Reverse wetting agent for improving oil recovery ratio as well as preparation method and application of reverse wetting agent

Abstract

The invention discloses a reverse wetting agent for improving the oil recovery rate and a preparation method and application thereof, and relates to the technical field of reverse wetting agents. Comprising the following components in parts by weight: 3-7 parts of olefin sulfonate, 2-5 parts of iso-tridecanol polyoxyethylene ether, 10-25 parts of a wetting reversal compound, 0.5-3 parts of isopropanol, 1-5 parts of triethanolamine and 60-70 parts of water. The preparation method comprises the following steps: adding olefin sulfonate, iso-tridecanol polyoxyethylene ether, isopropanol and triethanolamine into water, stirring and dissolving, then adding the wetting reversal compound, and continuously stirring and mixing uniformly, thereby obtaining the water-based cleaning agent. The wetting reversal component in the petroleum wetting reversal agent prepared by the invention has strong bonding force with rock, so that the wettability of the rock surface is maintained for a long time, and the recovery rate of petroleum is improved.

Description

Technical Field

[0001] This invention relates to the field of wetting reversal agents, specifically to a wetting reversal agent for improving oil recovery, its preparation method, and its application. Background Technology

[0002] In the field of oil extraction, enhancing oil recovery has always been a core issue of great concern to the industry. With the continuous exploitation and depletion of global oil resources, how to efficiently extract more oil from reservoirs has become a key challenge for the sustainable development of the oil industry. Currently, improving oil recovery by altering the wettability of rock surfaces is an important and widely researched method. Wetting reversal agents play a crucial role in this process, changing the wettability of rock surfaces, reducing the adhesion between crude oil and the rock surface, thereby promoting the detachment of crude oil from the rock surface, improving crude oil fluidity, and ultimately enhancing oil recovery. However, existing wetting reversal agents have a significant problem: insufficient binding and fixation ability with the rock. In actual oil extraction processes, reservoir environments are complex, with various external forces acting, such as the scouring effect of injected water and fluctuations in formation pressure. Under these external forces, existing wetting reversal agents can easily detach from the rock surface. Once the wetting reversal agent detaches from the rock surface, it can no longer perform its function of changing the wettability of the rock, causing the crude oil to re-adhere to the rock surface, increasing the resistance to crude oil flow, rendering the wetting reversal agent ineffective, and ultimately severely reducing the oil recovery rate, resulting in the waste of oil resources and increasing extraction costs. Summary of the Invention

[0003] The purpose of this invention is to provide a wetting reversal agent for improving oil recovery, its preparation method, and its application, thereby addressing the technical problem mentioned in the background art of insufficient binding and fixation ability of wetting reversal agent components with rocks. The wetting reversal component in the oil wetting reversal agent prepared by this invention has a strong binding force with rocks, thus maintaining the wettability of the oil surface for a long time, thereby improving oil recovery.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A wetting reversal agent for enhancing oil recovery comprises the following components in parts by weight: Olefin sulfonate 3-7 parts, isotridecyl alcohol polyoxyethylene ether 2-5 parts, wetting reversal complex 10-25 parts, isopropanol 0.5-3 parts, triethanolamine 1-5 parts, water 60-70 parts.

[0005] In this invention, olefin sulfonates are used to peel crude oil from the rock surface. Specifically, the hydrophobic alkyl chains of the olefin sulfonates can strongly insert into the oil film, while the sulfonic acid groups peel the oil film from the rock surface through charge repulsion (the rock surface is negatively charged). The isomeric tridecyl alcohol polyoxyethylene ether, based on C...13 The branched structure enhances the permeability of micropores, while the polyoxyethylene ether chains form a hydration layer to reduce flow resistance, thereby lowering the water contact angle on the rock surface and improving hydrophilicity. Isopropanol, as a dispersant, maintains the dispersion of the components of the wetting reversal agent, enhancing the wetting reversal effect. Triethanolamine, as a solubility promoter, primarily improves solubility by providing an alkaline environment (pH adjustment) to promote the ionization of anionic surfactants. After the olefin sulfonate strips crude oil from the rock surface, the wetting reversal complex strongly binds to the rock surface, covering its hydrophobic surface. Even under prolonged external force, it is not easily detached from the rock surface. Furthermore, the wetting reversal complex is loaded with hydrophilic groups, thus coating the rock surface with a hydrophilic film, achieving a hydrophilic and oleophobic effect on the rock surface.

