A self-dispersing nanoreducing fluid and a method for preparing the same

Abstract

The application provides a kind of self-dispersing nano drag reduction fluid and its preparation method, comprising the following steps: S1, using coating agent to carry out adsorption coating to hydrophobic nano silica particles, to obtain hydrophilic nano silica particles;S2, hydrophilic nano carbon dioxide particles are added to 0.05-10wt% auxiliary dispersant aqueous solution, and at 13-45 DEG C, it is clear to stand, namely the self-dispersing nano drag reduction fluid of the present application;The hydrophilic nano silica particles prepared by the present application can be self-dispersed in aqueous solution at low temperature and normal temperature, forming nano drag reduction fluid, and the nano silica particles in the nano drag reduction fluid are uniformly dispersed, and have good stability.

Description

Technical Field

[0001] This invention relates to the field of oilfield water injection development technology, and in particular to a self-dispersing nano-drag-reducing fluid and its preparation method. Background Technology

[0002] Low-permeability and tight oil reservoirs are characterized by sparse pores, small pore throats, high capillary pressure, and poor connectivity. During water injection development, they often experience rapid and high injection pressure, leading to severe under-injection and low recovery rates. Nanoscale drag reduction technology is a technique developed to address the "high-pressure under-injection" problem in low-permeability oilfields. Hydrophilic micropores have high water flow resistance; by injecting drag-reducing nanofluids, competitive adsorption and wettability reversal form super-hydrophobic pore walls, thereby achieving drag reduction. Nanoscale drag reduction technology can produce good pressure reduction and injection enhancement effects, and has reached small- to medium-scale application levels both domestically and internationally. However, its widespread application is limited by high costs, primarily stemming from the preparation and dispersion of the nanofluids.

[0003] There are generally two ways to prepare drag-reducing nanofluids. One is liquid phase dilution, in which the nanoemulsion is pre-dispersed indoors to a higher concentration, and then diluted and dispersed in water at the mine to the application concentration. The other is to use nanoparticles, in which the nanoparticles are added to the aqueous solution of the dispersant at the mine, initially stirred, and then heated to 60-80℃, so that the particles are evenly dispersed in hot water.

[0004] The current technology has one or more of the following problems: 1. Liquid phase transportation is inconvenient, and even requires transportation by hazardous chemical vehicles, especially over long distances, resulting in high transportation costs; 2. The particle size of the liquid phase dispersion in emulsions is generally 100-200nm, which is difficult to meet the design requirements of less than 100nm for oil phases; 3. Using powder for field dispersion requires heat treatment, which increases the complexity of construction and also increases the cost of measures. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a self-dispersing nano-drag-reducing fluid and its preparation method. The nano-drag-reducing fluid is a low-cost drag-reducing nano-fluid that is self-dispersing at room temperature and has strong stability.

[0006] This invention provides the following technical solution:

[0007] This invention provides a method for preparing self-dispersing nanodrag-reducing fluids, comprising the following steps:

[0008] S1. Hydrophobic nano-silica particles are adsorbed and coated with a coating agent to obtain hydrophilic nano-silica particles.

[0009] S2. Add the hydrophilic nano silica particles to an aqueous solution containing 0.05-10 wt% dispersant, and let it stand at 13-45°C until it becomes clear to obtain the self-dispersing nano drag-reducing fluid.

[0010] Nanoparticles are prone to agglomeration, and uneven dispersion can lead to particle aggregation, reducing their surface area and activity. Commonly used dispersion methods for nanoparticles in the present technology include mechanical dispersion, ultrasonic dispersion, and chemical dispersion, and the effects of factors such as temperature and pH on the particles need to be considered during the dispersion process.

[0011] The hydrophilic nano-silica particles prepared by this invention have a negative charge on their surface. Under conditions of 13-45℃, the coating layer and the dispersant can undergo a good neutralization reaction, which promotes particle dispersion. At the same time, the substance produced by the neutralization reaction is a surfactant, which is beneficial to the dispersion and stability of the particles.

