Pickering emulsion as well as preparation method and application thereof

Abstract

The invention provides Pickering emulsion and a preparation method and application thereof.The Pickering emulsion is prepared from styrene-acrylic polymer microspheres, inorganic salt, an oil phase and water in specific parts, the four components are matched, so that the Pickering emulsion has high stability and high viscosity retention rate in a high-temperature and high-salt environment, and the Pickering emulsion can be applied to the field of high-temperature and high-salt environments. The oil-displacing agent is suitable for displacement of heavy oil reservoirs, can effectively emulsify crude oil and improve the recovery efficiency of the crude oil when being used for crude oil extraction as an oil-displacing agent, and can reduce the concentration of a main agent used for crude oil extraction, thereby improving the economic benefit of crude oil extraction.

Description

Technical Field

[0001] The invention belongs to the technical field of colloids and interface materials, and particularly relates to a Pickering emulsion and a preparation method and application thereof. Background Art

[0002] Pickering emulsions are a new type of emulsion that uses solid particles instead of traditional organic surfactants to stabilize the emulsion system. More stable than conventional emulsions, these surfactant-free emulsions exhibit a metastable state. Their emulsification type depends primarily on which phase preferentially wets the solid particles. Typically, the phase that preferentially wets the solid particles is the external phase. For example, if the solid particles are more wetted by the oil phase, the emulsion is a water-in-oil (W / O) type. Conversely, if the solid particles are more wetted by the water phase, the emulsion is an oil-in-water (O / W) type. This type of emulsion has been widely used in various fields because it avoids the use of surfactants, requires fewer solid particles, and is easily recyclable.

[0003] CN113578190A discloses a low-concentration particle-stabilized switchable Pickering emulsion and its preparation method. The switchable Pickering emulsion is obtained by stirring and emulsifying an oil phase and an aqueous phase at 20,000-30,000 r / min. The oil phase comprises modified nano-silica particles and oil, and the aqueous phase comprises nano-silica particles and water. The switchable Pickering emulsion comprises 30-70 wt% of the aqueous phase, 70-30 wt% of the oil phase, 0.005-0.5 wt% of the nano-silica particles, and 0.005-0.5 wt% of the modified nano-silica particles. The modified nano-silica particles are nano-silica particles grafted with carboxyl groups, and the nano-silica particles themselves are non-surface active. Furthermore, the Pickering emulsion is pH-stimuli-responsive and has potential application prospects in achieving efficient oil-water separation.

[0004] At present, crude oil extraction can be divided into three stages according to the oil production stages and technical means: in the early stage of oil field development, self-flowing extraction is carried out through oil layer energy, and the recovery rate is only 15-20%. This stage is called primary oil recovery; in order to supplement the insufficient formation energy, artificial water injection or gas injection is used to supplement the reservoir energy to extract oil, and the recovery rate can reach 25-40%. This stage is called secondary oil recovery; in order to extract most of the remaining crude oil, new technologies such as physics, chemistry and biology are used to continue to extract residual oil on the basis of secondary oil recovery. Such extraction methods are collectively called tertiary oil recovery; tertiary oil recovery mainly includes chemical drive, gas drive and thermal drive.

[0005] Research has found that Pickering emulsions can be injected for extended periods and remain stable during flow, significantly improving recovery. Son et al. also used Pickering emulsions for oil displacement and proposed that alternating injection of emulsion and water yields even better oil displacement results. However, the high cost and poor stability of Pickering emulsions provided in the prior art, including the aforementioned invention, limit their widespread application in crude oil production.

[0006] Therefore, in order to solve the above technical problems, it is necessary to develop a Pickering emulsion with low cost and excellent stability. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the object of the present invention is to provide a Pickering emulsion and a preparation method and application thereof. The Pickering emulsion has high stability and high viscosity retention in a high-temperature, high-salt environment, is suitable for the displacement of heavy oil reservoirs, and can be used as an oil displacement agent in the crude oil production process to effectively emulsify crude oil, increase crude oil recovery, reduce the concentration of the main agent used, and improve economic benefits.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a Pickering emulsion, comprising the following components in parts by weight:

[0010]

[0011]

[0012] First, the Pickering emulsion provided by the present invention includes specific proportions of styrene-acrylic polymer microspheres, an inorganic salt, an oil phase, and water. By using the above four components in combination, the Pickering emulsion has high stability and high viscosity retention in high-temperature and high-salt environments, making it suitable for displacing heavy oil reservoirs.