[0006] Preferably, the preparation method of the wetting reversal complex includes the following steps: S1. Octadecyldimethylamine and potassium hydroxide catalyst are added to a high-pressure reactor, then ethylene oxide is introduced and heated to react, yielding polyetheramine; S2. Polyetheramine and hexadecane bromide are dissolved in isopropanol, heated and reacted, and the solvent is removed by vacuum distillation, followed by washing and drying to obtain polyether chain quaternary ammonium salt; S3. Dissolve the polyether chain quaternary ammonium salt in NaHCO3-Na2CO3 buffer solution, then add chloroacetic acid aqueous solution, stir the reaction, and after purification and drying, obtain carboxylated quaternary ammonium salt; S4. Dissolve the carboxylated quaternary ammonium salt in deionized water to obtain a carboxylated quaternary ammonium salt solution; ultrasonically disperse hydroxyapatite in deionized water to obtain a hydroxyapatite suspension; add the hydroxyapatite suspension dropwise to the carboxylated quaternary ammonium salt solution, heat and stir, and then centrifuge, wash and dry to obtain the final product.

[0007] In the technical solution of this invention, the preparation of the wetting reversal complex first involves reacting octadecyl dimethylamine with ethylene oxide to generate polyetheramine. Utilizing the strong hydrophilicity of the polyether chain, a hydrophilic film is formed on the rock surface, achieving a change in surface hydrophilicity. Then, the polyetheramine is reacted with hexadecyl bromide to generate a polyether chain quaternary ammonium salt. Because the polyether chain quaternary ammonium salt contains octadecyl and hexadecyl double long-chain hydrophobic groups, it can bind well to the hydrophobic surface of the rock, exhibiting excellent compatibility and bonding performance. Simultaneously, the positively charged cationic groups of its quaternary ammonium salt can form electrostatic attraction with the negative charge on the rock surface, firmly adhering to the rock surface through a dual effect of hydrophobic affinity and electrostatic adsorption. Finally, the polyether chain quaternary ammonium salt is carboxylated. The resulting carboxylated quaternary ammonium salt can form coordination bonds with calcium ions in hydroxyapatite through the carboxyl groups, thereby binding hydroxyapatite into its own structure. Hydroxyapatite can then embed itself into cracks and micropores on the rock surface, playing a riveting role and further enhancing its bonding force with the rock surface. Through the aforementioned multiple effects, this wettability reversal complex can not only strongly bind to the rock surface, but also effectively reverse the wettability of the rock surface, covering the surface with a hydrophilic film to achieve a long-lasting hydrophilic effect. This solves the problem that the wettability reversal functional components in existing technologies are easily detached from the rock surface under external forces, thereby improving the oil recovery rate. Figure 1 , Figure 2 The images show SEM images of the surface of a quartz sand core without wetting reversal agent treatment and the surface of a quartz sand core treated with the wetting reversal agent of this invention, respectively. From the scanning electron microscope images, it can be clearly observed that the surface of the quartz sand core treated with the wetting reversal agent is relatively rough, and there are particles adsorbed on the surface of the core, proving that the components in the wetting reversal agent can effectively bind with the core.

[0008] Preferably, in step S1, the mass ratio of octadecyl dimethylamine to ethylene oxide is 1:2 to 4.

[0009] Preferably, in step S2, the mass ratio of polyetheramine to hexadecane bromide is 6:2 to 3.

[0010] Preferably, in step S2, the reaction temperature is controlled at 75–80°C and the reaction time is 12–15 h.

[0011] Preferably, in step S3, the mass ratio of the polyether chain quaternary ammonium salt to chloroacetic acid is 5:1 to 3.

[0012] Preferably, in step S3, the reaction temperature is controlled at 5–10°C and the reaction time is 6–8 hours.

[0013] Preferably, in step S4, the mass ratio of carboxylated quaternary ammonium salt to hydroxyapatite is 3:1 to 2.

[0014] Preferably, in step S4, the hydroxyapatite undergoes a modification treatment, including the following steps: An epoxy silane coupling agent was added to an aqueous ethanol solution and stirred to hydrolyze it. Then, hydroxyapatite was added, and the mixture was heated and stirred to react, yielding epoxidized hydroxyapatite. Chitosan is added to an acetic acid solution and stirred to dissolve, thus obtaining a chitosan solution. Epoxidized hydroxyapatite is added to the chitosan solution, the pH is adjusted to alkaline, and the mixture is heated and stirred to react, thus obtaining the final product.

[0015] In the technical solution of this invention, the team discovered that hydroxyapatite cannot bond well with the rock surface; that is, most of the hydroxyapatite does not penetrate into rock crevices and micropores to form a rivet-like effect. In-depth research revealed that this is because the rock surface is oleophilic, while the hydroxyl groups on the hydroxyapatite surface have a certain degree of hydrophilicity, resulting in poor interfacial compatibility. To further solve the above technical problem, this invention modifies the hydroxyapatite by first grafting an epoxy silane stabilizer onto the hydroxyapatite surface, and then utilizing the ring-opening reaction between a small portion of the amino groups and the epoxy groups of chitosan to graft chitosan onto the hydroxyapatite surface. The amino groups abundant in the chitosan molecules carry a positive charge, which can form electrostatic attraction with the negatively charged rock surface, making it easier to embed into the rock crevices and micropores. This promotes the tight bonding between the wetting reversal functional component and the rock surface, effectively improving the bonding strength between the two.

