A bio-based nanofluid oil displacement agent, and a preparation method and application thereof

Abstract

The application provides a kind of bio-based nanofluid oil displacement agent and its preparation method and application, it is related to oilfield development technical field.The bio-based nanofluid oil displacement agent of the application includes: modified nanoparticle 0.1~0.5%, composite surfactant 0.2~0.5%, water balance;Wherein, the preparation method of the modified nanoparticle includes: using vinyltriethoxysilane to modify nano TiO2;The composite surfactant includes: gemini surfactant, polyglycerol fatty acid ester and cocoglycoside;The preparation method of the gemini surfactant includes the following steps: N, N-dibenzyl ethylenediamine is reacted with guaiacol glycidyl ether to obtain a first intermediate product, then reacts with 3-chloro-2-hydroxy propane sulfonic acid sodium to obtain.The bio-based nanofluid oil displacement agent of the application is used for low permeability reservoir, can effectively improve the recovery of crude oil, overcome the problem that traditional bio-based nanofluid oil displacement agent is poor in stability and sensitive to calcium and magnesium ions.

Description

Technical Field

[0001] This application relates to the field of oilfield development technology, and in particular to a bio-based nanofluid oil displacement agent, its preparation method, and its application. Background Technology

[0002] Low-permeability reservoirs are characterized by small pore throats, poor interpore connectivity, and complex formation structures, which hinder fluid flow. Traditional displacement methods often fail to achieve satisfactory development results, leading to high oil production costs and difficulties. Nanofluid flooding is an emerging technology. Due to the small particle size and good flow properties of nanoparticles, they can more easily penetrate the pores and fractures of low-permeability reservoirs. Through a combination of structural separation pressure and wettability reversal, the crude oil adsorbed on the rock surface is stripped away. Therefore, nanofluid flooding shows great promise for improving the recovery of low-permeability crude oil.

[0003] However, in nanofluid enhanced oil recovery (EOR) technology, nanoparticles, due to their large specific surface area, are prone to aggregation and precipitation. Therefore, surfactants are often added during formulation to promote particle dispersion. Traditional surfactants are mostly synthesized from petroleum-based raw materials, have poor biodegradability, and can easily cause groundwater and soil pollution when left in the formation. Compared to petroleum-based surfactants, bio-based surfactants use renewable biomass derivatives as raw materials, making their raw material sources green and sustainable, thus eliminating dependence on petrochemical resources. At the same time, bio-based surfactants are easily degraded and will not accumulate in soil and groundwater for a long time, reducing secondary pollution of the formation water and soil system. Currently, research on the combined use of nanoparticles and bio-based surfactants has made some progress. For example, patent CN109111905A discloses a bio-based nanofluid and its application in enhancing oil recovery in low-permeability reservoirs, which combines rhamnolipin biosurfactant with SiO2 nanoparticles and injects it into the formation to achieve the purpose of enhancing oil recovery.

[0004] However, in nanofluid processes, dilution with formation water is usually required before injection into oil wells. Formation water typically has high salinity and contains high concentrations of calcium and magnesium ions. Conventional bio-based surfactants have poor salt tolerance and are prone to aggregation when encountering high salt concentrations, failing to achieve the desired oil displacement effect. Therefore, researching a bio-based nanofluid that can withstand salt and high salinity is crucial for the development of low-permeability reservoirs. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects and deficiencies in the prior art and provide a bio-based nanofluid oil displacement agent, its preparation method and application. The bio-based nanofluid oil displacement agent of this application can be used in low-permeability reservoirs to effectively improve crude oil recovery and overcome the problems of poor stability and sensitivity to calcium and magnesium ions in traditional bio-based nanofluid oil displacement agents.

[0006] To achieve the above objectives, the technical solution adopted in this application is as follows: According to one aspect of this application, a bio-based nanofluid oil displacement agent is provided, comprising, by weight fraction: 0.1-0.5% modified nanoparticles, 0.2-0.5% composite surfactant, and the balance being water; wherein, The method for preparing the modified nanoparticles includes: modifying nano-TiO2 using vinyltriethoxysilane; The composite surfactant includes: gemini surfactant, polyglycerol fatty acid ester, and cocoyl glucoside; The preparation method of the Gemini surfactant includes the following steps: N,N-dibenzylethylenediamine reacts with guaiacol glycidyl ether to obtain a first intermediate product, and then reacts with sodium 3-chloro-2-hydroxypropanesulfonate to obtain the final product.

