Dual-response rare earth nanometer oil displacement and permeability enhancement agent, and preparation method and application thereof

Abstract

This invention discloses a dual-response rare-earth nano-oil displacement and permeation enhancer, its preparation method, and its application, belonging to the field of oilfield exploitation technology. The dual-response rare-earth nano-oil displacement and permeation enhancer of this invention comprises, by weight, 15-30 parts tracer, 25-45 parts amino acid-type zwitterionic surfactant, 10-20 parts thermosensitive block copolymer, 5-15 parts carboxymethyl chitosan, and 50-80 parts water. The tracer is rare-earth-doped nano-cerium oxide with a particle size of 5-30 nm and a zeta potential of -30 to -45 mV; it emits 550-600 nm light under 365 nm ultraviolet excitation. nm fluorescence; the amino acid-type zwitterionic surfactant is obtained by reacting sodium amino acid salt with fatty acid methyl ester; the sodium amino acid salt includes at least sodium methylhistidine salt; the thermosensitive block copolymer is obtained by polymerizing N-isopropylacrylamide, polyethylene glycol diacrylate, and propylene-1,3-sulfonyl lactone; the dual-responsive rare earth nano-oil displacement and permeation enhancer prepared by this invention has very high permeation and oil displacement capacity and salt resistance.

Description

Technical Field

[0001] This invention relates to the field of oilfield development technology, specifically to a dual-response rare earth nano-oil displacement and permeation enhancer, its preparation method, and its application. Background Technology

[0002] As the cornerstone of the global energy system, the efficient extraction of oil is crucial for ensuring national energy security. With the gradual depletion of conventional oil reservoirs, low-permeability reservoirs have become a development focus. However, traditional oil displacement technologies suffer from limitations such as single function, poor responsiveness, and high adsorption losses, resulting in limited recovery rates and high development costs, necessitating breakthrough technological innovation. Traditional oil displacement agents can only improve reservoir fluidity through single mechanisms such as viscosity enhancement and interfacial tension reduction, making them unsuitable for complex and variable reservoir environments such as high salinity and acidification. For example, significant changes in formation pH after waterflooding cause some oil displacement agents to experience a sharp decline in performance due to poor acid-base tolerance. While existing smart oil displacement agents possess single-response characteristics of temperature or pH, they cannot accommodate the multi-factor coupled reservoir conditions, leading to a mismatch between agent release timing and reservoir needs, thus limiting recovery rate improvements. Furthermore, while nanomaterials show potential, their high specific surface area and surface energy cause strong adsorption with the rock matrix in reservoir pores, resulting in significant loss of effective components, weakening oil displacement effects and significantly increasing extraction costs. Meanwhile, existing oil displacement agents lack effective tracer methods, making it difficult to monitor their distribution, release behavior, and effects in real time. This leads to delays in optimizing construction parameters and affects the improvement of oil recovery. Traditional tracer technologies (such as radioactive tracers) pose safety and environmental risks and have insufficient resolution.

[0003] In recent years, nanotechnology has brought new opportunities to the field of oil displacement, but existing nano-oil displacement permeation enhancers still have significant shortcomings: dual-response materials are mostly focused on the biomedical field and have poor adaptability to petroleum engineering; although imaging nanomaterials have fluorescence or MRI single-mode tracking functions, it is difficult to achieve both resolution and deep penetration; although surface modification technology can reduce adsorption, it often comes at the cost of sacrificing oil displacement performance and it is difficult to achieve a balance of multiple objectives.

[0004] To address the aforementioned problems, this invention proposes a dual-response rare earth nano-oil displacement and permeation enhancer. Summary of the Invention

[0005] The purpose of this invention is to provide a dual-response rare earth nano-oil displacement and permeation enhancer, its preparation method and application, in order to solve the technical problems mentioned in the background art.

[0006] The technical solution to achieve the objective of this invention is: The present invention provides a dual-response rare earth nano-oil displacement and permeation enhancer, wherein the raw material components, by mass parts, include: 15-30 parts by mass tracer, 25-45 parts by mass amino acid-type zwitterionic surfactant, 10-20 parts by mass thermosensitive block copolymer, 5-15 parts by mass carboxymethyl chitosan, and 50-80 parts by mass water.

[0007] The dual-response rare earth nano-oil displacement and permeation enhancer comprises, by mass parts: 20-25 parts tracer, 30-40 parts amino acid-type zwitterionic surfactant, 12-18 parts thermosensitive block copolymer, 8-12 parts carboxymethyl chitosan, and 60-70 parts water.

