Composite organic nano oil displacement agent and preparation method thereof

Abstract

The application provides a composite organic nanometer oil displacement agent and a preparation method thereof. The preparation method of the composite organic nanometer oil displacement agent controls the raw materials of the composite organic nanometer oil displacement agent and improves the preparation process, so that the prepared composite organic nanometer oil displacement agent has good recovery performance. Meanwhile, the addition of ethylenediamine improves the seepage performance of the composite organic nanometer oil displacement agent, enhances the oil washing performance, and improves the viscosity reduction effect in the oil displacement process. Further, the addition of the composite fatty acid methyl ester sulfonate and the modified nanometer silicon dioxide synergistically reduce the interfacial tension of the product, and further enhance the oil displacement performance of the composite organic nanometer oil displacement agent.

Description

Technical Field

[0001] This invention relates to a composite organic nano-oil displacement agent and its preparation method, belonging to the field of oilfield chemical additives. Background Technology

[0002] The development of oil fields is a process of continuously improving the recovery rate. After primary and secondary oil recovery, 60 to 70% of the remaining oil remains in the reservoir and cannot be extracted, thus leading to the proposal of tertiary oil recovery methods.

[0003] Nanomaterial-based oil displacement is a novel oil displacement technology in recent years. It has advantages such as large specific surface area, high specific surface energy and many active functional groups. However, it has poor dispersion stability in aqueous solution, is prone to agglomeration, and is not effective in reducing interfacial tension and improving wettability, which limits its practical application. Summary of the Invention

[0004] The purpose of this invention is to provide a composite organic nano-displacement agent and its preparation method. This composite organic nano-displacement agent has the characteristics of high stability and strong surface tension, which can effectively solve the problems of insufficient viscosity reduction ability and low oil washing efficiency of oil displacement agents in heavy oil and oil displacement processes. It has the advantages of improving the dispersion stability of nanomaterials in aqueous solution, reducing agglomeration, enhancing interfacial tension and improving wettability.

[0005] To achieve the above-mentioned objectives, this invention provides a method for preparing a composite organic nano-oil displacement agent; modified nano-silica is obtained by modifying silica with a coupling agent, and the modified nano-silica is mixed with ethylenediamine, sodium methyl ester sulfonate of compound fatty acids and water at 25°C and stirred (≥30 minutes) until a uniformly dispersed solution is obtained. The final solution is the composite organic nano-oil displacement agent.

[0006] This invention provides a method for preparing a composite organic nano-oil displacement agent, comprising the following steps: S1, preparation of modified silica: mixing nano-silica with an aqueous ethanol solution, adding a modifier to modify the nano-silica, and drying to obtain the modified silica; S2. Preparation of the composite solvent: At standard temperature, ethylenediamine and sodium methyl ester sulfonate of composite fatty acids are added to a solvent and mixed to obtain the composite solvent; S3. Preparation of composite organic nano-oil displacement agent: At standard temperature, the modified silica is added to the composite solvent until the modified silica is uniformly and stably dispersed in the composite solvent and forms a stable dispersion; thus, a composite organic nano-oil displacement agent is prepared.

[0007] As a further improvement of the present invention, S1 specifically includes: S11. The nano-silica and the ethanol aqueous solution are mixed at a mass ratio of 0.1:100 to 0.6:100, wherein the mass ratio of anhydrous ethanol to water in the ethanol aqueous solution is 1:1 to 3:1. S12. Add the modifier to the ethanol-water solution containing the nano-silica, and ultrasonically disperse the modifier until the nano-silica and the modifier are uniformly dispersed to obtain a dispersion; wherein the mass ratio of the modifier to the nano-silica is 20%~30%; S13. Heat the dispersion in S12 to 45~55℃, mechanically stir for 2~3h, and centrifuge to obtain the crude product of the modified silica. S14. The crude product is washed and vacuum dried at 75~85°C for at least 48 hours, and then pulverized to obtain the modified silica.