[0007] This application provides the above-mentioned bio-based nanofluid oil displacement agent, which combines modified nano-TiO2 with composite surfactants. This bio-based nanofluid oil displacement agent has good dispersibility in formation water, can effectively reduce the oil-water interfacial tension, change the wettability of rocks, adsorb and peel off the oil film on the rock surface, and significantly improve the oil recovery rate. At the same time, this oil displacement agent will not agglomerate or settle under high salinity and has strong resistance to salt and calcium and magnesium ions, thus making up for the defects of traditional bio-based nanofluid oil displacement agents.

[0008] Furthermore, the method for preparing the gemini surfactant includes the following steps: (1) Add N,N-dibenzylethylenediamine to methanol, heat to 45-55°C, add guaiacol glycidyl ether and triethylamine, heat to 60-65°C and react for 3-4 hours to obtain the first intermediate product; (2) Add sodium 3-chloro-2-hydroxypropanesulfonate to the first intermediate product, adjust the pH to 8-8.5, heat to 70-75℃ and react for 4-5 hours, distill under reduced pressure and dry to obtain the Gemini surfactant.

[0009] Optionally, in the preparation process of the above-mentioned gemini surfactant, the molar ratio of N,N-dibenzylethylenediamine, guaiacol glycidyl ether and sodium 3-chloro-2-hydroxypropanesulfonate is 1:(2-2.2):(2.2-2.5).

[0010] Optionally, the molar ratio of N,N-dibenzylethylenediamine to triethylamine is 1:(0.1 to 0.2).

[0011] This application designs a novel twin surfactant using the above method. Compared with traditional linear biosurfactants, the three-dimensional dendritic structure has large steric hindrance, which can effectively prevent high salt ions from invading the micelles. Moreover, the molecular structure contains multiple hydrophilic sites and twin hydrophobic long chains, which can resist the charge shielding of high salt ions, thereby achieving excellent anti-mineralization ability.

[0012] Further, the polyglycerol fatty acid ester is selected from at least one of polyglycerol-10 laurate, polyglycerol-10 oleate, polyglycerol-6 laurate, and polyglycerol-6 oleate; preferably, the polyglycerol fatty acid ester is selected from polyglycerol-10 laurate and polyglycerol-10 oleate in a mass ratio of (65-75):(25-35).

[0013] Furthermore, the composite surfactant comprises a gemini surfactant, polyglycerol fatty acid ester, and cocoyl glucoside in a mass ratio of (20-30):(40-60):(20-30).

[0014] Preferably, the composite surfactant comprises a gemini surfactant, a polyglycerol fatty acid ester, and a cocoyl glucoside in a mass ratio of 28:50:22.

[0015] This application selects the aforementioned composite surfactants, in which polyglycerol fatty acid esters can increase the uniform dispersion of modified nanoparticles and other surfactants in formation water, especially the dispersion effect under high salinity. Meanwhile, cocoyl glucoside enables the oil displacement agent to spread rapidly on the rock surface, transforming oil-wet surfaces into water-wet surfaces, making it easier for oil droplets to detach from the rock surface. The synergistic effect of these three surfactants achieves ultra-low interfacial tension, highly efficient crude oil emulsification, and a significant improvement in oil displacement efficiency. It also enhances the stability of the oil displacement agent under high salinity and high temperature conditions.

[0016] Furthermore, the method for preparing the modified nanoparticles includes the following steps: Mix vinyltriethoxysilane with a 75-95 v / v% aqueous ethanol solution, heat to 40-45℃ and react for 0.5-1 h, add nano-TiO2 and disperse evenly, then heat to 65-70℃ and react for 2.5-3 h, cool to room temperature, centrifuge, wash with anhydrous ethanol, and dry to obtain the final product.

[0017] Optionally, in the above-mentioned preparation process of modified nanoparticles, the particle size of nano-TiO2 is 10-30 nm.