[0008] Furthermore, the tracer employs rare-earth-doped cerium oxide nanoparticles with a particle size of 5-30 nm, a zeta potential of -30 to -45 mV, and emits 550-600 nm fluorescence under 365 nm ultraviolet light excitation, and exhibits longitudinal relaxation enhancement in MRI imaging mode; the rare-earth elements include one or more of lanthanum, neodymium, and samarium; the doping molar ratio is 3-8%.

[0009] Furthermore, the amino acid-type zwitterionic surfactant is obtained by reacting sodium salt of amino acids with fatty acid methyl esters.

[0010] The amino acid-type zwitterionic surfactants include sodium lauroyl glutamate, potassium cocoyl glycinate, and sodium lauroyl sarcosinate.

[0011] Furthermore, the sodium salt of the amino acid includes at least one of sodium methylhistidine and sodium histidine.

[0012] The fatty acid methyl esters include methyl laurate, methyl myristate, methyl palmitate, and coconut oil fatty acid methyl ester.

[0013] Furthermore, the temperature-sensitive block copolymer is obtained by polymerizing N-isopropylacrylamide, polyethylene glycol diacrylate, and propylene-1,3-sulfonyl lactone.

[0014] Secondly, the present invention provides a method for preparing a dual-responsive rare earth nano-oil displacement and penetration enhancer as described in the first aspect, the preparation steps of which are as follows: (1) Weighing and preparing materials; (2) Dissolve the amino acid-type zwitterionic surfactant in a mixed solution of 270-280 parts by weight of dimethyl sulfoxide and 108-110 parts by weight of toluene, add 18-22 parts by weight of sodium hydroxide, heat to 118-122°C and stir, azeotropically remove water until the reflux becomes clear, then remove toluene by vacuum distillation, cool to room temperature and transfer to an ice bath and stir, add the thermosensitive block copolymer and stir for 23-25 ​​h, then add excess acetone under stirring, let stand for 2-4 h and filter and dry to obtain mixture A; (3) Disperse the tracer in an equal mass of water and ultrasonically disperse for 30-60 min to obtain a tracer dispersion; mix the mixture A, carboxymethyl chitosan and the remaining water, stir and disperse for 1-3 h, then add the tracer dispersion dropwise, stir at 40-50℃ for 2-4 h to obtain a dual-response rare earth nano-oil displacement and permeation enhancer.

[0015] Further, the preparation steps of the tracer are as follows: Cerium salt, rare earth salt, and 50wt% ethanol solution are mixed at a molar volume ratio of 1mol:(0.03~0.08)mol:(2~5)L, and then 2~3 times the amount of cerium salt trisodium citrate is added. The pH is adjusted to 8~10, and the mixture is reacted at 60~80℃ for 4~8h. After centrifugation, washing, drying, grinding, and drying at 890~910℃ for 110~130min, the tracer is obtained.

[0016] Further, the preparation steps of the amino acid-type zwitterionic surfactant are as follows: Amino acids are stirred with a 20wt% sodium hydroxide solution at room temperature for at least 10 minutes, then heated to remove water to obtain an amino acid sodium salt, wherein the molar ratio of amino acids to sodium hydroxide is 1:1; an equimolar amount of the amino acid sodium salt is mixed with fatty acid methyl ester, and then PEG200 is added, with a molar volume ratio of amino acid sodium salt to PEG200 of (0.04~0.06) mol:50 mL. The mixture is then heated to 188~192℃ and kept at this temperature for 5~7 hours. After cooling to room temperature, ultrapure water is added to dissolve the precipitate, and 0.1mol / L hydrochloric acid is slowly added dropwise to acidify the pH to 1~2, resulting in a large amount of white precipitate. The precipitate is filtered, washed with water, dried at 50℃, and then mixed with a 1M NaOH solution in anhydrous ethanol, wherein the amount of sodium hydroxide is equimolar with that of the amino acids. The mixture is then distilled under reduced pressure to obtain the amino acid-type zwitterionic surfactant.

[0017] Further, the preparation steps of the thermosensitive block copolymer are as follows: 20 parts by weight of N-isopropylacrylamide, 3-5 parts by weight of polyethylene glycol diacrylate, 2-4 parts by weight of propylene-1,3-sulfonyl lactone, and 215-225 parts by weight of dimethyl sulfoxide are mixed and then ultrasonically dispersed for 18-22 minutes. Then, 0.3-0.5 parts by weight of azobisisobutyronitrile (AIBN) initiator are added. After sealing, the mixture is placed in an oil bath preheated to 68-72°C and reacted for 47-49 hours. After the reaction is completed, the mixture is soaked in distilled water for 7 days, with the water changed every 24 hours to remove unreacted raw materials, and then dried.

