Foam stabilizer raw material system, method of making nanofoam stabilizer, nanofoam stabilizer and applications

Abstract

The application provides a foam stabilizer raw material system, a method for preparing a nano stable foam agent, the nano stable foam agent and application. The raw material system comprises inorganic nanoparticles, an organic monomer, an initiator, a catalyst and a hydrophobic modifier; wherein the organic monomer has an electrically neutral hydrophilic group. According to the technical scheme of the application, the foam stabilizer prepared from the system is composed of nanoparticles, which not only have hydrophobic groups and can have hydrophobic interaction with the tail of a foaming agent, but also have electrically neutral hydrophilic polymer groups on the particles, which can play a role in temperature resistance and salt resistance on one hand; on the other hand, compared with some anionic polymers, such as 2-acrylamido-2-methylpropane sulfonic acid sodium polymer, the electric charge repulsion with the head group of a surfactant can be reduced or avoided, the adsorption of the nanoparticles on the gas-liquid interface is promoted, and then the stability of the foam is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of natural gas flooding, in particular to a foam stabilizer raw material system, a method for preparing a nano foam stabilizer, the nano foam stabilizer and application. BACKGROUND

[0002] As one of the tertiary oil recovery technologies, natural gas flooding has unique advantages in oil displacement efficiency and sweep efficiency, and has been highly concerned at home and abroad in recent years. In addition, many oilfield units also have the ability to exploit natural gas, thereby ensuring a rich gas source for this technology. However, due to the low mobility of natural gas, when applied in fracture-developed or high-permeability-contrast heterogeneous formations, there is a risk of more significant early breakthrough or gas channeling than water injection, which not only greatly reduces the oil recovery rate, but also constitutes a serious risk. Therefore, the prevention and treatment of gas channeling plays a crucial role in the development of natural gas flooding in the above-mentioned reservoirs.

[0003] Foam flooding is an effective method for preventing and delaying gas channeling. When foam passes through a heterogeneous formation, it will preferentially enter high-permeability layers, and through the superimposed Jamin effect, it can achieve the purpose of plugging, effectively improve the formation heterogeneity, and improve the subsequent gas flooding sweep efficiency. Since the foam is a thermodynamically unstable system, it will break down in the formation, affecting the effect and effective period of gas channeling treatment, so the foam stabilizing system is usually a necessary component in the composition of the foam liquid. In recent years, nano particles have been gradually used as a foam stabilizing system.

[0004] There has been experimental research on the use of anionic surfactant (SDS) and hydrophobic nano silicon dioxide (SiO2) particles to stabilize foam together. The results show that the hydrophobic nano SiO2 particles can enhance the stability of the foam, because the hydrophobic groups of the nano SiO2 have a hydrophobic interaction with the hydrophobic chains of the SDS, the nano SiO2 is attracted to the gas-liquid interface to form a skeleton structure, increasing the mechanical strength of the foam and playing a role in stabilizing the foam. However, with the increase of temperature and salinity, the stability of the nano particles will greatly decrease or even form a precipitate, which cannot play a role in stabilizing the foam. At the same time, the hydrophobically modified nano SiO2 and the SDS head group are both negatively charged, and there is also an electrostatic repulsion between them, which will offset part of the attraction between them, weaken the adsorption of the nano SiO2 on the gas-liquid interface, and also be not conducive to the stability of the foam. In a patent, a positively charged modified SiO2 nano particle and a mixture of anionic-nonionic surfactant sodium fatty alcohol polyoxyethylene ether sulfate are used to play a role in stabilizing natural gas foam. However, during the deep migration in the formation, the nano particles are prone to separate from the surfactant, which cannot play a role in stabilizing the foam in the deep formation. SUMMARY

[0005] The main purpose of the present application is to provide a foam stabilizer raw material system, a method for preparing nano foam stabilizer, the nano foam stabilizer and application, so as to solve the problem of insufficient temperature resistance and salt tolerance of the foam stabilizer in the prior art.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a foam stabilizer raw material system is provided, which comprises: inorganic nanoparticles, organic monomers, initiators, catalysts and hydrophobic modifiers; wherein the organic monomers have electrically neutral hydrophilic groups.

[0007] Further, the inorganic nanoparticles are any one or more of nano-SiO2, nano-TiO2, nano-ZnO and nano-Al2O3, preferably, the particle size of the inorganic nanoparticles is 20-100 nm;

[0008] Preferably, the initiator is 2,3-dihydroxypropyl propyl ether triethoxysilane;

[0009] Preferably, the hydrophobic modifier comprises any one or more of trimethyl monoethoxysilane, dimethyl diethoxysilane, isopropyl triethoxysilane, isobutyl trimethoxysilane and n-octyl triethoxysilane;

[0010] Preferably, the catalyst comprises any one or more selected from potassium copper diiodate and potassium nickel diiodate;

[0011] Preferably, the raw material system comprises 5-15 parts by weight of inorganic nanoparticles, 1.0-2.0 parts by weight of initiator, 3.0-10.0 parts by weight of organic monomers, 0.3-0.6 parts by weight of catalyst and 0.8-2.0 parts by weight of hydrophobic modifier;

[0012] Preferably, the raw material system further comprises a reaction medium, and the reaction medium is water.

