Method for delaying preparation of crosslinker and acidic fracturing fluid

Abstract

The application provides a preparation method of a delayed crosslinking agent and an acid fracturing fluid, and the method comprises the following steps: carrying out a chelation reaction on a transition metal substance and a ligand substance in a solvent to obtain the delayed crosslinking agent; the transition metal substance is a zirconium source and a titanium source, the zirconium source is one or more of zirconium nitrate, zirconium sulfate and zirconium oxychloride, and the titanium source is titanium tetrachloride; the ligand substance is at least three of glycerol, lactic acid, triethanolamine, sodium gluconate and sodium citrate; and the mass ratio of the transition metal substance and the ligand substance is 1:1-10. The acid fracturing fluid mainly comprises hydroxypropyl carboxymethyl guar gum, the delayed crosslinking agent and a pH regulator, and can still achieve the delayed crosslinking effect at high temperatures. The fracturing fluid is an acid fracturing fluid with temperature-controlled viscosity release, has the advantages of high-temperature resistance, temperature-controlled crosslinking, low friction drag and low residue, and is suitable for low-permeability oil and gas reservoirs, and solves the problems of clay swelling and migration and high pipe string friction drag.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield fracturing, in particular to a fracturing fluid for oil and gas field fracturing reconstruction, and more particularly to a preparation method of a delayed crosslinking agent and an acid fracturing fluid, such as an acid carboxymethyl hydroxypropyl guanidated gum fracturing fluid. BACKGROUND

[0002] With the continuous progress of society, the demand for energy consumption is also increasing, while high-grade oil reservoirs are decreasing, and low-permeability oil and gas reserves account for a gradually increasing proportion of total oil and gas resources. Unconventional oil and gas resources, including low-permeability and tight oil and gas, have attracted more and more attention. In the future, the oil and gas resources to be exploited in China will mainly rely on low-permeability or even ultra-low-permeability oil and gas fields. Therefore, it is particularly important and urgent to strengthen the exploration and development of low-permeability oil and gas reservoirs. The significant feature of low-permeability oil and gas reservoirs is that the lithology is extremely tight and the permeability is extremely low, and the reservoir is alkali-sensitive. Hydraulic fracturing is an effective technical means for developing ultra-low-permeability and tight oil reservoirs at present, and the fracturing fluid used in fracturing construction mainly includes thickening agents, crosslinking agents, and stabilizers and other additives. For low-permeability oil and gas reservoirs, the commonly used alkali fracturing fluid can cause clay migration and cause great damage to the reservoir. Therefore, the use of acid fracturing fluid has gradually been valued.

[0003] At present, some acid fracturing fluids have been developed in China. For example, a carboxymethyl guar gum acid fracturing fluid is disclosed in Chinese patent document with application publication number CN 102102014 A. The composition of the fracturing fluid is: water, carboxymethyl hydroxypropyl guar gum, CJ-2 temperature-resistant reinforcing agent, surfactant, COP-SH clay stabilizer, and JL-12 crosslinking agent (formed by complexing aluminum chloride with a short-chain organic ketone). The thickening agent of the fracturing fluid system can be used under acid conditions, the water-insoluble content is more than 5% lower than that of conventional hydroxypropyl guanidated gum, the system has low gel breaking residue, and the damage to the formation is small. However, the fracturing fluid is recommended for oil wells with well temperature lower than 90℃, and cannot meet the fracturing needs of high-temperature wells, and has no delayed crosslinking effect.

[0004] Therefore, for high-temperature alkali-sensitive reservoirs above 100℃, how to reduce the damage to the formation and improve the high-temperature resistance of the fracturing fluid system and achieve delayed crosslinking under high-temperature conditions has become one of the problems to be solved by the technical personnel in the field. SUMMARY

[0005] Therefore, the present application aims to provide a preparation method of a delayed crosslinking agent and an acid fracturing fluid. The delayed crosslinking agent prepared by the method can be used for delaying the crosslinking of the acid fracturing fluid, can achieve delayed crosslinking under high temperature, and can effectively reduce the friction.

[0006] The present application provides a preparation method of a delayed crosslinking agent, which comprises the following steps:

[0007] The transition metal substance and the ligand substance are subjected to a chelation reaction in a solvent to obtain a delayed crosslinking agent;

[0008] The transition metal substance is a zirconium source and a titanium source, the zirconium source is one or more of zirconium nitrate, zirconium sulfate and zirconium oxychloride, and the titanium source is titanium tetrachloride; the ligand substance is at least three of glycerol, lactic acid, triethanolamine, sodium gluconate and sodium citrate; and the mass ratio of the transition metal substance to the ligand substance is 1:(1-10).

