Polymeric surfactant for oil displacement and preparation method thereof
By preparing a multi-component graft copolymer containing a cationic surfactant, the problem of poor performance of existing oil displacement polymers in high-salinity environments was solved, and a highly efficient oil displacement effect was achieved in high-salinity environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-15
- Publication Date
- 2026-04-10
AI Technical Summary
Existing oil displacement polymers are ineffective in high-salinity environments, cannot effectively reduce oil-water interfacial tension, and their physical mixing methods are not conducive to on-site construction.
A polymeric surfactant for oil displacement is prepared by reacting palmitic acid, N,N-dimethyltrimethylenediamine and ethyl chloride acrylate to generate a cationic surfactant, which is then mixed with acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, tetrahydrofurfuryl acrylate, 4-hydroxybutylvinyl ether, dispersant and pH adjuster in a composite solvent to initiate a polymerization reaction, forming a multi-component graft copolymer with hydrophilic and hydrophobic groups.
This polymeric surfactant possesses excellent water solubility, thickening properties, salt resistance, and temperature and shear resistance. It does not require mixing with surfactants and can efficiently drive oil in high-salt environments, significantly reducing the interfacial tension between oil and water.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer materials technology, particularly to the field of polymer polymerization technology, and especially to an oil displacement agent and its preparation method. Background Technology
[0002] Polymer flooding is one of the most widely used and dominant technologies in oilfield chemical flooding. However, polymer flooding cannot reduce the oil-water interfacial tension, and residual oil in rock pores is difficult to initiate and flow. Surfactant flooding uses surfactant solutions as oil displacement agents to significantly reduce oil-water interfacial tension and alter rock wettability to improve oil recovery. However, it is highly sensitive to formation conditions and cannot be effective in high-salinity environments, especially in areas with high calcium content. 2+ Mg 2+ This may cause the surfactant to become ineffective.
[0003] Oil displacement polymerizers are oilfield additives that combine the functions of polymer flooding and surfactant flooding, forming multi-component graft copolymers with both hydrophilic and lipophilic groups. This structure allows them to possess both the thickening properties of polymers and the emulsifying and solubilizing capabilities of surfactants, significantly improving oil displacement efficiency.
[0004] In existing technologies, oil displacement agents are generally physical mixtures of polymers and surfactants, which are not conducive to efficient on-site construction.
[0005] Therefore, in order to address the above shortcomings, there is an urgent need for an oil displacement polymerizing agent and its preparation method. Summary of the Invention
[0006] This invention provides a polymeric surfactant for oil displacement and its preparation method. The polymeric surfactant has good water solubility, thickening properties, excellent salt resistance, temperature and shear resistance, and excellent interfacial activity. Moreover, it does not need to be mixed with surfactants, thus achieving efficient construction.
[0007] The present invention provides a method for preparing an oil displacement polymerizer in a first aspect, comprising: (1) Palmitic acid, N,N-dimethyltrimethylenediamine and ethyl chloride acrylate are reacted to obtain a cationic surfactant; (2) Acrylamide, acrylic acid, the cationic surfactant, 2-acrylamide-2-methylpropanesulfonic acid, tetrahydrofurfuryl acrylate, 4-hydroxybutylvinyl ether, dispersant, molecular weight regulator and pH regulator are added to the composite solvent and mixed to obtain a polymerization solution; (3) Nitrogen gas is introduced into the polymerization solution, and then an initiator is added to initiate the polymerization reaction to obtain the oil displacement polymer.
[0008] Preferably, step (1) includes the following sub-steps: (11) Palmitic acid, N,N-dimethyltrimethylenediamine and catalyst are added to a solvent and mixed well, and the prepolymer is obtained by reaction; (12) The prepolymer and ethyl chloride acrylate are added to the solvent, mixed and reacted to obtain the cationic surfactant.
[0009] More preferably, the molar ratio of palmitic acid to N,N-dimethyltrimethylenediamine is 1:(1.2~1.5).
[0010] More preferably, the molar ratio of the prepolymer to ethyl chloride acrylate is 1:(1.1~1.3).
[0011] Preferably, step (11) includes: The catalyst is at least one of K2O / Al2O3 and KF / La2O3.
[0012] More preferably, the mass of the catalyst is 0.02wt% to 0.05wt% of the sum of the masses of palmitic acid and N,N-dimethyltrimethylenediamine.
[0013] Preferably, step (11) includes: The mass of the solvent is 80wt% to 90wt% of the sum of the masses of palmitic acid and N,N-dimethyltrimethylenediamine.
[0014] Preferably, step (12) includes: The prepolymer and polymerization inhibitor are added to the solvent and mixed to obtain a first solution; ethyl chloride acrylate is added to the solvent and mixed to obtain a second solution; nitrogen gas is introduced into the first solution, and the second solution is added dropwise to the first solution to react and obtain the cationic surfactant.
[0015] More preferably, in step (12): the dripping time is 30~40 min; More preferably, in step (12): the mass of the polymerization inhibitor is 0.01wt% to 0.02wt% of the mass of the prepolymer.
[0016] More preferably, the polymerization inhibitor is 1,1-diphenyl-2-trinitrophenylhydrazine.
[0017] Preferably, the reaction temperature in step (11) is 120~140℃ and the reaction time is 10~12h.
[0018] Preferably, the reaction temperature of step (12) is 75~80℃ and the reaction time is 5~7h.
[0019] Preferably, in step (2): The dispersant is at least one of cocamidopropyl betaine, lauramide propyl betaine, and lauryl imidazoline betaine; The molecular weight regulator is at least one of glycerol, sodium hypophosphite, sodium formate, pentaerythritol, and thiourea.