[0018] Optionally, in the above-mentioned preparation process of modified nanoparticles, the mass ratio of nano-TiO2 to vinyltriethoxysilane is 10:(1-2).

[0019] Pure nano-TiO2 has a high surface energy, which causes it to rapidly aggregate and settle in formation water, affecting oil displacement efficiency. This application utilizes vinyltriethoxysilane to modify nano-TiO2, forming a coating layer on the surface of the nano-TiO2, enabling the nanoparticles to be stably dispersed in highly mineralized water for a long period of time.

[0020] However, the binding force between vinyltriethoxysilane-modified TiO2 and the composite surfactant is weak, resulting in insufficient long-term storage stability and affecting oil displacement efficiency. Research has found that further modification of vinyltriethoxysilane-modified nano-TiO2 with N-vinylimidazolium and 2-acrylamido-2-methylpropanesulfonic acid strengthens the interface between the nanoparticles and the surfactant, preventing short-term sedimentation and long-term stratification, thus balancing on-site solution stability and long-term formation displacement stability. The further modified nanoparticles and composite surfactant work together to reduce the oil-water interfacial tension, making crude oil easier to strip and improving oil recovery. Furthermore, the further modified TiO2 helps to further improve the high-temperature resistance and anti-mineralization ability of the oil displacement agent.

[0021] The modification process is as follows: Vinyltriethoxysilane-modified nano-TiO2 was dispersed in a 75-90 v / v% ethanol aqueous solution, and N-vinylimidazolium and 2-acrylamido-2-methylpropanesulfonic acid were added and dispersed evenly. Then, an initiator was added, and the temperature was raised to 70-75℃ for 3-5 h. After the reaction was completed, the temperature was lowered to room temperature, centrifuged, washed with anhydrous ethanol, and dried to obtain the final product.

[0022] Optionally, the mass ratio of the vinyltriethoxysilane-modified nano-TiO2, N-vinylimidazolium, and 2-acrylamido-2-methylpropanesulfonic acid is 10:(1-2):(2-3.5).

[0023] Optionally, the initiator is an initiator well known to those skilled in the art, such as an azo initiator, and its dosage is 0.5 to 1% of the total mass of N-vinylimidazolium and 2-acrylamido-2-methylpropanesulfonic acid.

[0024] Furthermore, the water in the bio-based nanofluid oil displacement agent is tap water, formation water, etc.

[0025] According to another aspect of this application, a method for preparing a bio-based nanofluid oil displacement agent is provided, comprising the following steps: dispersing modified nanoparticles in water, and then adding a composite surfactant and stirring until homogeneous, thereby obtaining the product.

[0026] Compared with the prior art, the beneficial effects of this application include, but are not limited to: 1. The above-mentioned bio-based nanofluid oil displacement agent of this application, through the combination of modified nano TiO2 and composite surfactant, has good dispersibility in formation water, can effectively reduce the oil-water interfacial tension, significantly improve the oil recovery rate, and at the same time, the oil displacement agent has strong resistance to salt and calcium and magnesium ions, thus making up for the defects of traditional bio-based nanofluid oil displacement agents.

[0027] 2. The aforementioned bio-based nanofluid oil displacement agent of this application, wherein polyglycerol fatty acid ester can increase the uniform dispersion of modified nanoparticles and other surfactants in formation water, especially the dispersion under high salinity, while cocoyl glucoside can enable the oil displacement agent to spread rapidly on the rock surface, transforming the oil-wetted surface into a water-wetted surface, making it easier for oil droplets to peel off from the rock surface. The synergistic effect of the above three surfactants achieves ultra-low interfacial tension, efficient crude oil emulsification, and a significant improvement in oil displacement efficiency, while also improving the stability of the oil displacement agent under high salinity.

[0028] 3. The above-mentioned bio-based nanofluid oil displacement agent of this application utilizes vinyltriethoxysilane to modify nano-TiO2. Vinyltriethoxysilane forms a coating layer on the surface of nano-TiO2, enabling the nanoparticles to be stably dispersed in highly mineralized water for a long time. Detailed Implementation

[0029] To more clearly illustrate the overall concept of this application, a detailed description is provided below with reference to embodiments. Numerous specific details are set forth in the following description to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described to avoid confusion with the invention.

