CN115403702B - Inhibitor and preparation method and application thereof - Google Patents
Inhibitor and preparation method and application thereof Download PDFInfo
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- CN115403702B CN115403702B CN202211066583.9A CN202211066583A CN115403702B CN 115403702 B CN115403702 B CN 115403702B CN 202211066583 A CN202211066583 A CN 202211066583A CN 115403702 B CN115403702 B CN 115403702B
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- C09K8/524—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning organic depositions, e.g. paraffins or asphaltenes
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- C09K2208/22—Hydrates inhibition by using well treatment fluids containing inhibitors of hydrate formers
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Abstract
The application relates to the technical field of oil gas development, and provides a preparation method of an inhibitor, which comprises the following steps: mixing vinyl caprolactam monomer, vinyl acetate monomer, initiator and solvent to obtain a mixture; under the condition of gas protection and stirring, the mixture reacts for a first time at a first temperature; cooling, and removing the solvent to obtain a precipitate; washing and drying the precipitate to obtain the poly (vinyl caprolactam-vinyl acetate) copolymer. The preparation method of the inhibitor provided by the application is simple to operate, mild in synthesis condition and suitable for popularization, and the poly (vinyl caprolactam-vinyl acetate) copolymer prepared by the method still has good natural gas hydrate inhibition effect under high supercooling degree as a kinetic inhibitor.
Description
Technical Field
The application belongs to the technical field of oil gas development, and particularly relates to an inhibitor and a preparation method and application thereof.
Background
In the natural gas development process, no matter in the drilling, testing and production processes or gathering and transportation processes, the problems of natural gas hydrate generation and pipeline blockage caused by the existence of low-temperature and high-pressure environments can be faced, so that serious safety accidents such as shaft blockage, gas well production stopping and pipeline transportation stopping are caused, and huge harm is brought to the normal production of a gas field.
The technology for preventing and controlling the natural gas hydrate in the present stage is widely adopted by an injection chemical inhibitor method, and the natural gas hydrate inhibitor comprises three types of thermodynamic inhibitors, kinetic inhibitors and anti-polymerization agents. The kinetic inhibitor has the advantages of small dosage, remarkable inhibition effect and high economic benefit, and can develop various inhibitors with different performances according to actual demands, thereby being a future development trend in the field.
Most of the existing commercial natural gas hydrate kinetic inhibitors are used in environments with supercooling below 10 ℃ because kinetic inhibitors fail at high supercooling (i.e., supercooling above 10 ℃). Because of the low air temperature in winter, the actual supercooling degree of many oil-gas wells is more than 10 ℃, and the supercooling degree of deep sea oil fields can even reach 18 ℃, so that the phenomenon of blocking pipelines by natural gas hydrate frequently occurs.
Disclosure of Invention
The application aims to provide an inhibitor, a preparation method and application thereof, and aims to solve the problem that the existing kinetic inhibitor is easy to lose efficacy under high supercooling degree.
In order to achieve the purposes of the application, the technical scheme adopted by the application is as follows:
in a first aspect, the present application provides a method of preparing an inhibitor comprising: mixing vinyl caprolactam monomer, vinyl acetate monomer, initiator and solvent to obtain a mixture; reacting the mixture for a first time at a first temperature under the conditions of gas protection and stirring; cooling, and removing the solvent to obtain a precipitate; washing and drying the precipitate to obtain the poly (vinyl caprolactam-vinyl acetate) copolymer.
Optionally, in the mixture, the mass ratio of the vinyl caprolactam monomer to the vinyl acetate monomer is 1-12.
Optionally, in the mixture, the mass ratio of the solvent to the total amount of the vinyl caprolactam and the vinyl acetate is 1-20.
Optionally, in the mixture, the mass ratio of the usage amount of the initiator to the total amount of the vinyl caprolactam and the vinyl acetate is 0.001-0.2.
Optionally, the mixture further comprises a chain transfer agent, wherein the mass ratio of the chain transfer agent to the total amount of the vinyl caprolactam monomer and the vinyl acetate monomer is 0.001-0.01.
Optionally, the first temperature is (60-90) °c.
Optionally, the first time is (5-8) h.
Optionally, the preparation method of the inhibitor further comprises the following steps: providing a compounding agent; compounding the poly (vinyl caprolactam-vinyl acetate) copolymer and the compounding agent.
Optionally, the compound agent comprises at least one of propylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, ethylene glycol phenyl ether, ethylene glycol methyl ether, methanol, ethanol, butanol, ethylene glycol, polyethylene glycol, pentanediol and hexanediol;
Optionally, the mass ratio of the poly (vinyl caprolactam-vinyl acetate) copolymer to the compounding agent is (1-10): 1-10.
In a second aspect, the present application provides an inhibitor comprising a poly (vinyl caprolactam-vinyl acetate) copolymer obtained by polymerizing a vinyl caprolactam monomer with a vinyl acetate monomer.
Optionally, the mass ratio of the vinyl caprolactam monomer to the vinyl acetate monomer is 4-8.
Optionally, the poly (vinylcaprolactam-vinyl acetate) copolymer has a number average molecular weight of 1000 to 1000000.
Alternatively, the poly (vinylcaprolactam-vinyl acetate) copolymer has a weight average molecular weight of 1000 to 1000000.
Alternatively, the poly (vinyl caprolactam-vinyl acetate) copolymer has a molecular weight distribution index of 1 to 10.
Optionally, a compounding agent is also included.
Optionally, the compound agent comprises at least one of propylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, ethylene glycol phenyl ether, ethylene glycol methyl ether, methanol, ethanol, butanol, ethylene glycol, polyethylene glycol, pentanediol and hexanediol.
Optionally, the mass ratio of the poly (vinyl caprolactam-vinyl acetate) copolymer to the compounding agent is (1-10): 1-10.
In a third aspect, the present application provides an application of the inhibitor prepared by the method for preparing the inhibitor provided in the first aspect of the present application or the inhibitor provided in the second aspect of the present application as a natural gas hydrate inhibitor.
Alternatively, the inhibitor is used in the form of an aqueous inhibitor solution in which the poly (vinylcaprolactam-vinyl acetate) copolymer is present at a concentration of (0.1 to 20) wt%.