[0020] Preferably, in step (2): The pH adjuster includes sodium hydroxide; The composite solvent is a mixture of deionized water and acetone.
[0021] More preferably, the pH value of the polymerization solution is 6.6 to 6.9.
[0022] Preferably, in step (3): The initiator includes a first initiator and a second initiator; The first initiator is at least one of azobisisobutyronitrile, azobisisobutyramidine hydrochloride, and azobisisobutyramidazole hydrochloride; The second initiator is a redox complex initiator, which includes an oxidant and a reducing agent.
[0023] More preferably, the oxidant is at least one of potassium persulfate, ammonium persulfate, tert-butyl peroxide, cumene hydroperoxide, and tert-amyl hydroperoxide; and the reducing agent is at least one of sodium bisulfite, sodium metabisulfite, and ferrous sulfate.
[0024] Preferably, in step (3): The polymerization reaction begins at a temperature of 0-2°C and continues until the temperature of the polymerization reaction no longer increases.
[0025] Preferably, the mass fractions of each raw material used to prepare the oil displacement surfactant are as follows: 130-150 parts acrylamide, 100-120 parts acrylic acid, 8-12 parts of the cationic surfactant, 20-30 parts of 2-acrylamido-2-methylpropanesulfonic acid, 2-4 parts of tetrahydrofurfuryl acrylate, 2-4 parts of 4-hydroxybutylvinyl ether, 1-3 parts of dispersant, 1.5-2 parts of molecular weight regulator, 50-70 parts of pH regulator, 500-700 parts of composite solvent, and 1-2 parts of initiator.
[0026] In a second aspect, the present invention provides an oil displacement polymer agent prepared by the preparation method of the first aspect described above.
[0027] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The oil displacement polymeric surfactant prepared in this invention incorporates acrylamide, acrylic acid, cationic surfactant, 2-acrylamido-2-methylpropanesulfonic acid, tetrahydrofurfuryl acrylate, and 4-hydroxybutyl vinyl ether, all of which contain unsaturated carbon-carbon double bonds. Moreover, the amide groups, carboxyl groups, and hydroxyl groups contained in these components are all hydrophilic groups, which gives the oil displacement polymeric surfactant good water solubility and thickening ability. The sulfonic acid group of 2-acrylamido-2-methylpropanesulfonic acid serves as a salt-resistant group, improving the salt resistance of the oil displacement polymeric surfactant. Furthermore, the saturated oxygen-containing five-membered ring contained therein has a certain degree of rigidity, which can further improve the temperature resistance and shear resistance of the oil displacement polymeric surfactant. This gives the polymer water solubility, thickening, salt resistance, and rigidity, achieving the purpose of polymer oil displacement.
[0028] (2) In this invention, the prepared cationic surfactant contains hydrophobic long-chain groups, which can adapt to the complex formation environment of oil fields with high salinity and high temperature; during the polymerization and grafting process, the aggregation of hydrophobic ends forms micro-regions, which improves the viscoelasticity of the solution; at the same time, the dispersant containing betaine and the cationic surfactant work together to give full play to the oil displacement effect of the cationic surfactant, significantly reduce the oil-water interfacial tension, and achieve the purpose of efficient oil displacement of the polymer surfactant together with the polymer flooding. Detailed Implementation
[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0030] In the description of the embodiments of the present invention, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; unless otherwise specified or stated, the term "multiple" refers to two or more. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.
[0031] This invention provides a method for preparing a surface-active polymer for oil displacement, the method comprising: (1) Palmitic acid, N,N-dimethyltrimethylenediamine and ethyl chloride acrylate are reacted to obtain a cationic surfactant; (2) Acrylamide, acrylic acid, cationic surfactant, 2-acrylamide-2-methylpropanesulfonic acid, tetrahydrofurfuryl acrylate, 4-hydroxybutylvinyl ether, dispersant, molecular weight regulator and pH regulator are added to the composite solvent and mixed to obtain a polymerization solution; (3) Nitrogen gas is introduced into the polymerization solution, and then an initiator is added to initiate the polymerization reaction to obtain an oil displacement agent.
[0032] In this embodiment of the invention, the oil displacement polymeric surfactant incorporates acrylamide, acrylic acid, a cationic surfactant, 2-acrylamido-2-methylpropanesulfonic acid, tetrahydrofurfuryl acrylate, and 4-hydroxybutyl vinyl ether, all of which contain unsaturated carbon-carbon double bonds. Furthermore, the amide, carboxyl, and hydroxyl groups in these components are all hydrophilic groups, giving the oil displacement polymeric surfactant good water solubility and thickening ability. The sulfonic acid group of 2-acrylamido-2-methylpropanesulfonic acid acts as a salt-resistant group, improving the salt resistance of the oil displacement polymeric surfactant. Moreover, its saturated oxygen-containing five-membered ring possesses a certain degree of rigidity, further enhancing the temperature and shear resistance of the oil displacement polymeric surfactant. This results in a polymer with water solubility, thickening properties, salt resistance, and rigidity, achieving the purpose of polymer-driven oil displacement.
[0033] It should be noted that after the polymerization reaction, there are also post-processing steps such as crushing, drying, grinding, and sieving to obtain the final product; among them, the particle size of the sieved particles is controlled at 200~800μm.
[0034] Specifically, the chemical structural formula of a cationic surfactant is: .
