Crosslinking agent for oilfield wastewater fracturing fluid and preparation method thereof

Abstract

The present application relates to the oil field chemical technology field, it is a kind of oil field sewage fracturing fluid crosslinking agent and its preparation method, the former raw material includes 5% to 20% metal compound, 0 to 10% organic carboxylic acid compound, 5% to 20% hyperbranched polyalcohol amine ligand, the rest is water;The latter is to mix the required amount of metal compound and water, heated to 40 to 60 DEG C, stirring hydrolysis reaction 0.5 to 1 hour, to the first reaction product obtained in required amount machine carboxylic acid compound and hyperbranched polyalcohol amine ligand, heated to 60 to 90 DEG C, complexation reaction 2 to 6 hours, obtain oil field sewage fracturing fluid crosslinking agent.The raw material of the present application is widely available, low cost, preparation process is simple, safe, efficient, with good water solubility, the fracturing fluid prepared by compounding has strong temperature resistance and shear resistance, can reduce the demand for fresh water in fracturing operation, effectively alleviate the environmental protection and fracturing water problem in the process of oil and gas field development.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field, and is a crosslinking agent for oilfield sewage fracturing fluid and a preparation method thereof. BACKGROUND

[0002] Fracturing is a main technical means to realize efficient exploration and development of unconventional oil and gas resources, increase production and stabilize production of conventional oil and gas fields, and improve reservoir reconstruction effect. At present, the most commonly used is water-based fracturing fluid, which needs to consume a large amount of fresh water resources, so that it is difficult to carry out fracturing construction in water-deficient areas. On the other hand, a large amount of oilfield sewage is produced in the process of fracturing and exploitation. The oilfield sewage is basically brine with a salinity of more than 20,000, rich in calcium and magnesium ions, and contains metal boron ions, gel breakers and a large amount of bacteria in the fracturing flowback fluid. These factors are not conducive to the reinjection and reuse of oilfield sewage. A large amount of oilfield sewage cannot be reused and can only be reinjected into the formation after treatment and reaching the standard, forming an ineffective water cycle. This not only brings huge economic losses to oilfield production and increases environmental protection costs, but also causes a large amount of water resource waste. If oilfield sewage is used to prepare fracturing fluid for fracturing construction, not only fresh water resources can be saved, but also oilfield sewage can be treated, which will save costs and relieve environmental pressure for oilfields.

[0003] Conventional water-based fracturing usually uses (modified) guar gum fracturing fluid, which has strict requirements on water quality and usually needs to be effectively crosslinked under strong alkaline conditions. If oilfield sewage is used to prepare fracturing fluid, the pH value needs to be adjusted to more than 8, which may cause the precipitation of metal ions in the sewage, consume a large amount of alkali, and affect the performance of the fracturing fluid. Therefore, in order to use oilfield sewage to prepare fracturing fluid, a matching organic metal crosslinking agent needs to be developed. In the face of the problem of oilfield sewage treatment and reuse, it is urgent to develop new technologies for oilfield sewage treatment and reuse. The development of an oilfield sewage crosslinking agent which can be used to prepare liquid with oilfield sewage, has good performance and low reservoir damage not only has significant practical significance, but also has good application prospect. SUMMARY

[0004] The present application provides a kind of oilfield sewage fracturing fluid crosslinking agent and preparation method thereof, overcome the deficiency of above prior art, it can effectively solve the problem of existing fracturing fluid crosslinking agent exists fracturing fluid performance, oilfield sewage is difficult to reuse after processing.

[0005] One of the technical solutions of the present application is realized by the following measures: a kind of oilfield sewage fracturing fluid crosslinking agent, raw material is according to percentage by weight, including metal compound 5% to 20%, organic carboxylic acid compound 0 to 10%, hyperbranched polyalcohol amine ligand 5% to 20%, the rest is water.

[0006] The following is a further optimization or / and improvement of the above-mentioned one of the technical solutions:

[0007] The metal compound is one or more of boric acid, borax, trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triethanolamine borate, zirconium oxychloride, zirconium tetrachloride, zirconium acetate, zirconium propionate, zirconium n-propyl alcohol, zirconium isopropyl alcohol, zirconium n-butyl alcohol, zirconium acetylacetone, zirconium sulfate, titanium tetrachloride, tetraethyl titanate, titanium n-propyl alcohol, isopropyl titanate, and tetrabutyl titanate.