[0008] As a further improvement of the present invention, S12 further includes adding a pH adjuster to the ethanol aqueous solution in which the nano-silica and the modifier are dissolved to adjust the pH so that the ethanol aqueous solution in which the nano-silica and the modifier are dispersed in the mixture is neutral.

[0009] As a further improvement of the present invention, the modifier is a silane coupling agent and the pH adjuster is dilute hydrochloric acid.

[0010] As a further improvement of the present invention, S14 specifically involves: washing the crude product in S13 at least three times with anhydrous ethanol, vacuum drying at 75~85°C for at least 48 hours, and pulverizing to obtain the modified silica.

[0011] As a further improvement of the present invention, in step S14, the crude product after vacuum drying is ground by a grinding mill, and the medium particle size of the modified silica after grinding is 2.7~2.85μm.

[0012] As a further improvement of the present invention, in step S2, the mass ratio of the ethylenediamine to the sodium methyl ester sulfonate of the complex fatty acid is 1:1 to 3:1.

[0013] As a further improvement of the present invention, the standard temperature is 25°C.

[0014] To achieve the above-mentioned objectives, the present invention also provides a composite organic nano-oil displacement agent, which is prepared using the aforementioned method for preparing composite organic nano-oil displacement agents.

[0015] As a further improvement of the present invention, the water flooding recovery rate of the composite organic nano-displacement agent is >80%.

[0016] The beneficial effects of this invention are: The preparation method of the composite organic nano-displacement agent of the present invention controls the raw materials and improves the preparation process, resulting in a composite organic nano-displacement agent with good recovery performance. Simultaneously, the addition of ethylenediamine improves the permeability of the composite organic nano-displacement agent, enhancing its oil washing performance while improving viscosity reduction during the oil displacement process. Furthermore, the addition of sodium methyl ester sulfonate of composite fatty acids synergistically reduces the interfacial tension of the product with modified nano-silica, further enhancing the oil displacement performance of the composite organic nano-displacement agent. Attached Figure Description

[0017] Figure 1 This is a flowchart of the preparation method of the composite organic nano-oil displacement agent of the present invention.

[0018] Figure 2 This is a scanning electron microscope image of a composite organic nano-oil displacement agent. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0020] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0021] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] In existing technologies, a large amount of residual oil remains after primary and secondary oil recovery in oilfields, making tertiary oil recovery technology crucial. Although nanomaterial-based oil displacement technology has advantages such as high specific surface area and active functional groups, nanoparticles are prone to agglomeration and sedimentation in aqueous media, resulting in poor dispersion system stability, insufficient interfacial tension regulation, and difficulty in effectively improving reservoir wettability, thus limiting the practical application effect.

[0024] To address these issues, researchers discovered that insufficient compatibility between the surface properties of nanoparticles and the solvent system is the primary cause of agglomeration. By analyzing the surface energy distribution of nanomaterials, they considered using chemical modification methods to alter the surface properties of the particles, while simultaneously constructing a composite solvent system with a dual stabilization mechanism. First, nano-silica was selected as the substrate, and organic functional groups were grafted onto its surface using a modifier. Subsequently, a composite solvent containing both polar groups and long-chain alkyl groups was developed, achieving dispersion stability control through synergistic intermolecular forces.

[0025] Therefore, this application proposes a method for preparing a composite organic nano-oil displacement agent, comprising the following steps: in the preparation stage of modified silica, nano-silica is mixed with an ethanol aqueous solution and then a modifier is added for surface treatment; in the preparation stage of composite solvent, ethylenediamine and sodium methyl ester sulfonate of composite fatty acids are mixed at a standard temperature; finally, the modified silica is uniformly dispersed in the composite solvent to form a stable dispersion.

