Intelligent nano-chemical oil displacement agent and preparation and application thereof

Abstract

This invention discloses a smart nano-chemical oil displacement agent containing smart microspheres. The smart microspheres comprise: a core formed by nano-SiO2 and dodecyl phosphate monoester clusters; polyacrylamide and Fe3O4 nanoparticles sequentially attached to the surface of the core; and a shell formed by crosslinking poly(N-isopropylacrylamide) and sodium methacrylate. This invention also discloses its preparation and application. The preparation method of this invention is simple, and in the oil displacement process, the smart nano-chemical oil displacement agent of this invention achieves a controllable oil displacement process.

Description

Technical Field

[0001] This invention relates to a smart nano-chemical oil displacement agent, its preparation, and its application. Background Technology

[0002] As oilfields enter the mid-to-late stages of development, declining production capacity and low water injection qualification rates are becoming increasingly serious, and the processing of emulsified crude oil is becoming increasingly difficult. Therefore, the development of oil displacement agents with adjustable emulsification and demulsification behaviors has become a focus of research for many scholars. The research and development of environmentally responsive oil displacement agents has become a hot topic in both academia and industry. Due to their unique and excellent performance and environmental responsiveness, they have enormous potential applications in many fields such as oilfield chemistry, materials science, extraction and separation, and catalysis.

[0003] Chemical flooding is the most promising enhanced oil recovery technology. Tertiary oil recovery utilizes chemical flooding to displace crude oil, effectively solving the technical bottlenecks of secondary oil recovery. After years of development, this technology has gradually matured. However, tertiary oil recovery also faces technical bottlenecks such as high energy consumption, high cost, and low recovery rate, necessitating the exploration of new oil displacement technologies to meet the needs of field applications.

[0004] To address the various problems caused by different chemical flooding agents, intelligent nano-flooding technology has emerged. Due to their large specific surface energy, strong adsorption, and strong hydrophobic and oleophilic properties, nanoparticles, as intelligent nano-chemical flooding agents, can respond to temperature, magnetic field, pH, etc., significantly reducing the interfacial tension between oil and water, and increasing the contact angle between oil and rock formations, making it easier for crude oil to detach from the rock formations and significantly improving crude oil recovery. Summary of the Invention

[0005] To further enrich the selection of oil displacement agents and provide an oil displacement agent with better oil displacement effect, this invention is made. The intelligent nano-chemical oil displacement agent provided by this invention, after being injected into the formation, can control the flow direction, range, and contact time of the nanofluid through the addition of a magnetic field. Simultaneously, it adjusts the pH to disperse and emulsify crude oil, facilitating oil-water separation. It can adapt to the characteristics of high-temperature and low-temperature reservoirs, achieving intelligent operation, thereby realizing efficient displacement and improved oil recovery.

[0006] As one aspect of the present invention, there is a smart nano-chemical oil displacement agent containing smart microspheres, the smart microspheres comprising: a core formed by nano-SiO2 and dodecyl phosphate monoester clusters, polyacrylamide and Fe3O4 nanoparticles sequentially attached to the surface of the core, and a shell formed by crosslinking polyN-isopropylacrylamide and sodium methacrylate.

[0007] In a specific embodiment, the smart microspheres are suspended in a 2.0%-2.1% sodium hydroxide aqueous solution.

[0008] In a specific embodiment, N,N′-methylenebisacrylamide is used as a crosslinking agent to crosslink poly(N-isopropylacrylamide) with sodium methacrylate.

[0009] In a specific embodiment, the mass ratio of the core (dodecyl phosphate monoester + nano SiO2), polyacrylamide, Fe3O4 nanoparticles, and shell (poly(N-isopropylacrylamide) + sodium methacrylate + N,N′-methylenebisacrylamide) in the smart microsphere is 3-4.5:0.5-1.0:0.5-1.25:0.4-0.5:0.9-1.1; preferably 4.3-4.5:0.5-1.0:1.0-1.25:0.4-0.5:0.9-1.1.

[0010] In a specific embodiment, in the core, the mass ratio of dodecyl phosphate monoester to nano-SiO2 is 1.8-2.0:1.0-2.5; in the outer shell, the mass ratio of poly(N-isopropylacrylamide), sodium methacrylate, and N,N′-methylenebisacrylamide is 0.4-0.5:0.1-0.3:0.3-0.5.

