Anion-cation surfactant, foam system, preparation method of anion-cation surfactant and foam system, and application of anion-cation surfactant and foam system in field of enhanced oil extraction

Abstract

The invention discloses a zwitterionic surfactant, a foam system, a preparation method of the zwitterionic surfactant and the foam system and application of the zwitterionic surfactant and the foam system in the field of enhanced oil extraction. The anion and cation surfactants comprise at least one of cationic surfactants containing a structure shown in the following formula (1) and at least one of anionic surfactants containing a structure shown in the following formula (2): # imgabs0 # R2-R3-SO3-1 / qMq + formula (2). According to the invention, amido or ammonium siloxane with a specific structure and an anionic surfactant are utilized to form a zwitterionic foam system, so that the carbon dioxide affinity of the foaming agent is improved, more balanced hydrophilic and carbon dioxide affinity can be realized, and the stability of carbon dioxide foam or emulsion is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of enhanced oil recovery, and particularly relates to an anionic-cationic surfactant, a foam system, a preparation method thereof, and an application thereof in the field of enhanced oil recovery. Background Art

[0002] CO 2 flooding can not only store CO for a long time 2 to fulfill the emission reduction obligation, but also can better improve the oil recovery rate. However, the viscosity of CO 2 is much smaller than that of underground crude oil, resulting in easy gas channeling of CO 2 during the injection process, reducing the reservoir sweep efficiency and the oil production. Foam is a dispersion system formed by insoluble or slightly soluble gas dispersed in a liquid phase. Forming foam with carbon dioxide can increase the viscosity and delay gas channeling. Since carbon dioxide exists in a supercritical state under formation conditions, its density and properties are close to those of a liquid, so carbon dioxide foam is also called carbon dioxide emulsion. According to the design idea of emulsion, one end of the foaming agent is hydrophilic and the other end is carbon dioxide-philic. When the two hydrophilicities are equivalent, it is more conducive to stabilizing the carbon dioxide emulsion. In patent US20200010756A1, an alkylamine surfactant is invented using the design idea of emulsion to stabilize the foam. The interaction between the foaming agent and water generally mainly relies on strong interactions such as electrostatic attraction and hydrogen bonds. In contrast, the interaction between the foaming agent and carbon dioxide is weak, mainly relying on Lewis acid-base interaction, making the hydrophilicity of the foaming agent much greater than its carbon dioxide-philic property, and the emulsion stability is poor.

[0003] Therefore, there is an urgent need for a new foam system that can improve the stability of carbon dioxide foam or emulsion. Summary of the Invention

[0004] To solve the problems existing in the prior art, the present invention provides an anionic-cationic surfactant, a foam system, a preparation method thereof, and an application thereof in the field of enhanced oil recovery. The present invention discovers that by using an amino or ammonium group siloxane with a specific structure to form an anionic-cationic foam system with an anionic surfactant, the carbon dioxide-philic property of the foaming agent is improved, a more balanced hydrophilic and carbon dioxide-philic property can be achieved, and the stability of carbon dioxide foam or emulsion is improved.

[0005] One object of the present invention is to provide an anionic-cationic surfactant, including at least one of the cationic surfactants containing the structure shown in the following formula (1) and at least one of the anionic surfactants containing the structure shown in the following formula (2):

[0006]

[0007] R 2 -R 3 -SO3 - 1 / qM q+ Formula (2);

[0008] In formula (1), R 1 and R 1 are each independently an alkylene group having 1 to 5 carbon atoms; Y is -NH 3 , -NH 2 R 4 , -NHR 4 R 5 or -NR 4 R 5 R 6 wherein R 4 and R 5 and R 6 are each independently -(R 7 O) m H, -CH 3 , -CH 2 CH 3 or -CH 2 CH 2 CH 3 wherein R 7 is an alkylene group having 2 to 3 carbon atoms, m is any integer from 1 to 100; Z is -(R 8 O) p1 (R 9 O) p2 H, wherein R 8 and R 9 are each independently an alkylene group having 2 to 3 carbon atoms, p1 and p2 are each independently any integer from 0 to 30; X is an anion or anionic group that balances the charge of the cationic surfactant, p is the absolute value of the valence of X; a:b:c = 1:(0.2 - 1):(0 - 1); a represents the average degree of polymerization of the structural unit , b represents the average degree of polymerization of the structural unit , c represents the average degree of polymerization of the structural unit , in formula (I), the structural units and are randomly arranged;