[0030] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers. Preparation methods that do not specify specific methods are generally prepared using equipment or conventional methods well known in the art.

[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0032] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0033] Unless otherwise specified, in the following embodiments, reagents or instruments whose manufacturers are not indicated are all conventional products that can be purchased commercially.

[0034] Unless otherwise stated, the experimental methods, detection methods, and preparation methods disclosed in this invention all employ conventional techniques in the fields of microbiology, biochemistry, analytical chemistry, cell culture, and related areas.

[0035] The present application will be further described below by way of specific embodiments.

[0036] Example 1 This embodiment provides a bio-based nanofluid oil displacement agent, comprising, by weight fraction: 0.1% modified nano-TiO2, 0.2% composite surfactant, and the balance being water; wherein, The composite surfactant comprises a gemini surfactant, polyglycerol-10 laurate, and cocoyl glucoside in a mass ratio of 20:60:20; Gemini surfactants were prepared by the following method: 1 mol of N,N-dibenzylethylenediamine was added to sufficient methanol, the temperature was raised to 45°C, 2 mol of guaiacol glycidyl ether and 0.1 mol of triethylamine were added, the temperature was raised to 60°C and the reaction was carried out for 3 h to obtain the first intermediate product; 2.2 mol of sodium 3-chloro-2-hydroxypropanesulfonate was added to the reaction solution of the first step, the pH was adjusted to 8, the temperature was raised to 70°C and the reaction was carried out for 4 h, the product was distilled under reduced pressure and dried to obtain the gemini surfactant.

[0037] Modified nano-TiO2 was prepared by the following method: 1 part by weight of vinyltriethoxysilane and 75 v / v% ethanol aqueous solution were mixed, heated to 40℃ and reacted for 0.5 h, 10 parts by weight of nano-TiO2 (particle size 10 nm) were added and dispersed evenly, heated to 65℃ and reacted for 2.5 h, cooled to room temperature, centrifuged, washed with anhydrous ethanol, and dried to obtain the product.

[0038] This embodiment also provides a method for preparing the above-mentioned bio-based nanofluid oil displacement agent, including the following steps: dispersing modified nanoparticles in water, and then adding a composite surfactant and stirring evenly to obtain the product.

[0039] Example 2 This embodiment provides a bio-based nanofluid oil displacement agent, comprising, by weight fraction: 0.5% modified nano-TiO2, 0.5% composite surfactant, and the balance being water; wherein, The composite surfactant includes a gemini surfactant, polyglycerol fatty acid ester, and cocoyl glucoside in a mass ratio of 28:50:22. The polyglycerol fatty acid ester includes polyglycerol-10 laurate and polyglycerol-10 oleate in a mass ratio of 65:35. Gemini surfactants were prepared by the following method: 1 mol of N,N-dibenzylethylenediamine was added to sufficient methanol, the temperature was raised to 55°C, 2.2 mol of guaiacol glycidyl ether and 0.2 mol of triethylamine were added, the temperature was raised to 65°C and the reaction was carried out for 4 h to obtain the first intermediate product; 2.5 mol of sodium 3-chloro-2-hydroxypropanesulfonate was added to the reaction solution of the first step, the pH was adjusted to 8.5, the temperature was raised to 75°C and the reaction was carried out for 5 h, the product was distilled under reduced pressure and dried to obtain the gemini surfactant.

[0040] Modified nano-TiO2 was prepared by the following method: 2 parts by weight of vinyltriethoxysilane and 75 v / v% ethanol aqueous solution were mixed, heated to 40℃ and reacted for 0.5 h, 10 parts by weight of nano-TiO2 (particle size 10 nm) were added and dispersed evenly, heated to 65℃ and reacted for 2.5 h, cooled to room temperature, centrifuged, washed with anhydrous ethanol, and dried to obtain the product.

[0041] This embodiment also provides a method for preparing the above-mentioned bio-based nanofluid oil displacement agent, including the following steps: dispersing modified nanoparticles in water, and then adding a composite surfactant and stirring evenly to obtain the product.

