Natural gas hydrate generation inhibitor for deepwater shaft working fluid as well as preparation method and application of natural gas hydrate generation inhibitor

Abstract

The invention relates to a natural gas hydrate generation inhibitor for deepwater shaft working fluid as well as a preparation method and application thereof. The natural gas hydrate inhibitor SYZ-3 provided by the invention is synthesized by taking a monomer containing a cyclic functional group and a monomer containing a chain functional group as raw materials, azodiisobutyronitrile as a free radical polymerization reaction initiator and dimethylformamide as a free radical polymerization reaction solvent through free radical polymerization reaction. The natural gas hydrate inhibitor SYZ-3 provided by the invention can effectively inhibit secondary generation of hydrates in a shaft, and also can reduce the requirements of a sea area natural gas hydrate drilling fluid system on salt and alcohol thermodynamic inhibitors, so that the drilling fluid performance is guaranteed, the shaft is prevented from being blocked, the well control risk is reduced, and the hydrate exploitation safety is guaranteed; the mining work efficiency is improved, and the method has important significance on construction of a sea area natural gas hydrate low-density strong-inhibition drilling fluid system.

Description

Technical Field

[0001] The invention relates to a natural gas hydrate formation inhibitor for deepwater wellbore working fluid and a preparation method and application thereof, belonging to the technical field of natural gas hydrate drilling and production. Background Art

[0002] The efficient development of oil and gas resources is related to the sustainable development of the national economy and energy security. The demand for oil and gas will continue to grow strongly as my country's high-quality economic development continues. Therefore, increasing the intensity of conventional natural gas exploration and development and expanding new areas of unconventional natural gas exploration and development are key measures.

[0003] Gas hydrates are composed of natural gas molecules (CO 2 , H 2 S, CH 4 In 1934, Hammerschmidt, an American researcher, first discovered that the formation of natural gas hydrates in natural gas transmission pipelines would seriously block the pipelines, and conducted relevant experimental studies to obtain the relationship between natural gas hydrates and temperature and pressure, which attracted the attention of oil and gas professionals. The problem of natural gas hydrate blockage has brought huge losses to the oil and gas industry. During deepwater operations, if natural gas hydrates are generated in the wellbore, the wellbore may be blocked, affecting the exploitation of oil and natural gas; if natural gas hydrates are formed in the pipeline, the pipeline will be blocked, resulting in a decrease in natural gas output and an increase in pipeline pressure, which will cause inaccuracy or damage to the metering instruments in the pipeline, and even cause the pipeline network to be paralyzed. During deepwater drilling and development, the high pressure and low temperature conditions on the seabed increase the possibility of the formation of natural gas hydrates, and the formation of hydrates will seriously affect the normal progress of oil and gas drilling operations. Inhibitors are an important means to inhibit hydrate formation and ensure the safety of wellbore flow. Hydrate thermodynamic formation inhibitors were developed early, but most of them need to be used in large quantities to meet the needs of field operations, which leads to a significant impact on the performance of the drilling fluid system.

[0004] Therefore, effectively preventing the formation of hydrates is of great significance for marine natural gas hydrate exploitation and natural gas transportation. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a natural gas hydrate formation inhibitor for deepwater wellbore working fluid, and a preparation method and application thereof.

[0006] The technical solution of the present invention is as follows:

[0007] A natural gas hydrate inhibitor SYZ-3, the structural formula of which is shown below:

[0008]

[0009] Among them, the ratio of m:n is 1-5.

[0010] The present invention also provides a method for preparing the above-mentioned natural gas hydrate inhibitor SYZ-3, which is synthesized by free radical polymerization reaction using a monomer containing a cyclic functional group and a monomer containing a chain functional group as raw materials, azobisisobutyronitrile as a free radical polymerization initiator, and dimethylformamide as a free radical polymerization solvent.

[0011] Preferably according to the present invention, the cyclic functional group-containing monomer is N-vinyl caprolactam.

