CN112358570B - Temperature-sensitive natural gas hydrate kinetic inhibitor and preparation method thereof - Google Patents
Temperature-sensitive natural gas hydrate kinetic inhibitor and preparation method thereof Download PDFInfo
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Abstract
The invention provides a temperature-sensitive natural gas hydrate dynamics inhibitor and a preparation method thereof, wherein the natural gas hydrate dynamics inhibitor is prepared by nucleophilic substitution reaction of N-vinylformamide and 2-bromoethyl ether to obtain a prepolymerized monomer NE, and then free radical copolymerization of the prepolymerized monomer NE and N-vinyl pyrrolidone. The invention also provides a preparation method of the temperature-sensitive hydrate kinetic inhibitor. The natural gas hydrate kinetic inhibitor is used for inhibiting the generation and growth of natural gas hydrate crystal nuclei, further inhibiting the coalescence and deposition of natural gas hydrate in a shaft, preventing the shaft from being blocked, and simultaneously adjusting the rheological property of drilling fluid, thereby ensuring the safe and efficient production of the natural gas hydrate.
Description
Technical Field
The invention relates to a temperature-sensitive natural gas hydrate kinetic inhibitor and a preparation method thereof, belonging to the technical field of water-based drilling fluid organic additives.
Background
The contradiction between oil and gas supply and demand in China is increasingly obvious, the conventional oil and gas resources can not meet the increasing national economic development demands, and the development of efficient and clean new energy has important strategic significance for guaranteeing the energy safety in China. The natural gas hydrate is used as a clean, high-heat-value and huge-reserve resource, the hydrate resource amount in the sea area of China is about 800 hundred million tons of oil equivalent, and the natural gas hydrate is expected to become one of novel clean energy sources for replacing oil and gas resources in the future. However, natural gas hydrates present a series of key technical problems during drilling: natural gas hydrates are easily generated in a shaft, and can cause shaft blockage and even drilling accidents when serious.
At present, in the drilling and production process, a natural gas hydrate inhibition method mainly comprises the steps of adding a hydrate thermodynamic inhibitor such as methanol, ethylene glycol, a salt electrolyte and the like into drilling fluid, and avoiding the formation of the hydrate in a shaft by changing the thermodynamic conditions of the formation of the natural gas hydrate. However, the thermodynamic inhibitor has the defects of high dosage, poor effect and the like, for example, the dosage of methanol, ethanol, sodium chloride and the like is up to 20-60 wt%, so that the development cost of natural gas hydrate is greatly increased, and chemical reagents such as methanol, ethylene glycol and the like can cause secondary damage to marine ecological environment; the salt electrolyte such as sodium chloride has higher corrosiveness to drilling tools, and even accidents such as pipeline fracture and the like can be caused when the salt electrolyte is serious, so that the risk of safety in production of natural gas hydrate is greatly brought. Thus, existing thermodynamic inhibitors have failed to meet the further needs of sea natural gas hydrate development.
The natural gas hydrate kinetic inhibitor is a low-dose inhibitor for inhibiting the generation and growth of hydrate by influencing the hydrate kinetic parameters, the phase balance condition of the generation of the hydrate is not required to be changed, the use amount is as low as below 3.0wt% of the total system, the nucleation time of the hydrate can be greatly prolonged, the growth rate of crystal nucleus is reduced, and the blockage of the hydrate in the drilling process is reduced. Compared with the traditional thermodynamic inhibition method, the hydrate dynamics inhibitor has the advantages of small dosage, obvious effect, good environmental benefit and the like, can effectively inhibit the formation and deposition of hydrate in a shaft, and can provide powerful guarantee for safely and efficiently exploiting hydrate resources.
In addition, in the drilling and production process of the natural gas hydrate, when the drilling fluid circularly flows through a deep water seabed area (below 4 ℃), the viscosity of the drilling fluid is increased sharply, so that the rheological property of the annular drilling fluid in the drilling process is difficult to control, the circulation resistance in a pipe column is increased, and the drilling and production safety of the natural gas hydrate is seriously threatened.
