An ultra-deep water gas hydrate kinetic inhibitor, preparation method and application thereof

Abstract

The present application relates to a kind of ultra-deep water gas hydrate kinetics inhibitor and preparation method and application, the hydrate inhibitor is by the copolymerization of first monomer and second monomer Binary copolymer or terpolymer;First monomer is 4-acryloyl morpholine, second monomer is at least one of N-vinyl pyrrolidone and N-vinyl caprolactam;4-acryloyl morpholine monomer is used in amount a, N-vinyl pyrrolidone monomer is used in amount b, N-vinyl caprolactam monomer is used in amount c, a:b:c=(20-60) %:(0-80) %:(0-80) %.The hydrate inhibitor of the present application can hinder the growth of hydrate, and the inhibitory effect is good, especially suitable for the environment under low temperature and high pressure;Preparation method is simple to operate, monomer is widely used, and the price is low, and the polymerization reaction condition is mild, and the yield is high.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas development technology, and particularly relates to an ultra-deepwater gas hydrate kinetic inhibitor, its preparation method, and its application. Background Technology

[0002] Natural gas hydrates, often referred to as "combustible ice," are a new energy source with numerous advantages, including high quality, cleanliness, and large reserves. However, in deepwater drilling, hydrate formation can easily cause pipeline blockages and equipment malfunctions, jeopardizing the safety of drilling and production operations. Adding inhibitors to drilling fluids can effectively control hydrate formation in water-based drilling fluids. Currently, thermodynamic inhibitors are widely used worldwide due to their excellent inhibitory effects. Sodium chloride (an inorganic salt) and ethylene glycol (an organic alcohol) are typical examples of thermodynamic inhibitors, exhibiting excellent inhibitory effects. Thermodynamic inhibitors have been used in numerous oil companies both domestically and internationally for many years, effectively inhibiting hydrate formation.

[0003] However, these typical thermodynamic inhibitors generally require relatively high doses (greater than 20%) to achieve a good inhibitory effect. For ultra-deepwater drilling operations, the dosage of thermodynamic inhibitors needs to be significantly increased to achieve an effective inhibitory effect. However, the large-scale addition of thermodynamic inhibitors to water-based drilling fluids has a series of problems, including deteriorating the rheological properties of the drilling fluid, increasing drilling fluid costs, and causing environmental pollution.

[0004] Compared to thermodynamic inhibitors, kinetic inhibitors generally achieve better inhibition effects at lower doses (approximately 1 wt%). Therefore, in recent years, some oilfields both domestically and internationally have experimented with combining kinetic and thermodynamic inhibitors in ultra-deepwater drilling operations to reduce the amount of thermodynamic inhibitors added to the drilling fluid. Currently, commonly used kinetic inhibitors include poly(N-vinylpyrrolidone) (PVP), poly(N-vinylcaprolactam) (PVCap), VP / VC, and VC-713. However, for ultra-deepwater drilling operations, due to factors such as low temperature and ultra-high pressure, the combination of commonly used kinetic and thermodynamic inhibitors often fails to effectively inhibit the formation of gas hydrates in water-based drilling fluids. Therefore, based on the inhibition mechanism of kinetic inhibitors, molecular design is needed to synthesize kinetic inhibitors with superior inhibition performance. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide an ultra-deepwater gas hydrate kinetic inhibitor, its preparation method, and its application, thereby solving the technical problem that the kinetic inhibitors in the prior art have poor inhibition effects during ultra-deepwater drilling operations.

[0006] To achieve the above-mentioned technical objectives, the technical solution provided by this invention is as follows:

[0007] In a first aspect, the present invention provides an ultra-deepwater gas hydrate kinetic inhibitor, which is a binary or ternary copolymer formed by copolymerizing a first monomer and a second monomer; the first monomer is 4-acryloylmorpholine, and the second monomer is at least one of N-vinylpyrrolidone and N-vinylcaprolactam; the amount of 4-acryloylmorpholine monomer is a, the amount of N-vinylpyrrolidone monomer is b, and the amount of N-vinylcaprolactam monomer is c, where a:b:c = (20-60)%:(0-80)%:(0-80)%.