[0012] Preferably according to the present invention, the monomer containing chain-like functional groups is N,N-dimethylacrylamide.

[0013] Preferably according to the present invention, the mass ratio of the monomer containing cyclic functional groups, the monomer containing chain functional groups and dimethylformamide is (12-15): (5-7): (70-85).

[0014] Preferably according to the present invention, the azobisisobutyronitrile is added in the form of a solution, and the amount of azobisisobutyronitrile added is 1 to 1.5% of the total mass of the monomers containing cyclic functional groups and the monomers containing chain functional groups.

[0015] According to a preferred embodiment of the present invention, the preparation method of the above-mentioned natural gas hydrate inhibitor SYZ-3 comprises the following specific steps:

[0016] Adding the monomer containing chain-like functional groups and the monomer containing chain-like functional groups into the reaction solvent, stirring continuously, and introducing nitrogen to maintain anaerobic conditions until they are completely dissolved to obtain a monomer mixed solution;

[0017] Adding the initiator to the reaction solvent and continuously stirring until it is completely dissolved to obtain an initiator solution;

[0018] The temperature is raised to 60-85° C., an initiator solution is added dropwise to the monomer mixed solution to carry out a free radical polymerization reaction, and the product is purified to obtain a natural gas hydrate inhibitor SYZ-3.

[0019] More preferably, the continuous stirring is stirring at 15 to 25 r / min for 15 to 25 min.

[0020] More preferably, the free radical polymerization reaction time is 6 to 8 hours.

[0021] The above-mentioned natural gas hydrate inhibitor SYZ-3 is used as a natural gas hydrate kinetic inhibitor in natural gas hydrate reservoir drilling.

[0022] The technical features of the present invention are as follows:

[0023] The present invention improves the functional groups in the molecular structure of the existing kinetic inhibitor, performs mechanism analysis by means of molecular simulation, takes the existing high-performance hydrate formation inhibitor as a template, preferably selects N-vinyl caprolactam as the cyclic functional group and N,N-dimethylacrylamide as the chain functional group, and prepares a hydrate kinetic inhibitor that can meet the drilling requirements of hydrate reservoirs within the density window.

[0024] Beneficial effects of the present invention:

[0025] 1. The natural gas hydrate inhibitor SYZ-3 provided by the present invention can effectively inhibit the secondary formation of hydrates in the wellbore, and can also reduce the demand for salt and alcohol thermodynamic inhibitors in the marine natural gas hydrate drilling fluid system, thereby ensuring the performance of the drilling fluid, preventing wellbore blockage, reducing well control risks, ensuring the safety of hydrate mining, and improving mining efficiency. It is of great significance to the construction of a low-density strong inhibition drilling fluid system for marine natural gas hydrates.

[0026] 2. The natural gas hydrate inhibitor SYZ-3 provided by the present invention is a kinetic inhibitor, which can effectively solve the problem of excessive system density caused by adding a large amount of NaCl or MEG to the drilling fluid system to inhibit hydrate formation, thereby improving development efficiency and economic benefits.

[0027] 3. The natural gas hydrate inhibitor SYZ-3 provided by the present invention has good compatibility, and has obvious synergistic effect when compounded with thermodynamic inhibitors. It has little effect on the rheological filtration and other properties of the drilling fluid system, and plays a supporting role in constructing a deepwater strong inhibition, high-efficiency and environmentally friendly drilling fluid system.

[0028] 4. The reaction conditions of the method for preparing the natural gas hydrate inhibitor provided by the present invention are easy to control, and it has the prospect of large-scale industrial production, which is of great significance for the exploitation of natural gas hydrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the natural gas hydrate inhibitor SYZ-3 in Example 1.

[0030] Figure 2 Figure 2 shows the temperature and pressure curves under the action of different natural gas hydrate inhibitor systems.

[0031] In the figure, a is sample 1; b is sample 2; c is sample 3; d is sample 4; and e is sample 5.

