Pickering emulsified solvent profile control agent, preparation method and application thereof

Abstract

The application provides a Pickering emulsified solvent profile control agent and a preparation method and application thereof. The Pickering emulsified solvent profile control agent comprises the following raw material components in percentage by mass: 1.0%-3.0% of nano-bentonite particles, 0.005%-0.05% of a surface modifier, 0.0005%-0.001% of a pH regulator, 5%-20% of solvent oil, and the balance of water. The Pickering emulsified solvent profile control agent has high viscosity, strong flow control and good stability. When applied to water flooding of thick oil cold production, the Pickering emulsified solvent profile control agent can effectively reduce the viscosity of thick oil, has high sweep efficiency, and can effectively improve the recovery rate of water flooding of thick oil cold production.

Description

Technical Field

[0001] This invention relates to a Pickering emulsified solvent modifier, its preparation method and application, belonging to the field of heavy oil water-drive cold production technology. Background Technology

[0002] With the reserves of light oil resources decreasing year by year, the efficient exploitation of heavy oil resources is of great significance to solving my country's energy problem. Due to the high viscosity and density of heavy oil, it has poor fluidity in formations, making conventional technologies difficult to develop economically and effectively. Currently, the main technology for heavy oil extraction is thermal recovery, with steam huff and puff and steam-assisted gravity drainage being the most successful. However, for deep reservoirs (>1000m), thin reservoirs (<5m), or reservoirs with edge and bottom water, excessive heat loss economically restricts the application of thermal recovery technologies. For heavy oil reservoirs unsuitable for thermal recovery, water-drive cold recovery is generally used. However, due to the significant viscosity difference between injected water and heavy oil, the water-oil mobility ratio is too high during water-drive, leading to severe fingering of the injected water, significantly reducing the sweep efficiency and resulting in low water-drive recovery. Therefore, how to effectively improve the water-drive recovery rate is a pressing technical challenge in the current development of heavy oil water-drive cold recovery.

[0003] Emulsion flooding possesses dual profile control and oil displacement effects. In particular, emulsion solvent flooding, where the oil phase is the solvent, also dilutes and reduces the viscosity of heavy oil, making it a promising method for water-driven cold recovery of heavy oil. Currently, conventional emulsion flooding agents are formed from surfactants. For example, Chinese patent document CN110129019A discloses a nano-flooding agent for tertiary oil recovery, comprising the following weight proportions: 3-6 parts oil phase, 0.4-1.5 parts anionic and cationic surfactants or 1-5 parts anionic surfactant, 0.02-0.2 parts co-surfactant, and 88-98 parts water. Although the O / W emulsion of this nano-flooding agent exhibits good stability and achieves ultra-low interfacial tension, the prepared O / W emulsion system has very low viscosity, and severe fingering still occurs when displacing heavy oil, making it difficult to effectively improve the sweep efficiency. Meanwhile, due to the adsorption loss of surfactants on the formation surface, the stabilization time of surfactant-formed emulsions is very short, and the ability of surfactant-formed emulsion systems to control flow rate is weak.

[0004] Therefore, developing an emulsified solvent system with high viscosity, strong flow control, long stability time, and the ability to effectively reduce the viscosity of heavy oil is of great significance for improving the recovery rate of heavy oil water-driven cold production. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a Pickering emulsified solvent modifier, its preparation method, and its application. The Pickering emulsified solvent modifier of this invention exhibits high viscosity, strong flow control, and good stability. When applied to water-driven heavy oil cold production, it can effectively reduce heavy oil viscosity, has a high sweep efficiency, and effectively improve the recovery rate of water-driven heavy oil cold production.

[0006] The technical solution of the present invention is as follows:

[0007] A Pickering emulsified solvent modifier comprises the following raw material components in weight percentages: 1.0%-3.0% nano-bentonite particles, 0.005%-0.05% surface modifier, 0.0005%-0.001% pH adjuster, 5%-20% solvent oil, and the balance being water.

[0008] According to a preferred embodiment of the present invention, the Pickering emulsifying solvent modifier comprises the following raw material composition in weight percentages: 1.0%-2.5% nano-bentonite particles, 0.005%-0.012% surface modifier, 0.0005%-0.001% pH adjuster, 5%-20% solvent oil, and the balance being water.

