Low-permeability heavy oil composite nano oil displacement agent and application thereof
By preparing composite nano-displacement agents with a particle size of 5-50 nm, the problem of difficult stripping of heavy oil in low-permeability heavy oil reservoirs has been solved, achieving efficient stripping and improved recovery, which is suitable for industrial application.
Patent Information
- Application Number
- CN202411304786.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-19
- Publication Date
- 2026-02-06
AI Technical Summary
Existing technologies are insufficient for efficiently stripping heavy oil from low-permeability pores. Conventional water flooding and chemical flooding cannot satisfactorily improve oil recovery. Nanoparticles tend to agglomerate, have poor stability, and are prone to clogging in low-permeability heavy oil reservoirs.
A composite nano-displacement agent, comprising betaine, fatty alcohol polyoxyethylene ether, polyacrylamide, and small-sized nanoparticles, is used to prepare nanoparticles with a particle size of 5-50 nm by reducing the surface tension at the oil-water interface and the viscosity of crude oil. This ensures stability and compatibility, avoids clogging, and improves oil recovery.
This invention enables the efficient stripping of crude oil in low-permeability heavy oil reservoirs by nano-displacement agents, thereby improving oil recovery. It exhibits good interfacial activity and rheological behavior, is not prone to clogging pores, and is suitable for industrial applications.
Smart Images
Figure HDA0005048808550000011 
Figure HDA0005048808550000012 
Figure HDA0005048808550000013
Abstract
Description
Technical Field
[0001] This invention relates to the field of oilfield development technology, and in particular to a method for improving oil recovery by using composite nanoparticle oil displacement agents in low-permeability heavy oil reservoirs. Background Technology
[0002] Extracting extra-heavy oil was once a global challenge, though technological breakthroughs have been made. However, extracting low-permeability heavy oil presents an even greater challenge. Conventional waterflooding and chemical flooding methods fail to achieve satisfactory results, as the bound crude oil cannot be effectively separated. Therefore, efficiently separating heavy oil from low-permeability pores and improving the recovery rate of such reservoirs is a pressing problem that needs to be solved.
[0003] Nanoparticle fluids have attracted widespread attention in the field of oilfield chemistry due to the following excellent properties: The preparation method of nanoparticle systems is simple; the nanoparticles suspended in the liquid undergo continuous Brownian motion, exhibiting good dispersibility and stability, and are not prone to aggregation; they avoid the problems of instability and low oil displacement efficiency of surfactants and polymers in high-temperature, high-salinity formations; nanofluids can further reduce the surface tension of the oil-water interface and reduce the viscosity of crude oil; nanoparticles can generate structural separation pressure, stripping crude oil; nanoparticles can weaken hydrogen bonding, converting large water molecules into smaller water molecules, which can then enter tiny pores and throats, expanding the swept volume and solving the problem of oil displacement in low-permeability reservoirs. Summary of the Invention
[0004] To address the aforementioned technical problems, this invention proposes the composition, preparation, and application of a composite nano-displacement agent based on reducing the surface tension at the oil-water interface, lowering crude oil viscosity, and improving the oil recovery rate in low-permeability heavy oil reservoirs. This invention preferentially utilizes surfactants, fatty alcohol polyoxyethylene ethers, polyacrylamide, and small-sized nanoparticles to obtain a nano-displacement agent with good stability that can reduce the surface tension at the oil-water interface and lower crude oil viscosity. This nano-displacement agent possesses excellent interfacial activity, emulsifying properties, and rheological behavior. It can penetrate minute pores without causing pore blockage and has the function of efficiently stripping crude oil, thereby improving oil recovery in low-permeability heavy oil reservoirs.
[0005] Specifically, the following technical solutions are included:
[0006] In a first aspect, the present invention provides a composite nano-displacement agent for improving the recovery rate of low-permeability heavy oil, comprising the following components by weight percentage: 40-60% betaine, 10-30% fatty alcohol polyoxyethylene ether, 20-40% polyacrylamide, 2-8% nanoparticles (particle size between 5nm and 50nm), 0.01-0.1% pH adjuster, with the balance being water.
