A pre-crosslinked surface active copolymer nano-microsphere profile control agent for oil production and its preparation method

Abstract

The present invention discloses a pre-crosslinked surface-active copolymerized nano-microsphere profile control agent for oil production and a preparation method thereof, belonging to the technical field of oilfield profile control and water plugging. The nano-microsphere profile control agent comprises the following components in parts by weight: 50-60 parts of acrylamide, 10-15 parts of acrylic acid, 5-10 parts of methacryloyloxyethyl trimethyl ammonium chloride, 2-4 parts of emulsifier, 0.5-1 parts of nonylphenol polyoxyethylene ether, 8-12 parts of coal-based Fischer-Tropsch liquid wax, 2-4 parts of 2-acrylamide-2-methylpropane sulfonic acid, 0.1-0.3 parts of cross-linking agent, and 0.05-0.1 parts of initiator; the emulsifier is prepared by reacting pentaerythritol with linoleic acid to generate a tetraester compound, then generating an epoxy compound under the action of formic acid and H2O2, and then reacting with lauryl alcohol. The copolymerized nano-microsphere profile control agent prepared by the present invention has a small particle size and can penetrate deep into the stratum. The moderate expansion property enables the microsphere solution to achieve step-by-step plugging.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield profile control and water plugging, and in particular to a pre-crosslinked surface active copolymer nano-microsphere profile control agent for oil production and a preparation method thereof. Background Art

[0002] The pores in low-permeability rocks are typically tiny pore throats and channels. Low permeability reservoirs in low-permeability oilfields present a significant challenge, resulting in insufficient crude oil production capacity. Common profile control and water-blocking agents, due to their large particle size, tend to form blockages at the formation entrance, preventing them from penetrating deeply into the formation. Therefore, their effective application in low-permeability reservoirs is limited. Microspheres, as a new type of profile control and water-blocking product, have attracted widespread attention due to their unique physical properties. Typical microsphere products typically have an initial diameter ranging from a few microns to tens of microns and are capable of expanding several times within a short period of time (e.g., minutes to hours). Once injected into the formation, the microspheres can penetrate deep into the formation, where their expansion effectively seals the formation's pore throats and pores, thereby increasing oil recovery. However, complex formation environments place higher demands on the use of microspheres. Existing polymer microspheres absorb water rapidly and expand rapidly upon contact with water. This can cause premature expansion at the formation entrance, hindering their migration deeper into the formation.

[0003] Chinese invention patent publication number CN110317289A discloses a polyacrylamide nanosphere profile control agent for oilfield chemical recovery. The agent comprises the following raw materials: an active agent, a reactive monomer, an oil-phase medium, a crosslinking agent, an initiator, a co-initiator, and water. The profile control agent prepared by this invention has controllable particle size, good salt tolerance, high water absorption, rapid expansion at room temperature, and a large particle size after swelling. It also exhibits high strength, elastic deformation, and resistance to breakage. However, its rapid expansion rate affects its migration into deeper formations. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a pre-crosslinked surfactant copolymer nano-microsphere profile control agent for oil production and a preparation method thereof.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A pre-crosslinked surface active copolymer nano-microsphere profile control agent for oil recovery, comprising the following components in parts by weight:

[0007] 50-60 parts of acrylamide, 10-15 parts of acrylic acid, 5-10 parts of methacryloyloxyethyltrimethylammonium chloride, 2-4 parts of emulsifier, 0.5-1 part of nonylphenol polyoxyethylene ether, 8-12 parts of coal-based Fischer-Tropsch wax, 2-4 parts of 2-acrylamido-2-methylpropanesulfonic acid, 0.1-0.3 parts of crosslinking agent, 0.05-0.1 parts of initiator;

[0008] The emulsifier is prepared by the following method:

[0009] S1: Pentaerythritol reacts with linoleic acid to form a tetraester compound; the reaction equation is as follows:

[0010] ;

[0011] S2: Tetraester compounds generate epoxy compounds under the action of formic acid and H2O2; the reaction equation is as follows:

[0012] ;

[0013] S3: The epoxy compound reacts with lauryl alcohol to form an emulsifier; the reaction equation is as follows:

[0014] ;

[0015] In step S1, the molar ratio of pentaerythritol to linoleic acid is 1:(4.1-4.5).

[0016] In step S2, the mass ratio of the tetraester compound to formic acid is 10:(3.5-4).