[0009] According to a preferred embodiment of the present invention, the nano-bentonite particles are sodium-based bentonite particles with an average particle size of 100-150 nm.

[0010] According to a preferred embodiment of the present invention, the surface modifier is N,N-dimethyl-N-dodecyl tertiary amine, N,N-dimethyl-N-tetradecyl tertiary amine, N,N-dimethyl-N-hexadecyl tertiary amine, or N,N-dimethyl-N-octadecyl tertiary amine.

[0011] According to a preferred embodiment of the present invention, the pH adjuster is acetic acid, carbonic acid, or citric acid.

[0012] According to a preferred embodiment of the present invention, the solvent oil is a mixed aromatic hydrocarbon or a mixed benzene solvent. The main components of the mixed aromatic hydrocarbon or mixed benzene solvent are aromatic hydrocarbons such as benzene, toluene, and xylene, with an aromatic hydrocarbon content greater than 65%.

[0013] The preparation method of the above-mentioned Pickering emulsified solvent modifier includes the following steps:

[0014] (1) Add nano-bentonite particles to water, add pH adjuster to adjust pH to 5.0-6.5, stir and mix evenly to obtain nano-bentonite dispersion solution;

[0015] (2) Add the surface modifier to the solvent oil and stir to mix evenly to obtain the solvent oil containing the surface modifier;

[0016] (3) Mix the nano-bentonite dispersion with solvent oil containing surface modifier and stir to obtain Pickering emulsified solvent modifier.

[0017] According to a preferred embodiment of the present invention, in step (1), the stirring rate is 1000-2000 r / min; in step (2), the stirring rate is 300-600 r / min; in step (3), a homogenizer is used for mixing, the stirring speed is 8000-12000 r / min, and the stirring time is 10 min-20 min.

[0018] The above-mentioned Pickering emulsified solvent modifier is used in water-driven cold production of heavy oil.

[0019] According to a preferred embodiment of the present invention, the viscosity of the heavy oil at 50°C is less than 5000 mPa·s and greater than 500 mPa·s.

[0020] The technical features and beneficial effects of this invention are as follows:

[0021] 1. The Pickering emulsified solvent displacement agent of the present invention is prepared using mixed aromatic hydrocarbons or mixed benzene solvents as the oil phase. Its main components contain aromatic organic solvents such as benzene, toluene, and xylene, which have a good dispersing and diluting effect on the asphaltenes in heavy oil, thus exhibiting excellent dilution and viscosity reduction effects on heavy oil. After the solvent droplets of the Pickering emulsified solvent come into contact with heavy oil during the displacement process, they can quickly dissolve in the heavy oil, significantly reducing the viscosity of the displaced heavy oil and significantly improving the flowability of heavy oil, thereby improving the displacement efficiency of heavy oil.

[0022] 2. This invention utilizes the protonation of long-chain alkyl tertiary amines under weakly acidic conditions, transforming them into positively charged cationic surfactants. These surfactants can then be adsorbed onto the surface of negatively charged nano-bentonite particles via electrostatic interactions. This causes the long-chain alkyl tertiary amine molecules to oriented and align on the nano-bentonite particle surface, with the hydrophobic ends facing outwards. This reduces the hydrophilicity of the nano-bentonite particles, achieving partial hydrophobic modification. Some of these hydrophobic nano-bentonite particles can then irreversibly adsorb onto the oil-water interface, forming a solid particle film. This improves the mechanical strength of the interfacial film, significantly inhibiting the coalescence of emulsion droplets and Ostwald ripening. Consequently, it greatly enhances the stability of the Pickering emulsion solvent system and prolongs the flooding time of the emulsion solvent modifier in the formation.