[0032] Figure 3 are the liquid phase temperature, supercooling degree and induction time of different natural gas hydrate inhibitor systems during hydrate formation;

[0033] In the figure, a is pure water; b is sample 5; c is sample 1; d is sample 2; e is sample 3; and f is sample 4.

[0034] Figure 4 This is the induction time test curve of sample 1.

[0035] Figure 5 This is the turbidity test chart of sample 1 at different temperatures.

[0036] Figure 6 This is the anti-aging performance test diagram of sample 1;

[0037] In the figure, a is before aging, and b is after aging at 65°C for 16 hours.

[0038] Figure 7 The effects of different natural gas hydrate inhibitors on hydrate decomposition;

[0039] In the figure, a represents different concentrations of NaCl, b represents different concentrations of ethylene glycol, c represents different concentrations of PVP, and d represents sample 1. DETAILED DESCRIPTION

[0040] The present invention is further described below by way of examples and in conjunction with the accompanying drawings, but is not limited thereto. The reagents, materials and equipment described above, unless otherwise specified, can all be obtained from commercial sources.

[0041] The N-vinyl caprolactam used in the embodiment has a CAS number of 2235-00-9, a molecular weight of 139.19, and a molecular structure of: N,N-dimethylacrylamide, CAS number: 2680-03-7, molecular weight is 99.13, molecular structure formula is;

[0042]

[0043] Example 1

[0044] A method for preparing a natural gas hydrate inhibitor SYZ-3, the specific steps are as follows:

[0045] (1) Experimental preparation: Place a three-necked flask in a constant temperature heated magnetic stirrer at 80°C and exhaust the air with nitrogen three times to ensure that the flask is oxygen-free and dry;

[0046] (2) Preparation of reaction solution: Weigh 75 g of dimethylformamide (DMF) solution into a beaker, then add 14 g of N-vinyl caprolactam (NVCL) and 6 g of N,N-dimethylacrylamide (DMAA), stir the mixture at 20 r / min for 20 min using a constant speed strong electric stirrer, and continuously introduce nitrogen to completely dissolve and disperse NVCL and DMAA in DMF to obtain a monomer mixed solution;

[0047] (3) Preparation of initiator solution: 6 g of DMF was weighed and added to a clean and dry beaker, and 0.24 g of recrystallized azobisisobutyronitrile (AIBN) was weighed and added to the beaker. A constant speed strong electric stirrer was used to stir at 20 r / min for 15 min to completely dissolve and disperse AIBN in DMF to obtain an initiator solution.

[0048] (4) Free radical polymerization reaction: 30 minutes after the completion of step (2), the temperature was raised to 80°C and the initiator solution was slowly added dropwise to the monomer mixed solution for 10 minutes. After the addition was completed, the reaction was continued for 7 hours. The product solution was dried in a 75°C constant temperature box for 24 hours to obtain the natural gas hydrate inhibitor SYZ-3.

[0049] Example 2

[0050] A method for preparing a natural gas hydrate inhibitor SYZ-3, the specific steps are as follows:

[0051] (1) Experimental preparation: Place a three-necked flask in a constant temperature heated magnetic stirrer at 80°C and exhaust the air with nitrogen three times to ensure that the flask is oxygen-free and dry;

[0052] (2) Preparation of reaction solution: 70 g of dimethylformamide (DMF) solution was weighed and added to a beaker, and then 12 g of N-vinyl caprolactam (NVCL) and 5 g of N,N-dimethylacrylamide (DMAA) were added. The mixture was stirred at 15 r / min for 25 min using a constant speed strong electric stirrer, and nitrogen was continuously introduced to completely dissolve and disperse NVCL and DMAA in DMF to obtain a monomer mixed solution.