[0011] As another aspect of the present invention, a method for preparing a smart nano-chemical oil displacement agent is provided, comprising:

[0012] (1) Add dodecyl phosphate monoester and nano SiO2 to a 2.0% sodium hydroxide aqueous solution and stir. The nano SiO2 and dodecyl phosphate monoester clusters form microspheres.

[0013] (2) Add polyacrylamide and stir to allow the polyacrylamide to adhere to the surface of the microspheres formed in step (1);

[0014] (3) Add Fe3O4 nanoparticles and stir. The Fe3O4 nanoparticles are further attached to the surface of the microspheres.

[0015] (4) Add N,N′-methylenebisacrylamide, mix thoroughly, then add poly(N-isopropylacrylamide) and sodium methacrylate, stir, and obtain intelligent nano-chemical oil displacement agent.

[0016] In a specific embodiment, the mass ratio of dodecyl phosphate monoester, nano-SiO2, polyacrylamide, Fe3O4 nanoparticles, poly(N-isopropylacrylamide), sodium methacrylate, and N,N′-methylenebisacrylamide is 1.8-2.0: 1.0-2.5: 0.5-1.0: 0.5-1.25: 0.4-0.5: 0.1-0.3: 0.3-0.5.

[0017] As another aspect of the present invention, the application of the above-mentioned intelligent nano-chemical flooding agent in oilfield development is involved.

[0018] The preparation method of this invention is simple, and the intelligent nano-chemical oil displacement agent of this invention achieves a controllable oil displacement process during oil displacement. The preparation conditions of the intelligent nano-chemical oil displacement agent of this invention are mild, resulting in low oil displacement cost and good effect, making it suitable for large-scale production. This is of great significance for reducing energy consumption, emissions, and pollution during the extraction process, and improving crude oil recovery. Detailed Implementation

[0019] The specific embodiments of the present invention are described below with reference to examples, but the present invention is not limited to the following examples.

[0020] In the following embodiments, the evaluation method for enhancing oil recovery by intelligent nano-chemical displacement agents adopts the existing evaluation method, specifically:

[0021] (1) After vacuuming the artificial rock core, saturate it with simulated formation water, take it out and wipe the surface water droplets with filter paper, weigh the wet weight of the rock core, calculate its pore volume, and finally immerse the rock core in simulated formation water for later use.

[0022] (2) Take out the pretreated core, record the basic parameters of the core, put it into the core holder, apply confining pressure, and set the experimental temperature to 75℃.

[0023] (3) Saturate the core with simulated formation water, record the injection volume, inlet and outlet pressures, etc. in real time, calculate the water phase permeability of the core, and then saturate the core with simulated oil until no more simulated oil flows out of the outlet. Record the oil and water volume and displacement pressure at the outlet in real time.

[0024] (4) Water flooding: until no more oil flows out of the outlet, record the oil and water volumes at the outlet, and calculate the water flooding recovery rate; Intelligent nano-chemical flooding agent flooding: inject the prepared intelligent nano-chemical flooding agent-water dispersion system until no more oil flows out of the outlet, record the oil volume at the outlet in real time, and calculate the crude oil recovery rate that the intelligent nano-chemical flooding agent can improve.

[0025] Example 1:

[0026] The preparation method of the intelligent nano-chemical oil displacement agent in this embodiment is as follows:

[0027] (1) 2.0g of dodecyl phosphate monoester and 2.5g of 50nm nano SiO2 material were added to 100mL of 2.0% sodium hydroxide aqueous solution and stirred for 3 hours with a magnetic stirrer. The nano SiO2 and dodecyl phosphate monoester clusters formed microspheres (in this invention, they serve as the core of the final spherical product).

[0028] (2) Add 0.5g of polyacrylamide and stir to allow the polyacrylamide to adhere to the surface of the microspheres formed in step (1);

[0029] (3) Add 1.0g of 80nm Fe3O4 nanoparticles and stir at room temperature for 4 hours. The Fe3O4 nanoparticles are further attached to the surface of the microspheres.

