Anionic-cationic surfactant, foam system, method for preparing the same and use thereof in the field of enhanced oil recovery

Abstract

The application discloses a kind of anion-cation surfactant, foam system and its preparation method and its application in the field of enhanced oil recovery.The anion-cation surfactant includes at least one of the cationic surfactant containing the structure shown in the following formula (1) and at least one of the anionic surfactant containing the structure shown in the following formula (2):R2-R3-SO3 ‑ 1 / qM q+ Formula (2).The application finds that the amine group or ammonium group siloxane with specific structure and anion surfactant form anion-cation foam system, improve the carbon dioxide affinity of foam agent, can realize more balanced hydrophilic carbon dioxide affinity, improve the stability of carbon dioxide foam or emulsion.

Description

Technical Field

[0001] This invention relates to the field of enhanced oil recovery technology, specifically to anionic and cationic surfactants, foam systems, their preparation methods, and their applications in enhanced oil recovery. Background Technology

[0002] CO2 flooding not only allows for long-term CO2 storage to fulfill emission reduction obligations but also improves oil recovery. However, CO2 viscosity is much lower than that of underground crude oil, leading to easy gas channeling during injection, reduced reservoir sweep efficiency, and decreased oil production. Foam is a dispersion system formed by insoluble or slightly soluble gases dispersed in a liquid phase. Carbon dioxide foam can increase viscosity and slow down gas channeling. Since carbon dioxide exists in a supercritical state under formation conditions, its density and properties are close to those of a liquid; therefore, carbon dioxide foam is also called carbon dioxide emulsion. According to the design concept of emulsions, the foaming agent is hydrophilic at one end and carbon dioxide-loving at the other; when the two affinities are roughly equal, it is more conducive to stabilizing the carbon dioxide emulsion. Patent US20200010756A1 invented an alkylamine surfactant using the design concept of emulsions to stabilize foam. The interaction between foaming agents and water is generally dominated by strong interactions such as electrostatic attraction and hydrogen bonding. In contrast, the interaction between foaming agents and carbon dioxide is weak, mainly Lewis acid-base interactions, making the hydrophilicity of the foaming agent much greater than its carbon dioxide-loving properties, resulting in poor emulsion stability.

[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 address the problems existing in the prior art, this invention provides anionic and cationic surfactants, a foam system, a preparation method thereof, and its application in enhanced oil recovery. This invention discovers that by utilizing amine or ammonium-based siloxanes with specific structures to form anionic and cationic foam systems with anionic surfactants, the carbon dioxide affinity of the foaming agent is improved, achieving a more balanced hydrophilic and carbon dioxide affinity, and enhancing the stability of carbon dioxide foams or emulsions.

[0005] One object of the present invention is to provide a cationic or anionic surfactant, comprising at least one of a cationic surfactant having a structure shown in formula (1) below and at least one of anionic surfactants having a structure shown in formula (2) below:

[0006]

[0007] R2-R3-SO3 - 1 / qM q+ Equation (2);

[0008] In equation (1), R1 and R1 Each is an alkylene group that is independently C1-C5; Y is one of -NH3, -NH2R4, -NHR4R5 or -NR4R5R6, wherein R4, R5, and R6 are each independently -(R7O). m One of H, -CH3, -CH2CH3 or -CH2CH2CH3, R7 is a C2-C3 alkylene group, m is any integer from 1 to 100; Z is -(R8O). p1 (R9O) p2 One of H, wherein R8 and R9 are independently C2-C3 alkylene groups, and p1 and p2 are independently any integers from 0 to 30; X is an anion or anionic group that balances the charge of the cationic surfactant, and p is the absolute value of the valence of X; a:b:c = 1:(0.2-1):(0-1); a represents a structural unit. The average degree of polymerization, b represents the structural unit. The average degree of polymerization, where c represents the structural unit. The average degree of polymerization, in equation (I), structural unit and Random arrangement;

[0009] In formula (2), R2 is a straight-chain or branched alkyl group of C10-C20; R3 is -C2H4-, -C2H2-, or -(OC2H4). n -or-(OC2H4) t One of O-, where n is any integer from 0 to 10, t is any integer from 0 to 10; n represents the average degree of polymerization of -OC2H4-, t represents the average degree of polymerization of -OC2H4-; M is a cationic 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 equation (1), R1 and R 1 Each of the following is independently a C1-C3 alkylene group; and / or, R4, R5, and R6 are each independently -(R7O). m H, R7 are C2-C3 alkylene groups, 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, bicarbonate ion, citrate ion, or 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), R2 is a straight-chain or branched alkyl group of C12-C18; and / or, R3 is -C2H2- or -(OC2H4). n -、-(OC2H4) t One of O-, wherein n and t are independent integers from 1 to 10, preferably 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 the value of any integer from 1 to 2.