[0026] Sodium methyl ester sulfonate (MES) is an anionic surfactant made from natural or recycled oils through esterification, sulfonation, and neutralization. The ethanol-water solution refers to a dispersion medium composed of anhydrous ethanol and deionized water in a specific ratio, typically 1:1 to 3:1 by mass. This ratio optimizes the wettability of nanoparticles and prevents hydrolysis side reactions during modification. The modifier is an organosilicon compound that can chemically bond with the hydroxyl groups on the surface of nano-silica, typically using a silane coupling agent to form a hydrophobic protective layer on the particle surface through covalent grafting. The composite solvent is a two-component system composed of ethylenediamine and sodium methyl ester sulfonate, typically a mixture with a mass ratio of 1:1 to 3:1. The protonation of the amine groups and the interfacial activity of the sulfonic acid groups synergistically enhance dispersion stability. The standard temperature refers to the equilibrium temperature that maintains the thermal motion of molecules and the formation of chemical bonds. Specifically, it can be achieved by using a constant temperature of 25°C to ensure that the solvent components are fully mixed and that phase separation does not occur.

[0027] Specifically, in the preparation of modified silica, the polarity gradient of the ethanol-water solution facilitates the uniform dispersion of nanoparticles. The modifier forms an organic coating layer on the particle surface through a condensation reaction, reducing surface energy and enhancing compatibility with organic solvents. In the composite solvent system, the amino groups of ethylenediamine provide steric hindrance through electrostatic repulsion, while the long-chain alkyl groups of the composite fatty acid methyl ester sulfonate adsorb onto the nanoparticle surface through hydrophobic interactions, forming a dual stabilization mechanism. During the dispersion stage, the surface-modified nanoparticles and the composite solvent have matching polarities, achieving uniform dispersion through mechanical stirring and the directional alignment of solvent molecules, ultimately forming a nanofluid with long-term stability.

[0028] Compared with existing technologies, traditional methods only suppress agglomeration through a single surfactant or physical dispersion, failing to fundamentally solve the interfacial compatibility problem between nanoparticles and solvents. This method constructs an organic layer on the particle surface through chemical modification, combined with the dual stabilizing effect of a composite solvent, achieving directional dispersion control of nanoparticles at the molecular level, overcoming the drawback of easy desorption when relying solely on surfactant adsorption.

[0029] Through the above technical solution, this application achieves long-term stable dispersion of nano-displacement agents in aqueous and oil phase media, effectively inhibiting sedimentation failure caused by particle agglomeration. The modified nanoparticles have enhanced surface hydrophobicity, which allows them to be better adsorbed at the oil-water interface to reduce interfacial tension. At the same time, the synergistic effect of the composite solvent ensures that the dispersion system remains stable under high temperature and high salinity environments, significantly improving the adaptability of the displacement agent to complex reservoir conditions.

[0030] Please see Figure 1 , Figure 2 As shown, this invention provides a method for preparing a composite organic nano-oil displacement agent and the prepared composite organic nano-oil displacement agent. The method for preparing the composite organic nano-oil displacement agent effectively improves the permeation performance and oil displacement performance of the prepared composite organic nano-oil displacement agent by selecting the components of the composite solvent and improving the specific preparation method.

[0031] Specifically, the preparation method of the composite organic nano-oil displacement agent includes the following steps: S1. Preparation of modified silica: Nano silica is mixed with an aqueous ethanol solution, and a modifier is added to modify the nano silica. After drying, the modified silica is obtained. S2. Preparation of the composite solvent: At standard temperature, ethylenediamine and sodium methyl ester sulfonate of compound fatty acids are added to a solvent and mixed to obtain the composite solvent; wherein, the mass ratio of ethylenediamine to sodium methyl ester sulfonate of compound fatty acids is 1:1 to 3:1; the solvent is water; S3. Preparation of composite organic nano-oil displacement agent: At a standard temperature, the modified silica is added to the composite solvent until the modified silica is uniformly and stably dispersed in the composite solvent to form a stable dispersion; the preparation of composite organic nano-oil displacement agent is completed; wherein, the standard temperature is 25℃.