[0008] The metal compound is one or more of boric acid, borax, trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triethanolamine borate, zirconium oxychloride, zirconium tetrachloride, zirconium acetate, zirconium propionate, zirconium n-propyl alcohol, zirconium isopropyl alcohol, zirconium n-butyl alcohol, zirconium acetylacetone, zirconium sulfate, titanium tetrachloride, tetraethyl titanate, titanium n-propyl alcohol, isopropyl titanate, and tetrabutyl titanate.

[0009] The organic carboxylic acid compound is one or more of glacial acetic acid, lactic acid, maleic acid, succinic acid, citric acid, sodium gluconate, disodium ethylenediaminetetraacetate, sodium hydroxyethyl ethylenediamine triacetate, and sodium diethylenetriamine pentaacetate.

[0010] The hyperbranched polyalcohol amine ligand is prepared by the following steps: first, a required amount of diethanolamine is added to anhydrous ethanol or isopropyl alcohol, and after stirring to uniformity, an equal molar mass of epichlorohydrin is slowly added dropwise, and the reaction is continued at room temperature for 2-6 hours to obtain a first reaction product; then, an equal molar mass of a 50% mass fraction NaOH solution is slowly added dropwise to the first reaction product, and the reaction is continued for 2-4 hours to obtain a second reaction product; finally, a required amount of organic polyamine is added to the second reaction product, and after the reaction is continued at 50-80°C for 2-6 hours, the generated sodium chloride is recovered by filtration, and the solvent is recovered by rotary evaporation to obtain the hyperbranched polyalcohol amine ligand, wherein, assuming that there are x primary amines and y secondary amines on the organic polyamine, the material ratio n (diethanolamine) / n (organic polyamine) ≤ (2x+y).

[0011] The organic polyamine is one or more of ethylenediamine, propylenediamine, p-phenylenediamine, m-phenylenediamine, diethylenetriamine, tris(2-aminoethyl)amine, triethylenetetramine, tetraethylenepentamine, polyethylenepolyamine, polyethylenamine, polyethyleneimine, and polyamide-amine.

[0012] The second technical scheme of the present application is realized by the following measures: a preparation method of a crosslinking agent for oilfield sewage fracturing fluid, which is prepared according to the following method: first, a required amount of metal compound and water are mixed, and then the mixture is heated to 40-60 DEG C, and stirred for 0.5-1 h to obtain an intermediate reaction product; second, a required amount of carboxylic acid compound and hyperbranched polyalcohol amine ligand are added to the intermediate reaction product, and then the mixture is heated to 60-90 DEG C, and stirred for 2-6 h to obtain the crosslinking agent for oilfield sewage fracturing fluid.

[0013] The following is a further optimization or / and improvement of the above-mentioned second technical scheme of the application:

[0014] The metal compound is one or more of boric acid, borax, trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triethanolamine borate, zirconium oxychloride, zirconium tetrachloride, zirconium acetate, zirconium propionate, zirconium n-propyl alcohol, zirconium isopropyl alcohol, zirconium n-butyl alcohol, zirconium acetylacetone, zirconium sulfate, titanium tetrachloride, tetraethyl titanate, titanium n-propyl alcohol, isopropyl titanate and tetrabutyl titanate; or / and the organic carboxylic acid compound is one or more of glacial acetic acid, lactic acid, maleic acid, succinic acid, citric acid, sodium gluconate, disodium ethylenediaminetetraacetate, sodium hydroxyethyl ethylenediamine triacetate and sodium diethylenetriamine pentaacetate.

[0015] The hyperbranched polyalcohol amine ligand is prepared according to the following steps: first, a required amount of diethanolamine is added to anhydrous ethanol or isopropanol, and then the mixture is stirred uniformly, and equal-molar-mass epichlorohydrin is slowly added dropwise, and the mixture is reacted at room temperature for 2-6 h to obtain a first reaction product; then, equal-molar-mass 50% NaOH solution is slowly added dropwise to the first reaction product, and the mixture is continuously reacted for 2-4 h to obtain a second reaction product; finally, a required amount of organic polyamine is added to the second reaction product, and the mixture is continuously reacted at 50-80 DEG C for 2-6 h, and then sodium chloride is recovered by filtration, and the solvent is recovered by rotary evaporation to obtain the hyperbranched polyalcohol amine ligand, wherein, assuming that the organic polyamine has x primary amines and y secondary amines, the material ratio n (diethanolamine) / n (organic polyamine) ≤ (2x+y).