[0013] Secondly, the Pickering emulsion provided by the present invention can be used for oil displacement to effectively emulsify crude oil, thereby improving the crude oil recovery rate, and can also reduce the concentration of the main agent used, thereby improving the economic benefits of crude oil extraction. Specifically, the Pickering emulsion provided by the present invention can be used for chemical flooding such as polymer flooding to further improve the crude oil recovery rate. At the same time, it can also increase the capillary bundles of water flooding from a microscopic perspective and reduce the resistance of water flooding.

[0014] In addition, the Pickering emulsion provided by the present invention can also sharply reduce the surface tension of crude oil remaining in the rock pores in the oil reservoir, change the wetting angle toward neutrality, and reduce the adhesion work of oil on the surface of the formation voids, so that oil veins can flow out from the narrow necks of the rock pores and aggregate into oil belts. Driven by the injected water, the oil belts move toward the oil producing wells and are produced, ultimately improving the oil recovery efficiency.

[0015] Among them, the styrene-propylene polymer microspheres can be 0.5 parts by weight, 0.55 parts by weight, 0.6 parts by weight, 0.65 parts by weight, 0.7 parts by weight, 0.75 parts by weight, 0.8 parts by weight, 0.85 parts by weight, 0.9 parts by weight or 0.95 parts by weight, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0016] The inorganic salt can be 0.55 parts by weight, 0.6 parts by weight, 0.65 parts by weight, 0.7 parts by weight, 0.75 parts by weight, 0.8 parts by weight, 0.85 parts by weight, 0.9 parts by weight or 0.95 parts by weight, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0017] The oil phase can be 58.5 parts by weight, 59 parts by weight, 59.5 parts by weight, 60 parts by weight, 60.5 parts by weight, 61 parts by weight or 61.5 parts by weight, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0018] The water can be 38.5 parts by weight, 39 parts by weight, 39.5 parts by weight, 40 parts by weight, 40.5 parts by weight, 41 parts by weight or 41.5 parts by weight, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0019] Preferably, the Pickering emulsion is transparent or translucent in color.

[0020] Preferably, the styrene acrylic polymer microspheres are prepared by suspension polymerization.

[0021] In the present invention, the "suspension polymerization method" refers to the polymerization of monomers initiated in monomer droplets suspended in water, followed by separation, washing and drying to obtain pure and well-dispersed polymer microspheres.

[0022] As a preferred technical solution of the present invention, the preparation of the styrene-acrylic polymer microspheres specifically includes the following steps:

[0023] (1) Add the emulsion containing SiO2 seed particles into a three-necked flask equipped with a reflux condenser and an electric stirrer and dilute it;

[0024] (2) In a water bath at room temperature and after nitrogen is passed through, the system is heated, and an aqueous solution of polymerization monomer and initiator is added to initiate polymerization, followed by separation, washing and drying to obtain the styrene-acrylic polymer microspheres.

[0025] Preferably, the polymerizable monomers include hydroxyethyl methacrylate, methyl methacrylate and divinylbenzene.

[0026] Preferably, the initiator comprises ammonium persulfate.

[0027] Preferably, the polymerization reaction temperature is 60-80°C, for example, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C or 78°C.

[0028] Preferably, the polymerization reaction time is 7 to 9 hours, for example, 7.2 hours, 7.4 hours, 7.6 hours, 7.8 hours, 8 hours, 8.2 hours, 8.4 hours, 8.6 hours or 8.8 hours.

[0029] Preferably, the particle size of the styrene acrylic polymer microspheres is 5 to 20 μm, for example, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm or 19 μm, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0030] Preferably, the inorganic salt includes any one of sodium chloride, sodium carbonate, sodium bicarbonate or magnesium chloride, or a combination of at least two thereof.

[0031] Preferably, the oil phase comprises any one of white oil, n-tetradecane or crude oil, or a combination of at least two of them.

[0032] Preferably, the water is deionized water.

[0033] In a second aspect, the present invention provides a method for preparing the Pickering emulsion as described in the first aspect, the preparation method comprising: mixing styrene acrylic polymer microspheres, an inorganic salt, an oil phase and water, and allowing the mixture to stand to obtain the Pickering emulsion.