[0008] Secondly, the present invention provides a method for preparing an ultradeepwater gas hydrate kinetic inhibitor, comprising the following steps: adding a first monomer and a second monomer to a solvent, stirring to dissolve, then adding an initiator solution, and reacting under a protective atmosphere; after the reaction is completed, adding a precipitant to precipitate the precipitate, filtering and drying to obtain the ultradeepwater gas hydrate kinetic inhibitor.

[0009] Thirdly, the present invention provides an application of an ultra-deepwater gas hydrate kinetic inhibitor as a natural gas hydrate inhibitor.

[0010] Compared with the prior art, the beneficial effects of the present invention include:

[0011] This invention provides binary or ternary copolymers based on monomers of 4-acryloylmorpholine, vinylcaprolactam, and vinylpyrrolidone. These polymers can adsorb onto the surface of hydrate crystals via hydrogen bonding, occupying hydrate growth sites and hindering hydrate growth, thereby effectively inhibiting the formation of natural gas hydrates. The inhibitory performance of the product was evaluated using a hydrate simulation evaluation device and a tetrahydrofuran (THF) test device. The results show that the hydrate inhibitor of this invention has excellent inhibitory effects; it achieves an inhibitory effect of 7 hours without freezing at a concentration of 1 wt%, and is particularly suitable for environments under low temperature and high pressure (compared to hydrates produced by tap water at 5 MPa and 4℃, the amount of hydrates produced under high pressure and low temperature conditions of 16 MPa and 3℃ with the addition of the inhibitor of this invention is significantly reduced), thus enabling its use in ultra-deepwater drilling operations. Furthermore, the preparation method of the inhibitor provided by this invention is simple to operate, the monomers are widely available and inexpensive, the polymerization reaction conditions are mild, and the yield is high, making it suitable for widespread application. Attached Figure Description

[0012] Figure 1 The yield curve of Example 1 of the present invention as a function of synthesis time was analyzed using a single-factor method.

[0013] Figure 2 The effect of initiator dosage on the induction period of polymerization reaction in Example 2 of this invention was analyzed using a single-factor method.

[0014] Figure 3 Images of hydrates generated within the hydrate evaluation device. (Left: Hydrates generated from tap water at 5 MPa, 4°C, and 24 h; Right: Hydrates generated from the inhibitor at a concentration of 1 wt% in Example 1 of this invention at 16 MPa, 3°C, and 24 h.)

[0015] Table 1 shows the initial crystallization time and crystallization solidification time of different concentrations of the present invention in Example 2, tested by the tetrahydrofuran method.

[0016] Figure 4 The curves showing the pressure change over time in the high-pressure reactor of the hydrate evaluation device for aqueous solutions of different concentrations described in Example 3 of the present invention.

[0017] Figure 5 The curves showing the change in initial crystallization time as a function of inhibitor concentration in Examples 1-3 and Comparative Example 1 of this invention were tested using the tetrahydrofuran method.

[0018] Figure 6 The infrared spectra are those of Examples 1-3 and Comparative Example 1 of the present invention.

[0019] Figure 7 The SEM image is obtained by dropping a 1 wt% aqueous solution onto a silicon wafer and allowing it to air dry at 25°C, as described in Example 1 of this invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] This invention conducts in-depth research on the mechanisms of kinetic inhibitor disturbance, adsorption, and layer mass transfer hindrance, and prepares kinetic inhibitors by copolymerizing 4-acryloylmorpholine with N-vinylpyrrolidone and N-vinylcaprolactam monomers.

[0022] 4-Acryloylmorpholine (ACMO), also known as acrylmorpholine, N-acryloylmorpholine, etc., is readily soluble in water, ethanol, and many other organic solvents. It is non-toxic and possesses good biocompatibility. Its homopolymers can be used as drug sustained-release agents, water treatment agents, and cosmetic support agents. Its copolymers with monomers such as acrylic acid and acrylamide can be used in oilfield chemicals, flocculants, ink additives, and adhesives. The 4-acryloylmorpholine molecule contains a six-membered ring and multiple nitrogen and oxygen atoms that readily form hydrogen bonds with water. Analysis suggests that when copolymerized with N-vinylpyrrolidone and N-vinylcaprolactam monomers, the polymer can adsorb onto the surface of hydrate crystals through hydrogen bonding, occupying hydrate growth sites and hindering hydrate formation.