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

[0014] The number average molecular weight of the cationic surfactant is 1,000-200,000, preferably 2,000-50,000, and more preferably 2,000-30,000.

[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, and more preferably (0.5-5):1.

[0017] Both the anionic and cationic surfactants described in this invention can be commercially available or prepared by any method disclosed in the art in the prior art. The anionic surfactant can be sodium α-olefin sulfonate, dodecyl polyoxyethylene ether ammonium sulfate, or octadecyl polyoxyethylene ether sulfonate. The cationic surfactant can be obtained by dissolving amino silicone oil (e.g., (20-25% aminopropylmethylsiloxane)-dimethylsiloxane copolymer) or amino polyether silicone oil or polyether-modified amino silicone oil in water and then adjusting the pH to 2-6 with at least one of carbon dioxide, hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, citric acid, and acetic acid.

[0018] A second objective of this invention is to provide a method for preparing anionic and cationic surfactants, which is one of the objectives of this invention. The method includes mixing at least one cationic surfactant containing the structure shown in formula (1) and at least one anionic surfactant containing the structure shown in formula (2). The mixing can be performed using any mixing method existing in the art.

[0019] A third objective of this invention is to provide an anionic and cationic foam system, comprising a gas phase and / or a supercritical phase and a liquid phase, wherein the liquid phase contains a solution of anionic and cationic surfactants according to one objective of this invention or a solution of anionic and cationic surfactants obtained by the preparation method according to another objective of this 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 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 mineral-containing water, preferably at least one of deionized water, tap water, and oil and gas field formation injection water, more preferably brine with a salinity range of 0-10 g / L; and / or,

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

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

[0028] Substances that adjust 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 supercritical phase is 1:(1-9), preferably 1:(1-5), and more preferably 1:(1-3).

[0032] Conventional additives, such as corrosion inhibitors, can also be added to the anion and cation foam system of the present invention. The dosage is also conventional, and those skilled in the art can add them according to the actual situation.

[0033] The fourth objective of this invention is to provide a method for preparing a foam system according to the third objective of this invention, comprising the steps of mixing components including the aforementioned cationic and anionic surfactants in a solvent to form a solution, and then mixing the solution with a gas phase and / or a supercritical phase to generate foam.

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

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

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

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

[0038] This invention has the following advantages:

[0039] Carbon dioxide exists primarily in a supercritical state in oil displacement applications, exhibiting both liquid and gaseous properties; therefore, carbon dioxide foam in this state is also known as carbon dioxide emulsion. This invention utilizes amine or ammonium-based siloxanes with specific structures. These siloxanes exhibit Lewis acid-base interactions and hydrogen bonding with carbon dioxide, enhancing its affinity. Simultaneously, they form anionic and cationic foam systems with anionic surfactants, resulting in reduced hydrophilicity compared to single anionic foaming agents. This improved carbon dioxide affinity and reduced hydrophilicity achieve a more balanced hydrophilic-carbon dioxide affinity, significantly improving the stability of carbon dioxide foam or emulsions in the supercritical state. Detailed Implementation

[0040] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection 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 are still within the scope of protection of the present invention.

[0041] In this embodiment of the invention, all raw materials used are conventionally available commercial raw materials.

[0042] In this embodiment of the 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 spectroscopy.

[0043] Apparent viscosity was obtained using a QCY-11 automatic core flooding device (Jiangsu Huaan Scientific Instruments Co., Ltd.); foam stability was obtained using a high-temperature and high-pressure foam performance tester (Jiangsu Huaan Scientific Instruments Co., Ltd.).