[0034] In a third aspect, the present invention provides an oil-displacing agent, comprising the Pickering emulsion as described in the first aspect.

[0035] In a fourth aspect, the present invention provides a use of the Pickering emulsion as described in the first aspect in crude oil production.

[0036] Preferably, the Pickering emulsion is used as an oil displacing agent.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The Pickering emulsion provided by the present invention comprises specific proportions of styrene-acrylic polymer microspheres, an inorganic salt, an oil phase, and water. By using the above four components in combination, the Pickering emulsion has high stability and high viscosity retention in a high-temperature and high-salt environment, and is suitable for displacement of heavy oil reservoirs;

[0039] (2) The Pickering emulsion provided by the present invention is used for oil displacement, which can effectively emulsify crude oil and thus improve the crude oil recovery rate. It can be used to further improve the crude oil recovery rate after chemical flooding such as polymer flooding. At the same time, it can also increase the capillary bundles of water flooding from a microscopic perspective, reduce the resistance of water flooding, and reduce the concentration of the main agent used, thereby improving the economic benefits of crude oil extraction and significantly increasing the recovery rate;

[0040] (3) The Pickering emulsion provided by the present invention can also sharply reduce the surface tension of crude oil remaining in the rock pores in the oil reservoir, and the wetting angle also changes to neutral, thereby reducing the adhesion work of oil on the surface of the formation voids, so that the oil veins can flow out from the narrow neck of the rock pores and aggregate into oil belts. Driven by the injected water, the oil belts move toward the oil wells and are produced, ultimately improving the oil recovery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A scanning electron micrograph of the Pickering emulsion provided in Example 1;

[0042] Figure 2 A scanning electron micrograph of the Pickering emulsion provided for Comparative Example 1;

[0043] Figure 3 A physical image of the Pickering emulsion provided in Example 1;

[0044] Figure 4 This is a physical image of the Pickering emulsion provided in Comparative Example 1;

[0045] Figure 5 This is a photo of the chip after being flooded with the Pickering emulsion provided in Example 1. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0047] Preparation Example 1

[0048] A styrene-acrylic polymer microsphere having a particle size of about 6 μm;

[0049] The preparation method of styrene-acrylic polymer microspheres provided in this preparation example comprises the following steps:

[0050] (1) Weigh 10 mL of the emulsion containing 1.0 g of SiO2 seeds into a 100 mL three-necked flask equipped with a reflux condenser and an electric stirrer, and dilute to 50 mL with deionized water.

[0051] (2) After nitrogen was passed through a water bath at room temperature for 10 minutes, the system was heated to 70° C., and polymerization monomers (including 0.2 mL of hydroxyethyl methacrylate, 2 mL of methyl methacrylate, and 1 mL of divinylbenzene) and 45 mL of an aqueous solution containing 20 mg of ammonium persulfate were added for initiation. The polymerization was carried out under a nitrogen atmosphere for 8 hours, and then the styrene-acrylic polymer microspheres were obtained by separation, washing, and drying.

[0052] Preparation Example 2

[0053] A styrene-acrylic polymer microsphere is prepared. The difference between the microsphere and the preparation example 1 is that the polymerization time is prolonged so that the particle size of the obtained styrene-acrylic polymer microsphere is about 10 μm. Other conditions and parameters are the same as those in the preparation example 1.

[0054] Preparation Example 3

[0055] A styrene-acrylic polymer microsphere is prepared. The difference between the microsphere and the preparation example 1 is that the polymerization time is prolonged so that the particle size of the obtained styrene-acrylic polymer microsphere is about 20 μm. Other conditions and parameters are the same as those in the preparation example 1.

[0056] Preparation Example 4

[0057] A styrene-acrylic polymer microsphere is prepared. The difference between the microsphere and the preparation example 1 is that the polymerization time is prolonged so that the particle size of the obtained styrene-acrylic polymer microsphere is about 25 μm. Other conditions and parameters are the same as those in the preparation example 1.

[0058] Preparation Example 5

[0059] A styrene-acrylic polymer microsphere is prepared. The difference between the microsphere and the preparation example 1 is that the polymerization time is shortened so that the particle size of the obtained styrene-acrylic polymer microsphere is about 4 μm. Other conditions and parameters are the same as those in the preparation example 1.