[0009] In formula (2), R 2 is a linear or branched alkyl group having 10 to 20 carbon atoms; R 3 is -C 2 H 4 -, -C 2 H 2 -, -(OC 2 H 4 ) n - or -(OC2 H 4 ) t One of O-, where n is any integer from 0 to 10 and t is any integer from 0 to 10; n represents the average degree of polymerization of -OC 2 H 4 -, and t represents the average degree of polymerization of -OC 2 H 4 -; M is a cation or cationic group that balances the charge of the anionic surfactant, and q is the absolute value of the valence of M.

[0010] In a preferred embodiment of the present invention,

[0011] In formula (1), the R 1 , R 1 are each independently an alkylene group of C1-C3; and / or, R 4 , R 5 , R 6 are each independently -(R 7 O) m H, R 7 is an alkylene group of C2-C3, and m is any integer from 1 to 20; and / or, p1 and p2 are each independently any integer from 1 to 10; and / or, X is one of a halide ion, a bicarbonate ion, a citrate ion, or an acetate ion; and / or, p takes any integer value from 1 to 2; and / or, a:b:c = 1:(0.2-0.5):(0-0.5) and / or,

[0012] In formula (2), R 2 is a linear or branched alkyl group of C12-C18; and / or, R 3 is -C 2 H 2 -, -(OC 2 H 4 ) n -, -(OC 2 H 4 ) t O-, where n and t are each independently any integer from 1 to 10, preferably any integer from 2 to 7; and / or, M is an alkali metal ion or an ammonium ion, preferably a sodium ion or an ammonium ion; and / or, q takes any integer value from 1 to 2.

[0013] In a preferred embodiment of the present invention,

[0014] The number-average molecular weight of the cationic surfactant is 1000-200000, preferably 2000-50000, more preferably 2000-30000.

[0015] In a preferred embodiment of the present invention,

[0016] The mass ratio of the anionic surfactant to the cationic surfactant is (0.1 - 10):1, preferably (0.1 - 5):1, more preferably (0.5 - 5):1.

[0017] In the present invention, both the anionic surfactant and the cationic surfactant can be obtained commercially or prepared by any method disclosed in the prior art in this field. The anionic surfactant can be sodium α-olefin sulfonate, ammonium dodecyl polyoxyethylene ether sulfate, or sodium octadecyl polyoxyethylene ether sulfonate. The cationic surfactant can be amino silicone oil (such as (20 - 25% aminopropylmethylsiloxane)-dimethylsiloxane copolymer), amino polyether silicone oil, or polyether-modified amino silicone oil. After being dissolved in water, the pH is adjusted to 2 - 6 with at least one of carbon dioxide, hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, citric acid, and acetic acid.

[0018] The second object of the present invention is to provide a preparation method of the anionic and cationic surfactants of the first object of the present invention, including the step of mixing at least one of the cationic surfactants containing the structure shown in formula (1) and at least one of the anionic surfactants containing the structure shown in formula (2). The mixing can adopt any mixing method in the prior art in this field.

[0019] The third object of the present invention is to provide an anionic and cationic foam system, including a gas phase and / or a supercritical phase, and a liquid phase. The liquid phase contains a solution of the anionic and cationic surfactants of the first object of the present invention or a solution of the anionic and cationic surfactants obtained by the preparation method of the second object of the present invention.