[0030] (4) Add 0.3g N,N′-methylenebisacrylamide (crosslinking agent), mix thoroughly, then add 0.5g poly-N-isopropylacrylamide and 0.3g sodium methacrylate, stir at room temperature for 5 hours to obtain the intelligent nano-chemical oil displacement agent.

[0031] The inventors discovered that when N,N′-methylenebisacrylamide (crosslinking agent), poly-N-isopropylacrylamide, and sodium methacrylate are added simultaneously, the poly-N-isopropylacrylamide and sodium methacrylate cannot uniformly coat the surface of the microspheres, resulting in unsatisfactory oil displacement effect. Therefore, in the embodiments of this application, the inventors add poly-N-isopropylacrylamide and sodium methacrylate only after the N,N′-methylenebisacrylamide (crosslinking agent) has been added and mixed evenly, to form a shell coating the surface of the microspheres.

[0032] In the artificial core displacement experiment at the Engineering Technology Research Center Laboratory of Tongji University, the experiment was conducted in accordance with the petroleum and natural gas industry standard SY / T5336-2006 "Core Analysis Methods". 0.3g of intelligent nano-chemical displacement agent was mixed with 100mL of deionized water to form an intelligent nano-chemical displacement agent-water dispersion system. Then, a physical model displacement experiment was conducted using an artificial core (core diameter 2.5cm, length 5.4cm, permeability 0.41μm). 2 First, water flooding was performed to a water cut of 95%, and the oil recovery rate was measured to be 58.6%. Then, 0.4 pV (pore volume) of the intelligent nano-chemical oil displacement agent-water dispersion system of this embodiment was injected, and water flooding was continued to a water cut of 98%, and the oil recovery rate was measured to be 77.1%. It was calculated that the intelligent nano-chemical oil displacement agent can improve the oil recovery rate by 18.5% on the basis of water flooding.

[0033] In the artificial core displacement experiment, the inventors divided the cross-section of the core into two parts. The intelligent nano-chemical oil displacement agent of this invention was applied to one part, and a magnetic field was applied. The results showed that the oil displacement agent only displaced the oil in its corresponding part, while the oil in the other part remained undisplaced. Therefore, it can be concluded that the intelligent nano-chemical oil displacement agent prepared in this embodiment can achieve directional oil displacement under magnetic action, i.e., intelligent oil displacement.

[0034] Example 2:

[0035] The preparation method of the intelligent nano-chemical oil displacement agent of the present invention is as follows:

[0036] (1) 1.8g of dodecyl phosphate monoester and 2.5g of 50nm nano SiO2 material were added to 100mL of 2.0% sodium hydroxide aqueous solution and stirred for 3 hours with a magnetic stirrer. The nano SiO2 and dodecyl phosphate monoester clusters formed microspheres.

[0037] (2) Add 0.5g of polyacrylamide and stir to allow the polyacrylamide to adhere to the surface of the microspheres formed in step (1);

[0038] (3) Add 1.0g of 100nm Fe3O4 nanoparticles and stir at room temperature for 4 hours. The Fe3O4 nanoparticles are further attached to the surface of the microspheres.

[0039] (4) Add 0.3g N,N′-methylenebisacrylamide (crosslinking agent), mix thoroughly, then add 0.4g poly(N-isopropylacrylamide) and 0.1g sodium methacrylate, stir at room temperature for 5 hours to obtain the intelligent nano-chemical oil displacement agent.

[0040] In the artificial core displacement experiment at the Engineering Technology Research Center Laboratory of Tongji University, the experiment was conducted in accordance with the petroleum and natural gas industry standard SY / T5336-2006 "Core Analysis Methods". 0.3g of recyclable multi-response intelligent nano-chemical oil displacement agent was mixed with 100mL of deionized water to form an intelligent nano-chemical oil displacement agent-water dispersion system. Then, a physical model displacement experiment was conducted using an artificial core (core diameter 2.5cm, length 5.3cm, permeability 0.38μm). 2 First, water flooding was performed to a water cut of 95%, and the oil recovery rate was measured to be 52.7%. Then, 0.4 pV (pore volume) of intelligent nano-chemical oil displacement agent-water dispersion system was injected, and water flooding was continued to a water cut of 98%, and the oil recovery rate was measured to be 68.5%. It was calculated that the intelligent nano-chemical oil displacement agent can increase the oil recovery rate by 15.8% on the basis of water flooding.