[0012] In nanofluids, solvation repulsion, electrostatic repulsion, and van der Waals attraction exist between particles. In this invention, the coating layer on the hydrophobic SiO2 nanoparticles weakens the van der Waals interactions between particles. Micromechanical model analysis shows that the solvation repulsion between nanoparticles dominates in the nanofluid prepared by this invention, resulting in strong thermodynamic stability. Simultaneously, the chemical reaction between the coating material and the dispersant on the particle surface enhances the hydrophilicity of the particles, promoting continuous self-dispersion. The hydrophilic nanoparticles prepared by this invention, relying on both chemical and mechanical mechanisms, can self-disperse to form uniform, stable nanofluids with significant drag reduction capabilities at both low and room temperatures. The hydrophilic nanoparticles prepared by this invention can be directly transported, avoiding liquid-phase transport, and can be directly self-dispersed in mines to prepare nanofluids without heating, reducing overall costs.

[0013] The hydrophilic nano-silica particles prepared by this invention can be uniformly dispersed in an aqueous solution containing 0.05-10 wt% dispersant under low temperature and room temperature conditions.

[0014] Furthermore, the coating agent includes one or more combinations of alkylphenol polyoxyethylene ether carboxylic acid, alkyl polyoxyethylene ether carboxylic acid, and alkyl polyether carboxylic acid.

[0015] Furthermore, the dispersant is one or more of potassium hydroxide, sodium hydroxide, and sodium bicarbonate.

[0016] Further, in step S1, the adsorption coating includes:

[0017] The coating agent is dissolved in an organic solvent to prepare a coating agent solution with a mass percentage of 5-20%.

[0018] Hydrophobic nano-silica particles were added to the coating agent solution and stirred for 3–10 hours.

[0019] The solution after the reaction was subjected to vacuum distillation and dried to obtain hydrophilic nano-silica particles.

[0020] Furthermore, the organic solvent is one or more of ethanol, isopropanol, and xylene.

[0021] Furthermore, the mass ratio of hydrophobic nano-silica particles to coating agent is 1:1 to 1:3.

[0022] Furthermore, in step S2, the mass ratio of hydrophilic nano-silica to dispersant is 3:1 to 1:10.

[0023] The present invention also provides a self-dispersing nanodrag-reducing fluid prepared by the above preparation method.

[0024] The particle size of the self-dispersing nanodrag-reducing fluid is 70–100 nm.

[0025] The present invention has the following beneficial effects:

[0026] 1. The hydrophilic nano-silica particles prepared by this invention can be self-dispersed in an aqueous solution containing a dispersant at 13-45℃ to form a nano-drag-reducing fluid. Compared with the prior art, it does not require heating to a high temperature, is convenient to use, and has a low cost.

[0027] 2. The preparation process of this invention is simple, and the nano-drag-reducing fluid is uniformly dispersed and has good stability. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below 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.

[0029] Figure 1 These are images showing the state of the nano-drag-reducing fluid prepared in Example 1 of this invention before and after dispersion.

[0030] Figure 2 These are images showing the state of the nano-drag-reducing fluid prepared in Example 2 of this invention before and after dispersion.

[0031] Figure 3 These are images showing the state of the nano-drag-reducing fluid prepared in Example 3 of this invention before and after dispersion.

[0032] Figure 4 These are images showing the state of the nano-drag-reducing fluid prepared in Example 4 of this invention before and after dispersion.

[0033] Figure 5 These are images showing the state of the nano-drag-reducing fluid prepared in Example 5 of this invention before and after dispersion.

[0034] Figure 6 These are images showing the state of the nano-drag-reducing fluid prepared in Example 6 of this invention before and after dispersion.

[0035] Figure 7 These are images showing the state of the nano-drag-reducing fluid prepared in Example 7 of this invention before and after dispersion.