[0017] In step S3, the molar ratio of the epoxy compound to lauryl alcohol is 1:(8.2-8.4).

[0018] The cross-linking agent is generated by the reaction of 4,4'-dibromodiphenyl ether and undecenyl alcohol; the reaction equation is as follows:

[0019] ;

[0020] The molar ratio of the 4,4'-dibromodiphenyl ether to the undecenyl alcohol is 1:2.5.

[0021] The initiator is a mixture of ammonium persulfate and sodium bisulfite, and the molar ratio thereof is 1:1.

[0022] A method for preparing a pre-crosslinked surface active copolymer nano-microsphere profile control agent for oil recovery comprises the following steps:

[0023] (1) Weigh by weight: 50-60 parts of acrylamide, 10-15 parts of acrylic acid, 5-10 parts of methacryloyloxyethyl trimethyl ammonium chloride, 2-4 parts of emulsifier, 0.5-1 part of nonylphenol polyoxyethylene ether, 8-12 parts of coal-based Fischer-Tropsch wax, 2-4 parts of 2-acrylamido-2-methylpropanesulfonic acid, 0.1-0.3 parts of cross-linking agent, and 0.05-0.1 parts of initiator;

[0024] (2) Dissolve acrylamide, acrylic acid, cationic monomer, and 2-acrylamido-2-methylpropanesulfonic acid in deionized water, add a diluent, stir, heat, and dissolve to obtain an aqueous phase; mix and emulsify the coal-based Fischer-Tropsch liquid wax with an emulsifier to obtain an oil phase; slowly add the aqueous phase to the oil phase and shear at high speed to form a W / O emulsion;

[0025] (3) Dissolve the initiator in deionized water to obtain an initiator solution; under nitrogen protection, add the crosslinker to the above W / O emulsion and heat it to 35-50°C; add the initiator solution dropwise and react for 4-6 hours to obtain a copolymerized nano-microsphere profile control agent.

[0026] Due to the adoption of the above technical solution, the beneficial effects of the present invention include:

[0027] The copolymerized nano-microsphere profile control agent prepared by the present invention has a small particle size and can penetrate deep into the stratum. The moderate expansion property enables the microsphere solution to achieve efficient step-by-step plugging. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the H NMR spectrum of the tetraester compound prepared in step S1 of Example 1;

[0029] Figure 2 This is the H NMR spectrum of the epoxy compound prepared in step S2 of Example 1;

[0030] Figure 3 This is the H NMR spectrum of the emulsifier prepared in step S3 of Example 1;

[0031] Figure 4 This is the H NMR spectrum of the cross-linking agent prepared in Example 4. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to these embodiments.

[0033] Example 1 Preparation of emulsifier:

[0034] S1: 500 ml of toluene, 0.1 mol of pentaerythritol, 0.41 mol of linoleic acid, and 5 g of p-toluenesulfonic acid were placed in a reaction flask, stirred and mixed, and heated to 80°C for 15 h. During the reaction, water produced by the reaction was removed through a water separator. The mixture was cooled to room temperature, and the pH was adjusted to 7 with 0.2 M NaOH solution. The mixture was separated and washed three times with deionized water (300 ml each time). The organic phase was dried with 20 g of anhydrous sodium sulfate, filtered, and distilled under reduced pressure at 70°C for 2 h to obtain a tetraester compound. Its H NMR spectrum data are as follows: 1 HNMR (300 MHz, Chloroform- d ) δ 5.57 - 5.34 (m, 16H), 4.14 (s, 8H), 2.43 - 2.30 (m, 16H), 2.09 - 1.97 (m, 16H), 1.64 - 1.50 (m, 8H), 1.41 - 1.21 (m, 56H),0.95 - 0.84 (m, 12H);