[0020] In a preferred embodiment of the present invention,

[0021] The solvent in the solution is water or a mixture of alcohol and water; and / or,

[0022] The total concentration of the anionic and cationic surfactants in the solution is 0.1 - 1%, preferably 0.2 - 0.5%; and / or,

[0023] The pH of the solution is 2 - 6, preferably 3 - 5.

[0024] In a preferred embodiment of the present invention,

[0025] The water is at least one of deionized water and water containing minerals, preferably at least one of deionized water, tap water, and formation injection water for oil and gas fields, more preferably brine with a salinity range of 0 - 10 g / L; and / or,

[0026] The alcohol is at least one of methanol, ethanol, and isopropanol; and / or,

[0027] In the mixture of the alcohol and water, the mass ratio of the alcohol to water is (0-1):1; and / or,

[0028] The substances for adjusting the pH include at least one of carbon dioxide, hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, citric acid, and acetic acid.

[0029] In a preferred embodiment of the present invention,

[0030] The gas phase includes gaseous carbon dioxide, and / or the supercritical phase includes supercritical carbon dioxide; and / or,

[0031] The volume ratio of the liquid phase to the gas phase and / or the supercritical phase is 1:(1-9), preferably 1:(1-5), more preferably 1:(1-3).

[0032] In the cationic and anionic foam system of the present invention, conventional additives in the art, such as corrosion inhibitors, can also be added, and their dosages are also conventional dosages, and those skilled in the art can add them according to actual situations.

[0033] The fourth object of the present invention is to provide a preparation method of the foam system of the third object of the present invention, including the steps of mixing components including the cationic and anionic surfactants in a solvent to form a solution, and then mixing the solution with the gas phase and / or the supercritical phase to form foam.

[0034] In a preferred embodiment of the present invention,

[0035] When the cationic and anionic surfactants are mixed in a solvent to form a solution, it further includes the step of adjusting the pH of the solution to 2-6, preferably 3-5; and / or,

[0036] The mixing to form foam includes the step of jointly injecting the solution with the gas phase and / or the supercritical phase into the formation; preferably, the total injection rate is 1-20 mL / min, preferably 2-10 mL / min, more preferably 2-5 mL / min; and / or, the volume flow rate ratio of the solution to the gas phase and / or the supercritical phase is 1:(1-9), preferably 1:(1-5), more preferably 1:(1-3); and / or, the injection pressure is 1-70 MPa, preferably 6-70 Mpa, more preferably 6-20 Mpa.

[0037] The fifth object of the present invention is to provide an application of the foam system obtained by using the foam system of the third object of the present invention or the preparation method of the fourth object of the present invention in the field of enhanced oil recovery, preferably in carbon dioxide flooding.

[0038] The present invention has the following advantages:

[0039] Carbon dioxide mainly exists in a supercritical state in oil displacement applications and has the properties of both liquids and gases. Therefore, carbon dioxide foam in this state is also called carbon dioxide emulsion. In the present invention, an amine group or ammonium group siloxane with a specific structure is used. There is a Lewis acid-base interaction and a hydrogen bond interaction between the siloxane and carbon dioxide, which improves the affinity of carbon dioxide. At the same time, it forms an anion-cation foam system with an anionic surfactant, and the hydrophilicity is lower than that of a single anionic foaming agent. The improvement of the carbon dioxide affinity and the reduction of the hydrophilicity can achieve a more balanced hydrophilic and carbon dioxide-philic property, thus significantly improving the stability of carbon dioxide foam or emulsion in the supercritical state. Specific Embodiments

[0040] The present invention will be specifically described below in conjunction with specific embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and cannot be understood as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0041] In the embodiments of the present invention, all raw materials used are conventional commercially available raw materials.

[0042] In the embodiments of the present invention, the number average molecular weight is determined by gel permeation chromatography, and the average degree of polymerization of each structural unit is obtained by nuclear magnetic resonance hydrogen spectrum testing.