[0060] Example 1

[0061] A Pickering emulsion comprising the following components in parts by weight:

[0062]

[0063] The preparation method of the Pickering emulsion provided in this embodiment comprises the following steps:

[0064] (1) Styrene-acrylic polymer microspheres (Preparation Example 1) and deionized water were mixed at 45° C., and ultrasonicated for 10 min to fully disperse the styrene-acrylic polymer microspheres in the water. After standing for 1.5 h, the remaining particles were removed by centrifugation to obtain a styrene-acrylic polymer microsphere dispersion;

[0065] (2) The styrene-acrylic polymer microsphere dispersion, sodium chloride and No. 15 white oil were mixed uniformly at 45° C., added to a beaker, stirred at a speed of 100 rpm at room temperature for 10 minutes, and then allowed to stand for 2 hours to obtain the Pickering emulsion.

[0066] Example 2

[0067] A Pickering emulsion comprising the following components in parts by weight:

[0068]

[0069] The preparation method of the Pickering emulsion provided in this embodiment is the same as that in Example 1.

[0070] Example 3

[0071] A Pickering emulsion comprising the following components in parts by weight:

[0072]

[0073] The preparation method of the Pickering emulsion provided in this embodiment is the same as that in Example 1.

[0074] Example 4

[0075] A Pickering emulsion is provided, which differs from Example 1 in that the styrene-acrylic polymer microspheres provided in Preparation Example 4 are used to replace the styrene-acrylic polymer microspheres provided in Preparation Example 1, and other components, amounts and preparation methods are the same as those in Example 1.

[0076] Example 5

[0077] A Pickering emulsion is provided, which differs from Example 1 in that the styrene-acrylic polymer microspheres provided in Preparation Example 5 are used to replace the styrene-acrylic polymer microspheres provided in Preparation Example 1, and other components, amounts and preparation methods are the same as those in Example 1.

[0078] Example 6

[0079] A Pickering emulsion is provided, which differs from Example 1 in that n-tetradecane is used to replace No. 15 white oil, and other components, amounts used, and preparation methods are the same as those in Example 1.

[0080] Comparative Example 1

[0081] A Pickering emulsion comprising the following components in parts by weight:

[0082] 0.4 parts by weight of SiO2 nanoparticles;

[0083] 55 parts by weight of No. 15 white oil;

[0084] 44.6 parts by weight of deionized water;

[0085] The preparation method of the Pickering emulsion provided in this comparative example includes: mixing SiO2 nanoparticles, No. 15 white oil and deionized water uniformly, adding the mixture into a beaker, stirring at a speed of 100 rpm at room temperature for 10 minutes, and then standing for 2 hours to obtain the Pickering emulsion.

[0086] Comparative Example 2

[0087] A Pickering emulsion is prepared, which differs from Example 1 in that sodium chloride is not added, the amount of deionized water added is 42.5 parts by weight, and the other components, amounts used, and preparation methods are the same as those in Example 1.

[0088] Comparative Example 3

[0089] A Pickering emulsion is prepared, which differs from Example 1 in that the amount of sodium chloride added is 1.5 parts by weight, the amount of deionized water added is 41 parts by weight, and the other components, amounts used, and preparation methods are the same as those in Example 1.

[0090] Comparative Example 4

[0091] A Pickering emulsion is prepared, which differs from Example 1 in that the added amount of styrene-acrylic polymer microspheres is 1.4 parts by weight, the added amount of deionized water is 41 parts by weight, and the other components, amounts and preparation methods are the same as those in Example 1.

[0092] Performance testing:

[0093] (1) Electron microscopy test: The Pickering emulsions provided in Example 1 and Comparative Example 2 were placed under a scanning electron microscope (ZEISS Sigma 300, Germany) for testing. The scanning electron microscopy images of the Pickering emulsions provided in Example 1 were obtained as follows: Figure 1 As shown, the scanning electron microscope image of the Pickering emulsion provided in Comparative Example 1 is shown in FIG. Figure 2 As shown;

[0094] from Figure 1 It can be seen that a large number of uniform spherical structures are still present in the Pickering emulsion provided in Example 1, indicating that the Pickering emulsion provided in Example 1 has strong stability;

[0095] from Figure 2 It can be seen that there is no obvious spherical structure in the Pickering emulsion provided in Comparative Example 1, indicating that the stability of the Pickering emulsion provided in Comparative Example 1 is poor.

