A nano oil-displacing agent and preparation method thereof

Abstract

The present invention provides a nano oil-displacing agent and a preparation method thereof, which belongs to the technical field of oil-displacing agents and comprises the following steps: S1, dissolving a template agent in water, and sequentially adding H 2 SO 4 , silica precursor solution, stand it and separate it to obtain a precipitate, wash it and dry it after aging, and calcine it to obtain mesoporous nano-SiO 2 S2, the nanoparticles are stirred with water and potassium sorbate to obtain a stable suspension, and the mesoporous nano-SiO 2 Stir evenly to obtain a composite nanoparticle suspension; S3, add fatty alcohol polyoxyethylene ether phosphate monoester and trehalose lipid to the composite nanoparticle suspension and stir to obtain an initial nano oil-displacing agent, and after two-step filtration, obtain a nano oil-displacing agent. The technical solution provided by the present invention improves the dispersibility of the nano oil-displacing agent and the ability to change the wettability of the rock surface, thereby achieving an improved recovery rate.

Description

Technical Field

[0001] The invention relates to the technical field of oil-displacing agents, and in particular to a nano oil-displacing agent and a preparation method thereof. Background Art

[0002] Oil resources are an important guarantee for China's industrial development. With the continuous development of my country's economy and the advancement of science and technology, my country's oil demand continues to grow, and its dependence on foreign oil continues to increase. my country's low-permeability oil reservoir reserves are about 23 billion tons, accounting for >70%, and the proportion is increasing year by year, with broad development prospects and potential.

[0003] For low permeability reservoirs, the pore throat radius of the reservoir rock matrix is ​​narrow, the connectivity between each other is poor, the porosity is low, and the pore type is complex, resulting in large seepage resistance and unclear seepage rules. Large-scale volume fracturing technology is to break rocks and form cracks by injecting fracturing fluid at high pressure, thereby increasing the production of oil and gas wells. This method is particularly important in the development of low permeability reservoirs, but after volume fracturing of low permeability reservoirs, as the mining time increases, the energy of the oil and gas layer itself is continuously consumed, the pressure continues to drop, the production drops sharply, and even production is stopped, resulting in a large amount of oil and gas remaining underground that cannot be recovered. Even if repeated fracturing is used, the fracturing effect is not ideal due to insufficient energy. Self-flowing oil production and water injection secondary oil production are common oil production methods for low permeability reservoirs. Spontaneous flow recovery is suitable for oil wells that can spontaneously generate pressure, while water injection secondary oil recovery is to increase the pressure by injecting water into the oil reservoir, thereby improving the recovery rate. Traditional water drive has difficulty in replenishing energy and is mainly based on non-Darcy seepage. It is difficult to establish an effective displacement system and production is difficult. Polymer injection tertiary oil recovery is a method used when water injection secondary oil recovery is not effective. By injecting polymers, the oil-water mobility ratio is improved to further improve the recovery rate.

[0004] In 2022, Yang Chaolan et al. published "Research Progress of Nano-Oil Displacement Agents in the Past Decade" in "Applied Chemical Industry". The article mentioned that "chemical flooding refers to adding a certain amount of chemical reagents to the injection fluid. Common chemical flooding can be divided into: polymer flooding, surfactant flooding and composite flooding. Polymer flooding has outstanding effects in improving mobility ratio and profile adjustment, and is the most widely used, but the synthesis of polymers is difficult to combine excellent properties such as temperature resistance and salt resistance, and improved mobility ratio; surfactant flooding increases crude oil recovery by reducing interfacial tension and changing wettability, but the surfactant sweep efficiency is low and the adsorption loss is large; composite flooding can coordinate the oil displacement mechanism of polymers and surfactants, and has high displacement efficiency but there is a chromatographic separation phenomenon. , affecting oil recovery efficiency; in summary, the current large-scale chemical flooding has certain defects, which limits the field application of chemical flooding, and it is urgent to study new technologies to improve recovery. "The article proposes that "nano oil-displacing agents have the ability to reduce interfacial tension, improve mobility ratio, generate separation pressure, and change the wettability of reservoir rock surface. They are prepared by coupling agent modification, polymerization modification, hybridization, and compounding with surfactants or polymers. According to the different states of existence, they are divided into nanopowders, nano-Pickering emulsions, and nano-emulsions. However, the research on nano-oil-displacing agents is still at the stage of theoretical analysis and laboratory research, and is not suitable for field application due to various factors."