Patent literature reports also exist on natural gas hydrate kinetic inhibitors. For example: chinese patent document CN105859963a provides a kinetic inhibitor of polycyclic polymeric natural gas hydrate, prepared by free radical polymerization using N-vinylpyrrolidone, N-vinylcaprolactam, acrylamide, acrylonitrile, which can effectively inhibit the formation of natural gas hydrate, but which cannot regulate the rheology of drilling fluid under low temperature conditions; chinese patent document CN108276512a provides a temperature-sensitive polymer prepared by radical polymerization using vinylcaprolactam monomer (VCL) as a high molecular Polymer (PVCL) capable of controlling the rheological property of drilling fluid, but has a weak hydrate inhibition property because it only contains a ring structure.
Chinese patent document CN111116797a provides a novel natural gas hydrate inhibitor, which is based on N-vinyl pyrrolidone, and is obtained by adding a novel structural group to the monomer ring structure thereof, wherein the structural group is a hydroxyl group containing C1-C6, a hydrocarbon group containing C1-C6 or an amino group containing C1-C6. Chinese patent document CN109735316a provides a natural gas hydrate inhibitor. The natural gas hydrate inhibitor takes N-vinyl pyrrolidone as a raw materialBased on the addition of-CF to the end groups by chemical synthesis 3 or-RCF 3 The group changes the end chain structure of the inhibitor to achieve the purpose of enhancing the inhibition effect. However, the two inhibitors only contain a multi-element ring structure in the repeating unit, do not contain a linear structure, have single inhibition type on hydrate and have insufficient inhibition capability. Meanwhile, the method is only used for inhibiting the generation of natural gas hydrate, but the drilling fluid rheological property regulation and control effect is poor, and the method is insufficient for meeting the current hydrate stratum development requirement.
Therefore, there is a need to develop a natural gas hydrate kinetic inhibitor that can effectively inhibit the formation of natural gas hydrates and can adjust the rheological properties of drilling fluids at low temperatures. For this purpose, the present invention is proposed.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a temperature-sensitive natural gas hydrate kinetic inhibitor and a preparation method thereof. The natural gas hydrate kinetic inhibitor can effectively inhibit the generation and growth of natural gas hydrate crystal nucleus, thereby further inhibiting the coalescence and deposition of natural gas hydrate in a shaft and preventing the shaft from being blocked; meanwhile, the rheological property of the drilling fluid can be adjusted, so that the safe and efficient production of the natural gas hydrate is ensured.
The technical scheme of the invention is as follows:
the temperature-sensitive natural gas hydrate dynamics inhibitor is prepared by nucleophilic substitution reaction of N-vinylformamide and 2-bromoethyl ether to obtain a prepolymerized monomer NE, and then free radical copolymerization of the prepolymerized monomer NE and N-vinylpyrrolidone, and has a structure shown in the following formula I:
in the formula I, m/n=0.5-3.0.
According to the present invention, the temperature-sensitive natural gas hydrate kinetic inhibitor preferably has a number average molecular weight of 10000 to 30000, more preferably 25000 to 30000.
According to the invention, the preparation method of the temperature-sensitive natural gas hydrate kinetic inhibitor comprises the following steps:
(1) Uniformly mixing N-vinylformamide, 2-bromoethyl ether and N, N-dimethylformamide, and stirring to obtain a mixed solution;
(2) Heating the mixed solution obtained in the step (1) to 50-60 ℃, then adding an initiator, and stirring for reaction; after the reaction is finished, extracting and purifying to obtain an N-vinylformamide grafted diethyl ether prepolymerization monomer NE;
(3) Adding the N-vinylformamide grafted diethyl ether prepolymerized monomer NE, N-vinylpyrrolidone and an initiator obtained in the step (2) into water, reacting at 50-70 ℃ in nitrogen atmosphere, and drying the obtained product to obtain the temperature-sensitive natural gas hydrate kinetic inhibitor.