[0044] Example 1

[0045] At room temperature and pressure, 2.5g of dodecyl polyoxyethylene ether ammonium sulfate and 0.5g of amino silicone oil ((20-25% aminopropylmethylsiloxane)-dimethylsiloxane copolymer, the number average molecular weight of which was determined to be 4364 by gel permeation chromatography, Shanghai Mairui Biochemical Technology Co., Ltd., product number: GEL-AMS-1203) were weighed and added to 1000g of deionized water and mixed. The pH was then adjusted to 3.5 with hydrochloric acid (1mol / L standard hydrochloric acid solution) to obtain an aqueous solution of anionic and cationic surfactants.

[0046] In the aqueous solution of the anionic and cationic surfactants, the cationic surfactants include the following structures: The nuclear magnetic resonance (NMR) spectrum of hydrogen spectroscopy showed that a:b:c = 1:0.3:0, where 'a' represents the structural unit. The average degree of polymerization, b represents the structural unit. Average degree of polymerization, structural unit With structural units Random arrangement, R1 is -C3H6-, Y is -NH3, 1 / pX p- It is a chloride ion.

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

[0048] 100g of AEO7 (dodecyl polyoxyethylene ether, Jiangsu Haian Petrochemical Plant) and 100g of thiourea were added to a 500mL four-necked flask and heated to 110℃. Sulfoamic acid was added in three portions at a molar ratio of (AEO7):1.1. The temperature was raised to 120℃ and the reaction was allowed to proceed for 3 hours. After the reaction was complete, the temperature was lowered to 55℃, and the organic matter was extracted with anhydrous ethanol. The ethanol was then removed by vacuum distillation to obtain dodecyl polyoxyethylene ether ammonium sulfate. The active ingredient content was determined to be 99% by two-phase titration. The structural formula of the obtained dodecyl polyoxyethylene ether ammonium sulfate is R2-R3-SO3. - 1 / qM q+ Where R2 is -C 12 H 25 R3 is -(OC2H4) t O-, t=7, t represents the average degree of polymerization of -OC2H4O-, 1 / qM q+ It is an ammonium ion.

[0049] Foam stability test (experimental temperature 100℃):

[0050] 200g of the aqueous solution of the anionic and cationic surfactants in Example 1 and 1000g of CO2 were stirred at pressures of 2MPa, 6MPa and 15MPa, respectively. At 2MPa and 6MPa, the carbon dioxide was in the gas phase, and at 15MPa, the carbon dioxide was in a supercritical state. The stirring speed was 3000rpm and the stirring time was 2min. The heights of the foams formed were recorded as 170mm, 200mm and 220mm, respectively, and the foam half-lives were 40min, 70min and 90min.

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

[0052] A plugging experiment was conducted using the aqueous solutions of anionic and cationic surfactants from Example 1 and CO2 in a sand-filled pipe with an aqueous phase permeability of 350 mD. The back pressures were set to 2 MPa, 6 MPa, and 15 MPa, respectively. A co-injection method was used, with a CO2 to anionic and cationic surfactant aqueous solution volume flow rate ratio of 1:1 and a total injection rate of 3 mL / min. The ratio of the pressure when the anionic and cationic surfactant injection volume was 1.0 PV to the pressure when water was injected was recorded. The apparent viscosities of the carbon dioxide foam formed by the surfactant were found to be 300 mPa·s, 360 mPa·s, and 400 mPa·s, respectively.

[0053] Comparative Example 1

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

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

[0056] Comparative Example 2

[0057] Using only the cationic surfactant from Example 1 (the amount of cationic surfactant and the pH of the aqueous solution were the same as in Example 1), and with other test conditions being the same, the half-lives of the carbon dioxide foam formed by the surfactant were found to be 0.3 min, 0.7 min, and 1 min, respectively, and the apparent viscosity was 1 mPa·s, which could not produce effective foam plugging.

[0058] Comparative Example 3

[0059] Using only the anionic surfactant from Example 1 (the amount of anionic surfactant and the pH of the aqueous solution were the same as in Example 1), and with all other test conditions being the same, the half-lives of the carbon dioxide foams formed by the surfactant were 20 min, 25 min, and 23 min, and the apparent viscosities were 210 mPa·s, 235 mPa·s, and 230 mPa·s, respectively.

[0060] Comparing Comparative Example 1 and Example 1, it can be seen that cationic and anionic foaming agents can form better foam at 2-15 MPa, but not at atmospheric pressure.