[0023] 3. The Pickering emulsified solvent modifier of this invention is a nanoparticle-stabilized water-in-oil solvent emulsion. The negative charge on the surface of the nano-bentonite particles, modified with long-chain alkyl tertiary amines, is reduced, leading to weak aggregation between the nano-bentonite particles. This results in a dense three-dimensional network structure in the continuous aqueous phase, significantly improving its bulk viscosity and interfacial viscoelasticity. Simultaneously, the Pickering emulsified solvent exhibits significant shear-dilution characteristics. Therefore, during injection, the viscosity of the Pickering emulsified solvent decreases significantly under high shear rates, which is beneficial for the injection of the Pickering emulsified solvent system. However, after injection into the formation, when the shear rate decreases, the nano-bentonite particles can reform the dense three-dimensional network structure, thereby restoring and improving the bulk viscosity and interfacial viscoelasticity of the emulsified solvent system. This enhances the flow control effect of the emulsified solvent system, thus significantly improving the sweep efficiency of the Pickering emulsified solvent modifier.

[0024] 4. The Pickering emulsified solvent modifier of this invention has high viscosity, strong mobility control capability, and good stability; it exhibits significant shear dilution characteristics and is easy to inject into formations; when applied to water-driven heavy oil cold production, it can effectively reduce the viscosity of heavy oil, has a high sweep efficiency, and can effectively improve the recovery rate of water-driven heavy oil cold production. Experiments show that the Pickering emulsified solvent of this invention has a stability time of over 180 days at 50°C, exhibits good shear dilution properties, and is easy to inject; for ordinary heavy oil with a viscosity of 500–5000 mPa·s at 50°C, the viscosity reduction rate of the Pickering emulsified solvent can reach over 90%; at 7.34 s -1 Under these conditions, the bulk viscosity of the emulsified solvent is 38–209 mPa·s, and a permeability of 2000 × 10⁻⁶ mPa·s is used. -3 μm 2 Injecting 0.50 PV of Pickering emulsified solvent modifier into sandstone cores can increase the recovery rate of water-driven heavy oil by more than 25%, making it a highly efficient modifier for water-driven heavy oil cooling.

[0025] 5. The raw material composition of the Pickering emulsified solvent modifier of the present invention is as a whole, and only through their combined action can the above-mentioned excellent effects of the present invention be achieved; any substitution or omission of any component, as well as unsuitable raw material ratio, will reduce the performance of the modifier. Attached Figure Description

[0026] Figure 1 Microscopic images and laser confocal fluorescence images of the Pickering emulsion solvent modulator prepared in Example 1.

[0027] Figure 2The bulk viscosity of the Pickering emulsified solvent modifiers prepared in Examples 1-4 under continuous shearing at different shear rates is shown. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. The embodiments described below 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 protection scope of the present invention.

[0029] In addition, the experimental methods described in the following embodiments are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0030] The density of the mixed aromatic hydrocarbons and mixed benzene solvent at 25°C is 0.80–0.89 g / cm³. 3 It contains more than 65% aromatic hydrocarbons, and its main components are aromatic hydrocarbons such as benzene, toluene and xylene. It is available from Jinan Yinrun Chemical Co., Ltd.

[0031] Example 1

[0032] A Pickering emulsifying solvent modifier comprises the following raw material composition in weight percentages: 1.0% sodium bentonite particles (average particle size 100-150 nm), 0.005% N,N-dimethyl-N-dodecyl tertiary amine, 0.0005% acetic acid, 5% mixed aromatics, and 93.9945% water.

[0033] The preparation method of the above-mentioned Pickering emulsified solvent modifier includes the following steps:

[0034] (1) After adding sodium-based bentonite particles to water, add acetic acid to adjust the pH to 5.5, stir at 1500 r / min until the mixture is uniform, and obtain a nano-bentonite dispersion solution.

[0035] (2) Add N,N-dimethyl-N-dodecyl tertiary amine to the mixed aromatic solvent oil and stir at 500 r / min to mix evenly to obtain a solvent oil containing a surface modifier;

[0036] (3) Add the solvent oil containing the surface modifier obtained in step (2) to the nano-bentonite dispersion obtained in step (1), and stir it for 20 minutes at a speed of 10000 r / min using a homogenizer to obtain Pickering emulsified solvent modifier.

[0037] Example 2

[0038] A Pickering emulsifying solvent modifier comprises the following raw material components in weight percentages: 1.5% sodium bentonite particles (average particle size 100-150 nm), 0.008% N,N-dimethyl-N-tetradecyl tertiary amine, 0.0006% acetic acid, 10% mixed benzene solvent, and 88.4914% water.