[0032] Furthermore, S1 specifically includes: S11. The nano-silica is added to an aqueous ethanol solution, wherein the mass ratio of the nano-silica to the aqueous ethanol solution is 0.1:100 to 0.6:100; and the mass ratio of anhydrous ethanol to water in the aqueous ethanol solution is 1:1 to 3:1. The mass ratio of nano-silica to ethanol aqueous solution is 0.1:100 to 0.6:100, which refers to controlling the solid content of nanoparticles to avoid excessive viscosity of the dispersion system. In a preferred embodiment of this application, this can be achieved by batch feeding.

[0033] S12. Add the modifier to the ethanol-water solution containing the nano-silica, and ultrasonically disperse the modifier until the nano-silica and the modifier are uniformly dispersed to obtain a dispersion; wherein the mass ratio of the modifier to the nano-silica is 20%~30%; With this setup, the chemical modification of nanoparticles can be achieved by optimizing the surface grafting amount, and silane coupling agents can be used as modifiers.

[0034] S12 further includes adding a pH adjuster to the ethanol aqueous solution containing the nano-silica and the modifier to adjust the pH so that the ethanol aqueous solution containing the nano-silica and the modifier is neutral.

[0035] In a preferred embodiment of the present invention, the modifier is a silane coupling agent and the pH adjuster is dilute hydrochloric acid.

[0036] S13. Heat the dispersion mixture in S12 to 45~55℃, mechanically stir for 2~3 hours, and centrifuge to obtain the crude product of the modified silica. S14. The crude product is washed and vacuum dried at 75~85°C for at least 48 hours, and then pulverized to obtain the modified silica.

[0037] Furthermore, in S14, the treatment of the crude product specifically involves washing the crude product from S13 at least three times with anhydrous ethanol, vacuum drying at 75~85°C for at least 48 hours, and then pulverizing it to obtain the modified silica.

[0038] Specifically, the crude product after vacuum drying is pulverized by dry grinding in a ball mill for 10 to 12 hours until the medium particle size of the modified silica after grinding is 2.50 to 2.85 μm; grinding is then completed.

[0039] In this application, by adjusting the polarity of the ethanol-water solution to match the surface characteristics of the nano-silica during the preparation of the composite organic nano-oil displacement agent, sufficient wetting and uniform dispersion of the silica are achieved, reducing agglomeration caused by solvent polarity mismatch. After adding a specific proportion of silane coupling agent, ultrasonic treatment promotes the chemical bonding between the modifier molecules and the hydroxyl groups on the nanoparticle surface, forming a stable organic-inorganic interface. Heating and mechanical stirring further enhance the uniform coating of the modifier on the particle surface, while centrifugation removes unreacted free modifier. The washing process uses anhydrous ethanol for multiple washes to remove residual impurities. Vacuum drying combined with pulverization effectively controls the particle size distribution, avoiding hard agglomeration caused by capillary forces during drying. The synergistic effect of parameters in each step, such as matching drying temperature and time to reduce internal stress in the particles, and controlling the particle size within the micron range after pulverization, ensures subsequent redispersibility in the composite solvent.

[0040] Compared to existing technologies, traditional nanoparticle modification methods often fail to optimize solvent ratios and modifier dosages, leading to uneven particle dispersion or insufficient surface grafting rates. For example, in existing technologies, when pure water or a single solvent is used for dispersion, nano-silica is prone to agglomeration due to hydrogen bonding between surface hydroxyl groups. This approach, however, uses a mixed solvent of ethanol and water to regulate system polarity, significantly reducing interparticle interactions. Furthermore, existing technologies often suffer from insufficient mechanical stirring time or lack of ultrasonic pretreatment, resulting in uneven modifier distribution. This approach achieves high efficiency and uniformity in surface modification through the synergistic effect of ultrasound and mechanical stirring.