[0023] This invention provides an ultra-deepwater gas hydrate kinetic inhibitor, its preparation method, and its application. This inhibitor is a novel and highly efficient hydrate inhibitor that requires a small dosage, has good water solubility, and can fully exert its ability to inhibit hydrate nucleation and aggregation. Specifically, the hydrate inhibitor of this invention is a binary or ternary copolymer formed by copolymerizing a first monomer (4-acryloylmorpholine) with a second monomer (at least one of vinylcaprolactam and vinylpyrrolidone), and its molecular structure is shown in Formula I below.

[0024]

[0025] Where a, b, and c represent the mass percentages of different monomers, rather than restrictions on the location of each monomer; the monomer mass percentages during the synthesis reaction of the hydrate inhibitor are:

[0026] 4-Acryloylmorpholine and N-vinylpyrrolidone are copolymerized to form a binary copolymer X, where c is 0 and 4-acryloylmorpholine (a): N-vinylpyrrolidone (b) = 20-60%: 40-80%;

[0027] 4-Acryloylmorpholine and N-vinylcaprolactam copolymerize to form a binary copolymer Y, where b is 0 and 4-acryloylmorpholine (a): N-vinylcaprolactam (c) = 20-60%: 40-80%;

[0028] 4-Acryloylmorpholine is copolymerized with vinylcaprolactam and vinylpyrrolidone to form a terpolymer Z, in which a, b and c are not 0, and 4-acryloylmorpholine (a): N-vinylpyrrolidone (b): N-vinylcaprolactam (c) = 20-60%: 20-60%: 20-60%.

[0029] Furthermore, the number-average molecular weight of the hydrate inhibitor of the present invention is between 1.0 × 10⁻⁶. 3 ~5.0×10 6 The molecular weight distribution width is between 2.0 and 2.5 mPa·s.

[0030] The preparation method of the ultra-deepwater gas hydrate kinetic inhibitor provided by the present invention includes the following steps:

[0031] S1: Turn on the water bath constant temperature heating magnetic stirrer, set the temperature, and turn on the heating button;

[0032] S2: Add solvent to a 250mL three-necked flask, add the first monomer (4-acrylomorpholine) and the second monomer (at least one of N-vinylcaprolactam and N-vinylpyrrolidone) in proportion, place the rotor in the flask, and stir to dissolve the monomers;

[0033] S3: Weigh the initiator according to the proportion, prepare the initiator solution, put it into the constant speed feeding device, and connect the device to one side of the three-necked flask. Connect the condenser to the other side of the three-necked flask, and connect the top to the venting hose and nitrogen gas. After ensuring that the reaction device is sealed, purge the air with nitrogen gas.

[0034] S4: After reaching the set temperature, add the initiator solution dropwise at a constant rate. After reacting at a constant temperature for a period of time under nitrogen protection, stop heating and stirring, cool to room temperature, and then disassemble the experimental apparatus.

[0035] S5: Add a precipitant to the solution to precipitate the product. After filtration, place the product in a vacuum drying oven to dry and then weigh it.

[0036] Furthermore, the solvent in step S2 is one of solvents such as ethanol, isopropanol, and n-butanol, and the total concentration of the first monomer and the second monomer in the solvent is 15-40 wt%.

[0037] Furthermore, the initiator in step S3 is one or more of the following in any proportion: 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylpropylimidazolium) hydrochloride, 2,2'-azabis(2-imidazoline) dihydrochloride, ammonium persulfate, etc., and the initiator accounts for 0.05 to 1% of the total mass of the first monomer and the second monomer.

[0038] Furthermore, in step S4, the reaction temperature is between 55 and 80°C, the reaction time is between 4 and 12 hours, and the rotation speed is between 200 and 800 rpm. The reaction temperature affects the reaction rate and the average molecular weight of the product. A lower reaction temperature results in a higher average molecular weight but a lower polymerization rate, while a higher temperature results in a lower average molecular weight but a higher polymerization rate. The reaction time affects the monomer conversion rate and production efficiency. Too short a reaction time leads to a low monomer conversion rate, while too long a reaction time reduces production efficiency. The rotation speed can also affect the average molecular weight of the product to some extent.