[0016] The organic polyamine is one or more of ethylenediamine, propylenediamine, p-phenylenediamine, m-phenylenediamine, diethylenetriamine, tris (2-aminoethyl) amine, triethylenetetramine, tetraethylenepentamine, polyethylenepolyamine, polyvinylamine, polyethyleneimine and polyamide-amine.

[0017] The present application has the following advantages:

[0018] (1) The raw materials of the present application are widely available and low in cost, and the preparation process is simple, safe and efficient.

[0019] (2) Hyperbranched polyolamine ligands have a large number of hydrophilic hydroxyl and tertiary amine groups, which have good water solubility and are dispersed in a star shape in all directions, increasing the space for complexation with metal ions. This makes the crosslinking agent and thickener crosslink to form a more stable three-dimensional network structure, enhancing the temperature resistance and shear resistance of the fracturing fluid.

[0020] (3) The crosslinking agent has multiple crosslinking points and can crosslink with multiple gum molecular chains at the same time, which is beneficial to enhance the strength and stability of the gel crosslinking network.

[0021] (4) The crosslinking agent has a large molecular size. When it crosslinks with the thickener, it is easy to form intermolecular crosslinks, thereby reducing the amount used and helping to control costs.

[0022] (5) The post-processing operation of the product of the present invention is simple and easy to realize industrial production.

[0023] (6) Using oilfield wastewater to prepare the fracturing fluid system, the crosslinking agent prepared in this invention is combined with conventional thickeners to obtain a fracturing fluid system with excellent performance, which can reduce the demand for fresh water in fracturing operations, make full use of oilfield wastewater, and save costs for oilfield development. Attached Figure Description

[0024] Appendix Figure 1 The rheological curves of the fracturing fluid gel formed by the crosslinking agent in Example 10 of the present invention are shown at 150°C, 170 s⁻¹, and 2 h.

[0025] Appendix Figure 2 The rheological curves of the fracturing fluid gel formed by the crosslinking agent in Example 11 of the present invention are shown at 150°C, 170 s⁻¹, and 2 h.

[0026] Appendix Figure 3 This is a schematic diagram of the synthesis reaction of the hyperbranched polyolamine ligand in this invention. Detailed Implementation

[0027] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.

[0028] The present invention will be further described below with reference to embodiments:

[0029] Example 1: the oilfield wastewater fracturing fluid crosslinking agent, raw materials according to the percentage by weight, including metal compounds 5% to 20%, organic carboxylic acid compounds 0 to 10%, hyperbranched polyalcohol amine ligand 5% to 20%, the rest is water.

[0030] Example 2: the oilfield wastewater fracturing fluid crosslinking agent, raw materials according to the percentage by weight, including metal compounds 5% or 20%, organic carboxylic acid compounds 0 or 10%, hyperbranched polyalcohol amine ligand 5% or 20%, the rest is water.

[0031] Example 3: as the optimization of the above examples, prepared according to the following method: first, the required amount of metal compound and water mixed after heating to 40 to 60 ℃, stirring hydrolysis reaction 0.5 to 1 hour, the intermediate reaction product is obtained; second, the intermediate reaction product is added to the required amount of machine carboxylic acid compound and hyperbranched polyalcohol amine ligand, heating to 60 to 90 ℃, complexation reaction 2 to 6 hours, the oilfield wastewater fracturing fluid crosslinking agent is obtained.

[0032] Example 4: as the optimization of the above examples, the metal compound is one or more of boric acid, borax, trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triethanolamine borate, zirconium oxychloride, zirconium tetrachloride, zirconium acetate, zirconium propionate, zirconium n-propyl alcohol, zirconium isopropyl alcohol, zirconium n-butyl alcohol, zirconium acetylacetone, zirconium sulfate, titanium tetrachloride, titanium acid tetraethyl ester, titanium n-propyl alcohol, titanium acid isopropyl ester and titanium acid tetrabutyl ester.

