A surface hydrophobically modified silica nanosheet, preparation method and application thereof, and a three-phase foam flooding system and preparation method thereof

Abstract

The present invention belongs to the technical field of oil and gas field development and discloses a surface-hydrophobically modified silica nanosheet, its preparation method and application, and a three-phase foam flooding system and its preparation method. The surface-hydrophobically modified silica nanosheet is a silica nanosheet with hydrophobic chains on its surface. The present invention enhances the structural strength of the association between the foaming agent and the foam stabilizer in the nano-enhanced foam stock solution, thereby enhancing the temperature, salt, and dilution resistance of the foam flooding system under gas reservoir conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas field development, and more specifically, relates to a surface hydrophobically modified silica nanosheet, a preparation method and application thereof, and a three-phase foam flooding system and a preparation method thereof. Background Art

[0002] my country has abundant gas reservoir resources, but most of them also have bottom water. However, as gas reservoir development progresses, the energy of bottom water reservoirs gradually depletes, and bottom water tends to flow along fractures, high-permeability layers, and strips, leading to earlier water breakthrough in the gas reservoir and a severe decline in gas field production, which in turn affects the development of the gas reservoir. Foam injection to control water is a typical method for oil reservoir profile adjustment and water blocking. However, due to the enormous energy and volume of bottom water in gas reservoirs, and the much greater flow rate of water in gas reservoirs than in oil reservoirs, the foam liquid is easily diluted after being injected into the gas reservoir, resulting in poor foaming ability and actual stability of conventional foams. Therefore, to improve the effectiveness of foam injection to control water in bottom water reservoirs, it is necessary to improve the conventional high-temperature and high-salt resistant foam system and develop a dilution-resistant foam system that is tailored to the water invasion characteristics of gas reservoirs.

[0003] In recent years, nano-SiO2, due to its low cost, low pollution, and easy production, has been frequently used in oil and gas field development as a standalone injection agent or as an additive in multiphase composite systems, such as nanofluid flooding agents, nanoparticle-enhanced gels, and nanoparticle-enhanced foams. As a foam stabilizer, nano-SiO2 can effectively enhance interfacial film strength through interfacial adsorption, slowing the foam's liquid separation rate, extending the foam's half-life, and improving its profile control and water plugging effectiveness. However, current nano-SiO2 is mostly spherical, with a small specific surface area and easy dilution, making it difficult to directly apply to foam injection water control technology after water invasion in gas reservoirs. Due to its hydrophobic properties, nano-SiO2 that has been hydrophobically modified easily agglomerates, resulting in poor dispersion and difficulty in long-term storage. Currently, there is no nano-SiO2 that can both uniformly disperse in the foam solution and effectively improve the foam's dilution resistance.

[0004] Numerous laboratory studies have focused on nano-SiO2 foam enhancement, primarily focusing on hydrophobic modification of nano-SiO2 surfaces and their integration into conventional foam systems. For example, CN107857775A proposes a method for preparing surfactant-grafted nano-SiO2, addressing the issue of foam instability in high-temperature environments; CN108410442A also proposes a method for preparing hydrophobic nano-SiO2 emulsions, improving their dispersibility. However, these methods, due to inherent drawbacks of spherical nano-SiO2, struggle to address the issue of post-dilution foam instability caused by water intrusion into gas reservoirs.

[0005] Therefore, it is urgent to propose a SiO2 nanosheet and a preparation method thereof, as well as a gas reservoir water control three-phase foam flooding system containing the SiO2 nanosheet and a preparation method thereof. Summary of the Invention

[0006] The present invention addresses the shortcomings of existing technologies by providing surface-hydrophobically modified silica nanosheets, their preparation method and application, and a three-phase foam flooding system for gas reservoir water control and its preparation method. This invention enhances the structural strength of the association between the foaming agent and the foam stabilizer in the nano-enhanced foam stock solution, thereby enhancing the foam flooding system's temperature, salt, and dilution resistance under gas reservoir conditions.