Optionally, the applied pressure is (0-25) MPa;
alternatively, the temperature of the application is (-10 to 40) deg.C.
The preparation method of the inhibitor provided by the first aspect of the application is simple to operate, mild in synthesis condition and suitable for popularization, and the poly (vinyl caprolactam-vinyl acetate) copolymer prepared by the method still has good natural gas hydrate inhibition effect under high supercooling degree as a kinetic inhibitor.
The inhibitor provided by the second aspect of the application still has good natural gas hydrate inhibition effect under high supercooling degree.
The inhibitor prepared by the preparation method of the inhibitor provided by the first aspect of the application or the inhibitor provided by the second aspect of the application is used as a natural gas hydrate inhibitor in the application provided by the third aspect of the application, and the inhibitor still has good natural gas hydrate inhibition effect under high supercooling degree.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments or the description of the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a Fourier infrared spectrum of 3 inhibitors provided in examples 1-3 of the present application;
FIG. 2 is a nuclear magnetic resonance spectrum of an inhibitor provided in example 3 of the present application;
FIG. 3 is a graph showing the results of the induction time test at a supercooling degree of 15℃for pure water, and the gas consumption in 12 hours for each of the 4 inhibitors of examples 1 to 3 and comparative example of the present application at an inhibitor concentration of 1wt% (A);
FIG. 4 is a graph showing the gas consumption of the inhibitor of example 3 of the present application for 12 hours at an inhibitor concentration of 0.25wt%, 0.5wt%, 0.75wt%, 1wt%, 1.5wt% and a supercooling degree of 15℃respectively, and a graph showing the gas consumption of the inhibitor of comparative example for 12 hours at an inhibitor concentration of 0.5wt%, 1wt%, 3wt%, 5wt% and a supercooling degree of 15℃respectively (B);
FIG. 5 is a graph showing the results of the induction time test of 4 kinds of inhibitors provided in examples 4 to 7 of the present application at a concentration of 1wt% and a supercooling degree of 15℃and a graph showing the gas consumption within 12 hours (B);
FIG. 6 is a graph showing the gas consumption amount (A) in 12 hours and the hydrate volume fraction (B) in 12 hours at a supercooling degree of 18℃for pure water, and the inhibitor concentrations of the 2 inhibitors provided in example 7 and comparative example of the present application are each 1 wt%.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects to be solved more clear, the application is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
In the present application, the term "and/or" describes an association relationship of an association object, which means that three relationships may exist, for example, a and/or B may mean: a alone, a and B together, and B alone. Wherein A, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship.
In the present application, "at least one" means one or more, and "a plurality" means two or more. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (individual) of a, b, or c," or "at least one (individual) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple, respectively.
It should be understood that, in various embodiments of the present application, the sequence number of each process described above does not mean that the execution sequence of some or all of the steps may be executed in parallel or executed sequentially, and the execution sequence of each process should be determined by its functions and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.
The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The weights of the relevant components mentioned in the description of the embodiments of the present application may refer not only to the specific contents of the components, but also to the proportional relationship between the weights of the components, so long as the contents of the relevant components in the description of the embodiments of the present application are scaled up or down within the scope of the disclosure of the embodiments of the present application. Specifically, the mass described in the specification of the embodiment of the application can be mass units known in the chemical industry field such as mu g, mg, g, kg.
The terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated for distinguishing between objects such as substances from each other. For example, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX, without departing from the scope of embodiments of the application. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature.
In a first aspect, an embodiment of the present application provides a method for preparing an inhibitor, including:
s10: mixing vinyl caprolactam monomer, vinyl acetate monomer, initiator and solvent to obtain a mixture;
s20: under the condition of gas protection and stirring, the mixture reacts for a first time at a first temperature;
s30: cooling, and removing the solvent to obtain a precipitate;
s40: washing and drying the precipitate to obtain the poly (vinyl caprolactam-vinyl acetate) copolymer.
The preparation method of the inhibitor provided by the embodiment of the application is simple to operate, mild in synthesis condition and suitable for popularization, and the poly (vinyl caprolactam-vinyl acetate) copolymer prepared by the method still has good natural gas hydrate inhibition effect under high supercooling degree as a kinetic inhibitor.
In some embodiments, step S10 includes five steps S101, S102, S103, S104, and S105. Specifically, S101 includes weighing vinyl caprolactam monomer and vinyl acetate monomer. Alternatively, the mass ratio of vinyl caprolactam monomer to vinyl acetate monomer is from 1 to 12, i.e. the amount of vinyl caprolactam monomer is greater than or equal to the amount of vinyl acetate monomer, which may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12. The monomer ratio can influence the performance of the polymer, further influence the supercooling resistance of the inhibitor, and the poly (vinyl caprolactam-vinyl acetate) copolymer prepared in the ratio range still has good natural gas hydrate inhibition effect under high supercooling degree. Optionally, the mass ratio of the vinyl caprolactam monomer to the vinyl acetate monomer is 4-8, and the poly (vinyl caprolactam-vinyl acetate) copolymer prepared in the proportion range still has good natural gas hydrate inhibition effect under the condition that the supercooling degree is 15 ℃; alternatively, the mass ratio of vinyl caprolactam monomer to vinyl acetate monomer may be 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5 or 8; in actual operation, 3g of vinyl caprolactam monomer, 0.5g of vinyl acetate monomer, 4g of vinyl caprolactam monomer, 1g of vinyl acetate monomer, 40g of vinyl caprolactam monomer and 5g of vinyl acetate monomer can be weighed, the mass range of each monomer is not limited, the ratio is only required, and if the weighed amount of one monomer is increased, the weighed amount of the other monomer is correspondingly increased. S102, weighing an initiator, wherein the initiator is used for initiating a monomer to perform polymerization reaction, namely initiating a vinyl caprolactam monomer and a vinyl acetate monomer to perform free radical copolymerization reaction. Alternatively, the mass ratio of the initiator to the total amount of the two monomers of vinylcaprolactam and vinyl acetate is 0.001 to 0.2, and may be, for example, 0.001, 0.005, 0.01, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18 or 0.2; the usage amount of the initiator can influence the performance of the polymer, further influence the supercooling resistance of the inhibitor, and the poly (vinyl caprolactam-vinyl acetate) copolymer prepared in the usage amount range of the initiator still has good natural gas hydrate inhibition effect under the condition of high supercooling. Alternatively, the mass ratio of the initiator to the total amount of the two monomers of vinyl caprolactam and vinyl acetate is 0.006-0.01, for example, 0.006, 0.007, 0.008, 0.009 or 0.01, and the poly (vinyl caprolactam-vinyl acetate) copolymer prepared within the initiator dosage range still has good natural gas hydrate inhibition effect under the supercooling degree of 15 ℃. Optionally, the initiator is an azo initiator. Optionally, the azo initiator comprises Azodiisobutyronitrile (AIBN), the use temperature of the azodiisobutyronitrile is (50-65) DEG C, and the azodiisobutyronitrile is uniformly decomposed to form only one free radical without other side reactions. S103, weighing a chain transfer agent, wherein the chain transfer agent is used for regulating the molecular weight of the polymer. The amount of chain transfer agent should not be too much. Alternatively, the mass ratio of chain transfer agent to the total amount of vinyl caprolactam and vinyl acetate monomers is 0.001 to 0.01, and may be, for example, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, or 0.01. Alternatively, the chain transfer agent comprises 3-mercaptoacetic acid or 3-mercaptopropionic acid. S104 includes measuring the solvent. Alternatively, the solvent is used in a mass ratio of 1 to 20 to the total amount of the two monomers of vinylcaprolactam and vinyl acetate, for example, 1, 2, 3, 3.3, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 8, 10, 13, 15, 18 or 20. Alternatively, the solvent comprises an alcoholic solvent, such as isopropanol. S105 comprises adding the weighed or measured vinyl caprolactam monomer, vinyl acetate monomer, initiator, chain transfer agent and solvent to a container, for example, a three-necked bottle, and mixing to obtain a mixture.
