Seawater-based guar gum fracturing fluid and preparation method thereof

Abstract

The invention provides a seawater-based guar gum fracturing fluid and a preparation method thereof, and belongs to the technical field of seawater-based fracturing fluids, the seawater-based guar gum fracturing fluid comprises the following components by volume: 100 parts of a guar gum aqueous solution; 0.1 to 1 part of an anti-swelling agent; 0.1-1 part of a discharge aiding agent; 0.1 to 1 part of a pH regulator; the guar gum aqueous solution is prepared by dissolving hydroxypropyl cationic guar gum in seawater, and the cross-linking agent is prepared by dissolving the hydroxypropyl cationic guar gum in the seawater. The anti-swelling agent is prepared by dissolving choline chloride in a cationic guar gum breaking solution; the cleanup additive is prepared by dissolving a nonionic surfactant in a cationic guar gum breaking solution. The seawater-based guar gum fracturing fluid provided by the invention can obviously improve the clay expansion inhibition performance.

Description

Technical Field

[0001] The present invention relates to the technical field of seawater-based fracturing fluids, and in particular to a seawater-based guar gum fracturing fluid and a preparation method thereof. Background Art

[0002] Unconventional oil and gas resources such as offshore low-permeability and tight oil and gas are playing an increasingly important role in oil and gas exploitation. However, the natural permeability of such resources is extremely low, and there is basically no natural production. In order to improve the seepage capacity of the reservoir and increase the single-well production, reservoir stimulation is usually achieved through fracturing. Conventional fresh water-based guar gum fracturing fluids have been gradually replaced by seawater-based guar gum fracturing fluids due to limitations such as difficult transportation. However, marine unconventional oil and gas fields mainly consist of sandstone reservoirs, which are characterized by relatively deep geological burial and large shale content. When using seawater-based guar gum fracturing fluids in fracturing operations, rock and soil swelling is also likely to occur, blocking the fluid flow channels, resulting in the post-fracture production not meeting expectations.

[0003] Therefore, how to improve the anti-swelling performance of seawater-based guar gum fracturing fluids is an urgent problem to be solved for seawater-based guar gum fracturing fluids. To improve the anti-swelling performance of traditional common fracturing fluids, small molecule organic ammonium salts and inorganic potassium compounds are added to the fracturing fluid system. Due to their relatively small molecular weight, their adsorption on clay and ability to inhibit swelling are relatively weak, and the clay anti-swelling effect is limited. Summary of the Invention

[0004] The seawater-based guar gum fracturing fluid of the present invention uses hydroxypropyl cationic guar gum as a thickener, and after crosslinking and gel breaking (it will break gel after entering the formation), an organic ammonium salt compound with a molecular weight of 10,000 to 50,000 is formed, which can efficiently adsorb clay with charges and inhibit clay swelling. In addition, the organic ammonium salt compound after gel breaking is added to the fracturing fluid system in the form of an auxiliary solvent, further increasing the dosage of the organic ammonium salt compound in the fracturing system, thereby further improving the anti-swelling effect of the fracturing fluid entering the reservoir.

[0005] One object of the present invention is to provide a seawater-based guar gum fracturing fluid.

[0006] Another object of the present invention is to provide a preparation method of the seawater-based guar gum fracturing fluid.

[0007] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0008] In the first aspect, the present invention provides a seawater-based guar gum fracturing fluid, including the following components by volume fraction:

[0009] 100 parts of an aqueous guar gum solution;

[0010] 0.1 - 1 part of an anti-swelling agent, preferably 0.3 part;

[0011] The drainage aid is 0.1 - 1 part, preferably 0.3 part;

[0012] The pH regulator is 0.1 - 1 part, preferably 0.5 part,

[0013] The crosslinking agent is 0.1 - 1 part, preferably 0.3 part,

[0014] wherein the guar gum aqueous solution is prepared by dissolving hydroxypropyl cationic guar gum in seawater;

[0015] The anti-swelling agent is prepared by dissolving choline chloride in the breaker solution of cationic guar gum;

[0016] The drainage aid is prepared by dissolving a non-ionic surfactant in the breaker solution of cationic guar gum.

[0017] The following is a detailed description of each component:

[0018] Guar gum aqueous solution:

[0019] The guar gum aqueous solution of the present invention is prepared by dissolving hydroxypropyl cationic guar gum in seawater.

[0020] In some embodiments, each 100 mL of seawater in the guar gum aqueous solution contains 0.2 - 0.5 g of hydroxypropyl cationic guar gum.