[0013] According to another aspect of the present application, a method for preparing nano foam stabilizer by using the above-mentioned raw material system is provided, which comprises: step S1, dispersing the inorganic nanoparticles in water, adjusting the pH value to be alkaline, adding the initiator in the system to form a first mixed solution for reaction, after the reaction is completed, separating the solid to obtain a first intermediate; step S2, dispersing the first intermediate and the organic monomers in water, purging the inert gas to remove oxygen, adding the catalyst to form a second mixed solution for polymerization reaction, after the polymerization reaction is completed, separating the solid to obtain a second intermediate; step S3, dispersing the second intermediate in water, adding the hydrophobic modifier to form a third mixed solution for modification reaction, after the modification reaction is completed, obtaining the nano foam stabilizer.

[0014] Further, in step S1, the mass percentage of the inorganic nanoparticles in the mixed solution is 5-15%, and the mass percentage of the initiator is 1.0-2.0%.

[0015] Preferably, the pH value is 8.0-9.0.

[0016] Preferably, the initiator is added in the form of an aqueous initiator solution, preferably the aqueous initiator solution is added dropwise, preferably an alkali solution is added to adjust the pH value to be alkaline during the dropwise addition, further preferably, the pH value is adjusted to 8.0-9.0 during the dropwise addition.

[0017] Preferably, the alkali solution is any one or more of an aqueous sodium hydroxide solution or an aqueous sodium carbonate solution.

[0018] Further, the temperature of the reaction in step S1 is 70-80℃, preferably, after the dropwise addition of the aqueous initiator solution is completed, the temperature is raised to the reaction temperature.

[0019] Preferably, the reaction time is 15-20h.

[0020] Further, the mass fraction of the first intermediate in the second mixed solution is 5-15%, the mass fraction of the organic monomer is 3.0-10.0%, and the mass fraction of the catalyst is 0.3-0.6%.

[0021] Preferably, the temperature of the polymerization reaction is 50-60℃, and preferably the polymerization reaction time is 5-8h.

[0022] Further, the mass fraction of the second intermediate in the third mixed solution is 8-15%, and the mass fraction of the hydrophobic modifier is 0.5-2.0%.

[0023] Preferably, the temperature of the modification reaction is 60-70℃, and preferably the modification reaction time is 20-25h.

[0024] According to still another aspect of the present application, a nano-stable foam agent is provided, which is prepared by any one of the above methods.

[0025] According to yet another aspect of the present application, a foam oil displacement system is provided, which comprises the above nano-stable foam agent.

[0026] According to another aspect of the present application, the above foam oil displacement system is applied in gas oil displacement, preferably the gas is natural gas.

[0027] The foam stabilizer prepared by the system is composed of nanoparticles, which not only have hydrophobic groups and can have hydrophobic interaction with the tail of the foaming agent, but also have electrically neutral hydrophilic polymer groups, which can play a role in temperature resistance and salt tolerance, and on the other hand, compared with some anionic polymers, such as 2-acrylamido-2-methylpropane sulfonic acid sodium polymer, it is beneficial to reduce or avoid the charge repulsion with the head group of the surfactant, promote the adsorption of the nanoparticles on the gas-liquid interface, and further help to improve the stability of the foam. In this way, when carried by injection of water, it is beneficial to its smooth migration in high-temperature and high-salinity reservoirs, and to generate foam in the deep part of the formation during the gas injection process, and when it is used in combination with the foaming agent, it can have a higher resistance factor than the foaming agent alone, realizing the function of deep plugging and delaying gas channeling. BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their descriptions are used to explain the present application, and do not constitute improper limitations on the present application. In the drawings:

[0029] Figure 1 A kinetic light scattering (DLS) particle size distribution diagram of the nano foam stabilizer of the embodiment 1 of the present application in simulated brine (salinity is 100000 mg / L) is shown;

[0030] Figure 2 An X-ray photoelectron spectrogram of the nano foam stabilizer of the embodiment 1 of the present application is shown;

[0031] Figure 3 A thermogravimetric analysis curve diagram of the nano foam stabilizer of the embodiment 1 of the present application is shown;

[0032] Figure 4 A natural gas injection resistance factor diagram of the foam stabilizer prepared in the application example 1 and the control group oil displacement system is shown. DETAILED DESCRIPTION

[0033] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments.

[0034] As analyzed in the background art of the present application, the foam stabilizer in the prior art has insufficient temperature resistance and salt tolerance, and the foam stabilizing effect in the deep part of the formation is difficult to meet the demand. In order to solve this problem, the present application provides a foam stabilizer raw material system, a method for preparing a nano foam stabilizer, a nano foam stabilizer and an application.

[0035] According to one embodiment of the present application, a foam stabilizer raw material system is provided, which comprises: inorganic nanoparticles, organic monomer initiator, catalyst and hydrophobic modifier; wherein the organic monomer carries electrically neutral hydrophilic groups.