[0007] In order to achieve the above-mentioned object, the first aspect of the present invention provides a surface hydrophobically modified silica nanosheet, wherein the surface hydrophobically modified SiO2 nanosheet is a SiO2 nanosheet with a hydrophobic chain modified on the surface.

[0008] According to the present invention, preferably, the hydrophobic group is derived from at least one of 3-methacryloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropyloxy)propyltrimethoxysilane.

[0009] According to the present invention, preferably, the thickness of the SiO2 nanosheet is less than 100 nm and the specific surface area is 87.1-217.3 m 2 / g, and the grafting rate of hydrophobic chains on SiO2 nanosheets was 4.68-10.09%.

[0010] The second aspect of the present invention provides a method for preparing the surface hydrophobically modified silica nanosheets, the preparation method comprising the following steps:

[0011] S1: Synthesis of SiO2 nanosheets

[0012] After uniformly mixing water, ammonia and an alcohol solvent, the mixture is ultrasonically mixed with magnetic metal nanoparticles to obtain a first mixed solution; after ultrasonically mixing the first mixed solution with TEOS (ethyl silicate), a pH regulator is added under nitrogen protection and stirred to obtain a product, which is then rinsed, ground, and the Fe2O3 nanoparticles are recovered and crushed to obtain the SiO2 nanosheets;

[0013] S2: Surface hydrophobic modification of SiO2 nanosheets

[0014] Under nitrogen protection, the surface hydrophobic modifier, ammonia water and DMF are stirred evenly to obtain a second mixed solution; the second mixed solution, water and the DMF suspension containing the SiO2 nanosheets are stirred evenly, and the mixture is centrifuged and washed to obtain the surface hydrophobically modified SiO2 nanosheets.

[0015] According to the present invention, preferably, in step S1,

[0016] The alcohol solvent is at least one of ethanol solvent, isopropanol solvent and butanol solvent;

[0017] The volume ratio of the alcohol solvent, water and ammonia water is (50-60):(8-12):1;

[0018] The magnetic metal nanoparticles are Fe2O3 nanoparticles; the concentration of the magnetic metal nanoparticles in the first mixed solution is 1200-1800 mg / L;

[0019] The ultrasonic mixing time of the first mixed solution is 1.5-2.5 hours;

[0020] The volume of the TEOS is 1 / 6-1 / 2 of the volume of the ammonia solution;

[0021] The time for ultrasonic mixing of the first mixed solution and TEOS is 1.5-2.5 hours;

[0022] The pH regulator is a salt of a strong base and a weak acid or a salt of a strong acid and a weak base, preferably at least one of FeCl2, FeSO4 and Na2SiO3;

[0023] The stirring time for adding the pH adjuster is 8-12 hours; the volume of the pH adjuster is (0.9-1.1) times the volume of the TEOS;

[0024] The crushing process is carried out by using water jets.

[0025] In the present invention, in step S1, as a preferred embodiment, the rinsing is to rinse the obtained product with deionized water and ethanol several times.

[0026] According to the present invention, preferably, in step S2,

[0027] The usage ratio of the surface hydrophobic modifier, ammonia water and DMF (dimethylformamide) is 1: (0.3-1.0): (80-120) g / mL / mL;

[0028] The conditions for uniformly stirring the surface hydrophobic modifier, ammonia water and DMF include: magnetic stirring, stirring temperature of 25-35° C., and stirring time of 2.5-3.5 h;

[0029] The volume ratio of the second mixed solution, water and the DMF suspension containing the SiO2 nanosheets is (100-120): (15-25): (90-120);

[0030] The conditions for uniformly stirring the second mixed solution, water and the DMF suspension containing the SiO2 nanosheets include: magnetic stirring, a stirring temperature of 25-35°C, and a stirring time of 4.5-5.5h;

[0031] The concentration of SiO2 nanosheets in the DMF suspension containing the SiO2 nanosheets is 450-550 mg / L;

[0032] The method for preparing the DMF suspension containing the SiO2 nanosheets comprises: ultrasonically dispersing the SiO2 nanosheets in DMF;

[0033] The surface hydrophobic modifier is 3-methacryloxypropyltrimethoxysilane.

