A paraffin removal and prevention agent for oil fields and a preparation process thereof

Abstract

The present application relates to the technical field of oilfield chemistry, and particularly relates to a kind of oilfield wax removal and prevention agent and its preparation process.The wax removal and prevention agent is composed of long-chain alkyl acrylate-maleic anhydride comb copolymer with tertiary amine ring-opening grafting, ethylene glycol monobutyl ether, isopropyl alcohol, toluene and deionized water, and is sequentially treated by carbon dioxide and nitrogen decarburization in the preparation process.The comb copolymer is prepared by three-stage feeding polymerization of stearyl acrylate, behenyl acrylate and maleic anhydride in the presence of RAFT chain transfer agent to obtain a precursor, and then ring-opening grafting reaction is carried out with N,N-dimethyl-1,3-propanediamine to obtain the comb copolymer.The wax removal and prevention agent has fast dispersion, high wax prevention rate, high wax removal rate and low low-temperature injection viscosity in carbon dioxide acidic produced liquid, and is suitable for wax removal and prevention treatment of CO2 flooding oil well.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, and in particular to an oilfield dewaxing and anti-waxing agent and its preparation process. Background Technology

[0002] With the widespread application of CO2 enhanced oil recovery (EOR) technology in oilfield development, CO2-treated acidic produced fluids place special demands on the performance of wax removal and prevention agents. Traditional solvent / surfactant compound wax removal and prevention agents mainly rely on organic solvents to dissolve wax deposits. However, in the acidic CO2 environment, solvents are prone to volatility and surfactants are easily deactivated, leading to a decrease in wax removal rate and a shortened wax prevention cycle. Although comb-like polymer wax removal and prevention agents can regulate wax crystal growth through long alkyl side chains, the active groups in conventional copolymers are randomly distributed and cannot form a directional responsive structure in the CO2 environment, thus limiting dispersion efficiency.

[0003] Existing technologies attempt to introduce tertiary amine-based CO2-responsive materials to improve dispersibility, but these often involve adding low-molecular-weight amines to the finished product, resulting in high levels of free amine residue. This not only easily reacts with CO2 to form carbonate deposits but also exacerbates pipeline corrosion. Some solutions graft tertiary amine groups onto polymer segments, but the polymer segment structure is not precisely designed, leading to uneven distribution of long alkyl side chains and tertiary amine sites, making it difficult to simultaneously achieve wax crystal embedding ability and CO2 response sensitivity. Furthermore, existing CO2-responsive wax-removing agents generally suffer from excessively high viscosity at low temperatures, requiring heating and dilution during winter or deep well injection, increasing on-site operating costs and safety risks.

[0004] The aforementioned defects make it difficult for existing wax-preventing agents to simultaneously meet the requirements of rapid dispersion, efficient wax prevention, and low-temperature injection in CO2-driven wells. There is an urgent need for a new type of wax-preventing agent with controllable structure, low free amine residue, and compatibility with the acidic environment of CO2. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose an oilfield dewaxing and anti-waxing agent and its preparation process, so as to solve the problems that existing CO2 flooding dewaxing and anti-waxing agents are difficult to achieve rapid response dispersion, high anti-waxing rate and low temperature and low viscosity injection in CO2 acidic produced fluid at the same time, and the addition of low molecular weight amines can easily lead to corrosion and poor dispersion stability.

[0006] To achieve the above objectives, the present invention provides an oilfield wax remover and preservative, which, by weight, is prepared from the following raw materials through carbon dioxide treatment and nitrogen decarbonization and back-up treatment: 140-165 parts of tertiary amination ring-opening grafted comb copolymer, 190-230 parts of ethylene glycol monobutyl ether, 130-155 parts of isopropanol, 25-35 parts of toluene, and 280-340 parts of deionized water; The tertiary amination ring-opening grafted comb copolymer is prepared by ring-opening grafting reaction of long-chain alkyl acrylate-maleic anhydride comb copolymer precursor with N,N-dimethyl-1,3-propanediamine. The long-chain alkyl acrylate-maleic anhydride comb copolymer precursor is prepared by three-stage feeding polymerization of octadecyl acrylate, docosyl acrylate, and maleic anhydride in the presence of 4-cyano-4-(phenylthiocarbamoylthio)valerate.

[0007] Preferably, the tertiary amination ring-opening grafted comb copolymer has an acid value of 121.6-136.9 mgKOH / g and a tertiary amine nitrogen content of 1.05-1.37 mmol / g.

[0008] Preferably, the mass fraction of free N,N-dimethyl-1,3-propanediamine in the oilfield dewaxing agent is not greater than 0.3%.

[0009] Preferably, in the preparation of the long-chain alkyl acrylate-maleic anhydride comb copolymer precursor, the mass ratio of octadecyl acrylate, docosyl acrylate, and maleic anhydride used as destabilizers in the subsequent polymerization reaction is 110-140:30-60:48-61.

[0010] Preferably, the three-stage feeding polymerization includes initial liquid polymerization, intermediate liquid droplet polymerization, and final liquid droplet polymerization; The starting liquid comprises 45-60 parts of octadecyl acrylate with destabilizer, 14-24 parts of docosyl acrylate with destabilizer, and 5-8 parts of maleic anhydride. The intermediate feed solution includes 16-22 parts of octadecyl acrylate with destabilizer, 4-8 parts of docosyl acrylate with destabilizer, and 38-45 parts of maleic anhydride. The final stage feed solution includes 45-60 parts of octadecyl acrylate as a destabilizer, 14-24 parts of docosyl acrylate as a destabilizer, and 5-8 parts of maleic anhydride.

[0011] Preferably, in the three-stage feeding polymerization, the starting feed solution further includes 320-390 parts of toluene, 6.5-10 parts of 4-cyano-4-(phenylthiocarbamoylthio)valerate, and 0.8-1.2 parts of 2,2′-azobis(2-methylpropionitrile); the intermediate feed solution further includes 130-170 parts of toluene; and the final feed solution further includes 75-90 parts of toluene and 0.8-1.2 parts of 2,2′-azobis(2-methylpropionitrile).

[0012] Preferably, the three-stage feeding polymerization is as follows: after purging with high-purity nitrogen for 30 minutes, the initial liquid is polymerized at 70°C and 300 rpm for 3 hours; then, while maintaining 70°C, the middle stage liquid is added dropwise over 2 hours, and the reaction continues for 3 hours after the addition is completed; then, the final stage liquid is added dropwise over 1 hour, and the reaction continues at 70°C for 6 hours after the addition is completed.

[0013] Preferably, in the ring-opening grafting reaction, the mass ratio of the long-chain alkyl acrylate-maleic anhydride comb copolymer precursor, toluene, isopropanol for dissolving the precursor, N,N-dimethyl-1,3-propanediamine, and isopropanol for preparing the grafting solution is 170-190:390-450:110-140:30-40:70-90; the ring-opening grafting reaction is as follows: the long-chain alkyl acrylate-maleic anhydride comb copolymer precursor, toluene, and isopropanol are stirred at 50°C and 300 rpm for 2 hours; the system is lowered to 45°C, and the grafting solution prepared by N,N-dimethyl-1,3-propanediamine and isopropanol is added dropwise over 2 hours; after the addition is complete, the temperature is raised to 55°C and maintained for 5-5.5 hours.