[0039] The preparation method of the Pickering emulsified solvent modifier is as described in Example 1.

[0040] Example 3

[0041] A Pickering emulsifying solvent modifier comprises the following raw material components in weight percentages: 2.0% sodium bentonite particles (average particle size 100-150 nm), 0.01% N,N-dimethyl-N-hexadecyl tertiary amine, 0.0008% acetic acid, 15% mixed benzene solvent, and 82.9892% water.

[0042] The preparation method of the Pickering emulsified solvent modifier is as described in Example 1.

[0043] Example 4

[0044] A Pickering emulsifying solvent modifier comprises the following raw material composition in weight percentages: 2.5% sodium bentonite particles (average particle size 100-150 nm), 0.012% N,N-dimethyl-N-octadecyl tertiary amine, 0.001% acetic acid, 20% mixed benzene solvent, and 77.487% water.

[0045] The preparation method of the Pickering emulsified solvent modifier is as described in Example 1.

[0046] Comparative Example 1

[0047] A Pickering emulsifying solvent modifier is described in Example 1, except that white oil is used instead of the mixed aromatic solvent; the other raw material composition is the same as in Example 1.

[0048] The preparation method of the Pickering emulsified solvent modifier is as described in Example 1.

[0049] Comparative Example 2

[0050] A Pickering emulsified solvent modifier is described in Example 2, except that the surface modifier is replaced with dodecyltrimethylammonium chloride instead of N,N-dimethyl-N-tetradecyl tertiary amine; the composition of other raw materials is the same as in Example 2.

[0051] The preparation method of the Pickering emulsified solvent modifier is as described in Example 2.

[0052] Comparative Example 3

[0053] A Pickering emulsified solvent modifier is described in Example 3, except that nano-silica particles (average particle size 20 nm) are used instead of sodium-based bentonite particles; the other raw material composition is the same as in Example 3.

[0054] The preparation method of the Pickering emulsified solvent modifier is as described in Example 3.

[0055] Comparative Example 4

[0056] A Pickering emulsifying solvent modifier is described in Example 4, except that acetic acid is not added to adjust the pH value; the other raw material composition is the same as in Example 4.

[0057] The preparation method of the Pickering emulsified solvent modifier is as described in Example 4.

[0058] Test case

[0059] (a) Experimental samples: emulsified solvent modifiers prepared in Examples 1-4 and Comparative Examples 1-4.

[0060] (1) Stability test:

[0061] The prepared Pickering emulsion solvent system was placed in a graduated stoppered test tube and in a constant temperature incubator at 50°C. The oil-water separation of the emulsion was observed daily, and the time for the aqueous phase to precipitate was recorded as the stabilization time. If no aqueous phase precipitated, it indicated that the emulsion had good stability. The results are shown in Table 1.

[0062] (2) The shear rate at 50°C was measured using a Brookfield viscometer, which was 7.34 s⁻¹. -1 The apparent viscosity of the Pickering emulsion solvent system prepared under the specified conditions is shown in Table 1.

[0063] (3) After stirring the prepared Pickering emulsified solvent system and heavy oil at a volume ratio of 3:7, the viscosity of the heavy oil after viscosity reduction was measured at 50°C using a Brookfield viscometer. The viscosity reduction rate was calculated according to the following formula: viscosity reduction rate = (original heavy oil viscosity - viscosity of heavy oil after viscosity reduction) / original heavy oil viscosity × 100%. The results are shown in Table 1.

[0064] (4) Testing of oil displacement performance:

[0065] a) Core (permeability 2000×10⁻⁶) -3 μm 2 After vacuuming, the core was saturated with water, and the core pore volume (PV) was measured.

[0066] b) After saturating the core with oil, age it at a constant temperature of 50°C for 24 hours.

[0067] c) Inject water for water flooding. Stop water flooding when the water content of the produced fluid is greater than 98%, and calculate the water flooding recovery rate.