[0018] Thirdly, the present invention provides an application of the dual-response rare earth nano-oil displacement and permeability enhancement agent as described in the first aspect, wherein the dual-response rare earth nano-oil displacement and permeability enhancement agent is applied to the exploitation of low-permeability oil reservoirs, and the dosage is 0.1% to 0.3% of the total wash oil mass.

[0019] By adopting the above technical solution, the present invention has the following beneficial effects: (1) The dual-response rare earth nano-oil displacement and permeation enhancer of the present invention comprises the following raw material components: tracer, amino acid-type zwitterionic surfactant, thermosensitive block copolymer, carboxymethyl chitosan, and water; the tracer endows the material with fluorescence / MRI dual-mode imaging tracking ability, which can monitor its distribution and release behavior in the reservoir in real time; the amino acid-type zwitterionic surfactant reduces the interfacial tension between oil and water through interfacial activity and enhances the fluidity of crude oil; the thermosensitive block copolymer, as a temperature-responsive unit, undergoes conformational changes in the high-temperature zone of the reservoir to regulate the release rate of the oil displacement agent; the carboxymethyl chitosan, as a pH-responsive carrier, releases active ingredients through protonation in acidified formations to achieve dual-mode intelligent regulation; the prepared dual-response rare earth nano-oil displacement and permeation enhancer can significantly improve the oil displacement efficiency with low usage and also has excellent salt resistance.

[0020] (2) The amino acid-type zwitterionic surfactant of the present invention is obtained by reacting sodium salt of amino acids with fatty acid methyl ester. Its molecular structure can undergo dynamic conformational transformation in the pH range of 6.5-8.5, thereby achieving precise interfacial activity regulation. When the pH value of the reservoir environment is in this range, the zwitterionic groups in the molecule are dynamically balanced through protonation / deprotonation, which triggers the molecular chain to transform from an extended conformation to a coiled conformation, thereby regulating its hydrophilic-lipophilic balance value. Specifically, under acidic conditions of pH≈6.5, the molecule is positively charged and enhances adsorption to the negatively charged rock surface through electrostatic interaction, reducing the oil-water interfacial tension. Under neutral to weakly alkaline conditions of pH≈8.5, the molecule is electrically neutral and its conformation shrinks, reducing adsorption loss and promoting oil droplet emulsification and dispersion. It can dynamically respond to changes in formation pH, intelligently regulate wetting reversal, interfacial activity and adsorption behavior, thereby improving oil displacement efficiency.

[0021] (3) The thermosensitive block copolymer of the present invention is obtained by polymerization of N-isopropylacrylamide, polyethylene glycol diacrylate and propylene-1,3-sulfonate lactone. It can undergo a reversible hydrophilic-hydrophobic phase transition in the temperature range of 35~45℃: when the reservoir temperature is lower than the lower critical dissolution temperature, the polyethylene glycol segments in the molecular chain are in an extended conformation and form hydrogen bonds with water molecules, exhibiting hydrophilicity; when the temperature is higher than the lower critical dissolution temperature, the hydrophobic group (N-isopropylacrylamide) dominates the molecular conformation contraction, which triggers phase separation, and macroscopically manifests as an increase in solution viscosity. This characteristic enables it to intelligently control the mobility ratio, maintain fluidity in the low temperature zone to penetrate into the reservoir pores, and block the high permeability layer by increasing viscosity in the high temperature zone, driving crude oil to flow to the low permeability zone, thereby inhibiting crossflow and expanding the swept volume; at the same time, the sulfonic acid group introduced by propylene-1,3-sulfonate lactone gives it salt resistance stability, ensuring that it can still maintain phase change responsiveness in high temperature and high salt reservoirs.

