Temperature-resistant and salt-resistant nanofluid oil-displacing agent as well as preparation and application thereof

Abstract

The invention relates to an oil field auxiliary agent, and particularly discloses a temperature-resistant salt-resistant nano fluid oil displacement agent and preparation and application thereof, the temperature-resistant salt-resistant nano fluid oil displacement agent comprises the following components by weight: 5-12 parts of modified nano SiO2 particles, 10-20 parts of a nonionic surfactant, 10-30 parts of a gemini benzoxazine surfactant, 1-5 parts of a dispersant, 10-20 parts of a mutual solvent, and 20-50 parts of water; wherein the modified nano SiO2 particles are obtained by modifying nano SiO2 particles through a macromolecular coupling agent. The nano-fluid oil-displacing agent has the beneficial effects that the recovery efficiency can be improved when the nano-fluid oil-displacing agent is used for exploiting a high-temperature and high-salt oil reservoir, and the nano-fluid oil-displacing agent is good in temperature resistance and salt resistance, small in particle size and capable of remarkably reducing the oil-water interfacial tension.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield additives, in particular to a temperature-resistant and salt-resistant nanofluid oil displacement agent and the preparation and application thereof. Background Art

[0002] Nanomaterials have attracted significant attention due to their small size, large surface area, and high surface atomic activity. Surface modification of the same nanomaterial can yield multiple oil recovery functions, leading to nanoscale flooding technology being considered one of the most promising technologies for enhancing oil recovery. Among these, nano-SiO2 particles are widely used due to their well-suited surface modification pathways, abundant resources, and favorable environmental receptivity.

[0003] Current technologies for modifying nano-SiO2 particles have shown that existing modified nano-SiO2 particles are unstable when dispersed in highly saline water. Furthermore, they tend to agglomerate at high temperatures. Consequently, when these modified nano-SiO2 particles are used in oil reservoirs exposed to high temperatures and high salinity, they exhibit poor stability and are prone to agglomeration, resulting in reduced oil recovery performance.

[0004] For example, Chinese patent CN116622355A discloses a nanofluid oil displacement agent prepared from a combination system of Janus nano-SiO2 particles and anionic / non-ionic surfactants. The Janus nanofluid enhanced by the surfactant can be stably dispersed for up to 12 hours at 90°C and 35,000 ppm, but it cannot meet the operational requirements of high-temperature and high-salinity oil wells. For another example, Chinese patent CN115340857A discloses an in-situ self-emulsifying nano-oil displacement agent and its preparation method. It is mainly prepared from hyperbranched nanomaterials, polymerized AOS and anionic surfactants. It can withstand temperatures of 30-130°C, has good stability and salt tolerance, but has a short stability time and an interfacial tension of only 10 -2 mN / m. For example, Chinese patent CN114437695A discloses a microemulsion multifunctional nano oil displacement agent and its preparation method, which is mainly prepared from nano-SiO2, diphenyl ether gemini surfactant, isothiazolinone derivatives and saturated alkanes, and has excellent stability in low-temperature oil reservoirs.

[0005] Therefore, it can be said that the dispersion stability of nanoparticles under high temperature and high mineralization conditions is still a challenge. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a temperature-resistant and salt-resistant nanofluid oil-displacing agent and its preparation and application, which solves the problems of poor stability and easy agglomeration of the existing fluid oil-displacing agent made from modified nano-SiO2 particles under high temperature and high mineralization conditions.

[0007] To address the above-mentioned problems, the present invention provides a solution: nano-SiO2 particles are modified using a macromolecular coupling agent. This improves the dispersibility of the nano-SiO2 particles through the mutual repulsion of the macromolecular coupling agent. Furthermore, the macromolecular coupling agent connects to the nano-SiO2 particles, increasing the solubility of the system for the nano-SiO2 particles and improving the stability of the nano-SiO2 particles. Furthermore, based on the good temperature and salt resistance of the benzoxazine functional group and its strong steric hindrance, which has a good dispersing effect on the nano-SiO2 particles, the present invention employs a gemini benzoxazine surfactant, which is compounded with the modified nano-SiO2 particles and a nonionic surfactant to form a nanofluid oil displacement agent.