[0035] In this embodiment of the invention, the cationic surfactant carries hydrophobic groups, enabling the formation of microdomains through the aggregation of hydrophobic ends during polymer grafting, thereby improving the viscoelasticity of the solution. Simultaneously, the synergistic effect of the betaine-containing dispersant and the cationic surfactant fully leverages the oil-displacing effect of the cationic surfactant, significantly reducing the oil-water interfacial tension, and together with polymer oil displacement, achieving the goal of highly efficient oil displacement by the surfactant.
[0036] In some preferred embodiments, step (1) includes the following sub-steps: (11) Palmitic acid, N,N-dimethyltrimethylenediamine and catalyst are added to a solvent and mixed well, and the prepolymer is obtained by reaction; (12) Add the prepolymer and ethyl chloride acrylate to the solvent, mix well and react to obtain a cationic surfactant.
[0037] In this embodiment of the invention, the chemical formula in the preparation process of the cationic surfactant is as follows: .
[0038] In some preferred embodiments, the molar ratio of palmitic acid to N,N-dimethyltrimethylenediamine is 1:(1.2~1.5) (e.g., it can be 1:1.2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45 or 1:1.5).
[0039] In some preferred embodiments, the molar ratio of the prepolymer to ethyl chloride acrylate is 1:(1.1~1.3) (e.g., it can be 1:1.1, 1:1.5, 1:1.2, 1:1.25 or 1:1.3).
[0040] In some preferred embodiments, step (11) includes: The catalyst is at least one of K2O / Al2O3 and KF / La2O3.
[0041] In some more preferred embodiments, the mass of the catalyst is 0.02wt% to 0.05wt% of the sum of the masses of palmitic acid and N,N-dimethyltrimethylenediamine (e.g., it can be 0.02wt%, 0.025wt%, 0.03wt%, 0.035wt%, 0.04wt%, 0.045wt% or 0.05wt%).
[0042] In some preferred embodiments, step (11) includes: The mass of the solvent is 80 wt% to 90 wt% of the sum of the masses of palmitic acid and N,N-dimethyltrimethylenediamine (e.g., 80 wt%, 82 wt%, 85 wt%, 86 wt%, 88 wt% or 90 wt%).
[0043] In some preferred embodiments, step (12) includes: The prepolymer and polymerization inhibitor are added to a solvent and mixed to obtain a first solution; ethyl chloride acrylate is added to a solvent and mixed to obtain a second solution; nitrogen gas is introduced into the first solution, and the second solution is added dropwise to the first solution to carry out the reaction, thereby obtaining a cationic surfactant.
[0044] In some preferred embodiments, in step (12): the dripping time is 30 to 40 minutes (e.g., 30 minutes, 35 minutes or 40 minutes).
[0045] In some preferred embodiments, in step (12): the mass of the polymerization inhibitor is 0.01wt% to 0.02wt% of the mass of the prepolymer (for example, it can be 0.01wt%, 0.012wt%, 0.015wt%, 0.016wt%, 0.018wt% or 0.2wt%).
[0046] In some preferred embodiments, the polymerization inhibitor is 1,1-diphenyl-2-trinitrophenylhydrazine.
[0047] Specifically, the prepolymer and polymerization inhibitor are added to a solvent and mixed to obtain a first solution, which is then transferred to a three-necked flask. Ethyl chloride acrylate is added to a solvent and mixed to obtain a second solution, which is then transferred to a constant-pressure dropping funnel. High-purity nitrogen gas is introduced into the three-necked flask to purge the first solution for 30 minutes to remove oxygen, while the temperature is simultaneously increased. The second solution is then added dropwise to the three-necked flask over 30-40 minutes to react and obtain a cationic surfactant.
[0048] In some preferred embodiments, the solvent in steps (11) and (12) is dimethyl sulfoxide; in step (12), the mass of the solvent is 80 wt% to 90 wt% of the sum of the mass of the prepolymer and the mass of chloroethyl acrylate (e.g., it can be 80 wt%, 82 wt%, 85 wt%, 86 wt%, 88 wt% or 90 wt%).
[0049] In some preferred embodiments, the reaction temperature of step (11) is 120~140℃ (e.g., 120℃, 125℃, 130℃, 135℃ or 140℃), and the reaction time is 10~12h (e.g., 10h, 10.5h, 11h, 11.5h or 12h).
[0050] In some preferred embodiments, the reaction temperature of step (12) is 75~80°C (e.g., 75°C, 76°C, 77°C, 78°C, 79°C or 80°C), and the reaction time is 5~7h (e.g., 5h, 5.5h, 6h, 6.5h or 7h).
[0051] In some preferred embodiments, in step (2): The dispersant is at least one of cocamidopropyl betaine, lauramide propyl betaine, and lauryl imidazoline betaine; The molecular weight regulator is at least one of glycerol, sodium hypophosphite, sodium formate, pentaerythritol, and thiourea.
[0052] In the embodiments of the present invention, the dispersant containing betaine has good compatibility and can be well compatible with various surfactants such as anionic, cationic and nonionic surfactants, and can be formulated to obtain a clear liquid or colloid.
[0053] In some preferred embodiments, in step (2): pH adjusters include sodium hydroxide; The composite solvent is a mixture of deionized water and acetone.
[0054] It should be noted that acetone in the composite solvent is used to dissolve tetrahydrofurfuryl acrylate.
[0055] In some preferred embodiments, the pH of the polymerization solution is 6.6 to 6.9 (e.g., 6.6, 6.7, 6.8 or 6.9).
[0056] In this embodiment of the invention, adjusting the pH of the polymerization solution to 6.6-6.9 not only avoids the acidity or alkalinity of the reaction medium from affecting the decomposition rate of the initiator and ensures the degree of polymerization of the oil displacement polymer, but also ensures that the reaction medium is neutral, making the preparation process more environmentally friendly.