[0053] (3) Preparation of initiator solution: 6 g of DMF was weighed and added to a clean and dry beaker, and 0.24 g of recrystallized azobisisobutyronitrile (AIBN) was weighed and added to the beaker. A constant speed strong electric stirrer was used to stir at 15 r / min for 15 min to completely dissolve and disperse AIBN in DMF to obtain an initiator solution.

[0054] (4) Free radical polymerization reaction: 30 minutes after the completion of step (2), the temperature was raised to 70°C and the initiator solution was slowly added dropwise to the monomer mixed solution for 10 minutes. After the addition was completed, the reaction was continued for 8 hours. The product solution was dried in a 75°C constant temperature box for 24 hours to obtain the natural gas hydrate inhibitor SYZ-3.

[0055] Example 3

[0056] A method for preparing a natural gas hydrate inhibitor SYZ-3, the specific steps are as follows:

[0057] (1) Experimental preparation: Place a three-necked flask in a constant temperature heated magnetic stirrer at 80°C and exhaust the air with nitrogen three times to ensure that the flask is oxygen-free and dry;

[0058] (2) Preparation of reaction solution: 75 g of dimethylformamide (DMF) solution was weighed and added to a beaker, and then 15 g of N-vinyl caprolactam (NVCL) and 7 g of N,N-dimethylacrylamide (DMAA) were added. The mixture was stirred at 25 r / min for 15 min using a constant speed strong electric stirrer and nitrogen was continuously introduced to completely dissolve and disperse NVCL and DMAA in DMF to obtain a monomer mixed solution.

[0059] (3) Preparation of initiator solution: 6 g of DMF was weighed and added to a clean and dry beaker, and 0.24 g of recrystallized azobisisobutyronitrile (AIBN) was weighed and added to the beaker. A constant speed strong electric stirrer was used to stir at 20 r / min for 15 min to completely dissolve and disperse AIBN in DMF to obtain an initiator solution.

[0060] (4) Free radical polymerization reaction: 30 minutes after the completion of step (2), the temperature was raised to 85°C and the initiator solution was slowly added dropwise to the monomer mixed solution for 10 minutes. After the addition was completed, the reaction was continued for 6 hours. The product solution was dried in a 75°C constant temperature box for 24 hours to obtain the natural gas hydrate inhibitor SYZ-3.

[0061] Comparative Example

[0062] 400 mL of pure water was measured with a measuring cylinder and placed in a slurry cup. The mixture was stirred at a speed of 6000 r / min. 4 g of kinetic inhibitor polyvinyl caprolactam (PVCap) was added and stirred thoroughly to completely dissolve the PVCap.

[0063] Experimental Example 1

[0064] 1. The molecular structure of the natural gas hydrate inhibitor SYZ-3 prepared in Example 1 was characterized using a 1H-NMR Bruker Avance III HD 500 MHz from Bruker, Switzerland. D2O was used as solvent and the chemical shift was recorded in ppm relative to tetramethylsilane (TMS) as a reference. The results are shown in Figure 1 shown.

[0065] Depend on Figure 1 It can be seen that the chemical shift of H near nitrogen is higher, and the ratio of e to f is 2:1. Therefore, it can be inferred that 1 H at 4.08-3.59ppm is f, 2 H at 3.30-3.05ppm are e; 2 H at 2.08-1.85ppm are b, c and d; 6 H at 3.06-2.68ppm are j; 3 H at 2.52-2.15ppm are a and i; H at the remaining positions is H of alkyl, that is, H at 1.81-1.29ppm is g and h. In addition, it can be inferred that the value of m:n is 1.167:1.

[0066] 2. The natural gas hydrate inhibitor SYZ-3 was prepared into different solutions for use in the subsequent examples, as follows:

[0067] Sample 1: 400 mL of pure water was measured with a measuring cylinder and placed in a slurry cup. The mixture was stirred at a speed of 6000 r / min. 4 g of the natural gas hydrate inhibitor SYZ-3 prepared in Example 1 was added and stirred thoroughly to completely dissolve the mixture.

