A thiazolidinone-based amphoteric Gemini surfactant for natural gas hydrate clean fracturing fluid and its preparation method

Abstract

This invention discloses a novel thiazolidinone-based amphoteric Gemini surfactant, its preparation method, and its application. The surfactant's molecule contains two thiazolidinone groups and a long hydrophobic chain, represented by the following formula 1. This surfactant, when combined with an inorganic salt, can produce a clean fracturing fluid exhibiting excellent viscoelasticity, shear resistance, and rheological properties in low-temperature environments. This fracturing fluid complies with national petroleum and natural gas industry standards and exhibits excellent sand-carrying performance, no residue, and high temperature resistance. Furthermore, it is easy to prepare on-site and can effectively remove gel-breaking substances. This fluid causes minimal damage to formations and requires a low fracturing margin, making it suitable for natural gas hydrate extraction in low-temperature, high-pressure deep-sea areas. #imgabs0#

Description

Technical Field

[0001] The present invention belongs to the field of petrochemical industry, and specifically includes the preparation of a thiazolidinone-based amphoteric Gemini surfactant and its application in natural gas hydrate fracturing in oilfield chemistry. Background Art

[0002] Natural gas hydrates are a highly efficient and strategic energy source. Their exploration and development hold broad prospects, and they are also crucial for environmental protection and the prevention of geological disasters, attracting significant attention worldwide. The estimated reserves of natural gas hydrates on Earth are enormous, reaching 210 trillion cubic meters, roughly twice the total reserves of organic carbon, including oil, natural gas, and coal. Terrestrial hydrates are primarily found in permafrost, while marine hydrates predominate, accounting for approximately 99% of the total resource.

[0003] Hydrate reservoirs are mainly composed of clay, silt and coarse sand, and hydrate crystals are discretely distributed in the pores and cracks of the sediments. When the hydrate saturation is high, it can play a good cementing and adhesion role on the reservoir, making the reservoir have mechanical properties similar to those of silty shale gas reservoirs, and thus making it possible for the sediments to be induced with hydraulic fractures.

[0004] Hydraulic fracturing of hydrate deposits is a key area of ​​exploration for improving the natural gas hydrate extraction process and a new topic in oil and gas science. Although fracturing fluid is one of the most important components of hydraulic fracturing technology, there is still no specific fracturing fluid system specifically designed for natural gas hydrate deposits.

[0005] Conventional fracturing fluids currently suffer from low flowback rates, significant environmental pollution, and high costs. Using Gemini surfactants to create clean fracturing fluids can address these shortcomings. Compared to traditional surfactants, Gemini surfactants have an additional pair of hydrophilic and lipophilic groups. This unique structure gives Gemini surfactants many unique properties, such as high surface activity, low critical micelle concentration, excellent wettability, and unique rheological properties.

[0006] Currently, fracturing fluid systems both domestically and internationally are moving toward low-damage, highly adaptable, low-cost, and environmentally friendly technologies. Given the challenges of energy shortages and environmental pollution, the development of a novel thiazolidinone-based amphoteric Gemini surfactant fracturing fluid with excellent sand-carrying capacity, low fluid loss, high fracturing efficiency, and superior flowback capabilities to meet these increasingly stringent demands is of great practical significance. This not only improves production efficiency and reduces production costs, but also effectively minimizes adverse environmental impacts, promoting sustainable development in the energy industry and contributing new insights and approaches to the development of fracturing fluid technology. Summary of the Invention

[0007] In view of the problems existing in the current related technologies, the present invention proposes a novel thiazolidinone-based amphoteric Gemini surfactant.

[0008] Based on the above technical objectives, according to one aspect of the present invention, one object of the present invention is to provide a novel thiazolidinone-based amphoteric Gemini surfactant, which contains two thiazolidinone groups and a long hydrophobic chain in its molecule, and is represented by the following formula 1:

[0009]

[0010] Where X is -C n H 2n - structure, wherein n is an integer from 2 to 8, preferably an integer from 2 to 6, more preferably 2, 3 or 4, more preferably 3; R is a long chain alkyl-C m H 2m+1 , m is an integer from 10 to 20, more preferably, m is an integer from 12 to 18, more preferably 14, 16 or 18, more preferably 16.