[0039] Furthermore, the precipitant in step S5 is one or more of anhydrous diethyl ether, acetone, ethyl acetate, tetrahydrofuran, and n-heptane.

[0040] Further, in step S5, the temperature of the drying oven is 40-60°C, and the drying time is 12-24 hours.

[0041] The present invention relates to the application of an ultra-deepwater gas hydrate kinetic inhibitor as a natural gas hydrate inhibitor.

[0042] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0043] To avoid redundancy, the method for evaluating the inhibitory effect of the present invention is described here:

[0044] The inhibitory effect of the inhibitor described in this invention was evaluated using a hydrate evaluation device and a tetrahydrofuran testing device. The hydrate evaluation device was used to measure the pressure change inside the reactor and observe the morphology and amount of hydrates formed within approximately 24 hours under a methane atmosphere. The tetrahydrofuran testing device was used to determine the initial crystallization time and the time of solidification (when the steel ball could not move).

[0045] The inhibitor solutions used for evaluating the inhibitory effect of the inhibitors described in this invention were all prepared in tap water with concentrations of 0.01 wt%, 0.1 wt%, 0.5 wt%, 1.0 wt%, 2.0 wt%, and 4.0 wt%, respectively.

[0046] The testing equipment and testing procedures are as follows:

[0047] (1) Hydrate evaluation device

[0048] This apparatus mainly includes: ① a visual high-pressure hydrate simulation reactor; ② a methane cylinder; ③ an air compressor; ④ a gas pressurization system; ⑤ a water bath temperature control system; and ⑥ a parameter control and data acquisition system. The apparatus has a temperature control range of -30℃ to 100℃ ± 0.1℃, a pressure tolerance range of 0 to 25MPa ± 0.01MPa, a simulation device volume of 500mL ± 0.1mL, and a magnetic stirrer speed of 0 to 1000rpm.

[0049] The evaluation experiment steps are as follows: ① Turn on the device and set the water bath temperature to 3℃; ② Add 250mL of the prepared inhibitor solution to the reactor, close the reactor, and completely immerse the reactor in the water bath; ③ Connect the temperature and pressure sensors; ④ After checking the airtightness of the device and purging the air inside the reactor, introduce approximately 16MPa of methane gas into the reactor; ⑤ After the temperature and pressure inside the reactor stabilize, set the rotation speed to 300rpm and collect pressure data every 5 minutes; ⑥ After the pressure data collection is completed, turn off the stirring, release the pressure, remove the reactor from the water bath control system and disassemble it, and observe the morphology and amount of methane hydrate formed.

[0050] (2) Tetrahydrofuran (THF) Evaluation Device

[0051] This device mainly includes ① a visual low-temperature constant temperature device (temperature control range -35℃~7℃±0.1℃); ② a speed-controlled reciprocating motion device (reciprocating speed 5~50 times / min); ③ a glass test tube with a length of 12.5cm and a diameter of 15mm and a stainless steel ball with a diameter of 0.95cm.

[0052] The evaluation experiment steps are as follows: ① Turn on the low-temperature thermostat, set the temperature, and maintain the temperature for 2 hours after reaching the set temperature. ② Add 3 mL of tetrahydrofuran, 9 mL of tap water, and the required dose of inhibitor to a test tube, mix thoroughly to dissolve, place a stainless steel ball inside, and seal the test tube with a rubber stopper. ③ Fix the test tube on the fixing plate (multiple test tubes can be fixed at once; label each test tube in the same group). ④ Place the fixing plate in the low-temperature thermostat and connect it to the constant-speed reciprocating device, setting the reciprocating speed to 6 times / min. ⑤ Timing, observation, and recording the initial crystallization time and crystallization solidification time of different test tubes.

[0053] Example 1:

[0054] Example 1 is a 4-acryloylmorpholine and N-vinylpyrrolidone binary copolymer, the synthesis process of which includes the following steps:

[0055] S1: Turn on the water bath constant temperature heating magnetic stirrer, set the temperature to 60℃, the speed to 400rpm, and turn on the heating button;

[0056] S2: Add anhydrous ethanol to a 250ml three-necked flask. Add 4-acryloylmorpholine and N-vinylpyrrolidone at a monomer mass ratio of 1:1, and control the total monomer concentration in the system to be about 20%. Place the rotor in the system and stir to dissolve the monomer.