[0035] S2: 300 ml of DMF, 50 g of a tetraester compound, and 3 g of a strong acid cation exchange resin were sequentially added to a reactor, stirred, and heated to 50°C. A mixed solution of 18 g of formic acid and 68 g of 30 wt% H2O2 was added dropwise over a period of 1 hour. The reaction was continued for 10 hours, cooled to room temperature, filtered, and distilled under reduced pressure at 60°C for 3 hours. The mixture was washed three times with deionized water (200 ml each time), and dried under vacuum at 60°C for 10 hours to obtain an epoxy compound. Its H NMR spectrum data are as follows: 1 H NMR (300 MHz, Chloroform- d ) δ 4.14 (s, 8H), 3.27 (q, J = 5.0 Hz, 8H), 3.18 (dt, J = 5.1, 4.1 Hz, 8H), 2.36 (t, J = 8.5Hz, 8H), 2.18 (dt, J = 13.6, 5.0 Hz, 4H), 1.92 (dt, J = 13.6, 4.9 Hz, 4H), 1.87 - 1.72 (m, 8H), 1.64 - 1.49 (m, 16H), 1.49 - 1.38 (m, 8H), 1.37 - 1.22(m, 48H), 0.95 - 0.82 (m, 12H);

[0036] S3: Add 1000 ml of dichloromethane and 0.82 mol of lauryl alcohol to a reaction flask, stir and mix, heat to 50°C, add 0.1 mol of epoxy compound and 5 g of fluoroboric acid, react for 8 h, cool to room temperature, and extract three times with deionized water (300 ml each time). Dry the organic phase with 50 g of anhydrous magnesium sulfate, filter, and distill under reduced pressure at 30°C for 2 h to obtain an emulsifier; its H NMR spectrum data are as follows: 1 H NMR (300 MHz, Chloroform- d ) δ 4.14 (d, J = 1.0 Hz, 8H), 3.86 (tdd, J = 8.4, 7.0, 5.8 Hz, 4H), 3.73 (td, J = 7.6, 6.2 Hz, 4H), 3.68 - 3.35(m, 24H), 3.01 (d, J = 5.8 Hz, 4H), 2.63 (d, J = 5.7 Hz, 4H), 2.36 (t, J =8.5 Hz, 8H), 1.87 (ddd, J = 14.4, 8.4, 7.7 Hz, 4H), 1.68 - 1.46 (m, 36H),1.45 - 1.17 (m, 208H), 0.96 - 0.82 (m, 36H).

[0037] Example 2 Preparation of emulsifier:

[0038] S1: 500 ml of toluene, 0.1 mol of pentaerythritol, 0.43 mol of linoleic acid, and 5 g of p-toluenesulfonic acid were placed in a reaction flask, stirred and mixed, and heated to 85°C for 12 h. During the reaction, water generated by the reaction was removed through a water separator. The mixture was cooled to room temperature, and the pH was adjusted to 7 with 0.2 M NaOH solution. The mixture was separated and washed three times with deionized water (200 ml each time). The organic phase was dried with 20 g of anhydrous sodium sulfate, filtered, and distilled under reduced pressure at 70°C for 2 h to obtain a tetraester compound.

[0039] S2: 300 ml of DMF, 50 g of a tetraester compound, and 3 g of a strong acid cation exchange resin were sequentially added to a reaction kettle, heated to 55°C with stirring, and a mixed solution of 19 g of formic acid and 71 g of 30 wt% H2O2 was added dropwise for 1 hour. The reaction was continued for 9 hours, cooled to room temperature, filtered, and distilled under reduced pressure at 60°C for 3 hours. The mixture was washed three times with deionized water (500 ml each time), and dried under vacuum at 60°C for 10 hours to obtain an epoxy compound.

[0040] S3: Add 1000 ml of dichloromethane and 0.83 mol of lauryl alcohol to a reaction flask, stir and mix, heat to 60°C, add 0.1 mol of epoxy compound and 5 g of fluoroboric acid, react for 7 hours, cool to room temperature, extract three times with deionized water (300 ml each time), dry the organic phase with 50 g of anhydrous magnesium sulfate, filter, and distill under reduced pressure at 30°C for 2 hours to obtain an emulsifier.

[0041] Example 3 Preparation of emulsifier:

[0042] S1: 500 ml of toluene, 0.1 mol of pentaerythritol, 0.45 mol of linoleic acid, and 5 g of p-toluenesulfonic acid were placed in a reaction flask, stirred and mixed, and heated to 90°C for 10 h. During the reaction, water generated by the reaction was removed through a water separator. The mixture was cooled to room temperature, and the pH was adjusted to 7 with 0.2 M NaOH solution. The mixture was separated and washed three times with deionized water (200 ml each time). The organic phase was dried with 20 g of anhydrous sodium sulfate, filtered, and distilled under reduced pressure at 70°C for 2 h to obtain a tetraester compound.