[0014] Preferably, the carbon dioxide treatment and nitrogen decarbonization back-off treatment are as follows: 140-165 parts of tertiary amination ring-opening grafted comb copolymer, 170-200 parts of ethylene glycol monobutyl ether, 85-100 parts of isopropanol and 25-35 parts of toluene are stirred at 45°C and 400 rpm for 2 hours, then cooled to 20°C; 190-220 parts of deionized water are added within 1 hour, while 2.5-4 parts of carbon dioxide are introduced, and stirring continues for 60 minutes; the temperature is then raised to 45°C, 90-120 parts of deionized water are added, while 1.5-3 parts of carbon dioxide are introduced, and stirring continues for 30 minutes; subsequently, 4-6.5 parts of nitrogen are introduced at 50°C, and finally 20-30 parts of ethylene glycol monobutyl ether and 45-55 parts of isopropanol are added, and the mixture is stirred at 45°C and 400 rpm for 40 minutes, and then filtered through a 100 μm filter.

[0015] Furthermore, the present invention also provides a preparation process for an oilfield wax remover and preservative, comprising the following steps: S1. Octadecyl acrylate and docosyl acrylate are subjected to destabilizing treatment to obtain destabilized octadecyl acrylate and destabilized docosyl acrylate. S2. Stabilized octadecyl acrylate, stabilized docosyl acrylate, and maleic anhydride are subjected to three-stage feeding polymerization in toluene with 4-cyano-4-(phenylthiocarbamoylthio)valerate as polymerization regulator and 2,2′-azobis(2-methylpropionitrile) as initiator to obtain a long-chain alkyl acrylate-maleic anhydride comb copolymer solution. S3. The long-chain alkyl acrylate-maleic anhydride comb copolymer solution is subjected to methanol precipitation, washing and drying to obtain the long-chain alkyl acrylate-maleic anhydride comb copolymer precursor. S4. The long-chain alkyl acrylate-maleic anhydride comb copolymer precursor is subjected to a ring-opening grafting reaction with N,N-dimethyl-1,3-propanediamine to obtain a tertiary amination ring-opening grafted comb copolymer solution. S5. The tertiary amination ring-opening grafted comb copolymer solution is subjected to methanol precipitation, washing and drying to obtain the tertiary amination ring-opening grafted comb copolymer. S6. The tertiary amination ring-opening grafted comb copolymer is mixed with ethylene glycol monobutyl ether, isopropanol, toluene and deionized water, and then subjected to carbon dioxide treatment and nitrogen decarbonization and reversion treatment in sequence to obtain an oilfield dewaxing and anti-waxing agent.

[0016] In this invention, N,N-dimethyl-1,3-propanediamine refers to 3-(dimethylamino)propylamine, CAS number 109-55-7, with the structural formula H2N-CH2CH2CH2-N(CH3)2; wherein the primary amine unit is used for ring-opening amidation reaction with maleic anhydride unit, and the dimethylamino unit serves as the tertiary amine site in response to carbon dioxide. Unless otherwise stated, the amount of carbon dioxide and nitrogen introduced in this invention refers to the cumulative mass of the introduced gas measured by a mass flow meter, and not the residual mass of carbon dioxide and nitrogen in the finished product.

[0017] The beneficial effects of this invention are: (1) In this invention, the long-chain side chains of octadecyl and docosyl are concentrated at both ends of the comb copolymer through three-stage feeding polymerization, and the active unit of maleic anhydride is concentrated in the middle section and subjected to tertiary amination ring-opening grafting, so that the wax-removing agent forms a synergistic structure of long alkyl wax crystal embedding and middle section tertiary amine response dispersion in CO2 acidic produced fluid; the data shows that the wax-removing rate of Example 4 reaches 92.1%, the apparent viscosity reduction rate at 35℃ reaches 78.1%, and the pour point reduction value reaches 18℃, which is 37 percentage points higher than that of Comparative Example 4 (without tertiary amination), which is significantly better than the existing technology of single long-chain polymer or added low molecular weight amine.

[0018] (2) The present invention strictly controls the mass fraction of free N,N-dimethyl-1,3-propanediamine ≤0.3% by methanol precipitation washing, and combines the time sequence treatment of 20℃ low-temperature pre-protonation, 45℃ chain segment relaxation and 50℃ nitrogen decarbonization and back-up, so that the wax removal and anti-wax agent can maintain rapid response dispersion in CO2 oil displacement environment (dispersion time 3.1 min in Example 6) and achieve a low viscosity of 118.4 mPa·s at 10℃ low temperature injection; compared with Comparative Example 9 (without nitrogen back-up), the viscosity is reduced by 28.3%, which solves the limitation of tertiary amine CO2 response materials that have fast response but excessively high viscosity at low temperature and are difficult to inject on site, and expands its application range in CO2 oil displacement wells. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0020] The raw materials used in the specific implementation method are as follows: the particle size of neutral alumina is 100-200 mesh; the melting point of paraffin is 58℃.

[0021] Example 1: Step 1: 150g of octadecyl acrylate was melted at 55℃, and 30g of toluene was added and mixed thoroughly. The mixture was then passed through a 90g neutral alumina column that had been dried at 120℃ for 4 hours and cooled to 55℃. The effluent was collected, and toluene was removed under reduced pressure at 40℃ and 5kPa to obtain destabilized octadecyl acrylate. 50g of docosyl acrylate was melted at 65℃, and 10g of toluene was added and mixed thoroughly. The mixture was then passed through a 30g neutral alumina column that had been dried at 120℃ for 4 hours and cooled to 65℃. The effluent was collected, and toluene was removed under reduced pressure at 45℃ and 5kPa to obtain destabilized docosyl acrylate. 126g of destabilized octadecyl acrylate and 42g of destabilized docosyl acrylate were weighed out for subsequent polymerization reactions. Step 2: Add 360g toluene, 54g octadecyl acrylate (a destabilizing agent), 18g docosyl acrylate (a destabilizing agent), 6g maleic anhydride, 8g 4-cyano-4-(phenylthiocarbamoylthio)valerate, and 1g nitrogen gas to a four-necked reaction flask equipped with a mechanical stirrer, condenser, thermometer, dropping port, and nitrogen inlet. 2,2′-Azobis(2-methylpropionitrile) was purged with high-purity nitrogen for 30 min and reacted at 70 °C and 300 rpm for 3 h. Then, while maintaining the temperature at 70 °C, a middle-stage solution consisting of 150 g toluene, 18 g octadecyl acrylate (a destabilizer), 6 g docosyl acrylate (a destabilizer), and 40 g maleic anhydride was added dropwise over 2 h. After the addition was complete, the reaction continued for 3 h. Then, a final-stage solution consisting of 80 g toluene, 54 g octadecyl acrylate (a destabilizer), 18 g docosyl acrylate (a destabilizer), 6 g maleic anhydride, and 1 g 2,2′-Azobis(2-methylpropionitrile) was added dropwise over 1 h. After the addition was complete, the reaction continued at 70 °C for 6 h to obtain a long-chain alkyl acrylate-maleic anhydride comb copolymer solution. Step 3: Cool the long-chain alkyl acrylate-maleic anhydride comb copolymer solution obtained in Step 2 to 25°C, add it to 1600g of methanol pre-cooled to 5°C while stirring at 300rpm, continue stirring for 30min, filter, wash the filter cake twice with 800g of methanol, and place the filter cake in a vacuum dryer at 45°C and 5kPa for 12h to obtain the long-chain alkyl acrylate-maleic anhydride comb copolymer precursor; Step 4: Add 180g of long-chain alkyl acrylate-maleic anhydride comb copolymer precursor, 420g of toluene and 120g of isopropanol to a four-necked reaction flask, and stir at 50℃ and 300rpm for 2h; lower the system to 45℃, and add the grafting solution prepared by 34g of N,N-dimethyl-1,3-propanediamine and 80g of isopropanol dropwise over 2h. After the addition is complete, raise the temperature to 55℃ and keep it at that temperature for 5h to obtain a tertiary amination ring-opening grafted comb copolymer solution. Step 5: Cool the tertiary amination ring-opening grafted comb copolymer solution obtained in Step 4 to 25°C, add 1400g of methanol pre-cooled to 5°C while stirring at 300rpm, continue stirring for 30min, filter, wash the filter cake twice with 600g of methanol, and then vacuum dry at 45°C and 5kPa for 12h to obtain the tertiary amination ring-opening grafted comb copolymer. Step Six: Add 150g of tertiary amination ring-opening grafted comb copolymer, 180g of ethylene glycol monobutyl ether, 90g of isopropanol and 30g of toluene to a stirred tank, and stir at 45℃ and 400rpm for 2h, then lower the temperature to 20℃; add 200g of deionized water within 1h, and simultaneously introduce 3g of carbon dioxide using a mass flow meter, and continue stirring for 60min; then raise the temperature to 45℃, add 100g of deionized water, and simultaneously introduce 2g of carbon dioxide, and continue stirring for 30min; then introduce 5g of nitrogen at 50℃, and finally add 20g of ethylene glycol monobutyl ether and 50g of isopropanol, stir at 45℃ and 400rpm for 40min, and filter through a 100μm filter to obtain an oilfield dewaxing agent.