[0036] The foam stabilizer prepared from the system is composed of nanoparticles, which not only carry hydrophobic groups that can interact with the tail of the foaming agent, but also carry electrically neutral hydrophilic polymer groups, which can play a role in temperature resistance and salt tolerance, and on the other hand, compared with some anionic polymers, such as sodium 2-acrylamido-2-methylpropanesulfonate polymer, it is beneficial to reduce or avoid the charge repulsion with the head group of the surfactant, promote the adsorption of the nanoparticles on the gas-liquid interface, and thus help to improve the stability of the foam. Thus, when carried by injection of water, it is beneficial to its smooth migration in high-temperature and high-salinity reservoirs, and to generate foam in the deep formation during the gas injection process, and when it is used in combination with the foaming agent, it can have a higher resistance factor than the foaming agent alone, realizing deep plugging and delaying gas channeling.

[0037] The above-mentioned inorganic nanoparticles can be selected from the prior art, and in some embodiments of the present application, the inorganic nanoparticles are any one or more of nano-SiO2, nano-TiO2, nano-ZnO and nano-Al2O3. Preferably, the particle size of the inorganic nanoparticles is 20-100 nm, which can further enhance the foam stabilizing performance of the foam stabilizer.

[0038] The above-mentioned organic monomer with electrically neutral hydrophilic groups can be selected from the prior art, and in some preferred embodiments of the present application, in order to further improve the foam stabilizing performance of the foam stabilizer at high temperature and high salt, the above-mentioned organic monomer includes any one or more of 2,3-dihydroxypropyl methacrylate, N-(2,3-dihydroxypropyl) methacrylamide, 3-methacryloylpropyl-dimethyl-3-sulfopropyl ammonium salt and 3-methacrylate propyl-dimethyl-3-sulfopropyl ammonium salt.

[0039] In some typical embodiments of the present application, the above-mentioned initiator is 2,3-dihydroxypropyl propyl ether triethoxysilane, which can promote the polymerization of the above-mentioned organic monomer to form a foam stabilizer with better foam stabilizing function, especially for the temperature resistance and salt tolerance performance.

[0040] The above-mentioned hydrophobic modifier can be selected from the prior art, and there is no particular requirement, and exemplary hydrophobic modifiers include, but are not limited to, any one or more of trimethyl monoethoxysilane, dimethyl diethoxysilane, isopropyl triethoxysilane, isobutyl trimethoxysilane and n-octyl triethoxysilane.

[0041] In some preferred embodiments of the present application, the catalysts mentioned above include any one or more selected from the group consisting of potassium copper (III) periodate and potassium nickel (IV) periodate, which can better cooperate with the initiator to promote the polymerization of the organic monomer and significantly improve the foam stabilizing performance of the foam stabilizer.

[0042] In some embodiments of the present application, in order to better exert the synergistic effect between the components, the raw material system includes 5-15 parts by weight of inorganic nanoparticles, 1.0-2.0 parts by weight of initiator, 3.0-10.0 parts by weight of organic monomer, 0.3-0.6 parts by weight of catalyst and 0.8-2.0 parts by weight of hydrophobic modifier.

[0043] Preferably, the raw material system further includes a reaction medium, and the reaction medium is water.

[0044] According to another embodiment of the present application, a method for preparing a nano foam stabilizer by the raw material system mentioned above is provided, which includes: step S1, dispersing the inorganic nanoparticles in water, adjusting the pH value to be alkaline, adding the initiator in the system to form a first mixed solution for reaction, after the reaction is completed, separating the solid to obtain a first intermediate; step S2, dispersing the first intermediate and the organic monomer in water, introducing inert gas to remove oxygen, adding the catalyst to form a second mixed solution for polymerization reaction, after the polymerization reaction is completed, separating the solid to obtain a second intermediate; step S3, dispersing the second intermediate in water, adding the hydrophobic modifier to form a third mixed solution for modification reaction, after the modification reaction is completed, obtaining the nano foam stabilizer.

[0045] The preparation method mentioned above prepares the nano foam stabilizer by first grafting the silane coupling agent type initiator on the inorganic nanoparticles, then under the action of the catalyst, the hydrophilic monomer is polymerized on the surface of the particles, and finally the particles are grafted with the hydrophobic silane coupling agent. The nano foam stabilizer prepared by the preparation method mentioned above not only has a hydrophobic group which can interact with the hydrophobic tail of the foaming agent, but also has an electrically neutral hydrophilic polymer group on the particle, which can play a role in temperature resistance and salt tolerance on the one hand; on the other hand, compared with some anionic polymers, such as sodium 2-acrylamido-2-methylpropanesulfonate polymer, it is beneficial to reduce or avoid the charge repulsion with the head group of the surfactant, promote the adsorption of the nanoparticles on the gas-liquid interface, and further help to improve the stability of the foam. When it is used in combination with the foaming agent, it can have a higher resistance factor than when the foaming agent is used alone, which is beneficial to its smooth migration in the high-temperature and high-salinity reservoir, and the generation of foam in the deep formation during the gas injection process, thereby realizing the functions of deep plugging and delaying gas channeling. Moreover, the reactions in the preparation method are all aqueous phase reactions, and no organic solvent is used, which is less polluting to the environment.