[0008] In addition, the present invention requires that the prepared nanofluid oil displacement agent be heated at 130°C and 2.0×10 5 It can be stably dispersed for more than 9 hours under the condition of mg / L, and the interfacial tension is less than 10 -2 mN / m, which can improve reservoir wettability, reduce interfacial tension, control the oil-water interface flow ratio, and increase crude oil recovery. It is suitable for high-temperature and high-salinity reservoirs.

[0009] The purpose of the present invention is achieved through the following technical solutions: In a first aspect, a temperature-resistant and salt-resistant nanofluid oil displacement agent is provided, comprising, by weight: 5-12 parts modified nano-SiO2 particles, 10-20 parts non-ionic surfactant, 10-30 parts gemini benzoxazine surfactant, 1-5 parts dispersant, 10-20 parts mutual solvent, 20-50 parts water; Wherein, the modified nano-SiO2 particles are nano-SiO2 particles modified by a macromolecular coupling agent.

[0010] Furthermore, the preparation of the modified nano-SiO2 particles comprises the following steps: Preparation of macromolecular coupling agent: (1) Add butyl acrylate, sodium styrene sulfonate, dibenzoyl peroxide, and dodecyl mercaptan to a reactor, heat to 78°C~81°C, and continue the reaction for 0.5h~2h; (2) Then slowly add γ-(methacryloyloxy)propyltrimethoxysilane, methyl methacrylate, dibenzoyl peroxide, and dodecyl sulfide dropwise, and control the addition time to be within 2h; (3) After the addition is completed, keep warm for 1h to obtain a colorless or light yellow transparent liquid, which is the macromolecular coupling agent; Modification: The prepared macromolecule is coupled and transferred into another reaction kettle, and nano-SiO2 particles are added while stirring; after heating to 80°C, stirring is continued for 1 hour to obtain modified nano-SiO2 particles.

[0011] Furthermore, when preparing the modified nano-SiO2 particles, the mass ratio of the nano-SiO2 particles to the macromolecular coupling agent is 1:1. The macromolecular coupling agent comprises, by weight, 50-70 parts of butyl acrylate, 10-30 parts of sodium p-styrenesulfonate, 1-10 parts of methyl methacrylate, 10-30 parts of γ-(methacryloyloxy)propyltrimethoxysilane, 3 parts of dibenzoyl peroxide, and 3 parts of dodecyl mercaptan.

[0012] Furthermore, the gemini benzoxazine surfactant is prepared from these raw materials and includes, by weight, 40-50 parts of a bisphenol compound, 20-40 parts of primary amine acetate, 20-30 parts of paraformaldehyde, and 40-50 parts of n-butanol. The bisphenol compound is one or more of bisphenol A, bisphenol E, bisphenol F, bisphenol M, bisphenol S, bisphenol Z, and bisphenol P. The structure of the primary amine acetate is H2N-(CH2) n -COOM, where n is a natural number from 1 to 18, and M is a monovalent metal ion (e.g., Na + , K + ion).

[0013] Furthermore, the gemini benzoxazine surfactant is prepared by adding n-butanol to a reaction kettle, and then sequentially adding a bisphenol compound and paraformaldehyde under stirring; raising the temperature to 60°C, slowly adding a primary amine compound containing a double bond, raising the temperature to 120°C and reflux, continuing the reaction for 6 to 8 hours, and removing the butanol solvent by reduced pressure distillation at 120°C to obtain a white solid, which is the gemini benzoxazine surfactant; The reaction equation of the surfactant containing oxazine ring is .

[0014] Furthermore, the nonionic surfactant is polyoxyethylene ether fatty alcohol, and the structure of polyoxyethylene ether fatty alcohol is R-(OCC) x -OH, where R is a carbon number of C6~C 15 Alkyl group, X is a natural number from 8 to 25.

[0015] Furthermore, the dispersant is C6~C 16 One or more of a combination of one or more of straight-chain saturated hydrocarbons, liquid paraffin, white oil, and kerosene.