[0011] According to another aspect of the present invention, another object of the present invention is to provide a method for preparing the thiazolidinone-based amphoteric Gemini surfactant, the preparation method comprising the following steps:

[0012] (1) First, thiourea, ethyl chloroacetate, and ethanol (95% by mass) were thoroughly mixed and stirred at room temperature. Nitrogen was introduced into the reaction system and the temperature was raised to react to synthesize 2-amino-4-thiazolidinone. After vacuum distillation, a white solid powder was obtained. The reaction is shown in the following reaction formula 1:

[0013]

[0014] (2) The 2-amino-4-thiazolidinone obtained in step (1) is dissolved or dispersed in a 60%-98% concentrated H2SO4 solution, the concentration range of which is cooled to -10 to 5°C, and a high-concentration NaNO2 solution is slowly added dropwise to the previous solution. After washing with water, a light yellow solid powder is obtained. The reaction is protected from light throughout the process. The reaction is shown in the following reaction formula 2:

[0015]

[0016] (3) The 2-hydroxy-4-thiazolidinone obtained in step (2) is prepared into a 0.1 mol / L solution, and an alkyl ether dioxirane compound is added dropwise. The mixture is thoroughly mixed with a Lewis acid catalyst at room temperature and stirred. The reaction temperature is raised to 30-60°C for 1-4 hours, and then raised to 60-120°C for 1-6 hours. After the reaction is complete, the mixture is washed with water and distilled under reduced pressure to obtain a colorless transparent liquid. The reaction is shown in the following reaction formula 3:

[0017]

[0018] (4) The intermediate obtained in step (3) is subjected to a quaternization reaction using a halogenated hydrocarbon (RI) to obtain the product alkylthiazolidinone diol, as shown in the following reaction formula 4:

[0019]

[0020] Preferably, the reaction time in step (1) is 1 to 5 hours, preferably 3.5 hours.

[0021] Preferably, the reaction temperature in step (1) is 30-50°C, preferably 50°C.

[0022] Preferably, the reaction temperature in step (2) is -10 to 5°C, preferably -5°C.

[0023] Preferably, the mass percentage concentration of the high concentration NaNO2 solution in step (2) is 30%-40%.

[0024] Preferably, X in the alkyldioxirane described in step (3) is (-C n H 2n -) is an integer of 2 to 8, preferably an integer of 2 to 6, more preferably 2, 3 or 4, and more preferably 3.

[0025] Preferably, the Lewis acid catalyst described in step (3) is selected from one or more of AlCl3, BF3, FeBr3, and ZnCl2, and the amount of the catalyst used is 1 to 3% by volume of the alkyl ether dioxirane compound.

[0026] Preferably, in step (3), the reaction temperature is first raised to 50° C. for 1 hour, and then raised to 80° C. for 3 hours.

[0027] Preferably, the halogenated hydrocarbon RI in step (3), wherein R is a long-chain alkyl-C m H 2m+1 , m is an integer from 10 to 20, more preferably, m is an integer from 12 to 18, more preferably 14, 16 or 18, more preferably 16.

[0028] According to another aspect of the present invention, another object of the present invention is to provide the use of the thiazolidinone-based amphoteric Gemini surfactant in natural gas hydrate fracturing fluid.

[0029] According to another aspect of the present invention, another object of the present invention is to provide a clean fracturing fluid, which comprises the thiazolidinone-based amphoteric Gemini surfactant (TG) according to the present invention at a mass percentage concentration of 0.7% to 2% and an inorganic salt at a mass percentage concentration of 0.1% to 0.5%, and the other component is water.

[0030] Preferably, the inorganic salt is selected from hydrochloride, nitrate, sulfate or phosphate of ammonium ion, alkali metal ion or alkaline earth metal ion, preferably hydrochloride, nitrate, sulfate or phosphate of ammonium ion, more preferably ammonium chloride.

[0031] The beneficial effects of the present invention are:

[0032] 1. The present invention provides a method for preparing a thiazolidinone-based amphoteric Gemini surfactant (TG) by synthesizing 2-amino-4-thiazolidinone from thiourea and ethyl chloroacetate, followed by diazotization to obtain 2-hydroxy-4-thiazolidinone, followed by a ring-opening reaction with an alkyldioxirane to produce an ether, and then quaternization. This synthesis method is environmentally friendly and simple.

