hours. After the reaction was completed, the ethanol was distilled off under reduced pressure, and 5 g of white oil was added for dissolution to obtain an oil-soluble organic aluminum high-temperature crosslinking agent.

[0071] 1.9 mL of the cross-linking agent was added into 100 mL of polyacrylamide emulsion to obtain a single-dose thickener containing the cross-linking agent.

[0072] Example 6

[0073] 120 g of aluminum chloride solution with a mass concentration of 1.5% was added to a three-necked reaction flask equipped with a condensation reflux device, and 56.39 g of a long-chain carboxylate (carbon chain number 14) solution with a mass concentration of 2% was added under sufficient stirring, and the mixture was heated to 70° C. in a water bath for reaction for 3.5 h. After washing with water three times, the mixture was dried to constant weight at 105° C. in the presence of phosphorus pentoxide, and then purified with anhydrous acetone to obtain 2.9 g of an intermediate product; the obtained intermediate product was mixed with 1.53 g of oxalic acid in a three-necked flask equipped with a condensation reflux device using 5 g of ethanol as a solvent, 0.46 g of concentrated sulfuric acid was added as a catalyst, and the mixture was heated to 85° C. in a water bath for reaction for 4.5 h. After the reaction was completed, the ethanol was distilled off under reduced pressure, and 5 g of white oil was added for dissolution to obtain an oil-soluble organic aluminum high-temperature crosslinking agent.

[0074] 1.8 mL of the cross-linking agent was added into 100 mL of polyacrylamide emulsion to obtain a single-dose thickener containing the cross-linking agent.

[0075] Example 7

[0076] To a three-necked reaction flask equipped with a condensation reflux device, add 120 g of an aluminum chloride solution with a mass concentration of 1.5%, add 63.61 g of a long-chain carboxylate (carbon chain number is 16) solution with a mass concentration of 2% under sufficient stirring, heat to 75° C. in a water bath for 4.5 hours, wash with water three times, dry to constant weight at 100° C. in the presence of phosphorus pentoxide, and purify with anhydrous acetone to obtain 3.1 g of an intermediate product; the obtained intermediate product and 1.51 g of oxalic acid are mixed in a three-necked flask equipped with a condensation reflux device using 5 g of ethanol as a solvent, add 5.98 g of concentrated sulfuric acid as a catalyst, heat to 75° C. in a water bath for 5.5 hours, and after the reaction is completed, ethanol is distilled off under reduced pressure, and 5 g of white oil is added for dissolution to obtain an oil-soluble organic aluminum high-temperature crosslinking agent.

[0077] 2.0 mL of the cross-linking agent was added into 100 mL of polyacrylamide emulsion to obtain a single-dose thickener containing the cross-linking agent.

[0078] Characterization and Testing:

[0079] In order to characterize the temperature resistance of the synthesized crosslinking agent, the viscosity of the thickener synthesized in Example 3 was tested at different temperatures. The results are as follows: Figure 2 shown.

[0080] Depend on Figure 2 It can be seen that with the increase of temperature, the viscosity of the synthesized thickener and the thickener without cross-linking agent both began to decrease, but the viscosity of the synthesized fracturing fluid decreased slowly after 80°C, and the viscosity could be basically maintained at about 100mPa·s after 130°C. The viscosity of the thickener without cross-linking agent was less than 50mPa·s after 100°C. This shows that the synthesized cross-linking agent has a specific high-temperature slow-release effect and has good temperature resistance.

[0081] In order to characterize the shear resistance of the synthesized crosslinking agent, the thickener synthesized in Example 3 was subjected to a shear test at 70°C with a shear rate of 170 s -1 The viscosity test was carried out under Figure 3 shown.

[0082] Depend on Figure 3 It can be seen that as the shear time increases, the viscosity of the system decreases. The viscosity decreases rapidly in the first 20 minutes and gradually stabilizes after 20 minutes. After 60 minutes of shearing, the viscosity of the system without crosslinking agent has dropped to 50mPa·s, while the viscosity of the system with the synthetic crosslinking agent is still 95mPa·s. This shows that the synthetic crosslinking agent has good shear resistance.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art can still modify or make equivalent substitutions to the specific implementation schemes of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention.

Claims

1. An oil-soluble organic aluminum high temperature crosslinking agent, Features: The structural formula of the cross-linking agent is as follows:

2. The method for preparing the oil-soluble organic aluminum high-temperature crosslinking agent according to claim 1, Features: The steps include: (1) adding aluminum chloride solution to a three-necked reaction flask equipped with a condensing reflux device, adding a long-chain carboxylate under sufficient stirring, and heating the reaction in a water bath to obtain a reaction product; washing the reaction product with water three times, drying it with phosphorus pentoxide to a constant weight, and then purifying it with anhydrous acetone and drying it to obtain an intermediate product; (2) The intermediate product and oxalic acid are added to a three-necked flask equipped with a condensing reflux device, mixed with ethanol as a solvent, a catalyst is added, and the reaction is heated in a water bath. After the reaction is completed, the ethanol is distilled off under reduced pressure, and white oil is added to dissolve, thereby obtaining an oil-soluble organic aluminum high-temperature crosslinking agent.

3. The preparation method according to claim 2, Features: The concentration of the aluminum chloride is 1.2-1.6wt%.

4. The preparation method according to claim 2, Features: The molar ratio of the long-chain carboxylate to aluminum chloride is 1:(2.5-3.5).

5. The preparation method according to claim 2, Features: The carbon chain number of the long-chain carboxylate is 12-18.

6. The preparation method according to claim 2, Features: The reaction time of step (1) is 3.5-4.5 h, and the reaction temperature is 65-75° C.

7. The preparation method according to claim 2, Features: The drying temperature after purification in step (1) is 95-105°C.

8. The preparation method according to claim 2, Features: The molar ratio of oxalic acid to the intermediate product in step (2) is (1-1.5):

1.

9. The preparation method according to claim 2, Features: The ratio of the mass of the ethanol described in step (2) to the total mass of oxalic acid and the intermediate product is (1-1.2):

1.

10. The preparation method according to claim 2, Features: The catalyst in step (2) is concentrated sulfuric acid; the mass of the concentrated sulfuric acid is 0.3-0.4 times the mass of oxalic acid.

11. The preparation method according to claim 2, Features: The reaction time is 4.5-5.5h, and the reaction temperature is 75-85°C.

12. The preparation method according to claim 2, Features: The ratio of the mass of the white oil to the total mass of oxalic acid and the intermediate product is (1-1.2):

1.

13. Use of the oil-soluble organic aluminum high temperature crosslinking agent according to claim 1 or the oil-soluble organic aluminum high temperature crosslinking agent prepared by the preparation method according to any one of claims 1 to 12 in an oilfield fracturing fluid system.

14. The use according to claim 13, Features: The oil-soluble organic aluminum high temperature crosslinking agent described in claim 1 or the oil-soluble organic aluminum high temperature crosslinking agent prepared by the preparation method described in any one of claims 1 to 12 is added to a polyacrylamide emulsion to obtain a single-dose thickener containing a crosslinking agent.

15. The use according to claim 14, Features: The volume ratio of the polyacrylamide emulsion to the cross-linking agent in the single-component thickener containing the cross-linking agent is 100:(1.5-2).

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