[0005] In addition, the above technical solution introduces the unique physical and chemical properties of SiO2 nanoparticles, which can more effectively strip crude oil by reducing the oil-water interfacial tension and changing the wettability of the rock surface, thereby achieving the purpose of increasing production. However, there are problems such as small particle size, easy agglomeration, and limited ability to change the wettability of the rock surface.

[0006] Therefore, it is necessary to provide a nano oil-displacing agent and a preparation method thereof to solve the problems existing in the above-mentioned prior art. Summary of the invention

[0007] In view of this, the present invention provides a nano oil-displacing agent and a preparation method thereof, which improve the dispersibility of the nano oil-displacing agent and the ability to change the wettability of the rock surface, thereby achieving improved recovery.

[0008] To achieve the above object, the present invention provides a method for preparing a nano oil-displacing agent, comprising the following steps:

[0009] S1, dissolving the template in water, adding H2SO4 and silica precursor solution in sequence, standing and separating to obtain a precipitate, washing and drying after aging, and calcining to obtain mesoporous nano-SiO2;

[0010] S2, stirring the nanoparticles with water and potassium sorbate to obtain a stable suspension, adding the mesoporous nano-SiO2 and stirring evenly to obtain a composite nanoparticle suspension;

[0011] S3, adding fatty alcohol polyoxyethylene ether phosphate monoester and trehalose lipid into the composite nanoparticle suspension and stirring to obtain an initial nano oil-displacing agent, and after two-step filtration, obtaining a nano oil-displacing agent.

[0012] The technical solution provided by the present invention first prepares mesoporous nano-SiO2 particles, which are embedded in the pores of mesoporous particles with their high specific surface area and pores through the interaction between particles, thereby reducing the aggregation and precipitation of nano-particles. At the same time, the formed composite nano-particles have a small volume and a large specific surface area, thereby increasing the contact area with crude oil and improving the desorption efficiency of crude oil. Secondly, potassium sorbate is used together with the nano-particles, and potassium sorbate is adsorbed on the surface of the nano-particles to prevent particle aggregation through electrostatic repulsion and steric hindrance effects, thereby improving the dispersibility of the nano-particles. Finally, potassium sorbate contains hydrophilic hydroxyl and carboxyl groups, which enhance the hydrophilicity of the nano-particles after combining with the nano-particles, and is more likely to form hydrogen bonds with hydroxyl groups in trehalose lipid and fatty alcohol polyoxyethylene ether phosphate monoester, thereby enhancing the stability of the system and facilitating the amphiphilic modification of trehalose lipid. The phosphate monoester group of the fatty alcohol polyoxyethylene ether phosphate monoester carries a negative charge, which forms an electrostatic interaction with potassium ions generated by potassium sorbate, thereby stabilizing the micelle structure and preventing particle aggregation, thereby further enhancing the dispersibility of the nano-particles.

[0013] The technical solution provided by the present invention adopts the use of fatty alcohol polyoxyethylene ether phosphate monoester and trehalose lipid together, and hydrogen bonds are formed between the hydroxyl group and the phosphate group of the polyoxyethylene chain in the fatty alcohol polyoxyethylene ether phosphate monoester and the hydroxyl group and water molecules of the trehalose lipid, thereby enhancing the compatibility of the oil displacement agent with water; the long chain of the fatty alcohol of the fatty alcohol polyoxyethylene ether phosphate monoester and the long chain fatty acid of the trehalose lipid can form a hydrophobic interaction, which is helpful to form a stable micelle structure, thereby improving the dispersibility and stability of the entire system, and forming a hydrophobic effect with the oil molecules, thereby improving the adsorption capacity of the oil displacement agent to oil, and combining with the trehalose lipid to improve the viscosity of the system and then enhance the adhesion of the system to the rock surface, thereby jointly achieving the hydrophilic and lipophilic effects of the oil displacement agent.