In some embodiments, step S20 includes the following three steps S201, S202, and S203. Specifically, S201 includes opening a gas shield, and degassing and sealing the entire reaction system under the gas shield because the presence of oxygen is detrimental to the reaction. Optionally nitrogen. It will be appreciated that in other embodiments other gases may be used as shielding gases, such as inert gases. S202 includes turning on stirring. Optionally, magnetic stirring is turned on. Alternatively, during the reaction, the stirring speed is controlled to be (200 to 600) rpm, which may be, for example, 200rpm, 300rpm, 400rpm, 500rpm or 600rpm. S203 comprises starting a temperature raising program, starting condensed water, and controlling the mixture to react for a first time at a first temperature so as to polymerize the monomer molecules. Alternatively, the first temperature is (60-90) C, which may be, for example, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃ or 90℃; the activity of an initiator is needed to be considered in the occurrence of the polymerization reaction, the first temperature can influence the polymerization reaction and further the polymer performance, and the poly (vinyl caprolactam-vinyl acetate) copolymer prepared in the temperature range still has good natural gas hydrate inhibition effect under the condition of high supercooling degree. Alternatively, the first time is (5-8) h, which may be, for example, 5h, 6h, 7h or 8h. Optionally, the mixture is heated by means of an oil bath.
In some embodiments, step S30 includes the following two steps S301 and S302. Specifically, S301 includes cooling, stirring and heating are turned off, and the entire reaction system is cooled to room temperature. S302 includes removing the solvent to obtain a resultant precipitate. Alternatively, the solvent is removed by evaporation under reduced pressure. Alternatively, the solvent is removed under reduced pressure using a vacuum rotary evaporator, leaving a precipitate. Alternatively, the evaporation temperature is (50-70) C, which may be, for example, 50℃, 60℃ or 70℃.
In some embodiments, step S40 includes the following two steps S401 and S402. Specifically, S401 includes washing the precipitate to remove residual initiator and residual monomer in the precipitate. Alternatively, the precipitate is washed with anhydrous diethyl ether, ethyl acetate or n-hexane to give a white precipitate after washing. S402 includes drying the precipitate. Optionally, the precipitate is dried by vacuum drying to obtain the kinetic inhibitor poly (vinyl caprolactam-vinyl acetate) copolymer. Alternatively, the drying temperature is (40-50) C, which may be, for example, 40℃, 45℃ or 50℃. Alternatively, the drying time is (10-15) h, which may be, for example, 10h, 11h, 12h, 13h, 14h or 15h.
In some embodiments, the method of preparing an inhibitor further comprises step S50: and (5) compounding. Alternatively, step S50 includes the following two steps S501 and S502. Specifically, S501 includes providing a compounding agent for further improving the supercooling resistance of the inhibitor. S502 includes compounding a poly (vinyl caprolactam-vinyl acetate) copolymer and a compounding agent. Optionally, the compound agent comprises at least one of propylene glycol methyl ether, ethylene glycol, diethylene glycol ethyl ether, diethylene glycol butyl ether, methanol, ethanol, butanol, ethylene glycol butyl ether, ethylene glycol phenyl ether, polyethylene glycol, ethylene glycol methyl ether, pentanediol and hexanediol; optionally, the compounding agent includes an alcohol ether, such as at least one of propylene glycol methyl ether, diethylene glycol ethyl ether, ethylene glycol methyl ether, ethylene glycol phenyl ether, ethylene glycol butyl ether, and diethylene glycol butyl ether. The alcohol ether has an oxygen atom with strong hydrogen bond forming capability, and can compete with water molecules, so that the water molecules in a free state cannot participate in forming a hydrate cage, and metastable state hydrate is prevented from forming. Hydroxyl on alcohol ether can also react with water to influence water to be accumulated into a cage; meanwhile, caprolactam groups in the poly (vinyl caprolactam-vinyl acetate) copolymer interact with hydroxyl groups of alcohol ether, and under the combined action of Van der Waals force and hydrogen bond, the caprolactam groups and water can prevent methane-propane mixed gas molecules from entering a hydrate cage, so that the inhibition capability is enhanced. In some embodiments, the compounding agent is diethylene glycol butyl ether, and the compound inhibitor formed by compounding the poly (vinyl caprolactam-vinyl acetate) copolymer and diethylene glycol butyl ether still has an inhibition effect on natural gas hydrate under the condition that the supercooling degree is 18 ℃, and the induction time can reach more than 1000 minutes. Optionally, the mass ratio of poly (vinyl caprolactam-vinyl acetate) copolymer to compounding agent is (1-10): (1-10), for example, may be 1:1, 1:2, 2:1, 4:5, 7:2, 6:9, 10:1, 9:7 or 3:10.