[0007] Preferably, the betaine is selected from at least one or more of dodecyl dimethyl betaine, cocamidopropyl betaine, cocamidopropyl-2-hydroxy-3-sulfopropyl betaine, and lauryl hydroxysulfobenzene.
[0008] Preferably, the fatty alcohol-containing polyoxyethylene ether is selected from at least one or more of AEO 3, AEO 5, AEO 7, AEO 9, and AEO 12.
[0009] Preferably, the polyacrylamide is selected from at least one or more of anionic, cationic, and nonionic polyacrylamides of different molecular weights.
[0010] Preferably, the particle size of the nanoparticles is between 5 nm and 50 nm; the nanoparticles are at least one or more of nano-alumina, nano-titanium dioxide, and nano-silica.
[0011] Preferably, the pH adjuster is at least one or more of hydrochloric acid, phosphoric acid, acetic acid, sodium hydroxide, and sodium bicarbonate.
[0012] Secondly, the present invention provides a method for preparing a composite nano-displacement agent to improve the recovery rate of low-permeability heavy oil, comprising:
[0013] S1. The nanoparticles are mixed with water in a certain proportion, magnetically stirred for 60 minutes, and sonicated for 30 minutes to obtain a dispersed nanoparticle solution.
[0014] S2. Mix the polyacrylamide with water in a certain proportion, place it in a constant temperature water bath at 60°C for 60 minutes, add an appropriate amount of pH adjustment solution, place it in a constant temperature water bath at 90°C for 60 minutes, and obtain a partially hydrolyzed polyacrylamide solution.
[0015] S3. Add the nanoparticle solution to the betaine and fatty alcohol polyoxyethylene ether solution and dissolve it to obtain the first reaction solution; place the first reaction solution in a constant temperature water bath at 80°C and stir until the solution is fully dissolved;
[0016] S4. Add the first reaction solution to the partially hydrolyzed polyacrylamide solution and dissolve it to obtain the second reaction solution; place the second reaction solution in a constant temperature water bath at 80°C and stir until the solution is fully dissolved;
[0017] S5. Add a pH adjuster to the second reaction solution to terminate the reaction and obtain a nano-oil displacement agent.
[0018] This invention also provides an application of a composite nano-displacement agent for improving the recovery rate of low-permeability heavy oil in enhanced oil recovery.
[0019] The beneficial effects of the technical solution provided by this invention include at least the following:
[0020] Conventional surfactants improve oil displacement efficiency by reducing the interfacial tension between oil and water. However, in low-permeability reservoirs, narrow pore throats make crude oil removal difficult. Traditional nanoparticles, due to their large particle size (>50nm), are prone to pore blockage, resulting in limited ability to drive crude oil removal through structural separation pressure. Therefore, composite nano-displacement agents must consider not only interfacial tension but also the dispersion stability of nanoparticles and their compatibility with pore sizes to ultimately improve oil recovery.
[0021] The nanoparticles in the nano-displacement agent of this invention can further reduce the viscosity of crude oil.
[0022] The nanoparticles in this invention have small particle sizes, with a particle size distribution of 550 nm and high uniformity, which is superior to existing nanotechnology. They exhibit active Brownian motion, which weakens hydrogen bonding and transforms large water molecules into small water molecules. This allows them to better adapt to the micro- and nano-scale pores and throats of low-permeability reservoirs, making them less prone to clogging and achieving better oil displacement effects. Attached Figure Description
[0023] To more clearly explain the technical solutions in the embodiments of the present invention, the accompanying drawings required to describe the embodiments will be briefly introduced. The drawings described are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0024] Figure 1 This describes the macroscopic morphology of the nanoparticles in the nano-oil displacement agent prepared in Example 1 of this invention.