[0041] Example 3:

[0042] The preparation method of the intelligent nano-chemical oil displacement agent of the present invention is as follows:

[0043] (1) 2.0g of dodecyl phosphate monoester and 2.5g of 50nm nano SiO2 material were added to 100mL of 2.0% sodium hydroxide aqueous solution and stirred for 3 hours with a magnetic stirrer. The nano SiO2 and dodecyl phosphate monoester clusters formed microspheres.

[0044] (2) Add 0.5g of polyacrylamide and stir to allow the polyacrylamide to adhere to the surface of the microspheres formed in step (1);

[0045] (3) Add 1.0g of 90nm Fe3O4 nanoparticles and stir at room temperature for 4 hours. The Fe3O4 nanoparticles further adhere to the surface of the microspheres to form a mixture.

[0046] (4) Add 0.3g N,N′-methylenebisacrylamide (crosslinking agent), mix thoroughly, then add 0.5g poly-N-isopropylacrylamide and 0.1g sodium methacrylate, stir at room temperature for 5 hours to obtain the intelligent nano-chemical oil displacement agent.

[0047] In the artificial core displacement experiment at the Engineering Technology Research Center Laboratory of Tongji University, the experiment was conducted in accordance with the petroleum and natural gas industry standard SY / T5336-2006 "Core Analysis Methods". 0.3g of recyclable multi-response intelligent nano-chemical oil displacement agent was mixed with 100mL of deionized water to form an intelligent nano-chemical oil displacement agent-water dispersion system. Then, a physical model displacement experiment was conducted using an artificial core (core diameter 2.5cm, length 5.4cm, permeability 0.39μm). 2 First, water flooding was performed to a water cut of 95%, and the oil recovery rate was measured to be 54.9%. Then, 0.4 pV (pore volume) of intelligent nano-chemical oil displacement agent-water dispersion system was injected, and water flooding was continued to a water cut of 98%, and the oil recovery rate was measured to be 71.6%. It was calculated that the intelligent nano-chemical oil displacement agent can improve the oil recovery rate by 16.7% on the basis of water flooding.

[0048] Example 4:

[0049] The preparation method of the intelligent nano-chemical oil displacement agent of the present invention is as follows:

[0050] (1) 2.0g of dodecyl phosphate monoester and 2.5g of 50nm nano SiO2 material were added to 100mL of 2.0% sodium hydroxide aqueous solution and stirred for 3 hours with a magnetic stirrer. The nano SiO2 and dodecyl phosphate monoester clusters formed microspheres.

[0051] (2) Add 0.5g of polyacrylamide and stir to allow the polyacrylamide to adhere to the surface of the microspheres formed in step (1);

[0052] (3) Add 1.0g of 80nm Fe3O4 nanoparticles and stir at room temperature for 4 hours. The Fe3O4 nanoparticles further adhere to the surface of the microspheres to form a mixture.

[0053] (4) Add 0.3g N,N′-methylenebisacrylamide (crosslinking agent), mix thoroughly, then add 0.5g poly(N-isopropylacrylamide) and 0.2g sodium methacrylate, and stir at room temperature for 5 hours to obtain the intelligent nano-chemical displacement agent. In the artificial core displacement experiment in the laboratory of the Engineering Technology Research Center of Tongji University, the experiment was carried out in accordance with the petroleum and natural gas industry standard SY / T5336-2006 "Core Analysis Method". 0.3g of recyclable multi-response intelligent nano-chemical displacement agent was mixed with 100mL of deionized water to form an intelligent nano-chemical displacement agent-water dispersion system. Then, a physical model displacement experiment was carried out on the artificial core (core diameter 2.5cm, length 5.1cm, permeability 0.42μm). 2 First, water flooding was performed to a water cut of 95%, and the oil recovery rate was measured to be 56.1%. Then, 0.4 pV (pore volume) of intelligent nano-chemical oil displacement agent-water dispersion system was injected, and water flooding was continued to a water cut of 98%, and the oil recovery rate was measured to be 73.3%. It was calculated that the intelligent nano-chemical oil displacement agent can improve the oil recovery rate by 17.2% on the basis of water flooding.