[0009] In the embodiment of the present application, the solvent is at least two of glycerol, isopropyl alcohol, ethanol and water, and more preferably glycerol and water.

[0010] In the embodiment of the present application, the mass ratio of water to glycerol in the solvent is 1:(0.3-0.6).

[0011] In the embodiment of the present application, the temperature of the chelation reaction is 60-100℃, and the time of the chelation reaction is 1-5 hours.

[0012] In the embodiment of the present application, the ligand substance is glycerol, lactic acid, triethanolamine and sodium gluconate, and the mass ratio is 1.0-2.0:1.0-1.8:0.5-1.0:0.2-0.6.

[0013] The delayed crosslinking agent prepared by the method of the present application is a zirconium-titanium complex metal chelate, which, on the basis of the complex main ligand, utilizes the molecular size and steric hindrance effect to strengthen the temperature-controlled release property of the crosslinking agent. In the present application, the delayed crosslinking agent can form a gel with the thickening agent to facilitate sand carrying and help to enhance the temperature resistance of the system, and has certain delayed crosslinking properties under the auxiliary action of the PH regulator.

[0014] The present application also provides an acid fracturing fluid comprising a vegetable gum thickening agent, a delayed crosslinking agent, a PH regulator and water, wherein the delayed crosslinking agent is prepared by the preparation method described above.

[0015] In the embodiment of the present application, the acid fracturing fluid comprises:

[0016] 0.3-0.8wt% of the vegetable gum thickening agent;

[0017] 0.5-1.0wt% of the delayed crosslinking agent;

[0018] 0.1-1.0wt% of the PH regulator;

[0019] and the balance is water.

[0020] In the embodiment of the present application, the vegetable gum thickening agent is carboxymethyl hydroxypropyl guanidine gum, and the PH regulator is acetic acid.

[0021] In the embodiments of the present application, the pH value of the acid fracturing fluid system is between 3 and 6.

[0022] In the embodiments of the present application, the crosslinking temperature of the acid fracturing fluid is controllable at room temperature to 60 DEG C.

[0023] At present, some acid fracturing fluids in China mainly have the following deficiencies: the temperature resistance is within 90 DEG C, which cannot meet the fracturing of high-temperature reservoirs; the crosslinking time is short, resulting in high pipe friction and large construction pressure.

[0024] Compared with the prior art, the acid fracturing fluid provided by the present application adopts the above-mentioned metal complex chelate (i.e. delayed crosslinking agent), which is a delayed crosslinking acid fracturing fluid, specifically a acid fracturing fluid with viscosity release controlled by temperature, and the crosslinking time of the fracturing fluid is controlled by temperature. The delayed crosslinking acid fracturing fluid provided by the present application is a fracturing fluid system comprising the metal chelate crosslinking agent, has good high-temperature resistance, and has a delayed crosslinking effect under high-temperature conditions, which can effectively reduce the pipe friction. Experiments show that the temperature resistance of the acid fracturing fluid can reach 130 DEG C, and it is suitable for high-temperature deep wells; at 130 DEG C, the viscosity of the acid fracturing fluid is greater than 100 mPa.s after shearing for 170 s -1 After shearing for 130 min, the viscosity of the base fluid is still greater than 100 mPa.s. By adjusting the pH value of the system, the present application realizes the effect of controllable crosslinking temperature, and can avoid crosslinking of the fracturing fluid during transportation to the bottom of the well, thereby reducing the pumping pressure.

[0025] Further, the thickening agent of the system of the present application adopts a double-modified carboxymethyl hydroxypropyl guanidated guar gum, i.e. introducing hydrophilic groups carboxymethyl and hydroxypropyl into the molecular structure of the guanidated guar gum. After modification, the water-insoluble substance is reduced, the water-soluble speed is accelerated, and the corrosion storage performance is improved. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The infrared spectrum of the delayed crosslinking agent prepared for some embodiments of the present application;

[0027] Figure 2 The rheological curve of the fracturing fluid with viscosity release temperature of about 25 DEG C in Example 1;

[0028] Figure 3 The rheological curve of the fracturing fluid with viscosity release temperature of about 40 DEG C in Example 1;

[0029] Figure 4 The rheological curve of the fracturing fluid with viscosity release temperature of about 50 DEG C in Example 1;

[0030] Figure 5 The rheological curve of the fracturing fluid with viscosity release temperature of about 60 DEG C in Example 1;

[0031] Figure 6 High temperature rheology curve of the acid fracturing fluid system of Comparative Example 1. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0033] The present application provides a method for preparing a delayed crosslinking agent, comprising the following steps:

[0034] The transition metal substance and the ligand substance are subjected to a chelation reaction in a solvent to obtain the delayed crosslinking agent.