[0043] S2: 300 ml of DMF, 50 g of a tetraester compound, and 3 g of a strong acid cation exchange resin were sequentially added to a reaction kettle, heated to 60°C with stirring, and a mixed solution of 20 g of formic acid and 75 g of 30 wt% H2O2 was added dropwise for 1 hour. The reaction was continued for 8 hours, cooled to room temperature, filtered, and distilled under reduced pressure at 60°C for 3 hours. The mixture was washed three times with deionized water (500 ml each time), and dried under vacuum at 60°C for 10 hours to obtain an epoxy compound.

[0044] S3: Add 1000 ml of dichloromethane and 0.84 mol of lauryl alcohol to a reaction flask, stir and mix, heat to 70°C, add 0.1 mol of epoxy compound and 5 g of fluoroboric acid, react for 6 hours, cool to room temperature, extract three times with deionized water (300 ml each time), dry the organic phase with 50 g of anhydrous magnesium sulfate, filter, and distill under reduced pressure at 30°C for 2 hours to obtain an emulsifier.

[0045] Example 4 Preparation of cross-linking agent:

[0046] 300 ml of tetrahydrofuran, 0.1 mol of 4,4'-dibromodiphenyl ether, 0.25 mol of undecenyl alcohol, and 0.01 mol of copper acetylacetonate were added to a reaction flask, stirred and mixed, and the temperature was raised to 90°C. 0.6 mol of potassium carbonate and 0.01 mol of 8-hydroxyquinoline were added, and the reaction was carried out for 9 h. The mixture was cooled to room temperature and distilled under reduced pressure at 40°C for 2 h. The mixture was washed three times with deionized water (150 ml each time), and dried under vacuum at 80°C for 24 h to obtain a cross-linking agent. Its H NMR spectrum data are as follows: 1 H NMR (300 MHz, Chloroform- d) δ 6.97 - 6.83(m, 8H), 5.87 - 5.67 (m, 2H), 5.13 (ddt, J = 10.3, 2.3, 1.5 Hz, 2H), 4.95(ddt, J = 17.2, 2.5, 1.3 Hz, 2H), 4.00 (t, J = 6.3 Hz, 4H), 2.03 (tdt, J =8.1, 6.9, 1.4 Hz, 4H), 1.83 - 1.68 (m, 4H), 1.52 - 1.39 (m, 4H), 1.39 - 1.22(m, 20H).

[0047] Example 5 Preparation of Copolymer Nanosphere Profile Control Agent:

[0048] (1) Weigh: 50 g acrylamide, 10 g acrylic acid, 5 g methacryloyloxyethyl trimethyl ammonium chloride, 2 g emulsifier (prepared in Example 1), 0.5 g nonylphenol polyoxyethylene ether, 8 g coal-based Fischer-Tropsch wax, 2 g 2-acrylamido-2-methylpropanesulfonic acid, 0.1 g cross-linking agent (prepared in Example 4), and 0.05 g initiator (0.034 g ammonium persulfate and 0.016 g sodium bisulfite).

[0049] (2) Dissolve the above-mentioned acrylamide, acrylic acid, methacryloyloxyethyl trimethyl ammonium chloride, and 2-acrylamido-2-methylpropanesulfonic acid in 1 L of deionized water, add nonylphenol polyoxyethylene ether, stir and heat to 40°C to dissolve, and obtain an aqueous phase; mix the coal-based Fischer-Tropsch liquid wax with the emulsifier, and emulsify at 8000 rpm for 10 minutes to obtain an oil phase; add the aqueous phase to the oil phase, and shear at 12000 rpm for 15 minutes to form a W / O emulsion;

[0050] (3) Dissolve the initiator in 20 ml of deionized water to obtain an initiator solution; under nitrogen protection, add the crosslinker to the above W / O emulsion and heat it to 35 °C; add the initiator solution dropwise for 5 minutes, react for 6 hours, cool to room temperature, add 2 L of anhydrous ethanol, stir and precipitate, filter, wash three times with anhydrous ethanol (300 ml each time), and vacuum dry at 60 °C for 10 hours to obtain a copolymerized nanosphere profile control agent.

[0051] Example 6 Preparation of Copolymer Nanosphere Profile Control Agent:

[0052] (1) Weigh: 56 g acrylamide, 13 g acrylic acid, 8 g methacryloyloxyethyl trimethyl ammonium chloride, 3 g emulsifier (prepared in Example 2), 0.8 g nonylphenol polyoxyethylene ether, 10 g coal-based Fischer-Tropsch wax, 3 g 2-acrylamido-2-methylpropanesulfonic acid, 0.2 g cross-linking agent (prepared in Example 4), and 0.08 g initiator (0.055 g ammonium persulfate and 0.025 g sodium bisulfite).