[0068] d) Inject 0.5 PV of Pickering emulsified solvent modifier and record the pressure and oil production rate;

[0069] e) Re-inject water for subsequent waterflooding. When the water cut of the produced fluid is greater than 98%, the displacement is terminated, and the total recovery is calculated. The total recovery value is obtained by subtracting the waterflooding recovery value from the total recovery value, and the results are shown in Table 1.

[0070] Performance and oil displacement effect of Pickering emulsified solvent modifiers prepared in Examples 1-4 and Comparative Examples 1-4

[0071]

[0072] As shown in Table 1, the embodiments of this invention use mixed aromatics or mixed benzene as solvents. The surface of nano-bentonite particles is hydrophobically modified by protonation of long-chain alkyl tertiary amines under weakly acidic conditions, thereby preparing a nano-bentonite-stabilized Pickering emulsion solvent modifier. This modifier exhibits excellent stability (stabilization time greater than 180 days), superior viscosity-reducing ability for heavy oils of different viscosities (viscosity reduction rate greater than 90%), and a significant increase in water-driven heavy oil recovery (recovery rate increase greater than 25%). The embodiments of this invention use mixed aromatics or mixed benzene solvents to prepare Pickering emulsion solvents. These solvents have excellent dilution and viscosity-reducing effects on heavy oils, significantly reducing viscosity and improving flowability. In Comparative Example 1, a Pickering emulsion was prepared using white oil as the oil phase. White oil has poor dilution and viscosity-reducing capabilities for heavy oil, resulting in a significantly lower viscosity reduction rate and consequently a lower enhanced oil recovery rate for water-driven heavy oil. Compared to the dodecyltrimethylammonium chloride cationic surfactant in Comparative Example 2, although it can achieve surface modification by electrostatic adsorption onto the nano-bentonite surface, the dodecyltrimethylammonium chloride promotes flocculation of the nano-bentonite particles, leading to decreased stability of the emulsion solvent system and a shorter regulation time. Compared to the nano-silica particles added in Comparative Example 3, while modified nano-silica can form a solid particle interface film, it cannot form a three-dimensional network structure in the continuous phase like nano-bentonite particles. Therefore, the resulting emulsion solvent system has a lower apparent viscosity and weaker flow control capability, resulting in a lower enhanced oil recovery rate for water-driven heavy oil. In contrast, Comparative Example 4 did not include a pH adjuster, which prevented the long-chain alkyl tertiary amine from being protonated. As a result, it could not be adsorbed onto the surface of nano-bentonite particles to achieve hydrophobic modification and could not form a stable emulsion solvent system, thus resulting in a poor effect on improving the recovery rate.

[0073] (ii) Experimental sample: Pickering emulsified solvent modifier prepared in Examples 1-4.

[0074] (1) Microstructure test of the interface of Pickering emulsion solvent prepared in Example 1

[0075] Sodium-based bentonite particles were added to water, followed by the addition of the fluorescent dye Rhodamine B and rapid mixing. Acetic acid was added to adjust the pH to 5.5, and the mixture was stirred at 1500 rpm until homogeneous, yielding a fluorescently labeled nano-bentonite dispersion. A solvent oil containing a surface modifier (prepared as in Example 1) was added, and the mixture was stirred at 10000 rpm for 20 minutes using a homogenizer to obtain a Pickering emulsified solvent modifier. After appropriate dilution, the sample was placed on a glass slide, carefully covered with a coverslip, and placed on a laser confocal microscope (Nikon Ti). A 543 nm laser was used to excite the sample, and fluorescence was collected in the 570-610 nm wavelength range to observe the interfacial microstructure of the emulsified solvent. The results are as follows: Figure 1 As shown.

[0076] from Figure 1 As can be seen, the Pickering emulsion solvent droplets prepared in this invention emit red fluorescence on their surface, indicating that the fluorescently labeled modified nano-bentonite particles are firmly adsorbed on the oil-water interface, forming a dense solid particle film. This increases the strength of the droplet interface film, thereby significantly inhibiting the aggregation and Ostwald ripening of the emulsion droplets. Consequently, the stability of the Pickering emulsion solvent system is greatly improved, which is beneficial for extending the modulating time of the emulsion solvent system.