[0022] Example 2: Step 1: 145g of octadecyl acrylate was melted at 55℃, and 29g of toluene was added and mixed thoroughly. The mixture was then passed through an 86g neutral alumina column that had been dried at 120℃ for 4 hours and cooled to 55℃. The effluent was collected, and toluene was removed under reduced pressure at 40℃ and 5kPa to obtain destabilized octadecyl acrylate. 45g of docosyl acrylate was melted at 65℃, and 9g of toluene was added and mixed thoroughly. The mixture was then passed through a 27g neutral alumina column that had been dried at 120℃ for 4 hours and cooled to 65℃. The effluent was collected, and toluene was removed under reduced pressure at 45℃ and 5kPa to obtain destabilized docosyl acrylate. 120g of destabilized octadecyl acrylate and 36g of destabilized docosyl acrylate were weighed out for subsequent polymerization reactions. Step 2: Add 340g toluene, 50g octadecyl acrylate (a destabilizing agent), 15g docosyl acrylate (a destabilizing agent), 5g maleic anhydride, 7g 4-cyano-4-(phenylthiocarbamoylthio)valerate, and 0.8g nitrogen gas to a four-necked reaction flask equipped with a mechanical stirrer, condenser, thermometer, dropping port, and nitrogen inlet. 2,2′-Azobis(2-methylpropionitrile) was purged with high-purity nitrogen for 30 min and reacted at 70 °C and 300 rpm for 3 h. Then, while maintaining the temperature at 70 °C, a middle-stage solution consisting of 140 g toluene, 20 g octadecyl acrylate (a destabilizer), 6 g docosyl acrylate (a destabilizer), and 38 g maleic anhydride was added dropwise over 2 h. After the addition was complete, the reaction continued for 3 h. Then, a final-stage solution consisting of 75 g toluene, 50 g octadecyl acrylate (a destabilizer), 15 g docosyl acrylate (a destabilizer), 5 g maleic anhydride, and 0.8 g 2,2′-Azobis(2-methylpropionitrile) was added dropwise over 1 h. After the addition was complete, the reaction continued at 70 °C for 6 h to obtain a long-chain alkyl acrylate-maleic anhydride comb copolymer solution. Step 3: Cool the long-chain alkyl acrylate-maleic anhydride comb copolymer solution obtained in Step 2 to 25°C, add it to 1500g of methanol pre-cooled to 5°C while stirring at 300rpm, continue stirring for 30min, filter, wash the filter cake twice with 700g of methanol, and place the filter cake in a vacuum dryer at 45°C and 5kPa for 12h to obtain the long-chain alkyl acrylate-maleic anhydride comb copolymer precursor; Step 4: Add 175g of long-chain alkyl acrylate-maleic anhydride comb copolymer precursor, 400g of toluene and 110g of isopropanol to a four-necked reaction flask, and stir at 50℃ and 300rpm for 2h; lower the system to 45℃, and add the grafting solution prepared by 30g of N,N-dimethyl-1,3-propanediamine and 75g of isopropanol dropwise over 2h. After the addition is complete, raise the temperature to 55℃ and keep it at that temperature for 5h to obtain the tertiary amination ring-opening grafted comb copolymer solution. Step 5: Cool the tertiary amination ring-opening grafted comb copolymer solution obtained in Step 4 to 25°C, add 1350g of methanol pre-cooled to 5°C while stirring at 300rpm, continue stirring for 30min, filter, wash the filter cake twice with 560g of methanol, and then vacuum dry at 45°C and 5kPa for 12h to obtain the tertiary amination ring-opening grafted comb copolymer. Step Six: Add 140g of tertiary amination ring-opening grafted comb copolymer, 170g of ethylene glycol monobutyl ether, 85g of isopropanol, and 25g of toluene to a stirred tank. Stir at 45℃ and 400rpm for 2 hours, then lower the temperature to 20℃. Add 190g of deionized water within 1 hour, while simultaneously introducing 2.5g of carbon dioxide using a mass flow meter, and continue stirring for 60 minutes. Raise the temperature back to 45℃, add 90g of deionized water, and simultaneously introduce 1.5g of carbon dioxide, continuing to stir for 30 minutes. Then, introduce 4g of nitrogen gas at 50℃, and finally add 20g of ethylene glycol monobutyl ether and 45g of isopropanol. Stir at 45℃ and 400rpm for 40 minutes, and filter through a 100μm filter to obtain an oilfield dewaxing agent.