[0016] A method for preparing a wetting reversal agent to enhance oil recovery includes the following steps: Olefin sulfonate, isotridecyl alcohol polyoxyethylene ether, isopropanol and triethanolamine are added to water and stirred to dissolve. Then, wetting reversal complex is added and stirred to mix evenly to obtain the final product.

[0017] Application of a wetting reversal agent for enhancing oil recovery in oil recovery.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. Isomeric tridecyl alcohol polyoxyethylene ether, with its branched structure, enhances microporous permeability. The polyoxyethylene ether chains form a hydration layer to reduce resistance. Combined with the hydrophilic groups on the wetting reversal complex, it can form a stable hydrophilic film on the rock surface, effectively transforming the rock surface from hydrophobic to hydrophilic and oleophobic, significantly improving hydrophilicity and aiding in oil recovery. Isopropanol ensures uniform dispersion of all components, while triethanolamine promotes the ionization of anionic surfactants by adjusting the alkaline environment, improving solubility. The synergistic effect of these components not only enhances the stability and effectiveness of the wetting reversal agent but also further improves the wetting reversal effect, thereby increasing oil recovery.

[0019] 2. Olefin sulfonates can strongly peel crude oil off the rock surface through the insertion of hydrophobic alkyl chains into the oil film and the electrostatic repulsion of sulfonic acid groups; the wetting reversal complex achieves strong bonding with the rock surface by means of the affinity of the double long-chain hydrophobic groups with the rock, the electrostatic attraction of the cationic groups with the rock, and the anchoring effect of hydroxyapatite embedded in the rock crevices. This solves the problem of easy detachment of functional components in the existing technology, ensures long-term adhesion, and thus improves the oil recovery rate.

[0020] 3. By modifying hydroxyapatite with chitosan, chitosan is grafted onto the surface of hydroxyapatite. The amino groups in the chitosan molecules are positively charged, which can form electrostatic attraction with the negatively charged rock surface, making it easier for the chitosan to embed into the cracks and micropores of the rock. This promotes the tight bonding between the wetting reversal functional components and the rock surface, effectively improving the bonding strength between the two. Attached Figure Description

[0021] Figure 1 This is a SEM image of the surface of a quartz sandstone core that has not been treated with a wetting reversal agent.

[0022] Figure 2 This is a SEM image of the surface of a quartz sandstone core after treatment with the wetting and reversing agent of this invention. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] A wetting reversal agent for enhancing oil recovery comprises the following components in parts by weight: Sodium α-alkenyl sulfonate (AOS 14-16) 6 parts, isotridecyl alcohol polyoxyethylene ether 4 parts, wetting reversal complex 23 parts, isopropanol 2.5 parts, triethanolamine 4 parts, water 68 parts.

[0026] Preparation of wetting reversal complex: Step 1: Add 3.0 g of octadecyldimethyl tertiary amine and 0.2 g of potassium hydroxide catalyst to a high-pressure reactor, purge with nitrogen, and heat to 100 ± 5 °C. Pour 10 g of ethylene oxide at a rate of 0.5 mL / min, maintain the pressure ≤ 0.2 MPa, and stir the reaction for 4 h. After the reaction is complete, cool to room temperature to obtain a pale yellow viscous polyetheramine. Step 2: Dissolve 6.0 g of polyetheramine and 2.8 g of hexadecane bromide in 350 mL of isopropanol and reflux at 78 °C for 13 h. Remove the solvent by vacuum distillation, wash three times with ethanol to remove residual bromide, and dry under vacuum at 60 °C for 6 h to obtain a white solid polyether chain quaternary ammonium salt.

[0027] Step 3: Dissolve 5.0 g of polyether chain quaternary ammonium salt in 100 mL of pH 8.5 NaHCO3-Na2CO3 buffer solution and cool to 5°C in an ice bath. Slowly add 2.5 g of chloroacetic acid aqueous solution, maintain the temperature at 7°C, and stir the reaction for 7 h. Transfer the reaction solution to a dialysis bag for purification for 48 h, and freeze-dry to obtain carboxylated quaternary ammonium salt; Step 4: Dissolve 3.0 g of carboxylated quaternary ammonium salt in 150 mL of deionized water to obtain a carboxylated quaternary ammonium salt solution; separately, ultrasonically disperse 1.7 g of modified hydroxyapatite in 100 mL of water. Add the modified hydroxyapatite suspension dropwise to the carboxylated quaternary ammonium salt solution at 30℃, stirring at 150 rpm for 2 h. Centrifuge (8000 rpm, 5 min) to collect the precipitate, wash three times with deionized water, and freeze-dry for 24 h to obtain the final product.