[0035] The transition metal substance is a zirconium source and a titanium source, the zirconium source is one or more of zirconium nitrate, zirconium sulfate and zirconium oxychloride, and the titanium source is titanium tetrachloride; the ligand substance is at least three of glycerol, lactic acid, triethanolamine, sodium gluconate and sodium citrate; and the mass ratio of the transition metal substance to the ligand substance is 1:(1-10).

[0036] The delayed crosslinking agent prepared by the method provided by the present application can realize delayed crosslinking at high temperature and effectively reduce the friction.

[0037] In the embodiments of the present application, the transition metal substance and the ligand substance are mixed and heated in a solvent in a certain proportion to perform a chelation reaction, thereby obtaining a metal chelate, i.e., a delayed crosslinking agent. The transition metal substance is a zirconium source and a titanium source. Zirconium ions complex water molecules in water, and then form polynuclear hydroxyl-bridged complex ions through a hydrolysis and hydroxyl bridging process. The polynuclear hydroxyl-bridged complex ions also have multiple active groups. In addition, because the atomic radius of the transition metal is large, the transition metal ion has strong electricity absorption capacity. The polynuclear hydroxyl-bridged complex ions have high reactivity with the hydroxyl groups and carboxyl groups of the gelling agent. Therefore, the transition metal ion crosslinking agent formed by the present application has the characteristics of high crosslinking efficiency and low dosage, and the formed crosslinking structure has high strength and good stability.

[0038] In the present application, the zirconium source is one or more of inorganic zirconium salts of zirconium nitrate, zirconium sulfate and zirconium oxychloride, and more preferably zirconium sulfate and / or zirconium oxychloride. The titanium source is titanium tetrachloride, and the mass ratio of the zirconium source to the titanium source is preferably (4.0-6.3):1. In the embodiments of the present application, the solvent is at least two of glycerol, isopropyl alcohol, ethanol and water, and more preferably glycerol and water. The ligand substance is at least three of glycerol, lactic acid, triethanolamine, sodium gluconate and sodium citrate, and can be glycerol, lactic acid, triethanolamine and sodium gluconate, or glycerol, lactic acid, triethanolamine and sodium citrate. Among them, glycerol, also known as glycerol, can play the dual role of ligand and solvent.

[0039] In the present application, the mass ratio of the transition metal substance to the ligand substance is 1:(1-10), and preferably 1:(3-6). In some embodiments, the mass ratio of each ligand is as follows: glycerol is 1.0-2.0, lactic acid is 1.0-1.8, triethanolamine is 0.5-1.0, and sodium gluconate or sodium citrate is 0.2-0.6. As a preferred, the mass ratio of water to glycerol in the solvent is 1:(0.3-0.6). The amount of the solvent used in the present application can ensure that the reaction can proceed smoothly in the solvent.

[0040] In the embodiments of the present application, the chelation reaction is preferably carried out under closed conditions. In the present application, the temperature of the reaction is preferably 60-100℃, and more preferably 80-90℃. In the present application, the reaction time is preferably 1-5 hours, and more preferably 1.5-3 hours. The raw material ratio and preparation conditions of the embodiments of the present application ensure that the obtained delayed crosslinking agent has good high-temperature resistance and delayed crosslinking effect, and is simple to prepare and efficient.

[0041] The method for preparing the metal chelate compound in some embodiments of the present application comprises: carrying out a chelation reaction of high-valence metal substance and ligand substance in water to obtain a metal chelate compound. The high-valence metal substance is zirconium oxychloride or zirconium sulfate, and titanium tetrachloride, and the ligand substance includes glycerol, lactic acid, triethanolamine, sodium gluconate (or sodium citrate). The delayed crosslinking agent prepared in the embodiments of the present application is generally a yellow transparent liquid with no viscosity, can form a gel with a densification agent to facilitate sand carrying, and has certain delayed crosslinking characteristics.