[0021] Hydroxypropyl cationic guar gum is obtained by hydroxypropylation and cationization of guar gum.

[0022] In some embodiments, hydroxypropyl cationic guar gum is prepared by the following method:

[0023] First, guar gum is hydroxypropylated, then washed and dried;

[0024] Then, the hydroxypropylated guar gum is cationized with a cationic etherifying agent, and then washed and dried.

[0025] Preferably, the degree of hydroxypropyl substitution is 0.15 - 0.25; the test method is nuclear magnetic resonance hydrogen spectroscopy.

[0026] Preferably, the degree of cationic substitution is 0.25 - 0.30; the test method is Kjeldahl method.

[0027] Preferably, the cationic etherifying agent is 3-chloro-2-hydroxypropyltrimethylammonium chloride;

[0028] Preferably, the washing is carried out with 80% ethanol aqueous solution, and the drying is carried out by air drying.

[0029] For every 100 mL of the guar gum aqueous solution, the typical but non-limiting weight of hydroxypropyl cationic guar gum is, for example, 0.2 g, 0.3 g, 0.4 g, 0.5 g, but not limited thereto.

[0030] The volume fraction of the guar gum aqueous solution is 100 parts.

[0031] By using hydroxypropyl cationic guar gum as a thickener, the hydrogen bond of guar gum is destroyed through hydroxypropylation modification of guar gum, and the instant solubility of guar gum is improved; through cationic modification of guar gum, a cationic compound with a molecular weight of 10,000 to 50,000 can be formed after the crosslinking and gel breaking of guar gum in the later stage, which can improve the anti-swelling performance of the fracturing fluid.

[0032] Anti-swelling agent:

[0033] The anti-swelling agent of the present invention is prepared by dissolving choline chloride in the gel-breaking liquid of cationic guar gum.

[0034] In some embodiments, the gel-breaking liquid of cationic guar gum is prepared by the following method:

[0035] Prepare an aqueous solution of cationic guar gum with a mass concentration of 0.8-1.1% (the cationic substitution degree of cationic guar gum is greater than 0.3), crosslink it with an organic boron crosslinking agent, and break the gel with ammonium persulfate with a concentration of 300-500 ppm to obtain a gel-breaking liquid (the molecular weight of the gel-breaking liquid is about 300,000-2,000,000); after the gel-breaking liquid is filtered or centrifuged, a gel-breaking liquid of cationic guar gum is obtained.

[0036] Preferably, the volume ratio of the organic boron crosslinking agent to the aqueous solution of cationic guar gum is 0.1-1.0:100, preferably 0.1:100.

[0037] Cationic guar gum is obtained by cationization of guar gum.

[0038] In some embodiments, the cationic guar gum is prepared by the following method:

[0039] Cationize guar gum with a cationic etherifying agent, and then wash and dry it.

[0040] Preferably, the cationic substitution degree is greater than 0.30; the test method is nuclear magnetic resonance hydrogen spectrum method.

[0041] Preferably, the cationic etherifying agent is 3-chloro-2-hydroxypropyltrimethylammonium chloride;

[0042] Preferably, the washing is carried out with an 80% aqueous ethanol solution, and the drying is carried out by air drying.

[0043] In some embodiments, the mass concentration of choline chloride in the gel-breaking liquid of cationic guar gum is 2-30%, such as 2%, 3%, 5%, 6%, 8%, 10%, 12%, 15%, 16%, 18%, 20%, 22%, 25%, 26%, 28%, 30%, but not limited thereto.

[0044] The volume fraction of the anti-swelling agent is, for example, 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.8 part, but not limited thereto.

[0045] Choline chloride is dissolved in a cationic guar gum breaker solution to prepare an anti-swelling agent. The solute is choline chloride, which is a cationic compound and has the property of preventing clay swelling; the solvent breaker solution contains a cationic compound with a molecular weight of 10,000 - 50,000, further enhancing the anti-swelling performance of the additive.

[0046] Flowback aid:

[0047] The flowback aid of the present invention is prepared by dissolving a non-ionic surfactant in a cationic guar gum breaker solution.