[0028] Preparation of modified hydroxyapatite: Step 1: Dissolve γ-glycidoxypropyltrimethoxysilane in an ethanol-water mixture (9:1, volume ratio) to prepare a 5wt% solution. Adjust the pH to 5.0±0.2 with glacial acetic acid, and hydrolyze at 25°C with magnetic stirring (300 rpm) for 30 minutes to obtain the hydrolysate. Step 2: Add 10g of hydroxyapatite to the above hydrolysate and react mechanically (500 rpm) in an oil bath at 80℃ for 2 hours. After the reaction is complete, collect the solid by centrifugation (8000 rpm, 10 min), wash three times with anhydrous ethanol to remove unreacted silane, and dry under vacuum at 60℃ for 12 hours to obtain epoxidized hydroxyapatite; Step 3: Dissolve 2 g of chitosan (degree of deacetylation ≥90%, viscosity 150 mPa·s) in 350 mL of 2% (v / v) acetic acid solution, and stir magnetically (400 rpm) at 25 °C until completely dissolved to obtain a chitosan solution. Add 5 g of epoxidized hydroxyapatite to the chitosan solution, adjust the pH to 8.5±0.2 with 0.1 M NaOH, and react mechanically (400 rpm) in a 60 °C water bath for 4 hours. After centrifugation, washing and drying, modified hydroxyapatite is obtained.

[0029] A method for preparing a wetting reversal agent to enhance oil recovery includes the following steps: Olefin sulfonate, isotridecyl alcohol polyoxyethylene ether, isopropanol and triethanolamine are added to water and stirred at 200 rpm for 35 min to dissolve. Then, wetting reversal complex is added and stirred for another 30 min to mix evenly.

[0030] Example 2

[0031] A wetting reversal agent for enhancing oil recovery comprises the following components in parts by weight: Sodium α-alkenyl sulfonate (AOS 14-16) 4 parts, isotridecyl alcohol polyoxyethylene ether 3 parts, wetting reversal complex 12 parts, isopropanol 1 part, triethanolamine 2 parts, water 63 parts.

[0032] Preparation of wetting reversal complex: Step 1: Add 3.0 g of octadecyl dimethyl tertiary amine and 0.2 g of potassium hydroxide catalyst to a high-pressure reactor, purge with nitrogen, and heat to 100 ± 5 °C. Pour 7 g of ethylene oxide at a rate of 0.5 mL / min, maintain the pressure ≤ 0.2 MPa, and stir the reaction for 4 h. After the reaction is complete, cool to room temperature to obtain a pale yellow viscous polyetheramine. Step 2: Dissolve 6.0 g of polyetheramine and 2.2 g of hexadecane bromide in 350 mL of isopropanol and reflux at 78 °C for 13 h. Remove the solvent by vacuum distillation, wash three times with ethanol to remove residual bromide, and dry under vacuum at 60 °C for 6 h to obtain a white solid polyether chain quaternary ammonium salt.

[0033] Step 3: Dissolve 5.0 g of polyether chain quaternary ammonium salt in 100 mL of pH 8.5 NaHCO3-Na2CO3 buffer solution and cool to 5°C in an ice bath. Slowly add 1.5 g of chloroacetic acid aqueous solution, maintain the temperature at 7°C, and stir the reaction for 7 h. Transfer the reaction solution to a dialysis bag for purification for 48 h, and freeze-dry to obtain carboxylated quaternary ammonium salt; Step 4: Dissolve 3.0 g of carboxylated quaternary ammonium salt in 150 mL of deionized water to obtain a carboxylated quaternary ammonium salt solution; separately, ultrasonically disperse 1.2 g of modified hydroxyapatite in 100 mL of water. Add the modified hydroxyapatite suspension dropwise to the carboxylated quaternary ammonium salt solution at 30℃, stirring at 150 rpm for 2 h. Centrifuge (8000 rpm, 5 min) to collect the precipitate, wash three times with deionized water, and freeze-dry for 24 h to obtain the final product.