[0042] The molecular structure of the delayed crosslinking agent in some embodiments of the present application is shown below, and the key structure groups are shown in the infrared data: 505cm -1 Zr-O stretching vibration peak, 1144cm -1 C-N bond stretching vibration peak, 1611cm -1 stretching vibration peak of carbonyl group, 3143cm -1 hydroxyl stretching vibration peak, 3623cm-1 Carboxylic acid hydroxyl stretching vibration peak.

[0043]

[0044] The crosslinking agent prepared by the method has a zirconium-titanium complex center ion, and on the basis of the complex main ligand, the molecular size and the steric hindrance effect are utilized to combine with the ligand, so that the temperature control release property of the crosslinking agent is strengthened.

[0045] The acid fracturing fluid provided by the application comprises a plant gum thickening agent, a delayed crosslinking agent, a PH adjusting agent and water, and the delayed crosslinking agent is prepared by the preparation method described above.

[0046] In the embodiment of the application, the acid fracturing fluid comprises 0.3-0.8 wt% of the plant gum thickening agent, and the wt% is the mass percentage, that is, the mass concentration of the plant gum thickening agent can be 0.3-0.8%, preferably 0.4-0.6%, and more preferably 0.55%. In the application, the thickening agent is used to increase the viscosity of the aqueous solution and form a gel with the crosslinking agent to carry the proppant into the formation in the fracturing operation. The plant gum thickening agent used in the application is preferably carboxymethyl hydroxypropyl guanidine gum (with a relative molecular mass of about 2 million), which is a commercially available product and is used to increase the viscosity of the aqueous solution. The guanidine gum is a long-chain high-molecular polymer composed of mannose and galactose, and the carboxymethyl hydroxypropyl guanidine gum is further used as the thickening agent in the application, that is, the hydrophilic groups carboxymethyl and hydroxypropyl are introduced into the molecular structure of the guanidine gum. After modification, the water-insoluble substance is reduced, the water-soluble speed is accelerated, and the corrosion storage performance is improved.

[0047] In the embodiment of the application, the acid fracturing fluid comprises 0.5-1.0 wt% of the delayed crosslinking agent; the mass concentration of the delayed crosslinking agent can be 0.5-1.0%, preferably 0.6-0.8%, and more preferably 0.7%. The delayed crosslinking agent is the product obtained by the preparation method described above, which can form a gel with the thickening agent to facilitate sand carrying and has a certain delayed crosslinking property.

[0048] In the application, the mass concentration of the PH adjusting agent can be 0.1-2.0%, preferably 0.1-1.0%, and more preferably 0.1-0.8%. The PH adjusting agent is preferably acetic acid, which is used to adjust the pH value of the fracturing fluid system, and the pH value of the system can be adjusted to 3-6, thereby assisting the crosslinking agent in controlling the crosslinking temperature.

[0049] In the present application, the preparation method of the acid fracturing fluid is preferably: mixing the balance of water and plant gum thickening agent to obtain a mixture; placing the mixture after mixing with a pH regulator to obtain a base fluid; mixing the base fluid with a delayed crosslinking agent to obtain a temperature-controlled acid fracturing fluid. The acid fracturing fluid provided in the present application is mainly composed of hydroxypropyl carboxymethyl guanidine gum, the metal chelate crosslinking agent described above, and a pH regulator, and can still achieve the effect of delayed crosslinking under high temperature conditions. The fracturing fluid is a temperature-controlled viscosity-released acid fracturing fluid, which has the advantages of high temperature resistance, temperature-controlled crosslinking, low friction, low residue, etc., and is suitable for low permeability oil and gas reservoirs, solving the problems of clay swelling and migration, and high pipe string friction.

[0050] In the embodiments of the present application, the mixing is preferably carried out under stirring. In the present application, the temperature of the placing is preferably 20-40℃, more preferably 25-35℃, and most preferably 30℃; the time of the placing is preferably 3-5 hours, more preferably 3.5-4.5 hours, and most preferably 4 hours; the placing makes the viscosity of the base fluid tend to be stable. In the embodiments of the present application, the pH value of the acid fracturing fluid system is between 3 and 6; the crosslinking temperature of the acid fracturing fluid is controllable at room temperature to 60℃, and is basically not affected by time.