[0034] In the present invention, in step S2, as a preferred embodiment, the washing treatment is multiple alcohol washings and centrifugal separation.

[0035] The third aspect of the present invention provides the use of the surface hydrophobically modified silica nanosheets in the preparation of a three-phase foam flooding system for water control in gas reservoirs.

[0036] A fourth aspect of the present invention provides a three-phase foam flooding system, which comprises an amphiphilic polymer, an anionic surfactant and the surface hydrophobically modified SiO2 nanosheets.

[0037] According to the present invention, preferably, the mass ratio of the amphiphilic polymer, the anionic surfactant and the surface hydrophobically modified SiO2 nanosheets is 1:(4.5-5.5):(0.8-1.2).

[0038] According to the present invention, preferably, the amphiphilic polymer is APP4 and / or APC16.

[0039] According to the present invention, preferably, the anionic surfactant is at least one of SDS, SDBS and petroleum sulfonate.

[0040] The fifth aspect of the present invention provides a preparation method of the three-phase foam flooding system, which comprises: mixing the amphiphilic polymer and the anionic surfactant to obtain a third mixed solution, wherein the concentration of the anionic surfactant in the third mixed solution is higher than its CMC value; mixing the surface hydrophobically modified SiO2 nanosheets with the third mixed solution and ultrasonically oscillating them to obtain the gas reservoir water control three-phase foam flooding system.

[0041] In the present invention, as a preferred embodiment, the surface hydrophobically modified SiO2 nanosheets are mixed with the third mixed solution and ultrasonically vibrated for 8-12 hours.

[0042] Beneficial effects of the technical solution of the present invention:

[0043] (1) Compared with spherical nano-SiO2, the SiO2 nanosheets of the present invention have a larger specific surface area and more hydrophobic chains grafted on the same nanosheet. A large number of silicon-oxygen bonds and hydrogen bonds are formed between the surface-hydrophobically modified SiO2 nanosheets and the amphiphilic polymer, which enhances the interaction between the two and facilitates the formation of an associative structure. At the same time, due to charge adsorption and hydrogen bonding, the surface-hydrophobically modified SiO2 nanosheets and the amphiphilic polymer can adsorb anionic surfactants to form a more complex associative network, thereby increasing the hydrodynamic radius of the complex associative structure with the surface-hydrophobically modified SiO2 nanosheets as the core, thereby enhancing its dilution resistance.

[0044] (2) The surface-hydrophobically modified SiO2 nanosheets, amphiphilic polymers, and surfactants of the present invention are intertwined, filled, and coated with each other, thereby enhancing the strength of the entire network structure system, providing excellent resistance to high-temperature and high-salinity oil reservoir environments and long-term stability. Utilizing the inorganic properties of SiO2 nanosheets can enhance the temperature and salt resistance of traditional foams, expanding their scope of application.

[0045] (3) The present invention synthesizes amphiphilic SiO2 nanosheets that are easily dispersed in surfactant solutions by grafting hydrophobic groups onto the surface of SiO2 nanosheets. By utilizing the high specific surface area, partial modification, and electrostatic adsorption properties of the nanosheets, the strength of the association structure of the foaming agent (anionic surfactant) and the foam stabilizer (amphiphilic polymer and surface hydrophobically modified SiO2 nanosheets) in the nano-enhanced foam stock solution is improved, thereby enhancing the temperature, salt, and dilution resistance of the foam flooding system under gas reservoir conditions. This is of great significance for the development of high-temperature, high-salinity, marginal bottom water gas reservoirs with foam injection for water control.

[0046] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0048] Figure 1 The process flow chart of the preparation method of a three-phase foam flooding system for controlling water in gas reservoirs provided in Example 1 of the present invention is shown.

[0049] Figure 2 The diagram shows the reaction process of surface hydrophobic modification of SiO2 nanosheets in a method for preparing a three-phase foam flooding system for controlling water in gas reservoirs provided in Example 1 of the present invention.