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

[0062] Example 2

[0063] At room temperature and pressure, 2.0 g of sodium octadecyl polyoxyethylene ether sulfonate and 1.0 g of amino polyether silicone oil were weighed and added to 1000 g of deionized water. After mixing, 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 500mL four-necked flask equipped with a stirrer, thermometer and reflux condenser, hydrogen-containing silicone oil (the structural units of the hydrogen-containing silicone oil were determined by 1H NMR spectroscopy) was added sequentially. With structural units The quantity ratio is 1:0.6) 50g, allylamine 13g, allyl polyoxyethylene polyoxypropylene ether (Jiangsu Haian Petrochemical Plant, molecular weight 348, structure is 80g of chloroplatinic acid catalyst and 0.2g of nitrogen gas were added and stirred for 10 min. The mixture was then heated to 90℃ and reacted for 4 h. After removing low-boiling substances, the mixture was cooled to room temperature to obtain amino polyether silicone oil. Its number-average molecular weight was determined to be 21142 by gel permeation chromatography.

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

[0066] Among them, the ratio of a:b:c was 1:0.3:0.3 as determined by 1H NMR spectroscopy, where a represents the structural unit. The average degree of polymerization, b represents the structural unit. The average degree of polymerization, where c represents the structural unit. Average degree of polymerization, structural unit Random arrangement, R1 is -C3H6-, R 1Z is -C3H6-, Z is -(C2H4O)3(C3H6O)3H, Y is -NH3, 1 / pX p- It is a bicarbonate ion.

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

[0068] 100g of A18EO5 (octadecyl polyoxyethylene ether, Haian Petrochemical Plant, Jiangsu Province) was added to a 500mL four-necked flask and heated to 110℃. The chlorosulfonate was added in three batches at a molar ratio of (A18EO5):sodium chlorosulfonate of 1:3. The temperature was raised to 120℃, and the reaction was allowed to proceed for 12 hours. After the reaction was completed, the temperature was lowered to 55℃, and the organic matter was extracted with anhydrous ethanol. The ethanol was then removed by vacuum distillation. The active ingredient content was determined to be 98% by two-phase titration. The pH of the product was adjusted to 8 with sodium hydroxide to obtain sodium octadecyl polyoxyethylene ether sulfonate. The structural formula of the obtained sodium octadecyl polyoxyethylene ether sulfonate is R2-R3-SO3. - 1 / qM q+ Where R2 is -C 18 H 37 R3 is -(OC2H4) n -, n = 5, where n represents the average degree of polymerization of -OC2H4-, 1 / qM q+ It is a sodium ion.

[0069] Foam stability test (experimental temperature 100℃):

[0070] 200g of the aqueous solution of the anionic and cationic surfactants in Example 2 was stirred with 1000g of CO2 at a pressure of 15MPa. At this time, the carbon dioxide was in a supercritical state, the rotation speed was 3000rpm, and the stirring time was 2min. The height of the foam was recorded as 230mm and the foam half-life was 115min.

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

[0072] A plugging experiment was conducted using the aqueous solutions of anionic and cationic surfactants from Example 2 and CO2 in a sand-filled pipe with an aqueous phase permeability of 350 mD. The back pressure was set to 15 MPa, and a co-injection method was used. The volumetric flow rate ratio of CO2 to the aqueous solutions of anionic and cationic surfactants was 1:2, and the total injection rate was 4 mL / min. The ratio of the pressure when the amount of anionic and cationic surfactant injected was 1.0 PV to the pressure when water was injected was recorded, and the apparent viscosity of the carbon dioxide foam formed by the surfactant was found to be 450 mPa·s.

[0073] Example 3

[0074] 36g of amino silicone oil ((20-25% aminopropylmethylsiloxane)-dimethylsiloxane copolymer) from Example 1 and 0.5g of potassium hydroxide were added to a reaction vessel, along with 44g of ethylene oxide. The mixture was reacted at 200°C for 1 hour to obtain polyether-modified amino silicone oil.