[0034] Preparation of modified hydroxyapatite: Step 1: Dissolve γ-glycidoxypropyltrimethoxysilane in an ethanol-water mixture (9:1, volume ratio) to prepare a 5wt% solution. Adjust the pH to 5.0±0.2 with glacial acetic acid, and hydrolyze at 25°C with magnetic stirring (300 rpm) for 30 minutes to obtain the hydrolysate. Step 2: Add 10g of hydroxyapatite to the above hydrolysate and react mechanically (500 rpm) in an oil bath at 80℃ for 2 hours. After the reaction is complete, collect the solid by centrifugation (8000 rpm, 10 min), wash three times with anhydrous ethanol to remove unreacted silane, and dry under vacuum at 60℃ for 12 hours to obtain epoxidized hydroxyapatite; Step 3: Dissolve 2 g of chitosan (degree of deacetylation ≥90%, viscosity 150 mPa·s) in 350 mL of 2% (v / v) acetic acid solution, and stir magnetically (400 rpm) at 25 °C until completely dissolved to obtain a chitosan solution. Add 5 g of epoxidized hydroxyapatite to the chitosan solution, adjust the pH to 8.5±0.2 with 0.1 M NaOH, and react mechanically (400 rpm) in a 60 °C water bath for 4 hours. After centrifugation, washing and drying, modified hydroxyapatite is obtained.

[0035] A method for preparing a wetting reversal agent to enhance oil recovery includes the following steps: Olefin sulfonate, isotridecyl alcohol polyoxyethylene ether, isopropanol and triethanolamine are added to water and stirred at 200 rpm for 35 min to dissolve. Then, wetting reversal complex is added and stirred for another 30 min to mix evenly.

[0036] Example 3

[0037] A wetting reversal agent for enhancing oil recovery comprises the following components in parts by weight: Sodium α-alkenyl sulfonate (AOS 14-16) 5 parts, isotridecyl alcohol polyoxyethylene ether 3 parts, wetting reversal complex 18 parts, isopropanol 2 parts, triethanolamine 3 parts, water 65 parts.

[0038] Preparation of wetting reversal complex: Step 1: Add 3.0 g of octadecyl dimethyl tertiary amine and 0.2 g of potassium hydroxide catalyst to a high-pressure reactor, purge with nitrogen, and heat to 100 ± 5 °C. Pour 9 g of ethylene oxide at a rate of 0.5 mL / min, maintain the pressure ≤ 0.2 MPa, and stir the reaction for 4 h. After the reaction is complete, cool to room temperature to obtain a pale yellow viscous polyetheramine. Step 2: Dissolve 6.0 g of polyetheramine and 2.5 g of hexadecane bromide in 350 mL of isopropanol and reflux at 78 °C for 13 h. Remove the solvent by vacuum distillation, wash three times with ethanol to remove residual bromide, and dry under vacuum at 60 °C for 6 h to obtain a white solid polyether chain quaternary ammonium salt.

[0039] Step 3: Dissolve 5.0 g of polyether chain quaternary ammonium salt in 100 mL of pH 8.5 NaHCO3-Na2CO3 buffer solution and cool to 5°C in an ice bath. Slowly add 2.0 g of chloroacetic acid aqueous solution, maintain the temperature at 7°C, and stir the reaction for 7 h. Transfer the reaction solution to a dialysis bag for purification for 48 h, and freeze-dry to obtain carboxylated quaternary ammonium salt; Step 4: Dissolve 3.0 g of carboxylated quaternary ammonium salt in 150 mL of deionized water to obtain a carboxylated quaternary ammonium salt solution; separately, ultrasonically disperse 1.5 g of modified hydroxyapatite in 100 mL of water. Add the modified hydroxyapatite suspension dropwise to the carboxylated quaternary ammonium salt solution at 30℃, stirring at 150 rpm for 2 h. Centrifuge (8000 rpm, 5 min) to collect the precipitate, wash three times with deionized water, and freeze-dry for 24 h to obtain the final product.

[0040] Preparation of modified hydroxyapatite: Step 1: Dissolve γ-glycidoxypropyltrimethoxysilane in an ethanol-water mixture (9:1, volume ratio) to prepare a 5wt% solution. Adjust the pH to 5.0±0.2 with glacial acetic acid, and hydrolyze at 25°C with magnetic stirring (300 rpm) for 30 minutes to obtain the hydrolysate. Step 2: Add 10g of hydroxyapatite to the above hydrolysate and react mechanically (500 rpm) in an oil bath at 80℃ for 2 hours. After the reaction is complete, collect the solid by centrifugation (8000 rpm, 10 min), wash three times with anhydrous ethanol to remove unreacted silane, and dry under vacuum at 60℃ for 12 hours to obtain epoxidized hydroxyapatite; Step 3: Dissolve 2 g of chitosan (degree of deacetylation ≥90%, viscosity 150 mPa·s) in 350 mL of 2% (v / v) acetic acid solution, and stir magnetically (400 rpm) at 25 °C until completely dissolved to obtain a chitosan solution. Add 5 g of epoxidized hydroxyapatite to the chitosan solution, adjust the pH to 8.5±0.2 with 0.1 M NaOH, and react mechanically (400 rpm) in a 60 °C water bath for 4 hours. After centrifugation, washing and drying, modified hydroxyapatite is obtained.