In a second aspect, embodiments of the present application provide an inhibitor comprising a poly (vinyl caprolactam-vinyl acetate) copolymer polymerized from vinyl caprolactam monomer and vinyl acetate monomer.
The poly (vinyl caprolactam-vinyl acetate) copolymer provided by the second aspect of the embodiment of the application still has good natural gas hydrate inhibition effect under high supercooling degree as a kinetic inhibitor.
In some embodiments, the poly (vinyl caprolactam-vinyl acetate) copolymer is polymerized from vinyl caprolactam monomer and vinyl acetate monomer in a ratio of 4 to 8 by mass. The monomer ratio can influence the performance of the polymer and further influence the supercooling resistance of the inhibitor, and the poly (vinyl caprolactam-vinyl acetate) copolymer prepared in the ratio range still has good natural gas hydrate inhibition effect under the condition that the supercooling degree is 15 ℃. Alternatively, the mass ratio of vinyl caprolactam monomer to vinyl acetate monomer may be 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5 or 8.
In some embodiments, the poly (vinyl caprolactam-vinyl acetate) copolymer has a number average molecular weight of 1000 to 1000000; alternatively, the poly (vinyl caprolactam-vinyl acetate) copolymer has a number average molecular weight of 19000 to 22000. Alternatively, the poly (vinyl caprolactam-vinyl acetate) copolymer has a number average molecular weight of 20750, 19657 or 21242.
In some embodiments, the poly (vinyl caprolactam-vinyl acetate) copolymer has a weight average molecular weight of 1000 to 1000000; alternatively, the poly (vinyl caprolactam-vinyl acetate) copolymer has a weight average molecular weight of 38000 to 42000. Alternatively, the poly (vinyl caprolactam-vinyl acetate) copolymer has a weight average molecular weight of 41167, 41449 or 38730.
In some embodiments, the poly (vinyl caprolactam-vinyl acetate) copolymer has a molecular weight distribution index of 1 to 10; alternatively, the poly (vinyl caprolactam-vinyl acetate) copolymer has a molecular weight distribution index of 2 to 3, which may be 2, 2.5 or 3, for example.
In some embodiments, the inhibitor further comprises a compounding agent for further enhancing the supercooling resistance of the inhibitor.
In some embodiments, the compounding agent comprises at least one of propylene glycol methyl ether, ethylene glycol, diethylene glycol ethyl ether, diethylene glycol butyl ether, methanol, ethanol, butanol, ethylene glycol butyl ether, ethylene glycol phenyl ether, polyethylene glycol, ethylene glycol methyl ether, pentanediol, and hexanediol.
In some embodiments, the compounding agent includes an alcohol ether, such as propylene glycol methyl ether, diethylene glycol ethyl ether, ethylene glycol methyl ether, ethylene glycol phenyl ether, ethylene glycol butyl ether, or diethylene glycol butyl ether. The alcohol ether has an oxygen atom with strong hydrogen bond forming capability, and can compete with water molecules, so that the water molecules in a free state cannot participate in forming a hydrate cage, and metastable state hydrate is prevented from forming. Hydroxyl on alcohol ether can also react with water to influence water to be accumulated into a cage; meanwhile, caprolactam groups in the poly (vinyl caprolactam-vinyl acetate) copolymer interact with hydroxyl groups of alcohol ether, and under the combined action of Van der Waals force and hydrogen bond, the caprolactam groups and water can prevent methane-propane mixed gas molecules from entering a hydrate cage, so that the inhibition capability is enhanced. In some embodiments, the compounding agent is diethylene glycol butyl ether, and the compound inhibitor formed by compounding the poly (vinyl caprolactam-vinyl acetate) copolymer and diethylene glycol butyl ether still has an inhibition effect on natural gas hydrate under the condition that the supercooling degree is 18 ℃, and the induction time can reach more than 1000 minutes.
In some embodiments, the mass ratio of poly (vinyl caprolactam-vinyl acetate) copolymer to compounding agent is (1-10): (1-10), which may be, for example, 1:1, 1:2, 2:1, 4:5, 7:2, 6:9, 10:1, 9:7, or 3:10.
According to a third aspect of the embodiment of the application, the application is the application of the inhibitor prepared by the preparation method of the inhibitor provided by the first aspect of the embodiment of the application or the inhibitor provided by the second aspect of the embodiment of the application as a natural gas hydrate inhibitor.
The inhibitor prepared by the preparation method of the inhibitor provided by the first aspect of the embodiment of the application or the inhibitor provided by the second aspect of the embodiment of the application is used as a natural gas hydrate inhibitor in the application provided by the third aspect of the embodiment of the application, and the inhibitor still has good natural gas hydrate inhibition effect under high supercooling degree.
In some embodiments, the inhibitor is used in the form of an aqueous inhibitor solution in which the concentration of poly (vinyl caprolactam-vinyl acetate) copolymer is greater than or equal to 0.1wt%. In the prior art, in order to solve the problem of high supercooling degree, the concentration of a kinetic inhibitor is obviously increased or a quaternary ammonium salt synergistic agent is added in most applications. However, the inhibitor poly (vinyl caprolactam-vinyl acetate) copolymer adopted by the application can still have an inhibiting effect on natural gas hydrate under the condition of high supercooling degree at a lower concentration, and is beneficial to effectively saving the cost of the inhibitor. Through tests, under the severe condition that the gas-liquid ratio of test gas (methane-propane mixed gas) to inhibitor aqueous solution is 3:1, the inhibitor poly (vinyl caprolactam-vinyl acetate) copolymer adopted by the application still has a good inhibition effect, and compared with the gas-liquid ratio of 1:1 adopted in the prior art, the test gas amount adopted by the tests is 3 times greater, because the more the gas is, the faster the generated hydrate is, and the larger the final gas consumption is. The inhibitor has good inhibition effect under the condition of large gas-liquid ratio, which indicates that the inhibitor has excellent inhibition effect. Alternatively, the concentration of poly (vinyl caprolactam-vinyl acetate) copolymer in the aqueous inhibitor solution is (0.1-20 wt), which may be, for example, 0.1, 0.25wt%, 0.3wt%, 4wt%, 4.5wt%, 5wt%, 10wt%, 15wt% or 20wt%. Compared with the quaternary ammonium salt which is unfavorable for pipeline corrosion prevention, the inhibitor poly (vinyl caprolactam-vinyl acetate) copolymer adopted in the application is more environment-friendly.