[0014] In addition, fatty alcohol polyoxyethylene ether phosphate monoester and trehalose lipids both have strong emulsifying ability. The combined use of the two can further enhance the emulsification effect and change the wettability of the rock surface, which helps to peel crude oil from the rock surface and disperse it into the water, thereby improving the recovery rate.

[0015] Optionally, the silicon dioxide precursor solution in S1 is a sodium silicate solution.

[0016] Optionally, the sodium silicate solution is prepared by mixing 14% by mass of NaOH and 27% by mass of SiO2 with water.

[0017] The sodium silicate solution used in the present invention improves the dispersibility of the oil displacement agent.

[0018] Optionally, the template agent in S1 is cocamidopropyl betaine.

[0019] Optionally, the nanoparticles in S2 are a combination of two or more of MgO, Fe2O3, NiO, Al2O3, CaO, ZnO and CuO.

[0020] The nanoparticles used in the technical solution of the present invention are all derived from the main components of rocks, have environmentally friendly characteristics, and can meet the long-term environmental harmlessness requirements of the nano system.

[0021] Optionally, the nanoparticles include MgO, NiO and Al2O3, and the mass ratio of MgO, NiO and Al2O3 is 2:1:2.

[0022] When the nanoparticles used in the technical solution of the present invention are MgO, NiO and Al2O3, the oil recovery effect is good.

[0023] Optionally, the template dissolution condition in S1 is 300-500 r / min for 3.5-4.5 h, the H2SO4 addition condition is dropwise addition, the silica precursor solution addition condition is injection at a flow rate of 1-2 ml / min, and the standing time is 3-4 h.

[0024] Optionally, the separation condition in S1 is centrifugation at 4500-5500 rpm for 10-20 min; the aging condition is vacuum, temperature 75-85° C., time 23-24 h; and the calcination condition is nitrogen atmosphere, 580-620° C., 3.5-4.5 h.

[0025] Optionally, the stirring condition is 400-500 r / min for 1-2 h; the two-step filtration in S3 includes preliminary filtration of the initial nano oil-displacing agent through a solvent filtration bottle with a 0.45 μm filter membrane, and then secondary filtration with a 0.22 μm filter membrane.

[0026] The technical solution of the present invention uses two-step filtration to filter out large particle impurities and reduce the aggregation and sedimentation of nanoparticles in the oil displacement agent.

[0027] In order to achieve the above object, the present invention also provides a nano oil-displacing agent, which is prepared by the above preparation method and comprises the following components in parts by weight: 90-110 parts of a template, 8-12 parts of H2SO4, 25-35 parts of a silicon dioxide precursor, 4-6 parts of nanoparticles, 1-1.5 parts of potassium sorbate, 0.2-0.6 parts of fatty alcohol polyoxyethylene ether phosphate monoester and 0.7-1.4 parts of trehalose lipid.

[0028] The above technical solution of the present invention includes at least the following beneficial effects:

[0029] In the preparation method provided by the present invention, potassium sorbate and nanoparticles are used together, and the adsorption and group bonding of the two are utilized to enhance the dispersibility of the nanoparticles and prevent the aggregation of the particles. The raw materials also include fatty alcohol polyoxyethylene ether phosphate monoester and trehalose lipid containing hydroxyl groups, which form hydrogen bonds with potassium sorbate to enhance the stability of the system. The hydrogen bonds formed between the hydroxyl groups between the fatty alcohol polyoxyethylene ether phosphate monoester and the trehalose lipid and water also enhance the compatibility of the oil displacement agent with water. The fatty alcohol long chain of the fatty alcohol polyoxyethylene ether phosphate monoester and the long chain fatty acid of the trehalose lipid can form a hydrophobic interaction, thereby enhancing the adsorption capacity of the oil displacement agent to oil, comprehensively enhancing the adhesion of the system to the rock surface, improving the wettability of the rock surface, and further enhancing the recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The contact angle diagrams of the oil displacing agents prepared in Examples 1 and 2 of the present invention and Comparative Example 1;