[0033] Example 5: as the optimization of the above examples, the organic carboxylic acid compound is one or more of glacial acetic acid, lactic acid, maleic acid, succinic acid, citric acid, sodium gluconate, ethylenediaminetetraacetic acid disodium, sodium hydroxyethyl ethylenediamine triacetate and diethylene triamine penta acetic acid sodium.

[0034] Example 6: as the optimization of the above examples, the hyperbranched polyalcohol amine ligand is prepared according to the following steps: first, the required amount of diethanolamine is added to anhydrous ethanol or isopropanol, stirring uniformly, then slowly droping the same molar mass of epichlorohydrin, room temperature reaction 2 to 6 hours, the first reaction product is obtained; then, slowly droping the same molar mass of 50% NaOH solution into the first reaction product, continue to react for 2 to 4 hours, the second reaction product is obtained; finally, adding the required amount of organic polyamine to the second reaction product, continue to react at 50 to 80 ℃ for 2 to 6 hours, then filter the generated sodium chloride, rotary evaporation to recover the solvent, the hyperbranched polyalcohol amine ligand is obtained, wherein, assuming that there are x primary amines and y secondary amines on the organic polyamine, the material ratio n (diethanolamine) / n (organic polyamine) ≤ (2x+y).

[0035] In the present application, the synthesis principle of the hyperbranched polyalcohol amine ligand prepared from diethanolamine, epichlorohydrin and organic polyamine is shown in the reaction formula as follows, taking diethylene triamine as an example. Figure 3

[0036] In Example 7, as an optimization of the above examples, the organic polyamine is one or more of ethylenediamine, propylenediamine, p-phenylenediamine, m-phenylenediamine, diethylenetriamine, tris(2-aminoethyl)amine, triethylenetetramine, tetraethylenepentamine, polyethylene polyamine, polyethylene amine, polyethylene imine and polyamide-amine.

[0037] In Example 8, the preparation method of the crosslinking agent for oilfield wastewater fracturing fluid is as follows: in the first step, a desired amount of metal compound and water are mixed, and then the mixture is heated to 40-60°C, and stirred for 0.5-1 hour to obtain an intermediate reaction product; in the second step, a desired amount of carboxylic acid compound and hyperbranched polyalcohol amine ligand are added to the intermediate reaction product, and then the mixture is heated to 60-90°C, and stirred for 2-6 hours to obtain the crosslinking agent for oilfield wastewater fracturing fluid.

[0038] In Example 9, the preparation method of the crosslinking agent for oilfield wastewater fracturing fluid is as follows: in the first step, a desired amount of metal compound and water are mixed, and then the mixture is heated to 40-60°C, and stirred for 0.5-1 hour to obtain an intermediate reaction product; in the second step, a desired amount of carboxylic acid compound and hyperbranched polyalcohol amine ligand are added to the intermediate reaction product, and then the mixture is heated to 60-90°C, and stirred for 2-6 hours to obtain the crosslinking agent for oilfield wastewater fracturing fluid.

[0039] ​Example 10: The oilfield wastewater fracturing fluid crosslinking agent is prepared by the following method: first, 100 parts of borax and 680 parts of water are mixed, heated to 60°C, and stirred for 1 hour to obtain an intermediate reaction product; second, 20 parts of diethylene triamine pentaacetic acid sodium, 80 parts of sodium gluconate and 100 parts of hyperbranched polyalcohol amine ligand are added to the intermediate reaction product, heated to 60°C, and complexed for 6 hours to obtain the oilfield wastewater fracturing fluid crosslinking agent, wherein the hyperbranched polyalcohol amine ligand is prepared by the following steps: first, 420 parts of diethanolamine is added to 800 parts of anhydrous ethanol, stirred uniformly, and then 370 parts of epichlorohydrin is slowly added dropwise, and the addition is completed in about half an hour, and the reaction is carried out at room temperature for 6 hours to obtain a first reaction product; then, a 50% NaOH solution by mass percentage is slowly added dropwise to the first reaction product, and the reaction is continued for 2 hours to obtain a second reaction product; finally, 60 parts of ethylenediamine is added to the second reaction product, and the reaction is continued at 80°C for 4 hours, then the generated sodium chloride is recovered by filtration, and the ethanol is recovered by rotary evaporation to obtain the hyperbranched polyalcohol amine ligand, wherein assuming that there are x primary amines and y secondary amines on the organic polyamine, the material ratio n (diethanolamine) / n (organic polyamine) ≤ (2x+y).