[0050] Figure 3 The foam half-life and liquid separation half-life curves of a three-phase foam flooding system for controlling water in a gas reservoir provided by Example 1 of the present invention under high temperature and high salinity conditions are shown.

[0051] Figure 4 The foam half-life and liquid separation half-life curves of a three-phase foam flooding system for controlling water in a gas reservoir provided in Example 1 of the present invention after dilution by 10 times under high temperature and high salinity conditions are shown. DETAILED DESCRIPTION

[0052] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Instead, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0053] Example 1

[0054] This embodiment provides a method for preparing a gas reservoir water control three-phase foam flooding system, such as Figure 1 Shown, including:

[0055] S1: Synthesis of SiO2 nanosheets

[0056] Water, ammonia and an alcoholic solvent were uniformly mixed (the volume ratio of the alcoholic solvent, water and ammonia was 55:10:1) to form a 100 mL mixed solution, which was then ultrasonically mixed with Fe2O3 nanoparticles for 2 h to obtain a first mixed solution (the concentration of Fe2O3 nanoparticles in the first mixed solution was 1500 mg / L); 5 mL of TEOS was then added to the first mixed solution while stirring, and ultrasonic dispersion was performed for 2 h; finally, 5 mL of FeCl2 was added under nitrogen protection and stirred for 10 h. After the mixture was complete, a solid sample was collected by centrifuge, rinsed 3 times with deionized water and ethanol, and the obtained Fe-Si nanoparticles were ground with a ball mill to peel off the SiO2 nanoshell film on the surface of the Fe2O3 nanoparticles. Finally, the SiO2 nanoshell film was dispersed in distilled water, and the dispersed system was ejected at a speed of 300 m / s using an ultra-high pressure jet collider to further impact and break the SiO2 nanoshell film to obtain SiO2 nanosheets.

[0057] S2: Surface hydrophobic modification of SiO2 nanosheets

[0058] Under nitrogen protection, 1 g of MPS, 0.5 mL of ammonia water and 100 mL of DMF were mixed and magnetically stirred at 30 ° C for 3 h to obtain a second mixed solution; the second mixed solution, 20 mL of water and 100 mL of DMF suspension containing the SiO2 nanosheets (the concentration of SiO2 nanosheets in the DMF suspension containing the SiO2 nanosheets was 500 mg / L) were further magnetically stirred at 30 ° C for 5 h, and after ultra-high speed centrifuge separation and multiple alcohol washing and centrifugation, the surface hydrophobically modified SiO2 nanosheets were obtained, such as Figure 2 shown.

[0059] S3: Preparation of a three-phase foam flooding system for water control in gas reservoirs (SiO2 nanosheet-enhanced foam stock solution)

[0060] APP4 and SDBS are mixed to obtain 1000 mL of a third mixed solution (an amphiphilic polymer-surfactant composite solution), and the concentration of SDBS in the third mixed solution is higher than its CMC value. The concentration of APP4 in the third mixed solution is 500 mg / L, and the concentration of SDBS is 2500 mg / L. 0.5 g of surface hydrophobically modified SiO2 nanosheets are mixed with the third mixed solution and ultrasonically vibrated for 10 hours to obtain the gas reservoir water control three-phase foam flooding system.

[0061] In this example, the obtained gas reservoir water control three-phase foam flooding system was tested under high temperature and high salinity conditions (temperature 85°C, salinity 80113 mg / L, calcium and magnesium ion concentration 3266 mg / L), and the foam half-life and liquid separation half-life curves were obtained, as shown in FIG. Figure 3 shown.

[0062] In this example, the obtained gas reservoir water control three-phase foam flooding system was diluted 10 times and tested under high temperature and high salinity conditions (temperature 85°C, salinity 80113 mg / L, calcium and magnesium ion concentration 3266 mg / L) to obtain foam half-life and liquid separation half-life curves, as shown in Figure 2. Figure 4 shown.