[0042] Example 3 This embodiment provides a bio-based nanofluid oil displacement agent, comprising, by weight fraction: 0.5% modified nano-TiO2, 0.5% composite surfactant, and the balance being water; wherein, The composite surfactant includes a gemini surfactant, polyglycerol fatty acid ester and cocoyl glucoside in a mass ratio of 30:40:30, and the polyglycerol fatty acid ester includes polyglycerol-10 laurate and polyglycerol-10 oleate in a mass ratio of 75:25. Gemini surfactants were prepared by the following method: 1 mol of N,N-dibenzylethylenediamine was added to sufficient methanol, the temperature was raised to 55°C, 2.2 mol of guaiacol glycidyl ether and 0.2 mol of triethylamine were added, the temperature was raised to 65°C and the reaction was carried out for 4 h to obtain the first intermediate product; 2.5 mol of sodium 3-chloro-2-hydroxypropanesulfonate was added to the reaction solution of the first step, the pH was adjusted to 8.5, the temperature was raised to 75°C and the reaction was carried out for 5 h, the product was distilled under reduced pressure and dried to obtain the gemini surfactant.

[0043] Modified nano-TiO2 was prepared by the following method: 2 parts by weight of vinyltriethoxysilane and 75 v / v% ethanol aqueous solution were mixed, heated to 40℃ and reacted for 0.5 h, 10 parts by weight of nano-TiO2 (particle size 10 nm) were added and dispersed evenly, heated to 65℃ and reacted for 2.5 h, cooled to room temperature, centrifuged, washed with anhydrous ethanol, and dried to obtain the product.

[0044] This embodiment also provides a method for preparing the above-mentioned bio-based nanofluid oil displacement agent, including the following steps: dispersing modified nanoparticles in water, and then adding a composite surfactant and stirring evenly to obtain the product.

[0045] Example 4 The difference from Example 1 is that the composite surfactant includes a gemini surfactant, polyglycerol fatty acid ester and cocoyl glucoside in a mass ratio of 40:30:30; the polyglycerol fatty acid ester includes polyglycerol-10 laurate and polyglycerol-10 oleate in a mass ratio of 75:25.

[0046] Example 5 The difference from Example 1 is that the composite surfactant includes a gemini surfactant, polyglycerol fatty acid ester and cocoyl glucoside in a mass ratio of 15:75:10; the polyglycerol fatty acid ester includes polyglycerol-10 laurate and polyglycerol-10 oleate in a mass ratio of 75:25.

[0047] Example 6 The difference from Example 1 is that the modified nanoparticles were prepared by the following method: 2 parts by weight of vinyltriethoxysilane and 75 v / v% ethanol aqueous solution were mixed, heated to 40°C and reacted for 0.5 h, 10 parts by weight of nano TiO2 (particle size 10 nm) were added and dispersed evenly, heated to 65°C and reacted for 2.5 h, cooled to room temperature, centrifuged, washed with anhydrous ethanol, and dried to obtain the product; 10 parts by weight of vinyltriethoxysilane modified nano TiO2 were dispersed in sufficient 75 v / v% ethanol aqueous solution, 1 part by weight of N-vinylimidazole and 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid were added and dispersed evenly, then an initiator was added, heated to 70°C and reacted for 3 h, cooled to room temperature after the reaction was completed, centrifuged, washed with anhydrous ethanol, and dried to obtain the product.

[0048] Example 7 The difference from Example 1 is that the modified nanoparticles were prepared by the following method: 2 parts by weight of vinyltriethoxysilane and 75 v / v% ethanol aqueous solution were mixed, heated to 40°C and reacted for 0.5 h, 10 parts by weight of nano TiO2 (particle size 10 nm) were added and dispersed evenly, heated to 65°C and reacted for 2.5 h, cooled to room temperature, centrifuged, washed with anhydrous ethanol, and dried to obtain the product; 10 parts by weight of vinyltriethoxysilane modified nano TiO2 were dispersed in sufficient 90 v / v% ethanol aqueous solution, 2 parts by weight of N-vinylimidazole and 3.5 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid were added and dispersed evenly, then an initiator was added, heated to 70°C and reacted for 3 h, cooled to room temperature after the reaction was completed, centrifuged, washed with anhydrous ethanol, and dried to obtain the product.