[0057] In some preferred embodiments, in step (3): Initiators include a first initiator and a second initiator; The first initiator is at least one of azobisisobutyronitrile, azobisisobutyramidine hydrochloride, and azobisisobutyramidazole hydrochloride; The second initiator is a redox complex initiator, which includes an oxidant and a reducing agent.
[0058] In some preferred embodiments, the oxidant is at least one of potassium persulfate, ammonium persulfate, tert-butyl peroxide, cumene hydroperoxide, and tert-amyl hydroperoxide; and the reducing agent is at least one of sodium bisulfite, sodium metabisulfite, and ferrous sulfate.
[0059] In this embodiment of the invention, both azo-based high-temperature initiators and redox-based low-temperature initiators are used simultaneously during the polymerization process, which enables temperature gradient control and reaction kinetic optimization. In this way, the redox composite initiator is used to quickly initiate monomer conversion in the early stage of polymerization, and the heat released by the polymerization reaction causes the temperature of the reaction system to rise. This allows the azo initiator to maintain the reaction activity in the middle and later stages of polymerization, avoiding polymerization termination caused by initiator depletion, reducing chain transfer side reactions, and improving the polymerization conversion rate and polymer molecular weight while reducing energy consumption.
[0060] In some preferred embodiments, in step (3): The polymerization reaction is carried out in a nitrogen atmosphere. The initial temperature of the polymerization reaction is 0 to 2°C (for example, it can be 0°C, 1°C or 2°C) until the temperature of the polymerization reaction no longer increases.
[0061] In this invention, oxygen, acting as a polymerization inhibitor, affects the polymerization reaction of the oil displacement polymer. Therefore, nitrogen is introduced to remove oxygen and ensure the polymerization reaction proceeds normally. Since the polymerization process is exothermic, to avoid accelerating the reaction rate at higher temperatures, causing excessive heat release that is difficult to control and could lead to spillage or even burns, the initiation temperature is limited to a relatively low temperature (0~2℃). This allows the polymerization reaction to be completed solely through the exothermic reaction itself after initiation, and prevents the system temperature from becoming excessively high at the end of the reaction.
[0062] In some preferred embodiments, the mass parts of each raw material used to prepare the oil displacement surfactant are as follows: 130-150 parts of acrylamide (e.g., 130, 135, 140, 145, or 150 parts), 100-120 parts of acrylic acid (e.g., 100, 105, 110, 115, or 120 parts), 8-12 parts of cationic surfactant (e.g., 8, 9, 10, 11, or 12 parts), 20-30 parts of 2-acrylamide-2-methylpropanesulfonic acid (e.g., 20, 22, 24, 25, 26, 28, or 30 parts), and 2-4 parts of tetrahydrofurfuryl acrylate (e.g., 2, 2.5, 3, or 3.5 parts). 4-Hydroxybutylvinyl ether 2-4 parts (e.g., 2, 2.5, 3, 3.5 or 4 parts), dispersant 1-3 parts (e.g., 1, 1.5, 2, 2.5 or 3 parts), molecular weight regulator 1.5-2 parts (e.g., 1.5, 1.6, 1.7, 1.8, 1.9 or 2 parts), pH regulator 50-70 parts (e.g., 50, 55, 60, 65 or 70 parts), composite solvent 500-700 parts (e.g., 500, 550, 600, 650 or 700 parts), initiator 1-2 parts (e.g., 1.2, 1.5, 1.6, 1.8 or 2 parts).
[0063] In the embodiments of this invention, experiments have confirmed that, with other components remaining constant, if the amount of cationic surfactant is less than 8 parts, the prepared oil displacement polymeric agent will have too few hydrophobic long-chain groups, resulting in weak hydrophobic association, low viscosity, and poor oil displacement effect. However, if the amount of cationic surfactant is greater than 12 parts, the viscosity of the oil displacement polymeric agent will be too high, causing poor injection performance and difficulty in quickly reaching the oil-water interface. With other components remaining constant, if the amount of 2-acrylamide-2-methylpropanesulfonic acid is less than 20 parts, the solubility of the oil displacement polymeric agent will decrease, and the molecular chains will easily coil and precipitate under high temperature and high salt conditions, resulting in a significant loss of viscosity and ineffective driving. If the amount of 2-acrylamide-2-methylpropanesulfonic acid is greater than 30 parts, the molecular chains will be excessively extended, the solution viscosity will increase abnormally, and the injection pressure will surge, especially in low-permeability reservoirs where blockage is likely. Moreover, its strong negative charge makes it easier to adsorb onto positively charged rock surfaces. Tetrahydrofurfuryl acrylate (THFA) introduces a rigid cyclic structure with significant hydrophobicity and steric hindrance, providing hydrophobic association, improving interfacial activity, and further enhancing temperature resistance. With other components remaining constant, if the amount of THAFA is less than 2 parts, the association is weak, interfacial activity is insufficient, the ability to reduce oil-water interfacial tension is limited, and the emulsification effect on crude oil is poor. If the amount of THAFA is more than 4 parts, the hydrophobicity is too strong, the solubility of the oil displacement polymer in the aqueous phase decreases significantly, and the excessively large molecular size / rigidity leads to poor injectability. 4-Hydroxybutylvinyl ether (HBE) enhances hydrophilicity, water solubility, and improves molecular chain flexibility by introducing hydrophilic hydroxyl groups and ether bonds, contributing to system stability. With other components remaining constant, if the amount of 4-hydroxybutylvinyl ether is less than 2 parts, insufficient dosage will lead to poor solubility and affect the viscoelasticity of the solution due to poor molecular flexibility. If the amount of 4-hydroxybutylvinyl ether is more than 4 parts, it will cause excessive hydrophilization, destroying hydrophobic association, resulting in a significant decrease in viscosity and weakening interfacial activity. Betaine-based dispersants can stabilize the dispersion of functional monomers (especially hydrophobic monomers) in polymerization systems and product solutions, preventing self-polymerization or precipitation, and improving system compatibility and stability. With other components remaining constant, if the amount of dispersant is less than 1 part, it will affect dispersion stability and may even make hydrophobic monomers prone to phase separation during polymerization or dissolution. However, if the amount of dispersant is more than 3 parts, it will cause excessive solubilization / destruction of association, leading to a significant decrease in viscosity. Therefore, by selecting the above-mentioned raw materials and limiting the mass fraction of each raw material, an oil displacement polymeric surfactant with a viscosity-average molecular weight of less than 1600w was obtained, exhibiting good water solubility, thickening properties, excellent salt resistance, temperature and shear resistance, and excellent interfacial activity. It should be noted that this oil displacement polymeric surfactant is an amphoteric polyacrylamide, and the viscosity-average molecular weight of the oil displacement polymeric surfactant is between 950w and 1600w.