According to the present invention, it is preferable that the mass of the N-vinylformamide in the step (1) is 3 to 10% of the total mass of N-vinylformamide, 2-bromoethyl ether, N-dimethylformamide; the mass of the 2-bromoethyl ether is 5-20% of the total mass of the N-vinylformamide, the 2-bromoethyl ether and the N, N-dimethylformamide; the mass of the N, N-dimethylformamide is 70-85% of the total mass of the N-vinylformamide, the 2-bromoethyl ether and the N, N-dimethylformamide.
According to the present invention, preferably, the mixing temperature in the step (1) is 0 to 2 ℃; the stirring speed of stirring is 200-500 r/min, the stirring temperature is 0-2 ℃, and the stirring time is 4-6 hours.
According to the invention, preferably, the initiator in the step (2) is azobisisobutyronitrile, and the initiator is added in an amount of 0.1 to 0.5% by weight of the total mass of N-vinylformamide, 2-bromoethyl ether and N, N-dimethylformamide.
According to the present invention, it is preferable that the stirring rate of the stirring reaction in the step (2) is 200 to 500r/min and the reaction time is 8 to 16 hours.
According to the present invention, preferably, the extraction and purification steps in step (2) are as follows: cooling the reaction system to room temperature, adding a mixed solvent of normal hexane, ethyl acetate and water for extraction, washing an obtained organic phase with water, drying the organic phase with anhydrous magnesium sulfate, removing the solvent, and purifying the obtained product by silica gel column chromatography to obtain an N-vinylformamide grafted diethyl ether prepolymerized monomer NE;
further preferably, the volume ratio of the n-hexane to the ethyl acetate in the mixed solvent is 1:4; the volume ratio of the total volume of the n-hexane and the ethyl acetate to the water is 1:1-4; the ratio of the total mass of the N-vinylformamide, the 2-bromoethyl ether and the N, N-dimethylformamide to the volume of the mixed solvent is 1 g:3-9 mL;
further preferably, the eluent of the column chromatography is a mixed solvent of n-hexane and ethyl acetate, wherein the volume ratio of n-hexane to ethyl acetate is 1:4.
According to the invention, preferably, the mass of the N-vinyl formamide grafted diethyl ether pre-polymerized monomer NE in the step (3) is 7-25% of the total mass of the N-vinyl formamide grafted diethyl ether pre-polymerized monomer NE, N-vinyl pyrrolidone and water; the mass of the N-vinyl pyrrolidone is 10-20% of the total mass of the N-vinyl formamide grafted diethyl ether prepolymerized monomer NE, the N-vinyl pyrrolidone and water; the mass of the water is 55-83% of the total mass of the N-vinylformamide grafted diethyl ether pre-polymerized monomer NE, N-vinylpyrrolidone and water.
According to the invention, preferably, the initiator in the step (3) is azobisisobutyronitrile, and the initiator is added in an amount of 0.1 to 1% by weight of the total mass of the N-vinylformamide grafted diethyl ether pre-polymerized monomer NE, N-vinylpyrrolidone and water.
According to the present invention, it is preferable that the reaction time in the step (3) is 4 to 6 hours; the drying is carried out for 10-12 hours under vacuum at 30-50 ℃.