[0023] Example 3: Step 1: 160g of octadecyl acrylate was melted at 55℃, and 32g of toluene was added and mixed thoroughly. The mixture was then passed through a 96g neutral alumina column that had been dried at 120℃ for 4 hours and cooled to 55℃. The effluent was collected, and toluene was removed under reduced pressure at 40℃ and 5kPa to obtain destabilized octadecyl acrylate. 55g of docosyl acrylate was melted at 65℃, and 11g of toluene was added and mixed thoroughly. The mixture was then passed through a 33g neutral alumina column that had been dried at 120℃ for 4 hours and cooled to 65℃. The effluent was collected, and toluene was removed under reduced pressure at 45℃ and 5kPa to obtain destabilized docosyl acrylate. 135g of destabilized octadecyl acrylate and 45g of destabilized docosyl acrylate were weighed out for subsequent polymerization reactions. Step 2: Add 380g toluene, 57g octadecyl acrylate (a destabilizing agent), 19g docosyl acrylate (a destabilizing agent), 7g maleic anhydride, 9g 4-cyano-4-(phenylthiocarbamoylthio)valerate, and 1.1g nitrogen gas to a four-necked reaction flask equipped with a mechanical stirrer, condenser, thermometer, dropping port, and nitrogen inlet. 2,2′-Azobis(2-methylpropionitrile) was purged with high-purity nitrogen for 30 min and reacted at 70 °C and 300 rpm for 3 h. Then, while maintaining the temperature at 70 °C, a middle-stage solution consisting of 160 g toluene, 21 g octadecyl acrylate (a destabilizer), 7 g docosyl acrylate (a destabilizer), and 44 g maleic anhydride was added dropwise over 2 h. After the addition was complete, the reaction continued for 3 h. Then, a final-stage solution consisting of 85 g toluene, 57 g octadecyl acrylate (a destabilizer), 19 g docosyl acrylate (a destabilizer), 7 g maleic anhydride, and 1.1 g 2,2′-Azobis(2-methylpropionitrile) was added dropwise over 1 h. After the addition was complete, the reaction continued at 70 °C for 6 h to obtain a long-chain alkyl acrylate-maleic anhydride comb copolymer solution. Step 3: Cool the long-chain alkyl acrylate-maleic anhydride comb copolymer solution obtained in Step 2 to 25°C, add it to 1700g of methanol pre-cooled to 5°C while stirring at 300rpm, continue stirring for 30min, filter, wash the filter cake twice with 850g of methanol, and place the filter cake under vacuum drying at 45°C and 5kPa for 12h to obtain the long-chain alkyl acrylate-maleic anhydride comb copolymer precursor; Step 4: Add 190g of long-chain alkyl acrylate-maleic anhydride comb copolymer precursor, 450g of toluene and 140g of isopropanol to a four-necked reaction flask, and stir at 50℃ and 300rpm for 2h; lower the system to 45℃, and add the grafting solution prepared by 38g of N,N-dimethyl-1,3-propanediamine and 90g of isopropanol dropwise over 2h. After the addition is complete, raise the temperature to 55℃ and keep it at that temperature for 5h to obtain a tertiary amination ring-opening grafted comb copolymer solution. Step 5: Cool the tertiary amination ring-opening grafted comb copolymer solution obtained in Step 4 to 25°C, add 1500g of methanol pre-cooled to 5°C while stirring at 300rpm, continue stirring for 30min, filter, wash the filter cake twice with 650g of methanol, and then vacuum dry at 45°C and 5kPa for 12h to obtain the tertiary amination ring-opening grafted comb copolymer. Step Six: Add 160g of tertiary amination ring-opening grafted comb copolymer, 190g of ethylene glycol monobutyl ether, 100g of isopropanol, and 35g of toluene to a stirred tank. Stir at 45℃ and 400rpm for 2 hours, then reduce the temperature to 20℃. Add 210g of deionized water within 1 hour, while simultaneously introducing 4g of carbon dioxide using a mass flow meter, and continue stirring for 60 minutes. Raise the temperature back to 45℃, add 120g of deionized water, and simultaneously introduce 2.5g of carbon dioxide, continuing to stir for 30 minutes. Then, introduce 6g of nitrogen gas at 50℃, and finally add 30g of ethylene glycol monobutyl ether and 55g of isopropanol. Stir at 45℃ and 400rpm for 40 minutes, and filter through a 100μm filter to obtain an oilfield dewaxing agent.

[0024] Example 4: Step 1: 130g of octadecyl acrylate was melted at 55℃, and 26g of toluene was added and mixed thoroughly. The mixture was then passed through a 78g neutral alumina column that had been dried at 120℃ for 4 hours and cooled to 55℃. The effluent was collected, and toluene was removed under reduced pressure at 40℃ and 5kPa to obtain destabilized octadecyl acrylate. 70g of docosyl acrylate was melted at 65℃, and 14g of toluene was added and mixed thoroughly. The mixture was then passed through a 42g neutral alumina column that had been dried at 120℃ for 4 hours and cooled to 65℃. The effluent was collected, and toluene was removed under reduced pressure at 45℃ and 5kPa to obtain destabilized docosyl acrylate. 112g of destabilized octadecyl acrylate and 56g of destabilized docosyl acrylate were weighed out for subsequent polymerization reactions. Step 2: Add 360g of toluene, 48g of octadecyl acrylate (a destabilizing agent), 24g of docosyl acrylate (a destabilizing agent), 6g of maleic anhydride, 8g of 4-cyano-4-(phenylthiocarboxylthio)valerate, and 1g of [unclear - possibly a specific ingredient or product] to a four-necked reaction flask equipped with a mechanical stirrer, condenser, thermometer, dropping port, and nitrogen inlet. 2,2′-Azobis(2-methylpropionitrile) was purged with high-purity nitrogen for 30 min and reacted at 70 °C and 300 rpm for 3 h. Then, while maintaining the temperature at 70 °C, a middle-stage solution consisting of 150 g toluene, 16 g octadecyl acrylate (a destabilizer), 8 g docosyl acrylate (a destabilizer), and 40 g maleic anhydride was added dropwise over 2 h. After the addition was complete, the reaction continued for 3 h. Then, a final-stage solution consisting of 80 g toluene, 48 g octadecyl acrylate (a destabilizer), 24 g docosyl acrylate (a destabilizer), 6 g maleic anhydride, and 1 g 2,2′-Azobis(2-methylpropionitrile) was added dropwise over 1 h. After the addition was complete, the reaction continued at 70 °C for 6 h to obtain a long-chain alkyl acrylate-maleic anhydride comb copolymer solution. Step 3: Cool the long-chain alkyl acrylate-maleic anhydride comb copolymer solution obtained in Step 2 to 25°C, add it to 1600g of methanol pre-cooled to 5°C while stirring at 300rpm, continue stirring for 30min, filter, wash the filter cake twice with 800g of methanol, and place the filter cake in a vacuum dryer at 45°C and 5kPa for 12h to obtain the long-chain alkyl acrylate-maleic anhydride comb copolymer precursor; Step 4: Add 180g of long-chain alkyl acrylate-maleic anhydride comb copolymer precursor, 420g of toluene and 120g of isopropanol to a four-necked reaction flask, and stir at 50℃ and 300rpm for 2h; lower the system to 45℃, and add the grafting solution prepared by 34g of N,N-dimethyl-1,3-propanediamine and 80g of isopropanol dropwise over 2h. After the addition is complete, raise the temperature to 55℃ and keep it at that temperature for 5h to obtain a tertiary amination ring-opening grafted comb copolymer solution. Step 5: Cool the tertiary amination ring-opening grafted comb copolymer solution obtained in Step 4 to 25°C, add 1400g of methanol pre-cooled to 5°C while stirring at 300rpm, continue stirring for 30min, filter, wash the filter cake twice with 600g of methanol, and then vacuum dry at 45°C and 5kPa for 12h to obtain the tertiary amination ring-opening grafted comb copolymer. Step Six: Add 150g of tertiary amination ring-opening grafted comb copolymer, 180g of ethylene glycol monobutyl ether, 90g of isopropanol and 30g of toluene to a stirred tank, and stir at 45℃ and 400rpm for 2h, then lower the temperature to 20℃; add 200g of deionized water within 1h, and simultaneously introduce 3g of carbon dioxide using a mass flow meter, and continue stirring for 60min; then raise the temperature to 45℃, add 100g of deionized water, and simultaneously introduce 2g of carbon dioxide, and continue stirring for 30min; then introduce 5g of nitrogen at 50℃, and finally add 20g of ethylene glycol monobutyl ether and 50g of isopropanol, stir at 45℃ and 400rpm for 40min, and filter through a 100μm filter to obtain an oilfield dewaxing agent.