[0064] It should be noted that at least one can be any one or several mixed in any proportion.
[0065] The present invention also provides an oil displacement polymerizer, which is prepared by any of the preparation methods described above.
[0066] Unless otherwise specified, the raw materials used in this invention can be commercially available products or synthesized using existing methods.
[0067] In this invention, the use of "and / or" between multiple technical features indicates that these technical features are connected by an "and / or" relationship, meaning that it can be any one of these technical features, or any combination of two or more of these technical features.
[0068] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments.
[0069] In the following examples and comparative examples, the mass of each raw material is expressed in parts by mass.
[0070] Example 1 A method for preparing an oil displacement surfactant, comprising: (11) Add 250 parts palmitic acid, 122 parts N,N-dimethyltrimethylenediamine, 300 parts dimethyl sulfoxide, and 0.06 parts K2O / Al2O3 to a sealed reactor equipped with a stirrer and thermometer, mix well, purge with nitrogen for 20 minutes, seal, control the temperature at 120℃ using an electronic temperature control system, and react for 10 hours to obtain the prepolymer; (12) Mix 340 parts of prepolymer, 0.04 parts of 1,1-diphenyl-2-trinitrophenylhydrazine and 200 parts of dimethyl sulfoxide from step (11) to obtain a first solution, and transfer the first solution to a three-necked flask equipped with a stirrer, thermometer and constant pressure bottom liquid funnel; add 148 parts of ethyl chloride acrylate to 200 parts of dimethyl sulfoxide and mix to obtain a second solution, and transfer the second solution to a constant pressure dropping funnel; after passing high-purity nitrogen gas into the three-necked flask to remove oxygen for 20 min, start heating at the same time, control the temperature at 77°C through the electronic temperature control system, add the second solution dropwise for 35 min, react for 5 h, and then place the product in a reflux condenser (rotary evaporator) for evaporation and purification to obtain a cationic surfactant; (2) 140 parts acrylamide, 110 parts acrylic acid, 9 parts cationic surfactant from step (12), 22 parts 2-acrylamide-2-methylpropanesulfonic acid, 2 parts tetrahydrofurfuryl acrylate, 2 parts 4-hydroxybutyl vinyl ether, 1.5 parts dispersant (cocamidopropyl betaine), 1.5 parts molecular weight regulator (sodium hypophosphite), and 57 parts pH regulator (sodium hydroxide) were added to a composite solvent (500 parts deionized water and 120 parts acetone) and mixed to obtain a polymerization solution (pH value 6.8). (3) Transfer the polymerization solution from step (2) into the reactor, purge with nitrogen for 30 min to remove dissolved oxygen, cool the polymerization solution to 0°C, add 1.2 parts of initiator (0.6 parts of azobisisobutyronitrile, a total of 0.6 parts of tert-butyl peroxide and sodium metabisulfite) to initiate polymerization, and when the reaction temperature rises to the maximum temperature and no longer rises after 2 h, the oil displacement polymer block is obtained. Granulate, dry, grind and sieve the block to obtain the oil displacement polymer.