[0054] Example 5:

[0055] The preparation method of the intelligent nano-chemical oil displacement agent of the present invention is as follows:

[0056] (1) 2.0g of dodecyl phosphate monoester and 2.5g of 100nm nano SiO2 material were added to 100mL of 2.0% sodium hydroxide aqueous solution and stirred for 3 hours with a magnetic stirrer. The nano SiO2 and dodecyl phosphate monoester clusters formed microspheres.

[0057] (2) Add 0.5g of polyacrylamide and stir to allow the polyacrylamide to adhere to the surface of the microspheres formed in step (1);

[0058] (3) Add 1.0g of 80nm Fe3O4 nanoparticles and stir at room temperature for 4 hours. The Fe3O4 nanoparticles further adhere to the surface of the microspheres to form a mixture.

[0059] (4) Add 0.3g N,N′-methylenebisacrylamide (crosslinking agent), mix thoroughly, then add 0.5g poly-N-isopropylacrylamide and 0.2g sodium methacrylate, stir at room temperature for 5 hours to obtain the intelligent nano-chemical oil displacement agent.

[0060] In the artificial core displacement experiment at the Engineering Technology Research Center Laboratory of Tongji University, the experiment was conducted in accordance with the petroleum and natural gas industry standard SY / T5336-2006 "Core Analysis Methods". 0.3g of recyclable multi-response intelligent nano-chemical oil displacement agent was mixed with 100mL of deionized water to form an intelligent nano-chemical oil displacement agent-water dispersion system. Then, a physical model displacement experiment was conducted using an artificial core (core diameter 2.5cm, length 5.3cm, permeability 0.37μm). 2 First, water flooding was performed to a water cut of 95%, and the oil recovery rate was measured to be 51.5%. Then, 0.4 pV (pore volume) of intelligent nano-chemical oil displacement agent-water dispersion system was injected, and water flooding was continued to a water cut of 98%, and the oil recovery rate was measured to be 65.3%. It was calculated that the intelligent nano-chemical oil displacement agent can improve the oil recovery rate by 13.8% on the basis of water flooding.

[0061] Example 6:

[0062] The preparation method of the intelligent nano-chemical oil displacement agent in this embodiment is as follows:

[0063] (1) 0.5g of dodecyl phosphate monoester and 2.5g of 50nm nano SiO2 material were added to 100mL of 2.0% sodium hydroxide aqueous solution and stirred for 3 hours with a magnetic stirrer. The nano SiO2 and dodecyl phosphate monoester clusters formed microspheres (in this invention, they serve as the core of the final spherical product).

[0064] (2) Add 0.25g of polyacrylamide and stir to allow the polyacrylamide to adhere to the surface of the microspheres formed in step (1);

[0065] (3) Add 0.25g of 80nm Fe3O4 nanoparticles and stir at room temperature for 4 hours. The Fe3O4 nanoparticles are further attached to the surface of the microspheres.

[0066] (4) Add 0.15g N,N′-methylenebisacrylamide (crosslinking agent), mix thoroughly, then add 0.25g poly-N-isopropylacrylamide and 0.05g sodium methacrylate, stir at room temperature for 5 hours to obtain the intelligent nano-chemical oil displacement agent.

[0067] In the artificial core displacement experiment at the Engineering Technology Research Center Laboratory of Tongji University, the experiment was conducted in accordance with the petroleum and natural gas industry standard SY / T5336-2006 "Core Analysis Methods". 0.3g of intelligent nano-chemical displacement agent was mixed with 100mL of deionized water to form an intelligent nano-chemical displacement agent-water dispersion system. Then, a physical model displacement experiment was conducted using an artificial core (core diameter 2.5cm, length 5.5cm, permeability 0.42μm). 2First, water flooding was performed to a water cut of 95%, and the oil recovery rate was measured to be 50.1%. Then, 0.4 pV (pore volume) of the intelligent nano-chemical oil displacement agent-water dispersion system of this embodiment was injected, and water flooding was continued to a water cut of 98%, and the oil recovery rate was measured to be 62.3%. It was calculated that the intelligent nano-chemical oil displacement agent can increase the oil recovery rate by 12.2% on the basis of water flooding.