[0043] The apparent viscosity is measured using a QCY-11 type automatic core flooding device (Jiangsu Hua'an Scientific Research Instruments Co., Ltd.); the foam stability is measured using a high-temperature and high-pressure foam property tester (Jiangsu Hua'an Scientific Research Instruments Co., Ltd.).

[0044] Example 1

[0045] At normal temperature and pressure, 2.5 g of ammonium lauryl polyoxyethylene ether sulfate and 0.5 g of amino silicone oil ((20-25% aminopropylmethylsiloxane)-dimethylsiloxane copolymer, the number average molecular weight of which is measured by gel permeation chromatography to be 4364, Shanghai Merck Chemical Technology Co., Ltd., product number: GEL-AMS-1203) are weighed and added to 1000 g of deionized water. After mixing, the pH is adjusted to 3.5 with hydrochloric acid (1 mol / L standard hydrochloric acid solution) to obtain an anion-cation surfactant aqueous solution.

[0046] In the anion-cation surfactant aqueous solution, the cationic surfactant includes the following structure: Among them, it is measured by nuclear magnetic resonance hydrogen spectrum that a:b:c = 1:0.3:0, where a represents the average degree of polymerization of the structural unit and b represents the average degree of polymerization of the structural unit of the structural unit Randomly arranged with structural units R 1 is -C 3 H 6 -, Y is -NH 3 , 1 / pX p- is chloride ion.

[0047] The preparation process of the ammonium lauryl polyoxyethylene ether sulfate is as follows:

[0048] Put 100 g of AEO7 (lauryl polyoxyethylene ether, Jiangsu Haian Petrochemical Factory) and 100 g of thiourea into a 500 mL four-necked flask, heat to 110 °C, add sulfamic acid in three batches according to the molar ratio of (AEO7):sulfamic acid of 1:1.1, raise the temperature to 120 °C, react for 3 h, after the reaction is completed, cool down to 55 °C, extract the organic matter with absolute ethanol, and then remove the ethanol by vacuum distillation to obtain ammonium lauryl polyoxyethylene ether sulfate. The active matter content measured by the two-phase titration method is 99%. The structural formula of the obtained ammonium lauryl polyoxyethylene ether sulfate is R 2 -R 3 -SO 3 - 1 / qM q+ , where R 2 is -C 12 H 25 , R 3 is -(OC 2 H 4 ) t O-, t = 7, t represents the average degree of polymerization of -OC 2 H 4 O-, 1 / qM q+ is ammonium ion.

[0049] Foam stability experiment (experimental temperature 100 °C):

[0050] Use 200 g of the cationic and anionic surfactant aqueous solution in Example 1 and CO 2 1000 g were stirred under the conditions of 2 MPa, 6 MPa and 15 MPa respectively. At 2 MPa and 6 MPa, carbon dioxide is in the gas phase, and at 15 MPa, carbon dioxide is in the supercritical state. The rotation speed is 3000 rpm, and the stirring time is 2 min. The recorded heights of the formed foams are 170 mm, 200 mm and 220 mm respectively, and the foam half-lives are 40 min, 70 min and 90 min.

[0051] Foam plugging experiment (experimental temperature 100 °C):

[0052] Use the cationic and anionic surfactant aqueous solution in Example 1 and CO 2A plugging experiment was carried out in a sand-packed tube with an aqueous phase permeability of 350 mD. The experimental back pressures were set at 2 MPa, 6 MPa, and 15 MPa respectively. The co-injection method was adopted in the experiment. CO 2 The volume flow rate ratio of the anionic and cationic surfactant aqueous solutions was 1:1, and the total injection rate was 3 mL / min. The ratio of the pressure when the anionic and cationic surfactant injection volume reached 1.0 PV to the pressure during water injection was recorded, and the apparent viscosities of the carbon dioxide foams formed by the surfactant were 300 mPa·s, 360 mPa·s, and 400 mPa·s respectively.