In some embodiments, the temperature of the application is (-10 to 40) C. The inhibitor poly (vinyl caprolactam-vinyl acetate) copolymer adopted by the application has the effect of high supercooling resistance, and the use temperature range of the inhibitor is effectively widened. Alternatively, the temperature of the application is-3 ℃, -1 ℃, 3 ℃,6 ℃, 30 ℃ or 40 ℃.
In some embodiments, the applied pressure is (0-25) MPa. Alternatively, the applied pressure is 0, 1MPa, 5MPa, 8MPa, 10MPa, 15MPa, 20MPa or 25MPa.
The following description is made with reference to specific embodiments.
Example 1
2g of monomeric vinylcaprolactam and 0.5g of vinyl acetate were weighed, 0.015g of Azobisisobutyronitrile (AIBN) as initiator was weighed, 0.012g of 3-mercaptopropionic acid as chain transfer agent was weighed, mixed with 10ml of isopropanol, and added to a 100ml three-necked flask. The reaction system was degassed and sealed under nitrogen. The condensed water and magnetic stirring are started, the stirring speed is 300rpm, the oil bath is reacted for 8 hours at 75 ℃, and the oil bath and stirring are closed. After the reaction solution cooled to room temperature, it was transferred to a round-bottomed flask and was distilled at 60℃until the solution appeared viscous. 3g of the product was taken and dropped into 30ml of dehydrated ether to obtain a white precipitate. Repeatedly washing for three times, and drying in a vacuum drying oven at 45 ℃ for 12 hours to obtain the white powder of the final product.
Example 2
3g of monomeric vinylcaprolactam and 0.5g of vinyl acetate were weighed, 0.035g of the initiator Azobisisobutyronitrile (AIBN) was weighed, 0.021g of the chain transfer agent 3-mercaptoacetic acid was weighed, mixed with 17.5ml of isopropanol, and added to a 100ml three-necked flask. The system was degassed and sealed under nitrogen. The condensed water and magnetic stirring are started, the stirring speed is 300rpm, the oil bath is reacted for 5 hours at 85 ℃, and the oil bath and stirring are closed. After the reaction solution cooled to room temperature, it was transferred to a round-bottomed flask and was distilled at 60℃until the solution appeared viscous. 3g of the product was taken and dropped into 30ml of dehydrated ether to obtain a white precipitate. Repeatedly washing for three times, and drying in a vacuum drying oven at 45 ℃ for 12 hours to obtain the white powder of the final product.
Example 3
4g of monomeric vinylcaprolactam and 0.5g of vinyl acetate were weighed, 0.027g of the initiator Azobisisobutyronitrile (AIBN) was weighed, 0.025g of the chain transfer agent 3-mercaptopropionic acid was weighed, mixed with 18ml of isopropanol, and added to a 100ml three-necked flask. The system was degassed and sealed under nitrogen. The condensed water and magnetic stirring are started, the stirring speed is 300rpm, the oil bath is reacted for 6 hours at 80 ℃, and the oil bath and stirring are closed. After the reaction solution cooled to room temperature, it was transferred to a round-bottomed flask and was distilled at 60℃until the solution appeared viscous. 3g of the product was taken and dropped into 30ml of dehydrated ether to obtain a white precipitate. Repeatedly washing for three times, and drying in a vacuum drying oven at 45 ℃ for 12 hours to obtain the white powder of the final product.
Example 4:
0.125g of the polymer of example 3 and 0.125g of propylene glycol methyl ether were dissolved in ultrapure water to prepare 25ml of an aqueous solution, and the aqueous solution was stirred uniformly.
Example 5:
0.125g of the polymer of example 3 and 0.125g of ethylene glycol were dissolved in ultrapure water to prepare 25ml of an aqueous solution, and the aqueous solution was stirred uniformly.
Example 6:
0.125g of the polymer of example 3 was taken and dissolved in 0.125g of diethylene glycol diethyl ether to prepare 25ml of an aqueous solution, and the aqueous solution was stirred uniformly.
Example 7:
0.125g of the polymer of example 3 and 0.125g of diethylene glycol butyl ether were dissolved in ultrapure water to prepare 25ml of an aqueous solution, and the aqueous solution was stirred uniformly.
Comparative example
The commercial inhibitor inhibex 501 is used as a comparative example, and the structural formula is shown as formula I.
To verify the progress of the examples of the present application, the inhibitors prepared in examples 1 to 7 were tested.
1. The inhibitors prepared in example 1, example 2 and example 3 were characterized by Fourier infrared spectra, and the synthetic substances were determined to be 3465-3487 cm in the infrared spectra as shown in the Fourier infrared spectra of FIG. 1 -1 The nearby peak is the telescopic vibration absorption peak of hydroxyl, which appears at 2928 and 2855cm -1 The peak at which is attributed to C-H stretching vibration of the amide ring, 1734cm -1 The peak at the position is a C=O double bond stretching vibration absorption peak in the ester group, 1632cm -1 The peak at the position is an amide ring C=O double bond stretching vibration absorption peak, 1480cm -1 And 1442cm -1 The peaks at the C-N bond stretch vibration absorption peaks on the amide ring and the pyrrolidone five-membered ring prove that the products of the example 1, the example 2 and the example 3 are poly (vinyl caprolactam-acetic acid)Vinyl esters). 1734cm as the vinyl acetate content in the monomer mixture ratio was decreased in the order of example 1 to example 3 -1 The area of the ester group peak is smaller and smaller.
2. The molecular weights and their distribution of the inhibitors prepared in example 1, example 2 and example 3 and of the commercial inhibitor inhibex501 of the comparative example were characterized by gel permeation chromatography, as shown in table 1:
table 1 molecular weights of examples 1 to 3 and comparative examples
As can be seen from Table 1, examples 1 to 3 each had a weight average molecular weight of more than 38000 and a molecular weight distribution index of about 1.8 to 2.2, whereas the comparative example had a weight average molecular weight of 11465 and a molecular weight distribution index of 5.21. The molecular weight of each of the 3 examples was greater than that of the comparative example, and the uniformity of the molecular weight distribution was also much better than that of the comparative example.