[0075] Under normal temperature and pressure, weigh out sodium α-olefin sulfonate (AOS1416, produced by China Light Industry Chemical Co., Ltd., with the structural formula R2-R3-SO3). - 1 / qM q+ Wherein, R2 is a C12-C14 alkyl group, R3 is -C2H2-, 1 / qM q+ 2.5g of sodium ions and 2.5g of the above-mentioned polyether-modified amino silicone oil were mixed in 1000g of deionized water, and the pH was adjusted to 3.5 with hydrochloric acid (1mol / L standard hydrochloric acid solution) to obtain an aqueous solution of anionic and cationic surfactants.

[0076] The cationic surfactant formed from the polyether-modified amino silicone oil in the above-mentioned aqueous solutions of cationic and anionic surfactants has the following structure:

[0077] Where a:b:c = 1:0.3:0, and a represents a structural unit. The average degree of polymerization, b represents the structural unit. Average degree of polymerization, structural unit With structural units Random arrangement, R1 is -C3H6-, Y is

[0078] -NH(C2H4O) m1 H(C2H4O) m2 H, calculated based on the amount of material fed, yields m1 + m2 = 10, 1 / pX p- It is a chloride ion.

[0079] Foam stability test (experimental temperature 100℃):

[0080] 200g of the aqueous solution of the anionic and cationic surfactants in Example 3 and 1000g of CO2 were stirred at pressures of 2MPa, 6MPa and 15MPa, respectively. At 2MPa and 6MPa, the carbon dioxide was in the gas phase, and at 15MPa, the carbon dioxide was in a supercritical state. The stirring speed was 3000rpm and the stirring time was 2min. The heights of the foams formed were recorded as 150mm, 210mm and 240mm, respectively, and the foam half-lives were 20min, 60min and 90min.

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

[0082] A plugging experiment was conducted using the aqueous solutions of anionic and cationic surfactants from Example 3 and CO2 in a sand-filled pipe with an aqueous phase permeability of 350 mD. The back pressures were set to 2 MPa, 6 MPa, and 15 MPa, respectively. A co-injection method was used, with a CO2 to anionic and cationic surfactant aqueous solution volume flow rate ratio of 1:1 and a total injection rate of 3 mL / min. The ratio of the pressure when the anionic and cationic surfactant injection volume was 1.0 PV to the pressure when water was injected was recorded. The apparent viscosities of the carbon dioxide foam formed by the surfactant were found to be 200 mPa·s, 370 mPa·s, and 430 mPa·s, respectively.

[0083] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention 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 herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

[0084] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein 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 the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0086] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In principle, various technical solutions can be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0087] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

[0088] Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or technical ideas shall be 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 the combination to be obviously unreasonable.

Claims

1. A cationic or anionic surfactant, comprising at least one of a cationic surfactant having a structure as shown in formula (1) below and at least one of anionic surfactants having a structure as shown in formula (2) below: Equation (1); R2-R3-SO3 - 1 / qM q+ Equation (2); In equation (1), R1 and R 1 Each is an alkylene group that is independently C1-C5; Y is one of -NH3, -NH2R4, -NHR4R5 or -NR4R5R6, wherein R4, R5, and R6 are each independently -(R7O). m One of H, -CH3, -CH2CH3 or -CH2CH2CH3, R7 is a C2-C3 alkylene group, m is any integer from 1 to 100; Z is -(R8O). p1 (R9O) p2 One of H, wherein R8 and R9 are independently C2-C3 alkylene groups, and p1 and p2 are independently any integers from 0 to 30; X is one of halide ions, bicarbonate ions, citrate ions or acetate ions, and p is the absolute value of the oxidation state of X; a:b:c=1:(0.2-1):(0-1); In formula (2), R2 is a straight-chain or branched alkyl group of C10-C20; R3 is -C2H4-, -C2H2-, or -(OC2H4). n -or-(OC2H4) t One of O-, where n is any integer from 0 to 10, t is any integer from 0 to 10; M is an alkali metal ion or an ammonium ion, and q is the absolute value of the oxidation state of M.

2. The cationic and anionic surfactants as described in claim 1, characterized in that: In equation (1), R1 and R 1 Each of them is independently a C1-C3 alkylene group; and / or, R4, R5, and R6 are independently -(R7O). m H, R7 are C2-C3 alkylene groups, m is any integer from 1 to 20; 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, In formula (2), R2 is a straight-chain or branched alkyl group of C12-C18; and / or, R3 is -C2H2- or -(OC2H4). n -、-(OC2H4) t One of O-, where n and t are independent integers from 1 to 10; and / or, q takes the value of any integer from 1 to 2.