[0041] Through the above technical solution, this application solves the problem of agglomeration caused by uneven dispersion of nano-silica in oil displacement agents, and improves its dispersion stability in composite solvents. By controlling the solvent ratio and the amount of modifier, a stable organic modification layer is formed on the surface of the nanoparticles, thereby enhancing their compatibility with composite solvents. The optimized drying and pulverizing process effectively inhibits secondary agglomeration of particles, enabling them to maintain a high specific surface area and active functional group density in subsequent applications, ultimately improving the interfacial activity and wettability of the oil displacement agent.

[0042] The following description will illustrate the preparation of the composite organic nano-oil displacement agent using the preparation method of the present invention through specific embodiments.

[0043] Example 1:

[0044] S1. Preparation of modified silica: 2g of nano silica and 500g of ethanol aqueous solution are mixed, wherein the mass ratio of anhydrous ethanol to water in the ethanol aqueous solution is 3:1. After mixing evenly, 0.5g of silane coupling agent is added to modify the nano silica. At the same time, dilute hydrochloric acid is added to adjust the pH value to neutral. After drying and grinding, the modified silica is obtained. S2. Preparation of the composite solvent: At a temperature of 25°C, 15g of ethylenediamine, 15g of sodium methyl ester sulfonate of compound fatty acids and 69g of water are mixed and stirred thoroughly to obtain the composite solvent. S3. Preparation of composite organic nano-oil displacement agent: At a temperature of 25°C, 1g of the modified silica is added to the composite solvent until the modified silica is uniformly and stably dispersed in the composite solvent; thus obtaining the composite organic nano-oil displacement agent.

[0045] Example 2:

[0046] S1. Preparation of modified silica: 2g of nano silica and 500g of ethanol aqueous solution are mixed, wherein the mass ratio of anhydrous ethanol to water in the ethanol aqueous solution is 2:1. After mixing evenly, 0.6g of silane coupling agent is added to the mixture to modify the nano silica. At the same time, dilute hydrochloric acid is added to adjust the pH value to neutral. After drying and grinding, the modified silica is obtained. S2. Preparation of the composite solvent: At a temperature of 25°C, 20g of ethylenediamine, 13g of sodium methyl ester sulfonate of compound fatty acids and 66g of water are mixed and stirred thoroughly to obtain the composite solvent. S3. Preparation of composite organic nano-oil displacement agent: At a temperature of 25°C, 1g of the modified silica is added to the composite solvent until the modified silica is uniformly and stably dispersed in the composite solvent; thus obtaining the composite organic nano-oil displacement agent.

[0047] Example 3:

[0048] S1. Preparation of modified silica: 2g of nano silica and 500g of ethanol aqueous solution are mixed, wherein the mass ratio of anhydrous ethanol to water in the ethanol aqueous solution is 1:1. After mixing evenly, 0.4g of silane coupling agent is added to the mixture to modify the nano silica. At the same time, dilute hydrochloric acid is added to adjust the pH value to neutral. After drying and grinding, the modified silica is obtained. S2. Preparation of the composite solvent: At a temperature of 25°C, 20g of ethylenediamine, 10g of sodium methyl ester sulfonate of compound fatty acids and 69g of water are mixed and stirred thoroughly to obtain the composite solvent. S3. Preparation of composite organic nano-oil displacement agent: At a temperature of 25°C, 1g of the modified silica is added to the composite solvent until the modified silica is uniformly and stably dispersed in the composite solvent; thus obtaining the composite organic nano-oil displacement agent.

[0049] Furthermore, a reservoir core or artificial core with a length of 10-30 cm is taken and supported by a cylinder with a diameter of 2.5-4.0 cm. The air permeability and pore volume of the core are determined in accordance with the provisions of 4.5.1 in SY / T 5336-1996.

[0050] The core is loaded into a holder and saturated with oil at the reservoir temperature to establish bound water saturation; the oil saturation of the core is as close as possible to the original oil saturation of the reservoir.