[0031] Figure 2 It is the emulsification water separation rate diagram of Example 2 of the present invention and Comparative Example 2;

[0032] Figure 3 A well location map of the oil displacement agent prepared in Example 3 of the present invention applied to oil well 1;

[0033] Figure 4 This is a production curve diagram of the oil displacement agent prepared in Example 3 of the present invention before and after being applied to oil well 1;

[0034] Figure 5 This is a well location map of the oil displacement agent used in oil well 2 in comparative example 5 of the present invention;

[0035] Figure 6 This is a production curve diagram of the oil displacement agent of comparative example 5 of the present invention before and after being applied to oil well 2. DETAILED DESCRIPTION

[0036] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the following will be combined with the appended drawings of the embodiments of the present invention. Figure 1 ~Attached Figure 6 , the technical scheme of the embodiment of the present invention is clearly and completely described. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0037] Example 1

[0038] 100 parts of cocamidopropyl betaine were added to 1L of deionized water and treated at 400r / min for 4h, during which 10 parts of H2SO4 were added dropwise to obtain a cocamidopropyl betaine solution. 30 parts of sodium silicate solution were poured into a dropping funnel and injected into the cocamidopropyl betaine solution at a flow rate of 1mL / min, and allowed to stand for 3h to form a precipitate. The supernatant of the precipitate was poured off, and the remaining precipitate solution was centrifuged at 5000rpm for 15min, the supernatant was poured off, and the precipitate was retained. The precipitate was vacuum aged at 80℃ for 24h, washed with deionized water 3~5 times, dried in an oven at 80℃ for 5h, and calcined in a nitrogen atmosphere at 600℃ for 4h to obtain mesoporous nano-SiO2.

[0039] Add 5 parts of nanoparticles (MgO, NiO, Al2O3 in a mass ratio of 2:1:2) and 1 part of potassium sorbate to 50 parts of deionized water and stir at 400r / min for 2h to obtain a stable suspension. Add mesoporous nano-SiO2 and treat at 500r / min for 1h to obtain a composite nanoparticle suspension.

[0040] 0.2 parts of fatty alcohol polyoxyethylene ether phosphate monoester and 1 part of trehalose lipid were added to the composite nano suspension and treated at 500r / min for 2h to obtain the initial nano oil-displacing agent. The initial nano oil-displacing agent was first filtered through a solvent filter bottle with a 0.45μm filter membrane, and then filtered twice with a 0.22μm filter membrane to further filter large particle impurities to obtain a nano oil-displacing agent.

[0041] Example 2

[0042] 90 parts of cocamidopropyl betaine were added to 1L deionized water and treated at 300r / min for 4.5h, during which 8 parts of H2SO4 were added dropwise to obtain cocamidopropyl betaine solution. 35 parts of sodium silicate solution were poured into a dropping funnel and injected into the cocamidopropyl betaine solution at a flow rate of 2mL / min. The sodium silicate solution was prepared by mixing 14% NaOH and 27% SiO2 with water, and the mixture was allowed to stand for 3.5h to form a precipitate. The supernatant of the precipitate was poured off, and the remaining precipitate solution was centrifuged at 4500rpm for 20min, the supernatant was poured off, the precipitate was retained, and the precipitate was vacuum aged at 85℃ for 23h, washed with deionized water 5 times, dried in an oven at 85℃ for 5h, and calcined in a nitrogen atmosphere at 580℃ for 4.5h to obtain mesoporous nano-SiO2.

[0043] 6 parts of nanoparticles (MgO, NiO, ZnO mass ratio of 2:2:2) and 1.5 parts of potassium sorbate were added to 50 parts of deionized water and stirred at 500r / min for 1h to obtain a stable suspension. Mesoporous nano-SiO2 was added and treated at 400r / min for 2h to obtain a composite nanoparticle suspension.