[0051] The acid fracturing fluid described in the present application is a water-based fracturing fluid. In some embodiments, under the conditions of 0.55% thickening agent and 0.1%-0.8% PH regulator, the viscosity of the fracturing fluid is 50 mPa·s, the pH is 3-6 (acidic), the density is about 1.0 mg / cm 3 .

[0052] The delayed crosslinking acid fracturing fluid provided in the embodiments of the present application is a temperature-controlled viscosity-released acid fracturing fluid. The delayed crosslinking acid fracturing fluid provided in the present application has the following advantages compared with the prior art:

[0053] The crosslinking time of the fracturing fluid is controlled by temperature; by adjusting the pH value of the system, the effect of controllable crosslinking temperature is achieved, which can avoid crosslinking of the fracturing fluid during transportation to the bottom of the well, and reduce the pumping pressure.

[0054] The temperature resistance can reach 130℃, which is suitable for high temperature deep wells; for high temperature alkali-sensitive reservoirs above 100℃, the damage to the formation can be reduced, and the high temperature resistance is good.

[0055] In order to further understand the present application, the preparation method of a delayed crosslinking agent and the acid fracturing fluid provided in the present application are described in detail below in combination with embodiments.

[0056] In the following examples, the thickening agent is carboxymethyl hydroxypropyl guar gum (relative molecular mass of about 2 million), provided by Beijing Baofengchunshi Petroleum Technology Co., Ltd.; the PH regulator is acetic acid, provided by Dongying Jiayi Chemical Industry.

[0057] Example 1

[0058] Water: glycerol is mixed in a mass ratio of 1:0.5 to prepare a solvent, and then high-valence metal substances (zirconium oxychloride: titanium tetrachloride = 4.0:1 in mass ratio), glycerol, lactic acid, triethanolamine, and sodium gluconate are mixed in a mass ratio of 1:1.5:1.3:0.8:0.4 in the above solvent to carry out a reaction, the reaction temperature is 80°C, and the reaction time is 2.5 hours, to obtain a delayed crosslinking agent.

[0059] Figure 1 The infrared spectrum of the crosslinking agent obtained in Example 1 and 2 is shown in the figure, wherein 505 cm -1 is the Zr-O stretching vibration peak, 1144 cm -1 is the C-N bond stretching vibration peak, 1611 cm -1 is the carbonyl stretching vibration peak, 3143 cm -1 is the hydroxyl stretching vibration peak, and 3623 cm -1 is the carboxylic acid hydroxyl stretching vibration peak.

[0060] Example 2

[0061] Water: glycerol is mixed in a mass ratio of 1:0.5 to prepare a solvent, and then high-valence metal substances (zirconium sulfate: titanium tetrachloride = 6.3:1 in mass ratio), glycerol, lactic acid, triethanolamine, and potassium gluconate are mixed in a mass ratio of 1:1.3:1.0:0.6:0.4 in the above solvent to carry out a reaction, the reaction temperature is 90°C, and the reaction time is 2 hours, to obtain a delayed crosslinking agent.

[0062] Example 3

[0063] Take 1000 mL of water in a mixer, start stirring, add 5.5 g of carboxymethyl hydroxypropyl guar gum, stir for 5 minutes, then add a certain amount (see Table 1 below) of pH regulator, stir for 3 minutes, and place it at 30°C for 4 hours to make its viscosity tend to be stable, to obtain a base solution.

[0064] Take 60 mL of the above base solution, add 0.42 g of the delayed crosslinking agent prepared in Example 1, and stir uniformly to obtain an acidic plant gum fracturing fluid.

[0065] Temperature resistance and shear resistance performance test:

[0066] The corresponding crosslinking temperature and rheological curve under different amounts of PH regulator are shown in Table 1 and Figures 2-6 According to the test results, the crosslinking temperature of the delayed crosslinking agent prepared in Example 1 is 70°C, and the crosslinking temperature of the delayed crosslinking agent prepared in Example 2 is 80°C.Figures 2-6 At 130℃, 170s -1 After shearing for 130 minutes, the viscosity of the base liquid was still greater than 100 mPa·s.

[0067] Table 1. pH Adjuster Dosage and Attached Diagram Explanation

[0068]

[0069] Test conditions: The high-temperature and shear resistance of the fracturing fluid was tested using an RS6000 high-temperature and high-pressure rheometer. The test temperature was 130℃ and the shear rate was 170s. -1 The shearing time was 90 minutes.