[0077] (2) Shear recovery test of the Pickering emulsion solvents prepared in Examples 1-4

[0078] The bulk viscosity change of Pickering emulsified solvent modulator during continuous shearing at different shear rates was determined using an MCR92 rheometer (Anton Paar, Austria). The results are as follows: Figure 2 As shown.

[0079] from Figure 2 As can be seen from the above, the Pickering emulsified solvent modulator prepared in this invention exhibits good performance at low shear rates (1 s⁻¹). -1 Under continuous shearing, the bulk viscosity of the emulsion solvent decreases slightly over time, but decreases further under high shear rates (100 s⁻¹). -1 The bulk viscosity of the emulsion solvent initially decreased significantly and then gradually stabilized, indicating that at high shear rates, the bulk structure of the emulsion solvent changed, leading to a significant reduction in viscosity. However, when the shear rate decreased to 1 s⁻¹... -1Subsequently, the viscosity of the emulsified solvent began to rise, returning to the high viscosity state at low shear rates. This indicates that the modified nano-bentonite can reform a dense three-dimensional network structure in the continuous phase, restoring the bulk viscosity of the system. Therefore, the Pickering emulsified solvent modifier prepared in this invention exhibits significant shear dilution properties. During injection, the system experiences lower bulk viscosity at high shear rates, which is beneficial for the injection of the emulsified solvent system. After injection into the formation, the Pickering emulsified solvent modifier experiences lower shear rates in the formation, thus restoring the bulk viscosity and interfacial viscoelasticity of the system, thereby exhibiting good flow control and modifier performance.

[0080] The above embodiments are merely illustrative examples of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention fall within the scope of protection of the present invention. Parts not specifically described in this embodiment are common knowledge and technology in this field, and will not be described in detail here.

Claims

1. A Pickering emulsified solvent modifier, characterized in that, The raw material composition includes the following percentages by weight: 1.0%-3.0% nano-bentonite particles, 0.005%-0.05% surface modifier, 0.0005%~0.001% pH adjuster, 5%-20% solvent oil, and the balance being water; The nano-bentonite particles are sodium-based bentonite particles; the surface modifier is... N,N -dimethyl- N -Dodecyl tertiary amine, N,N -dimethyl- N -Tetradecyl tertiary amine, N,N -dimethyl- N -Hexadecyl tertiary amine or N,N -dimethyl- N -Octadecyl tertiary amine; the pH adjuster is acetic acid, carbonic acid or citric acid; the solvent oil is a mixture of aromatics or a mixture of benzene solvents.

2. The Pickering emulsified solvent modifier according to claim 1, characterized in that, The Pickering emulsified solvent modifier comprises the following raw materials in weight percentages: 1.0%-2.5% nano-bentonite particles, 0.005%-0.012% surface modifier, 0.0005%~0.001% pH adjuster, 5%-20% solvent oil, and the balance being water.

3. The Pickering emulsified solvent modifier according to claim 1, characterized in that, The average particle size of the nano-bentonite particles is 100-150 nm.

4. A method for preparing the Pickering emulsified solvent modifier as described in any one of claims 1-3, comprising the steps of: (1) Add nano-bentonite particles to water, add pH adjuster to adjust pH to 5.0~6.5, stir and mix evenly to obtain nano-bentonite dispersion solution; (2) Add the surface modifier to the solvent oil and stir to mix evenly to obtain the solvent oil containing the surface modifier; (3) Mix the nano-bentonite dispersion with solvent oil containing surface modifier and stir to obtain Pickering emulsified solvent modifier.

5. The preparation method of the Pickering emulsified solvent modifier according to claim 4, characterized in that, In step (1), the stirring rate is 1000-2000 r / min; in step (2), the stirring rate is 300-600 r / min; in step (3), a homogenizer is used for mixing, the stirring speed is 8000-12000 r / min, and the stirring time is 10 min-20 min.

6. The application of Pickering emulsified solvent modifier as described in any one of claims 1-3 in water-driven heavy oil cold production.

7. The application according to claim 6, characterized in that, The viscosity of the heavy oil at 50°C is less than 5000 mPa·s and greater than 500 mPa·s.

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