[0022] (4) In the preparation of the dual-response rare earth nano-oil displacement and permeation agent of the present invention, an amino acid-type zwitterionic surfactant is first reacted with a thermosensitive block copolymer. The amino acid-type zwitterionic surfactant is obtained by reacting sodium amino acid salt with fatty acid methyl ester. The molecular structure has both hydrophilic groups and hydrophobic chains. The sodium amino acid salt includes at least sodium methylhistidine salt and sodium histidine salt. The amine on the imidazole ring of the amino acid-type zwitterionic surfactant reacts with the sulfonyl lactone in the thermosensitive block copolymer to form a structure containing sulfonate ions and imidazole quaternary ammonium salt cations. The strong hydrophilicity of the sulfonate ions synergistically enhances the charge of the quaternary ammonium salt. The effects are significant: it greatly reduces the interfacial tension between oil and water and enhances the wetting reversal ability; quaternary ammonium cations enhance adsorption in acidified formations through protonation, and sulfonate ions strengthen gelation transformation through hydrogen bonding networks at high temperatures, synergistically regulating the mobility ratio with the LCST behavior of the temperature-sensitive block copolymer; the ion crosslinking structure can effectively resist the ion shielding effect in high salinity environments and maintain molecular conformational stability, so that the prepared nano-oil displacement and permeation enhancer has both high interfacial activity, intelligent dual-response release and excellent salt resistance, adapting to complex reservoir conditions, significantly improving the oil displacement efficiency of the dual-response rare earth nano-oil displacement and permeation enhancer and reducing adsorption loss. Detailed Implementation

[0023] To better understand the above technical solution, the following will provide a detailed explanation of the technical solution in conjunction with specific implementation methods.

[0024] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0025] The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0026] Polyethylene glycol diacrylate was prepared by reacting polyethylene glycol (Mw: 6000) with acryloyl chloride. For specific preparation methods, please refer to "Jiang Yu, Wu Yanye, Wei Fengjun, et al. Preparation and performance study of novel highly absorbent PGA / PEG crosslinked PNIPAM hydrogels [J]. New Chemical Materials, 2025, 53(04): 290-294. DOI: 10.19817 / j.cnki.issn1006-3536.2025.04.049." The reaction mixture was prepared as follows: 3.0 g of PEG was dissolved in 50 mL of dichloromethane, triethylamine was added, and the mixture was placed in an ice bath at 0 °C and stirred until completely dissolved. Then, excess acryloyl chloride was added dropwise over a period of 2-3 h. After the addition was complete, the mixture was kept at 0 °C for 2 h, and then heated to 40 °C and reacted for 48 h. The mixture was washed twice with saturated sodium bicarbonate, twice with brine, and twice with water. After drying with anhydrous magnesium sulfate overnight, the mixture was concentrated by rotary evaporation to obtain a reddish-brown liquid. Then, the liquid was repeatedly precipitated with petroleum ether and freeze-dried under vacuum to obtain polyethylene glycol diacrylate. Example 1 A method for preparing a dual-responsive rare-earth nano-oil displacement and penetration enhancer, comprising the following steps: (1) Weighing and preparing materials: 15 parts by weight of tracer, 25 parts by weight of amino acid-type zwitterionic surfactant, 10 parts by weight of thermosensitive block copolymer, 5 parts by weight of carboxymethyl chitosan, and 50 parts by weight of water; (2) Dissolve the amino acid-type zwitterionic surfactant in a mixed solution of 270 parts by mass of dimethyl sulfoxide and 108 parts by mass of toluene, add 18 parts by mass of sodium hydroxide, heat to 118°C and stir, azeotropically remove water until the reflux becomes clear, then remove toluene by vacuum distillation, cool to room temperature and transfer to an ice bath and stir, add the thermosensitive block copolymer and stir for 23 h, then add excess acetone under stirring, let stand for 2 h and filter and dry to obtain mixture A; (3) Disperse the tracer in an equal mass of water and ultrasonically disperse for 30 min to obtain a tracer dispersion; mix the mixture A, carboxymethyl chitosan and the remaining water, stir and disperse for 1 h, then add the tracer dispersion dropwise, stir at 40°C for 4 h to obtain a dual-response rare earth nano-oil displacement and permeation enhancer.

[0027] The preparation steps of the tracer are as follows: Cerium nitrate, lanthanum nitrate, and 50wt% ethanol solution are mixed in a molar volume ratio of 1mol:0.03mol:2L. Then, twice the amount of cerium salt trisodium citrate is added, the pH is adjusted to 8, and the mixture is reacted at 60℃ for 8 hours. After centrifugation, washing, drying, grinding, and drying at 890℃ for 130 minutes, the tracer is obtained.