[0071] Example 2 A method for preparing an oil displacement surfactant, comprising: (11) Add 300 parts palmitic acid, 370 parts N,N-dimethyltrimethylenediamine, 550 parts dimethyl sulfoxide, and 0.07 parts K2O / Al2O3 to a sealed reactor equipped with a stirrer and thermometer, mix well, purge with nitrogen for 20 minutes, seal, control the temperature at 130℃ using an electronic temperature control system, and react for 11 hours to obtain the prepolymer; (12) Mix 365 parts of prepolymer, 0.04 parts of 1,1-diphenyl-2-trinitrophenylhydrazine and 230 parts of dimethyl sulfoxide from step (11) to obtain a first solution, and transfer the first solution to a three-necked flask equipped with a stirrer, thermometer and constant pressure bottom liquid funnel; add 159 parts of ethyl chloride acrylate to 200 parts of dimethyl sulfoxide and mix to obtain a second solution, and transfer the second solution to a constant pressure dropping funnel; after passing high-purity nitrogen into the three-necked flask to remove oxygen for 20 min, start heating at the same time, control the temperature at 78°C through the electronic temperature control system, add the second solution dropwise for 35 min, react for 5.5 h, and then place the product in a reflux condenser (rotary evaporator) for evaporation and purification to obtain a cationic surfactant; (2) 135 parts acrylamide, 120 parts acrylic acid, 8 parts cationic surfactant from step (12), 23 parts 2-acrylamide-2-methylpropanesulfonic acid, 3 parts tetrahydrofurfuryl acrylate, 3 parts 4-hydroxybutyl vinyl ether, 2 parts dispersant (lauromamide propyl betaine), 2 parts molecular weight regulator (sodium hypophosphite), and 59 parts pH regulator (sodium hydroxide) were added to a composite solvent (510 parts deionized water and 110 parts acetone) and mixed to obtain a polymerization solution (pH value 6.9). (3) Transfer the polymerization solution from step (2) into the reactor, purge with nitrogen for 30 min to remove dissolved oxygen, cool the polymerization solution to 1°C, add 1 part of initiator (0.5 parts of azobisisobutyronitrile, a total of 0.5 parts of tert-butyl peroxide and sodium metabisulfite) to initiate polymerization, and when the reaction temperature rises to the maximum temperature and no longer rises after 2 h, the oil displacement polymer block is obtained. Granulate, dry, grind and sieve the block to obtain the oil displacement polymer.
[0072] Example 3 A method for preparing an oil displacement surfactant, comprising: (11) Add 280 parts palmitic acid, 346 parts N,N-dimethyltrimethylenediamine, 510 parts dimethyl sulfoxide, and 0.06 parts K2O / Al2O3 to a sealed reactor equipped with a stirrer and thermometer, mix well, purge with nitrogen for 20 minutes, seal, control the temperature at 140℃ using an electronic temperature control system, and react for 12 hours to obtain the prepolymer; (12) Mix 380 parts of prepolymer, 0.04 parts of 1,1-diphenyl-2-trinitrophenylhydrazine and 260 parts of dimethyl sulfoxide from step (11) to obtain a first solution, and transfer the first solution to a three-necked flask equipped with a stirrer, thermometer and constant pressure bottom liquid funnel; add 165 parts of ethyl chloride acrylate to 200 parts of dimethyl sulfoxide and mix to obtain a second solution, and transfer the second solution to a constant pressure dropping funnel; after passing high-purity nitrogen into the three-necked flask to remove oxygen for 20 min, start heating at the same time, control the temperature at 80℃ through the electronic temperature control system, add the second solution dropwise for 35 min, react for 6 h, and then place the product in a reflux condenser (rotary evaporator) for evaporation and purification to obtain a cationic surfactant; (2) 130 parts acrylamide, 120 parts acrylic acid, 12 parts cationic surfactant from step (12), 25 parts 2-acrylamide-2-methylpropanesulfonic acid, 4 parts tetrahydrofurfuryl acrylate, 4 parts 4-hydroxybutyl vinyl ether, 1.5 parts dispersant (lauryl imidazoline betaine), 2 parts molecular weight regulator (sodium hypophosphite), and 60 parts pH regulator (sodium hydroxide) were added to a composite solvent (520 parts deionized water and 100 parts acetone) and mixed to obtain a polymerization solution (pH value 6.7). (3) Transfer the polymerization solution from step (2) into the reactor, purge with nitrogen for 30 minutes to remove dissolved oxygen, cool the polymerization solution to 0°C, add 1 part of initiator (0.5 parts of azobisisobutyronitrile, a total of 0.5 parts of tert-butyl peroxide and sodium metabisulfite) to initiate polymerization, and when the reaction temperature rises to the maximum temperature and no longer rises after 2 hours, the oil displacement polymer block is obtained. Granulate, dry, grind and sieve the block to obtain the oil displacement polymer.
[0073] Comparative Example 1 Comparative Example 1 is basically the same as Example 1, except that the catalyst K2O / Al2O3 is not added when preparing the cationic surfactant.
[0074] Comparative Example 2 Comparative Example 2 is basically the same as Example 1, except that cocamidopropyl betaine is not added when preparing the oil displacement polymer.
[0075] Specifically, in step (2), 140 parts of acrylamide, 110 parts of acrylic acid, 9 parts of the cationic surfactant from step (12), 22 parts of 2-acrylamide-2-methylpropanesulfonic acid, 2 parts of tetrahydrofurfuryl acrylate, 2 parts of 4-hydroxybutylvinyl ether, 1.5 parts of molecular weight regulator (sodium hypophosphite), and 57 parts of pH regulator (sodium hydroxide) are added to a composite solvent (501.5 parts of deionized water and 120 parts of acetone) and mixed to obtain a polymerization solution (pH value of 6.8).
[0076] Comparative Example 3 Comparative Example 3 is basically the same as Example 1, except that 2-acrylamide-2-methylpropanesulfonic acid is not added when preparing the cationic surfactant.
[0077] Specifically, in step (2), 140 parts of acrylamide, 110 parts of acrylic acid, 9 parts of the cationic surfactant from step (12), 2 parts of tetrahydrofurfuryl acrylate, 2 parts of 4-hydroxybutyl vinyl ether, 1.5 parts of dispersant (cocamidopropyl betaine), 1.5 parts of molecular weight regulator (sodium hypophosphite), and 57 parts of pH regulator (sodium hydroxide) are added to a composite solvent (522 parts of deionized water and 120 parts of acetone) and mixed to obtain a polymerization solution (pH value of 6.8).
[0078] Comparative Example 4 Comparative Example 4 is basically the same as Example 1, except that tetrahydrofurfuryl acrylate is not added when preparing the oil displacement polymer.