According to the invention, the N-vinylformamide-grafted diethyl ether pre-polymerized monomer NE obtained in step (2) has a structure shown in formula II:
the invention has the technical characteristics and beneficial effects that:
1. the natural gas hydrate kinetic inhibitor can inhibit the generation of natural gas hydrate and regulate the rheological property of drilling fluid. The invention utilizes nucleophilic substitution reaction of N-vinylformamide and 2-bromoethyl ether to obtain a pre-polymerized monomer, and then the pre-polymerized monomer and N-vinyl pyrrolidone are subjected to free radical copolymerization to obtain the temperature-sensitive natural gas hydrate dynamics inhibitor, the obtained temperature-sensitive natural gas hydrate dynamics inhibitor has a five-membered ring containing amide groups and a linear structure containing amide groups, and in the hydrate generation process, the amide groups can form hydrogen bonds with water molecules to prevent the hydrate from forming a cage structure; in addition, in the growth process of the hydrate, the five-membered ring can be embedded into the hydrate cage-shaped structure to form steric hindrance, so that the hydrate can grow in a malformation or can not grow, and the aggregation of the hydrate is inhibited, thereby avoiding the blocking of a shaft by the hydrate and ensuring the safety and the high efficiency of the drilling construction of the hydrate.
2. The N-vinyl formamide grafted diethyl ether chain link exists in the temperature-sensitive natural gas hydrate kinetic inhibitor, the proportion of hydrophilic groups in the polymer molecule is increased, and the hydrophilicity of the polymer is enhanced, so that the temperature sensitivity of the inhibitor is enhanced, the regulating and controlling capability of the temperature-sensitive natural gas hydrate kinetic inhibitor on the rheological property of drilling fluid is increased, and the temperature-sensitive natural gas hydrate kinetic inhibitor has a good steady flow effect on the drilling fluid. Experiments prove that when the temperature is increased, compared with the conventional water-based drilling fluid, the viscosity of the water-based drilling fluid containing the temperature-sensitive polymer is higher, and the viscosity change range of the water-based drilling fluid system added with the temperature-sensitive natural gas hydrate kinetic inhibitor is smaller than that of the conventional water-based drilling fluid in the temperature range of 0-50 ℃, so that the rheological property of the water-based drilling fluid system can be effectively regulated by the temperature-sensitive polymer.
3. The temperature-sensitive natural gas hydrate kinetic inhibitor can inhibit the generation of hydrate in a shaft, regulate and control the rheological property of a water-based drilling fluid system, and reduce the use of thermodynamic inhibitors and drilling fluid flow type additives. The drilling cost can be reduced while the drilling safety of the natural gas hydrate is ensured, and the method has higher economic value and use value.
Drawings
Fig. 1 is an infrared spectrogram of the temperature-sensitive natural gas hydrate kinetic inhibitor prepared in example 1.
FIG. 2 is a graph showing viscosity-temperature curves of the water-based drilling fluids to which the inhibitors prepared in example 1 and comparative example 1 were added and the water-based drilling fluids to which no inhibitor was added in test example 1.
FIG. 3 is a graph showing the pressure in the autoclave body as a function of time without addition of an inhibitor in test example 2, wherein the abscissa indicates time and the ordinate indicates pressure.
FIG. 4 is a graph showing the growth of pure water hydrate without addition of inhibitor in test example 2, wherein the abscissa indicates time and the ordinate indicates the thickness of hydrate.
FIG. 5 is a graph showing the pressure in the autoclave body as a function of time after the inhibitor prepared in example 1 was added to test example 2, wherein the abscissa indicates time and the ordinate indicates pressure.
FIG. 6 is a graph showing the growth of the hydrate after the addition of the inhibitor prepared in example 1 in test example 2, wherein the abscissa indicates time and the ordinate indicates the thickness of the hydrate.
FIG. 7 is a graph showing the pressure in the autoclave body as a function of time after the inhibitor prepared in comparative example 1 was added in test example 2, wherein the abscissa represents time and the ordinate represents pressure.
Detailed Description
The invention is further illustrated, but not limited, by the following examples.
Meanwhile, the experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents, materials, and apparatus, unless otherwise specified, are all commercially available.
Example 1
The preparation method of the temperature-sensitive natural gas hydrate kinetic inhibitor comprises the following steps:
(1) 6g N-vinylformamide, 6g of 2-bromoethyl ether and 48g of N, N-dimethylformamide were uniformly mixed at 0℃and stirred at 200r/min for 4 hours at 0℃to give a mixed solution.