[0053] (2) Dissolve the above-mentioned acrylamide, acrylic acid, methacryloyloxyethyl trimethyl ammonium chloride, and 2-acrylamido-2-methylpropanesulfonic acid in 1 L of deionized water, add nonylphenol polyoxyethylene ether, stir and heat to 40°C to dissolve, and obtain an aqueous phase; mix the coal-based Fischer-Tropsch liquid wax with the emulsifier, and emulsify at 8000 rpm for 10 minutes to obtain an oil phase; add the aqueous phase to the oil phase, and shear at 12000 rpm for 15 minutes to form a W / O emulsion;

[0054] (3) Dissolve the initiator in 20 ml of deionized water to obtain an initiator solution; under nitrogen protection, add the crosslinker to the above W / O emulsion and heat it to 40 °C; add the initiator solution dropwise for 5 minutes, react for 5 hours, cool to room temperature, add 2 L of anhydrous ethanol, stir and precipitate, filter, wash three times with anhydrous ethanol (300 ml each time), and vacuum dry at 60 °C for 10 hours to obtain a copolymerized nanosphere profile control agent.

[0055] Example 7 Preparation of Copolymer Nanosphere Profile Control Agent:

[0056] (1) Weigh: 60 g acrylamide, 15 g acrylic acid, 10 g methacryloyloxyethyl trimethyl ammonium chloride, 4 g emulsifier (prepared in Example 3), 1 g nonylphenol polyoxyethylene ether, 12 g coal-based Fischer-Tropsch wax, 4 g 2-acrylamido-2-methylpropanesulfonic acid, 0.3 g cross-linking agent (prepared in Example 4), and 0.1 g initiator (0.069 g ammonium persulfate and 0.031 g sodium bisulfite).

[0057] (2) Dissolve the above-mentioned acrylamide, acrylic acid, methacryloyloxyethyl trimethyl ammonium chloride, and 2-acrylamido-2-methylpropanesulfonic acid in 1 L of deionized water, add nonylphenol polyoxyethylene ether, stir and heat to 40°C to dissolve, and obtain an aqueous phase; mix the coal-based Fischer-Tropsch liquid wax with the emulsifier, and emulsify at 8000 rpm for 10 minutes to obtain an oil phase; add the aqueous phase to the oil phase, and shear at 12000 rpm for 15 minutes to form a W / O emulsion;

[0058] (3) Dissolve the initiator in 20 ml of deionized water to obtain an initiator solution; under nitrogen protection, add the crosslinker to the above W / O emulsion and heat it to 50 °C; add the initiator solution dropwise for 5 minutes, react for 6 hours, cool to room temperature, add 2 L of anhydrous ethanol, filter, wash three times with anhydrous ethanol (300 ml each time), and vacuum dry at 60 °C for 10 hours to obtain a copolymerized nanosphere profile control agent.

[0059] Comparative Example 1

[0060] The raw materials and preparation method of the nano-microsphere profile control agent are basically the same as those in Example 6, except that the emulsifier (prepared in Example 2) is replaced with an emulsifier of equal mass prepared by the following method:

[0061] The preparation method of the emulsifier is basically the same as that of Example 2, except that the linoleic acid used in step S1 is replaced by an equal molar amount of oleic acid.

[0062] Comparative Example 2

[0063] The raw materials and preparation method of the nano-microsphere profile control agent are basically the same as those in Example 6, except that the emulsifier (prepared in Example 2) is replaced with an emulsifier of equal mass prepared by the following method:

[0064] The preparation method of the emulsifier is substantially the same as that of Example 2, except that the pentaerythritol used in step S1 is replaced by an equal molar amount of 1,3-propylene glycol.

[0065] Comparative Example 3

[0066] The raw materials and preparation method of the nano-microsphere profile control agent are basically the same as those in Example 6, except that the emulsifier (prepared in Example 2) is replaced with an emulsifier of equal mass prepared by the following method:

[0067] The preparation method of the emulsifier is basically the same as that of Example 2, except that the lauryl alcohol used in step S3 is replaced by an equimolar amount of n-hexanol.