[0096] (2) Emulsion appearance: The appearance of the Pickering emulsions provided in Example 1 and Comparative Example 2 was visually observed, and the appearance photo of the Pickering emulsion provided in Example 1 was obtained as shown in FIG. Figure 3 The appearance of the Pickering emulsion provided in Comparative Example 1 is shown in FIG. Figure 4 As shown;

[0097] from Figure 3 It can be seen that the Pickering emulsion provided in Example 1 has no obvious stratification, which further illustrates that the Pickering emulsion has strong stability;

[0098] from Figure 4 It can be seen that the Pickering emulsion provided in Comparative Example 1 has obvious stratification, which further illustrates that the Pickering emulsion has poor stability.

[0099] (3) Visual displacement experiment: The chip was filled with oil phase, and the displacement fluid provided in Example 1 was added for displacement. After the displacement, 9 representative areas on the chip were photographed. The actual image of the chip after the Pickering emulsion displacement provided in Example 1 was obtained as shown below. Figure 5 As shown;

[0100] At the same time, the Pickering emulsions provided in Examples 1 to 6 and Comparative Examples 1 to 4 were tested according to the above method, and the residual oil saturation (S o ), the test results are shown in Table 1:

[0101] Table 1

[0102]

[0103]

[0104] According to the data in Table 1, we can see that:

[0105] Examples 1 to 6 show that the displacement effect of the prepared styrene-acrylic polymer microspheres will be affected if the particle size is too large or too small, and the optimal particle size range is 5 to 20 μm.

[0106] Among them, Examples 6 and 11 show that the prepared Pickering emulsion has a better displacement effect than using n-tetradecane because white oil is closer to the actual crude oil composition;

[0107] Comparative Examples 1 to 6 and Comparative Examples 1 to 4 show that the performance of the prepared styrene-acrylic polymer microspheres is better than that of traditional SiO2 nanoparticles, and the performance of the styrene-acrylic polymer microspheres prepared according to the weight ratio of the present invention is better.

[0108] The applicant declares that the present invention illustrates a Pickering emulsion, its preparation method, and application through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps for implementation. Those skilled in the art should understand that any improvements to the present invention, equivalent replacement of raw materials used in the present invention, addition of auxiliary ingredients, selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A Pickering emulsion, characterized in that The Pickering emulsion comprises the following components in parts by weight:

2. The Pickering emulsion according to claim 1, wherein The color of the Pickering emulsion is transparent or translucent.

3. The Pickering emulsion according to claim 1 or 2, characterized in that The styrene-acrylic polymer microspheres are prepared by suspension polymerization; Preferably, the styrene-acrylic polymer microspheres are prepared by the following method, comprising: weighing an emulsion containing SiO2 seed particles, adding the mixture to water for dilution, passing nitrogen in a water bath at room temperature, heating the mixture to 60-80°C, adding hydroxyethyl methacrylate, methyl methacrylate, divinylbenzene and an aqueous solution containing ammonium persulfate, polymerizing the mixture for 7-9 hours, separating, washing and drying the mixture to obtain the styrene-acrylic polymer microspheres; Preferably, the particle size of the styrene-acrylic polymer microspheres is 5 to 20 μm.

4. The Pickering emulsion according to any one of claims 1 to 3, characterized in that The inorganic salt includes any one of sodium chloride, sodium carbonate, sodium bicarbonate or magnesium chloride, or a combination of at least two thereof.

5. The Pickering emulsion according to any one of claims 1 to 4, characterized in that The oil phase includes any one of white oil, n-tetradecane or crude oil, or a combination of at least two of them.

6. The Pickering emulsion according to any one of claims 1 to 5, characterized in that The water is deionized water.

7. A method for preparing the Pickering emulsion according to any one of claims 1 to 6, characterized in that: The preparation method comprises: mixing styrene-acrylic polymer microspheres, inorganic salts, an oil phase and water, and allowing the mixture to stand to obtain the Pickering emulsion.

8. An oil-displacing agent, characterized in that The oil-displacing agent comprises the Pickering emulsion according to any one of claims 1 to 6.

9. Use of the Pickering emulsion according to any one of claims 1 to 6 in crude oil production.

10. The use according to claim 9, characterized in that The Pickering emulsion acts as an oil displacing agent.

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