[0016] Furthermore, the mutual solvent is C4~C 12 One or more of a combination of linear alcohol, ethylene glycol butyl ether, or one or more.

[0017] In a second aspect, a method for preparing a heat-resistant and salt-resistant nanofluid oil-displacing agent is provided. The heat-resistant and salt-resistant nanofluid oil-displacing agent is prepared by the following steps: The modified nano-SiO2 particles, nonionic surfactant, gemini benzoxazine surfactant, mutual solvent and water are mixed, and after ultrasonic dispersion, the dispersed phase is slowly added dropwise, and then ultrasonic dispersion is continued for 40 to 80 minutes to obtain a temperature-resistant and salt-resistant tension nanofluid oil displacement agent.

[0018] In a third aspect, an application of a temperature-resistant and salt-resistant nanofluid oil-displacing agent is provided, wherein the temperature-resistant and salt-resistant nanofluid oil-displacing agent is used in the exploitation of high-temperature and high-salt oil reservoirs.

[0019] The present invention has the following advantages: (1) The modified nano-SiO2 particles in the heat-resistant and salt-resistant tension nanofluid oil displacement agent prepared by the present invention have both hydrophilic and hydrophobic properties due to the macromolecular coupling agent, which ensures that the modified nano-SiO2 particles have good dispersibility and heat-resistant and salt-resistant stability in the system; (2) The Gemini benzoxazine surfactant in the temperature-resistant and salt-resistant tension nanofluid oil displacement agent prepared by the present invention contains a hydrophilic group on the one hand, which solves the problem of the hydrophobicity of benzoxazine; on the other hand, it contains a benzoxazine group, which has good temperature resistance and salt resistance, thereby improving the temperature resistance and salt resistance of the nanofluid oil displacement agent. At the same time, due to the large steric effect of the group, it has a good dispersing effect on the modified nano-SiO2 particles, ensuring the stability of the system; (3) The temperature-resistant and salt-resistant tension nanofluid oil displacement agent prepared by the present invention is heated to 130°C and 3.0×10 5 mg / L conditions, it can be stably dispersed for more than 9 hours. Therefore, the surfactant-enhanced modified nano-SiO2 particle fluid of the present invention has the potential to be applied to high-temperature and high-salinity oil reservoirs to enhance oil recovery. (4) The temperature-resistant and salt-resistant tension nanofluid oil displacement agent prepared by the present invention can reduce interfacial tension, enhance emulsion stability, and improve the ability to change rock wettability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the contact angle of the nanofluid oil displacement agent in Example 9 of the present invention; Figure 2 This is the production curve of TXXX well in 2024 in Example 10 of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description.

[0022] It should be noted that the experimental methods in the following examples, unless otherwise specified, are conventional methods and were performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials and reagents used in the following examples, unless otherwise specified, are all commercially available.

[0023] Example 1 This embodiment provides a temperature-resistant, salt-resistant, tension-resistant nanofluid oil-displacing agent and a preparation method thereof, wherein the preparation method specifically comprises the following steps: Step 1: Add 700 kg of butyl acrylate, 100 kg of sodium p-styrenesulfonate, 10 kg of dibenzoyl peroxide, and 10 kg of dodecyl mercaptan to a reactor equipped with a heating device, heat to 78-81°C, and react for 1 hour; then dropwise add 100 kg of γ-(methacryloyloxy)propyltrimethoxysilane and 10 kg of methyl methacrylate to the reactor, as well as 30 kg of dibenzoyl peroxide and 30 kg of dodecyl mercaptan, and control the dropwise addition time to 2 hours; after the dropwise addition is completed, keep warm for 0.5 hour to obtain a colorless to light yellow transparent liquid, which is the macromolecular coupling agent.

[0024] Step 2: Add 500 kg of macromolecular coupling agent to a reactor with a heating device, turn on the stirring and slowly add 500 kg of nano-SiO2 particles, stir and heat to 80°C, and continue stirring for 1 hour to obtain modified nano-SiO2 particles.