[0053] Comparative Example 1

[0054] The pressure for the foam stability (half-life) test and the back pressure for the foam plugging test in Example 1 were set to atmospheric pressure, and other conditions were the same. The half-life of the carbon dioxide foam formed by the surfactant was measured to be 20 min, and the apparent viscosity was 200 mPa·s.

[0055] The above Comparative Example 1 shows that the surfactant can better stabilize carbon dioxide foam under supercritical conditions.

[0056] Comparative Example 2

[0057] Only the cationic surfactant in Example 1 was used (the dosage of the cationic surfactant and the pH of the aqueous solution were the same as those in Example 1), and other test conditions were the same. The half-lives of the carbon dioxide foams formed by the surfactant were 0.3 min, 0.7 min, and 1 min respectively, and the apparent viscosity was 1 mPa·s, and effective foam plugging could not be generated.

[0058] Comparative Example 3

[0059] Only the anionic surfactant in Example 1 was used (the dosage of the anionic surfactant and the pH of the aqueous solution were the same as those in Example 1), and other test conditions were the same. The half-lives of the carbon dioxide foams formed by the surfactant were 20 min, 25 min, and 23 min respectively, and the apparent viscosities were 210 mPa·s, 235 mPa·s, and 230 mPa·s respectively.

[0060] By comparing Comparative Example 1 and Example 1, it can be seen that the anionic and cationic foaming agents can form better foams at 2 - 15 MPa, but not under atmospheric pressure conditions.

[0061] By comparing Comparative Examples 2 and 3 with Example 1, it can be seen that compared with using only the anionic surfactant or only the cationic surfactant, the anionic and cationic foaming agent of the present invention can form better foams at 2 - 15 MPa.

[0062] Example 2

[0063] At normal temperature and pressure, 2.0 g of sodium octadecyl polyoxyethylene ether sulfonate and 1.0 g of amino polyether silicone oil were weighed, added to 1000 g of deionized water, mixed, and carbon dioxide was introduced until the pH reached 4.5 to obtain an aqueous solution of anionic and cationic surfactants.

[0064] The preparation method of the above-mentioned amino polyether silicone oil is as follows: In a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser, 50 g of hydrogen-containing silicone oil (the ratio of the number of structural units to the structural unit was measured by 1H NMR to be 1:0.6), 13 g of allylamine, 80 g of allyl polyoxyethylene polyoxypropylene ether (Jiangsu Haian Petrochemical Factory, molecular weight 348, structure ), 0.2 g of chloroplatinic acid catalyst were added in sequence. Nitrogen was passed through and stirred for 10 min, the temperature was raised to 90 °C, and the reaction was carried out for 4 h. After removing low-boiling substances, it was cooled to room temperature to obtain amino polyether silicone oil. Its number-average molecular weight was determined to be 21142 by gel chromatography.

[0065] In the aqueous solution of the anionic and cationic surfactants, the cationic surfactant includes the following structure:

[0066] Among them, a:b:c = 1:0.3:0.3 was measured by 1H NMR. a represents the average degree of polymerization of the structural unit , b represents the average degree of polymerization of the structural unit , c represents the average degree of polymerization of the structural unit . The structural units are randomly arranged, R 1 is -C 3 H 6 , R 1 is -C 3 H 6 , Z is -(C 2 H 4 O) 3 (C 3 H 6 O) 3 H, Y is -NH 3 , 1 / pX p- is a bicarbonate ion.