[0063] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A surface hydrophobically modified silica nanosheet, characterized in that: The surface hydrophobically modified silica nanosheets are silica nanosheets with hydrophobic chains modified on the surface; The preparation method of the surface hydrophobically modified silica nanosheets comprises the following steps: S1: Synthesis of silica nanosheets After uniformly mixing water, ammonia water and an alcohol solvent, the mixture is ultrasonically mixed with magnetic metal nanoparticles to obtain a first mixed solution; after ultrasonically mixing the first mixed solution with TEOS, a pH regulator is added under nitrogen protection and stirred to obtain a product, which is then washed, ground, and the Fe2O3 nanoparticles are recovered and crushed to obtain the silica nanosheets; S2: Surface hydrophobic modification of silica nanosheets Under nitrogen protection, the surface hydrophobic modifier, ammonia water and DMF are stirred evenly to obtain a second mixed solution; the second mixed solution, water and the DMF suspension containing the silica nanosheets are stirred evenly, and the mixture is centrifuged and washed to obtain the surface hydrophobically modified silica nanosheets.

2. The surface-hydrophobically modified silica nanosheet according to claim 1, wherein The hydrophobic group is derived from at least one of 3-methacryloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropyloxy)propyltrimethoxysilane; The thickness of the silicon dioxide nanosheet is less than 100 nm and the specific surface area is 87.1-217.3 m 2 / g, and the grafting rate of hydrophobic chains on silica nanosheets was 4.68-10.09%.

3. The surface-hydrophobically modified silica nanosheet according to claim 1, wherein In step S1, The alcohol solvent is at least one of ethanol solvent, isopropanol solvent and butanol solvent; The volume ratio of the alcohol solvent, water and ammonia water is (50-60): (8-12): 1; The magnetic metal nanoparticles are Fe2O3 nanoparticles; the concentration of the magnetic metal nanoparticles in the first mixed solution is 1200-1800 mg / L; The ultrasonic mixing time of the first mixed solution is 1.5-2.5 hours; The volume of the TEOS is 1 / 6-1 / 2 of the volume of the ammonia solution; The time for ultrasonic mixing of the first mixed solution and TEOS is 1.5-2.5 hours; The pH regulator is a salt of a strong base and a weak acid or a salt of a strong acid and a weak base; The stirring time for adding the pH adjuster is 8-12 hours; the volume of the pH adjuster is (0.9-1.1) times the volume of the TEOS; The crushing process is carried out by using water jets.

4. The surface-hydrophobically modified silica nanosheet according to claim 3, wherein: The pH regulator is at least one of FeCl2, FeSO4 and Na2SiO3.

5. The surface hydrophobically modified silica nanosheet according to claim 1, wherein In step S2, The surface hydrophobic modifier, ammonia water and DMF are used in a ratio of 1: (0.3-1.0): (80-120) g / mL / mL; The conditions for uniformly stirring the surface hydrophobic modifier, ammonia water and DMF include: magnetic stirring, stirring temperature of 25-35° C., and stirring time of 2.5-3.5 h; The volume ratio of the second mixed solution, water and the DMF suspension containing the silica nanosheets is (100-120): (15-25): (90-120); The conditions for uniformly stirring the second mixed solution, water and the DMF suspension containing the silica nanosheets include: magnetic stirring, a stirring temperature of 25-35° C., and a stirring time of 4.5-5.5 h; The concentration of the silicon dioxide nanosheets in the DMF suspension containing the SiO2 nanosheets is 450-550 mg / L; The method for preparing the DMF suspension containing the silicon dioxide nanosheets comprises: ultrasonically dispersing the SiO2 nanosheets in DMF; The surface hydrophobic modifier is 3-methacryloxypropyltrimethoxysilane.