(2) Heating the mixed solution obtained in the step (1) to 50 ℃, then adding 0.03g of initiator azodiisobutyronitrile, and stirring and reacting for 8 hours under the condition of stirring speed of 200 r/min; after the reaction, the reaction system was cooled to room temperature, 400mL of a mixed solvent of N-hexane, ethyl acetate and water (the volume ratio of N-hexane to ethyl acetate is 1:4, the volume ratio of N-hexane to ethyl acetate to water is 1:3) was added for extraction, the obtained organic phase was washed with water, dried over anhydrous magnesium sulfate, the solvent was removed, the obtained product was purified by silica gel (200-300 mesh) column chromatography using a mixed solvent of N-hexane and ethyl acetate (the volume ratio of N-hexane to ethyl acetate is 1:4) as an eluent, the solvent was removed, and vacuum-dried at 50 ℃ for 12 hours to obtain the N-vinylformamide grafted diethyl ether pre-polymerized monomer NE.
(3) 6g of N-vinylformamide grafted diethyl ether prepolymerized monomer NE obtained in the step (2), 8g of vinyl pyrrolidone, 0.06g of initiator azodiisobutyronitrile and 46g of water are added into a three-neck flask provided with a thermometer, a mechanical stirring and a reflux condenser tube, and the mixture is reacted for 4 hours at 50 ℃ in a high-purity nitrogen atmosphere; and after the reaction is finished, the obtained product is dried in vacuum for 12 hours at 50 ℃ to obtain the temperature-sensitive natural gas hydrate kinetic inhibitor.
The temperature-sensitive kinetic inhibitor synthesized in this example was subjected to infrared spectroscopic analysis by using a Shimadzu IRTracer-100 type infrared spectrometer (KBr pellet), and the results are shown in FIG. 1. As can be seen from FIG. 1, 3431.3cm in the infrared spectrum of the synthesized product -1 ，1678.0cm -1 ，1421.5cm -1 Corresponds to the characteristic peak of N-H stretching vibration, C=O stretching vibration and C-N stretching vibration in the amide group, 2981.9cm respectively -1 Corresponds to C-H stretching vibration in alkyl, 1122.5cm -1 Corresponding to the characteristic peak of stretching vibration of ether bond in the branched chain. From the above analysis, each functional group corresponds to a characteristic peak of the functional group of the target product, which indicates that the target product has been synthesized.
Example 2
The preparation method of the temperature-sensitive natural gas hydrate kinetic inhibitor comprises the following steps:
(1) 6g N-vinylformamide, 12g of 2-bromoethyl ether and 42g of N, N-dimethylformamide are uniformly mixed at 0 ℃, and stirred for 4 hours at a temperature of 0 ℃ and a stirring rate of 200r/min to obtain a mixed solution.
(2) Heating the mixed solution obtained in the step (1) to 50 ℃, then adding 0.03g of initiator azodiisobutyronitrile, and stirring and reacting for 8 hours under the condition of stirring speed of 200 r/min; after the reaction, the reaction system was cooled to room temperature, 400mL of a mixed solvent of N-hexane, ethyl acetate and water (the volume ratio of N-hexane to ethyl acetate is 1:4, the volume ratio of N-hexane to ethyl acetate to water is 1:3) was added for extraction, the obtained organic phase was washed with water, dried over anhydrous magnesium sulfate, the solvent was removed, the obtained product was purified by silica gel (200-300 mesh) column chromatography using a mixed solvent of N-hexane and ethyl acetate (the volume ratio of N-hexane to ethyl acetate is 1:4) as an eluent, the solvent was removed, and vacuum-dried at 50 ℃ for 12 hours to obtain the N-vinylformamide grafted diethyl ether pre-polymerized monomer NE.