3. Characterization of the inhibitor prepared in example 3 by nmr as shown in the nmr hydrogen spectrum of fig. 2, the strong peaks at chemical shifts 3.3ppm and 2.5ppm in fig. 2 are the peaks of the solvent deuterated DMSO. In the figure, the chemical shift of hydrogen atom (-CH-N-) at b is between 4.2 and 4.3ppm, and hydrogen atom (-CH) at e 2 The chemical shift of-N-) is around 3.2ppm, hydrogen atom (-CH) at c 2 Chemical shifts of-CO-between 2.2 and 2.4ppm, hydrogen atoms (-CH) at a and d 2 -CH 2 -CH 2 -CH 2 The chemical shift of N-) is between 1.2 and 1.8ppm, while the peak of the hydrogen atom at f belonging to the ester group is between 1.8 and 1.95ppm of chemical shift. From nuclear magnetic resonance hydrogen spectroscopy, the product of example 3 was poly (vinylcaprolactam-vinyl acetate).
4. The inhibition performance of the inhibitor used as the natural gas hydrate inhibitor is characterized, and the characterization indexes are the induction time and the gas consumption in 12 hours.
The testing method comprises the following steps: the detection equipment is a high-pressure stirring experimental device, and the main components comprise a high-pressure reaction kettle, a stirring paddle, a constant-temperature water bath, a temperature sensor, a pressure sensor, a methane-propane mixed gas cylinder, a pressurizing system, a vacuum pump, a data acquisition device, a computer and the like. Wherein the number of the high-pressure stirring reaction kettles is 3-6, the highest working pressure is 25MPa, and the working temperature is in the range of-10 ℃ to 100 ℃. The temperature of the constant-temperature water bath is-10 ℃ to 100 ℃. The data acquisition system acquires the pressure and the temperature in the high-pressure reaction kettle in real time. The formation of hydrate can be judged and observed by the temperature or pressure change during the reaction.
Specific detection process at supercooling degree 15 ℃): the reaction experiment temperature is set to be 6 ℃, the experiment pressure is 7.8MPa, and the experiment gas is methane-propane mixed gas. The equilibrium temperature for methane propane hydrate formation at a pressure of 7.8MPa was 21 ℃, and therefore the experimental supercooling degree was 15 ℃. Before the experiment operation, the high-pressure reaction kettle is repeatedly cleaned with deionized water for 3 to 5 times, and then the high-pressure reaction kettle and the experiment pipeline system are purged with nitrogen, so that the drying of the system is ensured. The autoclave was evacuated, and 25mL of the prepared inhibitor solution was sucked in. And (3) introducing methane-propane mixed gas of 1MPa, vacuumizing, and repeating the process for three times to remove air in the high-pressure reaction kettle.
At the experimental temperature of 23 ℃, methane-propane mixed gas with the initial pressure of 8.5MPa is introduced, after the temperature and the pressure are stabilized for 1h, the water bath is started for cooling, the temperature is reduced to 6 ℃ for 102 minutes, the temperature is kept for 10 minutes, the timing is started, and the reaction is started.
(1) Test of induction time. To observe the inhibitor effect of the hydrate nucleation stage, the induction time test did not open the stirring, as turning on the stirring at high supercooling degree would rapidly generate hydrate, which is detrimental to data comparison. The experimental period was 20h. The longer the induction time, the better the hydrate inhibitor effect.
(2) And (3) testing the gas consumption. To observe the inhibitory effect of the hydrate growth phase, stirring was turned on and the reaction was continued for 12 hours with a rotation speed of 500 rpm. Based on the temperature and pressure data within 12 hours, the gas consumption for 12 hours was calculated using the gas state equation pv=nrt as an index for the inhibition performance evaluation. The larger the gas consumption amount for 12 hours, the worse the inhibiting effect of the hydrate inhibitor was represented.
Specific detection process at supercooling degree 18 ℃): the reaction experiment temperature is set to 3 ℃, the experiment pressure is 7.8MPa, and the experiment gas is methane-propane mixed gas. The equilibrium temperature for methane propane hydrate formation at a pressure of 7.8MPa was 21 ℃, and therefore the experimental supercooling degree was 18 ℃. Before the experiment operation, the high-pressure reaction kettle is repeatedly cleaned with deionized water for 3 to 5 times, and then the high-pressure reaction kettle and the experiment pipeline system are purged with nitrogen, so that the drying of the system is ensured. The autoclave was evacuated, and 25mL of the prepared inhibitor solution was sucked in. Introducing methane-propane mixed gas with the pressure of 1MPa, vacuumizing, and repeating the process for three times to remove air in the high-pressure reaction kettle.
At the experimental temperature of 23 ℃, methane-propane mixed gas with the initial pressure of 8.5MPa is introduced, after the temperature and the pressure are stabilized for 1h, a water bath is started for cooling, the temperature is reduced to 3 ℃ for 120 minutes, and the temperature is kept for 10 minutes, so that hydrate is rapidly generated under the high supercooling degree, and the induction time possibly does not exist; the stirring was turned on and the reaction was continued for 12 hours at 500rpm, and the gas consumption and the hydrate volume fraction for 12 hours were calculated from the temperature and pressure data for 12 hours using the gas state equation pv=nrt as an index for evaluation of inhibition performance. Theoretically, the lower the 12 hour gas consumption and the hydrate volume fraction, the better the hydrate inhibition performance.