[0041] A method for preparing a wetting reversal agent to enhance oil recovery includes the following steps: Olefin sulfonate, isotridecyl alcohol polyoxyethylene ether, isopropanol and triethanolamine are added to water and stirred at 200 rpm for 35 min to dissolve. Then, wetting reversal complex is added and stirred for another 30 min to mix evenly.

[0042] Example 4

[0043] A wetting reversal agent for enhancing oil recovery comprises the following components in parts by weight: 7 parts sodium α-alkenyl sulfonate (AOS 14-16), 5 parts isotridecyl alcohol polyoxyethylene ether, 25 parts wetting reversal complex, 3 parts isopropanol, 5 parts triethanolamine, and 70 parts water.

[0044] Preparation of wetting reversal complex: Step 1: Add 3.0 g of octadecyl dimethyl tertiary amine and 0.2 g of potassium hydroxide catalyst to a high-pressure reactor, purge with nitrogen, and heat to 100 ± 5 °C. Pour 12 g of ethylene oxide at a rate of 0.5 mL / min, maintain the pressure ≤ 0.2 MPa, and stir the reaction for 4 h. After the reaction is complete, cool to room temperature to obtain a pale yellow viscous polyetheramine. Step 2: Dissolve 6.0 g of polyetheramine and 3 g of hexadecane bromide in 350 mL of isopropanol and reflux at 80 °C for 15 h. Remove the solvent by vacuum distillation, wash three times with ethanol to remove residual bromide, and dry under vacuum at 60 °C for 6 h to obtain a white solid polyether chain quaternary ammonium salt.

[0045] Step 3: Dissolve 5.0 g of polyether chain quaternary ammonium salt in 100 mL of pH 8.5 NaHCO3-Na2CO3 buffer solution and cool to 5°C in an ice bath. Slowly add 3.0 g of chloroacetic acid aqueous solution, maintain the temperature at 10°C, and stir the reaction for 8 h. Transfer the reaction solution to a dialysis bag for purification for 48 h, and freeze-dry to obtain carboxylated quaternary ammonium salt; Step 4: Dissolve 3.0 g of carboxylated quaternary ammonium salt in 150 mL of deionized water to obtain a carboxylated quaternary ammonium salt solution; separately, ultrasonically disperse 2.0 g of modified hydroxyapatite in 100 mL of water. Add the modified hydroxyapatite suspension dropwise to the carboxylated quaternary ammonium salt solution at 30℃, stirring at 150 rpm for 2 h. Centrifuge (8000 rpm, 5 min) to collect the precipitate, wash three times with deionized water, and freeze-dry for 24 h to obtain the final product.

[0046] Preparation of modified hydroxyapatite: Step 1: Dissolve γ-glycidoxypropyltrimethoxysilane in an ethanol-water mixture (9:1, volume ratio) to prepare a 5wt% solution. Adjust the pH to 5.0±0.2 with glacial acetic acid, and hydrolyze at 25°C with magnetic stirring (300 rpm) for 30 minutes to obtain the hydrolysate. Step 2: Add 10g of hydroxyapatite to the above hydrolysate and react mechanically (500 rpm) in an oil bath at 80℃ for 2 hours. After the reaction is complete, collect the solid by centrifugation (8000 rpm, 10 min), wash three times with anhydrous ethanol to remove unreacted silane, and dry under vacuum at 60℃ for 12 hours to obtain epoxidized hydroxyapatite; Step 3: Dissolve 2 g of chitosan (degree of deacetylation ≥90%, viscosity 150 mPa·s) in 350 mL of 2% (v / v) acetic acid solution, and stir magnetically (400 rpm) at 25 °C until completely dissolved to obtain a chitosan solution. Add 5 g of epoxidized hydroxyapatite to the chitosan solution, adjust the pH to 8.5±0.2 with 0.1 M NaOH, and react mechanically (400 rpm) in a 60 °C water bath for 4 hours. After centrifugation, washing and drying, modified hydroxyapatite is obtained.

[0047] A method for preparing a wetting reversal agent to enhance oil recovery includes the following steps: Olefin sulfonate, isotridecyl alcohol polyoxyethylene ether, isopropanol and triethanolamine are added to water and stirred at 200 rpm for 35 min to dissolve. Then, wetting reversal complex is added and stirred for another 30 min to mix evenly.

[0048] Example 5

[0049] A wetting reversal agent for enhancing oil recovery comprises the following components in parts by weight: Sodium α-alkenyl sulfonate (AOS 14-16) 3 parts, isotridecyl alcohol polyoxyethylene ether 2 parts, wetting reversal complex 10 parts, isopropanol 0.5 parts, triethanolamine 1 part, water 60 parts.