[0049] Example 8 The difference from Example 6 is that N-vinylimidazole was not added during the preparation of the modified nanoparticles; only 2-acrylamido-2-methylpropanesulfonic acid was added.

[0050] Comparative Example 1 The difference from Example 1 is that the composite surfactant is only a gemini surfactant, and the total amount of composite surfactant remains unchanged.

[0051] Comparative Example 2 The difference from Example 1 is that the composite surfactant is only polyglycerol-10 laurate, and the total amount of composite surfactant remains unchanged.

[0052] Comparative Example 3 The difference from Example 1 is that the composite surfactant includes polyglycerol-10 laurate and cocoyl glucoside in a mass ratio of 3:1, while the total amount of composite surfactant remains unchanged.

[0053] Comparative Example 4 The difference from Example 1 is that the modified nanoparticles are replaced with unmodified nano-TiO2.

[0054] Experimental Example 1 Absorbance test The water in the bio-based nanofluid oil displacement agent (hereinafter referred to as oil displacement agent) prepared in the above embodiments and comparative examples is simulated formation water (the composition of simulated formation water is shown in Table 1 below). The absorbance was tested under a wavelength of 400 nm, and the absorbance of the nanofluid oil displacement agent was measured on the 2nd, 7th and 14th days. The results are shown in Table 2 below.

[0055] Table 1. Simulated Formation Water Composition

[0056] Table 2. Absorbance Changes

[0057] As shown in the table, the oil displacement agents provided in Examples 1-3 of this application, under the condition of a total mineralization of 189,000 mg / L, showed a small increase in absorbance from 0.116-0.120 to 0.125-0.128 within 14 days, indicating good system stability. This suggests that the components in the oil displacement agents provided in this application are evenly dispersed, and the combined effect of the components ensures the excellent resistance to salt and calcium and magnesium ions, thus overcoming the shortcomings of traditional bio-based nanofluid oil displacement agents.

[0058] Compared to Example 2, the composition of the composite surfactant in Comparative Examples 1-3 was changed, resulting in an increased initial absorbance of the oil displacement agent. After 14 days, the absorbance increased to over 0.160, indicating large absorbance fluctuations and poor stability. This demonstrates that only the combination of the three surfactants in this application can achieve the stability of the oil displacement agent under high salinity; the absence of one or two surfactants cannot achieve the desired effect.

[0059] In addition, in Comparative Example 4, the oil displacement agent obtained using unmodified nanoparticles had high absorbance and large changes over 14 days, indicating poor stability. This suggests that the modified nanoparticles and the composite surfactant work synergistically to maintain good stability of the oil displacement agent under high salinity.

[0060] Experimental Example 2 Interface tension test In the above-mentioned embodiments and comparative examples, the water in the oil displacement agents prepared was simulated formation water (the total salinity of the simulated formation water was 20450 mg / L and 189000 mg / L; the composition of the 20450 mg / L salinity simulated formation water is shown in Table 3 below, and the composition of the 189000 mg / L salinity simulated formation water is the same as in Experimental Example 1). The oil-water interfacial tension between the oil displacement agent and crude oil was tested at temperatures of 80°C and 120°C.

[0061] The results are shown in Table 4 below.

[0062] Table 3. Composition of simulated formation water at a salinity of 20450 mg / L

[0063] Table 4. Interfacial Tension Test Results

[0064] As shown in the table, the oil displacement agent provided in this application can effectively reduce interfacial tension, effectively weaken the intermolecular forces between oil and water molecules, enhance the ability to strip crude oil from the rock surface, and improve oil displacement efficiency. Compared to Example 2, in Comparative Examples 1-4, the composition of the composite surfactant was changed, or unmodified nanoparticles were used, resulting in an interfacial tension decrease to only 10. -2 The mN / m indicates that the composite surfactant and modified nanoparticles in the oil displacement agent of this application work synergistically to reduce interfacial tension and improve crude oil recovery.

[0065] Experimental Example 3 Core displacement experiment With a length of 30 cm, a diameter of 2.5 cm, and a permeability of 1.5 μm... 2 Indoor physical simulation oil displacement experiments were conducted on core samples. The core was vacuum-saturated with formation water, and dehydrated crude oil was introduced at a flow rate of 0.2 mL / min until the water cut at the core outlet was 0%. The core was then displaced with water until the outlet liquid had a water cut of 100%. A 0.3% oil displacement agent solution was then injected, and water displacement was repeated until the outlet liquid had a water cut of 100%. The improvement in crude oil recovery based on water displacement was calculated. The results are shown in Table 5 below. It can be seen that the oil displacement agent proposed in this application can effectively improve crude oil recovery.