[0046] In some embodiments of the present application, in step S1, the mass percentage of inorganic nanoparticles in the mixed solution is 5-15%, and the mass percentage of the initiator is 1.0-2.0%, which is conducive to the grafting reaction of the initiator and the inorganic nanoparticles. In some preferred embodiments of the present application, in step S1, the pH value is adjusted to 8.0-9.0, which is more conducive to the promotion of the grafting reaction of the initiator and the inorganic nanoparticles, and can significantly improve the performance of the prepared foam stabilizer.

[0047] In some typical embodiments of the present application, in order to further improve the efficiency of the grafting reaction in step S1, the initiator is added in the form of an aqueous initiator solution; preferably, the aqueous initiator solution is added in the form of drops, which can make the initiator more uniformly dispersed on the surface or around the inorganic nanoparticles, form more uniform grafts, and further enable the subsequent organic monomers to form uniform polymers on the surface of the inorganic nanoparticles, thereby achieving better foam stabilization effect. In some embodiments of the present application, in order to further improve the above-mentioned effect, the above-mentioned aqueous initiator solution is slowly added dropwise under stirring and gas protection, so that the initiator is more uniformly dispersed in the system. Illustratively, in the process of laboratory preparation, the dropwise addition speed of the aqueous initiator solution is 1.0-1.5 mL / min.

[0048] In some preferred embodiments of the present application, an alkali solution is added during the dropwise addition to adjust the pH value to alkaline, and more preferably, the pH value is adjusted to 8.0-9.0 during the dropwise addition, which is conducive to further improving the effect of the grafting product; the alkali solution can be selected from the prior art, including but not limited to any one or more of sodium hydroxide aqueous solution or sodium carbonate aqueous solution.

[0049] In some embodiments of the present application, the reaction temperature in step S1 is 70-80°C, and the grafting effect is better. Preferably, after the dropwise addition of the aqueous initiator solution is completed, the reaction temperature is further increased, which is conducive to the formation of more uniform initiator grafts on the surface of the inorganic nanoparticles. Preferably, the reaction time after the dropwise addition of the initiator is completed is 15-20 h, so that the initiator and the inorganic nanoparticles are fully combined.

[0050] In some embodiments of the present application, step S1 further comprises washing the separated solid with water and then drying to obtain the above-mentioned first intermediate, which can remove the alkali adhering to the surface of the inorganic particles or the initiator not grafted, thereby avoiding interference with the subsequent reaction.

[0051] In some embodiments of the present application, the mass fraction of the first intermediate in the second mixture is 5-15%, the mass fraction of the organic monomer is 3.0-10.0%, and the mass fraction of the catalyst is 0.3-0.6%, which is beneficial to improve the performance of the foam stabilizer. Preferably, the temperature of the polymerization reaction is 50-60°C, and the polymerization reaction time is 5-8h, and the second intermediate formed can further improve the foam stabilizing performance of the foam stabilizer, while the efficiency of the polymerization reaction is taken into account. In some embodiments of the present application, after the catalyst is added, the second mixture formed is raised to the reaction temperature for polymerization reaction. In some embodiments of the present application, after the polymerization reaction is completed, the separated solid is washed with water and dried to obtain the second intermediate, and the impurities attached to the second intermediate are removed.

[0052] In step S3, the second intermediate is grafted with a hydrophobic group to perform hydrophobic modification. In some embodiments of the present application, the mass fraction of the second intermediate in the third mixture is 8-15%, and the mass fraction of the hydrophobic modifier is 0.5-2.0%, which is beneficial to improve the foam stabilizing performance of the product. Preferably, the temperature of the modification reaction is 60-70°C, and the modification reaction time is 20-25h, and the foam stabilizer with good hydrophobic modification effect can be formed.

[0053] According to another embodiment of the present application, a nano foam stabilizer is provided, which is prepared by any of the above methods. The nano foam stabilizer is prepared by grafting a silane coupling agent type initiator on inorganic nanoparticles first, then polymerizing the hydrophilic monomer on the surface of the particles under the action of a catalyst, and finally grafting the hydrophobic silane coupling agent on the particles. The nano foam stabilizer prepared by the above preparation method not only has a hydrophobic group that can interact with the tail of the foaming agent, but also has a neutral hydrophilic polymer group on the particle, which can play a role in temperature resistance and salt resistance on the one hand, and on the other hand, compared with some anionic polymers, such as 2-acrylamido-2-methylpropane sulfonic acid sodium polymer, it is beneficial to reduce or avoid the charge repulsion with the head group of the surfactant, promote the adsorption of the nanoparticles on the gas-liquid interface, and further help to improve the stability of the foam. In this way, when carried by injection of water, it is beneficial to its smooth migration in high-temperature and high-salinity reservoirs, and to generate foam in the deep formation during the gas injection process, and when it is used in combination with the foaming agent, it can have a higher resistance factor than the foaming agent used alone, realizing the functions of deep plugging and delaying gas channeling.

[0054] According to still another embodiment of the present application, a foam flooding system is provided, which comprises the nano-stable foam agent described above. The foam flooding system has a high resistance factor when used in combination with a foaming agent, which is beneficial for its smooth migration in high-temperature and high-salinity reservoirs, and the generation of foam in the deep part of the formation during the gas injection process, thereby achieving the functions of deep plugging and delaying gas channeling.