[0050] Preparation of wetting reversal complex: Step 1: Add 3.0 g of octadecyl dimethyl tertiary amine and 0.2 g of potassium hydroxide catalyst to a high-pressure reactor, purge with nitrogen, and heat to 100 ± 5 °C. Pour 6 g of ethylene oxide at a rate of 0.5 mL / min, maintain the pressure ≤ 0.2 MPa, and stir the reaction for 4 h. After the reaction is complete, cool to room temperature to obtain a pale yellow viscous polyetheramine. Step 2: Dissolve 6.0 g of polyetheramine and 2 g of hexadecane bromide in 350 mL of isopropanol and reflux at 75 °C for 12 h. Remove the solvent by vacuum distillation, wash three times with ethanol to remove residual bromide, and dry under vacuum at 60 °C for 6 h to obtain a white solid polyether chain quaternary ammonium salt.

[0051] Step 3: Dissolve 5.0 g of polyether chain quaternary ammonium salt in 100 mL of pH 8.5 NaHCO3-Na2CO3 buffer solution and cool to 5°C in an ice bath. Slowly add 1.0 g of chloroacetic acid aqueous solution, maintain the temperature at 5°C, and stir the reaction for 6 h. Transfer the reaction solution to a dialysis bag for purification for 48 h, and freeze-dry to obtain carboxylated quaternary ammonium salt; Step 4: Dissolve 3.0 g of carboxylated quaternary ammonium salt in 150 mL of deionized water to obtain a carboxylated quaternary ammonium salt solution; separately, ultrasonically disperse 1.0 g of modified hydroxyapatite in 100 mL of water. Add the modified hydroxyapatite suspension dropwise to the carboxylated quaternary ammonium salt solution at 30℃, stirring at 150 rpm for 2 h. Centrifuge (8000 rpm, 5 min) to collect the precipitate, wash three times with deionized water, and freeze-dry for 24 h to obtain the final product.

[0052] Preparation of modified hydroxyapatite: Step 1: Dissolve γ-glycidoxypropyltrimethoxysilane in an ethanol-water mixture (9:1, volume ratio) to prepare a 5wt% solution. Adjust the pH to 5.0±0.2 with glacial acetic acid, and hydrolyze at 25°C with magnetic stirring (300 rpm) for 30 minutes to obtain the hydrolysate. Step 2: Add 10g of hydroxyapatite to the above hydrolysate and react mechanically (500 rpm) in an oil bath at 80℃ for 2 hours. After the reaction is complete, collect the solid by centrifugation (8000 rpm, 10 min), wash three times with anhydrous ethanol to remove unreacted silane, and dry under vacuum at 60℃ for 12 hours to obtain epoxidized hydroxyapatite; Step 3: Dissolve 2 g of chitosan (degree of deacetylation ≥90%, viscosity 150 mPa·s) in 350 mL of 2% (v / v) acetic acid solution, and stir magnetically (400 rpm) at 25 °C until completely dissolved to obtain a chitosan solution. Add 5 g of epoxidized hydroxyapatite to the chitosan solution, adjust the pH to 8.5±0.2 with 0.1 M NaOH, and react mechanically (400 rpm) in a 60 °C water bath for 4 hours. After centrifugation, washing and drying, modified hydroxyapatite is obtained.

[0053] A method for preparing a wetting reversal agent to enhance oil recovery includes the following steps: Olefin sulfonate, isotridecyl alcohol polyoxyethylene ether, isopropanol and triethanolamine are added to water and stirred at 200 rpm for 35 min to dissolve. Then, wetting reversal complex is added and stirred for another 30 min to mix evenly.

[0054] Comparative Example 1

[0055] The difference between Comparative Example 1 and Example 1 is that step 1 is omitted in the preparation of the wetting reversal complex.

[0056] Comparative Example 2

[0057] The difference between Comparative Example 2 and Example 1 is that step 2 is omitted in the preparation of the wetting reversal complex.

[0058] Comparative Example 3

[0059] The difference between Comparative Example 3 and Example 1 is that steps 3 and 4 are omitted in the preparation of the wetting reversal complex.

[0060] Comparative Example 4

[0061] The difference between Comparative Example 4 and Example 1 is that the modified hydroxyapatite used in step 4 was replaced with ordinary hydroxyapatite in the preparation of the wetting reversal compound.

[0062] Performance testing: 1. Water Contact Angle Test on Rock Surface: Simulated reservoir core samples (quartz sandstone, 2cm × 2cm × 0.5cm) were soaked in crude oil (density 0.85g / cm³) for 24 hours to form a hydrophobic surface. A 1% concentration of wetting reversal agent solution was evenly applied to the core surface. After standing for 30 minutes, the contact angle of deionized water was measured using a contact angle meter (θ / 2 method) at 25℃. Five tests were performed for each group, and the average value was taken. The smaller the contact angle, the stronger the hydrophilicity of the rock surface. The test results are shown in Table 1.