4.1 characterization of the inhibitory effect of pure water on methane propane hydrate at supercooling degree 15℃at the same use concentration of the inhibitor prepared in examples 1 to 3 and of the commercial inhibitor inhibex501 of the comparative example. Examples 1 to 3 gave poly (vinylcaprolactam-vinyl acetate) copolymers, with the difference that the mass ratios of monomeric vinylcaprolactam and monomeric vinyl acetate were 4:1, 6:1 and 8:1, respectively. Specifically, the inhibitors prepared in example 1, example 2 and example 3, and the commercial inhibitor inhibex501 of comparative example were respectively prepared in 4 inhibitor solutions each having a concentration of 1.0wt%, and then the inhibition effect of the 4 inhibitor solutions and pure water on methane propane hydrate at a supercooling degree of 15 ℃ was respectively tested, as shown in the induction time test result of fig. 3A and the gas consumption test result within 12 hours of fig. 3B. FIG. 3A shows that the induction time of pure water and comparative example is very short (less than 70 minutes) at a supercooling degree of 15 ℃; the induction time of example 1 and example 3 is above 1000 minutes, demonstrating that the effect of inhibiting hydrate nucleation is good; the induction time of example 2 was about 500 minutes, slightly worse than examples 1 and 3. FIG. 3B also shows the same rule, and the pure water and the comparative example both consume more than 90 mmol/mol of gas in terms of the hydrate growth stage, and the inhibition effect is poor; the gas consumption of example 2 was less in the first 300 minutes, and the 300-720 minutes gradually increased to 80 mmoles/mole, indicating that the inhibition ability against the hydrate growth phase was also poor; whereas examples 1 and 3 had low gas consumption over 12 hours, and in particular example 3, produced almost no hydrate at all over 12 hours, the inhibition was very good, probably due to the fact that the monomer ratio was different, the monomer mass ratio of 8:1 was most suitable, the rate of consumption of the monomer was kept at a relatively constant level with respect to the rate of production of the polymer, and it was also possible that the molecular weight distribution index PDI of example 3 was narrowest, and the polymer obtained by synthesis was more uniform.
4.2 characterization of the inhibition effect of the inhibitor prepared in example 3 and of the commercial inhibitor inhibex501 of the comparative example on methane propane hydrate at a supercooling degree of 15℃at different use concentrations. Example 3 gave poly (vinylcaprolactam-vinyl acetate) copolymer with a mass ratio of monomeric vinylcaprolactam to monomeric vinyl acetate of 8:1, respectively. Specifically, the inhibitor prepared in example 3 was prepared as 5 inhibitor solutions having concentrations of 0.25wt%,0.5wt%,0.75wt%,1.0wt% and 1.5wt%, respectively, and the commercial inhibitor inhbex 501 of comparative example was prepared as 4 inhibitor solutions having concentrations of 0.5wt%,1wt%,3wt% and 5wt%, respectively, and then the inhibition effect of the 9 inhibitor solutions on methane propane hydrate at a supercooling degree of 15 ℃ was tested, respectively, as shown in the gas consumption test results in 12 hours of fig. 4A and the gas consumption test results in 12 hours of fig. 4B. FIG. 4A shows that example 3 was used at concentrations of 0.25wt%,0.5wt%,0.75wt%,1.0wt% and 1.5wt%, with lower and lower gas consumption for 12 hours as the inhibitor concentration was increased; FIG. 4B shows that the comparative examples were used at concentrations of 0.5wt%,1wt%,3wt% and 5wt%, and that the gas consumption was lower and lower for 12 hours as the inhibitor concentration was increased. This shows that both inhibitors have better and better inhibition performance in the autoclave as the use concentration increases. Fig. 4B shows that at a supercooling degree of 15 ℃, the 12 hour gas consumption of the same concentration (1 wt%) of the commercial inhibitor Inhibex501 for methane propane hydrate is 18 times that of example 3, but the increase in inhibitor effect is not completely linear. FIGS. 4A and 4B show that commercial inhibitor Inhibex501 at a concentration of 5wt% at a gas consumption of 42.95mmol/mol for 12 hours is comparable to the data of example 3 at a concentration of 0.5wt%, which indicates that the same inhibition effect is to be achieved, and that example 3 can be used at least several times more than commercial inhibitor Inhibex501, which greatly reduces the cost of inhibitor use.
4.3, characterizing the inhibition effect of the inhibitor prepared in the examples 4 to 7 on methane propane hydrate at the supercooling degree of 15 ℃. Specifically, examples 4 to 7 were directly prepared to obtain aqueous inhibitor solutions each containing the poly (vinylcaprolactam-vinyl acetate) copolymer obtained in example 3 and a compounding agent compounded therewith. In detail, the aqueous inhibitor solution prepared in example 4 comprises poly (vinylcaprolactam-vinyl acetate) copolymer at a concentration of 0.5wt% and propylene glycol methyl ether at a concentration of 0.5wt%, i.e. the inhibitor concentration is 1.0wt%; the aqueous inhibitor solution prepared in example 5 contained 0.5wt% poly (vinyl caprolactam-vinyl acetate) copolymer and 0.5wt% ethylene glycol, the aqueous inhibitor solution prepared in example 6 contained 0.5wt% poly (vinyl caprolactam-vinyl acetate) copolymer and 0.5wt% diethylene glycol ethyl ether, and the aqueous inhibitor solution prepared in example 7 contained 0.5wt% poly (vinyl caprolactam-vinyl acetate) copolymer and 0.5wt% diethylene glycol butyl ether. It is clear that the aqueous solutions of the inhibitors prepared directly in examples 4 to 7 all contain the same concentration of poly (vinylcaprolactam-vinyl acetate) copolymer, and the concentrations of the compounding agents compounded with the aqueous solutions are the same, except that the compounding agents are different in type. The 4 inhibitor solutions prepared in examples 4 to 7 were respectively tested for inhibition effect on methane propane hydrate at a supercooling degree of 15 c, and as shown in the induction time test result of fig. 5A and the gas consumption test result within 12 hours of fig. 5B, induction times of the poly (vinylcaprolactam-vinyl acetate) copolymer prepared in example 3, 0.5wt%, after compounding with the 4 compounding agents, were 279.59 minutes, 76.09 minutes, 152.45 minutes and 1200 minutes, respectively, and gas consumption within 12 hours was 22.16 mmol/mol, 79.15 mmol/mol, 62.93 mmol/mol and 5.09 mmol/mol, respectively. The results show that the effect of compounding the poly (vinyl caprolactam-vinyl acetate) copolymer with 3 alcohol ethers is better than that of compounding the poly (vinyl caprolactam-vinyl acetate) copolymer with ethylene glycol in 4 compounding agents, wherein the effect of compounding the poly (vinyl caprolactam-vinyl acetate) copolymer with diethylene glycol butyl ether (i.e. example 7) is the best, the induction time is the longest, and the gas consumption of 12 hours is the lowest. The alcohol ethers such as ethylene glycol butyl ether and diethylene glycol butyl ether all have oxygen atoms with strong hydrogen bond forming capability, and can compete with water molecules, so that free water molecules cannot participate in forming a hydrate cage, and metastable hydrate is prevented from forming. The hydroxyl on the diethylene glycol butyl ether can act with water more strongly to influence water aggregation into a cage; meanwhile, caprolactam groups in the poly (vinyl caprolactam-vinyl acetate) copolymer interact with hydroxyl groups of diethylene glycol butyl ether, and under the combined action of Van der Waals force and hydrogen bond, the caprolactam groups and water can prevent methane-propane mixed gas molecules from entering a hydrate cage, so that the inhibition capability is enhanced.