[0044] 0.4 parts of fatty alcohol polyoxyethylene ether phosphate monoester and 0.7 parts of trehalose lipid were added to the composite nano suspension and treated at 400r / min for 2h to obtain the initial nano oil-displacing agent. The initial nano oil-displacing agent was first filtered through a solvent filter bottle with a 0.45μm filter membrane, and then filtered twice with a 0.22μm filter membrane to further filter large particle impurities to obtain a nano oil-displacing agent.

[0045] Example 3

[0046] 110 parts of cocamidopropyl betaine were added to 1L of deionized water and treated at 400r / min for 3.5h, during which 12 parts of H2SO4 were added dropwise to obtain cocamidopropyl betaine solution. 25 parts of sodium silicate solution were poured into a dropping funnel and injected into the cocamidopropyl betaine solution at a flow rate of 1.5mL / min. The sodium silicate solution was prepared by mixing 14% NaOH and 27% SiO2 with water, and the mixture was allowed to stand for 4h to form a precipitate. The supernatant of the precipitate was poured off, and the remaining precipitate solution was centrifuged at 5500rpm for 10min, the supernatant was poured off, the precipitate was retained, and the precipitate was vacuum aged at 75℃ for 23h, washed with deionized water 4 times, dried in an oven at 75℃ for 5h, and calcined in a nitrogen atmosphere at 620℃ for 3.5h to obtain mesoporous nano-SiO2.

[0047] 4 parts of nanoparticles (the mass ratio of CuO and NiO is 2:2) and 1.2 parts of potassium sorbate were added to 50 parts of deionized water and stirred at 450 r / min for 1.5 hours to obtain a stable suspension. Mesoporous nano-SiO2 was added and treated at 450 r / min for 1 hour to obtain a composite nanoparticle suspension.

[0048] 0.6 parts of fatty alcohol polyoxyethylene ether phosphate monoester and 1.4 parts of trehalose lipid were added to the composite nano suspension and treated at 500r / min for 2h to obtain the initial nano oil-displacing agent. The initial nano oil-displacing agent was first filtered through a solvent filter bottle with a 0.45μm filter membrane, and then filtered twice with a 0.22μm filter membrane to further filter large particle impurities to obtain a nano oil-displacing agent.

[0049] Example 4

[0050] 95 parts of cocamidopropyl betaine were added to 1L of deionized water and treated at 400r / min for 4h, during which 9 parts of H2SO4 were added dropwise to obtain a cocamidopropyl betaine solution. 32 parts of sodium silicate solution were poured into a dropping funnel and injected into the cocamidopropyl betaine solution at a flow rate of 1mL / min, and allowed to stand for 3h to form a precipitate. The supernatant of the precipitate was poured off, and the remaining precipitate solution was centrifuged at 5000rpm for 15min, the supernatant was poured off, and the precipitate was retained. The precipitate was vacuum aged at 80℃ for 24h, washed with deionized water 3~5 times, dried in an oven at 80℃ for 5h, and calcined in a nitrogen atmosphere at 600℃ for 4h to obtain mesoporous nano-SiO2.

[0051] Add 5 parts of nanoparticles (MgO, NiO, Al2O3 in a mass ratio of 2:1:2) and 1.4 parts of potassium sorbate to 50 parts of deionized water and stir at 400r / min for 2h to obtain a stable suspension. Add mesoporous nano-SiO2 and treat at 500r / min for 1h to obtain a composite nanoparticle suspension.

[0052] 0.5 parts of fatty alcohol polyoxyethylene ether phosphate monoester and 0.8 parts of trehalose lipid were added to the composite nano suspension and treated at 500r / min for 2h to obtain the initial nano oil-displacing agent. The initial nano oil-displacing agent was first filtered through a solvent filter bottle with a 0.45μm filter membrane, and then filtered twice with a 0.22μm filter membrane to further filter large particle impurities to obtain a nano oil-displacing agent.