[0055] According to another embodiment of the present application, the use of the foam flooding system described above in gas flooding is provided. The nano-stable foam agent described above not only has temperature resistance and salt tolerance, but also has a hydrophobic effect with the foaming agent and avoids or weakens the charge repulsion effect, thereby having a good foam stabilizing function and being suitable for application in the deep part of the formation to plug gas channeling.

[0056] The foam flooding system described above can be applied in various gas flooding, including but not limited to air flooding, natural gas flooding and carbon dioxide flooding, and the foam stabilizing effect of the nano-stable foam agent described above is particularly obvious when natural gas is used as the oil displacement gas.

[0057] The beneficial effects that can be achieved by the present application will be further illustrated below with examples and comparative examples.

[0058] The 2,3-dihydroxypropyl propyl ether triethoxysilane used in the examples of the present application is prepared by the following method: first, prepare 100 mL of dilute hydrochloric acid aqueous solution with pH = 2.0-3.0, then add 1.5 g of γ-glycidyl ether propyl triethoxysilane to it, and stir for 20-30 min to obtain an aqueous solution of 2,3-dihydroxypropyl propyl ether triethoxysilane.

[0059] (1) SiO2 nanoparticles (15 g, D = 30 nm) are added to 50 mL of NaOH aqueous solution (pH = 9.0) under stirring, and after uniform dispersion, 1.6 g of 2,3-dihydroxypropyl propyl ether triethoxysilane aqueous solution (100 mL) is added dropwise under inert gas protection, and during the addition process, 2M NaOH aqueous solution is added to the system to maintain the pH value of the system at 9.0. After the addition is completed, the system is heated to 80℃, and then constant temperature reaction is carried out for 20 h. After the reaction is completed, the system is separated to obtain a solid, which is washed with water and dried to obtain intermediate 1;

[0060] (2) Into a flask, H2O (100 mL), intermediate 1 (10.0 g) and 3-methylacryloylpropyl-dimethyl-3-sulfopropylammonium salt (8.8 g) were added successively, stirred uniformly, and then deoxygenated by nitrogen for 30 min. Then, copper (III) potassium periodate 0.87 g was added, and the temperature was raised to 50 °C. After reaction for 6 h under continuous nitrogen, the nitrogen was stopped, and the polymerization was terminated. The system was separated to obtain a solid, which was washed with water and dried to obtain intermediate 2.

[0061] (3) Into a flask, intermediate 2 (5.0 g) and water (40 mL) were added successively. The pH value of the system was adjusted to 9.0 by NaOH aqueous solution. Then, 10 mL of isobutyl trimethoxysilane (0.5 g) hydrochloric acid solution (pH = 2.0) was added dropwise under nitrogen protection. After the dropwise addition was completed, the system was raised to 70 °C, and reacted for 20 h at this temperature. The solid was separated, washed with water, and dried to obtain a nano foam stabilizer.

[0062] The kinetic light scattering (DLS) particle size distribution of the nano foam stabilizer prepared in this example in simulated brine (salinity 100000 mg / L) is shown in Figure 1 The X-ray photoelectron spectrum and the thermogravimetric analysis are shown in Figure 2 and Figure 3

[0063] Example 2

[0064] (1) Al2O3 nanoparticles (12 g, D = 25-30 nm) were added into 50 mL of NaOH aqueous solution (pH = 9.0) under stirring. After uniform dispersion, 2.0 g of 2,3-dihydroxypropyl propyl ether triethoxysilane aqueous solution (100 mL) was added dropwise under inert gas protection. During the dropwise addition, 2 M NaOH aqueous solution was added to the system to maintain the pH value of the system at 9.0. After the dropwise addition was completed, the system was raised to 80 °C, and then reacted for 15 h at this temperature. After the reaction was completed, the system was separated to obtain a solid, which was washed with water and dried to obtain intermediate 1';

[0065] (2) Into a flask, H2O (100 mL), intermediate 1' (10.0 g) and N-(2,3-dihydroxypropyl) methylacrylamide (7.0 g) were added successively, stirred uniformly, and then deoxygenated by nitrogen for 30 min. Then, copper (III) potassium periodate 0.80 g was added, and the temperature was raised to 50 °C. After reaction for 6 h under continuous nitrogen, the nitrogen was stopped, and the polymerization was terminated. The system was separated to obtain a solid, which was washed with water and dried to obtain intermediate 2';

[0066] ​(3) To the flask was added intermediate 2' (5.0 g) and water (40 mL) successively, the pH value of the system was adjusted to 9.0 by NaOH aqueous solution, and then 10 mL of n-octyltriethoxysilane (0.75 g) hydrochloric acid solution (pH = 2.0) was added dropwise under nitrogen protection. After the dropwise addition was completed, the system was heated to 60 °C, and then reacted at this temperature for 25 h. The solid was separated, washed with water and dried to obtain the nano foam stabilizer.

[0067] Example 3

[0068] The difference from Example 1 is that in step (1), the SiO2nanoparticles (15 g, D = 30 nm) were added into 50 mL of NaOH aqueous solution (pH = 8.0) under stirring, and the pH value of the system was maintained at 8.0 by adding 2M NaOH aqueous solution to the system during the dropwise addition.