[0025] Step 3: add 400 kg of n-butanol to a reactor with a heating device, and then add 400 kg of bisphenol S and 200 kg of paraformaldehyde in sequence under stirring, raise the temperature to 60 ° C, and slowly add 400 kg of sodium dodecylamine acetate. After completion, raise the temperature to 120 ° C and reflux, continue the reaction for 8 hours, and then remove the n-butanol solvent by reduced pressure distillation at 120 ° C to obtain a white solid, thereby obtaining a gemini benzoxazine surfactant.

[0026] Example 2 This example is based on Example 1. The modified nano-SiO2 particles and Gemini benzoxazine surfactant obtained in Example 1 are used to prepare a temperature-resistant and salt-resistant tension-resistant nanofluid oil displacement agent. The specific preparation steps are as follows: 50 kg of modified nano-SiO2 particles, 200 kg of non-ionic surfactant (polyoxyethylene ether fatty alcohol), 100 kg of Gemini benzoxazine surfactant, 200 kg of n-butanol and 400 kg of water were weighed in sequence and mixed. After ultrasonic dispersion, 50 kg of kerosene was slowly added dropwise, and then ultrasonic dispersion was continued for 40 minutes to obtain a temperature-resistant and salt-resistant tension nanofluid oil displacement agent.

[0027] The mineralization degree is 2.0×10 5The prepared temperature-resistant and salt-resistant tension nanofluid oil displacement agent was mixed with the mineralized water to prepare a nanofluid oil displacement agent solution with a mass concentration of 0.2%, and stirred and dissolved for 30 minutes. The interfacial tension between the nanofluid oil displacement agent and kerosene was measured using a spinning drop interfacial tension meter at room temperature for 30 minutes. The stable interfacial tension value was 0.0064 mN / m, and the interfacial tension was less than 10 -2 The low interfacial tension requirement is met; a 0.2% nanofluid oil-displacing agent solution is sealed in a pressure-resistant glass bottle, placed in a 130°C oven for curing, and observed for 18 hours without precipitation. The interfacial tension between the nanofluid oil-displacing agent solution and kerosene is measured using a spinning drop interfacial tension meter at room temperature after curing for 12 hours, and the result is 0.0068 mN / m, which meets the dispersibility requirement, indicating that the nanofluid oil-displacing agent has good temperature and salt resistance, and can significantly reduce the oil-water interfacial tension, and is suitable for improving the recovery rate of high-temperature and high-salt oil reservoirs.

[0028] Example 3 This example is based on Example 1. The modified nano-SiO2 particles and Gemini benzoxazine surfactant obtained in Example 1 are used to prepare a temperature-resistant and salt-resistant tension-resistant nanofluid oil displacement agent. The specific preparation steps are as follows: 120 kg of modified nano-SiO2 particles, 100 kg of non-ionic surfactant (polyoxyethylene ether fatty alcohol), 300 kg of Gemini benzoxazine surfactant, 100 kg of n-butanol and 200 kg of water were weighed in sequence and mixed. After ultrasonic dispersion, 30 kg of dodecane was slowly added dropwise, and then ultrasonic dispersion was continued for 80 minutes to obtain a temperature-resistant and salt-resistant tension nanofluid oil displacement agent.

[0029] The mineralization degree is 2.0×10 5 The prepared temperature-resistant and salt-resistant tension nanofluid oil displacement agent was mixed with 100 mg / L of mineralized water to prepare a nanofluid oil displacement agent solution with a mass concentration of 0.2%, and stirred and dissolved for 30 minutes. The interfacial tension between the nanofluid oil displacement agent and kerosene was measured using a spinning drop interfacial tension meter at room temperature for 30 minutes, and a stable interfacial tension value was obtained, which was 0.00087 mN / m. The interfacial tension was less than 10 -3 The low interfacial tension requirement is met; a 0.2% nanofluid oil-displacing agent solution is sealed in a pressure-resistant glass bottle, placed in a 130°C oven for curing, and observed for 12 hours without precipitation. The interfacial tension between the nanofluid oil-displacing agent solution and kerosene after curing for 12 hours is measured using a spinning drop interfacial tension meter at room temperature, and the result is 0.00098 mN / m, which meets the dispersibility requirement, indicating that the nanofluid oil-displacing agent has good temperature and salt resistance, can significantly reduce the oil-water interfacial tension, and is suitable for improving the recovery rate of high-temperature and high-salt oil reservoirs.