[0053] Example 5

[0054] 105 parts of cocamidopropyl betaine were added to 1L of deionized water and treated at 300r / min for 4.5h, during which 11 parts of H2SO4 were added dropwise to obtain cocamidopropyl betaine solution. 28 parts of sodium silicate solution were poured into a dropping funnel and injected into the cocamidopropyl betaine solution at a flow rate of 2mL / min. The sodium silicate solution was prepared by mixing 14% NaOH and 27% SiO2 with water, and the mixture was allowed to stand for 3.5h to form a precipitate. The supernatant of the precipitate was poured off, and the remaining precipitate solution was centrifuged at 4500rpm for 20min, the supernatant was poured off, the precipitate was retained, and the precipitate was vacuum aged at 85℃ for 23h, washed with deionized water 5 times, dried in an oven at 85℃ for 5h, and calcined in a nitrogen atmosphere at 580℃ for 4.5h to obtain mesoporous nano-SiO2.

[0055] 6 parts of nanoparticles (MgO, NiO, ZnO mass ratio of 2:2:2) and 1.1 parts of potassium sorbate were added to 50 parts of deionized water and stirred at 500r / min for 1h to obtain a stable suspension. Mesoporous nano-SiO2 was added and treated at 400r / min for 2h to obtain a composite nanoparticle suspension.

[0056] 0.5 parts of fatty alcohol polyoxyethylene ether phosphate monoester and 0.9 parts of trehalose lipid were added to the composite nano suspension and treated at 400r / min for 2h to obtain the initial nano oil-displacing agent. The initial nano oil-displacing agent was first filtered through a solvent filter bottle with a 0.45μm filter membrane, and then filtered twice with a 0.22μm filter membrane to further filter large particle impurities to obtain a nano oil-displacing agent.

[0057] Example 6

[0058] Compared with Example 2, the only difference is that the mass ratio of Fe2O3, NiO and Al2O3 used in the nanoparticles is 2:2:2, and the other steps and raw materials are the same as those in Example 1.

[0059] Comparative Example 1

[0060] Compared with Example 2, the only difference is that trehalose lipid is not used, and the other steps and raw materials are the same as those in Example 2.

[0061] Comparative Example 2

[0062] Compared with Example 2, the only difference is that fatty alcohol polyoxyethylene ether phosphate monoester is not used, and the remaining steps and raw materials are the same as those of Example 2.

[0063] Comparative Example 3

[0064] Compared with Example 2, the only difference is that potassium sorbate is not used, and the remaining steps and raw materials are the same as those of Example 2.

[0065] Comparative Example 4

[0066] Compared with Example 2, the only difference is that nano-SiO2 is used instead of mesoporous nano-SiO2, and the other steps and raw materials are the same as those in Example 2.

[0067] Comparative Example 5

[0068] Petroleum sulfonate oil displacement agent commonly used in this industry.

[0069] The performance test was performed on the oil displacing agents prepared in Examples 1 to 6 and Comparative Examples 1 to 5. The basic performance and performance data after aging of the oil displacing agents in Examples 1 to 6 at a concentration of 0.3% are shown in Table 1, the aging condition is 120°C, and the mineralization degree is 100000 mg / L; the contact angle comparison diagram of the examples and the comparative examples is shown in Figure 1, the emulsification water separation rate diagram of the embodiment and the comparative example is shown in Figure 2 .

[0070] Table 1 Basic performance table and performance after aging of oil displacement agents prepared in Examples 1 to 6 and Comparative Examples 1 to 5 at a concentration of 0.3%

[0071]

[0072] As can be seen from Table 1, the oil-displacing agents of Examples 1 to 6 prepared by the present invention have smaller contact angles, smaller contact angle decay time differences, and smaller interfacial tensions than the oil-displacing agents of Comparative Examples 1 to 5. That is, the oil-displacing agents prepared by the embodiments of the present invention have a greater change in the wettability of rocks, thereby improving oil recovery.