[0048] In some embodiments, the cationic guar gum breaker solution is prepared by the following method:

[0049] Prepare an aqueous solution of cationic guar gum with a mass concentration of 0.8 - 1.1% (the cationic substitution degree of cationic guar gum is greater than 0.3), crosslink it with an organic boron crosslinking agent, and break the gel with ammonium persulfate with a concentration of 300 - 500 ppm to obtain a breaker solution (the molecular weight of the breaker solution is about 30,000 - 200,000); after the breaker solution is filtered or centrifuged, a cationic guar gum breaker solution is obtained.

[0050] Preferably, the volume ratio of the organic boron crosslinking agent to the aqueous solution of cationic guar gum is 0.1 - 1:100, preferably 0.1:100.

[0051] Cationic guar gum is obtained by cationizing guar gum.

[0052] In some embodiments, the cationic guar gum is prepared by the following method:

[0053] Cationize guar gum with a cationic etherifying agent, and then wash and dry it.

[0054] Preferably, the cationic substitution degree is greater than 0.30; the test method is nuclear magnetic resonance hydrogen spectrum method.

[0055] Preferably, the cationic etherifying agent is 3-chloro-2-hydroxypropyltrimethylammonium chloride;

[0056] Preferably, the washing is carried out with an 80% aqueous ethanol solution, and the drying is carried out by air drying.

[0057] In some embodiments, the mass concentration of the non-ionic surfactant in the cationic guar gum breaker solution is 1 - 5%, such as 1%, 2%, 3%, 4%, 5%, but not limited thereto.

[0058] The non-ionic surfactant includes but is not limited to alkylphenol polyoxyethylene ether, etc.

[0059] The volume fraction of the flowback aid is, for example, 0.1 part, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.8 parts, but is not limited thereto.

[0060] The non-ionic surfactant is dissolved in the cationic guar gum breaker solution to prepare a flowback aid. The prepared flowback aid not only plays a role in assisting the flowback of the fluid after the gel breaking of the fracturing fluid, but also contains a cationic compound with a molecular weight of 10,000 to 50,000 in the solvent breaker solution, further improving the swelling prevention performance of the additive.

[0061] pH regulator:

[0062] In some embodiments, the pH regulator is prepared by compounding ammonia water-ammonium chloride buffer solution and hexamethylenediamine.

[0063] In a specific embodiment, the pH regulator is prepared according to the following ratio:

[0064] 5.4 g of ammonium chloride and 35 mL of ammonia water are diluted with water to 95 mL of aqueous solution, and then 15 mL of hexamethylenediamine is added.

[0065] The volume fraction of the pH regulator is, for example, 0.1 part, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.8 parts, but is not limited thereto.

[0066] Crosslinking agent:

[0067] The crosslinking agent can be an organic boron crosslinking agent.

[0068] The volume fraction of the crosslinking agent is, for example, 0.1 part, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.8 parts, but is not limited thereto.

[0069] In a second aspect, the present invention provides a preparation method of the above seawater-based guar gum fracturing fluid, comprising the following steps:

[0070] (1) Preparation of guar gum aqueous solution: Hydroxypropyl cationic guar gum is added to seawater to obtain a guar gum aqueous solution;

[0071] (2) Adding an anti-swelling agent, a flowback aid, a pH regulator and a crosslinking agent to the guar gum aqueous solution, and mixing evenly to obtain a seawater-based guar gum fracturing fluid.

[0072] Each component is the same as described in the first aspect.

[0073] Beneficial effects

[0074] The fracturing fluid of the present invention uses hydroxypropyl cationic guar gum as a thickener. After crosslinking and gel breaking in the later stage, an organic ammonium salt compound with a molecular weight of 10,000 to 50,000 is formed, which can efficiently adsorb clay with charges and inhibit clay swelling. In addition, the organic ammonium salt compound after gel breaking is added to the fracturing fluid system in the form of an auxiliary solvent to further increase the dosage of the organic ammonium salt compound in the fracturing system, thereby further improving the anti-swelling effect of the fracturing fluid entering the reservoir.

[0075] The present invention has been described in detail above, but the above embodiments are essentially illustrative only and are not intended to limit the present invention. In addition, the present invention is not limited by any theory described in the foregoing prior art or the summary of the invention or the following examples. Detailed Description of the Invention

[0076] The following examples are used to further illustrate the present invention. It should be noted that the following examples are provided for illustrative purposes only and do not constitute a limitation to the scope of the present invention claimed.

[0077] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the examples are all conventional raw materials, reagents, methods in the art.