[0063] 2. Erosion Resistance Test: The treated core was placed in a dynamic erosion device, and simulated formation water (total mineralization 10000 mg / L) was introduced at a flow rate of 0.5 m / s for 24 hours. After the erosion, the contact angle of the core surface was measured, and the rate of change of the contact angle before and after erosion was calculated. The rate of change of contact angle after erosion (%) = (contact angle after erosion - initial contact angle) / initial contact angle × 100%. The smaller the rate of change, the stronger the bond between the wetting reversal agent and the rock. The test results are shown in Table 1.

[0064] 3. Enhanced Oil Recovery Test: A sand-filled tube model (30cm in length, 2cm in inner diameter, sand particle size 0.1-0.3mm) was used. After saturating the crude oil, waterflooding was performed until no oil was produced, and the waterflooding recovery rate was recorded. Subsequently, 1PV (pore volume) of a 1% concentration wetting reversal agent solution was injected, and waterflooding was continued until no oil was produced. The difference between the total recovery rate and the waterflooding recovery rate was calculated as the enhanced oil recovery rate. The test results are shown in Table 1.

[0065] Table 1:

[0066] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 wetting reversal agent for enhancing oil recovery, characterized in that, Includes the following components in parts by weight: Olefin sulfonate 3-7 parts, isotridecyl alcohol polyoxyethylene ether 2-5 parts, wetting reversal complex 10-25 parts, isopropanol 0.5-3 parts, triethanolamine 1-5 parts, water 60-70 parts.

2. The wetting reversal agent for enhancing oil recovery according to claim 1, characterized in that, The preparation method of the wetting reversal complex includes the following steps: S1. Octadecyldimethylamine and potassium hydroxide catalyst are added to a high-pressure reactor, then ethylene oxide is introduced and heated to react, yielding polyetheramine; S2. Polyetheramine and hexadecane bromide are dissolved in isopropanol, heated and reacted, and the solvent is removed by vacuum distillation, followed by washing and drying to obtain polyether chain quaternary ammonium salt; S3. Dissolve the polyether chain quaternary ammonium salt in NaHCO3-Na2CO3 buffer solution, then add chloroacetic acid aqueous solution, stir the reaction, and after purification and drying, obtain carboxylated quaternary ammonium salt; S4. Dissolve the carboxylated quaternary ammonium salt in deionized water to obtain a carboxylated quaternary ammonium salt solution; ultrasonically disperse hydroxyapatite in deionized water to obtain a hydroxyapatite suspension; add the hydroxyapatite suspension dropwise to the carboxylated quaternary ammonium salt solution, heat and stir, and then centrifuge, wash and dry to obtain the final product.

3. The wetting reversal agent for enhancing oil recovery according to claim 2, characterized in that, In step S1, the mass ratio of octadecyl dimethylamine to ethylene oxide is 1:2 to 4.

4. The wetting reversal agent for enhancing oil recovery according to claim 2, characterized in that, In step S2, the mass ratio of polyetheramine to hexadecane bromide is 6:2-3.

5. A wetting reversal agent for enhancing oil recovery according to claim 2, characterized in that, In step S2, the reaction temperature is controlled at 75-80℃ and the reaction time is 12-15h.

6. The wetting reversal agent for enhancing oil recovery according to claim 2, characterized in that, In step S3, the mass ratio of polyether chain quaternary ammonium salt to chloroacetic acid is 5:1 to 3.

7. A wetting reversal agent for enhancing oil recovery according to claim 2, characterized in that, In step S4, the mass ratio of carboxylated quaternary ammonium salt to hydroxyapatite is 3:1 to 2.

8. A wetting reversal agent for enhancing oil recovery according to claim 2, characterized in that, In step S4, the hydroxyapatite undergoes a modification treatment, including the following steps: An epoxy silane coupling agent was added to an aqueous ethanol solution and stirred to hydrolyze it. Then, hydroxyapatite was added, and the mixture was heated and stirred to react, yielding epoxidized hydroxyapatite. Chitosan is added to an acetic acid solution and stirred to dissolve, thus obtaining a chitosan solution. Epoxidized hydroxyapatite is added to the chitosan solution, the pH is adjusted to alkaline, and the mixture is heated and stirred to react, thus obtaining the final product.

9. A method for preparing a wetting reversal agent for enhancing oil recovery as described in any one of claims 1-8, characterized in that, Includes the following steps: Olefin sulfonate, isotridecyl alcohol polyoxyethylene ether, isopropanol and triethanolamine are added to water and stirred to dissolve. Then, wetting reversal complex is added and stirred to mix evenly to obtain the final product.

10. The application of a wetting reversal agent for enhancing oil recovery as described in any one of claims 1-8 in oil recovery.

Images