[0030] Example 4 This example is based on Example 1. The modified nano-SiO2 particles and Gemini benzoxazine surfactant obtained in Example 1 are used to prepare a temperature-resistant and salt-resistant tension-resistant nanofluid oil displacement agent. The specific preparation steps are as follows: 80 kg of modified nano-SiO2 particles, 200 kg of non-ionic surfactant, 200 kg of Gemini benzoxazine surfactant, 100 kg of n-butanol and 500 kg of water were weighed in sequence and mixed. After ultrasonic dispersion, 10 kg of white oil was slowly added dropwise, and then ultrasonic dispersion was continued for 60 minutes to obtain a temperature-resistant and salt-resistant tension nanofluid oil displacement agent.

[0031] The mineralization degree is 2.0×10 5 The prepared temperature-resistant and salt-resistant tension nanofluid oil displacement agent was mixed with 100 mg / L of mineralized water to prepare a nanofluid oil displacement agent solution with a mass concentration of 0.2%, and stirred and dissolved for 30 minutes. The interfacial tension between the nanofluid oil displacement agent and kerosene was measured using a spinning drop interfacial tension meter at room temperature for 30 minutes, and a stable interfacial tension value was obtained, which was 0.0013 mN / m. The interfacial tension was less than 10 -2 The low interfacial tension requirement is met; a 0.2% nanofluid oil-displacing agent solution is sealed in a pressure-resistant glass bottle, placed in a 130°C oven for curing, and observed for 16 hours without precipitation. The interfacial tension between the nanofluid oil-displacing agent solution and kerosene after curing for 12 hours is measured using a spinning drop interfacial tension meter at room temperature, and the result is 0.0018 mN / m, which meets the dispersibility requirement, indicating that the nanofluid oil-displacing agent has good temperature and salt resistance, and can significantly reduce the oil-water interfacial tension, and is suitable for improving the recovery rate of high-temperature and high-salt oil reservoirs.

[0032] Example 5 This embodiment provides a temperature-resistant, salt-resistant, tension-resistant nanofluid oil-displacing agent and a preparation method thereof, wherein the preparation method specifically comprises the following steps: Step 1: Add 500kg of butyl acrylate, 300kg of sodium p-styrenesulfonate, 30kg of dibenzoyl peroxide and 30kg of dodecyl mercaptan to a reactor equipped with a heating device, heat to 78-81°C, and react for 2 hours; then dropwise add 300kg of γ-(methacryloyloxy)propyltrimethoxysilane and 100kg of methyl methacrylate to the reactor, as well as 20kg of dibenzoyl peroxide and 20kg of dodecyl mercaptan, and control the dropwise addition time to 2 hours; after the dropwise addition is completed, keep warm for 1 hour to obtain a colorless to light yellow transparent liquid, which is the macromolecular coupling agent.

[0033] Step 2: Add 500 kg of macromolecular coupling agent to a reactor with a heating device, turn on the stirring and slowly add 500 kg of nano-SiO2 particles, stir and heat to 80°C, and continue stirring for 1 hour to obtain modified nano-SiO2 particles.

[0034] Step 3: add 500 kg of n-butanol to a reactor with a heating device, and then add 500 kg of bisphenol S and 300 kg of paraformaldehyde in sequence under stirring, raise the temperature to 60 ° C, slowly add 200 kg of sodium glycinate, and after completion, raise the temperature to 120 ° C and reflux, continue the reaction for 6 hours, and then remove the n-butanol solvent by reduced pressure distillation at 120 ° C to obtain a white solid, thereby obtaining a gemini benzoxazine surfactant.