(3) 6g of N-vinylformamide grafted diethyl ether prepolymerized monomer NE obtained in the step (2), 8g of vinyl pyrrolidone, 0.06g of initiator azodiisobutyronitrile and 46g of water are added into a three-neck flask provided with a thermometer, a mechanical stirring and a reflux condenser tube, and the mixture is reacted for 4 hours at 60 ℃ in a high-purity nitrogen atmosphere; and after the reaction is finished, the obtained product is dried in vacuum for 12 hours at 50 ℃ to obtain the temperature-sensitive natural gas hydrate kinetic inhibitor.
Example 3
The preparation method of the temperature-sensitive natural gas hydrate kinetic inhibitor comprises the following steps:
(1) 6g N-vinylformamide, 10g of 2-bromoethyl ether and 44g of N, N-dimethylformamide were uniformly mixed at 0℃and stirred at 200r/min for 4 hours at 0℃to give a mixed solution.
(2) Heating the mixed solution obtained in the step (1) to 50 ℃, then adding 0.03g of initiator azodiisobutyronitrile, and stirring and reacting for 8 hours under the condition of stirring speed of 200 r/min; after the reaction, the reaction system was cooled to room temperature, 200mL of a mixed solvent of N-hexane, ethyl acetate and water (the volume ratio of N-hexane to ethyl acetate is 1:4, the volume ratio of N-hexane to ethyl acetate to water is 1:3) was added to conduct extraction, the obtained organic phase was washed with water, dried over anhydrous magnesium sulfate, the solvent was removed, the obtained product was purified by silica gel (200-300 mesh) column chromatography using a mixed solvent of N-hexane and ethyl acetate (the volume ratio of N-hexane to ethyl acetate is 1:4) as an eluent, the solvent was removed, and vacuum drying was conducted at 50 ℃ for 12 hours, to obtain an N-vinylformamide grafted diethyl ether pre-polymerized monomer NE.
(3) 6g of N-vinylformamide grafted diethyl ether prepolymerized monomer NE obtained in the step (2), 8g of vinyl pyrrolidone, 0.06g of initiator azodiisobutyronitrile and 46g of water are added into a three-neck flask provided with a thermometer, a mechanical stirring and a reflux condenser tube, and the mixture is reacted for 4 hours at 70 ℃ in a high-purity nitrogen atmosphere; and after the reaction is finished, the obtained product is dried in vacuum for 12 hours at 50 ℃ to obtain the temperature-sensitive natural gas hydrate kinetic inhibitor.
Comparative example 1
A method for preparing a polyvinylpyrrolidone inhibitor, comprising the following steps:
adding 38.994g of water into a three-neck flask, stirring, adding 11g N-vinyl pyrrolidone under the protection of nitrogen, heating to 70 ℃, stirring for 30 minutes, adding 0.0006g of initiator azodiisobutyronitrile, and uniformly mixing; after 8h of reaction, the obtained product is dried in vacuum at 90 ℃ for 12h, thus obtaining the polyvinylpyrrolidone inhibitor.
Test example 1
2g of the temperature-sensitive natural gas hydrate kinetic inhibitor prepared in example 1 and 2g of the polyvinylpyrrolidone inhibitor prepared in comparative example 1 were added to 400mL of 4% bentonite+0.5% XC (xanthan gum) +1% DSP-1+10% NaCl water-based drilling fluid system (the percentages are mass percent), respectively, and the rheological properties of the water-based drilling fluid and the water-based drilling fluid added with the inhibitor at different temperatures were tested by using a low temperature rheometer, and meanwhile, the water-based drilling fluid without the inhibitor was used as a comparison, and the results are shown in FIG. 2. As can be seen from fig. 2, the apparent viscosity of the water-based drilling fluid without inhibitor varies by more than 65% in the range of 0-50 ℃; the apparent viscosity of the drilling fluid changes by less than 50% after the inhibitor prepared in example 1 is added; the apparent viscosity change of the drilling fluid after adding the polyvinylpyrrolidone inhibitor prepared in comparative example 1 was smaller than that of the water-based drilling fluid without the inhibitor, but greater than that after adding the inhibitor prepared in example 1. Therefore, the natural gas hydrate kinetic inhibitor prepared by the invention better realizes the regulation and control of the rheological property of the drilling fluid, and meets the rheological property requirement of the drilling fluid when the hydrate stratum is developed.