[0025] Example 5: Step 1: 165g of octadecyl acrylate was melted at 55℃, and 33g of toluene was added and mixed thoroughly. The mixture was then passed through a 99g neutral alumina column that had been dried at 120℃ for 4 hours and cooled to 55℃. The effluent was collected, and toluene was removed under reduced pressure at 40℃ and 5kPa to obtain destabilized octadecyl acrylate. 40g of docosyl acrylate was melted at 65℃, and 8g of toluene was added and mixed thoroughly. The mixture was then passed through a 24g neutral alumina column that had been dried at 120℃ for 4 hours and cooled to 65℃. The effluent was collected, and toluene was removed under reduced pressure at 45℃ and 5kPa to obtain destabilized docosyl acrylate. 136g of destabilized octadecyl acrylate and 32g of destabilized docosyl acrylate were weighed out for subsequent polymerization reactions. Step 2: Add 360g of toluene, 58g of octadecyl acrylate (a destabilizing agent), 14g of docosyl acrylate (a destabilizing agent), 6g of maleic anhydride, 8g of 4-cyano-4-(phenylthiocarboxylthio)valerate, and 1g of [unclear - possibly a specific ingredient or product] to a four-necked reaction flask equipped with a mechanical stirrer, condenser, thermometer, dropping port, and nitrogen inlet. 2,2′-Azobis(2-methylpropionitrile) was purged with high-purity nitrogen for 30 min and reacted at 70 °C and 300 rpm for 3 h. Then, while maintaining 70 °C, a middle section solution consisting of 150 g toluene, 20 g octadecyl acrylate (a destabilizer), 4 g docosyl acrylate (a destabilizer), and 40 g maleic anhydride was added dropwise over 2 h. After the addition was complete, the reaction continued for 3 h. Then, a final section solution consisting of 80 g toluene, 58 g octadecyl acrylate (a destabilizer), 14 g docosyl acrylate (a destabilizer), 6 g maleic anhydride, and 1 g 2,2′-Azobis(2-methylpropionitrile) was added dropwise over 1 h. After the addition was complete, the reaction continued at 70 °C for 6 h to obtain a long-chain alkyl acrylate-maleic anhydride comb copolymer solution. Step 3: Cool the long-chain alkyl acrylate-maleic anhydride comb copolymer solution obtained in Step 2 to 25°C, add it to 1600g of methanol pre-cooled to 5°C while stirring at 300rpm, continue stirring for 30min, filter, wash the filter cake twice with 800g of methanol, and place the filter cake in a vacuum dryer at 45°C and 5kPa for 12h to obtain the long-chain alkyl acrylate-maleic anhydride comb copolymer precursor; Step 4: Add 180g of long-chain alkyl acrylate-maleic anhydride comb copolymer precursor, 420g of toluene and 120g of isopropanol to a four-necked reaction flask, and stir at 50℃ and 300rpm for 2h; lower the system to 45℃, and add the grafting solution prepared by 34g of N,N-dimethyl-1,3-propanediamine and 80g of isopropanol dropwise over 2h. After the addition is complete, raise the temperature to 55℃ and keep it at that temperature for 5h to obtain a tertiary amination ring-opening grafted comb copolymer solution. Step 5: Cool the tertiary amination ring-opening grafted comb copolymer solution obtained in Step 4 to 25°C, add 1400g of methanol pre-cooled to 5°C while stirring at 300rpm, continue stirring for 30min, filter, wash the filter cake twice with 600g of methanol, and then vacuum dry at 45°C and 5kPa for 12h to obtain the tertiary amination ring-opening grafted comb copolymer. Step Six: Add 150g of tertiary amination ring-opening grafted comb copolymer, 180g of ethylene glycol monobutyl ether, 90g of isopropanol and 30g of toluene to a stirred tank, and stir at 45℃ and 400rpm for 2h, then lower the temperature to 20℃; add 200g of deionized water within 1h, and simultaneously introduce 3g of carbon dioxide using a mass flow meter, and continue stirring for 60min; then raise the temperature to 45℃, add 100g of deionized water, and simultaneously introduce 2g of carbon dioxide, and continue stirring for 30min; then introduce 5g of nitrogen at 50℃, and finally add 20g of ethylene glycol monobutyl ether and 50g of isopropanol, stir at 45℃ and 400rpm for 40min, and filter through a 100μm filter to obtain an oilfield dewaxing agent.

[0026] Example 6: Step 1: 150g of octadecyl acrylate was melted at 55℃, and 30g of toluene was added and mixed thoroughly. The mixture was then passed through a 90g neutral alumina column that had been dried at 120℃ for 4 hours and cooled to 55℃. The effluent was collected, and toluene was removed under reduced pressure at 40℃ and 5kPa to obtain destabilized octadecyl acrylate. 50g of docosyl acrylate was melted at 65℃, and 10g of toluene was added and mixed thoroughly. The mixture was then passed through a 30g neutral alumina column that had been dried at 120℃ for 4 hours and cooled to 65℃. The effluent was collected, and toluene was removed under reduced pressure at 45℃ and 5kPa to obtain destabilized docosyl acrylate. 126g of destabilized octadecyl acrylate and 42g of destabilized docosyl acrylate were weighed out for subsequent polymerization reactions. Step 2: Add 360g toluene, 54g octadecyl acrylate (a destabilizing agent), 18g docosyl acrylate (a destabilizing agent), 6g maleic anhydride, 8g 4-cyano-4-(phenylthiocarbamoylthio)valerate, and 1g nitrogen gas to a four-necked reaction flask equipped with a mechanical stirrer, condenser, thermometer, dropping port, and nitrogen inlet. 2,2′-Azobis(2-methylpropionitrile) was purged with high-purity nitrogen for 30 min and reacted at 70 °C and 300 rpm for 3 h. Then, while maintaining the temperature at 70 °C, a middle-stage solution consisting of 150 g toluene, 18 g octadecyl acrylate (a destabilizer), 6 g docosyl acrylate (a destabilizer), and 40 g maleic anhydride was added dropwise over 2 h. After the addition was complete, the reaction continued for 3 h. Then, a final-stage solution consisting of 80 g toluene, 54 g octadecyl acrylate (a destabilizer), 18 g docosyl acrylate (a destabilizer), 6 g maleic anhydride, and 1 g 2,2′-Azobis(2-methylpropionitrile) was added dropwise over 1 h. After the addition was complete, the reaction continued at 70 °C for 6 h to obtain a long-chain alkyl acrylate-maleic anhydride comb copolymer solution. Step 3: Cool the long-chain alkyl acrylate-maleic anhydride comb copolymer solution obtained in Step 2 to 25°C, add it to 1600g of methanol pre-cooled to 5°C while stirring at 300rpm, continue stirring for 30min, filter, wash the filter cake twice with 800g of methanol, and place the filter cake in a vacuum dryer at 45°C and 5kPa for 12h to obtain the long-chain alkyl acrylate-maleic anhydride comb copolymer precursor; Step 4: Add 185g of long-chain alkyl acrylate-maleic anhydride comb copolymer precursor, 430g of toluene and 130g of isopropanol to a four-necked reaction flask, and stir at 50℃ and 300rpm for 2h; lower the system to 45℃, and add the grafting solution prepared by 39g of N,N-dimethyl-1,3-propanediamine and 90g of isopropanol dropwise over 2h. After the addition is complete, raise the temperature to 55℃ and keep it at that temperature for 5.5h to obtain the tertiary amination ring-opening grafted comb copolymer solution. Step 5: Cool the tertiary amination ring-opening grafted comb copolymer solution obtained in Step 4 to 25°C, add 1450g of methanol pre-cooled to 5°C while stirring at 300rpm, continue stirring for 30min, filter, wash the filter cake twice with 650g of methanol, and then vacuum dry at 45°C and 5kPa for 12h to obtain the tertiary amination ring-opening grafted comb copolymer. Step Six: Add 165g of tertiary amination ring-opening grafted comb copolymer, 200g of ethylene glycol monobutyl ether, 100g of isopropanol, and 35g of toluene to a stirred tank. Stir at 45℃ and 400rpm for 2 hours, then lower the temperature to 20℃. Add 220g of deionized water within 1 hour, while simultaneously introducing 4g of carbon dioxide using a mass flow meter, and continue stirring for 60 minutes. Raise the temperature back to 45℃, add 110g of deionized water, and simultaneously introduce 3g of carbon dioxide, continuing to stir for 30 minutes. Then, introduce 6.5g of nitrogen at 50℃, and finally add 25g of ethylene glycol monobutyl ether and 55g of isopropanol. Stir at 45℃ and 400rpm for 40 minutes, and filter through a 100μm filter to obtain an oilfield dewaxing agent.