6. The method for preparing surface hydrophobically modified silica nanosheets according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: S1: Synthesis of silica nanosheets After uniformly mixing water, ammonia water and an alcohol solvent, the mixture is ultrasonically mixed with magnetic metal nanoparticles to obtain a first mixed solution; after ultrasonically mixing the first mixed solution with TEOS, a pH regulator is added under nitrogen protection and stirred to obtain a product, which is then washed, ground, and the Fe2O3 nanoparticles are recovered and crushed to obtain the silica nanosheets; S2: Surface hydrophobic modification of silica nanosheets Under nitrogen protection, the surface hydrophobic modifier, ammonia water and DMF are stirred evenly to obtain a second mixed solution; the second mixed solution, water and the DMF suspension containing the silica nanosheets are stirred evenly, and the mixture is centrifuged and washed to obtain the surface hydrophobically modified silica nanosheets.

7. The method for preparing surface hydrophobically modified silica nanosheets according to claim 6, wherein: In step S1, The alcohol solvent is at least one of ethanol solvent, isopropanol solvent and butanol solvent; The volume ratio of the alcohol solvent, water and ammonia water is (50-60): (8-12): 1; The magnetic metal nanoparticles are Fe2O3 nanoparticles; the concentration of the magnetic metal nanoparticles in the first mixed solution is 1200-1800 mg / L; The ultrasonic mixing time of the first mixed solution is 1.5-2.5 hours; The volume of the TEOS is 1 / 6-1 / 2 of the volume of the ammonia solution; The time for ultrasonic mixing of the first mixed solution and TEOS is 1.5-2.5 hours; The pH regulator is a salt of a strong base and a weak acid or a salt of a strong acid and a weak base; The stirring time for adding the pH adjuster is 8-12 hours; the volume of the pH adjuster is (0.9-1.1) times the volume of the TEOS; The crushing process is carried out by using water jets.

8. The method for preparing surface hydrophobically modified silica nanosheets according to claim 7, wherein: The pH regulator is at least one of FeCl2, FeSO4 and Na2SiO3.

9. The method for preparing surface hydrophobically modified silica nanosheets according to claim 6, wherein: In step S2, The surface hydrophobic modifier, ammonia water and DMF are used in a ratio of 1: (0.3-1.0): (80-120) g / mL / mL; The conditions for uniformly stirring the surface hydrophobic modifier, ammonia water and DMF include: magnetic stirring, stirring temperature of 25-35° C., and stirring time of 2.5-3.5 h; The volume ratio of the second mixed solution, water and the DMF suspension containing the silica nanosheets is (100-120): (15-25): (90-120); The conditions for uniformly stirring the second mixed solution, water and the DMF suspension containing the silica nanosheets include: magnetic stirring, a stirring temperature of 25-35° C., and a stirring time of 4.5-5.5 h; The concentration of the silicon dioxide nanosheets in the DMF suspension containing the SiO2 nanosheets is 450-550 mg / L; The method for preparing the DMF suspension containing the silicon dioxide nanosheets comprises: ultrasonically dispersing the SiO2 nanosheets in DMF; The surface hydrophobic modifier is 3-methacryloxypropyltrimethoxysilane.

10. Use of the surface hydrophobically modified silica nanosheets according to claim 1 or 2 in preparing a three-phase foam flooding system for water control in gas reservoirs.

11. A three-phase foam flooding system, characterized in that: The three-phase foam flooding system comprises an amphiphilic polymer, an anionic surfactant and the surface hydrophobically modified silicon dioxide nanosheets according to claim 1 or 2.

12. The three-phase foam flooding system according to claim 11, wherein: The mass ratio of the amphiphilic polymer, the anionic surfactant and the surface hydrophobically modified silica nanosheets is 1:(4.5-5.5):(0.8-1.2).

13. The three-phase foam flooding system according to claim 11, wherein: The amphiphilic polymer is APP4 and / or APC16; The anionic surfactant is at least one of SDS, SDBS and petroleum sulfonate.

14. The method for preparing a three-phase foam flooding system according to any one of claims 11 to 13, characterized in that: The preparation method comprises: mixing the amphiphilic polymer and the anionic surfactant to obtain a third mixed solution, wherein the concentration of the anionic surfactant in the third mixed solution is higher than its CMC value; mixing the surface hydrophobically modified silica nanosheets with the third mixed solution and ultrasonically oscillating them to obtain the three-phase foam flooding system.

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