[0066] Table 5. Enhanced Oil Recovery

[0067] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, this application is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope of this application should be within the protection scope of this application.

Claims

1. A bio-based nanofluid oil displacement agent, characterized in that, By weight fraction, it includes: 0.1–0.5% modified nanoparticles, 0.2–0.5% composite surfactant, and the balance being water; wherein, The method for preparing the modified nanoparticles includes: modifying nano-TiO2 using vinyltriethoxysilane; The composite surfactant includes: gemini surfactant, polyglycerol fatty acid ester, and cocoyl glucoside; The preparation method of the gemini surfactant includes the following steps: (1) Add N,N-dibenzylethylenediamine to methanol, heat to 45-55°C, add guaiacol glycidyl ether and triethylamine, heat to 60-65°C and react for 3-4 hours to obtain the first intermediate product; (2) Add sodium 3-chloro-2-hydroxypropanesulfonate to the first intermediate product, adjust the pH to 8-8.5, heat to 70-75℃ and react for 4-5 hours, distill under reduced pressure and dry to obtain the Gemini surfactant; The molar ratio of N,N-dibenzylethylenediamine, guaiacol glycidyl ether, and sodium 3-chloro-2-hydroxypropanesulfonate is 1:(2-2.2):(2-2.5). The polyglycerol fatty acid ester is selected from at least one of polyglycerol-10 lauryl ester, polyglycerol-10 oleate, polyglycerol-6 lauryl ester, and polyglycerol-6 oleate.

2. The bio-based nanofluid oil displacement agent according to claim 1, characterized in that, The polyglycerol fatty acid ester is selected from polyglycerol-10 laurate and polyglycerol-10 oleate in a mass ratio of (65-75):(25-35).

3. The bio-based nanofluid oil displacement agent according to claim 1, characterized in that, The composite surfactant comprises a gemini surfactant, polyglycerol fatty acid ester, and cocoyl glucoside in a mass ratio of (20-30):(40-60):(20-30).

4. The bio-based nanofluid oil displacement agent according to claim 3, characterized in that, The composite surfactant comprises a gemini surfactant, polyglycerol fatty acid ester, and cocoyl glucoside in a mass ratio of 28:50:

22.

5. The bio-based nanofluid oil displacement agent according to claim 1, characterized in that, The method for preparing the modified nanoparticles includes the following steps: Vinyltriethoxysilane and an aqueous ethanol solution were mixed and heated to 40–45 °C for 0.5–1 h. Nano TiO2 was added and dispersed evenly. Then, the temperature was raised to 65–70 °C for 2.5–3 h. The mixture was cooled to room temperature, centrifuged, washed with anhydrous ethanol, and dried to obtain vinyltriethoxysilane-modified nano TiO2.

6. The bio-based nanofluid oil displacement agent according to claim 5, characterized in that, The mass ratio of nano-TiO2 to vinyltriethoxysilane is 10:(1-2).

7. The bio-based nanofluid oil displacement agent according to claim 5, characterized in that, Nano-TiO2 was further modified with N-vinylimidazolium and 2-acrylamido-2-methylpropanesulfonic acid. The modification steps were as follows: Vinyltriethoxysilane-modified nano-TiO2 was dispersed in an aqueous ethanol solution, and N-vinylimidazolium and 2-acrylamido-2-methylpropanesulfonic acid were added and dispersed evenly. Then, an initiator was added, and the temperature was raised to 70-75℃ for 3-5 hours. After the reaction was completed, the temperature was lowered to room temperature, centrifuged, washed with anhydrous ethanol, and dried to obtain the final product.

8. The method for preparing the bio-based nanofluid oil displacement agent according to any one of claims 1-7, characterized in that, Includes the following steps: The modified nanoparticles are dispersed in water, and then a composite surfactant is added and stirred until homogeneous to obtain the final product.

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