[0067] The preparation process of the above-mentioned sodium octadecyl polyoxyethylene ether sulfonate is as follows:

[0068] 100 g of A18EO5 (octadecyl polyoxyethylene ether, Jiangsu Haian Petrochemical Factory) was put into a 500 mL four-necked flask and heated to 110 °C. It was added in three batches according to the molar ratio of (A18EO5) to sodium chlorosulfonate of 1:3. The temperature was raised to 120 °C and reacted for 12 h. After the reaction, the temperature was lowered to 55 °C. The organic matter was extracted with absolute ethanol, and then ethanol was removed by vacuum distillation. The active matter content was measured by the two-phase titration method to be 98%. The product was adjusted to pH 8 with sodium hydroxide to obtain sodium octadecyl polyoxyethylene ether sulfonate. The structural formula of the obtained sodium octadecyl polyoxyethylene ether sulfonate is R 2 -R 3 -SO 3 - 1 / qM q+ , where R 2 is -C 18 H 37 , R 3 is -(OC 2 H 4 ) n -, n = 5, n represents the average degree of polymerization of -OC 2 H 4 ]-, and 1 / qM q+ is sodium ion.

[0069] Foam stability experiment (experimental temperature 100 °C):

[0070] 200 g of the aqueous solution of anionic and cationic surfactants in Example 2 was stirred with 1000 g of CO 2 at a pressure of 15 MPa. At this time, carbon dioxide was in a supercritical state, the rotation speed was 3000 rpm, and the stirring time was 2 min. The heights of the formed foams were recorded as 230 mm respectively, and the foam half-life was 115 min.

[0071] Foam plugging experiment (experimental temperature 100 °C):

[0072] The aqueous solution of anionic and cationic surfactants in Example 2 and CO 2 were used to carry out a plugging experiment in a sand-packed tube with a water-phase permeability of 350 mD. The experimental back pressure was set at 15 MPa. The co-injection method was used in the experiment. The volume flow rate ratio of CO 2 to the aqueous solution of anionic and cationic surfactants was 1:2, and the total injection rate was 4 mL / min. The ratio of the pressure when the injection amount of anionic and cationic surfactants reached 1.0 PV to the pressure during water injection was recorded, and the apparent viscosity of the carbon dioxide foam formed by the surfactant was obtained as 450 mPa·s.

[0073] Example 3

[0074] Add 36 g of the amino silicone oil ((20 - 25% aminopropylmethylsiloxane)-dimethylsiloxane copolymer) and 0.5 g of potassium hydroxide in Example 1 to a reaction kettle, add 44 g of ethylene oxide, and react at 200 °C for 1 hour to obtain a polyether-modified amino silicone oil.

[0075] At normal temperature and pressure, weigh 2.5 g of sodium α-olefin sulfonate (AOS1416, Zhongqing Chemical Industry, whose structural formula is R 2 -R 3 -SO 3 - 1 / qM q+ where R 2 is an alkyl group with C12 - C14, R 3 is -C 2 H 2 -, 1 / qM q+ is a sodium ion) and 2.5 g of the above polyether-modified amino silicone oil, add them to 1000 g of deionized water and mix. Then adjust the pH to 3.5 with hydrochloric acid (1 mol / L standard hydrochloric acid solution) to obtain an anionic and cationic surfactant aqueous solution.

[0076] The cationic surfactant formed by the polyether-modified amino silicone oil in the above anionic and cationic surfactant aqueous solution has the following structure:

[0077] Among them, a:b:c = 1:0.3:0, a represents the average degree of polymerization of the structural unit b represents the average degree of polymerization of the structural unit The structural unit and the structural unit are randomly arranged, R 1 is -C 3 H 6 -, Y is

[0078] -NH(C 2 H 4 O) m1 H(C 2 H 4 O) m2 H. According to the feeding amount, it is calculated that m1 + m2 = 10, and 1 / pX p- is a chloride ion.

[0079] Foam stability experiment (experimental temperature 100 °C):

[0080] Use 200 g of the anionic and cationic surfactant aqueous solution in Example 3 and CO 21000 g was stirred under the conditions of pressures of 2 MPa, 6 MPa, and 15 MPa respectively. At 2 MPa and 6 MPa, carbon dioxide was in the gaseous phase, and at 15 MPa, carbon dioxide was in the supercritical state. The rotation speed was 3000 rpm, the stirring time was 2 min, and the heights of the formed foams were recorded as 150 mm, 210 mm, and 240 mm respectively. The half-lives of the foams were 20 min, 60 min, and 90 min.