[0068] Comparative Example 4

[0069] The raw materials and preparation method of the nanosphere profile control agent are basically the same as those in Example 6, except that the cross-linking agent (prepared in Example 4) is replaced with an equal mass of a cross-linking agent prepared by the following method:

[0070] The preparation method of the cross-linking agent is substantially the same as that of Example 4, except that 4,4'-dibromodiphenyl ether is replaced by an equal molar amount of 4,4'-dibromobiphenyl.

[0071] Comparative Example 5

[0072] The raw materials and preparation method of the nanosphere profile control agent are basically the same as those in Example 6, except that the cross-linking agent (prepared in Example 4) is replaced with an equal mass of a cross-linking agent prepared by the following method:

[0073] The preparation method of the cross-linking agent is substantially the same as that of Example 4, except that 4,4'-dibromodiphenyl ether is replaced by an equal molar amount of 1,8-dibromooctane.

[0074] Comparative Example 6

[0075] The raw materials and preparation method of the nanosphere profile control agent are basically the same as those in Example 6, except that the cross-linking agent (prepared in Example 4) is replaced with an equal mass of a cross-linking agent prepared by the following method:

[0076] The preparation method of the cross-linking agent is substantially the same as that of Example 4, except that undecenyl alcohol is replaced by an equimolar amount of 3-buten-1-ol.

[0077] The raw materials used in the examples and comparative examples of the present application are as follows: nonylphenol polyoxyethylene ether model NP-10; strong acid cation exchange resin is a polymer of divinylbenzene and sodium vinylbenzene sulfonate, brand Amberlite® IMACHP1110 resin; coal-based Fischer-Tropsch liquid wax model is Fischer-Tropsch paraffin liquid wax No. 2, with a Saibot number of +30, a distillation range of 179.5-308.5°C, and an alkane content of 99.9wt%, produced by Ningxia Coal Industry Co., Ltd. of the State Energy Group.

[0078] The profile control agents prepared in Examples 5-7 and Comparative Examples 1-6 were subjected to a particle size test: 0.1 g of nanospheres were weighed in a beaker, 100 mL of 3# white oil was added, and the mixture was stirred for 15 min and then ultrasonicated for 10 min. The particle size of the copolymerized nanosphere profile control agent was measured using a laser particle size analyzer.

[0079] The copolymerized nanosphere profile control agents prepared in Examples 5-7 and Comparative Examples 4-6 were subjected to swelling performance testing: the copolymerized nanosphere profile control agents were placed in an aqueous dispersion with a NaCl concentration of 5000 mg / L, wherein the copolymerized nanosphere profile control agent content was 0.3 mg / L. The median particle size of the copolymerized nanosphere profile control agents at 0 h (initial, immediately after preparation), 1 d, 3 d, 5 d, and 15 d was measured using a laser particle size analyzer. The volume swelling ratio was calculated as follows: median particle size after swelling / initial median particle size.

[0080] Table 1 Performance test data table

[0081]

[0082] From the data of Examples 5, 6 and 7 in Table 1, it can be seen that the copolymerized nano-microsphere profile control agent prepared in the present invention has a small particle size and can penetrate deep into the formation. The moderate expansion property enables the microsphere solution to achieve efficient step-by-step plugging.

[0083] The emulsifier prepared by the present invention contains lipophilic long-chain alkyl groups, hydrophilic hydroxyl groups, and ether bonds, which can reduce the interfacial tension between the aqueous and oil phases, reduce the aggregation of droplets, and thus improve the stability of the emulsion. The polyhydroxyl hydrophilic groups in the emulsifier prepared by the present invention promote the formation of more polymer particles, thereby effectively reducing the particle size of the microspheres. The branched structure derived from pentaerythritol provides a steric hindrance effect, preventing droplet collision and merging, and inhibiting the coarsening of the nano-microspheres. The long alkyl chains fully extend in the oil phase, forming a thick hydrophobic barrier, effectively preventing droplet collisions and reducing the particle size of the nano-microspheres.