[0036] Figure 8 The images show the state of the nano-drag-reducing fluid prepared in Example 8 of this invention before and after dispersion. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] This invention provides a method for preparing a self-dispersing nanodrag-reducing fluid, comprising the following steps:

[0039] Hydrophilic adsorption coating: Hydrophobic nano-silica is adsorbed and coated with a coating agent to obtain hydrophilic nano-silica particles with negative surface charge.

[0040] Self-dispersibility: Hydrophilic nano-silica particles are added to an aqueous solution containing 0.05–10 wt% dispersant, and allowed to stand at 13–45°C until clear to obtain the nanofluid.

[0041] In a specific embodiment, the coating agent includes one or more combinations of alkylphenol polyvinyl ether carboxylic acid, alkyl polyoxyethylene ether carboxylic acid, and alkyl polyether carboxylic acid.

[0042] In a specific embodiment, the dispersant is one or more of potassium hydroxide, sodium hydroxide, and sodium bicarbonate.

[0043] In a specific embodiment, step S1, adsorption coating includes:

[0044] The coating agent is dissolved in an organic solvent to prepare a coating agent solution with a mass percentage of 5-20%.

[0045] Hydrophobic nano-silica particles were added to the coating agent solution and stirred for 3–10 hours.

[0046] The solution after the reaction was subjected to vacuum distillation and dried to obtain hydrophilic nano-silica particles.

[0047] In a specific embodiment, the organic solvent is one or more of ethanol, isopropanol, and xylene.

[0048] In a specific embodiment, the mass ratio of hydrophobic nano-silica particles to the coating agent is 1:1 to 1:3, specifically 1:1, 2:3, 1:2, 1:3, etc., but not limited to the above ratios.

[0049] In a specific embodiment, in step S2, the mass ratio of hydrophilic nano-silica to dispersant is 3:1 to 1:10, specifically 3:1, 3:2, 1:1, 1:2, 1:5, 1:10, etc., but not limited to the above ratios.

[0050] Based on the same inventive concept, this embodiment also provides a self-dispersing nanodrag-reducing fluid prepared by the above method.

[0051] The present invention will be further illustrated below through specific embodiments:

[0052] Materials used for drag reduction in oil fields need to have strong hydrophobic properties. The core of the coated particles is selected from hydrophobic nano-silica particles, which are available on the market. In the following examples, the hydrophobic nano-silica particles were purchased from the Shanghai University Nanotechnology Center.

[0053] Example 1

[0054] The specific preparation process of the self-dispersing nanodrag-reducing fluid in this embodiment is as follows:

[0055] 1. Dissolve 6g of alkyl polyoxyethylene ether carboxylic acid in isopropanol to prepare a coating agent solution with a mass fraction of 15%; add 6g of hydrophobic nano-SiO2 particles to the coating agent solution and stir to react. After the reaction is complete, distill the solution under reduced pressure and dry it to obtain hydrophilic nano-SiO2 particles.

[0056] 2. Prepare a 0.30 wt% NaOH aqueous solution. Add the hydrophilic nano-SiO2 particles to the dispersant at a mass ratio of 1:2. After manual stirring to start dispersion, let it stand at a constant temperature of 15℃ until it becomes clear to obtain the nano drag-reducing fluid.

[0057] like Figure 1 As shown in (a), the newly added hydrophilic nano-silica particles disperse to form a suspension emulsion, as... Figure 1 As shown in (b), the nano-drag-reducing fluid formed after standing for 11 hours is clear and transparent, and the nano-silica particles are well dispersed.

[0058] Example 2

[0059] The specific preparation process of the self-dispersing nanodrag-reducing fluid in this embodiment is as follows:

[0060] 1. Dissolve 6g of alkyl polyoxyethylene ether carboxylic acid in isopropanol to prepare a coating agent solution with a mass fraction of 15%; add 6g of hydrophobic nano-SiO2 particles to the coating agent solution and stir to react. After the reaction is complete, distill the solution under reduced pressure and dry it to obtain hydrophilic nano-SiO2 particles.