[0057] S3: The initiator 2,2'-azobisisobutyronitrile accounts for 0.1% of the total mass of the monomers. Dissolve the initiator in 20 mL of anhydrous ethanol. After it is fully dissolved, pour it into the constant-rate feeding device and connect the device to one side of the three-necked flask. Connect the other side of the three-necked flask to the condenser. Connect the top to the venting hose and nitrogen gas. After ensuring that the reaction device is sealed, purge the air with nitrogen gas.

[0058] S4: After reaching the set temperature, add the initiator solution dropwise to the polymerization system at a constant rate over 3 hours. After reacting at a constant temperature of 60°C for 8 hours under nitrogen protection, stop heating and stirring, cool to room temperature, and then disassemble the experimental apparatus.

[0059] S5: Add anhydrous diethyl ether as a precipitant to the solution to precipitate the product. After filtration, place the product in a vacuum drying oven at 40°C for 12 hours to obtain a hydrate inhibitor.

[0060] Example 2:

[0061] Example 2 is a binary copolymer of 4-acryloylmorpholine and N-vinylcaprolactam, and its synthesis process is the same as that of Example 1. The only difference between Example 2 and Example 1 is that the monomers are changed to 4-acryloylmorpholine and N-vinylcaprolactam.

[0062] Example 3:

[0063] Example 3 is a terpolymer of 4-acryloylmorpholine, N-vinylpyrrolidone, and N-vinylcaprolactam, synthesized according to the procedure in Example 1. The only difference from Example 1 is the change in monomer types and the mass percentage of the three monomers being 4-acryloylmorpholine:N-vinylpyrrolidone:N-vinylcaprolactam = 30%:30%:40%.

[0064] The molecular weight of the hydrate inhibitors obtained in the above examples was determined by gel permeation chromatography. The number-average molecular weights of the inhibitors obtained in Examples 1-3 were 2.71 × 10⁻⁶. 5 mPa·s, 2.40×10 5 mPa·s, 2.96×10 5 The molecular weight distribution widths were 2.246, 2.397, and 2.130 mPa·s, respectively.

[0065] Comparative Example 1

[0066] The hydrate inhibitor obtained by homopolymerization of monomer 4-acryloylmorpholine is Comparative Example 1.

[0067] Comparative Example 1 is a 4-acryloylmorpholine homopolymer, and its synthesis process is the same as in Example 1. The only difference between it and Example 1 is that the monomer type is changed to 4-acryloylmorpholine.

[0068] Effect evaluation

[0069] Tests were conducted on Examples 1-3 and Comparative Example 1 of the present invention, and the results are shown in Tables 1 and 2. Figures 1-7 As shown.

[0070] Figure 1 This is a single-factor analysis of the yield curve of Example 1 of the present invention as a function of synthesis time.

[0071] Depend on Figure 1 It can be seen that the yield of Example 1 increases with the increase of synthesis time. When the reaction time is less than 5 hours, the yield increases significantly with the increase of time. After that, the trend of yield increase slows down. When the reaction time reaches 6 hours, the yield basically reaches the maximum value, which is above 93%. Therefore, the reaction time of the present invention is 4 to 12 hours, preferably 6 to 9 hours.

[0072] Figure 2 The effect of the amount of initiator on the induction period in the synthesis reaction of Example 2 of the present invention was analyzed using a single-factor method.

[0073] Depend on Figure 2It is known that as the amount of initiator increases, the induction period of the synthesis reaction becomes shorter. However, when the amount of initiator accounts for 0.5 wt% of the total mass of the synthesized monomer, the decrease in induction period is no longer significant. This indicates that this amount of initiator can initiate monomer polymerization more quickly and provide higher synthesis reaction efficiency. Therefore, the preferred amount of initiator in this invention is 0.5 to 1% of the monomer mass.