[0033] 2. By combining the thiazolidinone-based amphoteric Gemini surfactant (TG) with an inorganic salt, a clean fracturing fluid with excellent viscoelasticity, shear resistance, and rheological properties in low-temperature environments was successfully developed. This fracturing fluid meets national petroleum and natural gas industry standards and features excellent sand-carrying performance, no residue, and high temperature resistance. Furthermore, it is easy to prepare on-site and can effectively remove breakers. This fluid causes minimal damage to the formation and requires a low fracturing margin, making it suitable for natural gas hydrate extraction in low-temperature, high-pressure deep-sea areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 Schematic diagram showing the interfacial tension curve of the thiazolidinone-based amphoteric Gemini surfactant (TG) prepared in Example 2;

[0036] Figure 2 Schematic diagram showing the viscoelasticity curve of the thiazolidinone-based amphoteric Gemini surfactant (TG) prepared in Example 2;

[0037] Figure 3Schematic diagram showing the viscosity curves of each fracturing fluid system in Examples 1 to 3;

[0038] Figure 4 The photographs show the clean fracturing fluids prepared in Examples 1 to 3 suspended in sand at 20°C for two hours;

[0039] Figure 5 The graph shows the viscoelasticity test curves of the thiazolidinone-based amphoteric Gemini surfactant (TG) prepared in Example 1 and the guar gum surfactant commonly used in the prior art. DETAILED DESCRIPTION

[0040] The present invention will be described in detail below. Before describing, it should be understood that the terms used in this specification and the appended claims should not be interpreted as limited to the general meaning and dictionary meaning, but should be interpreted according to the meaning and concept corresponding to the technical aspects of the present invention on the basis of the principle that allows the inventor to appropriately define the terms for the best interpretation. Therefore, the descriptions presented here are merely preferred examples for illustrative purposes and are not intended to limit the scope of the present invention. It should be understood that other equivalents or improvements can be obtained therefrom without departing from the spirit and scope of the present invention.

[0041] As used herein, the terms "comprises," "includes," "has," "contains" or any other similar terms are open conjunctions that are intended to cover non-exclusive inclusions. For example, a composition or article containing multiple elements is not limited to the elements listed herein, but may also include other elements that are not explicitly listed but are generally inherent to the composition or article. In addition, unless expressly stated to the contrary, the term "or" refers to an inclusive "or" rather than an exclusive "or." For example, any of the following situations satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist). In addition, as used herein, the terms "comprises," "includes," "has," and "contains" should be interpreted as specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as "consisting of" and "consisting essentially of."

[0042] Throughout this document, all features or conditions defined as numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered to encompass and specifically disclose all possible subranges and individual values ​​within those ranges, particularly integer values. For example, a description of a range "1 to 8" should be considered to specifically disclose all possible subranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, and so forth, particularly those defined by all integer values, and should be considered to specifically disclose individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, and 8. Unless otherwise indicated, the foregoing interpretation applies to all of the present disclosure, regardless of whether the ranges are comprehensive or not.

[0043] If a quantity or other value or parameter is expressed as a range, a preferred range, or a series of upper and lower limits, it should be understood that all ranges consisting of any upper limit or preferred value of the range and any lower limit or preferred value of the range have been specifically disclosed herein, regardless of whether these ranges are disclosed separately. In addition, when a numerical range is mentioned herein, unless otherwise specified, the range should include its endpoints and all integers and fractions within the range.

[0044] Meanwhile, in the present invention, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are polystyrene conversion molecular weights analyzed by gel permeation chromatography (GPC), and the molecular weight distribution can be calculated from the ratio Mw / Mn.

[0045] The following examples are merely examples of embodiments of the present invention and do not constitute any limitation thereto. Those skilled in the art will appreciate that modifications without departing from the spirit and scope of the present invention fall within the scope of protection of the present invention. Unless otherwise specified, the reagents and instruments used in the following examples are commercially available products.

[0046] Example 1:

[0047] (1) 7.6 g (0.1 mol) of thiourea and 12.2 g (0.1 mol) of ethyl chloroacetate were dissolved in ethanol (95%), nitrogen was introduced into the reaction system, the temperature was raised to 30-50° C., and the reaction was carried out for 1-5 hours to synthesize 2-amino-4-thiazolidinone, which was then distilled under reduced pressure to obtain a white solid powder. The 2-amino-4-thiazolidinone was then dissolved or dispersed in 0.1 mol of a 60%-90% H2SO4 solution by weight, the temperature was lowered to -10-5° C., and 0.1 mol of a 30%-40% NaNO2 solution by weight was slowly added dropwise to the solution. The reaction was shielded from light throughout, and a diazotization reaction was performed to obtain 2-hydroxy-4-thiazolidinone. 0.05 mol of an ethyl ether dioxirane compound was added dropwise, and the mixture was thoroughly mixed and stirred with 1-2 g of an AlCl3 catalyst at room temperature. Heat to 30-60℃ for 1-4 hours, then heat to 60-120℃ for 1-6 hours, wash with water after the reaction, and distill under reduced pressure to obtain the intermediate, then use 0.2 mol of C 14 H 29 I quaternizes the intermediate to obtain the product thiazolidinone-based amphoteric Gemini surfactant TG 14 , the actual yield is 57.82g.

[0048] (2) Preparation of clean fracturing fluid: Add ammonium chloride to the above-prepared thiazolidinone-based amphoteric Gemini surfactant TG 14 The clean fracturing fluid is prepared by adding ammonium chloride to an aqueous solution so that the mass percentage concentration of ammonium chloride is 0.3%, stirring the solution sufficiently to completely dissolve the ammonium chloride.

[0049] Example 2:

[0050] (1) 7.6 g (0.1 mol) of thiourea and 12.2 g (0.1 mol) of ethyl chloroacetate were dissolved in ethanol (95%), nitrogen was introduced into the reaction system, and the temperature was raised to 30-50° C. for 1-5 hours to synthesize 2-amino-4-thiazolidinone. After vacuum distillation, a white solid powder was obtained. The powder was then dissolved or dispersed in 0.1 mol of a 60%-90% H2SO4 solution by weight, and the temperature was lowered to -10-5° C. 0.1 mol of a 30%-40% NaNO2 solution by weight was slowly added dropwise to the solution. The reaction was shielded from light throughout the process, and a diazotization reaction was performed to obtain 2-hydroxy-4-thiazolidinone. 0.05 mol of a propyl ether dioxirane compound was added dropwise, and the mixture was thoroughly mixed and stirred with 1-2 g of an AlCl3 catalyst at room temperature. Heat to 30-60℃ for 1-4 hours, then heat to 60-120℃ for 1-6 hours, wash with water after the reaction, and distill under reduced pressure to obtain the intermediate, then use 0.2 mol of C 16 H 33I quaternizes the intermediate to obtain the product thiazolidinone-based amphoteric Gemini surfactant TG 16 , the actual yield is 66.13g.

[0051] (2) Preparation of clean fracturing fluid: Add ammonium chloride to the above-prepared thiazolidinone-based amphoteric Gemini surfactant TG 16 The clean fracturing fluid is prepared by adding ammonium chloride to an aqueous solution so that the mass percentage concentration of ammonium chloride is 0.3%, stirring the solution sufficiently to completely dissolve the ammonium chloride.

[0052] The surfactant prepared in this example was tested for interfacial activity, and the interfacial tension of the thiazolidinone-based amphoteric Gemini surfactant (TG) solution on crude oil was tested. First, surfactant solutions of different concentrations were prepared, with mass percentage concentrations of 0.1%, 0.2%, 0.3%...1%, and the same concentration of traditional surfactant sodium lauryl sulfate was selected for control. The oil-water interfacial tension was measured using a spinning drop interfacial tension meter. Before the test, the glass tube was first cleaned, and the test liquid was poured into the tube. The crude oil was preheated in an oven in advance, and the crude oil was squeezed into the glass tube with a syringe. The glass tube stopper was covered and the glass tube was placed in the interfacial tension meter. The temperature was kept constant at 50°C and the rotation speed was 6000r / min. The average value was obtained by three parallel measurements. The results are as follows Figure 1 As shown, Figure 1 The interfacial tension curve of the thiazolidinone-based amphoteric Gemini surfactant (TG) prepared in this example is shown in the figure. As can be seen from the figure, as the concentration of the thiazolidinone-based amphoteric Gemini surfactant (TG) increases, the interfacial tension of crude oil decreases, with the minimum oil-water interfacial tension being 0.99 mN / m. However, sodium lauryl sulfate, as a single-chain molecule, has little affinity for crude oil with increasing concentration. Therefore, when its concentration is increased, the interfacial tension does not decrease significantly and tends to stabilize, indicating that the product thiazolidinone-based amphoteric Gemini surfactant (TG) has high interfacial activity.