[0061] 2. Prepare a 0.10 wt% NaOH aqueous solution. Add the hydrophilic nano-SiO2 particles at a mass ratio of 3:2 to the dispersant. After manual stirring to start dispersion, let it stand at a constant temperature of 30°C until it becomes clear to obtain the nano drag-reducing fluid.

[0062] like Figure 2 As shown in (a), the newly added hydrophilic nano-silica particles disperse to form a suspension emulsion, as... Figure 2 As shown in (b), the nano-drag-reducing fluid formed after standing for 7 hours is clear and transparent, and the nano-silica particles are well dispersed.

[0063] Example 3

[0064] The specific preparation process of the self-dispersing nanodrag-reducing fluid in this embodiment is as follows:

[0065] 1. Dissolve 6g of alkyl polyoxyethylene ether carboxylic acid in isopropanol to prepare a coating agent solution with a mass fraction of 15%; add 6g of hydrophobic nano-SiO2 particles to the coating agent solution and stir to react. After the reaction is complete, distill the solution under reduced pressure and dry it to obtain hydrophilic nano-SiO2 particles.

[0066] 2. Prepare a 0.05wt% NaOH aqueous solution, add hydrophilic nano-SiO2 particles at a mass ratio of 3:1 to dispersant, stir manually to start dispersion, and let stand at a constant temperature of 45℃ until clear to obtain nano drag-reducing fluid.

[0067] like Figure 3 As shown in (a), the newly added hydrophilic nano-silica particles disperse to form a suspension emulsion, as... Figure 3 As shown in (b), the nano-drag-reducing fluid formed after standing for 9 hours is clear and transparent, and the nano-silica particles are well dispersed.

[0068] Example 4

[0069] The specific preparation process of the self-dispersing nanodrag-reducing fluid in this embodiment is as follows:

[0070] 1. Dissolve 6g of alkyl polyoxyethylene ether carboxylic acid in isopropanol to prepare a coating agent solution with a mass fraction of 15%; add 6g of hydrophobic nano-SiO2 particles to the coating agent solution and stir to react. After the reaction is complete, distill the solution under reduced pressure and dry it to obtain hydrophilic nano-SiO2 particles.

[0071] 2. Prepare a 0.15wt% NaOH aqueous solution, add hydrophilic nano-SiO2 particles to the dispersant at a mass ratio of 1:1, stir manually to start dispersion, and let stand at a constant temperature of 45℃ until clear to obtain nano drag-reducing fluid.

[0072] like Figure 4 As shown in (a), the newly added hydrophilic nano-silica particles disperse to form a suspension emulsion, as... Figure 4 As shown in (b), the nano-drag-reducing fluid formed after standing for 5 hours is clear and transparent, and the nano-silica particles are well dispersed.

[0073] Example 5

[0074] The specific preparation process of the self-dispersing nanodrag-reducing fluid in this embodiment is as follows:

[0075] 1. Dissolve 18g of alkyl polyoxyethylene ether carboxylic acid in xylene to prepare a coating agent solution with a mass fraction of 20%; add 6g of hydrophobic nano-SiO2 particles to the coating agent solution and stir to react. After the reaction is complete, distill the solution under reduced pressure and dry it to obtain hydrophilic nano-SiO2 particles.

[0076] 2. Prepare a 10wt% NaOH aqueous solution. Add the hydrophilic nano-SiO2 particles at a mass ratio of 1:10 to the dispersant. After manual stirring to start dispersion, let it stand at a constant temperature of 20℃ until it becomes clear to obtain the nano drag-reducing fluid.

[0077] like Figure 5 As shown in (a), the newly added hydrophilic nano-silica particles disperse to form a suspension emulsion, as... Figure 5 As shown in (b), the nano-drag-reducing fluid formed after standing for 4 hours is clear and transparent, and the nano-silica particles are well dispersed.

[0078] Example 6

[0079] 1. Dissolve 9g of alkyl polyether carboxylic acid in xylene to prepare a coating agent solution with a mass fraction of 15%; add 6g of hydrophobic nano-SiO2 particles to the coating agent solution and stir to react. After the reaction is complete, distill the solution under reduced pressure and dry it to obtain hydrophilic nano-SiO2 particles.