[0025] Figure 2 These are macroscopic and microscopic photographs (10x magnification) of the oil-water emulsion state after an emulsification experiment with the nano-oil displacement agent prepared in Example 1 of this invention, and macroscopic and microscopic photographs of the oil-water emulsion state after an emulsification experiment without the addition of the nano-oil displacement agent.
[0026] Figure 3 This is a schematic diagram of the structural separation pressure of the nano-oil displacement agent in Embodiment 1 of the present invention.
[0027] The accompanying drawings have illustrated some embodiments of the present invention, which will be described in more detail below. These drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to specific embodiments. Detailed Implementation
[0028] The technical solutions in the embodiments of the present invention will now be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are only a part, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.
[0029] Currently, low-permeability oil reservoirs account for 70%-80% of China's total proven reserves, and these reservoirs have become the main focus of exploitation and development. While the extraction of extra-heavy oil was once a global challenge, technological breakthroughs have been achieved. However, low-permeability heavy oil remains extremely difficult to extract. The small pore throats and poor flow characteristics of low-permeability heavy oil reservoirs hinder waterflooding for enhanced production. In recent years, nano-enhanced oil recovery systems have attracted widespread attention in the field of oilfield chemistry. Their unique surface effects, small size effects, and particle effects have demonstrated excellent performance in oil recovery applications.
[0030] However, in practical applications in low-permeability heavy oil reservoirs, existing nanotechnology generally suffers from problems such as easy aggregation, poor stability, and easy clogging of the reservoir, resulting in low crude oil recovery rates.
[0031] This invention provides a composite nano-displacement agent for improving the recovery rate of low-permeability heavy oil, comprising the following components by weight percentage: 40-60% betaine, 10-30% fatty alcohol polyoxyethylene ether, 20-40% polyacrylamide, 2-8% nanoparticles (particle size between 5nm and 50nm), 0.01-0.1% pH adjuster, with the balance being water.
[0032] This invention proposes the composition, preparation, and application of a composite nano-displacement agent based on reducing the surface tension at the oil-water interface, lowering crude oil viscosity, and improving the oil recovery rate in low-permeability heavy oil reservoirs. This invention preferentially utilizes surfactants and small-sized nanoparticles to obtain a nano-displacement agent with good stability that can reduce the surface tension at the oil-water interface and lower crude oil viscosity. This nano-displacement agent possesses excellent interfacial activity, can penetrate tiny pore throats without causing pore blockage, and has the function of efficiently stripping crude oil, thereby improving oil recovery in low-permeability heavy oil reservoirs. The composite nano-displacement agent has a better oil displacement effect than ordinary surfactants and nanoparticles used alone, making it suitable for industrial promotion and application.
[0033] Preferably, the betaine is selected from at least one or more of dodecyl dimethyl betaine, cocamidopropyl betaine, cocamidopropyl-2-hydroxy-3-sulfopropyl betaine, and lauryl hydroxysulfobenzene.
[0034] Preferably, the fatty alcohol-containing polyoxyethylene ether is selected from at least one or more of AEO 3, AEO 5, AEO 7, AEO 9, and AEO 12.
[0035] Preferably, the polyacrylamide is selected from at least one or more of anionic, cationic, and nonionic polyacrylamides of different molecular weights.
[0036] Preferably, the particle size of the nanoparticles is between 5 nm and 50 nm; the nanoparticles are at least one or more of nano-alumina, nano-titanium dioxide, and nano-silica.
[0037] Preferably, the pH adjuster is at least one or more of hydrochloric acid, phosphoric acid, acetic acid, sodium hydroxide, and sodium bicarbonate.
[0038] It is understandable that hydrochloric acid, phosphoric acid, acetic acid, sodium hydroxide, and sodium bicarbonate are all commonly used pH adjusters.
[0039] This invention also provides a method for preparing a composite nano-displacement agent to improve the recovery rate of low-permeability heavy oil, comprising:
[0040] S1. The nanoparticles are mixed with water in a certain proportion, magnetically stirred for 60 minutes, and sonicated for 30 minutes to obtain a dispersed nanoparticle solution.