[0053] The thixotropy test of the clean fracturing fluid prepared in this example was carried out. The dynamic shear viscosity of the fracturing fluid system at different temperatures was measured using an MCR302 rheometer. The CC27 system was selected, the constant temperature was 10°C, and the shear rate sweep range was from 1 to 170 s -1 , then from 170 to 1s -1 The result of the staircase scan is as follows Figure 2 shown. Figure 2 The schematic diagram of the thixotropy curve of the clean fracturing fluid prepared in this example shows that as the shear rate increases, the viscosity of the system decreases, which first shows that the system is a shear-thinning fluid. -1At the beginning, the viscosity gradually recovered until the shear rate returned to the initial value. The final viscosity was slightly lower than the initial viscosity value, indicating that the fracturing fluid system has good shear recovery.

[0054] Example 3:

[0055] (1) 7.6 g (0.1 mol) of thiourea and 12.2 g (0.1 mol) of ethyl chloroacetate were dissolved in ethanol (95%), nitrogen was introduced into the reaction system, the temperature was raised to 30-50° C., and the reaction was carried out for 1-5 hours to synthesize 2-amino-4-thiazolidinone, which was then distilled under reduced pressure to obtain a white solid powder. The 2-amino-4-thiazolidinone was then dissolved or dispersed in 0.1 mol of a 60%-90% H2SO4 solution by weight, the temperature was lowered to -10-5° C., and 0.1 mol of a 30%-40% NaNO2 solution by weight was slowly added dropwise to the solution. The reaction was shielded from light throughout, and a diazotization reaction was performed to obtain 2-hydroxy-4-thiazolidinone. 0.05 mol of a butyl ether dioxirane compound was added dropwise, and the mixture was thoroughly mixed and stirred with 1-2 g of an AlCl3 catalyst at room temperature. Heat to 30-60℃ for 1-4 hours, then heat to 60-120℃ for 1-6 hours, wash with water after the reaction, and distill under reduced pressure to obtain the intermediate, then use 0.2 mol of C 18 H 37 I quaternizes the intermediate to obtain the product thiazolidinone-based amphoteric Gemini surfactant TG 18 , the actual yield is 75.26g.

[0056] (2) Preparation of clean fracturing fluid: Add ammonium chloride to the above-prepared thiazolidinone-based amphoteric Gemini surfactant TG 18 The clean fracturing fluid is prepared by adding ammonium chloride to an aqueous solution so that the mass percentage concentration of ammonium chloride is 0.3%, stirring the solution sufficiently to completely dissolve the ammonium chloride.

[0057] Test Example 1

[0058] The viscosity of the clean fracturing fluids prepared in Examples 1 to 3 was tested, and a conventional surfactant, sodium lauryl sulfate, at the same concentration was used as a control. The shear viscosity of the surfactant fracturing fluid system with a certain mass fraction was measured using an MCR302 rheometer. The prepared fracturing fluid system was pre-stabilized for 5 minutes at a shear rate range of 1 to 170 s. -1 The sample was stabilized in a water bath for 10 minutes before measurement. Figure 3 As shown in the figure, it can be seen that the system has a high viscosity. As the shear rate increases, the viscosity of the system gradually decreases, which indicates that the fracturing fluid is a shear-thinning fluid.

[0059] Test Example 2

[0060] The viscoelasticity test of the fracturing fluid prepared in Example 2 was carried out. The viscoelasticity of the fracturing fluid system at different temperatures was measured using an MCR302 rheometer. The CC27 system was selected, the fixed angular frequency was 10 rad / s, the scanning strain range was 0.01-1000%, and the scanning rate was increased logarithmically. The results are shown in FIG. Figure 4 As shown. Figure 4 It can be seen that the clean fracturing fluid VES has excellent viscoelasticity at low temperatures.

[0061] Test Example 3

[0062] The clean fracturing fluids prepared in Examples 1 to 3 were subjected to a suspended sand test. At room temperature (20°C), ceramsite proppants (30 / 50 mesh) were used to observe the sedimentation rate of the sand particles. It is generally believed that the sedimentation rate of fracturing fluid proppants is 0.08 to 0.18 mm·s -1 The performance is good. From the effect of the clean fracturing fluid in this test example, it can effectively suspend sand, and the sand particles hardly settle within 6 hours. Figure 5 As shown in the figure, the sand-suspending performance of the fracturing fluid system fully complies with the standards of the oil and gas industry and has excellent sand-suspending performance.