[0073] Depend on Figure 1 It can be seen that compared with the oil-displacing agent prepared in Comparative Example 1, the contact angle of the oil-displacing agent prepared in Examples 1 and 2 of the present invention decreases faster over time, and the contact angle and interfacial tension are smaller. The smaller the contact angle, the better the wettability. It can be seen that trehalose lipid can be combined with other raw materials to improve the wettability of the oil-displacing agent.

[0074] Depend on Figure 2 It can be seen that the oil-displacing agent prepared in Example 2 of the present invention has a smaller water separation rate and a better emulsification effect than the oil-displacing agent prepared in Comparative Example 2, that is, the fatty alcohol polyoxyethylene ether phosphate monoester combined with the other raw materials improves the emulsification of the oil-displacing agent.

[0075] In summary, the oil displacing agent prepared by the present invention can improve the recovery rate by improving the basic performance of the oil displacing agent.

[0076] The following is the effect of oil displacement agent in actual application scenarios.

[0077] 1. Application in an oil field in Daqing

[0078] Reservoir background: A block in Daqing Oilfield belongs to a low-porosity and low-permeability reservoir, which is a fault-block-lithologic reservoir with poor inter-well connectivity. The fractures in the whole area are obviously developed in the east-west direction, and the fractures are close to the oil production wells, which can easily cause high water content in the oil production wells. The development time is relatively long. After two rounds of fracturing, the production drops rapidly, and the comprehensive water content is relatively high. After two stages of fracturing, although the oil production has increased, the overall production is not high. The current daily oil production has dropped to less than 1t. The water content is high, which has increased by about 90%. The cumulative production is not high, and the permeability is low, with an average permeability of 22.4mD. The production has increased significantly after fracturing, but it decays rapidly; most of the crude oil remains in the micro-cracks of the formation or in the matrix, and low-permeability production-increasing measures are needed to increase the production of the oil wells. The fractures in the whole area are obviously developed in the east-west direction, and the fractures are close to the oil production wells, which can easily cause water or high water content in the oil production wells, and there is a certain water sensitivity. The relevant information of a block in Daqing Oilfield is shown in Table 2, and the well location map of Oil Well 1 is shown in Figure 3The production curve of oil well 1 before and after using the oil displacement agent prepared in Example 3 is shown in Figure 4 ; The well location map of oil well 2 is shown in Figure 5 The production curve of oil well 2 before and after using comparative example 5, i.e., the petroleum sulfonate flooding agent commonly used in the industry, is shown in FIG. Figure 6 .

[0079] Table 2. Relevant information of a block in Daqing Oilfield

[0080]

[0081] In view of the reservoir characteristics of low porosity and ultra-low permeability, poor well connectivity, high water content, and water sensitivity, the two wells on site were designed to adopt the technical model of "core-shell nano-adjustment and flooding + anti-swelling + infiltration and absorption nano-oil flooding", with a design volume of >1000m³, combined with Figure 4 and Figure 6 It can be seen that after the oil displacement agent prepared by Example 3 of the present invention was used to treat oil well 1, the daily oil production increased from less than 1t / d to more than 8t / d at most, and the water content was significantly reduced. The daily liquid production, i.e., the actual liquid production of the oil field, including the total amount of liquid such as oil and water, was significantly improved. After the oil well 2 was treated with petroleum sulfonate commonly used in the industry, the daily oil production increased, but did not exceed 2t / d. That is, the oil displacement agent prepared by the present invention improves the recovery rate and is superior to the oil displacement agent in the prior art.

[0082] 2. Application in a certain oil field in Changqing

[0083] Reservoir background: The selected horizontal test well was put into production in December 2013, with an initial daily production of 21.28m 3 , daily oil production 12.24t, water content 31.5%, dynamic liquid level 991m, natural energy development; daily liquid production before measures 1.1m 3 , daily oil production of 0.25t, water content of 32.6%, dynamic liquid level of 1842m, salt content of 28733mg / L, cumulative oil production of 6077t. The well has low liquid and low production. Analysis shows that the sand is buried and the formation energy is insufficient. The oil displacement agent prepared in Example 4 is used in combination with sand flushing and well washing for oil production. The relevant process parameters of the measures are shown in Table 3.