[0040] Example 11: The oilfield wastewater fracturing fluid crosslinking agent is prepared by the following method: first, 80 parts of borax, 20 parts of zirconium tetrachloride and 680 parts of water are mixed, heated to 55°C, and stirred for 1 hour to obtain an intermediate reaction product; second, 20 parts of cis-butene diacid, 80 parts of sodium gluconate and 100 parts of hyperbranched polyalcohol amine ligand are added to the intermediate reaction product, heated to 85°C, and complexed for 6 hours to obtain the oilfield wastewater fracturing fluid crosslinking agent, wherein the hyperbranched polyalcohol amine ligand is prepared by the following steps: first, 521 parts of diethanolamine is added to 1000 parts of anhydrous ethanol, stirred uniformly, and then 463 parts of epichlorohydrin is slowly added dropwise, and the addition is completed in about half an hour, and the reaction is carried out at room temperature for 5 hours to obtain a first reaction product; then, a 50% NaOH solution by mass percentage is slowly added dropwise to the first reaction product, and the reaction is continued for 1 hour to obtain a second reaction product; finally, 103 parts of diethylene triamine is added to the second reaction product, and the reaction is continued at 80°C for 6 hours, then the generated sodium chloride is recovered by filtration, and the ethanol is recovered by rotary evaporation to obtain the hyperbranched polyalcohol amine ligand, wherein assuming that there are x primary amines and y secondary amines on the organic polyamine, the material ratio n (diethanolamine) / n (organic polyamine) ≤ (2x+y).

[0041] Example 12: The oilfield wastewater fracturing fluid crosslinking agent is prepared by the following method: first, 200 parts of borax and 680 parts of water are mixed, heated to 50°C, and stirred for 1 hour to obtain an intermediate reaction product; second, 20 parts of sodium hydroxyethyl ethylenediamine triacetate, 80 parts of sodium gluconate and 100 parts of hyperbranched polyalcohol amine ligand are added to the intermediate reaction product, heated to 85°C, and complexed for 4 hours to obtain the oilfield wastewater fracturing fluid crosslinking agent, wherein the hyperbranched polyalcohol amine ligand is prepared by the following steps: first, 631 parts of diethanolamine is added to 1200 parts of anhydrous ethanol, stirred uniformly, and then 555 parts of epoxy chloropropane is slowly added dropwise, and the addition is completed in about half an hour, and the reaction is carried out at room temperature for 4 hours to obtain a first reaction product; then, a 50% NaOH solution by mass percentage is slowly added dropwise to the first reaction product, and the reaction is continued for 1 hour to obtain a second reaction product; finally, 146 parts of tris(2-aminoethyl)amine is added to the second reaction product, and the reaction is continued at 80°C for 4 hours, then sodium chloride is recovered by filtration, and ethanol is recovered by rotary evaporation to obtain the hyperbranched polyalcohol amine ligand, wherein assuming that there are x primary amines and y secondary amines on the organic polyamine, the material ratio n (diethanolamine) / n (organic polyamine) ≤ (2x+y).

[0042] Example 13: The oilfield wastewater fracturing fluid crosslinking agent is prepared by the following method: first, 100 parts of borax and 780 parts of water are mixed, heated to 50°C, and stirred for 1 hour to obtain an intermediate reaction product; second, 20 parts of sodium gluconate and 100 parts of hyperbranched polyalcohol amine ligand are added to the intermediate reaction product, heated to 80°C, and complexed for 4 hours to obtain the oilfield wastewater fracturing fluid crosslinking agent, wherein the hyperbranched polyalcohol amine ligand is prepared by the following steps: first, 521 parts of diethanolamine is added to 1000 parts of anhydrous ethanol, stirred uniformly, and then 463 parts of epoxy chloropropane is slowly added dropwise, and the addition is completed in about half an hour, and the reaction is carried out at room temperature for 4 hours to obtain a first reaction product; then, a 50% NaOH solution by mass percentage is slowly added dropwise to the first reaction product, and the reaction is continued for 1 hour to obtain a second reaction product; finally, 230 parts of polyethyleneimine is added to the second reaction product, and the reaction is continued at 80°C for 4 hours, then sodium chloride is recovered by filtration, and ethanol is recovered by rotary evaporation to obtain the hyperbranched polyalcohol amine ligand, wherein assuming that there are x primary amines and y secondary amines on the organic polyamine, the material ratio n (diethanolamine) / n (organic polyamine) ≤ (2x+y).