[0051] Water flooding was performed until the produced fluid contained 98% water, and the water recovery rate was calculated.

[0052] After water flooding is completed, the composite organic nano-oil displacement agent from Examples 1-3 is injected, and then water is injected until the produced fluid has a water content of 98%, and the final recovery rate is calculated.

[0053] As shown in Table 1 below, the composite organic nano-oil displacement agent of the present invention can achieve an oil recovery rate of over 80%.

[0054] Table 1 Displacement recovery results

[0055] In summary, the preparation method of the composite organic nano-displacement agent of the present invention, by controlling the raw materials and improving the preparation process, results in a composite organic nano-displacement agent with excellent recovery performance. Simultaneously, the addition of ethylenediamine improves the permeability of the composite organic nano-displacement agent, enhancing its oil washing performance while improving viscosity reduction during the oil displacement process. Furthermore, the addition of sodium methyl ester sulfonate of composite fatty acids synergistically reduces the interfacial tension of the product with modified nano-silica, further enhancing the oil displacement performance of the composite organic nano-displacement agent.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a composite organic nano-oil displacement agent, characterized in that... Includes the following steps: S1. Preparation of modified silica: Nano silica and an aqueous ethanol solution are mixed at a mass ratio of 0.1:100 to 0.6:100, and a modifier is added to modify the nano silica. The mass ratio of the modifier to the nano silica is 20% to 30%. The modified silica is obtained after drying. S2. Preparation of composite solvent: At 25°C, ethylenediamine and sodium methyl ester sulfonate of composite fatty acids are added to a solvent in a mass ratio of 1:1 to 3:1 to obtain the composite solvent. S3. Preparation of composite organic nano-displacement agent: At standard temperature, the modified silica is added to the composite solvent until the modified silica is uniformly and stably dispersed in the composite solvent to form a stable dispersion; a composite organic nano-displacement agent is prepared, wherein the water flooding recovery rate of the composite organic nano-displacement agent is >80%.

2. The preparation method of the composite organic nano-oil displacement agent according to claim 1, characterized in that, S1 specifically includes: S11. The nano-silica is mixed with the ethanol aqueous solution, wherein the mass ratio of anhydrous ethanol to water in the ethanol aqueous solution is 1:1 to 3:

1. S12. Add the modifier to the ethanol aqueous solution in which the nano-silica is dispersed, and ultrasonically disperse the nano-silica until the modifier is evenly dispersed. S13. Heat the dispersion in S12 to 45~55℃, mechanically stir for 2~3 hours, and centrifuge to obtain the crude product of the modified silica. S14. The crude product is washed and vacuum dried at 75~85°C for at least 48 hours, and then pulverized to obtain the modified silica.

3. The preparation method of the composite organic nano-oil displacement agent according to claim 2, characterized in that, S12 further includes adding a pH adjuster to the ethanol aqueous solution in which the nano-silica and the modifier are dispersed to adjust the pH so that the mixture is neutral.

4. The preparation method of the composite organic nano-oil displacement agent according to claim 3, characterized in that, The modifier is a silane coupling agent, and the pH adjuster is dilute hydrochloric acid.

5. The preparation method of the composite organic nano-oil displacement agent according to claim 2, characterized in that, Specifically, S14 involves washing the crude product from S13 at least three times with anhydrous ethanol, vacuum drying it at 75-85°C for at least 48 hours, and then pulverizing it to obtain the modified silica.

6. The preparation method of the composite organic nano-oil displacement agent according to claim 5, characterized in that, In step S14, the crude product after vacuum drying is ground using a grinding mill, and the modified silica after grinding has a medium particle size of 2.50~2.85μm.

7. The preparation method of the composite organic nano-oil displacement agent according to claim 1, characterized in that, In S3, the standard temperature is 25°C.

8. A composite organic nano-oil displacement agent, characterized in that, The composite organic nano-oil displacement agent is prepared using the preparation method of any one of claims 1 to 7.

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