[0084] Table 3 Experimental measures and process parameters of a certain oil field in Changqing

[0085]

[0086] Test results of the test well: A chemical huff and puff test was carried out in the test well. In 2022, the horizontal well was sand flushed from September 15 to September 23, and a 0.3% nano oil-displacing agent was injected to discharge a 500m³ plug from September 25 to October 4. The well was started for production on October 23. The oil production increased from 0.25t / d to 2.15t / d, with an average daily increase of 1.35t and an average daily liquid increase of 7.75t per well. The effect was obvious, that is, the oil-displacing agent prepared by the present invention improved the recovery factor.

[0087] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a nano oil-displacing agent, characterized in that: The following steps are involved: S1, dissolving the template in water, adding H2SO4 and silica precursor solution in sequence, standing and separating to obtain a precipitate, washing and drying after aging, and calcining to obtain mesoporous nano-SiO2; S2, stirring the nanoparticles with water and potassium sorbate to obtain a stable suspension, adding the mesoporous nano-SiO2 and stirring evenly, the nanoparticles are embedded in the pores of the mesoporous nano-SiO2 particles through the interaction between the particles, and a composite nanoparticle suspension is obtained, wherein the nanoparticles are a combination of two or more of MgO, Fe2O3, NiO, Al2O3, ZnO and CuO; S3, adding fatty alcohol polyoxyethylene ether phosphate monoester and trehalose lipid into the composite nanoparticle suspension and stirring to obtain an initial nano oil-displacing agent, and after two-step filtration, obtaining a nano oil-displacing agent.

2. The method for preparing a nano oil-displacing agent according to claim 1, wherein The silicon dioxide precursor solution in S1 is a sodium silicate solution.

3. The preparation method of nano oil-displacing agent according to claim 2, characterized in that, The sodium silicate solution is prepared by mixing 14% by mass of NaOH and 27% by mass of SiO2 with water.

4. The preparation method of nano oil-displacing agent according to claim 1, characterized in that, The template agent in S1 is cocamidopropyl betaine.

5. The preparation method of nano oil-displacing agent according to claim 1, characterized in that, The nanoparticles include MgO, NiO and Al2O3, and the mass ratio of MgO, NiO and Al2O3 is 2:1:

2.

6. The preparation method of the nano oil-displacing agent according to claim 1, characterized in that, The conditions for dissolving the template in S1 are 300-500 r / min for 3.5-4.5 h, the conditions for adding H2SO4 are dropwise addition, the conditions for adding the silica precursor solution are injection at a flow rate of 1-2 ml / min, and the standing time is 3-4 h.

7. The preparation method of the nano oil-displacing agent according to claim 1, characterized in that, The separation condition in S1 is centrifugation at 4500-5500 rpm for 10-20 min; the aging condition is vacuum, temperature 75-85° C., and time 23-24 h; and the calcination condition is nitrogen atmosphere, 580-620° C., and 3.5-4.5 h.

8. The preparation method of nano oil-displacing agent according to claim 1, characterized in that, The stirring condition is 400-500 r / min for 1-2 hours; the two-step filtration in S3 includes preliminary filtration of the initial nano oil-displacing agent through a solvent filtration bottle with a 0.45 μm filter membrane, and then secondary filtration with a 0.22 μm filter membrane.

9. A nano oil-displacing agent, characterized in that: The preparation method of the nano oil-displacing agent according to any one of claims 1 to 8 comprises the following components in parts by weight: 90 to 110 parts of a template, 8 to 12 parts of H2SO4, 25 to 35 parts of a silicon dioxide precursor, 4 to 6 parts of nanoparticles, 1 to 1.5 parts of potassium sorbate, 0.2 to 0.6 parts of fatty alcohol polyoxyethylene ether phosphate monoester and 0.7 to 1.4 parts of trehalose lipid.

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