[0027] Comparative Example 1: The difference from Example 1 is that step two does not use the three-stage feeding method of initial liquid, intermediate liquid and final liquid. Instead, 590g of toluene, 126g of octadecyl acrylate destabilizer, 42g of docosyl acrylate destabilizer, 52g of maleic anhydride, 8g of 4-cyano-4-(phenylthiocarbamoylthio)valerate and 2g of 2,2′-azobis(2-methylpropionitrile) are added to a four-necked reaction flask at once. The mixture is purged with high-purity nitrogen for 30 min and reacted at 70°C and 300 rpm for 12 h to obtain a long-chain alkyl acrylate-maleic anhydride comb copolymer solution. The remaining conditions are the same as in Example 1.

[0028] Comparative Example 2: The difference from Example 1 is that 4-cyano-4-(phenylthiocarbamoylthio)valerate is not added in step two, and 8g of toluene is used to make up the total mass of the starting liquid. The other conditions are the same as in Example 1.

[0029] Comparative Example 3: The difference from Example 1 is that the 42g of docosyl acrylate used as a destabilizing agent in steps one and two is completely replaced by an equal mass of octadecyl acrylate as a destabilizing agent. That is, the total amount of octadecyl acrylate used as a destabilizing agent in step two is 168g, and no more docosyl acrylate as a destabilizing agent is added. The other conditions are the same as in Example 1.

[0030] Comparative Example 4: The difference from Example 1 is that in step four, instead of adding the grafting solution prepared with 34g of N,N-dimethyl-1,3-propanediamine and 80g of isopropanol, 80g of isopropanol is added dropwise at 45°C. After the addition is complete, the temperature is raised to 55°C and kept at that temperature for 5 hours. The other conditions are the same as in Example 1.

[0031] Comparative Example 5: The difference from Example 1 is that in step four, instead of adding the grafting solution prepared with 34g of N,N-dimethyl-1,3-propanediamine and 80g of isopropanol, 80g of isopropanol is added dropwise at 45°C. After the addition is complete, the temperature is raised to 55°C and kept at that temperature for 5 hours. In step six, 34g of N,N-dimethyl-1,3-propanediamine is added to the stirred tank before adding deionized water, and the 50g of isopropanol added at the end of step six is ​​reduced to 16g. The other conditions are the same as in Example 1.

[0032] Comparative Example 6: The difference from Example 1 is that in step five, the filter cake is not washed twice with 600g of methanol after filtration, but is directly dried under vacuum at 45°C and 5kPa for 12 hours. The other conditions are the same as in Example 1.

[0033] Comparative Example 7: The difference from Example 1 is that carbon dioxide and nitrogen are not introduced in step six, and 5g of deionized water is used to make up the mass corresponding to the amount of carbon dioxide introduced. The other conditions are the same as in Example 1.

[0034] Comparative Example 8: The difference from Example 1 is that step six does not involve the two-stage treatment of 20°C carbon dioxide low-temperature preprotonation and 45°C carbon dioxide chain relaxation. Instead, 300g of deionized water is added to the system at 45°C at once, and 5g of carbon dioxide is introduced at once within 90 minutes. Then, 5g of nitrogen is introduced at 50°C. The remaining conditions are the same as in Example 1.

[0035] Comparative Example 9: The difference from Example 1 is that in step six, after introducing 3g of carbon dioxide and 2g of carbon dioxide, the 50°C nitrogen decarbonization back-up treatment is not performed, and the other conditions are the same as in Example 1.

[0036] Performance testing: Sample preparation: The oilfield wax removers and anti-wax agents obtained in Examples 1-6 and Comparative Examples 1-9 were used directly as test samples. Before testing, they were allowed to stand at 25℃ for 24 hours and stirred at 300 rpm for 10 minutes to ensure homogeneity. Simulated waxy oil was prepared by stirring 90.0 g of liquid paraffin and 10.0 g of paraffin at 70℃ for 1 hour, and then cooled to 50℃ for later use. The test was conducted according to GB / T... 26982-2022 Verification of the wax content in the simulated waxy oil, controlling the wax content to be 10.0%±0.3%; Carbon dioxide acidic simulated produced fluid was prepared by mixing the simulated waxy oil and mineralized water at a mass ratio of 70:30, and then passing carbon dioxide through the mixture at 45℃ and 300rpm until the pH of the aqueous phase reached 5.30±0.05; In each performance test, the dosage of wax remover and anti-wax agent was 500mg / L based on the mass of the simulated waxy oil. No wax remover or anti-wax agent was added to the blank sample. The purity of raw materials, simulated waxy oil, mineralized water, temperature, stirring, dosage, and testing equipment were kept consistent in the examples and comparative samples.

[0037] Acid value determination: The acid value of the tertiary amination ring-opening grafted comb copolymer obtained in step five was determined according to GB / T 2895-2008. 0.5000 g of dried sample was weighed and placed in a 250 mL Erlenmeyer flask. 50.0 g of a mixed solvent of toluene and isopropanol in a mass ratio of 2:1 was added. The mixture was shaken and dissolved in a water bath at 45 °C for 30 min. After cooling to 25 °C, it was titrated to the endpoint with 0.1000 mol / L potassium hydroxide ethanol standard titration solution. A blank test was performed at the same time. The results are expressed as mgKOH / g.

[0038] Total nitrogen content determination: The total nitrogen content of the tertiary amination ring-opening grafted comb copolymer obtained in step five was determined according to GB / T 9170-1988. 0.3000g of dried sample was weighed, digested, and absorbed by distillation. The sample was titrated with standard acid solution and the blank value was subtracted. The result was converted to mmol / g. The nitrogen content of the precursor of the long-chain alkyl acrylate-maleic anhydride comb copolymer in the same batch was used as the background value. The tertiary amine nitrogen content was calculated by subtracting the background nitrogen content of the precursor from the total nitrogen content of the grafted sample.

[0039] Determination of free N,N-dimethyl-1,3-propanediamine residue: A gas chromatography external standard method was established according to GB / T 9722-2023. 2.000 g of oilfield wax remover sample was weighed, and 20.00 g of methanol was added. Extraction was performed at 25℃ and 300 rpm for 30 min. The sample was filtered through a 0.45 μm organic filter membrane and then injected. A flame ionization detector was used, with an injection port temperature of 220℃ and a detector temperature of 250℃. The column temperature program was 60℃ for 2 min, increasing to 180℃ at 10℃ / min and holding for 5 min. The external standard was N,N-dimethyl-1,3-propanediamine. The linear range was 0.01 mg / mL to 1.00 mg / mL. The results were expressed as the mass fraction of free N,N-dimethyl-1,3-propanediamine in the sample.