[0068] Sample 2: Add 14 g of NaCl to sample 1 and stir thoroughly to mix well.

[0069] Sample 3: Add 20g of NaCl to sample 1 and stir thoroughly to mix well.

[0070] Sample 4: Add 28g of NaCl to Sample 1 and stir thoroughly to mix well.

[0071] The comparative example was designated as Sample 5.

[0072] Experimental Example 2

[0073] The natural gas hydrate formation inhibition performance test was performed on samples 1 to 5, and pure water was used as the control group. The evaluation of natural gas hydrate inhibitors was based on the constant rate cooling method, and the specific experimental steps were as follows:

[0074] 1) Reactor preparation: Open the high-pressure window hydrate reactor and clean the inner wall, inject 370 mL of the test solution into the reactor, then install the reactor, tighten the screws on the clamp ring, and turn on the water bath to keep the reactor in a steady state at 18°C;

[0075] 2) Air tightness test: After ensuring that all pipelines are connected, turn on the vacuum pump to evacuate the air. When the pressure in the kettle remains stable at -0.09MPa for more than 15 minutes, the air tightness is considered good;

[0076] 3) Filling with methane gas: close the vacuum inlet valve, open the high-pressure gas injection valve, and inject 14MPa of methane gas into the high-pressure window hydrate reactor. The injection of methane gas is completed when the pressure in the reactor is maintained below 0.01MPa for 30 minutes;

[0077] 4) Evaluation of hydrate formation inhibition: Start the temperature control program and camera capture program of the experimental device, stabilize the reactor at 18°C ​​for 30 minutes, and then cool the reactor from 18°C ​​to 0°C at a cooling rate of 3°C / h within 6 hours to conduct a hydrate formation inhibition evaluation experiment.

[0078] 5) Result observation: When the temperature and pressure in the reactor remain stable within 30 minutes, the hydrate formation is considered complete. Finally, the methane gas consumption is counted. The results are as follows: Figure 2 shown.

[0079] Depend on Figure 2 It can be seen that under the influence of 1% natural gas hydrate inhibitor SYZ-3 (sample 1), the hydrate formation temperature decreased from 10.4°C / 9.4°C to 4.6°C / 2.7°C (liquid phase temperature / jacket temperature). When the NaCl concentration increased to 3.5% (sample 2) and 5% (sample 3), the temperature further decreased to 3.7°C / 1.8°C and 2.4°C / 0.7°C. In particular, when the NaCl concentration reached 7% (sample 4), the system successfully maintained the non-hydrate formation time at 0°C for more than 790 minutes.

[0080] right Figure 2 The key data were statistically analyzed, and the results were as follows Figure 3 shown.

[0081] Depend on Figure 3 It can be seen that the performance of sample 1 is improved by about 14% compared with sample 5. At the same time, when 1% SYZ-3 (sample 1) is compounded with 5% NaCl, the inhibition ability of the natural gas hydrate inhibitor is further improved by 43.7%.

[0082] Experimental Example 3

[0083] The induction time test of sample 1 was carried out under the conditions of 14 MPa and 8°C. The experimental steps are as follows:

[0084] 1) Reactor preparation: Open the high-pressure window hydrate reactor and clean the inner wall, inject 370 mL of the test solution into the reactor, then install the reactor, tighten the screws on the clamp ring, and turn on the water bath to keep the reactor in a steady state at 18°C;

[0085] 2) Air tightness test: After ensuring that all pipelines are connected, turn on the vacuum pump to evacuate the air. When the pressure in the kettle remains stable at -0.09MPa for more than 15 minutes, the air tightness is considered good;

[0086] 3) Filling with methane gas: close the vacuum inlet valve, open the high-pressure gas injection valve, and inject 14MPa of methane gas into the high-pressure window hydrate reactor. The injection of methane gas is completed when the pressure in the reactor is maintained below 0.01MPa for 30 minutes;

[0087] 4) Induction time test: Start the temperature control program of the experimental device and the camera capture program, keep the temperature of the reactor at 8°C, and conduct the induction time test experiment.