3. The cationic and anionic surfactant as described in claim 1, characterized in that: The number-average molecular weight of the cationic surfactant is 1,000-200,000.

4. The cationic and anionic surfactant as described in claim 3, characterized in that: The number average molecular weight of the cationic surfactant is 2000-50000.

5. The cationic and anionic surfactants according to any one of claims 1-4, characterized in that: The mass ratio of the anionic surfactant to the cationic surfactant is (0.1-10):

1.

6. The cationic and anionic surfactant as described in claim 5, characterized in that: The mass ratio of the anionic surfactant to the cationic surfactant is (0.1-5):

1.

7. A method for preparing anionic and cationic surfactants as described in any one of claims 1-6, 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).

8. A cationic and anionic foam system comprising a gas phase and / or a supercritical phase and a liquid phase, wherein the liquid phase contains a solution of the cationic or anionic surfactant according to any one of claims 1-6 or a solution of the cationic or anionic surfactant obtained by the preparation method according to claim 7.

9. The anion and cation foam system as described in claim 8, characterized in that: The solvent in the solution is water or a mixture of alcohol and water; and / or, The total mass concentration of anionic and cationic surfactants in the solution is 0.1-1%; and / or, The pH of the solution is 2-6.

10. The anion and cation foam system as described in claim 9, characterized in that: The total mass concentration of anionic and cationic surfactants in the solution is 0.2-0.5%; and / or, The pH of the solution is 3-5.

11. The anion and cation foam system as described in claim 9, characterized in that: The water is at least one of deionized water and mineral-containing water; and / or, The alcohol is at least one selected from 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, Substances that adjust pH include at least one of carbon dioxide, hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, citric acid, and acetic acid.

12. The anion and cation foam system as described in claim 11, characterized in that: The water is at least one of deionized water, tap water, or water injected into oil and gas field formations.

13. The anion and cation foam system as described in claim 12, characterized in that: The water is a saline solution with a mineralization range of 0-10 g / L.

14. The anion and cation foam system according to any one of claims 8-13, characterized in that: 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 supercritical phase is 1:(1-9).

15. The anion and cation foam system as described in claim 14, characterized in that: The volume ratio of the liquid phase to the gas phase and / or supercritical phase is 1:(1-5).

16. The anion and cation foam system as described in claim 15, characterized in that: The volume ratio of the liquid phase to the gas phase and / or supercritical phase is 1:(1-3).

17. A method for preparing an anionic and cationic foam system as described in any one of claims 8-16, comprising the steps of mixing components including the anionic and cationic surfactants in a solvent to form a solution, and then mixing the solution with a gas phase and / or a supercritical phase to generate foam.

18. The preparation method according to claim 17, characterized in that: When the anionic and cationic surfactants are mixed in a solvent to form a solution, the method further includes adjusting the pH of the solution to 2-6; and / or, The mixed foaming includes step a, which involves injecting a solution together with a gas phase and / or a supercritical phase into the formation.

19. The preparation method according to claim 18, characterized in that: When the anionic and cationic surfactants are mixed in a solvent to form a solution, the method further includes adjusting the pH of the solution to 3-5; and / or, The total injection rate of the solution, gas phase and / or supercritical phase into the formation is 1-20 mL / min; and / or, the volumetric flow rate ratio of the solution to the gas phase and / or supercritical phase is 1:(1-9); and / or, the injection pressure is 1-70 MPa.

20. The preparation method according to claim 19, characterized in that: The total injection rate of the solution, gas phase and / or supercritical phase into the formation is 2-10 mL / min; and / or, the volume flow rate ratio of the solution to the gas phase and / or supercritical phase is 1:(1-5); and / or, the injection pressure is 6-70 MPa.

21. The preparation method according to claim 20, characterized in that: The total injection rate of the solution, gas phase and / or supercritical phase into the formation is 2-5 mL / min; and / or, the volume flow ratio of the solution to the gas phase and / or supercritical phase is 1:(1-3); and / or, the injection pressure is 6-20 MPa.

22. The application of an anion-cation foam system according to any one of claims 8-16 or an anion-cation foam system obtained by the preparation method according to any one of claims 17-21 in the field of enhanced oil recovery, including its application in carbon dioxide flooding.

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