[0040] Low-temperature viscosity determination. Following the rotational viscosity measurement requirements of GB / T 10247-2008, the oilfield dewaxing and anti-waxing agents obtained in Examples 1-6 and Comparative Examples 1-9 were placed in a 10℃ constant temperature water bath for 2 hours for equilibration. The same rotational viscometer, rotor No. 2, and 60 rpm were used for testing. Viscosity was recorded after the reading stabilized for 60 seconds. Three parallel measurements were performed, and the average value was taken. The results are expressed in mPa·s.

[0041] Carbon dioxide response dispersion time determination: 200.0g of carbon dioxide acidic simulated produced fluid was placed in a 500mL jacketed glass reactor. The temperature was controlled at 45℃ and the stirring speed was 300rpm. 500mg / L of the test dewaxing agent was added based on the simulated waxy oil mass. The system was kept under micro-bubbling of carbon dioxide and the pH of the aqueous phase was maintained at 5.30±0.05. Timing started from the completion of the dosing. The agent agglomerates and wax crystal flocs at the oil-water interface were observed every 30s. The dispersion endpoint was recorded when no visible agglomerates were observed for 3 consecutive minutes and the wax crystals were uniformly dispersed under a microscope in the upper oil sample. The results are expressed in minutes.

[0042] Wax prevention rate determination: The wax prevention performance of the oilfield wax inhibitor was evaluated according to SY / T 6300-2024. 100.0g of simulated wax-containing oil was added to the test tube and kept at 50℃ for 30min to completely dissolve the wax. 500mg / L of the wax inhibitor to be tested was added based on the mass of the simulated wax-containing oil. After shaking by hand 120 times, the tube was placed in a 45℃ constant temperature water bath for 10min to equilibrate. A pre-weighed stainless steel plate was suspended in the test tube. The external cooling medium temperature of the test tube was controlled at 20℃, and the deposition time was 6h. After removing the plate, the oil was drained at 25℃ for 10min, and the mass of the deposited wax was weighed. At the same time, a blank test without additives was conducted. The wax prevention rate was calculated by dividing the difference between the mass of the blank deposited wax and the mass of the additive-treated deposited wax by the mass of the blank deposited wax and then multiplying by 100%. The result is expressed as a percentage (%).

[0043] Wax removal rate determination: The wax removal performance was evaluated according to SY / T 6300-2024. Molten paraffin wax was dripped into a spherical mold with an inner diameter of 20 mm. After cooling to 25℃, the mold was removed and the wax balls with a mass of 3.000 g ± 0.020 g were obtained. 100.0 g of the wax removal agent to be tested was placed in a 150 mL glass bottle with a stopper. After equilibration in a constant temperature water bath at 50℃ for 20 min, the wax balls were added. The temperature was maintained at 50℃ and the mixture was gently shaken at 100 rpm. The remaining mass of the wax balls after 60 min was recorded. The wax removal rate was calculated by dividing the decrease in mass of the wax balls by 60 min. The result was expressed as g / min.

[0044] Crude oil apparent viscosity reduction rate determination: The apparent viscosity of simulated waxy oil was determined using a coaxial cylindrical rotational viscometer according to GB / T 26985-2018. 100.0 g of simulated waxy oil was preheated at 60℃ for 30 min, and 500 mg / L of the wax inhibitor to be tested (based on the mass of the simulated waxy oil) was added. The mixture was stirred at 45℃ and 300 rpm for 20 min, then cooled to 35℃ and held at that temperature for 30 min. The mixture was then subjected to a shear rate of 50 s⁻¹. -1 The apparent viscosity was determined. The blank sample was prepared using the same simulated wax-containing oil and the same heat treatment process, but without the addition of a wax remover. The apparent viscosity reduction rate was calculated by dividing the difference between the apparent viscosity of the blank sample and the apparent viscosity after adding the wax by the apparent viscosity of the blank sample and then multiplying by 100%. The result is expressed as a percentage.

[0045] Pour point reduction determination: The pour point of the simulated waxy oil before and after the addition of the agent was determined according to SY / T 7551-2004. 100.0g of simulated waxy oil was preheated at 60℃ for 30min, and 500mg / L of the wax inhibitor to be tested was added based on the mass of the simulated waxy oil. After stirring at 45℃ and 300rpm for 20min, the mixture was transferred to a pour point test tube. The fluidity was observed every 3℃ according to the prescribed cooling procedure. The blank sample used the same simulated waxy oil and the same heat treatment process but without the addition of the wax inhibitor. The pour point reduction was calculated by subtracting the pour point of the treated sample from the pour point of the blank sample. The result is expressed in ℃.

[0046] Table 1 Performance Test Results

[0047] As shown in Table 1, Comparative Example 4 did not use N,N-dimethyl-1,3-propanediamine to perform tertiary amination ring-opening grafting on the maleic anhydride unit. Its tertiary amine nitrogen content was only 0.02 mmol / g, the carbon dioxide response dispersion time was extended to 18.5 min, and the wax prevention rate, wax removal rate, apparent viscosity reduction rate at 35℃ and pour point reduction were 55.1%, 0.035 g / min, 41.6%, and 6℃, respectively. This indicates that the simple long-chain alkyl acrylate-maleic anhydride comb copolymer is difficult to form an effective dispersion in carbon dioxide acidic produced fluid.

[0048] Although N,N-dimethyl-1,3-propanediamine was added during the compounding stage of Comparative Example 5, the tertiary amine nitrogen was not fixed on the comb copolymer segments, and the free amine mass fraction increased to 3.8%. The wax prevention rate and the apparent viscosity reduction rate at 35°C were only 63.4% and 48.9%, respectively, indicating that the added low molecular weight amine cannot replace the tertiary amination ring-opening graft structure.

[0049] Comparative Example 1 did not use the three-stage feeding method of initial liquid, intermediate liquid and final liquid, and Comparative Example 2 did not add 4-cyano-4-(phenylthiocarbamoylthio)valerate for polymerization control. Although the acid value and tertiary amine nitrogen content of both were similar to those of Example 1, the viscosity at low temperature of 10°C increased to 138.6 mPa·s and 176.3 mPa·s, respectively, and the wax prevention rate decreased to 70.5% and 66.8%, respectively. This indicates that the controllability of polymer chain segment distribution and structure has an important influence on the dispersibility of the wax removal agent and the wax crystal control effect.

[0050] Comparative Example 3, which did not introduce docosyl acrylate, had a low-temperature filling viscosity of 70.4 mPa·s at 10°C, but its wax prevention rate was only 74.2%, indicating that the docosyl side chain has a significant contribution to the embedding of high-carbon wax crystals and the wax prevention effect.

[0051] Compared with the comparative examples above, Examples 1-6 all formed a relatively stable wax-preventing and dewaxing system through three-stage feeding, tertiary amine ring-opening grafting, methanol purification, and carbon dioxide / nitrogen sequential treatment. Among them, Example 4 achieved a wax prevention rate of 92.1% and a wax removal rate of 0.049 g / min due to the increased proportion of docosyl acrylate, with an apparent viscosity reduction rate of 78.1% at 35°C and a pour point reduction of 18°C. In Example 6, the carbon dioxide response dispersion time was shortened to 3.1 min due to the increased tertiary amine response sites and carbon dioxide / nitrogen treatment intensity, while the viscosity at 10°C was still controlled at 118.4 mPa·s.

[0052] Comparative Example 9 did not undergo nitrogen decarbonization and reversal treatment. Although its carbon dioxide response dispersion time was 3.4 min, its viscosity increased to 165.2 mPa·s at 10℃. Its anti-wax rate and apparent viscosity reduction rate at 35℃ were lower than those of Examples 1, 3, 4 and 6, respectively. This indicates that the nitrogen reversal step is beneficial to balance carbon dioxide response dispersion and low-temperature refueling performance.