[0080] 2. Prepare a 1.50 wt% KOH aqueous solution, add hydrophilic nano-SiO2 particles at a mass ratio of 1:10 to dispersant, stir manually to start dispersion, and let stand at a constant temperature of 13℃ until clear to obtain nano drag-reducing fluid.

[0081] like Figure 6 As shown in (a), the newly added hydrophilic nano-silica particles disperse to form a suspension emulsion, as... Figure 6 As shown in (b), the nano-drag-reducing fluid formed after standing for 12 hours is clear and transparent, and the nano-silica particles are well dispersed.

[0082] Example 7

[0083] 1. Dissolve 10g of alkyl polyether carboxylic acid in ethanol to prepare a coating agent solution with a mass fraction of 10%; add 5g of hydrophobic nano-SiO2 particles to the coating agent solution and stir to react. After the reaction is complete, distill the solution under reduced pressure and dry it to obtain hydrophilic nano-SiO2 particles.

[0084] 2. Prepare a 0.75wt% KOH aqueous solution. Add the hydrophilic nano-SiO2 particles to the dispersant at a mass ratio of 1:5. After manual stirring to start dispersing, let it stand at a constant temperature of 14℃ until it becomes clear to obtain the nano drag-reducing fluid.

[0085] like Figure 7 As shown in (a), the newly added hydrophilic nano-silica particles disperse to form a suspension emulsion, as... Figure 7 As shown in (b), the nano-drag-reducing fluid formed after standing for 18 hours is clear and transparent, and the nano-silica particles are well dispersed.

[0086] Example 8

[0087] 1. Dissolve 5g of alkylphenol polyoxyethylene ether carboxylic acid in ethanol to prepare a coating agent solution with a mass fraction of 5%; add 5g of hydrophobic nano-SiO2 particles to the coating agent solution and stir to react. After the reaction is complete, distill the solution under reduced pressure and dry it to obtain hydrophilic nano-SiO2 particles.

[0088] 2. Prepare a mixed aqueous solution with NaHCO3 and NaOH each containing 1 wt%. Add hydrophilic nano-SiO2 particles to the dispersant at a mass ratio of 1:2. After manual stirring to start dispersion, let it stand at a constant temperature of 25°C until it becomes clear to obtain nano drag-reducing fluid.

[0089] like Figure 8 As shown in (a), the newly added hydrophilic nano-silica particles disperse to form a suspension emulsion, as... Figure 8As shown in (b), the nano-drag-reducing fluid formed after standing for 5 hours is clear and transparent, and the nano-silica particles are well dispersed.

[0090] Comparative Example 1

[0091] The difference from Example 1 is that in step 2, the hydrophilic nano-SiO2 particles are directly dispersed in deionized water.

[0092] The particle size of nano-silica particles in the nano-drag-reducing fluids prepared in Comparative Example 1 and Examples 1-8 was determined using a laser particle size analyzer. Three sets of parallel data were measured for each sample, and the average value was taken.

[0093] After micro-stirring in Comparative Example 1, a turbid liquid phase was observed, and the measured particle size reached 3-5 micrometers. This indicates that the nanoparticles were not completely dispersed and existed as aggregates. After being left for a long time, they would settle and produce precipitates.

[0094] In Example 1, no strong external forces such as high-speed mechanical stirring and ultrasound were applied, and the turbid liquid gradually became clear. The average particle size of the drag-reducing nanofluid obtained was 88 nm. After standing for 24 hours, the drag-reducing nanofluid became even clearer and more transparent, with an average particle size of 70 nm. In Example 2, the average particle size of the drag-reducing nanofluid obtained was 97 nm, and after standing for 24 hours, the average particle size was 78 nm. In Example 3, the average particle size of the drag-reducing nanofluid obtained was 92 nm. In Example 4, the average particle size of the drag-reducing nanofluid obtained was 84 nm. In Example 5, the average particle size of the drag-reducing nanofluid obtained was 72 nm. In Example 6, the average particle size of the drag-reducing nanofluid obtained was 90 nm. In Example 7, the average particle size of the drag-reducing nanofluid obtained was 78 nm. In Example 8, the average particle size of the drag-reducing nanofluid obtained was 82 nm.