[0078] The raw materials involved in the examples and comparative examples are as follows:

[0079] The guar gum powder was purchased from China National Petroleum Chemical Kunshan Co., Ltd., grade Guar first-class;

[0080] The organic boron crosslinking agent was purchased from China National Petroleum Chemical Kunshan Co., Ltd., grade OBC-2.

[0081] Example 1

[0082] 1. Preparation of hydroxypropyl cationic guar gum:

[0083] 100 g of guar gum powder was added with 20 g of propylene oxide and 100 g of 20% sodium hydroxide solution. Under nitrogen protection, at a pressure of 0.05 Mpa and a temperature of 60 °C, hydroxypropylation was first carried out. After the reaction, the degree of substitution was 0.23. After washing with 70% aqueous ethanol solution, it was dried by air flow. Then, 100 g of hydroxypropylated guar gum was reacted with 50 g of 3-chloro-2-hydroxypropyltrimethylammonium chloride and 100 g of 15% sodium hydroxide solution under nitrogen protection at 0.07 Mpa and 65 °C for cationization reaction. The degree of cationic substitution was 0.27. After washing with 80% aqueous ethanol solution, it was dried by air flow and then neutralized with citric acid to obtain hydroxypropyl cationic guar gum. 2 gas protection, at a pressure of 0.05 Mpa and a temperature of 60 °C, hydroxypropylation was first carried out. After the reaction, the degree of substitution was 0.23. After washing with 70% aqueous ethanol solution, it was dried by air flow. Then, 100 g of hydroxypropylated guar gum was reacted with 50 g of 3-chloro-2-hydroxypropyltrimethylammonium chloride and 100 g of 15% sodium hydroxide solution under nitrogen 2 gas protection at 0.07 Mpa and 65 °C for cationization reaction. The degree of cationic substitution was 0.27. After washing with 80% aqueous ethanol solution, it was dried by air flow and then neutralized with citric acid to obtain hydroxypropyl cationic guar gum.

[0084] 2. Preparation of hydroxypropyl cationic guar gum aqueous solution (base fluid):

[0085] Take 0.40 g of hydroxypropyl cationic guar gum and dissolve it in 100 mL of seawater to prepare a hydroxypropyl cationic guar gum aqueous solution (base solution).

[0086] 3. Preparation of cationic guar gum breaking liquid:

[0087] 100g guar gum powder, 53g 3-chloro-2-hydroxypropyltrimethylammonium chloride, and 100g 16% sodium hydroxide solution were mixed in N 2 The cationization reaction was carried out under the condition of 0.07Mpa and 65℃, and the degree of cationic substitution was 0.31. After washing with 80% ethanol aqueous solution, it was dried in air flow and neutralized with citric acid to obtain cationic guar gum.

[0088] Take 0.9 g of cationic guar gum with a substitution degree of 0.31, dissolve it in 100 mL of tap water to prepare a 0.9% aqueous solution, add 0.1 mL of an organic boron crosslinking agent for crosslinking, add 500 ppm of ammonium persulfate at 90° C. to break the crosslinked gel. After breaking the gel, filter or centrifuge to obtain a cationic guar gum clear solution.

[0089] 4. Preparation of drainage aid:

[0090] Take 2g of alkylphenol polyoxyethylene ether and dissolve it in 100g of cationic guar gum breaking liquid at a concentration of 2%.

[0091] 5. Preparation of anti-swelling agent:

[0092] Take 5g of choline chloride and dissolve it in 100g of cationic guar gum breaking liquid to a concentration of 5%.

[0093] 6. Preparation of pH adjuster:

[0094] 5.4g ammonium chloride + 35mL ammonia water is diluted with water to become 95mL aqueous solution, and then 15mL hexamethylenediamine is added to prepare in this proportion.

[0095] The fracturing fluid formula is: 100 mL of 0.4% hydroxypropyl cationic guar gum aqueous solution, 0.3 mL of drainage aid, 0.3 mL of anti-swelling agent, 0.5 mL of pH regulator, and 0.3 mL of organic boron cross-linking agent.

[0096] Example 2

[0097] 1. Preparation of Hydroxypropyl Cationic Guar Gum:

[0098] 100g of guar gum powder was added with 21g of propylene oxide and 100g of 17% sodium hydroxide solution. 2Under gas protection, at a pressure of 0.07 Mpa and a temperature of 65 °C, propoxylation was carried out first. After the reaction, the degree of substitution was 0.25. After washing with an 80% ethanol aqueous solution, it was dried by air flow. Then, 100 g of propoxylated guar gum was mixed with 47 g of 3-chloro-2-hydroxypropyltrimethylammonium chloride and 100 g of 15% sodium hydroxide solution in N 2 Under gas protection at 0.07 Mpa and 65 °C, cationization reaction was carried out, and the cationic degree of substitution was 0.26. After washing with an 80% ethanol aqueous solution, it was dried by air flow, and then neutralized with citric acid to obtain propoxylated cationic guar gum.