[0068] Example 7:

[0069] The preparation method of the intelligent nano-chemical oil displacement agent in this embodiment is as follows:

[0070] (1) 2.0g of dodecyl phosphate monoester and 1.0g of 50nm nano SiO2 material were added to 100mL of 2.0% sodium hydroxide aqueous solution and stirred for 3 hours with a magnetic stirrer. The nano SiO2 and dodecyl phosphate monoester clusters formed microspheres (in this invention, they serve as the core of the final spherical product).

[0071] (2) Add 1.0g of polyacrylamide and stir to allow the polyacrylamide to adhere to the surface of the microspheres formed in step (1);

[0072] (3) Add 1.25g of 80nm Fe3O4 nanoparticles and stir at room temperature for 4 hours. The Fe3O4 nanoparticles are further attached to the surface of the microspheres.

[0073] (4) Add 0.35g N,N′-methylenebisacrylamide (crosslinking agent), mix thoroughly, then add 0.5g poly(N-isopropylacrylamide) and 0.15g sodium methacrylate, and stir at room temperature for 5 hours to obtain the intelligent nano-chemical oil displacement agent.

[0074] In the artificial core displacement experiment at the Engineering Technology Research Center Laboratory of Tongji University, the experiment was conducted in accordance with the petroleum and natural gas industry standard SY / T5336-2006 "Core Analysis Methods". 0.3g of intelligent nano-chemical displacement agent was mixed with 100mL of deionized water to form an intelligent nano-chemical displacement agent-water dispersion system. Then, a physical model displacement experiment was conducted using an artificial core (core diameter 2.5cm, length 5.2cm, permeability 0.39μm). 2 First, water flooding was performed to a water cut of 95%, and the oil recovery rate was measured to be 55.2%. Then, 0.4 pV (pore volume) of the intelligent nano-chemical oil displacement agent-water dispersion system of this embodiment was injected, and water flooding was continued to a water cut of 98%, and the oil recovery rate was measured to be 72.0%. It was calculated that the intelligent nano-chemical oil displacement agent can increase the oil recovery rate by 16.8% on the basis of water flooding.

[0075] Example 8:

[0076] The preparation method of the intelligent nano-chemical oil displacement agent in this embodiment is as follows:

[0077] (1) 2.0g of dodecyl phosphate monoester and 2.5g of 50nm nano SiO2 material were added to 100mL of 2.0% sodium hydroxide aqueous solution and stirred for 3 hours with a magnetic stirrer. The nano SiO2 and dodecyl phosphate monoester clusters formed microspheres (in this invention, they serve as the core of the final spherical product).

[0078] (2) Add 1.0g of polyacrylamide and stir to allow the polyacrylamide to adhere to the surface of the microspheres formed in step (1);

[0079] (3) Add 1.25g of 80nm Fe3O4 nanoparticles and stir at room temperature for 4 hours. The Fe3O4 nanoparticles are further attached to the surface of the microspheres.

[0080] (4) Add 0.35g N,N′-methylenebisacrylamide (crosslinking agent), mix thoroughly, then add 0.5g poly(N-isopropylacrylamide) and 0.15g sodium methacrylate, and stir at room temperature for 5 hours to obtain the intelligent nano-chemical oil displacement agent.

[0081] In the artificial core displacement experiment at the Engineering Technology Research Center Laboratory of Tongji University, the experiment was conducted in accordance with the petroleum and natural gas industry standard SY / T5336-2006 "Core Analysis Methods". 0.3g of intelligent nano-chemical displacement agent was mixed with 100mL of deionized water to form an intelligent nano-chemical displacement agent-water dispersion system. Then, a physical model displacement experiment was conducted using an artificial core (core diameter 2.5cm, length 5.3cm, permeability 0.41μm). 2 First, water flooding was performed to a water cut of 95%, and the oil recovery rate was measured to be 57.8%. Then, 0.4 pV (pore volume) of the intelligent nano-chemical oil displacement agent-water dispersion system of this embodiment was injected, and water flooding was continued to a water cut of 98%, and the oil recovery rate was measured to be 73.1%. It was calculated that the intelligent nano-chemical oil displacement agent can increase the oil recovery rate by 15.3% on the basis of water flooding.