[0079] Specifically, in step (2), 140 parts of acrylamide, 110 parts of acrylic acid, 9 parts of the cationic surfactant from step (12), 22 parts of 2-acrylamide-2-methylpropanesulfonic acid, 2 parts of 4-hydroxybutyl vinyl ether, 1.5 parts of dispersant (cocamidopropyl betaine), 1.5 parts of molecular weight regulator (sodium hypophosphite), and 57 parts of pH regulator (sodium hydroxide) are added to a composite solvent (502 parts of deionized water and 120 parts of acetone) and mixed to obtain a polymerization solution (pH value of 6.8).
[0080] Comparative Example 5 Comparative Example 5 is basically the same as Example 1, except that no cationic surfactant is added when preparing the oil displacement polymer.
[0081] Specifically, in step (2), 140 parts of acrylamide, 110 parts of acrylic acid, 22 parts of 2-acrylamide-2-methylpropanesulfonic acid, 2 parts of tetrahydrofurfuryl acrylate, 2 parts of 4-hydroxybutyl vinyl ether, 1.5 parts of dispersant (cocamidopropyl betaine), 1.5 parts of molecular weight regulator (sodium hypophosphite), and 57 parts of pH regulator (sodium hydroxide) are added to a composite solvent (509 parts of deionized water and 120 parts of acetone) and mixed to obtain a polymerization solution (pH value of 6.8).
[0082] Comparative Example 6 Comparative Example 6 is basically the same as Example 1, except that 4-hydroxybutyl vinyl ether is not added when preparing the oil displacement polymer.
[0083] Specifically, in step (2), 140 parts of acrylamide, 110 parts of acrylic acid, 9 parts of the cationic surfactant from step (12), 22 parts of 2-acrylamide-2-methylpropanesulfonic acid, 2 parts of tetrahydrofurfuryl acrylate, 1.5 parts of dispersant (cocamidopropyl betaine), 1.5 parts of molecular weight regulator (sodium hypophosphite), and 57 parts of pH regulator (sodium hydroxide) are added to a composite solvent (502 parts of deionized water and 120 parts of acetone) and mixed to obtain a polymerization solution (pH value of 6.8).
[0084] Comparative Example 7 Commercially available oil displacement polymers, with molecular weights of 1600w to 1900w, were purchased from Henan Kaijie Water Treatment Co., Ltd.
[0085] The effects of the oil displacement surfactants prepared in each embodiment and the comparative example were compared and evaluated, and the test results are shown in Table 1. The evaluation methods were based on the national standard SY / T 5862-2020 "Technical Requirements for Polymers for Oil Displacement" and the Shengli Oilfield standard Q / SH1020 2191-2013 "Technical Requirements for the Selection of Surfactants for Oil Displacement", testing the filtration factor, interfacial tension, and emulsion water separation rate. The simulated brine viscosity test method is as follows: Weigh 1 / Sg (S is the solid content of the oil displacement polymer) of the oil displacement polymer sample, accurate to 0.001g, and slowly add it to (200-1 / S)g of simulated brine. Stir and dissolve at (500±20)r / min for 2h to obtain a solution with a mass concentration of 0.5%. Weigh 20g of the dissolved 0.5% concentration solution into a glass beaker, add 80g of simulated brine, and dissolve at (500±20)r / min for 30min to obtain a 0.1% test solution. Heat the 0.1% test solution to 85℃ and hold at that temperature for 10min. Use a Brookfield viscometer to test the viscosity at 6rpm on rotor #0.
[0086] The formula for the simulated saline solution used is as follows: take 5.0g magnesium chloride hexahydrate, 3.85g anhydrous calcium chloride and 39.7g sodium chloride, dissolve them in sequence, and then make up to a volume of 1L in a glass volumetric flask. The mineralization is 45890ppm.
[0087] Table 1 Analysis of the test data in Table 1 shows that the filter factor of the oil displacement polymer prepared in Example 1 is no higher than 1.14, indicating its fast dissolution rate and excellent solubility. Simultaneously, its viscosity in simulated brine at 85℃ is 58.5 cp, indicating excellent salt and temperature resistance. Furthermore, its interfacial tension is 0.0033 mN / m, and its emulsification water separation rate is 15.2%, thus exhibiting excellent surfactant displacement characteristics. Examples 2 and 3 also show similar effects. Therefore, the oil displacement polymer prepared in this invention possesses both surfactant and polymer displacement capabilities, which is beneficial for improving oilfield recovery.
[0088] The comparison between Example 1 and Comparative Example 1 shows that when a catalyst is not added during the preparation of cationic surfactants, the reaction is incomplete, leaving a large amount of unreacted raw materials. This results in a high amount of impurities in the prepared oil displacement surfactant, which greatly affects its solubility, leading to a high filtration factor, low viscosity of the simulated brine system, and a lack of oil displacement performance.
[0089] The comparison between Example 1 and Comparative Example 2 shows that when cocamidopropyl betaine is not added during the preparation of the oil displacement polymerizer, the compatibility and compatibility with the oil displacement polymerizer are lost during the dissolution process, resulting in poor solubility and low viscosity of the simulated brine system.
[0090] The comparison between Example 1 and Comparative Example 3 shows that when 2-acrylamide-2-methylpropanesulfonic acid is not added during the preparation of the oil displacement polymer, the loss of the salt-resistant group in the oil displacement polymer hinders the molecular weight extension, resulting in poorer solubility in the simulated wastewater system and a decrease in the viscosity of the simulated brine system.