[0041] S2. Mix the polyacrylamide with water in a certain proportion, place it in a constant temperature water bath at 60°C for 60 minutes, add an appropriate amount of pH adjustment solution, place it in a constant temperature water bath at 90°C for 60 minutes, and obtain a partially hydrolyzed polyacrylamide solution.
[0042] S3. Add the nanoparticle solution to the betaine and fatty alcohol polyoxyethylene ether solution and dissolve it to obtain the first reaction solution; place the first reaction solution in a constant temperature water bath at 80°C and stir until the solution is fully dissolved;
[0043] S4. Add the first reaction solution to the partially hydrolyzed polyacrylamide solution and dissolve it to obtain the second reaction solution; place the second reaction solution in a constant temperature water bath at 80°C and stir until the solution is fully dissolved;
[0044] S5. Add a pH adjuster to the second reaction solution to terminate the reaction and obtain a nano-oil displacement agent.
[0045] Example
[0046] The reservoir suitable for the composite nano-displacement agent provided in this application to function was selected. A block in the North China Oilfield was selected for analysis. The core was from a natural outcrop sandstone core, and the crude oil and well fluid were from the field well. The formation temperature was 64.5℃.
[0047] Different concentrations of the composite nano oil displacement agent (200ppm, 400ppm, 600ppm, 800ppm, 1000ppm, 1500ppm, 2000ppm, and 3000ppm) were placed in transparent vials and then placed in a water bath at 64.5℃ for 2 hours to observe their stability.
[0048] A 400 ppm composite nano oil displacement agent solution was dropped onto the surface of a sandstone core and left to stand for 48 hours. The changes in the wetting angle were then observed.
[0049] The interfacial tensions between oil and composite nanofluids (0ppm, 200ppm, 400ppm, 600ppm, 800ppm, 1000ppm, 1500ppm, 2000ppm, and 3000ppm) were measured using the pendant drop method to analyze whether the oil displacement effect was met.
[0050] Prepare 8 bottles of 30ml oil-water mixture (9ml crude oil, 21ml water), and then add 10ml of liquid (200ppm, 400ppm, 600ppm, 800ppm, 1000ppm, 1500ppm, 2000ppm, and 3000ppm nano-displacement agent) to analyze the emulsification state of the crude oil.
[0051] The oil sand (pre-mixed) and liquid (well fluid, 1000ppm, 2000ppm, 4000ppm, 6000ppm nano-displacement agent) were mixed in a centrifuge tube at a ratio of 1:2. After shaking and drying, the oil sand was weighed and the oil washing rate was calculated.
[0052] Core displacement experiments were conducted to obtain the most efficient and economical slug composition.
[0053] The pilot test well group is selected from those with a large number of corresponding oil wells, good injection and production results, and a production rate relatively high compared to water injection well groups.
[0054] Based on the pilot test, the scale was expanded and implemented in contiguous areas, with priority given to water injection wells with good connectivity and injection performance for expanded testing.
[0055] To further explore potential and improve development results, the next step is to continue expanding the scale of implementation.
Claims
1. A composite nano-oil displacement agent (hereinafter referred to as nano-oil displacement agent), said nano-oil displacement agent comprising surfactant, fatty alcohol polyoxyethylene ether, polyacrylamide, nanoparticles and water, characterized in that, The product comprises the following components by weight percentage: 40-60% betaine, 10-30% fatty alcohol polyoxyethylene ether, 20-40% polyacrylamide, 2-8% nanoparticles (particle size between 5nm and 50nm), 0.01-0.1% pH adjuster, and the balance being water.
2. The composite nano-displacement agent for improving the recovery rate of low-permeability heavy oil as described in claim 1, characterized in that, The betaine is selected from at least one or more of dodecyl dimethyl betaine, cocamidopropyl betaine, cocamidopropyl-2-hydroxy-3-sulfopropyl betaine, and lauryl hydroxysulfobenzene.