[0082] Example 9:

[0083] The preparation method of the intelligent nano-chemical oil displacement agent in this embodiment is as follows:

[0084] (1) 1.0g of dodecyl phosphate monoester and 2.0g of 50nm nano SiO2 material were added to 100mL of 2.1% sodium hydroxide aqueous solution and stirred for 3 hours with a magnetic stirrer. The nano SiO2 and dodecyl phosphate monoester clusters formed microspheres (in this invention, they serve as the core of the final spherical product).

[0085] (2) Add 0.5g of polyacrylamide and stir to allow the polyacrylamide to adhere to the surface of the microspheres formed in step (1);

[0086] (3) Add 0.5g of 80nm Fe3O4 nanoparticles and stir at room temperature for 4 hours. The Fe3O4 nanoparticles are further attached to the surface of the microspheres.

[0087] (4) Add 0.3g N,N′-methylenebisacrylamide (crosslinking agent), mix thoroughly, then add 0.5g poly-N-isopropylacrylamide and 0.1g sodium methacrylate, stir at room temperature for 5 hours to obtain the intelligent nano-chemical oil displacement agent.

[0088] In the artificial core displacement experiment at the Engineering Technology Research Center Laboratory of Tongji University, the experiment was conducted in accordance with the petroleum and natural gas industry standard SY / T5336-2006 "Core Analysis Methods". 0.3g of intelligent nano-chemical displacement agent was mixed with 100mL of deionized water to form an intelligent nano-chemical displacement agent-water dispersion system. Then, a physical model displacement experiment was conducted using an artificial core (core diameter 2.5cm, length 5.5cm, permeability 0.42μm). 2 First, water flooding was performed to a water cut of 95%, and the oil recovery rate was measured to be 54.2%. Then, 0.4 pV (pore volume) of the intelligent nano-chemical oil displacement agent-water dispersion system of this embodiment was injected, and water flooding was continued to a water cut of 98%, and the oil recovery rate was measured to be 68.4%. It was calculated that the intelligent nano-chemical oil displacement agent can improve the oil recovery rate by 14.2% on the basis of water flooding.

[0089] Data from Examples 1-9 show that the intelligent nano-chemical oil displacement agent of the present invention can not only effectively improve crude oil recovery, but also realize a controllable oil displacement process, which is beneficial to the demulsification of produced fluid, and ultimately achieve effective separation and purification of produced oil and wastewater.

[0090] The comparison shows that, compared with water drive, the crude oil recovery rate of Examples 1-9 has been improved by more than 13%. Among them, Examples 1, 3, 4 and 7 have better results, and Examples 1 and 4 have better results.

[0091] The intelligent nano-chemical oil displacement agents prepared in Examples 1-9 of this invention contain intelligent microspheres comprising: a core formed by nano-SiO2 and dodecyl phosphate monoester clusters, polyacrylamide and Fe3O4 nanoparticles sequentially attached to the surface of the core, and a shell formed by crosslinking polyN-isopropylacrylamide and sodium methacrylate.

[0092] The smart microspheres are suspended in a 2.0%-2.1% sodium hydroxide aqueous solution.

[0093] In this process, N,N′-methylenebisacrylamide is used as the crosslinking agent for the crosslinking of poly(N-isopropylacrylamide) and sodium methacrylate.

[0094] In the intelligent microspheres, the mass ratio of the core (dodecyl phosphate monoester + nano-SiO2), polyacrylamide, Fe3O4 nanoparticles, and shell (poly(N-isopropylacrylamide) + sodium methacrylate + N,N′-methylenebisacrylamide) is 3-4.5:0.5-1.0:0.5-1.25:0.4-0.5:0.9-1.1; preferably 4.3-4.5:0.5-1.0:1.0-1.25:0.4-0.5:0.9-1.1.

[0095] In the core, the mass ratio of dodecyl phosphate monoester to nano-SiO2 is 1.8-2.0:1.0-2.5; in the outer shell, the mass ratio of poly(N-isopropylacrylamide), sodium methacrylate, and N,N′-methylenebisacrylamide is 0.4-0.5:0.1-0.3:0.3-0.5.

[0096] The preparation method of the intelligent nano-chemical oil displacement agent provided by the present invention includes:

[0097] (1) Add dodecyl phosphate monoester and nano SiO2 to a 2.0% sodium hydroxide aqueous solution and stir. The nano SiO2 and dodecyl phosphate monoester clusters form microspheres.