[0028] The preparation steps of the amino acid-type zwitterionic surfactant are as follows: Methylhistidine is stirred with 20wt% sodium hydroxide solution at room temperature for at least 10 min, and then heated to remove water to obtain amino acid sodium salt, wherein the molar ratio of amino acid to sodium hydroxide is 1:1; an equimolar amount of amino acid sodium salt is mixed with coconut oil fatty acid methyl ester, and then PEG200 is added, with a molar volume ratio of amino acid sodium salt to PEG200 of 0.04 mol: 50 mL. The temperature is then raised to 188℃ and kept at that temperature for 5 h. After cooling to room temperature, ultrapure water is added to dissolve the mixture, and 0.1 mol / L hydrochloric acid is slowly added dropwise to acidify to pH 1, resulting in a large amount of white precipitate. The precipitate is filtered, washed with water, dried at 50℃, and then mixed with 1M NaOH in anhydrous ethanol solution, wherein the amount of sodium hydroxide and methylhistidine is equal. The mixture is then distilled under reduced pressure to obtain the amino acid-type zwitterionic surfactant.

[0029] The preparation steps of the thermosensitive block copolymer are as follows: 20 parts by mass of N-isopropylacrylamide, 3 parts by mass of polyethylene glycol diacrylate, 2 parts by mass of propylene-1,3-sulfonyl lactone, and 215 parts by mass of dimethyl sulfoxide are mixed and then ultrasonically dispersed for 18 min. Then, 0.3 parts by mass of azobisisobutyronitrile (AIBN) initiator are added. After sealing, the mixture is placed in an oil bath preheated to 68°C and reacted for 49 h. After the reaction is completed, the mixture is soaked in distilled water for 7 days, and the water is changed every 24 h to remove unreacted raw materials. Then, the mixture is dried.

[0030] Example 2 A method for preparing a dual-responsive rare-earth nano-oil displacement and penetration enhancer, comprising the following steps: (1) Weighing and preparing materials: 23 parts by mass tracer, 35 parts by mass amino acid-type zwitterionic surfactant, 15 parts by mass thermosensitive block copolymer, 10 parts by mass carboxymethyl chitosan, and 65 parts by mass water; (2) Dissolve the amino acid-type zwitterionic surfactant in a mixed solution of 275 parts by mass of dimethyl sulfoxide and 109 parts by mass of toluene, add 20 parts by mass of sodium hydroxide, heat to 120°C and stir, azeotropically remove water until the reflux becomes clear, then remove toluene by vacuum distillation, cool to room temperature and transfer to an ice bath and stir, add the thermosensitive block copolymer and stir for 24 h, then add excess acetone under stirring, let stand for 3 h and filter and dry to obtain mixture A; (3) Disperse the tracer in an equal mass of water and ultrasonically disperse for 45 min to obtain a tracer dispersion; mix the mixture A, carboxymethyl chitosan and the remaining water, stir and disperse for 2 h, then add the tracer dispersion dropwise, stir at 45°C for 3 h to obtain a dual-response rare earth nano-oil displacement and permeation enhancer.

[0031] The preparation steps of the tracer are as follows: Cerium nitrate, lanthanum nitrate, and 50wt% ethanol solution are mixed in a molar volume ratio of 1mol:0.05mol:4L. Then, twice the amount of cerium salt trisodium citrate is added, the pH is adjusted to 9, and the mixture is reacted at 70℃ for 6 hours. After centrifugation, washing, drying, grinding, and drying at 900℃ for 120 minutes, the tracer is obtained.

[0032] The preparation steps of the amino acid-type zwitterionic surfactant are as follows: Methylhistidine is stirred with 20wt% sodium hydroxide solution at room temperature for at least 10 min, and then heated to remove water to obtain amino acid sodium salt, wherein the molar ratio of amino acid to sodium hydroxide is 1:1; an equimolar amount of amino acid sodium salt is mixed with coconut oil fatty acid methyl ester, and then PEG200 is added, with a molar volume ratio of amino acid sodium salt to PEG200 of 0.05 mol: 50 mL. The mixture is then heated to 190℃ and kept at that temperature for 6 h. After cooling to room temperature, ultrapure water is added to dissolve the mixture, and 0.1 mol / L hydrochloric acid is slowly added dropwise to acidify the pH to 1, resulting in a large amount of white precipitate. The precipitate is filtered, washed with water, dried at 50℃, and then mixed with 1M NaOH in anhydrous ethanol solution, wherein the amounts of sodium hydroxide and methylhistidine are equal. The mixture is then distilled under reduced pressure to obtain the amino acid-type zwitterionic surfactant.