[0081] Foam plugging experiment (experimental temperature 100 °C):

[0082] The aqueous solution of cationic and anionic surfactants in Example 3 was used with CO 2 A plugging experiment was carried out in a sand-packed tube with an aqueous phase permeability of 350 mD. The experimental back pressures were set at 2 MPa, 6 MPa, and 15 MPa respectively. The co-injection method was used in the experiment. The volume flow rate ratio of CO 2 to the aqueous solution of cationic and anionic surfactants was 1:1, and the total injection rate was 3 mL / min. The ratio of the pressure when the injection amount of the cationic and anionic surfactants reached 1.0 PV to the pressure during water injection was recorded, and the apparent viscosities of the carbon dioxide foams formed by the surfactants were obtained as 200 mPa·s, 370 mPa·s, and 430 mPa·s respectively.

[0083] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention as stipulated, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same functions.

[0084] All publications, patent applications, patents, and other references mentioned in this specification are hereby incorporated by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0085] When this specification uses prefixes such as "well-known to those skilled in the art", "prior art", or their similar terms to derive materials, substances, methods, steps, devices, or components, etc., the objects derived by such prefixes cover those commonly used in the art at the time when this application is filed, but also include those that are not commonly used at present but will become commonly recognized in the art as suitable for similar purposes.

[0086] In the present application document, the endpoints and any values within the disclosed ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the values between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. In the following, in principle, the various technical solutions can be combined with each other to obtain new technical solutions, and this should also be regarded as specifically disclosed herein.

[0087] In the context of this specification, any matters or things not mentioned, except for what is explicitly stated, are directly applicable to those known in the art without any change.

[0088] Moreover, any implementation manner described herein can be freely combined with one or more other implementation manners described herein. The technical solutions or technical ideas thus formed are regarded as part of the original disclosure or original record of the present invention and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider such combination to be obviously unreasonable.

Claims

1. An anionic-cationic surfactant, comprising at least one of cationic surfactants containing the structure shown in the following formula (1) and at least one of anionic surfactants containing the structure shown in the following formula (2): R 2 -R 3 -SO 3 - 1 / qM q+ Equation (2); In formula (1), R 1 and R 1 are each independently an alkylene group having 1 to 5 carbon atoms; Y is -NH 3 , -NH 2 R 4 , -NHR 4 R 5 or -NR 4 R 5 R 6 , where R 4 , R 5 , and R 6 are each independently -(R 7 O) m H, -CH 3 , -CH 2 CH 3 or -CH 2 CH 2 CH 3 , R 7 is an alkylene group having 2 to 3 carbon atoms, m is any integer from 1 to 100; Z is -(R 8 O) p1 (R 9 O) p2 H, where R 8 and R 9 are each independently an alkylene group having 2 to 3 carbon atoms, p1 and p2 are each independently any integer from 0 to 30; X is an anion or anionic group that balances the charge of the cationic surfactant, p is the absolute value of the valence of X; a:b:c = 1:(0.2 - 1):(0 - 1); In formula (2), R 2 is a straight-chain or branched-chain alkyl group having 10 to 20 carbon atoms; R 3 is -C 2 H 4 -, -C 2 H 2 -,-(OC 2 H 4 ) n - or -(OC 2 H 4 ) t O-, where n is any integer from 0 to 10 and t is any integer from 0 to 10; M is a cation or cationic group that balances the charge of the anionic surfactant, and q is the absolute value of the valence of M.