[0098] (2) Add polyacrylamide and stir to allow the polyacrylamide to adhere to the surface of the microspheres formed in step (1);

[0099] (3) Add Fe3O4 nanoparticles and stir. The Fe3O4 nanoparticles are further attached to the surface of the microspheres.

[0100] (4) Add N,N′-methylenebisacrylamide, mix thoroughly, then add poly(N-isopropylacrylamide) and sodium methacrylate, stir, and obtain intelligent nano-chemical oil displacement agent.

[0101] The mass ratio of dodecyl phosphate monoester, nano-SiO2, polyacrylamide, Fe3O4 nanoparticles, poly(N-isopropylacrylamide), sodium methacrylate, and N,N′-methylenebisacrylamide is 1.8-2.0: 1.0-2.5: 0.5-1.0: 0.5-1.25: 0.4-0.5: 0.1-0.3: 0.3-0.5.

Claims

1. A smart nano-chemical oil displacement agent, characterized in that, The product contains intelligent microspheres, which include: a core formed by nano-SiO2 and dodecyl phosphate monoester clusters, polyacrylamide and Fe3O4 nanoparticles sequentially attached to the surface of the core, and a shell formed by crosslinking polyN-isopropylacrylamide and sodium methacrylate.

2. The intelligent nano-chemical oil displacement agent according to claim 1, characterized in that, The smart microspheres are suspended in a 2.0%-2.1% sodium hydroxide aqueous solution.

3. The intelligent nano-chemical oil displacement agent according to claim 1, characterized in that, The crosslinking of poly(N-isopropylacrylamide) with sodium methacrylate uses N,N′-methylenebisacrylamide as the crosslinking agent.

4. The intelligent nano-chemical oil displacement agent according to claim 1, characterized in that... In the intelligent microsphere, the mass ratio of the core, the polyacrylamide, the Fe3O4 nanoparticles, and the shell is 3-4.5:0.5-1.0:0.5-1.25:0.4-0.5:0.9-1.

1.

5. The intelligent nano-chemical oil displacement agent according to claim 4, characterized in that, The mass ratio of the core, the polyacrylamide, the Fe3O4 nanoparticles, and the shell is 4.3-4.5:0.5-1.0:1.0-1.25:0.4-0.5:0.9-1.

1.

6. The intelligent nano-chemical oil displacement agent according to claim 5, characterized in that, In the core, the mass ratio of dodecyl phosphate monoester to nano-SiO2 is 1.8-2.0:1.0-2.

5.

7. The intelligent nano-chemical oil displacement agent according to claim 5, characterized in that, In the outer shell, the mass ratio of poly(N-isopropylacrylamide), sodium methacrylate, and N,N′-methylenebisacrylamide is 0.4-0.5: 0.1-0.3: 0.3-0.

5.

8. A method for preparing intelligent nano-chemical oil displacement agents, characterized in that, include: (1) Add dodecyl phosphate monoester and nano SiO2 to a 2.0% sodium hydroxide aqueous solution and stir. The nano SiO2 and dodecyl phosphate monoester clusters form microspheres. (2) Add polyacrylamide and stir to allow the polyacrylamide to adhere to the surface of the microspheres formed in step (1); (3) Add Fe3O4 nanoparticles and stir. The Fe3O4 nanoparticles are further attached to the surface of the microspheres. (4) Add N,N′-methylenebisacrylamide, mix thoroughly, then add poly(N-isopropylacrylamide) and sodium methacrylate, stir, and obtain intelligent nano-chemical oil displacement agent.

9. The method according to claim 8, characterized in that, In the method, the mass ratio of dodecyl phosphate monoester, nano-SiO2, polyacrylamide, Fe3O4 nanoparticles, poly(N-isopropylacrylamide), sodium methacrylate, and N,N′-methylenebisacrylamide is 1.8-2.0: 1.0-2.5: 0.5-1.0: 0.5-1.25: 0.4-0.5: 0.1-0.3: 0.3-0.

5.

10. The application of the intelligent nano-chemical oil displacement agent according to any one of claims 1-7 or the intelligent nano-chemical oil displacement agent prepared by the method of claim 8 or 9 in oilfield development.