[0069] Example 4

[0070] The difference from Example 1 is that in step (1), the pH value of the system was not adjusted during the dropwise addition, and the pH value of the system was 3.0-4.0 after the dropwise addition was completed.

[0071] Example 5

[0072] The difference from Example 1 is that in step (1), the SiO2nanoparticles (15 g, D = 30 nm) were added into 50 mL of NaOH aqueous solution (pH = 10.0) under stirring, and the pH value of the system was maintained at 10.0 by adding 2M NaOH aqueous solution to the system during the dropwise addition.

[0073] Example 6

[0074] The difference from Example 1 is that in step (1), the SiO2nanoparticles (15 g, D = 30 nm) were added into 50 mL of water under stirring, and the pH value of the system was not adjusted during the dropwise addition.

[0075] Example 7

[0076] The difference from Example 1 is that in step (1), the SiO2nanoparticles (15 g, D = 30 nm) were added into 20 mL of NaOH aqueous solution (pH = 8.0) under stirring, and then 2.0 g of 2,3-dihydroxypropyl propyl ether triethoxysilane aqueous solution (40 mL) was added dropwise under inert gas protection. The pH value of the system was maintained at 9.0 by adding 2M NaOH aqueous solution to the system during the dropwise addition, and a total of 0.1-0.2 mL was added. The subsequent treatment steps were the same as those of Example 1.

[0077] Example 8

[0078] The difference from Example 1 is that in step (1), the time for constant temperature reaction is 10 h.

[0079] Example 9

[0080] The difference from Example 1 is that in step (1), the temperature is raised to 60°C, i.e. the reaction temperature is 60°C.

[0081] Example 10

[0082] The difference from Example 1 is that in step (2), the amount of water added to the flask is 50 mL.

[0083] Comparative Example 1

[0084] (1) SiO2nanoparticles (15 g, D = 30 nm) and 3-methacryloylpropyl-dimethyl-3- sulfopropylammonium salt (8.8 g) were added to H2O (100 mL) under stirring, and after uniform dispersion, 1.6 g of an aqueous solution (100 mL) of 2,3-dihydroxypropyl propyl ether triethoxysilane was added dropwise to the system under inert gas protection, and after uniform stirring, nitrogen was bubbled for 30 min, then 0.87 g of copper (III) potassium periodate was added, and the temperature was raised to 50°C, and the reaction was continued for 6 h under continuous nitrogen bubbling, then the nitrogen bubbling was stopped and the polymerization was terminated, and the system was separated to obtain a solid, which was washed with water and dried to obtain intermediate 2;

[0085] (2) Intermediate 2 (5.0 g) and water (40 mL) were sequentially added to a flask, and the pH value of the system was adjusted to 9.0 by means of an aqueous NaOH solution, and then 10 mL of an isobutyl trimethoxysilane (0.5 g) hydrochloric acid solution (pH = 2.0) was added dropwise to the system under nitrogen protection, and after the dropwise addition was completed, the system was raised to 70°C, and the constant temperature reaction was continued for 20 h at this temperature, then the system was separated to obtain a solid, which was washed with water and dried to obtain the foam stabilizer.

[0086] Comparative Example 2

[0087] (1) SiO2nanoparticles (15 g, D = 30 nm) were added to 50 mL of an aqueous NaOH solution (pH = 9.0) under stirring, and after uniform dispersion, 1.6 g of an aqueous solution (100 mL) of N-2-aminoethyl-3-aminopropyl trimethoxysilane was added dropwise to the system under inert gas protection, and during the dropwise addition, 2M aqueous NaOH solution was added to the system to maintain the pH value of the system at 9.0. After the dropwise addition was completed, the system was raised to 80°C, and then the constant temperature reaction was continued for 20 h, and after the reaction was completed, the system was separated to obtain a solid, which was washed with water and dried to obtain intermediate 1;

[0088] (2) Into a flask, H2O (100 mL), intermediate 1 (10.0 g) and 3-methylacryloylpropyl-dimethyl-3-sulfopropylammonium salt (8.8 g) were added successively, stirred uniformly, and then nitrogen was bubbled for 30 min. Then, copper (III) potassium periodate 0.87 g was added, and the temperature was raised to 50°C. After reaction for 6 h under continuous nitrogen bubbling, the nitrogen bubbling was stopped, and the polymerization was terminated. The system was separated to obtain a solid, which was washed with water and dried to obtain intermediate 2;

[0089] (3) Into a flask, intermediate 2 (5.0 g) and water (40 mL) were added successively. The pH value of the system was adjusted to 9.0 by using NaOH aqueous solution. Then, 10 mL of isobutyl trimethoxysilane (0.5 g) hydrochloric acid solution (pH = 2.0) was added dropwise under nitrogen protection. After the dropwise addition was completed, the system was raised to 70°C, and reacted for 20 h at this temperature. Then, a solid was separated, which was washed with water and dried to obtain the foam stabilizer.