[0074] Figure 3 Images of hydrates generated within the hydrate evaluation device. Left: Hydrates generated from tap water at 5 MPa, 4°C, and 24 h; Right: Hydrates generated from the inhibitor at a concentration of 1 wt% in Example 1 of this invention at 16 MPa, 3°C, and 24 h.

[0075] Depend on Figure 3 It can be seen that tap water produces a large amount of hydrates under conditions of 5 MPa and 4℃. However, when 1% of the present invention's Example 1 is added to the water, the amount of hydrates produced under high pressure and low temperature conditions of 16 MPa and 3℃ is significantly reduced. The mass ratio of the hydrates produced by Example 1 and tap water after dissolving into water is 5.71 / 100, indicating that the present invention's Example 1 has a good inhibition effect and is particularly suitable for environments under low temperature and high pressure conditions.

[0076] The hydrate inhibitor obtained in Example 2 of this invention was used to prepare inhibitor solutions of different concentrations. The initial crystallization time and crystallization solidification time of the inhibitor solutions of different concentrations were tested by the tetrahydrofuran method. The results are shown in Table 1.

[0077] Table 1. Inhibition effect of Example 2

[0078]

[0079] As shown in Table 1, when the inhibitor concentration was 0%, crystallization began in 13 minutes and solidified into ice in a -2℃ low-temperature constant temperature chamber. However, after adding Example 2 of the present invention to the water, both the initial crystallization time and the crystallization-solidification time were prolonged, and after the concentration of Example 2 reached 1wt%, it did not freeze or solidify for 7 hours. These test results further demonstrate that Example 2 of the present invention has a better inhibitory effect, and its optimal inhibitor concentration is slightly higher than 1wt%.

[0080] Figure 4 The pressure change curves over time in the high-pressure reactor of the hydrate evaluation device are obtained by preparing aqueous solutions of different concentrations of the hydrate inhibitor obtained in Example 3 of the present invention.

[0081] Depend on Figure 4It can be seen that as the concentration of the hydrate inhibitor in Example 3 increases, the pressure decrease in the high-pressure reactor of the hydrate evaluation device shows a trend of first decreasing and then slowly increasing, with the pressure in the reactor being most stable at a concentration of 1 wt%. Since hydrate formation consumes methane gas, a more significant pressure decrease in the reactor of the hydrate evaluation device indicates a greater consumption of methane gas and a greater amount of hydrate formation. This test result shows that Example 3 of the present invention has the best inhibition effect at a concentration of 1 wt%.

[0082] Figure 5 The curves showing the change in initial crystallization time as a function of inhibitor concentration in Examples 1-3 and Comparative Example 1 of this invention were tested using the tetrahydrofuran method.

[0083] Depend on Figure 5 It can be seen that the initial crystallization time of Examples 1-3 of the present invention is longer than that of Comparative Example 1 when the concentration is higher than 0.01wt%, indicating that the inhibition effect of Examples 1-3 of the present invention is better than that of Comparative Example 1, especially the inhibition effect of Example 3 is the best.

[0084] Figure 6 The infrared spectra are those of Examples 1-3 and Comparative Example 1 of the present invention.

[0085] Figure 6 3417cm -1 The absorption peaks near the amide bond are due to the stretching vibrations of the nitrogen-hydrogen (NH) and carbon-nitrogen (NC) bonds, around 1660 cm⁻¹. -1 The absorption peak near the amide bond is due to the stretching vibration of the carbonyl group (-C=O); 1444 cm⁻¹ -1 The absorption peaks are located near the in-plane bending vibrations of carbon-hydrogen bonds (CH); 2927–2869 cm⁻¹ -1 The absorption peak at this location represents the stretching vibration of the saturated carbon-hydrogen bond (-CH) in a polycyclic ring. Since the three structural units—4-acryloylmorpholine, N-vinylpyrrolidone, and N-vinylcaprolactam—share similar characteristic groups, therefore... Figure 6 The characteristic absorption peaks of the infrared spectra of the four polymers are quite similar.

[0086] Figure 7 The SEM image is obtained by dropping a 1 wt% aqueous solution onto a silicon wafer and allowing it to air dry at 25°C, as described in Example 1 of this invention.