[0099] 2. Preparation of propoxylated cationic guar gum aqueous solution:

[0100] Take 0.45 g of propoxylated cationic guar gum and dissolve it in 100 mL of seawater to prepare an aqueous solution.

[0101] 3. Preparation of cationic guar gum gel-breaking clear liquid:

[0102] Mix 100 g of guar gum powder with 58 g of 3-chloro-2-hydroxypropyltrimethylammonium chloride and 100 g of 15% sodium hydroxide solution in N 2 Under gas protection at 0.07 Mpa and 65 °C, cationization reaction was carried out, and the cationic degree of substitution was 0.35. After washing with an 80% ethanol aqueous solution, it was dried by air flow and neutralized with citric acid to obtain cationic guar gum;

[0103] Take 1 g of cationic guar gum with a degree of substitution of 0.35 and dissolve it in 100 mL of tap water to prepare a 1.0% aqueous solution. Add 0.1 mL of organic boron cross-linking agent for cross-linking, and add 500 ppm of ammonium persulfate to break the cross-linked gel at 90 °C. After breaking the gel, filter or centrifuge to obtain the cationic guar gum gel-breaking clear liquid.

[0104] 4. Preparation of flowback aid:

[0105] Take 2 g of alkylphenol polyoxyethylene ether and dissolve it in 100 g of the cationic guar gum gel-breaking clear liquid, with a concentration of 2%.

[0106] 5. Preparation of swelling inhibitor:

[0107] Take 15 g of choline chloride and dissolve it in 100 g of the cationic guar gum gel-breaking clear liquid, with a concentration of 15%.

[0108] 6. Preparation of pH regulator:

[0109] Mix 5.4 g of ammonium chloride + 35 mL of ammonia water, dilute with water to 95 mL of aqueous solution, and then add 15 mL of hexamethylenediamine, and prepare according to this ratio.

[0110] The fracturing fluid formula is as follows: 100 mL of 0.45% aqueous solution of hydroxypropyl cationic guar gum, added with 0.3 mL of a flowback aid, 0.5 mL of an anti-swelling agent, 0.5 mL of a pH regulator, and 0.3 mL of an organic boron crosslinking agent.

[0111] Comparative Example 1

[0112] The difference between this comparative example and Example 1 is that hydroxypropyl cationic guar gum is replaced with hydroxypropyl guar gum:

[0113] 100 g of guar gum powder is added with 20 g of propylene oxide and 100 g of 20% sodium hydroxide solution, and hydroxypropylation is carried out under the conditions of N 2 gas protection, 0.06 Mpa air pressure, and 60 °C. After the reaction, the degree of substitution is 0.23. After washing with 70% aqueous ethanol solution, it is dried by air flow to obtain hydroxypropyl guar gum.

[0114] The other components and their contents are the same as those in Example 1.

[0115] Comparative Example 2

[0116] Steps 1 and 2 are the same as those in Example 1.

[0117] 3. Preparation of the flowback aid:

[0118] Take 2 g of alkylphenol polyoxyethylene ether and dissolve it in 100 g of tap water, with a concentration of 2%.

[0119] 4. Preparation of the anti-swelling agent:

[0120] Take 5 g of choline chloride and dissolve it in 100 g of tap water, with a concentration of 5%.

[0121] The preparation of the pH regulator is the same as that in Example 1.

[0122] The fracturing fluid formula is as follows: 100 mL of 0.4% aqueous solution of hydroxypropyl cationic guar gum, added with 0.3 mL of a flowback aid, 0.3 mL of an anti-swelling agent, 0.5 mL of a pH regulator, and 0.3 mL of an organic boron crosslinking agent.

[0123] Performance evaluation

[0124] 1. Fracturing fluid anti-swelling rate: It is carried out according to the SY / T 7267-2021 standard;

[0125] 2. Viscosity increasing rate of the thickener in seawater: It is carried out according to the SY / T 7267-2021 standard. For Examples 1-2 and Comparative Example 2, the hydroxypropyl cationic guar gum thickener is tested, and for Comparative Example 1, the hydroxypropyl guar gum thickener is tested.