Test example 2
The natural gas hydrate kinetic inhibitors prepared in example 1 and comparative example 1 were tested for natural gas hydrate inhibition performance, and the specific steps are as follows:
and (3) testing by using a hydrate experimental device, cleaning the kettle body for three times by sequentially using deionized water and ethanol before the experiment, and vacuumizing the kettle body for half an hour before methane gas is filled into the kettle body. 220g of pure water and 220g of pure water plus 1.1g of the inhibitor prepared in the example 1 are respectively added into the kettle body, the kettle body is cooled circularly to 13.4 ℃, methane gas is introduced, and the growth process of the hydrate and the pressure change in the kettle body are recorded; in addition, with the inhibitor prepared in comparative example 1 as a comparison, 220g of pure water+1.1 g of the inhibitor prepared in comparative example 1 was added to the vessel, and the vessel was cooled to a temperature of 13.4℃by circulation, and the pressure change in the vessel in the presence of the polyvinylpyrrolidone (PVP) inhibitor of comparative example 1 was recorded.
The graphs of the pressure change in the kettle body and the growth condition of the pure water hydrate under the condition of no inhibitor addition are respectively shown in figures 3 and 4; the pressure change in the kettle body and the growth condition of the hydrate after the inhibitor prepared in the example 1 is added are respectively shown in figures 5 and 6; the pressure change in the autoclave body after the inhibitor was prepared by adding comparative example 1 is shown in fig. 7. As can be seen by comparing FIGS. 3,5 and 7, the induction time of pure water hydrate is 1min at about 10MPa, the induction time of hydrate after adding the inhibitor prepared in example 1 is 102min at the maximum, and the induction time of hydrate after adding the polyvinylpyrrolidone inhibitor prepared in comparative example 1 is 61min. The hydrate induction time and the hydrate generation rate can be intuitively reflected from figures 4 and 6, and the comparison shows that the hydrate induction time is obviously prolonged and the hydrate generation rate is greatly reduced after the inhibitor prepared by the embodiment of the invention is added, so that the inhibitor has good capability of inhibiting the generation of the hydrate, and is suitable for being used as the hydrate inhibitor for drilling fluid in the process of exploiting and drilling the hydrate.
Claims (8)
1. The preparation method of the temperature-sensitive natural gas hydrate dynamics inhibitor is characterized in that the natural gas hydrate dynamics inhibitor is prepared by nucleophilic substitution reaction of N-vinylformamide and 2-bromoethyl ether to obtain a prepolymerized monomer NE, and then free radical copolymerization of the prepolymerized monomer NE and N-vinyl pyrrolidone, wherein the temperature-sensitive natural gas hydrate dynamics inhibitor has a structure shown in the following formula I:
in the formula I, m/n=0.5-3.0; the number average molecular weight of the temperature-sensitive natural gas hydrate kinetic inhibitor is 10000-30000;
the preparation method comprises the following steps:
(1) Uniformly mixing N-vinylformamide, 2-bromoethyl ether and N, N-dimethylformamide, and stirring to obtain a mixed solution;
(2) Heating the mixed solution obtained in the step (1) to 50-60 ℃, then adding an initiator, and stirring for reaction; after the reaction is finished, extracting and purifying to obtain an N-vinylformamide grafted diethyl ether prepolymerization monomer NE;
(3) Adding the N-vinylformamide grafted diethyl ether prepolymerized monomer NE, N-vinylpyrrolidone and an initiator obtained in the step (2) into water, reacting at 50-70 ℃ in nitrogen atmosphere, and drying the obtained product to obtain a temperature-sensitive natural gas hydrate kinetic inhibitor; the mass of the N-vinyl formamide grafted diethyl ether pre-polymerized monomer NE is 7-25% of the total mass of the N-vinyl formamide grafted diethyl ether pre-polymerized monomer NE, N-vinyl pyrrolidone and water; the mass of the N-vinyl pyrrolidone is 10-20% of the total mass of the N-vinyl formamide grafted diethyl ether prepolymerized monomer NE, the N-vinyl pyrrolidone and water; the mass of the water is 55-83% of the total mass of the N-vinylformamide grafted diethyl ether prepolymerization monomer NE, the N-vinylpyrrolidone and the water;
the addition amount of the initiator is 0.1-1 per mill of the total mass of the N-vinylformamide grafted diethyl ether prepolymerization monomer NE, N-vinylpyrrolidone and water;
the reaction time is 4-6 hours.