4.4 continuing to characterize the inhibitory effect of the inhibitor prepared in example 7, the commercial inhibitor Inhibex501 of comparative example and pure water on methane propane hydrate under extremely severe temperature conditions with a supercooling degree of 18 ℃. Specifically, example 7 directly prepared an inhibitor aqueous solution, wherein the inhibitor aqueous solution contains the poly (vinyl caprolactam-vinyl acetate) copolymer obtained in example 3 and diethylene glycol butyl ether compounded with the poly (vinyl caprolactam-vinyl acetate) copolymer, and the concentration of the poly (vinyl caprolactam-vinyl acetate) copolymer and the diethylene glycol butyl ether in the inhibitor aqueous solution is 0.5wt%, namely, the inhibitor concentration is 1.0wt%; the commercial inhibitor inhibex501 of comparative example was formulated as an aqueous inhibitor solution having a concentration of 1wt%, and then the inhibition effect of 2 inhibitor solutions and pure water on methane propane hydrate at a supercooling degree of 18 ℃ was tested, respectively, as shown by the gas consumption test result in 12 hours of fig. 6A and the hydrate volume fraction test result in fig. 6B, the pure water, comparative example and 12 hours gas consumption of example 7 were 125.71, 92.05 and 10.33 mmol/mol, respectively, and the hydrate volume fractions in 12 hours were 82.80wt%,62.91wt% and 7.61wt%, respectively. The above results demonstrate that example 7 is able to withstand extremely severe temperature conditions (18 degrees supercooling), 8 to 9 times better than the commercial inhibitor Inhibex501 at the same concentration to inhibit hydrate growth. Example 7 can basically maintain the growth rate of the hydrate at a lower rate for a longer time (12 hours), and can avoid economic loss caused by blockage of the hydrate pipeline due to extreme temperature conditions caused by factors such as sudden drop of air temperature or sudden stop in the actual gas production and transportation process of the oil and gas field.
The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the application.
Claims (10)
1. A method of preparing an inhibitor comprising: mixing vinyl caprolactam monomer, vinyl acetate monomer, initiator and solvent to obtain a mixture; reacting the mixture for a first time at a first temperature under the conditions of gas protection and stirring; cooling, and removing the solvent to obtain a precipitate; washing and drying the precipitate to obtain a poly (vinyl caprolactam-vinyl acetate) copolymer;
wherein, in the mixture, the mass ratio of the vinyl caprolactam monomer to the vinyl acetate monomer is 1-12;
in the mixture, the mass ratio of the usage amount of the initiator to the total amount of the vinyl caprolactam and the vinyl acetate is 0.001-0.2.
2. The method for preparing the inhibitor according to claim 1, wherein the mass ratio of the solvent to the total amount of the vinylcaprolactam and the vinyl acetate in the mixture is 1 to 20;
And/or the mixture further comprises a chain transfer agent, wherein the mass ratio of the chain transfer agent to the total amount of the vinyl caprolactam monomer and the vinyl acetate monomer is 0.001-0.01;
and/or the first temperature is (60-90) DEG C;
and/or the first time is (5-8) h.
3. The method of preparing an inhibitor according to claim 1, further comprising: providing a compounding agent; compounding the poly (vinyl caprolactam-vinyl acetate) copolymer and the compounding agent.
4. The method of preparing the inhibitor according to claim 3, wherein the compounding agent comprises at least one of propylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, ethylene glycol phenyl ether, ethylene glycol methyl ether, methanol, ethanol, butanol, ethylene glycol, polyethylene glycol, pentanediol, and hexanediol;
and/or the mass ratio of the poly (vinyl caprolactam-vinyl acetate) copolymer to the compounding agent is (1-10): 1-10.
5. An inhibitor prepared according to any one of claims 1 to 4, characterized in that it comprises a poly (vinylcaprolactam-vinyl acetate) copolymer obtained by polymerization of a vinylcaprolactam monomer with a vinyl acetate monomer.
6. The inhibitor according to claim 5, wherein the mass ratio of the vinyl caprolactam monomer to the vinyl acetate monomer is 4 to 8;
and/or the poly (vinyl caprolactam-vinyl acetate) copolymer has a number average molecular weight of 1000 to 1000000;
and/or the poly (vinyl caprolactam-vinyl acetate) copolymer has a weight average molecular weight of 1000 to 1000000;
and/or the poly (vinyl caprolactam-vinyl acetate) copolymer has a molecular weight distribution index of 1 to 10.
7. The inhibitor of claim 5, further comprising a compounding agent.
8. The inhibitor of claim 7, wherein the compounding agent comprises at least one of propylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, ethylene glycol phenyl ether, ethylene glycol methyl ether, methanol, ethanol, butanol, ethylene glycol, polyethylene glycol, pentanediol, and hexanediol;
and/or the mass ratio of the poly (vinyl caprolactam-vinyl acetate) copolymer to the compounding agent is (1-10): 1-10.
9. Use of an inhibitor according to any one of claims 1 to 4 as a natural gas hydrate inhibitor or an inhibitor according to any one of claims 5 to 8.
10. Use according to claim 9, wherein the inhibitor is used in the form of an aqueous inhibitor solution, the concentration of the poly (vinylcaprolactam-vinyl acetate) copolymer in the aqueous inhibitor solution being (0.1-20% by weight);
and/or the applied pressure is (0-25) MPa;
and/or the temperature of the application is (-10-40) deg.C.
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