[0091] The comparison between Example 1 and Comparative Example 4 shows that when tetrahydrofurfuryl acrylate is not added during the preparation of the oil displacement polymer, the viscosity of the simulated brine system will decrease at 85°C because the oil displacement polymer loses its temperature and shear resistance.
[0092] The comparison between Example 1 and Comparative Example 5 shows that when a cationic surfactant is not added during the preparation of the oil displacement polymer, the resulting oil displacement polymer does not have surface activity, resulting in low solubility, low viscosity of the simulated brine system, high interfacial tension, and high emulsification and water separation rate.
[0093] A comparison between Example 1 and Comparative Example 6 shows that when 4-hydroxybutyl vinyl ether is not added during the preparation of the oil displacement polymer, the resulting oil displacement polymer has a slightly lower viscosity, poorer solubility, and a higher filtration factor.
[0094] The comparison between Example 1 and Comparative Example 7 shows that commercially available oil displacement polymers only have the properties of polymer oil displacement and do not have the ability of surfactant oil displacement.
[0095] The parts of this invention not described in detail are techniques known to those skilled in the art.
[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing an oil displacement surfactant, characterized in that, include: (1) Palmitic acid, N,N-dimethyltrimethylenediamine and ethyl chloride acrylate are reacted to obtain a cationic surfactant; (2) Acrylamide, acrylic acid, the cationic surfactant, 2-acrylamide-2-methylpropanesulfonic acid, tetrahydrofurfuryl acrylate, 4-hydroxybutylvinyl ether, dispersant, molecular weight regulator and pH regulator are added to the composite solvent and mixed to obtain a polymerization solution; (3) Nitrogen gas is introduced into the polymerization solution, and then an initiator is added to initiate the polymerization reaction to obtain the oil displacement polymer.
2. The preparation method according to claim 1, characterized in that, Step (1) includes the following sub-steps: (11) Add palmitic acid, N,N-dimethyltrimethylenediamine and catalyst to a solvent and mix well, and then react to obtain a prepolymer; preferably, the molar ratio of palmitic acid to N,N-dimethyltrimethylenediamine is 1:(1.2~1.5). (12) The prepolymer and ethyl chloride acrylate are added to the solvent, mixed and reacted to obtain the cationic surfactant; preferably, the molar ratio of the prepolymer and ethyl chloride acrylate is 1:(1.1~1.3).
3. The preparation method according to claim 2, characterized in that, Step (11) includes: The catalyst is at least one of K₂O / Al₂O₃ and KF / La₂O₃; preferably, the mass of the catalyst is 0.02wt% to 0.05wt% of the sum of the masses of palmitic acid and N,N-dimethyltrimethylenediamine; and / or, The mass of the solvent is 80wt% to 90wt% of the sum of the masses of palmitic acid and N,N-dimethyltrimethylenediamine.
4. The preparation method according to claim 2, characterized in that, Step (12) includes: The prepolymer and polymerization inhibitor are added to the solvent and mixed to obtain a first solution; ethyl chloride acrylate is added to the solvent and mixed to obtain a second solution; nitrogen gas is introduced into the first solution, and the second solution is added dropwise to the first solution to react and obtain the cationic surfactant. Preferably, the dripping time is 30-40 minutes; Preferably, the mass of the polymerization inhibitor is 0.01wt% to 0.02wt% of the mass of the prepolymer; more preferably, the polymerization inhibitor is 1,1-diphenyl-2-trinitrophenylhydrazine.
5. The preparation method according to claim 2, characterized in that, The reaction temperature in step (11) is 120~140℃, and the reaction time is 10~12h; and / or, The reaction temperature in step (12) is 75~80℃ and the reaction time is 5~7h.
6. The preparation method according to claim 1, characterized in that, In step (2): The dispersant is at least one of cocamidopropyl betaine, lauramide propyl betaine, and lauryl imidazoline betaine; The molecular weight regulator is at least one of glycerol, sodium hypophosphite, sodium formate, pentaerythritol, and thiourea. And / or, The pH adjuster includes sodium hydroxide; preferably, the pH value of the polymerization solution is 6.6 to 6.
9. The composite solvent is a mixture of deionized water and acetone.
7. The preparation method according to claim 1, characterized in that, In step (3): The initiator includes a first initiator and a second initiator; The first initiator is at least one of azobisisobutyronitrile, azobisisobutyramidine hydrochloride, and azobisisobutyramidazole hydrochloride; The second initiator is a redox complex initiator, which includes an oxidant and a reductant; preferably, the oxidant is at least one of potassium persulfate, ammonium persulfate, tert-butyl peroxide, cumene hydroperoxide, and tert-amyl hydroperoxide; and the reductant is at least one of sodium bisulfite, sodium metabisulfite, and ferrous sulfate.
8. The preparation method according to claim 1, characterized in that, In step (3): The polymerization reaction begins at a temperature of 0-2°C and continues until the temperature of the polymerization reaction no longer increases.
9. The preparation method according to any one of claims 1 to 8, characterized in that: The mass fractions of each raw material used to prepare the oil displacement surfactant are as follows: 130-150 parts acrylamide, 100-120 parts acrylic acid, 8-12 parts of the cationic surfactant, 20-30 parts of 2-acrylamido-2-methylpropanesulfonic acid, 2-4 parts of tetrahydrofurfuryl acrylate, 2-4 parts of 4-hydroxybutylvinyl ether, 1-3 parts of dispersant, 1.5-2 parts of molecular weight regulator, 50-70 parts of pH regulator, 500-700 parts of composite solvent, and 1-2 parts of initiator.
10. An oil displacement polymer agent prepared by any one of the preparation methods described in claims 1 to 9.