[0063] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A novel thiazolidinone-based amphoteric Gemini surfactant, which contains two thiazolidinone groups and a long hydrophobic chain in its molecule, is represented by the following formula 1: Where X is -C n H 2n - structure, wherein n is an integer from 2 to 8; R is a long chain alkyl-C m H 2m+1 , m is an integer from 10 to 20.

2. The thiazolidinone-based amphoteric Gemini surfactant according to claim 1, characterized in that wherein n is an integer from 2 to 6; and m is an integer from 12 to 18.

3. The thiazolidinone-based amphoteric Gemini surfactant according to claim 1, characterized in that wherein n is an integer of 2, 3 or 4; and m is an integer of 14, 16 or 18.

4. The method for preparing the thiazolidinone-based amphoteric Gemini surfactant according to any one of claims 1 to 3, comprising the steps of: (1) First, thiourea and ethyl chloroacetate are thoroughly mixed and stirred with 95% by mass ethanol at room temperature. Nitrogen is introduced into the reaction system and the temperature is raised to react to synthesize 2-amino-4-thiazolidinone. After vacuum distillation, a white solid powder is obtained. The reaction is shown in the following reaction formula 1: (2) The 2-amino-4-thiazolidinone obtained in step (1) is dissolved or dispersed in a 60%-98% concentrated H2SO4 solution, the concentration range of which is cooled to -10 to 5°C, and a high-concentration NaNO2 solution is slowly added dropwise to the previous solution. After washing with water, a light yellow solid powder is obtained. The reaction is protected from light throughout the process. The reaction is shown in the following reaction formula 2: (3) The 2-hydroxy-4-thiazolidinone obtained in step (2) is prepared into a 0.1 mol / L solution, an alkyl ether dioxirane compound is added dropwise, and the mixture is fully mixed and stirred with a Lewis acid catalyst at room temperature. The mixture is heated to 30-60° C. for reaction for 1-4 hours, and then heated to 60-120° C. for reaction for 1-6 hours. After the reaction is completed, the mixture is washed with water and distilled under reduced pressure to obtain a colorless transparent liquid. The reaction is shown in the following reaction formula 3: (4) The intermediate obtained in step (3) is subjected to a quaternization reaction using a halogenated hydrocarbon RI to obtain the product alkylthiazolidinone diol, as shown in the following reaction formula 4:

5. The preparation method according to claim 4, characterized in that: The reaction time in step (1) is 1 to 5 hours; The reaction temperature in step (1) is 30-50°C.

6. The preparation method according to claim 4, characterized in that: The reaction time in step (1) is 3.5 hours; The reaction temperature in step (1) is 50°C.

7. The preparation method according to claim 2, characterized in that: The reaction temperature in step (2) is -5°C; The mass percentage concentration of the high concentration NaNO2 solution in step (2) is 30%-40%.

8. The preparation method according to claim 2, wherein: In step (3), X in the alkyldioxirane is -C n H 2n -, n is defined as the same as n in any one of claims 1 to 3; The Lewis acid catalyst described in step (3) is selected from one or more of AlCl3, BF3, FeBr3, and ZnCl2, and the amount of the catalyst is 1 to 3% by volume of the alkyl ether dioxirane compound; In step (3), the reaction temperature was first raised to 50°C for 1 hour, and then raised to 80°C for 3 hours; The halogenated hydrocarbon RI described in step (3), wherein R is a long chain alkyl-C m H 2m+1 , the definition of m is the same as the definition of m in any one of claims 1 to 3.

9. Use of the thiazolidinone-based amphoteric Gemini surfactant according to any one of claims 1 to 3 in natural gas hydrate fracturing fluid.

10. A clean fracturing fluid, comprising 0.7% to 2% by mass of the thiazolidinone-based amphoteric Gemini surfactant according to any one of claims 1 to 3 and 0.1% to 0.5% by mass of an inorganic salt, with water as the other component.

11. The clean fracturing fluid according to claim 10, characterized in that: The inorganic salt is selected from the group consisting of hydrochloride, nitrate, sulfate or phosphate of ammonium ion, alkali metal ion or alkaline earth metal ion.

12. The clean fracturing fluid according to claim 10, characterized in that: The inorganic salt is hydrochloride, nitrate, sulfate or phosphate of ammonium ion.

13. The clean fracturing fluid according to claim 10, characterized in that: The inorganic salt is ammonium chloride.

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