[0087] Depend on Figure 7 It is evident that the product forms a large number of crystals under natural drying conditions, indirectly indicating that there is a strong intermolecular hydrogen bond between the hydrate inhibitor obtained in this invention and water, which can occupy hydrate growth sites and hinder hydrate growth, thereby effectively inhibiting hydrate formation.

[0088] This invention provides binary or ternary copolymers based on 4-acryloylmorpholine, vinylcaprolactam, and vinylpyrrolidone monomers. The preparation method of the inhibitor provided by this invention is simple to operate, the monomers are widely available and inexpensive, and the polymerization reaction conditions are mild, making it suitable for widespread application. The inhibitory performance of the synthesized product is evaluated using a hydrate simulation evaluation device and a tetrahydrofuran (THF) test device. The evaluation results show that the kinetic inhibitor prepared by this method has a good inhibitory effect, and is particularly suitable for the oil and gas development field. Specifically, this invention has the following advantages:

[0089] (1) Good inhibition effect: A novel hydrate inhibitor was synthesized in an innovative way. Its inhibition performance was evaluated by using a hydrate simulation evaluation device and a tetrahydrofuran test device, and it was determined that it has a good inhibition effect.

[0090] (2) Simple preparation method: The preparation method of the inhibitor described in this invention is simple, the synthesis conditions are mild, and it is suitable for promotion.

[0091] (3) Low pollution: 4-Acryloylmorpholine is non-toxic and has good biocompatibility. Its homopolymer can be used as a drug sustained release agent, water treatment agent and cosmetic support agent. The inhibitors formed by it with vinylcaprolactam and vinylpyrrolidone can reduce environmental pollution problems to a certain extent.

[0092] (4) Low cost: The raw materials used in this invention are bulk chemicals that are inexpensive and readily available.

[0093] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an inhibitor of gas hydrate kinetics in ultra-deepwater water, characterized in that, The hydrate kinetic inhibitor is a terpolymer composed of 4-acryloylmorpholine, N-vinylpyrrolidone and N-vinylcaprolactam; The mass percentage of 4-acryloylmorpholine monomer is a, the mass percentage of N-vinylpyrrolidone monomer is b, and the mass percentage of N-vinylcaprolactam monomer is c, where a:b:c = 30%:30%:40%; The preparation method includes the following steps: The three monomers were added to a solvent, stirred and dissolved, and then an initiator solution was added. The reaction was carried out under a protective atmosphere for 6 to 9 hours. After the reaction was completed, a precipitant was added to precipitate the precipitate, which was then filtered and dried to obtain an ultradeepwater gas hydrate kinetic inhibitor. The initiator is one or more of the following in any proportion: 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylpropylimidazolium) hydrochloride, 2,2'-azabis(2-imidazoline) hydrochloride, and ammonium persulfate; the initiator accounts for 0.5 to 1% of the total mass of the three monomers.

2. The method for preparing the ultra-deepwater gas hydrate kinetic inhibitor according to claim 1, characterized in that, The number-average molecular weight of the hydrate kinetic inhibitor is 1.0 × 10⁻⁶. 3 ~5.0×10 6 mPa·s; molecular weight distribution width is 2.0–2.

5.

3. The method for preparing the ultra-deepwater gas hydrate kinetic inhibitor according to claim 1, characterized in that, The solvent is ethanol, isopropanol, or n-butanol; the total mass concentration of the three monomers in the solvent is 15-40%.

4. The method for preparing the ultra-deepwater gas hydrate kinetic inhibitor according to claim 1, characterized in that, The protective atmosphere is nitrogen; the reaction is carried out under heating and stirring, with the reaction temperature between 55 and 80°C and the stirring speed between 200 and 800 rpm.

5. The method for preparing the ultra-deepwater gas hydrate kinetic inhibitor according to claim 1, characterized in that, The precipitant is one or more of anhydrous diethyl ether, acetone, ethyl acetate, tetrahydrofuran, and n-heptane.

6. The method for preparing the ultra-deepwater gas hydrate kinetic inhibitor according to claim 1, characterized in that, The drying temperature is 40–60℃, and the time is 12–24 hours.

7. The application of the ultradeepwater gas hydrate kinetic inhibitor prepared by any one of claims 1-6 as a natural gas hydrate kinetic inhibitor.

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