[0095] In Examples 1-8, a dispersant was added, and no strong external forces such as high-speed mechanical stirring or ultrasound were applied. The turbid liquid gradually became clear, and the particle size was less than 100 nm. Moreover, no obvious precipitation was observed after 15 days of standing, indicating that the nanoparticles not only underwent self-dispersion but also had strong thermodynamic stability.

[0096] This is because: after coating, the nanoparticles possess a certain degree of hydrophilicity, resulting in wetting between particles in the aqueous phase. Due to capillary forces in the water, water molecules are drawn into the pores between the particles. However, due to the small interparticle spacing, the water absorption rate is slow. In this invention, the coating material on the surface of the nanoparticles is weakly acidic. Through its reaction with an alkaline dispersant, the reaction accelerates the dispersion of the particles in water, and the continuous reaction further promotes the dispersion of the nanoparticles. On the other hand, it increases the hydrophilicity of the nanoparticles, strengthens the capillary action, promotes the absorption of water molecules, thereby enhancing particle wetting and accelerating particle self-dispersion. Simultaneously, the adsorption of water molecules by the particles forms a solvation film on the surface, generating solvation repulsion between particles; water replaces air, reducing the van der Waals attraction between particles. The dispersion of particles also reduces the particle size, lowers the particle potential, weakens the electrostatic repulsion, and also reduces the van der Waals attraction between particles, thereby reducing the ability of particles to agglomerate secondary.

[0097] The hydrophilic nano-silica particles prepared by this invention can self-disperse in an aqueous solution containing a dispersant at low and room temperatures to form a nano-drag-reducing fluid. The nano-silica particles in this nano-drag-reducing fluid are uniformly dispersed with a particle size of 70-100 nm and exhibit good stability.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a self-dispersing nanodrag-reducing fluid, characterized in that, Includes the following steps: S1. Hydrophobic nano-silica particles are adsorbed and coated with a coating agent to obtain hydrophilic nano-silica particles. S2. Add hydrophilic nano silica particles to an aqueous solution containing 0.05~10wt% dispersant, and let stand at 13~45℃ until clear to obtain the self-dispersing nano drag-reducing fluid. In step S1, the adsorption coating includes: Dissolve the coating agent in an organic solvent to prepare a coating agent solution with a mass percentage of 5-20%; Hydrophobic nano-silica particles were added to the coating agent solution and stirred for 3-10 hours. The solution after the reaction was subjected to vacuum distillation and dried to obtain hydrophilic nano-silica particles; The coating agent includes one or more of alkylphenol polyvinyl ether carboxylic acid and alkyl polyoxyethylene ether carboxylic acid; the dispersant is one or more of potassium hydroxide, sodium hydroxide, and sodium bicarbonate.

2. The method for preparing self-dispersing nanodrag-reducing fluid as described in claim 1, characterized in that: The organic solvent is one or more of ethanol, isopropanol, and xylene.

3. The method for preparing self-dispersing nanodrag-reducing fluid as described in claim 1, characterized in that: The mass ratio of hydrophobic nano-silica particles to coating agent is 1:1 to 1:

3.

4. The method for preparing self-dispersing nanodrag-reducing fluid as described in claim 1, characterized in that: In step S2, the mass ratio of hydrophilic nano-silica particles to dispersant is 3:1 to 1:

10.

5. A self-dispersing nanodrag-reducing fluid prepared by any of the preparation methods described in claims 1 to 4.

6. The self-dispersing nanodrag-reducing fluid as described in claim 5, characterized in that, The particle size of the nanodrag-reducing fluid is 70~100 nm.

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