2. The method for preparing a temperature-sensitive natural gas hydrate kinetic inhibitor according to claim 1, wherein the temperature-sensitive natural gas hydrate kinetic inhibitor has a number average molecular weight of 25000 to 30000.
3. The method for preparing a temperature-sensitive natural gas hydrate kinetic inhibitor according to claim 1, wherein the mass of the N-vinylformamide in the step (1) is 3-10% of the total mass of the N-vinylformamide, the 2-bromoethyl ether and the N, N-dimethylformamide; the mass of the 2-bromoethyl ether is 5-20% of the total mass of the N-vinylformamide, the 2-bromoethyl ether and the N, N-dimethylformamide; the mass of the N, N-dimethylformamide is 70-85% of the total mass of the N-vinylformamide, the 2-bromoethyl ether and the N, N-dimethylformamide.
4. The method for preparing a temperature-sensitive natural gas hydrate kinetic inhibitor according to claim 1, wherein the mixing temperature in the step (1) is 0-2 ℃; the stirring speed of stirring is 200-500 r/min, the stirring temperature is 0-2 ℃, and the stirring time is 4-6 hours.
5. The method for preparing the temperature-sensitive natural gas hydrate kinetic inhibitor according to claim 1, wherein the initiator in the step (2) is azodiisobutyronitrile, and the addition amount of the initiator is 0.1-0.5 per mill of the total mass of N-vinylformamide, 2-bromoethyl ether and N, N-dimethylformamide; the stirring speed of the stirring reaction is 200-500 r/min, and the reaction time is 8-16 hours.
6. The method for preparing a temperature-sensitive natural gas hydrate kinetic inhibitor according to claim 1, wherein the steps of extraction and purification in the step (2) are as follows: and cooling the reaction system to room temperature, adding a mixed solvent of normal hexane, ethyl acetate and water for extraction, washing an obtained organic phase with water, drying the organic phase by anhydrous magnesium sulfate, removing the solvent, and purifying the obtained product by silica gel column chromatography to obtain the N-vinylformamide grafted diethyl ether prepolymerized monomer NE.
7. The method for preparing a temperature-sensitive natural gas hydrate kinetic inhibitor according to claim 6, wherein the volume ratio of n-hexane to ethyl acetate in the mixed solvent is 1:4, and the volume ratio of the total volume of n-hexane to ethyl acetate to water is 1:1-4; the ratio of the total mass of N-vinylformamide, 2-bromoethyl ether and N, N-dimethylformamide to the volume of the mixed solvent was 1g: 3-9 mL; the eluent for the column chromatography is a mixed solvent of n-hexane and ethyl acetate, wherein the volume ratio of n-hexane to ethyl acetate is 1:4.
8. The method for preparing a temperature-sensitive natural gas hydrate kinetic inhibitor according to claim 1, wherein the drying in the step (3) is performed under vacuum at 30-50 ℃ for 10-12 hours.
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