[0053] In summary, this invention introduces octadecyl acrylate, docosyl acrylate, maleic anhydride, and N,N-dimethyl-1,3-propanediamine into the same controllable comb copolymer system, and combines this with carbon dioxide / nitrogen sequential treatment, enabling the wax-removing and anti-waxing agent to exhibit faster dispersion, higher anti-waxing rate, higher wax removal rate, and more significant viscosity reduction and pour point reduction effects in carbon dioxide acidic produced fluid. This demonstrates the synergistic effect between the long alkyl wax crystal-regulated structure and the tertiary amine-responsive dispersion structure.

[0054] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. An oilfield wax remover and preservative, characterized in that, By weight, the oilfield dewaxing agent is prepared from the following raw materials through carbon dioxide treatment and nitrogen decarbonization and back-up treatment: 140-165 parts of tertiary amination ring-opening grafted comb copolymer, 190-230 parts of ethylene glycol monobutyl ether, 130-155 parts of isopropanol, 25-35 parts of toluene, and 280-340 parts of deionized water; The tertiary amination ring-opening grafted comb copolymer is prepared by ring-opening grafting reaction of long-chain alkyl acrylate-maleic anhydride comb copolymer precursor with N,N-dimethyl-1,3-propanediamine. The long-chain alkyl acrylate-maleic anhydride comb copolymer precursor is prepared by three-stage feeding polymerization of octadecyl acrylate, docosyl acrylate, and maleic anhydride in the presence of 4-cyano-4-(phenylthiocarbamoylthio)valerate.

2. The oilfield wax remover and preservative according to claim 1, characterized in that, The tertiary amination ring-opening grafted comb copolymer has an acid value of 121.6-136.9 mgKOH / g and a tertiary amine nitrogen content of 1.05-1.37 mmol / g.

3. The oilfield wax remover and preservative according to claim 1, characterized in that, The mass fraction of free N,N-dimethyl-1,3-propanediamine in the oilfield dewaxing agent is no greater than 0.3%.

4. The oilfield wax remover and preservative according to claim 1, characterized in that, In the preparation of the long-chain alkyl acrylate-maleic anhydride comb copolymer precursor, the mass ratio of octadecyl acrylate, docosyl acrylate, and maleic anhydride used as destabilizers in the subsequent polymerization reaction is 110-140:30-60:48-61.

5. The oilfield wax remover and preservative according to claim 1, characterized in that, The three-stage feeding polymerization includes initial liquid polymerization, intermediate liquid droplet polymerization, and final liquid droplet polymerization; The starting liquid comprises 45-60 parts of octadecyl acrylate with destabilizer, 14-24 parts of docosyl acrylate with destabilizer, and 5-8 parts of maleic anhydride. The intermediate feed solution includes 16-22 parts of octadecyl acrylate with destabilizer, 4-8 parts of docosyl acrylate with destabilizer, and 38-45 parts of maleic anhydride. The final stage feed solution includes 45-60 parts of octadecyl acrylate as a destabilizer, 14-24 parts of docosyl acrylate as a destabilizer, and 5-8 parts of maleic anhydride.

6. The oilfield wax remover and preservative according to claim 5, characterized in that, In the three-stage feeding polymerization, the starting feed solution further includes 320-390 parts of toluene, 6.5-10 parts of 4-cyano-4-(phenylthiocarbamoylthio)valerate, and 0.8-1.2 parts of 2,2′-azobis(2-methylpropionitrile); the intermediate feed solution further includes 130-170 parts of toluene; and the final feed solution further includes 75-90 parts of toluene and 0.8-1.2 parts of 2,2′-azobis(2-methylpropionitrile).

7. The oilfield wax remover and preservative according to claim 1, characterized in that, The three-stage feeding polymerization is as follows: after purging with high-purity nitrogen for 30 minutes, the initial liquid is polymerized at 70°C and 300 rpm for 3 hours; then, while maintaining 70°C, the middle stage liquid is added dropwise over 2 hours, and the reaction continues for 3 hours after the addition is completed; then, the final stage liquid is added dropwise over 1 hour, and the reaction continues at 70°C for 6 hours after the addition is completed.

8. The oilfield wax remover and preservative according to claim 1, characterized in that, In the ring-opening grafting reaction, the mass ratio of the long-chain alkyl acrylate-maleic anhydride comb copolymer precursor, toluene, isopropanol for dissolving the precursor, N,N-dimethyl-1,3-propanediamine, and isopropanol for preparing the grafting solution is 170-190:390-450:110-140:30-40:70-90. The ring-opening grafting reaction is as follows: the long-chain alkyl acrylate-maleic anhydride comb copolymer precursor, toluene, and isopropanol are stirred at 50°C and 300 rpm for 2 hours; the system is lowered to 45°C, and the grafting solution prepared by N,N-dimethyl-1,3-propanediamine and isopropanol is added dropwise over 2 hours; after the addition is complete, the temperature is raised to 55°C and maintained for 5-5.5 hours.

9. The oilfield wax remover and preservative according to claim 1, characterized in that, The carbon dioxide treatment and nitrogen decarbonization and reversal process are as follows: 140-165 parts of tertiary amination ring-opening grafted comb copolymer, 170-200 parts of ethylene glycol monobutyl ether, 85-100 parts of isopropanol, and 25-35 parts of toluene are stirred at 45°C and 400 rpm for 2 hours, then cooled to 20°C; 190-220 parts of deionized water are added within 1 hour, while 2.5-4 parts of carbon dioxide are introduced, and stirring continues for 60 minutes; the temperature is then raised to 45°C, 90-120 parts of deionized water are added, while 1.5-3 parts of carbon dioxide are introduced, and stirring continues for 30 minutes; subsequently, 4-6.5 parts of nitrogen are introduced at 50°C, and finally 20-30 parts of ethylene glycol monobutyl ether and 45-55 parts of isopropanol are added, and the mixture is stirred at 45°C and 400 rpm for 40 minutes, and then filtered through a 100 μm filter.

10. A preparation process for an oilfield wax remover and preservative according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Octadecyl acrylate and docosyl acrylate are subjected to destabilizing treatment to obtain destabilized octadecyl acrylate and destabilized docosyl acrylate. S2. Stabilized octadecyl acrylate, stabilized docosyl acrylate, and maleic anhydride are subjected to three-stage feeding polymerization in toluene with 4-cyano-4-(phenylthiocarbamoylthio)valerate as polymerization regulator and 2,2′-azobis(2-methylpropionitrile) as initiator to obtain a long-chain alkyl acrylate-maleic anhydride comb copolymer solution. S3. The long-chain alkyl acrylate-maleic anhydride comb copolymer solution is subjected to methanol precipitation, washing and drying to obtain the long-chain alkyl acrylate-maleic anhydride comb copolymer precursor. S4. The long-chain alkyl acrylate-maleic anhydride comb copolymer precursor is subjected to a ring-opening grafting reaction with N,N-dimethyl-1,3-propanediamine to obtain a tertiary amination ring-opening grafted comb copolymer solution. S5. The tertiary amination ring-opening grafted comb copolymer solution is subjected to methanol precipitation, washing and drying to obtain the tertiary amination ring-opening grafted comb copolymer. S6. The tertiary amination ring-opening grafted comb copolymer is mixed with ethylene glycol monobutyl ether, isopropanol, toluene and deionized water, and then subjected to carbon dioxide treatment and nitrogen decarbonization and reversion treatment in sequence to obtain an oilfield dewaxing and anti-waxing agent.

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