[0043] Test Example 1

[0044] According to the purified water (mineralization 20,000-30,000 mg / L) of Fengnan evaporation pond in Xinjiang oil field: the mass ratio of hydroxypropyl thickening agent = 99.4:0.6, under stirring conditions, hydroxypropyl thickening agent is added into water, after the thickening agent is fully dissolved, 0.6% thickening agent base solution is obtained; the cleanup agent and the crosslinking agent prepared in Example 10 are added into the above thickening agent base solution at one time, after stirring uniformly, the crosslinked gel fracturing fluid which can be hung is formed.

[0045] The temperature resistance and shear resistance of the fracturing fluid prepared in the test example are tested by using RS6000 rheometer, and the results are shown in Figure 1 , Figure 1 It can be known that the fracturing fluid prepared in the test example can resist temperature of 150 DEG C, and the viscosity of the fracturing fluid is kept above 200 mPa.s after continuous shearing at 170 s-1 for 120 minutes, so the fracturing fluid prepared in the test example has good temperature resistance and shear resistance.

[0046] Test Example 2

[0047] According to the water (mineralization 270,000 mg / L) of Manasi salt lake: the mass ratio of hydroxypropyl thickening agent = 99.4:0.6, under stirring conditions, hydroxypropyl thickening agent is added into water, after the thickening agent is fully dissolved, 0.6% hydroxypropyl thickening agent base solution is obtained; the cleanup agent and the crosslinking agent prepared in Example 11 are added into the above thickening agent base solution at one time, after stirring uniformly, the crosslinked gel fracturing fluid which can be hung is formed.

[0048] The temperature resistance and shear resistance of the fracturing fluid prepared in the test example are tested by using RS6000 rheometer, and the results are shown in Figure 2 , Figure 2 It can be known that the fracturing fluid prepared in the test example can resist temperature of 150 DEG C, and the viscosity of the fracturing fluid is kept above 100 mPa.s after continuous shearing at 170 s-1 for 120 minutes, so the fracturing fluid prepared in the test example has good temperature resistance and shear resistance.

[0049] In summary, the raw materials of the application have wide sources, low cost, simple, safe and efficient preparation process, good water solubility, and the fracturing fluid prepared by compounding has strong temperature resistance and shear resistance, which can reduce the demand for fresh water in fracturing operation and effectively solve the problems of environmental protection and fracturing water in the development process of oil and gas fields.

[0050] The above technical features constitute the embodiments of the application, which have strong adaptability and implementation effect, and unnecessary technical features can be added or reduced according to actual needs to meet the needs of different situations.

Claims

1. A crosslinking agent for fracturing fluid in oilfield wastewater, characterized in that... The raw material comprises 5-20% of compound I, 0-10% of organic carboxylic acid compound, 5-20% of hyperbranched polyalcohol amine ligand, and the rest is water in percentage by weight, wherein the compound I is one or more of boric acid, borax, trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triethanolamine borate, zirconium oxychloride, zirconium tetrachloride, zirconium acetate, zirconium propionate, zirconium n-propyl alcohol, zirconium isopropyl alcohol, zirconium n-butyl alcohol, zirconium acetylacetone, zirconium sulfate, titanium tetrachloride, tetraethyl titanate, titanium n-propyl alcohol, isopropyl titanate, and tetrabutyl titanate, and the hyperbranched polyalcohol amine ligand is prepared according to the following steps: First, a required amount of diethanolamine is added to anhydrous ethanol or isopropyl alcohol, stirred uniformly, and then a same-molar-mass epichlorohydrin is slowly added dropwise, and the reaction is carried out at room temperature for 2-6 hours to obtain a first reaction product; Then, a same-molar-mass 50%-mass-percent NaOH solution is slowly added dropwise to the first reaction product, and the reaction is continued for 2-4 hours to obtain a second reaction product; Finally, a required amount of organic polyamine is added to the second reaction product, and the reaction is continued at 50-80℃ for 2-6 hours, sodium chloride is recovered by filtration, and the solvent is recovered by rotary evaporation to obtain the hyperbranched polyalcohol amine ligand, wherein, assuming that there are x primary amines and y secondary amines on the organic polyamine, the material ratio n (diethanolamine) / n (organic polyamine) ≤ (2x+y).