[0084] The molecular structure of the cross-linking agent prepared by the present invention contains a benzene ring structural unit, a flexible ether bond, and an alkyl chain segment. The rigid characteristics of the benzene ring structure and the hydrophobic alkyl chain form a physical barrier to the diffusion of water molecules, slowing down the solvent penetration rate, thereby slowing down the expansion rate of the copolymerized nano-microsphere profile control agent during the water absorption process; the presence of the flexible alkyl chain and the ether bond gives the polymer chain segment a certain flexibility and extensibility, which is conducive to the diffusion of water molecules, thereby improving the overall expansion performance of the profile control agent; the synergistic effect of the two enables the copolymerized nano-microsphere profile control to have good water absorption and expansion capabilities while maintaining structural stability. The profile control agents used in Comparative Examples 4 and 6 have a slow expansion rate and a small swelling multiple, making it impossible to establish an effective plugging in time, thereby weakening their plugging ability. The profile control agent used in Comparative Example 5 has an excessively fast expansion rate, which is not conducive to its entry into the deep formation, reducing its plugging performance.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. However, any equivalent changes, modifications and evolutions made by ordinary technicians in this field without departing from the scope of the technical solution of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of protection of the technical solution of the present invention.

Claims

1. A pre-crosslinked surface active copolymer nano-microsphere profile control agent for oil recovery, characterized in that: The composition comprises the following components in parts by weight: 50-60 parts of acrylamide, 10-15 parts of acrylic acid, 5-10 parts of methacryloyloxyethyltrimethylammonium chloride, 2-4 parts of emulsifier, 0.5-1 part of nonylphenol polyoxyethylene ether, 8-12 parts of coal-based Fischer-Tropsch wax, 2-4 parts of 2-acrylamido-2-methylpropanesulfonic acid, 0.1-0.3 parts of crosslinking agent, 0.05-0.1 parts of initiator; The emulsifier is prepared by the following method: S1: Pentaerythritol reacts with linoleic acid to form a tetraester compound; S2: Tetraester compounds generate epoxy compounds under the action of formic acid and H2O2; S3: Epoxide reacts with lauryl alcohol to form an emulsifier; The cross-linking agent is prepared by reacting 4,4'-dibromodiphenyl ether with undecenyl alcohol; The initiator is a mixture of ammonium persulfate and sodium bisulfite.

2. The pre-crosslinked surface active copolymer nano-microsphere profile control agent for oil production according to claim 1, characterized in that: In step S1, the molar ratio of pentaerythritol to linoleic acid is 1:(4.1-4.5).

3. The pre-crosslinked surface active copolymer nano-microsphere profile control agent for oil production according to claim 1, characterized in that: In step S2, the mass ratio of the tetraester compound to formic acid is 10:(3.6-4).

4. The pre-crosslinked surface active copolymer nano-microsphere profile control agent for oil production according to claim 1, characterized in that: In step S3, the molar ratio of the epoxy compound to lauryl alcohol is 1:(8.2-8.4).

5. The pre-crosslinked surface active copolymer nano-microsphere profile control agent for oil recovery according to claim 1, characterized in that: The molar ratio of the 4,4'-dibromodiphenyl ether to the undecenyl alcohol is 1:2.

5.

6. The pre-crosslinked surface active copolymer nano-microsphere profile control agent for oil production according to claim 1, characterized in that: The molar ratio of ammonium persulfate to sodium bisulfite is 1:

1.

7. A method for preparing the pre-crosslinked surface active copolymer nano-microsphere profile control agent for oil production according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Weigh by weight: 50-60 parts of acrylamide, 10-15 parts of acrylic acid, 5-10 parts of methacryloyloxyethyl trimethyl ammonium chloride, 2-4 parts of emulsifier, 0.5-1 part of nonylphenol polyoxyethylene ether, 8-12 parts of coal-based Fischer-Tropsch wax, 2-4 parts of 2-acrylamido-2-methylpropanesulfonic acid, 0.1-0.3 parts of cross-linking agent, and 0.05-0.1 parts of initiator; (2) Dissolve acrylamide, acrylic acid, cationic monomer, and 2-acrylamido-2-methylpropanesulfonic acid in deionized water, add a diluent, stir, heat, and dissolve to obtain an aqueous phase; mix and emulsify the coal-based Fischer-Tropsch liquid wax with an emulsifier to obtain an oil phase; add the aqueous phase to the oil phase and shear at high speed to form a W / O emulsion; (3) Dissolve the initiator in deionized water to obtain an initiator solution; under nitrogen protection, add the crosslinker to the above W / O emulsion and heat it to 35-50°C; add the initiator solution dropwise and react for 4-6 hours to obtain a copolymerized nano-microsphere profile control agent.

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