2. The anionic-cationic surfactant according to claim 1, wherein: In formula (1), the R 1 , R 1 are each independently an alkylene group having 1 to 3 carbon atoms; and / or, R 4 , R 5 , R 6 are each independently -(R 7 O) m H, R 7 is an alkylene group having 2 to 3 carbon atoms, and m is any integer from 1 to 20; and / or, X is one of a halide ion, a bicarbonate ion, a citrate ion, or an acetate ion; and / or, p takes any integer from 1 to 2; and / or, a:b:c = 1:(0.2 - 0.5):(0 - 0.5); and / or, In formula (2), the R 2 is a straight-chain or branched-chain alkyl group having 12 to 18 carbon atoms; and / or, R 3 is -C 2 H 2 -, -(OC 2 H 4 ) n -, -(OC 2 H 4 ) t O-; where n and t are each independently any integer from 1 to 10; and / or, M is an alkali metal ion or an ammonium ion; and / or, q takes any integer value from 1 to 2.

3. The anionic-cationic surfactant according to claim 1, wherein: The number-average molecular weight of the cationic surfactant is 1000 - 200000, preferably 2000 - 50000.

4. The anionic-cationic surfactant according to any one of claims 1 - 3, wherein: The mass ratio of the anionic surfactant to the cationic surfactant is (0.1 - 10):1, preferably (0.1 - 5):

1.

5. A method for preparing the anionic-cationic surfactant according to any one of claims 1 - 4, comprising the step of mixing at least one of cationic surfactants containing the structure shown in formula (1) and at least one of anionic surfactants containing the structure shown in formula (2).

6. An anionic-cationic foam system, comprising a gas phase and / or a supercritical phase, and a liquid phase, wherein the liquid phase contains a solution of the anionic-cationic surfactant according to any one of claims 1 - 4 or a solution of the anionic-cationic surfactant obtained by the preparation method according to claim 5.

7. The anionic-cationic foam system according to claim 6, wherein: The solvent in the solution is water or a mixture of alcohol and water; and / or, The total mass concentration of the anionic-cationic surfactant in the solution is 0.1 - 1%, preferably 0.2 - 0.5%; and / or, The pH of the solution is 2 - 6, preferably 3 - 5.

8. The anionic-cationic foam system according to claim 7, wherein: The water is at least one of deionized water and water containing minerals, preferably at least one of deionized water, tap water, and formation injection water for oil and gas fields, more preferably brine with a salinity range of 0 - 10 g / L; and / or, The alcohol is at least one of methanol, ethanol, and isopropanol; and / or, The mass ratio of alcohol to water in the mixture of alcohol and water is (0 - 1):1; and / or, The substances for adjusting the pH include at least one of carbon dioxide, hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, citric acid, and acetic acid.

9. The anionic-cationic foam system according to any one of claims 6 - 8, wherein: The gas phase includes gaseous carbon dioxide, and / or the supercritical phase includes supercritical carbon dioxide; and / or, The volume ratio of the liquid phase to the gas phase and / or the supercritical phase is 1:(1 - 9), preferably 1:(1 - 5), more preferably 1:(1 - 3).

10. A method for preparing the anionic-cationic foam system according to any one of claims 6 - 9, comprising the step of mixing the components including the anionic-cationic surfactant in a solvent to form a solution, and then mixing the solution with the gas phase and / or the supercritical phase to form foam.

11. The preparation method according to claim 10, wherein: When the anionic and cationic surfactants are mixed in a solvent to form a solution, it further includes the step of adjusting the pH of the solution to 2-6, preferably 3-5; and / or, The mixing and foaming includes the step of injecting the solution together with a gas phase and / or a supercritical phase into the formation; preferably, the total injection rate is 1-20 mL / min, preferably 2-10 mL / min, more preferably 2-5 mL / min; and / or, the volume flow ratio of the solution to the gas phase and / or the supercritical phase is 1:(1-9), preferably 1:(1-5), more preferably 1:(1-3); and / or, the injection pressure is 1-70 MPa, preferably 6-70 MPa, more preferably 6-20 MPa.

12. Application of the anionic-cationic foam system according to any one of claims 6-9 or the anionic-cationic foam system obtained by the preparation method according to any one of claims 10-11 in the field of enhanced oil recovery, preferably in carbon dioxide flooding.

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