[0033] The preparation steps of the thermosensitive block copolymer are as follows: 20 parts by mass of N-isopropylacrylamide, 4 parts by mass of polyethylene glycol diacrylate, 3 parts by mass of propylene-1,3-sulfonyl lactone, and 220 parts by mass of dimethyl sulfoxide are mixed and then ultrasonically dispersed for 20 min. Then, 0.4 parts by mass of azobisisobutyronitrile (AIBN) initiator are added. After sealing, the mixture is placed in an oil bath preheated to 70°C and reacted for 48 h. After the reaction is completed, the mixture is soaked in distilled water for 7 days, with the water changed every 24 h to remove unreacted raw materials, and then dried.

[0034] Example 3 A method for preparing a dual-responsive rare-earth nano-oil displacement and penetration enhancer, comprising the following steps: (1) Weighing and preparing materials: 30 parts by weight of tracer, 45 parts by weight of amino acid-type zwitterionic surfactant, 20 parts by weight of thermosensitive block copolymer, 15 parts by weight of carboxymethyl chitosan, and 80 parts by weight of water; (2) Dissolve the amino acid-type zwitterionic surfactant in a mixed solution of 280 parts by mass of dimethyl sulfoxide and 110 parts by mass of toluene, add 22 parts by mass of sodium hydroxide, heat to 122°C and stir, azeotropically remove water until the reflux becomes clear, then remove toluene by vacuum distillation, cool to room temperature and transfer to an ice bath and stir, add the thermosensitive block copolymer and stir for 25 h, then add excess acetone under stirring, let stand for 4 h and filter and dry to obtain mixture A; (3) Disperse the tracer in an equal mass of water and ultrasonically disperse for 60 min to obtain a tracer dispersion; mix the mixture A, carboxymethyl chitosan and the remaining water, stir and disperse for 3 h, then add the tracer dispersion dropwise, stir at 50 °C for 2 h to obtain a dual-response rare earth nano-oil displacement and permeation enhancer.

[0035] The preparation steps of the tracer are as follows: Cerium nitrate, lanthanum nitrate, and 50wt% ethanol solution are mixed in a molar volume ratio of 1mol:0.08mol:5L. Then, trisodium citrate is added in an amount three times that of cerium salt. The pH is adjusted to 10. After reacting at 80℃ for 4 hours, the mixture is centrifuged, washed, dried, ground, and dried at 910℃ for 110 minutes to obtain the tracer.

[0036] The preparation steps of the amino acid-type zwitterionic surfactant are as follows: Methylhistidine is stirred with 20wt% sodium hydroxide solution at room temperature for at least 10 min, and then heated to remove water to obtain amino acid sodium salt, wherein the molar ratio of amino acid to sodium hydroxide is 1:1; an equimolar amount of amino acid sodium salt is mixed with coconut oil fatty acid methyl ester, and then PEG200 is added, with a molar volume ratio of amino acid sodium salt to PEG200 of 0.06 mol: 50 mL. The mixture is then heated to 192℃ and kept at that temperature for 5 h. After cooling to room temperature, ultrapure water is added to dissolve the mixture, and 0.1 mol / L hydrochloric acid is slowly added dropwise to acidify the pH to 2, resulting in a large amount of white precipitate. The precipitate is filtered, washed with water, dried at 50℃, and then mixed with 1M NaOH in anhydrous ethanol solution, wherein the amounts of sodium hydroxide and methylhistidine are equal. The mixture is then distilled under reduced pressure to obtain the amino acid-type zwitterionic surfactant.

[0037] The preparation steps of the thermosensitive block copolymer are as follows: 20 parts by mass of N-isopropylacrylamide, 5 parts by mass of polyethylene glycol diacrylate, 4 parts by mass of propylene-1,3-sulfonyl lactone, and 225 parts by mass of dimethyl sulfoxide are mixed and then ultrasonically dispersed for 22 min. Then, 0.5 parts by mass of azobisisobutyronitrile (AIBN) initiator is added. After sealing, the mixture is placed in an oil bath preheated to 72°C and reacted for 47 h. After the reaction is completed, the mixture is soaked in distilled water for 7 days, with the water changed every 24 h to remove unreacted raw materials, and then dried.

[0038] Example 4 The difference between Example 4 and Example 2 is that the raw material components of the dual-response rare earth nano-oil displacement and penetration enhancer include: 20 parts by mass tracer, 30 parts by mass amino acid-type zwitterionic surfactant, 12 parts by mass thermosensitive block copolymer, 8 parts by mass carboxymethyl chitosan, and 60 parts by mass water.