2. The crosslinking agent for oilfield wastewater fracturing fluid according to claim 1, characterized in that The following method is used: first, a required amount of compound I and water are mixed, and the temperature is raised to 40-60℃, and the hydrolysis reaction is stirred for 0.5-1 hour to obtain an intermediate reaction product; second, a required amount of organic carboxylic acid compound and hyperbranched polyalcohol amine ligand are added to the intermediate reaction product, and the temperature is raised to 60-90℃, and the complexation reaction is carried out for 2-6 hours to obtain the crosslinking agent for oilfield sewage fracturing fluid.

3. The crosslinking agent for oilfield wastewater fracturing fluid according to claim 1 or 2, characterized by The organic carboxylic acid compound is one or more of glacial acetic acid, lactic acid, maleic acid, succinic acid, citric acid, sodium gluconate, disodium ethylenediaminetetraacetate, sodium hydroxyethyl ethylenediamine triacetate, and sodium diethylenetriamine pentaacetate.

4. The crosslinking agent for oilfield wastewater fracturing fluid according to claim 3, characterized in that The organic polyamine is one or more of ethylenediamine, propylenediamine, p-phenylenediamine, m-phenylenediamine, diethylenetriamine, tris(2-aminoethyl)amine, triethylenetetramine, tetraethylenepentamine, polyvinylamine, polyethyleneimine, and polyamidoamine.

5. The method for preparing the crosslinking agent for the oilfield sewage fracturing fluid according to claim 1, characterized in that The method is as follows: first, a desired amount of compound I and water are mixed, and the hydrolysis reaction is carried out at 40-60 DEG C for 0.5-1 h to obtain an intermediate reaction product; second, a desired amount of carboxylic acid compound and hyperbranched polyol amine ligand are added to the intermediate reaction product, and the complexation reaction is carried out at 60-90 DEG C for 2-6 h to obtain a crosslinking agent for oilfield sewage fracturing fluid, wherein the compound I is one or more of boric acid, borax, trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triethanolamine borate, zirconium oxychloride, zirconium tetrachloride, zirconium acetate, zirconium propionate, zirconium n-propyl alcohol, zirconium isopropyl alcohol, zirconium n-butyl alcohol, zirconium acetylacetone, zirconium sulfate, titanium tetrachloride, tetraethyl titanate, titanium n-propyl alcohol, isopropyl titanate and tetrabutyl titanate, and the hyperbranched polyol amine ligand is prepared by the following steps: First, a desired amount of diethanolamine is added to anhydrous ethanol or isopropanol, and then a slow drop of equal molar mass epichlorohydrin is added, and the reaction is carried out at room temperature for 2-6 h to obtain a first reaction product; Then, a slow drop of equal molar mass 50% NaOH solution is added to the first reaction product, and the reaction is continued for 2-4 h to obtain a second reaction product; Finally, a desired amount of organic polyamine is added to the second reaction product, and the reaction is continued at 50-80 DEG C for 2-6 h, then the generated sodium chloride is recovered by filtration, and the solvent is recovered by rotary evaporation to obtain the hyperbranched polyol amine ligand, wherein the material ratio n (diethanolamine) / n (organic polyamine) is ≤ (2x+y) assuming that there are x primary amines and y secondary amines on the organic polyamine.

6. The method for preparing a crosslinking agent for an oilfield wastewater fracturing fluid according to claim 5, characterized in that The organic carboxylic acid compound is one or more of glacial acetic acid, lactic acid, maleic acid, succinic acid, citric acid, sodium gluconate, disodium ethylenediaminetetraacetate, sodium hydroxyethyl ethylenediamine triacetate and sodium diethylenetriamine pentaacetate.

7. The method for preparing a crosslinking agent for an oilfield wastewater fracturing fluid according to claim 5 or 6, characterized in that The organic polyamine is one or more of ethylenediamine, propylenediamine, p-phenylenediamine, m-phenylenediamine, diethylenetriamine, tris (2-aminoethyl) amine, triethylenetetramine, tetraethylenepentamine, polyvinylamine, polyethyleneimine and polyamide-amine.

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