[0035] Example 6 This example is based on Example 5. The modified nano-SiO2 particles and Gemini benzoxazine surfactant obtained in Example 5 are used to prepare a temperature-resistant and salt-resistant tension nanofluid oil displacement agent. The specific preparation steps are as follows: 50 kg of modified nano-SiO2 particles, 200 kg of non-ionic surfactant, 200 kg of gemini benzoxazine surfactant, 100 kg of n-butanol and 400 kg of water were weighed in sequence and mixed. After ultrasonic dispersion, 50 kg of kerosene was slowly added dropwise, and then ultrasonic dispersion was continued for 40 minutes to obtain a temperature-resistant and salt-resistant tension nanofluid oil displacement agent.

[0036] The mineralization degree is 2.0×10 5 The prepared temperature-resistant and salt-resistant tension nanofluid oil displacement agent was mixed with 100 mg / L of mineralized water to prepare a nanofluid oil displacement agent solution with a mass concentration of 0.2%, and stirred and dissolved for 30 minutes. The interfacial tension between the nanofluid oil displacement agent and kerosene was measured using a spinning drop interfacial tension meter at room temperature for 30 minutes, and a stable interfacial tension value was obtained, which was 0.0079 mN / m. The interfacial tension was less than 10 -2 The low interfacial tension requirement is met; a 0.2% nanofluid oil-displacing agent solution is sealed in a pressure-resistant glass bottle, placed in a 130°C oven for curing, and observed for 15 hours without precipitation. The interfacial tension between the nanofluid oil-displacing agent solution and kerosene after curing for 12 hours is measured using a spinning drop interfacial tension meter at room temperature, and the result is 0.0082 mN / m, which meets the dispersibility requirement, indicating that the nanofluid oil-displacing agent has good temperature and salt resistance, and can significantly reduce the oil-water interfacial tension, and is suitable for improving the recovery rate of high-temperature and high-salt oil reservoirs.

[0037] Example 7 This example is based on Example 5. The modified nano-SiO2 particles and Gemini benzoxazine surfactant obtained in Example 5 are used to prepare a temperature-resistant and salt-resistant tension nanofluid oil displacement agent. The specific preparation steps are as follows: 120 kg of modified nano-SiO2 particles, 150 kg of non-ionic surfactant, 300 kg of Gemini benzoxazine surfactant, 100 kg of n-butanol and 300 kg of water were weighed in sequence and mixed. After ultrasonic dispersion, 30 kg of dodecane was slowly added dropwise, and then ultrasonic dispersion was continued for 80 minutes to obtain a temperature-resistant and salt-resistant tension nanofluid oil displacement agent.

[0038] The mineralization degree is 2.0×10 5 The prepared temperature-resistant and salt-resistant tension nanofluid oil displacement agent was mixed with the mineralized water to prepare a nanofluid oil displacement agent solution with a mass concentration of 0.2%, and stirred and dissolved for 30 minutes. The interfacial tension between the nanofluid oil displacement agent and kerosene was measured using a spinning drop interfacial tension meter at room temperature for 30 minutes, and a stable interfacial tension value was obtained, which was 0.00093 mN / m. The interfacial tension was less than 10 -3 The low interfacial tension requirement is met; a 0.2% nanofluid oil-displacing agent solution is sealed in a pressure-resistant glass bottle, placed in a 130°C oven for curing, and observed for 10 hours without precipitation. The interfacial tension between the nanofluid oil-displacing agent solution and kerosene is measured using a spinning drop interfacial tension meter at room temperature after curing for 12 hours, and the result is 0.0011 mN / m, which meets the dispersibility requirement, indicating that the nanofluid oil-displacing agent has good temperature and salt resistance, and can significantly reduce the oil-water interfacial tension, and is suitable for improving the recovery rate of high-temperature and high-salt oil reservoirs.

[0039] Example 8 This example is based on Example 5. The modified nano-SiO2 particles and Gemini benzoxazine surfactant obtained in Example 5 are used to prepare a temperature-resistant and salt-resistant tension nanofluid oil displacement agent. The specific preparation steps are as follows: 80 kg of modified nano-SiO2 particles, 200 kg of non-ionic surfactant, 300 kg of Gemini benzoxazine surfactant, 100 kg of n-butanol and 300 kg of water were weighed in sequence and mixed. After ultrasonic dispersion, 20 kg of white oil was slowly added dropwise, and then ultrasonic dispersion was continued for 60 minutes to obtain a temperature-resistant and salt-resistant tension nanofluid oil displacement agent.