[0039] Example 5 The difference between Example 5 and Example 2 is that the raw material components of the dual-response rare earth nano-oil displacement and permeation enhancer include: 25 parts by mass tracer, 40 parts by mass amino acid-type zwitterionic surfactant, 18 parts by mass thermosensitive block copolymer, 12 parts by mass carboxymethyl chitosan, and 70 parts by mass water.

[0040] Comparative Example 1 The only difference between Comparative Example 1 and Example 2 is the preparation method of the dual-responsive rare earth nano-oil displacement and penetration enhancer. The preparation steps are as follows: (1) Weighing and preparing materials; (2) Disperse the tracer in an equal mass of water, add an amino acid-type zwitterionic surfactant, and ultrasonically disperse for 45 min to obtain a pre-dispersed tracer. (3) Mix the thermosensitive block copolymer, carboxymethyl chitosan and the remaining water, slowly add the pre-dispersed tracer, and stir at 45°C for 3 hours to obtain a dual-response rare earth nano-oil displacement and permeation enhancer.

[0041] Comparative Example 2 The only difference between Comparative Example 2 and Example 2 is that the amino acid-type zwitterionic surfactant used is potassium cocoyl glycinate.

[0042] Comparative Example 3 The only difference between Comparative Example 3 and Example 2 is that the thermosensitive block copolymer is a poly(N-isopropylacrylamide-b-polyethylene glycol) block copolymer with a number average molecular weight of 5,000-20,000.

[0043] Example of effect Displacement experiments were conducted using simulated formation water with mineralization of 10206.6 mg / L and 32125.6 mg / L. The experimental temperature was 65℃, and the injection rate was 0.3 mL / min. First, low-permeability core samples were saturated with simulated formation water, then saturated with crude oil to establish bound water saturation. During the percolation experiment, the core sample was placed in a percolation bottle containing percolation fluid, and the percolation and oil discharge volumes were recorded at different times to achieve percolation equilibrium. During the oil displacement experiment, water was first driven until the produced fluid contained 98% water. Then, 0.1% of the total wash oil mass of a dual-response rare-earth nano-displacement agent was injected at a constant rate to enhance permeability. After standing for 24 h, water driving continued until 98% water was produced. The oil content of the produced fluid during the displacement process was recorded, and the recovery rate was calculated.

[0044] Table 1 below shows the performance test results of the dual-response rare earth nano-oil displacement and penetration enhancers prepared in Examples 1-3 and Comparative Examples 1-5: Table 1 As shown in Table 1, the dual-response rare earth nano-oil displacement and permeation enhancers prepared in Examples 1-3 have good oil displacement effect and salt resistance.

[0045] In Comparative Example 1, the amino acid-type zwitterionic surfactant and the thermosensitive block copolymer were not mixed and reacted beforehand. In Comparative Example 2, the amino acid-type zwitterionic surfactant was potassium cocoyl glycinate. In Comparative Example 3, the thermosensitive block copolymer was poly(N-isopropylacrylamide-b-polyethylene glycol) block copolymer. The oil displacement effect of the prepared dual-response rare earth nano-oil displacement and permeation agents was inferior to that of the dual-response rare earth nano-oil displacement and permeation agents prepared in Examples 1-3, which had good oil displacement effect and salt resistance. Among them, Comparative Example 3, which used poly(N-isopropylacrylamide-b-polyethylene glycol) block copolymer, had even worse salt resistance and oil displacement effect.

[0046] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dual-response rare earth nano-oil displacement and penetration enhancer, characterized in that, By mass, the raw material components include: 15-30 parts tracer, 25-45 parts amino acid-type zwitterionic surfactant, 10-20 parts thermosensitive block copolymer, 5-15 parts carboxymethyl chitosan, and 50-80 parts water.

2. The dual-response rare earth nano-oil displacement and penetration enhancer according to claim 1, characterized in that, The tracer is rare earth-doped nano-cerium oxide with a particle size of 5~30 nm, a zeta potential of -30~-45 mV, and emits 550~600 nm fluorescence under 365 nm ultraviolet light excitation.

3. The dual-response rare earth nano-oil displacement and penetration enhancer according to claim 1, characterized in that, The amino acid-type zwitterionic surfactant is obtained by reacting sodium salt of amino acids with fatty acid methyl ester.

4. The dual-response rare earth nano-oil displacement and penetration enhancer according to claim 3, characterized in that, The sodium salt of the amino acid includes at least one of sodium methylhistidine and sodium histidine.