[0088] (5) Result observation: When the temperature and pressure in the reactor remain stable within 30 min, the hydrate formation is considered complete. The induction time curve of sample 1 is as follows: Figure 4 shown.

[0089] Depend on Figure 4 It can be seen that the time for sample 1 to completely inhibit hydrate formation reached 243.95 hours, the time for inhibiting hydrate nucleation but not growing reached 383.56 hours, and the time for allowing hydrate growth but not blocking the wellbore reached 471.08 hours. Therefore, the natural gas hydrate inhibitor SYZ-3 can fully meet the time requirements of on-site drilling operations under reservoir conditions.

[0090] Experimental Example 4

[0091] Turbidity is an important parameter for evaluating the performance of hydrate inhibitors. It is the maximum temperature that the hydrate inhibitor can tolerate when dissolved in water. After exceeding this temperature, the hydrate inhibitor will precipitate from the water and then fail. Therefore, a turbidity test was conducted on sample 1. The specific experimental method refers to the national standard "Determination of Turbidity of Water Quality by Turbidimeter Method (HJ 1075-2019)". The results are as follows: Figure 5 shown.

[0092] Depend on Figure 5 It can be seen that the cloud point of the natural gas hydrate inhibitor SYZ-3 is 50°C.

[0093] Experimental Example 5

[0094] Sample 1 was placed in an aging tank and placed in a rolling furnace. After rolling at a constant temperature of 65°C for 16 hours, it was taken out and cooled to room temperature. It was then stirred at 5000r / min for 20 minutes. The natural gas hydrate formation inhibition performance test was then carried out. The test method was the same as that of Experimental Example 1. The results are shown in FIG. Figure 6 shown.

[0095] Depend on Figure 6 It can be seen that the anti-aging performance of sample 1 is better, and the performance has almost no change before and after aging.

[0096] Experimental Example 6

[0097] Sample 1, pure water, different concentrations of NaCl, different concentrations of ethylene glycol (MEG) and different concentrations of polyvinyl pyrrolidone (PVP) were tested for hydrate decomposition inhibition performance. The hydrate decomposition inhibition performance test steps are as follows:

[0098] 1) Reactor preparation: After opening the high-pressure hydrate reactor and cleaning the inner wall, inject 500 mL of pure water solution into the reactor, then install the reactor, tighten the screws on the clamping ring, and turn on the water bath to keep the reactor in a steady state at 18°C;

[0099] 2) Air tightness test: After ensuring that all pipelines are connected, turn on the vacuum pump to evacuate the air. When the pressure in the kettle remains stable at -0.09MPa for more than 15 minutes, the air tightness is considered good;

[0100] 3) Filling with methane gas: close the vacuum inlet valve, open the high-pressure gas injection valve, and inject 10MPa of methane gas into the high-pressure window hydrate reactor. The injection of methane gas is considered complete when the pressure in the reactor is maintained below 0.01MPa for 30 minutes;

[0101] 4) Initial hydrate formation: Start the temperature control program of the experimental device to rapidly reduce the jacket temperature of the reactor from 18°C ​​to 0°C for initial hydrate formation. When the temperature and pressure in the reactor remain unchanged for a period of time, the hydrate formation is considered to be complete;

[0102] 5) Evaluation of decomposition inhibition performance: Turn on the constant flow injection pump to inject the test solution into the reactor within 10 minutes. After the injection is completed, turn on the high-temperature water bath to 25°C to simulate the heating process of the drill pipe;

[0103] 6) Result observation: When the temperature and pressure in the reactor remain stable within 30 minutes, the hydrate decomposition is considered complete. Figure 7 shown.