[0070] Determination of residue content:

[0071] Referring to standard SY / T 5107-2016 "Performance Evaluation Method of Water-Based Fracturing Fluids", 50 ml of the base fluid prepared in Example 3 (50 ml water + 0.05 g pH adjuster + 0.275 g carboxymethyl hydroxypropyl guar gum) was taken, and 0.05 g of capsule breaker was added. After stirring evenly, 0.35 g of the crosslinking agent prepared in the example was added, and the mixture was stirred evenly to form a gel state. Under sealed conditions, the mixture was kept at 90°C for 3 hours to allow complete gel breaking.

[0072] All the gelling fluid was poured into a dried 50ml centrifuge tube and centrifuged at 3000 rpm for 30 minutes. After discarding the supernatant, 50ml of water was added, and the mixture was centrifuged again for 20 minutes. The supernatant was then discarded, and the centrifuge tube was dried to constant weight. The residue content was calculated and shown in Table 2 below. It can be seen that this acidic fracturing fluid has low residue and causes minimal damage to the reservoir.

[0073] Table 2 Comparison of Residue Content in Different Systems

[0074]

[0075] Comparative Example 1

[0076] The fracturing fluid prepared in Example 3 of this application has a pH value of 3-6. If the pH value of this system is adjusted to 2, its rheological curve is as follows. Figure 6 As shown, the system exhibits high initial viscosity (approximately 280 mPa·s) and poor temperature resistance under strong acid conditions (viscosity 72.5 mPa·s after 90 min at 130℃).

[0077] From the above examples, the crosslinking acid fracturing fluid provided by the application includes the metal chelate crosslinking agent, has good high temperature resistance, small reservoir damage, and a delayed crosslinking effect under high temperature conditions, and can effectively reduce the pipe friction. The application realizes the controllable crosslinking temperature effect by adjusting the PH value of the system to 3-6, can avoid crosslinking of the fracturing fluid during transportation to the well bottom, and reduces the pumping pressure.

[0078] The above only describes the preferred embodiments of the application, and it should be noted that the skilled in the art can make various modifications to the embodiments without departing from the technical principles of the application, and these modifications should also be considered as the scope of protection of the application.

Claims

1. A method for preparing a retarded crosslinking agent for acidic fracturing fluids, characterized in that, Includes the following steps: A chelation reaction between a transition metal substance and a ligand substance in a solvent yields a retarded crosslinking agent. The transition metal is a zirconium source and a titanium source, wherein the zirconium source is one or more of zirconium nitrate, zirconium sulfate, and zirconium oxychloride, and the titanium source is titanium tetrachloride; the ligand is at least three of glycerol, lactic acid, triethanolamine, sodium gluconate, and sodium citrate; the mass ratio of the transition metal to the ligand is 1:(1-10); and the solvent is at least two of glycerol, isopropanol, ethanol, and water. The chelation reaction is carried out at a temperature of 60-100°C for 1-5 hours.

2. The preparation method according to claim 1, characterized in that, The solvent is glycerol and water.

3. The preparation method according to claim 2, characterized in that, The mass ratio of water to glycerol in the solvent is 1:(0.3-0.6).

4. The preparation method according to any one of claims 1-3, characterized in that, The ligands are glycerol, lactic acid, triethanolamine and sodium gluconate in a mass ratio of 1.0-2.0:1.0-1.8:0.5-1.0:0.2-0.

6.

5. An acidic fracturing fluid, characterized in that, It includes a plant-based thickener, a crosslinking retarder, a pH adjuster, and water, wherein the crosslinking retarder is prepared by the preparation method according to any one of claims 1-4; the crosslinking temperature of the acidic fracturing fluid is controllable from room temperature to 60°C.

6. The acidic fracturing fluid according to claim 5, characterized in that, The acidic fracturing fluid includes: 0.3-0.8wt% plant-based gum thickener; 0.5-1.0 wt% crosslinking retarder; 0.1-1.0 wt% pH adjuster; The remainder is water.

7. The acidic fracturing fluid according to claim 5, characterized in that, The plant gum thickener is carboxymethyl hydroxypropyl guanidine gum; the pH adjuster is acetic acid.

8. The acidic fracturing fluid according to any one of claims 5-7, characterized in that, The pH value of the acidic fracturing fluid system is between 3 and 6.

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