[0126] The results are shown in Table 1.

[0127] Table 1

[0128] Sample Anti-swelling rate of fracturing fluid Viscosity increasing rate (dissolution rate) of thickener Example 1 89％ 85％ Example 2 91％ 87％ Comparative example 1 88％ 65％ Comparative example 2 70％ 85％

[0129] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: within the scope not departing from the spirit and essence defined by the claims of the present invention, the technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and these modifications or replacements are still within the scope defined by the claims of the present invention.

Claims

1. A seawater-based guar gum fracturing fluid, characterized in that, it comprises the following components in terms of volume parts: 100 parts of an aqueous guar gum solution; 0.1 - 1 part of an anti-swelling agent; 0.1 - 1 part of a flowback aid; 0.1 - 1 part of a pH regulator; 0.1 - 1 part of a crosslinking agent, wherein the aqueous guar gum solution is prepared by dissolving hydroxypropyl cationic guar gum in seawater; the anti-swelling agent is prepared by dissolving choline chloride in the cationic guar gum breaker solution; the flowback aid is prepared by dissolving a non-ionic surfactant in the cationic guar gum breaker solution.

2. The seawater-based guar gum fracturing fluid according to claim 1, characterized in that, each 100 mL of seawater in the aqueous guar gum solution contains 0.2 - 0.5 g of hydroxypropyl cationic guar gum.

3. The seawater-based guar gum fracturing fluid according to claim 2, characterized in that, the hydroxypropyl cationic guar gum is prepared by the following method: first carry out hydroxypropylation on the guar gum, then wash and dry it; then carry out cationization on the hydroxypropylated guar gum with a cationic etherifying agent, and then wash and dry it; preferably, the degree of hydroxypropyl substitution is 0.15 - 0.25; preferably, the degree of cationic substitution is 0.25 - 0.30; preferably, the cationic etherifying agent is 3-chloro-2-hydroxypropyl trimethyl ammonium chloride.

4. The seawater-based guar gum fracturing fluid according to claim 1, characterized in that, the cationic guar gum breaker solution is prepared by the following method: prepare an aqueous cationic guar gum solution with a mass concentration of 0.8 - 1.1%, crosslink it with an organic boron crosslinking agent, add ammonium persulfate for breaking, and obtain a breaker solution; after the breaker solution is filtered or centrifuged, the cationic guar gum breaker solution is obtained; preferably, the volume ratio of the organic boron crosslinking agent to the aqueous cationic guar gum solution is 0.1 - 1.0:100, preferably 0.1:100; preferably, the concentration of ammonium persulfate in the aqueous cationic guar gum solution is 300 - 500 ppm.

5. The seawater-based guar gum fracturing fluid according to claim 4, characterized in that, the cationic guar gum is prepared by the following method: carry out cationization on the guar gum with a cationic etherifying agent, and then wash and dry it; preferably, the degree of cationic substitution is greater than 0.30; preferably, the cationic etherifying agent is 3-chloro-2-hydroxypropyl trimethyl ammonium chloride.

6. The seawater-based guar gum fracturing fluid according to claim 5, characterized in that, the mass concentration of choline chloride in the cationic guar gum breaker solution is 2 - 30%.

7. The seawater-based guar gum fracturing fluid according to claim 5, characterized in that, the mass concentration of the non-ionic surfactant in the cationic guar gum breaker solution is 1 - 5%.

8. The seawater-based guar gum fracturing fluid according to claim 7, characterized in that, the non-ionic surfactant is alkylphenol polyoxyethylene ether.

9. The seawater-based guar gum fracturing fluid according to claim 1, characterized in that, the pH regulator is compounded by ammonia-ammonium chloride buffer solution and hexamethylenediamine.

10. A preparation method of the seawater-based guar gum fracturing fluid according to any one of claims 1 - 9, characterized in that, it comprises the following steps: (1) Preparation of guar gum aqueous solution: Add hydroxypropyl cationic guar gum to seawater to obtain a guar gum aqueous solution; (2) Add an anti-swelling agent, a flowback aid, a pH regulator, and a crosslinking agent to the guar gum aqueous solution, and mix evenly to obtain a seawater-based guar gum fracturing fluid; The anti-swelling agent is prepared by dissolving choline chloride in a cationic guar gum breaker solution; The flowback aid is prepared by dissolving a non-ionic surfactant in a cationic guar gum breaker solution.