[0104] Depend on Figure 7It can be seen that when low concentrations of NaCl act on the hydrate reservoir, the decomposition of the reservoir hydrate will not be significantly accelerated, but when the solubility of the NaCl solution increases, the decomposition rate of the hydrate will be significantly accelerated, and the peak value will be reached earlier. This also means that adding a large amount of NaCl solution to the drilling fluid can inhibit the formation of hydrates in the wellbore, but it will also significantly accelerate the decomposition of reservoir hydrates. When low concentrations of MEG act on the hydrate reservoir, the decomposition of the reservoir will not be significantly accelerated, but when the solubility of the MEG solution increases, the decomposition rate of the hydrate will be significantly accelerated, and the peak value will be reached earlier. Adding a large amount of MEG solution to the drilling fluid can inhibit the formation of hydrates in the wellbore, but it will also significantly accelerate the decomposition of reservoir hydrates. With the increase of PVP concentration, the hydrate decomposition rate shows a trend of slowing down. Therefore, PVP can not only inhibit the formation of hydrates, but also delay the decomposition of hydrates, that is, PVP has a dual effect on the stability of the hydrate phase, but PVP has the problem of easy failure at low temperatures.

[0105] For sample 1, in the first 21 minutes, under the action of 1% gas hydrate inhibitor SYZ-3, the decomposition rate of reservoir hydrate was slightly faster than that of reservoir hydrate under the influence of pure water system, but after 21 minutes, the decomposition rate of hydrate in the system with 1% gas hydrate inhibitor SYZ-3 was significantly lower than that in the pure water system, and the decomposed weight of hydrate was reduced by 8%. Therefore, the effect of gas hydrate inhibitor SYZ-3 on the decomposition of reservoir hydrate was small.

[0106] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A natural gas hydrate inhibitor SYZ-3, characterized in that: Its structural formula is shown below: Among them, the ratio of m:n is 1-5.

2. The method for preparing the natural gas hydrate inhibitor SYZ-3 according to claim 1, characterized in that: The invention is synthesized by free radical polymerization reaction, using a monomer containing a cyclic functional group and a monomer containing a chain functional group as raw materials, azobisisobutyronitrile as a free radical polymerization initiator, and dimethylformamide as a free radical polymerization solvent.

3. The preparation method according to claim 2, characterized in that: The cyclic functional group-containing monomer is N-vinyl caprolactam.

4. The preparation method according to claim 2, characterized in that: The monomer containing chain-like functional groups is N,N-dimethylacrylamide.

5. The preparation method according to claim 2, characterized in that: The mass ratio of the monomer containing cyclic functional groups, the monomer containing chain functional groups and dimethylformamide is (12-15): (5-7): (70-85).

6. The preparation method according to claim 2, characterized in that: The azobisisobutyronitrile is added in the form of a solution, and the added amount of the azobisisobutyronitrile is 1-1.5% of the total mass of the monomer containing the cyclic functional group and the monomer containing the chain functional group.

7. The preparation method according to claim 2, characterized in that: The specific steps are as follows: Adding the monomer containing chain-like functional groups and the monomer containing chain-like functional groups into the reaction solvent, stirring continuously, and introducing nitrogen to maintain anaerobic conditions until they are completely dissolved to obtain a monomer mixed solution; Adding the initiator to the reaction solvent and continuously stirring until it is completely dissolved to obtain an initiator solution; The temperature is raised to 60-85° C., an initiator solution is added dropwise to the monomer mixed solution to carry out a free radical polymerization reaction, and the product is purified to obtain a natural gas hydrate inhibitor SYZ-3.

8. The preparation method according to claim 7, characterized in that: The continuous stirring is stirring at 15 to 25 r / min for 15 to 25 min.

9. The preparation method according to claim 7, characterized in that: The free radical polymerization reaction time is 6 to 8 hours.

10. The use of the natural gas hydrate inhibitor SYZ-3 according to claim 1, characterized in that: It is used as a natural gas hydrate kinetic inhibitor in natural gas hydrate reservoir drilling.

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