[0040] The mineralization degree is 2.0×10 5 The prepared temperature-resistant and salt-resistant tension nanofluid oil displacement agent was mixed with 100 mg / L of mineralized water to prepare a nanofluid oil displacement agent solution with a mass concentration of 0.2%, and stirred and dissolved for 30 minutes. The interfacial tension between the nanofluid oil displacement agent and kerosene was measured using a spinning drop interfacial tension meter at room temperature for 30 minutes, and a stable interfacial tension value was obtained, which was 0.0021 mN / m. The interfacial tension was less than 10 -2 The low interfacial tension requirement is met; a 0.2% nanofluid oil-displacing agent solution is sealed in a pressure-resistant glass bottle, placed in a 130°C oven for curing, and observed for 18 hours without precipitation. The interfacial tension between the nanofluid oil-displacing agent solution and kerosene is measured using a spinning drop interfacial tension meter at room temperature after curing for 12 hours, and the result is 0.0024 mN / m, which meets the dispersibility requirement, indicating that the nanofluid oil-displacing agent has good temperature and salt resistance, and can significantly reduce the oil-water interfacial tension, and is suitable for improving the recovery rate of high-temperature and high-salt oil reservoirs.

[0041] Example 9 The mineralization degree is 2.0×10 5 mg / L of mineralization, the nanofluid oil displacement agents synthesized in Examples 2, 3, 6, and 7 of the present invention were added respectively, and after aging at 130°C for 9 hours, the contact angle was measured using a contact angle meter at 20°C. The experimental results are as follows Figure 1 As shown in the figure, it can be seen that after 9 hours, the contact angle of the nanofluid oil-displacing agent is 70-90°, indicating that the nanofluid oil-displacing agent provided by the present invention has good wettability.

[0042] Example 10 On-site implementation: The TXXX well reservoir is buried at a depth of about 4540m and has a reservoir temperature of 112°C. Trial production began in July 2011 and is currently in the water injection development stage. By the end of July 2023, the well had a cumulative oil production of 24.90×10 4 t, with a recovery rate of 39.24%. On July 2, 2024, the process of plugging first and then flooding was adopted for adjustment and flooding, and the injection formula was 0.2% nanofluid oil displacement agent + on-site water (mineralization of 23.8×10 4 mg / L) totaling 2066 m 3 The use of nanofluid flooding agent has obvious effect in increasing oil production. Before the measure, the well produced 0.89 tons of oil per day, and after the measure, the daily oil production was 6.8 tons, with a cumulative increase of 1218 tons of oil. The increase in production is as follows: Figure 2 shown.

[0043] The above embodiments merely represent preferred implementations, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art will be able to make various modifications and improvements without departing from the scope of the present invention, and these modifications and improvements are all within the scope of protection of the present invention.

Claims

1. A temperature-resistant and salt-resistant nanofluid oil-displacing agent, characterized in that: In parts by weight, including: 5-12 parts modified nano-SiO2 particles, 10-20 parts non-ionic surfactant, 10-30 parts gemini benzoxazine surfactant, 1-5 parts dispersant, 10-20 parts mutual solvent, 20-50 parts water; Wherein, the modified nano-SiO2 particles are nano-SiO2 particles modified by a macromolecular coupling agent.

2. A temperature-resistant and salt-resistant nanofluid oil-displacing agent according to claim 1, characterized in that: The preparation of the modified nano-SiO2 particles comprises the following steps: Preparation of macromolecular coupling agent: (1) Add butyl acrylate, sodium styrene sulfonate, dibenzoyl peroxide, and dodecyl mercaptan to a reactor, heat to 78°C~81°C, and continue the reaction for 0.5h~2h; (2) Then slowly add γ-(methacryloyloxy)propyltrimethoxysilane, methyl methacrylate, dibenzoyl peroxide, and dodecyl sulfide dropwise, and control the addition time to be within 2h; (3) After the addition is completed, keep warm for 1h to obtain a colorless or light yellow transparent liquid, which is the macromolecular coupling agent; Modification: The prepared macromolecule is coupled and transferred into another reaction kettle, and nano-SiO2 particles are added while stirring; after heating to 80°C, stirring is continued for 1 hour to obtain modified nano-SiO2 particles.