5. The dual-response rare earth nano-oil displacement and penetration enhancer according to claim 1, characterized in that, The thermosensitive block copolymer is obtained by polymerizing N-isopropylacrylamide, polyethylene glycol diacrylate, and propylene-1,3-sulfonyl lactone.

6. A method for preparing a dual-responsive rare-earth nano-oil displacement and penetration enhancer as described in any one of claims 1 to 5, characterized in that, The preparation steps are as follows: (1) Weighing and preparing materials; (2) Dissolve the amino acid-type zwitterionic surfactant in a mixed solution of 270-280 parts by weight of dimethyl sulfoxide and 108-110 parts by weight of toluene, add 18-22 parts by weight of sodium hydroxide, heat to 118-122°C and stir, azeotropically remove water until the reflux becomes clear, then remove toluene by vacuum distillation, cool to room temperature and transfer to an ice bath and stir, add the thermosensitive block copolymer and stir for 23-25 ​​h, then add excess acetone under stirring, let stand for 2-4 h and filter and dry to obtain mixture A; (3) Disperse the tracer in an equal mass of water and ultrasonically disperse for 30-60 min to obtain a tracer dispersion; mix the mixture A, carboxymethyl chitosan and the remaining water, stir and disperse for 1-3 h, then add the tracer dispersion dropwise, stir at 40-50℃ for 2-4 h to obtain a dual-response rare earth nano-oil displacement and permeation enhancer.

7. The preparation method of the dual-responsive rare earth nano-oil displacement and penetration enhancer according to claim 6, characterized in that, The preparation steps of the tracer are as follows: Cerium salt, rare earth salt, and 50wt% ethanol solution are mixed at a molar volume ratio of 1mol:(0.03~0.08)mol:(2~5)L, and then 2~3 times the amount of cerium salt trisodium citrate is added. The pH is adjusted to 8~10, and the mixture is reacted at 60~80℃ for 4~8h. After centrifugation, washing, drying, grinding, and drying at 890~910℃ for 110~130min, the tracer is obtained.

8. The preparation method of the dual-response rare earth nano-oil displacement and penetration enhancer according to claim 6, characterized in that, The preparation steps of the amino acid-type zwitterionic surfactant are as follows: Amino acids are stirred with a 20wt% sodium hydroxide solution at room temperature for at least 10 minutes, then heated to remove water to obtain amino acid sodium salt, wherein the molar ratio of amino acid to sodium hydroxide is 1:1; an equimolar amount of amino acid sodium salt is mixed with fatty acid methyl ester, and then PEG200 is added, with a molar volume ratio of amino acid sodium salt to PEG200 of (0.04~0.06) mol:50 mL. The mixture is then heated to 188~192℃ and kept at this temperature for 5~7 hours. After cooling to room temperature, ultrapure water is added to dissolve the precipitate, and 0.1mol / L hydrochloric acid is slowly added dropwise to acidify the pH to 1~2, resulting in a large amount of white precipitate. The precipitate is filtered, washed with water, dried at 50℃, and then mixed with a 1M NaOH solution in anhydrous ethanol, wherein the amount of sodium hydroxide is equimolar with that of the amino acid. The mixture is then distilled under reduced pressure to obtain the amino acid-type zwitterionic surfactant.

9. The preparation method of the dual-response rare earth nano-oil displacement and penetration enhancer according to claim 6, characterized in that, The preparation steps of the thermosensitive block copolymer are as follows: 20 parts by weight of N-isopropylacrylamide, 3-5 parts by weight of polyethylene glycol diacrylate, 2-4 parts by weight of propylene-1,3-sulfonyl lactone, and 215-225 parts by weight of dimethyl sulfoxide are mixed and then ultrasonically dispersed for 18-22 minutes. Then, 0.3-0.5 parts by weight of azobisisobutyronitrile (AIBN) initiator are added. After sealing, the mixture is placed in an oil bath preheated to 68-72°C and reacted for 47-49 hours. After the reaction is completed, the mixture is soaked in distilled water for 7 days, with the water changed every 24 hours to remove unreacted raw materials, and then dried.

10. The application of a dual-responsive rare earth nano-oil displacement and permeation enhancer as described in any one of claims 1 to 5, characterized in that, The dual-response rare earth nano-oil displacement and permeability enhancement agent is applied to the exploitation of low-permeability oil reservoirs, with a dosage of 0.1% to 0.3% of the total wash oil mass.

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