[0090] Comparative Example 3

[0091] (1) SiO2 nanoparticles (15 g, D = 30 nm) were added into 50 mL of NaOH aqueous solution (pH = 9.0) under stirring. After being uniformly dispersed, 1.6 g of 2,3-dihydroxypropyl propyl ether triethoxysilane aqueous solution (100 mL) was added dropwise into the system under inert gas protection. During the dropwise addition, 2M NaOH aqueous solution was added to the system to maintain the pH value of the system at 9.0. After the dropwise addition was completed, the system was raised to 80°C, and then reacted for 20 h at this temperature. After the reaction was completed, the system was separated to obtain a solid, which was washed with water and dried to obtain intermediate 1;

[0092] (2) Into a flask, H2O (100 mL), intermediate 1 (10.0 g) and 2-acrylamido-2-methylpropanesulfonic acid sodium salt (8.8 g) were added successively, stirred uniformly, and then nitrogen was bubbled for 30 min. Then, copper (III) potassium periodate 0.87 g was added, and the temperature was raised to 50°C. After reaction for 6 h under continuous nitrogen bubbling, the nitrogen bubbling was stopped, and the polymerization was terminated. The system was separated to obtain a solid, which was washed with water and dried to obtain intermediate 2;

[0093] (3) Into a flask, intermediate 2 (5.0 g) and water (40 mL) were added successively. The pH value of the system was adjusted to 9.0 by using NaOH aqueous solution. Then, 10 mL of isobutyl trimethoxysilane (0.5 g) hydrochloric acid solution (pH = 2.0) was added dropwise under nitrogen protection. After the dropwise addition was completed, the system was raised to 70°C, and reacted for 20 h at this temperature. Then, a solid was separated, which was washed with water and dried to obtain the foam stabilizer.

[0094] Application Example 1

[0095] The foam stabilizer and foaming agent prepared in the above examples and comparative examples were mixed to form a foaming agent-induced oil displacement system. The foaming agent was sodium α-olefin sulfonate (14C) at a content of 0.4 wt%, the foam stabilizer at a content of 0.2 wt%, and the balance was simulated brine (mineralization of 100,000 mg / L). The half-life and foam volume of natural gas foam (temperature 80℃, pressure 12 MPa) were tested on a visual high-temperature and high-pressure foam evaluation instrument. The test results are shown in Table 1 below, where the control test was conducted without the addition of foam stabilizer.

[0096] Table 1

[0097] Serial No. Source of foam stabilizer Foaming agent Half-life (min) Foam volume (mL) 1 Example 1 Sodium alpha-olefin sulfonate 410 305 2 Example 2 Sodium alpha-olefin sulfonate 385 300 3 Example 3 Sodium alpha-olefin sulfonate 395 303 4 Example 4 Sodium alpha-olefin sulfonate 185 130 5 Example 5 Sodium alpha-olefin sulfonate 335 263 6 Example 6 Sodium alpha-olefin sulfonate 170 121 7 Example 7 Sodium alpha-olefin sulfonate 330 258 8 Example 8 Sodium alpha-olefin sulfonate 381 290 9 Example 9 Sodium alpha-olefin sulfonate 375 274 10 Example 10 Sodium alpha-olefin sulfonate 360 185 11 Comparative Example 1 Sodium alpha-olefin sulfonate 175 145 12 Comparative Example 2 Sodium alpha-olefin sulfonate 143 135 13 Comparative Example 3 Sodium alpha-olefin sulfonate 145 142 14 No foam stabilizer Sodium alpha-olefin sulfonate 140 142

[0098] Among them, the system formed by the foam stabilizer and foaming agent prepared in Example 1, and the control group (without foam stabilizer), showed the resistance factor of natural gas as follows: Figure 4 As shown. The test conditions were: temperature 80℃, pressure 12MPa, gas-liquid slug ratio 1:1, core permeability 125mDa, injection rate 1mL / min, foaming agent content 0.4%, foam stabilizer content 0.2%, and simulated brine dispersion system (mineralization 100000mg / L).

[0099] Application Example 2

[0100] The difference from the application example is that the foaming agent is sodium dodecyl sulfate of the same amount, and the test results are shown in Table 2 below.

[0101] Table 2

[0102] Source of foam stabilizer Foaming agent Half-life (min) Foam volume (mL) Example 1 Sodium dodecyl sulfate 251 481 Example 2 Sodium dodecyl sulfate 235 402 No foam stabilizer Sodium dodecyl sulfate 90 166

[0103] Application Example 3

[0104] The difference from the application example is that the foaming agent is the same amount of alkyl glycoside (APG0814), and the test results are shown in Table 3 below.

[0105] Table 3

[0106] Source of foam stabilizer Foaming agent Half-life (min) Foam volume (mL) Example 1 Alkyl glycoside 362 320 Example 2 Alkyl glycoside 314 275 No foam stabilizer Alkyl glycoside 113 107

[0107] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects: the above-mentioned preparation method is to graft a silane coupling agent type initiator on inorganic nanoparticles first, then under the action of a catalyst, a hydrophilic monomer is polymerized on the surface of the particles, and finally the particles are grafted with a hydrophobic silane coupling agent to obtain the product. The nano foam stabilizer prepared by the above-mentioned preparation method not only has a hydrophobic group, which can interact with the tail of the foaming agent, but also has an electrically neutral hydrophilic polymer group on the particle, which can play a role in temperature resistance and salt resistance on the one hand; on the other hand, compared with some anionic polymers, such as 2-acrylamido-2-methylpropane sulfonic acid sodium polymer, it is beneficial to reduce or avoid the charge repulsion with the head group of the surfactant, promote the adsorption of the nanoparticles on the gas-liquid interface, and further help to improve the stability of the foam. In this way, when carried by injection of water, it is beneficial to its smooth migration in high-temperature and high-salinity reservoirs, and to the generation of foam in the deep formation during the gas injection process, and when it is used in combination with the foaming agent, it can have a higher resistance factor than the foaming agent alone, realize deep plugging and delay gas channeling function. Moreover, the reactions in the preparation method are all aqueous reactions, and no organic solvent is used, so the environmental pollution is small.