3. The composite nano-displacement agent for improving the recovery rate of low-permeability heavy oil as described in claim 1, characterized in that, The fatty alcohol-containing polyoxyethylene ether is selected from at least one or more of AEO 3, AEO 5, AEO 7, AEO 9, and AEO 12.
4. The composite nano-displacement agent for improving the recovery rate of low-permeability heavy oil as described in claim 1, characterized in that, The polyacrylamide is selected from at least one or more of anionic, cationic, and nonionic polyacrylamides of different molecular weights.
5. The composite nano-displacement agent for improving the recovery rate of low-permeability heavy oil as described in claim 1, characterized in that, The nanoparticles have a particle size between 5 nm and 50 nm; the nanoparticles are at least one or more of nano-alumina, nano-titanium dioxide, and nano-silica; the nanoparticles do not aggregate before the oil displacement agent is injected into the target reservoir.
6. The composite nano-displacement agent for improving the recovery rate of low-permeability heavy oil as described in claim 1, characterized in that, The pH adjuster is at least one or more of hydrochloric acid, phosphoric acid, acetic acid, sodium hydroxide, and sodium bicarbonate.
7. The preparation method of the composite nano-displacement agent for improving the recovery rate of low-permeability heavy oil as described in claim 1, characterized in that, Includes the following steps: S1. Mix the nanoparticles with water in a certain proportion, stir magnetically for 60 minutes, and sonicate for 30 minutes to obtain a dispersed nanoparticle solution. S2. Mix the polyacrylamide with water in a certain proportion, place it in a constant temperature water bath at 60°C for 60 minutes, add an appropriate amount of pH adjustment solution, place it in a constant temperature water bath at 90°C for 60 minutes, and obtain a partially hydrolyzed polyacrylamide solution. S3. Add the nanoparticle solution to the betaine and fatty alcohol polyoxyethylene ether solution and dissolve them to obtain the first reaction solution; Place the first reaction solution in a constant temperature water bath at 80°C and stir until the solution is fully dissolved. S4. Add the first reaction solution to the partially hydrolyzed polyacrylamide solution and dissolve it to obtain the second reaction solution; place the second reaction solution in a constant temperature water bath at 80°C and stir until the solution is fully dissolved; S5. Add a pH adjuster to the second reaction solution to terminate the reaction and obtain a nano-oil displacement agent.
8. The nano-oil displacement agent according to any one of claims 1 to 7, wherein, The pH value of the oil displacement agent is 6 to 7.
9. The nano-oil displacement agent according to any one of claims 1 to 7, wherein, The target reservoir is a reservoir whose main component is sandstone.
10. The nano-displacement agent according to any one of claims 1 to 7, wherein, The permeability of the target reservoir is less than 100 mD.
11. The nano-oil displacement agent according to any one of claims 1 to 7, wherein, The target reservoir has an oil viscosity greater than 50 mPa·s.
12. The application of the nano-oil displacement agent according to any one of claims 1 to 7, comprising the following steps: a) The nano-oil displacement agent was mixed with crude oil at a certain concentration and ratio, and stability, wettability and emulsification state experiments were carried out. b) Prepare a solution of the nano-displacement agent according to the corresponding ratio, and carry out oil washing rate and core displacement experiments to obtain the optimal oil displacement concentration. c) Conduct a pilot test of nano-displacement oil recovery. Inject the nano-displacement agent into the target reservoir through an injection well at the optimal oil displacement concentration until the nano-displacement agent can be seen in the production well. Continuously inject for 180 days, monitor continuously, and calculate the oil enhancement effect. This step can adjust the optimal oil displacement concentration of the nano-displacement agent. d) Conduct a large-scale nano-displacement oil recovery test, injecting the nano-displacement agent into the target reservoir through injection wells at the adjusted optimal oil displacement concentration until the oil displacement agent can be seen in the production wells; continuously inject for 180 days, continuously monitor, and calculate the oil enhancement effect. e) Continue to expand the scale of nano-enhanced oil recovery.