3. A temperature-resistant and salt-resistant nanofluid oil-displacing agent according to claim 2, characterized in that: When the modified nano-SiO2 particles are prepared, the mass ratio of the nano-SiO2 particles to the macromolecular coupling agent is 1:1; The macromolecular coupling agent comprises, by weight, 50 to 70 parts of butyl acrylate, 10 to 30 parts of sodium p-styrenesulfonate, 1 to 10 parts of methyl methacrylate, 10 to 30 parts of γ-(methacryloyloxy)propyltrimethoxysilane, 3 parts of dibenzoyl peroxide, and 3 parts of dodecyl mercaptan.

4. A temperature-resistant and salt-resistant nanofluid oil-displacing agent according to any one of claims 1 to 3, characterized in that: The gemini benzoxazine surfactant is prepared from these raw materials, which include, by weight: 40-50 parts of bisphenol compound, 20-40 parts of primary amine acetate, 20-30 parts of paraformaldehyde, and 40-50 parts of n-butanol; Wherein, the bisphenol compound is one or more of bisphenol A, bisphenol E, bisphenol F, bisphenol M, bisphenol S, bisphenol Z, and bisphenol P; Among them, the structure of primary amine acetate is H2N-(CH2) n -COOM, where n is a natural number from 1 to 18, and M is a monovalent metal ion.

5. The heat-resistant and salt-resistant nanofluid oil-displacing agent according to claim 4, characterized in that: The gemini benzoxazine surfactant is prepared as follows: Add n-butanol to a reactor, and then add a bisphenol compound and paraformaldehyde in sequence under stirring; raise the temperature to 60°C, slowly add a primary amine compound containing a double bond, raise the temperature to 120°C and reflux, continue the reaction for 6 to 8 hours, and remove the butanol solvent by reduced pressure distillation at 120°C to obtain a white solid, which is a gemini benzoxazine surfactant.

6. The heat-resistant and salt-resistant nanofluid oil-displacing agent according to claim 4, characterized in that: The nonionic surfactant is polyoxyethylene ether fatty alcohol, and the structure of polyoxyethylene ether fatty alcohol is R-(OCC) x -OH, where R is a carbon number of C6~C 15 Alkyl group, X is a natural number from 8 to 25.

7. The temperature-resistant and salt-resistant nanofluid oil-displacing agent according to claim 6, characterized in that: The dispersant is C6~C 16 One or more of a combination of one or more of straight-chain saturated hydrocarbons, liquid paraffin, white oil, and kerosene.

8. The temperature-resistant and salt-resistant nanofluid oil-displacing agent according to claim 7, characterized in that: The mutual solvent is C4~C 12 One or more of a combination of linear alcohol, ethylene glycol butyl ether, or one or more.

9. Preparation of a temperature-resistant and salt-resistant nanofluid oil-displacing agent, characterized in that: The heat-resistant and salt-resistant nanofluid oil-displacing agent according to any one of claims 1 to 8 is prepared by the following steps: The modified nano-SiO2 particles, nonionic surfactant, gemini benzoxazine surfactant, mutual solvent and water are mixed, and after ultrasonic dispersion, the dispersed phase is slowly added dropwise, and then ultrasonic dispersion is continued for 40 to 80 minutes to obtain a temperature-resistant and salt-resistant tension nanofluid oil displacement agent.

10. An application of a temperature-resistant and salt-resistant nanofluid oil-displacing agent, characterized in that: The temperature-resistant and salt-resistant nanofluid oil displacement agent according to any one of claims 1 to 9 is used for the exploitation of high-temperature and high-salt oil reservoirs.

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