[0108] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method of preparing a nanoemulsion, characterized in that, The nano-stabilized foam agent is prepared by a foam stabilizer raw material composition, which comprises inorganic nanoparticles, organic monomers, initiators, catalysts and hydrophobic modifiers. The method comprises the following steps: In step S1, the inorganic nanoparticles are dispersed in water, the pH value is adjusted to 8.0-9.0, the initiators are added into the system, a first mixed solution is formed and a reaction is carried out, after the reaction is completed, the solid is separated, and a first intermediate is obtained; In step S2, the first intermediate and the organic monomers are dispersed in water, oxygen is removed by introducing inert gas, the catalysts are added, a second mixed solution is formed and a polymerization reaction is carried out, after the polymerization reaction is completed, the solid is separated, and a second intermediate is obtained; In step S3, the second intermediate is dispersed in water, the hydrophobic modifier is added, a third mixed solution is formed and a modification reaction is carried out, after the modification reaction is completed, the nano-stabilized foam agent is obtained; The organic monomers have electrically neutral hydrophilic groups; the organic monomers comprise any one or more of 2,3-dihydroxypropyl methacrylate, N-(2,3-dihydroxypropyl) methacrylamide, 3-methacryloylpropyl-dimethyl-3-sulfopropyl ammonium salt and 3-methacrylate propyl-dimethyl-3-sulfopropyl ammonium salt; The initiators are 2,3-dihydroxypropyl propyl ether triethoxysilane; The catalysts are selected from any one or more of potassium copper periodate and potassium nickel periodate.

2. The method of claim 1, wherein, The inorganic nanoparticles are any one or more of nano-SiO2, nano-TiO2, nano-ZnO and nano-Al2O3.

3. The method of claim 1, wherein, The particle size of the inorganic nanoparticles is 20-100 nm.

4. The method of claim 1, wherein, The hydrophobic modifiers comprise any one or more of trimethyl monoethoxysilane, dimethyl diethoxysilane, isopropyl triethoxysilane, isobutyl trimethoxysilane and n-octyl triethoxysilane.

5. The method of claim 1, wherein, The raw material composition comprises 5-15 parts by weight of inorganic nanoparticles, 1.0-2.0 parts by weight of initiators, 3.0-10.0 parts by weight of organic monomers, 0.3-0.6 parts by weight of catalysts and 0.8-2.0 parts by weight of hydrophobic modifiers.

6. The method of claim 1, wherein, The raw material composition further comprises a reaction medium, which is water.

7. The method of claim 1, wherein, In step S1, the mass percentage of the inorganic nanoparticles in the mixed solution is 5-15%, and the mass percentage of the initiators is 1.0-2.0%.

8. The method of claim 1, wherein, The initiators are added in the form of an initiator aqueous solution.

9. The method of claim 8, wherein, The initiator aqueous solution is added in the form of drops.

10. The method of claim 9, wherein, During the dropwise addition, an alkali solution is added to adjust the pH value to 8.0-9.

0.

11. The method of claim 10, wherein, The alkali solution is any one or more of sodium hydroxide aqueous solution or sodium carbonate aqueous solution.

12. The method of claim 7, wherein, The temperature of the reaction in step S1 is 70-80°C.

13. The method of claim 9, wherein, After the dropwise addition of the initiator aqueous solution is completed, the temperature is raised to the reaction temperature.

14. The method of claim 7, wherein, The reaction time in step S1 is 15-20 h.

15. The method of claim 1, wherein, The mass fraction of the first intermediate in the second mixed solution is 5-15%, the mass fraction of the organic monomer is 3.0-10.0%, and the mass fraction of the catalyst is 0.3-0.6%.

16. The method of claim 1, wherein, The temperature of the polymerization reaction is 50-60°C.

17. The method of claim 1, wherein, The time of the polymerization reaction is 5-8h.

18. The method of claim 1, wherein, The mass fraction of the second intermediate in the third mixed solution is 8-15%, and the mass fraction of the hydrophobic modifier is 0.5-2.0%.

19. The method of claim 1, wherein, The temperature of the modification reaction is 60-70°C.

20. The method of claim 1, wherein, The time of the modification reaction is 20-25h.

21. A nanoemulsion characterized in that, Prepared by the method of any one of claims 1-20.

22. A foam flooding system, characterized by The nano-stable foam agent of claim 21.

23. Use of the foam flooding system of claim 22 in gas flooding.

24. The use according to claim 23, characterized in that, The gas is natural gas.

Images